http://en.wikipedia.org/wiki/Pumped-...droelectricity has a bit about pumped water storage.
We thought about doing this 20+ years ago when we had a place with a quarry on a hill top, but it wasn't the kind of quarry with pits full of water, so tanks or ponds would have had to be constructed. As it turned out, our wind generator located near the house at the bottom of the hill produced 90% of the power we needed, the rest supplied by rarely running an old engine driven generator, and later with PV panels, so we never did much except a rough estimate of piping cost, etc. , which was enough to scare me off.
Good old lead acid batteries work fine for me in this kind of situation, but using the power directly (such as solar hot water panels) can be cheaper.
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