GEMINI – Geothermal Energy Momentum on the Island of Ireland – is a cross-border geothermal energy demonstration project. Through its many and varied activities, the project aims to reduce greenhouse gas emissions associated with heating and cooling.

There are four sites – two in Belfast, one in Sligo and one in Dublin. These will use heat energy from the Earth to power large-scale heating systems in public sector buildings: a sports centre, housing project, utilities offices and a university campus. The development and operation of these sites will demonstrate the benefits of geothermal energy systems by fully engaging with communities, educational institutes and local authorities.

An additional site in Antrim will be the focus for geological and subsurface surveys to examine its potential for a geothermal energy installation.

The cross-border area of Lough MacNean will also be the focus of community engagement activities and feasibility studies.

As well as the activities focused at the demonstration sites, the project will be devoted to other activities that promote the use of geothermal energy for heating and cooling. These include:

• Developing skills-sharing platforms and training opportunities;

• Supporting businesses in the emerging geothermal market;

• Instigating national regulation frameworks and cross-border policy recommendations for geothermal energy uptake;

• Constructing toolkits for decision makers;

• Shaping community engagement models;

• Creating educational modules for various levels.

The project will also collect additional data for potential future sites, to increase and improve our knowledge of the subsurface and potential geothermal resources. These data will be used to compile heat resource maps which will be made available to everyone.

The project has received €20/£17.3 million from the PEACEPLUS programme, managed by the Special EU Programmes Body (SEUPB) with support from Department of Environment, Climate and Communications, Ireland and the Department for the Economy, Northern Ireland.

PEACEPLUS is a cross-border funding programme designed to support peace and prosperity across Northern Ireland and the border counties of Ireland. PEACEPLUS is co-funded by the European Union, the Government of the United Kingdom of Great Britain and Northern Ireland, the Government of Ireland, and the Northern Ireland Executive.

The project comprises 15 Project Partners and 8 Associated Partners from the local and national government, research sector, and community engagement groups both North and South of the border. The project is led by Codema, Dublin’s Energy Agency.

Click here for a full list of partners.

Geothermal energy technologies for heating and cooling release almost zero Greenhouse Gas Emissions and so this resource can play a significant role in contributing to meeting EU, UK and Irish 2050 carbon emissions targets.

The Climate Change Act (Northern Ireland) 2022 commits to net zero carbon dioxide emissions by 2050. 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).

The Climate Action Plan 2019 (Ireland, updated annually) states the government’s aim to achieve cutting Greenhouse Gas Emissions by at least 30% by 2030 and taking action which will lead the country towards a climate neutral, sustainable society by 2050. In 2021 24% of Ireland’s total Greenhouse Gas Emissions came from burning fossil fuels and other non-renewable fuel for heating and cooling (Sustainable Energy Authority of Ireland).

Geothermal energy and heat pumps represent two of the most promising technologies for tackling the carbon emissions from heating and cooling.

Geothermal energy is all energy stored in the form of heat beneath the surface of the Earth. It is a constant source of low-carbon, renewable heat. It is available at depths from a few metres to several kilometres, from where it can be extracted using different technologies for different applications.

Geothermal energy can be used directly for heating and cooling or higher temperature energy (e.g. over 100°C) can be used to generate electricity. Direct heating and cooling can be used for individual homes, and larger-scale geothermal systems can be used to heat and cool commercial sites.

Geothermal energy can contribute to reducing our carbon emissions and improve our local energy security. It is available 24 hours a day independent of the weather and has a very small surface footprint compared to other renewable energies such as wind and solar energy.

The very shallow surface of the Earth acts as a solar collector. Near-surface soils, sediments and rocks are kept at temperatures slightly above the annual average soil temperature (9 to 11°C on the island of Ireland), by the sun and the atmosphere. There are techniques available to extract the heat out of shallow ground and use it to heat our homes.

The Earth also contains huge amounts of thermal energy generated during its formation and which continues to be generated in its crust. This heat slowly migrates 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 near the surface. On average, the rate of increase in temperature is approximately 30°C per km depth in the Earth’s crust.

In regions that do not have active volcanic activity, such as on the island of Ireland, the crust is cooler, but it still contains significant thermal energy, and permeable rocks at depths of a few kilometres will contain hot fluids. 

No. 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.

Geothermal technology has been safely and successfully used across the world for decades, 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. The island of Ireland shares a similar climate and some aspects of geology with these countries and could benefit in the same way.

We can exploit the accessible, low temperature heat contained in shallow soils 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, an electric heat pump extracts the heat from the fluid, boosting the temperature to a level that is useful for heating a variety of buildings. The heat exchange process can also be reversed to transfer excess heat back to the subsurface, thereby cooling buildings.

Higher temperatures can be accessed by drilling deeper (3-4 km for a standard installation) and installing either:

• 'closed' systems which absorb the heat from the rocks, or

• 'open' systems which draw up the warmer groundwater directly to the surface, extract the heat, and re-inject the same groundwater back into the aquifer to be reheated by the rocks.

Although for regulation purposes a distinction is made between depths of less than 500m (shallow) and greater than 500m (deep), there is no clear physical boundary between the two; the temperature gradually increases with depth. The deeper we drill, the less work an electrically-powered heat pump needs to do to raise the temperature to the desired level. The decision on how deep to drill involves balancing the cost of deep drilling against the cost of electricity required to run heat pumps.

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

• It is secure, low-carbon and sustainable.

• It has a small ecological footprint.

• It is local, offering a domestic source of reliable, renewable energy.

• It is weather-independent and can be available 24 hours a day, 365 days a year.

• It can be used to both heat and cool homes, businesses and industrial processes.

• 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.

• Operating costs are generally low.

Compared to other renewable energy resources, the main challenges to developing geothermal energy are technical and economic.

• The resources need to be carefully managed and the systems designed to suit the heat source and user demand.

• Heat cannot be moved as efficiently as, for example, electricity. Therefore, geothermal energy systems tend to be used above or very close to the source.

• Not all types of rock provide efficient or cost effective geothermal heat, particularly for systems that require hotter (deeper) heat resources.

• The initial cost of installing geothermal energy is higher than other renewable energies.

• Neither Ireland nor Northern Ireland currently has specific geothermal legislation in place (although in Ireland a Geothermal Bill is in preparation according to the Policy Statement on Geothermal Energy for a Circular Economy [DECC, 2023]).
  

Other challenges relate to difficulties around fragmented regulatory frameworks, delays in obtaining permits and lack of a qualified workforce to install and maintain systems.

GEMINI aims to address and mitigate challenges and risks for deep-drilled geothermal energy exploration by:

• Accurately characterising and modelling the subsurface through modern remote geophysical methods.

• Carrying out comprehensive drilling risk assessments and designing drilling management strategies to minimise delays and cost escalation.

• Promoting and developing skills sharing and training opportunities to support installation and maintenance of geothermal systems.

• Contributing real world experience and knowledge to the regulatory and policy framework discussions.

Many types!

Shallow geothermal systems can be used for providing heating and/or hot water to individual residential homes and public buildings, such as sports centres, swimming pools and community halls. These systems also have many commercial applications, including greenhouses, warehouses and farm buildings.

Deep geothermal systems can heat multiple and larger buildings via district heating networks. Examples are as diverse as hospitals, schools, museums, university campuses, retail parks, apartment complexes, housing estates, airports, and so on. 

A heat energy source, or combination of sources, is connected to multiple energy consumers through a system of highly insulated pipes. Hot water is distributed through the pipes, supplying heat and hot water to the user as required. A range of energy sources can be used, including geothermal energy, and can be used in combination with, for example, solar thermal arrays, biofuels and waste heat.

District heating networks can be more energy efficient than individual heating systems because the heat is generated at a central plant and distributed through a network of insulated pipes, rather than being generated at each individual building. They can be more cost effective, because the costs of operating and maintaining the central plant can be shared among multiple users, and space saving, because individual heating units are not required in each building.

For shallow geothermal systems extracting the heat of the upper part of the subsurface does not itself have any adverse environmental impact.

The heat pumps are powered by electricity and contain refrigerants, although they are sealed within the system and not in contact with the environment. It’s worth noting that these ground-source heat pumps have higher efficiency than air-source heat pumps so their overall environmental impact is significantly less.

Once a deep geothermal energy system is in place, the impact on the environment is extremely low. These installations are zero-carbon at source and the footprint upon the land is very small. Electricity is commonly used to pump the geothermal circulation system and this may have a small associated carbon footprint.

For 'open' loop systems, the geothermal fluid is recycled locally back into the deep aquifer. Only the heat is extracted at the surface. In 'closed' loop systems a working fluid is circulated within a network of boreholes and does not come into contact with natural groundwater.

Environmental impacts are typically temporary and confined to the drilling phase when there is some local disruption in the form of noise and, potentially, minor vibrations similar to construction works. 

There is no specific regulation covering geothermal energy in place for Ireland or Northern Ireland but, in line with best practice from other countries, an assessment of impacts on biodiversity, natural habitats and the built environment should be completed at planning stage for deep geothermal systems. 

Deep drilling and circulation of fluids can cause very small-scale ground vibration (seismicity). It is not likely that these micro-seismic events will be felt at the surface, but it is best practice to monitor seismicity before, during and after drilling and injection of fluids.

The rate at which heat is extracted needs to be managed. Geothermal technologies make use of the ability of rocks and water in the subsurface to transfer and store heat. In a well-designed geothermal system, the heat that we extract and use is replenished by the natural movement of heat through the rocks from ongoing geological processes, or by the movement of warm water or, at shallow depths, by solar energy.

This is a difficult question to answer as it depends on the system being used, the cost of electricity, other renewable fuel energy costs at a location, and the timescale over which the costs are being calculated. 

Part of GEMINI's mission is to make it easier for potential users of geothermal energy to calculate the costs involved.

Some deep geothermal energy activities have been known to cause very small-scale ground vibrations (seismicity). Sometimes, minor seismic events (micro-shocks) can occur as the rocks re-adjust to new subsurface conditions. Usually, these micro-shocks are mostly so small, and at such depth, that they are not felt at the surface.

Comprehensive studies on the island of Ireland have demonstrated that we have a low level of natural seismicity and associated risk. Further studies and monitoring capacity will be developed during the GEMINI project, which will also work together with local communities. 

There are a few reasons:

• We have needed more geological information about the subsurface;

• There needs to be specific policy, legislation and regulations surrounding the use of geothermal energy;

• New and more efficient technology needed to be developed to be able to use lower temperature geothermal energy effectively;

• Government support for renewables has not included geothermal.

It is now easier than ever before to harness geothermal energy on the island of Ireland thanks to new and improved technology and our enhanced knowledge of the subsurface.

There are a few larger scale shallow geothermal projects currently operating. These include the School of Biological Sciences at Queen’s University Belfast (QUB), the conference centre at QUB’s Riddel Hall, IKEA Dublin, Vistakon Ireland in Limerick, Athlone City Centre Retail Complex, Westmeath, Giant's Causeway Visitor Centre, and various health and social care trusts.

The main opportunities for geothermal on the island of Ireland lie in heating and cooling applications, but under certain conditions geothermal energy can be used to generate electricity. This has a number of benefits, including releasing only about one-sixth of the CO2 of a natural gas power plant. Also, as geothermal power plants operate at capacity nearly all the time, they can complement intermittent sources of energy like wind and solar.

You may find the following links useful:

Geological Survey of Ireland - Geothermal

GeoEnergy NI

Ground Source Heat Pumps

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

View information here on Ireland's Policy Statement on Geothermal Energy for a Circular Economy (DECC, 2023).

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