The flywheel energy storage system is composed of flywheel rotor, motor, bearing, power electronic interface and casing. 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. In Germany, a 600 kW storage system from STORNETIC is operated by a large municipal utility company. These are both based on carbon composite rotors. These investments refer to a STORNETIC DuraStore unit (Fig. A FESS consists of several key components: (1) A rotor/flywheel for storing the kinetic energy. It is characterized by full magnetic levitation, low energy consumption, fast response, long life, high number of charge and discharge cycles.