Geothermal energy generation is not just limited to ground source heat pumps. Construction is set to begin on the UK’s first commercial-scale power station in October.
Gemma Goldfingle reports.
After four years in development, a 60MW geothermal power plant is set to get under way in Redruth, Cornwall.
A planning application was submitted in March following months of consultation with local residents.
Geothermal Engineering, the company behind the ground-breaking scheme, is confident it will be approved.
“We have been working with the local authority for a long time and they are very keen for this sort of development to be located in the area.
Residents have also been overwhelmingly positive about the scheme,” says Geothermal Engineering managing director Ryan Law.
“The area is remote so no disturbance will be caused during drilling. As the scheme is under the ground, there is no effect on aesthetics either.
Plus at the end of it, residents will benefit from very low-cost heating.”
While shallow drilling for geothermal energy can help heat and cool a building, deep geothermal drilling can heat and cool an entire community.
The method works on similar principles as shallow drilling, but at much greater depths.
Wells are drilled into granite to more than 4km deep, where temperatures exceed 170oC.
Water is pumped into the rock, where it is naturally heated, before being pumped back to the surface as hot water or steam.
Heated water will be used to power turbines to generate electricity and as a renewable heat source for the local area.
Initially, three wells will be drilled at Redruth.
From these three wells, more than 10MW of electricity will be generated, enough to power between 15,000 and 20,000 houses, and more than 50MW of thermal energy, enough to power 20 hospitals.
This thermal energy will be connected to a district heating system for the area around Redruth.
“Heat is essentially a waste product for us.
We are harnessing the electricity from the scheme and connecting into the grid.
However, this by-product can power an entire community,” says Law.
Deep drilling for geothermal energy is not new. From 1976 to 1991 the Hot Dry Rock research project was carried out in Cornwall, which involved water being pumped down a 2.5km well.
The aim of the government-funded project was to understand rock mechanics at such depths rather than to generate power.
In 1991 the project moved to Soultz on the French-German border, where it remains today, and the UK’s foray into geothermal energy came to a swift halt.
“Since the Hot Dry Rock project there has been a hiatus in the UK. In the meantime, geothermal has grown into a booming industry in many other countries including Germany, Australia and the US,” says Law.
“We have an unlimited energy resource under our feet, ready to be harnessed. If we can make it economically viable to drill down to 6km, as MIT say we can, then the whole of the UK can be opened up,”
Law cites The Future of Geothermal Energy report published by the Massachusetts Institute of Technology (MIT) in 2006 as a big turning point for the industry.
“The world started to take notice,” he says.
The report confirmed that deep geothermal could be a key energy source in the US. This started a global “heat rush” and encouraged large-scale investment in deep drilling schemes from both private and public investors.
At this point Law was a geotechnical engineer at consultant Arup, which had worked on several shallow and medium-sized geothermal schemes.
Law saw a real possibility of making large-scale geothermal schemes a reality in the UK.
Arup agreed to undertake research into the technical feasibility of a scheme.
“The Hot Dry Rock project gave us lots of data so we didn’t have to carry out any drilling.
We took the data apart to choose the site and the geological concept for the scheme,” says Law.
In 2008 Law set up Geothermal Engineering, a company dedicated entirely to getting the project off the ground, although Arup remains a close partner.
Law brought in geothermal expertise from throughout the UK to work on the plant, including Dr Tony Batchelor, who led the original Hot Dry Rock project.
For geothermal energy to be commercially viable, hot granite rock needs to be found relatively close to the surface.
Deep drilling is so expensive the return on investment will be diminished if depths exceed 5km.
The UK’s geology limits development to Cornwall and Devon, where hot granite is found at depths of 4km.
Redruth in Cornwall has been chosen for two reasons.
First, the patch of land is remote so there are no neighbours to disturb during the immense drilling operation and second, a fault line runs vertically through the site.
“We didn’t want to replicate the Hot Rock project. The principle of harnessing geothermal energy centres on drawing heated water back to the surface,” says Law.
“On the HRP, that didn’t happen at first. A further well had to be drilled to draw up the water. We can’t afford for this not to work the first time. Best practice from the Continent shows that drawback occurs when the water passes through the earth’s natural faults.”
Drilling on the first well begins in October this year.
A 50m high rig will drill continuously, 24 hours a day, for four months to create the 4.5km deep well that will intersect with the natural fault.
These rigs are designed for the oil and gas industry and have an enormous 350MT pulling power.
Water will then be pumped into the 914mm hole, which narrows to 203mm at the base.
At this point, unlike the Hot Dry Rock project, testing will be carried out to determine how water travels through the hot rock.
“Government financing is languishing behind other countries. Obama has pledged $330M into deep geothermal and the Australian government matches private investment funding to kickstart the industry,”
Geothermal Engineering is working with Durham University and the British Geological Society to monitor the water’s journey through the fractures in the granite.
Some 15 seisometers will be used at surface level to pick up seismic movements and generate a 3D map of how the reservoir has developed.
This allows the two further wells, which will draw the heated water back out, to be located with certainty.
At surface level the wells will only be 5m apart.
The drill will be angled to hit the water channel created, which could travel as far as 1km from the original well.
Deep drilling is not cheap - the three wells at Redruth will cost £40M.
The scheme was awarded £1.475M from the first tranche of the Department of Energy and Climate Change’s (DECC) Deep Geothermal Challenge Fund.
A total of £6M is up for grabs for geothermal projects across the UK.
Law is hoping Redruth will benefit further from the government fund when the next round of awards is announced.
Both European Commission and regional development agency funding is also being sought, although private investment is set to bankroll the bulk of the scheme.
“Government financing is languishing behind other countries. Obama has pledged $330M into deep geothermal and the Australian government matches private investment funding to kickstart the industry,” says Law.
“The rig has been ordered, it’s happening. Of course geothermal has high start up costs but it produces a lot of electricity from just three wells.”
Geothermal Engineering is currently in talks with many potential investors, including large oil and gas companies, renewables firms and private equity companies.
Law is confident the finance will be secured.
“We will be drilling in October”, Law emphasises.
“The rig has been ordered, it’s happening. Of course geothermal has high start up costs but it produces a lot of electricity from just three wells. As well as the 5p per kilowatt-hour (kWh) from the electricity produced, investors also get 1.5p per kWh from the heat produced following the introduction of the Renewable Heat Incentive.”
The geothermal plant takes a relatively short time to set up. Despite the extra testing needed on this start-up project, Redruth will be operational by 2013, before both the first new nuclear power plant and any Round Three offshore wind farms.
If the three wells prove successful, the plan is to develop 30 more plants across Devon and Cornwall.
“We have an unlimited energy resource under our feet, ready to be harnessed. If we can make it economically viable to drill down to 6km, as MIT say we can, then the whole of the UK can be opened up,” concludes Law.