As the seasons change and the Northern Hemisphere gets a taste of what the Southern Hemisphere was feeling during winter, commuters on London's Underground could not be more ready for winter than right now.

In the month of August, London observed a sweltering heat wave that scorched the region for days on end.

To quell the effects of the immense heat on one's body, travelers could opt to go underground and use the Tube to get around. Except, Londoners have been complaining about the heat in the Tube too — it has been running for so many years that the earth surrounding it can no longer absorb the heat it emits.

Source: Pixabay

The Tube's construction began in the 1800's, with the Bakerloo line opening in 1906. The initial marketing strategy included a line about how it was the ‘coolest place to be' in hot summer weather.

But all that has changed. Travelers have reported that the temperatures inside the Tube on the Central Line have skyrocketed, making for an uncomfortable commute. So, why is it so hot?

Basically, the heat felt in the tube comes from the train's mechanisms itself.

Rail Engineering's Brian Tinham compiled a report entitled ‘Cooling the Tube' in December 2007, that directly pointed out the sources of heat causing discomfort for passengers. They wrote:

"A little detail: primary heat sources are 38% breaking losses, 22% mechanical, 16% drivetrain, 13% train auxiliaries, 4% tunnel support systems, 3% passengers in trains and 4% passengers on stations."

The London Tube tunnels were dug under Subterranean clay. The clay has been heating up, essentially turning the Underground into a clay oven, with little space for air conditioners. Trains are hot, and in a clay oven, they are even hotter.

More worrying is the expansion of the tube. Engineers are currently rolling out the Elizabeth line, which is set to open in the autumn of 2019. The overarching problem with this new expansion is that more trains equals more heat. The older lines are deeper with less ventilation. The issue is, the hot trapped air is being absorbed by the walls, but the earth does not seem capable of absorbing much more heat than it already is. Temperatures inside the tube reach up to 30 degrees Celsius (86 degrees Fahrenheit).

In 2003, the mayor of London at the time, Ken Livingstone, offered a prize of £100,000 to the mastermind who could come up with a good solution to cooling down the Tube. But it seems that prize has gone unclaimed.

The layman's solution to this would simply be installing a lot of air conditioners to keep the tunnels cool.  But, Rail Engineering says, ‘not so fast'. Transport for London (TfL) Cooling the Tube programme director Kevin Payne told Rail Engineering that it is a bit more complex than just putting air conditioners in.

“Payne estimates that removing heat from the network this way costs the upper end of 10 to 50 times as much as putting it in. Partly, also, it’s because warm air from the heat exchangers would have to go somewhere and, given the restrictions on building new ventilation plants across central London, it simply can’t.”

Another problem on the Central Line is that the trains run too deep and don't leave enough space for air conditioners. Engineers have, however, promised that a more sophisticated air conditioning system is coming, but only in 2030. In the meantime, they have introduced an experimental fan-based cooling system at Paul's Tube station. A report by Wired explains how it works:

"The system, which was designed by London Underground's crack cooling squad, pulled fresh air from the street and pumped water around pipes at a rate of 16 liters per second to cool the air by seven degrees before pumping it out at platform level. As a result, St Paul's has gone from one of the hottest stations on the Central Line to one of the coolest."

Passengers have taken to social media to express their disdain with the temperatures inside the carriages of the Underground. The temperatures even rose past the EU guidelines for transporting cows and sheep. The end of the heat of the Central Line is not in sight just yet, so, it falls to engineers to be the light at the end of the tunnel and fix the heat woes in London's Underground.


Works Cited

Temperton, James. “Why Is London's Central Line so Hot? Science Has the Answer.” WIRED, WIRED UK, 10 July 2018, www.wired.co.uk/article/central-line-temperature-london-weather-heatwave.

Rail Engineering, Cooling the Tube, as reported by Brian Tinham : http://www.plantengineer.org.uk/article-images/23757/cooling.pdf

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