A flow battery is a rechargeable in which an containing one or more dissolved electroactive elements flows through an that reversibly converts to . Electroactive elements are "elements in solution that can take part in an electrode reaction or that can be on the electrode." Electrolyte is stored externally, generally in tanks, and is typically pumped through the cell (or c.
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Flywheel energy storage (FES) works by spinning a rotor (flywheel) and maintaining the energy in the system as rotational energy. When energy is extracted from the system, the flywheel's rotational speed is reduced as a consequence of the principle of conservation of energy; adding energy to the system correspondingly results in an increase in the speed of the flywheel. W. Main componentsA typical system consists of a flywheel supported by connected to a . The flywheel and sometimes motor–generator may be enclosed in a to reduce fricti. .
Compared with other ways to store electricity, FES systems have long lifetimes (lasting decades with little or no maintenance; full-cycle lifetimes quoted for flywheels range from in excess of 10 , up to 10 , cycles. .
In the 1950s, flywheel-powered buses, known as , were used in () and () and there is ongoing research to make flywheel systems that are smaller, lighter, cheaper and have.
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