Subterranean rail infrastructure can perform functions in addition to passenger and freight transport: these structures can transfer thermal energy to heat and cool homes.

The development of such energy delivery systems entails embedding heat transfer pipes in the linings of tunnels, typically during construction, to extract thermal energy from shallow geothermal resources and from within the tunnels themselves. Heat pumps then use this heat to provide low carbon heating or cooling to buildings sited above the tunnels or — if connected to a heat network — buildings and homes across a much wider area.

The feasibility of rail tunnels as thermal energy suppliers was explored by researchers from Politecnico di Milano (Italy), University of Leeds (U.K.), H2S Ltd. (U.K.) and Bechtel (U.K.). The potential to harness thermal energy from subterranean rail infrastructure on a rail route between Manchester and Crewe, U.K., was estimated to be as high as 98 GWh of heat per year, sufficient to heat 5,000 to 6,000 homes.

“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,” said project lead Fleur Loveridge, professor of geo-energy engineering at Leeds University. “Extracting heat from the tunnel also reduces the need for expensive ventilation systems to cool it from the heat that would otherwise accumulate.”

The research is published in Proceedings of the Institution of Civil Engineers — Civil Engineering.