Reflecting on London Underground's Overheating

#1

Post by CalvinBarrows » Sun, Dec 27, 2020, 1:49 AM UTC

There have been many theories about what to do to cure underground railways of overheating, but I have seen no evidence of monitoring to demonstrate the origin of the heats and how it progresses. One thing is certain - the problem is worse in the summer so reducing operational heat which is year-round will not hack it. Besides Glasgow, Warsaw and Prague do not overheat and they, obviously produce operational heat! So, I believe I have found the only answer that fits the evidence! Please see https://www.railbusinessdaily.com/a-reflective-perspective-the-whys-and-wherefores-of-metro-overheating/

Reflecting on London Underground's Overheating
railbusinessdaily.com

Re: Reflecting on London Underground's Overheating

#2

Post by CalvinBarrows » Sun, Dec 27, 2020, 2:18 AM UTC

There have been many theories about what to do to cure underground railways of overheating, but I have seen no evidence of monitoring to demonstrate the origin of the heats and how it progresses. One thing is certain - the problem is worse in the summer so reducing operational heat which is year-round will not hack it. Besides Glasgow, Warsaw and Prague do not overheat and they, obviously produce operational heat! So, I believe I have found the only answer that fits the evidence! Please see https://www.railbusinessdaily.com/a-reflective-perspective-t...

Re: Reflecting on London Underground's Overheating

#3

Post by aurizon » Sun, Dec 27, 2020, 2:22 AM UTC

Use less friction braking and more regenerative braking. This might mean adding bettery banks to absorb energy - later used as tractions, as they do in many electric cars. Often the power can not be dumped into the electricity lines for engineering reasons. This might effect some heat as well as cost savings, but needs a detailed study

Re: Reflecting on London Underground's Overheating

#4

Post by ggm » Sun, Dec 27, 2020, 2:31 AM UTC

I was led to believe the heart was retained in the London soil, had been accumulateing over years and so this theory of heat piston into the system being taken as true, surely there also needs to be a process to carry heat out of the tube in order to achieve the goal.

Heat pumping could make usable energy? Or, overcool trains, park them inside, absorb heat energy and carry outside to dissipate at night?

Re: Reflecting on London Underground's Overheating

#5

Post by CalvinBarrows » Sun, Dec 27, 2020, 3:05 AM UTC

I would support regenerative braking, but I do not think it is a massive contribution since braking happens year-round, but overheating is predominantly a summer problem! Yes everything gets hot, including the clay, but the clay does not spontaneously heat up, the heat has to come from somewhere and what I am suggesting is that its being reradiated from trains which have been solar irradiated on the overground section, which is why the problem did not happen in the early days of the Tube when it was all underground, and does not happen on Glasgow’s, Warsaw’s or Prague’s networks which are solely/predominantly underground. The principle is that the solar barriers stop the heat entering the tunnel so there will be no need to carry heat out!

Re: Reflecting on London Underground's Overheating

#6

Post by CalvinBarrows » Sun, Dec 27, 2020, 9:25 AM UTC

ggm wrote: post #4

I was led to believe the heart was retained in the London soil, had been accumulateing over years and so this theory of heat piston into the system being taken as true, surely there also needs to be a process to carry heat out of the tube in order to achieve the goal. Heat pumping could make usable energy? Or, overcool trains, park them inside, absorb heat energy and carry outside to dissipate at night?

Please see my comments on the first two posts

Re: Reflecting on London Underground's Overheating

#7

Post by CalvinBarrows » Sun, Dec 27, 2020, 9:26 AM UTC

aurizon wrote: post #3

Use less friction braking and more regenerative braking. This might mean adding bettery banks to absorb energy - later used as tractions, as they do in many electric cars. Often the power can not be dumped into the electricity lines for engineering reasons. This might effect some heat as well as cost savings, but needs a detailed study

Please see my comments on the first two posts

Re: Reflecting on London Underground's Overheating

#8

Post by aurizon » Sun, Dec 27, 2020, 1:21 PM UTC

CalvinBarrows wrote: post #7

aurizon wrote: post #3

Use less friction braking and more regenerative braking. This might mean adding bettery banks to absorb energy - later used as tractions, as they do in many electric cars. Often the power can not be dumped into the electricity lines for engineering reasons. This might effect some heat as well as cost savings, but needs a detailed study

Please see my comments on the first two posts

More intense acceleration as well as more intense braking produce heat. Steel on steel is efficient, thus energy lost on braking is on the order of 50% of that used for acceleration. This is moderated by the top speed, grade etc and gain/loss in height. So the cases are complex. I do not have data on the mass of the train as well as the live load, or the HP of the motors and what acceleration in fractional g is involved. In any event to move more people/unit time, higher acceleration, top speed and braking all increase the passengers/hour. It may well be the major culprit is this move to more people/hour via higher speed/acceleration/deceleration/efficiency etc, all of which are additive.

Re: Reflecting on London Underground's Overheating

#9

Post by CalvinBarrows » Sun, Dec 27, 2020, 5:39 PM UTC

aurizon wrote: post #8

CalvinBarrows wrote: post #7

Earlier quoted context omitted.

Please see my comments on the first two posts

More intense acceleration as well as more intense braking produce heat. Steel on steel is efficient, thus energy lost on braking is on the order of 50% of that used for acceleration. This is moderated by the top speed, grade etc and gain/loss in height. So the cases are complex. I do not have data on the mass of the train as well as the live load, or the HP of the motors and what acceleration in fractional g is invol…

I agree that all these things will make a difference but I'd be really interested in your explanation as to how it makes such a difference in the summer but not in the winter, and also why it does not seem to make much difference on underground only networks compared to mixed under/overground networks?

Re: Reflecting on London Underground's Overheating

#10

Post by aurizon » Sun, Dec 27, 2020, 9:36 PM UTC

CalvinBarrows wrote: post #9

aurizon wrote: post #8

Earlier quoted context omitted.

More intense acceleration as well as more intense braking produce heat. Steel on steel is efficient, thus energy lost on braking is on the order of 50% of that used for acceleration. This is moderated by the top speed, grade etc and gain/loss in height. So the cases are complex. I do not have data on the mass of the train as well as the live load, or the HP of the motors and what acceleration in fractional g is invol…

I agree that all these things will make a difference but I'd be really interested in your explanation as to how it makes such a difference in the summer but not in the winter, and also why it does not seem to make much difference on underground only networks compared to mixed under/overground networks?

I think the total underground temperature is less, compared to surface routes because the earth mass has a large moderating effect. Only as the surface warms does it gradually warm the depper levels, as we are seeing. Train that go up and down from the heated summer air to the averaged undergound get a net warming from that exposure. It needs a detailed study to nail these all down