Did find this:
cached but it may not be the article in question, looks like "Home Power Magazine Solar, Wind and Renewable Energy Issue 121"
Home Power Magazine Solar, Wind and Renewable Energy Issue 121
30 affordable solar
Denis Du Bois
Innovative financing for this town house development allowed
investors and homeowners to reap the benefits of solar energy.
40 efficiency details
Paul Scheckel
Put these top ten tips to use and make your household more energy
efficient and renewables-ready.
48 cashing in
Andy Black & Erin Moore Bean
Better your bottom line and find the best financial fit for your
renewable energy projects with these online resources.
50 sunshine states
Jon Sharp, Ray Furse & Robert Chew
Move over, California : Progressive incentive programs are giving
Northeastern home and business owners the ability to plug into
affordable solar energy.
56 plug-in hybrids
Sherry Boschert
Can plug-in hybrids deliver on their promises of fewer emissions
and improved fuel economy? An inside look at the future of
transportation.
contents
October & November 2007
home power 121 / october & november 2007
6
Clockwise from lower left: Courtesy Google.org; courtesy SolarWrights; David Lewis; Richard Hallman; courtesy Solmetric; courtesy Canadian Solar Inc.
64 pv parts
Scott Aldous, Zeke Yewdall & Sam Ley
Wondering how superthin slices of silicon can turn sunshine into
electricity? Here’s a closer look at what lies inside a photovoltaic module.
70 buyer’s guide
Joe Schwartz with Doug Puffer
Pick the perfect PVs with our comprehensive solar-electric module
buyer’s guide.
82 pump primer
Chuck Marken
Expert advice on how best to match a pump to your solar hot water
system for years of reliable performance and trouble-free service.
88 REview
Joe Schwartz
Looking for a professional-grade, solar site-analysis tool? Check out
Solmetric’s handheld, touch-screen SunEye.
94 solar savings
Regina Anne Kelly
Peter and Tanya Ptak tap into smart solar savings, and profit from their
investments in three different solar-electric systems.
102 system monitoring
Ryan Mayfield
Keep tabs on your solar energy system’s performance with these
options in inverter-based and third-party monitoring gear.
7
www.homepower.com
Regulars
8 From Us to You
Home Power crew
Potential…
14 Ask the Experts
Industry Professionals
Renewable energy Q & A
22 Mailbox
Home Power readers
Feedback forum
112 Code Corner
John Wiles
Code Q & A
116 Independent
Power Providers
Don Loweburg
Grounding options
120 Power Politics
Michael Welch
Show RE the money
124 Word Power
Ian Woofenden
On & off...grid
128 Home & Heart
Kathleen
Jarschke-Schultze
Everything is round
132 RE Happenings
136 Marketplace
138 Installers Directory
143 Advertisers Index
144 RE People
Bill & Debbi Lord
7
On the Cover
Our 2007 PV Buyer’s Guide surveys
more than 100 solar-electric modules
on the market today.
Photos courtesy: Day4Energy; Canadian Solar Inc.;
Advent Solar
7
Home Power (ISSN 1050-2416) is published bimonthly
from offices in Phoenix, OR 97535. Periodicals postage
paid at Ashland, OR, and at additional mailing
offices. POSTMASTER: Send address corrections to
Home Power, PO Box 520, Ashland, OR 97520.
home power 121 / october & november 2007
Think About It...
If I were to wish for anything, I should not wish for wealth and power,
but for the passionate sense of potential—for the eye which, ever young and
ardent, sees the possible. Pleasure disappoints; possibility never.
—Søren Kierkegaard
Americans represent 5% of the world’s population and consume close to 25% of the
global energy supply. You may have heard this statistic a few more times than you’ve
cared to. But instead of assuming this figure is a harbinger of the unavoidable global
energy debacle around the corner, I look at it as an opportunity. Then, the questions
become: Can we use energy more efficiently and produce more of it with renewables?
What resources do we have at our disposal, and how much renewable energy capacity
can the grid realistically support?
• In every issue, Home Power profiles homes and businesses that consume a fraction
of the energy required by their inefficient counterparts, while maintaining an equivalent
level of comfort and convenience. Using energy intelligently is the foundation of long-
term energy security.
• Nations that have implemented well-coordinated programs to increase renewable
energy generation have succeeded. In the United States, strong consumer-level support
exists for clean energy technologies, and a tangible, bipartisan shift in the collective
attitude of our federal representatives is underway.
• Average per capita income in America is among the highest in the world. U.S.
consumers and businesses have substantial financial resources, and represent the largest
potential market for renewables worldwide. Many countries that already have achieved
a high percentage of renewable energy generation have solar and wind resources—and
financial resources—that pale in comparison to the United States.
• Variable resources such as the sun and wind account for less than 2% of U.S. electrical
generation. In Denmark, wind energy provides more than 20% of the nation’s electricity.
Since the beginning, American utilities have successfully managed the variable nature of
the load side of the grid. There are no insurmountable hurdles to keep them from doing
the same on the generation side.
Turning a problem into an opportunity is a learned skill. The energy challenges that face
America represent a tremendous opportunity for leadership, technical innovation, job
creation, and lifestyles that are comfortable, satisfying, and sustainable.
—Joe Schwartz for the Home Power crew
from us to you
POTENTIAL…
ictor
www.outbackpower.com
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www.homepower.com
9
European Sales O ce
Barcelona, España
(+34) 600-843-845
Corporate Headquarters
19009 62nd Avenue NE
Arlington, WA USA 98223
(+1) 360-435-6030
www.outbackpower.com
OutBack Power Systems is a leading global manufacturer of power electronic
products for renewable energy, back-up power, and mobile applications. No
matter where your location, no matter what your power source, OutBack Power
Systems has the solution for you. OutBack’s ruggedized inverter/chargers
are designed to survive in environments that would normally cause other
inverter/chargers to fail, without compromising outstanding performance
and reliability. Utilizing our FLEXware line of balance-of-system components
allows you to customize your system to your needs, from 2 to 36kW. Visit
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products, are bridging the gap between imagination and reality.
Publishers Richard & Karen Perez
Executive Editor & CEO Joe Schwartz
Managing Editor Claire Anderson
Art Director Ben Root
Senior Editor Ian Woofenden
Senior Editor Michael Welch
Graphic Artist Dave Emrich
Solar Thermal Editor Chuck Marken
Green Building Editors Rachel Connor, Laurie Stone, Johnny Weiss
Transportation Editors Mike Brown, Shari Prange
Columnists Kathleen Jarschke-Schultze, Don Loweburg
Michael Welch, John Wiles, Ian Woofenden
Advertising Manager Connie Said
Advertising Director Kim Bowker
Chief Information Officer Rick Germany
Operations Director Scott Russell
Technical Assistant Doug Puffer
Customer Service & Fulfillment Jacie Gray, Shannon Ryan
Contact Us...
Independently Published Since 1987
Copyright ©2007 Home Power Inc. All rights reserved. Contents may not be reprinted or otherwise reproduced without
written permission. While Home Power magazine strives to publish only safe and accurate content, we assume no
responsibility or liability for the use of this information.
Interior paper is made from 85%–100% recycled material, including 20%–30% postconsumer waste.
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Home Power magazine • PO Box 520 • Ashland, Oregon 97520 • USA
Introducing the new Sunny Island 5048, designed to meet
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A completely new line of UL-compliant
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Introducing the new Sunny Island 5048, designed to meet
the most demanding system requirements. From remote
off-grid applications to urban battery-backup systems, the
Sunny Island inverter provides high efficiency, robust surge
capability, and unsurpassed reliability. Our unique AC
coupling system integrates solar, wind, hydro, batteries and
generators, distributes power more efficiently, and extends
the overall life of the batteries. See our free DVD on AC
coupled off-grid systems. Call or email us today for a copy.
Call us: (888) 476-2872
www.sma-america.com
trim
bleed
Extreme off-grid
with our new 5000 Watt battery-based solar inverter
trim
bleed
All new product
line for 2007
What makes our
solar inverters best?
Visit Booth #
130
to find out.
September 24–27
Long Beach, CA
A completely new line of UL-compliant
Sunny Boy inverters ranging from 700 to
7000 Watts. The new Sunny Tower simplifies
commercial installations and is available
in 36 or 42 kW models. Each “US” model
inverter has a standard 10-year warranty
and is compatible with our wireless and
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are designed, manufactured and tested
in Germany.
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A healthy new line
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Tel: 810-220-4414
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Models from 4 KW to 12 KW in a single inverter
Dramatically improved ef ciency
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Want to learn more?
Visit us at Solar Power 2007, Booth 131 in Long Beach, California for
information on this exciting new addition to the Fronius family.
Introducing the
Fronius IG Plus Grid-tie Inverter
Three power levels, proven technology, smart design –
what you’ve come to expect from Fronius, only better.
Smart ventilation design
Field programmable to 208, 240, and 277 volts
with no loss in output power
Field programmable to positive or negative ground
Removable power stage for eld service
Built-in, fused six circuit combiner
A healthy new line
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Fronius USA LLC, 10421 Citation Drive, Ste 1100, Brighton, MI 48116
Tel: 810-220-4414
Email: pv-us@fronius.com
Web: www.fronius-usa.com
Models from 4 KW to 12 KW in a single inverter
Dramatically improved ef ciency
Integrated technology to maximize energy harvest
even on cloudy days
Integrated DC disconnect
Enclosure allows for indoor/outdoor installation
Want to learn more?
Visit us at Solar Power 2007, Booth 131 in Long Beach, California for
information on this exciting new addition to the Fronius family.
Introducing the
Fronius IG Plus Grid-tie Inverter
Three power levels, proven technology, smart design –
what you’ve come to expect from Fronius, only better.
Smart ventilation design
Field programmable to 208, 240, and 277 volts
with no loss in output power
Field programmable to positive or negative ground
Removable power stage for eld service
Built-in, fused six circuit combiner
home power 121 / october & november 2007
14
(continued on page 16)
Peak Sun-Hours
I’ve read that the Seattle area averages only 3.7 peak sun-hours per day. Maybe that’s true
in December, but April through October, I’d say it must be more like 10 to 12 hours a day,
meaning that the average must be higher than 3.7 hours per day throughout the year. How
are peak sun-hours determined?
Jeff Huffman • Brier, Washington
Excellent question! “Peak sun-hours” are not the same as “hours of
sunlight.” Sunrise to sunset represents hours of sunlight. But peak
sun-hours describe how much solar energy is available during a day.
The daily amount of solar radiation striking any location on
earth varies from sunrise to sunset due to clouds, the sun’s position
in the sky, and what’s mixed into the atmosphere. Maximum solar
radiation occurs at solar noon—the time when the sun is highest in
the sky, compared to the rest of the day. Sunlight in the morning
and evening does not deliver as much energy to the earth’s surface
as it does at midday because at low angles more atmosphere filters
the sunlight. Besides day-to-day differences, there are also seasonal
effects. In midsummer, due to the sun’s higher position in the sky, an
hour of sunshine packs more energy than the same hour of sunshine
in the winter.
Batteryless Hydro
I’ve heard of large-scale batteryless AC hydro-electric turbines for both on- and off-grid
use, but are there any small batteryless hydro systems for on-grid applications?
Are there batteryless grid-tied inverters that will synchronize a small
hydro turbine’s output with utility electricity? What does it take to set
them up?
James Conklin • Manchester, New Hampshire
Coupling a batteryless inverter with a small hydro turbine in a grid-tied
application is definitely doable, but there are some important system design
considerations. As with a batteryless inverter using PV for input, you must
correctly match the hydro turbine’s output voltage to the inverter’s input voltage
window and maximum DC voltage limit. This can be done with low-head to high-
head hydro systems, but is usually easiest with mid- to high-head systems. Low-
head hydro systems might require a batteryless inverter with a DC input as low
as 48 VDC nominal, which is hard to find these days. For mid- to high-head sites, I
usually use an induction turbine configured for high voltage (200–500+ VDC) and
1,200 to 3,600 watts peak output.
The specifics of the turbine are very important, including the diameter of the
runner (which affects rpm and voltage), output voltage, and peak output. Unlike
a PV system, an important distinction of a hydro system is that it may not be able
to handle running without its load. Without protection, this will occur if there is
a utility failure, when the batteryless inverter is designed to shut down. In this
situation, the rpm of the turbine will increase, and the open circuit voltage (Voc)
of the turbine would likely exceed the inverter’s maximum DC input voltage and
damage the inverter—and possibly the hydro turbine too, due to overspinning.
For high-head situations (200+ feet), having a Voc that is too high for the inverter
is a real concern. Fortunately, special diversion loads and controllers are available
that will divert the energy fast enough to avoid damaging the inverter, while keeping
the turbine electrically loaded. These diversion load/controller combinations are not
cheap—they can cost more than $1,500 for 4,000 watts of diversion.
Because these small, batteryless hydro systems are still unusual, I recommend
that they be undertaken with the guidance of the turbine and inverter suppliers and
manufacturers to ensure optimum performance and reliability.
Jay Peltz • Peltz Power
Ask the EXPERTS!
+
Courtesy www.sma-america.com; www.microhydropower.com
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REFOCUS:
BLEED_8.125 X 11.875
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home power 121 / october & november 2007
16
...Ask the EXPERTS!
Batteryless or Backup?
I want to install a grid-tied solar-electric system,
and I’m having a hard time deciding between a
battery-based system and a batteryless system. Can
you give me the pros and cons in plain English? Is
there any way to have the best of both worlds—the
efficiency and economy of a batteryless system
paired with the reassurance of always having a
reliable source of backup energy?
Joan Beaudet • Milton, Massachusetts
Batteryless systems are simpler, more efficient, and less expensive
to install and maintain, but during a utility failure, these systems
will not provide any electrical backup, even if the sun is shining.
A grid-tied, battery-based system is designed to do just that, but
uninterruptible power comes at a price. With the same size solar
array, a grid-tied, battery-based system will yield about 7% to 10%
less energy than its batteryless counterpart. This is primarily due
to the inefficiencies involved with battery charging (even when
the grid is functioning). And keep in mind that the batteries will
need replacement roughly every seven to ten years, which can be
a major expense. If you don’t experience frequent or long utility
failures, you will likely be happier with a batteryless system.
If your grid electricity is unreliable (perhaps you depend
on a long rural line in an area that’s prone to lightning or ice
storms), consider a battery-based system. In battery-based, grid-
tied systems, you have to install a separate AC subpanel to
separate critical circuits from luxury loads. This ensures that
when the system switches to battery backup, the energy stored in
the batteries will not be depleted by loads that you can easily live
without.
An experienced photovoltaic installer can help you determine
which of your electrical appliances can realistically be backed up,
and how much battery storage will be required. In almost all cases,
it’s unrealistic to rely on backup electricity for space or water heating,
or for major cooking loads like an electric range, since the energy
consumption would be far beyond the capacity of an affordable
battery-based photovoltaic system. If your location experiences long
utility outages, think about investing in solar heating systems or gas
appliances for your heating and cooking needs.
During a utility outage, consider supplying emergency needs
with no electricity. Store water in a tank. Keep a stack of ice packs in
your freezer to increase its holdover period. Keep LED headlamps or
flashlights or fluorescent (or gas) lanterns handy. Be ready to ignite
your gas stove-top using a spark lighter or matches. Use wood heat, or
gas heaters that don’t require electricity. If you want battery backup for
your computer, Internet connection, radio, or TV, consider purchasing
an off-the-shelf uninterruptible power supply (UPS) unit just for
that purpose. These preparations will keep you from being overly
dependent on electricity when the grid goes down.
Windy Dankoff, founder (retired) • Dankoff Solar Products
A peak sun-hour is roughly the amount of solar energy striking a
1-square-meter area perpendicular to the sun’s location over a 1-hour
period straddling solar noon in the summertime. So we can compare
apples to apples, the amount of power is standardized at 1,000 watts
(1 kilowatt) hitting that 1-square meter surface. By adding up the
various amounts of solar irradiation over the course of a day, and
counting them as units equivalent to 1 solar-noon midsummer hour
(1,000 watts per square meter for 1 hour), we get a useful comparison
number—the peak sun-hour.
An analogy might help complete the picture. Imagine that you
have to pour sunshine into buckets that are 1 meter square, and each
holds 1,000 watt-hours of solar energy. The fastest rate of filling that
bucket will occur at solar noon in the summer, when the sunlight is
really streaming down. At that time, you could fill a 1,000-watt-hour
bucket in 1 hour (1 KWH per hour). At any other time of the day,
however, it will take longer than 1 hour to get an equivalent “bucket”
of 1 peak sun-hour.
On average, summertime Seattle conditions will net you 4.8 peak
sun-hour-equivalents from sunup to sundown. Wintertime sees an
average of about 2.5 sun-hours per day. Over the course of a year, the
daily average works out to about 3.76 peak sun-hours. For month-
by-month solar irradiation information for a variety of cities in the
United States, visit http://rredc.nrel.gov/solar/pubs/redbook.
Larry Owens • Shoreline Solar Project
Courtesy www.midnitesolar.com/www.concordebattery.com
home power 121 / october & november 2007
18
...Ask the EXPERTS!
Wiser Driving
I’ve heard that the way you drive an electric vehicle (EV) can affect range dramatically.
Does the same apply to fuel economy for engine-driven vehicles? Can you give me some
basic pointers on how to drive so I use less energy and create less pollution?
James Fallow • Big Pine, California
Many factors affect driving range, but air drag and weight are
certainly two of the most important. For an EV moving at less than
30 mph, it’s the weight of the vehicle that kills driving range; as
speeds increase beyond 35 mph, air drag takes over as the biggest
culprit of dragging down fuel economy.
Some idea of air drag’s insidious nature can be gained from
data for the RAV4 EV—one of the most-studied EVs ever built. At
45 mph, the car can travel almost 150 miles on a single charge; at
60 mph, driving range plummets to about 100 miles (just imagine
what happens at 80 mph).
In the case of a conventional internal-combustion-engine (ICE)
vehicle, gains in fuel economy are there for the taking—if you’re willing
to drive at a more leisurely speed. My 1993 Dodge minivan delivers its
highest fuel economy—29 mpg—at a constant speed of 45 mph. (For
safety reasons, I suggest not driving at this speed on the open highway.)
When I dare to keep up with traffic on the Michigan interstate (80+
mph), my minivan’s fuel economy drops to about 17 mpg.
Stop-and-go city driving also reduces fuel economy for ICE-
based vehicles. This is a consequence of the operating characteristics
of typical engines that are designed to operate at higher loads (and,
hence, higher driving speeds), and the need for constant acceleration
and deceleration. Most hybrid-electric vehicles have circumvented
these problems and actually do as well, if not better, in the city as on
the highway.
You can improve your city mileage with an ICE-based vehicle if
you drive more intelligently. Learn how to coast, rather than braking,
into a stop, and time traffic lights so you keep moving at a relatively
(continued on page 20)
Financing an off-grid home or property is not entirely different
than financing a home in a typical subdivision. There are three
major categories that apply to residential real estate financing—
income, credit, and collateral.
Collateral is the most important factor in financing an off-grid
home, and it is up to an appraiser to address the typical issues and
evaluate the property’s features for potential underwriters. You’ll
need to find an appraiser in your area who specializes in out-of-the-
ordinary properties, with experience appraising off-grid properties.
Many off-grid homes are near other off-grid homes, which can
be used for appraisal comparisons. Have the appraiser prepare an
addendum to the property’s appraisal that details other nearby
off-grid properties and their sales histories. This will help show
underwriters that your property is not an anomaly for the area.
Your appraiser will not necessarily be bound by the normal
rule of having to use sales comparables within five miles. The
lending company Fannie Mae will allow greater distances as long
as the appraiser is able to support the necessity for using a sales
comparable outside normal guidelines. The appraiser may also
Financing Off-Grid Homes
I am writing to you from Vermont where I would like to purchase
an off-grid home. I have spoken to a few local banks and have
received a lukewarm response to the possibility of taking out
a mortgage for a property that is off the grid. How can I find a
receptive lender?
Mickel Zuidhoek • Pawlet, Vermont
search for older sales comparables of off-grid homes to support the
value of the home. If you know of any off-grid homes in the area, let
the appraiser know—sometimes sales of off-grid homes are private
sales and do not show on the multiple listing system, which is how
many appraisers find comparables.
Once an underwriter is able to see how the value of the property
is supported with reasonable sales comparables, you will soon be
enjoying your off-grid property or home.
Terry Phenicie • First Priority Financial
David Lewis
Courtesy Ed Marue
home power 121 / october & november 2007
20
To submit a question to
Home Power’s Ask the Experts,
write to: asktheexperts@homepower.com
or, Ask the Experts
Home Power, PO Box 520, Ashland, OR 97520
Published questions will be edited for content and length. Due to
mail volume, we regret that unpublished questions may not receive
a reply.
...Ask the EXPERTS!
Although there are several factors that affect tower height, your
choice will most likely be a compromise between energy production
and economics.
Proper tower height is essential for two reasons: Turbulent
wind is not only a poor quality fuel, but it dramatically increases
wear and tear on the turbine and tower. To provide the turbine with
high quality “fuel,” the tower must be tall enough to be well above
the turbulence layer created by obstructions such as buildings and
vegetation. The wind is stronger up there, and smoother. Ground
drag created by obstructions and the ground itself reduces the energy
available in the wind. To minimize ground drag, we need altitude.
Put simply, wind speed increases with height.
Minimum guidelines for tower height require the turbine rotor
to be a minimum of 30 feet higher than obstructions within 500 feet.
You should go even taller if the obstructions are young trees that will
continue to grow. Finding the average annual wind speed at your
site at a given tower height is a bit more difficult, but I would highly
recommend trying to determine or at least estimate it, starting with
regional wind energy consultants and dealers.
Now for the economics. Once I know the minimum tower
height needed to get above the turbulence, I let the turbine and the
customer’s budget help determine the maximum tower height. I look
at the cost of the turbine, its estimated energy production at various
tower heights, and the cost of the towers.
The following example uses wind data from my hilltop in
western New York, a Bergey Excel-S grid-tie turbine, and three
different heights of guyed lattice tower:
constant speed. These measures will help increase your city fuel
economy (as well as increase the time between brake replacements).
Likewise, mountain driving offers a number of challenges to fuel
economy. Here again, coasting (when possible) and driving slower
(when no one is tailing you) will save fuel and reduce pollution.
Another means of saving fuel is to consider carpooling. If you
put four people in one car, you’ll cut pollution and fuel consumption
by about 75 percent compared to four people driving their individual
cars. Now that’s impressive!
Dominic Crea • Institute for Sustainable Energy & Education
How Tall?
I hear a lot of talk about wind generators needing tall towers. How do I decide what’s tall
enough? Is there such a thing as too tall?
Jon Powell • Duluth, Minnesota
Why install a $28,000 turbine
on a short tower and lose 25%
or more of its potential energy
production to save $2,750,
which is roughly 5% of the
overall system cost? Spending
that additional $2,750 up front
yields an estimated additional
62,880 KWH over a 20-year
turbine life span. Here in my
neck of the woods, that has a
value of $11,318. And that’s at
our current utility rate of $0.18
per KWH, which I’m pretty sure
will increase over time!
A low-cost, small-diameter
turbine on a short tower may
be a small investment, but it
will only yield a small amount
of electricity each month. And
you won’t be any further ahead
with a larger turbine installed on a short tower, since you may
be sacrificing a large percentage of the turbine’s potential energy
production, and increasing maintenance costs.
At some point, of course, the law of diminishing returns usually
asserts itself and the tower choice becomes clear. And don’t forget
about zoning or height restrictions, which can be a limiting factor in
many areas. Of course, the final factor is the budget for the project.
The bottom line for most folks seems to be maximum bang for
minimum bucks. So, yes, there is such a thing as too tall a tower,
for economic reasons. But other than the money, you’ll just keep
improving a wind turbine’s performance by going higher.
Roy Butler • Four Winds Renewable Energy
Tower
Height (Ft.)
Average
Wind
Speed
(MPH)
Production
(KWH
Per Yr.)Tower Cost
Annual Energy
Value*
80
11.3
9,960
$8,100
$1,793
100
11.9
11,468
9,200
2,064
120
12.6
13,104
10,850
2,359
*At $0.18 per KWH
Sample Tower Height
Economics
The Whole Ball of Wax
SunWize pre-packaged grid-tie systems and grid-tie systems with
battery backup contain everything you need for a complete installation.
OFFICES THROUGHOUT THE US AND CANADA
home power 121 / october & november 2007
22
Solar Pride
I drove up to our new property last
Thursday to take the last walk-through
with the former owner and my real estate
agent. I got a primer on the solar-electric
system, and managed to get the solar-
Mailbox
powered well pump working without too
much trouble. Greg, the former owner,
was gracious enough to let me spend the
night in the cabin (and gave me the keys),
despite the property not closing until the
next day.
So I spent the afternoon playing
with the solar-electric system. Turned
the lights on. Then off. Then on again. I
peeked into the water tank maniacally,
watching the slow dribble of water into
the tank. I watched with satisfaction as
the battery monitor said, “Good,” even
with the lights on and the pump running.
After an afternoon of playing with the
system (can’t tell you how much joy it
gave me to see it running so perfectly),
I drove down to Oroville to get some
provisions, called my wife Joni to brag
about the solar pumping system actually
working, and then drove back up the
bumpity 2.2-mile gravel road to the 2.75-
acre compound.
I got out my sleeping bag, placed it
on the deck, and watched the moon rise.
I took it as a good omen that the property
was to close on the day of a blue moon. I
toasted the moon. Gave a wine offering to
the property. Neighbors drove by in their
pickup trucks. All of them waved. The
neighbor’s chickens were quite busy with
their clucking. Dogs barked. Generators
McMansions
I’ve been an avid reader of Home Power for
five years. Recently, I heard the derogatory
term “McMansion” used on a green blog
for the thousandth time. I myself live in
what qualifies to some as a McMansion
(large subdivision home) in San Diego.
Should I feel guilty?
After reading your latest issues, I’ve
found the answer. In our home, we use
a gas heater in the early morning for
20 minutes per day (on a timer) about
two months each year. We use the air
conditioning about five days each year for
about two to three hours each day. In one
year, our heating and cooling bill is what
someone in Montana or Phoenix would
likely pay in a week.
Bottom line: We use far less energy in
our McMansion than many of the people
featured in your magazine. They often
have thick jackets on in the photos. Their
homes are in either extremely cold places
or deserts, and require constant heating
or air conditioning. After choosing to live
in a very non-green location (from an
energy standpoint), they go to extremes
to make their living more green, and are
then dubbed energy heroes.
By contrast, we coastal southern
Californians in our McMansions that
people love to judge, just by living here,
may end up using less energy at home.
Even without solar, wind, or sealing up
our houses airtight, we use far less energy
per person than those in more severe
climates.
Should we feel guilty? Yes, for our
swimming pools, SUVs, and hour-long
solo commutes to work. But, alas, not
for our McMansions. As the magazine
writers have said so many times, it is
better to conserve than to generate your
way out of large consumption. And the
very choice of where we live can be an act
of conservation. Keep up the great work!
Vinod Lobo • San Diego, California
It is better to conserve than to generate your way
out of large consumption. And the very choice of
where we live can be an act of conservation.
(continued on page 24)
Courtesy Vinod Lobo
Courtesy Allan Stellar
home power 121 / october & november 2007
24
...Mailbox
ran. Sound travels well out here. It was
a little spooky in the Sierra foothills as
night descended, but I slept like a baby on
the deck. Woke up to a jackrabbit nibbling
on my weeds. “Have at it, fella”—keeps
the fire danger down and I won’t have to
weed-whack it.
Again I played with the solar-electric
system. Filled the tank halfway. Battery
monitor still said, “Good.” Got a drink
out of the spigot and washed up with my
own solar-pumped water. Kept giggling
at my good fortune. Simple pleasure.
Old Bill dropped by. Bill has lived up
here for fifteen years. Off the grid with 24
solar-electric modules and a 2,500-gallon
water tank. A former Ford factory worker,
he proudly stated he raised a family. Had
a car. A wife. Children. All supported on
his good union job. He sold his house and
now is an “off-the-grid, solar Libertarian–
Republican.” I quickly learned that up
here in this off-the-grid community, your
wealth is measured by the number of
solar panels you have, multiplied by the
size and flow of your water tank…
On my way back to Calistoga (in the
Napa Valley), I received a message from
my real estate agent on my cell phone
(which doesn’t work at the property).
“Congratulations—you now own the
property.” Called Joni and left a message
that all was well. The solar cabin is ours.
Allan Stellar • Concow, California
Wanted:
Performance Data
I just read through the twentieth
anniversary issue. Such fun, looking at
the journey…
Looking at the past prompted me
to think of the future. Do you think it is
at all likely that you will be doing more
In this off-the-grid community, your wealth
is measured by the number of solar panels you
have, multiplied by the size and flow of your
water tank…
The original Solar Pathfinder
with its reflective properties gives an excellent
“instant solar blueprint” of the prospective site.
Now, the new Solar Pathfinder Assistant software,
and your digital camera, carry that shading information
into a concise, thorough, professional-looking
solar site analysis report in just seconds.
Solar Pathfinder Assistant: automatically adjusts for magnetic
declination, latitude, azimuth, tilt angle, & tracking mode
(fixed, 1-axis, 2 axis); automatic yearly energy computations
using included NREL data (no WWW necessary);
displays “before/after” results of removing obstructions;
CSI-EPBB compliant.
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info@solarpathfinder.com • www.solarpathfinder.com
The BEST Tool for Solar Site Analysis
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www.homepower.com
25
...Mailbox
equipment reviews? It is nice to read
about somebody’s personal experiences
in setting up a system, especially when
it’s similar to what I have set up. And
seeing that they used some new item
that makes the system more efficient
is helpful. But those articles, useful as
they may be in motivating newbies, do
little to help those who are already sold
on the idea and need more specific info
to aid buying decisions. Or, like me,
already have a system and may want
to upgrade. We need to know that “X”
piece of equipment performs as well as
it is advertised, or not. And that among
the best-selling brands in a particular
category, “A” stands out in one regard
and “B” in some other regard…
An example: Several years ago, I
decided to upgrade my system, adding
50% to my PV array capacity. I knew I
would have to increase the controller
capacity over the Trace C-40 I had. So
I took a look at MPPT controllers. I was
able to get enough information in Home
Power and elsewhere to determine that
this type of controller would increase
my system’s efficiency. But as to which
brand of MPPT controller to use, I found
little hard data. Yes, there was some
word-of-mouth info, which helped a
little. But I needed an outright review
with some hard data. I did not find any.
I finally selected an OutBack MX60 and
have been happy with it. But I may have
just been lucky…
Much of the new technology I run
into comes from the dealers’ ads. If it’s
something I might find useful, I do a
Web search for reviews, comparisons,
etc., and I usually find very little. And
even now, a search for MX60 reviews
brings up nothing of substance.
Why am I concerned at this juncture?
Well, my system is just over ten years
Looking at the past prompted me to think of
the future: Do you think it is at all likely that
you will be doing more equipment reviews?
home power 121 / october & november 2007
26
...Mailbox
old now. While I don’t see any real signs
of their coming death, my twelve Trojan
L-16 batteries will have to be replaced
in the foreseeable future, with the same
or perhaps with fewer but larger cells.
Also, I don’t have a “backup” inverter
to my Trace 4024, and supposedly the
technology has been improving. At some
time I would like to upgrade, while keeping
my old inverter as
a backup.
What I am
saying is that there
is a need for hard
data on all the
various pieces of
equipment and, if
anyone is in position
to provide that data,
it is Home Power.
John Bertrand •
Holualoa, Hawaii
Home Power is ramping
up our hardware
reviews (see the
Solmetric SunEye review on page 88 of this
issue), and we’re increasing the frequency
of our in-depth equipment buyer’s guides
as well. In addition, we have two additional
equipment data collection and review
projects in the works. Look for more on
this in future issues of Home Power, and on
www.homepower.com in 2008.
Joe Schwartz • Home Power
Overseas RE
It was a pleasure to read the “Clean
Energy Pioneers” piece (HP120), which hit
my mailbox in Bangkok today. I remember
helping with a bunch of those articles—
seems like yesterday. I was especially
tickled to see in your retrospective article
a photo of myself as a long-haired 19-
year-old in front of the solar oven I built.
And now, here I am, twice as old! What
a ride!
In a nutshell, here’s what I’ve been
up to. In 2004, I finally finished a doctoral
degree at UC–Berkeley’s Energy and
Resources Group, with a dissertation
on community microhydro power in
Renewable energy pro
Chris Greacen:
Then…and now.
www.homepower.com
27
...Mailbox
To send a letter to
Home Power’s Mailbox,
write to:
mailbox@homepower.com
or
Mailbox, c/o Home Power
PO Box 520, Ashland, OR 97520
Published letters will be edited for content
and length. Due to mail volume, we regret
that unpublished letters may not receive a
reply.
Thailand. In the process, I got diverted
by working on various renewable energy
projects. Since 2000, I’ve been living in
Bangkok.
In 2003, my wife and I started Palang
Thai (www.palangthai.org), an NGO
that works to improve conditions for
clean, decentralized energy in Thailand
and the Mekong region. One success
we had was drafting Thailand’s net-
metering regulations, which are now in
place. An upgraded version approved in
December 2006 allows RE generators up
to 10 megawatts (MW) to net meter and
to sell excess electricity at a premium feed-
in tariff. More than 280 MW of projects
(mostly biomass from sugar cane and rice-
husk residues) have been approved under
the regulations. Despite some successes,
the clean energy community in SE Asia is
a tiny minority and for every MW of RE,
another 20 or so MW of dirty conventional
coal/gas is in the pipeline. In the past few
months, nuclear energy is raising its ugly
head all over the region, with plans in place
in Thailand, Vietnam, and (gasp!) Burma…
Home power technologies and
sensibilities are sorely needed over here...
We’re always looking for talented long-
term volunteers! I’m real proud of all that
y’all have done over the years. We’re now
a force to be reckoned with. The forces
of light, creativity, logic, and compassion
are chipping away at the old, dirty, greasy
hegemony.
Chris Greacen • Bangkok, Thailand
Window Tips
I’m about to mention something small
but effective. It took me until this year to
realize it, after fifty years of solar energy
awareness. On sunny autumn, winter,
and spring days, when you can use
more heat in your home, take off your
window screens! Compared to leaving
your screens on, it will significantly
increase the solar energy input.
Somehow I missed this until I made a
PV power meter and checked the output
of a module through my new double-pane
windows. Then I thought about what
would happen to module output through
a screen. (PV output is not the same
as solar thermal gain, but it reminded
me that I’m losing solar potential by
leaving my screens on.) And the rest is
history, which we need to share, even
if everyone says in retrospect, “I know
that—it’s obvious!”
S. Premena • via e-mail
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home power 121 / october & november 2007
30
HIGH-PERFORMANCE HOUSING
+ SMART INVESTING
Affordable
Solar
by Denis Du Bois
31
Innovative financing for this Mosier,
Oregon, town house development
allows investors and homeowners alike
to share in the incentives and financial
benefits of harnessing solar energy.
www.homepower.com
These modern town houses in northern Oregon are shining examples of building
with energy use in mind.
Richard Hallman (2)
Would home buyers pay a premium to
have renewable energy integrated into
their new town homes? Peter Erickson,
owner of Urban Fund Inc., a Pacific
Northwest development company,
was pretty sure of it. “The public is
very aware of and concerned about the
rising costs of utilities. If a prospective
buyer can purchase a home that consumes less energy than a
typical home and produce a portion of its own energy,” says
Erickson, “then it’s not a tough business decision.”
So he worked with his architects and a solar consulting
firm to integrate photovoltaic and solar hot water systems
into his 34-unit development in Mosier, Oregon. After some
preliminary number-crunching, he wasn’t confident that
homeowners would be willing to front the large $28,000 per
unit initial expense that the two RE systems would require.
But some savvy financial planning saved the day, allowing
Erickson to realize his plans to add a strong renewable energy
component to high-performance housing.
Making RE a Reality
Erickson tapped into the talents of solar consultant Doug
Boleyn of Cascade Solar Consulting, to figure out an attractive
financial strategy for incorporating renewables into the
development.
In Oregon, financial support for both residential and
commercial solar systems is strong. The state offers generous
tax credits for both home and business owners of qualifying
grid-tied systems, and the nonprofit Energy Trust of Oregon
offers additional cash incentives. Adding in federal tax credits
for residential and commercial solar energy made the decision
to install renewable systems a sound financial move.
Boleyn compared private and commercial solar incentives
and laid out two possible scenarios, based on a goal of
producing about half of the development’s electricity and hot
water with solar energy.
One approach was to leverage federal incentives available
to private individuals for residential solar installations. Each
homeowner would qualify for a maximum $6,000 Oregon
state PV tax credit, plus a one-time $2,000 federal solar tax
credit. Although this would take care of a chunk of the up-
front cost, the combined credits represented less than 30% of
the total capital cost of the solar equipment on each home.
Plus, Mosier is a vacation destination, with Washington State
right across the river. Washington residents who purchased
a town house as their second home wouldn’t be able to use
Oregon’s tax credits.
The second option was to arrange for the solar equipment
to be commercially owned by a subsidiary of the development
company. Business owners of solar installations qualify for
much higher incentives than do individuals under both
the state and federal programs. With no caps, the state and
federal business tax credits have potentially higher value,
and businesses can also depreciate the solar equipment, a tax
write-off not available to individuals.
In addition to the tax breaks, the Energy Trust of Oregon
offers incentives to property developers who install solar-
home power 121 / october & november 2007
32
affordable solar
”The utilities no longer have a monopoly on supplying
power. Mosier Creek Solar is doing it, and at lower
electric rates.”
—Doug Boleyn, Cascade Solar Consulting
electric and solar thermal systems on
buildings. The result: The combined
business incentives would be enough
to offset 70% of the systems’ installed
costs, a savings Erickson couldn’t pass
up—and would be able to pass on to the
homeowners.
To capitalize on the largest incentives,
Erickson formed a subsidiary, Mosier
Creek (MC) Solar LLC, to own and operate
the systems for a minimum of five years.
This third-party investment group bought
the solar equipment and took all the utility
and tax credit incentives. In addition,
they took accelerated depreciation for the
improvements over a five-year period.
In effect, MC Solar became its own
solar utility, selling the solar electricity
generated by the rooftop systems to the
homeowners at about 15% less than the
local utility’s retail rate, a significant
savings. Each homeowner has a net-
metering agreement with the primary
utility (Pacific Power) and can offset
with solar up to 100% of their electricity
use at the same rate that the utility
charges.
The addition of Btu meters would
have made it possible to meter the energy
produced by the solar water collectors as
well, but the investors were satisfied with
their return on investment without having
to claim the water heating savings. So the
By clustering the 34 residences into eight
buildings, Mosier Creek Place devotes half of
its 5-acre site to maintaining the existing creek
and grasslands.
Large windows admit an abundance of
natural light into each townhome’s interior,
reducing the need for artificial lighting.
affordable solar
www.homepower.com
33
Richard Hallman (2)
approximately 2,500 kilowatt-hours equivalent annual energy
from the solar water heating system on each town house is
provided to the homeowner at no additional cost.
At the end of five years, homeowners who wish to
purchase their rooftop solar systems will be able to buy them
at a fraction of their initial cost from MC Solar. Owning the
systems will mean that homeowners get low-cost solar energy
from their systems, helped by renewable energy credits
(green tags) and other available incentives.
A Model of Success
Erickson and his team, including Cascade Solar, Surround
Architecture in Portland, and local green building certification
agency Earth Advantage, have broken new ground for
renewable energy with Mosier Creek Homes. “This is a first-off
model for this sort of arrangement—a developer selling power
that’s produced right there on the building,” says Boleyn.
“The utilities no longer have a monopoly on supplying power.
Mosier Creek Solar is doing it, and at lower electric rates.”
Boleyn says they checked Oregon utility law to make
sure that MC Solar would not be considered a public utility
and subject to regulation, and acknowledged that the
utilities were “quite cooperative in setting everything up,
including the net metering agreements.”
Erickson is pleased with the outcome and says that high-
performance housing offers “distinct marketing advantages
34
affordable solar
100KWH
G
KWH Meter:
To utility grid
AC Service Entrance:
To 120/240 VAC loads
System
Performance
Meter
DC
Disconnect
Inverter: PV Powered PV2880 XV, 450 VDC
maximum input, 200–390 VDC MPPT window,
240 VAC output
Photovoltaics: Eighteen Sharp NE-170U1 or NT-180U1, 170 W or 180 W each at 34.8
or 35.9 Vmp, wired in two 9-module series strings for 3,240 W total at 323 Vmp
Note: All numbers are rated, manufacturers’ specifications, or nominal unless otherwise specified.
PV
Combiner
Box
PV Powered
H2
H1
100KWH
AC
Disconnect:
Exterior
Right: PV modules cover the roofs of this
modern town house complex.
Below: PV Powered inverters convert DC
electricity from the arrays into typical
household AC electricity.
Mosier Creek Homes On-Grid PV System
home power 121 / october & november 2007
Courtesy Tod LeFevre (2)
that protect the developer in a down-
market cycle. In fact, we came online
having received our final occupancy
permits this past June in the middle of
a national slowdown in real estate and
have sold ten of our thirty-four units
to date.”
“The public is very concerned about
the rising costs of energy. If a prospective
buyer can find a home that is LEED-H
certified and produces 50% of its energy
needs, then it’s an easy decision,” says
Erickson. “I wouldn’t have engaged in
the process if it didn’t pencil for both us
and the home buyer.”
Access
Denis Du Bois was hooked on solar
energy in 2001 when he installed a PV
system at his off-grid summer home.
He is CEO of P5 Group Inc., a Seattle
firm that helps energy-related companies
market successfully. Du Bois founded
Energy Priorities magazine and hosts the
popular “Energy Minute” podcast series.
Cascade Solar Consulting • 503-655-
1617 • www.cascadesolar.com •
RE planning
www.homepower.com
affordable solar
35
Solar Incentives
for Better Business
Mosier Creek Solar LLC took advantage of three solar-electric and hot water
incentives available to businesses:
• Oregon state tax credit: 35% of system cost, no limit. (This has since been
raised to 50%.)
• Federal solar investment tax credit: 30% of system cost, no limit.
• Equipment depreciation: 5-year accelerated.
In addition, the Energy Trust of Oregon kicked in $35,000 (the maximum, per
project) through two incentives:
• $1 per watt of rated PV capacity.
• $0.40 per kilowatt-hour of electricity saved for hot water.
The Mosier Creek Homes formula for making PV financially appealing to both
developer and buyer:
• Install PV and solar water heating systems on each unit.
• Set up a separate business to own the solar equipment.
• Use business tax incentives and other subsidies to cover as much as 70% of
the cost.
• Price the homes at a premium, because of their renewable energy features.
• Sell the solar-generated electricity to the homeowners below retail rates, and
let them sell any excess to the utility.
• Consider leasing or selling the equipment to the homeowners, which offers
another potential source of profit for developers and investors.
Location: Mosier, Oregon
Solar resource: 3.9 average daily peak sun-hours
Heating & cooling system: Carrier Performance series,
Energy Star-rated heat pump/air conditioning system
Electricity: 3.2 KW grid-tied PV system
Water heating: Solar, with electric backup
Average monthly production, PV system: 366 KWH
Average monthly production, SHW system: 208 KWH
Photovoltaic System Details
Modules: Sharp NE-170U1 or NT-180U1, 170 W or 180 W STC,
34.8 or 35.9 Vmp
Array (per housing unit): Two 9-module series strings, 3,240 W
STC total, 323 Vmp
Array installation: UniRac SolarMount, on south-facing roofs,
14-degree tilt
Total PV installed capacity (entire complex): 86.7 KW
Inverters: PV Powered PVP2800 XV, 450 VDC maximum DC
input voltage, 200-390 VDC MPPT voltage window, 240 VAC
output
Solar Hot Water System
Collector: Sol-Reliant, 56 sq. ft.
Collector installation: Roof mount, south-facing, 14-degree tilt angle
Heat transfer fluid: Propylene glycol
Circulation pump: PV-powered Hartell HEH18
Storage tank: Rheem Solaraide 120-HE/1, 120 gal. (provides
SHW storage and backup electric water heating); integrated
heat exchanger
Town House Tech Specs
(continued on page 37)
home power 121 / october & november 2007
36
affordable solar
Single-Tank Solar Hot Water
Manufacturers of the single-tank solar/electric system
place a single 240 VAC element about one-third of the
way down from the top of the tank. With a 120-gallon
tank, this assures at least 40 gallons of standby hot
water—even if the sun doesn’t shine. The heat in the
tall, vertically oriented tank naturally stratifies, with the
hottest water at the top. The solar heat exchanger is
located in the bottom half of the tank, using the sun’s
energy to warm the coldest water first.
On a sunny day, the solar gains will exceed the electric
element’s temperature setting, with solar energy heating
the whole tankful of water to 140°F or more. A water
heater timer can be used to keep the electric element off
during the middle of the day, “prioritizing” solar energy
over heating with electricity. (A tempering valve should
be installed to ensure that scalding hot, solar-heated
water doesn’t flow into the hot water service.)
In a single-tank solar-integrated system, solar energy is
generally able to achieve temperatures well above the
thermostat setting, and the heat lost down to that setting
is all solar generated—and all free. The typical standby
loss of a two-tank system can be 15 to 20% of the total
energy required for the water heating system. In a single
tank system, standby losses are about half this amount.
Potable Hot
Water Outlet
Cold
Supply In
Pressure
Relief
Valve
Isolating
Ball Valve
Isolating
Ball Valve
12 VDC
Pump
Low Point Drain
and Fill Valve
Solar Heat Exchange Tank:
Rheem Solaraide 120-HE/I,
120 gal.
Tempering
Valve
Potable Cold Water Line
4x14 ft. Sol-Reliant Collector
Spring
Check
Valve
Mosier Creek Homes
Solar Hot Water System
Besides electricity, the sun also provides domestic hot water
via solar thermal collectors.
Powerfully Efficient Homes
With an estimated total energy load of 13,560 kilowatt-
hours per year for each townhome, the combined output of
the 3-kilowatt PV array and a 56-square-foot thermal solar
collector is expected to supply a little more than 50% of the
residence’s energy requirement. Doug Boleyn, consulting
engineer for the project, says that’s impressive for an all-
electric home on Oregon’s chilly Columbia River Gorge.
But this shouldn’t be surprising, given that the Mosier
Creek development was built to the highest energy
specification. This LEED-certified project features high-
efficiency heat pumps, and Energy Star appliances and
lighting. Two-by-six studs framed at 24 inches on center
conserve lumber and reduce thermal bridging, and R-21
insulation in walls, R-30 in the floors, R-38 in ceilings, and
low-emissivity, high-performance windows throughout help
ensure each townhome’s excellent thermal performance. The
townhomes are sited in an east–west orientation to maximize
solar gain. In all, the buildings use 30% less energy than
energy-efficient buildings of a decade ago.
Richard Hallman
www.homepower.com
37
affordable solar
At just under 1,600 square feet, space was at a premium
in the two-bedroom townhomes—both inside and on the
roof. So the common two-tank solar water heating system—
with a solar preheat tank and conventional backup water
heater—was abandoned. Instead, a 120-gallon solar tank
with built-in heat exchanger and a single upper electric
element serves as both the solar preheating tank and
backup electric water heater within a single footprint. The
tank fits neatly beside the energy-efficient clothes washer
and dryer in each townhome’s laundry room.
Twenty-eight individual PV systems, with a total
installed capacity of 86.7 KW, were installed by Tod LeFevre,
P.E., of Hood River, Oregon-based Common Energy LCC.
PV Powered inverters, which are manufactured in Bend,
Oregon, were specified to synchronize the output of the
PV arrays with the utility grid.
On the roof, keeping the solar collectors and PV
modules at a low profile was important to the streamlined
architecture of the development. The long side-to-side
layout of the Sol-Reliant collectors fits nicely with the roof
plan and individual PV arrays.
—John Patterson
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THE STANDARD IN PV MOUNTING STRUCTURES
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Common Energy LLC • 541-308-0988 •
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Mr. Sun Solar • 503-222-2468 • www.mrsunsolar.com •
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Mosier Creek Homes • www.mosiercreek.com
Surround Architecture • 503-224-6484 •
www.surroundinc.com • Architect
Urban Fund Inc. • 206-623-1234 • www.urbanfundinc.com •
Developer
PV & Solar Thermal Systems Components Manufacturers:
PV Powered • 541-312-3832 • www.pvpowered.com •
Inverters
Rheem • 334-260-1525 • http://waterheating.rheem.com •
SHW storage tank
Sol-Reliant • 888-765-7359 • www.solreliant.com •
Solar thermal collectors
Sharp Solar • 800-765-2706 • www.solar.sharpusa.com • PVs
UniRac • 505-242-6411 • www.unirac.com • PV mounts
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Does Your Distributor
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GRO Home Power Ad #121 B.qxp 8/3/2007 12:26 PM Page 1
energy use, allow us to do more in our homes with reduced
energy input—the very essence of efficiency. But don’t
expect technology to do it all. Habits and behaviors greatly
influence your energy consumption.
If you’re connected to the utility grid, implementing
these easy measures translates into lower utility bills. If
you’re planning an off-grid home, smart appliance and
building design choices will both minimize renewable
energy equipment costs, and reduce or even eliminate your
reliance on a backup engine generator.
No matter where you live—an uptown loft, a
drafty old farmhouse, or a contemporary home—
addressing your dwelling’s energy efficiency
and reducing your household’s energy use
should be done before you invest in any renewable energy
(RE) gear.
You can reduce your use—without giving up modern
comforts—by putting technology to work for you. New,
energy-efficient appliances and heating equipment, along
with advances in building science and awareness of our
home power 121 / october & november 2007
40
by Paul Scheckel
EFFICIENCY DETAILS
If you’ve been
dreaming about
lowering your
electricity, space or
water heating bills,
but are daunted by
the seemingly high
up-front investment
in renewable energy
equipment, fear no
more. Simple, energy-
smart strategies can
help you reduce both
the size and cost of
that renewable energy
system you’ve been
dreaming about.
FOR A CLEAN ENERGY CHANGE
www.homepower.com
efficiency details
41
INEXPENSIVE ENERGY FIXES
Tip 1: Know Your Loads
The first step on the renewable path is to get
familiar with how much energy your household
uses and identify where your energy dollars
are going. Take a look at a year’s worth of your
energy bills. Determine how much energy is used
for space and water heating, air conditioning,
and other electrical loads.
Depending upon where you live, you may
find certain seasonal trends that lead to increased
energy consumption. For most of us, space
conditioning consumes the most energy and
generally warrants the most attention when it
comes to efficiency efforts. Water heating is
typically the second largest home energy user.
Electronics
5%
Cooking
5%
Refrigeration
8%
Space Cooling
11%
Water Heating
13%
Lighting
12%
Other
10%
Space Heating
31%
5%
Washer/
Dryer
Point-of-use energy monitors
allow you to determine
which of your appliances
are efficient, and which of
them aren’t. In addition,
whole-house electric energy
monitors can conveniently
report instantaneous and daily
kilowatt-hour consumption
via a handy display. Both are
excellent tools to help put
electric use into perspective
and will help you track your
overall reduction efforts.
However, you probably
already have a meter provided
by the electric company that
can also give you useful
information (many will
display both instantaneous
power and total energy)—you
just need to read it.
Point-of-use energy monitor.
Electric appliances also can account for a sizable portion
of your overall energy consumption and have a large impact
on a renewable electricity system’s size and cost. For 120-volt
electrical appliances, measuring energy use with a digital
power meter, such as the Brand Electronics, Watts Up?, or
Kill A Watt, will help you determine actual consumption and
prioritize which appliances need to be replaced with more
efficient units (see Access).
Typical Household Energy Uses
Tip 2: Adopt RE-Ready Habits
Simply being aware of what appliances are in use, and what needs to be
used and when, can help you adjust habits to minimize household energy
use. Learn to read your electric meter so that you can see how much power
you’re using at any given time or how much energy was consumed over a
period of time.
The most efficient practices are those that don’t require any extra energy
input, such as hanging clothes to dry on a clothesline. The next tier of
efficiency is to install the most efficient technology and minimize use. For
example, wash clothes in a front-loading washer with a high “modified
energy factor” rating, dry for only a few minutes (or not at all) in the clothes
dryer, and hang until completely dry. Take advantage of passive cooling
techniques to minimize or even eliminate the need for air conditioning. In
many climates, opening the windows at night and closing windows and
shades in the morning to keep the sun out, along with using ceiling or floor
fans, can be an effective cooling strategy.
Courtesy www.eere.energy.gov
home power 121 / october & november 2007
42
efficiency details
Tip 3: Take Control
Lowering the thermostat
is one sure way to reduce
heating costs. On average,
you can expect to save
about 2% of the energy
you use to heat (or cool)
your home for every
degree you lower (or raise)
the temperature setting.
Use a programmable
thermostat and set it to
lower the temperature
10°F when you’re sleeping
or away from home—or if
there’s no danger of pipes
freezing, you can turn off
your furnace completely.
(And no, it will not take
more energy to reheat the
house than you saved by
keeping the thermostat turned down.)
Wrap your water heater in an insulating blanket and set the
temperature as low as possible. Typically, a 1°F adjustment in
your water heater’s temperature will result in a 1% change in
energy use. You can use a timer to turn an electric water heater
off when you don’t need it, but you will gain more in efficiency
by using conservation strategies such as low-flow showerheads
Call in the Energy Experts
Expert energy auditors can help you identify the
best way to spend your energy improvement
dollars. You can find such experts through
your state’s energy office, the Residential
Energy Services Network, or the U.S. EPA’s
growing Home Performance with Energy Star
program (see Access).
An energy auditor will examine every room
in your home, using tools such as an infrared
camera to check for insulation voids inside
a wall or a “blower door” test to pinpoint
air infiltration. A typical audit can take from
two to four hours depending upon the tests
performed, and auditors may charge a flat rate
or by the hour. Always ask what specific tests
they will perform, how they charge for services,
what the cost will be, and how the results
will be presented to you. An average home
might save up to 30% on energy costs if all the
auditor’s recommendations are followed.
INEXPENSIVE ENERGY FIXES
and insulating water heater tank wraps. If you’ll
be away for more than a few days, simply turn off
your water heater entirely.
Timer controls and occupancy sensors work
well on lights that tend to get left on, and multiple
lighting circuits help put light only where you need
it. Switched wall outlets or power strips allow you
to turn things off (such as the entire entertainment
center or office peripherals) with ease.
GOOD GADGETS & QUICK FIXES
Tip 4: Plug In to Power Strips
A “phantom load” occurs when an appliance that appears to be
off still consumes some electricity. Examples include appliances
with clocks or indicator lights, remote controls, and plug-in
power adapters. Although a few watts of standby energy use
per appliance may sound like small potatoes, the combined
energy use of these small loads adds up fast. Phantom loads
in a typical American household use about 1.2 kilowatt-hours
per day—the equivalent of some superefficient off-grid whole-
house PV systems! Make efficiency easy to practice by using
switched outlets or power strips to control these loads and
make the switch on the strip easily accessible.
www.homepower.com
efficiency details
Tip 5: Bright Lighting
Wherever you can, replace incandescent
bulbs with compact fluorescents (CFs).
CFs provide the same level of lighting,
at about one-quarter of the energy use of
incandescents. Although their up-front
cost is higher, their reduced energy use
paired with their longevity translates into
long-term energy and cost savings. Use
compact fluorescent bulbs everywhere
except inside your fridge, where the cold
temperature, short on-times, and frequent on-and-off cycling will reduce the
lifetime of the bulb and offer little savings. In the fridge, remove the 40-watt
bulbs it probably came with and replace them with a single 15-watt (or lower)
incandescent bulb.
For electricity-free lighting during the day in windowless or dark rooms,
consider installing light tubes, which bring in natural light. (Skylights can
serve the same function but may also bring in unwanted heat during certain
seasons.) In areas where excess heat is not a concern, clear roofing panels can
provide a fairly inexpensive solution to provide additional daylighting. My
(unheated) garage, porch, and chicken coop each have a few clear roofing
panels that really brighten these areas during the day.
Tip 6: Seal Leaks & Deal with Ducts
Similar to appliances and electricity, the tighter your home, the less
fuel you’ll need to keep it warm. Start by identifying and sealing air
leaks, which can be found around chimneys, window frames, the top
of the foundation walls where wood meets concrete, and plumbing
and electrical chases. Sealing your home against air leaks is the most
cost-effective improvement you can make to reduce heating and
cooling consumption while increasing your home’s comfort.
Unless they are properly designed, sealed against leaks, and well
insulated, heating and cooling ducts can account for tremendous
energy loss to the unconditioned spaces through which they travel, like
attics and basements. If you have forced-air heating or cooling, be sure
to seal and insulate ducts everywhere you can.
Tip 7: Go Low-Flow to Save on Heating
In most homes, heating water is second only to space conditioning in energy
use. Low-flow showerheads and faucet aerators can help lower your household
water consumption and water-heating demand. So can using only cold water
for clothes washing and laundering only full loads. If you have a private water
system, conserving water will also reduce your pumping energy requirements
and the load on your septic system.
Courtesy Solatube
gwmullis
Wagner Furlan
43
home power 121 / october & november 2007
44
efficiency details
Tip 8: Improve Insulation
Take a look in your attic. Depending upon
your climate, if there is less than 1 foot of
insulation, it will be worthwhile to add more.
Walls are a bit harder to examine. One trick
to inspect wall insulation is to either find or
make a small hole in the wall, and then poke
a wooden skewer into the hole. By wiggling
the skewer, you might be able to pull out a few
fibers of insulation. This is also a quick way to
determine the depth of the walls and, therefore,
the thickness of the insulation.
Insulation won’t work well if it’s not properly
installed. Avoid gaps and compressions,
especially around plumbing pipes and electrical
wiring, and be sure the insulation material
is in contact with all sides of the cavity into
which it is installed. The best time to add
insulation to walls is when you’re making other
improvements or renovations. Make sure air
leaks are sealed before adding insulation.
INVEST IN ENERGY EFFICIENCY
Tip 9: Get New Views
Replacing older, single-pane windows with new
double- or triple-glazed units can save energy if
they are installed to include air-leakage control
around the frame. However, you can get almost
as much savings by adding storm windows as
you can with new double-glazed windows, at
a fraction of the cost. Again, pay close attention
to air-sealing when improving older windows.
When it comes time to buy new windows, pay
more for more efficient units. Over the long-
term, the up-front cost will pay for itself in
efficiency gains and reduced energy use.
On Your Way to Renewables
With renewable energy, a little advanced planning can add up to
significant savings. Here are two quick tips to get you on the right track:
✔ Design right. Whether you’re building a new home or remodeling an
old one, proper design and planning can offer savings once you’re ready
to install your RE systems. Orient additions or new buildings to true
south and reconsider rooflines and gables that interfere with solar access.
Provide an unobstructed south-facing roof surface that allows plenty of
solar collection area.
If you’re planning to install a PV or SHW system, consider incorporating
a chase between the roof and the basement to allow easy access and
plenty of space for running cables and insulated plumbing. And don’t
forget to construct your roof to handle the additional weight of collectors,
if necessary. Purchase a long-lasting roofing material too, and then, if you
know what equipment you’re planning to use, consider pre-installing rack
stanchions before the new roof goes on.
✔ Double up. If you identify what you want ahead of time, you can
piggyback projects with little or no extra cost. When we had some
driveway work done, I had the backhoe and crew already on site dig
trenches for conduit between my house and a future wind turbine site,
as well as for piping between rain collection barrels. It took less than an
hour of backhoe time for all that work and now I’m a step ahead on two
future projects.
Courtesy Pella.com
David Lewis
www.homepower.com
efficiency details
45
Access
Paul Scheckel is a senior energy analyst for the Vermont
Energy Investment Corporation and author of The Home
Energy Diet (New Society Publishers, 2005,
www.nrgrev.com).
Digital Power Meters:
Brand Electronics • www.brandelectronics.com
Kill A Watt • www.p3international.com
Watts Up? • www.doubleed.com
Energy Efficiency & RE Incentive Information:
Database of State Incentives for Renewables & Efficiency •
www.dsireusa.org
Energy Star • www.energystar.gov • Information on
household energy efficiency and energy-efficient household
appliances
Residential Energy Services Network (RESNET) •
www.natresnet.org • Professional home energy raters
directory
Tax Incentives Assistance Project (TIAP) •
www.energytaxincentives.org
Tip 10: Seek the Star
Energy Star labels indicate a generally high level of efficiency
for different classes of appliances, from dishwashers and
refrigerators to furnaces and air conditioners. Qualifying
products are compared to minimum federal efficiency
standards, and savings vary by product. For example, Energy
Star-labeled refrigerators must use at least 15% less energy
than the current federal maximum allows.
While the Energy Star label helps you instantly identify
more efficient products, be sure to compare energy use among
labeled products by reviewing the yellow Energy Guide tag
and choose the appliance that uses the least amount of energy
in its class.
Courtesy www.eere.energy.gov
What’s the Secret to High
Performance Solar Heating?
For your FREE information kit, call today!
1-800-288-0667
www.viessmann-us.com
“Viessmann has been a leader in innovative hot
water heating technology since 1917, with over 30
years experience in solar heating. Their high-
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products, provide you with some of the cleanest,
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Innovative System Technology
• Viessmann provides solar collectors,
hot water tanks, controls – everything
you need to collect the clean, powerful
energy of the sun.
• All parts are designed and manufactured
by Viessmann to integrate perfectly,
ensuring maximum performance.
Quality and Reliability
• Premium-quality materials mean
Viessmann high-performance solar
systems are reliable and built to last.
• All solar system components are
designed for fast and easy installation
and maximum system performance.
Comprehensive Product Line
• Vacuum tube and flat plate solar
collectors are available individually or
as fully-integrated system packages,
including matching tanks and controls.
• Viessmann offers all the components
you need for solar hot water, pool or
supplemental space heating.
Easy Integration
• Viessmann solar systems integrate
easily with virtually any existing
heating system.
• Unique mounting hardware allows
easy freestanding installation or on
flat or sloped roofs.
C
M
Y
CM
MY
CY
CMY
K
Solar06-HomePower-US.ai 4/4/2007 1:47:48 PM
home power 121 / october & november 2007
48
Unsure how much energy a PV
system will generate at your site? Use
the PVWatts performance calculator
to find out (http://rredc.nrel.gov/solar/
codes_algs/PVWATTS). This calculator
estimates electricity production based
on the peak sun-hours at your location.
Arm yourself with this information to
ensure that your economic analysis is
founded on accurate production figures.
Tap into Incentives. Once you get
an idea of system sizes and costs,
check out your incentive options
at the Database of State Incentives
for Renewables & Efficiency (www.
dsireusa.org), which offers the
most comprehensive compilation of
federal, state, and utility incentives
for RE systems and building efficiency
upgrades. Click on your state on the
interactive map to find out what’s
available, or peruse the summary
tables to see incentives broken down by
category.
Estimate Energy Production & Costs.
Before investigating incentives for
your project, you’ll need an accurate
estimate of your energy use and
potential savings from RE or from
energy-efficient upgrades. FindSolar’s
“My Solar Estimator” (www.findsolar.
com/index.php?page=rightforme) is
a handy resource for both home and
business owners interested in investing
in solar electricity. The online calculator
can quickly give you an idea what a
photovoltaic (PV), solar hot water,
or solar swimming pool system will
cost, and estimate the financial and
environmental benefits. Plug in your
location and some info from your utility
bills, and the estimator will display
available incentives, and also give a
rough estimate of your system’s cost
and return on investment (ROI).
Many federal and state tax
credits, rebates, and utility
incentives are available for
residential and commercial
renewable energy projects.
To better the bottom line
and find the best financial
fit for your project, here
are your best Web bets for
discovering—and cashing
in on—your own RE
returns!
Alex Mathers
Cashing In on Renewable Energy
businesses, the Solar Energy Industries
Association’s federal tax manual (www.
seia.org/manualdownload.php) will
help you and your accountant more
easily understand and navigate the new
federal incentives.
Finance an RE System. Buying or
building an energy-efficient home, or
making an existing home more efficient
can call for a larger-than-normal initial
cash outlay. Fortunately, financing,
both through government-insured and
conventional loan programs, is now
available to support your efforts. In
many cases, lenders can approve a
larger mortgage payment based on the
projected savings on monthly utility
bills, or roll the costs of proposed
improvements into the mortgage. Use
this site to find qualified lenders and
a certified home energy rater in your
area: www.natresnet.org/consumer.
—Resource recommendations
by Andy Black • andy@ongrid.net;
written by Erin Moore Bean •
erinmoorebean@gmail.com
If you’re thinking about investing
in PV, read OnGrid Solar’s Payback
and Other Financial Tests for Solar
Electric Systems (www.ongrid.net/
papers/PaybackOnSolarSERG.pdf)
to acquaint yourself with the nitty-
gritty of PV payback, then check with
your state’s energy office, utilities,
or energy commission for any public
information or guides. If need be,
consult a tax professional to best
apply any available incentives. For
home power 121 / october & november 2007
50
If you’re thinking that only Californians and Southwesterners
can reap the rewards of solar energy, it’s time to think again.
Progressive and workable incentive programs, strong net-
metering support, increasing utility rates, and ample year-
round solar resources are giving home and business owners
in several Northeast states plenty of opportunities to plug
into affordable renewable energy.
by Jon Sharp, Ray Furse & Robert Chew
Solar Success
in the Northeast
Courtesy SolarWrights
www.homepower.com
northeast solar
51
our dollars spent.” According to the Energy Information
Administration, average retail rates for electricity in New
York have risen about 22% in the past four years—from 13.5
to 16.6 cents per kilowatt-hour.
Consumers are experiencing similar trends in other
northeastern states. Connecticut Light & Power Company
recently requested a 4.6% hike in retail electricity rates
starting in 2008—this in a state whose residents have
suffered a whopping 90% increase in rates over the past
seven years.
Thankfully, these states also have initiated renewable
energy goals—of which solar comprises a varying share—
as well as differing funding solutions, paperwork, and
procedures for installation oversight. SolarWright’s founder
Robert Chew, who has both written and advised on subsidy
program legislation, feels that Connecticut’s incentive program
for photovoltaics is a good model for the Northeast. Its
performance-based approach takes into account the PTC (PV
USA test conditions) rating of modules and inverter efficiency,
which better reflects real-world PV system production.
By requiring that approved PV installation professionals
install systems that are receiving financial incentives, the
Connecticut Clean Energy Fund is balancing the necessary
increase in installation capacity to handle this fast-growing
market with maintaining high installation standards. In
Solar Energy
in Any State
How will solar work for you and what might the payback
be? Before calling an installer, you can get some
preliminary information using one of several online
calculators. (See “Cashing In on Renewable Energy” on
page 48 for Web site resources.)
Consumers are advised to independently research the
support that is available in their own state and to keep
that in mind when discussing energy solutions with
contractors. For the most up-to-date information about
RE incentives, visit www.dsireusa.org.
After California and New Jersey—states with longer
histories of support for renewable energy—the Northeast
has become the third-largest market for photovoltaic
systems in the United States. Solar thermal technologies
have enjoyed a parallel surge in popularity—in particular,
rooftop collectors for domestic hot water or radiant
heating.
SolarWrights, our Rhode Island-based renewable energy
company with offices in Connecticut, Massachusetts, New
York, and Vermont, has seen an annual sales volume
increase from less than $100,000 in 2000 to more than $5
million and is experiencing continued rapid expansion. Jim
Grundy, president of Elemental Energy in East Montpelier,
Vermont, reports, “We’ve had a five-fold growth in sales
since 1999.” In New York alone, the number of applications
for PV system incentives has increased by a factor of 3.5
during the past three years.
So what’s behind the northeastern rush to renewables?
Favorable economics, says Jonathan Klein, a consultant
specializing in emerging technology trends. Klein says
that “solar energy still requires substantial subsidies” to
compete with subsidized fossil-fuel generated electricity,
and “stretching subsidy dollars means focusing on the
customers who require the least amount to make solar
power a profitable investment.” These customers, he says,
are the “small” utility customers—homeowners and small
businesses—who end up paying the highest rates for
utility electricity.
And in the Northeast, it’s these small customers
who pay some of the highest retail electricity rates in
the nation. Paired with progressive incentives, solar-
generated electricity quickly becomes an economically
viable energy solution for these customers. In fact, when
states are ranked in order of the subsidies required to
make solar energy break even with utility electricity costs,
six northeastern states—Massachusetts, New Hampshire,
New York, Rhode Island, Connecticut, and Maine—appear
in the top eight, the other two being California (No. 1) and
Nevada (No. 3).
Solar electricity is particularly helpful to the notoriously
creaky Northeastern electrical grid. As more and more PV
systems are installed, the combined generation capacity
will help stabilize the utility infrastructure,
and reduce brownouts and blackouts during
summertime peak loads.
Tech Trends
Mary and Jack Brennan had eyes for the
future when they had a 9.7-kilowatt grid-
tied PV system installed at their Guilderland,
New York, home. “We strongly believe in
preserving the earth for future generations,
and ‘going green’ is a portion of what we
can do to help the environment,” says Jack.
“Plus, our already-high electric rates will
probably go even higher…[so] our PV system
will reduce the amount of utility electricity
we need to purchase and eventually reduce
PV System Comparison:
New York vs. California
Area
PV
System
Size
(KWp)
AC Output
(KWH Per
Year)
Average
Utility Rate
($ Per KWH)
Electricity
Value
($ Per Year)
Capitol region of New York
5.0
5,839
$0.159
$930
Southern California
3.9
5,839
$0.140
$817
Ratio of CA : NY
78.0%
100.0%
87.9%
87.8%
The system size advantage goes to the smaller system in California, but the energy value in dollars
is greater in New York, making the point that solar electricity is not only effective in the sunniest
parts of the United States, but also in the Northeast due to high retail electricity rates.
Owner Name: Robert & Lisbeth Chew
Location: Bristol, Rhode Island
Average Peak Sun-Hours: 4.46
System Type: Grid-tied PV
System Size: 4 KW
Average Annual Production: 4,960 KWH
Although this hundred-year-old home in
Bristol is not governed by the stricter rules of
the historical district that begins one block to the west, its
new owners wanted to respect traditional aesthetics while
installing a modern PV system. The steep pitch of the south-
facing roof threatened to make a typical PV installation stand
out, so careful array design and module selection was key.
The Chews opted for a rectangular design that followed the
home’s roof lines, and chose SunPower SPR-200 modules,
with their less obtrusive flat-black appearance.
Twenty modules feed into two SunPower SPR-2000
inverters. During its first twelve months of operation, the
system produced just over 4,960 kilowatt-hours. This has
delighted Robert and Lisbeth, as it has effectively freed
them from paying a monthly utility bill. Rhode Island’s net-
metering regulation zeros out excess PV production annually,
which means the Chews can build up credits during the
sunnier months, and then use them in the winter. The Chews
say the array has the added benefit of shading the roof,
making their upstairs office cooler in the summer, reducing
the use of a window-mounted air conditioner and further
decreasing their need for electricity.
home power 121 / october & november 2007
52
northeast solar
Rhode Island, the utility National Grid has worked closely
with industry leaders to develop a streamlined and effective
interconnection application process that may also serve as a
valuable model.
Solar Support
It hasn’t escaped the notice of savvy politicians that solar
technology is simply good business: It is one of the most
labor-intensive fields in the energy industry, and is on track
to create more than 30,000 new jobs in the United States by
2015. These are not low-wage temporary positions, but quality
careers in manufacturing, engineering, and installation.
According to a Solar Energy Industries Association report,
“each megawatt of installed systems supports 32 jobs, a
quarter of which are local installation and sales positions.”
The success that solar is seeing in the Northeast should
put to rest any doubts about its effectiveness and value.
The region receives more sunshine than Germany, which
boasts the most installed PV of any country in recent years.
Solar installers and energy professionals agree that, unlike
the “boom and bust” environment created by quickly
established—and quickly snuffed—subsidy programs in
the ’70s and ’80s, interest and investment in renewable
energy is here to stay.
Although occasional predictions of “breakthroughs”
in module efficiency appear in the press regularly, it is
unlikely that this will result in significantly decreased
consumer prices in the near term. More likely, increased
manufacturing capacity will bring down the price of tried-
and-true silicon-based modules. Many industry experts
are forecasting continued equipment-cost reductions in the
years ahead. As the installed cost per watt of PV declines,
financial incentives will likely be scaled back and ultimately
eliminated. But that is not necessarily a bad thing: It would
simply mean that solar technology is finally coming into its
own as an economically viable, clean energy choice.
To respect the traditional aesthetics
of their historic neighborhood, Lisbeth
and Bob Chew installed an unobtrusive
rooftop PV system that followed their
home’s roof lines.
RE on the
East Coast
Owner Name: Pine Point School
Location: Stonington, Connecticut
Average Peak Sun-Hours: 4.46
System Type: Grid-tied PV
System Size: 72.6 KW
Average Annual Production: 80,000 KWH
At Pine Point School, children learn the four R’s: reading,
’riting, ’rithmetic—and renewables—with a 72.6-kilowatt
rooftop solar-electric array that provides 40% of the school’s
electricity needs. The system was funded in part through a
special grant from Connecticut’s On-Site Renewable Energy
Generation program, with the balance of costs funded through
the solar developer. The school purchases the solar electricity
at a reduced rate through a green power purchase agreement
with the system owner.
Under this agreement, common for large commercial
projects, the system developer owns the PV system and sells
renewable energy to the host at a reduced rate, adjusted
annually depending on the cost of electricity provided by the
local utility. This allows Pine Point School to avoid budgeting
the large cost of purchasing the system. As retail rates for
utility electricity continue to climb, the school will benefit by
having reduced its grid usage.
“This is the first small-scale project in Connecticut to
incorporate a creative power purchase agreement between the
system developer and the host site,” says Lise Dondy, chief
operating director of the Connecticut Clean Energy Fund.
www.homepower.com
northeast solar
53
Pine Point students are proud of their solar-electric school.
Owner Name: Mark & Lisa Nelson
Location: Westerly, Rhode Island
Average Peak Sun-Hours: 4.64
System: Evacuated tube solar hot water
System Size: Viessman V300, 30-tube collector
Average Annual Production: 9.0 MBtu (2,638 KWH)
The Nelsons chose a solar hot water system to offset their
use of an oil-fueled boiler that provides both space heating
and domestic water heating. With two children and frequent
guests, their boiler was running much of the time, which was
especially annoying in the summer months. By switching to a
solar hot water system, the boiler rarely needs to run to heat
water for their household.
The Nelsons’ roof, which faces 40 degrees west of true
south, offered a particular design challenge for a typical flat-
plate solar hot water system. Finally, it was decided that an
evacuated tube system would be a better match because it
is easier to rotate the tubes toward the south for maximum
solar exposure. A 20-watt PV module powers the system’s
circulation pump. Because of this, the system can continue to
function in the event of power outages. At 80 gallons of 120°F
water per day, their hot water use is a bit higher than the
62 gallons typically used by a family of four. But the effect of
installing the system has been that they rarely rely on using
their oil-fueled boiler in the summer—the system provides
about 70% of their yearly hot water needs.
“Pine Point wants to reduce its carbon footprint,” says Pine
Point head of school Paul Geise. “In doing so, it hopes to serve
as a model for other schools in Connecticut and throughout the
country. There’s no doubt that in the last year there has been
a sea of change in the public’s perception of the environment,
most notably regarding the topic of global warming. Pine Point
is committed to being a good steward of the environment, both
institutionally and through its work with students. That spirit
and commitment have been most tangibly demonstrated with
the installation of a photovoltaic system that will supply well
over a third of the school’s electricity.”
Homeowners Lisa and Mark
Nelson installed a Viessman
collector on their home’s
rooftop to provide hot
water for their household.
Courtesy John Koulbanis, SunPublishing Co. (2)
Courtesy SolarWrights (4)
Owner Name: Cheryl Wheeler & Cathleen Joyce
Location: Swansea, Massachusetts
Average Peak Sun-Hours: 4.51
System: Solar pool heater
System Size: 9 Aquatherm 1500, 4 x 8 ft. collectors
Average Daily Production: 0.2 MBtu per day during
summer (58.6 KWH)
When folk singer Cheryl Wheeler and her partner Cathleen
Joyce built an in-ground saltwater swimming pool, they
wanted to heat it with solar energy and extend their swimming
season. But they had already filled the south roof of their barn
with a 4-kilowatt PV array, and no other south-facing roof
space was available. That called for innovative problem-
solving from the installers. The barn’s shallow-pitched north-
facing roof offered a solution. The unglazed collectors were
mounted at a low pitch on the roof, and still produce a
significant amount of hot water for pool heating. The pool’s
filter pump circulates pool water to the collectors, where it is
heated before its return trip to the pool.
Over the years, Cheryl and Cathleen have become strong
proponents of renewable energy and often promote its
concepts to concert audiences. At home, both walk the walk
by driving Toyota Priuses, and relying on a PV array for
electricity and a solar thermal system for water heating.
Cathleen says that “the pool heating system has met all of our
goals,” with the pool easily reaching the preset temperature
of 88°F on sunny days. Although the temperature drops on
cool mornings after the cover is taken off, water coming from
the collectors arrives 8°F to 10°F hotter than when it leaves the
pool, allowing them to extend the swimming season by eight
to twelve weeks each year.
Jon Sharp and Ray Furse are regional managers for
SolarWrights, in Saratoga Springs, New York, and Litchfield,
Connecticut, respectively. Robert Chew is the founder and
president of their employee-owned RE firm, based in Bristol,
Rhode Island.
home power 121 / october & november 2007
54
northeast solar
Installing in the
Northeast
PV and solar thermal system siting, design, and
performance issues in the Northeast can vary greatly
by location, as the terrain includes coastal plains in the
east, and the Appalachian range and foothills in the west.
PV mount design should take into account high coastal
winds and special wind regions: canyons through which
wind may be funneled at high speeds, and the upper
reaches of isolated hills and ridges.
Heavy snow loads typical in higher altitudes or caused
by lake-effect snows will require consideration. Roof-
mounted systems installed at very low tilt angles may
need to be hand-cleared, or will suffer decreased output
until the snow melts. In snowy regions, pole-mounted
systems should be designed to keep the lowest modules
out of the snow.
As with other structures, ground-mounted systems must
take into consideration the depth of the frost lines to
avoid frost heave. And the subsoil rocky ledge of western
New England may require “pinning” or other special
installation methods for pole and ground mounts.
Finally, all PV systems must use durable materials
that can withstand the elements for 25 years or more,
especially the corrosive effects of salt air near the coast.
Your local installers and the manufacturers of system
components are excellent resources for dealing with
special considerations in your climate.
Courtesy SolarWrights (3)
Cathleen Joyce and Cheryl Wheeler enjoy sunny days for more
than just one reason: a solar pool heating system (above)
extends their swimming season and a solar hot water system
(below right) heats household water.
MK_HMEv1_07.qxd 3/27/07 11:56 AM Page 1
all-electric vehicles (EVs). General Motors unveiled an electric
car in 1990, inspiring California’s clean-air regulators to
demand that all the major car companies start producing
zero-emission vehicles. Thousands of leased electric cars hit
the roads, but a weakening of the clean-air mandate in 2003
allowed automakers to cancel the leases and destroy the cars,
as documented in the 2006 film, Who Killed the Electric Car?
EVs are powered solely by an electric motor and a large
bank of batteries—not by a gasoline engine. When the driver
steps on the accelerator pedal, a controller sends electricity
from the batteries to the motor, making the vehicle move.
Regenerative braking systems use the electric motor to
convert some of the car’s kinetic energy into electricity that
gets fed back into the batteries as the vehicle slows down.
The plug is the best thing—and the worst thing—about
EVs: On one hand, you get to plug them in (which is
generally a cheaper and lower-emissions source of energy
than gasoline), and on the other hand you have to plug them
in to recharge their batteries after 30 to 200 miles of driving,
depending on the car, driving conditions, and the battery type
and size.
While the car companies were making EVs, they also began
building hybrid gas-electric vehicles like the Toyota Prius,
Last summer, Google.org (the philanthropic arm of the
Internet giant) launched a plug-in hybrid car project and
Web site called RechargeIT.org, proclaiming, “Recharge
your car. Recharge the grid. Recharge the planet.” It could just
as well have added, “Recharge your home.”
Plug-in cars, some that rely solely on electricity and some
that marry an electric motor with a gasoline motor for better
mileage and fewer emissions (plug-in hybrid-electric vehicles
or PHEVs), are slowly making their way into the mainstream.
And it’s not just because they replace most or all of the
gasoline used to fuel the typical car with cleaner, cheaper,
domestic electricity. The ability of electricity to flow into a
car’s batteries and also to be pulled back out and returned to
the electrical grid has caught the imagination of consumers
and environmentalists alike. That return trip—commonly
called vehicle-to-grid (V2G) technology—could power some
of a home’s electrical appliances during a grid outage, or
could be used by the electrical grid in ways that will increase
the storage of and our access to clean, renewable energy.
An Electric Evolution
The story of plug-in hybrids has been unfolding within the
past two decades or so, beginning with the battle over modern
home power 121 / october & november 2007
56
by Sherry Boschert
Fueling
the Future
Courtesy General M
otors Corp.
plug-in
Honda Civic, and the Ford Escape. Hybrids are gasoline-
dependent vehicles with internal combustion engines that
also have an electric motor and a small bank of batteries. The
electric-drive components work with the engine, providing
boosts of power or increasing the overall fuel efficiency of the
vehicle. The most popular hybrid, the Toyota Prius, typically
gets 45 to 55 miles per gallon.
Hybrids on the market today aren’t designed to be
plugged in. Instead they use the gas engine and, to a much
lesser degree, the drive motor via regenerative braking, to
recharge the batteries. Depending on a hybrid’s design, the
gasoline engine may shut down when the electric motor
can meet propulsion needs—saving energy and reducing
emissions—and automatically restarts when more power is
demanded. The fuel efficiency of hybrids depends on whether
they are “full” hybrids that include all the hybrid features,
or “hollow” hybrids that claim the name but incorporate
minimal features, such as stopping the engine while idling
but not using regenerative braking. Hollow hybrids may
add merely 1 mpg in efficiency, and are often more about
increased power than increased fuel efficiency.
Plug-In Promises
People are realizing that hybrids can be improved by adding
more batteries and an AC charger that can be plugged into the
grid. With overnight grid charging, a plug-in hybrid like the
Prius can travel 100 miles on 1 gallon of gasoline and about
33 kilowatt-hours (KWH) of electricity. And PHEV drivers
still don’t need to think about finding someplace to recharge
the car if they want to drive long distances. If the owner
forgets to plug in overnight, it’s no big deal—a plug-in hybrid
then operates just like a conventional hybrid.
www.homepower.com
plug-in hybrids
57
Fueling
the Future
A few dozen Prius owners, eager for the benefits that plug-
in hybrids offer and tired of waiting for auto manufacturers
to produce them, have converted their hybrids into PHEVs,
even though the modifications may void parts of the cars’
warranties. Felix Kramer of Redwood City, California, did it.
So did Ryan Fulcher of Seattle, Todd Dore of Chicago, and
Ron Gremban of Corte Madera, California, among others.
Google’s RechargeIT.org site shows a map of vehicles that
have been converted to PHEVs, and they are popping up all
over the country.
These plug-in pioneers modified their cars for more than their
own benefit. They did it to make a point: If they could make a
plug-in hybrid, the major car companies could too—and should.
Kramer, Gremban, and a cadre of volunteers formed the
California Cars Initiative (CalCars.org) and in 2004 converted
Gremban’s Prius to a plug-in hybrid, doing the work in
his garage. They added inexpensive lead-acid
batteries and some innovative software to
fool the car’s computerized controls
into using more of the energy
stored in the batteries instead of
using the engine, dramatically
increasing fuel efficiency.
Several small companies like
EnergyCS in Southern California
and Hymotion in Canada have
started doing small numbers
of conversions for fleets and
government agencies, using
longer-lasting, more energy-
dense lithium-ion batteries.
Kramer hired EnergyCS to convert his Prius as a
test case, and has reported on a typical day traveling
51 miles, mostly on the highway. At fuel efficiencies of
1 gallon of gasoline and 15.3 KWH of electricity expended
to travel 124 miles (the equivalent of about two to four cents
per mile for electricity, depending on local retail rates), his
plug-in hybrid used 61% less gasoline and cut the vehicle’s
greenhouse emissions in half. The total fuel cost? $1.76
instead of the $3.17 the car would have required on gasoline
alone.
CalCars.org and the national Electric Auto Association have
created an open-source “Wiki” Web site with instructions for
do-it-yourselfers who want to convert their own hybrids to
plug-ins. They hope to put together a video and eventually
sell a package of components for individuals wanting to
convert their hybrids. (See www.eaa-phev.org.)
Plug-In Pioneers
CalCars founder Felix
Kramer’s Prius, converted
by EnergyCS, was one of
the first consumer-owned
PHEVs to hit the road.
Courtesy CalCars.org
Opposite: General Motors’
concept plug-in hybrid electric
vehicle, the Chevrolet Volt.
Improved Efficiency. At an average fuel efficiency of
20 mpg, a conventional gasoline car needs 5 gallons of gas
to travel 100 miles. The Toyota Prius hybrid needs about
2 gallons to go that distance. In comparison, Toyota’s RAV4-
EV all-electric SUV goes 30% farther—about 130 miles—on the
energy equivalent of just 1 gallon of gasoline (34 KWH). That’s
half the energy required by a conventional Prius hybrid and
one-fifth of the energy required by a standard gas-engine car.
So how do PHEVs pencil out?
Using the average price for residential off-peak electricity
in the United States—about 8 cents per KWH—the equivalent
of 1 gallon of gasoline in energy (34 KWH) costs $2.72.
Assuming that amount of electric energy can move a car
at least 110 miles, driving on electricity costs about 2 cents
per mile. In comparison, for a conventional hybrid that gets
50 mpg on gasoline costing $3 per gallon, each mile in a
hybrid costs 6 cents—more than double the cost of fueling
with electricity.
Terry Penney, manager of the National Renewable Energy
Laboratory’s (NREL) FreedomCAR program, compared the
costs associated with electricity rates and gasoline prices for
a plug-in hybrid with enough batteries for a mere 10-mile all-
electric range. He found that in 45 out of 50 states (all but the
few states with the highest electricity rates), driving a plug-
in hybrid would put money in the driver’s pocket: The fuel
savings would more than offset a plug-in hybrid’s slightly
higher projected sales price.
Cash-Back Cars. With vehicle-to-grid technology, a plug-
in hybrid can become a “cash-back hybrid,” a term coined
by Jon Wellinghoff, Federal Energy Regulatory Commission
member. According to Wellinghoff, some electrical utilities
and power aggregation companies have already expressed
interest in the idea of contracting with plug-in hybrid owners
to get occasional access to the electricity stored in their
vehicles’ batteries. V2G on plug-in hybrids is likely to be used
to supply electricity for what’s called
“spinning reserves,” for times when it
is difficult for the utilities to meet the
instantaneous demand of the grid. They
could also be used to shave peak loads by
some individual V2G utility customers.
That, says Wellinghoff, would make
dollars and sense for a plug-in hybrid
owner, especially if the owner also had
a V2G contract. Wellinghoff says that,
in the future, plug-in hybrid owners
could conceivably make profits of $400
for spinning reserve V2G contracts and
$2,700 per year for regulation contracts.
The owner’s contract would specify how
much energy may be drawn from the
car’s batteries. For example, they could
specify that their vehicle must retain at
least 50% of its battery charge.
Reduced Pollution. While electric
utilities are waking up to the possibilities of plug-in hybrids,
some environmentalists are concerned about an increase in
power plant pollution if everyone starts plugging in their
cars. Most electricity in the United States is still generated by
fossil-fueled (read: polluting) power plants and adding cars to
the grid’s loads would increase electricity demands.
The data on plug-in hybrids, however, has calmed most
environmentalists’ fears. Even plugged into the U.S. electrical
grid, which gets more than half of its energy from coal, plug-
in hybrids would produce 42% less carbon dioxide, and
reduce emissions of other greenhouse gases and pollutants
when compared to conventional fossil-fueled cars, according
to NREL.
As more wind and solar generation is added to the grid
mix, driving with grid electricity becomes cleaner still. Plug-
in cars are synergistic with renewable energy, and V2G
expands that synergy. For example, in many locations the
wind blows mostly at night, when few people are awake to
make use of wind energy. In fact, it’s estimated that there’s
more than enough of an untapped wind resource in the
United States to meet all current U.S. electrical needs, but
there’s no place to store that wind energy during times of off-
peak demand. However, nighttime is when people usually
plug in to recharge their EV batteries, and the batteries could
serve as distributed storage for that additional wind energy.
The U.S. Department of Energy estimates that plug-in electric
vehicles with V2G technology could increase America’s
access to wind energy by a factor of three. And owners of
off-grid RE-powered homes, which store renewable energy
in batteries, could be driving cars that run partially on their
surplus homemade renewable electricity and use the vehicle
battery as further reserve capacity.
A Japanese Web site created in 2005 prominently
showcases another important possibility of plug-in hybrid
vehicles—providing a source of emergency backup electricity
home power 121 / october & november 2007
58
plug-in hybrids
Larry Brilliant, Google.org executive
director, recharges the RechargeIT car.
Courtesy Google.org
for a home during blackouts. It showed the plug-in Prius
as an integral part of the “Toyota Dream House PAPI”—
one example of environmentally friendly, energy saving,
intelligent home design. The project suggested that if a
hurricane or other disaster knocks out the electric grid, the car
could supply electricity for some of a home’s critical electrical
loads for up to 36 hours.
Pulling for Plug-Ins
Unfortunately, while the merits of plug-ins have been pimped
by the popular press and garnered the favor of an impressive
aggregation of advocates, ranging from G. W. Bush to the
activist environmental organization Rainforest Action Network,
plug-in hybrids have yet to hit the mainstream market.
To convince automakers that there is a market for these
cars, the City of Austin, Texas, launched a Plug-in Partners
campaign and has gathered more than 8,000 advance “soft”
(no financial commitment) orders for plug-in hybrids.
Austin’s green energy comes from west Texas wind, and the
city would like to use more of it. With plug-in hybrids, Austin
aims to “replace Middle East oil with west Texas wind,”
according to the campaign motto.
And another famous Texan is helping drive the plug-
in revolution: The day after his State of the Union speech
in January 2007, President Bush issued an executive order
saying that when plug-in hybrids become available, federal
fleets with 20 or more vehicles must buy them. With the
stroke of a pen, he signified his administration’s support for
these cars.
Are automakers listening? Maybe.
Several automakers developed plug-in hybrid prototypes
in the 1990s, but cast them aside during their battle to
weaken California’s Zero Emission Vehicle mandate. Stung
by bad publicity from Who Killed the Electric Car?, at least one
automaker has started to reverse its course. At the 2007 North
American International Auto Show in Detroit, General Motors
showcased its prototype plug-in hybrid—aptly named the
Volt. With electricity stored in a lithium-ion (Li-ion) battery
pack, this car purportedly can deliver 40 miles before the
flex-fuel (gasoline, E85, petrodiesel, or biodiesel) engine turns
on to recharge the batteries and extend the car’s range to
640 miles.
In the past year, at least five other major car companies
have said they’re developing plug-in vehicles. But the
automakers are quick to say that plug-in hybrids won’t hit
the market until more research is done on advanced Li-ion
batteries (see Better Batteries sidebar).
Move for the Future
The same day that Google switched on a 1.6-megawatt solar-
electric array at its California headquarters—the largest
PV installation on a corporate campus in North America—
Google.org made another strong move toward energy
independence, launching RechargeIT.org. They unveiled five
plug-in hybrid conversions and plans to build a fleet of up
www.homepower.com
plug-in hybrids
59
Better Batteries?
Although car companies say they’re waiting for better
battery technology before they mass-market plug-in
hybrids, that doesn’t sit well with drivers like Marc
Geller of San Francisco, a PV systems salesman who
co-founded the nonprofit group Plug In America. The
nickel-metal hydride (NiMH) batteries in Geller’s all-
electric 2002 Toyota RAV4-EV give the compact SUV
plenty of power, take him all over the Bay Area, and
are expected to last the life of the car, based on utility
company fleet tests.
Long before unveiling its “new” plug-in hybrid Volt,
GM displayed a prototype plug-in hybrid version of its
EV1 electric car at auto shows in the 1990s. The EV1
plug-in hybrid could go 25 miles on electricity stored
in NiMH batteries before the gasoline engine turned
on, which would then extend the range to 320 miles.
Professor Andrew Frank at the University of California
at Davis collaborated with the NiMH battery company
Energy Conversion Devices in 1998 to convert an early
Toyota Prius to a plug-in hybrid, with similar results.
Toyota will be testing their plug-in Prius in Japan,
and will be delivering one each to UC–Berkeley and
UC–Irvine. The cars are expected to have only a 7- to
8-mile range on their NiMH batteries, but if the cars
move into production, more advanced batteries are
likely to be used.
People who have been driving electric cars for years
using NiMH batteries suggest that the car companies are
stalling by insisting on Li-ion batteries. The major auto
manufacturers say that Li-ion batteries are preferable
because they store more energy in less space, so fewer
batteries are needed and less weight is added to the
vehicle. It’s unclear, however, whether Li-ion batteries
will last as long as expected in conventional warranties.
California state regulators are considering modifying
warranty requirements for hybrids, which could jump-
start production of plug-in cars with Li-ion batteries.
Or, as GM’s CEO Robert Lutz acknowledged in a recent
interview on PodTech.net, if Li-ion doesn’t work out,
“we might use NiMH for plug-in hybrids after all.”
Lithium-ion battery pack in CalCars’
EnergyCS/EDrive converted Prius.
Courtesy CalCars.org
to 100 plug-in hybrids for employee use. The company also
awarded a $150,000 grant for a large-scale V2G planning and
implementation research project, and is set to take proposals
for $10 million in funding for companies focused on plug-
in hybrids, electric vehicles, batteries, and V2G technology,
demonstrating that where there’s a will (and some substantial
financial backing), there’s a way.
In the meantime, plug-ins might not be hitting the
showroom floor soon, but you can still support the push for
these resource-efficient vehicles. Here’s how:
• Support plug-in hybrids by joining Austin’s Plug-in
Partners campaign, and by using collective buying power
as leverage. Plug In America lists the phone numbers of the
major automakers on its Web site and urges consumers to
call them. “Tell the automakers that you won’t buy a new
car unless it has a plug on it,” says EV driver and Plug In
America cofounder Marc Geller.
• Push for government incentives or interventions to help
plug-in hybrids get to market. Plug In America and other
advocates have been lobbying the California Air Resources
Board—which this year is revising its weakened Zero
Emission Vehicle Mandate—to put some teeth back into
clean-car regulations.
• Do it yourself. If you have some experience in high-voltage
electronics, you can convert a conventional hybrid to a plug-
in hybrid. Costs vary widely depending on components
home power 121 / october & november 2007
60
plug-in hybrids
and the type and number of batteries. And there’s no
standard conversion kit available yet, so be prepared to do
lots of research first. (See Plug-In Pioneers sidebar.)
Access
Sherry Boschert (info@sherryboschert.com) is the author of
Plug-in Hybrids: The Cars that Will Recharge America (New
Society Publishers) and is on the steering committee of Plug
In America.
California Cars Initiative • www.CalCars.org
Do-it-yourself plug-in hybrid conversions •
www.eaa-phev.org
Electric Auto Association • www.eaaev.org
Plug In America • www.PlugInAmerica.com
Plug-in Partners • www.PlugInPartners.org
RechargeIT.org • Google.org’s initiative to reduce CO
2
emissions, cut oil use & stabilize the electrical grid by
accelerating the adoption of PHEVs
Toyota Dream House PAPI: http://tronweb.super-nova.co.jp/
toyotadreamhousepapi.html
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Homepower-2007-04-02.indd 1
06.04.2007 10:57:39
Photovoltaic (PV) cells are made of a special class of
materials called semiconductors. Of all the semiconductor
materials, silicon is most commonly used because of its
availability (it’s the second-most abundant element in Earth’s
crust) and its special chemical properties.
An atom of silicon has fourteen electrons arranged in
three different levels, or shells. The first two shells, those
closest to the center, are completely full. The outer shell, with
four electrons, is only half full. A silicon atom will always
look for ways to fill up its last shell (which would like to have
eight electrons). To do this, it will share electrons with four
of its neighboring silicon atoms. It’s like every atom holds
hands with its neighbors, except that in this case, each atom
has four hands joined to four neighbors. That’s what forms
the crystalline structure, and that arrangement turns out to be
important to the function of a PV cell.
home power 121 / october & november 2007
64
ow a slice of silicon often thinner
than a human hair can harvest
sunlight to make electricity
may seem like magic. But what may
appear as a bit of sorcery actually
boils down to uniting science and
engineering wizardry with some of
Earth’s most abundant resources—
sunshine and silicon.
Scott Aldous,
Zeke Yewdall
& Sam Ley
14
Si
28.09
2s2
3p2
Silicon Atom:
14 protons
14 neutrons
14 electrons
K Shell:
2 electrons
L Shell:
8 electrons
M (Valence) Shell:
4 electrons
Polycrystalline silicon, ready to be manufactured into
photovoltaic cells.
Courtesy www.recgroup.com
around. A P–N junction is commonly known as a diode—an
electrical one-way valve for electricity. The special thing
about PV cells is that they are diodes designed to absorb
energy from sunlight.
When a photon—the electromagnetic energy of sunlight—
with enough energy hits the N-layer, it knocks an electron
free. These electrons stay in the N-layer. When a photon
of light hits an atom in the P-layer, it knocks an electron
free that can easily cross into the N-layer. The result is that
extra electrons accumulate in the N-layer. A series of metal
www.homepower.com
photovoltaic effect
65
Making a Better Carrier
Energy added to pure silicon can cause a few electrons to break
free of their bonds and leave their atoms, leaving a “hole” (an
unfilled bond) behind. These “free carrier” electrons wander
randomly around the crystalline lattice structure, eventually
falling into another hole. But there are so few free carriers
available in pure silicon that they aren’t very useful. Scientists
found they could improve silicon’s electron carrier ability
(conductivity) by adding other atoms in a process know as
“doping.”
Silicon doped with an atom of phosphorous here and
there (maybe one for every million silicon atoms), will still
bond with its silicon neighbor atoms. But phosphorous,
which has five electrons in its outer shell, has one electron that
doesn’t have anyone to hold hands with, so it takes a lot less
energy to knock it loose. As a result, most of these electrons
do break free, resulting in more free carriers. Phosphorous-
doped silicon is called N-type (“n” for “negative”) because of
the prevalence of free electrons.
But only one part of our solar cell can be N-type. The other
part is typically doped with boron, which has three electrons
in its outer shell. Instead of having free electrons, P-type (“p”
for “positive”) has free holes.
The interesting part starts when you put N-type silicon
next to P-type silicon—a silicon sandwich of sorts. When the
electrons and holes mix at the junction between N-type and
P-type silicon, silicon’s neutrality is disrupted and the free
electrons mix to form a barrier, making it harder and harder
for electrons on the N side to cross to the P side. Eventually,
equilibrium is reached, and an electric field separates the two
sides. The electric field allows (and even pushes) electrons
to flow from the P side to the N side, but not the other way
Polycrystalline wafers: uncoated (left) and with the telltale blue
antireflective coating (right).
C
o
u
r
t
e
s
y
w
w
w
.
a
d
v
e
n
t
s
o
l
a
r
.
c
o
m
Electron Flow:
Through circuit, from N-layer to P-layer
Holes
Extra Electrons
Silicon Atom: 4 electrons in outer shell. Shares with other silicon atoms
to form a stable crystal bond of 8 electrons.
Phosphorus Atom: 5 electrons in outer shell. Shares with silicon atoms
to form a crystal bond of 8, plus one extra electron.
Boron Atom: 3 electrons in outer shell. Shares with silicon atoms to form
a crystal bond of 7 electrons and 1 hole, readily attracting extra electrons.
Electron: Knocked around by energy of sunlight; moves through circuit
from N-layer to P-layer.
N-Layer:
Phosphorus doped;
extra electrons create
negative charge
P-Layer:
Boron doped;
deficient electrons
create positive charge
P/N Barrier:
Electrically neutral;
allows electrons to
move from P-layer to
N-layer, but not back
Traces:
Conductors on cell surface
collect electrons from N-layer
and distribute electrons to P-layer
Free Electrons:
Pile up in N-layer and can
only move to P-layer
through circuit
Free Electrons:
In P-layer can be bumped
across P/N junction by
sunlight, attracting more
electrons through circuit
Load:
Electrons passing
through circuit
do work
Sunlight:
Energy (photons) knocks electrons loose
to move throughout crystal structure
P/N Silicon and the Function of a PV Cell
wires (traces) attached to the N-layer gives the electrons
someplace to go, and they enter a DC circuit, flowing from
the negative side of the cell and re-entering the cell through
the positive side.
PV modules are made by connecting numerous cells in
series, parallel, or series/parallel to achieve useful levels of
voltage and current. These cell networks include positive and
negative wiring terminals so we can channel the electricity
generated to our uses. As long as sunlight is coming in, the
electrons will keep flowing and can deliver electrical energy
to a load that’s connected to the circuit.
Electrons & Efficiency
One way to think about the process of electron movement is
to imagine that the P-layer is a pool filled with electrons and
your deck is the N-layer. If a sufficiently strong photon hits
one of the electrons in the pool (P-layer), it can kick it up onto
the deck (N-layer) where you can catch it and put it to useful
work. Ideally, every photon coming into the pool would
bump an electron up onto the deck that you could collect and
put to use. However, silicon’s limitations, along with design
challenges, prevent PV cells from being 100% efficient. In
reality, most commercially available cells are between 4% and
22% efficient at converting the energy in the photons to useful
electricity. Here are several reasons why:
Too Little or Too Much Energy. The light that hits a cell
contains photons with a wide range of energies, but a PV
cell will only respond to certain energies, or wavelengths.
The required level of photon energy to activate an electron
is referred to as the band gap. Different types of photovoltaic
home power 121 / october & november 2007
66
photovoltaic effect
Measuring single-crystalline silicon ingots at the SolarWorld
PV plant in Vancouver, British Columbia.
Courtesy www.solarworld-ca.com
Antireflective
Coating
Glass:
Tempered, antiglare
Traces: Metallic
conductors
N-Layer Silicon:
Phosphorus doped
P-Layer Silicon:
Boron doped
Traces: Metallic
conductors
Back Sheet:
Polyvinyl fluoride
film
Note: Material
thicknesses not to scale
Module Encapsulant:
Ethylene vinyl acetate
Module
Encapsulant:
Ethylene vinyl
acetate
PV Module Anatomy
Densely spaced traces on the back of a PV cell
help transfer electrons to the P-layer.
materials have different band gaps—higher and lower decks,
so to speak. Some photons don’t have enough energy, and
although they bump electrons, they don’t give them enough
energy to get them up on the “deck.” This energy is wasted
as heat. The lower the deck (lower band gap), the lower the
minimum energy required.
So why can’t we choose a material with a really low band
gap, so we can use more of the photons? Unfortunately, the
band gap also determines the voltage of our solar cell. If it’s
too low, what we make up in extra current (by absorbing
more photons) we lose by having a small voltage (remember
that power is voltage times current). If the incoming photon
Courtesy www.adventsolar.com
PV Cell Particulars
Model-T maker Henry Ford was fond of telling consumers
they could have any color car, “so long as it was black.”
Options in PV module choices used to be as limited, but
that’s changing. Today, you can choose from three basic
types of PV modules: monocrystalline, polycrystalline,
and thin-film.
Most of us are familiar with the iridescent-blue faces of
monocrystalline and polycrystalline modules. In both
cases, fragile razor-thin wafers of silicon are embedded
in a rigid frame and protected behind a layer of tempered
glass. The difference between the two crystallines lies in
the production of the cell. Monocrystalline ingots are
extracted from melted silicon and then sawed into thin
plates. Polycrystalline cells are created by pouring liquid
silicon into blocks that are sawed into plates.
In the thin-film process, a silicon film (or other materials,
such as cadmium telluride or copper indium gallium
selenide) is deposited on glass or stainless steel, or
within a flexible laminate. Although production costs
are lower due to lower material costs, the efficiency of
thin-film modules is typically about half that of either
mono- or polycrystalline cells.
is too strong, it bumps the electron up higher than the deck,
before it falls back down. In a PV cell, this energy expenditure
is also wasted in the form of heat.
To capitalize on the higher energies of some photons,
some exotic PV materials have two levels of decks. If a photon
has enough energy, it can bump the electron all the way up to
a higher deck where it can be collected. Some amorphous PV
modules have two or three levels of decks, so if an electron
isn’t excited enough to get on the highest deck, it might at
least end up on a lower one and be used there.
These two effects alone—too little energy and too much
energy in incoming photons—account for the loss of about
70% of the radiation energy incident on our cell.
Imperfect Junctions. A second source of inefficiency is that a
lot of electrons just roll through slots between the deck boards
before you can collect them. A perfect crystal doesn’t have any
holes—every electron that is collected stays on the deck until
it can be collected. However, polycrystalline solar cells have
joints between crystals, resulting in an imperfection in the P–N
junction—holes in the deck, so to speak, that allow electrons to
slip back into the pool before they can be collected.
Even in a single-crystal solar cell, you still can’t collect
all the electrons. The metal traces that collect electrons in a
PV cell are spaced apart, and an electron that ends up too far
from it may be lost before it can travel to the nearest trace and
be collected.
www.homepower.com
photovoltaic effect
67
Amorphous silicon has a similar problem
called hydrogen diffusion. Instead of being a
solid silicon crystal, it has all kinds of loose
hydrogen atoms, which function like a deck
full of gaps. Also, electrons in a position to
be bumped by photons are fewer and farther
between because the hydrogen leaves less
silicon to hit. The hydrogen atoms are the
reason that amorphous silicon decreases in
efficiency over the first few months before
stabilizing: Hydrogen in the atmosphere
slowly diffuses into the module.
Reflection, Obstruction & Temperature.
Silicon is very reflective, which makes
harvesting sunlight challenging, since a cell
can’t use photons that are reflected. For that
reason, an antireflective coating (typically
titanium dioxide or silicon nitride) is applied
to the top of the cell to reduce reflection losses
to less than 5%. This coating is what gives
solar cells their blue appearance, instead
of gray, as raw silicon would appear. The
antireflective coating can be modified to get
different colors, such as red, yellow, green,
or gray, but these colors are less efficient
than dark blue, so you very rarely see PV
modules in these other colors. The glass on a
module also has a special textured surface to
minimize the reflection of sunlight.
R&D technicians inspect a monocrystalline wafer
at a Suntech Power PV plant in China.
Courtesy www.suntech-power.com
Because silicon is a semiconductor, it’s not nearly as
good as a metal for transporting electrical energy. Its internal
resistance is fairly high, and high resistance means high losses.
To minimize these losses, a cell is covered by a metallic contact
grid that shortens the distance that electrons have to travel from
one side of the cell to the other while covering only a small part
of the cell surface. We could cover the bottom with a metal,
allowing for good conduction, but if we completely cover the
top too, photons can’t get through the opaque conductor and
we lose all of our energy. If we put our contacts only at the
sides of our cell, the electrons have to travel an extremely long
distance (for an electron) to reach the contacts.
Various solutions to this obstruction have been considered,
from BP Solar’s laser-grooved buried-grid modules that put
the collection grid in trenches instead of using flat ribbons
on the surface, to placing the metal contacts on the back
surface of the cell (as on SunPower modules), to transparent
conducting layers that are being used for some amorphous
and organic PV materials.
Temperature also affects a cell’s efficiency. Typically, for
each degree centigrade increase in operating temperature
over its rated temperature, a PV cell loses about 0.5% of its
specified power. For example, a PV module that experiences
temperatures 50°C higher than its rated temperature (which
is quite common for rooftop modules) may produce 25%
less than its rated power. This happens because the thermal
energy is distributed unevenly, with some electrons having
enough energy to “go the wrong way”—back across the
barrier, where they fall into holes we don’t want them to.
home power 121 / october & november 2007
68
photovoltaic effect
The Reality of Efficiency
After all this talk about efficiency, you might be surprised to
discover that buying the most efficient module on the market
shouldn’t be your only goal. When you’re talking about
energy production, it’s watts that we’re really after. If a less
efficient PV module allows us to get those same watts for
less cost, it may be a more cost-efficient choice than a more
efficient, but more expensive, module.
If you have limited space on your roof or a small solar
window, using more efficient modules can often make sense.
But if you have acres of warehouse roof, for example, it may
not. It all depends on your particular situation. To optimize
your investment, prioritize cost per installed kilowatt-hour,
longevity, and efficiency, in that order, if space is not a
consideration.
Access
Zeke Yewdall (zeke@cosunflower.com) is chief engineer
at Sunflower Solar, a PV design/install company in Boulder,
Colorado.
Sam Ley (sam@cosunflower.com) is a physicist who works
at Sunflower Solar, and has extensive experience in science
education at museums.
Portions of this article were adapted from Scott Aldous’s
article, “How Solar Cells Work,” courtesy ©2007
HowStuffWorks.com.
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home power 121 / october & november 2007
70
hen we talk with people interested in investing
in PV, we often get the same question: “What’s
the best module?” Our stock reply is that choosing
a module is similar to buying a Ford versus a Chevy—both
are dependable trucks that will get the job done. While
this response is oversimplified, it is sound general advice.
Compared to most consumer products, the cost, performance,
and durability of PV modules are relatively consistent—as long
as you purchase UL-listed modules that carry a warranty of
20 years or more.
But when you dig into module specs and compare them
side by side, the distinguishing characteristics begin to emerge.
Because PV modules have 25-year-plus operational life spans,
small distinctions in performance or suitability for a given
application will be magnified over time. What may seem to be
minor differences in daily array output can result in megawatt-
hours of energy lost or gained over the life of the system.
A Changing PV Market
Over the last few years, a shortage of silicon—the main material
in nearly all PV modules—resulted in a tight seller’s market.
This left many installers who had been loyal to a specific brand
scrambling to get their hands on any available modules to keep
their projects rolling. The silicon shortage limited options for
choosing the optimal module for a given application.
More recently, increased investment in production
and long-term contracts between module manufacturers
and silicon producers has eased the availability crunch
significantly. Existing PV manufacturers have ramped
up production capacity, and new players are joining the
manufacturing base. As a result, consumer choice is back
on the table, and that’s good for the PV industry, good for
installers, and good for businesses and individuals ready to
invest in solar electricity.
How to Use This Guide
This article provides a comprehensive listing of PV modules
that are UL listed and available in the United States (or in a
few cases, conservatively projected to be available in the first
quarter of 2008). Included modules have a rated output of
100 watts or higher at standard test conditions (STC) and a
minimum power output warranty of 20 years.
To navigate the detailed specifications tables on the
following pages, get familiar with the definitions and
descriptions provided. They’ll give you an understanding
of each spec’s relevance to designing a high performance
system. The specifications included in the table will help you
determine which modules will allow optimal integration
with a given system’s inverters or charge controllers, and
overcurrent protection. They will also assist you in specifying
the highest power array for sites with mounting space
limitations. (Note that specifications were collected from spec
sheets, provided directly by the manufacturers or calculated,
and are subject to change.)
PV systems represent a significant financial investment.
How an individual module model performs when coupled
with a given inverter or charge controller can make the
difference between a design that is simply functional and a
design that performs optimally over the system’s decades-long
operational life.
Home Power’s 2007
Solar-Electric Module Guide
THE PERFECT
PV
SPECS...
Manufacturer
Definition: A company that designs and builds a line of PV
modules.
Importance: PV manufacturers include global energy
companies like BP and GE. Manufacturers with long histories
of producing consumer or industrial electronics such as Sanyo,
Sharp, and Kyocera are devoting significant resources to PV
production capacity. And there are “pure play” companies that
focus on one thing—manufacturing photovoltaic modules.
Examples include Advent Solar, Canadian Solar, Day4Energy,
Evergreen, SolarWorld, and Suntech Power.
Model
Definition: The identifier used to distinguish one module
from another.
Importance: Other than giving you a reference point to
compare modules, model specifications and availability
often change and should be verified prior to purchasing.
Rated Power at STC (watts)
Definition: Module wattage rating at standard test conditions
(STC)—1,000 watts per square meter solar irradiance, 25°C
(77°F) cell temperature.
Importance: The STC rating establishes a consistent basis
for comparing the power output of individual PV models—
but this specification shouldn’t be mistaken for the actual
power a module will generate consistently in the field. Rated
power tolerance (described below) and array operating
temperatures are two factors that result in real-world module
output that, in most instances, will be significantly lower
than a module’s rating at STC. If you purchased a 100-watt
module with a measured power tolerance of minus 3%,
that module could potentially generate 97 watts in the field.
If the module was installed in a hot climate like Southern
California and the array spent much of its life operating
at 50°C (122°F), the actual output of that 100-watt module
during the heat of the day might be about 85 watts. The
real-world wattage would be better if the module had a
0% power tolerance rating and was operating in a cooler
climate, and worse if it had a lower tolerance rating and was
installed in a hotter climate.
Rated Power Tolerance (%)
Definition: The specified range within which a module will
either overperform or underperform its rated power at STC.
Importance: Power tolerance is the most contentious module
specification. Depending on the module, this specification can
vary from as much as plus 10% to minus 9%. With only a
positive power tolerance (plus 2.5%), Evergreen’s new 195-watt
module is guaranteed to generate at least 195 watts at STC.
Shuco also manufactures two modules with no negative power
tolerance. Due to the recent trend of rating modules in small
increments, for example, a 5-watt difference between models,
the reality is that modules that meet the power tolerance of
the next highest model will be classified as such. The result?
Modules are more likely to produce at the lower end of the
tolerance range. The bottom line is that the tighter the rated
power tolerance, the better, so you can be assured that you’re
getting the wattage you pay for.
www.homepower.com
PV buyer’s guide
71
by Joe Schwartz
with Doug Puffer
THE PERFECT
PV
home power 121 / october & november 2007
72
PV buyer’s guide
Rated Power per Square Foot (watts)
Definition: Power output at STC per square foot of module (not
cell) area; calculated by dividing module rated power by the
module’s area in square feet.
Importance: If you have limited space available for a PV array,
this metric will help you determine which module will maximize
power output in a given area (power density). Rated power per
square foot is one tangible way to compare the efficiency of one
module to another. Currently, specific modules manufactured by
Sanyo and SunPower achieve the highest power densities.
Module Efficiency (%)
Definition: The ratio of output power to input power, or how
efficiently a PV module uses the photons in sunlight to generate
DC electricity.
Importance: Module efficiency is another indicator of which
modules will generate the highest power if space is limited.
While high efficiency is great, it typically comes at an increased
cost. For the modules surveyed, efficiencies range from 10.3%
to 19.3%. Manufacturers may also advertise the efficiency of
individual cells, which should not be confused with overall
module efficiency—a more important figure to consider. Finally,
there has been a fair amount of hype on the Internet recently
about solar technologies reaching efficiencies greater than 40%
in the lab. But these devices are not ready for prime time, and
probably won’t be for decades. Most importantly, they shouldn’t
be compared to warranted, commercially available modules that
you can put to work today.
Module Physical Dimensions (inches)
Definition: Length, width, and depth of a given module.
Importance: Module dimensions vary, often significantly. Careful
consideration of module dimensions during the system design
phase will result in an attractive array that is visually integrated
with the building and uses available space wisely. Poor layout
planning can result in an installation that’s less aesthetically
pleasing, such as arrays extending past the roof’s ridgeline or
gable ends.
Weight (lbs.)
Definition: Module weight in pounds.
Importance: The total weight of an installed array (including
modules and racking) is not usually a factor that needs to be
considered unless ballasted mounts will be used or engineering is
required for the project. The weight figures here are for modules
only and do not include packaging for shipping.
Series Fuse Rating (amps)
Definition: Amperage value of a series fuse used to protect a
module from overcurrent, under fault conditions.
Importance: Series strings of modules wired in parallel at a
combiner box typically require overcurrent protection for each
string. The module manufacturer specifies the amperage rating
of the required fuse or breaker. Many batteryless inverters are
designed to accept the individual output wiring of two or more
series strings without additional series fusing.
Connector Type
Definition: Module output terminal or cable/connector
configuration.
Importance: To decrease installation time, most PV manufacturers
have moved away from accessible junction boxes where
installers terminated module wiring at screw-type connectors.
Preinstalled cabling that includes “plug and play” weather-tight
connectors is now the standard. The most common connector
types are manufactured by Multi-Contact USA, which offers a
line of connectors commonly referred to as MC connectors. Two
manufacturers, Day4Energy and GE, use Solarlok connectors
manufactured by Tyco Electronics.
Courtesy www.bpsolar.us
Courtesy www.isofoton.com
www.homepower.com
PV buyer’s guide
73
Materials Warranty (years)
Definition: A limited warranty on module
materials and workmanship under normal
application, installation, use, and service
conditions.
Importance: Of the modules surveyed,
materials warranties vary from 1 to
10 years.
Power Warranty (years)
Definition: A limited warranty for module
power output based on the minimum peak
power rating (STC rating minus power
tolerance percentage) of a given module.
Importance: Few consumer products have
warranties that come anywhere close
to those carried by PV modules: at least
20 years. The fine print typically breaks
down module power warranties based on
a percentage of minimum peak power
output within two different time frames—
90% of minimum peak power is typically
guaranteed for 10 years, and 80% for 20
to 25 years.
Cell Type
Definition: The material that comprises a specific cell, based on
the cell manufacturing process.
Importance: There are three general types of PV cell materials—
monocrystalline, polycrystalline, and thin film. As the specs
here indicate, neither mono- nor polycrystalline cells show a
clear performance advantage. A module’s performance is more
directly related to the specifications of the particular cells used,
and the specific design of a given module. Thin-film modules
have roughly half the power density of crystalline module
types, and other than a couple of companies that combine two
smaller thin-film modules together, no framed thin-film modules
rated at more than 100 watts at STC are available in the United
States. UniSolar manufactures flexible roof laminates that are
adhered to standing-seam metal roofing. Depending on their
length, they may generate more than 100 watts per laminate.
An interesting note is that Sanyo manufactures modules that
combine monocrystalline cells with layers of thin-film material,
which enables the modules to use a wider range of the sun’s light
spectrum.
Cell Size (inches)
Definition: Indication of relative cell size.
Importance: The voltage of PV cells is relatively consistent no
matter what their size, while cell current directly correlates to cell
area. Roofs with limited space may benefit from modules with
smaller cells to increase series string voltage to match a specific
inverter. Modules with larger cells are well suited for high-power
commercial installations.
Cells in Series
Definition: Number of individual PV cells wired in series to
generate the module design voltage.
Importance: Module voltage increases as additional cells
are wired in series. Historically, module design voltage was
based on recharging a battery bank of a specific voltage
(typically multiples of 12 volts nominal). Today, most PV
systems operate at high voltages (up to 600 VDC), are grid
connected, and use inverters and charge controllers that
optimize array output over a wide voltage range. As a result,
some modules have a maximum power voltage (based on
the number of cells in series) that will not be compatible with
systems using non-maximum power point tracking (MPPT)
charge controllers.
Cells in Series per Bypass Diode
Definition: Bypass diodes provide an alternate path for electricity
to flow if a portion of a module is shaded. A certain number of
cells in series are configured with bypass diodes wired in parallel
between series strings.
Importance: Poorly designed arrays may operate near the
bottom of the voltage-tracking window of a batteryless inverter.
In this instance, module shading can cause the array voltage
to drop below the minimum inverter voltage threshold, and
power output will cease until the array is again sufficiently
illuminated. Bypass diodes allow nonshaded cell series strings
within a module to continue to generate electricity if another
series string within the same module is shaded, keeping
the array voltage as high as possible to keep the system
functioning.
Maximum Power Voltage (Vmp)
Definition: The voltage generated by a PV module or array
when exposed to sunlight and connected to a load—typically a
batteryless inverter or a charge controller and battery.
Importance: Batteryless inverters have a range in which they
track and optimize the output of a PV array as its voltage and
current vary throughout the day. The maximum power voltage of
an array should be designed to stay within the tracking window
of your inverter or MPPT charge controller.
Courtesy www.suntech-power.com
Manufacturer
Model
Rated
Power at
STC (W)
Rated
Power
Tolerance
(%)
Rated
Power
Per Sq.
Ft. (W)
Module
Efficiency
(%)
Length
(In.)
Width
(In.)
Depth
(In.)
Weight
(Lbs.)
Series Fuse
Rating
(Amps)
Connector
Type
Materials
Warranty
(Yrs.)
Power
Warranty
(Yrs.)
90%/80%
Cell Type
Cell
Size
(In.)
Cells in
Series
Cells in
Series per
Bypass
Diode
Max.
Power
Voltage
(Vmp)
Max.
Power
Current
(Imp)
Open-
Circuit
Voltage
(Voc)
Short-
Circuit
Current
(Isc)
Max. Power
Temp.
Coefficient
(%/Deg. C)
Open-Circuit
Voltage Temp.
Coefficient
(mV/Deg. C)
Short-Circuit
Current Temp.
Coefficient
(mA/Deg. C)
Advent
Solar
Advent 200
200
+/-3.0
11.2
12.0
66.14
38.98
1.97
50
15
MC
NA
10 / 25
Poly
5
60
20
28.1
7.1
34.9
8.0
-0.52
-126
4.07
Advent 205
205
+/-3.0
11.5
12.3
66.14
38.98
1.97
50
15
MC
NA
10 / 25
Poly
5
60
20
28.4
7.2
35.1
8.1
-0.52
-126
4.12
Advent 210
210
+/-3.0
11.7
12.6
66.14
38.98
1.97
50
15
MC
NA
10 / 25
Poly
5
60
20
28.4
7.4
35.1
8.2
-0.52
-126
4.20
Advent 215
215
+/-3.0
12.0
12.9
66.14
38.98
1.97
50
15
MC
NA
10 / 25
Poly
5
60
20
28.7
7.5
35.4
8.3
-0.52
-127
4.22
Advent 220
220
+/-3.0
12.3
13.2
66.14
38.98
1.97
50
15
MC
NA
10 / 25
Poly
5
60
20
29.1
7.6
35.7
8.4
-0.52
-129
4.28
Advent 225
225
+/-3.0
12.6
13.5
66.14
38.98
1.97
50
15
MC
NA
10 / 25
Poly
5
60
20
29.3
7.8
36.0
8.5
-0.52
-130
4.35
Advent 230
230
+/-3.0
12.8
13.8
66.14
38.98
1.97
50
15
MC
NA
10 / 25
Poly
5
60
20
29.7
7.8
36.3
8.6
-0.52
-131
4.37
Advent 235
235
+/-3.0
13.1
14.1
66.14
38.98
1.97
50
15
MC
NA
10 / 25
Poly
5
60
20
29.7
7.9
36.3
8.6
-0.52
-131
4.41
Advent 240
240
+/-3.0
13.4
14.4
66.14
38.98
1.97
50
15
MC
NA
10 / 25
Poly
5
60
20
30.0
8.0
36.6
8.7
-0.52
-132
4.43
BP Solar
BP 3115J
115
+/-3.0
10.5
11.3
59.45
26.54
1.97
26.64
15
J-Box
5
10, 12 / 25
Poly
6
36
18
17.1
6.7
21.8
7.5
-0.50
-80
4.88
BP 3125J
125
+/-3.0
11.4
12.3
59.45
26.54
1.97
26.64
15
J-Box
5
10, 12 / 25
Poly
6
36
18
17.4
7.2
22.0
8.1
-0.50
-80
5.27
SX 3140J
140
+/-9.0
12.8
12.8
59.45
26.54
1.97
26.64
15
J-Box
5
10, 12 / 25
Poly
6
36
18
17.5
8.0
22.0
8.2
-0.50
-80
5.33
SX 165B
165
+/-9.0
12.2
13.1
62.72
31.10
1.97
33.88
15
MC
5
10, 12 / 25
Poly
5
72
24
35.2
4.7
44.2
5.1
-0.50
-160
3.32
SX 170 I
170
+/-9.0
12.4
13.3
62.48
31.61
1.97
33.88
15
MC
5
10, 12 / 25
Poly
5
72
24
35.4
4.8
44.2
5.3
-0.50
-160
3.43
BP 170 I
170
+/-5.0
12.4
13.3
62.48
32.61
1.97
33.88
15
MC
5
10, 12 / 25
Poly
5
72
24
35.4
4.8
43.6
5.3
-0.50
-160
3.43
BP 170 B
170
+/-5.0
12.6
13.5
62.72
31.10
1.97
33.88
15
MC
5
10, 12 / 25
Poly
5
72
24
35.4
4.8
43.6
5.3
-0.50
-160
3.43
SX 175B
175
+/-9.0
12.9
13.9
62.72
31.10
1.97
33.88
15
MC
5
10, 12 / 25
Poly
5
72
24
36.1
4.9
44.2
5.3
-0.50
-160
3.45
BP 175 B
175
+/-5.0
12.9
13.9
62.72
31.10
1.97
33.88
15
MC
5
10, 12 / 25
Poly
5
72
24
36.1
4.9
43.6
5.3
-0.50
-160
3.45
BP 175 I
175
+/-5.0
12.8
13.7
62.48
32.61
1.97
33.88
15
MC
5
10, 12 / 25
Poly
5
72
24
36.1
4.9
43.6
5.3
-0.50
-160
3.45
BP 4175 B
175
+/-5.0
12.9
13.9
62.72
31.10
1.97
33.88
15
MC
5
10, 12 / 25
Mono
5
72
24
35.4
4.9
43.6
5.5
-0.50
-160
3.54
BP 4175 I
175
+/-5.0
12.8
13.7
62.48
32.61
1.97
33.88
15
MC
5
10, 12 / 25
Mono
5
72
24
35.4
4.9
43.6
5.5
-0.50
-160
3.54
BP 4180 B
180
+/-5.0
13.3
14.3
62.72
31.10
1.97
33.88
15
MC
5
10, 12 / 25
Mono
5
72
24
35.5
5.1
43.6
5.6
-0.50
-160
3.64
BP 4180 I
180
+/-5.0
13.1
14.1
62.48
32.61
1.97
33.88
15
MC
5
10, 12 / 25
Mono
5
72
24
35.5
5.1
43.6
5.6
-0.50
-160
3.64
SX 3190 N, B
190
+/-9.0
12.6
13.5
66.14
32.95
1.97
37.84
15
MC
5
10, 12 / 25
Poly
6
50
10, 20
24.3
7.8
30.6
8.5
-0.50
-111
5.53
SX 3195 N, B
195
+/-9.0
12.9
13.9
66.14
32.95
1.97
37.84
15
MC
5
10, 12 / 25
Poly
6
50
10, 20
24.4
8.0
30.7
8.6
-0.50
-111
5.59
SX 3200 B, W
200
+/-9.0
13.2
13.2
66.14
32.95
1.97
37.84
15
MC
5
10, 12 / 25
Poly
6
50
10, 20
24.5
8.2
30.8
8.7
-0.50
-111
5.66
BP 3200 B, W
200
+/-5.0
13.2
13.2
66.14
32.95
1.97
37.84
15
MC
5
10, 12 / 25
Poly
6
50
10, 20
24.5
8.2
30.8
8.7
-0.50
-111
5.66
Canadian
Solar
CS5A-170
170
+/-3.0
12.4
13.3
62.80
31.54
1.57
34.17
10
MC
2
10 / 25
Mono
5
72
24
34.4
5.0
43.2
5.4
-0.30
-158
3.49
CS6A-175
175
+/-3.0
12.5
13.5
52.13
38.66
1.57
35.27
15
MC
2
10 / 25
Poly
6
48
16
23.2
7.5
28.8
8.2
-0.30
-105
5.33
CS6A-180
180
+/-3.0
12.9
13.8
52.13
38.66
1.57
35.27
15
MC
2
10 / 25
Poly
6
48
16
23.2
7.8
28.8
8.4
-0.30
-105
5.47
CS5A-180
180
+/-3.0
13.1
14.1
62.80
31.54
1.57
34.17
10
MC
2
10 / 25
Mono
5
72
24
34.4
5.2
43.2
5.7
-0.30
-158
3.70
CS6A-185
185
+/-3.0
13.2
14.2
52.13
38.66
1.57
35.27
15
MC
2
10 / 25
Poly
6
48
16
23.2
8.0
28.8
8.7
-0.30
-105
5.62
CS5P-210
210
+/-3.0
11.5
12.4
63.07
41.77
1.57
44.09
10
MC
2
10 / 25
Mono
5
96
24
46.0
4.6
57.6
5.0
-0.30
-208
3.23
CS6P-210
210
+/-3.0
12.1
13.1
64.49
38.66
1.57
40.79
15
MC
2
10 / 25
Poly
6
60
20
28.9
7.3
36.1
7.9
-0.30
-131
5.15
CS5P-220
220
+/-3.0
12.0
12.9
63.07
41.77
1.57
44.09
10
MC
2
10 / 25
Mono
5
96
24
46.4
4.7
57.9
5.2
-0.30
-208
3.36
CS6P-220
220
+/-3.0
12.7
13.7
64.49
38.66
1.57
40.79
15
MC
2
10 / 25
Poly
6
60
20
29.1
7.6
36.2
8.3
-0.30
-131
5.38
CS5P-230
230
+/-3.0
12.6
13.5
63.07
41.77
1.57
44.09
10
MC
2
10 / 25
Mono
5
96
24
46.8
4.9
58.1
5.4
-0.30
-208
3.51
Day4
Energy
Day4 36MC 115
115
+/-3.5
10.8
11.6
57.70
26.59
1.38
28.44
15
Solarlok
5
10 / 25
Poly
6
36
18
16.8
6.9
21.0
7.6
-0.48
-110
7.80
Day4 36MC 120
120
+/-3.5
11.3
12.1
57.70
26.59
1.38
28.44
15
Solarlok
5
10 / 25
Poly
6
36
18
17.0
7.1
21.2
7.7
-0.48
-110
7.80
Day4 36MC 125
125
+/-3.5
11.7
12.6
57.70
26.59
1.38
28.44
15
Solarlok
5
10 / 25
Poly
6
36
18
17.2
7.3
21.5
7.9
-0.48
-110
7.80
Day4 36MC 130
130
+/-3.5
12.2
13.1
57.70
26.59
1.38
28.44
15
Solarlok
5
10 / 25
Poly
6
36
18
17.6
7.5
21.9
8.1
-0.48
-110
7.80
Day4 36MC 135
135
+/-3.5
12.7
13.6
57.70
26.59
1.38
28.44
15
Solarlok
5
10 / 25
Poly
6
36
18
17.8
7.6
22.1
8.1
-0.48
-110
7.80
Day4 36MC 140
140
+/-3.5
13.1
14.1
57.70
26.59
1.38
28.44
15
Solarlok
5
10 / 25
Poly
6
36
18
18.0
7.8
22.3
8.2
-0.48
-110
7.80
Day4 36MC 145
145
+/-3.5
13.6
14.6
57.70
26.59
1.38
28.44
15
Solarlok
5
10 / 25
Poly
6
36
18
18.2
8.0
22.6
8.3
-0.48
-110
7.80
Day4 48MC 160
160
+/-3.5
11.5
12.4
51.46
39.01
1.38
38.28
15
Solarlok
5
10 / 25
Poly
6
48
24
22.6
7.1
28.3
7.7
-0.48
-110
7.80
Day4 48MC 165
165
+/-3.5
11.8
12.7
51.46
39.01
1.38
38.28
15
Solarlok
5
10 / 25
Poly
6
48
24
23.0
7.2
28.6
7.8
-0.48
-110
7.80
Day4 48MC 170
170
+/-3.5
12.2
13.1
51.46
39.01
1.38
38.28
15
Solarlok
5
10 / 25
Poly
6
48
24
23.0
7.4
28.8
7.9
-0.48
-110
7.80
Day4 48MC 175
175
+/-3.5
12.6
13.5
51.46
39.01
1.38
38.28
15
Solarlok
5
10 / 25
Poly
6
48
24
23.4
7.5
29.2
8.1
-0.48
-110
7.80
Day4 48MC 180
180
+/-3.5
12.9
13.9
51.46
39.01
1.38
38.28
15
Solarlok
5
10 / 25
Poly
6
48
24
23.7
7.6
29.4
8.1
-0.48
-110
7.80
Day4 48MC 185
185
+/-3.5
13.3
14.3
51.46
39.01
1.38
38.28
15
Solarlok
5
10 / 25
Poly
6
48
24
23.8
7.8
29.5
8.2
-0.48
-110
7.80
Day4 48MC 190
190
+/-3.5
13.6
14.7
51.46
39.01
1.38
38.28
15
Solarlok
5
10 / 25
Poly
6
48
24
24.0
7.9
29.7
8.3
-0.48
-110
7.80
Evergreen
ES-170
170
+4.0/-5.0
10.6
11.4
61.80
37.50
1.60
40.10
15
MC
5
10 / 25
Poly Ribbon6 x 3
108
18
25.3
6.7
32.4
7.6
-0.49
-112
4.50
ES-180
180
+4.0/-2.0
11.2
12.0
61.80
37.50
1.60
40.10
15
MC
5
10 / 25
Poly Ribbon6 x 3
108
18
25.9
7.0
32.6
7.8
-0.49
-112
4.60
ES-190
190
+4.0/-2.0
11.8
12.7
61.80
37.50
1.60
40.10
15
MC
5
10 / 25
Poly Ribbon6 x 3
108
18
26.7
7.1
32.8
8.1
-0.49
-113
4.80
ES-195
195
+2.5/-0.0
12.1
13.1
61.80
37.50
1.60
40.10
15
MC
5
10 / 25
Poly Ribbon6 x 3
108
18
27.1
7.2
32.9
8.2
-0.49
-114
4.80
GE
GEPVc-170-MS
170
+/-5.0
12.5
13.5
62.50
31.30
1.40
32.30
15
Solarlok
5
10 / 25
Mono
5
72
18
36.5
4.7
43.9
5.1
-0.37
-150
4.60
GEPVp-200-MS
200
+/-5.0
12.8
13.7
58.50
38.60
1.40
39.00
15
Solarlok
5
10 / 25
Poly
6
54
18
26.3
7.6
32.9
8.1
-0.50
-120
5.60
Kyocera
KC130TM
130
+10.0/-5.0
13.0
14.0
56.00
25.70
2.20
26.90
15
J-Box
1
10 / 20
Poly
6
36
18
17.6
7.4
21.9
8.0
-0.49
-82
3.18
KC130GT
130
+10.0/-5.0
13.0
14.0
56.00
25.70
1.40
26.90
15
MC
1
10 / 20
Poly
6
36
18
17.6
7.4
21.9
8.0
-0.49
-82
3.18
KC175 GT
175
+10.0/-5.0
12.7
13.7
50.80
39.00
1.40
35.30
15
MC
1
10 / 20
Poly
6
48
16
23.6
7.4
29.2
8.1
-0.49
-109
3.18
KC200GT
200
+10.0/-5.0
13.1
14.2
56.20
39.00
1.40
40.80
15
MC
1
10 / 20
Poly
6
54
18
26.3
7.6
32.9
8.2
-0.49
-123
3.18
home power 121 / october & november 2007
74
PV buyer’s guide
Notes: a-Si = Amorphous silicon • Poly = Polycrystalline • Mono = Monocrystalline • MC = Multi-Contact • J-Box = Junction box • NA = Not available
Manufacturer
Model
Rated
Power at
STC (W)
Rated
Power
Tolerance
(%)
Rated
Power
Per Sq.
Ft. (W)
Module
Efficiency
(%)
Length
(In.)
Width
(In.)
Depth
(In.)
Weight
(Lbs.)
Series Fuse
Rating
(Amps)
Connector
Type
Materials
Warranty
(Yrs.)
Power
Warranty
(Yrs.)
90%/80%
Cell Type
Cell
Size
(In.)
Cells in
Series
Cells in
Series per
Bypass
Diode
Max.
Power
Voltage
(Vmp)
Max.
Power
Current
(Imp)
Open-
Circuit
Voltage
(Voc)
Short-
Circuit
Current
(Isc)
Max. Power
Temp.
Coefficient
(%/Deg. C)
Open-Circuit
Voltage Temp.
Coefficient
(mV/Deg. C)
Short-Circuit
Current Temp.
Coefficient
(mA/Deg. C)
Advent
Solar
Advent 200
200
+/-3.0
11.2
12.0
66.14
38.98
1.97
50
15
MC
NA
10 / 25
Poly
5
60
20
28.1
7.1
34.9
8.0
-0.52
-126
4.07
Advent 205
205
+/-3.0
11.5
12.3
66.14
38.98
1.97
50
15
MC
NA
10 / 25
Poly
5
60
20
28.4
7.2
35.1
8.1
-0.52
-126
4.12
Advent 210
210
+/-3.0
11.7
12.6
66.14
38.98
1.97
50
15
MC
NA
10 / 25
Poly
5
60
20
28.4
7.4
35.1
8.2
-0.52
-126
4.20
Advent 215
215
+/-3.0
12.0
12.9
66.14
38.98
1.97
50
15
MC
NA
10 / 25
Poly
5
60
20
28.7
7.5
35.4
8.3
-0.52
-127
4.22
Advent 220
220
+/-3.0
12.3
13.2
66.14
38.98
1.97
50
15
MC
NA
10 / 25
Poly
5
60
20
29.1
7.6
35.7
8.4
-0.52
-129
4.28
Advent 225
225
+/-3.0
12.6
13.5
66.14
38.98
1.97
50
15
MC
NA
10 / 25
Poly
5
60
20
29.3
7.8
36.0
8.5
-0.52
-130
4.35
Advent 230
230
+/-3.0
12.8
13.8
66.14
38.98
1.97
50
15
MC
NA
10 / 25
Poly
5
60
20
29.7
7.8
36.3
8.6
-0.52
-131
4.37
Advent 235
235
+/-3.0
13.1
14.1
66.14
38.98
1.97
50
15
MC
NA
10 / 25
Poly
5
60
20
29.7
7.9
36.3
8.6
-0.52
-131
4.41
Advent 240
240
+/-3.0
13.4
14.4
66.14
38.98
1.97
50
15
MC
NA
10 / 25
Poly
5
60
20
30.0
8.0
36.6
8.7
-0.52
-132
4.43
BP Solar
BP 3115J
115
+/-3.0
10.5
11.3
59.45
26.54
1.97
26.64
15
J-Box
5
10, 12 / 25
Poly
6
36
18
17.1
6.7
21.8
7.5
-0.50
-80
4.88
BP 3125J
125
+/-3.0
11.4
12.3
59.45
26.54
1.97
26.64
15
J-Box
5
10, 12 / 25
Poly
6
36
18
17.4
7.2
22.0
8.1
-0.50
-80
5.27
SX 3140J
140
+/-9.0
12.8
12.8
59.45
26.54
1.97
26.64
15
J-Box
5
10, 12 / 25
Poly
6
36
18
17.5
8.0
22.0
8.2
-0.50
-80
5.33
SX 165B
165
+/-9.0
12.2
13.1
62.72
31.10
1.97
33.88
15
MC
5
10, 12 / 25
Poly
5
72
24
35.2
4.7
44.2
5.1
-0.50
-160
3.32
SX 170 I
170
+/-9.0
12.4
13.3
62.48
31.61
1.97
33.88
15
MC
5
10, 12 / 25
Poly
5
72
24
35.4
4.8
44.2
5.3
-0.50
-160
3.43
BP 170 I
170
+/-5.0
12.4
13.3
62.48
32.61
1.97
33.88
15
MC
5
10, 12 / 25
Poly
5
72
24
35.4
4.8
43.6
5.3
-0.50
-160
3.43
BP 170 B
170
+/-5.0
12.6
13.5
62.72
31.10
1.97
33.88
15
MC
5
10, 12 / 25
Poly
5
72
24
35.4
4.8
43.6
5.3
-0.50
-160
3.43
SX 175B
175
+/-9.0
12.9
13.9
62.72
31.10
1.97
33.88
15
MC
5
10, 12 / 25
Poly
5
72
24
36.1
4.9
44.2
5.3
-0.50
-160
3.45
BP 175 B
175
+/-5.0
12.9
13.9
62.72
31.10
1.97
33.88
15
MC
5
10, 12 / 25
Poly
5
72
24
36.1
4.9
43.6
5.3
-0.50
-160
3.45
BP 175 I
175
+/-5.0
12.8
13.7
62.48
32.61
1.97
33.88
15
MC
5
10, 12 / 25
Poly
5
72
24
36.1
4.9
43.6
5.3
-0.50
-160
3.45
BP 4175 B
175
+/-5.0
12.9
13.9
62.72
31.10
1.97
33.88
15
MC
5
10, 12 / 25
Mono
5
72
24
35.4
4.9
43.6
5.5
-0.50
-160
3.54
BP 4175 I
175
+/-5.0
12.8
13.7
62.48
32.61
1.97
33.88
15
MC
5
10, 12 / 25
Mono
5
72
24
35.4
4.9
43.6
5.5
-0.50
-160
3.54
BP 4180 B
180
+/-5.0
13.3
14.3
62.72
31.10
1.97
33.88
15
MC
5
10, 12 / 25
Mono
5
72
24
35.5
5.1
43.6
5.6
-0.50
-160
3.64
BP 4180 I
180
+/-5.0
13.1
14.1
62.48
32.61
1.97
33.88
15
MC
5
10, 12 / 25
Mono
5
72
24
35.5
5.1
43.6
5.6
-0.50
-160
3.64
SX 3190 N, B
190
+/-9.0
12.6
13.5
66.14
32.95
1.97
37.84
15
MC
5
10, 12 / 25
Poly
6
50
10, 20
24.3
7.8
30.6
8.5
-0.50
-111
5.53
SX 3195 N, B
195
+/-9.0
12.9
13.9
66.14
32.95
1.97
37.84
15
MC
5
10, 12 / 25
Poly
6
50
10, 20
24.4
8.0
30.7
8.6
-0.50
-111
5.59
SX 3200 B, W
200
+/-9.0
13.2
13.2
66.14
32.95
1.97
37.84
15
MC
5
10, 12 / 25
Poly
6
50
10, 20
24.5
8.2
30.8
8.7
-0.50
-111
5.66
BP 3200 B, W
200
+/-5.0
13.2
13.2
66.14
32.95
1.97
37.84
15
MC
5
10, 12 / 25
Poly
6
50
10, 20
24.5
8.2
30.8
8.7
-0.50
-111
5.66
Canadian
Solar
CS5A-170
170
+/-3.0
12.4
13.3
62.80
31.54
1.57
34.17
10
MC
2
10 / 25
Mono
5
72
24
34.4
5.0
43.2
5.4
-0.30
-158
3.49
CS6A-175
175
+/-3.0
12.5
13.5
52.13
38.66
1.57
35.27
15
MC
2
10 / 25
Poly
6
48
16
23.2
7.5
28.8
8.2
-0.30
-105
5.33
CS6A-180
180
+/-3.0
12.9
13.8
52.13
38.66
1.57
35.27
15
MC
2
10 / 25
Poly
6
48
16
23.2
7.8
28.8
8.4
-0.30
-105
5.47
CS5A-180
180
+/-3.0
13.1
14.1
62.80
31.54
1.57
34.17
10
MC
2
10 / 25
Mono
5
72
24
34.4
5.2
43.2
5.7
-0.30
-158
3.70
CS6A-185
185
+/-3.0
13.2
14.2
52.13
38.66
1.57
35.27
15
MC
2
10 / 25
Poly
6
48
16
23.2
8.0
28.8
8.7
-0.30
-105
5.62
CS5P-210
210
+/-3.0
11.5
12.4
63.07
41.77
1.57
44.09
10
MC
2
10 / 25
Mono
5
96
24
46.0
4.6
57.6
5.0
-0.30
-208
3.23
CS6P-210
210
+/-3.0
12.1
13.1
64.49
38.66
1.57
40.79
15
MC
2
10 / 25
Poly
6
60
20
28.9
7.3
36.1
7.9
-0.30
-131
5.15
CS5P-220
220
+/-3.0
12.0
12.9
63.07
41.77
1.57
44.09
10
MC
2
10 / 25
Mono
5
96
24
46.4
4.7
57.9
5.2
-0.30
-208
3.36
CS6P-220
220
+/-3.0
12.7
13.7
64.49
38.66
1.57
40.79
15
MC
2
10 / 25
Poly
6
60
20
29.1
7.6
36.2
8.3
-0.30
-131
5.38
CS5P-230
230
+/-3.0
12.6
13.5
63.07
41.77
1.57
44.09
10
MC
2
10 / 25
Mono
5
96
24
46.8
4.9
58.1
5.4
-0.30
-208
3.51
Day4
Energy
Day4 36MC 115
115
+/-3.5
10.8
11.6
57.70
26.59
1.38
28.44
15
Solarlok
5
10 / 25
Poly
6
36
18
16.8
6.9
21.0
7.6
-0.48
-110
7.80
Day4 36MC 120
120
+/-3.5
11.3
12.1
57.70
26.59
1.38
28.44
15
Solarlok
5
10 / 25
Poly
6
36
18
17.0
7.1
21.2
7.7
-0.48
-110
7.80
Day4 36MC 125
125
+/-3.5
11.7
12.6
57.70
26.59
1.38
28.44
15
Solarlok
5
10 / 25
Poly
6
36
18
17.2
7.3
21.5
7.9
-0.48
-110
7.80
Day4 36MC 130
130
+/-3.5
12.2
13.1
57.70
26.59
1.38
28.44
15
Solarlok
5
10 / 25
Poly
6
36
18
17.6
7.5
21.9
8.1
-0.48
-110
7.80
Day4 36MC 135
135
+/-3.5
12.7
13.6
57.70
26.59
1.38
28.44
15
Solarlok
5
10 / 25
Poly
6
36
18
17.8
7.6
22.1
8.1
-0.48
-110
7.80
Day4 36MC 140
140
+/-3.5
13.1
14.1
57.70
26.59
1.38
28.44
15
Solarlok
5
10 / 25
Poly
6
36
18
18.0
7.8
22.3
8.2
-0.48
-110
7.80
Day4 36MC 145
145
+/-3.5
13.6
14.6
57.70
26.59
1.38
28.44
15
Solarlok
5
10 / 25
Poly
6
36
18
18.2
8.0
22.6
8.3
-0.48
-110
7.80
Day4 48MC 160
160
+/-3.5
11.5
12.4
51.46
39.01
1.38
38.28
15
Solarlok
5
10 / 25
Poly
6
48
24
22.6
7.1
28.3
7.7
-0.48
-110
7.80
Day4 48MC 165
165
+/-3.5
11.8
12.7
51.46
39.01
1.38
38.28
15
Solarlok
5
10 / 25
Poly
6
48
24
23.0
7.2
28.6
7.8
-0.48
-110
7.80
Day4 48MC 170
170
+/-3.5
12.2
13.1
51.46
39.01
1.38
38.28
15
Solarlok
5
10 / 25
Poly
6
48
24
23.0
7.4
28.8
7.9
-0.48
-110
7.80
Day4 48MC 175
175
+/-3.5
12.6
13.5
51.46
39.01
1.38
38.28
15
Solarlok
5
10 / 25
Poly
6
48
24
23.4
7.5
29.2
8.1
-0.48
-110
7.80
Day4 48MC 180
180
+/-3.5
12.9
13.9
51.46
39.01
1.38
38.28
15
Solarlok
5
10 / 25
Poly
6
48
24
23.7
7.6
29.4
8.1
-0.48
-110
7.80
Day4 48MC 185
185
+/-3.5
13.3
14.3
51.46
39.01
1.38
38.28
15
Solarlok
5
10 / 25
Poly
6
48
24
23.8
7.8
29.5
8.2
-0.48
-110
7.80
Day4 48MC 190
190
+/-3.5
13.6
14.7
51.46
39.01
1.38
38.28
15
Solarlok
5
10 / 25
Poly
6
48
24
24.0
7.9
29.7
8.3
-0.48
-110
7.80
Evergreen
ES-170
170
+4.0/-5.0
10.6
11.4
61.80
37.50
1.60
40.10
15
MC
5
10 / 25
Poly Ribbon6 x 3
108
18
25.3
6.7
32.4
7.6
-0.49
-112
4.50
ES-180
180
+4.0/-2.0
11.2
12.0
61.80
37.50
1.60
40.10
15
MC
5
10 / 25
Poly Ribbon6 x 3
108
18
25.9
7.0
32.6
7.8
-0.49
-112
4.60
ES-190
190
+4.0/-2.0
11.8
12.7
61.80
37.50
1.60
40.10
15
MC
5
10 / 25
Poly Ribbon6 x 3
108
18
26.7
7.1
32.8
8.1
-0.49
-113
4.80
ES-195
195
+2.5/-0.0
12.1
13.1
61.80
37.50
1.60
40.10
15
MC
5
10 / 25
Poly Ribbon6 x 3
108
18
27.1
7.2
32.9
8.2
-0.49
-114
4.80
GE
GEPVc-170-MS
170
+/-5.0
12.5
13.5
62.50
31.30
1.40
32.30
15
Solarlok
5
10 / 25
Mono
5
72
18
36.5
4.7
43.9
5.1
-0.37
-150
4.60
GEPVp-200-MS
200
+/-5.0
12.8
13.7
58.50
38.60
1.40
39.00
15
Solarlok
5
10 / 25
Poly
6
54
18
26.3
7.6
32.9
8.1
-0.50
-120
5.60
Kyocera
KC130TM
130
+10.0/-5.0
13.0
14.0
56.00
25.70
2.20
26.90
15
J-Box
1
10 / 20
Poly
6
36
18
17.6
7.4
21.9
8.0
-0.49
-82
3.18
KC130GT
130
+10.0/-5.0
13.0
14.0
56.00
25.70
1.40
26.90
15
MC
1
10 / 20
Poly
6
36
18
17.6
7.4
21.9
8.0
-0.49
-82
3.18
KC175 GT
175
+10.0/-5.0
12.7
13.7
50.80
39.00
1.40
35.30
15
MC
1
10 / 20
Poly
6
48
16
23.6
7.4
29.2
8.1
-0.49
-109
3.18
KC200GT
200
+10.0/-5.0
13.1
14.2
56.20
39.00
1.40
40.80
15
MC
1
10 / 20
Poly
6
54
18
26.3
7.6
32.9
8.2
-0.49
-123
3.18
www.homepower.com
PV buyer’s guide
75
Manufacturer
Model
Rated
Power at
STC (W)
Rated
Power
Tolerance
(%)
Rated
Power
Per Sq.
Ft. (W)
Module
Efficiency
(%)
Length
(In.)
Width
(In.)
Depth
(In.)
Weight
(Lbs.)
Series Fuse
Rating
(Amps)
Connector
Type
Materials
Warranty
(Yrs.)
Power
Warranty
(Yrs.)
90%/80%
Cell Type
Cell
Size
(In.)
Cells in
Series
Cells in
Series per
Bypass
Diode
Max.
Power
Voltage
(Vmp)
Max.
Power
Current
(Imp)
Open-
Circuit
Voltage
(Voc)
Short-
Circuit
Current
(Isc)
Max. Power
Temp.
Coefficient
(%/Deg. C)
Open-Circuit
Voltage Temp.
Coefficient
(mV/Deg. C)
Short-Circuit
Current Temp.
Coefficient
(mA/Deg. C)
Mitsubishi
PV-UE115MF5N
115
+10.0/-5.0
10.6
11.4
58.90
26.50
1.81
29.80
15
MC
1.25
10 / 25
Poly
6
36
18
17.1
6.8
21.5
7.6
-0.45
-74
4.08
PV-UE120MF5N
120
+10.0/-5.0
11.1
11.9
58.90
26.50
1.81
29.80
15
MC
1.25
10 / 25
Poly
6
36
18
17.2
7.0
21.6
7.8
-0.45
-74
4.16
PV-UE125MF5N
125
+10.0/-5.0
11.5
12.4
58.90
26.50
1.81
29.80
15
MC
1.25
10 / 25
Poly
6
36
18
17.3
7.2
21.8
7.9
-0.45
-75
4.24
PV-UE130MF5N
130
+10.0/-5.0
12.0
12.9
58.90
26.50
1.81
29.80
15
MC
1.25
10 / 25
Poly
6
36
18
17.4
7.5
21.9
8.1
-0.45
-75
4.32
PV-UD175MF5
175
+/-3.0
11.8
12.7
65.30
32.80
1.81
37.00
15
MC
1.25
10 / 25
Poly
6
50
20
23.9
7.3
30.2
7.9
-0.45
-104
4.26
PV-UD180MF5
180
+/-3.0
12.1
13.0
65.30
32.80
1.81
37.00
15
MC
1.25
10 / 25
Poly
6
50
20
24.2
7.5
30.4
8.0
-0.45
-105
4.31
PV-UD185MF5
185
+/-3.0
12.4
13.4
65.30
32.80
1.81
37.00
15
MC
1.25
10 / 25
Poly
6
50
20
24.4
7.6
30.6
8.1
-0.45
-105
4.37
PV-UD190MF5
190
+/-3.0
12.8
13.7
65.30
32.80
1.81
37.00
15
MC
1.25
10 / 25
Poly
6
50
20
24.7
7.7
30.8
8.2
-0.45
-106
4.42
Sanyo*
HIP-180BA3
180
+10.0/-5.0
14.2
15.3
51.90
35.20
1.40
30.86
15
MC
2
10 / 20
Mono, a-Si
4
96
24
54.0
3.3
66.4
3.7
-0.33
-173
1.10
HIP-186BA3
186
+10.0/-5.0
14.7
15.8
51.90
35.20
1.40
30.86
15
MC
2
10 / 20
Mono, a-Si
4
96
24
54.4
3.4
67.0
3.7
-0.30
-168
0.85
HIP-190BA3
190
+10.0/-5.0
15.0
16.1
51.90
35.20
1.40
30.86
15
MC
2
10 / 20
Mono, a-Si
4
96
24
54.8
3.5
67.5
3.8
-0.30
-169
0.86
HIP-195BA3
195
+10.0/-5.0
15.4
16.5
51.90
35.20
1.40
30.86
15
MC
2
10 / 20
Mono, a-Si
4
96
24
55.3
3.5
68.1
3.8
-0.30
-170
0.87
HIP-200BA3
200
+10.0/-5.0
15.8
17.0
51.90
35.20
1.40
30.86
15
MC
2
10 / 20
Mono, a-Si
4
96
24
55.8
3.6
68.7
3.8
-0.29
-172
0.88
HIP-205BA3
205
+10.0/-5.0
16.2
17.4
51.90
35.20
1.40
30.86
15
MC
2
10 / 20
Mono, a-Si
4
96
24
56.7
3.6
68.8
3.8
-0.29
-172
0.88
Schott
ASE-250-DGF/50
250
+/-4.0
9.6
10.3
74.50
50.50
2.00
107.00
12
MC
1
10 / 20
Poly
4
108
18
48.3
5.2
60.3
5.8
-0.47
-229
5.80
ASE-270-DGF/50
270
+/-4.0
10.3
11.1
74.50
50.50
2.00
107.00
12
MC
1
10 / 20
Poly
4
108
18
49.1
5.5
61.3
6.1
-0.47
-233
6.10
ASE-300-DFG/50
300
+/-4.0
11.5
12.2
74.50
50.50
2.00
107.00
12
MC
1
10 / 20
Poly
4
108
18
50.6
5.9
63.2
6.5
-0.47
-240
6.50
Schuco
S 130-SP
130
+5.0/-0.0
12.1
13.0
49.13
31.61
1.81
27.56
15
MC
5
12 / 25
Poly
6
40
20
19.2
6.8
24.2
7.4
-0.49
-88
4.80
S 165-SP
165
+5.0/-0.0
12.1
13.1
62.20
31.50
1.81
34.17
15
MC
5
12 / 25
Poly
6
50
25
24.2
6.8
30.4
7.4
-0.48
-111
4.19
S 165-SPU
165
+/-5.0
12.1
13.1
62.20
31.50
1.81
34.17
15
MC
5
12 / 25
Poly
6
50
25
24.2
6.8
30.4
7.4
-0.48
-111
4.19
S 170-SPU
170
+/-5.0
12.5
13.1
62.20
31.50
1.81
34.17
15
MC
5
12 / 25
Poly
6
50
25
24.2
6.8
30.4
7.4
-0.48
-111
4.19
Sharp
ND-L3EJEA
123
+10.0/-5.0
11.5
12.4
59.02
26.06
1.81
30.86
15
J-Box
1
10 / 25
Poly
6
36
18
17.2
7.2
21.3
8.0
-0.49
-72
3.20
ND-L5E1U
125
+10.0/-5.0
11.7
12.6
59.02
26.06
1.81
30.86
15
MC
1
10 / 25
Poly
6
36
18
17.2
7.3
21.7
8.1
-0.49
-72
3.24
ND-N2ECU
142
+10.0/-5.0
11.4
12.3
45.87
38.98
1.81
31.96
15
MC
1
10 / 25
Poly
6
42
21
20.0
7.1
24.9
7.9
-0.49
-84
3.16
ND-162U1F
162
+10.0/-5.0
11.5
12.4
51.90
39.10
1.81
36.40
15
MC
1
10 / 25
Poly
6
48
16
22.8
7.1
28.8
8.0
-0.49
-96
3.20
ND-167U1F
167
+10.0/-5.0
11.9
12.7
51.90
39.10
1.81
36.40
15
MC
1
10 / 25
Poly
6
48
16
23.0
7.3
29.0
8.0
-0.49
-96
3.20
NE-170U1
170
+10.0/-5.0
12.1
13.1
62.01
32.52
1.81
37.49
10
MC
1
10 / 25
Poly
5
72
24
34.8
4.9
43.2
5.5
-0.49
-144
2.20
NT-180U1
180
+10.0/-5.0
12.9
13.8
62.00
32.50
1.81
37.50
10
MC
1
10 / 25
Mono
5
72
24
35.9
5.0
44.8
5.6
-0.49
-144
1.68
ND-181U1F
181
+10.0/-5.0
11.4
12.3
58.30
39.10
2.26
39.60
15
MC
1
10 / 25
Poly
6
54
18
25.8
7.0
32.4
7.9
-0.49
-108
3.16
ND-187U1F
187
+10.0/-5.0
11.7
12.7
58.70
39.10
2.26
39.60
15
MC
1
10 / 25
Poly
6
54
18
25.8
7.3
32.7
8.0
-0.49
-108
3.20
ND-200U1F
200
+10.0/-5.0
11.4
12.3
64.60
39.10
1.81
46.30
15
MC
1
10 / 25
Poly
6
60
20
28.4
7.0
36.0
7.9
-0.49
-120
3.16
ND-208U1F
208
+10.0/-5.0
11.9
12.8
64.60
39.10
1.81
46.30
15
MC
1
10 / 25
Poly
6
60
20
28.7
7.3
36.3
8.0
-0.49
-120
3.20
SolarWorld
SW 155 - Mono
155
+/-3.0
11.0
11.9
63.39
31.89
1.34
33.00
15
MC
2
10 / 25
Mono
5
72
24
34.8
4.5
43.6
4.9
-0.35
-145
1.40
SW 165 - Mono
165
+/-3.0
11.8
12.7
63.39
31.89
1.34
33.00
15
MC
2
10 / 25
Mono
5
72
24
35.3
4.7
44.0
5.1
-0.35
-145
1.40
SW 175 - Mono
175
+/-3.0
12.5
13.4
63.39
31.89
1.34
33.00
15
MC
2
10 / 25
Mono
5
72
24
35.8
4.9
44.4
5.3
-0.35
-145
1.40
SunPower
SPR-205-BLK
205
+/-5.0
15.3
16.5
61.39
31.42
1.81
33.00
15
MC
10
12 / 25
Mono
5
72
24
40.0
5.1
47.8
5.5
-0.38
-137
3.50
SPR-210-WHT
210
+/-5.0
15.7
16.9
61.39
31.42
1.81
33.00
15
MC
10
12 / 25
Mono
5
72
24
40.0
5.3
47.7
5.8
-0.38
-137
3.50
SPR-315-WHT
315
+/-5.0
17.9
19.3
61.39
41.18
1.81
53.00
15
MC
5
12 / 25
Mono
5
96
24/48
54.7
5.8
64.6
6.1
-0.38
-177
3.50
Suntech
Power
STP 160S-24/Ab-1
160
+/-3.0
11.6
12.5
62.20
31.81
1.38
34.17
15
MC
5
12 / 25
Mono
5
72
24
34.4
4.7
43.2
5.0
-0.48
-150
0.87
STP 160-24/Ab-1
160
+/-3.0
11.6
12.5
62.20
31.81
1.38
34.17
15
MC
5
12 / 25
Poly
5
72
24
34.4
4.7
43.2
5.0
-0.47
-150
2.30
STP 165S-24/Ab-1
165
+/-3.0
12.0
12.9
62.20
31.81
1.38
34.17
15
MC
5
12 / 25
Mono
5
72
24
34.8
4.7
43.6
5.0
-0.48
-150
0.87
STP 165-24/Ab-1
165
+/-3.0
12.0
12.9
62.20
31.81
1.38
34.17
15
MC
5
12 / 25
Poly
5
72
24
34.8
4.7
43.6
5.0
-0.47
-150
2.30
STP170S-24/Ab-1
170
+/-3.0
12.4
13.3
62.20
31.81
1.38
34.17
15
MC
5
12 / 25
Mono
5
72
24
35.2
4.8
43.8
5.1
-0.48
-150
0.87
STP170-24/Ab-1
170
+/-3.0
12.4
13.3
62.20
31.81
1.38
34.17
15
MC
5
12 / 25
Poly
5
72
24
35.2
4.8
43.8
5.1
-0.47
-150
2.30
STP 175S-24/Ab-1
175
+/-3.0
12.7
13.7
62.20
31.81
1.38
34.17
15
MC
5
12 / 25
Mono
5
72
24
35.2
5.0
44.2
5.2
-0.48
-150
0.87
STP175-24/Ab-1
175
+/-3.0
12.7
13.7
62.20
31.81
1.38
34.17
15
MC
5
12 / 25
Poly
5
72
24
35.2
5.0
44.2
5.2
-0.47
-150
2.30
STP180S-24/Ab-1
180
+/-3.0
13.1
14.1
62.20
31.81
1.38
34.17
15
MC
5
12 / 25
Mono
5
72
24
35.6
5.1
44.4
5.4
-0.48
-150
0.87
STP180-24/Ab-1
180
+/-3.0
13.1
14.1
62.20
31.81
1.38
34.17
15
MC
5
12 / 25
Poly
5
72
24
35.6
5.1
44.4
5.4
-0.47
-150
2.30
Sunwize
SW100C
100
+/-5.0
9.9
15.0
56.93
25.43
1.34
26.00
10
J-Box
1
NA / 25
Mono
8 x 3.5
48
24
23.0
4.4
28.5
5.0
-0.50
-143
3.39
SW115
115
+/-5.0
11.4
15.0
56.93
25.43
1.34
26.00
12
J-Box
1
NA / 25
Mono
6
36
18
16.7
6.9
21.0
7.7
-0.50
-105
6.01
SW120
120
+/-5.0
11.9
15.0
56.93
25.43
1.34
26.00
13
J-Box
1
NA / 25
Mono
6
36
18
16.7
7.2
21.0
8.0
-0.50
-105
6.24
SW150
150
+/-5.0
10.7
15.0
66.61
30.27
1.65
44.00
15
MC
1
NA / 25
Mono
8 x 3.5
72
36
33.4
4.5
42.0
5.1
-0.50
-210
3.99
SW155
155
+/-5.0
11.1
15.0
66.61
30.27
1.65
44.00
15
MC
1
NA / 25
Mono
8 x 3.5
72
36
33.4
4.7
42.0
5.3
-0.50
-210
4.12
SW160
160
+/-5.0
11.4
15.0
66.61
30.27
1.65
44.00
15
MC
1
NA / 25
Mono
8 x 3.5
72
36
33.4
4.8
42.0
5.4
-0.50
-210
4.24
Yingli
YL 120 (17)
120
+/-5.0
12.4
12.0
51.90
26.80
1.45
26.40
N/A
J-Box
2
10 / 25
Poly
NA
36
NA
17.5
6.9
22.0
7.6
-0.45
-81
7.60
home power 121 / october & november 2007
76
PV buyer’s guide
Notes: a-Si = Amorphous silicon • Poly = Polycrystalline • Mono = Monocrystalline • MC = Multi-Contact • J-Box = Junction box • NA = Not available
*Also available: Sanyo’s DA3 series (double-sided) modules, which generate up to 130% of rated wattage at STC in certain conditions
Manufacturer
Model
Rated
Power at
STC (W)
Rated
Power
Tolerance
(%)
Rated
Power
Per Sq.
Ft. (W)
Module
Efficiency
(%)
Length
(In.)
Width
(In.)
Depth
(In.)
Weight
(Lbs.)
Series Fuse
Rating
(Amps)
Connector
Type
Materials
Warranty
(Yrs.)
Power
Warranty
(Yrs.)
90%/80%
Cell Type
Cell
Size
(In.)
Cells in
Series
Cells in
Series per
Bypass
Diode
Max.
Power
Voltage
(Vmp)
Max.
Power
Current
(Imp)
Open-
Circuit
Voltage
(Voc)
Short-
Circuit
Current
(Isc)
Max. Power
Temp.
Coefficient
(%/Deg. C)
Open-Circuit
Voltage Temp.
Coefficient
(mV/Deg. C)
Short-Circuit
Current Temp.
Coefficient
(mA/Deg. C)
Mitsubishi
PV-UE115MF5N
115
+10.0/-5.0
10.6
11.4
58.90
26.50
1.81
29.80
15
MC
1.25
10 / 25
Poly
6
36
18
17.1
6.8
21.5
7.6
-0.45
-74
4.08
PV-UE120MF5N
120
+10.0/-5.0
11.1
11.9
58.90
26.50
1.81
29.80
15
MC
1.25
10 / 25
Poly
6
36
18
17.2
7.0
21.6
7.8
-0.45
-74
4.16
PV-UE125MF5N
125
+10.0/-5.0
11.5
12.4
58.90
26.50
1.81
29.80
15
MC
1.25
10 / 25
Poly
6
36
18
17.3
7.2
21.8
7.9
-0.45
-75
4.24
PV-UE130MF5N
130
+10.0/-5.0
12.0
12.9
58.90
26.50
1.81
29.80
15
MC
1.25
10 / 25
Poly
6
36
18
17.4
7.5
21.9
8.1
-0.45
-75
4.32
PV-UD175MF5
175
+/-3.0
11.8
12.7
65.30
32.80
1.81
37.00
15
MC
1.25
10 / 25
Poly
6
50
20
23.9
7.3
30.2
7.9
-0.45
-104
4.26
PV-UD180MF5
180
+/-3.0
12.1
13.0
65.30
32.80
1.81
37.00
15
MC
1.25
10 / 25
Poly
6
50
20
24.2
7.5
30.4
8.0
-0.45
-105
4.31
PV-UD185MF5
185
+/-3.0
12.4
13.4
65.30
32.80
1.81
37.00
15
MC
1.25
10 / 25
Poly
6
50
20
24.4
7.6
30.6
8.1
-0.45
-105
4.37
PV-UD190MF5
190
+/-3.0
12.8
13.7
65.30
32.80
1.81
37.00
15
MC
1.25
10 / 25
Poly
6
50
20
24.7
7.7
30.8
8.2
-0.45
-106
4.42
Sanyo*
HIP-180BA3
180
+10.0/-5.0
14.2
15.3
51.90
35.20
1.40
30.86
15
MC
2
10 / 20
Mono, a-Si
4
96
24
54.0
3.3
66.4
3.7
-0.33
-173
1.10
HIP-186BA3
186
+10.0/-5.0
14.7
15.8
51.90
35.20
1.40
30.86
15
MC
2
10 / 20
Mono, a-Si
4
96
24
54.4
3.4
67.0
3.7
-0.30
-168
0.85
HIP-190BA3
190
+10.0/-5.0
15.0
16.1
51.90
35.20
1.40
30.86
15
MC
2
10 / 20
Mono, a-Si
4
96
24
54.8
3.5
67.5
3.8
-0.30
-169
0.86
HIP-195BA3
195
+10.0/-5.0
15.4
16.5
51.90
35.20
1.40
30.86
15
MC
2
10 / 20
Mono, a-Si
4
96
24
55.3
3.5
68.1
3.8
-0.30
-170
0.87
HIP-200BA3
200
+10.0/-5.0
15.8
17.0
51.90
35.20
1.40
30.86
15
MC
2
10 / 20
Mono, a-Si
4
96
24
55.8
3.6
68.7
3.8
-0.29
-172
0.88
HIP-205BA3
205
+10.0/-5.0
16.2
17.4
51.90
35.20
1.40
30.86
15
MC
2
10 / 20
Mono, a-Si
4
96
24
56.7
3.6
68.8
3.8
-0.29
-172
0.88
Schott
ASE-250-DGF/50
250
+/-4.0
9.6
10.3
74.50
50.50
2.00
107.00
12
MC
1
10 / 20
Poly
4
108
18
48.3
5.2
60.3
5.8
-0.47
-229
5.80
ASE-270-DGF/50
270
+/-4.0
10.3
11.1
74.50
50.50
2.00
107.00
12
MC
1
10 / 20
Poly
4
108
18
49.1
5.5
61.3
6.1
-0.47
-233
6.10
ASE-300-DFG/50
300
+/-4.0
11.5
12.2
74.50
50.50
2.00
107.00
12
MC
1
10 / 20
Poly
4
108
18
50.6
5.9
63.2
6.5
-0.47
-240
6.50
Schuco
S 130-SP
130
+5.0/-0.0
12.1
13.0
49.13
31.61
1.81
27.56
15
MC
5
12 / 25
Poly
6
40
20
19.2
6.8
24.2
7.4
-0.49
-88
4.80
S 165-SP
165
+5.0/-0.0
12.1
13.1
62.20
31.50
1.81
34.17
15
MC
5
12 / 25
Poly
6
50
25
24.2
6.8
30.4
7.4
-0.48
-111
4.19
S 165-SPU
165
+/-5.0
12.1
13.1
62.20
31.50
1.81
34.17
15
MC
5
12 / 25
Poly
6
50
25
24.2
6.8
30.4
7.4
-0.48
-111
4.19
S 170-SPU
170
+/-5.0
12.5
13.1
62.20
31.50
1.81
34.17
15
MC
5
12 / 25
Poly
6
50
25
24.2
6.8
30.4
7.4
-0.48
-111
4.19
Sharp
ND-L3EJEA
123
+10.0/-5.0
11.5
12.4
59.02
26.06
1.81
30.86
15
J-Box
1
10 / 25
Poly
6
36
18
17.2
7.2
21.3
8.0
-0.49
-72
3.20
ND-L5E1U
125
+10.0/-5.0
11.7
12.6
59.02
26.06
1.81
30.86
15
MC
1
10 / 25
Poly
6
36
18
17.2
7.3
21.7
8.1
-0.49
-72
3.24
ND-N2ECU
142
+10.0/-5.0
11.4
12.3
45.87
38.98
1.81
31.96
15
MC
1
10 / 25
Poly
6
42
21
20.0
7.1
24.9
7.9
-0.49
-84
3.16
ND-162U1F
162
+10.0/-5.0
11.5
12.4
51.90
39.10
1.81
36.40
15
MC
1
10 / 25
Poly
6
48
16
22.8
7.1
28.8
8.0
-0.49
-96
3.20
ND-167U1F
167
+10.0/-5.0
11.9
12.7
51.90
39.10
1.81
36.40
15
MC
1
10 / 25
Poly
6
48
16
23.0
7.3
29.0
8.0
-0.49
-96
3.20
NE-170U1
170
+10.0/-5.0
12.1
13.1
62.01
32.52
1.81
37.49
10
MC
1
10 / 25
Poly
5
72
24
34.8
4.9
43.2
5.5
-0.49
-144
2.20
NT-180U1
180
+10.0/-5.0
12.9
13.8
62.00
32.50
1.81
37.50
10
MC
1
10 / 25
Mono
5
72
24
35.9
5.0
44.8
5.6
-0.49
-144
1.68
ND-181U1F
181
+10.0/-5.0
11.4
12.3
58.30
39.10
2.26
39.60
15
MC
1
10 / 25
Poly
6
54
18
25.8
7.0
32.4
7.9
-0.49
-108
3.16
ND-187U1F
187
+10.0/-5.0
11.7
12.7
58.70
39.10
2.26
39.60
15
MC
1
10 / 25
Poly
6
54
18
25.8
7.3
32.7
8.0
-0.49
-108
3.20
ND-200U1F
200
+10.0/-5.0
11.4
12.3
64.60
39.10
1.81
46.30
15
MC
1
10 / 25
Poly
6
60
20
28.4
7.0
36.0
7.9
-0.49
-120
3.16
ND-208U1F
208
+10.0/-5.0
11.9
12.8
64.60
39.10
1.81
46.30
15
MC
1
10 / 25
Poly
6
60
20
28.7
7.3
36.3
8.0
-0.49
-120
3.20
SolarWorld
SW 155 - Mono
155
+/-3.0
11.0
11.9
63.39
31.89
1.34
33.00
15
MC
2
10 / 25
Mono
5
72
24
34.8
4.5
43.6
4.9
-0.35
-145
1.40
SW 165 - Mono
165
+/-3.0
11.8
12.7
63.39
31.89
1.34
33.00
15
MC
2
10 / 25
Mono
5
72
24
35.3
4.7
44.0
5.1
-0.35
-145
1.40
SW 175 - Mono
175
+/-3.0
12.5
13.4
63.39
31.89
1.34
33.00
15
MC
2
10 / 25
Mono
5
72
24
35.8
4.9
44.4
5.3
-0.35
-145
1.40
SunPower
SPR-205-BLK
205
+/-5.0
15.3
16.5
61.39
31.42
1.81
33.00
15
MC
10
12 / 25
Mono
5
72
24
40.0
5.1
47.8
5.5
-0.38
-137
3.50
SPR-210-WHT
210
+/-5.0
15.7
16.9
61.39
31.42
1.81
33.00
15
MC
10
12 / 25
Mono
5
72
24
40.0
5.3
47.7
5.8
-0.38
-137
3.50
SPR-315-WHT
315
+/-5.0
17.9
19.3
61.39
41.18
1.81
53.00
15
MC
5
12 / 25
Mono
5
96
24/48
54.7
5.8
64.6
6.1
-0.38
-177
3.50
Suntech
Power
STP 160S-24/Ab-1
160
+/-3.0
11.6
12.5
62.20
31.81
1.38
34.17
15
MC
5
12 / 25
Mono
5
72
24
34.4
4.7
43.2
5.0
-0.48
-150
0.87
STP 160-24/Ab-1
160
+/-3.0
11.6
12.5
62.20
31.81
1.38
34.17
15
MC
5
12 / 25
Poly
5
72
24
34.4
4.7
43.2
5.0
-0.47
-150
2.30
STP 165S-24/Ab-1
165
+/-3.0
12.0
12.9
62.20
31.81
1.38
34.17
15
MC
5
12 / 25
Mono
5
72
24
34.8
4.7
43.6
5.0
-0.48
-150
0.87
STP 165-24/Ab-1
165
+/-3.0
12.0
12.9
62.20
31.81
1.38
34.17
15
MC
5
12 / 25
Poly
5
72
24
34.8
4.7
43.6
5.0
-0.47
-150
2.30
STP170S-24/Ab-1
170
+/-3.0
12.4
13.3
62.20
31.81
1.38
34.17
15
MC
5
12 / 25
Mono
5
72
24
35.2
4.8
43.8
5.1
-0.48
-150
0.87
STP170-24/Ab-1
170
+/-3.0
12.4
13.3
62.20
31.81
1.38
34.17
15
MC
5
12 / 25
Poly
5
72
24
35.2
4.8
43.8
5.1
-0.47
-150
2.30
STP 175S-24/Ab-1
175
+/-3.0
12.7
13.7
62.20
31.81
1.38
34.17
15
MC
5
12 / 25
Mono
5
72
24
35.2
5.0
44.2
5.2
-0.48
-150
0.87
STP175-24/Ab-1
175
+/-3.0
12.7
13.7
62.20
31.81
1.38
34.17
15
MC
5
12 / 25
Poly
5
72
24
35.2
5.0
44.2
5.2
-0.47
-150
2.30
STP180S-24/Ab-1
180
+/-3.0
13.1
14.1
62.20
31.81
1.38
34.17
15
MC
5
12 / 25
Mono
5
72
24
35.6
5.1
44.4
5.4
-0.48
-150
0.87
STP180-24/Ab-1
180
+/-3.0
13.1
14.1
62.20
31.81
1.38
34.17
15
MC
5
12 / 25
Poly
5
72
24
35.6
5.1
44.4
5.4
-0.47
-150
2.30
Sunwize
SW100C
100
+/-5.0
9.9
15.0
56.93
25.43
1.34
26.00
10
J-Box
1
NA / 25
Mono
8 x 3.5
48
24
23.0
4.4
28.5
5.0
-0.50
-143
3.39
SW115
115
+/-5.0
11.4
15.0
56.93
25.43
1.34
26.00
12
J-Box
1
NA / 25
Mono
6
36
18
16.7
6.9
21.0
7.7
-0.50
-105
6.01
SW120
120
+/-5.0
11.9
15.0
56.93
25.43
1.34
26.00
13
J-Box
1
NA / 25
Mono
6
36
18
16.7
7.2
21.0
8.0
-0.50
-105
6.24
SW150
150
+/-5.0
10.7
15.0
66.61
30.27
1.65
44.00
15
MC
1
NA / 25
Mono
8 x 3.5
72
36
33.4
4.5
42.0
5.1
-0.50
-210
3.99
SW155
155
+/-5.0
11.1
15.0
66.61
30.27
1.65
44.00
15
MC
1
NA / 25
Mono
8 x 3.5
72
36
33.4
4.7
42.0
5.3
-0.50
-210
4.12
SW160
160
+/-5.0
11.4
15.0
66.61
30.27
1.65
44.00
15
MC
1
NA / 25
Mono
8 x 3.5
72
36
33.4
4.8
42.0
5.4
-0.50
-210
4.24
Yingli
YL 120 (17)
120
+/-5.0
12.4
12.0
51.90
26.80
1.45
26.40
N/A
J-Box
2
10 / 25
Poly
NA
36
NA
17.5
6.9
22.0
7.6
-0.45
-81
7.60
www.homepower.com
PV buyer’s guide
77
home power 121 / october & november 2007
78
PV buyer’s guide
Maximum Power Current (Imp)
Definition: Maximum amperage produced by a module or array
when exposed to sunlight and connected to a load.
Importance: Maximum power current is one specification used
when sizing an array for a given inverter or charge controller.
Open-Circuit Voltage (Voc)
Definition: The maximum voltage generated by a PV module or
array when exposed to sunlight with no load (inverter or battery)
connected.
Importance: Open-circuit voltage will increase as PV module
temperature decreases. To eliminate the possibility of
overvoltage conditions that will damage most inverters and
charge controllers, a maximum Voc calculation based on the
coldest historical temperature for a given site is required during
system design.
Short Circuit Current (Isc)
Definition: The amperage generated by a PV module or array
when exposed to sunlight with output terminals shorted.
Importance: Modules will not operate at short circuit in the field
unless they are incorrectly wired. Using a digital multimeter to
check the current of an individual module will briefly short the
terminals while the measurement is being taken, allowing you
to compare the actual output to the manufacturer’s specification
during troubleshooting. Additionally, Isc specifications are used
for calculating the appropriate amperage rating of overcurrent
protection devices.
Maximum Power Temperature Coefficient
(% per degree C)
Definition: The change in module output power in percent-per-
degree Celsius at temperatures other than 25°C (STC temperature
rating).
Importance: Module voltage decreases as cell temperature
increases. A maximum power temperature coefficient is one metric
that enables you to predict the real-world power output of an array
that’s operating at elevated cell temperatures. In hot climates, cell
temperatures can reach an excess of 70°C (158°F). For example,
consider a module maximum power rating of 200 watts at STC, with
a temperature coefficient of minus 0.5% per degree C. At 70°C, the
actual output of this module would be approximately 155 watts.
Open-Circuit Voltage Temperature Coefficient
(mV per degree C)
Definition: The change in module open-circuit voltage in
millivolts per degree Celsius at temperatures other than 25°C
(STC temperature rating).
Importance: Open-circuit voltage will increase as cell temperature
decreases, based on the 25°C STC reference temperature. In
turn, Voc will decrease as cell temperature increases. Applying
the open-circuit voltage temperature coefficient is one way to
determine absolute maximum Voc at a site’s coldest historical
temperature, and allows you to calculate the reduction in module
or array voltage at elevated temperatures.
Short-Circuit Current Temperature Coefficient
(mA per degree C)
Definition: The change in module short-circuit current in
milliamps per degree C at temperatures other than 25°C (STC
temperature rating).
Importance: Short-circuit current will increase in varying degrees
as cell temperature increases and Voc decreases. This relationship
is interesting in terms of module function, but is not particularly
relevant in most system designs.
Access
Joe Schwartz (joe.schwartz@homepower.com), Home Power CEO
and executive editor, holds a Renewable Energy Technician license
in Oregon. His home and home office are powered exclusively by
renewable energy.
Special thanks to Home Power Technical Assistant Doug Puffer for
module specification research and compilation.
Images on pages 70 & 71 (clockwise from upper left): Courtesy of
BP Solar (SX 3195 module); Canadian Solar Inc. (CS5A-180 module);
Advent Solar (240 module); Day4Energy (48MC 190 module).
Module Manufacturers:
Advent Solar • www.adventsolar.com
BP Solar • www.bpsolar.com
Canadian Solar Inc. • www.csisolar.com
Day4Energy • www.day4energy.com
Evergreen • www.evergreensolar.com
GE • www.gepower.com/solar
Kyocera • www.kyocerasolar.com
Mitsubishi • www.mitsubishielectric.com/solar
Sanyo • www.sanyo.com
Schott • www.us.schott.com
Schuco • www.schuco-usa.com
Sharp • www.solar.sharpusa.com
SolarWorld • www.solarworld-usa.com
SunPower • www.sunpowercorp.com
Suntech Power • www.suntech-power.com
Sunwize • www.sunwize.com
Yingli • www.yinglisolar.com
Courtesy www.solarworld-usa.com
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Midnitesolar #121 cheers ad mnpvPage 1 7/19/2007 12:43:14 PM
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home power 121 / october & november 2007
82
CHOOSING A CIRCULATOR FOR
SOLAR HOT WATER SYSTEMS
by Chuck Marken
Pick the
Right Pump
Some things—the coldest beer or the biggest slice of pizza— are easy to pick, but
selecting the right pump for a solar hot water (SHW) system isn’t that simple. Pump
choices are numerous—DC or AC powered; bronze, stainless steel, iron, or plastic;
high, medium, or low head. But picking the right pump doesn’t have to be a painful
experience. Here’s some sound advice on how to best match a pump to your SHW
system for years of trouble-free service and high performance.
Grundfos 15-18 SU pump. The “S” stands for stainless steel
and the “U” is for union (union set shown, extra cost).
El-Sid 10 PV, DC pump. Although it may run on a 10-watt PV
module, this pump is usually coupled with a 20-watt module to
make sure it starts in all applications.
Low-Head Pumps
Pumps used in solar heating systems
are called hot water circulators. They
move fluid through the solar collectors
and/or heat exchanger to where the
heated fluid can be stored or used. A
circulation pump is made up of a motor,
impeller, and impeller housing. The
motor spins the impeller in the housing
and, through centrifugal force, moves
liquid through a plumbing circuit.
Circulation pumps must be primed
or wet when they start, as they are
not designed to suck liquid into the
impeller. Unlike positive-displacement
pumps, which can lift a fluid from
below the pump, circulation pumps
must have the impeller housing filled
with the circulating fluid at all times.
They are used in closed plumbing loops
that are always entirely filled, or in
systems with the pump situated lower
than a tank’s water level.
Common circulation pumps have
maximum service temperatures of
about 140°F, but almost all hot water
circulators are rated above 200°F. Hot
water circulators are a must for virtually
all active-type solar water heating
systems.
Selecting a pump is not difficult—your solar hot water
system design will dictate which pumps are suitable, with
alternatives falling into three application criteria:
• Pump material
• Pump head and flow rate
• Power source
The Right Materials
Oxygen is good for us, but bad for iron pumps. Oxygen
creates a corrosion problem in cast iron pumps, just as steel or
iron rusts (oxidizes) when exposed to water and air. The less
expensive circulation pumps are made with an iron impeller
housing. They are usable in closed-loop systems where little
or no oxygenated water exists.
But in open and potable water loops, an iron pump will
corrode, impeding the flow or stopping it completely, often
within a few months. Domestic hot water loops need pumps
with a bronze, stainless steel, or plastic impeller housing
and impeller. These corrosion-resistant materials are also
recommended for any drainback system that does not use
distilled water as the collector loop fluid.
The most common domestic hot water (DHW) pumps are
bronze or stainless steel but plastic housing DHW pumps also
can last for decades. The cost of bronze pumps has increased
quite a bit in the last few years with the increase in copper
prices. This has made stainless steel pumps more attractive.
Head & Flow
Depending on their application, pumps must overcome two
different types of head—atmospheric and friction. Atmospheric
head is the difference in height between the natural level of the
liquid when the pump is off, and the height to which the pump
needs to push the liquid when the system is operating. The
pump must develop enough pressure to push the circulating
fluid to the top of the loop or, in the case of a drainback solar
water heater, to the top of the collectors. If the pump falls short,
www.homepower.com
pump primer
83
Pick the
Right Pump
Taco 006-B4, domestic hot water pump. Note the 3
/4-inch
copper solder connections.
Impeller
Impeller
Housing
Pump
Motor
Capacitor Cover
(AC pumps only)
Typical flange pump pieces.
Flange Set
Medium-Head Pumps
the system will not function. Pumps in a plumbing circuit that
always remains full of liquid do not need to overcome any
atmospheric head. These kinds of loops include closed-loop
antifreeze and direct-pump open systems.
Friction-head loss is the resistance to flow due to the
circulating fluid’s contact with the pipe walls. Frictional
head increases with smaller pipe diameter, increased length,
changes in direction (like elbows, etc.), and increased flow.
Given the details of those factors, frictional head loss can
be accurately calculated. But normally, those factors are
not significant enough to bother calculating in small solar
heating systems—except in rare circumstances such as very
long piping runs (100 feet or more) with small tubing.
The flow rate through solar collectors should meet the
manufacturers’ specifications, but there is a good deal of fudge
home power 121 / october & november 2007
84
pump primer
Installation Notes
✔ You can put two pumps in series to double the
total head pumped. But beware: Using series or
stacked pumps to achieve the head required in some
drainback systems can cause big problems. If one
pump quits during colder months (and they all quit
eventually), and the other keeps pumping, it could
lift the water just high enough to where it can sit and
freeze. The frozen pipe can burst, and then the system
could pump all the water in its drainback tank into
the attic. This is one reason for the less-than-stellar
reputation of drainback systems in some parts of the
United States. The solutions to this head problem
are to raise the drainback tank to a level that will
accommodate the head of the chosen pump (see how
James Dontje solved this in his article in HP120) or to
select a higher-head pump if available.
✔ Many new pump installations will need a flange set
or union set to connect the pump to the piping system.
Make sure you have the additional parts you need before
you start work on the system.
✔ Installing two pumps in a parallel piping arrangement
will increase the flow of the circulating fluid, but will not
increase the total head.
✔ All the SHW pumps mentioned in this article are
classified as “fractional horsepower” and don’t require a
separate electrical circuit. However, fractional hp pumps
do require a disconnect—an appropriately rated switch
or breaker or a UL-approved cord and plug connection.
A Grundfos 15-42 iron pump suitable for most small-
and medium-sized antifreeze-type solar water heaters
(shown with pump flange set).
The March 809-HS magnetic drive, bronze DC pump needs a 50-
watt module to pump to its rated 15-foot head. The magnetic
drive tends to be noisier than other types of pumps.
Head (Ft.)
Flow (GPM)
35
30
25
20
15
10
5
0
0
5101520253035404550
1 UP 26-116 F; 2 UP 26-99 F; 3 UP 43-75 F/UP 50-75 F; 4 UP 26-96 F;
5 UP 26-64 F; 6 UP 15-42 F BRUTE II; 7 UPS 15-58F/FC (Spd 3);
8 UP 15-10 F/FR; 9 UP 15-100 F; 10 UP 26-120 U
4
2
1
5
3
7
8
96
10
Grundfos AC Pump
Performance Curves
A pump’s performance under various conditions is shown
by its “pump curve.” This performance curve is typically
presented as a graph or a table, with selected flow rates given
at different pump pressures. The pressure a pump exerts is
usually expressed in feet (sometimes decimeters) of head.
Feet of head is a more useful way of expressing the pressure
in real-world circumstances and is used in most pump curves.
It can also be expressed in pounds per square inch (psi),
where 1 psi equals 2.31 feet of head. In graph form, the head
is the vertical axis and the flow is the horizontal axis. As you
can see in the example graph (opposite page), as the head
decreases, the flow increases.
AC or DC?
One of your final considerations for choosing a pump depends
on whether you’re planning to use AC or DC to power it.
Both kinds of pumps are available, but the range of available
DC pumps is much narrower than for AC. AC pumps have
an unlimited energy supply if they are powered by a reliable
utility grid. DC pumps can be run directly by a PV module and
make a solar water heating system independent of the grid.
One way to approach the DC and AC pump choice is to
examine relative system efficiencies. The efficiency of some
heating systems is rated by the relationship of the amount of
energy output to the energy input. If you have a system that
produces a certain amount of heat with half the equivalent
electrical input, the “coefficient of performance” (COP) is 2.
Produce four times as much hot water as the amount of energy
input from electricity and the COP is 4. We can use this same
methodology in evaluating the efficiency of SHW pumps.
pump primer
85
A Taco 009F high-head iron pump, suitable for most
drainback and larger antifreeze systems.
High-Head Pumps
factor here. Solar collector loops will operate efficiently over a
wide range of flow rates, but choosing too large a pump can cost
more up-front and will use more energy. And an undersized
pump without sufficient head in a drainback system is a
disaster—the system just won’t work. Collector manufacturers’
recommended flow rates are usually published in their literature.
If not, you can find this information in the OG-100 ratings
directory (see Access).
www.homepower.com
Solar Pump Specifications
AC Pumps
VoltsWatts
Head
Category
Cutoff
Head (Ft.)
Gpm at
Head
Pump
Material
Suitable Applications
Price
Taco 009F
120
168
High
34.00
5 at 20 ft.Iron
Drainback or large antifreeze systems
$255
Taco 009B
120
168
High
34.00
5 at 20 ft.Bronze
Drainback systems
420
Grundfos 26-96 F
120
205
High
30.00
15 at 14 ft.Iron
Drainback or large antifreeze systems
297
Grundfos 26-96 BF
120
205
High
30.00
15 at 14 ft.Bronze
Drainback or large antifreeze systems
325
Taco 011F
120
211
High
30.00
15 at 18 ft.Iron
Drainback or large antifreeze systems
273
Grundfos 15-42 F
120
85
Medium
16.00
10 at 9 ft.Iron
Drainback or large antifreeze systems
108
Taco 008F
120
95
Medium
16.00
10 at 8 ft.Iron
Drainback or large antifreeze systems
158
Taco 008B
120
95
Medium
16.00
10 at 8 ft.Bronze
Drainback systems
319
Taco 006B
120
62
Low
8.00
5 at 5 ft.Bronze
DHWb
systems
179
Grundfos 15-18 SU
120
85
Low
7.00
5 at 5 ft.Stainless DHWb
systems
179
DC Pumps
March 809-BR-HS, 12 VDC
12
50
Medium
15.50
4 at 8 ft.Bronze
Drainbacks or large antifreeze systems$228
March 809-BR, 12 VDC
12
20
Low
7.00
3 at 3 ft.Bronze
DHWb
systems
200
El-Sid 20 PV-direct
12
20a
Low
4.17
3 at 42 in.Bronze
DHWb
or small antifreeze systems
334
El-Sid 10B12
12
10
Low
3.33
2 at 35 in.Bronze
DHWb
or hydronic heating systems
242
El-Sid 10 PV-direct
12
10a
Low
3.33
2 at 35 in.Bronze
DHW or small antifreeze systems
245
Note: The El-Sid warranty only covers pumps to temperatures up to 175°F, which could be a problem in collector loops that experience higher temperatures.
a
Double the PV wattage when not using water as a heat-transfer fluid; in some cases, even circulating water will require a larger PV module to start the pump
reliably. b
Potable water
Using a utility-powered AC pump for your solar
water heating system will give you a COP between
12 and 25, and this is an excellent value compared to
electric water heaters, which have a COP of 1.
But the COP will never be as good as a DC PV-powered SHW
system. DC hot water circulation pumps can have a higher
COP than AC pumps because there is no traditional energy
input if a PV module powers the system. If you use a solar-
electric module to power the pump, your COP is infinite—
you’re not adding any input energy. The sun provides
it all, and you get something for nothing after the initial
investment. PV-powered systems are also immune to utility
outages. This is a big plus with antifreeze systems, since the
collectors can overheat on sunny days if the pump stops
operating due to a power failure. An overheated collector can
actuate the pressure-relief valve, which will make it necessary
to recharge the system with antifreeze solution. In some cases,
the overheating can be so severe that the antifreeze solution
will be compromised to the point of needing replacement.
Although it seems like a no-brainer to go with a DC PV-
direct power source for your solar water heater pump—not
so fast. A few other factors can influence your decision about
the power source:
• Some DC pumps are noisier than AC pumps, which can
make an installer think twice about the placement of a
DC pump.
• High-head drainback DC pumps are few and far between.
Finding a reliable high-head DC hot water circulator
is impossible at this time, limiting the head of a DC
drainback system to about 15 feet.
• Any given PV module and SHW collector are rarely a
perfect match. The PV module often will “outproduce”
the collector and the pump may run early in the morning
or late in the afternoon when the collector isn’t producing
useful heat. The result? Unwanted pump operation can
actually cool the water in the solar storage tank. Until
recently, no DC-powered differential controllers were
available to limit this unwanted pump operation. Art
Tec (see Access) recently began manufacturing a DC
differential controller that optimizes pump run-time in
PV-direct SHW systems.
AC hot water circulators are firmly entrenched in
normal distribution in the United States and are therefore
less expensive and easier to procure. A DC pump will cost
more than an AC pump of the same head and category, and
the PV module will add to the cost—but if it fits into your
design and budget, the extra cost is well worth the expense.
PV-powered DC pumps are normally the optimal choice for a
solar heating system except in high-head drainback and very
large antifreeze systems.
The Fine Print
Knowing how to decipher the fine print on the pump can give
you valuable insight into whether or not it’ll be a good match for
your SHW system. For example, the “15-18 SU” model number
of a Grundfos pump tells you that the impeller housing inlet is
15 millimeters and the maximum head is 18 decimeters; “S” is
for stainless steel, and “U” is for union attachment.
Other manufacturers have model numbers that may also
denote the power consumed or the pump construction. An
“F” in a model name usually denotes a flange iron pump,
which can make the pump housing easily removed and
replaced. “B” stands for bronze, so a “BF” would be a bronze
flange pump. Look at the Solar Pump table (previous page)
to see some of the relationships between model numbers and
specifications.
Common Pumps
Several pumps and manufacturers are listed in the table and
Access. The models listed were included because they are
readily available and most folks in the solar industry are
familiar with them, but there are also others on the market.
One very important point: Make sure any circulation pump
you consider for a SHW system is intended for hot water—at
least 200°F for most systems.
Besides that, knowing a few simple rules and the
manufacturer’s pump specifications is all you need to make
an intelligent choice, whatever your needs. After almost thirty
years installing and servicing solar hot water circulation
pumps, almost all the models I’ve used seem very durable
and long lasting. So pick your pump(s) and get into some
really hot water.
Access
Contributing editor Chuck Marken (chuck.marken@homepower.
com) is a New Mexico licensed plumber, electrician, and heating
and air conditioning contractor. He has been installing and servicing
solar thermal systems since 1979. Chuck is a part-time instructor
for Solar Energy International and the University of New Mexico.
Art Tec • 866-427-8832 • www.arttec.net • DC differential
temperature controller
Solar Rating and Certification Corp. • www.solar-rating.org •
OG-100 ratings directory
Pump Manufacturers:
Bell & Gossett • 847-966-3700 • www.bellgossett.com
Grundfos Pumps Corp. • 913-227-3400 •
www.grundfos.com
Ivan Labs • 561-747-5354 • El-Sid pumps
March Manufacturing Inc. • 847-729-5300 •
www.marchpump.com
S. A. Armstrong Ltd. • 416-755-2291 •
www.armstrongpumps.com
Taco Inc. • 401-942-8000 • www.taco-hvac.com
home power 121 / october & november 2007
86
pump primer
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Your Partner for Windows and Solar Products
In August 2006, I heard from a friend at
Hewlett-Packard that a former co-worker
of hers had designed a new solar shading
analysis tool that I should check out. Two
weeks later at the SolFest renewable
energy fair, Willard MacDonald,
president of Solmetric, walked up to
the Home Power booth with the tool my
friend had mentioned. After a 15-minute
guided tour of Solmetric’s SunEye, it
felt like solar site analysis had just been
launched into the twenty-first century.
Solar Site Analysis
Home Power regularly stresses the
importance of accurate solar site
assessment. PV generation will be
crippled if the array is installed in
a location with excessive shading.
Shading also affects the productivity of
solar hot water collectors, although to a
lesser degree than for PV modules. And
shading analysis is important when
designing passive solar buildings—it
helps determine optimal building
orientation, window locations, or trees
that might need to be removed (or
planted) to improve or limit solar access
for particular sides of a structure.
SunEye Overview
The Solmetric SunEye is a handheld solar access and shade
analysis tool. It integrates a Hewlett-Packard iPAQ PDA, used as
the processor and user interface, with a digital camera, compass,
and bubble level. Solmetric has refitted the iPAQ with custom
software. The touch-screen interface provides easy navigation
and operation with the touch of a finger. With a suggested
retail price of $1,355, the SunEye is designed and built for PV,
solar thermal, and passive solar building professionals (and is
compliant with California’s incentive programs).
Setup
The initial SunEye setup takes just a few minutes—complete the
guided touch-screen calibration, set the date and time, and the
unit is good to go. The SunEye Desktop Companion software,
home power 121 / october & november 2007
88
Solar Site Evaluation Tool
by Joe Schwartz
Solmetric SunEye
Fish-Eye Lens &
Digital Camera
Compass
Protective
Cover
Power On/Off
Button
Touch Screen
USB &
Charge Port
Five-Way Navigation
Button
Neck Strap
Attachment Points
Bubble
Level
provided on CD-ROM, enables you to export collected site
data to a Windows-based computer for further analysis, report
generation, and archiving. Free connectivity software can be
downloaded to allow the SunEye to interface with your PC,
and SunEye software updates are made available on Solmetric’s
Web site. Mac operating systems are not supported.
Surveying a Site
Once you’re ready to perform a solar site survey, power up
the SunEye, create a new session, and select the city and state
nearest to the site location. Alternatively, latitude, longitude,
and magnetic declination can be entered manually. The array
orientation (azimuth) and tilt angle default to true south
and latitude respectively. But both of these variables can be
changed in the Skyline Properties menu. This feature also
allows you to determine solar access for arrays oriented east
or west of true south, as well as at different tilt angles.
To capture a skyline graphic of the site, fully open the
SunEye cover and select “Skyline” from the Display menu.
Orient the compass toward magnetic south (declination is
automatically calculated based on the selected location), and
use the bubble level to level the tool. Then, simply touch the
“Snap” icon to capture the image. Holding the curved edge
of the SunEye firmly against your body will help you keep
the tool steady.
The SunEye can store skylines and data for more than 50
site readings before uploading to your computer for archiving.
The captured skyline is automatically saved, and an annual
solar access percentage is instantly generated, along with
separate percentages for May to October, and November to
April. Changing to the “Monthly Solar Access” view generates
a month-by-month bar graph of solar access percentages.
One great feature of the SunEye is its option to average
multiple skylines from a single survey session. This is useful
when surveying the entire area being considered for a large PV
array. For example, a skyline from each corner of the potential
array site can be captured to calculate the average solar access.
This approach also helps determine daily shading patterns on
various segments of the proposed array to plan the optimal
configuration and layout of individual PV series strings.
Image Editing & Reports
Both the SunEye and the Desktop Companion include skyline
image editing software to fine-tune any shading patterns that
may not have been interpolated accurately by the SunEye
software. The image-editing tool also lets you “remove”
objects, such as trees that are creating unwanted shade in
a skyline/sun path image. At the touch of a finger, you
can remove a tree that’s causing excessive shading, and
automatically recalculate the solar access that would be
available if the real obstruction were removed.
The SunEye Companion software generates a
comprehensive report that includes sun-path images, monthly
solar access bar graphs, and links to spreadsheet-compatible
tables for a survey session. The tables include data for daily
www.homepower.com
89
Solmetric SunEye
Details
MSRP: $1,355
Warranty: One year
Computer System Minimum Requirements: Windows
Vista, Windows XP, or Windows 2000; 700 MHz
processor, 256 MB RAM, 20 MB hard drive space; and
Internet Explorer
Solmetric SunEye
SunEye’s “Monthly Solar Access” display.
SunEye’s sun-path display.
solar access, insolation, shading, and obstruction elevations
for further analysis.
SunEye Battery Basics
The SunEye can be charged using the provided AC charger,
from a computer via the USB cable, or using an optional DC
car charger. The lithium-ion (Li-ion) battery in the iPAQ has
an expected life of 400 to 500 full charge cycles. At a typical
discharge of 50%, the manufacturer estimates a battery life
of 800 to 1,000 cycles. The battery is not removable, so in
the case of failure, the unit must be shipped to Solmetric
for replacement. Solmetric policy keeps the typical battery
replacement turnaround time to one day, plus shipping time.
Loaner units are available if a battery replacement would
result in unacceptable downtime for the user.
In good condition, a fully recharged SunEye battery will
power the unit for about three hours of continuous use. The
Li-ion battery has a fairly high self-discharge rate and will
completely lose charge after about nine days if left unused
without charging. Data will be held in memory in this case,
but the touch-screen and date and time will need to be reset. If
you’re used to keeping cell phones, MP3 players, PDAs, and
the like recharged and ready for use, adding the SunEye to
your charging routine will be easy.
Solmetric recommends keeping the unit continuously
connected and charging so it’s ready to go when you are.
I was curious about how much energy the SunEye would
draw under a constant float charge. After 24 hours, the Kill
home power 121 / october & november 2007
90
REview
A Watt power meter I used for testing didn’t register a single
kilowatt-hour (KWH). In float service, the SunEye draws
between 0 and 1.2 watts. Over 24 hours, I estimate the unit
would consume less than 20 watt-hours.
More to Come
Solmetric is developing a new version of their SunEye
software package called SunEye Pro. This major software
upgrade is expected to cost less than $200 and will be
compatible with existing SunEye units. The upgrade will
incorporate state-specific incentive program shading criteria.
The SunEye Pro software will report the optimal array tilt and
azimuth for a given site, and data output will be converted
to KWH in addition to the percentage figures provided by
the current SunEye software. One great advantage of the
SunEye’s software-based design is the ability to upgrade the
unit as new features become available—this tool will just get
better and better.
Access
Joe Schwartz (joe.schwartz@homepower.com), Home
Power CEO and executive editor, holds a Renewable Energy
Technician license in Oregon. His home and home office are
powered exclusively by renewable energy.
Solmetric Corp. • www.solmetric.com • Manufacturer
DC Power Systems • www.dcpower-systems.com •
SunEye distributor
E L E T
C R O N C O N N E C T I O N
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home power 121 / october & november 2007
94
f you were to stop people on the street and ask them to name states
known for strong growth in solar-electric system installations, chances
are that few would mention New Jersey. But the state has some of the
most favorable residential and commercial solar incentives in the nation.
Here’s how a New Jersey couple put solar electricity to work for them—
at home and on their rental properties.
by Regina Anne Kelly
Profiting
Peter, Tanya, and Noelle Ptak in front of their PV-powered residence.
fromPV
In 2006, the total number of residential and small business
grid-tied solar-electric systems in New Jersey topped 1,500.
This was an exponential increase from just five years earlier,
when there were only six installed in the state. The impetus
for this amazing change? New Jersey’s incentive-based clean
energy program, which was launched in 2001.
Strong financial incentives enticed Peter and Tanya Ptak
to invest in three solar-electric systems. In 2005, they installed
a system on their Red Bank home and, because New Jersey’s
solar support was so sweet, decided to have two more
systems installed on their rental properties in 2006.
PV’s Appeal
The Ptaks wanted to put an end to their electric bills and
support clean energy in a state that generates almost half its
electricity by burning coal. Then they discovered that New
Jersey’s Clean Energy Program (NJCEP) could allow even a
family with an average income to afford an investment in
solar electricity.
Especially enticing was the short economic payback period
for PV systems under NJCEP’s program. “Many people here
pay [their utility] $200 per month for electricity,” says Peter.
“When do they finish paying that off? Never!” In contrast,
investing in a solar-electric system can be likened to paying
electricity bills several years in advance, and at a fixed rate.
With New Jersey’s attractive renewable energy incentives, the
Ptaks calculated that a properly sized PV system that would
meet all their electricity needs could pay for itself within
seven to ten years. After that, all the electricity it produces is
not only free, but surplus electricity generated means that the
system will be earning them money.
When the Ptaks installed their first system, they
received a one-time rebate of 70% of the system’s total
cost. New Jersey also issues Solar Renewable Energy
Certificates (SRECs)—financial credits granted by the
state’s public utility commission. Owners of systems that
produce energy from renewable sources receive credits
for the clean energy their systems generate—credits they
can then sell to electricity suppliers to help them meet the
state’s renewable portfolio standard.
Another important financial incentive is net metering,
by which utilities credit owners of grid-tied PV systems at
the retail rate for any electricity their systems produce, until
their cumulative electricity use is offset. In New Jersey,
annualized net metering zeroes a customer’s account at
the end of a 12-month cycle, based on the system’s initial
commissioning date. This allows surplus energy generated
during sunnier months to be banked, and the credits
applied against utility electricity used during seasons when
the PV system produces less energy. At the anniversary
date, any surplus energy credit generated beyond what the
home or business has consumed is purchased by the utility
at their “avoided cost” rate (usually about 25% to 30% of
the retail rate per kilowatt-hour), and a check is issued to
the customer.
The up-front incentives, coupled with solar energy
certificates, a solid net-metering program, and the prospect of
generating pollution-free power, appealed to the Ptaks. They
www.homepower.com
solar profit
95
were consuming approximately 6,800 KWH of electricity per
year, and spending up to $90 per month on electricity for
lighting, localized space heating, and appliances. Investing
in PV systems to power both their home and rental buildings
would be good for the environment—and their pocketbooks.
Solar Savings
Sea Bright Solar, a PV system design and installation company,
provided the Ptaks with an estimate for a batteryless 5.44
kilowatt (KW) solar-electric system that would offset all their
home’s annual electricity usage. The Ptaks took advantage
of Sea Bright’s payment program of floating the rebate, a
common practice among New Jersey installers that allows
customers to divide the after-rebate cost into installments. To
ease any impact on their budget, they divvied the total cost
into three payments: a deposit, a payment upon equipment
delivery, and a final payment after the system passed local
electrical and building inspections.
Since the system’s installation in 2005, besides eliminating
their electricity bill and saving them $780 in their first year, it
has earned the Ptaks $1,000 through SREC sales. In 2006, on
the system’s first anniversary, they also received a $65 check
from Jersey Central Power & Light for the surplus energy
their system generated.
The Ptaks predict additional “future” savings beyond their
utility bills and SRECs if they ever decide to sell their home.
According to a report funded by the U.S. Environmental
Protection Agency and the Department of Housing and Urban
Development, every dollar saved in utility bills the first year
that a PV system is installed represents a $20 increase in
property value. Based on this estimate, the Ptaks’ PV system’s
first-year savings would translate into a property value
increase of $15,600—well above their initial investment of
about $13,000. Not factoring in the increase in property value,
their financial break-even point to recoup the system’s initial
cost will only be about eight years.
After installing PV on their residence, the Ptaks also installed
solar-electric systems on their rental properties.
Renewable Rentals
Their home PV system’s many benefits inspired Peter and
Tanya to consider solar electricity for their two rental homes,
across the street from their house. After some serious number-
crunching, they realized installing PV systems on the two
rentals would make them eligible for a combined rebate of
more than $50,000. Plus, they’d own the SREC production of
their rental properties’ systems, estimated to generate about
$2,500 in annual income. Installing the systems as a business
venture also meant the Ptaks could take a 30% federal
investment tax credit.
It was too good to pass up. In the fall of 2006, the Ptaks
had a 5.27 KW system installed on one three-bedroom, single-
family rental property and a 4.59 KW system installed on their
other Cape Cod-style rental home, as part of a Solar Energy
International PV design and installation class. Three primary
criteria determined the size of each system: the area of the
available south-facing roof, the Ptaks’ desire to eliminate as
home power 121 / october & november 2007
96
solar profit
KWH
Meter:
To utility
grid
AC Service
Entrance:
To 120/240 VAC
loads
G
Inverter:
Aurora PVI-3000, 3,000 Wp,
90–580 VDC operating
range, 240 VAC output
Photovoltaics: 12 BP SX170, 170 W
each at 35.4 Vmp, wired in two
6-module series strings for 2,040 W
total at 212.4 Vmp
DC Combiner &
Disconnect
Photovoltaics: 20 BP SX170, 170 W each at 35.4 Vmp,
wired in two 10-module series strings for 3,400 W total at
354 Vmp
Inverter:
Aurora PVI-3000, 3,000 Wp,
90–580 VDC operating
range, 240 VAC output
Note: All numbers are rated, manufacturers’
specifications, or nominal unless otherwise specified.
H2
H1
H2
100KWH
H1
AC
Subpanel
DC Combiner &
Disconnect
G
Two Power-One Aurora inverters synchronize the solar-electric
system’s output with the utility grid.
Ptak On-Grid PV
System (Home)
much of the buildings’ grid electricity use as possible, and a
unique rebate policy that considers two adjacent properties
with the same owner to be eligible for one combined rebate.
Under the current NJCEP solar rebate schedule, the greatest
rebate is available on systems that are no greater than 10 KW.
To maximize the rebate, Sea Bright Solar’s system design
fully utilized the available roof space on both houses, for a
combined system size of 9.86 KW—just under the maximum.
“Before installing the PV systems, I found that our
renters had a tendency to use—if not waste—more energy
than we, as homeowners, did,” says Peter. Housemates
typically would split the electric bill evenly, resulting in lower
individual costs—with little incentive to conserve energy.
Peter and Tanya were interested in encouraging more energy
conservation, while passing the solar savings on to their
tenants. They charge their tenants about 90% of the utility
value for the solar-generated electricity, while the tenants
are responsible for paying any utility balance beyond what
the PV system generates. “Charging a slightly reduced rate
for electricity makes it more enticing for them to rent,” says
Peter. “This keeps the properties rented longer, which keeps
our profit margin higher over the years.”
Practical PV Payoff
The Ptaks are passionate about the practical benefits of
tapping into the sun for electricity. They now have a minimal
to nonexistent electric bill and annually receive a check for
any surplus electricity their systems generate. They are also
proud to have effectively reduced their “carbon footprint,”
environmental pollution, and other associated impacts of
burning fossil fuels. Their home’s PV system alone saves about
9,100 pounds of carbon dioxide, 32 pounds of nitrogen oxide,
www.homepower.com
solar profit
97
Tech Specs
(Ptak Residence)
Overview
System type: Batteryless, grid-tie solar-electric
Location: Red Bank, New Jersey
Solar resource: 4.7 average daily peak sun-hours
Production: 540 AC KWH per month, average
Utility electricity offset annually: 100%
Photovoltaics
Modules: Thirty-two BP SX170, 170 W STC, 35.4 Vmp
Array: Two 6-module series strings parallel, 2,040 W
STC, 212.4 Vmp; two 10-module series strings parallel,
3,400 W STC, 354 Vmp; 5.44 KW STC total
Array disconnect: Two Square D, 30 A, 600 VDC
Array installation: UniRac mounts; south-facing; 12
modules mounted parallel to roof at 35 degree tilt; 20
modules mounted on elevated racks at 10 degree tilt
Balance of System
Inverters: Two Power-One (Magnetek) Aurora PVI-3000,
600 VDC maximum input voltage, 90–580 VDC operating
range, 240 VAC output
System performance metering: Internal inverter meters
& utility KWH meter
To maximize the solar energy rebate, the system design fully utilized the available roof space on the Ptaks’ rental properties.
and 52 pounds of sulfur dioxide from
being emitted each year, according to
National Renewable Energy Laboratory
estimates.
The Ptaks’ multiple PV systems also
have had a positive influence on their
community. “Everyone was basically
blown away,” says Peter. “I tell them
all about the program, and they become
very interested and want to learn more.
[Some of them may be] a bit put off by
the initial cost, but those who really
understand the concept realize that it is
ultimately an investment that pays off
in the long run.” One of Peter’s co-workers decided to have
an 8.5 KW ground-mounted system installed in 2006. Peter
says that several other homeowners he knows “have been
very interested in learning more about the systems that they
could feasibly install. People are intrigued by the ‘no electric
bill’ factor.”
Access
Regina Anne Kelly is a professional writer and the author
of Energy Supply and Renewable Resources (Facts On File,
2007). Her articles have appeared in several scientific and
trade journals. She holds an M.A. in English literature from
Fordham University and a B.A. in journalism and English
from Rutgers College.
Peter & Tanya Ptak • ptakpeter@hotmail.com
Sea Bright Solar • 866-SOLAR-1-S •
www.seabrightsolar.com • System installer
New Jersey Clean Energy Program •
www.njcleanenergy.com
Solar Energy International • www.solarenergy.org •
Workshop presenter
PV System Components:
BP Solar • www.bpsolar.com • PV modules
Power-One • www.power-one.com • Aurora inverter
UniRac • www.unirac.com • Array mounts
home power 121 / october & november 2007
98
solar profit
With favorable financial incentives for PV systems, it’s no
surprise that solar energy has had a strong start in New Jersey.
During the first six years of the New Jersey Clean Energy
Program (NJCEP), the state granted more than $120 million
in rebates for PV projects, with the highest number of rebates
and installations occurring in 2006. The total amount of rebates
given in 2006 was 1,670 times greater than that in 2001.
But with so many new systems going online with the help
of state funds, New Jersey’s Board of Public Utilities began
reducing the rebate in 2005. When the solar rebate program
launched, the NJCEP offered $5.50 per watt, or 70% of the
cost of the installed system (whichever was lower), up to a
maximum of 10 KW of installed capacity. As of August 2007,
the rebate is $3.80 per watt—smaller, but still substantial. The
NJCEP has announced a new rebate reduction to $3.50 per watt
effective September 1, 2007. However, due to high demand and
rapid growth of the program, some customers and installers
have been waiting more than a year to find out whether their
rebate applications have been accepted.
In an effort to smooth what has at times been a roller-coaster ride
for New Jersey PV system installers and potential customers,
NJCEP is investigating a performance-based rebate structure
for commercial systems and a performance-based/smaller up-
front rebate structure for systems less than 10 KW. Under the
performance-based model, consumers receive their incentives
on an ongoing basis as their systems produce clean energy, and
solar facility owners are awarded a cost-per-KWH incentive for the
electricity they generate with PV systems. This past spring, the
NJCEP implemented a pilot program in which the state does not
offer an up-front rebate, but instead compensates system owners
by awarding them SRECs (Solar Renewable Energy Certificates),
financial credits granted by the state’s public utility commission.
Significant financial incentives that support solar electricity
are not limited to New Jersey. About 20 states have their
own clean energy rebate programs that make solar energy an
attractive investment for residential and commercial energy
consumers alike, and individual utilities in these and other
states may offer their own incentive programs as well. (For
specifics, see the Database for State Incentives for Renewables
& Efficiency at www.dsireusa.org.)
A one-time federal tax credit of up to $2,000 is also available
for residential solar energy systems, and business owners
investing in renewable energy technologies are eligible for a
federal tax credit equal to 30% of their system’s costs.
Ptak System Economics
Residence (5.44 KW)
Rentals (9.86 KW)
Item
Amount$ Per KW
Amount$ Per KW
Installed cost
$42,704
$7,850
$75,922
$7,700
State rebate
-29,892
-5,495
-50,286
-5,100
SREC payments
-1,200
-221
-2,400
-243
Electrical savings
-850
-156
-1,600
-162
Federal tax credit & depreciation
0
0
-7,691
-780
Net Cost $10,762
$1,978
$13,945
$1,414
PV in New Jersey—Incentive Ups & Downs
www.homepower.com
99
Things that Work!
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Ordering or Information call
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ONEMeter: NEW FEATURES! Standard Features include Multiple
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home power 121 / october & november 2007
100
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home power 121 / october & november 2007
102
THE WHOLE PICTURE
Computer-Based Solutions
for PV System Monitoring
by Ryan Mayfield
he beauty of batteryless grid-tie PV
systems lies in their simplicity: Few, if
any, components with moving parts
translate into virtually maintenance-free
electricity generation. But the hands-
off nature of grid-tie PV can make it
easy for an owner to lose track of their
system’s daily operation and assume it
is functioning optimally—even if it isn’t.
Unless you tend to keep a close eye on
your electric utility bill, in some cases
months might go by before a problem is
detected.
PV Array
Inverter
AC Service
Panel
Production
Meter
Utility
Net Meter
Datalogger
or Gateway
Modem
1234
1234
10110101
01100111
Optional Sensors:
Irradiance,
ambient temperature,
cell temperature,
wind speed, etc.
World Wide Web
Web
Monitoring
Server
Web Browser
Several inverter
manufacturers now
provide wireless meters
to allow system monitoring
from any room in your house.
Local Monitoring Options
Meters & Wireless Displays. The simplest method for local
PV monitoring relies on the built-in meter that accompanies
most batteryless grid-tie inverters. Here, you can view basic
performance data that typically includes AC power, voltage,
and current, as well as DC array voltage, daily energy
production, and cumulative energy production since the
inverter was commissioned. Some inverters have transmitters
that broadcast data to a small wireless receiver that you
can place in a convenient location in your home for easy
viewing.
www.homepower.com
PV monitoring
103
While infrequent, PV system equipment failures or faulty
installation work can have a significant financial impact when
they go unnoticed. This is especially true of large installations,
or systems that receive performance-based incentive payments
tied to the kilowatt-hours a system generates. These potential
issues are being met by a wave of inverter-based and
third-party system monitoring solutions that, with a few
components and a computer or handheld mobile device with
Internet access, allow PV owners, installers, and integrators
to verify system performance on-site—or from the other side
of the globe.
There are two basic approaches for monitoring the
performance of your PV system with a computer—local
and Web-based. Local monitoring can be as simple as
checking the data your inverter collects and displays daily,
or using a local storage device, such as a datalogger or
computer, to store information collected by the inverter.
Web-based monitoring relies on either independent or
inverter-based communications, and a “gateway.” Besides
aggregating the data and serving as a node on your local
network, this can provide the connection to an outside
network (like your Internet service provider) to send the
data to the Web for display.
The Fronius datalogger can record information from up to
ten inverters. Fronius also offers free Web-based data hosting
via their new SolarWeb site.
Monitoring Battery-
Based Systems
Battery-based systems, both off- and on-grid, can be
monitored with more sophisticated equipment than a
standard battery amp-hour meter. Regular monitoring of
battery state of charge can make the difference between a
battery bank lasting ten years—or less than a year, if the
batteries are overdischarged or not fully recharged on a
regular basis.
Most battery-based inverter manufacturers offer local
monitoring solutions, using software either designed by the
manufacturer or by a third-party developer. Several third-
party solutions allow battery-based systems to be monitored
over the Web, including Chuck Wright Consulting, Draker
Solar, Fat Spaniel Technologies, RightHand Engineering,
and Watt Plot. Software that interfaces with inverter-direct
communication, as well as stand-alone, inverter-independent
datalogging equipment, is available.
Depending on the inverter design, performance data may
be available for only a fixed amount of time, and some of the
information may disappear with the sun when the system
stops producing energy for the day. In this case, reviewing
the details of your system’s performance after sunset becomes
an impossible task. Your utility KWH meter will always be
tracking the amount of energy your PV system generates, but
for users who enjoy or require access to both ongoing and
cumulative system data, basic inverter-based collection may
not be sufficient.
Computers & Dataloggers. If you want to collect and store
data over longer periods of time, or want the ability to
export system data to a spreadsheet program for further
analysis, the next step in local monitoring is to incorporate
an interface between the inverter and a data storage medium.
A common method is to connect the inverter directly to a
computer via a standard RS232 or RS485 serial connection.
The computer monitors and logs the system data, which
is generally the same information that’s tracked by the
inverter’s integrated meter. Software, either developed by
the inverter manufacturer or a third-party developer, runs
on the computer, stores the data, and presents it in a simple
graphical format. One potential drawback to this method is
that the computer must be running the monitoring software
for data to be collected. Another minor inconvenience is that
many newer computers do not have the older-style serial
ports. To make the connection to a USB port, you’ll need to
pick up an adapter.
Some inverter manufacturers offer add-on datalogging
devices that interface between the inverter and a computer.
These dataloggers usually have the ability to monitor multiple
inverters, allowing you to track individual inverter operation,
as well as the functioning of the entire PV system. The
datalogger collects and stores data independently, and enables
you to connect a computer at a convenient time to download
home power 121 / october & november 2007
104
PV monitoring
the data. The amount of data that can be stored is a function
of the datalogger’s memory capacity, the number of different
types of data being collected, and the rate of collection.
Many dataloggers have the flexibility to accept information
from additional environmental sensors, such as temperature
probes, irradiance sensors, and anemometers. You can essentially
build your own weather station and synchronize the collected
environmental data with your PV system data. When viewed
together, environmental and PV performance data can shed a
lot of light on how things like temperature and cloud cover affect
the voltage, current, and KWH output of your PV system. Some
dataloggers can also be used to monitor electrical loads or even
individual series strings within a PV array.
SMA’s WebBox provides a link the between the PV plant
and the Internet.
Web-Based Monitoring
Web-based monitoring is a great way for both individuals
and businesses to promote the benefits of their PV systems
to a larger audience. In addition, it allows system installers
easy, remote access to performance data if troubleshooting
is required. An increasing number of installers are including
Web-based monitoring during system installation for just this
reason.
The two most common approaches for “pushing” PV
system data to the Web use equipment and services provided
by the inverter manufacturer or use a third-party data
service provider. Some system integrators offer Web-based
monitoring options as well.
Inverter-to-Web. Most batteryless grid-tie inverter
manufacturers have developed equipment for displaying PV
system data on the Internet. With a moderate investment in
additional communications hardware, you can access system
data from any Internet-connected computer or handheld
mobile device. Some manufacturers also offer free data
hosting services.
Data can be accessed for free through the SunnyPortal site.
www.homepower.com
PV monitoring
105
California’s
Production-Based
Incentive Programs
The majority of PV incentive programs in the United States
are capacity based, with an up-front financial incentive
provided based on the size (in rated KW) of the installed
PV array. Although this approach can be attractive to home
and business owners because it lowers the initial expense of
investing in PV, it does not necessarily encourage optimal
system installation, maintenance, or performance.
In 2007, California implemented a new production-based
incentive (PBI) program that ties financial incentives to the
number of kilowatt-hours a system generates, rather than a
one-time up-front rebate. Not surprisingly, the PBI program
requires an independent third-party monitoring system (see
list below for approved monitoring systems). PV systems that
are larger than 10 KW and receive incentives from California’s
Emerging Renewables Program also require the installation
of an approved production-monitoring solution. For updates
on California Solar Initiative-approved monitoring and
reporting services, visit: www.consumerenergycenter.org/
erprebate/monitors+rsp.html.
CSS Technologies • www.css-technologies.com
Draker Solar Design • www.drakersolar.com
Energy Recommerce • www.energyrecommerce.com
Fat Spaniel Technologies • www.fatspaniel.com
Glu Networks • www.glunetworks.com
Meteocontrol • www.meteocontrol.com
PowerNab • www.powernab.com
Pyramid Solar • www.pyramidsolar.com
Thompson Technology Industries • www.thompsontec.com
Inverter direct-to-Web connectivity requires an inverter
with communications capability and, ideally, a high-speed
Internet connection—although most manufacturers can
facilitate communications with a dial-up service. The inverter
is connected to the Internet through a gateway, and the data
is sent to a server either hosted by the manufacturer or a third
party, where it is compiled and placed in graphical format for
display. Some manufacturers offer additional services such as
monitoring environmental conditions or sending notifications
when abnormal or fault conditions occur.
Manufacturers that currently offer inverter-to-Web
solutions include Fronius, GridPoint, Kaco, Power-One, PV
Powered, SatCon, Solectria, SMA, and Xantrex. The level of
sophistication varies from manufacturer to manufacturer, so
make sure to ask your installer what options are available, or
do your own research on the manufacturers’ Web sites.
If your PV incentive program does not require independent,
third-party energy production tracking, perhaps the simplest
and least expensive approach for pushing system data to the
Web is to choose an inverter manufacturer that also offers
free data hosting. Several manufacturers, including Fronius,
Kaco, PV Powered, and SMA, currently offer this service, and
in the next few years it will likely become a standard feature
industry wide.
Kaco Solar has developed a Web-based monitoring solution
that offers PV system fault notifications via e-mail, as well as
data hosting services.
Kaco Solar has partnered
with Meteocontrol and
Integrated Metering
Systems to develop
the PBI Log, which has
been designed to meet
the performance-based
metering requirements
of the California Solar
Initiative.
Third-Party Web-Based Monitoring Systems
Vendor
Web Site
Data Collection Equipment
Method*
Local Data
Storage
Off-Site
Server
Residential
Commercial
Chuck Wright Consulting
www.cwc-das.com
Dedicated datalogger
connects to external transducer, meter, or
inverter
Inverter-direct or
independent
4
4
4
4
CSS Technologies
www.css-technologies.com
Gateway & datalogger
Inverter-direct or
independent
4
4
4
4
Draker Solar Design
www.drakersolar.com
Campbell Scientific datalogger
& sensor clusters
Inverter-direct or
independent
4
4
4
Energy Recommerce
www.energyrecommerce.com
Gateway & datalogger
Inverter-direct
4
4
4
4
Revenue-grade energy meter
Independent
4
4
4
4
Fat Spaniel Technologies
www.fatspaniel.com
Gateway & datalogger
Inverter-direct
4
4
4
4
Gateway, datalogger, revenue-grade energy
meter
Independent
4
4
4
4
Glu Networks
www.glunetworks.com
Gateway, datalogger, revenue-grade energy
meter
Independent
4
4
4
4
Heliotronics
www.heliotronics.com
Datalogger & dedicated computer
Independent
4
4
4
4
Intellact
www.wattplot.com
Dedicated computer
Inverter-direct
(OutBack Mate)
4
4
4
4
Meteocontrol
www.meteocontrol.com
Datalogger
Independent
4
4
4
4
PowerNab
www.powernab.com
Application control engine
Inverter-direct or
independent
4
4
4
4
Pyramid Solar
www.pyramidsolar.com
Revenue-grade energy meter
Inverter-direct
(SMA) or
independent
4
4
4
4
RightHand Engineering
www.righthandeng.com
SWCA for Xantrex SW inverter; Mate for
OutBack equipment
Inverter-direct
4
4
4
4
rMeter
www.rmeter.com
Datalogger
Independent
4
4
SG Technologies
www.solar-guppy.com/forum
Dedicated computer
Inverter-direct
(Xantrex Suntie &
GT)
4
4
4
Soltrex
www.soltrex.com
Integrated datalogger & gateway
Independent
4
4
4
4
Thompson Technology
Industries
www.thompsontec.com
Utility-grade meter & datalogger
Inverter-direct
(Satcon) or
independent
4
4
4
*Inverter-direct: Collects data as measured by inverter. Independent: Collects data using stand-alone hardware.
Third-Party Solutions. Third-party datalogging services
with Web hosting are another popular approach to Web-based
monitoring. These services typically involve a monthly or annual
service fee that is included in the base price. Once the initial service
time has expired, a periodic service fee will be applied.
There are two main data collection methods: use a
computer to log system information and upload it to the
Internet, or use a gateway to continuously transfer data to
a remote server via the Internet. Most third-party systems
also give you the capability to monitor multiple pieces
of system performance data, independent of the inverter,
that is compiled into a single stream of information to be
used by the host’s servers. If the connection between your
site and the host’s servers is lost, the on-site hardware will
store information and send it to the remote servers once the
connection is re-established.
Some third-party monitoring systems obtain data directly
from the inverter’s internal protocol, which reduces the need
(and expense) of additional hardware. For systems that do not
communicate directly with the inverter, additional hardware to
capture the data is required. One common method is to use an
home power 121 / october & november 2007
106
PV monitoring
GridPoint manufactures an integrated, battery-based line
of products that provide backup energy during grid failures.
Advanced Web-based monitoring is included.
Monitoring Advantages
for Commercial
Systems
Including advanced performance-monitoring hardware
with a PV system installation is becoming the standard for
commercial applications. Large commercial installations
are often technically complex, require significant capital
investment, and also offer a great public relations opportunity
for the system owner or owners.
Like residential systems, monitoring commercial PV
systems can be done either locally or over the Internet.
The latter is more common, since it is easier to aggregate
the information and generate a useful format for system
owners, installers, and the public to view. As with residential
systems, commercial Web-based monitoring services can
be hosted by an independent, third-party service provider or
directly by the inverter manufacturer. Collected data can be
routed to the Internet through the site’s existing computer
infrastructure or via a dedicated IT network.
The most commonly monitored parameters include AC
power and AC energy production (daily, weekly, monthly, and
annual calculations). These are inexpensive to monitor and
are included in standard packages. Options can be added to
monitor additional parameters such as local environmental
conditions (including ambient air temperature, PV cell
temperature, wind speed and direction, and irradiance)
and the building’s energy consumption. For large arrays,
the voltage and current of individual PV strings are often
monitored to aid with troubleshooting. Each subarray is
brought into a combiner box through a current transducer,
which is connected to the datalogger, allowing the system
installer to remotely diagnose component-level problems.
Many commercial installations include an informational display
in a prominent location to make the PV system more visible to
employees and customers. Displays can range from a single
monitor showing only a few pieces of PV system production
information to interactive kiosks that allow individuals to
select from different menus to access detailed reports about
the PV system’s production and components.
Automated notifications of PV system performance anomalies
sent via e-mail, fax, or text message are commonly found
in commercial monitoring systems. The alerts can notify
users about reduced power output, problems with a particular
section of the array, or even
a specific fault code from
the inverter. These alerts
allow remote management
and maintenance of the PV
system, minimizing system
downtime.
Third-Party Web-Based Monitoring Systems
Vendor
Web Site
Data Collection Equipment
Method*
Local Data
Storage
Off-Site
Server
Residential
Commercial
Chuck Wright Consulting
www.cwc-das.com
Dedicated datalogger
connects to external transducer, meter, or
inverter
Inverter-direct or
independent
4
4
4
4
CSS Technologies
www.css-technologies.com
Gateway & datalogger
Inverter-direct or
independent
4
4
4
4
Draker Solar Design
www.drakersolar.com
Campbell Scientific datalogger
& sensor clusters
Inverter-direct or
independent
4
4
4
Energy Recommerce
www.energyrecommerce.com
Gateway & datalogger
Inverter-direct
4
4
4
4
Revenue-grade energy meter
Independent
4
4
4
4
Fat Spaniel Technologies
www.fatspaniel.com
Gateway & datalogger
Inverter-direct
4
4
4
4
Gateway, datalogger, revenue-grade energy
meter
Independent
4
4
4
4
Glu Networks
www.glunetworks.com
Gateway, datalogger, revenue-grade energy
meter
Independent
4
4
4
4
Heliotronics
www.heliotronics.com
Datalogger & dedicated computer
Independent
4
4
4
4
Intellact
www.wattplot.com
Dedicated computer
Inverter-direct
(OutBack Mate)
4
4
4
4
Meteocontrol
www.meteocontrol.com
Datalogger
Independent
4
4
4
4
PowerNab
www.powernab.com
Application control engine
Inverter-direct or
independent
4
4
4
4
Pyramid Solar
www.pyramidsolar.com
Revenue-grade energy meter
Inverter-direct
(SMA) or
independent
4
4
4
4
RightHand Engineering
www.righthandeng.com
SWCA for Xantrex SW inverter; Mate for
OutBack equipment
Inverter-direct
4
4
4
4
rMeter
www.rmeter.com
Datalogger
Independent
4
4
SG Technologies
www.solar-guppy.com/forum
Dedicated computer
Inverter-direct
(Xantrex Suntie &
GT)
4
4
4
Soltrex
www.soltrex.com
Integrated datalogger & gateway
Independent
4
4
4
4
Thompson Technology
Industries
www.thompsontec.com
Utility-grade meter & datalogger
Inverter-direct
(Satcon) or
independent
4
4
4
*Inverter-direct: Collects data as measured by inverter. Independent: Collects data using stand-alone hardware.
PV monitoring
107
www.homepower.com
independent, Internet-ready utility-grade meter connected to
the inverter’s output to measure power and energy production.
If your incentive program includes production-based incentives
or renewable energy credits, inverter-independent monitoring
is usually required to provide accurate tracking of every
kilowatt-hour your system produces.
The number of components and sensors required by
third-party, Web-based monitoring systems varies depending
on the amount of information you wish to record. When
shopping for a monitoring system, ask what components are
standard and if your particular application will require add-
on components or sensors that will increase the total cost.
Most programs can also incorporate weather data and keep
track of the building’s energy consumption. Other features
may include sending alerts when abnormal conditions arise
and issuing regular production summaries.
Surfing for Solar Data
Web-based or local computer monitoring is not usually
considered a “must have” for residential, grid-tied PV systems
unless your incentive program is production-based and
Energy Recommerce
manufactures UL-listed,
data-ready combiner
boxes that allow the
performance of individual
array series strings to be
monitored remotely.
requires it. But if you are interested in a precise look at how
your system functions and performs, and want convenient
access to the data, Web-based monitoring is a great option.
In addition, it will give your system installer the information
they need to remotely troubleshoot problems if they occur.
For commercial systems, Web-based monitoring is rapidly
becoming the standard. Compared to residential systems,
commercial systems are more complex and have a significantly
higher capital investment. As equipment and software
development continue to progress, it is likely that in the next
few years the majority of grid-tied systems will include remote
monitoring via the Web—commercial and residential alike.
Access
Ryan Mayfield (ryan_mayfield@earthlink.net) earned
a degree in environmental engineering from Humboldt
State University and now lives in Corvallis, Oregon. He
has been working in the RE field since 1999 and founded
Mayfield Solar Design, focusing on PV system design,
implementation, and industry-related training. He holds a
Limited Renewable Energy Technician license in Oregon.
home power 121 / october & november 2007
108
PV monitoring
Fat Spaniel Technologies’ Web-based monitoring solutions
provide user-friendly graphical representations.
Draker Solar Design specializes in Internet-based monitoring for
commercial-scale PV systems.
www.homepower.com
109
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halfpage_08-2005 2/6/07 11:07 AM Page 1
torque is needed to loosen and tighten large terminals,
slipping screwdrivers and wrenches are possible. Tools
should be insulated, and insulated gloves (lineworker’s
gloves) and a protective face shield should be worn while
working in the meter socket. Touching those “hot” input
meter jaws could electrocute you.
The maximum output current from the PV system should
be no greater than the rating of the service entrance. Careful
consideration should be given to conductor sizes if the PV AC
output current approaches the rating of the service entrance.
Table 310.15(B)(6) for reduced conductor sizes may no longer
apply to a very large PV system. For larger systems, the basic
ampacities found in Table 310.16 may have to be used. Since
these service-entrance tap conductors have no overcurrent
protection, they should be as short as possible and be installed
in a metal conduit (RMC, EMT, or IMC). The local jurisdiction
may have requirements for protecting the service-entrance
conductors that need to be followed for these tap conductors.
I do not believe the “tap rules” in Article 240 apply to service-
entrance taps since these taps are fully addressed in Article 230.
As for other locations, some existing service-entrance
disconnects and meter cabinets have an additional set of
terminals that are in parallel with the input connections to the
main breaker. These are located to allow the main disconnect
enclosure to be easily fed from either the top or bottom of the
enclosure.
Some combination meter socket/main disconnect
enclosures have the meter socket on one side and the
disconnects on the other side of the enclosure. Busbars or
cables connect the meter socket to the main breaker. After
getting the approval of the enclosure manufacturer and the
local inspector, it may be possible to tap these circuits with
either bolt-on terminals for the busbars or splicing blocks for
the cables. However, normally, busbars may not be drilled
and tapped to add terminals for a tap.
Safety for ourselves as installers, for the utility, and for the
system owner/operator should be primary considerations.
Any work on electrical service-entrance conductors must be
done only when those electrical conductors are de-energized.
That usually involves notifying the utility and having them
turn off all power to the building or structure. Although some
electricians will work with “hot” (energized) conductors, this
procedure is strongly discouraged. As the old saying goes,
“There are old electricians. There are bold electricians. But there are
no old, bold electricians.”
I’m working on a large grid-tied PV installation
and could use some advice on connecting the
system to the utility. It’s too large to connect via
a backfed breaker on the existing 200-amp load center,
so what other options exist? I have read the Code Corner
in HP112 about supply-side taps, but I could use some
additional guidance. I am a master electrician, and have
installed few PV systems.
Existing load centers may not have enough room
to make the necessary connections. The National
Electrical Code (NEC) limits the number of conductors
and splicing devices that can be in any space (Articles 312
and 408). The photo below shows an overcrowded disconnect
enclosure that does not meet NEC requirements. Even when the
conductors between a separate meter and the main disconnect
enclosure are accessible, they should not be tapped there
unless an enclosure is
added to hold the tap
device.
In places where
net-metering laws are
in effect, the utility-
side (supply-side)
interconnection will
be made between the
meter and the main
service disconnect. In
that case, the utility
will need to remove
the meter from the
socket (meter base)
to de-energize the
service
entrance
conductors.
If the point of
connection is to be the load-side terminals of the meter
socket (only when double conductors on these terminals
are allowed by the socket listing), extreme caution must
be exercised when connecting the new conductors to these
terminals. The utility-energized (“hot”) input terminals and
meter socket jaws are in the same socket and are only a few
inches away from each other. Those energized terminals
should be covered with a heavy, insulated, protective shield
so that they cannot be touched accidentally. Because high
home power 121 / october & november 2007
112
code corner
Q
Code Q & A
John Wiles
Sponsored by the U.S. Department of Energy
A
What is the best way to ground the frame of a
photovoltaic module?
This is an apparently simple question, with a complex
answer. When exposed to sunlight, PV arrays can
generate dangerous levels of voltage (up to 600 volts)
and current. The frames of these modules must be effectively
and continually grounded to earth to prevent electrical shocks
and to reduce fire hazards from stray ground-fault currents.
When ground faults occur in a PV system, these currents
may circulate indefinitely under certain conditions. Unlike a
ground fault in an AC power system, which is interrupted
immediately, a DC ground fault may exist whenever the
module is illuminated. In larger commercial (nonresidential)
systems, the ground-fault detection system does not interrupt
these currents. The connections that are used for grounding
PV modules may have to be as robust as those used for the
circuit conductors.
Grounding PV modules is complicated by several factors.
A typical aluminum-framed PV module has a clear or colored
anodizing on its surface that must be removed or breached
for good electrical contact. When these coatings are removed,
the bare aluminum will oxidize very quickly (in seconds) and
build up an insulating film that also prevents good electrical
contacts. Plus, the copper equipment-grounding conductor
must not come directly into contact with the aluminum
surface, since galvanic corrosion between these two dissimilar
metals will occur, eventually resulting in a failed connection.
Unfortunately, although inspectors have been providing
examples of failed grounding methods and devices, the
grounding hardware and instructions provided by PV module
manufacturers have not yet been tested and evaluated by
Underwriters Laboratories (UL). Under pressure from the
PV industry and the electrical inspection community, UL
now has undertaken a major investigation of PV module
grounding. However, the results of the UL investigation are
not yet known.
Based on discussions with grounding-lug manufacturer
FCI–Burndy and using utility company procedures to
connect copper wires to aluminum busbars in an outdoor
environment, I’m employing the following procedure to
make equipment-grounding connections to module frames.
These procedures are used only when they do not directly
contradict manufacturer’s instructions provided with the
listed module.
At one of the marked grounding points on the module
frame, an abrasive material like emery cloth is used to
remove the clear coat, anodizing, and aluminum oxide from
the surface where the ground lug will contact the aluminum
surface. Immediately, a thick layer of antioxidant compound
is applied to the exposed aluminum surface. Any excess
compound will be squeezed out when the lug is bolted in
place. A tin-plated, solid-copper, direct-burial-rated lay-in
lug is used to connect a copper conductor to the exposed
aluminum frame.
A bolt, nut, two flat washers, two split-lock washers and
a Belleville (cupped spring) washer are used to bolt the lug
to the frame. The flat washers are used to prevent the hard
steel split-lock washers and Belleville washers from digging
into the relatively soft copper and aluminum. The split-lock
washers and the Belleville washer are used to maintain the
assembly under the correct tension. Use a calibrated torque
screwdriver set to 12 to 15 inch–pounds (depending on
the type of bolt) to ensure a reliable connection. A copper
conductor (generally from #12 to #4) is attached to this lug.
The size of the conductor depends on the electrical grounding
requirements, the need for physical protection, and the
requirements of the local inspecting agency.
Other Questions or Comments?
If you have questions about the NEC or the implementation
of PV systems that follow the requirements of the NEC, feel
free to call, fax, e-mail, or write me at the location below. See
the SWTDI Web site (below) for more detailed articles on
these subjects. The U.S. Department of Energy sponsors my
activities in this area as a support function to the PV industry
under Contract DE-FC 36-05-G015149.
Access
John Wiles (jwiles@nmsu.edu) works at the Southwest
Technology Development Institute, which provides
engineering support to the PV industry and provides
industry, electrical contractors, electricians, and electrical
inspectors with information on code issues related to
PV systems. An old solar pioneer, he lives in his utility-
interactive PV-powered home in the suburbs.
Sandia National Laboratories, Ward Bower, Sandia National
Laboratories, Dept. 6218, MS 0753, Albuquerque, NM
87185 • 505-844-5206 • Fax: 505-844-6541 •
wibower@sandia.gov • www.sandia.gov/pv • Sponsor
Southwest Technology Development Institute, New Mexico
State Univ., Box 30,001/ MSC 3 SOLAR, Las Cruces, NM
88003 • www.nmsu.edu/~tdi
The 2005 National Electrical Code and the NEC Handbook
are available from the National Fire Protection Association
(NFPA) • 800-344-3555 or 508-895-8300 • www.nfpa.org
www.homepower.com
code corner
113
Q
A
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115
using appropriate lugs and wire, to the equipment ground of
the system.
UniRac’s ground clips work similarly to the WEEBs,
with the clip being sandwiched between the rack frame and
the module frame. When the module frame’s hold-down is
tightened, the piercing teeth complete the ground connection
between the module frame and the rack frame.
Neater, Cheaper PV Installations
These new systems offer the potential for better-looking
installations—and labor and material savings, since
installation is usually quicker and the need for copper wire is
reduced. Reports from the field estimate that these products
can reduce time spent grounding arrays by approximately
50 percent.
August Goers, an installer with Luminalt in San Francisco,
reports that “the clips drastically reduce installation time
and cost because we can complete the entire racking ground
system before placing the modules. It also reduces the amount
of tin-coated copper lugs used.”
But others say that time and cost reductions really depend
on the installation specifics. “Our first ‘try-it-out’ WEEB
installation was a big off-grid job, involving twenty-seven
BP160 modules on three trackers,” says Allan Sindelar of
Positive Energy in Santa Fe, New Mexico. “[Using the WEEB
method] turned out to be not much of a cost or labor savings
because of the multiple tracker layout. But a later installation
of 40 roof-mount modules as four rows of ten modules made
for a significant wire and labor savings.”
Grounding metal enclosures, raceways, module frames,
and mounting structures in electrical systems provides
essential protection from electrical shock and fire. The
National Electrical Code (NEC) dictates the basic methods for
accomplishing this safety requirement. For PV arrays, an
often-used method of meeting this requirement is to run a
ground wire from each PV module frame, and connect it to
the racking system and to the electrical system’s equipment-
grounding conductor (see this issue’s Code Corner for a
discussion of this method). For system installers, this method
adds time and expense to the installation.
But in 2006, two manufacturers introduced new
Underwriters Laboratories-listed grounding products that
eliminate the need to run a wire to each module frame.
Both Wiley Electronics’ WEEB (washer, electrical equipment
bond) product and UniRac’s grounding clips are listed to UL
Standard 467, which covers bonding washers and grounding
devices. In addition, Sharp Solar recently introduced their
SRS racking system with integral module grounding, though
UL approval is still pending.
WEEB’s grounding method uses a special stainless-steel
bonding washer. The washer has piercing teeth on both sides,
situated so that when the washer is placed between the module
frame and the racking system, a water- and airtight, sealed
electrical connection between the module frame and racking is
created. Tightening the module hold-down nuts to the required
torque is critical to making a good ground connection when
using these devices. The racking structure is then connected,
home power 121 / october & november 2007
116
independent power providers
New Grounding
Options
Mounting Rail
Solar Module Frame
WEEB Tooth:
Pierces through the
anodized coating to
obtain electrical contact
between mounting rail
and solar module frame
by Don Loweburg
PV Module Guides
Nib
UniRac’s grounding clip is designed for use with their
SolarMount array racking system.
Detail of Wiley Electronics’ WEEB grounding product.
Code Contentions
Not all installers and PV professionals are comfortable with
the use of grounding washers. William Miller of Miller Power
and Communications in Atascadero, California, expresses
his concern around the fact that modern grid-connected PV
systems operate at up to 600 volts DC, posing an extreme
hazard if the system isn’t adequately grounded.
Thomas W. Bowes, assistant director of the Detroit
JATC (an IBEW union training center) and PV installation
instructor, shares Miller’s concern. In his recently published
paper, Bowes cites several sections of the NEC that could be
interpreted to cast doubt on the use of grounding washers
(see Access).
“Even though this method (grounding washers) is
available, it is rarely used in the field because of the difficulties
in establishing and maintaining a solid, low-impedance
grounding connection between electrical devices and their
associated mounting racks,” says Bowes in his report. “In fact,
general practice in the industry is to require a properly sized
copper equipment-grounding conductor instead of any other
means recognized by the NEC.” Bowes says he favors the use
of a ground wire because this is the general practice, industry-
wide, and that this method has been reliable. He questions
the ability of other methods to establish and maintain a solid,
low-impedance grounding connection. He does not, however,
cite any NEC sections that specifically prohibit the use of
grounding washers.
Brian Wiley, developer of WEEB, responded to Bowes’s
assertions (see Access). In his response, Wiley engages
in a bit of the “code dance” with Bowes by stating his
interpretations of the NEC articles that allow ground washers.
The most convincing part of Wiley’s response is his report
of the actual tests performed as part of the UL 467 listing
process. According to Wiley, “WEEB products are certified
to carry a current of 1,530 amps for 6 seconds…results [that]
have been tested by Intertek ETL, a nationally recognized
testing laboratory.” He also points to WEEB’s “long-term
reliability,” citing accelerated lifetime tests conducted in-
house in which the WEEB product was subjected to thermal
cycle tests and salt water environment tests that “indicate
exceptional reliability,” especially when compared to the
lay-in lug method.
Phil Crosby, product development manager at UniRac,
says that UniRac’s grounding clips have undergone similar
rigorous testing by the company. According to Crosby, the
washers tested as good as or better than other approved
grounding methods.
But Bowes says that “it is one thing to do a bench
evaluation of a product under ideal conditions in a controlled
environment, but something quite different to consider the
field application of the product and try to examine it in light
of how it will actually be used.”
Proposed code changes to NEC Section 690.43, Equipment
Grounding (Revised), due in 2008, seek to clarify this
contention. The salient change that would specifically speak
to using ground washers would read, “Devices listed and
identified for grounding the metallic frames of PV modules
are permitted to ground the exposed metallic frames of PV
modules to grounded mounting structures.”
Grounding Details
Most parties do agree on one particular safety issue that
may arise with either the traditional lay-in lug or the new
clip-grounding approaches. Ground faults can occur if a
module frame becomes energized due to faulty equipment or
installation work. When removing a ground-faulted module
from an energized PV array, an extreme shock hazard will
exist if the module equipment ground is removed before the
power wiring is opened.
This is a major safety concern, but it has nothing to
do with grounding methods. Rather, this safety issue is
directly a result of the fact that PV modules cannot be easily
turned off. This reality must be understood and respected
by all installers. The solution requires safe work practices
and knowledgeable, experienced installers. All module
manufacturers, in their instructions, require modules to be
covered during service. As an extra precaution, a separate,
temporary ground jumper can be attached to the module
frame and rack before the module is lifted from the rack and
disconnected from the power circuit wiring. Because safety
is paramount, servicing PV systems and arrays should only
be done by qualified persons.
www.homepower.com
independent power providers
117
Introducing
Inspectors to
Innovations
Inspectors are trained to look for an equipment
ground wire connected to each module frame during
field inspections, so it is prudent to clearly document
your intention to use any new grounding approach.
Installers planning to use grounding washer products
should include explicit reference to the grounding
method in their plans. This can be done with a note
on the electrical one-line diagram that is required for
most projects. Also include installation instructions
for the grounding washer, UL listing information, and
a copy of the module installation directions.
Few module manufacturers explicitly allow bonding
washers in their instructions. By providing advance
notice to the inspector and full documentation before
the inspection, my experience is that there will be no
grounding corrections from the inspection. I’ve been
successful gaining approval from the inspectors in all
four of the local jurisdictions (Central California) in
which I work.
Installer August Goers says he’s had similar
experiences. “We work mainly in San Francisco, which
has very strict grounding policies. When obtaining
the permit for our first job with the UniRac clips
we brought in a sample UniRac rail, ground clip,
and module clamp for the head inspector to see. He
approved our use of the product and we haven’t had
any problems with inspectors.”
home power 121 / october & november 2007
118
Moving Forward
The future of the PV industry depends on the safety and
reliability of installed systems. Manufacturers, installers, and
inspectors must continually strive for high standards. And
although intelligent, well-meaning people may not always
agree, engaging an issue from a conversational context
often produces great results and better, safer, and more
durable products. After all, today’s innovation may likely be
tomorrow’s tradition.
Access
Don Loweburg (don.loweburg@homepower.com)
is a solar pioneer in Central California. He owns and
operates Offline Independent Energy Systems, and sits
on the boards of the California Solar Energy Industries
Association and the North American Board of Certified
Energy Practitioners.
Bowes, Thomas. “A Critical Look at PV Module Grounding” •
www.nmsu.edu/~tdi/Photovoltaics/Codes-Stds/Codes-Stds.
html
Wiley, Brian. “A Progressive Look at PV Module Grounding” •
www.we-llc.com/WEEB.html
Proposed NEC code changes for 2008 • www.nmsu.
edu/~tdi/pdf-resources/2008NECproposals2.pdf
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irenew@irenew.org; (319)643-3160
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An example of a very intangible subsidy is the Price–
Anderson Act, which limits the liability of nuclear power
plant utilities in the event of an accident. The only way we
will find out the cost of this subsidy is if a major U.S. nuclear
accident occurs, in which case the largest share of the burden
(potentially hundreds of billions of dollars) will be shifted
to taxpayers. Yet this very subsidy is crucial to keeping the
industry alive, since nuclear utilities would not accept (and
could not afford) the risk on their own.
The most important result of subsidies should be to give
favor to a product or industry that needs a boost to break into
a market, or to make a product more readily available. This
assumes that availability is needed or desirable by society.
Green energy technologies that are promising or developing
too slowly are appropriate targets for subsidies. Given the
right breaks, solar, wind, and alternative transportation
industries can be boosted to help replace nonrenewable
Giant energy-related companies continue to feast
on the abundance of fat government subsidies,
while renewable energy industries scramble for
meager scraps, trying to find the means to make
RE the commonplace energy source that it should
be. What are government subsidies for, and how
do they impact business in the United States,
including our slowly growing renewable energy
industries?
The original goal of most subsidies is to
lower the consumer cost of the targeted product.
Subsidies are designed to work within basic market
economics of supply and demand, supporting
businesses so they will develop, manufacture,
and sell more of a product to increase supply
(such as R&D incentives) or stimulating consumer
demand (such as PV rebates).
Occasionally, subsidies are used to discourage
production of a product to give a competing
product an advantage or to stabilize prices for the
target product. An example of this is when some
dairy farmers are paid to not bring milk to market,
which manages supply to keep prices up so other
farmers can make a living.
Most subsidies have a dollar amount associated
with them and are “direct,” since the payments
usually go straight to the recipient. Indirect
subsidies include just about everything else, like tax breaks
and international trade barriers. But in all cases, it is important
to remember that somebody (taxpayers) or something (like the
environment) is paying the price of subsidies.
Intangibility
There are other less tangible means of subsidizing products and
industries. For example, federal issuance of inexpensive or free
leases for drilling for natural gas or crude oil on public lands
and waters makes it cheaper for oil companies to produce more
of their end product. Allowing the flooding of vast watersheds
makes it possible for utilities to use dams to provide hydro
electricity. While the government incurs little or no monetary
expense for allowing the use of public spaces, there are larger
costs to the general citizenry—such as loss of land that is held on
behalf of the public good and loss of habitat that is important to
non-human species.
home power 121 / october & november 2007
120
power politics
Show RE the
Money
by Michael Welch
technologies, furthering the environmental and sociopolitical
goals that are important to the public good, like reversing
human-caused climate change and decreasing acid rain, and
eliminating wars over diminishing oil resources.
In theory, “mature” technologies, which have approached
or achieved their pinnacle of development, don’t need
the subsidies that newer technologies can benefit from. In
fact, subsidizing those mature technologies can impede
the advancement of desirable, immature technologies when
the technologies are competing for the same market share.
In the energy industry, subsidizing fossil fuel and nuclear
technologies just makes it more difficult for renewable
technologies to get the momentum they need.
Corporate Welfare
But “need” is a very subjective concept and is often misused.
After a few decades of government handouts, many businesses
that have become accustomed to receiving public funds make
it their goal to continue getting subsidies. Corporations
are the worst of the bunch, because by design they are just
money-making vehicles—nothing more, nothing less. To
them, subsidies are just another source of money that they
can tap into.
Ironically, the bigger and more powerful the industry,
the more likely it is to get government handouts—the exact
opposite of the way it should be working. For example, the
2005 federal energy bill included $8.1 billion in tax breaks,
with mature fossil fuel and nuclear industries receiving
93% of the subsidies and renewable energy industries
receiving only about 7%. The bill included about $80 billion
in authorized direct spending largely being paid out to
nonrenewable-based industry. Indirect subsidies were also
included in the bill, like exempting “hydraulic fracturing,”
a particular natural gas well-drilling method, from the
Clean Water Act. These inappropriate allocations make it
very difficult for renewable energy to get a solid foothold
in the energy market.
Determining appropriate need is where government
subsidy programs often get on the wrong track, helped, of
course, by fat campaign contributions, bevies of aggressive
lobbyists, and the “revolving door” syndrome that
often puts industry heads in charge of the very agencies
designed to regulate them (which is also a kind of indirect
subsidy). The constant pressure by business interests for
our government to take care of the business’s particular
needs results in passing massive government handouts
to mature industries—many of which are at odds with
national environmental and social priorities.
Good, Bad, or Just Ugly
Government subsidies are, depending upon any individual’s
priorities, one of the best government ideas ever to be
implemented, an evil to be tolerated, or very bad policy.
People adept at playing the stock market have learned
to keep an eye out for many different indicators, and try to
predict which corporations are going to be the beneficiaries
or losers of government funds, both contracts and subsidies.
Successfully making such predictions gives the opportunity
to buy or sell stocks before prices change as a result of
subsidies. Other investors who buy stock for longer-term
investments benefit when their companies are subsidized—
it makes it more likely that their dividends and stock values
will go up, while often bringing future payoffs for new and
successful products.
Free-market advocates are certain that subsidies, and
nearly every other kind of government meddling in business
affairs, are the worst thing that can happen in our economy.
They believe that the most appropriate products, industries,
and technologies will automatically win out on a truly
competitive and even playing field. But this would require
a nearly pure economic system devoid of government
interference, along with highly informed consumers—both
highly improbable situations under any known form of
government.
Under the current political system, the reality is that
corporations are too powerful to be stripped of their
unwarranted subsidies, so if and until control of politics
and government changes, advocates for a clean and safe
future must swallow a bitter pill and continue to ask that
a share of government money be allocated to fund their
priorities.
Take It Back
In many cases, our government’s system of subsidies is
failing to support its citizenry’s efforts toward a more
sustainable future, and this is going to be difficult to
change. A recent example of this is the 2007 Farm Bill,
which was passed in the House, and now has the blessing
of Senate leadership. Massive efforts by progressive
activists and leaders were put into trying to remove the
billions of dollars in subsidies for corporate agribusiness,
which is already profitable, instead of supporting the
independent family farms that continue to struggle. But
corporate America prevailed in their efforts to include
those unneeded payments.
Two major areas need to be addressed to bring the system
of subsidies back on track. First, political power needs to
be removed from the hands of big business, and put back
into the hands of the citizenry. Second, until that happens,
the renewable energy industry must continue fighting for
consumer incentives, research and development funds, and
other forms of assistance to be on a fair playing field with
the fossil fuel, nuclear, and transportation industries. Until
then, it will be difficult, if not impossible, to adequately
address solutions to climate change and other environmental
problems that are so important to the public welfare.
Michael Welch (michael.welch@homepower.com) has
been working for a clean, safe, and just energy future since
1978 as a volunteer for Redwood Alliance and with Home
Power magazine since 1990.
www.homepower.com
power politics
121
home power 121 / october & november 2007
122
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excess energy is used to offset utility energy consumed
when the customer is using more than their home system
produces. The inverter also maintains the batteries at a
set voltage, shunting excess energy generated to the grid.
Utility-supported systems aren’t configured to send excess
electricity to the grid, but to use the grid for backup and
battery charging when necessary.
Batteryless grid-tied systems have no batteries for
storage, offering no utility outage protection. When the
grid fails, these systems are designed to automatically
shut down. When the grid is operational, any renewable
energy that isn’t being used at a given time is sent back to
the utility to offset energy used from the grid. Batteryless
systems are simpler, less expensive, and more efficient, but
they provide no backup. No single inverter on the market
today will let you choose between batteryless and battery-
based grid-tie at the flip of a switch—you must make this
decision up front.
Derivation: From gridiron, from Middle English
gridire or griddle, and indicating something
consisting of or covered with a network.
In 1880, Thomas Edison electrified a
string of streetlamps on Broadway in New
York City—one of the first steps toward our
modern utility grid. Gradually, companies
selling electricity to homes and businesses in
the United States strung wires to connect their
generating plants to their customers. This
evolved into our present-day electricity grid,
which connects about 140 million customers
with about 17,000 generating plants in the
Continental states, using millions of miles of
cable. This network is an incredibly useful
tool that makes good use of energy resources
to feed the varying load demand.
Gradually over the last 40 years, renewable
energy technology for homes and businesses
has hit the mainstream. This has led to two
general types of renewable energy systems,
with variations in each.
ON-GRID systems come in a few different
flavors. One major distinction is between
battery-based systems and batteryless systems.
Battery-based on-grid systems include
energy storage to power critical loads during grid outages.
They require a battery bank sized to handle the loads needing
backup and for the number of hours or days of outage
protection desired.
These systems can be configured to sell surplus energy
back to the grid, crediting the user’s account. Or they
can be similar to off-grid systems, not selling back any
energy, but using the grid to charge batteries or run loads
directly when there isn’t enough renewable energy. We
don’t have standardized terminology to distinguish these
two types of on-grid systems from each other. Calling
them “utility-interactive” and “utility-supported” might
be appropriate.
In the case of utility-interactive systems, the inverter
(an electronic device that converts DC electricity to AC
electricity) is programmed to synchronize with the grid
and send to it any electricity the home or business isn’t
using at the moment, “spinning the meter backward.” This
home power 121 / october & november 2007
124
word power
On & Off…Grid
The Utility Network
by Ian Woofenden
kajetan
OFF-GRID renewable energy systems run independently of
the utility grid, using batteries to store and deliver energy.
Many people live and work beyond the reach of utility lines,
and the cost of line extension can be very high (in my area,
more than $20 a foot). Others have a desire to cut the cord and
be off grid even though the utility lines are near. This is an
impractical choice in my opinion, but may be more attractive
if the utility does not allow you to sell your surplus electricity,
or if they have unreasonable charges or requirements for
connection. But off-grid systems cannot use the grid as a
“battery,” so once the batteries are filled, any surplus energy
they generate is wasted. These systems also must supply 100
percent of the electricity needed, which usually means having
a backup, fossil-fueled generator (a dirty and expensive
source of electricity), unless you have sufficient renewable
resources at your site.
Off-grid homes are a good microcosmic example of
the responsibilities and challenges of gradually making
the grid more and more sustainable. We either live within
the capacities of our renewably powered systems and deal
with the vagaries of the wind, sun, and water; or we wrestle
with ways to wean ourselves from depending on fossil
fuels (with its costs and impacts) for backup energy. Off-
gridders also must take on all the responsibilities that the
rest of the population pays a utility to handle—financing,
R&D, design, installation, maintenance, troubleshooting,
operation, and replacement. As years go by, we try to
invest in more renewable capacity, and learn to use it
wisely. This long-term investment gives us cleaner, more
reliable energy.
With the perspective and experience of more than 25 years
living off grid, I encourage you to view the grid as a useful
tool, and use it to your advantage when it comes to installing
an RE system. But whether you cook your waffles off-grid or
on, I hope you too will move toward using more and more
renewable energy.
Ian Woofenden (ian.woofenden@homepower.com) lives
off grid in Washington’s San Juan Islands, using sun, wind,
and a bit of propane to make electricity and hot water for
his family. In addition to his work with Home Power, he
organizes workshops for SEI, consults, and teaches.
www.homepower.com
word power
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a day, rain or shine, was preferable to running a gas or
diesel generator.
My husband Bob-O bought his hydro turbine years before
I met him, and we used it at our high-head, low-flow site. It
was a great unit, but the regulator failed almost immediately.
In HP2, publisher Richard Perez wrote about a circuit for an
alternator controller for a gas engine. Bob-O adapted it for our
hydro turbine, made the controller, and it worked pretty well.
Bob-O wrote Richard a fan letter, which led to our meeting
Richard and his wife Karen.
In our home, most of the electrical devices, including
lights, were 12 volt. We had a very small inverter for when
we needed 120 VAC. If we needed more energy, we used
a gas driven generator/arc welder. At that time, because
Bob-O’s work kept him away from the cabin for lengths of
time, I had a crash course in microhydro maintenance and
repair. I learned how to clean the intake of forest debris,
how to reset the alternator, and how to check the batteries.
Most importantly, I learned how to check the nozzle for
plugging at the wheel before climbing the mountain to check
the intake.
One day, while walking along our water ditch with a
rakehoe and cleaning the length up and then down, I spotted
a large madrone tree with fresh bear-claw marks on it at about
Both of my parents were
born off grid. Oh, there was
electricity back then, just not
where they were. The doctor
who delivered my mother
drove out from Stockton,
California, in a horse and
buggy. My father was born
in a log cabin in the wilds of
Manitoba, Canada.
When my father was seven
years old, my grandfather
sold the homestead, loaded
his five kids and trunks into
the horse-drawn wagon and
drove to town. Later that
day, my father saw his first
automobile, his first electric
light, and his first train.
Face the Changes
It amazes me to think of all the world and technological changes
my father has seen in his lifetime. He has enthusiastically
embraced it all. When we were kids, he used to wake us up
so we could see the Mercury and Gemini space shots live
on TV. “You’re watching history,” he’d say. We recently
celebrated at Dad’s annual birthday bonfire. He’s ninety now.
Technology is at a dead run, from zero to global warming
during my dad’s lifetime.
My dad gave me a good grounding in the common-sense
basics of living with renewable energy, although he didn’t
know it. He taught us to turn off lights when we left a room
and to turn off electrical devices if we weren’t using them.
Long before recycling was popular, he taught us to separate
our trash. He got more satisfaction out of rebuilding or
reusing old parts than buying new.
Stepping Off
With my dad’s conservation ethic, it’s no surprise I had
little trouble adapting to an off-grid, self-sufficient lifestyle.
The first renewable energy I lived with was microhydro
power. In the mountainous area along the Salmon River in
California, where little streams and creeks abounded, a lot
of people used small AC or DC hydro plants. Old mining
ditches and ponds were utilized. Hydro, twenty-four hours
home power 121 / october & november 2007
128
home & heart
What Goes ‘Round,
Comes ‘Round
by Kathleen Jarschke-Schultze
my eye level (I’m 5’10”). At first, this made me very nervous
to go up there alone. Old Dick Haley, a decorated Iwo Jima
veteran from downriver, told me to take a knife and carve
some of my own marks above the bear’s. While my dad was
visiting, we did just that in an effort to make the bear think
we were the bigger bear.
Appliance Adventures
Although mountain living offered almost daily adventures with
wildlife, my housekeeping chores also provided me with some
interesting episodes. My ringer washing machine, for instance,
had its own engine. A pull-start Briggs and Stratton. Bob-O always
called it the “Briggs and Scrap Iron,” but it was pretty reliable. I
learned to check the oil and gas before I did the laundry.
It sat outside, under some oak trees, and was a pleasant
place to be in the summer. The winter, however, was a
different matter. I told Bob-O that the water was just too damn
cold to put my hands into in the winter. He sympathized. A
couple of weeks later, he surprised me with elbow-length,
flannel-lined, rubber gloves.
We had two refrigerators. Both small, aged Servel propane
models, named Harold and Sylvia. Harold had a right-hand
hinge and Sylvia’s was left-handed. They sat side by side on
our enclosed screen porch. In the summer they were barely
adequate and in the winter they were freezers.
As part of a neighborhood purchase, we did buy two solar-
electric panels one time. The PV modules sat in their boxes for
over a year. With our year-round hydro system providing
for all our electrical needs, we just never seemed to need the
modules. Then we moved across the county, where our hydro
resource is seasonal, and solar became our mainstay.
In the cabin, I was short on mainstream household
appliances. Over time, I have remedied that. For more than
15 years now I’ve used a Sun Frost RF16 refrigerator. My
Sun Frost F10 freezer is about 10 years old. My front-loading
clothes washer is a Frigidaire, as is my gas dryer. My automatic
dishwasher is a Swedish Asko. I use a Dyson vacuum cleaner.
All my appliances are very efficient. They need to be.
Finally, mainstream American manufacturers and
consumers are getting the point of energy conservation.
Household appliances have gotten more efficient and energy-
conscientious consumers have a wider array of choices.
Renewable Explosion
Recently Bob-O and I saw a commercial for a national real
estate company. In it, the clean-cut young couple queried,
“What if we want a home that uses solar power? Or wind
power?” The advertising company assured that it was no
problem for their agents.
Boy, have things changed. Not that long ago, the image
most folks had of the renewables lifestyle was two hippies
living in a teepee and listening to a PV-powered 12-volt
car stereo. In fact, when we started our renewable energy
design and installation business, all our jobs were for off-
grid systems. It is still true that land beyond the grasp of the
power lines is cheaper, which is where our “stand-alone”
clients are.
While we still design and install off-grid systems and
provide service for off-gridders like us, what we’re seeing
more and more are people on the utility grid who want to
use renewables—even if the system doesn’t completely cover
their energy usage. And in states like ours that financially
encourage grid-tie solar-electric systems, the response is
steadily growing.
My dad understood the value of conservation and passed
this ethic on to me, where I’ve made it my business to share
it with others. Being married to Bob-O, one of the silverbacks
of solar, has given me an early view of what RE can do. I see
my RE past becoming actively sought-after in the present,
and, like my dad, I’m eagerly looking forward to new
technological developments in renewable energy. After all,
necessity is the mother—or father—of invention.
Kathleen Jarschke-Schultze (kathleen.jarschke-schultze@
homepower.com) is the ant, not the grasshopper, at her
off-grid home in northernmost California.
www.homepower.com
home & heart
129
home power 121 / october & november 2007
130
Sun Frost
Energy Efficient
Refrigerators & Freezers
Customized To Fit Your Needs
4 Available in DC
or AC
4 Select From Over 10
Models
4 Choose from 1000’s
of Colors, Finishes &
Woods
We also Manufacture
Composting Toilets!
Please Contact Us For More Info
P.O. Box 1101, Arcata, CA 95518
tel: (707)822-9095 • fax: (707)822-6213 info@
sunfrost.com • www.sunfrost.com
ONLINE RENEWABLE ENERGY EDUCATION
PV DESIGN:
Oct. 22 - Nov. 30
ADVANCED PV:
Oct. 29 - Dec. 7
SUSTAINABLE
HOME DESIGN:
Oct. 29 - Dec. 7
The online PV course
provides 60 cumulative
hours of training that
may be used towards
NABCEP certi cation
purposes
SOLAR ENERGY INTERNATIONAL
PO BOX 715 • Carbondale, CO 81623 • 970.963.8855
www.solarenergy.org
SEI
Renewable Energy Education
for a Sustainable Future
Over 20 years experience in RE training
www.homepower.com
131
BZ Products Model MPPT500
500 watt 45 amp Maximum Power Point Solar Control
• Boost charge current up to 30%
• Up to 45 amp output current
• Microprocessor control
• 95 % efficacy
• 500 watt PV input
• Universal PV input 12 to 48 volts
• 12, 24 or 48 volt output
• Digital metering
• PWM float control
• Battery temperature sensor standard
• Five year warranty
• Made in U.S.A.
BZ Products, Inc.
314-644-2490 • www.bzproducts.net • bzp@bzproducts.net
7914 Gravois, St. Louis, MO 63123, USA
MALLARD WIND GENERATORS
Economical, Strong, & Very Reliable
Mike’s Windmill Shop
MALLARD
800E
MALLARD
800E
SALE
800 Watt
$425
Regular price
$475
Package
Deal 3-800E
& Regulator
$1250
We also have charge regulators, tower kits & plans, PMAs,
blades, and lots of friendly advice & customer support.
Mike’s Windmill Shop
www.mikeswindmillshop.com • 928-532-1607
Email: gossmj@wmonline.com
Major Credit Cards Accepted • Call for Volume Pricing
Precision Wedge Wire
Coanda Screens
for Hydro, Agricultural, and
Domestic Diversions from
10 gpm to 500 cfs
• Self Cleaning
• Easy Installation
• High Capacity
• No moving parts
• Pipe, ramp and
box mountings
– We specialize in creatively engineering solutions
for your unique hydro diversion screening needs.
– Our solutions are cost effective with numerous
screen mounting options; we also have
durable 304 SS mounting boxes.
Visit us at www.hydroscreen.com
or call (303) 333-6071
e-mail: RKWEIR@AOL.COM
We don’t just sell screens,
we engineer solutions!
Lorentz ETATRACK
Trackers and Centralized
Controls for Solar Parks
US Distributor:
Colorado Solar, Inc
800-766-7644
www.solarpanelstore.com
www.cosolar.com
Integrated Systems Available up to Several Megawatts
Harris Hydro
Harris Hydro
Hydro-Power for Home Use
Manufactured by Lo Power Engineering
P.O. Box 1567
Redway, CA 95560
Manufactured by Lo Power Engineering
P.O. Box 1567
Redway, CA 95560
Adjustable Permanent Magnetic
Brushless Alternator
• 25 - 30% more efficient than Hi Output Alternator
• Marine Grade Construction throughout
• Re-connectable Stator
• Retrofittable on existing turbine
Denis Ledbetter
707-986-7771
delejo@humboldt.net
Denis Ledbetter
707-986-7771
delejo@humboldt.net
IOWA
Feb. 20–22, ’08. Des Moines. Forum on
Energy Efficiency in Agriculture. Info: ACEEE •
202-429-8873 • agforum@aceee.org •
www.aceee.org
Iowa City, IA. Iowa RE Assoc. meetings. Info:
319-341-4372 • irenew@irenew.org •
www.irenew.org
MASSACHUSETTS
Hudson, MA. Workshops: Intro to PV;
Advanced PV; RE Basics; Solar Hot Water &
more. Info: The Alternative Energy Store •
877-878-4060 • support@altenergystore.com •
http://workshops.altenergystore.com
MICHIGAN
West Branch, MI. Intro to Solar, Wind &
Hydro. 1st Fri. each month. System design &
layout for homes or cabins. Info:
989-685-3527 • gotter@m33access.com •
www.loghavenbbb.com
MISSOURI
New Bloomfield, MO. Workshops, monthly
energy fairs & other events. Missouri
Renewable Energy • 800-228-5284 •
info@moreenergy.org •
www.moreenergy.org
MONTANA
Whitehall, MT. Seminars, workshops &
tours. Straw bale, cordwood, PV & more.
Sage Mountain Center • 406-494-9875 •
www.sagemountain.org
NEW HAMPSHIRE
Dec. 1, ’07. Manchester, NH. Home Energy
Conference. Incorporating RE, efficiency,
green building, geothermal, biofuels &
other sustainable technologies into the
home. Info: NH Sustainable Energy Assoc. •
603-497-2302 • nh.sustain.energy@tds.net •
www.nhsea.org
Rumney, NH. Green building workshops.
Info: D Acres • 603-786-2366 •
info@dacres.org • www.dacres.org
NEW MEXICO
Six NMSEA regional chapters meet
monthly, with speakers. NM Solar Energy
Assoc. • 505-246-0400 • info@nmsea.org •
www.nmsea.org
NORTH CAROLINA
October 20–21, ‘07. Boone, NC. Small-
Scale Wind Installation workshop. Info:
Appalachian State Univ. • 828-262-2933 •
wind@appstate.edu •
www.wind.appstate.edu
U.S.A.
Oct. 6, ’07. National Tour of Solar Homes.
Tours in most states. Info: American Solar
Energy Society • www.nationalsolartour.org
CALIFORNIA
Oct. 18, ’07. Berkeley. NorCal Solar Energy
Assoc. annual membership meeting &
solar party. Share camaraderie & industry
contacts. Info: NorCal Solar •
www.norcalsolar.org
Nov. 7–9, ’07. Sacramento. Behavior, Energy
& Climate Change Conf. National conf.
on behavior & decision-making to help
accelerate transition to an energy-efficient
& low-carbon economy. Info: see ACORE
listing under Washington, DC.
Nov. 13, ’07. Winters, CA. Smart Energy
Management in Agriculture. RE & energy
efficiency for farmers, dairies, ranchers
& wineries. Info: Ecological Farming
Association • 831-763-2111 ext. 4 •
jasmine@eco-farm.org •
www.eco-farm.org/energy
Arcata, CA. Workshops & presentations on
RE & sustainable living. Campus Center for
Appropriate Technology, Humboldt State
Univ. • 707-826-3551 • ccat@humboldt.edu •
www.humboldt.edu/~ccat
Hopland, CA. Workshops on PV, wind,
hydro, alternative fuels, green building &
more. Solar Living Institute • 707-744-2017 •
sli@solarliving.org • www.solarliving.org
COLORADO
Carbondale, CO. Workshops & online
courses on PV, water pumping, wind, RE
businesses, microhydro, solar domestic hot
water, space heating, alternative fuels, straw
bale, green building, women’s PV courses &
more. Solar Energy Intl. (SEI) •
970-963-8855 • sei@solarenergy.org •
www.solarenergy.org
FLORIDA
Melbourne, FL. Green Campus Group
meets monthly to discuss sustainable
living, recycling & RE. Info: fleslie@fit.edu •
http://my.fit.edu/~fleslie/GreenCampus/
greencampus.htm
INDIANA
Oct. 1–3, ’07. Indianapolis. Conf. on RE from
Organics Recycling. For project managers,
policy makers, investors, technology
providers, utilities, consultants, etc. Info:
BioCycle • biocycle_magazine@vresp.com •
www.biocycle.net
home power 121 / october & november 2007
132
RE happenings
Saxapahaw, NC. Solar-Powered Home
workshop. Solar Village Institute •
336-376-9530 • info@solarvillage.com •
www.solarvillage.com
OREGON
Cottage Grove, OR. Adv. Studies in
Appropriate Tech., 10-week internships.
Aprovecho Research Center • 541-942-8198 •
apro@efn.org • www.aprovecho.net
PENNSYLVANIA
Philadelphia Solar Energy Assoc. meetings.
Info: 610-667-0412 • rose-bryant@verizon.net •
www.phillysolar.org/psea.htm
TENNESSEE
Summertown, TN. Workshops on PV,
alternative fuels, green building & more.
The Farm • 931-964-4474 •
ecovillage@thefarm.org • www.thefarm.org
TEXAS
El Paso Solar Energy Assoc. Meets 1st
Thurs. each month. EPSEA • 915-772-7657 •
epsea@txses.org • www.epsea.org
Houston RE Group, quarterly meetings.
HREG • hreg@txses.org •
www.txses.org/hreg
WASHINGTON, D.C.
Oct. 12–20, ’07. Solar Decathlon. Twenty
teams compete on the National Mall
to design, build, and operate the most
attractive & energy-efficient solar-powered
home. Info: www.solardecathlon.org
Nov. 28–29, ’07. RE in America: Policies for
Phase II. Policy forum with U.S. legislators.
Info: American Council on RE (ACORE) •
202-429-2037 • conroy@acore.org •
www.acore.org
WASHINGTON STATE
Guemes Island, WA. SEI 2007 workshops.
Oct. 6: Intro to RE; Oct. 8–13: Solar-
Electric Design & Installation; Oct. 15–17:
Grid-Tied Solar Electricity; Oct. 19–20:
Successful Solar Businesses; Oct. 22–24:
Solar Hot Water; Nov. 5–10: Electric Vehicle
Conversion. Info: See SEI in Colorado
listing. Local coordinator: Ian Woofenden •
360-293-5863 •
ian.woofenden@homepower.com
WISCONSIN
Oct. 1–3, ’07 (again Nov. 2–4, ’07). Amherst,
WI. Installing a Solar Water Heating System.
Hands-on workshop on solar thermal
closed-loop pressurized & drainback
systems for domestic hot water and space
heating. Info: Artha Sustainable Living
Center LLC • 715-824-3463 • chamomile@
arthaonline.com • www.arthaonline.com
Custer, WI. MREA ’07 workshops: Basic,
Int. & Adv. RE; PV Site Auditor Certification
Test; Veg. Oil & Biodiesel; Solar Water &
Space Heating; Masonry Heaters; Wind Site
Assessor Training & more. MREA •
715-592-6595 • info@the-mrea.org •
www.the-mrea.org
INTERNATIONAL
AUSTRALIA
Feb. 17–21, ’08. Adelaide, S. Australia. Intl.
Solar Cities Congress. Support cities in UN
energy & climate policies by stimulating
interest in RE & energy efficiencies. Info:
Plevin & Associates • 61-8-8379-8222 •
events@plevin.com.au •
www.solarcitiescongress.com.au
COSTA RICA
Jan. 21–27, ’08. Pursical County, C.R. RE for
the Developing World. Hands-on workshop.
Info: See SEI listing for WA State •
www.ranchomastatal.com
Feb. 2–10, ’08. Palmital, C.R. Solar Electricity
for the Developing World. Hands-on
workshop. Info: See SEI listing for WA State •
www.durika.org
ITALY
Nov. 11–15, ’07. Rome. Wind Expo 2007.
International conf. for commercial wind
industry. Info: Artenergy •
info@windexpo.eu • www.windexpo.com
NEW ZEALAND
Jan. 26–27, ’08. Canterbury. Sustainability
Expo. PV, wind, Solar hot water, energy
efficient building design, housing &
transport, & other sustainable technologies.
Info: Solar Electric Specialists Ltd. •
027-457-6527 •
www.sustainabilityexpo.co.nz
WALES
Aberystwyth. RE workshops. Oct. 19–21:
Wind & Solar; Oct. 23–24: RE for Planners;
Oct. 26–28: Intro to RE. Info: Green Dragon
Energy • 49-0-30-486-249-98 •
info@greendragonenergy.co.uk •
www.greendragonenergy.co.uk
www.homepower.com
133
Send your renewable
energy event info to
happs@homepower.com
RE happenings
PV GRID CONNECTED | PV OFF GRID | SOLAR THERMAL
SOLAR ELECTRONICS
www.stecasolar.com
PV OFF GRID
Foto: junichiro aoyama, „energy ball“, CC-Lizenz (BY 2.0) http://creativecommons.org/licenses/by/2.0/de/deed.de
Quelle: Bilddatenbank www.piqs.de
Solar Charge Controller
Steca Solarix PRS
– Low-loss serial controller
– Battery charging with automatic
charging mode selection
(float, boost, equal)
– User-friendly LED display
– Deep discharge protection
– 10 A ~ 30 A power input / output
– 12V / 24 V automatic switch
– Electronic fuse integrated
NEW
Temperature Differential
Controller
Steca TR 0301U
– Easy to read lighted LCD display
– Displays system temperatures
at up to three locations
– Animated representation of
system operation
– 3 sensor inputs / 1 fused
120 VAC output
– Varistor high voltage spike
protection
SOLAR THERMAL
Steca_Anz_HomePower_57x244_4c.in1 1
20.07.2007 11:44:31
home power 121 / october & november 2007
134
OtherPower
Make your electricity from scratch!
www.otherpower.com
Orders: 970.484.7257
877.944.6247 (toll free)
Forcefield
2606 W Vine Dr
Fort Collins, CO 80521
Product information:
info74@otherpower.com
• Magnets
• Magnet wire
• Templates
• Stators
• Metal parts
• Frame kits
• SS Hardware
• Blades
Build your own wind turbine with our kits, com-
ponents, parts, books and plans. You can make a
sturdy, slow-spinning, quiet, heavy and extremely
reliable wind turbine in your home workshop for a
fraction of the cost of a commercial model.
• Books
• Plans
• Free info!
• Fast service!
• Fun and free
wind power
forum here:
fieldlines.com
User Friendly Hydro Power
Alternative Power & Machine
4040 Highland Ave. Unit #H • Grants Pass, OR 97526 • 541-476-8916
altpower@grantspass.com
www.apmhydro.com
Now Featuring Permanent Magnet Alternators
(303) 952-0830
Reduce winter heat loss and summer heat gain
Reflects 97% of radiant heat
Save up to 55% on heating and a/c bills
Vapor barrier, unaffected by moisture
14.5 R value, out-performs R30 fiberglass batt insulation
Call or order online for discount pricing
www.barnworld.com
We ship direct to save you money!
ELECTRO AUTOMOTIVE
Electric Car Conversions Since 1979
Books Videos Kits Components
Catalog Send $6.00 for our catalog, or visit our web site.
"Convert It" We wrote the book on electric car conversions - literally!
Send $30.00 postage paid for this hands-on how-to conversion manual,
written in plain English for the home hobbyist mechanic.
Conversion Kits Complete custom bolt-in kits for the VW Rabbit
and Porsche 914, or a universal kit for other small cars and light trucks.
Web Site Visit our web site for our complete catalog, price list,
gallery of conversions, and extensive conversion information section.
P.O Box 1113-HP, Felton, CA 95018-1113
831-429-1989
WWW.ELECTROAUTO.COM
ELECTRO@CRUZIO.COM
www.homepower.com
135
Wind Data Logger for wind
site assessment, turbine
monitoring, and weather
station applications
High performance and very low
cost. Supports multiple anemo-
meters, wind vanes, temperature,
relative humidity, light level,
voltage and current, and many
other sensors.
Logs directly to removable Secure
Digital card. PC and cell phone
interfaces available to capture live data and send to the internet or
through e-mail. Ready to go packages available — just give us a
call or visit our website!
APRS World, LLC
Phone: +1-507-454-2727 Web: www.winddatalogger.com
902 East Second Street, Suite 320, Winona, MN 55987
BZ Products Model MPPT250
250 watt 25 amp Maximum Power Point Solar Control
• Boost charge current up to 30%
• Up to 25 amp output current
• Microprocessor control
• 95 % efficacy
• 250 watt PV input
• 12 to 24 volt input
• Digital metering
• PWM float control
• Battery temperature sensor
standard
• 15 amp low voltage
disconnect standard
• Aux battery trickle charger standard
• Five year warranty
• Made in U.S.A.
BZ Products, Inc.
314-644-2490 • www.bzproducts.net • bzp@bzproducts.net
7914 Gravois, St. Louis, MO 63123, USA
www.acgreenenergy.com
High Quality - Reliable - Guaranteed
A&C GREEN ENERGY
PO BOX 941122
Plano, TX 75094-1122
866-WNDPWR-3
Premium
Do-It-Yourself
Materials
Blades
Magnets
Magnet Wire
Generators
Batteries
Plans
Mo
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Renewable Energy for Life
A&CGREENENERGY
Save Over 90% On Your Lighting Bill
60,000 Hour Bulb Life (est.)• 2-year Warranty • ULListed
LEDLIGHTBULBS
LEDLIGHTBULBS
• Ceiling or Garden
Accent Lighting
• 36 BrightWhiteLEDs
• 3 Watts / 120 Volt
•Ceilingor Garden
AccentLighting
•60 Bright White LEDs
•6 Watts / 120 Volt
CCVivid PAR 30
LEDFloodlight
•Porch, Reading or
Ambient Light
•36 Bright White LEDs
•3 Watts / 12 or 120 Volt
CCVivid +
LED Light Bulb
CCVivid PAR 38
LED Spotlight
•Outdoor Sensor
or Exterior Lighting
•72Bright WhiteLEDs
•8 Watts/ 12 or 120 Volt
These bulbs fit most standard fixtures.
Additional sizes and voltages available.
800-522-8863•ccrane.com
CCVivid PAR 20
LED Flood & Spot
Ad.CraneHomePower0407 1/16/07 2:47 PM Page 1
Gorilla
Gorilla
www.
www.GorillaVehicles
GorillaVehicles..com
com
info@GorillaVehicles.com
PLEASE SEE OUR WEBSITE
or call for a brochure package
Gorilla Vehicles
5842 McFadden Ave, Unit R
Huntington Beach, CA 92649
(714) 377-7776
Electric
Electric
ATV
ATV -- Tractor
Tractor
NO Gas
NO Oil
NO Smog
NO Smell
NO Noise
NO Warming
NO Carbon
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Solar Charging
Solar Charging
I AM A SOLAR WHOLESALER looking
for retailers to carry my solar electronic,
educational & hobby goods. Phone # (916)
486-4373. Please leave message • HP12109
PORTABLE AND STANDBY GENERATORS
from Honda, Yamaha, Subaru, Kipor, and
More + Wireless Remote Start Available.
www.hayesequipment.com
1-800-375-7767 • HP12107
NEMO DC SUBMERSIBLE WELL PUMPS.
Complete, ready to install. $229 includes
IMMEDIATE FREE SHIPPING. Visit
www.nemopumps.com or call
1-877-684-7979 • HP12108
TELLURIDE COLORADO, Quality solar
homes and appropriate land for sale.
Highest quality of life, environment and
cultural opportunities. Enjoy working
with the world’s only completely solar
powered Real Estate office. JOHN JANUS
(970) 728-3205---800-571-6518
WWW.JANUSREALESTATE.com
Email:John@JanusRealEstate.com •
HP12110
EDTA RESTORES SULFATED BATTERIES.
EDTA tetra sodium salt, $16/lb. plus $6
S&H for 1st lb. plus $2 S&H for each
additional lb. Trailhead Supply, 325 E.
1165 N., Orem, UT 84057, (801) 225 3931,
email: trailheadsupply@webtv.net, info
at: www.webspawner.com/users/edta •
HP12111
DC POWERED CEILING FANS: 12 & 24
volts: The Best in the World: RCH Fanworks
info@fanworks.com www.fanworks.com
PH: 509-685-0535 • HP12112
HYDROELECTRIC SYSTEMS: Pelton
and Crossflow turbines or complete
AC systems for standalone or grid
interconnect operation. Site evaluation
and equipment selection assistance.
Manufacturing home and commercial
size turbines since 1976. Free brochure:
Canyon Industries, PO Box 36HP,
Deming, WA 98244, 360-592-5552. Email:
info@canyonhydro.com Web page:
canyonhydro.com • HP12102
FOLLOW THE SUN! Light seeking single
and dual axis solar tracker controls.
www.theanalogguy.com • HP12103
ECOMALL: The largest environmental
portal of earth-friendly companies and
resources. Renewable energy companies,
news and information. www.ecomall.com.
To advertise, call 845-679-2490 • HP12104
LARGE GAS REFRIGERATORS 12, 15 &
18 cubic foot propane refrigerators. 15
cubic foot freezers 800-898-0552 Ervin’s
Cabinet Shop, 220 N County Rd. 425E.,
Arcola, IL 61910 • HP12105
XXXXXXXUNI-SOLAR XXXXXXXX
XXXXXX 64 Watts $359 XXXXXXXX
M55 Siemens panels $225. Almost new
135 AH AGM 12-volt battery $175. TraceX
SW5548 $2450. Ex 2KW inverter SB
$850. Buy, sell New/Used 760-949-0505 •
HP12106
Help for DIY HYDRO! 66+ Custom
TURBINES, 82-400mm diameter, cast
aerospace alloy or molded plastic from
$120 www.h-hydro.com • HP12114
BE TRULY INDEPENDENT IN THE
ALASKAN BUSH. For Sale - Modern
home with power system. For photos &
full details, see www.remoteproperties.
com , click on “Western Alaska”, then
click on “Aniak” • HP12120
SURVIVAL UNLIMITED.COM - Emergency
Preparedness & Survival Supplies.
Wind Power from 439.00+. Many great
products & prices! 1-800-455-2201
www.survivalunlimited.com • HP12113
GAIN ENERGY INDEPENDENCE Wind
Power - Solar PV - Solar Hot Water -
Renewable Energy Workshops - Biodiesel
- LED Lighting - Edmonton AB Canada
780 466-9034,
www.trimlinedesigncentre.com •
HP12115
SOLAR CELLS New 5” monocrystal
50 per pack - 125 watts $150.00 make
your own solar panels email for specs:
none1120@juno.com • HP12116
HYDROS, P.M. BRUSHLESS DC units with
Harris housing and wheel. Up to 70%
efficiency. From $1350.
www.homehydro.com 707-923-3507 CA •
HP12118
SOLARVENTI: - THE SOLAR POWERED
HOME FRESH AIR SOLUTION. SolarVenti
is the ecological solution for household
problems of condensation, mold, mildew
and musty odors. Unlimited fresh air in
your home, Boat or RV, powered by the
sun! Contact www.solar-imports.com or
mail: Evert@solar-imports.com or call
949-715-7477 • HP12123
home power 121 / october & november 2007
136
marketplace
Complete Biodiesel Production System
Process, Wash, Dry...80 Gallons of B100
The Ester Machine
- Make Fuel the Day It Arrives
- Safe, Durable, Effective
- Completely Assembled and Tested
- Handles New or Used Vegetable Oil
- Consultation Services Available
- Monthly Biodiesel Seminars!
Green World Biofuels 319-545-7022 www.greenworldbiofuels.com
SOLAR THERMAL BUSINESS FOR SALE
Well established, good income, growth
potential, in a beautiful area in the Pacific
Northwest. Will train the right person.
Contact: solar4sale@gmail.com • HP12121
BP4150,150 watt, solar modules 43.6
Voc, 34.8 Vmp, 4.75 Isc (Amps), 4.33 Imp
(Amps) single crystalline, 67 units for sale.
Four years old 20 year factory warranty,
upgrading system. Ready for pick-up,
Contact Greg @ 805-497-9808 Ventura,
Calif. $ 3 per watt.
www.solarelectricalsystems.com • HP12122
TESLA TURBINES Gas pressure input,
shaft HP output. What power do you
need? Designed to power solar thermal
Rankin systems. Send $5 for photos,
tutorial and details. RD, 2909 Cadillac,
Durham NC 27704 • HP12127
BERGEY XL-I, NEW IN BOX, $1800 &
miniaturized, galvanized, Rohn style
tower, for 70’ to XL-1 hub…assembled,
but not erected in N. Michigan…also
15 KW diesel generator, 1.7 hrs.total,
$5000…1-231-548-5482 OR
lelco@racc2000.com • HP12125
BRECKENRIDGE COLORADO OFF-GRID
HOME FOR RENT Christmas/New Year
within National Forest 1.5 miles to town.
1 bedroom and loft. Best view in town.
(970) 390-4477 • HP12128
www.homepower.com
marketplace
137
WINDMILL BLADES - 4’ Sitka spruce with
stainless leading edges, professionally
made for a home power system.
$400+S&H. Send $5 for photos and
details. RD, 2909 Cadillac, Durham NC
27704 • HP12126
NO MORE UTILITY BILLS, EVER! 440
watts Solar/ wind System. Professionally
engineered System will power a large
home or Business. Top of the line
equipment in excellent condition and
ready to install. 40 UNI-SOLAR Solar
Electric Modules and 3 AIR 403 Wind
Generators power this awesome
system. A Trace Engineering Custom
Application Interface Controller provides
controls. Photos included for installation.
Replacement cost $72,000. Buy below
cost $37,095.01 Delivery available. Call for
complete inventory list. 615-599-5901 •
HP12124
BEAUTIFUL NW WOODS LIVING AT
ITS BEST. Twenty private acres, remote
off grid, 45 min to Olympia/Shelton/
Aberdeen/Centralia. About 15 acres
wooded and 5 cleared. Land high and
dry with two creeks. Established fruit and
nut trees, garden space waiting to be
reclaimed. Abundant wildlife. $269,000.
MLS# 27088229 Teri Bevelacqua, RE/MAX
Four Seasons. 360-791-4704 • HP12129
DELUXE GAS REFRIGERATORS. Save
on large 15 & 18 cubic feet sizes. Also
freezers. We ship nationwide. Free
brochure. (888) 607-1110 • HP12119
Marketplace Advertising
Rates: $2.50 per word. $50 minimum per
insertion, paid in advance of publication.
Submit your ad to marketplace@
homepower.com or call 800-707-6585.
WANT TO LIVE RENT-FREE? Property
owners need trustworthy people to live in
their empty homes as property caretakers
and housesitters! The Caretaker Gazette
contains these property caretaking/
housesitting openings in all 50 states
and foreign countries. Published since
1983, subscribers receive 1,000+ property
caretaking opportunities each year,
worldwide. Some of these caretaking
and housesitting openings also offer
compensation in addition to the free
housing provided. Subscriptions: $29.95/
yr. The Caretaker Gazette, PO Box 4005-E,
Bergheim, TX 78004. (830) 755-2300.
www.caretaker.org • HP12117
OFF-GRID GOAT DAIRY seeks ranch
hand/caretaker. Will train in dairy
skills. Internships available. Beautiful
unique situation. Drug and Alcohol
free. Tobacco free a plus. 505 250 8553
organicgoatcheese@yahoo.com
www.organicgoatcheese.com Box 47
Pie Town NM 87827 • HP12130
E LIGHT SAFETY RECALL! A possible
electrical component failure may cause
Risk of Fire. E Light is a white rectangular
LED fixture. For details: E-Light-Recall.
com; Hotline: 866-522-1368 • HP12131
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MAKING
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Off the grid since ����
PLASTIC BATTERY BOXES
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radiantsolartech.com
707-485-8359
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