How much power is generated by dynamic braking?

[dldance]

The threads on energy and the SP runaway (an others) have got me thinking about dynamic braking. In mountain railroading with a heavy train - such as a coal train, what percentage of time on the downhill grade is dynamic braking in use? I suspect that the answer depends on the locomotive model and whether is is AC or DC.

dd

[tree68]

What I thought the question was going to be was how much (ie wattage) power was generated, and thus had to be dissipated by the grids. But the original question is a good one, too.

On the electric roads, that power was put back into the system, often helping power another train up hill elsewhere.

[Randy Stahl]

If you want to know how much power thats easy, On an SD40 the power expressed in watts is about 522900 watts in braking.
Randy

[dldance]

so if I were thinking in terms of dynamic brakes solely as a power generating device - it has the capability of about 1/2 megawatt at full load?

dd

[jchnhtfd]

right -- or, very VERY roughly (before Randy jumps on me) about 600 horsepower...

[Anonymous]

Is there anyway that the Power could be banked in Batterys so it is not waisted?

[dldance]

As I thought - my subject question what is the horsepower equivalent of a dynamic braking system has been easily answered. Thanks to the smart people who participate in this furm.

However, my second question - how much of the time is it used - is also a part of the power equation.

Based on the information thus far, the collective dynamic braking systems of the continent's railroads represent a batch of small, randomly intermittent generators, operating in generally remote locations, and often in economically less rewarding time periods.

Hard to make the argument that its worth doing anything with other than just braking.

Comments?

dd

[Randy Stahl]

The duty cycle of a locomotive is really terrible from a productivity standpoint. A locomotive spends the bulk of it's lifetime in idle ! Other duty cycles depend on the specific railroad. If you were to compare the N&W and the IC the N&W would be the harder working engine of the two, both up hill and down. The IC didn't even have dynamic brake equipment until recently.
Randy

[Randy Stahl]

QUOTE: Originally posted by Clevelandrocks

Is there anyway that the Power could be banked in Batterys so it is not waisted?

It would be difficult to find space for batterys that will be big enough to absorb 500,000 watts of power.
Randy

[Anonymous]

QUOTE: Originally posted by dldance

As I thought - my subject question what is the horsepower equivalent of a dynamic braking system has been easily answered. Thanks to the smart people who participate in this furm.

However, my second question - how much of the time is it used - is also a part of the power equation.

Based on the information thus far, the collective dynamic braking systems of the continent's railroads represent a batch of small, randomly intermittent generators, operating in generally remote locations, and often in economically less rewarding time periods.

Hard to make the argument that its worth doing anything with other than just braking.

Comments?

dd

Except that there is technology known as energy storage systems, such as batteries, flywheels, etc. The idea being that you store the energy generated during braking and then use it during power demands, thus saving fuel. It is irrelevant whether the power is generated out in the boonies, or on an intermittent basis, it would be stored as it is generated. The question then is whether these systems would be more of a problem to deal with than the value of the stored energy itself.

[dldance]

QUOTE: Originally posted by futuremodal

QUOTE: Originally posted by dldance

As I thought - my subject question what is the horsepower equivalent of a dynamic braking system has been easily answered. Thanks to the smart people who participate in this furm.

However, my second question - how much of the time is it used - is also a part of the power equation.

Based on the information thus far, the collective dynamic braking systems of the continent's railroads represent a batch of small, randomly intermittent generators, operating in generally remote locations, and often in economically less rewarding time periods.

Hard to make the argument that its worth doing anything with other than just braking.

Comments?

dd

Except that there is technology known as energy storage systems, such as batteries, flywheels, etc. The idea being that you store the energy generated during braking and then use it during power demands, thus saving fuel. It is irrelevant whether the power is generated out in the boonies, or on an intermittent basis, it would be stored as it is generated. The question then is whether these systems would be more of a problem to deal with than the value of the stored energy itself.

Yes let's look at alternative energy storage technologies:

- Battery - as Randy pointed out it is hard to find space for 500,000 watt/hours of batteries. That's about 2,000 Die Hards - of course there are denser battery technologies but even at double the storage density that is still 1,000 Die Hard equivelents.

- Flywheel - this one has real possibilities. One of the major manufacturers of flywheel storage devices is based here in Austin and I have been fortunate enough to see their prototype but 500,000 watts is still a tall order for flywheels. In addition, the complexities of having 2 generators in a locomotive would add at least one more electrical cabinet to an already complex electrical system. I don't know of anyone working on this.

-Compressed air is another possibility. I have just been recently made aware of a compressed air backup generator for computer installations. Interestingly, most of the energy is stored thermally because as compressed air expands it cools. The thermal storage reheats the compressed air improving expansion efficiency. However, the system I saw was good for 4 SECONDS. Not sufficient to be useful in traction applications. However, trains use a lot of compressed air -- there might be possibilities here.

Back to batteries. The Green Goat makes use of another of Randy's points - most of the time most locomotives are idling. This energy is captured in the Green Goat's batteries for use when actually moving cars. I am excited to see growth in this niche market.

Let's keep thinking about it -- there might still be solutions.

thanks

dd

[Anonymous]

QUOTE: Originally posted by Randy Stahl

QUOTE: Originally posted by Clevelandrocks

Is there anyway that the Power could be banked in Batterys so it is not waisted?

It would be difficult to find space for batterys that will be big enough to absorb 500,000 watts of power.
Randy

Also.. the engines burn the fuel by keeping the cylinder hot. No need for a spark. With so much power availible to DRIVE the traction motors, batteries would be kind of irrevelant. Once the power quits or goes down and you suddenly need the battery for something... there is no power being dynamically generated.

[Anonymous]

Regarding energy storage, a while back someone mentioned super capacitors being developed by Siemens. Anyone know anything about this energy storage technology?

[mandelswamp]

Besides flywheels, fuel cells are another alternative energy storage device. The power being stored is usually used to separate water into hydrogen and oxygen which can then be re-burned to produce energy when needed. I don't know if fuel cells would be lighter than batteries but they are more effcient storage devices.

[Bikerdad]

One of the dings on battery storage is, I think, not really applicable. Modern diesel locomotives have a fair amount of "dead space" down low. It is my understanding that much of this space is filled with concrete (heavy & cheap) in order to boost the locomotive's weight. If so, some of that space can be used for batteries instead, without any loss of tractive effort.

[ericsp]

QUOTE: Originally posted by Randy Stahl

QUOTE: Originally posted by Clevelandrocks

Is there anyway that the Power could be banked in Batterys so it is not waisted?

It would be difficult to find space for batterys that will be big enough to absorb 500,000 watts of power.
Randy

Plus, they would probably be lead-acid batteries. How much energy would be wasted hauling all of these around all the time? It would not be worth it.

If a railroad has a SD40-2 that was always hauling heavy trains around at low speeds the added weight might not be detrimental. However, I am sure any large railroad that this would be applicable to (and probably EMD & GE) have investigated this and found that this is not worth the cost.

[ericsp]

QUOTE: Originally posted by Bikerdad

One of the dings on battery storage is, I think, not really applicable. Modern diesel locomotives have a fair amount of "dead space" down low. It is my understanding that much of this space is filled with concrete (heavy & cheap) in order to boost the locomotive's weight. If so, some of that space can be used for batteries instead, without any loss of tractive effort.

In regards to the concrete, perhaps you are thinking about slugs.

Something else that I should point out that tractive effort is limited by three factors. How much power can be delivered to the wheels, the weight of the locomotive, and the coefficient of kinetic friction between the locomotive wheels and the rails. The more a locomotive weights for a given coefficient of kinetic friction, the more tractive effort it has, assuming there is enough power available to increase the tractive effort. Hopefully that was clearer than mud.

[Anonymous]

Correct me if i'm wrong, but slugs are ususally the victims of "ballasting" as a way to replace the mass of the prime mover, generator and associated systems. So, in places where slugs are used to put power-on-rail for hill climbs, mass is a good thing and the entire fuel tank volume is available for use. In that scenario, a battery storage system makes a lot of sense. Back of the envelope (15lbs/ gallon, incl. cables, blowers, etc.), a fuel tank would hold about 1/2 the batteriessomeone (forget who) cites above. Using his energy numbers, and applying the electric-car rule-of-thumb 80% total system efficiency, that's a little more than 500HP-hours put on the rail, or about 45 gallons of diesel fuel (at 0.5lb/HP-hr) that could be re-used per slug, per charge cycle. If you don't deep-deep-cycle the cells too often, you could get something like 2000+ cycles out of a good set of vibration-resistant batteries.
Figuring a 50% depth-of discharge limit, that's about $45k in fuel savings alone, (California prices to the tourist line I sometimes wrench for) which about pays for the batteries and labor to swap them. (lead-acid recycles, so disposal is essentially free)
I'll let someone else speak to the maintenance requirements of locomotive electricals, but batteries are pretty simple beasts; as long as you don't let them get too hot or too cold and add water every week or or so, they're fine.

The biggest wrinkle I can see is that you can safely draw a higher energy rate out of lead-acid than you can put back in. Some sort of electrolyte cooling could help, but any engineered cooling you add to the battery system hurts cost and reliability.

which brings us to:

Flywheels can be designed for much better charge and discharge rate curves and aren't inherently cycle-life-limited like batteries. They do better on a mass-energy density basis, but really lose out on volume-energy density.
They DO add another wrinkle, in that highly stressed rotors don't like vibration; it tends to eat delicate bearings and crack things; and cracked flywheels tend to come apart violently. (the tip speeds of high-density flywheels are near that of a rifle bullet, and the tips is where the majority of the energy is stored.) Vibration can be engineered around, however, and orientation, containment and distance are good mitigating factors against rotor burst events. (Plus, show me the rifle that can shoot lengthwise though a 16-645 and generator, and I'll be your slave for a week <G>)
Net result, you could leave the full-size hood on a slug, and get probably twice the benefit from a 'flywheel slug' as you could from a 'battery slug.'

Using either technology, that's effectively 500+ fuel-, maintnenance- and emission-free horsepower made out of what is basically a used-up locomotive; you'd have to balance the conversion cost against what you'd get on the used locomotive market and the utility of having that 500 HP available as continuous duty. That again could be engineered around by adding an autostart OTR truck powerplant, and add that much more "surge" power to your 'powered slug' for a slight increase in cost, complexity and volume.

In summary: It's not a silver bullet, by any means, but a 'storage slug' arrangement could be a net money saver to a railroad with a few short, steep hills, or lots of slippery ones. I wonder how long it'll take RailPower to iron out the wrinkles? (I hear they are working on it.)


(someone asked about Supercaps- Great discharge and charge rates, lousy energy density. Watch the technology though, there's lots of room for innovation yet.)

[Paul Milenkovic]

My thinking on this is partial electrification. Use Diesel locomotives, but put pantographs or perhaps 3rd rail shoes on them in the manner of the FL9s (these days the LIRR DM-whatevers and the Metro North P32ACs). Run Diesel in the flatlands but run electric in what would be the helper districts and take advantage of regenerative braking and all of that.

With all of that fancy wheel slip control, they are wanting to put 6000 HP in a single C-C locomotive, and they want to use those high HP locomotives on coal trains. Put in maybe a 2000-3000 HP Diesel, adequate for the flatlands, electrify the ruling grades, and the same locomotives can put out 6000 HP or more under wire because the electrical equipment can handle it, but it is hard getting a reliable rail Diesel for 6000 HP. You would get the fuel economy advantage of regenerative braking and coal or nuclear-supplied electricity to lift trains up the hill, and you can put in a smaller Diesel and get better fuel economy on the flatlands.

I suppose wires had been looked at for the Wyoming coal trains and found wanting, but the electronic power conversion equipment for the high HP ACs had come into being after the studies making perhaps a Diesel/wire hybrid more attractive. My thinking is that a Diesel/wire hybrid makes more sense in mainline railroad applications than a Diesel/battery or Diesel/flywheel hybrid.

[arbfbe]

I have checked the power meter logs on the Oakway SD60s on the BNSF several times. The three highest use positions are Run 8, Idle and Dynamic braking but I don't remember the particular order. Idle was way up there. Throttle 1-7 were negligible.

Flywheels have one major problem on a locomotive. They do not like to change directioins which may cause serious problems going around curves. Flywheels also work the best when they have a larger diameter and relatively speaking locomotive carbodies are sort of narrow for the weights involved.

The newest diesels can produce far more dynamic braking horsepower than locomotive horsepower. Those traction motors have way more capacity than the diesels that feed them.

[ericsp]

Here are the major problems I see with a flywheel.
1) Power transmission.
A) There would have to be a motor to turn the electric energy into work to rotate the flywheel.
B) There would have to be a generator to convert the engery in the flywheel into electrical energy. Alternative, there would have to be a complex mechanical or hydraulic power transmission system to deliver power to the wheels.
2) Safety, this would probably have to be a large flywheel turning at high speeds. If it does come apart there will be shrapnel flying. However, thick steel and/or concrete used for weight may provide the necesary protection.
3) Coriolis effect, the bearings will need to take a large torque.

In conclusion, this is something that can be done. However, calculations, and probably test, will need to be performed to determine if this is economically feasible.

[M636C]

My rough recollection was that about one third more power was available in dynamic braking than in traction, since it was based on motor limits, not on the prime mover.

Peter

[Anonymous]

QUOTE: Originally posted by Paul Milenkovic

My thinking on this is partial electrification. Use Diesel locomotives, but put pantographs or perhaps 3rd rail shoes on them in the manner of the FL9s (these days the LIRR DM-whatevers and the Metro North P32ACs). Run Diesel in the flatlands but run electric in what would be the helper districts and take advantage of regenerative braking and all of that.

With all of that fancy wheel slip control, they are wanting to put 6000 HP in a single C-C locomotive, and they want to use those high HP locomotives on coal trains. Put in maybe a 2000-3000 HP Diesel, adequate for the flatlands, electrify the ruling grades, and the same locomotives can put out 6000 HP or more under wire because the electrical equipment can handle it, but it is hard getting a reliable rail Diesel for 6000 HP. You would get the fuel economy advantage of regenerative braking and coal or nuclear-supplied electricity to lift trains up the hill, and you can put in a smaller Diesel and get better fuel economy on the flatlands.

Paul, that's an idea I had been wondering about for a long time. You have the savings in reduced fuel consumption, need for fewer diesel units (albeit probably more expensive with the modifications), and the expense of the cantenary is restricted to the major grades.

When the GN and Milwaukee were still running electrics and diesels together, I wonder if this option was even technically available to motive power engineers in the 1950's and 1970's?

[daveklepper]

A better solution is the idea of "the compatibles". Electric and diesel locomotives designed to either work singly or as pairs, with the electric being the "road-slug" for the diesel when off wire, and the diesel being the "road slug" for the electric when under catenary (or over third rail, probably centered Lional Like, just in tunnels and the approach overlaps to avoid clearance problems). Jumper cables between, just like between a diesel and a road slug, except that the cables are the steady traction power and control is via conventional train-line multiple unit controls.

If Harrisburg (Enola) - Pittsburgh (Conway?) and Council-Bluffs - Sacramento were proved good freight electrification lines, such power could still run through beyond the limits ofo the wire.

[Randy Stahl]

QUOTE: Originally posted by M636C

My rough recollection was that about one third more power was available in dynamic braking than in traction, since it was based on motor limits, not on the prime mover.

Peter

You're correct, you caught me ! I gave the #s for a single grid set. The actual firgures are a bit higher. Max grid current is 700 amps, therefor since a pair of motors are connected in series to a pair of grids the formula is as follows: 1.72 grid ohms Times 700 grid amps =1204 grid volts. 1204 grid volts times 700 grid amps = 842800 watts. divideby efficiency factor of 700 = 1204 horsepower times 3 sets of motor/ grids= 3612 total braking horsepower.
I couldn't sleep last night because that original figure seemed too low, I simply forgot how many wheels an SD40 had.
Randy

[tree68]

I recall reading about some B&O (?) locos that were "specially ballasted" for some heavy haul service - on a grade as I recall. Think I've seen other similar examples, but it does prove the point.

[oltmannd]

Concrete for ballast always seems like such a good idea, until you try it.

A short story.

When Conrail was rebuilding NJTs GP40Ps, the rearragement of equipment meant that some ballast was needed in the front to keep the weight distribution even front to rear. Us engineering types calculated how much and where to put it. We told Juniata to weld some steel below the front walkway - there's room there above the draft arrangement and between the frame rails. The local mgt at Juniata thought that was a lot of trouble - so they decided to fill that area with concrete instead. This caused three problems. First, that area was not water tight and the concrete oozed out. Second, once they go it to stay put - it didn't weigh enough to fix the imbalance. And third, they had to chip it all out and weld in steel - like we told'em in the first place! Juniata is like that.......

[oltmannd]

QUOTE: Originally posted by ericsp

Here are the major problems I see with a flywheel.
1) Power transmission.
A) There would have to be a motor to turn the electric energy into work to rotate the flywheel.
B) There would have to be a generator to convert the engery in the flywheel into electrical energy. Alternative, there would have to be a complex mechanical or hydraulic power transmission system to deliver power to the wheels.
2) Safety, this would probably have to be a large flywheel turning at high speeds. If it does come apart there will be shrapnel flying. However, thick steel and/or concrete used for weight may provide the necesary protection.
3) Coriolis effect, the bearings will need to take a large torque.

In conclusion, this is something that can be done. However, calculations, and probably test, will need to be performed to determine if this is economically feasible.

This has actually been studied, well 20 years ago or so, anyway. From memory, the biggest issues were the economics and safety.

You'd use a motor/generator to spin the flywheel up and to reclaim the energy. In this era of computer controlled, high power semiconductors (GTOs et. al.), this would not pose any engineering problems.

The torque reaction to change in angular momentum (gyroscope effect) could be minimized by mounting the flywheel horizontally. You'd have no reaction to hoziontal curves, only change in grade or locomotive carbody roll. If this was still a problem, a pair of flywheels rotating in opposite directions at the same speed could be used. They would cancel each other out.

[Anonymous]

I like the idea of partial electrification. Altho not in a form of electric-desel mutual slugging :).

What I envision - all diesels being fitted with machinery to share power - effectively slug each other (and for example - keep engines warm without the need for idling). This way when an engine of one unit dies - the train will not lose traction - less stalls.

But - the system benefits mostly in difficult streches of the railroad, where diesels are not powerful enough, or artifically ventilated tunnels were drilled (Moffat or Cascade tunnles come to mind).

On such stretches a powerful electrics would be provided to lead the train through - and would power the diesels - which could idle/be shut down (depending on the length of the stretch).

Since difficult railroad = mountains then such electrics could use dynamic brakes to power up other trains. If there was no train to power, then farms of flywheels (or small hydro plants) would be powered (energy from which would be used was climbing up) and if that fails - then the energy would be dumped through resistor grids.

[dwil89]

QUOTE: Originally posted by tree68

QUOTE: Originally posted by M.W. Hemphill

Some unusual locomotives in the past have had concrete ballast added...

I recall reading about some B&O (?) locos that were "specially ballasted" for some heavy haul service - on a grade as I recall. Think I've seen other similar examples, but it does prove MWH's point.

I thought that CSX has fairly recently ordered GE's..either Dash Nines, or AC4400's with extra ballast in them for heavy-haul service. Dave Williams http://groups.yahoo.com/group/nsaltoonajohnstown