Design and Testing of a Flywheel Battery for a Transit Bus

Access full-text files




Hayes, R.J.
Kajs, J.P.
Thompson, R.C.
Beno, J.H.

Journal Title

Journal ISSN

Volume Title


Society of Automotive Engineers, Inc.


The University of Texas at Austin Center for Electromechanics (UT-CEM) has designed and tested a flywheel energy storage system conventionally referred to as a flywheel battery (FWB) for power averaging on a hybrid electric transit bus. The system incorporates a high speed (40,000 rpm) 150 kW permanent magnet motor generator with magnetic bearings to levitate a 2 kWh composite flywheel. This paper summarizes: design goals, required operating parameters, system design, analysis completed prior to fabrication, and initial performance testing completed in the laboratory. The paper includes information on the motor/generator, power electronics, magnetic bearing sensors and controls, and FWB subsystems (including containment). Finally, recommendations for continued testing are made along with recommendations for improvements to the existing design.


LCSH Subject Headings


R.J. Hayes, J.P. Kajs, R.C. Thompson, and J.H. Beno, “Design and testing of a flywheel battery for a transit bus,” 1999 SAE International Congress and Exposition, Detroit, Michigan, U.S.A., March 1-4, 1999.