Analyses and Tests of HTS Bearing For Flywheel Energy System

Flywheel energy system (FES) is a non-pollution energy storage system which uses high-speed rotation flywheel to store energy. As high temperature superconducting (HTS) bearings have very low friction and self-stability characteristic, they are applied to FES increasingly. In this paper, for the optimal structure of permanent magnet rotor, 3 topologies were presented and their magnetic field characteristics were analyzed. For effective cooling of YBCO bulks, a thermal model of the superconductor magnet stator using alumina shims was set up and its temperature distribution was analyzed. The result shows that the structure of the stator in which alumina shims were put between the neighboring YBCO bulks is better than that without alumina shims, and the temperature of YBCO bulks in the structure is lower. Then a radial-type HTS bearing prototype with outer diameter of 200 mm, inner diameter of 40 mm and height of 120 mm was built. The axial force, the axial stiffness and the levitation characteristics of the device were measured and analyzed in field cooling and zero-field cooling respectively.