Thursday, March 26, 2020

Solar, And Temperature

These cool, partly cloudy spring days provided me an opportunity to see the temperature dependence of solar panel energy generation right up close and personally.

In one particular instance, it had been cloudy for at least an hour.  There was a gentle breeze blowing and the temperature was in the high 40s.  Because of the breeze and the shade, my solar panels were cool.

Then the clouds parted and the sun came out, pretty much all at once.

551.6 watts

I know it's a little hard to read, but the blue system monitor at the lower right is showing 551.6 watts.

A few minutes later, the solar panels were still in full sun - that is, no change in energy falling on the panels.  Yet, here is the output:

Later, 532.4 watts

Yup, output has dropped to 532.4 watts as the panels heated up...  that's a drop of 3%.  That is a pretty significant drop.  You folks in the tropics should be able to get a pretty substantial increase in solar output if you can figure out some way too cool your panels...

(FWIW, the biggest reading I saw came later in the day when the sun was higher, and again just after a cloud has passed:  571 watts.  I love seeing that current meter needle buried!)



Unknown said...

Regarding keeping solar panels cool to optimize output, is there a clear material that blocks infrared light, yet still permits the correct wavelengths to pass through for electrical output?

Robert Salnick said...

There are many (low ‘Energy glass for one). But solar cells derive a majority of their power from the long wavelength portion of the spectrum... blocking infrared could also decrease performance. I think cooling is a better answer.

Besides, I built my panels on the cheap - I used shower doors, which I am pretty sure are not low E glass...

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