Pumped hydro

Pumped hydro storage is a way of saving large amounts of energy for a city. When electricity is readily available, like when wind turbines are turning quickly, water is pumped up a hill into a reservoir. When the demand for energy increases, the water is allowed to flow back down the hill, creating more electricity as it spins a turbine. This is currently the largest form of energy storage for the grid, but it has limited use because it requires a large reservoir of water and a hill to pump the water up. Some companies are trying to find alternatives, like using pebbles instead of water or pumping water underground and releasing it to turn a turbine. If successful, this could be a great solution as it would reduce the amount of equipment needed above ground.

Gates, Bill. How to Avoid a Climate Disaster (pp. 92-93). Penguin Books Ltd. Kindle Edition.