If you’re looking for an interesting winter project, you could do worse than taking inspiration from this excellent DIY solar shower video. The shower is designed to fit on a roof rack, be heated by the sun, and provide a 30 psi stream of water with pressure generated by an air compressor. It’s reported to get to about 95˚F after a day of driving around in mixed sun and clouds. Not bad.
I don’t think I’ve seen a more well thought out project. And the project’s creator calls it H2OT. Watch him explain and demonstrate the whole thing in a sub-six-minute video. Excellent!