<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1">
<META content="MSHTML 6.00.2800.1458" name=GENERATOR></HEAD>
<BODY style="MARGIN: 4px 4px 1px; FONT: 10pt Arial">
<DIV><SPAN class=629113519-04102004>Smita, </SPAN></DIV>
<DIV><SPAN class=629113519-04102004>
<P>Your understanding of how EnergyPlus accounts for <SPAN
class=629113519-04102004>PV </SPAN>shading seems <SPAN
class=629113519-04102004>to be </SPAN>correct. <SPAN
class=629113519-04102004> </SPAN>I would add that for the advanced PV<SPAN
class=629113519-04102004> </SPAN>models, cell performance is a function of
incident radiation and that it is important to reduce this before applying the
model. <SPAN class=629113519-04102004> </SPAN>With EnergyPlus, you can use
single-module arrays and define separate surfaces for each module. This way the
shading will be handled separately for each module. <SPAN
class=629113519-04102004> </SPAN>But currently in EnergyPlus, the whole array
performance would not be treated any differently than summing up each module's
contribution.<SPAN class=629113519-04102004> </SPAN> You could take the
output from each surface/module and reassemble the performance of the array
outside of the program. <SPAN class=629113519-04102004> This is in
general a hard thing to model as one would need a large amount of data
on exactly how the modules in the array (and cells in the modules)
are wired with bypass and blocking diodes. Nowadays, clever
electrical engineering can minimize the degradation effects of shading,
so it isn't always the case that entire strings go dead.
</SPAN></P>
<P><SPAN class=629113519-04102004>Brent Griffith</SPAN></P></SPAN><FONT
face=Tahoma>
<P><SPAN class=629113519-04102004> </SPAN>-----Original
Message-----<BR><B>From:</B> postman@gard.com [mailto:postman@gard.com]<B>On
Behalf Of </B>Smita Gupta<BR><B>Sent:</B> Friday, October 01, 2004 4:50
PM<BR><B>To:</B> BLDG-SIM@gard.com<BR><B>Subject:</B> [BLDG-SIM] effect of
partial shading on PV performance<BR><BR></P></FONT></DIV>
<BLOCKQUOTE dir=ltr
style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV>Hi,</DIV>
<DIV> </DIV>
<DIV>A PV related query again. This time I would like to find out if
anyone can suggest an algorithm or tool that accounts for the effect of
partial shading on an array. From what I understand, EnergyPlus and
eQuest algorithms factor the effect of shading through adjusting the
effective irradiation incident on the surface to which the array is attached.
Please correct me if I am wrong in understanding this. </DIV>
<DIV> </DIV>
<DIV>But the effect of partial shading is quite different depending on the
location of the actual cell in series. The shaded cell depending on its
location in the series can degrade the performance a lot more than
proportional to the % of area shaded. Can anyone confirm if any tool or
algorithm takes into account his fact.</DIV>
<DIV> </DIV>
<DIV>Any help and advise regarding this issue is appreciated.</DIV>
<DIV> </DIV>
<DIV>Thank you,</DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV>PS-
<DIV>eQuest output for PV performance states that</DIV>
<DIV>"NOTE: PARTIAL SHADING OF A PV ARRAY CAN SEVERELY DEGRADE ITS
PERFORMANCE, BUT IS NOT TAKEN INTO ACCOUNT SEE REPORT LS-SH FOR SHADING
INFORMATION"</DIV>
<DIV> </DIV>
<DIV>Smita Gupta<BR>Energy Analyst, LEED AP</DIV>
<DIV> </DIV>
<DIV>Buildings & Appliances Office<BR>California Energy Commission<BR>1516
Ninth St. MS-25<BR>Sacramento, CA 95814<BR>Phone: (916) 657-4034<BR>Fax: (916)
654-4304<BR></DIV></DIV><PRE>
======================================================
You received this e-mail because you are subscribed
to the BLDG-SIM@GARD.COM mailing list. To unsubscribe
from this mailing list send a blank message to
BLDG-SIM-UNSUBSCRIBE@GARD.COM
</PRE></BLOCKQUOTE><PRE>
===========================
You received this e-mail because you are subscribed
to the BLDG-SIM@GARD.COM mailing list. To unsubscribe
from this mailing list send a blank message to
BLDG-SIM-UNSUBSCRIBE@GARD.COM
</PRE></BODY></HTML>