Flywheel Energy Capacity

A flywheel is a mechanical component used for the storage of energy under the angular momentum conservation principle. Flywheels are well suited for this task because they are designed to have high moments of inertia.

Energy Conservation

• The principle of energy conservation tells us that energy is neither created nor destroyed but instead conserved. Even when energy changes forms, such as transitioning from translational (linear motion) energy to rotational energy, the amount of energy in each form (and in all combinations of the two forms in between) remains the same. Therefore spinning objects such as flywheels that do not release any of their rotational energy to the surrounding environment are said to store energy for the duration of their motion.

Energy Storage

• The kinetic energy (KE) of a flywheel depends on its moment of inertia (I) and its angular acceleration (w). The explicit relationship is KE = (1/2)Iw^2. A cylindrical wheel of mass m and radius r will have a moment of inertia I = mr^2. Therefore, KE = 1/2m(rw)^2.

Energy Capacity

• Since the mass of the flywheel and its radius are constant quantities, the energy capacity of a flywheel depends solely on its angular velocity. Although there are more technical considerations for engineering applications such as the tensile strength of the flywheel materials, theoretically the faster it spins, the more energy it stores.