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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)."
sPh
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.
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.
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...
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.