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Geothermal Opportunities and Developments in Northern Ireland

By Michelle O’Grady, Deputy Project Manager (Geothermal Pioneer Project), GSNI

The UK has a legal target of net zero greenhouse gas emissions by 2050. Additionally, Northern Ireland has committed to net zero carbon dioxide emissions by 2050 and set a target of achieving 80% of electricity from renewable sources by 2030 under The Climate Change Act (Northern Ireland) 2022.

Between October 2021 and September 2022, “49.3% of total electricity consumption in Northern Ireland was generated from renewable sources located in Northern Ireland” (DfE, 2022). It is evident, however, that more renewable energy sources will be required to meet targets and to develop and support a greener, low-carbon sustainable economy.

Geothermal energy is a widespread, but poorly publicised and underutilised low-carbon, renewable energy source. In Northern Ireland, it has significant potential to contribute to our decarbonisation of the energy sector by optimising the electrification of heating and cooling.

Geothermal energy “refers to any heat derived from the ground, from depths of a few metres to multiple kilometres beneath the Earth’s surface” (BGS, 2022). It is sustainable, reliable, local and can provide energy continuously.

There are different technologies applied to make use of this resource at the various depths and temperatures required (Figure 1). For example, Ground Source Heat Pumps (GSHP) are used to access low-temperature, shallow geothermal resources in two ways; open-loop requires the presence of a shallow aquifer, whereas closed-loop involves fluid circulation in a horizontal or vertical closed pipe network in the ground.

There are different opportunities for geothermal at different locations in Northern Ireland, and the potential will vary based on factors such as geological setting, temperature or cost for example. Over half of our energy use is for heating purposes (DfE, 2022), which is still heavily reliant on hydrocarbons as a fuel source, so geothermal has the greatest potential in the decarbonisation of our heating.

Across Northern Ireland, there is widespread, shallow heat located in unconsolidated sediment and the underlying rocks, which can be readily accessed by ground source heat pumps.

For example, several hundred metres of the Sherwood Sandstone (Figure 2) underlies much of the Lisburn, Greater Belfast and Newtownards areas. There is great potential for this productive shallow aquifer to be used for heating, cooling and even seasonal energy storage by using open-loop ground-source heat pump technology. Some organisations, e.g. the Lyric Theatre and the School of Biological Sciences at Queen’s University Belfast, are already using the aquifer to heat or cool their buildings.

The very same rocks are buried more deeply across other parts of Northern Ireland, and these higher-temperature geothermal resources offer some potential to decarbonise heat on a larger scale. Northern Ireland has deeply buried hot sedimentary aquifers, and the resource was proven in studies conducted since the late 1970s; the water in the Sherwood Sandstone of one exploratory borehole near Ballymena was 66 °C at 1.9 km, and temperatures of 91 °C were encountered at 2.8 km depth in the Larne No. 2 geothermal borehole. Other more recent data and calculations suggest that the geothermal gradient (temperature per kilometre depth) may be even greater than these borehole temperature measurements suggest.

In June 2022, the Minister for the Economy announced funding for shallow and deep geothermal demonstrators that are included in the Northern Ireland Energy Strategy Action Plan 2022.

These feasibility studies will provide a better understanding of the subsurface, identification of drilling sites and installation of the geothermal systems. These data and the learning will support the growth of the geothermal sector in Northern Ireland by demonstrating a viable geothermal heat resource is accessible at depth, which will encourage private investment and inform the development of policy and regulatory framework.

As well as the Department for the Economy (DfE) demonstrators, 20 million Euros are allocated within the forthcoming EU PEACE PLUS Programme and will see a range of geothermal pilot projects undertaken in Ireland and Northern Ireland.

Through implementing these geothermal demonstrator and pilot projects, we are on our way to realising the geothermal potential and opportunity for the implementation and development of the sector to contribute to decarbonisation in Northern Ireland.