Flywheel energy storage advances using HTS bearings

High-temperature-superconducting (HTS) bearings have the potential to reduce rotor idling losses and make flywheel energy storage economical. Demonstration of large, high-speed flywheels is key to market penetration. Toward this goal, we have developed and tested a flywheel system with 5- to 15-kg disk-shaped rotors. Rim speeds exceeded 400 m/s, and stored energies were >80 Wh. Test implementation required technological advances in nearly all aspects of the flywheel system. Features and limitations of the design and tests are discussed, especially those related to achieving greater energy storage levels.