I wouldn't call pumped-storage Hydro[1] super-cheap but it is the default and less expensive than trying to scale lithium. There are also cheaper battery chemis

I wouldn't call pumped-storage Hydro[1] super-cheap but it is the default and less expensive than trying to scale lithium. There are also cheaper battery chemistries than lithium when weight doesn't matter. [1]: https://www.energy.gov/eere/water/pumped-storage-hydropower https://www.energy.gov/eere/water/pumped-storage-hydropower