Flywheel Energy Storage Calculator

A spinning flywheel stores kinetic energy that can be released later.

How the Math Works

The Flywheel Energy Storage Calculator uses the fundamental physics equation for rotational kinetic energy: E = ½·I·ω². Here, E represents energy in joules, I is the moment of inertia (which depends on the flywheel's mass distribution), and ω is the angular velocity in radians per second. The calculator automatically converts revolutions per minute (rpm) to radians per second using the relationship ω = rpm·2π/60, accounting for the fact that one rotation equals 2π radians and there are 60 seconds in a minute. This conversion ensures accurate energy calculations regardless of the input unit.

Practical Applications

To use this calculator practically, you'll need two key measurements: the flywheel's moment of inertia and its rotational speed. For a solid disk flywheel, I = ½mr², where m is mass and r is radius. Enter these physical specifications along with the operating rpm into the calculator to determine how much energy your flywheel can store. Engineers use this calculation when designing regenerative braking systems, grid-scale energy storage, or mechanical battery prototypes, where maximizing stored energy per unit mass is critical.

Day-to-Day Use

While you may not calculate flywheel energy daily, this principle powers technologies that affect your life regularly. Hybrid and electric vehicles use regenerative braking to capture kinetic energy in flywheels, extending driving range. More dramatically, flywheel energy storage helps stabilize electrical grids by storing excess renewable energy and releasing it during peak demand. Understanding this calculation illuminates how mechanical systems can efficiently store and transfer energy, from your car's smoother acceleration to the reliable electricity powering your home.

Worked example

I = 5 kg·m² at 3000 rpm → about 246.7 kJ.

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