Superconducting energy storage flywheel—An attractive technology for energy storage

Abstract

Flywheel energy storage (FES) can have energy fed in the rotational mass of a flywheel, store it as kinetic energy, and release out upon demand. The superconducting energy storage flywheel comprising of magnetic and superconducting bearings is fit for energy storage on account of its high efficiency, long cycle life, wide operating temperature range and so on. According to the high temperature superconducting (HTS) cooling mode, there are zero field cooling (ZFC) bearings and field cooling (FC) bearings. In practice, the superconducting bearings are formed by field-cooled superconductors and permanent magnets (PMs) generally. With respect to the forces between a permanent magnet and a superconductor, there are axial (thrust) bearings and radial (journal) bearings. Accordingly, there are two main types of high-temperature superconducting energy storage flywheels, and if a system comprising both the thrust bearing and the radial bearing will have the characteristics of both types of bearings. Magnetic force, magnetic stiffness and damping are these three main parameters to describe the levitation characteristics. Arrangement and shape of superconductors, thickness of superconductor, superconducting flux creep and critical current density of the superconductor affect the magnetic levitation force of these superconducting bearings. The key factors of FES technology, such as flywheel material, geometry, length and its support system were described, which directly influence the amount of energy storage and flywheel specific energy. All these results presented in this paper indicate that the superconducting energy storage flywheel is an ideal form of energy storage and an attractive technology for energy storage.