Performance Testing of a Vehicular Flywheel Energy System

The University of Texas at Austin Center for Electromechanics has designed and integrated a 40,000 rpm, 150 kW, 1.93 kWh flywheel energy storage system into a hybrid electric transit bus as a demonstration of the technology. The flywheel stores energy recovered during braking and returns it to the power train during acceleration, reducing the peak power requirements and size for the prime power unit. Additionally, the system provides a longer life energy storage alternative to the more traditional chemical battery bank. While the flywheel system was demonstrated on a transit bus, similar improvements are possible on other terrestrial or marine mobile applications. This paper presents the results and information learned during several multi-thousand-cycle duration tests, composite flywheel tests, terrain-simulating shaker tests, and on-bus road tests.