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<DIV><FONT size=2 face=Arial>Wrenches,</FONT></DIV>
<DIV><FONT size=2 face=Arial>PVWatts does not accurately predicate Unisolar and
Sunpower module performance because it uses a generic single
crystal silicon solar module power temperature coefficient (I think -0.4% per
degree C). Does someone have the technical paper that specifies
PVWatts module temperature coefficient? Thank you.</FONT></DIV>
<DIV><FONT size=2 face=Arial>Joel Davidson</FONT></DIV>
<DIV><FONT size=2 face=Arial></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=kirk@vtsolar.com href="mailto:kirk@vtsolar.com">Kirk Herander,
VSE</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=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> Sunday, April 18, 2010 4:32
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> [RE-wrenches] Enphase derate
(was Tilt biased....)</DIV>
<DIV><BR></DIV>
<DIV class=Section1>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">Enphase
has a tech note pdf for download that recommends and rationalizes a PV watts
derate of .819 instead of the standard .77 (which IMO is a little conservative
to begin with). <o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><A
href="http://www.enphaseenergy.com/downloads/EnphaseAppNote_PVWatts.pdf">http://www.enphaseenergy.com/downloads/EnphaseAppNote_PVWatts.pdf</A><o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><o:p> </o:p></SPAN></P>
<DIV>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">Kirk
Herander<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">Vermont
Solar Engineering<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">802.863.1202
fax 802.863.7908<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">VT
RE Incentive Program Partner<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">NYSERDA
Incentive-eligible Partner<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">NABCEP<SUP>TM
</SUP>Certified Installer<o:p></o:p></SPAN></P></DIV>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><o:p> </o:p></SPAN></P>
<DIV>
<DIV
style="BORDER-BOTTOM: medium none; BORDER-LEFT: medium none; PADDING-BOTTOM: 0in; PADDING-LEFT: 0in; PADDING-RIGHT: 0in; BORDER-TOP: #b5c4df 1pt solid; BORDER-RIGHT: medium none; PADDING-TOP: 3pt">
<P class=MsoNormal><B><SPAN
style="FONT-FAMILY: 'Tahoma','sans-serif'; COLOR: windowtext; FONT-SIZE: 10pt">From:</SPAN></B><SPAN
style="FONT-FAMILY: 'Tahoma','sans-serif'; COLOR: windowtext; FONT-SIZE: 10pt">
re-wrenches-bounces@lists.re-wrenches.org
[mailto:re-wrenches-bounces@lists.re-wrenches.org] <B>On Behalf Of </B>Allan
Sindelar<BR><B>Sent:</B> Sunday, April 18, 2010 3:18 AM<BR><B>To:</B>
RE-wrenches<BR><B>Subject:</B> Re: [RE-wrenches] Tilt
biased....<o:p></o:p></SPAN></P></DIV></DIV>
<P class=MsoNormal><o:p> </o:p></P>
<P style="MARGIN-BOTTOM: 12pt" class=MsoNormal>Holt,<BR>Feedback re the low
tilt angle: Go for it, you're good.<BR><BR>Re wind loading: check out UniRac's
Code Compliant Installation Manual, <A
href="http://www.unirac.com/pdf/ii227.pdf">http://www.unirac.com/pdf/ii227.pdf</A>,
especially pages 3-9.<BR><BR>Less wind loading is one of the main reasons for
going with a lower tilt angle. Another is closer module row spacing (at 3X
height RoT) without inter-row shading.<BR><BR>No experience with
Enphase.<BR>Allan<o:p></o:p></P>
<DIV>
<P class=MsoNormal><SPAN class=il><B>Allan</B></SPAN><B> Sindelar</B><SPAN
style="FONT-SIZE: 10pt"><BR><A href="mailto:Allan@positiveenergysolar.com"
target=_blank><SPAN
class=il><U>Allan</U></SPAN><U>@positiveenergysolar.com</U></A><BR>NABCEP
Certified Photovoltaic Installer<BR>EE98J Journeyman
Electrician<BR><B>Positive Energy, Inc.</B><BR>3201 Calle Marie<BR>Santa Fe,
New Mexico 87507<BR><B>505 424-1112</B><BR><A
href="http://www.positiveenergysolar.com/"
target=_blank><U>www.positiveenergysolar.com</U></A></SPAN><o:p></o:p></P></DIV>
<P class=MsoNormal><BR><BR><A
href="mailto:holtek@sbcglobal.net"><U>holtek@sbcglobal.net</U></A> wrote:
<o:p></o:p></P>
<DIV>
<P class=MsoNormal><SPAN style="FONT-FAMILY: 'Calibri','sans-serif'">Searching
for opinions.....is this "over design"?</SPAN><o:p></o:p></P></DIV>
<DIV>
<P class=MsoNormal><SPAN style="FONT-FAMILY: 'Calibri','sans-serif'">Designing
small system (2.35kW). Customer uses gas for heating. Typical A/C unit. I was
thinking of biasing the tilt to summer production for greater offset of summer
demand (lat 31.6, proposing 18). No net metering in this part
of the world. PVwatts shows a drop of 2% /yr. in production , 5%
higher production for A/C months. Feedback?</SPAN><o:p></o:p></P></DIV>
<DIV>
<P class=MsoNormal> <o:p></o:p></P></DIV>
<DIV>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'"> Also, this array will go on
a carport. I understand that windloading is actually greater for an open
structure than one with walls (another reason for lower tilt) - is there any
one that can direct me to data on finding out how much more?
</SPAN><o:p></o:p></P></DIV>
<DIV>
<P class=MsoNormal> <o:p></o:p></P></DIV>
<DIV>
<P class=MsoNormal><SPAN style="FONT-FAMILY: 'Calibri','sans-serif'">Lastly,
what is a good avg. target derate factor for Enphase inverters (real
world)?</SPAN><o:p></o:p></P></DIV>
<DIV>
<P class=MsoNormal> <o:p></o:p></P></DIV>
<DIV>
<P class=MsoNormal><SPAN style="FONT-SIZE: 10pt">Holt E. Kelly<BR>Holtek
Fireplace & Solar Products<BR>500 Jewell Dr.<BR>Waco TX.
76712<BR>254-751-9111<BR><A
href="http://www.holteksolar.com"><U>www.holteksolar.com</U></A></SPAN><o:p></o:p></P></DIV><PRE><o:p> </o:p></PRE><PRE style="TEXT-ALIGN: center">
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