The UK’s first deep geothermal energy project in nearly four decades will start operating on Monday, a plan that supporters hope will boost the case for geothermal energy despite its high cost.
Reaching about 5km below the Earth’s surface, the geothermal well at the Eden Project in Cornwall will tap water at temperatures of up to 200C and heat nearby greenhouses and enclosed rain biomes.
“Rainforests are an expensive thing to heat,” explains Gus Grand, chief executive of Eden Geothermal, adding that the system will cut the Eden project’s energy bills by about 40 percent.
The project comes at a time when there is growing interest in geothermal energy in the UK, including the National Health Service, which is planning to use geothermal heating for some hospitals to reach its net zero targets.
A government white paper on deep geothermal energy is expected next week, which will assess its potential in the UK and make policy recommendations.
Drawing heat from the earth’s core by tapping into hot water underground, geothermal power is reliable energy around the clock 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 the majority of existing UK geothermal projects, wells deeper than 500m access water that is extremely hot and can be used to generate heat and electricity.
When switched on, the Eden geothermal well will be the only working deep geothermal well in the UK.
“There will be a lot of eyes on this, and rightly so,” says Professor John Gluyas, executive director of the Durham Energy Institute. “It will show that deep geothermal can generate low-carbon heat for customers around the area.”
Other efforts include the United Downs Deep Geothermal Power Project, also in Cornwall, which will produce both power and heat and has completed drilling two deep wells with plans for a second plant.
The UK’s first deep geothermal energy system came online in 1986 in Southampton. However, it is currently closed for repairs.
A continuing challenge for geothermal energy in the UK is the cost of drilling wells. Unlike Iceland, the UK is not located near tectonic plate boundaries, which means that heat is further away from the Earth’s surface.
At Eden Geothermal, Grande admitted that drilling the well was difficult and expensive.
“We had to drill through granite, which is very difficult and very expensive. And we were doing it during Covid, which was very expensive,” she explained. “It’s an exhibition – it’s a research project. If you were doing a commercial project, you wouldn’t do it this way.”
Partly funded by money from the European Regional Development Fund and Cornwall County Council, the well will cost around £24mn to build and the existing system will produce around 1.4MW of energy.
Another challenge for such projects is the length of time required to get a connection to the grid – something that continues to be an obstacle for renewable projects across Europe.
“We would love to turn it into electricity. But it’s a nightmare — my grid connection is for December 2036,” Grand said. “It’s a big, big issue.”
One area where geothermal energy can make a difference more quickly is in heating systems, which do not require the deep, expensive wells typically required to generate electricity.
