Hydro-Electric locomotive??

Well, sure it's possible. You just have to decouple the hydro and the electric parts. You have a hydro plant generate the electricity, then you supply it to the engine as electric power to run the motors.

.... unless you can't GET electric motors, in which case you use the electricity to heat water to make steam to drive the piston to turn the crank to run the wheels.

.... which may sound ridiculous, but there was at least one of these built during WWII because they had hydropower, catenary, and a disused steam engine.

The important point about using water for power in a mobile situation is that you cant compress water . so a 10 gallon container holds 10 gallons of water , no matter what pressure it is under . ( this is why water is used to pressure test things such as steam boilers by the way ) .if you used air on the other hand , a 10 gallon container could hold 100 gallons of air , if it was pressurised to 10 times its normal pressure ( probably a square thing happening but for e.g ) . so you could have a compressed air powered loco , indeed there are air powered cars around .

Otto Vondrak wrote:

steamal wrote:Would it be possible to design a hydroelectric locomotive?

It seems the answer is "No."

Guess not. Oh, well. I guess electric locomotives will always have to have an external power source (3rd rail or catenary) to work.

steamal wrote:

Otto Vondrak wrote:

steamal wrote:Would it be possible to design a hydroelectric locomotive?

It seems the answer is "No."

Guess not. Oh, well. I guess electric locomotives will always have to have an external power source (3rd rail or catenary) to work.

My original purpose in launching this thread was to explore the idea of a hydroelectric locomtive, but a thought just occurred to me: How about methane? (Anyone remember the movie Mad Max Beyond Thunderdome?)

I dont think you can force all passengers to eat large quantities of beans and drink prune juice .

the problem with methane is storae , probably better off used in land based power plants , and then electrifiy the railroad .

Methane has the sort of storage problems that hydrogen does, though its boiling point is at a higher temperature, 112 K instead of 20 K. By comparison, oxygen has a boiling point of 90 K and nitrogen of 77 K.

From thermodynamics, it is possible to estimate the minimum amount of energy input necessary to do a certain amount of refrigerator heat transfer:

(Coefficient of Performance) = (heat transfer)/(energy input)

and by Carnot's theorem, COP <= Tc/(Th - Tc) -- Th is the hot-end temperature and Tc is the cold-end temperature. So the smaller the Tc/Th ratio, the lower the cooling efficiency. Gases' thermal energy content is proportional to their temperature, to first approximation, though one has to be careful about constant volume vs. constant pressure: E = C*T

The energy input, W = E(gas)/COP = C*(Th - Tc)^2/Tc

So refrigerating methane to its boiling point requires only about 1/15 the energy that is necessary for the same number of molecules of hydrogen, ignoring differences of specific-heat ratio (won't give a large effect, but it's another complication I'm ignoring).

Source: Wikipedia on thermal efficiency - Wikipedia is often a good starting point for technical stuff. For temperatures and heats of phase change, and heats of formation, NIST's Web Book has lots of data.

lpetrich wrote:Methane has the sort of storage problems that hydrogen does, though its boiling point is at a higher temperature, 112 K instead of 20 K. By comparison, oxygen has a boiling point of 90 K and nitrogen of 77 K.

From thermodynamics, it is possible to estimate the minimum amount of energy input necessary to do a certain amount of refrigerator heat transfer:

(Coefficient of Performance) = (heat transfer)/(energy input)

and by Carnot's theorem, COP <= Tc/(Th - Tc) -- Th is the hot-end temperature and Tc is the cold-end temperature. So the smaller the Tc/Th ratio, the lower the cooling efficiency. Gases' thermal energy content is proportional to their temperature, to first approximation, though one has to be careful about constant volume vs. constant pressure: E = C*T

The energy input, W = E(gas)/COP = C*(Th - Tc)^2/Tc

So refrigerating methane to its boiling point requires only about 1/15 the energy that is necessary for the same number of molecules of hydrogen, ignoring differences of specific-heat ratio (won't give a large effect, but it's another complication I'm ignoring).

Source: Wikipedia on thermal efficiency - Wikipedia is often a good starting point for technical stuff. For temperatures and heats of phase change, and heats of formation, NIST's Web Book has lots of data.

Pi are squared? Wrong!!! Pi are round, cake are squared.

Nelson Bay wrote:

lpetrich wrote:Methane has the sort of storage problems that hydrogen does, though its boiling point is at a higher temperature, 112 K instead of 20 K. By comparison, oxygen has a boiling point of 90 K and nitrogen of 77 K.

From thermodynamics, it is possible to estimate the minimum amount of energy input necessary to do a certain amount of refrigerator heat transfer:

(Coefficient of Performance) = (heat transfer)/(energy input)

and by Carnot's theorem, COP <= Tc/(Th - Tc) -- Th is the hot-end temperature and Tc is the cold-end temperature. So the smaller the Tc/Th ratio, the lower the cooling efficiency. Gases' thermal energy content is proportional to their temperature, to first approximation, though one has to be careful about constant volume vs. constant pressure: E = C*T

The energy input, W = E(gas)/COP = C*(Th - Tc)^2/Tc

So refrigerating methane to its boiling point requires only about 1/15 the energy that is necessary for the same number of molecules of hydrogen, ignoring differences of specific-heat ratio (won't give a large effect, but it's another complication I'm ignoring).

Source: Wikipedia on thermal efficiency - Wikipedia is often a good starting point for technical stuff. For temperatures and heats of phase change, and heats of formation, NIST's Web Book has lots of data.

Pi are squared? Wrong!!! Pi are round, cake are squared.

No, cake are round, too!

i tohught methane had similiar properties to natural gas , and they do run shunting locomotives on liquidfied natural gas . or compressed natural gas .
I think here in Christchurch , they are running vechicles off compressed methane from the sewage works .
but for mainline use , i think the storage problems would rule it out .

David Benton wrote:i tohught methane had similiar properties to natural gas , and they do run shunting locomotives on liquidfied natural gas . or compressed natural gas .
I think here in Christchurch , they are running vechicles off compressed methane from the sewage works .
but for mainline use , i think the storage problems would rule it out .

Well, couldn't you store it in canisters, like propane?

BTW: I'm not trying to get in an argument with anyone; I just keep thinking of things.

i think you would probably have to compress it , or liquidfy it . but i dont know enough about it .

David Benton wrote:i think you would probably have to compress it , or liquidfy it . but i dont know enough about it .

Natural gas is shipped in both compressed and liquid form and experiments have been conducted in running converted diesel locomotives off on it. There are several companies offering it. Technically it is feasible but it's a matter of it being cost competitive with conventional diesel.

Natural gas is mostly methane.

So it would have to either be compressed or refrigerated to cryogenic temperatures for it to be stored.

That aside, I've decided to consider nuclear-powered locomotives. Nuclear fission has a certain problem: there will always be a minimum nuclear-reactor size for it to work, even in the best of cases. The existence of such a limit is easy to understand, though finding it is another story entirely. A nuclear reactor works by nuclear fissions making neutrons that cause other nuclear fissions, something like a fire continuing its existence by igniting more material with its heat. And for the reaction to continue, each neutron must have a sufficiently-large probability of hitting a fissionable nucleus, and to ensure that, the neutron must travel more than some distance in the reactor. This means that a reactor cannot be too small, or else its neutrons will escape, like a fire that loses heat too rapidly.

So I searched for "smallest feasible nuclear reactor" and "smallest possible nuclear reactor", and found very little; the closest I found was What is the smallest possible nuclear reactor?, where elephantwalker claimed:

A nuclear reactor design is based upon three things:
1) the neutron crossection of the fuel
2) the density of the fuel
3) the method of heat removal

higher neutron crossection, and higher density gives more reactivity for the reactor per volume. This is why dense forms of u-235 such as UN or uranium nitride give the smallest size reactors. This type of reactor is in the megawatt range, and is the size of a small trash can.

This type of reactor has been tested for space travel (JIMO).

Such a reactor uses highly enriched uranium (HEU; more than 20% U-235); naval nuclear reactors go up to 50% U-235. By comparison, weapons-grade uranium is 90% U-235, most nuclear power plants use 3% to 5% U-235, and natural uranium is 0.7% U-235.

Its volume is about 0.1 m^3, and its mass is about a ton, assuming that it is all uranium nitride (density 11.3 g/cm^3). This is not much different from various structural materials, like steel (iron alloy; 7.8 g/cm^3).


Could it fit in a locomotive and power it? A 4000-hp locomotive is a 3-megawatt one by units conversion, and locomotives can weigh in at 100 - 200 tons. This means that this kind of nuclear reactor has a size, mass, and power suitable for locomotive duty. By comparison, on flat roads, one of the most powerful vehicles is the Mack Titan truck, at 605 / 451 kW. It is just below the limits of this kind of nuclear reactor.

Locomotive nuclear reactors are a potential safety nightmare, since they are not buried inside of big containment buildings or ships or submarines. But there has been some effort to design reactors with passive safety, meaning that they do not need outside intervention to shut themselves down if they suffer a loss-of-coolant accident (LOCA). Thus, in some designs, if the coolant (usually water) starts to boil, then the reaction slows down from neutrons not being slowed down enough by collisions with coolant nuclei.

But even if it shuts itself down, it will still have a heat source: its decaying fission products. This means that it would still need to be cooled, though by the square-cube law, this will likely be a less serious problem for a small nuclear reactor than for a large one.

I think that such a reactor ought to be torture-tested with a LOCA or a collision to see how well it holds up.

In any case, locomotive nuclear reactors would likely provoke a strong NIMBY reaction in many populated areas.


The heated water in the reactor could boil, and the resulting steam could drive a turbine, which would drive a generator, thus making the locomotive a steam-electric one. The locomotive could also be the traditional direct-drive sort of steam engine.

lpetrich wrote:Natural gas is mostly methane.

So it would have to either be compressed or refrigerated to cryogenic temperatures for it to be stored.

That aside, I've decided to consider nuclear-powered locomotives. Nuclear fission has a certain problem: there will always be a minimum nuclear-reactor size for it to work, even in the best of cases. The existence of such a limit is easy to understand, though finding it is another story entirely. A nuclear reactor works by nuclear fissions making neutrons that cause other nuclear fissions, something like a fire continuing its existence by igniting more material with its heat. And for the reaction to continue, each neutron must have a sufficiently-large probability of hitting a fissionable nucleus, and to ensure that, the neutron must travel more than some distance in the reactor. This means that a reactor cannot be too small, or else its neutrons will escape, like a fire that loses heat too rapidly.

So I searched for "smallest feasible nuclear reactor" and "smallest possible nuclear reactor", and found very little; the closest I found was What is the smallest possible nuclear reactor?, where elephantwalker claimed:

A nuclear reactor design is based upon three things:
1) the neutron crossection of the fuel
2) the density of the fuel
3) the method of heat removal

higher neutron crossection, and higher density gives more reactivity for the reactor per volume. This is why dense forms of u-235 such as UN or uranium nitride give the smallest size reactors. This type of reactor is in the megawatt range, and is the size of a small trash can.

This type of reactor has been tested for space travel (JIMO).

Such a reactor uses highly enriched uranium (HEU; more than 20% U-235); naval nuclear reactors go up to 50% U-235. By comparison, weapons-grade uranium is 90% U-235, most nuclear power plants use 3% to 5% U-235, and natural uranium is 0.7% U-235.

Its volume is about 0.1 m^3, and its mass is about a ton, assuming that it is all uranium nitride (density 11.3 g/cm^3). This is not much different from various structural materials, like steel (iron alloy; 7.8 g/cm^3).


Could it fit in a locomotive and power it? A 4000-hp locomotive is a 3-megawatt one by units conversion, and locomotives can weigh in at 100 - 200 tons. This means that this kind of nuclear reactor has a size, mass, and power suitable for locomotive duty. By comparison, on flat roads, one of the most powerful vehicles is the Mack Titan truck, at 605 / 451 kW. It is just below the limits of this kind of nuclear reactor.

Locomotive nuclear reactors are a potential safety nightmare, since they are not buried inside of big containment buildings or ships or submarines. But there has been some effort to design reactors with passive safety, meaning that they do not need outside intervention to shut themselves down if they suffer a loss-of-coolant accident (LOCA). Thus, in some designs, if the coolant (usually water) starts to boil, then the reaction slows down from neutrons not being slowed down enough by collisions with coolant nuclei.

But even if it shuts itself down, it will still have a heat source: its decaying fission products. This means that it would still need to be cooled, though by the square-cube law, this will likely be a less serious problem for a small nuclear reactor than for a large one.

I think that such a reactor ought to be torture-tested with a LOCA or a collision to see how well it holds up.

In any case, locomotive nuclear reactors would likely provoke a strong NIMBY reaction in many populated areas.


The heated water in the reactor could boil, and the resulting steam could drive a turbine, which would drive a generator, thus making the locomotive a steam-electric one. The locomotive could also be the traditional direct-drive sort of steam engine.

Here's an article about using a new type of mini reactor to power a locomotive:

http://www.internationalsteam.co.uk/tra ... rn16.htm
You will see this built when you see nuclear powered airliners i.e never.....................

Thanx for that page, but it's a bit short on specifics, like how big the reactor would be.

I also checked on the question of nuclear-reactor radiation shielding, and the only numbers I could find were in Chapter 2. SHIELDING THE HAZARD -- about 1 m / 3 ft of water will stop nearly all of the slower neutrons, those with kinetic energies less than about 10 MeV.

I've also found an overview of shielding materials (part of a big book on nuclear-reactor engineering that's online), and, of course, a Wikipedia article. These references have some qualitative overviews, but are short on numbers, except for Wikipedia including some tables on shielding from gamma rays (energetic photons).

So a small reactor with shielding can be 2 to 3 m across. If it is all water, then it will weigh 9 to 27 tons, which is well within the weight range of typical freight locomotives.

Turning to whether such a reactor can fit into a typical railroad loading gauge, I find that it can, though it is a tight squeeze. Most loading-gauge widths are at least 10ft / 3m , with the UK's being slightly narrower. And most loading-gauge center heights are at least 13ft / 4m, though side heights can be as low as 10ft / 3m.