Homemade solar heaters?

[Aranon]

What if you built a 2x4 frame and used 1 1/2" ISO board (polyisocarnate) with the black tarpaper finish on the bottom and sides and plexiglass or glass for glass for the top glasing. It will make it like the inside of a car during summer.But you have to be careful or you might melt your plastic pipe. I understand you can almost get the water to boiling that way and it holds the heat more after the sun goes down. This is how if I understand correctly that hot water solar heaters are made for home hot water heaters but they use a storage tank where you pool would act as the storage tank. Some use copper piping in this system for better heat transfer. If you really want to get it hotter put the system in a parabolic dish like two curved sections of three ft. dia. pipe painted silver to reflect the sun's energy to increase the heat even more.