This is not my idea but I have been thinking about it lately (credit Scott Walker), especially with the crazy petro fuel costs lately.
There are many railroads today that decend grades useing dynamic brakes to slow / controll there trains. This retards the train by converting the energy to heat and dissipateing the heat to the atmosphere, thus letting it go to waste. How about captureing that wasted energy for re-use.
The idea is this: Instead of wasteing that energy in the DB grids, how about captureing it and selling it to the electric car market. On long sustained grades where helpers are (or were before DPU) used for ascending trains, do the opposite and use dynamic brake sleds, like helpers would be used, for decending trains that take that energy and store it for re-use / re-sale. These brake sleds would be units with traction motors balasted for max adheasion that would take the energy and would store it instead of wasteing it, either directly to batteries or through an intermediate medium for later use rechargeing batteries at the bottom of the hill.
An example: A train traveling west over Donner pass would stop at the top and pick up a break sled(s) and use the sled to retard the train on its way down the hill. When the train reaches the bottom it cuts the sled out (the opposite of helpers on the ascent). At the bottom of the hill the sled discharges it’s energy to a rechargeing station for electric / hybrid cars. The energy is sold to the automobile market. Then when enough sleds accumulate at the bottom of the hill a eastbound returns them to the top of the hill to start the process all over again.
This would not be economical on every decent, but I would think it would work on the long grades. Here is a few of examples:
I think in the long run stopping at the top of a grade to ad a brake sled w/ batteries might end up being cost prohibitive. There would have to be allot of batteries to come close to penciling out. It is a thought though. Having more privately owned and run fish hatcheries and more hydro, nuke power and alternative fuel (not corn Ethanol) makes more sense to me.
Can anybody provide the power quantity that is produced by dynamic braking for an average train on one of these grades? How much of a battery pack would it take to store it? No doubt the energy would have significant value, but there would be cost in those dedicated sleds.
That was my question as well. You’d need one heck of a battery car to hold all the energy that a locomotive would generate in its dynamic brake grid. I know on the Milwaukee the locomotives dumped the energy back into the grid, made possible by a connection through the pantograph. Batteries are not perfect, there is always some electrical leakage. Toss in the possibility for acid spills and you’ve got a major mess on your hands. I highly doubt it would be economical.
1 6000 ton train decending 4000+ feet should lift 300 2 ton cars 4000 feet. Of course that would be at 100% efficiency (which would never happen). But even at 50% efficency that should be 150 2 ton cars or 300 2 ton cars at 2000’ rise, not to mention flat ground running.
So… stop at the top of the hill… tie down the train, test handbrakes, get authority to add a brake sled… go in to get brake sled… do a Class-1 if its been off air for more than 4 hours… bring it out… authority to recouple to train…charge train…knock off handbrakes… take it down the hill. Then stop the train…tie it down…test brakes…get your authority to cut the brakesled off and put it in the siding… tie it down in the siding…test its handbrakes…uncouple…back to the train…couple back up…charge the train…knock off the brakes… listen to the dispatcher yell and scream about how you are holding up the UPS trian…
Then what goes down must go up. So now we have to reverse the process and waste more fuel to drag the brake sled back up the hill, park it on the siding (which we probably have to build, otherwise the brakesled will be too far away to be of any use). All for what? To sell a couple of bucks of electricity? Then the railroads will have to become licensed for that, register with the state PUC. Also need another craft of workers to plug and unplug the cars (not my job).
And all this in addition to building and maintaining the sleds (and if we’re not returning them up the hill right away, we need lots more, plus the extra crews to return them up the hill. Don’t see it happening.
Since you and the dispatcher don’t like all the stops, let’s attack this from another angle. String cantenary on the slopes you want to capture all that wasted energy. Add pantographs to the locomotives and put the dynamic braking energy into the cantanary and sell it on the spot utility market. Better yet, wire the pantograph so it works both ways. Then, if the dispatcher is good, a decending train can add power to the wire while an acending train can draw it to offeset some of the diesel fuel burned hauling a train up the grade. Now no-one has to stop for a brake test, just raise the pantograph hit the button to shunt from the resistance grid to the pan and away you go, no special train handling.
The down-side, every locomotive would need a pantograph to make use of it. I don’t think you can make m.u. cables heavy enough to handle all the energy from many units, so only one per train needs an operational pan. Cantenary is currently expensive and adding pans isn’t cheap.
The Milwaukee Road solicited engineering studies from both GE and EMD on equipping a fleet of SD40 units as dual power locomotives with pantographs, so your idea is technically feasible…It seems to me that the “slug-mother” concept discussed in earlier posts could work as well. There are electric freight locomotives operating in Europe and elsewhere that use a single pantograph to power multiple units through a common power bus so the engineering is do-able…
Why would it be more profitable to capture the electricity and commercialize it, then simply use the electricity for the purpose of powering the train, as in the GE hybrid battery/diesel locomotive? If there’s a higher-profit outcome here, I’m interested in knowing about it.
Using the electricity to move the train itself avoids incurring all of the valid objections posed above to delaying trains, building infrastructure, entering a non-core market, providing a distribution system for the product, and so forth. The diesel-electric locomotive cares not whether the traction motors are fed by batteries or a main generator.
If the battery pack can be made long-life and zero-maintenance, I think the economics of a hybrid locomotive will be irresistible even at a 7-digit premium. The thought of getting 2,000 or so free horsepower for an hour or two in which the diesel prime mover is shut down or idling is mouth-watering.
The dynamic brakes on a modern locomotive are usually rated at a higher horsepower than the prime mover itself. In back-of-the-envelope terms, if the DBs can generate say 3,000 hp/hours on a one-hour descent of a mountain grade, and the capture/return rate on the battery is a little as 66%, it still means 2,000 hp/hours free of charge other than the amortization of the capital cost of the battery and control gear.
I did! It’s been another 15-hour workday and it’s small wonder I can even remember which floor in the hotel I’m on. I fiddled with the keycard in the elevator for 15 seconds until I realized I was putting it in upsidedown.
When I posted that I stared at the “hp/hours” for a few seconds and I knew there was something not quite right about it. But my mind was too fuddled to diagnose the problem. I think I’ll get some sleep.
The stuff that I’ve seen on the GE hybrid is fairly light on details, especially battery weight, battery specific energy and battery specfic power. I have seen a couple of references to the battery being a sodium-sulfur battery - specific energy for that chemistry is probably between 150 to 200 w-hrs/kg and specific power is probably on the order of 150 w/kg, based on a guessed weight of about 10 tonnes (11 short tons). I would be a bit surprised if you could get more than 2,000 hp-hr from the battery.
I also wonder how many times the battery can be cycled from full charge to full discharge - typical Li-ion batteries are good for 500 to 3,000 such cycles. It may be that the intent was to recover the energy from ‘stop-n-go’ traffic as opposed to descending “The Hill”. Another benefit from the battery is that the engine may change rpm’s a lot less than in a non-hybrid locomotive, which could do wonders for the emissions. Yet another possibility is that the group working on the battery has found a way of greatly increasing the number of cycles the battery can handle.
I would be very surprised if that another goal for this battery technology is for electric utility energy storage - as per RWM’s comment from another thread about the wind generation using up all the swing generation capacity from hydro at one utility comes to mind. A123 is testing their Li batteries for utility stabilization and GE is one of the primary investors in A123, so it would make sense that GE would be looking into batteries that would provide hours as opposed to minutes of capacity. (I’m taking a bit of a guess in assuming that Li batteries may cost less per watt, but the sodium batteries will cost less per watt-hour - sodium is a LOT cheaper than lithium).
Another thought comes to mind. A 16 cylinder 7FDL engines weighs 22 tonnes, I guess that the alternator weighs in on the order of 10 tonnes, figure another 8 tonnes for the cooling system and dynamic brakes and
I believe both GN and Milwaukee did use something like this in the 1920’s and later in their electrified lines. Dynamic braking for diesels is based on regenerative (?) braking on straight electric engines. The electricity created by the regenerative braking of an engine going downhill would be sent thru the wires to help power a train going up the other side of the mountain.
Which assumes that there will actually be a train going upgrade that can use the power right then…
I can’t help thinking that the idea is definitely do-able, with battery-loaded road slugs cabled to otherwise unmodified prime-mover-equipped locos. Not only could they store the breaking force for later use, they could also store excess power from the prime-mover unit(s) during the flatland run, to be made available for traction when the grade steepens. Most nasty grades are upgrade from both sides to a summit at the top…