An exploration team in Newcastle plan to drill through old mining tunnels to search for geothermal energy under the city centre.
Researchers from Newcastle University who are leading the project hope it could initially provide up to 5MW of thermal energy, with potentially more heat and electricity from future boreholes.
This would provide heat for a new campus that will combine research facilities with affordable housing, while some energy may be siphoned off the power a nearby shopping centre.
Drilling is expected to begin next week, pending a number of official permissions, on an exploratory 2km borehole at the planned 20-acre Science Central campus, the site of the former Scottish and Newcastle Breweries.
The borehole will be the deepest ever drilled in a UK city, according to scientists from the Newcastle Institute for Research on Sustainability, who believe that water will be pumped out at a temperature of 80oC.
The Institute’s director, Paul Younger, said the project would be a flagship for the city’s plan to become an exemplar for sustainable urban environments.
‘The vast majority of the world’s population for many decades to come will be in existing cities, not in small eco-developments, so the real challenge is increasing the sustainability of old industrial cities,’ he told The Engineer.
If successful, the borehole will access water heated by naturally occurring low-level background radiation found in the granite that underpins the landscape surrounding Newcastle.
Rather than tapping into the granite directly, the borehole will drill into sandstone under the city connected to the granite by a major inactive geological fault, which allows heated, mineral-rich water to circulate through the rock strata.
The borehole will also have to pass through a layer, a few hundred metres deep, of coal mining tunnels that sit directly beneath the city centre. This presents particular challenges for the company managing the project, County Durham-based Drilcorp.
‘We’ll be drilling with a mud flush, which means we keep the borehole full of mud, and that disappears if we hit a hole,’ said Drilcorp’s contracts manager, Matthew Dale.
‘We can seal it with a steel tube but if there are lots of layers of holes it restricts the size of the borehole each time you put a tube in. The other option is to effectively seal up the seam with concrete.’
The mud flush is necessary to seal the borehole against potential gas leaks as drilling progresses, and gas monitoring is required all the way down.
‘The mines are unknown so we don’t know how long it will take to go though them – we might never even encounter them,’ said Dale. ‘We hope we’ll do it within 12 weeks.’
The project was funded with £400,000 from the Department of Energy and Climate Change’s Deep Geothermal Challenge Fund, with another £500,000 coming from the university and Newcastle City Council.
If the first project is successful, future boreholes may be able to provide tens of megawatts of thermal energy and could even provide a source of power for electricity generation, said Younger.
‘You have to get water to probably about 120ºC so we’d need to go even deeper for that, maybe to about 3km. If we did do that you could probably rely on each megawatt of electrical energy providing you with about 5MW thermal.
‘That’s one of the nice things about geothermal: it does produce a hell of a lot of useful heat energy.’