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

[Nathan Charles]

So I read this paper, Smith, R. M., Jordan, D. C., & Kurtz, S. R. (2012).
Outdoor PV Module Degradation of Current-Voltage Parameters, which seems to
seems to suggest that Voc doesn't degrade like Isc degrades. Based on that
and other data I've seen it seems like panels that degrade at 0.5%/year are
outliers on the low side.

Thoughts from other wrenches?




On Tue, Jun 3, 2014 at 11:59 PM, Bill Hoffer <sunengser at gmail.com> wrote:

> 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 Bill Brooks, passed on past data, ( correct me Bill if I am out of date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
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> sunengser at gmail.com <bhoffer at sunergyengineeringservices.com>
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-- 
Nathan Charles
Engineer
NABCEP Certified PV Installation Professional #042013-20
Paradise Energy Solutions
(717) 283-2021 direct
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