I think that depends on battery tech. If they get magnesium air or metal free organic flow working I would imagine it would probably be chosen over mechanical m

I think that depends on battery tech. If they get magnesium air or metal free organic flow working I would imagine it would probably be chosen over mechanical methods. Ideally I suspect you don't really want utility storage anyway, you want something so cheap, small, and renewable you can do point of load storage and have a bit of grid independence, and not need as much transmission infrastructure.