Anotherpower.com Forum
Renewable Energy Questions/Discussion => Solar (heating or electric) => Topic started by: philb on June 23, 2012, 09:39:07 pm
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This is a question I have asked myself time after time. I have been testing the open circuit voltage against another panel in full sun. If both panels are within 5%, I called them good and mounted them.
So far, all have been good. I dread the day when I'll have to peel a panel from its mounting because I didn't properly test it.
I thought about using a carbon pile tester like the ones made for testing batteries.
At any rate, must be better ways than I'm using. What are your thoughts?
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Not sure how many you have to make, and how much effort you want to go to, but if I had a whole bunch to do, I think I'd invest in a decent xenon strobe and some peak-and-hold gear. Put the cell to test in a "test enclosure" - could even have spring-loaded connection points - subduded lighting. Hit test. The xenon fires, you record the peak volts and current from the panel under a (nearly) identical test condition. The circuits don't need to be very complex, basically just a couple of opamps and some meters. Doesn't need calibrated - just a comparison against your master. Testing its effectiveness should be as simple as shading part of a test cell and seeing what happens.
** Note: I have not done this on anything recently, but it worked in a similar application many years ago when I was testing batches of photodetectors.
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I did some "unusual" testing of same lot factory made panels (all 3 types, single, poly and amorphous) a few years ago for Amanda. Then more tests later for myself.
It is not apples-to-apples.
One may do better in high humidity, or at a slight angle, than the one that does best in good clean straight sun.
The output variation could get to double digit percentages, even with a slight variation in input variables.
I did not do much testing regarding temps, though I expect it is similar.
A cabon pile tester would be roughly Isc, so just need a meter than can handle the expected Isc and test Isc under several conditions.
I go old school on this type of thing now... get some batteries at low, mid and high voltage, then see what each will put into a battery under a few different conditions. I figure that's about as good as it gets without a lab.
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