UK’s first deep geothermal energy project for 37 years switched on

The UK’s first deep geothermal energy project in nearly four decades will start operating on Monday, a scheme that proponents hope will bolster the case for geothermal energy despite its high costs.

Reaching almost 5km below the Earth’s surface, the geothermal well at the Eden Project in Cornwall will tap into water of temperatures up to 200C and provide heating to nearby greenhouses and enclosed rainforest biomes.

“A rainforest is an expensive thing to heat,” explains Gus Grand, chief executive of Eden Geothermal, adding that the system will reduce the energy bills of the Eden Project by about 40 per cent.

The project comes at a time of growing interest in geothermal energy in the UK, including from the National Health Service, which is planning to use geothermal heating for some hospitals to reach its net zero goals.

A government white paper on deep geothermal energy is expected in coming weeks, which will assess the its potential in the UK and make policy recommendations.

The geothermal project at the Eden Project in Cornwall — The geothermal well will tap into water up to 200C © Eden Project

Drawing heat from the Earth’s core by tapping into hot water underground, geothermal power is reliable round-the-clock energy and has very low emissions.

Although the UK flirted with the idea of geothermal projects during the energy crisis of the 1970s, there is no specific policy support for geothermal energy.

Unlike shallow geothermal projects, which represent most of the UK’s existing geothermal projects, deep wells of more than 500m reach water that is extremely hot and can be used for heating and generating electricity.

When switched on, the Eden geothermal well will be the only operational deep geothermal well in the UK.

“This will have a lot of eyes on it, and rightly so,” says Professor Jon Gluyas, executive director of the Durham Energy Institute. “It will demonstrate that deep geothermal can generate low-carbon heat to customers around the region.”

Other efforts under way include the United Downs Deep Geothermal Power Project, also in Cornwall, which will produce both power and heat, and has finished drilling two deep wells with plans for another plant under way.

Visitors inside a rainforest biome at the Eden Project © Kai Greet/FT

The UK’s first deep geothermal energy system came online in Southampton in 1986. However, it is currently closed for repairs.

A persistent challenge for geothermal energy in the UK has been the cost of drilling wells. Unlike Iceland, the UK is not located near tectonic plate boundaries, which means the heat is further away from the Earth’s surface.

At Eden Geothermal, Grand admitted that drilling the well had been difficult and costly.

“We had to drill through granite, which is very hard, and very expensive. And we were doing it during Covid, which was very expensive,” she explained. “It is a demonstration — it is a research project. If you were doing a commercial project, you wouldn’t do it like this.”

Funded in part by money from the European Regional Development Fund and from Cornwall county council, the well cost about £24mn to build and the current system will produce around 1.4MW of energy.

Another challenge for such projects is the length of time needed to get a connection to the grid —something that is becoming a bottleneck for many renewables projects across Europe.

“We would love to turn it into electricity. But it’s a nightmare — my grid connection is for December 2036,” said Grand. “That is a big, big issue.”

One area where geothermal energy could make a difference more quickly is in heating systems, which generally do not require the same deep, expensive wells that are needed for electricity production.