Some of the newer EMD/GE road power has enough battery power dwell/reserve to get them out the shop doors w/o starting the diesel engines . (IAIS' new locomotive shop outside Cedar Rapids/ Homestead, IA was designed around this concept, no locomotives were to be started or left running in the building - there are no power exhaust fans for diesel fumes in the roof) The units cannot go far on just battery.
OvermodSulfation and other problems result with large numbers of chemical 'cycles' between charge and discharge. (Some of this was addressed in the design of Norfolk Southern's 999.) Reading between the lines, somebody failed miserably to understand exactly what is involved with flat switching -- it's often actually the opposite of what you might expect, kicking cars up to high speed quickly and then using high levels of braking.
The original poster raised the question in the context of a road locomotive. The #999 was conceived as a yard switcher or possibly limited road switching. It failed to meet expectations. Perhaps the developers underestimated the work of switching, as you suggest.
But if the design engineering were to properly address the work of switching, would a battery powered yard switcher be economically feasible, even though battery powered road locomotives appear to be infeasible?
Overmod First, a straight BEV locomotive would involve enormous capital cost for the required energy density. To get to required voltage and amperage for traction motors involves large serial AND parallel strings of cells, and this runs the cost of the overall battery up tremendously. Some means of configuring around 'open' cells, as the battery ages, must be considered. The draw must be carefully regulated, as overcurrent damages most cost-effective battery structures and chemistries. Range... well, it should tell you something that current battery-electric designs are intended for relatively short-range yard service. Then there is the problem of peak charging current in regeneration. This is one of the things that killed the original Green Goat system. The inertia of a train is much greater than that of even the heaviest trucks, and this results in very high peak currents if dynamic braking is not carefully excited -- and high peak charging currents for an acceptable 'average' even when it is. Sulfation and other problems result with large numbers of chemical 'cycles' between charge and discharge. (Some of this was addressed in the design of Norfolk Southern's 999.) Reading between the lines, somebody failed miserably to understand exactly what is involved with flat switching -- it's often actually the opposite of what you might expect, kicking cars up to high speed quickly and then using high levels of braking.
First, a straight BEV locomotive would involve enormous capital cost for the required energy density. To get to required voltage and amperage for traction motors involves large serial AND parallel strings of cells, and this runs the cost of the overall battery up tremendously. Some means of configuring around 'open' cells, as the battery ages, must be considered. The draw must be carefully regulated, as overcurrent damages most cost-effective battery structures and chemistries. Range... well, it should tell you something that current battery-electric designs are intended for relatively short-range yard service.
Then there is the problem of peak charging current in regeneration. This is one of the things that killed the original Green Goat system. The inertia of a train is much greater than that of even the heaviest trucks, and this results in very high peak currents if dynamic braking is not carefully excited -- and high peak charging currents for an acceptable 'average' even when it is. Sulfation and other problems result with large numbers of chemical 'cycles' between charge and discharge. (Some of this was addressed in the design of Norfolk Southern's 999.) Reading between the lines, somebody failed miserably to understand exactly what is involved with flat switching -- it's often actually the opposite of what you might expect, kicking cars up to high speed quickly and then using high levels of braking.
No argument from me about the issues of capital cost and energy density. I would also had the problems with limited cycle lifetime, e.g. a battery costing $500/kWhr and having a life of 1,000 charge discharge cycles would cost $0.50 per kWhr on top of the cost of the "raw" electric energy.
Peak charging is a function of battery chemistry, with some of the Lithium technologies capable of very high charging rates as well as discharge rates, though at a possible expense of reducing cycle time. There has been some promising research into technologies that will greatly increase power density (NOT energy density) with some promise of increasing cycle time as well.
One way to get around the battery charge/discharge rate problem is to use some flavor of quickly-reversible energy storage in the link between the motors/controllers and the battery itself. These include super/ultracapacitors, and flywheel storage (with magnetic bearings, perhaps in a hydrogen atmosphere with the flywheel made insensitive to hydrogen embrittlement), both of which when done right can absorb a significant current and then 'buffer' it out at the rate battery chemistry can accommodate it.
I'd bet on ultracapacitors, no moving parts, present specific energy of 4 w-hrs/kg with potential of 40 w-hrs/kg, specific power greater than 1 kW/kg, terminal voltage giving state of charge and 500,000 cycle lifetime. There have been claims that some Lithium batteries can attain a very high cycle life by limiting charge/discharge to 5-10% of battery capacity and keeping the battery around 50% charged.
In my opinion, the cost of any effective road-locomotive BEV would be out of all proportion to its value, even in air-quality management districts, and the risk of 'going dead on the road' takes on a whole new ominous meaning. Hybrids, especially hybrid genset locomotives, pose a much more interesting class of solutions...
Or a straight electric with battery back-up. One of the high costs of electrification is improving vertical clearances, it may be cheaper to provide a few minutes of power onboard the locomotives and put dead wires at the low clearance spots.
- Erik
P.S. For what CA is proposing to spend on HSR, I wonder if the same funding could be used to develop short haul electric airliners. Batteries could be kept in underwing pods (think drop tanks) that could be swapped out quickly.
A data facility I worked at had a 160 KVA (3 phase/408V) uninterruptible power supply (UPS) with a two hour reserve. I wish I could remember how many batteries (more or less standard marine deep cycle) it required. I think there were at least 8 cabinets involved just for the batteries, each holding around 8-10 batteries on each of maybe 4 shelves, for around 250 batteries.
Obviously, a battery operated locomotive would be capable of holding more batteries (at what price?), but someone else can do the calculations as to how long that 160KVA would last flat switching a yard.
Too - the UPS "floated" it's power across the top of those batteries - turning the 3 phase AC into DC, then using an inverter to turn the DC back into AC. If the batteries got sucked down during a power outage, it took a considerable amount of time to get them back up to rated capacity.
Larry Resident Microferroequinologist (at least at my house) Everyone goes home; Safety begins with you My Opinion. Standard Disclaimers Apply. No Expiration Date Come ride the rails with me! There's one thing about humility - the moment you think you've got it, you've lost it...
Not exactly. It is technically possible to build a storage-battery locomotive, and a number of them have been built. In the very olden days, the battery was used as a 'buffer' to reduce some of the control issues with motor-electric locomotives. Perhaps the most interesting use was the 'tri-power' setup used on a couple of Eastern roads in the 1920s (third rail, motor-electric, and battery). In England, but there are problems in railroad service that are more extreme than found in roadgoing BEVs.
The 'best' solution for battery-electric, here as well as in road vehicles, is some sort of hybrid solution, where there is some generating capacity in parallel with a large traction battery . As I mentioned, the Comsol company has a good description of GE battery design for their hybrid road locomotive -- it's on a 'free' DVD you can request that shows how various kinds of CFD and other computer simulations can help with design. (I suspect you would not get a description at all if you were to ask GE directly!)
The modern 'trick' with battery-vehicle control is the use of effective DC-DC conversion to keep voltage high even in relatively deep discharge. This comes with a painful downside (from the standpoint of robust battery structure) because increasing power is required from the battery toward the end of its charge. If you need high peak current low down in the discharge cycle ... as you would in railroad operation over a substantial distance ... your risk of being stranded is very high.
An intermediate stage between BEV and hybrid is the system (used on some Swiss buses) where intermittent electrical contact or induction supplies current to spin up flywheels which are then adequate to get the bus to the next 'charge' location. This method will also work with some battery configurations, the additional weight and bulk not being a substantial negative issue on something the size of a locomotive.
zardoz I would surmise that the cost of the batteries alone would be prohibitive. And the charging time needed would make the unit not very productive.
I would surmise that the cost of the batteries alone would be prohibitive. And the charging time needed would make the unit not very productive.
And then a crew will probably run over the cord.
It's been fun. But it isn't much fun anymore. Signing off for now.
The opinions expressed here represent my own and not those of my employer, any other railroad, company, or person.t fun any
Maybe for a light-rail application, or a trolley, but not for hauling tonnage.
Unless it was downhill both ways.
I know that Tesla Motors has created a car that can run 300 miles on a single full charge, but have rail-related companies been able to develop, let alone look into, battery operated locomotives that, with the same technology Tesla Motors uses, could power a train for a lengthy distance, say, the route of the IAIS from Blue Island to Council Bluffs?
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