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)."

Comments

Regenerative braking

[nuggz]

Why not just use regenerative braking.
Aren't they already electric?
It is probaly easier to implement (mechanically) and less additional weight on the subway.

Re:Regenerative braking

[GigsVT]

The third rail is already highly charged. Trying to push power from a battery would be like trying to save on power bills by hooking a 9V battery w/ an AC Adaptor to the wall outlet - there's too much power there to push more back in.

Yeah, it's almost as ludricrous as putting solar panels on your roof and then trying to sell power back to the grid. Oh wait.

Re:Regenerative braking

[mcg1969]

Actually, I'm pretty sure that the power is put back into the third rail. The article does not, in fact, say that the resistance in the third rail is always too high. Rather, it says that the resistance is too high if there are no trains close by. After all, resistance is proportional to distance.

So basically, the plan will be to distribute these flywheel batteries throughout the subway system so that there is always one close by when a car is generating power through its regenerative braking system.

The author's attempt to simplify the description of the system probably made this hard to see.

Gyroscopes

[Maniakes]

Since the flywheels are just great big gyroscopes, what happens when the train makes a sharp turn?

Could we get a "No NYT" option?

[wowbagger]

I would like to ask if it would be possible to have a preference option that says "No stories with a New York Times link" in them - I refuse to register, I refuse to play games to work around registering, and therefor any /. story where the bulk of the information is on a NYT-hosted page is useless to me, unless/until somebody posts the article contents. And since I'd like not to encourage karma-whoring and copyright violation, I'd sooner just remove such stories.

No heat? What about the homeless?

[TheLocustNMI]

What about the homeless people who rely on the subway heat vents in the winter?

Braking power?

[ldopa1]

I understand the concept of harvesting braking to push a flywheel to greater speeds, therefore storing the energy, but I have a couple of questions:

Aren't flywheels tremendously heavy? Wouldn't the additional weight cause longer stopping distances, especially under emergency braking?

I do understand that the braking would be assisted by the flywheel itself (spinning it up), but you never get anything for free (See The First Law of Thermodynamics.). When spinning up the wheels, you'd have heat loss, and loss again when they are spun down. Secondly, again, because of the 1st Law, wouldn't the heat generated by all of those flywheels spinning up and down exactly equal the heat savings? Moreover, thinking of emergency braking - What is the top speed of the flywheels? How strong do the gears need to be to spin up the flywheel to top speed very quickly? And at what tremendous gear ratio?

Don't think that I'm against it, cause I'm not. I think the electricity savings alone make it worth the effort and expense, but I'm not convinced that the trains would be as safe as the existing ones, and that there would be any heat savings. That said, CA needs to convert the BART next....

Overkill. Try slopes

[Anonymous Coward]

Flywheels are overkill.

The New York Subway stations are currently elevated from the surrounding tunnels, so that a train slows down as it climbs into the station, and accelerates as it glides down out of the station. Real simple, no High Tech required, maybe not as interesting, though.