Gravity-Based Energy Storage Begins Trials 2021

Other energy storage media, besides batteries, include underground compressed air, where the weight of earth on top substitutes for an expensive pressure vessel; and molten material, often salt, maintained at high temperature and ready on demand to vaporize a working fluid (such as water) to drive a conventional turbine. And, of course, the old standby is pumping water up to a dam or water tower.

The useful characteristic of all these methods is that they can ramp up power production very quickly. The turbine methods, like present natural gas fired generators, would keep the turbines ticking over at a low rate, and quickly increase the rate when needed. The advantage of the mine-staft weight, like the batteries, is that it can sit entirely turned off as long as you like, and start up instantly anytime.

The advantage of the turbine methods is that there are lots of existing turbines, already wired into the grid, that will soon be going unused.

Another form of gravity-based energy storage, already in production:

https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricit...