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The open core composite flywheel

In low-Earth orbit satellite applications, spacecraft power is provided by photovoltaic cells and batteries. Unfortunately, the use of batteries presents difficulties due to their poor energy density, limited cycle lifetimes, reliability problems and the uncertainty in measuring their state-of-charge. Flywheel energy storage offers a viable alternative to overcome some of the limitations presented by batteries. This paper discusses the University of Maryland's (USA) operational 300 Wh open core composite flywheel, called the Engineering Development Unit, and the research being conducted to enhance its performance. Current research in this area focuses on the control system, the touchdown surface material and the magnetic bearing actuator. FARE, Inc. has designed a state-of-the-art 50 Wh flywheel energy storage system. This system, called the open core rotator (OCR), is based on the Engineering Development Unit and will incorporate some of the innovative features of the University of Maryland system as well as those under development by its subcontractors. The OCR is intended to be a prototype energy storage device for low-Earth orbit satellite applications.