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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Kelly,<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Your area is a prime example of needing to find a data site that
is not geographically closest, but climatically closest. In Washington, the
microclimates are so extreme, that data from PV:Watts must be manually
selected. It is not because the program is that far off, it is the climatic
input information that is not relevant to your location.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Bill.<o:p></o:p></span></p>
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color:#1F497D'><o:p> </o:p></span></p>
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<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>
re-wrenches-bounces@lists.re-wrenches.org
[mailto:re-wrenches-bounces@lists.re-wrenches.org] <b>On Behalf Of </b>Kelly
Keilwitz, Whidbey Sun & Wind<br>
<b>Sent:</b> Friday, June 11, 2010 9:55 AM<br>
<b>To:</b> RE-wrenches<br>
<b>Subject:</b> Re: [RE-wrenches] Real world PV production<o:p></o:p></span></p>
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<p class=MsoNormal>Joel, <o:p></o:p></p>
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<p class=MsoNormal>Thanks for the information. 35% loss due to to smog or
soiling is a big hit and, I'm sure, an exception. Still, if the loss is even
20% it supports the concept that an array here on the cool, cloudy west side of
the WA Cascades can perform on par with an equivalent array in a hot,
dusty/smoggy location in CA.<o:p></o:p></p>
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<p class=MsoNormal><o:p> </o:p></p>
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<p class=MsoNormal>I'd still like to hear of actual less-than-stellar
production numbers recorded in such situations.<o:p></o:p></p>
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<p class=MsoNormal><o:p> </o:p></p>
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<p class=MsoNormal>-Kelly<o:p></o:p></p>
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<p class=MsoNormal><o:p> </o:p></p>
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<p class=MsoNormal>On Jun 10, 2010, at 9:02 AM, Joel Davidson wrote:<o:p></o:p></p>
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<br>
<o:p></o:p></p>
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<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:black'>PVWatts is a good general estimator when you fine-tune
the derate factor. For single crystal and multicrystalline arrays, I
generally use 0.65 for battery-based PV and inverter systems and 0.82 for
batteryless inverter systems. PVWatts annual results are l5% low for
Unisolar arrays because PVWatts uses the crystalline silicon temperature
coefficient.</span><span style='font-size:13.5pt;font-family:"Helvetica","sans-serif";
color:black'><o:p></o:p></span></p>
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<p class=MsoNormal><span style='font-size:13.5pt;font-family:"Helvetica","sans-serif";
color:black'> <o:p></o:p></span></p>
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<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:black'>Even though PVWatts2 may seem more accurate, it does not
factor in unique local climate conditions like California coastal
morning and afternoon fog or inland persistent winter Tule fog. However,
NREL's climate data does include LA's "June gloom" see<span
class=apple-converted-space> </span><a
href="http://en.wikipedia.org/wiki/June_Gloom">http://en.wikipedia.org/wiki/June_Gloom</a></span><span
style='font-size:13.5pt;font-family:"Helvetica","sans-serif";color:black'><o:p></o:p></span></p>
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<p class=MsoNormal><span style='font-size:13.5pt;font-family:"Helvetica","sans-serif";
color:black'> <o:p></o:p></span></p>
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<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:black'>For flat roofs in snowy climates like the Unisolar project in
Rochester NY, I deduct 30% from PVWatt's November through March estimates
for a fairly accurate annual estimate. Powerlight (now SunPower) also uses
an additional 30% monthly derating for flat roofs in snowy locations.</span><span
style='font-size:13.5pt;font-family:"Helvetica","sans-serif";color:black'><o:p></o:p></span></p>
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<p class=MsoNormal><span style='font-size:13.5pt;font-family:"Helvetica","sans-serif";
color:black'> <o:p></o:p></span></p>
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<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:black'>PVWatts does not account for really dusty and dirty air locations.
Bill Brooks worked at PVUSA and is very knowledgeable about power loss
from soiling from agricultural dust in central California. Bill also
measured 35% power loss at the Long Beach CA harbor waste-to-energy
powerplant PV systems. That location and most LA county freeways
experience particulate pollution that not only reduces PV production
but causes permanent respiratory damage to children and shorten the lives of
elderly people, sort of like the canary in the mine.</span><span
style='font-size:13.5pt;font-family:"Helvetica","sans-serif";color:black'><o:p></o:p></span></p>
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<p class=MsoNormal><span style='font-size:13.5pt;font-family:"Helvetica","sans-serif";
color:black'> <o:p></o:p></span></p>
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<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:black'>Joel Davidson</span><span style='font-size:13.5pt;font-family:
"Helvetica","sans-serif";color:black'><o:p></o:p></span></p>
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<blockquote style='border:none;border-left:solid black 1.5pt;padding:0in 0in 0in 4.0pt;
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z-index:auto'>
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<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:black'>----- Original Message -----<o:p></o:p></span></p>
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<div>
<p class=MsoNormal style='background:#E4E4E4'><b><span style='font-size:10.0pt;
font-family:"Arial","sans-serif";color:black'>From:</span></b><span
class=apple-converted-space><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:black'> </span></span><span style='font-size:10.0pt;font-family:
"Arial","sans-serif";color:black'><a href="mailto:kelly@whidbeysunwind.com"
title="kelly@whidbeysunwind.com">Kelly Keilwitz, Whidbey Sun & Wind</a><o:p></o:p></span></p>
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<div>
<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:black'>To:</span></b><span class=apple-converted-space><span
style='font-size:10.0pt;font-family:"Arial","sans-serif";color:black'> </span></span><span
style='font-size:10.0pt;font-family:"Arial","sans-serif";color:black'><a
href="mailto:re-wrenches@lists.re-wrenches.org"
title="re-wrenches@lists.re-wrenches.org">RE-wrenches</a><o:p></o:p></span></p>
</div>
<div>
<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:black'>Sent:</span></b><span class=apple-converted-space><span
style='font-size:10.0pt;font-family:"Arial","sans-serif";color:black'> </span></span><span
style='font-size:10.0pt;font-family:"Arial","sans-serif";color:black'>Thursday,
June 10, 2010 7:57 AM<o:p></o:p></span></p>
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<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Arial","sans-serif";
color:black'>Subject:</span></b><span class=apple-converted-space><span
style='font-size:10.0pt;font-family:"Arial","sans-serif";color:black'> </span></span><span
style='font-size:10.0pt;font-family:"Arial","sans-serif";color:black'>Re:
[RE-wrenches] Real world PV production<o:p></o:p></span></p>
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<p class=MsoNormal><span style='font-size:13.5pt;font-family:"Helvetica","sans-serif";
color:black'><o:p> </o:p></span></p>
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<p class=MsoNormal><span style='font-size:13.5pt;font-family:"Helvetica","sans-serif";
color:black'>Thanks, Don,<o:p></o:p></span></p>
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<div>
<p class=MsoNormal><span style='font-size:13.5pt;font-family:"Helvetica","sans-serif";
color:black'>Performance predictions such as from PV Watts VASTLY underestimate
PV production in our area. For example, PV Watts estimates 940 kWh/kW for
a 4:12 pitch at 180˚, whereas such systems are actually producing up to 1300
kWh/kW (as measured by a renenue-grade production meter). We have to set the
derating factor to nearly 100% in order for the predictions to match.<o:p></o:p></span></p>
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<p class=MsoNormal><span style='font-size:13.5pt;font-family:"Helvetica","sans-serif";
color:black'><o:p> </o:p></span></p>
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<p class=MsoNormal><span style='font-size:13.5pt;font-family:"Helvetica","sans-serif";
color:black'>I assume that is partly due to coarse irradiance data (not
accounting for higher irradiance for our location in the rain shadow of the
Olympic Mountains), but also due to our clear, cool, windy summers, good
natural washing, and (perhaps) dispersed distribution of irradiance.<o:p></o:p></span></p>
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<p class=MsoNormal><span style='font-size:13.5pt;font-family:"Helvetica","sans-serif";
color:black'><o:p> </o:p></span></p>
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<p class=MsoNormal><span style='font-size:13.5pt;font-family:"Helvetica","sans-serif";
color:black'>I want to know if the opposite is true: Do performance predictions
OVERESTIMATE PV production in areas with historically high irradiance, but
significant soiling and temperature issues.<o:p></o:p></span></p>
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<p class=MsoNormal><span style='font-size:13.5pt;font-family:"Helvetica","sans-serif";
color:black'><o:p> </o:p></span></p>
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<p class=MsoNormal><span style='font-size:13.5pt;font-family:"Helvetica","sans-serif";
color:black'>Thanks,<o:p></o:p></span></p>
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<p class=MsoNormal><span style='font-size:13.5pt;font-family:"Helvetica","sans-serif";
color:black'>-Kelly<o:p></o:p></span></p>
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<p class=MsoNormal><span style='font-size:13.5pt;font-family:"Helvetica","sans-serif";
color:black'><o:p> </o:p></span></p>
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<p class=MsoNormal><span style='font-size:13.5pt;font-family:"Helvetica","sans-serif";
color:black'>Kelly Keilwitz, P.E.<o:p></o:p></span></p>
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<p class=MsoNormal><span style='font-size:13.5pt;font-family:"Helvetica","sans-serif";
color:black'>Whidbey Sun & Wind<o:p></o:p></span></p>
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<p class=MsoNormal><span style='font-size:13.5pt;font-family:"Helvetica","sans-serif";
color:black'>Renewable Energy Systems<o:p></o:p></span></p>
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<p class=MsoNormal><span style='font-size:13.5pt;font-family:"Helvetica","sans-serif";
color:black'><a href="mailto:kelly@whidbeysunwind.com">kelly@whidbeysunwind.com</a><o:p></o:p></span></p>
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<p class=MsoNormal><span style='font-size:13.5pt;font-family:"Helvetica","sans-serif";
color:black'>360-678-7131<o:p></o:p></span></p>
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<p class=MsoNormal><span style='font-size:13.5pt;font-family:"Helvetica","sans-serif";
color:black'>On Jun 9, 2010, at 8:59 AM, i2p wrote:<o:p></o:p></span></p>
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<p class=MsoNormal><span style='font-size:13.5pt;font-family:"Helvetica","sans-serif";
color:black'>On Jun 9, 2010, at 8:22:12 AM, "Kelly Keilwitz, Whidbey Sun
& Wind" <<a href="mailto:kelly@whidbeysunwind.com">kelly@whidbeysunwind.com</a>>
wrote:<o:p></o:p></span></p>
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margin-left:3.75pt;margin-top:5.0pt;margin-bottom:5.0pt'>
<p class=MsoNormal><span style='font-size:13.5pt;font-family:"Helvetica","sans-serif";
color:black'><o:p> </o:p></span></p>
<p class=MsoNormal><span class=apple-style-span><span style='font-size:8.5pt;
font-family:"Helvetica","sans-serif";color:black'>Thanks, Joel</span></span><span
style='font-size:8.5pt;font-family:"Helvetica","sans-serif";color:black'><br>
<span class=apple-style-span>How about PV systems away from the coast, in a
hotter, dustier</span><span class=apple-converted-space> </span><br>
<span class=apple-style-span>location, like Bakersfield, Fresno, Sacramento,
Palm Springs,</span><span class=apple-converted-space> </span><br>
<span class=apple-style-span>etc........?</span><br>
<br>
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</span><span style='font-size:13.5pt;font-family:"Helvetica","sans-serif";
color:blue'><o:p></o:p></span></p>
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<p class=MsoNormal><span class=apple-style-span><span style='font-size:13.5pt;
font-family:"Helvetica","sans-serif";color:black'>In central CA we do a little
better. I casually monitor several systems in this area and expect around
1500-1600 kwh/kw. per year.</span><span style='color:black'><o:p></o:p></span></span></p>
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<p class=MsoNormal><span class=apple-style-span><span style='font-size:13.5pt;
font-family:"Helvetica","sans-serif";color:black'>Don Loweburg</span></span><span
style='font-size:13.5pt;font-family:"Helvetica","sans-serif";color:black'><o:p></o:p></span></p>
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