United Downs Deep Geothermal Power

United Downs Deep Geothermal Power is the United Kingdom's first geothermal electricity project. It is situated near Redruth in Cornwall, England. It is owned and operated by Geothermal Engineering (GEL), a private UK company. The drilling site is on the United Downs industrial estate, chosen for its geology, existing grid connection, proximity to access roads and limited impact on local communities.^[1] Energy is extracted by cycling water through a naturally hot reservoir and using the heated water to drive a turbine to produce electricity and for direct heating. The company plans to begin delivering electricity (2MWe) and heat (<10MWth) in 2024. A lithium resource was discovered in the well.^[2]

History

The Camborne School of Mines led Cornish Hot Dry Rocks (HDR) project, undertaken in the 1980s at Rosemanowes Quarry, was designed to test the theory of inducing a fracture network within granite to create a geothermal reservoir.^[3][1]

Geothermal Engineering was founded in 2008 to specialise in the development of geothermal resources. Project funding was secured over the following five years from the European Regional Development Fund, Cornwall Council and private investors.^{[4][5][6][7][8][9][10]}

GEL drilled two wells into the Porthtowan fault zone between November 2018 and June 2019. The geothermal production well reached a depth of 5,275 m and the fluid injection well 2,393 m.^[3][1]

Between August 2020 and July 2021, the wells underwent a series of injection tests to analyse the hydrology within the fractured geothermal reservoir. In addition, in July 2021, full reservoir testing (simultaneous production and injection) was undertaken for seven days.^[1] During this process, the reservoir was destressed to prevent microseismic events occurring during long term operation.^[1][11] GEL adhered to a strict monitoring, management and mitigation procedure to ensure that any induced seismicity was understood by community members.^[12]

In August 2020, the project's operations were further funded by the UK Getting Building Fund. GEL received a share of £14.3 million to demonstrate that lithium could be produced from geothermal brines.^[13] As of 2021, project costs were approximately £30 million.

In January 2021, GEL agreed to sell 3 MW of power for ten years to Ecotricity.^[14][15] In March 2023, the company received another £15 million in private funding.^[2]

Geology

The geothermal system employed to generate power at United Downs targeted a radiogenic granite batholith that exhibited enhanced permeability due to its intersection with the Porthtowan fault zone.^{[16][17][18][19]}

The Cornubian granite batholith stretches from Dartmoor to the Isles of Scilly and contains a high concentration of heat-producing isotopes such as thorium (Th), uranium (U) and potassium (K). This natural heat production means that the heat flow at United Downs is approximately double the UK average at 120 mWm⁻², and geothermal gradient is ~33-35 °C/km, almost 10 °C/km hotter than large parts of the UK.^[1][20]

Cornwall is also divided by a number of faults and fracture zones with a preferred orientation of NNW-SSE or ENE-WSW, believed to have been reactivated by post-orogenic extension after the Variscan Orogeny, with the ENE-striking fractures hosting magmatic mineral lodes and ‘elvans’ that were mined throughout the 19th and 20th centuries.^[21] NNW-SSE striking 'crosscourse' faults, which are often long and show evidence of significant displacement, are aligned parallel to the regional maximum horizontal stress and therefore are believed to be the most ‘open’ structures, providing enhanced permeability.^[22][23][1]

The United Downs wells encountered three main lithologies:

1. Killas (a low-grade, regionally metamorphosed and deformed mudstone of the Upper Devonian Mylor Slate Formation^[24]);
2. Microgranite
3. Granite.^[3][1]

The wells also intersected open NW-SE-striking fracture corridors related to the major 'crosscourse' of the Porthtowan Fault Zone.^[3][1]

Community engagement

GEL's community engagement programme has been extremely important for the successful continuation of the United Downs geothermal project. From an early stage it was established that time, effort and a personal approach were crucial to finding the extent of the community and reaching a diverse range of its members. As a result, accurate, up-to-date information has been communicated to a broad range of the community via public visits to the GEL site, external presentations to interested groups, exhibitions at public events, printed flyers, online resources and through the wider media.^[25]

An inclusive and interactive education programme and careers events have also been run by GEL to give an insight into Cornwall's new and growing geothermal power and heat industry to students throughout Cornwall.^[25][26]

GEL also established a significant community fund, supporting sustainable and community-led projects in four local parishes with a shared grant of £40,000. This ensured that the local economy, people and environment benefitted as widely as possible from the project.^[27][28]

See also

Geothermal power in the United Kingdom

References

1. Farndale, H., Law, R. and Beynon, S. (2022). "An Update on the United Downs Geothermal Power Project, Cornwall, UK". European Geothermal Congress, Berlin, Germany | 17–21 October 2022.{{cite journal}}: CS1 maint: multiple names: authors list (link)
2. Cariaga, Carlo (8 March 2023). "GEL receives £15 million funding for deep geothermal in UK". Think Geoenergy. Retrieved 8 August 2023.
3. Farndale, H. and Law, R. (2022). "An Update on the United Downs Geothermal Power Project, Cornwall, UK" (PDF). PROCEEDINGS, 47th Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, California, February 7–9, 2022.{{cite journal}}: CS1 maint: multiple names: authors list (link)
4. "Geothermal power plant gets funds". BBC News. 21 December 2009. Retrieved 30 January 2010.
5. "'Hot rocks' geothermal energy plant promises a UK first for Cornwall". Western Morning News. 17 August 2010. Retrieved 15 August 2015.
6. "Drilling to begin for Cornwall geothermal power plant in 2011". The Guardian. 16 August 2010. Retrieved 17 August 2010.
7. "Geothermal projects get funding boost". The Ecologist. 22 December 2009. Retrieved 30 January 2010.
8. "UK's first geothermal plant given go-ahead". Financial Times. 15 October 2010. Retrieved 17 August 2010.
9. "£6 Million Grant For Geothermal Energy Project in Cornwall". Invest in Cornwall. 1 November 2011. Retrieved 2 September 2013.
10. "Geothermal project on rocks after funding blow". this is Cornwall. 4 April 2013. Retrieved 2 September 2013.
11. Jupe, A., Law, R. and Farndale, H. (2022). "Implementation of an Induced Seismicity Protocol for the United Downs Deep Geothermal Power Project, United Kingdom". European Geothermal Congress, Berlin, Germany | 17–21 October 2022.{{cite journal}}: CS1 maint: multiple names: authors list (link)
12. "Seismicity – Geothermal Engineering Ltd". Retrieved 29 April 2022.
13. "LEP agrees £14M investment". Business Cornwall. 4 August 2020. Retrieved 17 July 2021.
14. "Sold! The UK's first geothermal electricity to the grid |". 4 January 2021. Retrieved 7 January 2021.
15. "Ecotricity seals 10-year agreement to take geothermal power from Cornish plant". Energy Live News. 7 January 2021. Retrieved 15 March 2021.
16. "Geothermal power plant set to become a reality in Cornwall". New Civil Engineer. Emap Ltd. 19 October 2009. Retrieved 30 January 2010.
17. Halper, Mark (11 October 2009). "We're mining for heat in Cornwall". The Independent. London. Retrieved 30 January 2010.
18. Rezaie, Behnaz; Rosen, Marc A. (1 May 2012). "District heating and cooling: Review of technology and potential enhancements". Applied Energy. 93: 2–10. doi:10.1016/j.apenergy.2011.04.020. ISSN 0306-2619.
19. Ozgener, Leyla; Hepbasli, Arif; Dincer, Ibrahim (1 October 2007). "A key review on performance improvement aspects of geothermal district heating systems and applications". Renewable and Sustainable Energy Reviews. 11 (8): 1675–1697. doi:10.1016/j.rser.2006.03.006. ISSN 1364-0321.
20. Beamish, David; Busby, Jon (24 March 2016). "The Cornubian geothermal province: heat production and flow in SW England: estimates from boreholes and airborne gamma-ray measurements". Geothermal Energy. 4 (1): 4. doi:10.1186/s40517-016-0046-8. ISSN 2195-9706. S2CID 55659348.
21. Alexander, A.C. and Shail, R.K. (1995). "Late Variscan structures on the coast between Perranporth and St Ives, Cornwall" (PDF). Annual Conference of the Ussher Society, January 1995.{{cite journal}}: CS1 maint: multiple names: authors list (link)
22. Brereton, Robin; Müller, Birgit (15 October 1991). "European stress: contributions from borehole breakouts". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences. 337 (1645): 165–179. Bibcode:1991RSPTA.337..165B. doi:10.1098/rsta.1991.0114. S2CID 123973444.
23. Puritch, E.; Routledge, R.; Barry, J.; Wu, Y.; Burga, D. and Hayden, A. (2016). "Technical Report and Resource Estimate on the South Crofty Tin Project, Cornwall, United Kingdom". P&E Mining Consultants Inc. For Strongbow Exploration Inc. Technical Report 295.{{cite journal}}: CS1 maint: multiple names: authors list (link)
24. "Record details | Geology of the country around Falmouth : memoir for the 1:50 000 geological sheet 352 (England & Wales) | BGS publications | OpenGeoscience | Our data | British Geological Survey (BGS)". webapps.bgs.ac.uk. Retrieved 29 April 2022.
25. Charman, J., Law, R. and Beynon, S. (2022). "Effective Community Engagement: The United Downs Geothermal Power Project, Cornwall, UK". European Geothermal Congress, Berlin, Germany | 17–21 October 2022.{{cite journal}}: CS1 maint: multiple names: authors list (link)
26. "Education – Geothermal Engineering Ltd". Retrieved 29 April 2022.
27. "First community grants awarded by United Downs Community Benefit Fund". Cornwall Community Foundation. 4 December 2018. Retrieved 29 April 2022.
28. "CCF announces funding from the United Downs Geothermal Community Fund". Cornwall Community Foundation. 6 September 2018. Retrieved 29 April 2022.

External links

• United Downs Deep Geothermal Power website