Startup Claims Breakthrough in Long-Duration Batteries

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31. Here's what we have now for storing surplus electrical energy: pumped storage.

Pumped-storage hydroelectricity


Diagram of the TVA pumped storage facility at Raccoon Mountain Pumped-Storage Plant in Tennessee, United States


Shaded-relief topo map of the Taum Sauk pumped storage plant in Missouri, United States. The lake on the mountain is built upon a flat surface, requiring a dam around the entire perimeter.

Pumped-storage hydroelectricity (PSH), or pumped hydroelectric energy storage (PHES), is a type of hydroelectric energy storage used by electric power systems for load balancing. The method stores energy in the form of gravitational potential energy of water, pumped from a lower elevation reservoir to a higher elevation. Low-cost surplus off-peak electric power is typically used to run the pumps. During periods of high electrical demand, the stored water is released through turbines to produce electric power. Although the losses of the pumping process make the plant a net consumer of energy overall, the system increases revenue by selling more electricity during periods of peak demand, when electricity prices are highest. If the upper lake collects significant rainfall or is fed by a river then the plant may be a net energy producer in the manner of a traditional hydroelectric plant.

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It's not an efficient method of storing energy.