How efficient is a steam engine?

[Boyd]

For the BTU used to operate one, how efficient is a steam engine. And I'm talking about with the most current technology.

[Paul Milenkovic]

There are three things working against the efficiency of a steam locomotive.  One is that it is a non-condensing cycle.  Condensing is not very practical in a steam locomotive as you are not carrying a cooling pond with you, and the few instances of condensing locomotives (South Africa had some) had limited efficiency gain owing to the inefficiences of an air cooled condensor.  A second is the low boiler pressure, and that in part is tied to the non-condensing cycle.  You are using water that hasn't been distilled and purified, a necessity for the very high boiler pressures used in modern steam electric power plants.  A third is until the very end of steam when some people (Chapelon, Porta and others) started looking at steam engines on a scientific basis, there are a variety of combustion losses, heat losses, and pressure-drop losses to contend with.

The figures I have heard are around 5 percent for the sort of Northerns towards the latter days of steam, maybe 10 percent for Chapelon's compounds where he paid a lot of attention to minimizing the losses I mention above, with maybe 16-20 percent being a theoretical upper bound for the kind of boiler pressures and for the non-condensing cycle.  Electric power generation runs in the 30-40 percent range, using condensing cycles, insane boiler pressures, high superheat, and compound expansion in turbines running at near steady-state conditions.

The thing about the steam engine and dwelling on the thermal efficiency, it was a good system back in the day.  The cost of labor can be thought of negatively as men wearing out their backs shoveling coal and men getting black lung or worse working in mines.  Or the cost of labor could be thought of as men having paying jobs to support familes.  However you view it, the system was that you dug what were otherwise worthless rocks out of the ground (lumps of coal), fed them into steam engine boilers, and carried people and goods around.  It was an effective system as it carried a lot of people and goods around that would have otherwise stayed put.  The moving of people and more importantly of goods, especially food, was transformative in way that is now hard to imagine.

The other thing about the thermal efficiency is that according to Porta, if you optimized the design of the conventional steam locomotive (what he called Generation 0) to produce Generation 1 -- pretty much the same boiler pressure and non-condensing, just better insulation, steam passages, and valve events -- you could at least double the efficiency, in the process cutting water and coal consumption in half.  That may have been enough to keep steam around for another 10-20 years, but after that, hey, they have replaced all of the steam powerplants on boats and ships with Diesels as a labor saving measure if nothing else.

[jfallon]

It would have to be a very well designed and built steam locomotive to get more than 7 or 8% efficiency. Very little of the energy prouced from combustion is turned into mechanical force, most of it goes up the stack. Even condensing steam engines, such as those used in power plants and on ships, have to release a majority of the heat energy in the condensing process.

     Internal combustion is somewhat more efficient, but still more energy is thrown off as heat (through the radiators) than actually turns the wheels.

                                                               John

[JimValle]

Using statistics collected during the early 1940's, the Santa Fe Railroad measured the efficiency of their fleet of steam locomotives in comparison with the FT units that they were just putting into service in significant numbers.  They determined that the cost of a ton of oil fuel used in steam engines was $ 5.04 and yeilded 20.37 train miles system wide on average.  Diesel fuel cost $ 11.61  but produced 133.13 train miles per ton.  In effect, diesels ran six times as far as steamers utilizing fuel that cost only twice as much.  This was due to the much better thermal efficiency of diesel engines compared to steam.  Persumably the trains used as a milage standard were 4000 ton freight consists  which was the normal tannage l at that time.

[LNER4472]

Scraping some random cites from Albert Churella's "From Steam to Diesel" (1998, Princeton University Press):

By the late 1930s, RR executives said diesel could reduce fuel costs for RRs by 75%.  Diesels could run further between refuelings, did not need water (a serious concern for railroads like the SP and Santa Fe in Arizona and New Mexico), and one tank car of diesel fuel was said to pack the equivalent of eight hopper cars of coal, thus reducing transport costs.  One railroad executive said the cost of new fueling facilities could be paid for just from eliminating the hopper car fleet needed to haul locomotive fuel.

Horsepower and tractive effort: at ten mph, a 600-hp diesel switcher provided more actual tractive effort than a 2,000-hp steam locomotive, while a 6,000-hp steam locomotive produced 135,000 lbs T.E compared to a 6,000-hp diesel packed 230,000 lbs. T.E. at the same speed.  This led to the adage that a steamer could move a train at speed that it couldn't start, while a diesel could start a train it couldn't hustle.

I've heard various figures over the years cited for the outright thermal efficiency of steam and diesel locomotives.  Suffice it to say that 8-10% for steam is probably realistic, with a "pie in the sky" (or "what are you smoking?") figure of 20-25% sometimes cited.  Diesel, on the other hand, would muster 20% on a bad day, with 30-45% being equivalent "wishful thinking".  So even in worse case scenarios, you're looking at double the output per BTU for diesel.

[trime1851]

Yes, economics doomed the steam locomotive.

I still think they are great!

It's sad that Norfolk Southern destroyed their excellent steam excursion program in 1994.  It was a truly a flawed and short-sighted decision to save a minor amount of money and lose a tremendous amount of publicity and good will.  Shame on you Norfolk Southern Management!

 

 

[JamesP]

To put a finer point on cost, let's take a look at a coal burning steam engine vs. an infernal combustion diesel locomotive.  I am using a retail cost of $15 for 50lbs of coal and $3.30 for a gallon of diesel.  The coal I priced has a BTU content of 14373 BTU's / lb, so we get 47190 BTU's per dollar spent on coal.  Diesel has 147,000 BTU's per gallon, so we get 44545 BTU's per dollar spent on diesel.  Using efficiencies of 10% for steam and 25% for diesel, we get 4790 BTU's of work for every dollar spent on steam locomotives vs. 11136 BTU's of work for every dollar spent on diesel locomotives.  Add in labor and maintenance costs, and it's easy to see why railroads were eager to dieselize.  Modern technology could probably replace the fireman, as well as easing some of the maintenance requirements.  However, the efficiency of the steamer would have to be raised significantly to make it cost effective against the diesel locomotive. 

 - James

 

[selector]

Is the price of $15/50 lbs of decent coal what it really costs today?  How would the numbers have crunched in 1946?  Was the price ratio roughly the same?

Crandell

[ndbprr]

Since the last steam engine is early 50s technology thereis no "current" comparison.  Only speculation.

[Paul Milenkovic]

ndbprr

Since the last steam engine is early 50s technology thereis no "current" comparison.  Only speculation.

 

Speculation, yes, along with a detailed design study from the last living "great steam engine designer" David Wardale http://www.5at.co.uk/.  The claim is that one could squeeze out 14 percent thermal efficiency by careful design of a "conventiona Stephenson-pattern" non-condensing steam locomotive.

As to the high coal price, if you are buying coal in small lots for live steam operations, I guess that is what you would have to pay.  Even with the runnup in coal prices, however, a major user of coal would work out some supply arrangement and much lower prices.

[JamesP]

selector

Is the price of $15/50 lbs of decent coal what it really costs today?  How would the numbers have crunched in 1946?  Was the price ratio roughly the same?

Crandell

The price I quoted is indeed retail for small quantities intended for the live steamer or blacksmith.  Certainly, a railroad would negotiate a much cheaper price for large amounts of coal, just the same as they negotiate a much cheaper price for diesel fuel than the price per gallon that I quoted (from our local filling station - including road taxes).  I was just using some easily attainable retail numbers as a reference.  To get an accurate comparison in today's market, we would need to know what price per gallon large railroads have recently contracted diesel fuel for as well as a bulk price per ton of coal, perhaps from a large utility.  I'll have to do some more research to see if those numbers are readily available, as well as numbers from the transition era... when I get some free time later tonight!

 - James

[JamesP]

OK everyone, let's chalk this up to "The more I learn, the more I find out how ignorant I are!"  The only place I could find definite bulk pricing information, with somewhat current figures, was the U.S. Energy Information Administration's website.  The information I chose from there (which may or may not be the proper choices) was Central Appalachia coal, 12,500 BTU's per lb, $71.15 per short ton for a total of 351,370 BTU's per dollar (I know, PRB coal is cheaper, but for goodness sakes it has the BTU content of peat...can you say Wooten Firebox?).  For diesel fuel, I chose low sulfer no. 2 that was sold directly to non-highway end users for $2.31 per gallon for a total of 63636 BTU's per dollar.  These were based on late 2010 prices.  At the previously assumed effieciencies of 10% steam/coal vs 25% diesel, we would get 35137 BTU's of work per dollar out of coal vs 15909 BTU's of work per dollar out of diesel, over 2:1 in favor of steam... but hold of the celebrations for a moment.  For some reason, the government calculates the price of diesel as an average that includes transportation.  No such luck on the spot price of coal - as far as I can tell - so we don't know if transport costs would increase the price of coal so much as to tip the scales to diesel.  For what it is worth, diesel has 20137 BTU's per pound vs coal's 12500 BTU's per pound, which would indicate (based on weight) that coal might cost 61% more to ship than diesel.  This would not even reflect any difference in price based on ease of handling of diesel vs. coal.  I have no way of calculating a shipping cost for either coal or diesel, so I can't make an apple to apple comparison.  No doubt about it, the professional bean counters at the railroad would know the exact price of each commodity delivered on location and would be able to make a better comparison than the barnyard guestimate that I have scribbled out.  I suspect that with fuel transport and locomotive maintenance costs figured in, the diesel would still be the economic winner in today's market... otherwise we would have the ACE3000 polishing the rails!

And I never did find any definite prices for coal and diesel from the transition era...

My brain hurts... does anybody have any aspirin? - James

[schlimm]

Not really sure, but I think I read that Diesel fuel back in the 50's was cheaper than gasoline, so maybe it would have been relatively cheaper in your calculations than now.

[Paul Milenkovic]

schlimm

Not really sure, but I think I read that Diesel fuel back in the 50's was cheaper than gasoline, so maybe it would have been relatively cheaper in your calculations than now.

The story back in the "Steam-Diesel Transition Era" was that oil was being discovered/developed in Saudi and the US hadn't reached it's 1970 Hubbert Peak, and the United Mine Workers were flexing their muscles with regard to the mine workers getting better pay for the dirty dangerous work they do.  Oil was particularly cheap compared to now, and it seems with the low price of oil and the much higher thermal efficiency of Diesel engines, Diesel locomotives had a clear fuel cost advantage over steam.

At the time of the ACE 3000 project -- what was that, mid '70's in response to the 70's Oil Embargo and Middle East tensions -- I believe that a mid teens thermal efficient coal burning steam locomotive had a clear fuel cost advantage over a Diesel locomotive.  Even a 5 percent efficient steam engine (the ACE people tested a Northern) had a slight fuel cost savings over Diesel at that time.

Today, the price of coal is increasing along with many other things, but the price of oil in inflation-adjusted terms is not too far off from conditions in the 1970's -- early '80's.

The other thing to remember about the ACE 3000 project is that when was this, early '70's, and when did Norfolk and Western drop the fire of the last mainline steamer, 1960?  Yes the railroads were thoroughly Dieselized and the thought of bringing coal-fired steam back -- think of Don Oltmann's shop foreman thinking the best thing to do with a locomotive boiler was to fill it with cement so it could not be put in service and have a boiler explosion accident.  But there were probably enough old-timers around the railroads to make this steam thing work, if that was the direction.

Today, we are 40 years away from the ACE 3000, 50 years since the end of steam on N&W, 60 years since when the railroads pretty much pulled the plug on steam.  During the steam-Diesel transition, the railroads were "investing" in a hodge podge of 1st Generation Diesels with various levels of maintenance expense.  By the ACE 3000, they were competing with the SD-40 and later SD-40-2, perhaps the most "bullet proof" locomotives known to mankind, steam or Diesel.

Ah steam!  The dream doesn't die.

[Firelock76]

Just my quick two cents worth:  In the early 50s the Lackawanna was running commuter trains in New Jersey and surprisingly finding them cheaper to run using steam engines rather than diesels.  The Erie was getting the same results.  What pushed them over the edge to complete dieselizaton  was a series of coal strikes from the late 40s through the early 50s.  Who ever heard of a strike in the oil business?  And of course diesel fuel was abundant and dirt cheap.  I can't blame the miners for striking, though, few groups of people have been so consistantly been treated so poorly.  One thing's for certain, everybody loves steam except railroad management!

[richg1998]

Sulfur content in coal would prevent going back to steam in the USA. Much of USA coal is shipped to China which has no emission restrictions because the USA coal has higher sulfur content.

A coal fired power plant not far from me gets lower sulfur coal from China via a port in RI. And they still  need stack scrubbers to comply. Stack scrubbers on steam locos, never happen.

Rich

[Paul of Covington]

    All this talk of relative fuel costs of diesel vs steam brought to mind an article in TRAINS in the early 90's, I think, about N&W's tests when EMD had loaned them four F's to try out.    I've been looking for that issue, but haven't found it yet.    ( I guess I need that DVD).    N&W found that they could haul more tonnage for less fuel cost with a Y6b than with the F's.    The article mentioned that N&W had tweaked the Y by boring out the cylinders a little and increasing the boiler pressure to 315psi.    However, EMD had also tweaked their units, so that the horsepower was higher than standard.    Of course, being a coal-hauler, they probably got their coal at a pretty good price.

[AltonFan]

Something to keep in mind about railroad coal:  railroads often didn't use decent coal.  A lot of the time, railroads were using the leftovers of the grading process.  Even when oil was used, Bunker C originated as a waste product of the refining process.  How would thermal efficiency and maintenance been improved if railroads had been picky about fuel?  (Of course, being particular about fuel would have raised the price of the fuel.)

 

[selector]

To me, thermal efficiency would be maximized by generating no more heat than would be required to sublimate liquid water for demand use in cylinders that were insulated with about R20 factor, and the cylinder exhaust should have been condensed and fed back to a feedwater heater/pump. Better ones.

Even the waste heat up the stack should have been scavenged more than it ever was.  It should have been expelled with a small jet of steam when the smoke was taken down to about 60-80 degrees.  How one would achieve all these things in a machine under 260 tons is beyond me.  Maybe towing a special radiator car, or a heat-echanger car.   Weighing 30 tons or less.  How that would work with 6000 trailing tons I dunno.

Steam beeth dead.  Long liveth steam.

[BigJim]

The article mentioned that N&W had tweaked the Y by boring out the cylinders a little and increasing the boiler pressure to 315psi. 

Aw gee whiz! Not this falsehood again. Let me guess the author. Is it the same guy that proclaimed that there was a super Class A? LeMassena.

[AnthonyV]

Paul of Covington

    All this talk of relative fuel costs of diesel vs steam brought to mind an article in TRAINS in the early 90's, I think, about N&W's tests when EMD had loaned them four F's to try out.    I've been looking for that issue, but haven't found it yet.    ( I guess I need that DVD).    N&W found that they could haul more tonnage for less fuel cost with a Y6b than with the F's.    The article mentioned that N&W had tweaked the Y by boring out the cylinders a little and increasing the boiler pressure to 315psi.    However, EMD had also tweaked their units, so that the horsepower was higher than standard.    Of course, being a coal-hauler, they probably got their coal at a pretty good price.

 

The title of the article is "N&W's Secret Weapons" from November 1991.

Anthony V.

[Firelock76]

Gets back to what I've said on other Forum posts.  N&W only went diesel because they were ordered to by the Pennsy, who held controlling interest at the time.  I'm sure they realized diesels were coming eventually but they just weren't in any rush. 

[feltonhill]

Hi Big Jim,

Yup, same guy that not only created the Y6c out of thin air and lots of factual errors, but also the A1.  N&W never had any such classes and they didn't need to.  This stuff will never die!!!!  See Trains Nov 1991 and the  response of someone who participated in the steam vs diesel tests in the May 1992 issue (only a portion of his letter was published.).  There were also two lengthy articles rebutting this nonsense  in N&W Historical Society's magazine The Arrow, one by the same person that participated in the tests and another by a disinterested party that came to the same conclusions.  There were no such alterations, and no reason to make them.

[Paul of Covington]

       Sorry about my last post.    I guess I missed the May '92 letter.

    But were the results on fuel cost comparison correct, or was that part of the myth, too?

[CSSHEGEWISCH]

Firelock76

Gets back to what I've said on other Forum posts.  N&W only went diesel because they were ordered to by the Pennsy, who held controlling interest at the time.  I'm sure they realized diesels were coming eventually but they just weren't in any rush. 

A 33% interest in N&W is a controlling interest only if you can persuade enough other shareholders to agree with you.  Anyway, as mentioned elsewhere, N&W was running into the position of being able to operate steam locomotives efficiently but no longer being able to maintain them properly because of parts unavailability. 

[feltonhill]

The steam vs diesel test report is available at the N&WHS archives in Roanoke.  There is no mystery to it.  All of the findings are documented including cost comparisons.  I've been through the report page by page many times over the past 15 years or so and keep a copy here. The person I referred to above that participated in the tests comes to almost every archives work session.  His memory is sharper than most people half his age.  On top of that, he kept a diary of the events he saw during the individual  tests where he had a role.  You can't get much better than that.   That's why many of us can't understand where that article came from.  The conclusions are not supported by the historical  information available.

[Paul of Covington]

    Okay, I've overcome my embarrassment enough to thank you all for setting me straight.    All these years I've accepted the story about the enhancements as fact even though I thought it curious that I never found it mentioned anywhere else.     

[oltmannd]

Paul Milenkovic

 

schlimm:

 

Not really sure, but I think I read that Diesel fuel back in the 50's was cheaper than gasoline, so maybe it would have been relatively cheaper in your calculations than now.

 

 

The story back in the "Steam-Diesel Transition Era" was that oil was being discovered/developed in Saudi and the US hadn't reached it's 1970 Hubbert Peak, and the United Mine Workers were flexing their muscles with regard to the mine workers getting better pay for the dirty dangerous work they do.  Oil was particularly cheap compared to now, and it seems with the low price of oil and the much higher thermal efficiency of Diesel engines, Diesel locomotives had a clear fuel cost advantage over steam.

At the time of the ACE 3000 project -- what was that, mid '70's in response to the 70's Oil Embargo and Middle East tensions -- I believe that a mid teens thermal efficient coal burning steam locomotive had a clear fuel cost advantage over a Diesel locomotive.  Even a 5 percent efficient steam engine (the ACE people tested a Northern) had a slight fuel cost savings over Diesel at that time.

Today, the price of coal is increasing along with many other things, but the price of oil in inflation-adjusted terms is not too far off from conditions in the 1970's -- early '80's.

The other thing to remember about the ACE 3000 project is that when was this, early '70's, and when did Norfolk and Western drop the fire of the last mainline steamer, 1960?  Yes the railroads were thoroughly Dieselized and the thought of bringing coal-fired steam back -- think of Don Oltmann's shop foreman thinking the best thing to do with a locomotive boiler was to fill it with cement so it could not be put in service and have a boiler explosion accident.  But there were probably enough old-timers around the railroads to make this steam thing work, if that was the direction.

Today, we are 40 years away from the ACE 3000, 50 years since the end of steam on N&W, 60 years since when the railroads pretty much pulled the plug on steam.  During the steam-Diesel transition, the railroads were "investing" in a hodge podge of 1st Generation Diesels with various levels of maintenance expense.  By the ACE 3000, they were competing with the SD-40 and later SD-40-2, perhaps the most "bullet proof" locomotives known to mankind, steam or Diesel.

Ah steam!  The dream doesn't die.

Ross Roland was making the rounds with his ACE3000 model in 1979 or 1980.  The office sent me to his presentation.  I was the new guy.  None of the old "steam guys" wanted to go.  This already tells you how important they thought it was....

But, I was excited to go.  

Here's what I remember taking away from the presentation.  The ACE3000 was an attempt to construct a state of the art steam locomotive with diesel locomotive availability.  Not reliability.  Availability.  They were going  to do it by making the components modular.  Great.  That doesn't make them reliable, just easy to swap out.

One of the components was the cab.  Theoretically, the cab could be "unplugged" and a few air connections undone, and it could be lifted out.  The current isolated cabs are built this way, yet no one I know is swapping them out for trouble.

Some other things I remember.  The condensing tender.  Big condensing radiators with fans power by the low pressure steam (or hot water? I don't really remember)  Exactly how reliable was this going to be?  I remember at the time thinking about how we couldn't keep SD45 radiators from leaking all over the place, and they were only 8 row soldered core running just hot water.  Wheelslip control.  IDAC/WS-10 plus HTC trucks had gotten reliable adhesion up close to 20% and Super Series wheel creep control was just around the corner.  The ACE3000 was going to automate wheelslip control.  All that rotating equipment?  How exactly is would work out was anybody's guess at that point.

The Dash 2 locomotives running around at the time were the product of 30 years development at that point, and they were extremely reliable.  The ACE3000 was to be a large collection of new or nearly new technology, almost none of it RR hardened or perfected.  Add in that, at 300 tons, it would only do the work of a 140 ton locomotive.  It looked like it could eat you alive in maintenance and development.  A risky proposition at a time when the scarce capital was going to very, very low risk investments, like rail and ties.

[Firelock76]

33% is controlling interest if you're the majority stockholder.  Besides, why do you think N&W's passenger coaches were painted Tuscan Red?

[Paul Milenkovic]

oltmannd

Some other things I remember.  The condensing tender.  Big condensing radiators with fans power by the low pressure steam (or hot water? I don't really remember)  Exactly how reliable was this going to be?  I remember at the time thinking about how we couldn't keep SD45 radiators from leaking all over the place, and they were only 8 row soldered core running just hot water.  

Yeah, well the temptation is to go with a condensing "tender" because of not needing the watering stops and the more thermodynamically efficient cycle and the need to not worry about hard water.  I have come to accept that a condensing steam cycle without access to a cooling pond, however, is the wrong way to go.  Not that this would have answered your objections, Don, but I believe Livio Dante Porta was trying to pull the ACE 3000 team back from the abyss by trying, as their first effort, to simply build a better non-condensing steam engine as their first effort.

With respect to Diesel reliability, that had to have been developed over time and didn't start out as a given.  I believe the EMD 567 engine was something of a breakthrough as whatever Winton engine they had -- wasn't the story that the pre-war Winton-engine E units had technicians riding in the engine compartments to make repairs underway?  Or is this part of the mythology of railroading?

One other thing about Diesel reliability, I had been reading late-50's vintage railroad trade magazines in the Engineering College library at the U.  I can go look up what the magazine title is, but it had a monthly column on the Mysterious Diesel Problem of the Month.  A steam engine is essentially a big tea kettle -- keep a fire going, keep water in it, keep the bearings oiled, keep the flues unplugged, and the thing pretty much runs.  The Diesel had a complex electrical system -- it was anybody's guess why a Diesel wouldn't run or wouldn't "load up."

If one would indulge me with one last question regarding what could have been done to keep steam going.  The ACE 3000 was probably a Bridge Too Far with its condensing cycle and most certainly a Bridge Too Late what with Diesels being into their second and third generation and having solutions to the aforementioned problems -- the Dash 2 modular electrical cabinet?

The Jawn Henry was also a Bridge Too Far with mating an electric drive to a steam turbine.  But Jawn Henry must have been a non-condensing cycle -- I believe the coal bunker was in the front part of the locomotive portion, but it pulled a water tender?  And Jawn Henry had a non-conventional boiler -- some kind of Babcock and Wilcox 600 PSI water tube affair that was considerably more compact than the massive steam engine boiler?

The Jawn Henry had its turbine knocked out of wack in a hard coupling impact, and it was said to have had trouble with coal dust or leaking water getting into the electrics.  Not much has been said about its boiler.  Was that part of it reasonably successful, to go to a more compact water-tube boiler with higher steam pressure, getting some increase in thermodynamic efficiency (although not the full effect of having a condensor), perhaps mitigating the hazard of boiler explosion by not having that massive amount of water at the boiling temperature.  Could that boiler have been mated to a conventional steam locomotive?  Or was Jawn Henry in service for such a short time and having that many other problems that we never learned if that boiler worked out?