🔄
TaskJunction Calculator

Flywheel Energy Storage Calculator

Free flywheel energy storage calculator. Compute moment of inertia, kinetic energy, coefficient of speed fluctuation and energy fluctuation for solid disk, thin ring and hub configurations.

🔄 Flywheel Parameters
N1 = max speed, N2 = min speed during cycle
📊 Results
Moment of Inertia (I)
--
kg.m²
Energy Stored
--
Joules
Speed Fluctuation (Cs)
--
dimensionless
Max KE at N1
--
Joules
Mean Angular Speed
--
rad/s
Energy Fluctuation (dE)
--
Joules
Reference Formulas
Moment of Inertia
I = k x m x r^2
k = shape factor: 0.5 (solid disk), 1.0 (thin ring), 0.6 (disk with hub)
Coefficient of Speed Fluctuation
Cs = (N1 - N2) / N_mean
Typical values: 1/100 for pumps, 1/30 for crushing mills
Kinetic Energy
KE = 0.5 x I x omega^2
omega in rad/s = 2 x pi x N / 60
Energy Fluctuation
dE = I x omega_mean x (omega1 - omega2)
Energy that the flywheel must absorb / release per cycle
From the builder
Why I built this

Flywheel problems come up constantly in Theory of Machines and Machine Design. The standard calculation needs you to know I, then work out the energy fluctuation, then pick the right Cs for your application and size the flywheel accordingly. Every time I tried to do this on exam papers or in practice, I would mix up units between RPM and rad/s.

I built this so you can just select the flywheel shape, put in mass, radius and operating speeds and get all the important outputs in one shot. I included the shape factor selector because most calculators assume a solid disk by default, which is almost never the actual case in real machines where you have a rim with spokes.

Vaibhav Dhokpande, Creator of TaskJunction