How do you clean your panels?

[littleharbor]

80 pounds?? How did you figure that out?

[Mike90250]

If you like taking a risk, you can use a power washer on your panels. I would recommend against it. Panel seals are designed for rainfall, not power washing, and once you blow the seals and water gets in, your panels are toast.

[J.P.M.]

I am surprised no one has mentioned RV power washers. Stores like Lowe's and Home Depot sell them. They are just a hose nozzel that compresses the water acting like a power washer. This is important because if your solar panels are 20 feet high like mine water pressure will be low. It also extends up to 6 feet making it perfect for cleaning all of the solar panels. An example of one of these RV cleaners is "Orbit Telescoping Cleaning Wand". I bought something similiar at lowes for $12 and it power washed 80 pounds of bird poop off my roof. It did the best job.

The argument that rain is all you need to clean solar panels is rain is stupid because birds will poop on them, there will be dirt on other debris that easily doesnt come off with rain. You need to power wash them.

I've found rain to be comparable to simple hosing and that simple hosing can restore most of the production lost from the usual types of array fouling that I, and I suspect most folks get - in SO CA anyway.

Power washing panels may seem the manly thing to do, but it's simply a bad idea. It may break the seal between the panel and the glazing. It also may void a warranty. It's also overkill. Simply hosing off panels will remove enough of the fouling to restore about 3/4 of the performance lost to fouling.

As for rain and it's efficacy, I've got a fair amount of data for my array that shows precipitation can be an effective way to clean an array. Depending on how long, how sustained and how intense, precipitation can restore somewhere between, say, maybe 25 -50 % of the lost performance for, say 0.25" precip., to restoring virtually all of the performance for a something like a hard, 2 day soaker. Amounts are hard to quantify. Generally, and up to a point, more liquid for a longer time leads to more performance restoration. High velocity from high pressure doesn't get better results - just more chance for water ingress.

Perhaps interestingly (or not), and maybe a little off topic, I get a fair amount of fog/dew overnite - enough to register precipitation of ~ 0.01" to, say, 0.03 " - the kind that leaves the driveway wet and windshields dripping. After measuring array performance for 4+ years, under clear skies on consecutive days on either side of such a fog event, my array fouling always calcs/measures out lower after the fog than before the fog. How much lower varies, but always lower.

Simply hosing my array at a rate of ~ 3/4 gal./panel from above (north of) the array and letting it drip/air dry seems to restore about 3/4 of the lost performance so that, for example, A condition of a 10 % performance loss to fouling may get reduced to, say, 2 - 3 % or so from such a hosing. To get the array all the way clean takes a hosing, dish soap and a SOFT cloth followed by a hose rinse.

Without rain or rinsing, my array seems to foul at a rate that causes production to fall at an approx. rate of about 0.75% to about 1.0% per week. It also seems to level off at roughly about 8 to 10 % after 2 or 3 months. I've theorized that the dew I mention above may have something to do with that asymptotic leveling off but I haven't figured out a way to determine if my hunch has any validity and if so, how.

I've also found that soaping and rinsing with hose water and leaving hard water spots vs. soaping and rinsing with distilled water and wiping the array dry so that no water spots remain produced no discernable or measurable difference in array output or performance. Simply put: If there is an advantage to using D.I. or distilled H2O over tap water, I can't measure one.

[J.P.M.]

80 pounds?? How did you figure that out?

Maybe it's not guano. Apparently Dumbo lives in his neighborhood.

[littleharbor]

Must be estimated. I can't see shoveling it up and weighing it.

[J.P.M.]

Must be estimated. I can't see shoveling it up and weighing it.

Old Marine head graffiti: Flush hard - it's a long way to the chow line.

[ImInPhxAZ]

For what it's worth most solar panel maintenance sheets say no water over 125psi and ok to use regular commercial glass cleaners (Windex, alcohol, etc).

You can always look up the manual for the particular modules in question but generally they are all the same. Absolutely no pressure washing.

I imagine a hose with a sprayer attachment that let's you add chemicals, some glass cleaner in it, an a microfiber cloth on a pole is about all one would ever need if desired to clean the panels.

I was up on my roof yesterday just 6 hours after rain and the panels looked dusty already.

Safe to say ill take JPMs advice and I'm not going to play the constant cleaning game.

[J.P.M.]

For what it's worth most solar panel maintenance sheets say no water over 125psi and ok to use regular commercial glass cleaners (Windex, alcohol, etc).

You can always look up the manual for the particular modules in question but generally they are all the same. Absolutely no pressure washing.

I imagine a hose with a sprayer attachment that let's you add chemicals, some glass cleaner in it, an a microfiber cloth on a pole is about all one would ever need if desired to clean the panels.

I was up on my roof yesterday just 6 hours after rain and the panels looked dusty already.

Safe to say ill take JPMs advice and I'm not going to play the constant cleaning game.

With my array fouling @ ~ 1% performance degradation/week, I figure a 1X/month simple hosing at a rate of ~ 3/4 gal./panel if it doesn't rain will hold the average fouling penalty for my array to maybe a bit less than 3% or so. Common wisdom is that fouling rates are local condition and climate dependent as well as tilt angle dependent.

Horizontal arrays will need a lot more cleaning to keep from becoming silt pans.

[Friday]

Yesterday I went on my roof to clean under my solar panels. Someone quoted me $700 to remove several bird nests, bird poop under my solar panels. All by myself I cleaned everything out in less than 3 hours.

What I use is a Bionaire water blaster, or as I simply call it my "RV pressure washer". It is designed to clean RV's, so it has an extendable nozzle up to 6 feet, and it compresses the water like a pressure washer. This is important because I have a 2 story house. With a normal hose nozzle there is no water pressure and it doesnt do a good job. With this its like having a pressure washer, it does a great job. I would highly recommend buying something like this. I even used it to remove the bird nests.

For reference this is what I have, but any home improvement store will have something similiar for only $10-15:

https://www.lowes.com/pd/BONAIRE-Ultimate-Water-Blaster/3597668

There's just no comparision to rain water or a normal hose nozzle with this. You have to be careful the first time I used it it surprised me how powerful it was and I was fell over lol.

[Kingram]

I picked up one of these Little big Shot Super nozzle to reach the panels on my two story home-https://www.youtube.com/watch?v=Rsp_mDLSeOY

[Mike90250]

backside of panels is not meant to be washed, be careful cleaning out nests with water back there.

[JohnyWalter]

Note! Dont use a pressure washer. There are too many seals and electrical components. Just hose off and use a car washing brush. One of the long handled rotating head car-washing brushes is ideal. Use a little dish washing detergent if you wish but make sure you rinse thoroughly to avoid detergent degarding any seals. Lichen can grow along the bottom edge of panels and may need a little more mechanical action than a hose off. I suggest using a plastic (rather than metal) scraper.

One thing to note is that water will cool the panels resulting in a short term bump in production. When you look at the inverter is will seem like there has been a big jump in production after cleaning however this is the result of cool panels not cleaning. People who operate as solar panel cleaners often use this to demonstrate the effectiveness of cleaning however once the panels dry off and heat up again production returns to about pre-cleaning value.

[ImInPhxAZ]

I had quite a bit of bird poo on a corner of my array and when compared to a panel three columns over that had no bird poop, power was identical as was daily kwh output.

I've decided the rain can do the work for me, even in AZ where it hardly rains. It just doesn't matter enough to do anything for it.

[J.P.M.]

Note! Dont use a pressure washer. There are too many seals and electrical components. Just hose off and use a car washing brush. One of the long handled rotating head car-washing brushes is ideal. Use a little dish washing detergent if you wish but make sure you rinse thoroughly to avoid detergent degarding any seals. Lichen can grow along the bottom edge of panels and may need a little more mechanical action than a hose off. I suggest using a plastic (rather than metal) scraper.

One thing to note is that water will cool the panels resulting in a short term bump in production. When you look at the inverter is will seem like there has been a big jump in production after cleaning however this is the result of cool panels not cleaning. People who operate as solar panel cleaners often use this to demonstrate the effectiveness of cleaning however once the panels dry off and heat up again production returns to about pre-cleaning value.

+1 on not using a pressure washer. Dumb idea and not necessary.

I use a VERY SMALL quantity of mild dish detergent ~ 1X/yr. and rinse thoroughly. Otherwise it's 1 X/month rinse with H2O only. BTW: The hard water spots don't seem to impair performance in any way I've been able to measure over the last close to 5 yrs.

NEVER scrape panels with anything more abrasive than a soft cloth, or risk damaging the ARC. Same for harsh cleaners/chemicals.

On cooling of panels: For starters, NEVER apply water to a panel when the panel is warm enough to be generating much electricity. Do it early in the A.M. before the panels get much above ambient temp. If you can see a momentary rise in array voltage/output, that is an indication that the array was probably too warm to safely rinse it.

As for the length of, or being able to spot any temporary temperature rise after cooling by rinsing, it's mostly a function of the diff. between initial panel and water temp., how cool the water got the panel, ambient air temp., dew point, wind vector and irradiance and some other stuff, all of which results in a panel temp. change, probably an increase relative to the cold condition immediately after the water was turned off. Then, if the panel is undisturbed by more water cooling, the panel temp. will increase depending on it's thermal mass, the irradiance level, and less the rate electric production to the panel as expressed very approximately by something called the thermal time constant of the panel. For my array, which is pretty typical, after a morning rinse with about 3/4 gal. H2O/panel, my best guess is that the thermal time constant is ~ 6 - 9 min. or so in an average wind of ~ 2m/sec.

Long, boring story, but bottom line, it doesn't take a panel long to reheat as f(irradiance), but if it's rinsed before the sun is strong enough to cause a panel to heat up in the first place, any production change will be mostly unnoticeable and unimportant.

[J.P.M.]

I had quite a bit of bird poo on a corner of my array and when compared to a panel three columns over that had no bird poop, power was identical as was daily kwh output.

I've decided the rain can do the work for me, even in AZ where it hardly rains. It just doesn't matter enough to do anything for it.

Well, if you can't notice a difference in output and you trust your instrumentation and methods, where's the problem ?