Hey Janne, thank you so much for taking the time to explain your idea in full details. Much appreciated.
After all the ideas I have recieved, I feel very inclined towards a simple heating of a metal bucket/tank inside of a stove, probably a rocket mass one. And directly connected to a short pipe leading to a closeby shower.
I didn't understand entirely the mechanism you had back at your place in Germany, but you think a coil without water in it would be a good enough conductor?
A solid copper rod is more efficient, but more difficult to bend.
Yes it will transmit heat if the distance is short.
It would be easier if you told us more in detail how your house/ shelter is. Is it a house?
With my bucket idea I assumed it is a shelter type a tent, with an open fire outside. If you have a house or cabin there are better solutions, but just as easy.
Basically two buckets, the lower one adopted for a fire, the top one as described.
The house I owned on the German border ( in Czech Republic) was built in the early 1800's, comletely original and oldfashioned.
The iron plate ( not cast iron) cooking / hot water device was incredibly simple, yet ingenious. Built in in a large brick construction with the flue zig zagging inside, an brick oven beside and a bed above.
They were not stupid in those days, they used the fuel to the max. It takes a lot of hard work to get wood, so they used it as efficiently as possible.
Making fire 3 times a day, maybe one hour a time, cooked all our meals and drink, gave all the hot water for me and my family and heated the room. The brick construction as like a heat sink, radiated heat all the time.
Never baked any bread, just roasted chicken and pork in the oven.
It was our holliday getaway for 10 years. We did gently modernize it though. Electricity, pump fed water, sewage. But we hardly used the modern kitchenette I installed, the wood fired range/oven was much cheaper and better.
( I did buy the wood though)