In some areas, the water use just from cleaning solar panels becomes a serious issue (let alone using more water to cool them). It's not much water to spray on some panels you are experimenting with, but for a large installation it seems like it would be a lot of water.
The best areas for solar are hot, those are also likely to be the areas where water supply is the most constrained, so this is definitely a no-go solution
Sorry if this is too basic of a question but for places close enough to the sea, would sea water for cooling and cleaning be an option? Too much salt residue?
Now I'm waiting for the seaside solar power plant/salt works proposal to pop up!
Seriously: Maybe residue wouldn't be an issue if it was never allowed to dry, but the corrosion-proof construction, drainage system, and pumping costs would be considerable. Then there's the 100 problems we're not aware of yet...
