Advice on cleaning PV panels

[J.P.M.]

Just out of curiosity, has anyone ever heard any actual reports of panels getting damaged because they were hit with cold water during the daytime?

It seems to me that if this is a real risk, then it would also happen if there was a sudden rainshower on a sunny afternoon.

Here in the midwest, in the summer we can get isolated convective showers in the afternoon where it will be bright sunshine right up to the moment when the rain hits the ground. I've certainly never heard of a solar panel breaking because of an afternoon rainshower.

I have a feeling those showers happen in other parts of the world as well. As do hailstorms and hurricanes. Every situation is different. The probability of a panel cover cracking due to thermal stress is unknown to a large degree, but hitting a hot panel with a hose seems a moron's invitation to a disaster.

Why take the chance ?

Talking about dimensional changes, when things like glass fail in such situations as being discussed here, usually and often the failure is caused by a sudden dimensional change of a PART of the light of glass relative to some other PART of the light, not necessarily because of edge constraints.

BTW, thin(ner) glass has some minor advantages in this respect, as does low iron glass to a greater degree because it runs cooler (less absorption of solar irradiance --->>> cooler operating temps).

A rainstorm, even a deluge, USUALLY produces a more uniform temp. change across the entire light of glass. That mitigates the differential expansion within and across the glass to a great degree. A hose usually/often hits one part/portion of a light and not other portions first, and usually with large amounts of water. It's the internal differential dimensional change of a relatively brittle material that lacks a predictable "yield" point and goes immediately to brittle fracture/failure over a "short" time that causes all or most of the problems.

[DanKegel]

No, but when I was a kid, I broke our 1967 Ford station wagon's windshield by spraying it with a hose on a hot day in Seattle.

I remember watching that crack creep across the windshield with a sense of dread.

[pleppik]

Wash with plain tap water in the AM, before the sun hits them (cold water & hot panels = damage) and then rinse with the DI (spot free) feature.

Just out of curiosity, has anyone ever heard any actual reports of panels getting damaged because they were hit with cold water during the daytime?

It seems to me that if this is a real risk, then it would also happen if there was a sudden rainshower on a sunny afternoon.

Here in the midwest, in the summer we can get isolated convective showers in the afternoon where it will be bright sunshine right up to the moment when the rain hits the ground. I've certainly never heard of a solar panel breaking because of an afternoon rainshower.

[Mike90250]

re-posting a safe, cheap method

Look at the Mr Clean Car Wash kit, and it's DI water filter cartridge. Forget the soap. Wash with plain tap water in the AM, before the sun hits them (cold water & hot panels = damage) and then rinse with the DI (spot free) feature. You can get the rinse DI refills @ amazon or ebay.

http://www.amazon.com/Mr-Clean-AutoDry-System-Starter/dp/B0006M56CE

mr-clean-auto.jpg

[J.P.M.]

FWIW, as my panel fouling research continues, I become more convinced that my array, in a semi rural area, without rain of some sort, loses performance due to fouling at an approximate rate of about 1% per week.

A rain of, say, .25" or so will restore about 2/3 of the accumulated performance deficit. So, 6 weeks after a wash, without some precip., there's about a 6 % performance penalty. If it then rains, about a 4% improvement down to about 2% dirty or so. 4 more weeks after that, about a 6% penalty (the remaining 2% + 1% for each of 4 weeks). After all this measuring is done I'll probably hose down the array with a hose (IN THE EARLY MORNING !!) about 1X/month or a month after a sig. rain, and wash it at each equinox.

Without washing, I believe that the rate of fouling will become asymptotic at somewhere between 10 and 12% for my location, but don't have enough long term non-rain conditions to say much that's substantive on that (yet).

Two other points:

I see no quantifiable benefit to D.I. rinse. If it exists, it's too small for me to identify. I washed and rinsed w/plain H2O, Washed and rinsed w/D.I. water, and also washed and rinsed with regular water during a continuing rainstorm (03/01 +03/02/2015) and the next fouling measurements showed no quantifiable diff. between the three methods.

I'd add that due to instrument limitations, about the best I can claim is about +/- 1 to 1.5% or so in accuracy if I'm careful and lucky, maybe a bit better on precision which is one reason why all this is an approximation, perhaps made better by consistent repetition on clear, cloudless days.

Also, morning fog that results in measureable precip. in the rain gauge tends to mud and cake things up some on the entire panel, particularly at the lower 10"-12" of a panel. That's a pretty common sight around here and I expect elsewhere as well.

Take what you want of the above. Scrap the rest.

[silversaver]

Best of luck my ass. Only a moron would spray water on a panel when the sun is shining.

+1


lately I have been reading noob starting business without proper knowledge of business they are after.

[J.P.M.]

without being redundant... you need to use something that has a spot free rinse, these panels get so hot in the sun. There is a system that we use that produces 99.99% pure water. You can spray this water on a solar panel on the hottest day of the year and it will dry without any water spots. It has been the biggest secret to our success as a solar panel cleaning company. If

I hope this helps and best of luck

Best of luck my ass. Only a moron would spray water on a panel when the sun is shining.

[russ]

without being redundant... you need to use something that has a spot free rinse, these panels get so hot in the sun. There is a system that we use that produces 99.99% pure water. You can spray this water on a solar panel on the hottest day of the year and it will dry without any water spots. It has been the biggest secret to our success as a solar panel cleaning company. If you would like to see the system we use, it is listed here: Www.bs.com

I hope this helps and best of luck cleaning your system.

- John at Professional Solar Cleaning and Care

Redundant or noyt you are being wrong - do not speay cold water on hot glass

[DanKegel]

I've cleaned mine a few times, and the main thing I needed was a way to reach 'em all.

I got a long window washer's pole / squeegee / pad from the local janitorial supply store
(I live near several - it's like service industry central here and expect it'll be a lot
easier now.

I don't worry about getting them too clean anymore, just getting the worst crud off every year seems like the right balance for me.

I tried measuring best kwh/day generated during the week before vs. the week after cleaning to get a rough idea how much it helped last time, and it wasn't huge, worth doing myself but not worth paying anyone else to do.

[PSCCHawaii]

Deionized water

without being redundant... you need to use something that has a spot free rinse, these panels get so hot in the sun. There is a system that we use that produces 99.99% pure water. You can spray this water on a solar panel on the hottest day of the year and it will dry without any water spots. It has been the biggest secret to our success as a solar panel cleaning company. If

I hope this helps and best of luck

[Mike90250]

Well, the MR Clean was a great system. But the Zeolite resin bed used to create the DI water for the spot free rinse, is expensive. Car dealerships have the roll-around cart with 2 DI tanks on them for their daily rinse of their stock. Maybe a local water softner company can supply you with a DI tank, and you just return it when exhausted and swap for a new one. Culligan home delivery service is expensive.

[Librehombre]

I discovered that P&G have discontinued the Mr Clean Auto-dry product. It is still widely available on ebay, but I am surprised at the cost of consumables. The filters are expensive and supposedly have to be (should be) replaced after ten car washes. Your mileage may vary.

Do any users have experience they can share? If the product is discontinued does this mean the consumables are also going away?

[solarpowered]

Hose, tap water, and a squeegee. Phoenix is very dusty and the panels will need to be cleaned regularly.

Its not recommended to squeegee if panels have AR coating on them, only water.
Not recommended to use any pressure higher than 60PSI, which is standard water pressure.

If by chance the panels don't come with AR coating I apply a water proofing agent such as automotive rainex, it takes both water and dust off when washing with just a hose.

Look at the Mr Clean Car Wash kit, and it's DI water filter cartridge. Forget the soap. Wash with plain tap water in the AM, before the sun hits them (cold water & hot panels = damage) and then rinse with the DI (spot free) feature. You can get the rinse DI refills @ amazon or ebay.

http://www.amazon.com/Mr-Clean-AutoDry-System-Starter/dp/B0006M56CE

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The mister clean approach works, but then again you have to make sure the chemicals and degreasers don't effect AR coating.

[Naptown]

I would do some serious research on the aquapel product to see how well it plays with the sealants and encapsulants in the PV panels before I would think of applying something like that. You could damage or destroy the seals on the panels rendering them dead prematurely.

[Librehombre]

Cleaning PV panels

I like the Mr Clean approach and agree with you not to use soap. For one thing soap and sloping roofs don't make a good combination. None the less it may came in handy in the case of pigeons in our area that occasionally have serious diarrhea issues. Will have to hope for the best and prepare for the worst.

While I was cogitating about the water spot problem I recalled a product I used to use in California on my car windshield. Cannot recall the name right now, but you may know what I mean. It makes water sheet up and quickly run off. Apparently there is more than one product like this -- I recently found Aquapel quite by accident:

quote
See Clearly and Drive Safer, Longer with Aquapel Windshield and Glass Treatment.
Aquapel Windshield and Glass Treatment uses technology originally innovated for the aviation industry. When applied to your vehicle's windshield, Aquapel dramatically improves vision when driving in the rain, day or night. Aquapel forms a chemical bond with glass - unlike other products that simply coat glass - to increase water repellency, causing it to bead and easily roll right off the glass. Aquapel is easy to apply and can last up to 6 times longer than other products. Each box contains one applicator and one treatment good for months of improved vision!

/quote

If it works well using Mr Clean and Aquapel together may solve all my problems. I would experiment first on one panel and see what happens.