[RE-wrenches] calculating low string voltage

Exeltech exeltech at yahoo.com
Tue Nov 29 15:44:27 PST 2011


This reply from Scott actually answered the original question.  To that end, I
would like to include my vote for the accuracy of his information.

Measurements conducted here at Exeltech affirm the ~30C temperature delta
directly behind any cell near the center of the PV for an array with sufficient
area to allow convective cooling.

We have also found a few other variables impact cell temperature *slightly*,
but not enough to worry about.

The figures given by Scott below are as accurate a value as can be utilized.


Dan
Sr. Engineer
Exeltech










--- On Tue, 11/29/11, Scott McCalmont <re-wrenches at scottmccalmont.com> wrote:

From: Scott McCalmont <re-wrenches at scottmccalmont.com>
Subject: Re: [RE-wrenches] calculating low string voltage
To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
Date: Tuesday, November 29, 2011, 1:58 PM

Usually you increase the temperature above ambient by an amount which depends on the mounting method. Close to the roof is +35 degrees C, more than 6 inches above the roof is +30 degrees C, and pole or ground mount is +25 degrees C.
Scott

On Nov 29, 2011, at 11:48 AM, Kirk Herander wrote:
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 HeranderVT Solar, LLCdba Vermont Solar EngineeringNABCEPTM Certified installer Charter MemberNYSERDA-eligible InstallerVT RE Incentive Program Partner   _______________________________________________
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