solar power

Take a license or buy where they are manufactured already.

What I said is valid for solar electric generation. If you only want to heat water then you can use more or less traditional technologies since due to the high power density even a low efficiency is acceptable.

Here is one link that describes a cuprous oxide based cell:

http://worldwatts.com/homemade_solar_cell/homemade_solar_cell.html

There are a number of variations on this concept, and other designs using other materials. Googl "Homemade solar cells" to begin. Also, there was a previous thread here on CR4 discussing this same topic, but I do not have a reference for that. Try the CR4 search engine to find that.

Hot water or electricity?

Here is a discourse on solar cell of recent on this forum