Researchers from Nottingham Trent University in the UK have discovered that abandoned coal mines are a potential source of renewable thermal energy.
Research carried out in collaboration with renewable energy company Alkane Energy found that residual heat available in mine groundwater can be condensed to regulate building temperatures.
The project is said to have explored redundant mines over a 30km area, which are thought to produce enough energy to heat 45,000 homes.
Professor Amin Al-Habaibeh from the School of Architecture, Design and the Built Environment led the study and said: "In a way we may never have previously envisaged, coal mines could once again be used to provide warmth to thousands of homes across the UK."
Alkane Energy project director Keith Parker said: "Alkane has traditionally utilised gas contained in disused coal mines to power its core electricity generation business."
"The utilisation of heat from mine water gives rise to a further opportunity to make use of the mines to provide green, sustainable energy to homes and businesses in the UK.
It also found that the technology, which uses a ground source heat pump system, could still be four times better when running on mains electricity, when solar or wind energy is not sufficient.
As part of the extraction process, higher temperatures can be produced using a heat pump, condensing the energy and circulating it in another central heating-type system.
The cooler groundwater is then circulated back to the mine where it again becomes lukewarm from the ground heat.
Image: Researchers explored redundant mines over a 30km area. Photo: courtesy of Victor Habbick/FreeDigitalPhotos.net.