TfL trials new solution to reduce temperatures at deep Tube stations

Transport for London (TfL) is trialling a novel cooling panel to determine its suitability for reducing temperatures on the deep Tube network - the Bakerloo, Central, Jubilee, Northern, Piccadilly, Victoria and Waterloo & City lines. 

TfL's trial comes as the UK recently experienced its hottest temperatures on record and the tube network became potentially dangerous for many passengers. Furthermore managing the heat generated by users is one of the limiting factors on increasing capacity at key points in the Tube network.

The cooling panel, currently being tested on a disused platform at Holborn station, 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 cooling 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 Transport Infrastructure Efficiency Strategy, 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 per cent 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 is earmarked to take place at Knightsbridge in a station open to customers with a planned roll out at Green Park, Holborn, Leicester Square and Piccadilly Circus on the Piccadilly line. 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 per cent 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. 

Without long-term sustained investment from Government, only projects already underway or those required to be compliant with safety and other statutory regulations would continue - meaning no new investment by TfL at all in the transport network. This would mean that while the new Piccadilly line trains, which are currently on order, will be honoured, any new order for Bakerloo and Central line trains to replace the ageing fleet would be delayed by a further 10 years until at least 2040.

In the past it has been challenging to lower temperatures on the deep Tube lines, as traditional cooling systems have proved prohibitively expensive and difficult to install within the 120-year-old tunnels and stations. In recent tests on a prototype cooling panel in a lab environment, an air temperature reduction of 10-15 degrees in the vicinity of the panel was achieved. TfL is now keen to see if this can be replicated on the disused platform at Holborn, which mimics the live environment that these panels would operate in. 

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.

"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."