So essential this is about using a grid to provide electricity for locomotives vs using portable diesel generators to provide electricity. I’m also mostly focusing on overhead catenaries
off the top of my head advantages and disadvantages of each
Diesel
lower infrastructure cost
Less infrastructure maintenance
Are not limited by power outages
Larger amount of manufacturers produce diesel electric vs All electric
Electric
Higher efficiency
Better power to weight ratio
No need to refuel locomotives at stops
Many sources of available energy at generally lower cost (This varies though!)
Potentially much lower emissions (this also varies)
Railfan perspective: their catenaries which are cool to look at and add a human element, electrics seam to come in more shapes and sizes then diesels.
Decreases the height of the right of way available for freight - both NS & CSX have untaken billion dollar infrastructure projects to increase the clearance height of their lines for the transportation of 20 foot 2 inch double staks - putting wires over these project would make that expenditure worthless - would then need at least 25 feet or more for clearance.
Increased liability for those who think catenary can’t electrocute them - already happens too frequently on the NEC.
Higher efficiency for electrics is probably not true. A diesel locomotive makes electricity at least as efficiently as a coal fired power plant and has no transmission losses from the plant to the locomotive.
Power to weight ratio is also questionable. Diesel locomotives are ballasted to weigh a much as possible. A six axle electric would weigh the same as a diesel. Would an electric locomotive have more HP? Maybe. It’s possible that RRs would take 6-8,000 HP locomotives, but if they ran at higher HP/ton, the energy consumption would go up.
Locomotive reliability would be traded off against catenary reliability, but overall, electrics should come out on top as you’d have a system with fewer parts (lots and lots of moving parts in all those diesel engines!)
Electric motors have the advantage that so long as the CAT is not power overloaded then short time ratings of the traction motors can be much higher. ( ie diesel’s 4400 HP per unit vs what ? [ unknown [ ).
One item that may have limited post WW-2 electrification was the power limit of DC traction motors? Nose mounted DC mtors may have been too heavy . Now the HHP-8’s put 8000 HP on just 4 axels. Although starting tractive effort needs to be limited to about 400,000 # to prevent train separations the higher HP at speeds above 40 MPH CAN BE VERY ADVANTAGEOUS.
Passenger motors can quickly accelerate their trains using their extra HP wheras freights have to slowly accelerate.
Of course a diesel locomotive does have “transmission losses from the plant to the locomofive.” Unless the locomotive is always fueled at a refinery where the diesel is produced, the diesel fuel has to be transported to the fueling point. Whether that transportation/transmission is by pipeline, truck, barge or rail, there are always “losses.” How is that different from electrical transmission loss over high tension wires?
The efficiency lossses in diesel electrics are actually greater than energy olosses in a modern high voltage AC electrification scheme. A lot does depend on substation spacing, loading of the catenary, type fo feeder cable, etc.
Diesel electrics have their horsepower limited by the capacity of the on-board diesel engine, so straight electrics can have significantly higher horsepower. That becomes very useful for higher speeds typical of passenger service, and fast intermodal freights. For drag freights tractive effort is perhaps more important.
Modern wheel slip control has harnessed locomotives of 4400 horsepower and above, but I will ask the experts to clarify how. I suspect it may be by reducing the actual horsepower to match the adhesion available. If so, additional horsepower will not change the tonnage rating on a ruling grade, although it will enable the train to climb the hill faster. And of course then we would have to consider the economic value of a much higher rate of power consumption but for a shorter time.
Since it could be considered impractical to electrify every last mile of track, electrics lose a certain amount of flexibility when compared to diesel-electrics. Railroads would be maintaining and operating two sets of locomotives: Straight electrics for mainline freights and diesel-electrics for yard and transfer, locals, branchline operations, etc.
Dual-powered locomotives are as yet an untried option. Realistically, FL9’s and P32’s are diesel-electrics with some extra gear to handle a short third-rail operation (less than five miles). NJ Transit’s ALP45’s appear to be the first genuine dual-powers to be operated in North America.
There are some projects internationally (China,for instance) to introduce double stacked container trains although IINM the containers used are not as high as domestic containers used in North America so the catenary will not need to be as tall.
I am sure it would be technically possible to build an electrificati
Regeneration of the dynamic braking effort enables a signifcant fraction (said to be in a range of 12 to 33 %) of the energy that was used to propel the train to be recovered and reused, instead of just wasted as dissipated heat from the resistance grids of the diesels. This recovery is most significant in descending mountain grades.
A well-designed electric locomotive (though not all are, see PRR’s early electrics and the GE E60C’s for Amtrak . . . [:-^] ) can have an economic service last 30 to 50 years with only ‘running’ maintenance and none or only a few partial rebuildings and upgrades, depending on the interim advances in the technology - PRR’s GG1 fleet and the Amtrak AEM-7 series are good examples of these. In the meantime, several models of diesels have come and gone, or at least been rebuilt 2 or 3 times - only the SD40 series can claim to be equally as long-lived in heavy service.
It’s interesting that in Europe, where electrification is common and fuel oil costs at least twice what it does here, heavy freight often uses diesel on electrified lines. The electrical infrastructure for the caternary has to be able to support very high amp loads for drag freights and many areas there apparently aren’t up to it.
Modern electric for the USA would probably use an extremely high voltage for the caternary, say 20,000 volts + at 60 Hertz so that substations could be spaced a realistic distance apart and amp loads at the caternary-pantograph interface would be reasonable. This would be stepped down to say 2000 volts single phase AC, rectified to DC, and then inverted to say 2000 V AC three phase variable frequency for the traction motors, borrowing from current inverter based AC diesels. I see the locomotive as looking similar to a modern diesel with pantographs, with the diesel engine replaced by a transformer.
AC would be used on the caternaries so that the high voltage can be stepped down to something usable within the confines of the locomotive. 60 Hz because that is what commercial power is in the US. Using a lower frequency, like 25 Hz, had its uses in the days before inverter technology, but that is largely obsolete now.
The railroad could avoid setting up its own power infrastructure and the power company may have use for the caternary right of way for other transmission uses.
Current AC traction motors are easily capable of 1000 HP per axle, as seen by the SD-90 Mac and the new A1A trucked GE’s that BNSF is using. This means at least 6000 HP per 6 axle locomotive shouldn’t be out of the question, more than most railroads want or can use. Tractive effort at low speed should be in the 140,000 lb range like a current AC locomotive, which is more than enough to start busting knuckles if not controlled. This is limited by axle loading more than anything else. Distributed power
Many European railroads use hydroelectric power for their trains, which we don’t have here except in very limited locations. I don’t know an exact figure, the but German railway system probably has fewer track miles than a single U.S. state like California or New York.
Catenary across the Mohave desert would cost billions of dollars for very little return.
The electrical infrastructure for the caternary has to be able to support very high amp loads for drag freights and many areas there apparently aren’t up to it.
That is correct especially in the DC or 16.7 Hz CAT.
Modern electric for the USA would probably use an extremely high voltage for the caternary, say 20,000 volts + at 60 Hertz so that substations could be spaced a realistic distance apart and amp loads at the caternary-pantograph interface would be reasonable.
The world standard for new CAT is either 25 Kv OR 50 Kv.
This would be stepped down to say 2000 volts single phase AC, rectified to DC, and then inverted to say 2000 V AC three phase variable frequency for the traction motors, borrowing from current inverter based AC diesels.
These values would be decided by various manufacturers and may vary.
AC would be used on the caternaries so that the high voltage can be stepped down to something usable within the confines of the locomotive.
already is done
60 Hz because that is what commercial power is in the US. Using a lower frequency, like 25 Hz, had its uses in the days before inverter technology, but that is largely obsolete now.
The main reason not to use 25 Hz is that 25 Hz frequency requires a larger transformer than 60 Hz for the same power. This problem is current on the NEC with the dual voltage (12 Kv 25 hZ & 12.5 KV / 25KV 60 Hz ). That requires a bigger transformer on both electric motors and the latest EMU’s that run on NJ TRANSIT. Silverliner - 5s are built for these various powers. It is fortunate that the transformers can be center tapped when CAT IS 25 kv. My understanding is that the new M-8s are only good on 12.5 or 25 Kv 60 Hz.
According to the table from the US Energy Information Administration linked below, conventional hydroelectric plants combined with pumped storage plants produce approximately 10% of the total US power requirements, which is comparable to the 10% of US power produced by nuclear plants.
Oh please. NO ONE has hydroelectric power. Electricity is a fungible commodity. What is put into the grid is mixed with every other source of power generation and is indistinguishable from any other source. If there is a difference it lies in the fact that hydroelectric sources are fully exploited and many are being removed for environmental reasons. Nuclear, on the other hand, is just beginning to come into its own .
Diesel #2 gas turbine-electric has been proven to match electric in power and weight for high speed passenger service. In March, 1996, Bombardier recieved an order for a 5000 hp turbine electric demonstration locomotive in conjunction with their Acela order. it had already been shown that such a unit matching the weight and performace of the Acela electric locomotive could be made. To avoid conflict with the Acela, speed was to be limited to 125 mph and no provision for operation in the Penn Station tunnel was to be included. The unit was delivered in Octber of 2002 and it perforemed as promised in every respect. (Rumor had it that it’s top speed was well above 125 mph buy this could not be confirmed for obvious reasons.) Power is a PW SD40 5000 hp gas turbine weighing just 1157 lbs, 38,000 lbs less than equivelent diesel. BSFC is 0.43 , slightly higher than a diesel but it consumes no lubricating oil, which, coupled with the lighter weight partially compensates for the difference. While it was a succesful demonstrator, no one bought it and it presently sits in the weeds at Bombardier’s facility.
In the 50’s Union Pacific experimented with turbine electric freight locomotives using industrial turbines burning Bunker “C” oil… The incentive was lower cost fuel and cleaner exhaust in the tnnels (UP was still running steam) Between 1952 and 1968 UP bought 50 turbine lectric locomotives with HP of 4500 to 10,000
The UP application was less than satisfactory, not because of basic problems with turbine propulsion, but rather because of lack of good control technology, inappropriate operating practices and misapplication of particular industrial turbines to railroad use. Never the less, the UP op
Diesel #2 gas turbine-electric has been proven to match electric in power and weight for high speed passenger service.<<
There is no question that gas turbines can produce a huge amount of power in a very small space, and when they are running flat out they are reasonably efficient. They are also very reliable. UP proved those statements 60 years ago.
The main problem in the day was the fuel consumption, even in those cheap oil days. UP used Bunker C which was the cheap of cheap oil leftovers back then. It’s so thick it needs heating to pump it, but it has very high BTU /lb, much higher than No. 2 fuel oil or gas. They still did not like the fuel costs of a turbine.
The main problem was not running flat out going up Sherman Hill, but idling going back down and running at less than full throttle, where turbine engines are very inefficient. Maybe today’s technology in both turbines and traction motor control might take a notch out of that, but it would probably still not match the fuel cost of an equivalent diesel.
UP even went to the point for experiments of splicing a GP-9 into the turbine locomotives so that the main turbine could be shut down when not needed. This was fuel cost driven.
The closest analogy today is some Coast Guard icebreakers that have a dual turbine and diesel power plant. The diesel provides the normal propulsion and the gas turbine steps in when extreme horsepower is needed to break ice. In light of this, I suspect that the high fuel consumption at less than full power in a turbine is still there.
The GP9 was added for dynamic braking. The traction motors on the gas turbine units could not provide enough. Bunker C was used to save money, about 2 cents per gallon. Diesel 2 costs came down which made the bother of Bunker C hard to justify.
The anwer to gas turbine fuel consumption is recuperation. This is a proven technology but the added first cost can not be justified on aerospace applications. Allied Signal (now Honeywell) offered to make the change to their TF-50 if someone would pay the bill. DOT was not interested so it never happened. Turbomeca built a prototype 1400 kw unit but left the lndustrial turbine business before it went into production I wrote a 13 page illustrated and annotated piece, “Gas Turbine Motive Power History” a short time ago to preserve details of the technology while some of the participants were still alive. I offered it to “Trains” but they rejected it sight unseen on the basis that their readers would not be interested.
I do owe you an apology for my inadequately informed denigrating comments about the Rohr TurboLiners a couple weeks ago over on that thread - and it will be forthcoming shortly. However, part of that mea culpa was going to look forward and ask if an article or book had ever been written about the whole experience with them - the turbines, the trains, the engineering and management of same, the interface with traditional railroaders, and the train’s performance and service record, etc. I’m not aware of any, and it seems not, except for your effort mentioned above ? If the present staff under Editor Jim Wrinn would rather publish ‘fluffier’ pieces, I’m truly disappointed in them. But I wouldn’t want to see that technology and ‘1st person participant’ history lost due to such short-sightedness. Have you considered or looked into ‘self-publishing’ it, either on a website or as a blog (free or nominal fee), or as an e-book kind of thing ? I have no insights or expertise in that, other than I understand that’s becoming an accepted "end-around’ the stultified world of traditional publishing - just a thought.