New railways could hold the key to cleaner, cheaper heating, through using underground tunnels as a heat source.
Harnessing heat from tunnels and other buried infrastructure could produce locally-sourced, secure, affordable heating – and cooling – for nearby homes and businesses, according to a new University study.
Researchers have found that, depending on the specific location, tunnels on the previously planned HS2 Phase 2b route could generate between 54-98 Gigawatt-hours of heat per year, enough to heat 5,000-6,000 homes.
In addition to reducing reliance on costly energy imports, the study also showed a carbon saving of between 271 and 490 tonnes per year when compared to using another low carbon alternative, air source heat pumps. When compared to how we currently heat our homes, using gas boilers, the carbon saving is between around 2,000 and 3,500 tonnes per year – equivalent to a small town’s emissions.
Crucial to explore options early on
The study, published in Proceedings of the Institution of Civil Engineers – Civil Engineering, concludes that “energy tunnels” are both technically and economically viable to offer heating and cooling and help meet our future energy needs.
With the Government’s recent commitment to Northern Powerhouse Rail (NPR), the paper’s authors say now is the ideal time to consider this, so that if the route permits, the process can be built into construction plans from the start.
Project lead Fleur Loveridge, Professor of Geo-Energy Engineering at the University, said: “There would be dual benefits if tunnel heating and cooling systems were implemented during construction: better transport links along with home-grown, cheaper, low-carbon heating and cooling. Extracting heat from the tunnel also reduces the need for expensive ventilation systems to cool it from the heat that would otherwise accumulate.”
She added: “The early project stage we’re currently in is the critical time to seriously consider integrating an energy tunnel system, with new rail lines due to be built in the 2030s.
“If further investigation suggests this isn’t right for this project, there will be ample time to decide against it later in the planning process. But to make an informed decision, we need to continue exploring these possibilities – and the only time to do that is now: right at the very beginning, before the first plans are drawn up.”
NPR plans include a new line connecting Liverpool and Manchester – on a route via Manchester Airport and Warrington that follows part of the axed HS2 high-speed rail plan. This much-needed investment in transport links in the north is likely to include new tunnels whilst discussions about station options at Manchester Piccadilly, including one that’s underground, are ongoing.
To make an informed decision, we need to continue exploring these possibilities – and the only time to do that is now: right at the very beginning, before the first plans are drawn up.
The Department for Transport has confirmed the Government is reviewing the study’s findings and will consider how they can be incorporated into planning requirements. They will also help to inform detailed design work on NPR - expected later this decade and early in the next - as well as a broader partnership between Government and academia to explore how new transportation projects can help the low carbon agenda.
Consideration of any technology adoption would be balanced against available funding and construction risks.
Heating and cooling
Anyone who has used the London Underground will have experienced how warm the tunnels can get. This is caused by the natural heat of the earth, as well as trains, equipment and people. Instead of just getting warmer and holding that heat underground, creating “energy tunnels” means that fluid in pipes in the tunnel lining absorb heat and carry it to the surface.
A heat pump uses this energy to efficiently provide heating or cooling, as needed. This can be supplied to buildings above the tunnel or if connected to a heat network, to homes and businesses nearby. These underground pipe systems that move hot water from a central heat source to many buildings are seen as vital to the UK’s energy future. However, many areas do not yet have them.
The team explored how the system could be used by the railway operator to heat and cool its own buildings and also identified significant interest from large energy users, including a hospital and local authority located near ventilation shafts on the route, meaning they could connect directly to the system, with no need for a heat network.
Despite the potential benefits of sourcing thermal energy via tunnels, few commercial schemes exist globally, partly due to high initial costs, long payback periods, technical uncertainties, and the need to minimise construction risk and delays.
Lessons learned
Dr David Barns, lead author of the paper, was a Research Fellow in Geosolutions in the School of Earth, Environment and Sustainability at Leeds during the study and its write-up. He is now a postdoctoral researcher in the Department of Energy Sciences at Lund University, Sweden.
He said: “Our study establishes that energy tunnels can be done if the right planning and arrangements are in place.
“We found the system can pay for itself through energy savings, and the additional upfront cost is small when compared to the cost of new railways: an extra spend of around 0.2%.”
A trial energy tunnel was installed in part of the Turin Metro extension in Italy. In the UK, attempts were made to develop projects during Crossrail and in Phase 1 of HS2, but neither proceeded to construction.
Leeds collaborated with HS2 on this research, which funded the project through the UK Collaboratorium for Research on Infrastructure and Cities (UKCRIC). Though Phase 2 of HS2 was cancelled in 2023, and Government is yet to appoint a delivery partner for Northern Powerhouse Rail, the research continued. They set out to learn lessons from these previous attempts, understand potential social and economic impacts of doing this for the northern leg of HS2, and identify steps needed to enable wider uptake.
Steps highlighted include:
- Cross-department support from Government on transport infrastructure and energy-related targets
- Sufficient lead time to fully incorporate the system into designs, contracts and construction practices
- Further feasibility and business modelling to establish future users and the financial case for installing energy tunnels
- Careful planning to manage long construction timeframes and uncertainty around future energy users.
Further Information
Main image credit: HS2 Ltd
The paper ‘Barriers and enablers to dual use of transportation tunnels for heating and cooling decarbonisation’ was published in print in Proceedings of the Institution of Civil Engineers – Civil Engineering, May 2026.
For further information or to arrange interviews please contact Deb Newman via d.newman@leeds.ac.uk