NYC Subways Testing Flywheels 363
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)."
Regenerative braking (Score:2, Insightful)
Aren't they already electric?
It is probaly easier to implement (mechanically) and less additional weight on the subway.
Re:Regenerative braking (Score:2, Interesting)
Flywheels: Just Say No!! (Score:4, Funny)
Save the planet. Vote NO on flywheels.
Re:Flywheels: Just Say No!! (Score:3, Funny)
Re:Regenerative braking (Score:3, Interesting)
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.
Re:Regenerative braking (Score:3, Interesting)
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.
Do they manufacture spell checkers? (Score:2)
Re:Regenerative braking (Score:4, Informative)
Please read the article before posting, next time.
Re:Regenerative braking (Score:2, Interesting)
Re:Regenerative braking (Score:2)
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.
Re:Regenerative braking (Score:2)
I don't see any reason why there can't be an unpowered third rail specifically for returning power at the stations where most of the braking will take place. If for some reason a train gets stuck there, then the power can be turned back on for long enough to get the train into the next section.
Re:Regenerative braking (Score:3, Insightful)
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. [tracegridtie.com]
Re:Regenerative braking (Score:5, Informative)
IAAEE, so I'll hazard a guess. They say in the article that the 3rd rail uses 650V DC. For power distribution, this is a relatively low voltage. To minimize resistance losses, power is typically distributed at thousands of volts. To be able to easily convert voltages, you need AC, not DC so you can run it through a transformer.
I'll bet that they have high-voltage AC power distribution throughout the system, and they step it down to 650 V and rectify to DC it at frequent intervals along the tracks. The distance the power needs to run at low voltage along a high-resistance steel rail would never be very long, so losses are minimal. (I assume they use DC becuase it's easier to design train motors for DC, or something like that.)
The AC -> DC rectification is not reversible, however, so there would be no way for power generated by a train to get back into the main distribution grid, and the average distance the 650V DC would have to flow throught the 3rd rail to the next train would be too far to be economical.
(Of course, I could be wrong about all of this, since I don't really know anything about their system.)
Re:Regenerative braking (Score:5, Informative)
It's only within the last ten years that they finally retired all of the old pre-solid-state rotary converters [nycsubway.org] in the system - running power backwards through them would have actually worked.
The new cars actually have AC motors - the DC third rail powers a battery on board, I'm not sure exactly what the AC conversion tech is. There's still a couple thousand DC-motored cars riding the rails, so I'm not expecting to see the system switch over to AC distribution....
Re:Regenerative braking (Score:5, Funny)
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?
It's all tied together with social security.
Politicians are often heard saying something along the lines of
You've probably noticed that Social Security benefits are mostly received by old people.
You've probably also noticed that those old people move slowly. The reason they move more slowly than you or me and the reason they can't drive more than 20 mph under the speed limit is simply because they are encountering resistance.
Hope that clears it up.
Re:Regenerative braking (Score:2, Insightful)
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.
Re:Regenerative braking (Score:2)
But one of the biggest reasons not to use the electric motors as generators during breaking to store the power in batteries, is it is probally more efficient to not conver the mechanical energy to electrical, and then when you start rolling again, to turn the stored electrical back to mechanical. Just store the energy as mechanical in the first place.
On the other hand high energy flywheels are about as scary as wet cell batteries when things go wrong. I saw a video of a Kevlar flywheel coming apart and doing its best to take apart the shield around it.
Re:Regenerative braking (Score:2)
Re:Regenerative braking (Score:2)
If the flywheels are built into the subway stations, they can be more than shielded. They will probably be sealed into massive metal chambers surrounded with concrete. Sure, if one breaks it'll be a huge undertaking to replace, but you won't have lost any efficiency compared to now, and you won't kill people as 100-pound chunks of flywheel go flying at 80MPH.
And you don't really design a system like this with the intent to have it break down.
Flywheels won't make it into vehicles for some time, especially cars - there's too many unpredictable problems. You wold have to install self-destructive safety mechanisms in your flywheel to avoid killing people.
Imagine yourself stopping at a light, and when someone rear-ends you, your flywheel immediately blows itself into dust to save your life. Only your life didn't need saving, and now you need a new car.
Re:Regenerative braking (Score:3, Informative)
Re:Regenerative braking (Score:4, Informative)
I'm usually a little kinder than this, but you plainly don't know what regenerative braking actually is. It's a lot more than just a feature of your R/C car. The story is all about regenerative braking. Rather than using friction to convert kinetic energy to heat and getting rid of it, using the motor to convert it back to electrical energy. The flywheels are just the most efficient place to hold on to that energy until it's needed again. It's more efficient to store it near where it's generated, since a stopping train is likely to start again, from the place where it stopped, than to send it all along the system on the rail, where it will mostly be wasted in heating the third rail before it reaches a useful load.
The thing i found surprising about this story was learning that they weren't already doing something like this.
levitrain (Score:4, Funny)
Boeing, get on it!
Re:levitrain (Score:3, Funny)
Re:levitrain (Score:2)
Re:levitrain (Score:3, Funny)
Yeah and all the entries on that timetable read,
"when we get around to it." The New York City
subway system is a study in chaos theory sometimes.
Wow - that would take us all the way to 1920! (Score:4, Interesting)
sPh
Gyroscopes (Score:3, Insightful)
Re:Gyroscopes (Score:2)
Re:Gyroscopes (Score:2)
Hee hee. That's a good question. That explains why gyro sandwiches always upset my stomach.
Re:Gyroscopes (Score:2)
Re:Gyroscopes (Score:2)
Re:Gyroscopes (Score:2)
M@
Re:Gyroscopes (Score:2)
You got me thinking. Can you do such a thing? Another flywheel rotating in the opposite direction would have no additional effect (or would it make it twice as hard to turn an object?). Two gyroscopes mounted perpendicular to each other would make it difficult to turn an object in any direction, wouldn't it?
Re:Gyroscopes (Score:2)
Re:Gyroscopes (Score:2)
A Wired article (Score:4, Informative)
Re:A Wired article (Score:2, Funny)
Silly journalist....there is no such thing as centrifugal force.
Centripital. Yes.
Oh how I love rotating bodies.
Pros and Cons (Score:4, Funny)
Unfortunately, it takes 45 minutes of winding for 4-5 seconds of run time.
Best quote from the article (Score:2, Funny)
"Oh that?" Mr. Lobenstein smiled like a child. "That's just to amuse us. Sometimes we get bored."
Re:Best quote from the article (Score:2, Informative)
"The only problem is that when the power goes back into the rail, it is quickly eaten up by the resistance of the metal. So if other trains are not close by, to scoop up the power, the extra electricity dissipates like so many ripples in a pool."
If other trains are not close by? How close do they want trains to be?
That quip about the heat in the stations is no joke. If you go to the yellow line (N/R/Q/W) stations, it is like 110 deg F down there minimum, at 2 AM! People stagger around down there panting and sweating like they're Ozzy.
Re:Best quote from the article (Score:2)
This system is essentially giant battery (or rather, 10 small ones) in every station to suck up the power put back into the rail by trains stopping at that station. If a train slows down far away from another train or station battery, there's not much good that power being pumped back into the rails are gonna do anyone.
Oh, by the way. The reason that the resistance is such a problem? They're DC motors. That's why they can be REVERSED and used as generators. You can't do that with alternators/AC motors. For reasons why DC has problems with transmission across long conductors, ask your local Slashdot geek about the "war" between Edison and Tesla.
Re:Best quote from the article (Score:2)
I don't buy it (Score:5, Funny)
Heat due to A/C (Score:3, Interesting)
Re:Heat due to A/C (Score:2)
Where to stick your flywheel.... (Score:5, Informative)
The modifications to the trains are actually significant to support this, but it's about how the braking systems work and how the motor controllers work on the trains. There are a class of motor controllers that are not really compatible with regenerative braking, and they are fairly commonly used since they are cheaper than the others. The conversion to regenerative braking may involve replacing a fair bit of gear on the rolling stock. They were considering this kind of thing in San Diego, which is where I picked up lots of this trivia.
Many rail systems and streetcar systems have regenerative braking, but frequently they don't store the energy. What they do is have one unit braking while another is accellerating, so the excess power is in effect transferred via the wire to the other vehicle. Think of cable car systems where the guy at the top of the hill counterbalances the one at the bottom. This is hard to make work though, the timing issues being what they are.
My $.02
Re:Where to stick your flywheel.... (Score:2, Informative)
Besides, 10 batteries, each the weight of a Volkswagen, might have some negative impact on the performance characteristics and power usage of your average subway train.
Registration Required ? (Score:2, Informative)
If you dont wanna register at NYTimes visit NYT Random Login Generator [majcher.com]
But because NYTimes block based on referrers you got two chances 1 - Disable Javascript or a better one get Multizilla Toolbar for Mozilla [mozdev.org]
It has a nice option like "Dont send referrer" .
Choose it and boom you are in !
A little too excited? (Score:3, Funny)
Ok, this guy needs to get laid. Now.
Smell (Score:2)
Now, if they could just do something about the smell. The Broadway-Fulton-Nassau station certainly gets rank in the summer.
Wow, 36,000 is a lot of RPM... (Score:5, Informative)
Let's hope those flywheels are enclosed in something pretty solid.
Storing that much energy is one thing. Accidentally releasing it is another. When I was a student at MIT there was a permanent display in a glass case in the hallway of the biology department showing a centrifuge rotor that exploded, just to remind everyone of what happens when something spins too fast.
Let's also hope there's something to muffle that 600 Hz whine (which is close to the peak of human hearing sensitivity).
And I thought the wheels on Boston's Green Line screeching when going around sharp turns was bad...
Re:Wow, 36,000 is a lot of RPM... (Score:2)
Re:Wow, 36,000 is a lot of RPM... (Score:2)
A flywheel's mode of failure is catastrophic. A failure in a set of flywheels that stored a *megawatt* of power is going to kill a lot of people unless it is properly contained.
Exploded centrifuge images (Score:3, Informative)
Re:Wow, 36,000 is a lot of RPM... (Score:5, Informative)
Re:Wow, 36,000 is a lot of RPM... (Score:3, Interesting)
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.
Re:Wow, 36,000 is a lot of RPM... (Score:3, Informative)
We can hear as low as 20hz and as high as 20,000hz (20k). However, most people perceive stuff above 16k as some sort of noise, but they can't really make it out or get a directional location on it.
The human voice has a smaller range... around 85hz for a really good male bass singer up to 1.1k for a really good female soprano.
That's not the whole of it though, because you get into things about even/odd harmonics, plus the fact that one octave around 20hz doesn't take many additional cycles to hit the next octave, but it takes thousands of cycles around 20k to jump an octave.
Human hearing isn't linear by any means. We are nearly deaf at the lower end of the scale; that's why we often "feel" bass -- not because when its loud enough to hear it is also felt, but more like to get enough energy so that our ears can even hear it you have to put out a LOT of power. But I digress...
Parry People Mover (Score:2)
They have been trialed on the Welsh Highland Railway [bangor.ac.uk] and on the island of Mauritius [railway-technology.com] omngst several other schemes - a quick Google search [google.com] will turn up a lot more information about some of the trials.
While not a total success it is good to see innovation in this area.
More information here (Score:5, Informative)
No heat? What about the homeless? (Score:2, Insightful)
Re:No heat? What about the homeless? (Score:2)
Re:No heat? What about the homeless? (Score:2)
Don't believe me? Want to mod me down? Go ahead, just don't try to not have a job or a home or any money in NY, otherwise they'll throw you in jail.
Is there any danger? (Score:2)
There's one safety concern I have that I haven't yet seen addressed, though I've probably just missed it. If a flywheel is spinning at several tens of thousands of RPM (such as the 36,000 RPM flywheel mentioned in the story), what happens if the flywheel's physical supports are damaged or destroyed?
Basically, let's say a truck crashes into the building storing a spinning flywheel. The flywheel's housing is hit and breaks, putting the flywheel into physical contact with other materials. What happens? I have visions of a thousand-kilo ceramic disc either spinning off like the Tazmanian Devil, leaving a disc-shaped cartoon hole in whatever it encounters, or shattering upon impact and spraying shards of material at hundreds of meters per second in sundry directions.
The problem is, I don't know if this is actually true or not. Can anyone with an actual knowledge of such things answer? Thanks.
Re:Is there any danger? (Score:2)
Re:Is there any danger? (Score:2)
Re:Is there any danger? (Score:2)
This is old news! (Score:2)
Of course, I don't recommend loop the loops, and the CrossRoads of Danger(TM) would have to go.
The cool cardboard desert backgrounds and grandstands could stay, though. And the orange plastic track would make an excellent subway defense weapon!
"Mom, he's beating me with the track again!" "Well, hit him back, I'm busy!"
Flywheel info (Score:2)
nycsubway (Score:2, Interesting)
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 [nycsubway.org]
Re:nycsubway (Score:2)
Jumbo Capacitor (Score:2, Interesting)
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...
Re:Jumbo Capacitor (Score:2)
Danger involved! (Score:2)
They'll put your eye out.
Braking power? (Score:2, Insightful)
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 [maricopa.edu].). 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....
Re:Braking power? (Score:2, Interesting)
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.
Re:Braking power? (Score:2)
I think we're missing the big picture... (Score:2)
Has anyone told Boeing yet? [slashdot.org]
Another little contributor... (Score:2)
Little Effect on Subway Heat (Score:2)
Are we to take this seriously? (Score:2)
A very, very big battery. Or, to be more accurate, 10 of them, each weighing as much as a Volkswagen Bug and together able to store up to a million watts of power.
Are we to take this article seriously, or to believe anything it says? If they do not know the difference between power and energy, there is no telling what else in the article may be untrue.
a few years ago (Score:2, Interesting)
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'.
Re:Subway trains shouldn't stop (Score:2)
BBK
Re:Subway trains shouldn't stop (Score:2)
Re:Subway trains shouldn't stop (Score:2)
Yes, and what do you do when you get to the end of the moving sidewalk; get thrown off the platform at 20 MPH?
Re:Subway trains shouldn't stop (Score:2)
Yes, and what do you do when you get to the end of the moving sidewalk; get thrown off the platform at 20 MPH?
I dunno, lay down some foam or somthing.
It's been done, for elevators (Score:2)
Both require some physical agility, and are rarely seen today.
Re:Arthur C. Clarke (Score:2)
Re:Arthur C. Clarke (Score:2)
sPh
Re:Arthur C. Clarke (Score:2, Informative)
Honda Insight (Score:2, Informative)
regenerative braking [hondacars.com], not sure what technologies are used by it.
Re:thank goodness (Score:2, Funny)
Yeah, 'cause here in Califronia we're all huddled in the dark trying to cook food with power from the rationed 9-volt batteries that FEMA hands out once a month.
Re:Could we get a "No NYT" option? (Score:2)
I wonder how much the NYT pays Michael to post their articles links here. I swear almost every article he posts is from the NYT page.
Re:Could we get a "No NYT" option? (Score:2)
Sorry. Too much caffeine today.
Re:Could we get a "No NYT" option? (Score:3, Funny)
Why can't you just post without reading the articles - like everyone else?
Re:Could we get a "No NYT" option? (Score:2)
Re:Flywheels -- the REAL ULTIMATE POWER. (Score:2)
Re:Slashdot NYTimes Login (Score:2)
Re:Slashdot NYTimes Login (Score:2)
Oh well, guess I deserve to be considered troll then. :)
Re:Very cool idea. (Score:2)
Re:Very cool idea. (Score:2)