Reducing Losses in a 150 kW Vehicular Flywheel Battery
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Over the past several years a number of technological advancements have been made to improve flywheel energy storage designs. These include the use of high-strength composites, magnetic bearings, and rare earth magnets. Combined, these advances have made possible the consideration of flywheel systems for load leveling and power management on all-electric and hybrid electric vehicles. However, issues remain with heat generation and losses – particularly on the rotor where cooling is available only in the form of radiation – of the high power flywheel systems required for these vehicles. This paper describes how experimental demonstrations have shown that moderate improvements in hardware, software, and control algorithms can dramatically reduce heat generation. This paper (1) identifies and discusses the impact of specific types of losses on overall flywheel performance; (2) provides a discussion of the losses and analysis on the baseline flywheel design; (3) discusses the steps taken to reduce losses in the baseline design; and (4) presents test data taken from the 150 kW vehicular flywheel system. While the flywheel battery system was designed for and demonstrated on a transit bus, the technology described herein is applicable to a wide variety of applications including additional mobile and marine power and propulsion systems.