Pumped hydrogen storage
“How can we use a gravitational potential to store energy?”
If you have ever taken an introductory physics class, then you know that anything with a mass at some distance from the Earth has an energy potential associated with it given by the equation P.E = mgh, with m being the mass g being gravity and h being the height. So logically speaking, if we were to vastly increase the mass then we would also vastly increase the potential energy. So if we have a large enough mass, we can store enough energy for an electric grid!
This is the exact idea behind a technology known as pumped hydrogen storage. Pumped hydrogen storage takes two water reservoirs at a height gradient, and discharges energy to the grid by moving the water through a turbine and stores more energy by using a grid powered pump increase the level of water on the top layer