Pretty Fly - For A Wheel

THIS is cool.

Flywheel Energy Storage (FES) works by accelerating a rotor to a very high speed and maintaining the energy in the system as inertial energy. Commercially available FES systems are used for small uninterruptible power systems. The rotors normally operate at 4000 RPM or less and are made of metal. Advanced flywheels are made of high strength carbon-composite filaments that spin at speeds from 20,000-100,000 RPM in a vacuum enclosure. Magnetic bearings are necessary as speeds increase to reduce friction found in conventional mechanical bearings. Quick charging is done in less than 15 minutes. Long lifetimes of most flywheels, plus high energy (~ 130 Wh/kg) and high power are positive attributes. The round trip energy efficiency of flywheels can be as high as 80%. Since FES can store and release power quickly, they have found a niche providing pulsed power.