Kinetic energy storage is the use of motion to store energy, generally for short periods of time. The most common way to do this is with a flywheel—a weighted wheel that is spun as fast as possible using excess energy. When that energy is needed, the rotary motion of the wheel is harnessed to turn kinetic energy into electricity. Alternatively, it could be used to power mechanical devices directly.
A new flywheel design could re-establish flywheels as a competitive energy storage method.