I have a great 1940's vintage book (A Practical Evaluation of Railroad Motive Power, by P.W. Kiefer 1948) comparing steam, diesel and electric for the New York Central. They were looking at cost of operation. The fuel cost was comparable then. So thermal efficiency was not the issue. Most of the maintenace was scheduled out-of-service time that cut the availability and added shop and labor costs. So the boiler washes and retubes and ash dumping cut the locomotive's availability and showed up as a disadvantage for steam.
Now, even with the current relatively low price of diesel, coal is cheaper from a fuel cost standpoint. Eg: Today's Nymex heating oil future is $1.48/gal, probably less than delivered off-road diesel since it does not have guaranteed cetane rating and it's wholesale. At, say 30% efficiency of a diesel-electric (there is conversion loss from prime mover to electric back to mechanical...don't know exactly how much) and 130,000 BTU/gal, and assuming 6% for superheated steam loco with no feedwater heater or other modern stuff, and 12,000 BTU/lb coal we have:
($1.48 / gallon)*(1/1.3x10^5 BTU input /gal)*(100 BTU input/ 30 BTU output) = 3.79 x 10^-5 $/BTU output.
Using that to convert to equivalent coal cost for coal-fired steam:
(3.79x10^-5 $/BTU output)*(6 BTU output/100 BTU input) * (12,000 BTU input/lb)*(2000lb/ton) =$54.65/ton
This is more than the current cost of coal.
This will go to a drastic advantage for steam/coal when there is an oil price spike or if we have another embargo.
But now there are many other considerations. From a railroad perspective, the diesel's MU capability and the lack of need for firemen makes the operating crew of a locomotive one person. No one has automated steam to that level, although it is technically quite possible.
Now we also have to worry about global warming and the desire to cut carbon emissions. Here a coal-fired steamer is at a real disadvantage.
But my interest is not in fossil fuel firing. My interest is in renewable biofuels, which are generally considered separate from fossil carbon global warming.
So how do we compare biofuel powered steam to other biofuel powered trains? This gets much harder than simple fuel costs.
Probably the best and ultimate train solution is electric. This can take advantage of any power source. However, there is a huge infrastructure cost. In 1980 the BN calculated $1M/mile. That would probably be triple now. And catenary has a huge and unpredicible maintenance requirement. Thermal efficiency of a steam plant and transmission (eg 30% with 50% line and conversion loss would still give 15%...higher than the best reciprocating steam) should be better for electric, although it would require moving the fuel to central power plants.
It is also possible to make synthetic diesel from biomass. This would require some more r&d (it has been figured out for coal eg Sasol but biomass material will have other challenges) and a very expensive facility. The wild ball-park figure for coal is 50% loss to liquify. If this works for biomass then the efficiency would end up like the electric, once again with huge infrastructure cost and in this case partly unproven technology.
So I can't claim to compete on an efficiency basis. However, wood- and biofuel-fired steam is available right now. Pelletizing and fuel desifying equipment is available, and old-fashioned cordwood is available. There are two Chinese QJ 2-10-2's in Iowa looking for work. Dare we hope?
Copyright © 2007 Charles Turner