I am doing a project where in a pedestal fan is alternatively powered using a flywheel. The flywheel is brought to some initial angular velocity by the electric motor. Now, if the power goes off, the fan blades would be coupled to the flywheel and it continues to rotate for the next 10 minutes. After the power goes off, we have considered that Energy-flywheel + Energy-fan = ∫ (Torque-drag force * ω -fan) dt I'm having trouble calculating the torque due to the drag force and how to geometrically simplify the fan blades. Any solution would be very much helpful.