Steam better than diesel - New Scientist

[Peter Ware <pware@ozemail.com.au>]

In the few years that I have been "lurking" in this newsgroup, I have
noticed the odd posting about steam making a come back. These postings
have often appeared very early in April giving considerable doubt to
their authenticity.

However, this weeks issue of the prestigious magazine "New Scientist"
(17 July) contains a well written feature article on this very subject.

Engineers at the Swiss Locomotive and Machinery (SLM) company have not
only designed, built and tested a truly modern steam locomotive, but
they have so far sold eight of them as working revenue earning units.
The locos, all oil fired, are designed to work on the steep mountain
lines in Switzerland and Austria were they out perform their diesel
rivals. Their purchase cost is about 20% lower than equivalent diesel.

The design incorporates modern features not found in the steam dinosaurs
of yesteryear - features such as all welded construction for the boiler
and cylinders, advanced lighter metals and other materials, a highly
efficient fuel injection system, fully sealed roller bearings, and
better modern insulation around the boiler. In fact the boiler
insulation is so good that after leaving it switched off overnight, over
half the boiler pressure is still present the next morning.

The performance figures quoted in the article reveal that in thermal
efficiency (converting heat to motive power) the diesel is still well
ahead of steam but in fuel consumption per passenger, a more realistic
measure of efficiency, the steam engine could equal the diesel on some
services. But the lower fuel costs for the oil fired steam engine tips
the economic balance in favour of steam even in situations where diesel
is more efficient.

But the area where it really stands out is, surprisingly, in pollution
emissions. Slightly higher sulphur dioxide emissions are the only
penalty of the steam engine they have designed but even this can be
reduced with some tinkering with the fuel chemistry. In emissions of
carbon monoxide the steam engine is significantly lower but in the
emission of highly damaging Nitrous Oxides, diesel is nine time worse.
The engine is hardly the "moving smokestack" that is often envisioned
when the term "steam locomotive" is used.

Despite all this, the prospect of using steam as a serious motive power
is met with derision by most railway engineers. The articles author
states that "most railway engineers nowadays do not have enough
knowledge of steam locomotives to be able to judge the possibilities".
While it does not claim that steam should replace diesel, it does make a
good case for looking at the economics and efficiencies of modern steam
in some situations.

Peter Ware