Incline tracks to save power

markpb · 13-02-2012 1:00pm #1

I was watching this video about the construction of the LA metro back in the 90s. About 12 seconds in, they mention using incline tracks at stations to save energy. I did some Googling but haven't been able to come up with anything.

Logically, it seems to make sense to me that if you have to rise from the tunnel to the station (slightly), you don't have to brake and if you descent from the station to the tunnel, you can use gravity to reduce the amount of energy you need to get the train moving.

Am I correct or crazy?

L1011 · 13-02-2012 1:36pm

Nearly certain the Paris Metro does something similar. Regenerative braking makes it either less useful or pointless though.

corktina · 13-02-2012 1:53pm

Glascow underground does thsi I beleive

cgcsb · 13-02-2012 2:44pm

Luas has regenerative breaking anyway.

AngryLips · 13-02-2012 3:18pm

London Underground has it as well.

Cool Mo D · 13-02-2012 7:27pm

The Victoria line on the London Underground has hump-backed approaches to stations, which speeds up the trains and saves energy.

It only makes sense when every train will stop at a station though.

Carawaystick · 13-02-2012 9:37pm

cgcsb wrote: »

Luas has regenerative breaking anyway.

While the luas has regenerative breaking, the energy is wasted as heat. You need an ac power system to transfer the energy back to the overhead line to allow reuse

DART is the same

dowlingm · 14-02-2012 1:04am

That doesn't sound right on several levels.

a) if electric braking is wasted it's just dynamic brakes. If brakes don't allow the energy to be reused under at least some circumstances (return to grid, return to wayside storage, onboard battery or flywheel) the term regenerative is null.
b) this article points out that UK Electrostars return to the system, albeit that it is "tricky" compared to AC
http://www.railwaypeople.com/rail-news-articles/regenerative-braking-on-the-third-rail-dc-network-1590.html

101sean · 15-02-2012 12:04am

The Victoria line on the London Underground has hump-backed approaches to stations, which speeds up the trains and saves energy

All the deep tube lines on LU do this, I've recently done drainage record drawings of the whole of the Central and Victoria Lines and am currently doing the Bakerloo (in my study in Tipp, thank god for rermote working

)

The gradients are fairly steep in railway terms and help with accelerating and braking, it's looks like a roller coaster in the exaggerated long sections!

Solair · 15-02-2012 10:42am

Carawaystick wrote: »

While the luas has regenerative breaking, the energy is wasted as heat. You need an ac power system to transfer the energy back to the overhead line to allow reuse

DART is the same

It would seem that the DART does use regenerative braking :

http://www.enterprise-ireland.com/en/Events/OurEvents/European-Green-Transport-Conference-5-May-2011/Irish-Rail1.pdf

That was one of the main reasons why the refit was done to the older units, they cut power consumption by 26%

The Luas trams also have regenerative breaking and it cuts power consumption by up to 30%

Mentioned in this:

http://www.transport21.ie/MEDIA/Press_Releases/Cullen_views_tram_extensions_for_Tallaght_Luas_line.html

L1011 · 15-02-2012 11:01am

Solair wrote: »

That was one of the main reasons why the refit was done to the older units, they cut power consumption by 26%

The 1984 units had regenerative braking when supplied... it may not have been as efficient as modern units, though.

Solair · 15-02-2012 11:07am

There was also a major upgrade done to the DART electrical systems a few years ago to allow for more capacity, but it also probably made regenerative braking more useful and selling power back into the local ESB Networks grid even more possible.

Newer power systems don't really pose much of a problem in terms of these kinds of things as they employ high-voltage solid state technologies rather than relying on traditional heavy electrical gear.

Compared to a big old system like the Paris Metro or the London underground, the Dublin system's very small and relatively modern so I would doubt that regenerative braking was ever much of an issue.

It's only 1 electric train line and a couple of simple Citadis tram lines.

101sean · 15-02-2012 2:10pm

this article points out that UK Electrostars return to the system,

The UK can get planning badly wrong sometimes too, when the Electrostars were introduced to the SE they had to upgrade the power distribution in a hurry as they draw a lot more power than the old units. Apparantly there was a lack of communications along the lines of "but I thought you were sorting that out?"

Company I work for also had to sort out the vacuum tank discharge systems at two depots as they connected them to drains that didn't work :rolleyes:

Solair · 15-02-2012 2:34pm

Modern UK rail is *definitely* not a good model to follow since it was privatised and broken up anyway.

Carawaystick · 16-02-2012 5:21pm

Fair enough, I thought they (darts/trams) just burnt the power in a big resistor on the roof when using the motors as generators

L1011 · 16-02-2012 7:23pm

Carawaystick wrote: »

Fair enough, I thought they (darts/trams) just burnt the power in a big resistor on the roof when using the motors as generators

That'd be a rather expensive thing to design to save on a few consumable brake pads...

Carawaystick · 17-02-2012 12:03am

MYOB wrote: »

That'd be a rather expensive thing to design to save on a few consumable brake pads...

Dynamic breaking was what I was thinking of
http://en.wikipedia.org/wiki/Dynamic_braking
http://www.railroad.net/articles/columns/shopnotes/blendedbrake/index.php

Consumable parts over a 30+ year life add up

chooochooo · 19-02-2012 9:38am

Cool Mo D wrote: »

The Victoria line on the London Underground has hump-backed approaches to stations, which speeds up the trains and saves energy.

It only makes sense when every train will stop at a station though.

incorrect

Incline tracks to save power

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