eraser1;
As you can see from the posts there are quite a few things that can be done.
Some of it will come from your own imagination.
Sice you're already building a solar heater for your water you could build into it some type of co-generation system where a part of the design is to heat a much smaller diameter tube of water wound so that it gets to steam hot, this will do too things.
- ) boil the water so that it is safer to drink
- ) steam for running a steam powered generator.
Or if you wanted to leave the current box alone, go get a stainless steel mixing bowl from the dollar store, don't get the better 1/2 mad by taking one from the kitchen ;-) find the focal point and use the heat focused on that point to do the water distilling and steam production.
Sky's the limit for doing stuff with solar heat. <<< Pun intended>>>
Hope this helps
Bruce S