High-speed, low-cost flywheels for energy storage in sustainable power systems with distributed generation

This paper covers the technical aspects of an electromechanical battery. A permanent magnet motor-generator is incorporated in a composite flywheel, running at high speed in a vacuum containment to minimize air friction losses. The flywheel is to be suspended on cascaded, Teflon coated, high-speed roller bearings. A composite flywheel requires a simple containment to sustain the vacuum for the moving parts, since most of the energy is dissipated in the fracture process in case of catastrophic failure. A three-phase, switch mode bridge converter, driven by a bipolar pulse width modulation board, achieves the variable speed control for the flywheel and the control of the DC bus voltage. The target storage capacity is 250 Wh with a power rating of 40 W.