Pumped Hydroelectric Energy Storage

Basic Technology Characteristics Cross section of a pumped hydroelectricity station. Image Courtesy of Voith Hydro.
How it Works:	Gravitational potential energy ↔ kinetic energy ↔ electricity Water is pumped up hill with excess electrical energy which is stored as gravitational potential energy. When energy is needed, water flows down through the generator to produce electricity.
Benefits:	Ability to integrate inverter-based renewables Mature, flexible, bulk storage
Challenges:	Capital intensive Geographical limits Permitting (open-loop)
Technology Variations:
Applications:	Bulk, long-duration services, power regulation and load following
AC RTE Efficiency:	70-85%
Cycle Life:	60-100 years1
Technology Readiness Level (TRL):	9 - Fully Mature
Installed Capacity:	>160 GW