Flywheel Energy Storage Calculator

How Does a Flywheel Store Energy?

A flywheel stores kinetic energy in a spinning mass. Faster rotation and larger moment of inertia increase the energy capacity of the system.

$$E = \frac{1}{2} I \omega^2$$ $$I = k \cdot m \cdot r^2$$ $$\omega = \frac{2\pi \cdot \mathrm{RPM}}{60}$$

Common geometric constants: solid disk $k = 0.606$, hollow disk $k = 0.333$.

Example: a 250 lb hollow disk with 12 in radius at 60,000 RPM stores about 19,200 Wh of rotational energy. Related tools: Angular Frequency Calculator, Torque Calculator, and Earth Curvature Calculator.

What is moment of inertia?

It measures resistance to angular acceleration. For flywheels, it depends on mass, radius, and shape through the constant $k$.

Why convert RPM to rad/s?

The energy formula uses SI angular velocity in rad/s. Multiply RPM by $2\pi/60$ before squaring.

Which shape constant should I pick?

Use hollow disk for ring-like rotors and solid disk for uniform thick wheels. Custom $k$ fits specialized geometries.

Does doubling RPM quadruple stored energy?

Yes. Energy scales with $\omega^2$, so doubling angular speed quadruples stored energy if inertia stays the same.

What are practical flywheel applications?

Flywheels smooth engine output, store grid energy for short durations, and appear in some vehicle and spacecraft systems.