Heating up! Geothermal district heating as a low-carbon solution for the UK.
“Heat is the largest energy consuming sector in the UK today” (the Department for Business, Energy and Industrial Strategy, BEIS, 2018). It contributes over one third of the UK’s annual carbon emissions and much of this (43%) stems from domestic space heating alone. Low carbon heat solutions such as heat pumps (air, water and ground source), biomass systems and water solar heating are available, but the vast majority of domestic heating in the UK comes from the gas network… not for much longer.
In 2019 the Chancellor announced that from 2025 gas heating for new housing developments would be banned. Although a step in the right direction for sustainable growth, the blanket statement did not necessarily provide an immediate solution for construction companies and the challenge ahead is enormous. With a large amount of development happening across the country and with many schemes extending beyond 2025, developers are having to adapt and turn to alternative methods for low carbon heating. One such method is geothermal district heating systems.
District heating from geothermal energy is not a new concept. There are currently around 250 district heating systems in Europe supplied by geothermal energy, with a total installed capacity of more than 4.5GWth (European Geothermal Energy Council, EGEC, 2018). They vary in size from less than 1MWth to more than 50MWth (L. Angelino et al., 2014), often with heat pumps assisting the shallower or lower enthalpy geothermal resources.
Installed geothermal district heating capacity per European country. EGEC Geothermal Market Report 2018, P. 10. Accessed here: https://www.egec.org/wp-content/uploads/2019/05/KeyFindings_MR-18.pdf
France is one of the leaders of the geothermal district heating market in Europe and a recent article in “ThinkGeoEnergy” quoted a study from the French Agency for Energy and the Environment (ADEME) which established that “the cost of geothermal district heating and cooling is cheaper than using (natural) gas” (Richter, 2020). This shift in economics could be a gamechanger and the much-needed incentive that makes geothermal energy not only a technically viable but also a competitive option for the future of heating
Geothermal for district heating is not a ‘one solution fits all’ scenario. Borehole-based systems can be designed to incorporate the local geology or surrounding existing infrastructure (such as flooded mines) to increase their efficiency and carbon savings and reduce running costs. Depending on the thermal conductivity of the ground, the geothermal gradient and the presence of nearby warm water resources, systems can range from pipe loops installed in a network of shallow holes or horizontal trenches to pairs of medium (500m) or deep (~1000-2000m) wells accessing specific reservoirs for open-loop systems. Both have their advantages but choosing the right system to get the most out of a district heating scheme is location-specific.
The Dunston Innovation Centre in Chesterfield UK, is heated and cooled by one of the UK's larger closed-loop ground source heat systems. GeoScience was involved in the design and installation. https://www.innovationchesterfield.co.uk/
The UK has a wealth of natural geothermal resources and flooded mine workings which can be used for both open and closed-loop purposes. The take-up for shallow resources has been relatively good; there are several thousand closed- loop ground source heat pump systems in the UK. But for deeper resources, and mine water resources, we are far behind most of Europe. There is only one operating district heating scheme with a geothermal component; in Southampton. It utilises a deep well drilled for research purposes in the 1980s. But there is a move towards other schemes such as mini-heat networks in Manchester with low temperatures boosted by heat pumps at substations, and innovative systems like the proposal for the new Seaham Garden Village development in County Durham, which plans to use heat from the Coal Authority’s nearby Dawdon Mine.
Heat Network infographic from The Association of Decentralised Energy. Accessed here: https://www.theade.co.uk/resources/what-is-district-heating
Further encouragement in the UK has recently been provided by the announcement of the £1 Billion Public Sector Decarbonisation Scheme (PSDS) which provides grants for “public sector bodies to fund energy efficiency and heat decarbonisation measures” (Salix, Oct 2020). Additionally, advice from the Committee on Climate Change this year in their Progress Report to Parliament on “Reducing UK Emissions” recommends heat networks and heat pumps should be supported by tax or levy changes that favour low-carbon heating over fossil fuels.
With opinions from influential bodies slowly moving in a more sustainable direction and targeting decarbonised heat and climate resilient infrastructure, it is clear that a lot could be gained from further interaction between the UK's geothermal and construction industries to help achieve net zero carbon by 2050.