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

[Jerry Shafer]

If it modules not diodes which will give you different issues, no voc
change but a combination with less power at 25c best to use a iv curve tool
like the solmetric product very cool and printable
On Jun 4, 2014 10:36 AM, "Nathan Charles" <
ncharles at paradiseenergysolutions.com> wrote:

> 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 Bill Brooks, passed on past data, ( correct me Bill if I am out of date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
>> P.O. Box 1823
>> White Salmon, WA 98672-1823
>> 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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