6 ms·

> This system stores the current in stationary flywheels Well, rotating flywheels. It amazes me just how much energy you can story in a flywheel. They're real

by davefp 8y ago

> This system stores the current in stationary flywheels Well, rotating flywheels. It amazes me just how much energy you can story in a flywheel. They're really neat devices.

saynay 8y ago
I believe Verizon has a datacenter that has a number of 15 ft concrete flywheels that provides emergency power.
- toast0 8y ago
  This is a pretty common way to bridge the gap between when utility power drops and when emergency generators are started and ready to handle the load. I believe flywheel systems can be more compact and don't have the same maintenance demands, but may be more limited as to energy capacity and duration of service.
- reaperducer 8y ago
  Didn't Twitter have one of these on its roof in SoMa? I vaguely remember reading that somewhere.
sandworm101 8y ago
What is amazing is the rotational speeds involved. Say the flywheel weighed as much as a tesla. Think of the energy. Say you want to store enough energy so that a tesla can accelerate itself from zero to 100mph ten times. That amount of energy in a flywheel weighing the same as the tesla would mean the flywheel spinning at +/- 1000mph. Either this flywheel weighs hundreds of tons, or it is spinning at supersonic speeds. Either way, you better have some good bearings.
- endymi0n 8y ago
  The magical word here is „angular momentum“. The energy that a chunk of mass can store in a flywheel is squared with the distance of that mass to the center of its rotation axis. If you distribute the Tesla sized mass around the edges of a 4m sized Flywheel now (spare a few % for the wheel and structural support), it can store quite a few dozen times the energy of the same sized Tesla going the same speed.
  - akrasuski1 8y ago
    I'm pretty sure it doesn't matter whether the eneergy is stored in rotating body, or one moving in a straight line. Kinetic energy of rotation is 0.5 * I * w^2, or for that extreme case of "concrete ring" - 0.5 * m * r^2 * w^2, which is exactly equal to 0.5 * m * v^2, or kinetic energy as calculated for body moving in straight line.
  - sandworm101 8y ago
    Are you sure that you aren't confusing force with energy? Angular or not, it's just accelerated mass.
- oneiric 8y ago
  Modern flywheels spin extremely fast in a vacuum, so supersonic is moot.
- bigiain 8y ago
  So let's do a little high school "perfectly spherical cow of uniform density" physics here. Imagine we take that 1 Tesla mass and turn it into a infinitely thin ring of infinite density material. Now we can calculate how fast it's need to be spinning to get all that mass doing "1000mph". Lets make our infinitely dense 1 Tesla mass into an infinitely thin ring 1m in radius. Each point on that ring moves around it (2pir) circumference every revolution so ~6.3m per revolution. 1000mph =~ 440m/s SO we only need to spin this flywheel ay ~70 revolutions per second, just over 4000RPM. 4000RPM doesn't seem unreasonable... (Note:I don't think your 1000mph stacks up though. The kinetic energy of a moving mass is 1/2mv^2. So the speed of a 1 Tesla mass object which has 10 times the energy of a 1 Tesla object doing 100mph is only sqrt(10)*100 closer to 320mph than 1000. My high school physics flywheel might only need to spin at 1500RPM...)
gameswithgo 8y ago
When I was in middle school? maybe high schoo? 1990s somewhere, there was a long article about flywheel batteries for cars, they were claiming some very impressive range and power numbers. I remember it was one of a million things I read about in sciencey magazines that never went anywhere, but maybe it was the one I was most sad about never happening (at least so far) The one product I do remember happening that I first read about back then was e-paper! That happened! Cool.
- baddox 8y ago
  They do (or did) exist. https://en.wikipedia.org/wiki/Gyrobus https://en.wikipedia.org/wiki/Gyrobus
- tamler 8y ago
  Was it Omni magazine? I think I read the article as well. If memory serves, they discussed a flywheel for each wheel of the car?
- justasitsounds 8y ago
  I always wondered how they dealt with gyroscopic forces in flywheel vehicles. Maybe I'm being naive and the effects can be compensates for with gimbals, but I'm stuck with the mental image of cars that don't turn corners
lb1lf 8y ago
-I've seen a small-ish one disintegrate under test. (Some 480kg of mass in a ~600mm diameter configuration, at some 8-9000rpm maximum if memory serves) It amazes me how hard it is to contain that kind of energy if it wants to get out. They're really terrifying devices. Particularly when left in the hands of engineers who do not fully appreciate that any sufficiently rapid release of stored energy is indistinguishable from an explosion.
- rurban 8y ago
  The ones in Formula 1 cars had 140.000 rpm, but not much mass. It's terrifying indeed, so much that Kubica refused to sit in such a thing.
  - King-Aaron 8y ago
    Having seen a flywheel + clutch assembly disintegrate on a drag car in the lane next to me (10,000rpm - bits of flywheel came through the bodywork of his car), I can understand why you'd be hesitant to sit on top of something spinning at 140,000rpm.
    - bigiain 8y ago
      Isn't that fairly typical turbocharger turbine speed though? I saw a Mazda RX3 Sport Sedan (a circuit racing class here in Australia ~25-30 years back) spectacularly blow a flywheel/clutch at the end of the main straight (at Oran Park) a long time back - it pretty much perforated all the bodywork in the plane of the flywheel - bonnet and both guards - as though it was a tearoff line on a set of stamps. We could hear bits landing 10+ seconds later hundreds of meters behind us in the parking lot. Depending on what port job he had, that could have been up around 12k rpm (if my vague 30 year old car modifying memory serves...)
      - King-Aaron 8y ago
        > Isn't that fairly typical turbocharger turbine speed though? I believe so, but compressor/turbine wheels don't have a lot of mass to them, so fragments don't usually escape very far if they blow up. I've seen a few compressor housings split, and the main damage is done to the engine itself really. I guess if your turbo was sitting high up and exposed, it might be a danger. Flywheels however just seem to fail more regularly from my experience. (Also, yeah anything rotary powered deals with scary rpm's, haha!) For anyone interested, here's some in-car footage of what we're describing here: https://www.youtube.com/watch?v=qOHUwL0zeXc https://www.youtube.com/watch?v=qOHUwL0zeXc and an image of what the result can look like: http://images.thetruthaboutcars.com/2011/04/LNJ11-BlowedUpParts-08.jpg http://images.thetruthaboutcars.com/2011/04/LNJ11-BlowedUpPa...

by davefp 8y ago

> This system stores the current in stationary flywheels Well, rotating flywheels. It amazes me just how much energy you can story in a flywheel. They're really neat devices.

saynay 8y ago

I believe Verizon has a datacenter that has a number of 15 ft concrete flywheels that provides emergency power.

toast0 8y ago
This is a pretty common way to bridge the gap between when utility power drops and when emergency generators are started and ready to handle the load. I believe flywheel systems can be more compact and don't have the same maintenance demands, but may be more limited as to energy capacity and duration of service.
reaperducer 8y ago
Didn't Twitter have one of these on its roof in SoMa? I vaguely remember reading that somewhere.

sandworm101 8y ago

What is amazing is the rotational speeds involved. Say the flywheel weighed as much as a tesla. Think of the energy. Say you want to store enough energy so that a tesla can accelerate itself from zero to 100mph ten times. That amount of energy in a flywheel weighing the same as the tesla would mean the flywheel spinning at +/- 1000mph. Either this flywheel weighs hundreds of tons, or it is spinning at supersonic speeds. Either way, you better have some good bearings.

endymi0n 8y ago
The magical word here is „angular momentum“. The energy that a chunk of mass can store in a flywheel is squared with the distance of that mass to the center of its rotation axis. If you distribute the Tesla sized mass around the edges of a 4m sized Flywheel now (spare a few % for the wheel and structural support), it can store quite a few dozen times the energy of the same sized Tesla going the same speed.
- akrasuski1 8y ago
  I'm pretty sure it doesn't matter whether the eneergy is stored in rotating body, or one moving in a straight line. Kinetic energy of rotation is 0.5 * I * w^2, or for that extreme case of "concrete ring" - 0.5 * m * r^2 * w^2, which is exactly equal to 0.5 * m * v^2, or kinetic energy as calculated for body moving in straight line.
- sandworm101 8y ago
  Are you sure that you aren't confusing force with energy? Angular or not, it's just accelerated mass.
oneiric 8y ago
Modern flywheels spin extremely fast in a vacuum, so supersonic is moot.
bigiain 8y ago
So let's do a little high school "perfectly spherical cow of uniform density" physics here. Imagine we take that 1 Tesla mass and turn it into a infinitely thin ring of infinite density material. Now we can calculate how fast it's need to be spinning to get all that mass doing "1000mph". Lets make our infinitely dense 1 Tesla mass into an infinitely thin ring 1m in radius. Each point on that ring moves around it (2pir) circumference every revolution so ~6.3m per revolution. 1000mph =~ 440m/s SO we only need to spin this flywheel ay ~70 revolutions per second, just over 4000RPM. 4000RPM doesn't seem unreasonable... (Note:I don't think your 1000mph stacks up though. The kinetic energy of a moving mass is 1/2mv^2. So the speed of a 1 Tesla mass object which has 10 times the energy of a 1 Tesla object doing 100mph is only sqrt(10)*100 closer to 320mph than 1000. My high school physics flywheel might only need to spin at 1500RPM...)

gameswithgo 8y ago

When I was in middle school? maybe high schoo? 1990s somewhere, there was a long article about flywheel batteries for cars, they were claiming some very impressive range and power numbers. I remember it was one of a million things I read about in sciencey magazines that never went anywhere, but maybe it was the one I was most sad about never happening (at least so far) The one product I do remember happening that I first read about back then was e-paper! That happened! Cool.

baddox 8y ago
They do (or did) exist. https://en.wikipedia.org/wiki/Gyrobus https://en.wikipedia.org/wiki/Gyrobus
tamler 8y ago
Was it Omni magazine? I think I read the article as well. If memory serves, they discussed a flywheel for each wheel of the car?
justasitsounds 8y ago
I always wondered how they dealt with gyroscopic forces in flywheel vehicles. Maybe I'm being naive and the effects can be compensates for with gimbals, but I'm stuck with the mental image of cars that don't turn corners

lb1lf 8y ago

-I've seen a small-ish one disintegrate under test. (Some 480kg of mass in a ~600mm diameter configuration, at some 8-9000rpm maximum if memory serves) It amazes me how hard it is to contain that kind of energy if it wants to get out. They're really terrifying devices. Particularly when left in the hands of engineers who do not fully appreciate that any sufficiently rapid release of stored energy is indistinguishable from an explosion.

rurban 8y ago
The ones in Formula 1 cars had 140.000 rpm, but not much mass. It's terrifying indeed, so much that Kubica refused to sit in such a thing.
- King-Aaron 8y ago
  Having seen a flywheel + clutch assembly disintegrate on a drag car in the lane next to me (10,000rpm - bits of flywheel came through the bodywork of his car), I can understand why you'd be hesitant to sit on top of something spinning at 140,000rpm.
  - bigiain 8y ago
    Isn't that fairly typical turbocharger turbine speed though? I saw a Mazda RX3 Sport Sedan (a circuit racing class here in Australia ~25-30 years back) spectacularly blow a flywheel/clutch at the end of the main straight (at Oran Park) a long time back - it pretty much perforated all the bodywork in the plane of the flywheel - bonnet and both guards - as though it was a tearoff line on a set of stamps. We could hear bits landing 10+ seconds later hundreds of meters behind us in the parking lot. Depending on what port job he had, that could have been up around 12k rpm (if my vague 30 year old car modifying memory serves...)
    - King-Aaron 8y ago
      > Isn't that fairly typical turbocharger turbine speed though? I believe so, but compressor/turbine wheels don't have a lot of mass to them, so fragments don't usually escape very far if they blow up. I've seen a few compressor housings split, and the main damage is done to the engine itself really. I guess if your turbo was sitting high up and exposed, it might be a danger. Flywheels however just seem to fail more regularly from my experience. (Also, yeah anything rotary powered deals with scary rpm's, haha!) For anyone interested, here's some in-car footage of what we're describing here: https://www.youtube.com/watch?v=qOHUwL0zeXc https://www.youtube.com/watch?v=qOHUwL0zeXc and an image of what the result can look like: http://images.thetruthaboutcars.com/2011/04/LNJ11-BlowedUpParts-08.jpg http://images.thetruthaboutcars.com/2011/04/LNJ11-BlowedUpPa...