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GEOTHERMAL IN THE UK

The UK has not traditionally been thought of as a geothermal country. Although hot springs have been sporadically used since Roman times there is only one operating commercial system; a deep well provides heat to a district heating scheme in Southampton.

But the UK does have geothermal resources. The granites underlying Cornwall and west Devon are heat-producing and have abnormally high geothermal gradients that make electricity generation possible. Developers at United Downs and the Eden Project are hoping to bring heat and power plants online in the next two years.

Elsewhere, in other granitic rocks and in sedimentary basins, there are geological and thermal conditions that are suitable for the production of renewable heat that could meet the needs of large residential and commercial developments or specific industrial and agricultural applications. In the depth range 500m to 2500m, rock temperatures of 30°C to 100°C can be found in many places.

Ground Source Heat Pump (GSHP) systems are long-established here as standalone systems but coupling them with moderate depth wells producing primary geothermal heat can both increase the supply temperature available at individual sites and also widen the geographical area capable of sustaining geothermal utilisation.

Flooded mines also represent a very significant source of low grade geothermal energy that could be harnessed for both heating and cooling.

The inclusion of geothermal in the energy mix for the UK, particularly for heat, would make a significant contribution to the ‘green recovery’ and meeting our emissions targets and low-carbon economy goals. A significant proportion of the UK’s energy use and carbon emissions result from space heating.

Heat flow in the UK, (BGS, 1986; this version from Busby, 2010).

Red areas show heat-producing outcrops of granite in Cornwall

Types of geothermal in the UK

types-of-geothermal-for-web-Right--size.

Boreholes

Ground Source Heat Pumps

Mine water

Deep geothermal

Ground Source Heat Pumps:

  • Heating & Cooling

  • Commercial & domestic applications

  • Depths of 0 - 100m

  • Temperatures range from 10 - 25ºC

  • Open-loop or closed-loop systems

  • Available across 100% of the UK

Mine water:

  • Heating & Cooling

  • Commercial & domestic applications

  • Depths of 0 - 900m

  • Temperatures range from 10 - 40ºC

  • There are 23,000 abandoned mines in the UK, many of them close to urban areas and heat loads

Boreholes:

  • Heating & Cooling

  • Commercial & domestic applications

  • Depths of 0 - 2500m

  • Temperatures up to 100ºC

  • May be drilled specifically for geothermal or re-purposed abandoned exploration holes

  • Hot water co-produced with oil or gas in operating fields

The benefits of Geothermal Energy:

Very low to zero carbon emissions when in operation

Small footprint on the surface

Baseload power - no intermittency issues

Green, sustainable and renewable energy source

Deep Geothermal/EGS:

  • Electricity Production

  • Heating & Cooling

  • Commercial applications

  • Depths of 2000 - 5000+m

  • Temperatures range from 100 - 200ºC

  • Available in areas with high heat production granites. 

Wherever you are in the world, the rocks get hotter with depth.

This is known as the geothermal gradient

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