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Conceptual Design of a Flywheel Energy Storage System.

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Final rept.,

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A conceptual design of a flywheel energy storage system suitable for on-site interfacing with residential photovoltaic PV energy sources has been developed. The basic design objective was to provide a generous margin of safety and above average reliability and efficiency at the lowest practical cost. This report describes the basic design concept and the general approach to the conceptual design of the energy storage system. The basic concept to interface with PV energy sources utilizes a constant voltage motorgenerator directly coupled to a flywheel rotor. The voltage level of the motor is maintained at the optimum operating voltage of the array of PV cells and permits peak power tracking. Power is withdrawn from the flywheel-driven generator when the voltage output of the array drops below its optimum value, and power is delivered to the flywheel via the generator then operating as a motor when the voltage rises above the optimum value. A variety of motor types and flywheel rotor types has been studied to arrive at a conceptual design to meet the program objectives. A fiber-composite rotor driving a separately-excited motor satisfies the basic requirements. To obtain acceptable efficiency and low run-down losses, the flywheel operates in a vacuum and has a combination of magnetic thrust support and ball bearings to reduce bearing friction in an economical fashion. The need for rotary vacuum seal is eliminated by the use of a hermetically-sealed magnetic power coupling. MM

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  • Electric Power Production and Distribution
  • Energy Storage

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