New railway tunnels planned for the north of England could provide low-carbon heating for up to 6,000 homes annually, according to research from the University of Leeds.
The study, published in the Proceedings of the Institution of Civil Engineers, found that tunnels on the Northern Powerhouse Rail (NPR) route could generate between 54 and 98 gigawatt-hours of heat per year – enough to serve between 5,000 and 6,000 households.
The technology, known as “energy tunnels”, works by embedding pipes within tunnel linings to absorb heat that builds up underground from the earth, trains, equipment and passengers. A heat pump then transfers that energy to the surface, where it can supply heating and cooling to nearby homes and businesses, or feed into a district heat network.
Compared with gas boilers – the current standard for home heating – the approach could deliver carbon savings of between 2,000 and 3,500 tonnes per year. Even measured against air source heat pumps, another low-carbon alternative, energy tunnels would save between 271 and 490 tonnes of CO2 annually.
The researchers concluded that the system is both technically and economically viable. The additional upfront construction cost was estimated at around 0.2% of a new railway’s total price – a figure the team described as modest given the potential long-term benefits.
Dr David Barns, lead author of the paper, 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.”
The team also identified significant interest from large nearby energy users, including a hospital and a local authority located close to ventilation shafts on the route, which could connect directly without needing a district heat network.
Dual benefits
Project lead Professor Fleur Loveridge, professor of geo-energy engineering at Leeds, said decisions must be made at the earliest stage of planning.
“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,” she said.
“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.”
NPR plans include a new line linking Liverpool and Manchester via Manchester Airport and Warrington, with potential underground station options at Manchester Piccadilly under discussion.
The Department for Transport confirmed it is reviewing the study’s findings and will consider how they can be incorporated into planning requirements for NPR, as well as a broader partnership with academia to explore how transport infrastructure can support the low-carbon agenda.
Despite the potential, the researchers acknowledged that few commercial energy tunnel schemes exist globally. High initial costs, long payback periods, technical uncertainties and construction risk have all slowed uptake. Previous attempts to develop projects during Crossrail and HS2 Phase 1 did not proceed to construction.
The team set out steps needed to enable wider adoption, including cross-departmental government support, sufficient lead time to integrate the system into designs and contracts, further feasibility and business modelling, and careful planning to manage long construction time frames.
The research was funded through the UK Collaboratorium for Research on Infrastructure and Cities (UKCRIC), in collaboration with HS2.
Image credit: Toranote/Shutterstock
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