Design and experimental evaluation of a superconducting flywheel energy storage system with contactless power transmission

Flywheel energy storage systems are promising for large-scale applications due to their high energy density, long cycle life, and environmental compatibility. Conventional flywheel energy storage systems, however, depend on mechanical bearings and couplings for torque transmission, resulting in significant frictional losses, high no-load power consumption, and limited vibration stability. In this study, a high-temperature superconducting flywheel energy storage systems with contactless power input and output was developed and experimentally evaluated. A planar eddy current coupler enabled non-contact power transfer between the motor and rotor, while system stiffness was enhanced by employing a radial high-temperature superconducting magnetic bearing with an internal permanent magnet rotor. An experimental platform was constructed to examine the system's static properties, vibration response, and energy storage performance. The prototype achieved a maximum stored energy of 350 J and a peak rotational speed of 3100 rpm. Results showed that the vibration response of the support frame was strongly affected by cooling height. Introducing a 1 mm axial offset increased radial stiffness by about 30%, while reducing the radial vibration amplitudes of the frame and bearing by 77% and 46%, respectively. These findings verify the feasibility of the proposed contactless coupling scheme and provide insights for the design of efficient, low-loss flywheel energy storage systems.