Geothermal power station at United Downs in Cornwall, UK
Thomas Frost Photography/Geothermal Engineering Limited
Britain’s electricity grid has started to receive its first geothermal power amid a worldwide resurgence of interest in geothermal, thanks to improved well technologies and increasing power demand from data centres. The United Downs plant in Cornwall will generate 3 megawatts of electricity while producing lithium for battery production.
“Let’s call it a renaissance,” says Ryan Law, CEO of Geothermal Engineering Ltd., the company behind United Downs. “There’s a lot going on in the US. There’s quite a bit going on in Europe as well, I think, partly driven by our kind of insatiable demand for 24/7 renewable energy.”
As energy grids come to depend on wind and solar production that changes with the weather, geothermal energy can provide continuous clean power with a shorter construction time than a nuclear power plant and less environmental impact than hydropower.
Although geothermal power heated Roman baths 2,000 years ago and has produced electricity for decades in volcanic hotspots such as Iceland and Kenya, it currently meets less than 1 percent of global energy needs.
That may soon change. The International Energy Agency says geothermal energy could cover up to 15 percent of the expected growth in electricity demand until 2050, producing more electricity than the US and India consume today.
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 beneath Cornwall, and a test well was drilled in the area in a short amount 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 low returns, “and that’s why it wasn’t that popular,” he says.
United Downs eventually won £20 million in grants, mainly from the EU, and drilled two wells in 2018 and 2019 to a depth of 2,393 meters and 5,275 meters, 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 draws the water to the surface, where it produces steam to spin a turbine and generate electricity.
Law later rediscovered something else miners had noticed: the water that came up was rich in lithium, an element critical to electric vehicle batteries. This will be removed by chemically coated plastic balls, flushed with fresh water and injected with CO2 to produce 100 tonnes of lithium carbonate powder a year initially, with an aim to eventually scale up to 2,000 tonnes. The geothermal fluid will then flow down the shallower well and through faults in the rock towards the deeper well, maintaining the pressure in the reservoir.
Partly thanks to the lithium, which could generate 10 times more income than electricity, United Downs was able to raise £30 million in private equity investment.
“The mineral subsidy has suddenly started to make this sector very attractive,” says Law, who has permits for two 5-megawatt plants.
The outlook is more promising in EU countries such as Hungary, Poland and France than in the UK. They have warm water closer to the surface and can generate 43 billion watts of geothermal energy for less than €100 per megawatt hour, equivalent to coal and gas, according to think tank Ember.
“You’re still looking at grids dominated by wind and solar and hydro and batteries,” says Frankie Mayo at Ember. “But that doesn’t mean there isn’t a really valuable role for predictable low-carbon production.”
And geothermal energy is now becoming economical beyond shallow hotspots thanks to techniques from oil and gas fracking. Fervo Energy, a spin-out from Stanford University in California, is building a 115-megawatt geothermal plant to power Google’s data centers in Nevada, and has cut the time to drill a well from 60 days to 20 with diamond bits.
It has also drilled horizontal wells and pumped in high-pressure water to break the rock between them. That creates dozens of hot fractures through which water can flow, rather than just a few in a vertical well project like United Downs.
This “enhanced geothermal” is expected to cost less than $80 per megawatt-hour by 2027, making it viable in most of the United States, according to a study by Roland Horne of Stanford University and his colleagues. The administration of President Donald Trump has preserved a geothermal tax credit that was put in place under the previous administration.
In the United States, geothermal energy could generate at least 90 billion watts by mid-century, about 7 percent of current capacity, according to the Department of Energy.
“Your costs are somewhat higher if you’re fracking,” says Horne. “But if you get three to four times more energy out of it, it improves the economics and makes it competitive with solar and wind and gas on average.”
An improved geothermal plant in Germany had to temporarily close after causing a 2.7 magnitude earthquake in 2009, and concerns have also been raised about possible water contamination. But Horne says that these can be prevented. And as more improved geothermal is built — at least half a dozen 20-megawatt-plus projects are underway in the U.S. — communities and lenders are likely to become more comfortable, says Ben King of the Rhodium Group think tank.
“I wouldn’t expect it everywhere, but it certainly could play an increasing role in the grid,” King says, “especially if you look out to 2050, if you have double, triple the amount of electricity that we need, because we have all this new stuff that we’re connecting.”
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