Flywheel storage power system

A flywheel-storage power system uses a flywheel for energy storage, (see Flywheel energy storage) and can be a comparatively small storage facility with a peak power of up to 20 MW. It typically is used to stabilize to some degree power grids, to help them stay on the grid frequency, and to serve as a short-term compensation storage. Unlike common storage power plants, such as the pumped storage power plants with capacities up to 1000 MW, the benefits from flywheel storage power plants can be obtained with a facility in the range of a few kW to several 10 MW. They are comparable in this application with battery storage power plants.

Possible areas of application are places where electrical energy can be obtained and stored, and must be supplied again to compensate for example, fluctuations in the seconds range in wind or solar power. These storage facilities consist of individual flywheels in a modular design. Energy up to 150 kW can be absorbed or released per flywheel. Through combinations of several such flywheel accumulators, which are individually housed in buried underground vacuum tanks, a total power of up to several 10 MW can be achieved. The electrical connections power low voltage motors via a DC intermediate circuit and the power converter systems are comparable to those found in plants used in the high-voltage direct current transmissions application.

Sometimes battery storage power stations are built with flywheel storage power systems in order to conserve battery power. Flywheels can handle rapid fluctuations better.

In vehicles small storage of power flywheels are used as an additional mechanism with batteries, to store the braking energy by regeneration. Power can be stored in the short term and then released back into the acceleration phase of a vehicle with very large electrical currents. This conserves battery power.

Flywheel storage for trams are a good application. During braking (such as when arriving at a station), high energy peaks are found which can not be always fed back into the power grid due to overloading danger. The flywheel energy storage power plants are in containers on side of the tracks and take the excess electrical energy. For example, up to 200 000 kWh energy per brake system are annually recovered in Zwickau.

In Stephentown, New York, Beacon Power 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 CFRP fibers which are filled with resin. The installation is intended primarily for frequency control. This service is sold to the New York power grid.

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Wikipedia