I am on road so I have no texts with me, but the same formula applies about
0.4% per degree (less voltage) or use the module label voltage coefficent.
However you must use the MPPT voltage and the temperature = (temperature
ambient (2% high) plus roof temperature warming) The roof temperature is hard
to find good values because it depends upon spacing between roof and module. I
add 15 deg C for most situations.
Best I can do from memory.
DT
________________________________
From: Kirk Herander <k...@vtsolar.com>
To: RE-wrenches <re-wrenches@lists.re-wrenches.org>
Sent: Tuesday, November 29, 2011 1:48 PM
Subject: [RE-wrenches] calculating low string voltage
I am in debate with a PE over calculation of low voltage of a series string on
a hot day. He insists that an arbitrary high cell temp is factored in, not just
ambient temperature. Could someone please give an accepted formula for this
calculation? Thanks. I cannot find a clear reference to low voltage calculation
on a hot day (but every reference material is clear on how to calculate high
voltage on a cold day).
Kirk Herander
VT Solar, LLC
dba Vermont Solar Engineering
NABCEPTM Certified installer Charter Member
NYSERDA-eligible Installer
VT RE Incentive Program Partner
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