General flywheel questions

[Mr.Entropy]

Hi Ken,

In other words is there a limit for a given flywheel for energy storage? Or is the capacity unlimited? For example I can imagine just spinning a flywheel faster would allow it to store more energy.

Is this similar to voltage vs. amperage?

More volts = faster spinning slywheel
More amps = heavier flywheel

watts = amps x volts
flywheel power = weight x rpm

I ask because I am wondering if a flywheel that I am using in a device just doesn't have the "capacity" to store the energy being pushed into it. I don't think I can push the device to operate quicker, so I think my only choice is to use a larger/heavier flywheel.

The energy stored in a flywheel is proportional to its mass x rpm x rpm x radius x radius, i.e., the rpm and radius terms are squared.

For a flywheel of a given shape, both the stored energy and the centrifugal force that tries to tear it apart are proportional to mass x rpm x rpm, so the amount of energy you can store is limited by the tensile strength of the material that it's made from.

Because centrifugal force is proportional to radius, and energy is proportional the the _square_ of the radius, you can make the most out of a given amount of a given material by shaping it into a thin disc.

Cheers,

Mr. Entropy