Storage

What is Pumped Storage Hydropower? 

Pumped storage hydropower (PSH) is a type of hydroelectric energy storage. It is a configuration of two water reservoirs at different elevations that can generate power as water moves down from one to the other (discharge), passing through a turbine. The system also requires power as it pumps water back into the upper reservoir (recharge). PSH acts similarly to a giant battery, because it can store power and then release it when needed. The Department of Energy's "Pumped Storage Hydropower" video explains how pumped storage works.

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

https://www.energy.gov/eere/water/pumped-storage-hydropower