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Will Cool Water Break Hot Solar Panels?

05/14/2009 12:48 PM

Greetings! I'm new to the site. I've read several comments about cooling solar panels but I haven't seen anything about this: Will spraying the hot surface of solar panel glass with cool water break the glass? I am concerned about the sudden temperature change introducing stress to the glass surface. I contacted a solar panel manufacturer and they recommended not to cool with water spray because of this. It could just be a case of CYA. I have seen numerable times when rain will fall in full sun because of wind carrying the rain from a nearby thunderstorm. Of course, the effect would be the same; cool water on a hot surface. I don't think using cooling tubes/jackets from underneath would be a viable option for me. My panels are surface mounted to the roof due to high wind loads. We got 75 MPH winds over here from hurricane Gustav. Due to the mounting brackets, there is about 4" clearance from the roof surface to the underside of the panels. Anyway, I am considering using landscaping type mini-sprinklers mounted on the fascia and directing the spray up onto the panels. I have the option of using community well water (about $10/month for the quantity I would use) or I could pump water from a bayou about 200' from my home. Either way I would use sediment filters and possibly a filter for dissolved minerals. I've read about some concerns pertaining to the dissolved minerals etching the glass panels. I could use rainwater captured in rain barrels but I would have to supplement it with another source. Whew! Sorry for the long post. I just wanted to try to get all of the information in. Thanks for your suggestions.

Don

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#1

Re: Will Cool Water Break Hot Solar Panels?

05/14/2009 4:51 PM

I can offer this anecdotal observation: without worrying about the concern you raise, I hosed off my new Andalay 175W panels (24 of them) during the heat of the day, in direct sunlight (~3 pm) to remove the ash from the recent fires here in Santa Barbara. Although steam appeared and the panel surfaces dried in moments, none broke. The Pac reading went from ~2.8kW to 3.1kW after rinsing. Come to think of it, I have done the same thing to the two 75W Siemens panels on my boat - without damage.

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#2
In reply to #1

Re: Will Cool Water Break Hot Solar Panels?

05/14/2009 5:24 PM

in research : i asked this question :

was told that periodic cleaning of the panels was essential for optimum operation.

got that from 3 or 4 manufactures here in Calif.

both from flexable and " rigid " panel makers..

don't own any , yet..

So all i can contribute is a rumor

my two cents

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#3
In reply to #2

Re: Will Cool Water Break Hot Solar Panels?

05/14/2009 5:53 PM

Ahua and Hogdmo,

Thanks for your replies. I agree with both of you. I guess I just needed some positive reinforcement. I'm still doing research on how best to water cool my 36 panels (6kw). I'm still leaning towards using the landscape type mini-sprayers.

Hogdmo: I hope you make out OK with those wildfires. I can kinda identify with the situation. I'm a retired firefighter from New Orleans.

Any further comments concerning the glass panels, water cooling systems, etc. will be much appreciated. From what I've read, cooling increases the panel efficiency as well as their life expectancy.

Thanks again,

Don

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#7
In reply to #1

Re: Will Cool Water Break Hot Solar Panels?

05/15/2009 7:56 AM

This reply is not so much about cold water on panels but why are you using panels in the first place?

From what I have researched by placing a solar pre heated black tank before the inlet of a conventional water heater the thermostat of the water heater will rarely go on since water coming in the tank will be most times hotter than the thermostat setting.

Any reason this does not make sense? Solar panels attempt to be the primary source of water using all sorts of gizmos where a metal black box will solve the same goal?

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#4

Re: Will Cool Water Break Hot Solar Panels?

05/14/2009 7:50 PM

Just a thought, but, you might ask your insurance carrier what they do and don't cover.

Does the manufacturer warrant them against rain damage?

My non-expert opinion is that no solar panel manufacturer is going to sell an outdoor device that can't withstand the outdoors.

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#5

Re: Will Cool Water Break Hot Solar Panels?

05/14/2009 11:08 PM

Water and hot glass generally don't mix BUT what is the purpose of mixing the two.

If you want to wash - water wash after 8pm and before 8am...

If you want to cool the unit for some reason use the finest spray nozzle you can afford and provide adequate pressure to MIST or fine spray (1mm droplet dia)...If the unit is very hot...fine spray will vaporize before it contacts the glass BUT cool the air layer over the glass...once it doesn't vaporize the glass will be cool enough to not have any problems and the droplets will then wash the surface...

YankeeFlasher

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#6

Re: Will Cool Water Break Hot Solar Panels?

05/15/2009 1:11 AM

There shouldn't be an issue with slowly cooling the panels. They are made to withstand temperature extremes... just not rapid changes. I fine mist will slowly cool the panels, a bucket of ice-water will break them.

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#8

Re: Will Cool Water Break Hot Solar Panels?

05/15/2009 11:29 PM

Hello Don in LA,

No problems with 'long posts'! Can I assume you are talking of direct sun/electronic solar panels?

Just a point here..........They are designed to withstand 'cold' rain, so I would think it would be OK to use a sprinkle system on them?

You may have said and I missed it, can you tell me what the name of the solar panels is please? I can then find more info'. Have you tried getting in touch with the manufacturers?

bb

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#9
In reply to #8

Re: Will Cool Water Break Hot Solar Panels?

05/16/2009 4:19 PM

Babybear,

Thanks for your reply and ideas. Yes, I am speaking of direct sun photo voltaic solar panels. The manufacturer is Solar World. I did check with another manufacturer some time back before my installer suggested going with Solar World. The original manufacturer told me on the telephone not to cool with water because the cold water could break the panels. In its brochure, Solar World writes that panels can be cleaned "with lots of water". No mention of time of day and temperature. Of course, I should have read the brochure first. I will call Solar World on Monday. If I do use water I will use as fine a spray as possible that can throw water 15 feet (3 panels high). I have read several reports that say, depending on temperature, the PV panel can loose 10% efficiency or more due to elevated temperatures. Thanks again. I welcome any more suggestions/comments.

FWI: My state, Louisiana, is paying for half of my PV system. And the federal government is paying another 30%. Both are through tax rebates/credits. I've read that some European countries also have some very good enticements.

Don

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#10

Re: Will Cool Water Break Hot Solar Panels?

05/16/2009 11:10 PM

I am considering putting something like the aluminum heat radiators they use with pex tubing under floors and attach them to the back of solar panels.

The heat can be used for pre-heating domestic hot water, and if you have a relatively large tank (450 gal 'totes' are readily available in this area, roughly 4' cubes with large plastic vessle covered by an aluminum cage that is fork truckable) and use a small pump to pump water through the pex placed on the back of panels to cool them.

It doesn't fix the issue of cleaning the front surface, but can cool the panels and help increase productivity of some cells.

Is it enough to make a difference? I have no idea, but if you want to ALSO collect low quality hot water, it shounds reasonable to me.

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#11
In reply to #10

Re: Will Cool Water Break Hot Solar Panels?

05/17/2009 10:00 AM

That sounds like a good idea using the aluminum heat radiators. It's something I would consider if my panels weren't already installed. I guess I should have done more research before. One thing I did have the foresight to do was to pay to have a heat collector installed with my HVAC heat pump. It basically collects the heat generated by the running of the HVAC and pumps it to my water heater. It provides hot water as long as the HVAC is used. We get enough rain here to keep the panels clean most of the time. There are times when pine pollen will be a problem.

Don

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#13
In reply to #10

Re: Will Cool Water Break Hot Solar Panels?

05/18/2009 11:42 PM

Hello servant74,

I built a row of south facing ordinary radiators painted black, and encased in plexiglass.

With the whole thing heating a swimming pool. It was very successful. Everything was second-hand, and it really did work well. And it was in Europe about the same latitude as London. It was a tennis court sized pool outside.

bb

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#12

Re: Will Cool Water Break Hot Solar Panels?

05/18/2009 3:32 AM

Presumably the panels will be constructed so as to minimise the effect of damage to things falling on them:

  • leaves
  • twigs
  • rain droplets
  • snow
  • hailstones
  • etc.

won't they?

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#14
In reply to #12

Re: Will Cool Water Break Hot Solar Panels?

05/20/2009 6:53 PM

Yea, I guess the key word is "minimize". I've read several different company's instructions and, basically, they say to not use water on hot panels. I still wonder if it is just a case of CYA. If anyone out there has had good or bad experiences with this please let me know. There was one reply by someone in California (Sorry, I don't remember your name) who said he hosed his panels off in the heat of the day with no problems.

Another option would be to cool the underside of the panels with evaporative cooling via a mist on the roof under the panels, not directly on the panels. Any ideas?

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#15
In reply to #14

Re: Will Cool Water Break Hot Solar Panels?

05/23/2009 2:48 PM

If they are designed for outdoor installation and use in that area, then the CYA factor sounds like it is pretty high. I agree, don't throw ice water on them, but if you would be comfortable putting your hand or foot in it, it is probably OK.

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#16

Re: Will Cool Water Break Hot Solar Panels?

01/19/2011 6:58 AM

Hi, Really a long but a very informative post! Please provide more details on Solar Panel systems!

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Users who posted comments:

ahuha (1); Anonymous Poster (1); babybear (2); buck3647 (1); ctwiliams (1); Don in LA (4); hodgmo (1); lighthasmass (1); lyn (1); PWSlack (1); servant74 (2)

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