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

Re:Subway trains shouldn't stop

[bbk]

While a worthy idea, there are simply to many frail/handicapped/uncoordinated people who would make a system like this a nightmare...

BBK

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

[Maniakes]

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%).

Re:Regenerative braking

[Noofus]

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.

Re:Regenerative braking

[Snar Bloot]

http://www.ctts.nrel.gov/analysis/advisor_doc/rege n.htm for a quick explanation of Regenerative Braking.

Re:Regenerative braking

[marauder404]

If you read the article, you'd know: they can't put power right back into the third rail because the resistance of the rail is too high. And they can't put it into batteries because there aren't batteries big enough to solve the problem. So they use a flywheel.

Please read the article before posting, next time.

Re:Regenerative braking

[Neon Spiral Injector]

I'm thinking the batteries aren't that much lighter than a flywheel.

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

[mosch]

They are using regenerative braking. That's what the whole article is about, a new application of regenerative braking in a place that people don't usually associate with relatively new technologies.

Re:Regenerative braking

[antirename]

Flywheels aren't lighter (at least not when you consider the shielding :) just more efficient. And I agree, they fail VERY catostropically when they break.

Re:Regenerative braking

[Anonymous Coward]

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.

Re:Regenerative braking

[snatchitup]

Does it say that in the Article? I think max is 25% efficient. You have to lose 50% in transferring to the flywheel. Then lose 50% of that remaining to get back into the train.

Re:Regenerative braking

[WolfWithoutAClause]

Batteries are heavier. Still, they didn't actually say AFAIK, but I think that they were planning to put the flywheels in the station, not on the train; so the weight doesn't matter much. It may be that the flywheels are cheaper than the batteries, and they only have to store the energy for a short time in this case anyway- so it's a perfect application.

Re:Regenerative braking

[n9hmg]

Why not just use regenerative braking
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.

Re:Regenerative braking

[pfalstad]

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?

Re:Regenerative braking

[Oculus Habent]

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

[km790816]

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.

Re:Regenerative braking

[Karma Farmer]

Clue me in... is there a reason why you're able to log in to slashdot to post, but not able to log into the NY Times site to read the article?

Re:Regenerative braking

[martyn s]

Well, the power supplying the trains use a very high voltage. You wouldn't really be able to generate such a high voltage to put it back into the third rail.

I don't know this for sure, but I believe the voltage is high enough to jump through the air, so there doesn't have to be contact with the rail. I think that's where the resistance comes in. The gap through the air is where the resistance is.

Re:Regenerative braking

[Oculus Habent]

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

[gorilla]

'The third rail' should really be 'The third rails'. No subway system has a single third rail which powers the whole system, they're always broken into short sections.

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

[Karma Farmer]

Wow. Maybe they could use regenerative braking, and then store the excess power generated in a battery. Maybe they could even use a mechanical battery, like a flywheel!

That would be really cool!

Is there some reason why you're able to log into slashdot to post, but unable to log into the NY Times site to read the article?

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.

Re:Regenerative braking

[Waffle Iron]

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?

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

[nelsonal]

Fly wheels can store more energy newer ones come much closer to hydrocarbons as far as energy stored to volume than batteries. The low energy to volume ratio is the main problem impeding electric cars.

Re:Regenerative braking

[pfalstad]

Cute, but the article doesn't answer my question. Please quote the line in the article which answers the question. The article just gives some non-technical handwaving about electricity dissipating like ripples in a pond.

Re:Regenerative braking

[4of12]

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

"Social Security is the third rail. Don't touch it."

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

[candover]

That's how the system works, yes. The MTA has 214 substations around the city, which are fed something between 11-27 kV AC, transformed to 400 V AC, and rectified to 600 V DC.

It's only within the last ten years that they finally retired all of the old pre-solid-state rotary converters 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

[Phil Karn]

This explanation makes as much sense as any. But still, why the flywheel? Why work with a new, bulky and quite likely hazardous technology instead of replacing those AC->DC rectifiers with bidirectional inverters that allow excess DC power to be pumped back to the AC side? The grid is the best stationary flywheel there is.

Inverters that do this already exist, at least at lower power levels. The Trace SW4048 in my grid-tied PV system is an example.

Re:Regenerative braking

[Glass of Water]

I assume they use DC becuase it's easier to design train motors for DC, or something like that.

Yeah, I think it's because DC motors are better when you need a large motor (but not sure why) and also because dc motors are much better at being variable speed.

Anyway, nice to know that this job is in the hands of some serious geekz.

Here is an article to grok if you want to know about DC: http://farside.ph.utexas.edu/~rfitzp/teaching/302l /lectures/node77.html

That will tell you more than me.

Re:Regenerative braking

[AugustFalcon]

The article is a little light on the technical side.

In the old days in a DC circuit Power was equal to Amperage times the Voltage, or P=I*E.

Voltage was equal to Amperage times the Resistance, or E=I*R.

Which gives P=Isquared*R. So to reduce power losses when transmitting you want to keep the amperage as low as possible which mans keep the voltage as high as possible.

When you speak of a flywheel being more efficient than a chemical battery there are a couple of considerations. In order to spin the flywheel you have to turn it or apply torque. You do that with a MOTOR. Motors are not 100% efficient so you lose some power there. Then you lose more power through the mechanical inefficiences of the flywheel, e.g friction and drag effects. Then you need to extract the energy from the flywheel so you must convert it by running it back through what was once a motor but now a generator so you have more losses doing this. Then you must transport it to the place on the rail where it is being used.

Compared to a battery it would seem that the magnitude of the losses might be less, i.e., are the losses associated with the conversion from electrical to chemical less than the electrical to mechanical to electrical in the flywheel? Or are there other considerations, such as the size of the batteries, attaining the high battery voltage, peak current rates, heat disipation, long term battery maintenance, internal battery resistance, etc. Big batteries are far from being maintenance free (ask an old time submariner about battery maintenance, equalizing charges, etc.) Also, there may e considerations of matching the internal resistance to the external load, i.e., they should be equal to transfer maximum power and minimize internal losses.

Then what about the costs. Probably you could make more of the flywheel power storage units than the huge batteries so there could be more of them attached to the system which would tend to reduce the amount of rail the power must transit to reach a train.

Re:Regenerative braking

[Weh]

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.

Re:Regenerative braking

[homer_ca]

Any storage mechanism has its safety downside. If it's not a 36000rpm flywhell, it'll be a compressed gas cylinder or a chemical battery with lots of nasty stuff you don't want leaking out- acid, lithium, or my favorite hot molten sodium and sulfer.

Re:Regenerative braking

[ross.w]

Large DC motors are only used in vehicle applications because of the need to run at a wide range of speeds, even close to zero RPM. In stationary applications AC motors are used even for variable speed because they don't require a commutator.

Commutators are constantly switching heavy currents while the motor is running and therefore tend to have a short life.

Re:Regenerative braking

[Karma Farmer]

So if other trains are not close by, to scoop up the power, the extra electricity dissipates like so many ripples in a pool.

I assume this means that if other trains are not close by, to scoop up the power, the extra electricy dissipates like so many ripples in a pool.

I'm also assuming this means that they generally pump energy into the system physically close to the trains, to minimize the amount of rail they have to pump the energy through.

From the article, it sounds like the current, already existing subway system already pumps energy from a train slowing down on one side of town into trains speeding up on the other side of town. But, they're losing a lot of energy that way, as the the energy travels along the rail (as opposed to being pumped into the rail close to the accelerating train).

So in this new system, they're taking the energy that the trains are already pumping into the rail when they brake, and instead of trying to push for miles and miles and miles along the rail until it (hopefully) finds a train (or all dissipates as heat), instead they're pushing the energy into big batteries near the station, to be pumped back out again when a physically close train starts to accelerate.

At least, that's how I read the article.

Re:Regenerative braking

[Phil Karn]

>you can waste the energy as heat (uncomfortable), use it to charge batteries (wasteful, since the efficiency is low, probably less than 50% for the round trip), pump water uphill (might be problematic in NYC, might not be very efficient), or spin up a flywheel attached to a generator

You left out another alternative. You can pump the regenerated energy back into the AC power grid, thereby offloading (for a moment) some of the grid's generating capacity.

>DC->AC requires big switches and transformers. It's not terribly efficient, and it's heavy and expensive.

It's getting easier all the time with modern power semiconductors. Very high power DC->AC converters have been used for quite some time in DC power transmission, e.g., on the 3+ GW DC Pacific Intertie that runs from the Columbia River to LA. DC power transmission is also common in Europe, e.g., under the English Channel.

Re:Regenerative braking

[Breakfast Pants]

why not just use 2 flywheels, one turning clockwise the other counterclockwise, that would solve your inertial problems by cancling them out.

Re:Regenerative braking

[Phil Karn]

AC motors are starting to displace DC in electric traction, thanks to modern power semiconductors that can replace mechanical commutators.

Think of it this way: every motor is really an AC motor. The so-called "DC motor" is really an AC motor that performs an internal DC->AC conversion, usually mechanically. So the change is not from DC to AC, but from mechanical to solid-state DC->AC conversion.

My EV1 electric car uses a 3-phase AC induction motor driven by a variable frequency, variable voltage inverter that uses IGBTs (insulated gate bipolar transistors), a hybrid between bipolar transistors and MOSFETs. On routine driving around San Diego, regeneration gives me back maybe 10-20% of the energy I move from the batteries to the car. It's not a large percentage, but every little bit helps, and it's not hard to do.

Re:Regenerative braking

[CTachyon]

IIRC, two counter-rotating flywheels will cancel out linear motion, but any rotation causes the flywheels to violently jerk about. For instance, a mild right turn would make the CW flywheel veer into the turn but make the CCW flywheel veer away from it, placing a torque (Is that right? My kinetics are rusty) on the shared axis of rotation. Much simpler to make the flywheels stationary, pump the regenerated electricity back into the grid, then power the flywheels from the excess power.

Re:Regenerative braking

[thebigmacd]

I'm wondering about stepper motors. In a stepper motor, doesn't DC go through the coils? I assume this because some stepper motors are designed to hold a position, which wouldn't really be possible with AC (magnets switching poles all the time). I understand that there are very large stepper motors in use (maybe I understand incorrectly) in industries.

Re:Regenerative braking

[thebigmacd]

Isn't resistance proportional to the SQUARE of the distance, or am I confusing that with resistance being proportional to the cross-sectional area? ...

Re:Regenerative braking

[Ungrounded Lightning]

If you are doing regenerative braking (using the motor to generate electricity, and slowing yourself down in the process), you can waste the energy as heat (uncomfortable), use it to charge batteries (wasteful, since the efficiency is low, probably less than 50% for the round trip), pump water uphill (might be problematic in NYC, might not be very efficient), or spin up a flywheel attached to a generator. This last might actually have lower efficiency than the battery solution ...

No way! Motors and generators can easily be designed with efficiencies approaching 100%. Excluding electric heaters (which are exactly 199%, since all the waste is heat B-) they're about the most efficient electrical devices known.

They'd slag down otherwise - ONE horsepower is almost exactly 3/4 of one KILOwatt - or half a high-end portable electric space heater. So one percent of loss in a 10,000 horsepower motor, generator, or rotary converter is 50 space heaters running full-blast at once. Much of that appears as heat in the copper windings and nearly all the rest as heat in the iron cores they wrap (with negligible losses as bearing friction and air resistance). So you'd quickly have molten copper and red-hot soft iron rather than a rotary machine if it weren't hysterically efficient.

The flywheel is even better: Bearing and air friction are the main drags, and they're tiny. (If you could put it in a magnetically-shielded perfect vaccuum bottle on hypothetical frictionless bearings the next biggest loss would be tidal heating - which won't stop it for geologic time.)

Batteries aren't in the same league.

Re:Regenerative braking

[Ungrounded Lightning]

electric heaters (which are exactly 199%, since all the waste is heat B-)

Oops. Typo: 100%

(I'd have proofread it better but previewing or posting through the company's firewall and proxy server tends to crap out 19 times in 20.)

Re:Regenerative braking

[rew]

Flywheels are (theoretically) more efficient than batteries or fuel cells. IIRC,

If you have a connection to the power grid you can deliver the energy back to the power grid. You can then hope that some other subway is "using" your regenerated power.

Generators can be had at 98% efficiency, electrical motors around 90%.

Roger.

Re:Regenerative braking

[ebh]

RTFA. 650VDC. But MONSTER current.

A trip to the NYC Transit Museum is very enlightening when you start looking at the hardware required to get all that current to the right place (think of what a 2000 amp circuit breaker would look like).

thank goodness

[tps12]

After the power outages a couple weeks ago (most of Lower Manhattan was affected), it was starting to feel a little too much like California, if you ask me.

Seriously, flywheels are a really cool energy storage technique. They are a little scary when you consider the damage that a giant, heavy disk spinning very quickly could do in the event of a collision, but that is a small price to pay with the cost of energy so high these days.

When can I get one in my car?

Re:thank goodness

[Vlad_the_Inhaler]

Your 'small price to pay' would be a monster if it really happened and a lawyer could prove that someone in the chain of responsibility had said that.
Having said that, when was the last collision in the NY system? If the event is sufficiently unlikely then flywheels could still be a good move.

Re:thank goodness

[snatchitup]

Close.

Replace "mass" with I = Moment of Inertia in the above equation, and you've got it.

Moment of inertia is related to mass and the shape. So, this would depend on the construction of the thing.

Re:thank goodness

[lokki]

when was the last collision in the NY system?

1997, AFAIR. On the G line, no fatalities or major injuries.

Re:thank goodness

[Russ Steffen]

it was starting to feel a little too much like California

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:thank goodness

[bev_tech_rob]

If I read the article right, the flywheels were not on the train itself, but in a box connected into the circuit.

Re:thank goodness

[bleckywelcky]

I think people all over the country are being hit with blackouts due to the unseasonably hot and humid weather. Here in SE Michigan we have been routinely having 90%+ humidity levels on 90+ F days. People run their A/Cs non-stop and power consumption is extremely high overall. So far I think we have run into 10 or more blackouts over the last 2 to 3 months. I sweat like a fking pig out in the weather during the day (classes , plus I install and service A/Cs heh) so I crank my A/C down to 65 or 70 during the day depending on how I feel, and 65 or below during the night. Feels like winter when I wake up, but damn I sleep good! :P

levitrain

[Mt._Honkey]

Now if they just make the flywheel out of a superconductor, then not only will it store energy, but the train will be weightless!!!

Boeing, get on it!

Re:levitrain

[Anonymous Coward]

Considering how trains in the US are rarely on time, I'd prefer they be waitless :)

Re:levitrain

[dbrutus]

Of course they have a timetable. If they didn't, they couldn't plan properly and avoid crashes. They just don't publish the timetable to avoid the moaning and whining that they're late.

Re:levitrain

[MyHair]

But then it would fly into space at 25,000 miles per hour. . .

Re:levitrain

[flink]

They publish one in Boston. Our subway system is kinda small though.

Re:levitrain

[Surlyboi]

Of course they have a timetable.

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.

Re:levitrain

[zilly]

They do have a timetable, and they do publish it. Copies on paper are available in most stations, in fact, if you ask for them.

Of course, these timetables have nothing to do with how long you actually have to wait for your train to show up. This seems to be more a factor of the temperature in the station (sweltering hot or freezing cold: add ten minutes), what time you were _supposed_ to be where you're going (for every five minutes late, add another ten) and whether or not you have to pee (add half an hour to an hour, depending how badly you have to go).

Although, if a train is running too early, sometimes the conductor will hold the train in the station so people on the local/express across the platform can make their connections. As far as I can tell, this only happens to you when you're on the train being held. If you're the guy hoping to make the connection... well, let's just say I hope you did your number one before you left.

ken

Wow - that would take us all the way to 1920!

[sphealey]

Wow - that would take us all the way to 1920 and the Milwaukee Road's use of regenerative braking on their electrified lines through the Cascade Mountains!

sPh

Re:Wow - that would take us all the way to 1920!

[tcm614ce]

Wow - that would take us all the way to 1920

Once again proving that what goes around comes around!

Re:Wow - that would take us all the way to 1920!

[linzeal]

Shhhh, new yorkers think they are superior in every way.

Gyroscopes

[Maniakes]

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

Re:Gyroscopes

[Anonymous Coward]

Usually a train will fall of the tracks when making a sharp turn. Regardless of whether they got a flywheel or not...

Re:Gyroscopes

[Anonymous Coward]

tracked vehicles don't make "sharp turns"...

Re:Gyroscopes

[L. VeGas]

Who said they are mounted vertically?

Re:Gyroscopes

[lokki]

Who said they're mounted on the train at all?

(hint: they're not. read the damn article!)

Re:Gyroscopes

[WolfWithoutAClause]

Since the flywheels are going to be in the station, not the train; not a lot.

Re:Gyroscopes

[msheppard]

Mount them horionztally, or implment two with conteracting spins.

M@

Re:Gyroscopes

[jmoloug1]

Read the article! The flywheels are not stored on the train, but are attached to the tracks.

Re:Gyroscopes

[Baba Abhui]

Geesh. The flywheels are not on board the train. Did you actually read the story?

Re:Gyroscopes

[Provincialist]

Who said they are mounted vertically?

OK, then what happens when they enter a sharp downhill section?

Re:Gyroscopes

[L. VeGas]

OK, then what happens when they enter a sharp downhill section?

Hee hee. That's a good question. That explains why gyro sandwiches always upset my stomach.

Re:Gyroscopes

[iabervon]

Plus, this'll help tourists by keeping the stations from flipping around when you're not paying attention...

Re:Gyroscopes

[L. VeGas]

"two with conteracting spins"

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

[Kryzon]

I work for the Automation and Controls department of a very large company and we are exploring this technology. This is a very real problem, but the solution is pretty easy. Instead of using just one large flywheel, use many smaller ones. You can then take these smaller flywheels and pair them together but have them rotate in opposite directions, this way they negate each other.

Other people have asked, "why not just convert it back to electricity?" This is a solution for some rail lines but not all. It depends on the transmission system used by the railway. Most likely it is an AC system. Now its easy to just turn the train motors into generators to stop, but now you have to perform power filtering and conversion twice. You need to convert it to DC and then back to AC in order to get the correct frequency (AC to AC frequency changes are very hard) Next you have to get your phase correct when you send it back out on the line... It is expensive to have all of this equipement on a single train. Thus, flywheels have emerged as a solution for now.

Re:Gyroscopes

[thebigmacd]

FYI, "gyro" (Greek) is pronounced "euro", or something very close. Whenever anyone I know talks about what they bought at the local Greek takeout restaurant, I have to take a few seconds to get it into my little noggin that no, they DIDN'T ingest money.

Re:Gyroscopes

[thebigmacd]

A second flywheel spinning in the opposite direction WILL cancel the inherent stability in the first. Some people added a free-spinning third wheel to the front of their bike for a demo once. The bike did not become stable as normal when it was moving. For a do-it-yourself demonstration of the ill effect of having a single gyro spin the WRONG way, try riding your bike as it rolls backwards down an incline. NEGATIVE stability if there ever was any.

Re:Gyroscopes

[thebigmacd]

If you installed a single massive (in the scientific sense) gyroscope on the train, with axis of rotation horizontal and lateral, and forward spin, the train would lean INTO the turn, whether the track banked or not. And it wouldn't FALL into the turn because the gyroscope in that config would seek a position with the net result of centripetal and gravitational acceleration vertical relative to the CAR.

Re:Gyroscopes

[yesthatguy]

Isn't it pretty close to "hero"? Hence hero also being a name for that type of sandwich.

Re:Gyroscopes

[Inthewire]

Well, most efficent aside from supertankers and barges. Of course, not everyone has a port handy.

Re:Gyroscopes

[AndrewHowe]

That's due to the steering geometry, not the gyroscopic effect. You could look at it like this: You are sitting backwards on the bike, and it is going forwards down the hill. The problem is that real wheel steering is inherently unstable.

Slashdot NYTimes Login

[d3xt3r]

Here's a user account I created to see this article at NY times without everyone having to register: username: slashdot2233 password: slashdot I'd hate to see anyone posting without having actually read the article. ;-)

Re:Slashdot NYTimes Login

[d3xt3r]

oops, forgot the paragraphs:

username: slashdot2233
password: slashdot

sorry!

Re:Slashdot NYTimes Login

[cryptor3]

user: qwerty pass: qwerty

Re:Slashdot NYTimes Login

[d3xt3r]

Try to do people a favor and this is the thanks one gets around here. ;)

Re:Slashdot NYTimes Login

[Ashtangi]

slashdot2233, slashdot did not work for me. Something about not finding the "Subscriber ID". It was a good idea, but is it possible the NYT site has a way to block this kind of shared login?

Re:Slashdot NYTimes Login

[d3xt3r]

Weird, i just tried to log back into NYT and that user/pass fails for me too. Maybe they did block it. Or maybe they blocked it because I gave them a fake email address.

Oh well, guess I deserve to be considered troll then. :)

A Wired article

[L. VeGas]

Wired ran an article about the new flywheels a while ago.

Re:A Wired article

[borgasm]

...spin a flywheel 20 times faster, at 100,000 rpm, producing 400 times the centrifugal force.

Silly journalist....there is no such thing as centrifugal force.

Centripital. Yes.

Oh how I love rotating bodies.

Re:A Wired article

[n9hmg]

Yes, and the fourth month of the year is spelled "capital a, p, r, i, l". (I still hate that teacher for calling me out in the third grade spelling bee on that one).
Centrifugal force is an apparent force, useful for visualizing the stress on the wheel.
You could say that gravity doesn't pull two masses together, either. Instead, an apparently falling object is just naturally following the curvature of space, and the surface of the Earth is pushing it off-course when they meet.

Pros and Cons

[teamhasnoi]

Every seat will have a little crank to turn to help drive the flywheel.

Unfortunately, it takes 45 minutes of winding for 4-5 seconds of run time.

What about Urine power?

[tcd004]

the title says it all.

Play the stock market drinking game!

tcd004

Best quote from the article

[displacer]

Before the visit ended the other day, a final question had to be asked: What is the purpose of the floating ping-pong ball?

"Oh that?" Mr. Lobenstein smiled like a child. "That's just to amuse us. Sometimes we get bored."

Re:Best quote from the article

[fatbastard10101]

I liked this one more, concerning putting the excess joules right back into the rail:

"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

[gpinzone]

If you've ridden on the NYC subway system, you'd know that the trains can be VERY close to each other. But that's not the point...

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

[haa...jesus christ]

come on, give the F/V/B/D line some credit. especially the 34th st. station. the rubber soles on my shoes started to melt down there this morning. good thing i'm wearing a nice wool suit and a tie or all the water in my body might escape!

Re:Best quote from the article

[BrookHarty]

Yes, but the trains have AC, so its nice and cool, then the doors open, and its 110 degrees blast of air. Doors Close and its nice and chilled again. Real problem to using trains, the heat.

Re:Best quote from the article

[Nightpaw]

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.

That's because they're on drugs like Ozzy.

Re:Best quote from the article

[Mignon]

Here's my goofy idea for dissapating all that extra power - when the train brakes, charge up some mondo capacitors and have them pop off a big-ass EMP, which will fry all those damn cell-phones that people start yammering on the second they get out of the tunnel.

Re:Best quote from the article

[zenyu]

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.

The resistance is a problem because the voltage is only 600V vs 720,000V on an above ground transmission line. 32,000V is the most I know of on underground line. A bigger problem they didn't talk about is that there isn't one big 600V third rail. Each station, more or less, converts grid electricity into 600V DC for the area surrounding it. So two trains, one accelerating and one decelerating near a single station would be needed to use the electricity. Maybe true during rush hour, but definitely not most of the time.

The AC vs. DC isn't really an issue the new trains that will be running on the L use AC motors. The L line is the only totally isolated track so they will be testing unmanned trains there too. The third rail is 600 V DC. The AC motors will generate AC on a range of frequencies when stopping, but this is all converted to DC before being shunted to the third rail. Normally this would raise the voltage unless another train was accelerating out of the station, since the stations don't try to convert the DC back to AC and send it back to the grid. But with the flywheels the energy will instead be stored for when the train leaves the station.

I believe the old trains do have regenerative breaking, but mostly to save wear and tear on the breaks. This is only an experiment, maybe it's better to get the generated power back to the grid. It depends on how reliable these things are. The iron rich air in the subway tends to be brutal on electronics, hopefully they have isolated space to put them in. The track power distribution has system has changed a couple times since the original 11,000V 25 Hz. First cuz mercury arc rectifiers were invented and later cuz solid state rectifiers became usable for high power applications. They don't care much about higher frequencies, so they allowed the switch to 60Hz grid power. The original rotary converters probably did distribute regenerative breaking power to other trains much better than the current system, but the cost was still much greater since the subway operators had to run their own power generation and distribution systems. I don't know if the trains had regenerative breaking back then anyway, some of them were wood with coal heaters, not exactly high tech.

PS IANSE, just an EE with an interest in trains.

Flywheels future

[wastedbrains]

I have read about fly wheels for a few years now. They are amazingly interesting. I really hope they are used more places. The use of flywheels in this type of situationw ill help push the technology further. Besides uses for trains and mobile towers where else have flywheels already been put to use? I heard NASA would be using some? Does anyone beleive flywheels will eventually be the solution to the terrible battery storage? Could flywheels be used in electric hybrid cars instead of 1000 lbs of batteries? Long live the flywheel and i hope this technology finds its place in every day uses.

Re:Flywheels future

[Duck_Taffy]

Flywheels have been used in prototype electric cars, as a way of supercharging the engine. Unfortunately, this hasn't been mass-produced, but it was very cool, and definitely increased the car's "mileage" - of course, they did have to run the engine for a bit before they could take off.

Flywheels have also been used in high-end turntables, specifically by VPI, as a means of speed regulation. They basically think of it as a kinetic capacitor, which is pretty cool.

Also, gyros have been used in tank turret rotation - in the acceleration and breaking, with really good results, although they were hydraulically actuated. Also, not a mass-produced item, but they do exist...mostly for military training as far as I know.

Re:Flywheels future

[mattster999]

Hybrid Electric cars don't have 1000 lbs of batteries... My Insight only weighs ~1800 lbs, and the batteries aren't more than half of that.

Re:Flywheels future

[0biJon]

Massive flywheel storage isn't really suitible for mobile applications because to store lots of energy in the form of rotational energy requires that the flywheel be larger/heavier (I could go on and explain why but you can find that on your own if you really want).
As a result, you have this really heavy (and not perfectly efficent) flywheel that your car has to lug around with it. As you know, the lighter the car the better.
Therefore, large flywheels in cars don't make sense. They do make sense in stationary applications though, where size and mass aren't an issue.

BTW, cars with either manual OR automatic transmissions DO have flywheels, but they're relatively lightweight and they're main purpose is to transfer energy, not store it (although it can help to maintain speed on uphills, but you loose acceleration due to more mass you have to start rotating).

Here's a couple links showing the flywheels. Go here or here

While we're on the topic of regenerative braking, here's a solution from Ford using HPA (Hydraulic Power Assist) to help trucks accelerate.
Go here Or Here

Re:Flywheels future

[IknowNothinMuch321]

There is someone who has been trying to get a flywheel powered car together. I saw a clip about it last year on the Discovery channel. The guy's name is Charles Bitterly and has been designing it for years. The clip I saw was a bomb, unfortunately, the car failed to go more than a few inches (but it moved!). Who knows, maybe he'll get it, and if it does work, think of the possibilities!

Do they manufacture spell checkers?

[Jailbrekr]

I believe thats what they are doing, except they are using flywheel batteries to store the electricity generated during braking.

Arthur C. Clarke

[crow]

Didn't Arthur C. Clarke describe something like this in "The City and the Stars?" It's been a long time since I read it, but I believe that they had a transportation system that was essentially a wide moving sidewalk; the closer to the middle you moved, the faster it went.

Re:Arthur C. Clarke

[Rhombus]

Yup....they were called 'moving ways'.

Re:Arthur C. Clarke

[gilroy]

Blockquoth the poster:

I believe that they had a transportation system that was essentially a wide moving sidewalk; the closer to the middle you moved, the faster it went.

I haven't read enough Clarke to be sure, but you're definitely describing something like Asimov's "strips" in the novel The Caves of Steel -- set, appropriately enough, in New York City (albiet a NYC that had expanded to consume north Jersey and Connecticut).

Re:Arthur C. Clarke

[Shadow Wrought]

I don't know about Clarke, but I know Asimov used the idea in Robot series. They were called strips, and there were something like 5 of them. Each one moved faster than the other until you reached the center.

Kids would even play games on them, playing follow the leader;-)

Good read.

Re:Arthur C. Clarke

[sphealey]

I haven't read enough Clarke to be sure, but you're definitely describing something like Asimov's "strips" in the novel The Caves of Steel.

Clarke's Against the Fall of Night (later rewritten as The City and the Stars) predates Asimov's Caves of Steel. Clarke's ciy of Dispar had the variable speed walkways.

sPh

Re:Arthur C. Clarke

[ethereal]

And also in a Heinlein short story "The Roads Must Roll", I believe - rather than having freeways stretching across the nation, he had moving belts of different speeds, where you could quickly and safely step up to high-speed belts for mass transit.

Re:Arthur C. Clarke

[Myrcurial]

As seen in ACClarke, Asimov and Heinlein....

• Clarke - The City and the Stars
• Asimov - Caves of Steel
• Heinlein - The Roads Must Roll

Re:Arthur C. Clarke

[matthewn]

Heinlein's "The Roads Must Roll" (1940) predates Clarke's Against the Fall of Night (1953). You can read the Heinlein tale in The Past Through Tomorrow. It tells the story of what happens when the blue-collar workers who run and maintain the moving-sidewalk "roads" go on strike. (Hint: Mayhem.)

Re:Arthur C. Clarke

[homer_ca]

Safe except for the time it was sabotaged in "The Man Who Sold The Moon". They stopped just the center high speed belt and the next slower belt was still whizzing by at 50 mph.

I don't buy it

[L. VeGas]

I still think my hamster could spin a wheel faster than some dumb fly.

Honda Insight

[qurob]

regenerative braking, not sure what technologies are used by it.

There already is a flywheel in your car...

[Anonymous Coward]

If you drive a car with a manual transmission the flywheel is connected directly to crankshaft at the engine. The clutch then rubs up against the flywheel to transfer power through the transmission to the wheels.

Who made the flywheels?

[Timwit]

Anybody know who made the flywheels? There are only a few flywheel companies in business, for example Beacon Power (BCON)--but they are concentrating on other applications.

Re:Subway trains shouldn't stop

[ceejayoz]

they'd still have to slow to a crawl, unless you want to jump off a train going 35 mph...

Heat due to A/C

[yasth]

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.)

Re:Heat due to A/C

[Sweetums]

Not all of it. One of the braking systems on electric vehicles is to alter the phase on the motors, making them generators, and run the current through resistors on the tops of the cars. Railroad engines do this, for example, and many streetcars do.

Re:Heat due to A/C

[kappax]

Do you have any idea how much frken heat is casued when breaking a car? little alown a train? a flywheels not only ruduce the friction but convert it to usabe energy, thus making less heat, heat is energy taking the heat away making enerrgy so less heat. go drive your car for a few hours (in stop and go areas) then go slap hand on the wheel if your car , yeah right were the breaks are, and tell me if the burn you get on your hand is caused from your AC ? ( some cars have more protection agents ppl burning them self, older cards have less)

Re:Heat due to A/C

[afidel]

600M Watts is what the system uses, thats a crapload of power. I am guessing total efficiency of the system for actually moving people is like 20%, that means the heat from 480M watts of wasted electricity is given off into the subway system, quite a bit. I just got back from vacation and my brain is still mostly off or I would compute how many BTU's.

Re:Heat due to A/C

[hugecrow]

There would be no need for AC if the heat wasn't produced in the first place...

Re:Heat due to A/C

[southpolesammy]

That's not really true. The stations are hot during the summer and cold during the winter because even though they are underground, they are essentially prone to the elements. When it rains, it's humid in the stations, when it's hot outside, it's even worse down there. When it snows, it gets arctic-like in the stations, and when the wind from the train blows through during the winter, it's bone-chilling.

The A/C on the cars in the summer and the heat from the 3rd rails almost certainly have little to do with the heat down there, IMHO.

Re:Heat due to A/C

[UranusReallyHertz]

480 MW == 455,357.2 BTUs/sec.

Re:Could we get a "No NYT" option?

[Arcturax]

I wouldn't mind that myself.

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.

Where to stick your flywheel....

[Sweetums]

Several posts refer to the flywheel as being on the train. I don't think it explicitly says in the article, but I think it's clear that they are talking about stationary equipment in the stations, not flywheels on the trains. Lots of advantages to this.

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....

[MayorQ]

Excellent point. I hadn't really thought about thef lywheel placement but having them at the stations allows the trains to be 10 Volkswagen Bugs lighter. Also, most trains do their stopping and starting at or near the stations so this system could actually work.

I do not think that timing will be an issue since each train will charge and un-charge the flywheels as each approaches and leaves a station. This solution also allows for fewer modifications to the trains themselves.

- MayorQ

Re:Where to stick your flywheel....

[gspeare]

I wouldn't say the article does an exceptional job of describing where the flywheels are placed, but a closed read does imply very strongly that they are outside.

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.

Re:Where to stick your flywheel....

[Overand]

I'd tend to disagree. Placing the flywheel in the station would be just the same as the electrical regenerative braking they were describing, if my understanding is right. Unfortunately, since I doubt the engineers are going to post here, it'll just be a matter of opinion. Still, if they're in the trains, then there's less distance for the energy to travel, but if they're in EVERY station, then the distance to travel wouldn't be too bad. Hmm, on second thought, they could be anywhere, as long as they're close to (or in) the trains.

Re:Where to stick your flywheel....

[Sandlund]

Ummm...just where exactly are you going to put this equipment in the already cramped Manhattan stations? Sure, cost of re-building the trains is big. But space is a serious consideration, too, and something that costs dearly in Gotham.

Re:Where to stick your flywheel....

[Surlyboi]

Ummm...just where exactly are you going to put this equipment in the already cramped Manhattan stations? Sure, cost of re-building the trains is big. But space is a serious consideration, too, and something that costs dearly in Gotham.

New York subway stations are constantly being worked
on. Just look at the recent work on the Broadway
line. Sure most of it was/is cosmetic, but consider
72nd street. They're expanding the whole station
almost an entire block. There's plenty of space
to add these devices if they're going to improve
the efficiency of the trains.

Of course, if this plan goes through, expect a
fare increase...

Re:Where to stick your flywheel....

[Karma Farmer]

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.

I got the idea that they don't have to modify the trains at all to support this. It sounded like the trains are already just dumping extra energy back into the third rail when they brake, but that the design of the current power delivery system doesn't really allow them to realize much gain from this.

It sounds like they've simply reached a point where a lot of "small" local power storage can be added to the system and integrated with the current power delivery system, and they're just expirimenting with reasonable ways to do it. It really doesn't seem to be a change in the trains as much as it is a change in the power delivery system (and maybe an improvement in the reliability of flywheels?)

I don't know... that's just the impression I got from the article.

Registration Required ?

[unixmaster]

From the out_of_the_topic dept.

If you dont wanna register at NYTimes visit NYT Random Login Generator
But because NYTimes block based on referrers you got two chances 1 - Disable Javascript or a better one get Multizilla Toolbar for Mozilla
It has a nice option like "Dont send referrer" .
Choose it and boom you are in !

A little too excited?

[dr_dank]

Or, as Robert Schmitt, another transit electrical official, put it, excitedly: "They're sitting here, saying: `Give it to me! Give it to me! Give it to me!'

Ok, this guy needs to get laid. Now.

Smell

[cporter]

"it will help relieve a lot of the heat subways generate (always appreciated during the summer)."

Now, if they could just do something about the smell. The Broadway-Fulton-Nassau station certainly gets rank in the summer.

Re:Subway trains shouldn't stop

[Rhombus]

Develop a separate "life-on-the-edge" line that never stops and has no doors.

Flywheels: Just Say No!!

[dfn5]

Yes, but they have a nasty habit of slowing down the Earth's rotation.

Save the planet. Vote NO on flywheels.

Re:Flywheels: Just Say No!!

[Nightpaw]

No no, keep using them until our day is 25 hours long. Then we can get another hour of sleep each day.

Re:Flywheels: Just Say No!!

[Xenographic]

But the boss will just make us work a day longer :(

Re:Flywheels: Just Say No!!

[Have Blue]

Why not just randomly alternate the spin direction of all manufactured flywheels? It can't be that hard.

Wow, 36,000 is a lot of RPM...

[dpbsmith]

and a million watts is a lot of power.

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...

[loomis]

Small correction. A perfect human ear can hear up to 20,000hz or so.

Loomis

Re:Wow, 36,000 is a lot of RPM...

[GigsVT]

He's saying that a 600 Hz sound at the same "sound force" level as other frequencies will sound louder.

The peak of human sensitivity.

Re:Wow, 36,000 is a lot of RPM...

[ford42]

Actually, the peak of human hearing sensitivity is around 3 KHz -- the frequency at which we scream. 600 Hz is only a bit more than an octave above middle C. (Think about the difference between a flute in the lower part of its range and a piccolo in the upper part of its range.)

Re:Wow, 36,000 is a lot of RPM...

[Tim Doran]

Last I heard, high-performance flywheels were being made of graphite fibre... spin 'em too fast and the fibres separate, dissapating the energy (and turning your very expensive flywheel into a box of cotton candy).

Re:Wow, 36,000 is a lot of RPM...

[Mr]-[at]

I don't know about you, but the new trains, like the ones on the 6 line.. SUCK when it comes to braking.

The horrible, high-pitched squeal they produce is definately at the fringe of what a New Yorker's (!) ears can take.

I say bring back the red birds! (jk, I like the a/c too much..)

Re:Wow, 36,000 is a lot of RPM...

[aeoo]

Actually, modern flywheels are almost never solid. They are usually made from rings, or fiber. There is a Russian scientist named Gulia who invented and patented (to my knowledge) a way to wind fiber so that both ends end up inside the flywheel. This is critical because at high RPM a loose end can undo the entire flywheel. Using kevlar and other fiber like that allows you to have flywheels that can withstand incredible forces. In general, flywheels are far more efficient than any battery in terms of energy storage, and how fast they can store and release energy. Also, modern flywheels can fly on a magnetic suspension and in vacuum as well. Flywheels, in my opinion, are simply the best way to store energy. When fiber flywheel explodes, it does so one thread at a time. They are relatively safe and the only thing they generate when they explode is heat.

Re:Wow, 36,000 is a lot of RPM...

[khendron]

But that cotton candy still contains all the energy that was stored in the flywheel, and that energy has to go somewhere.

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.

Re:Wow, 36,000 is a lot of RPM...

[rabtech]

I work with pro audio, and let me clue you in on the range of human hearing...

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...

Re:Wow, 36,000 is a lot of RPM...

[Sandlund]

Let's also hope there's something to muffle that 600 Hz whine (which is close to the peak of human hearing sensitivity).

The real question is, how close is it to the hearing sensitivity of rats? Now that could be useful even if it doesn't conserve any energy.

Re:Wow, 36,000 is a lot of RPM...

[Tablizer]

Flywheels, in my opinion, are simply the best way to store energy. When fiber flywheel explodes, it does so one thread at a time.

Spiderman might be interested to hear more about this technology.

Re:Wow, 36,000 is a lot of RPM...

[Tablizer]

(* Umm, aren't flywheels supposed to be encased in a vacuum? Hence, no noise? *)

If the entire mechanism was, perhaps (such as magnetic levitation). However, if there are bearings and gears and axiles, then these can transmit noise to the outside.

Re:Wow, 36,000 is a lot of RPM...

[lordgert]

The AC on the 6 is just too nice to leave room for complaining about anything else about thattrain.

Re:Wow, 36,000 is a lot of RPM...

[Anonymous Coward]

The neat thing about composite flywheels is that, if they fail, they tend to explode into alot of small fagments, which are much easier to contain then metal flywheels. When a metal flywheel fails, it typically comes apart into 3 large chunks.

And, IIRC, composite flywheels are almost never built using filament winding. Thsi would put the fibers mostly tangential, and just matrix supporting the highest stress radial directions.

Flywheels failures tend initiate in tension near the hub, not at the rim. That's why optimal flywheel radius profiles are thicker in the middle & taper toward the edges, and why a filament-wound flywheel probably wouldn't work very well.

I did some research on this back in grad school. The best arrangement for a laminated composite flywheel was to have alternating +-theta plys, with theta slowly increasing through the thickness (and symmetric about the center plane). Or use a woven pre-preg, and again rotate it through the thickness.

Re:Wow, 36,000 is a lot of RPM...

[Reverberant]

Let's also hope there's something to muffle that 600 Hz whine (which is close to the peak of human hearing sensitivity)

Just a nit: the "peak of human hearing sensitivity is 4kHz," 600 Hz is 4 octaves away...

Re:Wow, 36,000 is a lot of RPM...

[Perdo]

10 inch diameter 25 pound carbon fiber flywheel at 36,000 rpm.

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 .50 cal sniper rifle = 16,539 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...

[Storm Damage]

What you're not calculating is the dispersion effect. 80 Sniper bullets contain a lot of kinetic energy, sure, but all that energy is divided up around several thousand tiny little pieces of shrapnel, the size of a cornflake or smaller...

Random account generator?

[Lethyos]

Did the NYT defeat the random account generator? It no longer seems to work for me which is extremely disappointing. My personal information is far more valuable than the right to read a few newspaper articles. (Really, how does one weigh intimate knowledge to a few quarters?)

Re:Random account generator?

[Mr. Slippery]

On most "login required" sites, someone has set up a "cypherpunks" login id, same password. On the NYT site, that used to work, they disabled it, but "cypherpunks01" (same for password) still works.

Parry People Mover

[gwernol]

Related to this is the Parry People Mover which has been developed by a small company in Wales. This is designed as a light urban tansit system using flywheel to run the "people movers". The flywheels in these lightweight cars are recharged by either onboard LPG internal combustion engines or by electric motors fed from recharging points at stations.

They have been trialed on the Welsh Highland Railway and on the island of Mauritius omngst several other schemes - a quick Google search 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

[brandonsr]

Right here A very good article (with illustrations) that tells how flywheels work and store energy. Pretty neat stuff.

Oh no need to worry...

[The_Guv'na]

If the flywheel is mounted horizontally, i.e. like a record player, then the turning would have no noticeable effect.

Might have problems if you wanna loop-the-loop though.

OT bit: You know, its really fscking annoying seeing one of those "cool ideas you think of when bored" appear for real.

I'm still working on the linear gearbox.

Ali

No heat? What about the homeless?

[TheLocustNMI]

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

Is there any danger?

[Dirtside]

I personally love the idea of using flywheels to store energy in this manner -- it seems very elegant to simply transfer the energy into rotational motion, rather than simply losing it all as heat.

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?

[Dirtside]

Actually, I already had one idea for avoiding this (potential) problem... if the flywheels are rotating around an axis perpendicular to the ground, then you can place the flywheel in a pit dug into the ground. That way, if the flywheel "crashes" or spins off, it will (in theory) embed itself a few meters into solid rock. Seems better than having it above-ground, anyway.

Re:Is there any danger?

[MindStalker]

Shrugs, these are underground. And there arn't that many earthquakes in NY, (though some are predicted) I assume they have figured most of this out already.

Re:Is there any danger?

[GigsVT]

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.

It does the latter. In an article I read years ago about the first magnetically suspended flywheels, they discussed the explosions in detail. It just sort of vaporizes and all the energy dissapates, spectacularly. It would make for quite an explosion.

They will probably store these things underground with much concrete around them. I'd say there isn't as much risk as you would think, with a well designed containment chamber.

Re:Is there any danger?

[dacarr]

I would so like to see a camera shot of that. =^_^=

Re:Is there any danger?

[afidel]

They are carbon fibre so they disintigrate, though the immediate surroundings may take some punishment. That is why they are usually entoumbed in several feet of concrete.

This is old news!

[teamhasnoi]

I used flywheel technology many years ago with my Hot Wheels Destuction Alley Playset(TM). The flywheels would drive the cars at unpossible! speeds.

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!"

Very cool idea.

[ehud42]

Ok, I read the article - the flywheels are in stationary (re)generating stations scattered throughout the grid - very cool concept. The excess current (introduced by cars dumping electricity produced by breaking into the grid)spins up the wheels, and the any increase in the load (as cars accelerate away from a stop) "borrows" from the wheels. Very nice.

The Wired article made me wonder about the probabilty of using a flywheel for a UPS? Any thoughts? Seems simple enough - get a heavy wheel on a decent bearing train and connect to a small motor that can eventually spin it up to high RPM and then use an electric clutch to keep it DISengaged from a generator. Add a really small UPS to cover the switch over time and viola! As soon as the power fails, the clutch engages the flywheel to generate power for 15+ minutes (enough time to perform a clean shut down). I like it....

Re:Very cool idea.

[Real World Stuff]

Flywheel UPS information is here.

Re:Very cool idea.

[dacarr]

The only problem I would forsee is the Maytag problem - that is, if the flywheel gets off balance, your UPS will start walking across the room it's contained in.

Of course, as discussed in another post, that probably won't matter, as your flywheel will likely explode spectacularly. And this brings up another problem.

And that reminds me, how much does it cost to replace one of those flywheels? Is it really cheaper than a UPS?

Re:Very cool idea.

[ALternate]

wonder about the probabilty of using a flywheel for a UPS?

Congratulations, you've invented the motor-generator. Well, sort of.

I haven't seen one lately, but a mainframe computer center I once worked at had such -- electric motor -> heavy flywheel -> generator. In large part it was just to smooth out ripples in the AC line (might also have converted the frequency). Forget running the computers for fifteen minutes -- a flywheel with that much energy is downright dangerous (consider, if it stops suddenly, it has to dump all that energy in a matter of milliseconds).

For UPS needs, batteries are better since the store/withdraw rates are reasonable. A flywheel is good where you want to store or dump a lot of energy fast. (Basically, the flywheel is the motor/generator rotor.)

Re:Very cool idea.

[gpinzone]

That would assume that a flywheel would be a better battery than fuel cells. At the power output level that you need for a UPS, the answer is probably no.

Re:Could we get a "No NYT" option?

[Overand]

I'm pretty sure that the effort it would take them to code that in wouldn't be worth it, simple as it might be.

Spend the 15 seconds typing in gibberish, and let it save the bloody cookie, rather than taking just as much time to post a complaint. Sure, we all hate NYT's registration, but HOW lazy ARE you?

Mirror of NYTimes Page

[screenbert]

http://www.screenbert.com/ntimes/rail.htm

Re:Subway trains shouldn't stop

[lungofish]

If you've got moving sidewalks, what do you need subways for?

Duh.

It works for George Jetson just fine.

Flywheel info

[Real World Stuff]

A good break down of Power vs. Energy located here . Not here.

nycsubway

[nycsubway]

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

Re:nycsubway

[dbrutus]

Also, it never closes, unlike many other subway systems.

Re:nycsubway

[Arcturax]

So is the London Underground and many other subways in big cities around the world.

I wish there was better public transportation out here in Cincinnati, light rail at the very least... You have to drive everywhere here unless you live in the inner city slums.

Re:Subway trains shouldn't stop

[Oculus Habent]

Yes, and what do you do when you get to the end of the moving sidewalk; get thrown off the platform at 20 MPH?

Jumbo Capacitor

[dnoyeb]

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.

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 :D

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

[dacarr]

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.

I know LACMTA has effectively solved the problem by building vast ventilation systems in teh red line stations. I think the principle idea here would be to direct the heat elsewhere through a grating outside. It has to go somewhere, why not put it someplace where it's going to have an easier time dissipating than the subway station?

This would work if they encased the flywheels in outside-vented rooms, and would help cool things off by installing a blower in the room. Side effect: outside air is pulled in. Perhaps others can throw in other factors I'm missing and solutions to the inherent problems?

Re:Jumbo Capacitor

[dnoyeb]

True but the main objective is to preserve power. They would have to evaluate if more power is lost in the transmission line, or if more power is lost through the jarring of the flywheels.

Re:Could we get a "No NYT" option?

[ardmhacha]

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,

Why just pick on NYT, there are other websites that require registering before viewing their content which Slashdot has linked to.

You are a registered Slashdot user so you obviously don't mind registering for some sites.

Clever in the extreme!

[dacarr]

Maybe the LA County MTA can take a few hints from these guys on the Metro Rail. Or for that matter, any mass transit system using rails.

Not lazy at all...

[wowbagger]

I'm not lazy at all. I simply have no desire to support the idiotic practice of web publishers trying to mine my information in return for content. If the content is truly free, then it is free. If the cost of the content is "We sell your contact info, and you get the unholy excrement spammed out of your email account", then the price is too high - I refuse to pay. And since I also prefer not to lie, I choose not to enter garbage, but rather simply not go to the site.

And unlike the many folks who will bitch every time a NYT story is submitted, I simply asked for the ability to make my own choice about whether I would see such stories. I don't ask that others be prevented from seeing them - I don't berate the story poster for linking to NYT. I simply ask that the same sort of choice that I can make for Katz, MS or YRO stories be extended to NYT registration required stories.

And I think the moderation history on my previous comment is itself hilarious. While I can whole-heartedly support the "Off-topic" mods, the Redundant moderation is quite amusing - were there any other posts expressing my sentiment? And the less said about those metamoderations posing as moderations (overrated and underrated) the better.

Re:Not lazy at all...

[great om]

pollute their database then. IF the data they have is useless, then no one will want it, and if no one wants their data (enough to pay for it), it will go away

Of course, so might the new york times on line for free, but c'est la vie.

Re:Not lazy at all...

[martyn s]

What part of "typing in gibberish" did you not understand? If you really want to screw 'em then sign up over and over by typing in gibberish and screw up their expectation to mine worthwhile data from it.

Re:Not lazy at all...

[wowbagger]

What part of "prefer not to lie" did you not understand?

Re:Not lazy at all...

[martyn s]

Oh, I understand it now. I'm not a very efficient skimmer :)

Re:Not lazy at all...

[aengblom]

First I must say I respect anyone not willing to enter garbage but I think you're not really considering the situation.

NY Times says it will not sell your e-mail. The Times takes it's reputation pretty darn seriously, so if you catch them doing it, they will be quite embarresed. Also many of their registered users are SUBSCRIBERS. You don't want to piss them off.

The site does not even ASK for your real address (just zip) or any specific information that can identify you.

Also, it promises to tell you if there is a true change in the policy via e-mail. (As, no doubt, slashdot will too)

NY TIMES PRIVACY POLICY BELOW

Privacy Policy

his Overall Privacy Policy verifies that The New York Times on the Web is a member of the TRUSTe program and is in compliance with TRUSTe privacy principles. We also participate in the Council of Better Business Bureaus' BBBOnLine Privacy Program, and comply with all BBBOnLine Privacy standards.

This policy discloses the privacy practices for The New York Times on the Web and The New York Times Learning Network. (The New York Times Home Delivery website maintains a separate privacy statement.) For further information, please also visit our Member Center, where under the Site Help tab, you can view our Subscriber Agreement and read Frequently Asked Questions about Cookies. In the Member Center you can also review Your Profile as well as manage your E-mail Preferences.

TRUSTe

When you visit a Web site displaying the TRUSTe trustmark, you can expect to be notified of what personally identifiable information of yours is collected; what organization is collecting the information; how the information is used; with whom the information may be shared; what choices are available to you regarding collection, use and distribution of the information; what kind of security procedures are in place to protect the loss, misuse or alteration of information under the company's control; and how you can correct any inaccuracies in the information. Questions regarding this statement should be directed to The New York Times on the Web Customer Service; if the Web site has not responded to your inquiry or your inquiry has not been satisfactorily addressed, please contact TRUSTe.

BBBOnLine

A wholly owned subsidiary of the Council of Better Business Bureaus, BBBOnLine's mission is to promote trust and confidence on the Internet through the BBBOnLine Reliability and the BBBOnLine Privacy programs. Launched in March 1999, BBBOnLine Privacy awards seals to online businesses that have been verified to be following good information practices. Further information about this program is available at www.bbbonline.org.

The New York Times on the Web has adopted a set of information management guidelines which serve as the basis for our customer and advertiser relationships. These guidelines have been developed with the recognition that Internet technologies are rapidly evolving, and that underlying business models are still not established. Accordingly, guidelines are subject to change. Any such changes will be posted on this page. If the changes represent a material departure from our current practices with respect to the use of personal information, the changes will be posted on this page thirty days prior to taking effect and registered users will be notified via email.

The New York Times on the Web is not responsible for the content or the privacy policies of Web sites to which it may link.

What information does The New York Times on the Web gather/track about you?

Registration: During a free registration process prior to using the site, The New York Times on the Web requires that you supply a unique member ID, e-mail address, and demographic information (country, zip code, age, sex; household income, industry, job title, job function, and subscription status to The New York Times newspaper). You must agree to the terms of our Subscriber Agreement.

Premium Products and Services: While the majority of The New York Times on the Web is offered free of charge, we do charge fees for select premium products and services. These products include our Premium Archive, Premium Crosswords, Editors' Picks, Topics of The Times, among others. To enable the purchase of these products, The New York Times on the Web collects and stores billing and credit card information. This information will only be shared with third parties who perform tasks required to complete the purchase transaction. Examples of this include fulfilling orders and processing credit card payments. You may review and update your Premium Account information, view your most recently purchased products and transaction history in the secured Premium Account area of the Member Center.

Contests, Surveys, Special Offers: On occasion, The New York Times on the Web also collects additional personal information from subscribers in connection with optional contests, surveys, or special offers.

Cookies: The New York Times on the Web employs cookies to recognize you and your access privileges on The New York Times on the Web, as well as to track site usage. Subscribers who do not accept cookies from the domain "nytimes.com" cannot access most areas of The Times on the Web. For detailed information about our use of cookies see Frequently Asked Questions About Cookies in the Site Help area of our Member Center.

We use a proprietary advertising server to display ads on our site. In addition, advertisers may elect to use third-party advertising companies to serve ads onto our website. Please click here to see a list of these advertising agencies and their privacy policies. In the course of serving these advertisements, the third-party advertisers may place or recognize a unique "cookie" on your browser. We do not have access to these cookies or any information that they may contain. If you would like more information about this practice and about your option not to accept cookies placed by these companies, please click here. Acceptance of cookies from domains other than nytimes.com is optional.

IP Addresses: The New York Times on the Web logs IP addresses, or the location of your computer on the Internet, for systems administration and troubleshooting purposes. We do not use IP address logs to track your session or your behavior on our site.

What does The New York Times on the Web do with the information it gathers/tracks?

Statistical Analysis and Banner Advertising: The New York Times on the Web may perform statistical analyses of user behavior in order to measure interest in the various areas of our site (for product development purposes) and to inform advertisers as to how many consumers have seen or "clicked" their advertising banners. We also use demographic and preference information to allow advertising banners on our Web site to be targeted, in aggregate, to the users for whom they are most pertinent. This means that users see advertising that is most likely to interest them, and advertisers send their messages to people who are most likely to be receptive, improving both the viewer's experience and the effectiveness of the ads. In this statistical analyses and banner advertisement targeting, we will disclose information to third parties only in aggregate form. Personal information about you as an individual subscriber will not be provided to any third party without your consent, except under the circumstances described in Compliance with Legal Process below.

E-Mail: If you so elect at registration or in the E-mail Preferences section of our Member Center, The New York Times on the Web will periodically send you promotional email about services offered by The New York Times on the Web and its advertisers. The New York Times on the Web may contact you regarding account status, changes to the Subscriber Agreement, and to confirm registration.

The E-Mail This Article feature is an easy way for New York Times on the Web users to send articles through email. The e-mail addresses that you supply to use this service will not be used for any other purpose without your consent. The New York Times on the Web does not send unsolicited e-mail.

We use e-mail links located in the Site Help area our Member Center to allow you to contact us directly with any questions or comments you may have. We will use your email address to respond directly to these questions or comments.

Data Security: To prevent unauthorized access, maintain data accuracy, and ensure the appropriate use of information, we have put in place appropriate physical, electronic, and managerial procedures to protect the information we collect online.

With whom does The New York Times on the Web share the information it gathers/tracks?

The New York Times on the Web shares the information it gathers, in aggregate form only, with advertisers and other partners. We will not release personal information about you as an individual to third parties, except under the circumstances described in Compliance with Legal Process below. You can review and modify all of your personal information provided during the free registration process by visiting the secured Your Profile section of our Member Center. If you do not remember your Member ID and password, please go to www.nytimes.com/forgot for assistance.

Programs From Our Partners: During the registration process, new users who select to register for certain featured offers from our partners will begin receiving e-mail from these companies. You will only receive e-mail messages from these companies if you elect this opt-in service. The New York Times on the Web may use this information as set forth in this privacy policy. Should you decide to discontinue your e-mail subscription or would like more information on these companies, please see our list of partners that have participated in this program.

YesMail: Users who selected to register for YesMail during the NYTimes.com registration process became YesMail members. If you selected this option, YesMail uses the information collected on the NYTimes.com registration form to provide targeted e-mails to you on behalf of its advertisers. The New York Times on the Web may use this information as set forth in this privacy policy. You will only receive e-mail messages from YesMail if you elected this opt-in service. Please contact membercare@yesmail directly if you no longer wish to receive e-mail messages from them.

Forums: The New York Times on the Web offers Forums, or message boards. Any information you disclose when posting a message in these Forums becomes public. Moreover, Members who post a message in our Forums make their e-mail address available to others through a feature of our Forums software, which could result in unsolicited e-mail from other subscribers or parties. For more information about Forums see the Posting Policy, or write to the Forums moderators at threadmaster@nytimes.com.

How do I change or update my personal information?

The Member Center: The Member Center is a centralized area where you can manage your relationship with The New York Times on the Web. There are a number of things you can do in the Member Center to ensure your personal information is accurate and up to date. Under the Your Profile tab, you can gain secure access to update the information you provided during the free registration process. The E-mail Preferences tab is the place to go to sign up for our E-mail newsletters and manage your delivery options. If ever you purchase a premium product on nytimes.com, you can visit the secure Premium Account tab in the Member Center to update your billing and credit card information and review your transaction history. In order to gain access to the areas of the Member Center containing personal information, you will be asked to re-enter your password. If you do not remember your password, please go to www.nytimes.com/forgot for assistance. If you need further assistance, please contact Customer Service.

Compliance with Legal Process

We may disclose personal information if we are required to do so by law or we in good faith believe that such action is necessary to (1) comply with the law or with legal process; (2) protect and defend our rights and property; (3) protect against misuse or unauthorized use of The New York Times on the Web; or (4) protect the personal safety or property of our users or the public (among other things, this means that if you provide false information or attempt to pose as someone else, information about you may be disclosed as part of any investigation into your actions).

Re:Flywheels -- the REAL ULTIMATE POWER.

[3-State Bit]

It's been done.

Danger involved!

[teamhasnoi]

Here is an article describing some early testing of flywheels and how dangerous they can be in the wrong hands. Please take care when experimenting with flywheels.

They'll put your eye out.

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....

Re:Braking power?

[Sweetums]

The flywheels are on the same shaft with an electric motor, no gearing involved.

Per my other post, the youo don't stick the flywheels on the trains... they go in the stations.

Re:Braking power?

[boarder]

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.

Re:Braking power?

[Arcturax]

Yes, you don't get back out exactly what was put in, but it does make the system more efficient and saving $20 million a year in electric costs is nothing to sneeze at. Nothing wrong with making the system a bit more efficient, helps both the environment and the city at the same time.

Re:Braking power?

[Veles]

It wouln't be lost as heat, since it's work, and work can be perfectly (ok, maybe 94%) transformed from one form to another. (The energy would be used to accelerate, not to heat)

Though the energy used in the morning when they power the train the first time would be lost at the end of the day. (If they don't keep the spinning at night)

Re:Braking power?

[ldopa1]

My point precisely. Like I said, I'm in favor of it.

Re:Braking power?

[Phil Karn]

Look at it this way: if the claim of $20M annual savings in electricity is accurate, that's $20M worth of electricity that won't be dissipated as heat in the subway tunnels.

Re:Braking power?

[MicroBerto]

You're probably right about the weight, but think about situations that are currently using batteries. These guys are saying that you'll get more energy output than batteries, and they are lighter and longer-lasting!

But since there's no batteries on subways (right?), you're probably right because we're just adding a bunch of metal components.

I think we're missing the big picture...

[3am]

The article says that the chief electricians were able to get a ping-pong ball to levitate!

Has anyone told Boeing yet?

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.

Re:Could we get a "No NYT" option?

[wowbagger]

True, but:

1) Slashdot won't sell my e-mail address. NYT will.
2) Being a registered /. user provides me with significant benefits (increased posting level, accumulation of karma, a journal area, friend/foe tracking) above and beyond simple access. Obviously, you can read everything on /. as an AC, unlike NYT.

I agree that there are other sites that prevent any access to their content without registration - and ideally they would ALL be grouped under the same preference item.

Another little contributor...

[mlinksva]

...to the conservation bomb.

It's been done, for elevators

[Animats]

Cyclic elevators that don't stop have been built. In Europe, they're called "Paternosters". There's also the vertical conveyer belt with steps, the Manlift, a rather scary device sometimes found in parking garages, grain elevators, and factories.

Both require some physical agility, and are rarely seen today.

Re:Could we get a "No NYT" option?

[gorilla]

I think he's saying NYT, because NYT is the registration required website which has the highest likelyhood of being on /.?

Exploded centrifuge images

[uberstool]

http://web.mit.edu/charliew/www/centrifuge.html

Re:Could we get a "No NYT" option?

[dschuetz]

How about we all simply agree that we all know that NYT requires registration, and stop putting "free registration, blah blah blah" in all the damned stories!

Sorry. Too much caffeine today.

Little Effect on Subway Heat

[MoNickels]

Most of the warmth in the subways is caused by heat that has been absorbed by the roadbeds above radiating downward into the stations, to a lesser degree by the exhaust of the air conditioning on subway cars, and to a still smaller degree by steam tunnels that border some of the tunnels and run in parallel conduits. Not by braking trains.

Re:Little Effect on Subway Heat

[mihalis]

Most of the warmth in the subways is caused by heat that has been absorbed by the roadbeds above radiating downward into the stations, to a lesser degree by the exhaust of the air conditioning on subway cars, and to a still smaller degree by steam tunnels that border some of the tunnels and run in parallel conduits. Not by braking trains.

Well, that directly contradicts what I've read about it, so perhaps you'd like to cite your sources. Even just thinking about it a moment shows that the heat of the brakes must be significant. A huge amount of energy is used to accelerate these trains, and what brakes do is convert the momentum into heat. That heat is dissipated from the brakes into the air in the tunnels/stations.

You are retarded. Really.

[Lethyos]

It's not about lying on the form, fuck head. True, I don't want them to have correct information. The crux of the issue is that I do not feel like taking the time to fill-out 20+ fields of nonsense, then go back and correct it repeatedly when it says "your ZIP/email/state/whatever is invalid".

As for personal information, spam is not the issue. NYT doesn't need to know my gender, age, region, etc. It's an issue of privacy.

Re:No heat? What about the homeless?

[dbrutus]

Well, maybe the next time the cops offer them a spot at the shelter, they won't turn it down. Police and social services go out every night and round up the homeless so they don't freeze to death. Some of the homeless prefer a subway grate to the shelters and if they're not obviously nuts, the police have to let them do it. 1/3 of the homeless population is mentally ill.

Re:No heat? What about the homeless?

[Lord Omlette]

It's illegal to be homeless in New York City.

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.

Are we to take this seriously?

[treat]

Considering this confused statement:

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.

Re:Are we to take this seriously?

[croftj]

That's it, pick on the non-technical. I guess you really wanted him to tell you the number of joules they were storing. That way, 15,000,000 readers would think that the article was about a famous author!

Re:Are we to take this seriously?

[treat]

Power, measured in wattage, is the sum total energy that is available from a system.

Power, measured in wattage, is the rate at which energy is being used.

However, I believe that a different problem does exist in their statement, a P=IE is only part of what is necessary. I believe that stored power is supposed to be measured in watt hours.

A different problem with their statement? That is the problem which I referred to.

Re:Are we to take this seriously?

[delcielo]

They're dumbing it down for the simple folk. Kind of like I do for my three-year old daughter.

"We're going to Grandma's later."
"How much later?"
"8 Sponge Bobs"

The London Eye

[magicianuk]

The large ferris wheel in London doesn't stop, but it is only going at slow walking pace and there are people to assist wheelchair bound should they require it, but many "handicapped" people would push you under the train rather than accept that they "need your help".

Many airports have travelling walkways and I've seen all sorts of "uncoordinated" people on them (I've even bumped into a couple of them, which makes me wonder who is the more uncoordinated!)

Might as well say that blind people can't travel on the existing system ... of course they can, you just have to make sure it is designed so that everyone (or as near as damn it) can travel safely and don't leave big gaps between cars for blind people to walk into etc. Flexible material to cover those gaps is used in many countries, but not in the UK ...

I agree

[theLOUDroom]

I agree with the parent.
I'm just not going to register.
The IP of the NYT random login generator has been blocked, and I don't feel like using some huge group account that some jerk will change the password on.
I don't like giving websites personally identifying data unless it's for a decent reason and I trust the website. And I don't want to bother remembering whatever bogus login I generate.
It would be really nice to be able to shut off all NYT stories. How about an option to not see any stories where you can't just click the link and see the story? I already have fifty or so username:password combinations to remeber and I'd rather not have to deal with any more.

Subway Discomforts

[mchummer]

The use of flywheels and/or regenerative braking will do much to improve the energy efficiency of subway trains, but will do little to improve subway comfort.

The heat generated during a trains accelleration was nearly eliminated when the resistive motor controls formerly used were replaced with energy efficient solid-state chopper controls. The heat generated from the use of the motors in the braking cycle is considerably less - most of the braking being mechanical.

The problem is subway discomfort is another modern technology - air conditioning.

Air heated by the hot, sweaty, sardine packed passengers, from the doors opening and closing and thermal (exterior heat and sun) load on the train is passed through the cold coils of a heat pump and then over electric heating coils to raise its temperature (dehumidifying it) and then passed back into the train.

All this heat and humidity has to go somewhere.

Humidity removed from the air is dumped (drip drip drip ...) into the outside envronment as is heat from the hot coils of the heat pump. This is what makes the enclosed environment of the subway intolerable.

When the Subways were being built in the early 1900's extensive studies, testing and engineering changes were done to ensure passenger comfort. I can remember the pleasure of riding the subways at the open front gratings on the trains - soaking up the COOL breaze as the train rushed through the subway.

When air conditioning was introduced the trains became cooler but the stations became intolerable. The answer then was to increase the ventilation of the subway to allow all this additional heat to escape. However, opening up the subways to vent the heat resulted in the subways being COLD in the winter and even Hotter in the summer.

Technology, go figure. Like the Victorians - we're Throughly Modern (tm) ! But have we advanced ?

Anyone out there have an answer to this?

Re:Subway Discomforts

[Edmund Blackadder]

so they have to figure out a way to close off the stations ventilation during the winter. there is not going back :)

a few years ago

[KingPrad]

I remember Discover magazine doing an article about a scientist named Bitterly workeing for US Flywheel Systems developing flywheel technology for use in cars. At that time he had developed a way to make superdense flywheels from (I think) carbon thread spun into solid rings. It was extremely rigid and dense and maintained shape for a long time and at high (1700) rpm.

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:a few years ago

[Edmund Blackadder]

if a car with flywheel crashes it gets very bad.

these things can jump all over the place still spinning and cutting any one they hit in two.

thats the main reason flywheels are not used on cars.

Re:Could we get a "No NYT" option?

[donutello]

any /. story where the bulk of the information is on a NYT-hosted page is useless to me

Why can't you just post without reading the articles - like everyone else?

Re:Subway trains shouldn't stop

[spike hay]

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.

why 25,000 mph?

[Mt._Honkey]

I saw this figure mentioned in the boeing article as well. I don't understand where it comes from.

If an object sitting on the ground were to no longer feel the earth's gravitational pull, I don't think that it will fly up into the air. At first, it would just hover up against the ground. It would continue moving at ~1050mph (the tangential velocity of an object on the earth's surface) in the direction it was moving when the gravity stoped. It's like if you were to stand on the edge of a fast moving merry-go-round, and slip off. In the first few instants, you would have almost no speed relative to the ride, but you would continue going the same speed that you were before, in the same direction. If you were to continue flying away for some time, the greatest speed relative to the center of the ride would be the origional tangential speed. In the case of the earth, that's ~1050 mph.

Re:why 25,000 mph?

[Mt._Honkey]

*scratches head*

yeah, the earth not being flat part is where the tangential velocity came in...

Re:why 25,000 mph?

[MyHair]

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.

NYC Subway is a DC system.

[dudeman2]

See here: Rotary Converters Very cool info about 1900-era technology used to convert AC to DC power for use on the subway lines.

Flywheels at the station not on the train

[ScrewTivo]

is a way kewl idea. Now about that Russian's anti-gravity bit that Boeing just picked up on, maybe we could just float around on the platform while we wait for the next train :)

Oh yeah... and it saves BIG $$$ on power

[Sweetums]

Something the article does not state... A system like this can make a major difference in the power cost. Big commercial consumers pay based on their *peak* power draw (at least in CA). If you can reduce the peak draw, you change your costs for your entire usage. Cost/megawatt is significantly higer on a 600Amp peak circuit than it is on a 300Amp peak draw circuit. Major major difference, especially when multiplying that across the entire system.

Cool!

[csnydermvpsoft]

When can I get this in my notebook? Combined with the Transmeta processor, I could probably get 30 hours out it instead of the 15 I get now!

Of course, it'd probably be a bit heavier, and if the flywheel broke, I wouldn't want my notebook to explode.

Re:You are retarded. Really.

[Mignon]

"your ZIP/email/state/whatever is invalid".

I was thinking about this the other day, when signing up for some similar site: I thought the WTC used to have their own ZIP code(s). I was too lazy to look them up to use them, but I wonder if they would have worked.

Weapon?

[Tablizer]

Out of morbid couriosity, has anybody researched using fast flywheels as weapons?

Re:Arthur C. Clarke? Heinlein, too.

[budalite]

Did Heinlein's "The Roads Must Roll" roads use conveyer belts? That was a Nation-wide system of conveyer belts that moved people from city to city, I think. The story was about the engineers that maintained them. Heinlein was the only guy who ever made the work of (us) engineers sound exciting. ("I'll keep those transistors humming, if it's the last thing I do, golldarnit!") Maybe cuz he was one.

Have fun, MadDad32

Slashdot NYT Login

[AnalogDiehard]

Username=allyourbaseare
password=belongtous

Gyroscope effect?

[Vainglorious Coward]

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...?

Re:Gyroscope effect?

[Edmund Blackadder]

i cant see why that would be a problem, unless they positioned the fly wheel verticaly which would not be very smart.

Re:Gyroscope effect?

[Vainglorious Coward]

...positioned the fly wheel verticaly...

Um, but then up/down motions of the vehicle would create lateral forces.

Re:Subway trains shouldn't stop

[isorox]

Yes, and what do you do when you get to the end of the moving sidewalk; get thrown off the platform at 20 MPH?

Move onto a 15mph one

The Cincinnati Subway

[Doktor Memory]

Amusingly enough, there is a subway in Cincinnati. Well, about three or four stations worth, anyway. They started construction on it in the 70s, ran out of money, and never completed it.

More details here.

Re: Urine power offtopic?

[Mr. Tuvix]

Whoever modded this "offtopic" has clearly never been on a New York City subway train.

Re:Could we get a "No NYT" option?

[Snibor Eoj]

And, of course, there's no chance that he posts them because the NYT writes high-quality articles on interesting topics, right?

Not Arthur C. Clarke

[Jack Brennan]

"The Roads Must Roll"
by Robert Heinlein c1940
First scifi I know of mentioning moving sidewalks.
Great read if you can find it - it's in Science Fiction Hall of Fame volume I, but that's out of print.

Re:Not Arthur C. Clarke

[hplasm]

"Future History, Vol 1"

How many DEBs is 36,000 RPM

[joshsnow]

Can someone do the Math please?

Re:How many DEBs is 36,000 RPM

[thebigmacd]

If "DEBs" is in reference to Decibels, there is no answer. A Decibel is a measure of volume of a sound, whereas the RPM of a flywheel changes the frequency of the sound produced, which is measured in Hz. The mass of the flywheel is what affects the volume of the sound, by affecting the amplitude of the wave. A 36,000 RPM flywheel that weighs as much as a car is likely to generate a high volume sound, unless of course it is housed in a vacuum, which is VERY likely. A 36,000 RPM flywheel with the mass of a junebug won't generate a very loud sound. Of course, it is all relative because the surface area of the container can affect volume, as well as the surface area/texture of the flywheel. My $0.02 CDN.

Re:How many DEBs is 36,000 RPM

[yesthatguy]

Hmm. I think you missed it.
DEB = Debian package
RPM = RedHat package

Geek site. Geeks trying to show their mental quickness. This is the result you get, take it or leave it. Ha.

Trust, and the lack of it

[wowbagger]

First of all, I trust any website that displays the TRUSTe logo approximately as far as I can urinate into a strong Kansas wind - all TRUSTe says is "we have a policy", that policy might be "We sell your address to everybody with five cents" and you can still get a TRUSTe logo. Additionally, TRUSTe is unwilling to revoke a logo once given, so it is essentially meaningless.

Second, the stated goal of the NYT registration is to garner better demographics for their advertising - in other words, by looking at the data they have on me, they try to ram the ads down my throat that have the highest chance of making buy something - something I in all probability wasn't planning on buying. I dislike such things - why should I support them?

Again, I don't wish to tell others how to go about their lives - but I choose to neither help nor hinder this sort of "targeted advertising", and I'd like to be able to configure /. to reflect my desires.

Re:Could we get a "No NYT" option?

[Pyrrus]

*sigh* how about a "no bitching" option...

They use DC...

[Newer Guy]

They use DC for the same reasons that elevators use DC..smooth braking and acceleration.... Also, DC is necessary because as part of the power distribution there are 'breaks' in the third rail...and the rail actually uses the car to complete the break. An AC system would have to maintain phase scycronization for this to work.

Re:They use DC...

[Zazm]

Actually you can get smooth power delivery from AC power, all the trains where I live (Queensland Australia) run on overhead AC power.

Basically the most efficient kind of electical motor is the birdcage type inductance motor, but they operate only at one speed which is a factor of the electical current frequency.

So the trains here rectify the AC overhead line to DC and then use a sophisticated variable inveror to generate a full range of AC frequencies, just dial in the frequency that corresponds to the speed you want the motors to run at.

In operation this system produces a really unique sound as the inverted AC ramps up and down.

Re:WOW thats fast!!

[MicroBerto]

Carbon fibers, but that will change with nanotubes within 10 years.

Many small flywheels

[mbstone]

I work for the Automation and Controls department of a very large company and we are exploring this technology. This is a very real problem, but the solution is pretty easy. Instead of using just one large flywheel, use many smaller ones.

There's an idea. Just make the smaller flywheels, the size of, um, TURNSTILES.....

Re:No heat? What about the homeless?

[zenyu]

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

They actually hang out near the steam vents so it's not really a problem. I live near a co-generation plant so there are a few extra citizens on cold winter days around here.

I thought it said "Party People Mover"

[brianvan]

... and I'm thinking about all these drunk people never going home, and some Guinness world records being set for party length and alcohol consumption.

They need to have this.

A little OT: Noise reduction

[fractaltiger]

Let's also hope there's something to muffle that 600 Hz whine (which is close to the peak of human hearing sensitivity).

I'm not sure which of the noises you are talking about but I agree with you!

It's kinda like a forced upgrade
The new trains like those that operate on the 6 line actually drown out a lot of the track noise and have less jumpy/noisy ractions to track imperfections, right? However, whatever it is, their new turbine-like humming is very noisy, though it sounds more like something between 440+ and 512- Hz (near the key of B). The train ride is more comfortable, but I have found it hard to talk to girls because the noise drowns out their voices. The loud whine starts up as soon as the train accelerates and I have not heard it inside or outside the older trains (A, B and D, older 4 models, etc)

I hope someone notices the whine before the state spends millions replacing the trains that didn't have that 'feature.'

Re:Subway trains shouldn't stop

[BasilBibi]

Dear Duh,

Because moving "sidewalks" can't cross junctions without going over/under them.

And "subways" keep you dry in the rain.

Heat due to A/C = not true

[eldimo]

No most of the heat really comes from the brakes. I live in Montreal and here we do not have A/C (it would really be a total waste since there's about 20 very hot summer days per year here). The subway is also much deeper in the ground than in NY (it usually takes you two big escalators to get to the subway cars, sometimes three). And on the very hot summer day, it is also very hot in the subway (almost unbearable in some station). In fact, some people fainted the very first year . They had to add fans to push air in so it get cooler.

Re:Could we get a "No NYT" option?

[NickV]

1) Slashdot won't sell my e-mail address. NYT will.

They say they won't, and they're the most reputable and respected news source in the WORLD. They depend on their reputation. I'd expect /. (with VA as their parent company) to sell our email addresses WAAAAAAAAAAAAAAAAAY before the largest, richest, and arguably most powerful news source in the world.

2) Being a registered /. user provides me with significant benefits (increased posting level, accumulation of karma, a journal area, friend/foe tracking) above and beyond simple access. Obviously, you can read everything on /. as an AC, unlike NYT.

Since you aren't a NYT registered user, you have NO clue as to what extras you get for being a subscriber. How about trying it to see? (customization, custom stories sent to your email, custom story pages... very very nice overall)

Re:Subway trains shouldn't stop

[Frizzle Fry]

What about the young? Don't you think little kids might get themselves injured or killed a lot?

Re:Subway trains shouldn't stop

[scilec]

Will all due respect, did you forget to take your medication this morning?