Ireland's geothermal resources are ideal for space heating

by Brian P. Connor, consultant on geothermal energy technologies

Only lowgrade heat can be expected from geothermal sources in Ireland. Research is required to find sites to supply industrial and horticultural heating needs.

Geothermal energy is the earth's natural heat. Heat is transferred to the earth's surface by conduction through rock and via convection in moving fluids. Heat flow is highest in regions of active tectonism and volcanics and lowest in stable shield areas. Geothermal energy can be used for (a) electricity production or (b) direct heating applications. Geothermal energy available on demand, unlike wind energy which is only available when there is sufficient wind speed.

Geothermal energy systems can be classified into four categories:

  1. hot dry rock system
  2. high enthalpy systems
  3. low enthalpy systems
  4. shallow geothermal energy

The geographical extent of potential hot dry rock systems is limited. The system involves a temperature of over 200oC at a depth greater than 3km (5-7km). Water is injected into the hot rock through deep boreholes and the hot water or steam returns up another borehole to be used for electrical generation. This system does not have potential in Ireland but experiments have been conducted in Cornwall in the UK.

High enthalpy systems are associated with active tectonic and volcanic areas. These are water or vapour dominated systems. The temperature of the source is over 200oC. These systems are generally used for electricity generation. They are not suitable for Ireland due to the geological conditions in the country.

Low enthalpy systems are applicable for stable geological areas e.g. North West Europe. Suitably warm rocks occur at depths of up to 2km with temperatures up to 100oC. This system is used for direct heating in, for example, the Paris basin and in Southampton, England. Applications include industrial and horticultural heating. This system has potential in Ireland but research is needed to locate suitable sources of this geothermal heat.

Shallow geothermal energy uses geothermal energy with a source temperature of about 10oC. The temperature is increased using heat pumps. There are four main production configurations currently in use in Ireland - horizontal loops, vertical loop, groundwater and building foundations. Current applications include space heating in commercial buildings, private houses and swimming pools. The most common configurations use horizontal loops or the direct use of aquifer water. There are 500-600 installations in Ireland at present.

The status, needs and potential for future development of the geothermal resource in Ireland can be summarised as follows:

Low temperature geothermal using heat pumps

Status at present

  • technology developed
  • demonstration installations are available for inspection
  • limited number of installers

Required to develop use of technology on a large scale

  • promotion of technology
  • training of installers
  • regulation and certification of installers

Potential of resource

  • most sites can support installations using locally available geothermal energy

Low enthalpy systems

Status at present

  • no development in Ireland
  • lack of data on potential aquifers that could be developed to produce geothermal energy

Required to develop use of technology on a large scale

  • study to evaluate resource
  • demonstration of technology to develop and use the resource

Potential of resource

  • unknown at present until preliminary evalua tion studies are carried out

The Geothermal Association of Ireland was founded in 1997. It has over 30 members, with representation from academic institutes, energy management agencies, consultants and contractors. The association is the Irish representative on the European Geothermal Energy Council. The objectives of the Geothermal Association of Ireland are as follows:

  • Promote the use of geothermal energy in Ireland
  • Carry out research on geothermal energy in Ireland.

The activities of the association include:

  • lectures on current development worldwide on geothermal energy
  • provision of training courses for installers of geothermal energy systems
  • organising site visits to geothermal installations.

The secretary of the Geothermal Association of Ireland can be contacted through:
Cork County Energy Agency,
Spa House,
Co. Cork.
Ph: +353.22.43610
Fax: +353.22.43678

This is one of almost 50 chapters and articles in the 336-page large format book, Before the Wells Run Dry. Copies of the book are available for £9.95 from Green Books.

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