As the need for energy storage increases on future hybrid electric vehicles, the desire for increased performance, energy/power densities, and component life increases proportionally. Flywheel batteries have demonstrated power density and life superiority over conventional chemical batteries; however, fears of unexpected and uncontained failures may prevent their widespread acceptance in the United States marketplace. The University of Texas at Austin Center for Electromechanics (UT-CEM) has designed, built, and tested a full-scale composite flywheel containment system for use in mobile applications. The flywheel containment system that will be described stems from an in-depth investigation into the type of faults that are most likely to occur in mobile applications. In all cases, the worst-case scenario results in a challenge to flywheel integrity; therefore, a comprehensive flywheel containment system is considered the “last line of defense” in protecting personnel and equipment.
The containment system described is an energy absorption device used in parallel with a UT-CEM flywheel on the hybrid electric Advanced Technology Transit Bus (ATTB). The most important aspect of the containment device is the free-rotating composite liner intended to absorb the energy of a flywheel failure. The current containment design has been developed over a six-year period during the participation of UT-CEM in the DARPA/DOT Flywheel Containment Program. A comparison between a previous full scale containment test (November 1999) and the current configuration is made, illustrating how “lessons learned” from the previous test are integrated into the latest design.
The test was conducted in August 2002 and a detailed description of the mounting configuration, test setup, and data acquisition is presented along with results. Of particular interest to the design team was torque on the aluminum containment housing, axial and hoop stresses in the housing, and acceleration. The test was successful in that the composite debris was contained and all metallic structures remained fully intact.