The Cost Savings of Steam Today.

NW Mailing List nw-mailing-list at nwhs.org
Tue Jan 15 10:11:33 EST 2008



"Simple questions" from a layman-lawyer neither an engineer nor a physicist
(and questions that are, I suppose, very elementary from a professional
engineer's standpoint):

What are the cost factors of running steam vs. running diesels aside from
the inherent cost-efficiency of the diesel engine itself vs the efficiency (or
lack thereof) of the steam engine itself? That is to say, what non-engine
indirect factors enter into the equation, such as maintenance of
coaling/watering facilities, labor costs, and other factors/facilities related to steam
operations that are absent from diesel operations?

In a long passenger run - say the Powhatan Arrow - from Norfolk to
Cincinnati, was it necessary for the J and its tender to be serviced (coaled and
watered, lubricated, etc.) at one or more points along the run? And was more than
one J used for the run, or did just one J suffice?

When a diesel engine powered the Arrow did it require stops for servicing
along the way?

Assuming that the Arrow had been a true "express" non-stop train running
from Norfolk to Cincinnati, and assuming further that either one steam engine or
one diesel engine was able to make the run without even one servicing stop,
which engine would prove out to be the more "efficient" of the two, given
today's oil-vs-coal costs?


>From a beady-eyed cost-accountant's standpoint, is there any real way to

bring cost-efficiency standards for a modern steam engine up to those of the
modern diesel, all operational elements being considered?

In short, is a "return to steam" merely a pipe-dream?

John Carnahan
Columbus



In a message dated 1/14/2008 5:38:11 P.M. Eastern Standard Time,
nw-mailing-list at nwhs.org writes:


John:
Yes, And yes, that is what I said. The diesel engine will always be more
thermally efficient, but it is the total system efficiency that is the
important value. Also, the life cycle cost- development, implementation plus
continuing maintenance/ up-keep and operating costs- is the value that must be
worked with.
The hassle is that in introducing new technology the above factors don’t
have known and reliable values. Thus, getting a company or society to adopt the
new technology is difficult as the risk cannot be accurately assessed and
the true future cost determined. Societies and companies are almost always
conservative.
Gary Rolih
Cincinnati






____________________________________

From: nw-mailing-list-bounces at nwhs.org
[mailto:nw-mailing-list-bounces at nwhs.org] On Behalf Of NW Mailing List
Sent: Saturday, January 12, 2008 10:37 AM
To: NW Mailing List
Subject: Re: The Cost Savings of Steam Today.
Gary,

Have you read the paper? With the massive cost difference between Coal and
Diesel fuel, the steam locomotive can have lower thermal efficiency and still
be cheaper. The number I quoted in the email i originally sent was based
on steam locomotives having about 10% thermal efficiency compared to diesels
running at 25-30% thermal efficiency depending on type. Steam locomotives in
service in other countries have exceeded the thermal efficiency I used for
the locomotives in my comparison.

John Rhodes.

On Jan 11, 2008 6:26 PM, NW Mailing List <_nw-mailing-list at nwhs.org_
(mailto:nw-mailing-list at nwhs.org) > wrote:




Guys: No matter what, physics still dictate the overall thermal efficiency
of the diesel cycle and thee steam locomotive cycle. The thermal efficiency
is a function of the temperature difference achieved when expanding the gas
in a cylinder from te beginning of the cycle to the end. In this case,
burning inside the gas to be expanded in the cylinder (diesel and about 5000F) and
burning outside the gas to be expanded (steam locomotive and a steam inlet
temperature of about 800F after transferring to steam in a boiler) gives the
advantage to the diesel for thermal efficiency FOREVER.
The conversion efficiency of each type ultimately matters: i. e. steam
requires burning coal which burns at a high temeperture (roughly 4000F), heat gets
transferred to water in the boiler with a lot of losses, losses in heat and
pressure in flowing the steam through the piping, parasitic losses when
taping steam off to run electrical turbines, feed water heaters and so on.
Diesels have similar conversion issues.
Turbines can be very efficient, but the meaning of this is that the flow of
gas through the turbine blading AT DESIGN CONDITIONS can transfer most of the
energy in the gas ( heat energy, kinetic energy and pressure energy) to the
blades as mechanical work very, very well. However, "part throttle"
operation means that the flow is not at the design conditions ( the vectors of the
flow of the gas are not at the optimum direction) and the transfer of energy is
much, much less efficient. ( think of the turbine blades as little wings
that are forced to take different angles of attack from the on-coming gas
flow; at part throttle, little wings don't work very well at all at the wrong
flow angle- they can stall!) Turbine can be as much as 98-99% efficient with
repect to capturing the energy in the flow. Off design, the efficiency can
drop significantly to levels as low as 30%. But what about the rest of the
system needed to make steam for the turbine? How efficient is that?
Could steam be used today again in a profitable and efficient way?
Probably not, the conversion cycle is not very efficient and the opportunities to
make improvements in it are not good ones.
Coal fired turbines? Tried for years, but burning raw coal in the gas
stream has always caused serious slag issues in the combustors. The slag either
erodes away turbine blades or coats the blades and ruins the wing shape. This
is a virtually intractable problem. The coal needs to be refined to get rid
of the slag products--- which leads one right back to refining petroleum to
make diesel fuel or converting coal to an oil in another refining type cycle
(the Nazis did it but it is an expensive and inefficient process). And
turbines lead right back to the off-design issues at part throttle.
While a cycle or an energy conversion process can be proposed, the devil IS
in the details. Developing a process to work reliably, economically and
environmentally acceptably take a whole bunch of time and money. Then you have
to get the entire world to adopt this way of doing business.
Ed and Harry are right to voice skepticism at this early stage. Adopting
new technology and getting it into place is a very, very difficult process.
The internet was invented in about 1970- 37 years ago- and only part of the
human race has access to this today.
Gary Rolih
Cincinnati





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