Water mist cooling for increased panel efficiency?

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

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