Cooling the Tube

Elsewhere, conventional air-conditioning units have been installed above platforms at Oxford Circus and Green Park, but these are expensive to install and difficult to maintain. 

Jamie Burns, a programme delivery manager with the cooling team, explains: “Where there are no shafts, it requires a different approach. St Paul’s was only made possible by an empty lift shaft, and the Victoria ground water project was a one-off. 

“We can increase the speed of fans where they exist, and install platform air management systems, which works well and generally takes six degrees Celsius off platform temperatures. But they are hard to service when they sit above public areas and running tracks. Actively removing heat using energy is expensive and has to be a last option.”

With restrictions on adding ventilation shafts in central London, and air-conditioning on or off trains generating additional heat to the environment, LU has been busy seeking a third way. In 2005 former London Mayor Ken Livingstone memorably offered a prize of £100,000 for suggestions from the public, but this failed to produce any workable ideas or concepts that LU was not already considering.

McInulty stresses that the silver bullet to reducing temperatures on the network can only come from placing the removal of heat within a wider mathematical equation. 

Historically LU has focused purely on taking heat out of the system, without serious efforts being made to reduce the amount of heat being put in. This has now become LU’s first preference. 

As 80% of inputted heat comes from train motion and brakes, and 15% from equipment including lighting, LU has been able to examine a host of ways to reduce how much heat enters the tunnels in the first place, thereby reducing the need for cooling.

“It’s not just about cooling, it’s a whole energy management approach. Power and cooling are two sides of the same coin,” says McInulty.

“There’s no escaping the fact that a more intensive service requires extra power. Trains coasting is a great idea to reduce acceleration and save power, but that’s hard when in some parts you’re running a service of over 30 trains per hour. 

“We can make gains from deceleration, and we are buying trains with regenerative braking, which produces electrical energy from braking rather than all that heat from friction. 

“And there are other things that go unseen by the public that make a difference - we have put a thin film on the windows of Central Line trains, so they absorb less energy on the outside parts of the line which is then dumped underground. We’ve also made massive steps in using LED lights which give out less heat.”

The aim of the game might be achieving lower temperatures, but it has not escaped LU’s attention that biting down on energy use will bring other welcome benefits, not least substantial energy bill savings and reductions to the network’s carbon footprint.

“Customers are always our priority, but so is efficient use of their money,” adds McInulty. 

“We have a £90 million annual energy bill, and it is incumbent on us to reduce that. We are clearly conscious of our environmental credentials, too, and measure that in all sorts of ways. We can become energy efficient, but having so much of the network outside also gives us a great opportunity to work with solar panels. 

“In the meantime, we will continue to incrementally reduce temperatures on the network, so it’s win-win all round.” 

Growing the network and increasing service frequency might be the most noticeable end-result of LU’s investment in meeting the demands of London’s growing population, but thanks to McInulty’s team and their hidden efforts, more comfortable temperatures may not be far round the corner. 

  • This feature was published in RAIL 793 on February 3 2016

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  • Andrewjgwilt1989 - 23/04/2016 01:11

    Most tube stations that are underground do need better air-conditioning to keep stations cool and to reduce overheating with passengers feeling hot during the hot weather as they use the Underground across London and Crossrail stations that are underground will also have new air-conditioning systems to keep the stations cool and clean.

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  • Calvin Barrows - 27/07/2018 19:56

    Has anyone else noticed the correlation between the extreme summer weather conditions and the heat on the tube? All the mechanical and electrical systems don’t know it’s summer! My car hadn’t moved all day yesterday but the temperature on the gauge was registering 32 degrees. Cars and trains are fundamentally constructed of similar material so why wouldn’t the summer weather make the trains super-hot? The trains carry all the summer heat into the tunnels and discharge some of it. Please think about it! It may surprise you that the numerous temperature readings I have taken all indicate that the trains gain much more heat in the summer when on the surface than they do underground. These tests could easily and cheaply be replicated and verified. Overheating wasn’t a problem in the winter – you probably kept your coat on in the tube then? Perhaps not surprising when the annual temperature range varies from say minus 5 to 35 degrees! Cooling stations is not addressing the real danger. That of being stuck in an overheated train in a tunnel when one is unable to escape. From the point of view of comfort, most passengers spend more time in a train than on a platform. So, what has been achieved does not, I believe, address the real issues. This would be part of my suggested solution.

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    • Anthony Collyer - 07/08/2019 18:07

      I understand it is intended new 2030 deep level tube trains will have some form of integrated air-conditioning. Does anyone have information on how this is to be achieved? If not I have a suggestion which is really a much-preferable extension of the interim experimental solution which might be considered by London Underground in the meantime Temporary solution – when temperatures on the, say, Central line between White City and Stratford exceed 30 C: As Per “Different systems have been proposed to cool Underground trains, including the use of large blocks of ice inside the train. The blocks would be kept in refrigeration units, preventing them from melting completely” Instead of ice use cheap and readily available sealed picnic “ice packs”. 50kg of these could be installed in wheeled insulated containers with battery-powered thermostatically controlled fans. My calculations indicate two of these units per carriage would be capable of cooling the air in the carriage from 30 C to 20 C for the duration of the journey from White City to Stratford. At Stratford the units would be substituted with fresh ones by LU staff (hired for the duration of the warm conditions) for the return journey to White City. Both White City and Stratford have sufficient space and access to fresh are for commercial deep-freezes (rented for the duration of the warm conditions) to have fresh freezer packs available. The 50kg wheeled units would need to be secured appropriated to prevent theft/malicious damage Similar approach to be used for other sections of the deep tube network What do people think?

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      • MR Anthony Collyer - 15/09/2019 17:12

        p.s. Page 45 "In tube hybrid cooling" shows what is promised for deep-level tubes in 2030 ....

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