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The Project

What is the project about?

The GeoEnergy NI geothermal demonstrator project comprises two geothermal exploratory and feasibility studies at two locations, which will help us ‘unearth the heat beneath our feet’. It is anticipated that the project will be delivered incrementally in the coming years.

The first phase of this project at the Stormont Estate in Belfast will identify suitable drill sites. The next phase will involve the drilling and testing of water and rocks in five shallow exploratory boreholes. The intention is that the results will inform the design and installation of a shallow geothermal system on the Estate in the future. Activities at the second site at College of Agriculture, Food and Rural Enterprise (CAFRE) Greenmount Campus near Antrim will involve site investigations and geophysical surveys to identify suitable locations for the siting of a deeper geothermal borehole as part of future project delivery.

Why do we need a demonstrator project?

The Department for the Economy’s Energy Strategy, published in December 2021, recognised that geothermal energy has a role to play in decarbonising how we heat and cool our homes and buildings.  The responses to the Energy Strategy consultation highlighted that, unlike other countries with similar geology, there was a lack of visibility and uptake of the technology in Northern Ireland (NI).  Research by the Queen’s University Belfast (QUB)’s School of Management confirmed that the NI geothermal sector was in its infancy and recommended that government should take the lead in promoting and demonstrating this technology. This project will be used to help inform the development of a policy and regulatory framework that supports and promotes opportunities to unearth NI’s geothermal potential.

Project Partners

How is this project funded?

The Department for the Economy’s 2022 Energy Strategy Action Plan committed to commence delivery of a geothermal demonstrator project as part of its pathway to reach net zero targets.

In June 2022, the Department for the Economy recognised the importance of ensuring that there is a secure supply of locally available energy, and therefore announced that up to £3 million of funding had been secured for this project.

The project has been designed to evaluate the potential to harness geothermal energy at two locations – a shallow geothermal system for heating and cooling buildings on the Stormont Estate in Belfast and a deep geothermal system at the Greenmount Campus near Antrim.  The ultimate objective is to showcase the potential of geothermal energy to provide heating and cooling, and to encourage future private sector investment in geothermal technology in NI.

Who is delivering this project?

A contract has been awarded to a team of specialist contractors, led by Tetra Tech, who will work with DfE and the Geological Survey of Northern Ireland (GSNI) to deliver phase one of the project.

Geothermal Energy

What is geothermal energy?

Geothermal is energy stored as heat within the Earth. The word geothermal comes from the Greek words geo (Earth) and therme (heat). Use of geothermal energy harnesses a sustainable, low carbon supply of natural heat from the Earth.

Geothermal energy can be used to both heat and cool our homes, buildings and industrial processes. It has the potential to reduce our carbon emissions, improve our local energy security and promote better working and living environments.

Geothermal energy is available 24 hours a day independent of the weather and has a very small surface footprint. It can provide ‘always on’ decarbonised heat to buildings through the transfer of stored natural heat from the ground to buildings, either directly or via heat pump systems.

Where does the heat come from?

The Earth contains huge amounts of thermal energy generated during its formation and which continues to be generated in its crust.

This heat slowly migrates upwards towards the cooler surface of the Earth. The increase in the temperature with depth is called the geothermal gradient. The geothermal gradient of the Earth is not uniform and volcanically active areas can have significantly increased heat flow (e.g., Iceland, Italy, Turkey, and Indonesia). In such regions, the high temperatures in the subsurface rocks are able to produce steam that can generate electricity.

In non-volcanically active regions such as NI, the crust is cooler, but it still contains significant geothermal energy, and permeable rocks at depths of a few kilometres will contain hot water. This water can be pumped to the surface for direct use or can support district heat networks.

The surface of the Earth also acts as a solar collector. Near-surface soils, sediments and rocks are kept at temperatures slightly above the annual average soil temperature which is 9 to 11°C in NI, by the sun and the atmosphere. In fact, we don’t need to drill deep boreholes to obtain heat; there are techniques available to extract the heat out of shallow ground and use it to heat our homes. These techniques involve using ground source heat pumps.

How do we access geothermal energy?

Hot springs have been used by people for thousands of years for bathing and for heating. Geothermal energy was first used for industrial purposes 200 years ago and today it is used in many countries around the world.

Geothermal energy is heat which is stored within the Earth. Geothermal technologies make use of the ability of rocks and water in the subsurface to transfer and store energy. In a well-designed geothermal system, the heat that we extract, and use is replenished by the movement of heat through the rocks or the movement of warm waters or, at shallow depths, by solar energy.

Geothermal heat can be utilised at the surface directly or, if hot enough, can create steam to power a turbine and generate electricity. Deep drilling is usually required for direct use of the heat.

But how do we exploit the more accessible, low temperature heat contained in shallow soils, rocks and groundwater at, say, 9 to 14°C? In most cases, we can access this low temperature heat by installing a set of heat exchange pipes in trenches or boreholes. A water-based fluid is circulated through the pipes; it absorbs heat from the soil or rocks and conveys it to the surface. At the surface, a heat pump extracts the heat from the fluid, boosting the temperature to a level that is useful for space heating.  The heat exchange processes can also be reversed to transfer excess heat back to the subsurface, thereby cooling buildings.

There is, of course, no clear boundary between shallow ground source heat and deep geothermal energy; the temperature merely increases with depth. The deeper we drill, the less work the electrically powered heat pump needs to do to raise the temperature to the desired level. We can use the heat directly when we drill to depths where it is hot enough. The decision on how deep to drill will involve balancing the cost of deep drilling against the cost of electricity required to run heat pumps. Some different ways of accessing geothermal heat are shown in Figure 1.

A graphical representation of the different types of geothermal available, the depths at which each need to be drilled to and what they can be used for.

Figure 1 taken from – Unlocking the potential of geothermal energy in the UK, Abesser et al

The map below shows areas where geothermal heat is likely to be available in NI.

Figure 2 taken from – Raine et al., 2020 The Sherwood Sandstone as a Potential geothermal aquifer across Northern Ireland. Irish Geological Research meeting (IGRM) 2020. (unpublished). This map contains material that is based upon Crown Copyright and is reproduced with the permission of Land and Property Services under Delegated Authority from Keeper of Public Records, © Crown Copyright and database right 2023. Permit number MOU577.3.

For decades, geothermal technology has been safely and successfully used across the world, particularly in countries like New Zealand, Italy and Iceland. Parts of the world that don’t have active volcanic systems, such as Sweden, the Netherlands and Germany, have also made good use of their cooler geothermal resources. NI shares a similar climate and some aspects of geology with these countries and could benefit in the same fashion. The use of geothermal heat across Europe has been increasing and it is playing an ever-greater part in the decarbonisation of heating and cooling needs.

While geothermal technology is relatively new and underutilised in NI, there are several larger scale shallow geothermal projects currently operating. These include various Health & Social Care Trusts, the School of Biological Sciences at Queen’s University Belfast (QUB) and the new conference centre at QUB’s Riddel Hall

Is geothermal used to heat domestic homes in Northern Ireland?

There are currently relatively few domestic geothermal systems in NI. As of March 2023, data held by the Microgeneration Certification Scheme suggested that 386 small ground (and water) source heat pumps have been installed in NI, representing around 0.05% of households.

What are the benefits of geothermal energy?

Several aspects make geothermal a beneficial source of heating and cooling, including:

  • It is secure, low-carbon and sustainable, providing an alternative to fossil fuels.
  • It is local, offering a domestic source of reliable, renewable energy.
  • It can be available 24 hours a day, 365 days a year, regardless of the weather.
  • It can be used to both heat and cool homes, businesses and industrial processes, either with geothermal heat pumps or through direct use.
  • It reduces the need for energy imports and improves our energy security.
  • Geothermal systems have long life spans: many components operate reliably for up to 100 years. They do require some maintenance, but this should be modest if the system is well-designed.

In regard to geothermal electricity, there are also a significant number of benefits:

  • Using geothermal to produce electricity releases only about one-sixth of the carbon dioxide of a natural gas power plant.
  • Geothermal power plants have a high-capacity factor, meaning that they can operate at maximum capacity nearly all the time. Thus, geothermal can complement intermittent sources of energy like wind and solar, making it a critical part of the national renewable energy mix.

The main opportunities for geothermal use in NI lie in heating and cooling applications, including heating of buildings and greenhouses, as well as for applications in agriculture, aquaculture, industry, and district heating.

Modern district heating and cooling networks comprise webs of water-filled underground pipes to transfer heat between sources (such as geothermal) and customers. They also transfer heat between customers who require heat and those who have “waste” heat to remove.

Benefits of the Demonstrator Projects

What targets will the project help Northern Ireland to meet?

NI has committed to achieving net zero carbon energy by 2050. The Climate Change Act (Northern Ireland) 2022 aims to ensure NI contributes to the UK efforts to tackle climate change. Specifically, the Act commits to net zero carbon dioxide emissions by 2050 as well as sectoral plans to support decarbonisation of carbon intensive sectors and a target of 80% of electricity from renewable sources by 2030.

Energy-related sectors accounted for 59% of Northern Ireland’s total emissions in 2019. Heat is the largest sector, contributing 38% of Northern Ireland’s energy-related emissions (The Path to Net Zero, Northern Ireland Executive, December 2021). Geothermal and heat pumps represent two of the most promising technologies for tackling the carbon emissions from heating and cooling.

NI has significant geothermal energy potential and development of a geothermal sector will be important to help achieve the challenging targets coming out of the Act.

The data and learnings from the GeoEnergy NI geothermal exploratory and feasibility studies will help us better understand the subsurface and be essential in helping us unearth the heat beneath our feet.

What benefits will the project potentially deliver at a local level?

The data and learnings from the GeoEnergy NI project will be used to demonstrate:

  • That a viable geothermal heat resource is accessible from the near surface via shallow trenches to a range of depths via boreholes, providing confidence to local people when deciding on whether to install a geothermal (or ground source) heating and cooling system;
  • Encourage investment by making more detailed information on the current regulatory system and the subsurface publicly available;
  • Inform the development of a policy and regulatory framework that supports and promotes opportunities to unearth NI’s geothermal potential.

Geothermal energy has a host of economic, environment and social benefits associated with it at both a local and a community level including.

  • Security of energy supply – potential for local communities to adopt ground source heat pump technology to heat or cool their properties.
  • Potential job creation along a geothermal supply chain.
  • Skills and education opportunities in a geothermal sector.
  • Carbon and financial savings, over the lifespan of the system.
  • Cleaner air and CO2 emissions savings.

Project Details and Locations

Why is Northern Ireland and these specific locations suitable for geothermal?

NI geology provides ample opportunities for the development of geothermal energy. This resource is found within unconsolidated sediments and underlying rocks that can be accessed by closed-loop geothermal ground source heat pump systems. In many areas, NI also has buried sandstone aquifers, such as those under the Greater Belfast area and the Lagan Valley. These sandstones have additional potential for another type of shallow geothermal system called “open-loop geothermal”, where groundwater from the aquifer can be used for larger scale heating, cooling and thermal storage requirements.

In a few places in NI, permeable sandstone aquifers are buried to sufficient depth such that their groundwater is warm enough to be used for direct heating of industrial and horticultural processes or large numbers of houses.

Recent analysis of geological data across NI, by GSNI, has identified areas with potential for deep geothermal heating projects, particularly around Antrim. In combination with shallow geothermal projects, which have a wider applicability, there is no shortage of options for geothermal development in NI.

For more information, you can access recent reports including:

Where exactly will the feasibility studies be carried out?

This project aims to assess the feasibility of both a prestigious shallow geothermal (ground source heat pump) application and a deep geothermal borehole.

The feasibility study for the shallow geothermal project will be on the Stormont Estate, Belfast.  It aims to identity the most suitable geothermal solution to provide heating and cooling for a number of pre-identified buildings. We will find the optimum numbers, geometries and depths of boreholes or wells that are best able to deliver cost-effective heat harvesting. It is anticipated that the geothermal boreholes at Stormont will be up to 250 metres deep.

The deep geothermal feasibility study will be completed at the Greenmount Campus in Antrim. It will identify target drilling depths and the most suitable heat recovery system. We anticipate that the findings will point the way for future similar deep geothermal projects in NI. Our study will include:

  • A geophysical survey to allow imaging of geological structure of the area using methods such as seismic reflection, magnetotelluric and gravity measurements.
  • Development of a 3D geological model of the sub-surface using existing and newly acquired data.
  • Identification of the best drilling site.

How do the sites differ?

The Stormont site sits on top of a shallow aquifer containing water in the region of 15° C, whereas the Greenmount site overlies a deeper aquifer that potentially contains waters at around 70° C (an aquifer is a body of rock and/or sediment that stores and transmits groundwater).

Shallow systems generally require ground source heat pumps to modify (‘upgrade’) the temperature obtained from the geothermal resource for use in domestic or commercial heating or cooling applications.

In deep systems, the resource is usually at a high enough temperature to be used directly for heating or commercial purposes.

Will the local communities be consulted about these projects?

A public event was held in May 2023 to inform and consult with the local community in the Stormont area as part of the associated planning process and before any drilling takes place.

The Greenmount works do not involve any exploratory drilling. Instead, the works will be limited to non-intrusive surveys and subsequent recommendations. Any land access needed will be agreed with local landowners.

As part of the GeoEnergy NI project, there will also be an extensive community outreach programme where people can engage with the project and learn more about geothermal energy and its benefits.

What happens once the demonstrator project is complete?

Decisions about the potential next phase of the project will be dependent on the findings of this first phase.

At Stormont, it is hoped that the results of the project will ultimately inform the design of a geothermal heat network that will replace the current fossil fuel heating systems at some of the buildings on the estate. This will help NI meet the Executive’s carbon reduction targets. The higher efficiencies and lower operating costs of geothermal systems should also reduce the costs of managing the buildings.

Stormont Estate

Where is the proposed site?

Five locations for shallow boreholes have been identified within the Stormont Estate, Belfast. These are predominately located in private areas near government buildings west of Stoney Road and the area around Dundonald House, Castle Buildings and Stormont Castle. It is hoped that one borehole location will be accessible for public viewing for those who wish to learn more about geothermal energy.

Why has Stormont been chosen?

This location has been chosen because it sits on top of a productive aquifer with good shallow geothermal potential for both closed-loop and open-loop geothermal systems. The same aquifer underlies Belfast, Lisburn other large towns in NI and the results of this study will increase our understanding of this aquifer and help inform future projects. Reports by QUB’s Business School recommend that government should lead in demonstrating the contribution that geothermal energy can make in decarbonising the way we heat our homes and buildings.

Is planning permission required and what if this isn’t granted?

Planning permission will shortly be sought for the project at Stormont. If planning permission is not granted, an alternative site may be sought.

What will be happening at Stormont and why?

The drilling and testing of five boreholes. It aims to identify the most suitable geothermal solution to provide potential heating and cooling for buildings at the site.

Will the public areas have access to the sites in the Stormont Estate?

The public do not have access to all areas of Stormont Estate, particularly the areas where there are government buildings. However, once the precise location of the various borehole sites is agreed, we hope to identify and create a viewing area at one borehole location so visitors can see the geothermal demonstrator project in action. This will be enhanced with a nearby mobile information centre in the public access part of the Estate, which will be fully equipped with educational resources to help explain the entire process.

How long will the project last at Stormont Estate?

The full drilling and testing project at the Stormont Estate will take approximately six months and operate during normal working hours, 6 days a week, depending on weather. The drilling of each borehole will last up to a few weeks and the rig will be moved to the next site after drilling.

College of Agriculture, Food and Rural Enterprise (CAFRE) Greenmount Campus, Antrim

Where is the proposed site?

The site will be in the grounds of the Greenmount Campus, near Antrim. Due to the nature of the Greenmount site and location and the nature of the works, planning permission is not required, nor is the area open to the public.

The Greenmount project will involve a number of geophysical surveys, some of which will require access to lands beyond the CAFRE Greenmount site. All land access requirements will be agreed with local landowners.

Why has Greenmount been chosen?

The site has been chosen because it lies above a sedimentary rock sequence that is likely to contain naturally occurring hot waters at depths of one to two kilometres. This deep aquifer is an exciting geothermal source and presents an opportunity to explore development of a geothermal district heating network or, potentially, to decarbonise horticulture or other agrifood processes.

What will be happening at Greenmount Campus?

The project at Greenmount will inform the identification of a target drill site and optimum depth for accessing the aquifer. Included in the project will be a ground-based survey to provide drilling prognoses, to identify the precise site, and to image any geological structures.

A seismic reflection survey will be carried out, accompanying data processing and interpretation. This will be undertaken along public roads and on some farm tracks. It involves a specially designed truck (vibroseis) which will stop at 16 metre intervals and lower a pad onto the ground. The pad will vibrate the ground for a short period to generate sound waves that pass into the ground. Small receivers will be placed along the road/track in front and behind the vehicle at 4 metre intervals and these will pick up the reflections of the sound waves as they pass through and bounce back through the underlying subsoils and bedrock.

This will be combined with magnetotelluric and gravity surveys. Supporting ecological and water quality surveys will be carried out in the area. The Greenmount works do not involve any exploratory drilling. A full description of these surveys can be found in the ‘Greenmount’ section below.

What technology will be used to undertake the surveys

What technology will be used to undertake the surveys

Three different types of geophysical survey are planned.

Seismic Survey: This will be undertaken along public roads and on some farm tracks. It involves a specially designed truck (vibroseis) which will stop at 16 metre intervals and lower a pad onto the ground. The pad will vibrate the ground for a short period to generate sound waves into the ground. Small receivers will be placed along the track in front and behind the vehicle and these will pick up the reflections of the sound waves as they pass through the underlying subsoils and bedrock.

Magnetotelluric (MT) Survey: This will involve shallow burial (tens of centimetres) of small electrodes and magnetic tube sensors and the laying out of thin wires at the surface, all connected to a recording device. The equipment is designed to collect information on electrical resistivity distribution in the Earth. Recording at around 20 locations across the area will be undertaken with each recording taking about one day.

Gravity Survey: Gravity surveys provide measurements of variations in the Earth’s gravitational field between different locations. These gravity variations represent changes in the density of the rock types below the measuring point and assist in interpretating changes in rock types at depth across a selected survey area. The survey itself involves field technicians deploying gravity measurement equipment on the ground surface at a survey location for a short time (less than 30 minutes) and surveying the location and ground level in using standard GPS survey equipment. After the reading is taken the team move on to the next location.

Are there any risks to wildlife or ecology from the survey works?

There is very little risk from the planned survey works. All works are of very limited duration and the whole survey is expected to be completed in less than two weeks. Ecologists will review potential sensitive locations where survey work is planned and if required the survey will be adjusted to mitigate potential for impact at such areas, as an additional precaution.

Will the ground vibrations from the Vibroseis truck cause damage to buildings?

No impact on buildings is expected. Such surveys have been undertaken in a range of settings including urban areas. The ground at each ‘shot’ location is vibrated for only a short time (seconds) and then the truck moves on the next location. Survey design will take into account proximity of buildings and other structures and a precautionary approach will be taken where required.

Will there be any drilling or construction works?

No, other than the temporary installation of measurement devices in the shallow soils during the geophysical survey no investigative drilling or construction works will be undertaken associated with this phase of the project.

What happens after the survey is completed?

Once collected the data will be processed and combined with other existing datasets to develop a 3D geological model down to circa two kilometre depth below the local area. An assessment will be made of the available natural heat resource present at depth that could potentially be tapped in to, to provide a low carbon heat source for local use.

After that, if the indications are positive, proposals can be developed and funding sought for accessing the actual resource through deep drilling. The current project is only associated with the initial survey and interpretation stage.

Have similar surveys been undertaken in the area in the past?

Yes, there have been a number of similar surveys undertaken in the last 50 years. These were associated with exploration companies who were looking for oil and gas reserves. Whilst the survey techniques are the same, as both are designed to understand the geology at depths down to several km’s, this project is not looking for oil or gas reserves. The objective of this survey work is to investigate whether there are rocks which contain natural groundwater at a suitable elevated temperature and in sufficient quantities which could be tapped in to, to provide a low carbon source of heat. Where this can be achieved, this can be used instead of oil or gas to heat buildings/support industry, with the many associated environmental benefits this would bring.

How would the resource be used?

To tap into the natural heat stored in the bedrock at depth would require drilling of one or more deep boreholes down to the target reservoir. Water at this depth would be naturally hotter with potential temperature of 70-90oC. This water would be pumped to surface and the heat extracted for local use directly to buildings and/or transported to other users via a district heating network. The cooled abstracted water would be returned to the reservoir at depth via the existing borehole or another borehole where it would warm up again so that the system is operated sustainably.

Will a deep borehole be drilled as a result of the survey proposed?

Whether a deep borehole is drilled in the area will partly be dependent upon the findings of the surveys proposed. If geological conditions look favourable funding/investment would need to be secured. Any proposed scheme would be subject to a full environmental impact assessment and would require planning permission before any works could begin.

Would a deep borehole affect groundwater used for local water supplies from springs, wells and boreholes?

No, water would be abstracted at significantly greater depth than the groundwater used for other local purposes and no effect would be observed on local water supplies or watercourses. Deep boreholes are constructed so that they are sealed through the upper bedrock and can only actively interact with the much deeper reservoir of groundwater they are designed to tap in to.

Have similar schemes with deep drilling scheme been developed elsewhere?

Yes. A four and a half kilometre deep borehole has been drilled at the Eden Project in Cornwall. The project is designed to decarbonise the heat supply to the world-famous Biomes, new commercial greenhouses and other buildings at the Eden Project by creating a deep geothermal heating system.

In Southampton a deep borehole was drilled which, in 1986, began delivering heat to a district heating network. A number of other test boreholes have been drilled in the UK and there are many locations being actively considered for further survey and investigative drilling.

In Europe deep wells have been developed in many countries including France, Germany and Iceland with much active research underway to develop further systems.

The Technology

What technology will be used to drill the boreholes identified?

Given the relatively shallow depths involved at the Stormont site, a mobile truck-mounted drilling rig will be used to construct the exploratory boreholes. It uses the same techniques as those used in conventional water well drilling.

What testing is involved?

As the works are exploratory in nature, a wide range of borehole tests are planned to help evaluate the potential for use of ground source energy. The planned testing includes:

  • Downhole CCTV/camera surveys.
  • Downhole geophysical surveys to help understand changes in the ground properties with depth.
  • Water quality testing and water flow tests (packer tests – depth targeted tests and pumping tests).
  • Thermal response tests to evaluate the ease with which heat moves through the ground (these involve the introduction of small amounts of heat into the ground – typically a few tens of watts per metre).

When will the drilling and exploratory work commence and how long will it take?

Site preparations followed by drilling and testing will take approximately 6 months in total and it is aimed that the project will be completed by Summer 2024.

Hours of operation

The full drilling and testing project at the Stormont Estate across all boreholes will take approximately six months and operate during normal working hours, 6 days a week, depending on weather.

What happens after drilling and what remains on the sites at the end of the exploratory phase?

Once the drilling is complete, the drilling rig will leave the site. Borehole test equipment will be brought to site and temporarily placed into selected boreholes. The equipment will remain in situ for several weeks until the testing is complete. The test equipment will be removed from site at the end of the works and the boreholes will be finished just above the ground surface with a protective casing so that it can be used for further demonstrations, research or integration into any future ground source heat pump system adopted at the site.

How tall is the drilling rig going to be?

We anticipate using a mobile rig with a maximum mast height of 12 metres; it will only be on site temporarily. For comparison, Dundonald House, near to the drilling sites is 46 metres high.

Heat Pumps

What is a heat pump?

A heat pump is like a vacuum cleaner for heat. Your household vacuum cleaner has a low-pressure nozzle that sucks in air and dirt. It also has a high-pressure exhaust which expels the air and dirt to a collection bag. A heat pump has a low temperature heat exchanger (the “evaporator”) which can absorb heat from the environment (the ground, air, water). It also has a high temperature “exhaust” (the “condenser”), where the collected heat can be expelled, for example, to a central heating system.

You almost certainly already have a heat pump in your home – your fridge or freezer.  Your fridge draws heat out from foodstuff therein and expels the heat to your kitchen via a warm heat exchanger on the back of the fridge. Because these items contain relatively little heat, they are soon cooled down and the fridge cuts out. In a ground source heat pump, the “evaporator” is in contact with soil, rock or groundwater, which contains huge amounts of heat – so the heat pump can continue extracting heat and warming your house without the heat source running out. Heat pumps extract natural environmental heat from the ground, groundwater, air, rivers, the sea or even sewage; they boost its temperature and deliver it as useful space heating for buildings, homes, offices, swimming pools, fish farms or greenhouses.

If need be, heat pumps can be reversed, so that they suck heat out of the building (when it becomes too hot in summer) and disperse it to the air or the ground, providing space cooling, air conditioning and even dehumidification.

The most common type of ground source heat pump (a “closed-loop” system”) obtains heat from sealed pipes buried in the ground or in boreholes. Circulating fluid within these pipes collects heat from the surrounding ground and delivers it to the heat pump.

In an “open-loop” heat pump system, groundwater is pumped from a drilled well and circulated through a heat exchanger connected to the heat pump. The heat pump extracts heat from the pumped groundwater, which is typically at 10-14oC at shallow depths. The cooled groundwater (after the heat has been extracted) would typically be returned into the ground via a reinjection borehole, with no overall loss of water.

How does a heat pump work?

Just as in your domestic fridge or freezer, at the heart of a heat pump is a refrigerant cycle. This is driven by an electrically powered compressor. The refrigerant cycle.

  • chills down the evaporator (which absorbs heat from the environment),
  • raises the temperature of the heat (by compressing the refrigerant),
  • heats up the condenser, which delivers the heat to the building via radiators (ideally with a large surface area), underfloor heating or air heating systems.

The heat pump can also be designed to work in reverse and extract heat from the building space, to provide cooling.

What are the benefits of a heat pump?

Heat pumps are a very efficient way of providing heating for buildings. They represent a low-carbon replacement option for existing combustion fossil fuel systems such as oil and gas boilers. There are no emissions from heat pumps, which helps to improve air quality.

Ground source heat pumps are powered by electricity, which is used to drive the compressor. For every one kilowatt of electricity the heat pump uses, around two to three kilowatts of heat are drawn from the ground, resulting in three to four kilowatts of usable heat being provided to the building.

Thus, you may get three to four kilowatts of heat effect by using only one kilowatt of electricity. And if that electricity is derived from renewable source, it means that the heat pump is one of very few ways of efficiently providing low-carbon heating.

Can a heat pump be used for all types of buildings?

Heat pumps can be used for all building types from single houses to large offices, hospitals and schools. Schemes have been implemented in apartment blocks, with small heat pumps installed in individual flats/apartments, connected to a buried borehole array adjacent to the building.

Heat pumps can also be used to heat greenhouses, fish farms and swimming pools; in short, any process that requires low temperature heat.

Heat pumps can be installed in old or modern buildings. In older, poorly insulated buildings, while heat pumps are fully technically feasible, they can sometimes be expensive to install or run. When considering heat pumps in older buildings, it can therefore be wise to consider investing in upgrading the heat efficiency of the building itself (insulation) before installing a heat pump.

What size are heat pumps?

Heat pumps are available in a range of sizes depending on proposed heating/cooling requirements. They can be small enough to fit into cupboards in houses/apartments. The largest can be the size of a small car!

Do they also provide hot water?

Yes, heat pumps can be set up to deliver hot water to 60oC or higher in some cases.

Are heat pump systems difficult to operate?

They certainly shouldn’t be! Heat pumps can be fitted with controls to suit the needs and abilities of the user. Modern domestic heat pumps should be user-friendly and largely automated, linked to thermostats, weather compensation systems and smart technology.  As a non-combustible heating system there are no specific annual servicing requirements for a heat pump. Basic maintenance checks are recommended, however, to ensure the system is set correctly, that operating pressures are adequate and that it is operating at its most efficient.

Does a ground source heat pump work in all weather conditions?

Yes. There is a lot of natural heat energy stored in the ground which continually gets replenished from natural solar radiation and from deeper sources within the earth. While air source heat pumps may struggle to deliver adequate heat on the very coldest days, ground source heat pumps will be drawing on a subsurface heat store of more constant temperature, naturally insulated from the extremes of surface weather.

Are heat pumps expensive to install or run?

Initial installation costs may be more expensive than traditional oil and gas installations. However, it could be argued, that the boreholes or trenches required for a ground source heat pump should be regarded as an infrastructure investment that will add to the value of the property.  The subsurface infrastructure has a lifespan of up to a century.

A well-designed ground source heat pump system should save money in terms of running costs, although the saving will depend on whether a comparison is made with expensive fuels such as oil or bottled gas, or cheaper fuels such as mains gas. These savings will most likely increase as the cost of renewable electricity becomes cheaper relative to gas.

Further information can be found at In-depth guide to heat pumps – Energy Saving Trust.

Addressing Concerns

Is geothermal linked to ‘fracking’?

No. Accessing geothermal energy does not require the use of the fracking process and it is important that it is not confused in any way.  Deep geothermal projects such as the one planned simply circulate geothermal waters that flow naturally from the aquifer and can then be pumped to the surface. Once some of the heat has been extracted, the fluid is returned down a second borehole to the same geological formation to be re-heated.

In shallow geothermal systems, if the aquifer is not used, then a closed loop system can be deployed that recirculates fluids in a sealed system. Both techniques are straightforward, safe and well-practiced techniques.

By contrast, high-volume hydraulic fracturing or fracking for shale gas involves the injection of large quantities of water into the rock to deliberately fracture it under pressure and enable gas to be extracted.

The aim of this geothermal project is to capture natural heat and use it as renewable energy, so that we can move away from fossil fuel use.

Will this geothermal drilling impact groundwater?

The project will not adversely impact groundwater. The technology used is designed to ensure that the groundwater is protected. This will be assessed within the planning process and the boreholes will be drilled to industry best practice and in full compliance with groundwater regulations and guidance issued by the Northern Ireland Environment Agency (NIEA).

Do you anticipate any adverse impact on local habitats?

No. An environmental assessment has been carried out and the site has been surveyed to identify any ecosystems that could be affected. Most of the drill sites are located on or close to private car parks and the sites have been chosen to ensure that the risk to local habitats is minimised.

Will the project be noisy?

Typical drilling noise can be in the order of 100 to 120 decibels. As a comparison, a lawnmower produces noise at around 110 decibels. The level of noise and how it might travel has been a consideration in choosing suitable sites. Efforts are also being made as part of this demonstration project to trial new low noise emitting borehole construction plant, equipment and technology.

What about traffic around the sites and movement of heavy vehicles – will this impact the local areas?

Traffic levels will be very low. The drilling rig is mounted to a truck (similar to an eight wheeler truck). Once the drilling rig and associated plant has been mobilised to site, traffic will be limited to two to three vehicles per day.

How visible will the two projects be and what will physically be left behind when the exploratory work is complete?

As the drilling locations at the Stormont Estate are located in predominately private areas, it will largely be shielded from public view.

Once drilling and testing is finished, the equipment will be removed and the boreholes will be completed at the ground surface with a lockable cap so that they can be used for ongoing research and monitoring or incorporated in a future ground source heat pump system.

Will there be any ground vibration during drilling?

No. Ground vibration during drilling works is not anticipated.

Will the geothermal drilling cause earth tremors?

Geothermal drilling such as that planned at Stormont does not cause earth tremors.

Future work at Greenmount Campus will involve drilling to greater depths.  Sometimes, when a deep geothermal project reaches the test or operational phase, and geothermal fluids are re-injected to very deep boreholes, minor seismic events (micro-shocks) can occur as the rocks re-adjust themselves to the new subsurface conditions. Experience from such schemes has indicated that the micro-shocks are mostly so small, and at such depth, that they are not felt at the surface. Even where an event is large enough to be felt at surface it is still very unlikely to cause any damage. For such schemes there would be a requirement to assess the potential risks as part of any application seeking permission to develop such a scheme. Recent projects, such as United Downs in Cornwall, have worked together with local communities to monitor any micro-seismic events.

What about potential for radon gas?

We do not anticipate that we will encounter any increased levels of radon when drilling the shallow boreholes at the Stormont Estate.

Radon mapping for NI is available here.

Find Out More and Contact Information

Can I visit the sites?

We welcome the opportunity to showcase the benefits of geothermal energy. A mobile visitor unit will be established on the Stormont Estate and will be accessible to the public later this year. There are plans to provide public access at Stormont to at least one of the drill sites during the drilling and testing phase.

I’m interested in finding out more about geothermal energy for my business or home, where do I find out more?

For more information on ground source heat pumps, visit NI Direct.

Other organisations that might be of interest include:

I want to know more about Northern Ireland’s Energy Strategy and Pathway to Net-Zero, where can I find out more?

For information on Northern Ireland’s Energy Strategy, please visit the DfE website here.

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