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NYC Subways Testing Flywheels
socolow writes "The New York Times (free registration required) has an article about the NYC subway system's use of flywheels to store the braking energy of trains approaching stations. Not only does this advance the development of flywheel energy storage, but it will help relieve a lot of the heat subways generate (always appreciated during the summer)."
if they taper to a smaller edge along the outside edge of the flywheel, if they taper to thicker along the outside edge compared to the inside edge they flywheel apart causeing many distractions among the people that happen to be looking at the time
sPh
Flywheels are (theoretically) more efficient than batteries or fuel cells. IIRC, batteries are 10% efficient, fuel cells 30-40%, while flywheels can be as efficient as the motors (up to 80%).
A legparnasom tele van angolnaval.
I think the reason for not using regenerative braking is that it would essentially requirew the flywheel to be ON the train. This isnt necessaraly a bad thing. You could regenerativly brake INTO your on-board flywheel and then use the stored energy to get the train moving again (with a little help from the third rail).
They may not have wanted to implement it this way because it might have been easier to build a few flywheels into each station rather than build them into every train in the system. Also this way they can get the idea implemented quickly (install flywheels at stations) rather than have to wait many years while the trains get replaced slowly as they wear out and die.
The Times article says that regenerative braking doesn't work because the units that supply power to the third rail don't know it's happening, so the power is just wasted. They would have to completely overhaul the power distribution system in order for regenerative braking to work.
Hmmm the heat has little to do with the electric motors, and much more to do with Air Conditioned Subway cars. The heat in the cars has to go somewhere so it (and some energy involved in moving it) goes out into the tunnels and the stations. Suposedly before A/C the cars were hot but the stations were cool(as one would expect for what is bassicaly a basement.)
I'd do something interesting, but my server can't handle a slashdotting.
clue me in please... why is the resistance such a problem, if the third rail is how they are powering the trains in the first place? Why does the braking energy from the trains get wasted, but the energy from the systems that are powering the third rail does not?
I love the NYC Subway system. It smells bad at times, but its an engineering marvel. So many people, tunnels, electrical, mechanical systems. a good website is http://www.nycsubway.org
http://github.com/gbook/nidb
Effectively this is like a big capacitor. I surmise a chemical battery would have issues with constant discharge/recharge. Whereas a flywheel couldn't care less.
:D
The flywheels could not go in the train because the bumpy ride would continuously siphon off power, and you know power siphoned off would be in the form of heat. Not to mention that each battery weighs as a small volkswagen
Their solution to the voltage loss in the 3rd rail is a half-assed one. They claim the distance between the trains would cause too much loss in the line if they tried to transmit power back across it. Yet they are still transmiting power across it anyway?!? They must plan on the average distange between a train and the battery station to be smaller than between a train and another train, though the article strangely failed to say.
I really didnt enjoy 1/2 the article being fluff about the lack of glory in being a transit engineer...
Slow down, turbo.
Fly wheels have one big issue: very low tolerance for movement. A lot of time and money has gone into using flywheels for cars, but the biggest issue was always trying to keep the thing from crashing--it moves so much that it can't be held by the magnetic ball bearings and it touches the side of the container. This is really bad. Not only do you loose a lot of speed, but it increases the chance of an explosion of carbon-fiber.
Better to make big flywheels that are stationary and burried in a mountain of cement.
A speech...
the wheels aren't on the trains, they are on the tracks. yes, putting heavy wheels on the train would increase stopping distances, but these are ground fixed and change the translational motion of the train to rotational motion. because of friction and other losses, the energy isn't completely transfered, but it's better than nothing. the way this will help braking is that the brakes won't have to work so hard on the trains themselves so it will help emergency braking (IF it is near one... there will only be a certain number of them spread throughout the grid).
Of course, I didn't read the article so I may be wrong... but I've read a lot of posts and this is what they are saying.
IANAL, but I play one on
Each flywheel gave steady 25 horespower and could double that for short kicks. Four would drive a car, but you could fit about 16 in an engine compartment (don't need engine, transmission, etc). That's 400 horsepower, and if you floor it you get 800 instantly! Also they would take you about 300 miles on a spin-up, which was accomplished by plugging the car into a wall socket, revving up the wheels with an electric motor - a charge would cost about 6 dollars of electricity.
Flywheels are better than batteries in a lot of ways. I'm glad to see they are finally being used for commercial applications. I haven't heard anything about the automobile flywheel guy since, but I'm sure his work won't be for nought. I'm equally sure car manufacturers and oil companies would stop him flat if he tried to market it though.
http://www.discover.com/search/index.html
You can search for it here with 'flywheel' as keyword - article name is 'Reinventing the Wheel'.
Stop the Slashdot Effect! Don't read the articles!
I seem to recall reading many years ago about testing on a bus that had a flywheel for regenerative breaking (in Scandinavia IIRC). The main problem with it was the gyroscope effect - trying to turn left or right creates a force at ninety degrees (ie up or down) and this proved too much for the suspension to deal with. Guess it's less of an issue with a subway train...?
My next sig will be ready soon, but subscribers can beat the rush
Afaik the problem is not that the flywheel moves too much but that it moves very little and tends to resist movement due to it's large axial momentum. This creates a problem when it's surroundings (car etc.) moves a lot because the flywheel will resist the movement and thus cause large forces on the bearings etc. If the metro would slow down while spinning up the wheel it wouldn't be that much of a problem I guess, especially if the flywheel is directed in a horizontal plane.
I don't know where I heard the story, but some guy was telling about how he had a small flywheel which he and his mates would spin up and put into a suitcase, then they would take the suitcase into a hotel and ask the porter to carry the suitcase to their room. The porter would have a real hard time turning the suitcase around any corners and wouldn't understand what was going on.
I just pulled that figure from the anti-grav story for a silly reference.
In all the discussion in how a gravity-shielded object would fly off the Earth I never saw anyone consider the effects of air friction or the fact that the gravity shielding situation would change depending on whether the anti-grav spinning disc were fixed to the ground or the flying object, and if it were fixed to the flying object then if there were some mechanism to rotate the gyroscopic superconductor to new angles as it's angular position over Earth changed, etc. Plus it would block gravity from certain angles; there would be plenty of gravitational pull from other nearby sources if you blocked Earth's gravity. To me the whole discussion was silly. But hey, this is Slashdot and I'm by no means a physicist.
Also, tangential speed on the Earth depends on your latitude.
And speaking of gyroscopic tendencies--and getting back on topic--some people thought the flyweels would be on the trains. A flywheel heavy and fast enough for this purpose would interefere with/be interfered with by the train's motions, wouldn't it? Plus the refrigerator-sized boxes (one of which featuring a hovering ping pong ball) the article describes are presumably the flywheel batteries, and they were in a control/monitoring station and not on the train, although the article didn't seem to clearly state this.
10 inch diameter 25 pound carbon fiber flywheel at 36,000 rpm.
.50 cal sniper rifle = 16,539 Joules
Edge speed is 1071 Miles per hour.
A "flander" is a large splinter that explodes off the inside of a ship's hull when a cannon ball hits broadside at sub-sonic velocities. Thus the term "smash to flanders".
a 25 pound cannonball will completely breach 8 inches of wood creating a manticore of wood splinter shrapnel.
A tornado will drive pieces of straw through a wall at subsonic speeds.
A winch cable will crack at supersonic speeds if it snaps. A winch cable will shear an engine block.
100 lashes is a death penalty.
Kinetic Energy = 1/2*I*w*w
I = moment of inertia --> ability of an object to resist changes in its rotational velocity
w = rotational velocity (rpm)
I = k *M*R*R (M=mass; R=Radius); k = intertial constant (depends on shape)
Inertial constants for different shapes:
Wheel loaded at rim (bicycle tire): k =1
solid disk of uniform thickness; k = 1/2
I assumed 4/5 because of the design they used
Kinetic Energy of flywheel = 68,428,800 Joules
357 Magnum = 937 Joules
4000 sniper rifle bullets worth of energy exploding outward in the form of tiny splinters of a substance that happens to have one of the highest tensile strengths. Assume 98% of the kinetic energy is lost to heat. 80 sniper bullets.
Bad news.
If voting were effective, it would be illegal by now.