A long time ago I was interested in alternative ways to store energy, one good method but quite expensive is to convert it to Rotational energy of a flywheel, N

A long time ago I was interested in alternative ways to store energy, one good method but quite expensive is to convert it to Rotational energy of a flywheel, NASA had pretty good results with magnetic bearings and vacuum. https://en.m.wikipedia.org/wiki/Flywheel_energy_storage https://en.m.wikipedia.org/wiki/Flywheel_energy_storage It isn't practical and much more complicated than the other alternatives mentioned