Water mist cooling for increased panel efficiency?

2twisty · June 2016

I know that panels lose efficiency as they heat up. I know that cooling the panels has been discussed and it's been concluded that the power gains wouldn't be worth the power expenditure to cool them.

I got this hare-brained idea the other day when washing the dust off my panels.

What about evaporative cooling? I live in the West Texas desert where it is VERY dry (<16% humidity, my digital hygrometer only goes that low), and very hot (105F yesterday). A periodic gentle water mist would cool the panels substantially, no? I'm not talking about flowing water on them, but just a mist to cool them off.

If feasible, would there be risk to the panels from water droplet lensing effects or should the water mist be applied to the back of the panels?

BB. · June 2016

I would suggest that you would eventually get hard water deposits on the glass/etch the glass and have other problems. Corrosion, algae growth, water in electrical boxes, possible using up local water source capacity, etc.). Creating a marsh/possible mosquito habitat would be a draw back too.

Water on solar panels does creates lensing and reflective effects--And I do not know if that reduces panel output or not. On my house (105 degree days are vary rare here), I tried cooling my roof top panels with water on my Grid Tied system, and I did not really see any noticeable effect.

In the end, get 10-20% more solar panels (one time expense for not much money) and avoid the wet array.

-Bill

Dave Angelini · June 2016

Bad Idea !
Temperature cycling is how you damage things when you want to test for a failure point.

BB. · June 2016

Temperature cycling is one problem (night/noon temperature cycling). And thermal shock (very high rate of temperature change--such as cold water on hot panel) is another potential cause of early life failure. And there is simply elevated temperatures (every 10C increase is 1/2 cut off of life... Running at 40C is 1/4 life -- 1/2 * 1/2). Just like Dave says--Engineers use thermal cycling (and thermal shock) as major design verification tools (and high temperature operation as accelerated life testing).

If you could run cold water through a heat exchanger on the rear of a solar panel--Yes--You could have increased power output and increased life.

However, the cost/complexity/power required to run pump/water leaks/weight all add to the downside. A decade ago, panels were $10 per Watt. Today, they are less than $1 per Watt. It is not (in my ever so humble opinion) to build $10 per Watt panels (not even a SWAG) panel cooling system to extend the life of a solar panel by 2x and 10-20% increase in electrical output power.

Get good quality "glass" panels--And they will last you 20-40 years pretty easily. And if/when they fail, replace at $1.00 per Watt.

If you still want to look at water "cooled" solar panels, you can check out Sun Drum:

http://www.sundrumsolar.com/products--services.html

From my point of view, they do not really "cool the panels" for increased power output/life--But are doing secondary thermal solar collections under the solar electric panels (pool heating/domestic hot water/etc.).

Perhaps a good idea if you have limited space for solar panels--But otherwise, would not be my first choice.

-Bill

2twisty · June 2016

I was looking for a way to get closer to my panel rating in the summer. In the winter (because I adjust angles) I often see 2KW+ production out of my array (array combined panel rating is 2170W). In the summer (again with adjusted angles) I rarely see 1.8KW. Since in summer I use more energy for cooling, it's a "worst of both worlds" scenario.

Since adding panels for me is expensive (I have to buy them in groups of 3), I was looking for a way to eke out a bit more efficiency during the time of year that I consume the most energy.

There is a lengthy (and heated) discussion of this over on SolarPanelTalk.

https://www.solarpaneltalk.com/forum/solar/solar-energy-facts/18035-water-cooled-solar-panels-for-significant-output-boost

I'm still reading it, but the consensus I'm getting is:

Cooling the panels *will* increase the production
Finding a way to do it that uses minimal energy is a challenge
The discussd methods all seem to be "too fiddly" for customer installation, but if you're a tinkerer and consider your labor to be free, it might be worth it...maybe.

I'm going to continue to read the thread. I may give it a try if the costs aren't too high in terms of materials. I'm thinking to mist the underside with either sprinkler system parts or those vegetable misters you see in the produce section.

Your point about thermal cycling is a good one. So far in the thread mentioned above that has not come up... I will certainly add that to my deliberations. I don't want to harm the panels, that's for sure!

vtmaps · June 2016

2twisty said:

In the winter (because I adjust angles) I often see 2KW+ production out of my array (array combined panel rating is 2170W). In the summer (again with adjusted angles) I rarely see 1.8KW. Since in summer I use more energy for cooling, it's a "worst of both worlds" scenario.

I also have higher peaks of POWER production in the winter, but that in no way makes up for the lower daily ENERGY production in the winter. When you consider the length of the day, I'm sure you will find greater daily energy (kilowatthours) production in the summer.

--vtMaps

BB. · June 2016

I used to evaluate disk drives decades ago--Thermal cycling 2x per day from min to max data sheet temp specification--I could get about 3/4 of them to fail in two weeks. Was a really quick/good way to weed out the weak devices.

The "good ones" would not fail even in 1 month of cycling.

-Bill

Photowhit · June 2016

You might find that running a sprinkler on the area that you wish to cool, might be a more effective way to use in essence the same idea. I know the pool room I use to shoot at tried it and ended up installing sprinkler in the roof. They claimed it saved them a couple hundred a month.

2twisty · June 2016

Water is a precious commodity out here, so I'd want to have a direct effect rather than a passive one. That's why I was considering directly spraying the panels, to get the most out of the water use.

Mountain Don · June 2016

2twisty said:

Water is a precious commodity out here, ............

Yep, and I believe using water to cool panels is a waste of water. We don't even use evaporation cooling here in my part of NM any more because the water is precious and from the municipal system very expensive.

FWIW after we installed a new higher efficiency furnace and refrigerated air (replacing the swamp cooler) our total of the electric, natural gas and water was reduced by a notable amount.

Water mist cooling for increased panel efficiency?

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