THE Parry people-mover in the UK (picture) is operated by a flywheel, not by batteries.
Flywheel energy storage (FES) works by accelerating a rotor (flywheel) to a very high speed and maintaining the energy in the system as rotational energy.
When energy is extracted from the system, the flywheel’s rotational speed is reduced as a consequence of the principle of conservation of energy; adding energy to the system correspondingly results in an increase in the speed of the flywheel.
Advanced FES systems have rotors made of high strength carbon-composite filaments, suspended by magnetic bearings, and spinning at speeds from 20,000 to over 50,000 rpm in a vacuum enclosure.
Such flywheels can come up to speed in a matter of minutes — much quicker than some other forms of energy storage.
More:
http://en.wikipedia.org/wiki/Parry_People_Mover
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