[lolc]

Flywheels (no matter their size) can be operated in near vacuum with magnetic bearings[0]. Friction can be really low. A funny aside is that they have to be aligned with earth's rotation so they don't resist it.

[0] https://en.wikipedia.org/wiki/Magnetic_bearing

[yboris]

Thank you for the response.

My thought is that the weight of the flywheel matters. To be able to absorb / release a tremendous amount of power, I imagine this flywheel would need to be very heavy. If so, wouldn't it non-linearly differ in efficiency from the near vacuum & magnetic bearing designs we've built before?

Perhaps the proposal is to build a large array of smaller flywheels that don't have to deal with the problem I imagine?

I'm not familiar with any part of engineering here -- just a curious soul -- sincerely asking!

[lolc]

Not that I know much about flywheel engineering. But machines tend to become more efficient the bigger you build them.

With flywheels, I don't see the bearings as difficult. I mean it's sure a challenge to keep a few tons afloat, but nothing unsolved. I'd assume (but don't know) that you can scale magnetic bearings a few orders of magnitude with their properties staying the same.

On the other hand, the faster you spin flywheels, the more energy they store. And here comes the limitation: The material they're made of has to sustain all tearing force. So at some point you'll add mass instead of spinning faster.