Geothermal energy is a natural form of renewable energy generated from the heat of the earth’s core. This heat continuously travels through the earth’s layers, warming rocks and aquifers. Developments in drilling technology and geophysical techniques mean that systems can be engineered at depths in excess of 5km.


Deep geothermal energy can be used for electricity production, or to provide heat for commercial, industrial and residential buildings. It is ideal for providing heat to district heating schemes, universities and hospitals. It can also be used in industrial processes, such as cooling, or in aquaculture and horticulture.

Boreholes are drilled to access natural reservoirs of hot water and transferred to heat exchangers for use as direct heat. In the case of ‘hot rocks’ or ‘Engineered Geothermal Systems (EGS)’ schemes, water is pumped from the surface into rock formations where it is heated and returned to the surface. Old mine workings are another source of heat and are a good resource if located close to a heat load. The heat is then used to generate electricity via a turbine/engine and, if a heat load is present, the residual heat can be used via a combined heat and power (CHP) process. After the heat has been exploited the water is recycled back down into the ground via a second borehole.

Deep geothermal energy is available 24 hours per day, 7 days a week, and produces base load electricity and/or large quantities of heat to be used in industrial processes, farming and district heating. It has a very small surface footprint, and is a reliable, cost effective form of energy. Once built, a deep geothermal plant can be expected to continue in production for fifty years or more.

Independent analysis shows that the UK’s deep geothermal potential equates to 20% of our electricity consumption and 100GW of heat production. The technology could therefore make a substantial low carbon contribution to the UK’s energy mix. There is also the potential to significantly expand the drilling, geophysical, manufacturing and support sectors in the UK.

The REA was successful in securing a dedicated Renewable Heat Incentive tariff for deep geothermal heating that makes heat projects in well suited areas viable. We have also secured changes to planning regulations that make it easier to develop projects in the UK.

For more detailed information and to find out more about this technology please see the REA’s Innovative & Strategic Technologies Forum.

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Deep Geothermal drilling rig GEL - Redruth, Cornwall