Decarbonising the London Underground rail system; Decarbonising the London Underground rail system;

Reusing waste heat from the London Underground rail network, London

How can cities capture and reuse low carbon waste heat?

The London Underground is preparing to be a net zero carbon railway by 2030. Although more sustainable than fuel-powered cars, there is much to be done across the underground network for this to be achievable. Transport for London (TfL) has been exploring several avenues for carbon reduction and Arup has been supporting three of its decarbonisation areas;

  • how waste heat produced by underground trains can be captured and repurposed;

  • how TfL land can be used for solar PV power generation;

  • and how to procure long term renewable power from third party generators. 

The first project exploring waste heat recovery concluded in 2020.

Heat from the London Underground has the potential to be a significant low-carbon energy source but the feasibility of doing so has been unclear. Arup undertook a technical, economic, operational, construction and deliverability analysis to identify how and where heat from 55 ventilation shafts and 20 pumped groundwater locations across the underground network could be best captured – a scale not attempted before. 

The findings of our work are delivering ground-breaking new insights into the decarbonisation of London, uncovering viable routes to heating local homes and businesses sustainably and affordably. 

Project Summary

260ktCO₂ potential emissions savings over 40 years, up to 80% per site. 

15,000homes could be powered by repurposed heat

40+stakeholder groups engaged with

Repurposing waste heat

The ventilation systems across the London Underground operate continuously to reject heat from the network, providing a year-round potential source of low carbon heat suitable for utilisation by nearby consumers via electronically driven heat pumps. However, TfL’s complex infrastructure presents challenges in selecting appropriate sites to test the approach and designing commercially and operationally feasible heat extraction systems.

Our approach combined desktop research with site surveys to develop a bespoke scoring matrix that assessed sites on several factors such as access, constructability and space availability. We identified and engaged with potential and existing heat off-takers in the vicinity of each site, which enabled us to determine the viability of transferring the waste heat to nearby buildings and to calculate system financial performance based on the customers’ heat demands.

The matrix acted as a single source of data. Using this method, each site was compared conveniently and consistently to determine the optimal sites for the reuse of waste heat. Now established, the tool can be used by TfL at future locations to help assess future opportunities for heat recovery as the demand for low carbon heat continues to increase.

Demonstrating the impact

The six highest scoring ventilation sites were progressed to a detailed feasibility stage. This phase involved further engagement with off-takers, ranging from Local Authorities and developers to multinational heat network Energy Services Companies, as well as design development and technical and economic modelling of systems against the business as usual case.

Coupled with a similar analysis carried out on pumped water locations around London, which unveiled three viable locations, our study's final nine feasibility sites could heat 15,000 homes and several significant commercial buildings in London, helping to save over 260 kilo-tonnes of CO² emissions over 40 years.

TfL is a world leader in many environmental initiatives and we are constantly striving to do more to reduce our carbon footprint and help tackle the climate emergency. Heat from the London Underground has the potential to be a significant low-carbon energy source and we have carried out further research with Arup, as part of our energy and carbon strategy, to identify opportunities for low carbon projects across London Underground. This would contribute towards the Mayor of London’s ambition to make London carbon-neutral by 2030. ” Lilli Matson, Chief Safety, Health and Environment Officer, TFL

Planning for low carbon heat

On successful completion of the feasibility work, we worked with TfL to undertake a market sounding exercise to better understand the route to market and procurement options for waste heat schemes. This involved engagement with over 40 heat network operators, suppliers, Local Authorities, and developers, supporting pioneering steps towards waste heat reuse and decarbonisation across London’s underground network.

Find out more about our services in waste to energy solutions