How Flywheels Work

Flywheels have proven their usefulness for thousands of years (i.e. potter’s wheels and Neolithic spindles); modern implementations offer a host of new benefits in the most high-tech and demanding environments.

A flywheel energy storage system or "flywheel battery" is a mechanical battery that stores energy kinetically in the form of a rotating mass, and uses the inertia of the spinning mass to store or generate power. Kinetic energy is the energy of motion as quantified by the amount of work an object can do as a result of its motion, expressed by the formula:

Kinetic Energy = ½ (mass)*(velocity) 2  

The amount of energy available and its duration is proportional to its mass and the speed squared. Low-speed flywheels take advantage of mass- more mass means more energy, and double mass equals double energy.  High-speed flywheels, like the VYCON® systems, take advantage of speed- the higher the speed, the higher the energy, and double RPM equals quadruple energy.

 Architect of the Flywheel

The flywheel is the heart of the system storing kinetic energy in the form of a rotating mass. A system may contain mechanical or magnetic bearings, which are housed in a vacuum sealed chamber that reduces friction and increases efficiency.

The bearings support the rotor and keep it in position to rotate at high speeds. The type of bearings used can determine the speed of the flywheel, performance and maintenance issues. Mechanical bearings are the most common, but require frequent maintenance and system downtime as they produce friction, which can hinder rotation at high rates. In turn, magnetic bearings are used in high-speed flywheel systems. Magnetic bearings have many advantages over mechanical bearings, as they eliminate friction between the rotor and its supports. Magnetic bearings have a long life and low maintenance costs.

In addition to the bearings, a typical flywheel system also consists of an electric motor generator and a rotor. The design of the rotor is important in determining the effectiveness and efficiency of the system. The shaft of the flywheel is connected to an electric motor generator, which is levitated in an electromagnetic field allowing the system to cycle on demand.

When called upon, the integrated flywheel will discharge energy by using the stored energy in the rotating mass to produce output power. When the device functions as a motor, energy is supplied to the flywheel, and when the device acts as the generator, energy is stored, hence it is often known as a "flywheel battery." The amount of energy available and its duration is governed by the mass and speed of the flywheel. They produce a high power output for short periods of time, typically 1-30 seconds.