Use of flowing water to create electricity is called hydroelectric energy. The most common type of hydroelectric plant uses a dam on a river to store water in a reservoir. Water released from the reservoir flows through a pipe and into a turbine, which spins to drive a generator, producing electricity.
Pumped storage plants use a two-reservoir system, pumping water from a river or a reservoir to a higher reservoir when electricity prices are low during the night. When the value of electricity on the grid is higher during the day, water is released from the upper reservoir, spinning the turbines to produce electricity.

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