Britain's first geothermal plant opens in Cornwall: Green project will provide power to 10,000 homes - but sceptics raise fears of earthquakes across the south-west

Cornwall's idyllic landscape was once home to the UK's most valuable mining industry, but now a very different project will begin plumbing England's depths.

From today, Britain's first geothermal power plant will begin producing clean electricity 24 hours a day without pause.

The United Downs deep geothermal plant, located just outside of Redruth, will produce enough electricity to power 10,000 homes.

Developed by Geothermal Engineering Ltd (GEL), the project works by drawing water from an underground reservoir more than three miles (5.2 km) beneath the surface.

This water reaches the surface at around 190°C (374°F), at which point it is run through a heat exchanger to create steam and drive an electric turbine.

The water is then fed back into the ground through a second well, where it filters through natural cracks and eventually recharges the reservoir.

The result is an effectively 'free' source of power that produces electricity around the clock, no matter the weather, for about 96 per cent of the year.

However, sceptics have raised fears of earthquakes spreading across the south–west as geothermal power becomes more popular.

While geothermal power has major advantages over other renewable energy sources, the downside is what scientists call 'seismicity'.

Drilling over three miles into the ground and injecting water into fractures in the rock has the almost inevitable consequence of producing tremors.

GEL CEO Ryan Law told the Daily Mail: 'It's because we're moving water underground, and that can sometimes cause little fractures to slip because they're lubricated by the water.'

For two days in 2020, GEL induced 15 mini–quakes of magnitudes up to 1.5 as it was carrying out drilling at United Downs.

Residents nearby reported that their windows rattled and they heard a sound like a heavy thunderstorm.

Likewise, drilling at a geothermal project at the Eden Project in Cornwall was put on pause in 2022 after triggering a magnitude 1.6 earthquake.

These are very similar to the tremors produced by fracking, which has been all but banned under legislation that limits operations that produce anything larger than a 0.5 magnitude tremor.

Geothermal power, meanwhile, is restricted by the surface vibrations – which measure what someone would actually feel – allowing for bigger tremors.

However, experts say that there is no chance of these mini earthquakes causing any serious problems.

Mr Law says: 'You can never trigger events that are bigger than would happen naturally.

'I would never drill into the San Andreas Fault, because that is a tectonically active zone, but in the UK we're just incredibly stable, so there's never going to be that danger.'

Likewise, since the operation moved from drilling to pumping, there haven't been any signs of renewed seismic activity.

Dr Alison Monaghan, Head of Geothermal at the British Geological Survey, told the Daily Mail: 'Very small tremors were observed deep in the subsurface when the geothermal project was in construction – during drilling and testing.'

However, she adds that 'it is extremely unlikely that any seismicity will be felt once the power plant is online and the geothermal system is in operation.'

Even with those concerns in mind, many argue that the positives of geothermal power outweigh the risk of any minor tremors.

When geothermal power is mentioned, most people probably think about the volcanic hotspots of Iceland or America's Yellowstone National Park. 

However, Mr Law says that Cornwall has two unique benefits: geology and history.

The geology of the southwest is extremely rich in mildly radioactive granite, which generates enormous amounts of heat deep below the Earth.

As long as someone is prepared to drill down deep enough, this offers an essentially limitless source of thermal power.

The second benefit, according to Mr Law, is that Cornwall's geothermal potential was the source of intense research following the 1980's fuel price crisis.

This meant much of the groundwork for establishing the UK's first geothermal power plant had already been laid, long before GEL was even founded.

Unlike other solar or wind power, geothermal sites are tiny – with the United Downs plant only taking up 6,000 square metres (1.5 acres).   

Most importantly, once the well has been drilled, geothermal power will produce energy around the clock.

By contrast, weather–dependent solar farms only produce power about 25 per cent of the time, while wind farms are active for 20 to 40 per cent of the year.

As demand for round–the–clock energy for data centres, electric vehicles, and industrial applications rises, consistent green power is vital for hitting net zero.

But at the United Downs site, there is another added incentive which might prove even more tempting.

In addition to being naturally hot, the rocks beneath Cornwall are staggeringly rich in minerals.

By complete chance, when GEL started testing the water at United Downs, they realised that it contained a 'stellar' concentration of lithium.

The water drawn to the surface for heating has a lithium concentration of about 360 parts per million, roughly twice that found at some of Europe's best sites.

Once the water has been cooled to 60°C (140°F) by the heat exchange, it also happens to be the perfect temperature for lithium extraction.

This allows the power plant to process vast amounts of valuable lithium as a byproduct, which can be processed and used in batteries for electric vehicles.

That chance discovery allowed GEL to draw £1.8 million in government support for critical minerals and secure an £119–per–megawatt–hour electricity contract.

GEL plans two other combined lithium power projects nearby, and expects them to produce around half of the UK's demand within the decade.

By 2030, these sites could be churning out almost 20,000 tonnes of lithium carbonate a year, enough to produce 250,000 electric vehicles.

Colin Walker, Head of Transport at the Energy and Climate Intelligence Unit (ECIU), said: 'This is net zero as a driver of economic growth in action, and an example of how green technologies are creating jobs and growing the UK’s economy.

'With plants like this opening in the South West, we could see lithium mined in Cornwall, refined on Teesside, used to build batteries in Somerset, which then go on to power EVs being built in the West Midlands.'