Geothermal energy: A new, green lease of life for old coal mines

Stephen Williams-Dixon has vivid memories of his former life as a miner: a total of 23 years spent working 500 metres underground, at the Dawdon mine in the north-east of England. He remembers the water flowing in the collieries and having to be pumped out.

"Underground there’s always faults and where you have a fault you get water coming through. That water was a big problem," he explains. 

"We had to pump water out because you drowned."

Like Dawdon, coal mines across the UK are no longer in service, and water has slowly infiltrated the abandoned pits. But what could have been a liability has turned out to be an opportunity, giving the old coal mines a new, green lease of life.

The whole process is fairly straightforward, says Gareth Farr from the British Coal Authority: "Mine water is almost 20°C all year round. Once we abstract the mine water from underground we can then pass it through heat exchangers to recover heat from the water."

There are now plans to use this source of energy to heat 1,500 new homes in the coastal city of Seaham.

With some 23,000 pits no longer in use in the UK, there is huge potential in former mines waiting to be unlocked. An estimated 2 billion cubic metres of warm mine water are believed to be occupying old mine shafts, enough to heat millions of homes. This would make mine water one of the UK's largest clean energy sources, but so far it remains underused.

Nearby, the city of Gateshead has set itself an ambitious goal: carbon neutrality by 2030. Mine water, and the heat extracted from it, could help it get there. 

"We have invested £16 million," says John McElroy, a Gateshead Council cabinet member.

The mine water could become a serious contender to replace carbon-intensive sources of