I saw something similar to this, using the power of a nearby stream, but in this case it was to generate heat. Apparently it used the difference in temperature between two parts of the river and magnifed this somehow to generate hot water. It was called a vortex valve or something like that (but I can only see this relating to gas in my google searches), I never have been able to find it again, anyone know what it was?
Ah, I finally found it, including the full show. If anyone is interested it was Science Shack with Adam Hart Davis. I've not rewatched the show but I guess it was either the heat pump or the vortex tube...
In 1988 R.T.Balmer applied liquid water as the working medium. It was found that when the inlet pressure is high, for instance 20-50 bar, the heat energy separation process exists in incompressible (liquids) vortex flow as well.
