Potentially relevant, with much less moving parts: A bigger kind of "Hubspeicherkraftwerk" (not sure about the english name, wikipedia does not offer one ;)) -

Potentially relevant, with much less moving parts: A bigger kind of "Hubspeicherkraftwerk" (not sure about the english name, wikipedia does not offer one ;)) - carve out a large cylindrical block of a mountain and pump water below. http://www.spektrum.de/news/ein-granitblock-voller-energie/1061069 http://www.spektrum.de/news/ein-granitblock-voller-energie/1... (In German, though the pictures should be enough)