FLYWHEELS FOR ENERGY-STORAGE

Advanced flywheel technology offers a competitive technique for storin g energy for electric utility and hybrid or electric vehicle applicati ons. The relatively recent availability of suitable and affordable hig h strength, lightweight composite materials for construction of the ro tating wheel is a major reason for recent technical developments. This paper will briefly describe the major applications of flywheel techno logy, design considerations for the composite wheel and other portions of the systems, and the status of current device developments. United Technologies Corporation (UTC) has concentrated on an automotive Flyw heel Surge Power Unit (FSPU) and utility power quality unit having a r ated power of 25 to 50 kW and an energy storage capability of 800 Wh a t 35,000 RPM. Other developments of larger units for buses and utility load leveling applications have also begun. Several failure mode test s of composite wheels have been demonstrated. Efforts to intentionally fail these filament wound graphite/thermo-plastic wheels at operation al speeds have so far been unsuccessful, indicating a robust design. T he technology is ready for producing initial prototype flywheel system s.