A quarter of British homes sit above disused coal mines flooded with enough warm water to keep them toasty, says Alasdair Lane on the BBC’s Future Planet website. The Coal Authority claims naturally heated water beneath towns in Wales, central Scotland, northern England and the Midlands represents one of the UK’s largest underused clean energy sources. Seaham, on the coast of Co Durham, is already benefitting from mine-water heating. More than 150 litres of floodwater from the disused Dawdon colliery, at a temperature of 18C-20C, is pumped to the surface every second; its warmth is then transferred to a pipe network via a heat exchanger and fed into individual heating systems. Finally the water is returned hundreds of metres below earth to reheat. The process produces just 25% of the carbon emissions of gas heating – and, when fully developed, will be about 10% cheaper.
The world’s most advanced mine-water energy scheme is across the North Sea. The Dutch city of Heerlen has been tapping into its flooded collieries since 2008, and mine water now heats 500 homes and businesses. A “closed loop” system allows waste heat from businesses such as data centres to be reabsorbed and stored in the old mines. There are challenges: retrofitting houses and sinking boreholes isn’t cheap. But keeping ourselves warm accounts for about half of the UK’s emissions, and renewables won’t fill the energy gap as we phase out gas boilers from 2025. We urgently need an alternative, and Britain’s two billion cubic metres of warm mine water, waiting to be tapped, represents “one of our best options”.