I imagine you might dismiss as science fiction the following ‘press release’ I have invented for a decade ahead.

June 2035: GB Geothermal has announced ‘first heat’ at another gigawatt scale zero-carbon geothermal cogeneration project in the Tyneside region, three years after breaking ground on the latest of these increasingly commonplace ‘enhanced geothermal system’ projects. This one will supply 1 GW of free zero-carbon heat (1 GWth) to all connecting district heat networks, lidos, city growers and food processing businesses, along with competitively priced refrigeration and high-pressure steam for industry. To pay back the investment, most of the 1 GWe of firm electric power will be sold by private wire to local data centres and hydrogen factories, with the balance used to bring voltage stability to the grid.

However, a similar announcement is likely to occur in the US in the 2020s. The US government has financed the development and demonstration of geothermal technology for decades. One current project, GEODE, brings together 100 entities from the oil and gas, and geothermal industries to adapt oil and gas technology to catalyse a step-change in geothermal capacity. Meanwhile, a field laboratory project, Utah FORGE, develops, tests and optimises ‘next generation enhanced geothermal systems’ (EGS).

EGS re-purposes technology developed for oil and gas directional drilling and hydraulic fracturing to create a massive subsurface heat exchanger in very hot, previously impermeable rock. Long horizontal well pairs, measuring 1–3 km in length and 100–200 metres apart, are connected by 1–3 km² of typically 5 mm wide flow-conduits. Cold water is injected into one well and emerges very hot (>200°C) from the other. This heat is transferred by a heat exchanger to a power turbine and heat network, and the now-cold water reinjected.

EGS extracts stored heat in rock faster than nature replenishes it, but there is around 24,000 times more geothermal energy stored in the Earth’s crust than fossil fuel energy. Continuity of supply is achieved by drilling additional horizontal well pairs either deeper or horizontally offset, after perhaps 15 years of production.

The larger the created surface area of the subsurface heat exchanger, the larger the long-term sustainable power output per well-pair (MW/well-pair) and hence the lower $/kW energy price to the consumer. A project next year will try to create a 500-metre radius heat exchanger in 350°C rock.

Enhanced geothermal systems re-purpose technology developed for oil and gas directional drilling and hydraulic fracturing to create a massive subsurface heat exchanger in very hot, previously impermeable rock.

US and UK private sector activity
The private sector is developing rapidly: dry-hole costs of granite wells at Fervo Energy’s 400 MWe Cape project dropped by 50% to $4.8mn between 2023 and 2024, and the first well-pair produced 10 MWe. Cape is due to start commercial production in 2026. Another start-up, Sage Geosystems, is building a geothermal battery; and will also supply Meta with 150 MWe of firm power.

‘Next-gen’ geothermal start-ups are mostly founded by oil industry veterans. The major investors are US banks, energy traders, private equity, Japanese heavy industry, oil companies and oil service companies.

I believe the UK can and should deploy next-gen EGS technology now. UK companies Geothermal Engineering (GEL) and Eden Project have overcome cost and technology unavailability barriers. GEL has successfully developed a ‘natural-fault’ version of EGS in Cornwall. Drillers with Utah FORGE experience are already training UK firms.

For US oilfield service companies to transfer high tech equipment and teams to the UK, they need to be offered multi-year work-programmes. Domestic industry could then acquire US knowledge and build its own field laboratory: ‘UK FORGE’, if you will. The techno-economic analysis below is based on next-gen EGS technology applied to the North Pennine and Devon-Cornwall-Cornubian granites to produce 250°C water. There are other EGS-applicable regions.

In these granites, wells need to be drilled to 6.5 km depth with a horizontal length of 3 km (roughly 10 km measured depth) and so represent a significant upfront capital cost. However, EGS eliminates the exploration risk attendant on both hydrocarbon and traditional geothermal drilling. At the 16 p/kWh contract-for-difference (CfD) electricity price awarded to GEL, the return on capital is investable. Private wire prices are similar. The 80°C water byproduct can be supplied to heat networks at very low cost, justifying their extension to more distant communities.

Support mechanisms for geothermal
It may be that, as with any nascent industry and despite the extensive and successful deep EGS drilling programme in the US, some non-private institutions will be required to fill the funding gap for initial wells in the UK, but on commercial terms.

An extension of the public support in place for local heat network schemes – to private wire schemes – would accelerate projects currently constrained by grid capacity. The continuance of the CfD scheme for geothermal electricity would improve investor confidence, whilst Ofgem’s reforms continue. Clear roadmaps, ministerial statements, multi-level US-UK dialogue, and oil and gas retraining programmes would be highly beneficial.

The scale of the opportunity needs to be underlined: a minor four-well development in either UK granite would yield a 25-year-average capacity of 11.5 MWe and 28 MWth, saving over 60,000 tonnes of CO₂ per year compared with grid electricity and natural gas heating. It won’t take a lot of drilling to get us to gigawatt scale in the UK.

The views and opinions expressed in this article are strictly those of the author only and are not necessarily given or endorsed by or on behalf of the Energy Institute.

• Further reading: ‘Geothermal energy: Germany’s gateway to a more sustainable future’. Dutch multinational banking and financial services corporation ING Group has its own climate action approach and is helping to finance an innovative geothermal energy plant in Germany. Olaf Beyme, Renewables & Power Lead for ING Germany, explains.
• Find more about the potential of geothermal energy in Europe following the European Parliament’s adoption of a resolution calling for a European strategy on geothermal energy, tabled by Poland MEP and University of Bremen Professor Zdzisław Krasnodębski. The resolution calls for mapping geothermal assets, launching an industrial alliance on geothermal energy, and the introduction of a harmonised insurance scheme to mitigate financial risk for the sector.