Comment by myrmidon

There's some plausible concepts:

https://gravity-storage.com/technical-concept/

But battery storage is a proven technology now and the cost trends with such bespoke megaprojects are not looking promising, so I'm not holding my breath.

Burning (regenerable) metal fuel in old coal power plants is also an interesting approach:

https://www.sciencedirect.com/science/article/pii/S2666352X2...