TfL trials innovative cooling solution designed to reduce temperatures on the Tube network

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 temperatures on the deep Tube network - the Bakerloo, Central, Jubilee, Northern, Piccadilly, Victoria and Waterloo & City lines.  

TfL's trial comes as the UK experienced its hottest temperatures on record earlier this 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 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 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 would need to take place in a station open to customers (Knightsbridge) before TfL could look to potentially introduce them at four additional stations on the Piccadilly line (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trains with walk-through carriages are introduced to the line from 2025, the current fleet will be gradually withdrawn from service and the frequency of trains in peak hours will rise from 24 to 27 trains per hour from mid-2027.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 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. 

"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.   

Notes to editors

• The combination of the limited fleet size (86 trains) and current signalling system design restricts the current peak period service on the Piccadilly line to 24 trains per hour (tph). The introduction of an initial fleet of 94 trains on the line, which will be delivered from 2025, will enable 27 trains per hour to operate at peak times from mid-2027. Subject to TfL securing a long-term funding settlement from the Government - which could lead to the completion of line-wide re-signalling - and with the purchase of seven additional trains (up to a total of 101 trains), the service levels on the Piccadilly line could progressively be increased to 33 tph. A new signalling system would be designed with a capability to allow further timetable enhancements up to a maximum of 36 tph - as is the case on the Victoria line currently - to meet expected future demand. This capability would require the purchase of a further eight trains (to a maximum fleet size of 109 trains), subject to affordability. This would mean an additional 21,000 customers able to board trains every hour during peak times 
• TfL's modelling indicates that the following Piccadilly line stations would require cooling to mitigate temperature increases associated with running a 33 or 36 trains per hour service: Green Park, Holborn, Knightsbridge, Leicester Square and Piccadilly Circus 
• The cooling panel demonstrator project has been funded by TfL, the Department for Transport and Innovate UK as part of the Government's TIES Living Lab programme. Direct Engineering / INAL manufactured the cooling panel and OCL installed it at Holborn station 
• There are three TfL demonstrator projects included in the TIES Living Lab programme: the Cooling Panels project, a new generic template for Signalling Equipment Rooms, and the digitalisation of Cable Route Management Systems. More information on the TIES Living Lab programme is available here: https://tieslivinglab.co.uk/ 
• There are 192 air-conditioned Tube trains covering 40 per cent of the Underground network and there are enhanced tunnel ventilation systems on both the Victoria and Jubilee lines. All London Overground and Elizabeth line trains are air-conditioned 
• On older parts of the Tube network which have fewer ventilation shafts, TfL has introduced a range of station cooling systems including industrial-sized fans and chiller units to pump in cold air 
• A number of stations across the network have water points where customers can refill their water bottle when travelling, in addition to the Mayor of London's network of over 100 water fountains around the city 
• Actions designed to protect infrastructure and keep the network running during periods of hot weather include monitoring track temperatures, enhanced regime responding to air-conditioning faults, and regular checks on moving parts of tracks and crossings. Other measures specific to the railway include having response teams standing by and an enhanced focus on stalled trains and times, crowding and customer advice 
• Customers are advised to carry water with them when they travel during hot weather and to offer a seat to those who may need it. Anyone feeling unwell should contact a member of staff at the next station or speak to the bus driver