Trompes

renewable-energy/hydro-power

Further links from this site
https://permies.com/t/16261/Mollison-Trompe-alternative-energy

I haven't watched this video, but trompes are a really interesting idea. No moving parts, but can extract useful work from following water, provided there is a decent drop between sides of the system. They aren't terribly efficient though; I don't know what fraction of the available energy they can extract, but it is not high.

I've thought previously that they could be used to provide passive cooling - potentially to icebox temperatures - as they extract heat from the air and sink it into the water stream. As the the air re-expands again it cools down. If you had exactly the right circumstances of geography you could make trompe cooled fridge/freezer icehouse.