So we have more complexity for not very much return. And how is this supposed higher efficiency calculated?
Everyone has opinions and opinions do not matter. Well, they do in politics and stuff, but...
When you are dealing with engineering and process systems, systems operations etc., the data has to be what counts.
So firstly, there are numerous NG conversion options being studied. One is 10% Diesel plus NG injection so no spark plugs. In this are low pressure late-stroke injection or early stroke high pressure injection. There are also dual-fuel but pure NG options.
Separate and apart from a future transition to a next-gen fleet which is gas-turbine.
Also - locomotives are NOT diesel driven. The traction motors are electric. Locomotives are deisel-electrics, just like all modern drilling rigs are. They are not gears/chains/transmissions mechanical drive systems.
SO all modern locomotives MOVE using electricity. The issue is where does the electricity come from.
Most high-speed rail uses overhead lines, but some have also used gas-turbines to generate the electricity. And he diesel electric trains, obviously, use diesel engines to power generators to make the electricity that the traction motors use.
Another factor is that using natural gas for transportation fuel on long-haul commercial applications such as rail and over-the-road trucks directly reduces the need to import oil for fuel. Great on one primary front. The money stays in the US, taxes are paid in the US, dollars are not exported from the US. Even if the cost was exactly the same, we would be better off using US-based fuels and not imported fuel stocks.
Also, LNG is storing liquefied natural gas in insulated tanks. It is not the same as storing natural gas under pressure, which is CNG. So there are some pretty big differences there. Of course the proper safety technology has to be incorporated.
The issue of hauling the fuel is a non-issue. 1-2-3 cars of LNG, versus XX tons of diesel, in a mile-long train, just really doesn't matter. This aspect is in the weeds.
1 million BTU = 12.1 gallons LNG = 42.4 lbs LNG
1 million BTU = 7.2 gallons diesel = 51.5 lbs diesel
Diesel - less volume to carry but more weight vs LNG.
Just in the case of a spill, LNG is not nearly as dangerous as CNG. It is not an explosion hazard It is more like diesel. It has to boil to make vapor, so it doesn't explode. CNG will quickly expand to a vapor cloud, just like propane etc. will, that can explode. But not LNG.
You can extinguish a pool of burning LNG with chemical extinguishers, but you NEVER EVER EVER put water on an LNG fire. That just makes the LNG boil and vaproize faster. Safer to just let it sit there and burn out. And of course LNG is smoke-free as it burns, NOT like diesel.
Experience with CNG conversions show the burning natural gas instead of gasoline reduces engine wear and maintenance issues, and increases lubricating oil life dramatically.
As far as switching from nukes in Europe and going to coal instead? They have to buy most of their natural gas from Russia at some high prices and with some degree of uncertainty in delivery, where the coal infrastructure is again already in place. They have yet to expand natural gas production by using the new technologies.
2011 Natural Gas Production Statistics
Russia - 669 billion M^3 (bcm)
USA - 651 bcm
European Union - 167 bcm
Canada - 160 bcm
“Since (its development began in 1998), natural gas from shale has been the fastest growing contributor to total primary energy (TPE) in the United States, and has led many other countries to pursue shale deposits. According to the IEA, the economical extraction of shale gas more than doubles the projected production potential of natural gas, from 125 years to over 250 years.[26]”
So I am not saying this or that or the other is going to be the best way to use natural gas...
BUT it clearly is worthwhile to begin seriously looking at how to use natural gas options for long-haul transportation such as the railroad and trucking industries in North America.
Not huge complexity. Having duplex injection doesn't add all THAT much. And I suspect the efficiency was measured rather than calculated. But I haven't studied up all that much on the dual-injetion case...it is just something that I ran across while reading about other subjects.