Advocates claim enough geothermal energy in abandoned coal mines to heat 180m homes. The weed-lined disused road beside Lanchester Wines’ ageing warehouse on a north-east England industrial estate could not be more low key. But beneath the roadway’s many manhole covers are shafts which descend 200m into what could be the UK’s most widespread unused energy source – minewater. Lanchester Wines’ facility in Gateshead has by far the UK’s biggest commercial minewater heating scheme. It supplies all the warehouse’s needs, keeping millions of bottles of wine temperate, and also heats a neighbouring distribution depot. Advocates of using minewater for heating regard it as having particularly significant potential after the UK set the ambitious goal earlier this year of net zero greenhouse gas emissions by 2050. A quarter of all UK homes and businesses, some 9m buildings, and most of its largest cities outside London sit on former coalfields. Coal mining, which employed 1.25m people at its peak, powered the British economy for well over a century but the last deep mine closed in 2015. One of its underground legacies is the warrens of galleries through which run an estimated 2bn cubic metres of water, heated by surrounding rocks to 12-16 degrees Celsius. At present, minewater is a problem. Often high in iron and pollutants and potentially a threat to drinking water and rivers, its management by the publicly funded Coal Authority cost £18m last year. Yet Lisa Pinney, the authority’s chief executive, said minewater “could be a real contribution to zero carbon”. Opportunities she cited included horticulture, new housing and leisure schemes. According to Coal Authority data, heating currently accounts for 45 per cent of the country’s energy use and 32 per cent of its emissions. Meeting the government’s net zero carbon emissions target will require slashing fossil fuel use. Three extraction shafts outside the warehouse raise 39 litres of minewater a second to the surface using an open loop water source heat pump system. The minewater travels by pipe around the plant room into a heat exchanger. Here, the minewater heat boils liquid ammonia, concentrating the ammonia’s heat at 50 degrees C. This heat is then used to warm water which circulates around the factory’s heating system. Meanwhile the minewater, above ground for only two minutes, is sent back underground to warm up again. Now the 60-year-old Gateshead warehouse has a 2.4MW system yielding 6KW of heat for each kilowatt of electricity used. Its installation has brought the company its first payment, of £117,000 payment, under the government’s renewable heat incentive scheme. The company’s other nearby warehouse, which has hit an even better minewater supply yielding 67 litres a second, will within weeks start operating its own heating scheme. Mr Black expects payback on the £3.5m investment, part of £8m spent on renewable energy to make the company carbon neutral, within seven years. In Bridgend, in south Wales, the local authority is working with scientists to develop a minewater heating network for a local community. And in Durham the county council has invited tenders for heating a leisure centre swimming pool using minewater. Mike Stephenson, the BGS’s chief scientist, said the Glasgow studies were focusing on “de-risking” minewater heat use and that the research should be sufficiently advanced to enable investment decisions in two years. “The wonderful irony here is we used coal to carbonise the economy,” he said. “Now we are going to use the coal mines that exist to decarbonise.”
