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The UK’s electricity grid has started getting its first geothermal power amid a worldwide resurgence of interest in geothermal, thanks to improving well technologies and rising power demand from data centres. The United Downs plant in Cornwall will generate 3 megawatts of electricity while also producing lithium for battery production.

“Let’s call it a renaissance,” says CEO of Geothermal Engineering Ltd., the company behind United Downs. “There is a lot going on in the US. There is quite a lot going on in Europe too, I think, in part driven by our sort of insatiable demand for 24/7 renewable energy.”

As energy grids come to rely on wind and solar generation that changes with the weather, geothermal can provide continuous clean power with a shorter build time than a nuclear plant and a smaller environmental impact than hydropower.

Although geothermal power heated Roman baths 2000 years ago and has produced electricity for decades in volcanic hotspots like Iceland and Kenya, it currently meets less than 1 per cent of global energy demand.

That could soon change. The International Energy Agency says geothermal could meet up to 15 per cent of the expected growth in electricity demand through 2050, producing more electricity than the US and India consume today.

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The United Downs facility has encapsulated the industry’s ups and downs. Tin and copper miners have long struggled with water flowing through faults in the hot granite below Cornwall, and a test well was drilled in the area in a brief flurry of geothermal exploration during the oil crisis of the 1970s and 80s. Law, a geologist, started the project in 2009 but had trouble raising money.

“It’s like oil-and-gas risk” but with a low return, “and hence it wasn’t that popular,” he says.

United Downs eventually won £20 million in grants, mostly from the European Union, and drilled two wells in 2018 and 2019 to a depth of 2393 metres and 5275 metres, deeper than most projects at the time. There, the radioactive decay of uranium, thorium and potassium isotopes heats water to 190°C (374°F) under high pressure. A pump in the deeper well pulls the water to the surface, where it produces steam to spin a turbine and generate electricity.

Law later rediscovered something else miners had noted: the water coming up was rich in lithium, an element critical for electric vehicle batteries. This will be stripped out by chemically coated plastic beads, flushed with fresh water and injected with CO2 to produce 100 tonnes of lithium carbonate powder a year initially, with a goal of eventually scaling up to 2000 tonnes. The geothermal fluid will then flow down the shallower well and through faults in the rock towards the deeper well, maintaining pressure in the reservoir.

Thanks in part to the lithium, which could bring in 10 times more revenue than electricity, United Downs was able to raise £30 million in private equity investment.

“The minerals add-on has suddenly started to make this sector very appealing,” says Law, who has permits for two 5-megawatt plants.

Prospects are more promising in EU countries like Hungary, Poland and France than in the UK. They have hot water closer to the surface and could 43 billion watts of geothermal for less than €100 per megawatt-hour, similar to coal and gas, according to the think tank Ember.

“You’re still looking at power grids dominated by wind and solar and hydro and batteries,” says at Ember. “But that doesn’t mean that there’s not a really valuable role for predictable low-carbon generation.”

And geothermal is now becoming economical beyond shallow hotspots thanks to techniques from oil and gas fracturing. Fervo Energy, a spin-out from Stanford University in California, is building a 115-megawatt geothermal plant to power Google data centres in Nevada, and has cut the time to drill a well from 60 days to 20 with diamond bits.

It’s also been drilling horizontal wells and pumping in high-pressure water to crack the rock between them. That creates dozens of hot fractures water can flow through, rather than just a few in a vertical-well project like United Downs.

This “enhanced geothermal” is expected to less than $80 per megawatt-hour by 2027, making it viable in most of the US, according to a study by at Stanford University and his colleagues. The administration of President Donald Trump has preserved a geothermal tax credit put in place during the previous administration.

In the US, geothermal could generate at least 90 billion watts by mid-century, about 7 per cent of current capacity, to the Department of Energy.

“Your costs are somewhat higher if you’re fracking,” says Horne. “But if you’re getting three to four times more energy out of it, that improves the economics and makes it competitive with solar and wind and gas on average.”

An enhanced geothermal plant in Germany had to temporarily shut down after causing a magnitude-2.7 earthquake in 2009, and concerns have also been raised about possible water contamination. But Horne says these can be prevented. And as more enhanced geothermal is built – at least half a dozen 20-megawatt-plus projects are under way in the US – communities and lenders will probably grow more comfortable, says at the think tank Rhodium Group.

“I wouldn’t expect it everywhere, but it can certainly play an increasing role on the grid,” says King, “particularly if you look out to 2050, if you’ve got double, triple the amount of electricity that we need, because we’ve got all this new stuff that we’re plugging in.”