While in motion, energy is lost through friction with railway and frontal air drag.

When stopping, obviously through braking system ...

Hi Jonathan,

I will vote for energy lost during acceleration to and deceleration from running speed to standstill.

Cheers !

-Sanjay

Good question!

More info is needed, I think, to get a total energy cost for rail transportation and be able to evaluate, which are the energy cost factors.

Energy fed into the train can be recovered to some degree; if electrified, a lot can be recovered, but once mechanical brakes are used, that energy is lost.

Other major energy sinks in the system need also to be reviewed, perhaps they are significant, I don't know:

• heating/cooling of stations and trains,
• lighting
• repairs and maintenance
• auxiliary facilities (work shops, crew quarters)
• cleaning of trains inside and out.
• The energy expenditure for construction of railway and cars need also to be included as a per year energy cost, since the life of these are not infinite. Building a railway system is probably very high in energy cost, since it is so expensive.

Finding some of this data might be tricky, good luck!

Olof

Found an example of a construction energy cost calculation, see chapter 5.11 in "Phase 1 Regional Rail System, Durham and Wake Counties: Environmental Impact Statement, Volume 1"

https://play.google.com/store/books/details?id=5Bs3AQAAMAAJ&rdid=book-5Bs3AQAAMAAJ&rdot=1

Maybe you could contact with firms who design and manufacture trains (and their automatic controls), rails, etc. In Spain for instance, CAF produces trains for all over the world. You can maybe first visit thei technology page on their website. For CAF:

http://www.caf.net/en/innovacion-tecnologia/index.php

Remi,

When you mentioned the 2nd law of thermodynamics, did you mean to say that the entropy of the system would increase regardless of whether energy were to enter or exit? Or that the more energy conversions within the system that occurred, the more disorder the system would have, and the more energy it would lose?

What possible solutions or methods of reducing this effect would be plausible for an MRT?

If we exclude the acceleration and deceleration phases the biggest energy lost sources are the friction on the wheels and aerodynamic drag. These contributions will change according the train speeds. If the speed is increasing the drag will increase with the square of the speed. This problem may be lightened by an aerodynamic design. During the acceleration phase the energy lost will be due to inertia change where it may be lightened by light weight and the lost in deceleration  phase the inertia may be used to restore energy as an mechanical or electrical energy. If the high speed is a requirement the train may function in a vacuum tube but in the stations the vacuum must be allocated by atmosphere. 

Here a few major sources of energy losses for trains and subways:

1) frictional energy lost as the train or subway as moves forward (air resistance). In particular when they move inside tunnels due to the air piston effect.

2) Repeated opening and closing of the train/ subway doors at each stop.

3) Energy lost during braking at each stop.

Hope this helps answer your question.

Professor Yehia Khalil

Yale University

USA