Save Energy: Why don't we build train stations on hills?

Question

I know, weird question. But if a station is on even slightly higher ground, then an approaching train will lose speed naturally, without braking (as much). The saved energy would then be used to help the train accelerate (down-hill) as it leaves the station the other side.

I realise that the differences in speed/acceleration involved would be marginal, but with the energy needed to move the hundred tons plus of just an average commuter train, any small help would translate into a substantial saving of energy.

Now I may be being a muppet, and there may be a very obvious reason why this is a bad idea, but I can't find it. OK, ok, considerable start up costs of hoiking Waterloo up 10 feet in the air, but aside from that........ can anyone tell me why this wouldn't work in principle?

Answer 1

Interesting idea. You are "on the right track": accelerating the train out of the station uses the most energy; but I think it would be cheaper to just buy a hybrid train than redesign every station, don't you? They are available already. I don't know why they aren't used more on commuter trains. Railpower Inc makes hybrid locomotives.

Answer 2

You are working on some very unclear logical grounds:
1. You think that the energy saving would be significant. If a train is travelling 100 miles, the percentage saved by starting on a slope would be minimal. Why do you think it would be significant? If the saving was 10% over, generously, 400 metres, that would be an overall energy saving of 40 metres worth of energy over 160,000 metres or 0.025%. It is difficult to imagine that this would compensate for moving the station from the location that would otherwise have been chosen .
2. You are assuming that this choice is available. Do you know of one example of a train station which is being built where there is an actual real choice available between a hill and flat ground?
3. A train can lose speed naturally without the aid of a hill.

Answer 3

That is just one of millions of really expensive things you could do for a really small benefit. Expensive because since hills are not always where you need train stations, you would have to build an artificial hill. You could do that, but it would be expensive and use a lot of fuel to move all that dirt or build the bridge needed or whatever. And the benefit would be really small. Not totally, technically, exactly, zero benefit, but so small as to definitely not be worth the effort and cost. If we did all the expensive funny little things that every person in the world though up like that, we would spend 100 times all the money in the world and only reduce energy use by 1%.

Answer 4

Depending on the length of the train, that could be one long hill.
Another thing is that train stations are often cluttered with auto ingress egress that cross rail tracks which means any train leaving will have to limit speed at crossings.
Train engines are actually one of the most efficient designs that auto makers are just now taking notice of, (funny kind of since GM makes locomotives) a diesel powered generator supplying energy to run the electric motors and they can also be run using Bio-diesel which some already do.
All in all, your idea has merit since trains rely a lot on momentum.

Answer 5

Several reasons:
-the construction of train lines itself (regular ones) is almost as energy intensive as the operation of the line over 50 years. You would displace an energy loss by braking to fuel for the bacco which would have to eventually level more or even create the hill
-the maximum slope for trains carrying goods is like 0.5-1.0%... light high speed train can handle up to 3.5% but that’s the limit. Over this, you might encounter slippage.
-several other possibilities exist to recover this energy (reverse the motor as a generator, use a battery, an inertia wheel, etc.)
-train carrying goods and passengers have really different characteristics regarding the required acceleration/deceleration
-the saving is minimal compared to other measures

FYI: I do at no cost something similar: I put my AC to the max when driving sharply downhill… instead of turning the kinetic energy in heat in my brakes, I use it form y comfort by creating cooled air.

Answer 6

Rather than physical hills, electric trains can use regenerative braking that generates electric back into the system a bit like an electric hill, ie kinetic energy back to potential energy for accelerating vehicles. Electrical systems generally have less losses than mechanical ones.

or you could check the water powered hill railway at Centre for Alternative Technology http://www.cat.org.uk

Answer 7

Wait a minute. Aren't they already built on high ground?