I finally have been getting some good sunny days, unfortunately the solar panels haven’t produced as much as I thought they would because I didn’t factor in temperature.
The panels are rated at 190 watts at 77F and they drop off 0.32% for every degree F over 77F.
The temperature today was in the low 70s, but my roof shingles were 140F and the solar panels were at 100F ( according to my infra red thermometer )
I hosed down every panel in one of the strings until the nearest one was down to about 77F. I did this twice ( I was really thorough the first time, and did a little less the 2nd time. )
Here is the chart:
See those two spikes in the blue line? That is the increased production that came from cooling the panels down. It was about a 10% increase in output. The specifications say that it should be about a 7.5% improvement, but I was getting 10%
Notice that it takes about 40 minutes for the panels to heat back up and the output to return to the curve it was on.
( The “red” string produces slightly better – I don’t know why. It also is shaded for slightly longer in the morning, which is why its production starts later )
I think that if I could cool the solar panels down to ambient air temperature I would get about 10% more total output for the day.