What does a flywheel do and how does it work?
In: Engineering
A flywheel is an energy storage device. It stores rotational kinetic energy according to
E = (I * omega^2 )/2
…where I is the rotational moment of inertia about the flywheel axis, and omega is the angular velocity of the flywheel.
This is analogous to the formula for linear kinetic energy, where
E = (m * v^2 )/2
…where the terms in the equation are mass and linear velocity.
So, large flywheels with high inertia store a lot of power, but you gain even more from higher rotational speeds, since that variable is squared. Power storage flywheels are often light weight but have operating speeds in the several tens of thousands of rpm for this reason.
Flywheels are used in car engines in order to smooth out the power delivery to the transmission. In the absence of a flywheel, the individual pulses from the detonations in each cylinder would lead to excessive vibration as the drivetrain responds.
Large power generation systems often use flywheels to ride through variances in delivered power. You can think of a flywheel like a battery or a hydraulic accumulator. It is a buffer of stored energy that can absorb peaks in power, or deliver power when there is a dropout.
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