"John Williamson" wrote in message
...
Doctor Drivel wrote:

"John Williamson" wrote in message
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Yes, and also at constant power, given the direct coupling to the
propellers. The makers all state 60 - 200 rpm as the operating speeds,
though, without mentioning efficiency at the lower speeds. Even in the
1950s, they were doing over 40% thermal efficiency at best speed/ power,
and are now up to 54% for the best of them. Train diesels aren't all
that far behind, which leads to the interesting thought that unless
you're generating your electricity by nuclear power, a diesel locomotive
may well generate less pollution overall than an electric one.

Highly unlikely.You also have soot and they pollute where people are.

Please read what I wrote, not what you wish I'd written. *Overall*
pollution from a diesel train may be less than *overall* pollution from an
electric train. Fuel efficiency from fuel supply to wheel in a diesel
train is better then fuel efficiency from fuel supply to wheel on an
electric train, especially in this country, where a sizeable proportion of
the electricity used is generated by burning coal.

You are wrong. A diesel train "may" get 40% efficiency. Power stations are
at just over 50%. Line losses are less than 10%. You have also got to cost
in the transportation of the diesel fuel to the depots, refining,
maintaining a large fleet of diesel engines, the cost of making all these
diesel engines, etc. A gas powered power station easily beats on efficiency
in "fuel burn" to wheel. A nuclear station is even better.