Development of high speed composite flywheel rotors for energy storage systems

A composite flywheel rotor was developed. The rotor was designed, which was based on the finite element analysis, and fabricated to achieve the peripheral speed of 1300 m/s. The rotor consisted of a composite rim and aluminum alloy hub. The inner diameter of the rim was 340 nun, the outer diameter was 400 nun and thickness was 25 mm. The rim comprised press fitted multiple concentric rings(multi-ring) to prevent radial tensile failures at high rotational speed. Rings were fabricated by a filament winding process using high strength carbon fiber. The configuration of the hub was like a steering wheel with 4 spokes. The cross-section area of these spokes was changed to withstand a centrifugal force. Spin tests of flywheel rotors were performed, using an air turbine driven spin tester in a vacuum chamber. The rotor was spun to maximum peripheral speed at 1310 m/s, whose stored energy was 354 Wh, and the specific energy density was 195 Wh/kg.