New cooling system trialled on Tube network

A thermal image of the cooling panel - image from TfL.

A new cooling system is being trialled on the London Tube with a view to reducing temperatures at the network’s deep stations. 

Transport for London (TfL) is now trialling a state-of-the-art cooling panel on a disused platform at Holborn station to test its suitability for reducing platform and tunnel temperatures at five stations on the Piccadilly line - one of the network’s deep Tube lines which also includes the Bakerloo, Central, Jubilee, Northern, Victoria and Waterloo and City lines. 

The trial comes as the UK experienced its hottest temperatures on record last week. 

The cooling panel aims to provide cooler air to passengers waiting on platforms, as well as mitigating potential temperature increases associated with running an increased number of trains on the Piccadilly line, as part of the line’s future capacity upgrade. 

The panel works by circulating cold water around pipework within a curved metal structure to chill it. It then circulates air, using an industrial-sized fan, through gaps in the panel’s structure, which in turn is cooled. 

The panel could also have the additional benefit of halving operational and maintenance costs, compared to existing technology used to manage temperatures on Tube lines. 

The trial is part of the government’s TIES Living Lab programme, a collaboration of 25 partners focusing on 10 infrastructure, data research and digital demonstrator projects, of which the cooling panels are one. 

The cooling panel project was 70% funded by the Department for Transport and Innovate UK. The convection cooling system has been designed by TfL and developed by SRC Infrastructure, which also managed its build. 

Following the trial at Holborn station, and subject to funding being available, TfL will explore whether the panels could provide a cooling solution for other deep Tube lines in the future. 

Further testing would take place at a station open to customers -  Knightsbridge - before TfL could look to potentially introduce them at four additional stations on the Piccadilly line. These would be Green Park, Holborn, Leicester Square and Piccadilly Circus. 

TfL could then identify other locations where the panels could provide a benefit. Progressing this trial at other locations would ultimately be subject to TfL having sufficient long-term capital funding available.   

The Piccadilly line was chosen for this trial as when new, air-conditioned trains with walk-through carriages are introduced to the line from 2025, the current fleet will be gradually withdrawn from service and the frequency of trains in peak hours will rise from 24 to 27 trains per hour from mid-2027

This is a train every 135 seconds at the busiest times and represents a 23% increase in peak service capacity. 

Although currently unfunded, line-wide re-signalling would enable TfL to increase train frequencies on the Piccadilly line to 33 and then 36 trains per hour. It is at this point that additional cooling at five Piccadilly line stations would be necessary, according to TfL’s modelling. 

Paul Judge, TfL’s project director for the Piccadilly Line Upgrade, said: “This innovative trial is taking place as we are experiencing record high temperatures. This new technology could play an important role in ensuring we are doing everything we can to protect TfL’s network against future temperature increases, helping to keep staff and customers safe and comfortable. 

“The TIES Living Lab project has given us a great collaborative platform for sharing innovative ideas, data, and good practice with a range of suppliers. The cooling panel project is supporting the Piccadilly Line Upgrade, which will see new state-of-the-art trains with more space, air-conditioning, walk-through carriages and improved accessibility running at greater frequencies on the line. 

“By seeking innovative solutions to cool platforms on the deep Tube network, we will be able to support future Piccadilly line train frequency increases with the possibility that the technology could be used on other Underground lines.”  

The aim of the new cooling panels is to significantly out-perform the existing Platform Air Handling Units, which are currently installed at some stations on the deep Tube network. Initial results show that the new cooling panels are much better equipped to operate in the unique conditions of the deep Tube environment.

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