Lanner residents may already have heard about a geothermal project at United Downs Industrial Estate, with drilling planned for a 2018 start.
The project is to be run by Geothermal Engineering Ltd (GEL) whose planning consent was secured way back in 2010 but only now have they been able to raise the money to begin drilling. The project has secured £10.6m funding from the European Regional Development Fund (ERDF) – yes, we’re still taking up EU funds notwithstanding Brexit – and £2.4m from Cornwall Council. Together with £5m of private investment, this funding will allow GEL to drill and test two deep holes and construct a small demonstration power plant.
Geothermal energy is heat from the earth. The granite that lies beneath Cornwall is heat-producing and the rocks here are hotter than anywhere else in the UK, making it the best place to extract energy for both heat and electricity generation. In the 1980s three holes were drilled at Rosemanowes Quarry near Penryn to develop and test ideas for creating geothermal reservoirs in the granite. The United Downs Deep Geothermal Power (UDDGP) project aims to build on this research by drilling deeper holes (called ‘wells’) to explore and test the resources at commercial depth.
Two wells will be drilled: one 2,500m (about 1.5 miles) deep and the other 4,500m (about 2.8 miles) deep. The deeper of the two would be the deepest onshore hole in the UK. Water will be circulated between the wells, collecting heat from the rocks, before being brought to surface at a temperature of about 1750C and being fed into the demonstration power plant. The plant will generate 1MW of electricity, which is enough to meet the needs of about 1,500 households.
The drilling will begin in early 2018 and take about 6 months. Testing the wells, characterising the geothermal system and installing the power plant will take a further 18 months, with a target commissioning date in early 2020. If this pilot project is a success, it will be a catalyst for further investment in Cornwall and the Isles of Scilly with the potential to develop a new geothermal industry in the county according to GEL Operations Director Peter Ledingham.
It should be noted that this is a trial: success is not guaranteed. The process uses natural fissures in the rock – unlike the Rosemanowes experiment which created its own fractures. Whilst there will be some seismic activity from the process it is expected to be so minimal that people won’t be aware: unlike Rosemanowes which created a few very noticeable earth tremors. Seismic activity will be monitored continuously.
Perhaps less clear is the operators’ claim that this is to produce clean renewable energy. For one thing, the turbines which will convert the hot water to power will themselves be run on diesel. But also, the wells themselves are estimated to “use up” the natural heat in the rocks within 25 years to the point where heat extraction is no longer viable. It is thought that it will (theoretically) take several decades for the rocks to recover sufficiently for the wells to be reopened: suggesting that this might be more in the nature of extractive energy than renewable energy.