Fig. 7.8 shows the integration of the flywheel energy storage system with the grid. In this method the stored energy is transferred to the grid by a generator, alternative current (AC)/direct current (DC) rectifier circuit, and DC/AC inverter circuit. Figure 7.8. Flywheel energy storage system topology.
Their efficiency is high during energy storage and energy transfer (>90 %). The performance of flywheel energy storage systems operating in magnetic bearing and vacuum is high. Flywheel energy storage systems have a long working life if periodically maintained (>25 years).
Small applications connected in parallel can be used instead of large flywheel energy storage systems. There are losses due to air friction and bearing in flywheel energy storage systems. These cause energy losses with self-discharge in the flywheel energy storage system.
To connect the Flywheel Energy Storage System (FESS) to an AC grid, another bi-directional converter is necessary. This converter can be single-stage (AC-DC) or double-stage (AC-DC-AC). The power electronic interface has a high power capability, high switching frequency, and high efficiency.
Flywheel energy storage system topology. Another method used in flywheel energy storage systems is to store energy with high speed. In this method the rotating object is rotated up to 100,000 rpm . The rotating object weight is low in this method. This method is used in small applications in terms of volume and weight.
Think of it as a mechanical storage tool that converts electrical energy into mechanical energy for storage. This energy is stored in the form of rotational kinetic energy. Typically, the energy input to a Flywheel Energy Storage System (FESS) comes from an electrical source like the grid or any other electrical source.