Cooling the tube – Engineering heat out of the Underground (2017)
ianvisits.co.uk
ianvisits.co.uk
Thinking wildly, tube trains are like pistons (they're actual plungers, I guess) if you had a smooth walled section of tunnel then you could have a seal at the head of the train that fans out and provides pneumatic braking, you could maybe use the pressure to drive the ventilation system. Unlikely to be practical (you'd have to have a pre-platform door to prevent all the passengers from getting exposed to the pressure increase, I think).
Or if the braking resistors have to be close the the coils, then you could use a heat-exchanger to move the heat somewhere else...
Another approach that can be used when initially building the system is to have a slope leading into/out of stations so that energy can be stored as gravitional potential. I know the Montreal Metro was built this way.
Actually regenerative braking is common on electric trains. Stock bought since at least the 1990s for London Underground has regenerative braking of various forms, with the more modern being fitted to S-stock (the sub-surface lines which were all gradually replaced with a single type of train, if you went on a "Tube" train and it was actually walk-through the length of the train and seemed vaguely modern inside, that was S-stock and you weren't in the deep tube where heat is a bigger problem)
In the 1970s when the oldest stock still in use was purchased, regenerative braking was not a thing.
Some old freight routes used electric haulage because the regenerative braking going downhill almost completely offset the electricity consumption going uphill.
the more elegant solution in use around in the world is to put the stations on hills
Well that's horrifying. Is there no health and safety monitoring being conducted?
Sounds like we need to knock down a few houses. This isn't unreasonable for critical infrastructure.
Also sounds like giving people free ground source heat pumps along the tube line would be best - they would be pumping out the heat thats in the clay. The article talk about a scheme, but this needs to be done at scale
Reducing the heat entering the system slows it down, but at some point you have to cool it again.
Reducing input heat will lower this equilibrium temperature.
Actually, I'm kind of sad that Montreal has so few cars left that play "Fanfare" [0]
[0] https://web.archive.org/web/20090823173621/http://observator...
tbh London is fine too. Problem is if it is the main form of transport then the at-risk members of society use it too. Very old & frail etc.
Uncaptured energy is likely turned into pure heat.
They mention energy generation, but what about heat pumps and water heaters for the above ground buildings? Probably cost prohibitive, but wouldn't it be neat if the waste heat from the brakes ended warming a building or hot water heater?
Any kind of capture heat and use it because much more workable if concentrated
Perhaps not coincidentally, the inefficiency also has a massive carbon and budget impact... Or it would, if the train system had to pay for the electricity it used - which it doesn't! Trains in the UK are given free unmetered electricity, so there is no reason to conserve energy. Hot tunnels are just an extreme symptom of that.
If they had to pay for usage, at todays wholesale electricity rates, it would cost nearly a billion pounds a year. Which is ~20% of their revenue! I can see why they don't want to pay that bill!
In fact, the level of effort required to estimate electricity uses for multiple franchises on one physical section of railway has resulted in nearly all British rolling stock having built-in electricity metering.
That Is Insane!!
Rail needs a complete rethink of design from the ground up. There are certainly vast efficiencies from rolling steel wheels on steel rails. But I've seen little evidence of light-weighting and indeed active resistance to steps like making cars using composites, which would save enormous amounts of energy and cost over the lifetime, as well as reduce maintenance costs. Yet their approach to everything seems to be sticking with an approach of 'brute force and ignorance'. Sure that works in the 19th century when you're just starting to put some carbon in iron and make it stronger than pig iron, but materials are sooo far past that now, yet it's still the same old approach. (&yes, I strongly support the Chesterton's Fence checking but this seems way beyond that)
https://www.cressall.com/applications/rail-traction-dynamic-...
(scroll down to "MOTOR STARTING AND SPEED CONTROL RESISTORS")
Whenever possible regenerative braking is used. In this case the drive motors convert the kinetic energy of the train into electricity, which is fed back into the power supply and used elsewhere on the network.
If it cannot be absorbed by the system the energy may have to be dissipated with braking resistors. These braking resistors can be either mounted on the rail vehicle or as a fixed (trackside) installation connected to the third rail or overhead catenary via Automatic Assured Receptivity Unit (AARU) systems.
But anyway, the affected trains are the oldest in use in Britain, from 1972 (Bakerloo Line, 36 trains) and 1973 (Piccadilly Line, 87 trains), out of 620 passenger trains across the whole system. New trains have been ordered and should be introduced in 2025.
There's been a 10 year delay, due in part to the 1990s attempt to privatize chunks of the system.
TFL used to have its own generating stations, which helped keep costs manageable and also meant the trains kept running during power cuts.
That ended around 2000. Now it has at least four separate connections to the National Grid, and is supposed to be moving to 100% renewables within the next decade.
[1] https://content.tfl.gov.uk/fc-20171205-part-1-item08-tfl-ene...
The new ones are much better, although they still recover very little braking energy.