[RE-wrenches] Module Degradation - voltage or current?

Bill Hoffer sunengser at gmail.com
Tue Jun 3 20:59:59 PDT 2014


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Bill Brooks, passed on past data, ( correct me Bill if I am out of date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 <dana at ecotechenergy.com> 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
> Ecotech Energy Systems, LLC
> www.ecotechenergy.com
> dana at ecotechenergy.com
> 360.318.7646
>
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-- 
William Hoffer
161 SE Fourth Ave
P.O. Box 1823
White Salmon, WA 98672-1823
sunengser at gmail.com <bhoffer at sunergyengineeringservices.com>
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