Pumped-storage hydro[1] is an established concept and is in active use all over the world (Europe, US, Japan, ...). Austria for example has a lot of hydro (ove

Pumped-storage hydro[1] is an established concept and is in active use all over the world (Europe, US, Japan, ...). Austria for example has a lot of hydro (over 70% of total production!) including multiple pumped-storage installations. There's huge excess capacity at night here thanks to all the hydro, so you might as well use it for something useful. [1] https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricit...