Here is our ‘no effort, no-tech, solar thermal hot water’ system. Once built, it collects, heats and distributes hot water without any pumps, heating elements, energy consumption or moving parts. Can’t get any simpler. Can’t get any lazier. In this experimental design, water is caught, stored, and heated on the roof, before being gravity fed down to a super low flow shower head. Interestingly, when we did the calculations to figure out how much surface area would be needed to keep a modest supply of hot rainwater on demand for showers (1″ of rain on 1sq/ft of roof space produces 0.6 gallons of water), it was the same surface area as the solar panels (the PV panels used for electricity).
So a gutter off the solar panels was built to feed rain directly into a maze of PVC pipes that have been sized to hold the recquired amount of water and keep it hot. In an ideal situation everything is sized so that the pipes never go empty in between rain storms.
The good news is that the calculations seemed to work and so far (even in this dry summer) there is always shower water ready. The bad news is that its hardly more than luke warm most of the time.
There are plenty of ways of making DIY solar thermal panels. Some of the best seem to include sending water through the grill you find on the back of any junked refridgerator. Our PVC system was really just an experiment. The next phase will make hotter water, and also address the obvious problems of winter.