[pfdietz]

Pumped thermal storage has no geographic limits. The idea is: compress argon, transfer the heat to thermal store, expand the argon back to the starting pressure to recover some work, then transfer the "cold" to another thermal store. For long term storage, use very cheap materials, like rocks, for the thermal stores. To discharge, reverse the flow, so argon is cooled, then compressed, then heated, then expanded. All this can be done with existing technologies and with a round trip efficiency of perhaps 60%.