Climate change in the South West: Going deeper underground with Eden Geothermal

Posted in: Clean Technology

Posted on: 12.08.2021

Good Energy is collaborating with award-winning environmental photographer Toby Smith to produce a series of photo-essays visualising climate change in the UK. Toby will be focussing on the changes and challenges of land-use but also cultural and technology innovations in sustainability around the South West of England.  

Across Cornwall, a host of exciting joint ventures and engineering projects are digging deep in the hope of extracting renewable geothermal energy.

During the formation of Britain’s land mass, large slabs of granite - a dense igneous rock - were forced deep into layers of sedimentary rock which concentrated valuable minerals and created fluid faults that make subsurface volcanic heat accessible. Cornwall’s strong sense of identity and proud history of 4,000 years of mjning are also founded upon this unique and valuable geology. Tin and copper has been prized here since the Bronze age with continued production documented until 1998 when Cornwall’s last commercial mine closed.

In an exciting re-invest of capital and optimism, the EU, institutional investors and the Cornish Council all funded Eden Geothermal Ltd. This three way partnership between Eden Project Limited, EGS Energy Limited and Bestec (UK) Limited has now successfully negotiated the planning, bureaucracy and narrow lanes of central Cornwall to install an epic 450 tonne, 55m tall drilling rig.  Their incongruous structure, part hidden within a retired China clay pit, is aiming vertically down and hoping to strike the prize of limitless renewable geothermal energy trapped in hot rocks over 4,500m below the surface. 

Manned and rotating 24 hours a day, 7 days a week the drill head is today at 2,747m below the surface.

Every 4-5 hours, downward progress is momentarily paused whilst an engineer ascends upwards to the ‘monkey cage’ - marking another 45m of progress with an additional drill string.

On the drill platform below - another engineer completes the well-rehearsed choreography -  swiftly cleaning and attaching the new length into place. This momentary calm allows the survey team to conduct sensitive seismic tests - helping establish the characteristics and even navigate the rock at depth.

Within minutes, the platform resumes its incessant rotation and the slow descent continues as the tungsten-carbide tipped drill bit ‘scratches’ ever deeper.

Back in the visitor’s area, its seven predecessors are on display -  proudly showing the depths they accomplished before - after thousands of revolutions -  their bearings expire.

Below the drilling deck, just above the ground surface, specially mixed organic lubricating fluids and water are re-captured after a 3 km loop into the centre of the earth. Carefully cleaned and recycled, the fluid contains fragments of the rock below; and a taste of the fault’s thermal energy.

Progress has been good -  and now at just over half way to the target depth - there is a real excitement on site. The mud returning to the surface is already at 45°C and warm to the touch. 

A team of geologists and academics from local universities frequently examine the rock fragments for clues - combining microscopic analysis with periodic seismic data to help understand the changes in strata at different depths.  

At the target depth of 4,500 the temperature is expected to rise steeply and enable the super heating of water, which is predicted to heat the Eden Project’s energy intensive biomes, greenhouses and ancillary buildings. This first well and its structures could make Eden carbon positive by 2023 and beyond this a second well could produce enough energy to heat local homes and other businesses.  

The output from geothermal schemes when compared to large wind-farms is modest, but the delivery is constant and so contributes sustainably to the UK baseload without the need for battery storage. This perfectly complements Britain’s intermittent weather and resulting output from wind and solar projects.

Cornwall with its relatively accessible hot-rocks is hosting the first of these innovative energy projects - but if proved successful - geothermal could be rolled out nationally and meet 5% of our future energy needs.

Toby Smith

Toby Smith is an award winning environmental photographer, based in Stroud. We're collaborating with him to produce a series of photo-essays visualising climate change in the UK. 


Read more stories by Toby Smith

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