Flywheel batteries come around again

R. Hebner, J. Beno, A. Walls
2002 IEEE spectrum  
hat goes around comes around" is not just a popular expression and the title of a Bob Marley song, it is also a good description of what is happening these days with flywheel energy storage. The technology is coming around again after undergoing a round of improvements in materials, magnetic bearing control, and power electronics. Of course, scientific and technical advances by themselves are not enough to renew interest in a technology, however good it may be. The advanced wizardry must also
more » ... izardry must also serve a genuine need. Today's flywheel batteries, which depend on a rotating mass to store energy, score well in both areas: they embody several exciting technological advances, and they are serious contenders for a variety of important energy-storage applications. They are, for example, competitive with chemical batteries in applications like transportation or improving power quality, which involve many charge-discharge cycles and little in the way of long-term storage. Progress in power electronics, particularly in high-power insulated-gate bipolar transistors (IGBTs) and field-effect transistors (FETs), underlies higher-power flywheel operation. While the stored energy is determined by the speed, mass, and geometry of the wheel, the limits on input and output power are in general set by the power electronics. With these higherpower devices, fewer individual components are needed, so the power electronics package can be comparable in size to the flywheel plus motor-generator combination. The growing density of energy storage is to be attributed mainly to advances in fibers, resins, composite manufacturing techniques, and manufacturing quality control. Together, these have made it possible to construct flywheels strong enough to operate reliably at high speed [see photo, opposite]. Exploiting such developments, US Flywheel Systems (Pasadena, Calif.) has operated a composite flywheel at 60 000 r/min with a corresponding rim speed of about 1 km/s. On the lifetime reliability front, the University of Texas at Austin has subjected a composite flywheel spinning at " W
doi:10.1109/6.993788 fatcat:ixxourozbngibiph7ooqxut644