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<div class="moz-cite-prefix">I agree that Voc doesn't seem to
degrade as much. I've had a chance to measure several modules
over 20 years old, and the Voc is only dropping about 1/2 the rate
suggested by others here. I think a more appropriate number
might be 0.25% V drop/ year. <br>
<pre class="moz-signature" cols="72">R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760</pre>
On 6/4/2014 11:36 AM, Nathan Charles wrote:<br>
</div>
<blockquote
cite="mid:CANdZe6LD2Zo+cKdRjui5iqN3zt7TdjZF6syh=d-9NreuJJkAKA@mail.gmail.com"
type="cite">
<div dir="ltr">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.
<div>
<br>
</div>
<div>Thoughts from other wrenches?</div>
<div><br>
</div>
<div><br>
</div>
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<div class="gmail_extra"><br>
<br>
<div class="gmail_quote">On Tue, Jun 3, 2014 at 11:59 PM, Bill
Hoffer <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:sunengser@gmail.com" target="_blank">sunengser@gmail.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr">Dana
<div><br>
</div>
<div>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if I am out of date here) recommends 1% Power loss per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.</div>
<div><br>
</div>
<div>Bill</div>
</div>
<div class="gmail_extra"><br>
<br>
<div class="gmail_quote">On Tue, Jun 3, 2014 at 3:41 PM,
Dana Brandt <span dir="ltr"><<a
moz-do-not-send="true"
href="mailto:dana@ecotechenergy.com" target="_blank">dana@ecotechenergy.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr">Hi Wrenches,<br>
<br>
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. <br>
<br>
Thanks,<br>
<br clear="all">
<div>
<div>
<div>
<div dir="ltr">Dana<span><font color="#888888"><br>
<br>
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Ecotech Energy Systems, LLC<br>
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<div dir="ltr">Nathan Charles
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