In, operates in a flywheel storage power plant with 200 flywheels of 25 kWh capacity and 100 kW of power. Ganged together this gives 5 MWh capacity and 20 MW of power. The units operate at a peak speed at 15,000 rpm. The rotor flywheel consists of wound fibers which are filled with resin. The installation is intended primarily for frequency control. This service is sold.
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Electricity can be stored directly for a short time in capacitors, somewhat longer electrochemically in, and much longer chemically (e.g. hydrogen), mechanically (e.g. pumped hydropower) or as heat. The first pumped hydroelectricity was constructed at the end of the 19th century around in Italy, Austria, and Switzerland. The technique rapidly expanded during the 1960s to 1980s,.
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