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How much power is generated by dynamic braking?

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Composite flywheels in vacuum are a fantasic technology that almost works. the problem isn't the rotors or the motors, or even the vacuum. it's the bearings. supporting 20 lbs rotating at 250kRPM is hard enough without vibration and shock to deal with. magnetic levitation bearing technology sshows promise, but are particularly sensitive to orientation changes. if anyone has ever played with a conventional steel gyroscope toy, you may have encountered a mode where a sharp jolt or several well-timed nudges can get the whole assembly to wobble violently around its center of mass at something near the fundamental rotational speed of the rotor. (try it sometime with a bike wheel) when a power-storage flywheel gets into that mode, the forces are usually sufficient to destroy the rotor. As Dldlance points out, the composite sort usually don't get far outside their containers, but there's still all that energy being released as heat, noise and vibration-- something akin to dynamite exploding inside the can; it happens about that fast-- a memorable experience, according to a co-worker. Even though the rotor is contained, the energy has to go somewhere. . . I'm not saying the problem is unsolvable, just that it hasn't been solved for mobile applications yet. Wire hybrid: Neat idea, and workable with todays' technologies, but (as MWH likes to explain) capital intensive. (Though once the initial investment is in place, the incremental cost to add trains is attractive. Any government policy makers in the house? Here's a place where throwing money at a problem might do some good.) It also moves a portion of the emissions produced moving goods over hills to large, fixed places where they can be more effectively mitigated, and allows the USA's HUGE stocks of coal to be directly used as a primary power source to transportation. Another advantage (from a railroad point of view) is all those diesels that are idling to stay warm could earn money pumping power into the national grid at the same time; or, as an alternate, they could be shut down and use grid power to say warm and restart-- no more waiting for jumper cables when a battery goes south; just raise the pan.
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