Abstract - This study gives a critical review of flywheel energy storage systems and their feasibility in various applications. How. . A flywheel-storage power system uses a flywheel for grid 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. . Flywheel Energy Storage Systems (FESS) rely on a mechanical working principle: An electric motor is used to spin a rotor of high inertia up to 20,000-50,000 rpm. Electrical energy is thus converted to kinetic energy for storage. For discharging, the motor acts as a generator, braking the rotor to. . Electrical energy storage systems (EESSs) enable the transformation of electrical energy into other forms of energy, allowing electricity to be stored and reused when needed. These systems provide greater flexibility in the operation of the grid, as electrical energy can be stored and released. . There is noticeable progress in FESS, especially in utility, large-scale deployment for the electrical grid, and renewable energy applications. This paper gives a review of the recent developments in FESS technologies. Due to the highly interdisciplinary nature of FESSs, we survey different design. . Flywheel energy storage systems have gained increased popularity as a method of environmentally friendly energy storage. Can flywheels be used for power. .