Drilling commenced at the UK’s first geothermal energy plant in November 2018. Based at United Downs in Cornwall, the project will demonstrate the potential for geothermal to produce electricity from renewable heat by supplying power to 3,000 homes.
Sarah Newton, MP for Falmouth and Truro, said that the project would “help trigger further development of a renewable energy source beneath our feet that is available 24/7 and offers both electricity and heat”.
To date, UK emission reductions have predominantly been achieved in the power generation sector. Therefore, attention is now being given to tackling emissions from both heat and transport. Heat’s fossil fuel dependency is high, with 77% generated from burning natural gas. There are a number of routes to decarbonising the heat sector, such as injecting biogas to the grid, using hydrogen gas, or an increase in the use of electricity for heat. Geothermal presents a largely untapped opportunity for the UK, which in many locations could provide a secure supply of renewable heat. Heat can be captured form a variety of sources such as sedimentary basins and abandoned mines.
On average, the geothermal gradient in the UK is 20 to 35o C for every Km underground, and the Brit Geothermal Institute advises that basins and granite could deliver more than 100 years supply of heat. The project at United Downs targets a permeable geological structure called the Porthtowan Fault Zone. The temperature at the bottom of the production well is expected to be about 190˚C.
Communities close to abandoned mines could benefit from projects to extract heat from tunnels, where it is feasible. At Heerlen in the Netherlands (an area of closed mines), a scheme has been operating since 2008, supplying low-carbon heat to 500,000 square metres of commercial and residential buildings.
A weakness of geothermal is that heat does not travel well and, therefore, systems must be local. However, it has been successfully adopted around the world and is already in operation in Beijing, Copenhagen, and Paris. In President Macron’s speech ahead of the COP 24 climate change talks in December, he highlighted the need for France to reduce its reliance on natural gas and to focus on geothermal. The Alsace region hopes that its energy consumption will be 100% renewable by 2050, through the use of geothermal.
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