Volvo Car Corporation, Flywheel KERS, component details, with explaining texts.

Flywheel KERS (Kinetic Energy Recovery System), is fitted to the rear axle. During retardation, the braking energy causes the flywheel to spin at up to 60,000 revs per minute. When the car starts moving off again, the flywheel’s rotation is transferred to the rear wheels via a specially designed transmission. The fuel consumption is expected to be reduced by 20%. Also horse powers are boosted and acceleration improved. This is a research project in cooperation with Volvo Powertrain and SKF.