Dirt Abatement

At 1PM yesterday I took out the hose and ladder and washed off the solar panels; actually, I scrubbed them, they really hold onto the dirt, even with a 19 degree slope.

Before washing, I was producing 1550 watts. It took me about 13 minutes to scrub them down, and then I noticed I was up to 1720 watts. A massive change! I wasn't sure if it was due to the removal of dirt or that I cooled off the hot panels with the water...but at the end of the day I produced 8.25kWh, besting every day over the last month, so I'm convinced it wasn't the cooling, which was only temporary, but the dirt abatement that made the difference.

I'll likely get 8.5 today, about 1kWh a day better than before, so this is a huge difference, about 13%. In this respect, I'm glad I mounted the panels where I can easily wash them off.

Edit: Now I'm lost. The following day I was back down to 7.5kWh...so now I really don't know what to believe. Both the 4th and the 5th were identical days -- same temps with no cloud cover. Was it the temporary cooling of the panels? I suppose I will just hose them off today at about noon to see if there's any change. The panels, of course, are quite thin, so I think that they certainly do cool off readily when hosed, not a whole lot of stored heat energy.

We'll see.

Further Edit (Aug 2): I did see. Cooling the panels is significant. Today at peak I simply watered the panels down and saw the same immediate increase, from 1550W to 1710W, along with a 55V increase, from 315V to 370V. If there was a way to cycle cooling water up with a small pump (something that uses less than .25kWh a day) I could make some impressive long term gains...especially as my water is not metered.

I would thus find a way to recycle that water to the lawn and offset sprinkling. This is something I should look into...is it possible to get a sufficient water stream up to the roof before it warms up? Perhaps a system that cycles; cold water is brough up and misted over the panels, it cycles off, and excess water in the tubes/pipes is discharged out to the grass so when I cycle again it isn't at roof temperature. This would give me perhaps 25kWh per month over the three or four summer months, for a total gain of ~90kWh. And remember, I only hosed down the panels for about 9 total minutes and saw a 1kWh daily gain...what would I get if it were cooled down for 5 hours a day? A 90kWh yearly gain would be a 3.5% increase in efficiency.