Giant flywheel project in Scotland could prevent UK blackouts • Hacker News Board

Re: Giant flywheel project in Scotland could prevent UK blackouts

#111

Post by msandford » Tue, Jul 07, 2020, 3:29 PM UTC

Johnythree wrote: post #103

msandford wrote: post #42

Earlier quoted context omitted.

The spinning flywheel doesn't just spin on its own. It gets spun up and kept spinning by an electric motor/generator I have to imagine. So you're limited as to how much power can go in or out by the size of that motor/generator. If it's a 100kw peak electrical machine then it can provide at most 100kw of instantaneous power to the grid while at the same time slowing down by however much is required to deliver that po…

No. It's a synchronous motor which normally idles at the Mains frequency, but if the Mains frequency attempts to change, the rotor inputs massive amount of current (leading or lagging) into the mains which prevents the change. There is no need for a drive motor. In the industry they are known as a "Synchronous Condenser" or Syncom. They have been in use for a long time. https://www.pv-magazine-australia.com/2019/04/0…

So are you saying that the entire mass of the whole flywheel is all the synchronous motor?

I guess I had assumed -- especially based on the picture and description -- that a portion of the mass of the device was the synchronous motor and that a portion of the mass of the device is just "dead weight" whose purpose is just to act as energy storage via rotational inertia.

The parallels to the steam turbine would seem apt; the turbine end of a generator has a lot of mass relative to the electrical end. Isn't that a part of the point? Or did I miss something?

Re: Giant flywheel project in Scotland could prevent UK blackouts

#112

Post by yboris » Wed, Jul 15, 2020, 8:01 PM UTC

lolc wrote: post #89

yboris wrote: post #60

Feels like friction would eat away a lot of electricity, no?

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

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!

Re: Giant flywheel project in Scotland could prevent UK blackouts

#113

Post by lolc » Sat, Jul 18, 2020, 1:01 AM UTC

yboris wrote: post #112

lolc wrote: post #89

Earlier quoted context omitted.

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

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 p…

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.