Fighting heat in the underground – Rail Technology Magazine (RTM) looks at the successes of the Cooling the Tube programme so far and what TfL hopes to achieve in the coming years.
Despite what was a relatively mild summer, in this year’s June/July edition we decided to take a look at the reasons behind the sweltering temperatures in London’s underground rail network. For the millions of residents and tourists jumping on-board jam-packed Tube trains, temperatures in the Underground are often hotter than those outside, even at season’s peak.
As RTM explained then, the London Clay, through which deep-level tunnels were bored, is largely to blame for this. It originally provided such a cool environment that the network was advertised as a refuge from the warmth. But over time, the thick clay began soaking up the heat generated from the braking trains to the point where its temperature rose from an average of 14° to a whopping 26°.
To prevent this situation from becoming untenable, TfL launched its long-running Cooling the Tube programme, created specifically to address the problem of excessive heat in the Underground.
A number of ‘quick wins’ were achieved at first, such as temporary summer fans across stations; platform-level supply ventilation, where fresh air was pumped via existing shafts; impulse fans to circulate air along platforms; a variable refrigerant flow system to reduce the heat in ticket halls and staff areas; and chiller units at Euston, one of the capital’s most-used stations. Already from these measures, TfL learned that improving temperatures could have a considerable impact on customer satisfaction.
This article is far from new. It actually came out last November. The thing that tipped me off was the part that talked about “a relatively mild summer”…
@Anon E. Mouse
But otherwise more relevant this summer, no?
@LBM
I didn’t say it was a bad thing that this was being linked to now, but that is a good point you make that I didn’t think of.
There is a more recent article about Cooling the Tube in Wired magazine 28 Jun 2018 https://www.wired.co.uk/article/central-line-temperature-london-weather-heatwave and talked about in the Wired podcast Ep 375 29 Jun 2018 https://www.wired.co.uk/article/podcast-375.
I wonder why heatpipes can`t be used.Heatpipes are used to prevent the permafrost melting on the Qinghai-Tibet Railway.My guess is that heatpipes can be narrower than ventilation shafts and cheaper to install.
Every article keeps trotting out the same old story. And it comes straight from TfL with no critique. They (TfL) haven’t even robustly monitored the train temperatures. If they had they would know that the trains absorb more heat on the overground section in the summer than on the underground section. Knowing that would inform a different problem, and solution!
But then if the press helped solve the problem they might not have anything to write about NEXT SUMMER.
Calvin: Does what you say here imply that someone else has “robustly monitored the train temperatures”? If that is so, can you inform us who has done so, and with what level of confidence?
But anyway it is not immediately obvious to me that exact knowledge of where the heat comes from does make it a “different problem” anyway. If the problem is excessive temperatures in the underground sections, and the difficulty of removing heat in such sections, then that would be the problem that requires solving, regardless of where exactly the heat comes from.
Hi Malcolm
Obviously, I am limited to the monitoring I can do as a passenger. However, like my car it is reasonable to assume that there is a correlation between the internal space and the external temperature when there is no air conditioning of the internal space.
The problem has always been looked at as a tunnel problem, but the trains are uncomfortably hot on the surface in the summer, just like my house on a summers day. Hence the ambient air and the train body temperature through solar absorbed heat must affect the heat being carried into the tunnels in summer and that would explain why it is only a summer problem. I don’t think anything else that has been describe addresses why it is a summer problem. Hence, that being the case I believe one should concentrate on solutions that reduce the carry-in heat.
Calvin Burrows,
I am beginning to suspect a classic case of equating correlation with causation.
Trains in summer outside tunnels can be very hot because they act in a similar way to a greenhouse. Also you have the same problem as the tunnels, if the surrounding air is hot then there is nowhere for the heat to go. Underground, overground, two very different problems producing the same effect.
First thing in the morning in winter, Underground trains can be very cold due to them starting off cold when outside in the open. It actually can take a surprising time for them to warm up.
Equally, the temperature underground in winter (not just the trains but the stations too) can be surprisingly warm later in the day. But because you have probably come from a cold outdoors you not only tolerate a relatively short period of unsustainable heat, you positively welcome it.
If being objective you really need to measure the true temperature and not be subjective on the basis of how warm or cold you feel.
Hi Pedantic of Purley
The point I was making is that measuring the inside of the carriage on a summers day, which I have done, indicates what is happening outside. The greenhouse effect inside and the increase in train surface skin temperature outside. The sun, it is claimed, buckles rails, because it can increase the rail temperature but 20 degrees above ambient, so why would it not have a similar effect on the train’s external skin?
Hence a train on the surface is absorbing heat which it can emit without detriment until it reaches the tunnel. When in the tunnels it carries on emitting heat to try to reach a state of equilibrium, and hence heats the tunnel. Moreover, the difference in ambient air being carried in, by piston and drag effect, could be up to 40 degrees higher in the summer, than the depths of winter.
I was hoping for a continuing debate!?
@Calvin Barrows
We don’t trade in debate for the sake of it, but in facts. The fact that no-one has posted a response in almost a month means that this thread has run its course, unless new facts come to light. LBM