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<DIV>Joel:</DIV>
<DIV> </DIV>
<DIV>The PV system in Long Beach was built within a stone's throw of a twin
smoke stack for a big furnace devoted to a "Trash to Energy" project. It
burns garbage to produce energy.... and LA has plenty of trash. Combine
that with all of the diesel soot being generated by ocean long haulers
which bring cars, refrigerators and yes, PV modules into the busiest port
and rail hub on the left coast for our consumption. The modules, and everything
else in the port, are just plain dirty.</DIV>
<DIV> </DIV>
<DIV>We install mostly in southern LA County. Our systems are always
above predicted outputs by PV Watts 2 & the CSI EPBB. The
degradation over the years seems not be have been as severe as
predicted, except for some of the PhotoWatt units we installed for a
brief while. I think that the lower degradation may be due to our mild
climate? Since we are coastal, we really stress tilting the mods at least
10 degrees to help them weep from the almost daily condensation, which also has
the effect of cleaning the panels. Then the soot-laden sludge at the lower
edge accumulates to the point that we recommend annual scrubbing. Simple
Green has been suggested as a good product for cleaning the modules and that is
what we tell our customers (but is it really 'bio-degradable'?)</DIV>
<DIV> </DIV>
<DIV> <EM>Patrick A. Redgate<BR><FONT lang=0 size=3 face=Arial FAMILY="SANSSERIF" PTSIZE="12">Ameco Solar, Inc.</FONT></EM><FONT lang=0 size=3 face=Arial FAMILY="SANSSERIF" PTSIZE="12"><BR><EM>7623 Somerset
Blvd<BR>Paramount, CA 90723<BR>888-595-9570</EM></FONT></DIV>
<DIV> </DIV>
<DIV>
<DIV>In a message dated 6/10/2010 4:19:23 P.M. Pacific Daylight Time,
joel.davidson@sbcglobal.net writes:</DIV>
<BLOCKQUOTE style="BORDER-LEFT: blue 2px solid; PADDING-LEFT: 5px; MARGIN-LEFT: 5px"><FONT style="BACKGROUND-COLOR: transparent" color=#000000 size=2 face=Arial>
<DIV><FONT size=2 face=Arial>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.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>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 <A title=http://en.wikipedia.org/wiki/June_Gloom href="http://en.wikipedia.org/wiki/June_Gloom">http://en.wikipedia.org/wiki/June_Gloom</A></FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>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.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>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.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>Joel Davidson</FONT></DIV>
<BLOCKQUOTE style="BORDER-LEFT: #000000 2px solid; PADDING-LEFT: 5px; PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV style="FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color: black"><B>From:</B>
<A title=mailto:kelly@whidbeysunwind.com href="mailto:kelly@whidbeysunwind.com">Kelly Keilwitz, Whidbey Sun &
Wind</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=mailto:re-wrenches@lists.re-wrenches.org href="mailto:re-wrenches@lists.re-wrenches.org">RE-wrenches</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Thursday, June 10, 2010 7:57
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [RE-wrenches] Real world
PV production</DIV>
<DIV><BR></DIV>
<DIV>Thanks, Don,</DIV>
<DIV>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.</DIV>
<DIV><BR></DIV>
<DIV>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.</DIV>
<DIV><BR></DIV>
<DIV>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.</DIV>
<DIV><BR></DIV>
<DIV>Thanks,</DIV>
<DIV>-Kelly</DIV><BR>
<DIV apple-content-edited="true"><SPAN style="WIDOWS: 2; TEXT-TRANSFORM: none; TEXT-INDENT: 0px; BORDER-COLLAPSE: separate; FONT: medium Helvetica; WHITE-SPACE: normal; ORPHANS: 2; LETTER-SPACING: normal; COLOR: rgb(0,0,0); WORD-SPACING: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px" class=Apple-style-span>
<DIV style="WORD-WRAP: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space">
<DIV>
<DIV>Kelly Keilwitz, P.E.</DIV>
<DIV>Whidbey Sun & Wind</DIV>
<DIV>Renewable Energy Systems</DIV>
<DIV><A title=mailto:kelly@whidbeysunwind.com href="mailto:kelly@whidbeysunwind.com">kelly@whidbeysunwind.com</A></DIV>
<DIV>360-678-7131</DIV>
<DIV><BR></DIV></DIV></DIV></SPAN></DIV>
<DIV>
<DIV>On Jun 9, 2010, at 8:59 AM, i2p wrote:</DIV><BR class=Apple-interchange-newline>
<BLOCKQUOTE type="cite">
<DIV name="Mail Message Editor">
<DIV><SPAN class=Apple-style-span><BR></SPAN></DIV>
<DIV id=replyPrefaceElement>On Jun 9, 2010, at 8:22:12 AM, "Kelly
Keilwitz, Whidbey Sun & Wind" <<A title=mailto:kelly@whidbeysunwind.com href="mailto:kelly@whidbeysunwind.com">kelly@whidbeysunwind.com</A>>
wrote:</DIV><BR>
<BLOCKQUOTE style="BORDER-LEFT: blue 2px solid; PADDING-LEFT: 5px; COLOR: blue; MARGIN-LEFT: 5px"><SPAN style="WIDOWS: 2; TEXT-TRANSFORM: none; TEXT-INDENT: 0px; BORDER-COLLAPSE: separate; FONT: medium Helvetica; WHITE-SPACE: normal; ORPHANS: 2; LETTER-SPACING: normal; COLOR: rgb(0,0,0); WORD-SPACING: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px" class=Apple-style-span><SPAN style="FONT-SIZE: 11px; font-f: monospace" class=Apple-style-span>Thanks, Joel<BR>How about PV systems away from
the coast, in a hotter, dustier<SPAN class=Apple-converted-space> </SPAN><BR>location, like Bakersfield,
Fresno, Sacramento, Palm Springs,<SPAN class=Apple-converted-space> </SPAN><BR>etc........?<BR><BR></SPAN></SPAN></BLOCKQUOTE>
<DIV><SPAN class=Apple-style-span>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.
<DIV><SPAN class=Apple-style-span><BR></SPAN></DIV>
<DIV><SPAN class=Apple-style-span>Don Loweburg</SPAN></DIV></SPAN></DIV>
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<DIV> </DIV>
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