There were a couple of reasons for building a solar powered shower at the Traumschule when I showed up for the skill sharing camp in March; it'd been something I'd wanted to learn for a while, the only existing shower they had was a cold hose in the basement, and it was the north of Germany, in March.
Generally if the only way to get clean involves water slightly above freezing, I just won't get clean. The other people there didn't seem to mind too much, but Germans, like Scandinavians, are insane.
Most of what you see here was built in about two weeks, but wasn't actually finished until October, and not by me. I had an epic struggle with first the bends for the copper tubing (below) and then the water tank, which simply would not stop exploding, often spectacularly.
(I wasn't aware the water pressure was 5 bar, or twice that of a car tyre. That kind of psi simply will not be contained.)
In the end we went with a non-pressurised system using a toilet cistern. It worked pretty good and we still got a good rate of flow from the shower head.
It all works off a simple thermosyphon principle, where the water circulates itself through the heating panel due to the fact that hot things rise.
The actual metal panel we ended up using was donated to us, but not before I'd spent longer than intended trying to make this one. We had a bunch of old copper pipe, but I had massive problems joining it together.
The proper way is to get copper elbows and solder the whole thing, but we didn't have the money or soldering setup for that, so I had to try to make do with plastic hose, which kept going soft and collapsing when it got hot.
Finally the solution was to use two types of hose, one inside that other. The outer hose is the right diameter to fit snugly over the copper, with ridged washing machine hose inside to keep it strong and evenly curved.
However, shortly after coming to this I decided I really had to get back to the solarflower, and then we were donated the other panel anyway, so it never got finished.
But it's a good way of doing it.
Then a month later we discovered a full industrial grade water heating panel just laying around in the basement which made all of this unnecessary in the first place.