Geothermal Energy and Heat Pumps

Geothermal energy is the energy stored below the surface of the Earth. The thermal energy is contained within the rock and fluids which can be found from shallow ground to several miles below the surface. In some countries, thermal energy has even been harvested from the magma chambers found below the Earth’s crust.

Interesting Facts

  • The first geothermally generated electricity was produced in Larderello, Italy, in 1904
  • Geothermal energy is generated in more than 25 countries
  • In 2019 over 90,000 GWh of electricity was generated from geothermal energy
  • The US is the world’s largest producer of geothermal energy
  • The Geysers Geothermal Complex in California is the biggest geothermal development in the world
  • In Iceland, a country with over 25 active volcanoes, many of the buildings and even swimming pools are heated with geothermal hot water
  • Around 25% of Iceland’s electricity needs are generated from harnessing the Earth’s thermal energy


  • The UK has around 100GW of potential geothermal energy – enough to meet the country’s heating demand
  • The planned United Downs geothermal power plant, in Redruth, Cornwall, is predicted to reduce greenhouse gas emissions by more than 3,000 tonnes per year once completed
  • The UK’s extensive history of coal mining has left a network of tunnels snaking below the surface. Many of these caverns have filled with water which has become heated and can be exploited to capture energy
  • Geothermal plants operate more than 90% of the time and use far less land per MW than other renewable energy sources


  • Geothermal targets need to be of suitable depth and temperature and contain fractures and pores for the storage and passage of water. Current geological surveys for some areas of the UK are lacking in the detail required to make development decisions
  • Drilling wells for geothermal energy is relatively expensive – around £500,000 for a test well
  • Heat is much less portable than electricity so geothermal heat systems must be located close to populated areas to ensure an efficient supply line
  • The extraction of geothermal energy from the ground leads to a release of greenhouse gases, including carbon dioxide, hydrogen sulphide, methane and ammonia
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