The world’s largest demonstration plant for a new kind of renewable energy storage is up and running in the west of the China. Called liquid-air energy storage (LAES) the plant uses renewable electricity to compress air to extreme densities until it turns to liquid. It can then be rapidly released to power a turbine and discharge that green energy back into the grid.
Basically liquid nitrogen? I guess its a question of how much energy you have to put in to get it to expand rapidly enough. Presumably just exposing it to atmospheric conditions will be quite a slow expansion.
But maybe , at scale, that’s enough to get astable flow into a turbine.
It doesn’t sound quite as convenient as pumped hydro (in terms of controllability) but if you don’t need a lake at top of mountain, then that’s cool.