Self-Inertia-Varying Fixed-Speed Flywheel Energy Storage System

Abstract

Flywheel energy storage systems (FESSs) store kinetic energy corresponding to the rotation of an object as Jω²/2, where J is the moment of inertia, and ω is the angular rotation speed. Conventional FESSs implement charging and discharging by varying ω. In contrast, the authors have proposed a fixed-speed FESS that implements charging and discharging by varying not ω but J. However, the net power output in the discharge operation for a fixed-speed FESS was not positive owing to the low efficiency of the mechanism of varying J. This paper reports on the prototype development of a self-inertia-varying fixed-speed FESS that varies J by using the rotational inertia force of the flywheel itself. In the prototype test, actual charging and discharging operations were demonstrated, and a net mechanical power generation was observed during the discharge operation.