A typical system consists of a flywheel supported by rolling-element bearing connected to a motor–generator. The flywheel and sometimes motor–generator may be enclosed in a vacuum chamber to reduce friction and energy loss. First-generation flywheel energy-storage systems use a large steel flywheel rotating on mechanical bearings. Newer systems use carbon-fiber composite rotors tha. OverviewFlywheel energy storage (FES) works by spinning a rotor () and maintaining the energy in the system as . When energy is extracted from the system, the flywheel's rotational speed is reduced a. . 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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