CARBON AND ENERGY REDUCTION Recovered heat


in Munich are supplied with geothermal heating, saving about 75,400 tonnes of carbon dioxide (CO2


) per year compared


with natural gas.1 Figure 1 shows the sedimentary basins


Recovered hydrogen Hydrogen Natural gas input


Reaction initiator


Recovered carbon Carbon


Electricity input


Figure 4: Hydrogen at point of use. (See Part 5.)


Drilling of deep wells Exploitation of these deep geothermal systems requires the drilling of two or more deep wells (typically 1 to 3 km) to reach the higher temperature heat resources. This heat can be used directly to supply heating to users with large heat demands, including hospitals, domestic or commercial space heating, or industrial users. Geothermal technologies are scalable and combinable across the spectrum of drillable depths and temperatures. In some cases, for example, heat pumps are being used in conjunction with moderately deep wells


(500 to 1000 m) to boost temperatures, and achieve the required operational temperatures for the heat network. Such hybrid systems benefit from higher temperatures at depth, while avoiding the high capital costs and risks associated with even deeper drilling.


District heating at a city scale Where a good resource exists, geothermal can supply district heating at the city scale. For example, Paris receives geothermal heating from its deep geothermal aquifer for around 250,000 homes via 50 heat networks, while around 50,000 homes


The challenge is truly set


Pete Sellars, IHEEM’s CEO, said: “If the UK government’s commitment to ensuring that the UK reduces its greenhouse gas emissions by 100% from the 1990 levels by 2050 is to be delivered, then action is needed now to develop new ways of embedding new, more sustainable, carbon-reducing energy production technologies within both existing and new public sector infrastructure. The NHS set a more ambitious challenge to become the world’s first Net Zero health system by 2040, and achieve an 80% reduction by 2028-2032. The NHS became the first health system to embed Net Zero into legislation through the Health & Care Act on 1 July 2022. Achieving Net Zero in the NHS will require a considerable commitment across every part of the service’s business activities.


“Along with the deployment of staff 32 Health Estate Journal May 2023


activities, transport, and purchasing of goods, medicines, and food, the NHS estate and its directly related services are one of the critical NHS areas that will need to step up and embrace and deliver new engineering technologies if the Net Zero challenge is to be delivered on time. “The NHS has always been at the forefront in embracing and successfully delivering energy and


carbon reductions. IHEEM and its professional and affiliate company members have been instrumental in ensuring that both the challenges and new technologies relating to providing Net Zero engineering solutions are highlighted to our members. This year at our Manchester flagship conference in October, Healthcare Estates 2023, there will be several targeted workshops exploring further the detail of delivering geothermal and hydrogen solutions for the NHS.”


(yellow and blue areas on the map) where deep geothermal prospects exist in England. Also shown on the map are locations of NHS hospitals that have been prioritised for decarbonisation because of their high heat demand. An initial assessment suggests that, out of the 210 sites, 109 overlie potential geothermal aquifers. The estimated drilling depths to reach a temperature of 50 °C range between 1.2 and 3 km. Developing geothermal projects for these sites could save between 1.3 and 22.7 Kt CO2


equivalent emissions per year for individual hospital sites. It is important to note that Figure 1 only shows the extent of the geothermal basins, and that there is great variability in terms of the reservoir properties and temperatures within individual basins. Further analyses, in the form of a more detailed feasibility study followed by site-specific investigations, are required to assess the feasibility of geothermal exploitation at any particular site before any drilling takes place. To find out more about feasibility for using geothermal energy at your site, contact BGS Enquiries (enquiries@bgs. ac.uk). For further information about geothermal energy, see Abesser and Walker (2022).1


Part 4


Deep Geothermal possible ‘with the right skillsets and risk management’


Rik Evans, GT Energy


Deep geothermal technology allows us to extract the heat of the earth from more than 500 m beneath our feet. It offers a potential route for the decarbonisation of traditional heat sources such as gas, which is a source of about 40% of the carbon emissions in the UK. Aside from the people of Roman Britain enjoying the natural thermal springs of Bath (which still flow today), only one purpose-built exploration well has been drilled – in Southampton in the 1980s – and a couple of more recent pilot projects in Cornwall, yet other countries around the world have been successfully harnessing the heat of the earth for many decades. Our historically heavy reliance on gas in the UK has meant that geothermal heat has largely been ignored. However, with a focus on the need for a rapid decarbonisation of heat as we drive to Net Zero, a flurry of projects at varying stages of maturity from early stage concept, or even on the cusp of construction, are emerging – and it finally looks as though we are set to join the likes of Germany, France, and The Netherlands, in exploiting this exciting renewable technology.


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