Well known as "pumped storage". They're competing with it, but dry and upside down. Is it more economical? Maybe. Is it safer? See http://en.wikipedia.org/wiki/

Well known as "pumped storage". They're competing with it, but dry and upside down. Is it more economical? Maybe. Is it safer? See http://en.wikipedia.org/wiki/Taum_Sauk_Hydroelectric_Power_Station http://en.wikipedia.org/wiki/Taum_Sauk_Hydroelectric_Power_S... At least if this contraption breaks, there's nothing important below it.