Effect of ash on PV output

We’re about to have a natural experiment:
after fires, ash in California, rain is in the forecast.

Anyone planning to analyze PV output data to
estimate the lost PV production due to the ashfall?

Here is what I am seeing here in Northern California…

How does the previous year compare?

I’ll have to check my data in more detail; but, I DEFINITELY see a difference due to the haze and smoke here in Eastern Washington state. We also get a lot of blowing dust, and I’ve noticed that hosing my panels off every few weeks can make a 3-5% difference. We have a split grid-tie system and one bank is easily accessible, the other is not. I’ve ALSO noticed that during the summer, when we get days with ambient air temps over 100F, my performance degrades - I’m actually considering putting some sort of a misting system up (our RH is typically below 20%, so mist systems are quite common for cooling patios and the like.

My peak power typically is around 9.5 kW near noon but with the smoke, it has decreased to 8 kW. Likewise, my generation is typically 60-70 kWh, it is now between 50-60 kWh.

I live in Santa Rosa, CA. I had a lot of ash on my panels. I used a leaf blower after the fires to blow off the loose stuff, but still have a general grey dust stuck to my panels. I have two adjacent panels that have historically had almost identical production. I went out with a warm bucket of soapy water and thoroughly cleaned one of them.

That panel is now producing about 8% more, both in terms of daily production and peak power.

I actually thought it would be more, but 8% is probably worth a quick clean.

It will be interesting to see how much of the ash comes off with rain, or if it needs more of a scrub. I had to scrub on the one panel a bit with a microfiber to get it all off. It’s really clean now (like brand new), and probably doesn’t have to be that clean to restore most of the production.



Do you think PV Output might be willing to add a feature to tag a given array (or panel) as having been cleaned? Or just a way to add date stamped notes to the data?

That would help keep track of any later data analysis.

I found a pressure washer was very limited in cleaning.
I really had to attack the panels with a nylon bath puff sponge to loosen things up enough for the pressure washer to work.

Not sure I’d use a pressure washer on solar panels. Quite some potential for damage.

I just cleaned my panels off hopefully for the last time this year of all the accumulated dust and ash. They were pretty filthy. Only been 3 weeks since the last cleaning.

I normally see from 3-5% increase in power and energy output after cleaning. At least for the typical highest production period of summer.

Picked up another kWh of energy production and another 200 watts more in peak power for the same conditions on Friday post-cleaned to Thursday pre-cleaned.

I use a two sided, scrubber-micro fiber mop head on a window washer 12’ extensible pole to wash my ground mount array off and then climb on the garage roof to clean the array there.

brycenesbitt Hi you can already add a comment, for the day you cleaned your system.

just go to day view select the day you want to add a comment too, click edit output scroll down to comments, an add a comment, easy as Jim

I live in Marin County, Bay Area and I did 2 cleanings of my 11.4kW system after ash “rain” and I both times gained around 11%!

Both days measured at noon, both days blue sky same temp.

Before last cleaning 5.4, next days 6 kWh