For example, flywheels are used in power hammers and riveting machines.įlywheels can be used to control direction and oppose unwanted motions. This is achieved by accumulating energy in the flywheel over a period of time, at a rate that is compatible with the energy source, and then releasing energy at a much higher rate over a relatively short time when it is needed. Ī flywheel may also be used to supply intermittent pulses of energy at power levels that exceed the abilities of its energy source. High energy density flywheels can be made of carbon fiber composites and employ magnetic bearings, enabling them to revolve at speeds up to 60,000 RPM (1 kHz).
Once suitably abstracted, this shared principle of energy storage is described in the generalized concept of an accumulator. Since a flywheel serves to store mechanical energy for later use, it is natural to consider it as a kinetic energy analogue of an electrical inductor. In particular, assuming the flywheel's moment of inertia is constant (i.e., a flywheel with fixed mass and second moment of area revolving about some fixed axis) then the stored (rotational) energy is directly associated with the square of its rotational speed. A flywheel is a mechanical device which uses the conservation of angular momentum to store rotational energy a form of kinetic energy proportional to the product of its moment of inertia and the square of its rotational speed.