The Rocky Road to a new source of power

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 finds out how large scale geothermal energy can be generated.

After four years in development, a 60MW geothermal power plant is finally set to get underway in Redruth, Cornwall. A planning application was submitted in March following months of consultation with local residents. Geothermal Engineering, the company behind the groundbreaking 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 heat and cool an entire community. The scheme works much on the same principle as shallow drilling but at much greater depths. Wells are drilled down to over 4km in depth into granite where temperatures exceed 170oC.

Water is pumped down into the rock, where it will be 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, over 10MW of electricity will be generated, enough to power 15,000-20,000 houses, and over 50MW of thermal energy, which can power 20 hospitals. This thermal energy will be connected to a district heating system and will provide “very low cost heating” for the local 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 bi-product can power an entire community”, says Law.

Deep drilling for geothermal is not new. From 1976 to 1991 the Hot Dry Rock research project was carried out in Cornwall, where water was pumped down a 2.5km well. The aim of the government funded project was to understand rock mechanics at such depths rather than generate power.

In 1991, the project moved to Soultz on the France-Germany 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 Geothermal Engineering managing director Ryan Law.

Law cites “The Future of Geothermal Energy” report published by 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 major investment in deep drilling schemes from both private and public investors.

At this point Law was a geotechnical engineer at consultant Arup who had worked on several shallow to medium geothermal schemes. He saw a real possibility in making large scale geothermal schemes a reality in the UK. The consultant 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.”






"We have an unlimited energy resource under our feet. If we can make it economically viable to drill down 6km, the whole of the Uk can be opened up." Ryan Law
In 2008, Law set up Geothermal Engineering, a company dedicated entirely to getting this project off the ground, although Arup remains a close partner on the scheme. Law brought in the greatest geothermal expertise in the UK to work on the plant, including Dr Tony Batchelor who led the original Hot Rocks Project.

To make geothermal energy 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 is the chosen site. Firstly, the patch of land is remote so there are no neighbours to disturb during the immense drilling operation. Secondly, 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. 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”, says Law.

Drilling begins in October this year on the first well. A 50m high rig will drill continuously, 24 hours a day, for four months to create the 4.5km deep well which 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 find out how water travels through the hot rock.

Geothermal Engineering is working with Durham University and the British Geological Society to monitor the waters 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 view mapping how the reservoir has developed.

This allows certainty in the location of the two further wells which will draw the heated water back out. 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.






The three wells will generate more than 10MW of electricity and around 50MW of thermal energy
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 tranche 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 match private investment funding to kickstart the industry”, says Law.

Geothermal Engineering is currently in talks with many potential investors, including large oil and gas companies, renewables firms and private equity companies. He remains confident that 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 (kW/h) from the electricity produced, investors also get 1.5pkW/h from the heat produced following the introduction of the Renewable Heat Incentive”.

The geothermal plant takes relatively little 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 produce over 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”, says Law.