Bill and all,
Dana asked for good conservative data for long-term performance. This is not necessarily what you would use when you are trying to make yourself look as good as possible for a financier. The real question is, where did this data come from confirming lower losses? It takes about 7-10 years of data to establish a degradation rate. The newer data is based on an NREL study that was released several years ago. This means that the study was based on modules manufactured in the U.S., Japan, and Germany with very few Chinese or other Asian origins. The numbers may have improved-or they could be worse. Ultimately, if you do not have long term data on any module (which you clearly don't) any assumption about voltage or current degradation is a guess at best. Figures lie and liars figure. Cynicism in this area is a positive character trait. Bill. From: RE-wrenches [mailto:[email protected]] On Behalf Of Bill Hoffer Sent: Tuesday, June 03, 2014 9:00 PM To: RE-wrenches Subject: Re: [RE-wrenches] Module Degradation - voltage or current? Dana Bill Brooks, passed on past data, ( correct me Bill if I am out of date here) recommends 1% Power loss per year with approximately 0.5% current and 0.5%voltage. That is also what Solar Energy International Best Practices curriculum recommends. Based on some newer data from larger projects requiring testing to actually determine those values for the Bankability requirements ( PVsyst PAN files), I believe we are seeing lower numbers than that now. In general, quality of modules are higher than the older modules. We of course are usually not privy to those results and may not even be getting the same level of binning for small residential projects as the MW projects do. 0.5% V loss per year seems like a like a good conservative number to me, especially if you add a little buffer (1-2%) in there. Bill On Tue, Jun 3, 2014 at 3:41 PM, Dana Brandt <[email protected] <mailto:[email protected]> > wrote: Hi Wrenches, Does anyone know what percentage of module degradation over time is voltage and what is current? I'm wanting to make sure we give ourselves plenty of breathing room on the minimum Vmp of the inverters over the long term so need to try to anticipate how much voltage we'll lose on the array over 30 years. Thanks, Dana Dana Brandt --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com
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