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Makes me wonder if we can do something more productive with the 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?
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Magnetic (eddy current) brakes work by converting kinetic energy into heat, which doesn't really solve the problem here. I'm not sure if anyone has devised a system that actually captures electrical energy from the braking action, or if such a thing is even plausible.
Yes. It's called "electric generator" and can be performed by almost all electric motors.
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.
Makes me wonder if we can do something more productive with the 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?
Converting heat into useful amounts of energy usually requires a temperature gradient that'd be unbearable for humans.
Could using magnets to break and start be a solution to reduce the heat generation ?
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It really doesn't matter much - any amount of heat going into the underground system that is not able to be dispelled in a year-round cycle will heat the ground eventually. Reducing the heat entering the system slows it down, but at some point you have to cool it again.
Every amount of heat generated will have an equilibrium average temperature. Reducing input heat will lower this equilibrium temperature.
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
Earlier quoted context omitted.
Yes. It's called "electric generator" and can be performed by almost all electric motors.
Indeed. Electricity and magnetic fields are so closely related we have a single term, electromagnetism, the motor and generator are thus almost the same thing and it's relatively easy to build a single device which can serve both purposes. 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 mo…
Some old freight routes used electric haulage because the regenerative braking going downhill almost completely offset the electricity consumption going uphill.
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I wonder if you could fit a magnetic braking system mainly at platforms, when engaged trains would be slowed. That could reduce weight on the trains themselves? 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…
piston effect already does a lot of ventilation work the more elegant solution in use around in the world is to put the stations on hills
Regenerative braking would improve a lot with not just the heat issue, but also air quality. Commuters on the London Underground get a characteristic grey/black snot from the brake dust they inhale. If you stare into the tunnel after a train left you can literally see a haze of brake dust in the air.
I wonder if you could fit a magnetic braking system mainly at platforms, when engaged trains would be slowed. That could reduce weight on the trains themselves? 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…
I think the Montreal metro faces a lot of these same issues. It works out in the winter where you don't need to actively heat the space. In the summer, it can be unbearable. I'm not sure if the type of rolling stock (rubber tires + tunnel track) has a major difference from other typical subway cars.
I personally don't find Toronto or Montreal subways unbearable (warm, but not crazy), while my time in the London Underground was absolutely miserable - I'm not sure how locals handle that kind of stifling heat. Actually, there was one time I was in the old Toronto Osgoode (pre-opera house) station with a -30 degree wind blowing through - that was chilly! Actually, I'm kind of sad that Montreal has so few cars left t…