Geothermal Energy Resource Map of Ireland
Geothermal Energy Resource Map of Ireland
Final Report
July 2004
Report prepared for Sustainable Energy Ireland by:
The CSA GroupRóisín Goodman
Gareth Ll Jones (Conodate)
John Kelly
Ed Slowey
Nick O’Neill
Geothermal Energy Resource Map of Ireland
EXECUTIVE SUMMARY...............................................................................................................................1
1 Introduction.........................................................................................................................................3
1.1
Terms of reference ..................................................................................................................3
1.2
Objectives of this study .........................................................................................................3
1.3
Outputs........................................................................................................................................4
2 Available data sources.....................................................................................................................5
2.1
Geological data.........................................................................................................................5
2.2
Previous geothermal energy investigations in Ireland .............................................5
2.3
Literature review ......................................................................................................................6
2.3.1
Imperial College London.............................................................................................7
2.3.2
Tara Prospecting Ltd.....................................................................................................7
2.3.3
Irish Geothermal Project 1981-1983.......................................................................7
2.3.4
University College Galway..........................................................................................8
2.3.5
Cork City Council, UCC and Cork Energy Agency, .............................................9
2.3.6
Geological Survey of Ireland......................................................................................9
2.3.7
Petroleum Affairs Division ....................................................................................... 10
2.3.8
Geothermal Association of Ireland....................................................................... 10
2.4
EU Altener Programme....................................................................................................... 10
3 Geothermal source types, exploitation and output / efficiency................................... 11
3.1
Definition of source types/categories........................................................................... 11
3.1.1
Shallow soil and sediment (ground source heat pump – GSHP).............. 11
3.1.2
Surface water................................................................................................................ 11
3.1.3
Warm springs................................................................................................................ 12
3.1.4
Gravel aquifers and Urban Heat Island Effect................................................... 12
3.1.5
Shallow groundwater bedrock aquifers............................................................. 15
3.1.6
Intermediate and deep aquifers............................................................................ 16
3.1.7
Enhanced Geothermal or Hot Dry Rock Systems............................................ 16
3.2
Types of geothermal exploitation.................................................................................. 17
3.2.1
Horizontal closed-loop collectors......................................................................... 17
3.2.2
Horizontal open-loop collector ............................................................................. 18
3.2.3
Vertical borehole open-loop collectors.............................................................. 18
3.2.4
Vertical borehole closed-loop collectors ........................................................... 18
3.3
Heat-pump technology...................................................................................................... 19
3.3.1
Residential heat-pumps – proper sizing and installation............................ 20
3.3.2
Some practical aspects of residential heat-pump systems......................... 21
3.3.3
Co-efficient of performance (COP) and CO2 savings...................................... 21
4 Current geothermal exploitation - Ireland and international ....................................... 24
4.1
Ground source heat-pump usage in Ireland .............................................................. 24
4.1.1
History of GSHP in Ireland........................................................................................ 24
4.1.2
Current GSHP usage in Ireland............................................................................... 25
4.2
Surface water source heat-pumps ................................................................................. 25
4.2.1
Tramore Civic Offices................................................................................................. 26
4.2.2
City of Stockholm........................................................................................................ 26
4.3
Shallow borehole source (open loop) heat-pumps................................................. 27
4.3.1
UCC Art Museum......................................................................................................... 27
Geothermal Energy Resource Map of Ireland
5
6
7
8
9
4.3.2
Mallow swimming pool ............................................................................................ 28
4.4
Intermediate and deep borehole source heat-pumps/heat exchangers........ 28
4.5
Deep geothermal heat-pumps/heat exchangers..................................................... 28
4.5.1
Paris Basin ...................................................................................................................... 29
4.5.2
Southampton ............................................................................................................... 30
4.5.3
Aachen ............................................................................................................................ 31
4.6
Enhanced Geothermal or Hot Dry Rock (HDR)Systems.......................................... 32
4.6.1
Basel ................................................................................................................................. 34
4.6.2
Soultz-sous-Forêts ...................................................................................................... 35
4.6.3
Los Alamos..................................................................................................................... 37
4.7
Application of deep geothermal heat exchangers in Ireland.............................. 37
Warm springs data collation and modelling........................................................................ 39
5.1.1
Geological modelling ................................................................................................ 40
Borehole temperature monitoring and data collation .................................................... 46
6.1
Equipment............................................................................................................................... 48
6.1.1
Temperature probe.................................................................................................... 48
6.1.2
Other equipment ........................................................................................................ 48
6.2
Borehole results..................................................................................................................... 49
6.2.1
Procedure for modelling temperature and geothermal gradient ........... 50
6.2.2
Boreholes monitored by CSA ................................................................................. 51
6.2.3
Boreholes monitored by mineral exploration companies .......................... 53
6.2.4
Boreholes monitored by oil exploration companies..................................... 53
6.2.5
Data for Northern Ireland......................................................................................... 55
6.2.6
Imperial College monitoring programme ......................................................... 56
Data modelling for temperature & geothermal gradient ............................................... 57
7.1
Temperature and geothermal gradient maps........................................................... 57
7.1.1
Data modelling techniques..................................................................................... 57
7.2
Shallow geothermal modelling....................................................................................... 59
7.2.1
Temperature and geothermal gradient modelling at 100m...................... 60
7.3
Intermediate (100-1,000m) and deep (1,000-5,000m) modelling...................... 60
7.3.1
Intermediate (100-1,000m) and deep (1,000-5,000m) geothermal and
geological modelling .................................................................................................................... 60
7.3.2
Intermediate (100-1,000m) and deep (1,000-5,000m) structural
modelling .......................................................................................................................................... 61
7.3.3
Temperature and geothermal gradient modelling at 500m...................... 61
7.3.4
Temperature and geothermal gradient modelling at 1,000m .................. 62
7.3.5
Temperature and geothermal gradient modelling at 2,500m .................. 64
7.3.6
Temperature and geothermal gradient modelling at 5,000m .................. 64
Geothermal database – User’s Manual................................................................................... 65
8.1
Downloading a geothermal dataset ............................................................................. 65
8.2
Viewing the dataset using Proviewer ........................................................................... 67
8.3
Querying the datasets......................................................................................................... 69
Current Irish geothermal resources......................................................................................... 71
9.1
Shallow soil and sediment (0-3m) geothermal resources - GSHP...................... 71
9.1.1
The future for GSHP in Ireland ............................................................................... 71
9.2
Surface water resources ..................................................................................................... 72
9.3
Shallow (0-100m) groundwater geothermal resources......................................... 72
Geothermal Energy Resource Map of Ireland
9.3.1
Warm springs geothermal resources .................................................................. 72
9.3.2
Shallow (0-50m) gravel aquifer geothermal resources ................................ 73
9.3.3
Urban Heat Island Effect geothermal resources ............................................. 73
9.4
Other shallow geothermal resources............................................................................ 74
9.5
Shallow (0-100m) bedrock aquifer geothermal resources ................................... 74
9.6
Intermediate (100-1,000m) and deep (1,000-5,000) groundwater geothermal
resources................................................................................................................................................. 74
9.7
Enhanced Geothermal Systems or Hot Dry Rock resources................................. 75
9.7.1
Potential for Enhanced Geothermal or Hot Dry Rock Systems in Ireland
75
9.7.2
Heat flow in the continental crust ........................................................................ 75
10
Technical summary and conclusions ................................................................................. 76
10.1 Shallow geothermal............................................................................................................. 76
10.1.1
Soil (0-2m)...................................................................................................................... 76
10.1.2
Surface water................................................................................................................ 76
10.1.3
Shallow (0-50m) gravel aquifers............................................................................ 76
10.1.4
Urban Heat Island Effect resources ...................................................................... 77
10.1.5
Warm springs................................................................................................................ 77
10.1.6
Shallow (0-100m) bedrock aquifers ..................................................................... 78
10.2 Medium (100-1,000m) to deep (1,000-5,000m) geothermal................................ 78
10.2.1
Data .................................................................................................................................. 78
10.2.2
Geology........................................................................................................................... 79
10.2.3
Geothermal gradient and temperature variation........................................... 79
10.2.4
Heat flow ........................................................................................................................ 80
10.3 Enhanced Geothermal Systems or Hot Dry Rock ..................................................... 80
11
Non-technical conclusions..................................................................................................... 81
11.1 General...................................................................................................................................... 81
11.2 Shallow geothermal............................................................................................................. 81
11.2.1
Soil .................................................................................................................................... 81
11.2.2
Surface Water ............................................................................................................... 81
11.2.3
Shallow gravel aquifers and Urban Heat Island Effect.................................. 81
11.2.4
Warm springs................................................................................................................ 81
11.2.5
Shallow bedrock aquifers......................................................................................... 81
11.3 Medium to deep geothermal........................................................................................... 82
11.4 Enhanced Geothermal Systems or Hot Dry Rock ..................................................... 82
11.5 Relevant Irish legislation .................................................................................................... 83
12
Geothermal energy potential – recommendations for increased use .................. 84
12.1 Recommended Actions...................................................................................................... 84
12.1.1
Heat-pump technology recommended actions ............................................. 84
12.1.2
Statutory perspective recommended actions ................................................. 85
12.1.3
Public awareness recommended actions.......................................................... 85
12.1.4
Medium to deep geothermal exploitation recommendations ................. 85
13
References, Bibliography and Further Reading ............................................................. 86
Geothermal Energy Resource Map of Ireland
List of Figures
Fig. 1.
Louisa Bridge Pool 2004.
Fig. 2.
The old Bathing Pool at Louisa Bridge
Fig. 3.
The Warm Spring at Mallow
Fig. 4.
Spa House, Mallow, site of the Cork County Energy Agency
Fig. 5.
Buried valleys in the Lee Valley
Fig 6.
Typical sections across the buried valleys. See T. Davis poster Appendix XI.
Fig. 7.
Map of the gravels associated with the small rivers Poddle, Stern, Swan and Dodder in south central
Dublin
Fig. 8.
The location of buried and uplifted palaeo-valleys. (Phillips 2001).
Fig. 9.
Diagrammatical cross-section for HDR
Fig. 10. Vertical borehole closed-loop collector
Fig. 11. Modern heat exchange system
Fig. 12. The benefits of geothermal energy.
Fig. 13. Exploitation options for warm and hot water, from Lindall (1973).
Fig.14. Collector site preparation, house site Kinsale.
Fig.15. Heat exchange set-up, house site Killavullen
Fig. 16. Tralee Motor Tax office
Fig. 17. Heat Exchanger
Fig. 18. Tramore Civic Office
Fig. 19. The collector reservoir
Fig. 20. The heat exchange room
Fig. 21. The City of Stockholm.
Fig. 22. Sea Water Heat Pump Facility
Fig.23. The UCC Arts Museum Building.
Fig. 24. One of the two wellheads yielding 10 l/s
Fig. 25 & 26. Mallow swimming pool and part of the heating system
Fig. 27. Low enthalpy geothermal plant, Paris
Fig. 28. Southampton district heating flowchart
Fig. 29. Deep GHE system
Fig. 30. Architects drawing of proposed Super-C building at Aachen
Fig. 31. Diagrammatical cross-section for HDR
Fig. 32. Details of the Swiss Deep Mining drilling at Basle, both current and expected.
Fig. 33. Potential deep heat mining sites in Switzerland. Based on logistics, heat distribution and geology
Fig. 34. The European HDR-project in Soultz-sous-Forêts, France
Fig 35. Aerial view to the platform of GPK2/3/4 with the actual drilling activities
Fig 36. Diagrammatical cross-section for Soultz-sous-Forêts, France
Fig. 37. Lady’s Well, Mallow.
Fig. 38. St. Gorman’s Well, Enfield.
Fig. 39. Logging the warm borehole at the Cork County Council reservoir site at Glanworth.
Fig. 40. Munster Warm Springs model, after Brück et al. 1983.
Fig. 41. Knocksouna Hill and Rising.
Fig. 42. Knocksouna Rising
Fig. 43. The temperature probe
Fig. 44. Temperature readout
Fig. 45. The metal detector
Fig. 46. The hand-held thermometer at Kingscourt.
Fig. 47. Field trials with the GeoRemediation temperature probe.
Fig. 48a,b&c. Point dataset, grid created over dataset and modelled surface generated from grid.
Fig. 49. Highly clustered dataset.
Fig. 50. Comparison of modelling techniques for clustered data.
Fig. 51. Extracting datafiles etc. from a downloaded zip file.
Fig. 52. The Open Mapinfo Tables or Workspaces dialog box.
Fig. 53. The Workspace
Fig. 54. Minimising the Layout window
Fig. 55. Mapinfo Proviewer tools
Fig. 56. Map window resized and enlarged using zoom in tool.
Fig. 57. Hotwell House.
Fig. 58. St. Gorman’s Well April 2004
Geothermal Energy Resource Map of Ireland
List of Tables
Table 1:
Carbon dioxide emissions
Table 2:
Large GSHP installations in Ireland
Table 3.
North Leinster warm springs and boreholes
Table 4. Munster warm springs and boreholes
Table 5.
Sources of new data
Table 6.
Boreholes tested by CSA and summary results
Table 7:
Boreholes monitored by Outokumpu and summary results
Table 8:
Oil exploration boreholes (Republic of Ireland) summary results
Table 9:
Porosity and permeability measurements for oil exploration boreholes in
the Republic of Ireland
Table 10.
Imperial College London boreholes used in this study
Table 11.
Average thermal conductivity values (Brück & Barton 1984)
Table 12.
From Ball (1990) The possible development of seven sites in south central
Dublin
Geothermal Energy Resource Map of Ireland
List of Appendices
APPENDIX I:
Warm Spring Temperature Monitoring Data
APPENDIX II:
Warm Spring Temperature Monitoring Charts
APPENDIX III: Borehole Temperature and Geothermal Gradient Data
APPENDIX IV: Borehole Temperature and Geothermal Gradient Logs
APPENDIX V:
Borehole monitoring discussion
APPENDIX VI: Geology and Location Maps
Map 1A:
Map 1B:
Map 2:
Map 3:
Map 4:
Map 5:
Geology: Principle Rock Types
Geology: Main Geologic Regions
Urban Areas (with lakes and counties)
Major Aquifers; Gravels and Bedrock (KTC and GSI)
Warm Spring Locations and shallow boreholes (with urban areas, lakes
& counties)
Locations of boreholes used for modelling (with urban areas, lakes &
counties)
APPENDIX VII:
Modelled Temperature Maps
Map 6A:
Modelled Temperature of warm springs and shallow (<10m)
groundwater (with urban areas, lakes and counties)
Modelled Temperature of warm springs and shallow (<10m)
groundwater with major geological regions
Modelled Temperature of warm springs and shallow (<10m)
groundwater with major geological structure
Modelled Temperature of warm springs and shallow (<10m)
groundwater North Leinster (with urban areas, lakes and counties)
Modelled Temperature of warm springs and shallow (<10m)
groundwater with surface geology: North Leinster
Modelled Temperature of warm springs and shallow (<10m)
ground-water:
Mallow area (with urban areas, lakes and
Map 6B:
Map 6C:
Map 7A:
Map 7B:
Map 8A:
counties)
Map 8B:
Map 9A:
lakes
Map 9B:
geology)
Map 10A:
Map 10B:
Map 11A:
Modelled Temperature of warm springs and shallow (<10m)
groundwater with surface geology: Mallow area
Modelled temperature at 100m (measured data) (with urban areas,
and counties)
Modelled temperature at 100m (measured data) (with surface
Modelled temperature at 500m (measured and calculated data) (with
urban areas, lakes and counties)
Modelled temperature at 500m (measured and calculated data) (with
surface geology)
Modelled temperature at 1,000m (measured and calculated data) (with
urban areas, lakes and counties)
Geothermal Energy Resource Map of Ireland
Map 11B:
Map 12A:
(with
Map 12B:
Map 13A:
Map 13B:
geology)
Modelled temperature at 1,000m (measured and calculated data) (with
surface geology)
Modelled temperature at 2,500m (measured and calculated data)
urban areas, lakes and counties)
Modelled temperature at 2,500m (measured and calculated data) (with
surface geology)
Modelled temperature at 5,000m (calculated data) (with urban areas,
lakes and counties)
Modelled temperature at 5,000m (calculated data) (with surface
APPENDIX VIII:
Modelled Geothermal Gradient Maps
Map 14A:
data)
Map 14B:
data)
Map 15A:
data)
Map 15B:
data)
Map 16A:
data)
Map 17A:
Modelled geothermal gradient at 500m (measured and
(with urban areas, lakes and counties)
Modelled geothermal gradient at 500m (measured and
(with surface geology)
Modelled geothermal gradient at 1,000m (measured and
(with urban areas, lakes and counties)
Modelled geothermal gradient at 1,000m (measured and
(with surface geology)
Modelled geothermal gradient at 2,500m (measured and
(with urban areas, lakes and counties)
Modelled geothermal gradient at 5,000m (calculated data)
calculated
calculated
calculated
calculated
calculated
APPENDIX IX: Modelled Temperature and Geothermal Gradient Maps with Measured
Data only
Map 18A:
Map 18B:
Map 19A:
counties)
Map 19B:
Map 20A:
counties)
Map 20B:
Measured temperature at 500m (with urban areas, lakes and counties)
Measured geothermal gradient at 500m
Measured temperature at 1,000m (with urban areas, lakes and
APPENDIX X:
Heat flow Density
Map 21A:
Map 21B:
Modelled Heat Flow Density Map (contour type 1)
Modelled Heat Flow Density Map (contour type 2)
Measured geothermal gradient at 1,000m
Measured temperature at 2,500m (with urban areas, lakes and
Measured geothermal gradient at 2,500m
APPENDIX XI: Recent Source Publications
APPENDIX XII: Glossary of Technical terms
Geothermal Energy Resource Map of Ireland
EXECUTIVE SUMMARY
Major Conclusions
The results of this review indicate that Ireland is particularly well suited for the utilization of ground
source heat pumps, due to its temperate climate and rainfall levels that ensure good conductivity and
year round rain-fall recharge. The current installation rate is increasing rapidly and requires immediate
attention to set and maintain high standards of equipment installation and operation.
There are abundant marine and surface water geothermal resources which could be exploited in
Ireland, but they need some encouragement for their development.
There are two main areas of warm spring development in Ireland, in north Leinster and the Mallow area.
They are undeveloped, except for the heat-pump in the Mallow swimming pool, and there is currently
available exploitation potential, especially in the light of the recent discovery at Glanworth, Co. Cork.
This study has added new data from 39 boreholes including newly monitored boreholes. Considering
the Republic of Ireland and Northern Ireland together, this review has indicated a regional increase in
temperatures ranging from 17ºC – 19ºC in the south to 25ºC – 27ºC in the north at 500m depth. At
2,500m temperatures range from 28ºC – 45ºC in the south to 64ºC – 97ºC in the north. This indicates a
significant economic resource with potential for commercial development.
Major Recommendations - Nine Action Areas
1. Select a short list of deep borehole sites – choose one for a major demonstration project –
provide support.
2. Support a medium depth pilot borehole e.g. on the Blackrock – Rathcoole Fault in an area with
with many potential users.
3. Maintain monitoring of borehole temperatures across the country as they become available.
4. Delineate Urban Heat Island Shallow Aquifers beneath major towns and cities across the
country and encourage exploitation – use UCC Arts Museum building as example.
5. Investigate continuation of the warm spring development along the Killarney – Mallow line,
where there is considerable exploitation potential.
6. Encourage warm spring exploitation, e.g. Hotwell House, Enfield, Co. Meath – use Mallow
swimming baths as example.
7. Examine exploitation of Surface Water Source Heat Pumps – especially the marine
environment, but also in rivers and lakes.
8. Encourage utilization of Ground Source Heat Pumps in office / apartment block developments–
use Tramore Civic office and Tralee Tax office as good examples.
9. Encourage countrywide usage of single-dwelling Ground Source Heat Pumps with particular
attention to Quality - equipment certification, installer accreditation, technician training and
follow-up.
The statutory perspective
It is crucial that local and national government take a composite approach to geothermal developments
so that projects are effective and sustainable. Initial support for geothermal systems is important as has
been demonstrated in Sweden, Switzerland and other countries. Although some incentive (financial
and technical) may be required to stimulate the take-up of geothermal systems, the primary
requirement is that projects are economically viable in their own right.
Integration of geothermal systems with other renewable options is considered one of the best ways to
encourage the uptake of this technology.
1
Geothermal Energy Resource Map of Ireland
Acknowledgements
CSA Group wishes to sincerely acknowledge the dedication, enthusiasm and sound research
that comprised earlier studies on geothermal potential in Ireland which were reviewed and
compiled in this study. There is no doubt that the present study would not be possible, nor its
conclusions relevant, were it not for the work carried out in these earlier studies. Specifically
the authors wish to thank Bob Aldwell, Michael O’Brien, Peter Brück, Andrew Brock, Geoff
Wright, Paul Sikora, Alister Allen, Brian Connor, Sarah O’Connell, Tara Davis, Roland Gaschnitz
and the late David Burdon.
We particularly wish to thank Bob Aldwell for reviewing this study and making several
pertinent comments which significantly enhance the report.
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Geothermal Energy Resource Map of Ireland
Geothermal Energy Exploitation in Ireland – Review of Current Status and
Proposals for Optimising Future Utilisation
1
Introduction
Under the present drive for reduction in greenhouse gases and the resulting need for more
widespread use of renewable sources of energy, geothermal energy has remained somewhat
in the background and has yet to become a commonly used and understood energy source.
This statement is especially true when applied to Ireland. It is widely speculated that the current
limits imposed on CO2 emissions for Ireland will not be reached by 2005 unless there is dramatic
change in the habits of energy usage in Ireland as a whole. It is envisaged that in fact Ireland will
have to trade for green certificates for the 2005 deadline. It was in this context that the CSA
Group and partners Conodate, Geological Survey of Ireland (GSI) and Cork Institute of
Technology (CIT) responded to the call for proposals from Sustainable Energy Ireland (SEI) for
projects to promote utilisation of renewable energy in Ireland. Though currently at a very low
level, the usage of geothermal energy is beginning to show an upward trend (mostly, though
not exclusively through the installation of ground source heat exchangers in private homes).
Current output country wide is approximately 13,500kWh and this is estimated to be climbing
by 10,000kWh extra installation capacity per year. No estimates exist for the potential upper
limit to geothermal capacity in Ireland but it is the aim of this report to set the influencing
factors in context and thereby facilitate a phase of more informed planning and
implementation of the necessary supports to encourage uptake of a relatively well tested and
advanced technology.
1.1
Terms of reference
The terms of reference agreed with SEI for this study can be summarised as follows;
• To review the current status of knowledge and utilisation of geothermal energy resources
in Ireland and to evaluate existing exploitation projects in the context of International
Best Practice.
• To identify potential sources of geothermal energy utilisation in Ireland and undertake
geological, structural and hydrodynamic analysis of these areas. Areas will be prioritised
based on proximity to existing and future users of heat.
• To produce a GIS-linked geothermal database, an up-to-date map series, and a report
with recommendations for expanded use of Ireland’s geothermal resources.
• Arising from the above, to produce strategic recommendations regarding future utilisation
of geothermal energy in Ireland in the context of European Union commitment to
Sustainable Energy.
1.2
Objectives of this study
The CSA Group aims to achieve the following:
Add new data and reinterpret Ireland’s geothermal database
Significantly enhance the available information on Ireland’s geothermal potential by
providing a concise review of earlier work that has taken place
Model the available information so that it is possible to integrate it with the European
geothermal databank
Provide the data in a clear and easily updated format
Increase awareness of the potential of geothermal energy in Ireland
3
Geothermal Energy Resource Map of Ireland
Identify strategies for geothermal energy development
Help the acceleration of geothermal utilisation
Create a positive environmental impact through increased geothermal usage – SO4 &
CO2 reduction
1.3
Outputs
These objectives will be achieved through production of the following in the current study:
Compilation of a database of all recorded geothermal sources, including previously
unavailable mineral exploration and mining data.
Identification of new areas of geothermal potential and the undertaking of geological,
structural and hydrodynamic analysis of these areas.
Geothermal Database/GIS System – with linkage to website (SEI or other)
Geothermal Map series – formats compatible with other European states
Recommendation of potential sites for future investigation and development.
Report in hard copy and CD format with results, conclusions and recommendations
Scoping of a Seminar to disseminate information and promote increased geothermal
exploitation
Provision for the continued dissemination of data via a website
Proposals for strategic development of Ireland’s geothermal potential (in partnership
with SEI and other relevant groups)
A glossary of technical terms used throughout this report is included in Appendix XI.
4
Geothermal Energy Resource Map of Ireland
2
Available data sources
2.1
Geological data
The sub-surface geology of Ireland has been a subject of study for more than 200 years since
the first geology maps were drawn up and small scale local mining and quarrying comprised
the main activity of the extractive industries. More recently, particularly since the 1960s,
Ireland’s sub-surface has been the focus of an intensive search for economic minerals which
has resulted in many major successes to date, including the discovery and development of the
modern zinc-lead mines at Navan, Co, Meath, Lisheen, Co. Tipperary and Galmoy, Co. Laois.
Onshore oil potential has also been the target of focussed exploration in prospective areas in
parts of the deeper on-shore limestone sedimentary basins of Ireland. This period of intensive
exploration has resulted in large databases of geological information being available in
Ireland. In the search for economic minerals, data on rock types, soil and water chemistry as
well as electrical, magnetic and gravity profiles at surface and in vertical boreholes have been
collected and used to establish a picture of the geological geometry in the area of interest.
Academic studies on all aspects of the sub-surface geology have also contributed vast
amounts of information to the understanding of the processes and geometry of Irish geology.
Data on surface processes and landforms produced by glaciation have also been compiled.
In more recent times testing and collation of data on hydro-geological and sub-surface
geotechnical parameters has become the focus of geological effort. Much of these new data
have been collected in order to meet the requirements of new EU directives which have
become law in Ireland in the last 10 years or so and provide new sources of data available in
geothermal assessment.
Most of these geological data, which have been generated over the past 30-40 years, are
archived and available through the Geological Survey of Ireland (GSI), the Exploration and
Mining Division (EMD) and the Petroleum Affairs Division (PAD) of the Department of
Communications, Marine and Natural Resources (DCMNR). These data archives form the basic
resources used in the present study and have been augmented by other data collected by
exploration and mining companies and also additional testing undertaken by CSA Group.
Other investigations into specific aspects of the potential in Ireland for geothermal energy
have been carried out by various organisations and individuals within statutory bodies, the
most noteworthy of these studies are briefly reviewed below.
2.2
Previous geothermal energy investigations in Ireland
The first documentation of spas in the European context began when the springs at Spa near
Liege in Belgium became renowned for their healing properties after they were first
discovered in 1326 AD. The types of spas varied widely from place to place. Some, as in Bath
Spa near Bristol, were developed as public bath and a place of worship by the Romans and
then later enjoyed a renewal in the fashion trends of the 1300s and in later revivals
culminating with the recent re-development of Bath Spa reopened this year (Musgrave 2004).
The growth in popularity was gradual but, as word spread, spas began to be developed in
Britain and finally in Ireland in the 1700s in the case of Mallow and Leixlip. The health
enhancing value of these popular spas is often questioned but what can not be
underestimated is how important these places of rest and relaxation became in the fashion
culture of the time. They continue to be widely used in continental Europe today. At present
there are no warm water spa developments in Ireland, though some effort is currently being
5
Geothermal Energy Resource Map of Ireland
made to made to utilize St. Gorman’s warm spring at Hotwell House near Enfield, County
Meath.
Fig. 1. Louisa Bridge Pool 2004.
Fig. 2. The old Bathing Pool at Louisa Bridge
The motivation for the investigation of the potential in Ireland for geothermal energy started
with the 1970s oil crisis. This created an interest in examining Ireland’s geothermal potential.
At this time Aldwell & Burdon (1978) proposed the first geothermal project, whilst Brock (1980)
reported to the National Board for Science and Technology This lead to the Irish Geothermal
Project (1981 – 1983), which took place within the EEC Geothermal R&D Programme and was
co-funded by the EEC and the Irish Dept, of Energy. The project was technically co-ordinated
by the GSI and undertaken by UCC, UCG, and Minerex Ltd. There followed a drilling project
(1986-1989), again co-funded by the EEC and Dept. of Energy, with the same universities and
GSI providing drilling support and overall liaison. Drilling was limited to 500m in depth and
confined to warm springs and the main Irish granites. Interest in Irish geothermal energy
waned as the immediate effects of the oil crisis lessened and the availability of significant
geothermal energy in Ireland remained unproven. It was only as the energy demands of the
rapidly expanding Irish economy in the late 1990s began to increase, at rates that threatened
to make our Kyoto commitments impossible to reach, that the profile of geothermal energy
was again to be considered as an option in the search for clean and sustainable energy
sources.
2.3
Literature review
The initial part of the present study by the CSA Group and its partners comprised a review of
the historical data available for previous geothermal assessment undertaken in Ireland. In the
aftermath of the 1970s oil crises there was a major shift in view in relation to the perception of
the stability of an economy based on fossil fuel energy. This led to a new phase of awareness
of the need to review alternative energy sources, which subsequently resulted in a series of
funded studies into the potential for alternatives to oil in the EEC. It was this period which led
to an examination of the potential for renewable energy in the EEC as a whole and
interestingly also gave rise to the now very successful wind energy industry in Denmark
(Balling et al. 1981) and elsewhere in Europe. In assessing the potential for geothermal energy
in the EEC a number of studies were carried out in Ireland. The most significant of these are
reviewed below. Interviews with organisations and individuals directly involved in previous
geothermal assessments were also carried out in order to get an overview of past work.
6
Geothermal Energy Resource Map of Ireland
2.3.1
Imperial College London
A funded study of geothermal measurements was carried out in Ireland in the early 1970s at
Imperial College London (Wheildon in Burdon 1983a). This study involved liaison with
members of the Irish mineral exploration industry of the time and access was gained to a total
of 39 drill holes. Temperature profiles were measured in these boreholes and later
incorporated into the study undertaken by Minerex and the GSI under EEC funding in the early
1980s (Section 2.3.3.) (Aldwell & Burdon 1983a,b). Some data were also collected on heat-flow
and were later incorporated into studies on heat-flow distributions by UCG (Section 2.3.4).
These data have been reviewed and, where appropriate, incorporated into the CSA study.
2.3.2
Tara Prospecting Ltd.
Tara Prospecting Ltd. carried out intensive mineral exploration in the years before and after
the discovery of the Navan Zinc-Lead deposit in Co. Meath. One of the ideas tested was that
there was potential for using the geothermal attributes in the surface soil to identify areas of
enhanced conductivity indicating high Fe values and therefore potential for related base
metal mineralization in the underlying rocks. These data have not been accessed in this study
but comments from some of those who worked on the project indicate that the survey was
successful in delineating the known extent of the mineralization in the Navan area at that time
and also highlighted areas to the south which were investigated later and found to be
underlain by mineralization. Additional temperature data collected by Outukumpu (now
Boliden), (the subsequent owners of the mine at Navan) in more recent years has been
incorporated into the database produced in the present study and is discussed in section 6.2.
2.3.3
Irish Geothermal Project 1981-1983
The ‘Irish Geothermal Project’ was initiated by Bob Aldwell and David Burdon (1978) of GSI and
Minerex Ltd. (a service company to the mineral exploration industry in Ireland) respectively.
The project was successful in securing EU funding for a large scale review of Irish geothermal
resources from 1981 – 1983. The study reviewed the potential for geothermal energy in
Ireland (Republic of Ireland mainly) from the information available and also carried out a
comprehensive monitoring programme of all available boreholes drilled by the mineral
exploration industry during that period. A significant part of the funding received, went into
the borehole monitoring programme thus providing much new data. The Minerex study also
compiled most of the monitoring work that had been carried out by others up to that point
including data from earlier research carried out at Imperial College London (section 2.3.1.
above) and any oil exploration boreholes that had been drilled. All these monitoring data
have been incorporated into the present study and integrated with new data. The Minerex
report and subsequent reports by D. Burdon and C.R. Aldwell also hold significant amounts of
information on some of the more subtle parameters relating to geothermal investigation such
as detailed hydrochemistry, isotope studies and modelling of individual springs which were
not replicated in the CSA study and have not been superseded.
The reader is therefore
encouraged to refer to these studies.
Following the Irish geothermal project, GSI commissioned the most comprehensive warmsprings monitoring programme undertaken in Ireland (Burdon 1983a). Besides periodic
monitoring of the temperatures in the springs, Minerex also carried out tests on
hydrochemistry, dissolves gases, electrical conductivity and pH, and flow-rates. A number of
interesting observations emerge.
• It was proven through hydrochemistry, that except for Louisa Bridge, Leixlip, that all
warm springs are comprised of meteoric water and therefore the mechanism for their
formation is likely to be relatively rapid deep circulation of surface waters along
7
Geothermal Energy Resource Map of Ireland
•
•
•
•
•
•
•
fractures / faults as proposed for the ‘Mallow convection model’ described in section
5.
It was found that temperatures of the warm springs generally increase as discharge
increases and decrease as discharge decreases. Water level and flow measurement at
the springs show that flow is greatest during Spring. There is therefore a need for
constant recharge from surface to maintain the Mallow convection model (Brück et al,
1983).
Run-off infiltration is considered the most important source of groundwater recharge.
In the Louisa Bridge spring there is some evidence for the presence of connate waters
or waters with long residence times in the earth therefore implying that there may be
deeper circulation in this spring than seen in other springs.
Minerex interpreted that faults/fractures are responsible for substantial circulation of
waters that may contribute to warm springs.
Geothermal gradients are not higher in areas of warm spring development and the
warm springs themselves may be contributing to this by acting as a local heat sink for
the surrounding rocks.
Northwest trending faults are an important feature of the Dublin/Meath warm springs.
Variations in warm spring temperatures can be significant and must be analysed
together with flow rates.
The effect of earth tides, barometric pressure and temperature versus flow are believed to
have little effect on the overall patterns of warm spring occurrence for the present study.
Later additional work by Burdon (1983b) provides additional analysis of geothermal data and
includes some comments on porosity, permeability and transmissibility to the surface. For this
report warm springs are defined as those >13ºC. It is interpreted by Burdon that most warm
springs consist of 2 components - a shallow circulation component (<100m) and a deep
circulation component (850m- 1000m). Burdon calculates that at all depths <100m
groundwater temperatures average 10.33ºC in the northern part of Ireland and 10.9ºC in the
southern part and that, though solar heat is the main contributor, that 1.8 – 1.9ºC is
contributed by geothermal heat flow. It is interpreted that most of the potential porosity and
permeability at depth is either the result of faults and fractures or dolomitization and karst.
There is also some potential for aquifers forming as a result of dissolution of evaporites. The
interpreted limit of karst development is 250m depth based on ongoing karst development to
100m and an additional 130 – 150m palaeo-karst as a result of past sea levels 130 – 150m
lower than today.
With regard to regional variations in geothermal gradient Burdon interprets that the location
of the Limerick – Dundalk line of the Iapetus Suture, may still have an effect on the ambient
geothermal gradient reflecting the regional change seen from south to north also in the
present study.
2.3.4
University College Galway
Initiated by Professor A. Brock (1979) a series of studies were carried out on the thermal
properties of Irish rocks by Galway University in the late 1970s and 1980s (Brock & Barton 1984,
1988a, 1988b and 1989). In the latter parts of these studies tests were carried out on some of
the Irish granites as it was perceived that there was greater potential for geothermal heating
there as a consequence of the radioactive decay occurring in all granites over time. Some
drilling was carried out in the Galway and Leinster Granites and recording of the temperature
8
Geothermal Energy Resource Map of Ireland
and the thermal characteristics were carried out. Data on heat flow has been remodelled and
reproduced here (Map 21A & B)
2.3.5
Cork City Council, UCC and Cork Energy Agency,
A study was carried out by Michael O’Brien (1987) towards a Masters in Engineering in the
Dept. of Civil Engineering, UCC to assess ‘The Development of Geothermal Resources in the
Mallow Area for Heating Purposes’. This study examined the potential in the Mallow region
and in turn led to the successful application for funding from the Thermie programme, for a
project (No. GE./00475/85/IR) to assess that resource. The latter project involved a programme
of drilling and temperature logging in the Mallow warm springs area. One of the 4 boreholes
drilled in the area now provides heat for the municipal swimming pool in Mallow, but the
source of the warm water was found to be fault/fracture controlled and more restricted than
previously understood. A later study was carried out by UCC, within the framework of the
1986-1989 drilling project, by F. X. Murphy and Professor P.M. Brück (1989) to investigate how
temperature varied with depth at Mallow, Ballynagoul and St. Gormans well / Hotwell House.
Temperature information from drilling in that project has been incorporated here. The report
indicated that at depths greater that 300m under areas of warm springs as at Mallow and St.
Gormans geothermal gradients are less than in the surrounding areas. Mallow ‘Spa House’ on
the site of the warm spring at Mallow is now occupied by the Cork Energy Agency.
Fig. 3. The Warm Spring at Mallow Fig. 4. Spa House, Mallow, site of the Cork County Energy Agency
2.3.6
Geological Survey of Ireland
The GSI co-ordinated many of the studies carried out on geothermal assessment. Bob Aldwell
in the GSI in the 1980s and 1990s was very involved in the assessment of these projects and
later oversaw a collation of warm springs data in the GSI (Aldwell 1981a, b 1984, 1990).
Wherever possible the GSI has carried out field validation of poorly recorded warm and tepid
spring occurrences and also has carried out follow-up fieldwork to any recordings of warm
springs that had not been measured. Monitoring and data compilation of warm springs data
has been carried out by Geoff Wright (pers. comm. 2004).
In general the chemical characteristics of Irish ground-waters show that calcium and
bicarbonate are the main ions present in abundance (except again in the Louisa Bridge area
where there is some heavy metal content). More acid waters are present in areas where the
groundwater has circulated through volcanic, Lower Palaeozoic and the Old Red Sandstone
9
Geothermal Energy Resource Map of Ireland
rocks. Sulphate is encountered at deeper levels and has been recorded in some of the deep oil
boreholes of the northwest midlands. Occasionally localised saline waters are found at depth
especially in more northerly regions.
There is currently no separate section within the GSI with a specific mandate for geothermal
energy but responsibility for all related activities and information is held by the groundwater
section. The GSI holds a library with copies of most geothermal studies which have taken
place in Ireland.
2.3.7
Petroleum Affairs Division
The PAD section of the DCMNR has administered to a moderately active hydrocarbon
exploration industry over the past 30 years. Most of this exploration has taken place off-shore,
but 10 deep (1000m – 3200m) on-shore oil exploration drill-holes have been drilled in the
Republic of Ireland (PAD, Oil Company Reports 1970-2001). In the same period another 12
deep (1000m – 2800m) on-shore boreholes have been drilled for oil exploration in Northern
Ireland (DETI, GSNI provisional data). This data is critical to the evaluation of Ireland’s
geothermal potential because of the depth of the boreholes and is used in the CSA study.
2.3.8
Geothermal Association of Ireland
The Geothermal Association of Ireland (GAI) was established in 1998 as a non profit making
organisation to promote the development of geothermal resources in Ireland. This
organisation invites participation from all professionals with an interest in geothermal energy
resources and exploitation from geologists, engineers, planners, architects, installers,
electricians and builders. This broad spectrum of involvement reflects the fact that the
exploitation of geothermal energy involves a multidisciplinary team and a broad
understanding of the issues involved. The GAI continues an active role in promoting and
demonstrating geothermal and other renewable energy technologies through fieldtrips to
renewable energy installations and also through its newsletters and lectures.
2.4
EU Altener Programme
Funding was received from the EU Commission DGXVII ALTENER II Programme to carry out a
study entitled ‘Renewable Energy Development through Community Ownership and
Partnership’ (REDCOP) (Tipperary Energy Agency 2004). This project proposed the utilization
of a deep drill-hole in the area to provide geothermal heating and cooling. A feasibility study
was carried out into the planned drill-hole and heat pump scheme and the estimated output
and viability of such a project. This study examined the feasibility of such a project from the
planning and economic viewpoint.
10
Geothermal Energy Resource Map of Ireland
3
Geothermal source types, exploitation and output / efficiency
In order to explain the range of sources and different possible systems used in the utilisation
of geothermal energy the source types and exploitation systems are set out separately below
3.1
Definition of source types/categories
3.1.1
Shallow soil and sediment (ground source heat pump – GSHP)
Shallow soil and sediment heat pump sources are the most common form of geothermal
energy used in Ireland to date. For this study they are defined as soils and lake/river sediments
in which horizontal collectors can be installed in a closed-loop system. Depth of emplacement
is usually 0.6 – 1m but occasionally where circumstances require it collectors can be placed as
deep as 2m. Irish soils are highly suited as heat-pump collector sources due to Ireland’s thick
soil development and temperate, wet climate. Soil temperatures in Ireland generally range
from 10ºC to 11ºC according to Aldwell & Burdon (1980) and vary little throughout the year at
depths greater than 40cm. This compares very favourably with places such as Sweden which
is one of the highest users of heat-pumps with horizontal loop collectors, despite having less
favourable soil conditions than Ireland.
Continuous recharge of moisture in the surface sediments allows good conductivity and yearround warming giving optimal conditions for collectors laid at depths below. High soil
conductivity due to high moisture content also allows maximum solar heating potential in
Irish soils. Other sediment sources such as lake and estuarine sediments and river beds are not
well exploited in Ireland to date and remain areas that require some investigation and
demonstration of suitability as heat-pump collector sources.
Also in this category are fore-shore muds which have had some initial investigation by
interested individuals but the need for a fore-shore licence prior to emplacement of the
collector has reduced the attractiveness of this option.
3.1.1.1
Ground source heat pumps versus air source heat pumps
It should be noted that the strength of GSHP systems in Ireland, is the constant temperature of
the ground year round. Although air source heat pumps (ASHP) have many apparent
advantages, there are particular problems in trying to extract enough heat from very cold
winter air, at a time when the maximum possible heat supply is required. Problems include
icing up of the source system and this may not be appropriate for Irish conditions. GSHPs do
not need defrost cycles nor expensive back-up electric heat systems during cold air
temperatures.
3.1.2
Surface water
This area of potential for heat-pump usage includes lakes/reservoirs, rivers and estuary/sea
sources. Average surface water temperatures in Ireland vary between 5°C and 15°C
throughout the year, whilst sea water varies from 8°C to 16°C. This relatively broad
temperature range necessitates more careful monitoring and control of the heat pump system
to account for these temperature changes (which are much broader than for soil in Ireland)
throughout the year.
Sea sources for geothermal collectors may have great potential in Ireland based on the
Stockholm experience (Lindroth 2004) but as yet have not been investigated here and require
demonstration to encourage the take-up of this technology.
11
Geothermal Energy Resource Map of Ireland
3.1.3
Warm springs
The temperature of water at the surface of the earth varies widely from place to place around
the world. Temperatures up to 150ºC are not uncommon in areas of hot springs such as those
in the Iceland geothermal fields, the extensive Yellowstone National Park in the US and hot
springs in the circum-Mediterranean area (eg. Sicily and Turkey). These areas of the earths
crust have particular properties that cause regional or localised heating from deep in the
earths crust to be able to penetrate through at hot spots and create thermal anomalies at
surface. Hot-springs are currently extensively used in Iceland and in parts of western US and
many other countries world-wide to generate electricity. These extremes of geothermal
activity are not present in Ireland but there are some local variations in the geothermal
properties of the sub-surface of Ireland which result in the presence of warm springs with
temperatures elevated between 3ºC and 12ºC above the average groundwater of the
surrounding areas. Though these changes are subtle and result in only cool to warm springs
with temperatures from 13ºC – 23ºC, if reliable on a yearly basis, they can be used in
conjunction with heat-pumps to provide very effective heating and cooling in insulated and
purpose built structures, such as houses, offices, swimming pools, horticultural buildings and
spas. For this study boreholes with significantly enhanced shallow (0-50m) groundwater are
included in the definition of warm springs.
3.1.4
Gravel aquifers and Urban Heat Island Effect
These are defined as shallow aquifer sources with high water volume yield from glacial and
river gravels and are located in a number of places throughout the country. When located in
an extensive urban area such as Dublin or Cork there can be an added component of
increased groundwater temperature due to the insulating effect of the buildings and
infrastructure.
The Urban Heat Island Effect is produced by major conurbations. The increase in heat of a city
or town affects both the local atmosphere and the ground. It is caused by these factors:
• Waste heat from city buildings, cars and trains makes its way into the ground or the
atmosphere. This heat contribution can be as much as one-third of that received from
solar energy.
• Buildings conduct heat to the air, whilst tar, asphalt, brick and concrete are better
conductors of heat than the vegetation of rural areas.
• During the day, solar energy is trapped by multiple reflections off buildings, while
infrared heat losses are reduced by absorption.
• During the day in rural areas, solar energy absorbed near the ground evaporates water
from vegetation and soil. Whilst there is a net solar energy gain, this is partly
compensated by evaporative cooling. In cities there is less vegetation and buildings,
streets and sidewalks absorb the majority of solar energy input.
• Runoff is greater in the cities because the pavements are largely nonporous. Thus,
evaporative cooling is less, which contributes to the higher ground and air
temperatures.
All these effects increase the temperature of the air, the city, the ground and the groundwater.
The temperature can be increased by up to 4°C and this can be exploited by heat-pump
systems.
12
Geothermal Energy Resource Map of Ireland
Fig. 5. Buried valleys in the Lee Valley
Fig 6. Typical sections across the buried valleys. See T. Davis poster Appendix XI.
These are considered together as, in the cases of both Dublin and Cork where some
exploitation and assessment of these resources has taken place (Ball 1991, Allen et al. 2003,
Davis 2003). The central part of Cork city, adjacent to the River Lee, overlies an area of Buried
Valley Gravels which have been shown to be a rich aquifer (Figs. 5 - 6). This resource is
currently used as a heat-pump source for the new Art Gallery at UCC in Cork and utilization of
the resource at other sites is planned. Buried Valleys are valleys formed at a time when sea
level was lower, as it was during the last glaciation, and which were subsequently drowned
after the ice thawing resulted in higher sea levels. It is estimated that sea levels rose between
130 – 150m after the last glaciation. Parts of Dublin city adjacent to the River Liffey and close
to the estuary have been shown or contain gravel aquifers along small tributary streams with
locally enhanced temperatures. A system was emplaced in the O’Reilly Hall in Trinity College
Dublin to exploit these enhanced temperatures though it is currently temporarily out of
commission.
13
Geothermal Energy Resource Map of Ireland
Fig. 7. Map of the gravels associated with the small rivers Poddle, Stern, Swan and Dodder in south
central Dublin
Large volumes of gravel including surface features such as eskers are present throughout
Ireland. There are also many glacial outwash and other gravel deposits in Ireland that form
more planar features and are often below the water-table and thus act as large reservoirs of
easily accessible water which can be utilized in conjunction with open-loop heat-pump
systems. The advantage of gravel aquifers is that the high volumes of water are available
relatively close to the surface. Some sensitivity exists in the exploitation of this resource
especially for example the gravels of the Curragh Plain in County Kildare and exploitation may
be best considered in conjunction with local or county water supplies.
14
Geothermal Energy Resource Map of Ireland
Large water saturated gravel channels have
been also been identified in the centre of the
Irish midlands and are thought to be preQuaternary in age. Termed ‘palaeo-channels’
these large gravel bodies have not been
delineated in detail (Hardy 2003, Philips 2001
and R. Pasquali pers. comm. 2004) but are
postulated to be the result of a large river
drainage system from north-east to southwest across Ireland during a period of uplift in
the area of the Irish sea at that time. These
channels potentially contain large volumes of
saturated gravels and therefore represent
additional high yield gravel aquifer resources
suitable
for
open-loop
heat-pump
exploitation. Some reference has been made
to the fact that one of the more easterly of
these channels may run close to the
Dublin/Meath warm springs and therefore
has potential for enhanced temperatures as
well as large volumes of water.
Fig. 8 The location of buried and uplifted palaeovalleys. (Phillips 2001).
3.1.5
Shallow groundwater bedrock aquifers
Shallow water aquifers are defined for this study as bedrock aquifers between surface and
300m depth. A large percentage of Ireland’s water supply is obtained from shallow
groundwater sources from between 30m and 100m depth. The 300m cut-off for shallow
sources is defined based on variations in temperature and geothermal gradients observed in
the compilation of water temperature data in boreholes in this study. Above this depth
temperature and geothermal gradient is regionally very variable and the understanding of the
details of local geology is essential in any estimate of temperature in groundwater and its
variation. The cause of this variability can be the result of the presence of karst and fracture
zones which allow rapid percolation of relatively cool surface waters deep within aquifers, thus
distorting any prediction of what would otherwise be increasing temperatures with depth.
There are a number of lithologies and geological conditions in which large volumes of
groundwater are more easily located including dolomitised and/or karstified Waulsortian
mudmound limestone and other clean limestones including the Upper Limestones. The
Kiltorcan Sandstone is a regionally important aquifer especially in the south midlands. There is
also good potential in Asbian mudmound and Shelf Limestones. Dolomitisation, allowing the
opening up of fractures in originally non-porous and permeable limestones, is critical in
identifying large volumes of groundwater in the south of the country. Karstification of
limestones is more pervasive in the Carboniferous basins in the northwest of Ireland and also
creates the potential for the movement and storage of large volumes of water. Some volcanic
15
Geothermal Energy Resource Map of Ireland
units within Lower Palaeozoic aged sediments also have potential for localised aquifer
development.
3.1.6
Intermediate and deep aquifers
Intermediate aquifers are defined for this study as those at between 300m and 1500m depth.
A cut-off of 1500m is chosen because the majority of the measured data available in Ireland
are between 100m and 1200m depth and the resultant predictions of temperature for depths
down to 1500m are more reliable and evidence-based. Temperatures and geothermal
gradients in this intermediate zone vary widely from south to north in Ireland and show
regional correlation with geological interpretations across the country. The relationship
between geothermal gradient and temperature changes across Ireland, as a function of
geology and structural/fracture geometry, is discussed in Section 7 below.
Deep aquifers are defined as those at depths of 1,500m or greater. High enthalpy resources
even at depths >1500m are generally located in the most tectonically active areas of the earth
such as Iceland and parts of the US and of New Zealand (Cascades mountains area). Generally
all intermediate and deep geothermal resources as well as warm springs are situated in areas
that are structurally fractured, creating a pathway for the fluids to access to surface.
An example of an area using low enthalpy, geothermal energy resources from >1500m is the
Paris Basin where there is considerable usage of geothermal resources. In the Aquitaine Basin
geothermal source area, water is typically extracted from depths of 1500m to 2000m,
temperatures range from 50ºC - 80ºC (after extraction to the surface) and flow rates average
200m3/hour. The warmer parts of Ireland’s geothermal resources (section 7) compare
favourably with these temperatures.
3.1.7
Enhanced Geothermal or Hot Dry Rock Systems
The concept of Hot Dry Rock (HDR), now referred to as Enhanced Geothermal Systems (EGS),
was first evaluated in the United States in the Los Alamos project between 1970 and 1996. Oil
supply uncertainties generated much interest in the potential for geothermal energy in the US
at the time as it did a little later in Ireland in the 1970s. EGS is also sometimes referred to as
heat mining and is based on the use of heat recovered from the sub-surface to create
electricity. The process consists of a power plant connected to a ‘heat reservoir’ at depth with
temperatures of 150ºC or higher. The reservoir is developed by drilling wells into hot rock at
depths of 4km or greater, depending on the local geothermal gradient, and connecting the
wells through hydraulic fracturing so that water can be pumped into the system through one
well and collected through another.
16
Geothermal Energy Resource Map of Ireland
An European project is currently underway
at Soultz-sous-Forêts, France (see Section 4)
to examine the parameters involved in this
new technology. In the late 1980s and
1990s in Urach (Tenzer et al. 1996),
southwest Germany hydraulic tests were
carried out in a borehole of 2800m which
intersected crystalline basement. At this site
monitoring of water levels was carried out
continuously over 13 years, giving unique
and valuable information on the likely
variations of water levels in deep boreholes
which might be used for geothermal
energy. During extended pumping tests,
water levels were seen to continuously drop
over the period, indicating that hydraulic
potential decreases with depth and
apparently potentially setting limits on the
usage of EGS with depth.
Fig. 9. Diagrammatical cross-section for HDR
3.2
Types of geothermal exploitation
3.2.1
Horizontal closed-loop collectors
Generally referred to as ground source heat pumps (GSHPs), the most common type of
geothermal system currently installed in Ireland is one with a closed loop collection systems.
The same system can be used in surface water sources. These systems consist of a closed
circuit of pipes in shallow soil or other collector source where it warms to the ambient
temperature and then is circulated through a heat pump where heat is extracted (see section
3.3). These loops are normally placed in soil and occasionally in rivers or reservoirs, in the
systems installed so far in Ireland. As the temperature of shallow soil and sediment
throughout Ireland varies between 9ºC and 11ºC, these systems have proven to be highly
suitable to Irish conditions as the space required for the collector is usually readily available. In
general terms the ground area required for the collector is approximately equal to that of the
foot-print of the house or building to be heated. Surface water in Ireland is obviously very
abundant in lakes, rivers and comparatively large estuarine areas. However, exploitation of
this source with horizontal closed-loop collectors is extremely limited in Ireland. In this study
the only such installation documented is one where the collector is located in a water tank at
the Iniscarra Renewable Energy Office, Cork.
It is generally considered that Ireland is very suitable for closed loop GSHPs as the ground
temperature is relatively high, the ground moisture content is high and the winter
temperature is high. For an average home GSHP installation takes 6-8 months from the initial
survey, with 3-4 site days required. Installation is less disruptive when undertaken during
building construction, but retrospective installation can be carried out.
It is possible to place a GSHP collector in the filtration area of domestic or other waste-water
where there will be an enhanced temperature profile. Outflows from puraflow systems can be
17
Geothermal Energy Resource Map of Ireland
used if filtered over the collectors. Generally domestic grey water cannot be used as a heat
pump source due to the grease and sludge problem except where filtered through a puraflow
system. With one of these systems up to 25% of the energy required to heat the water can be
returned to the system.
3.2.2
Horizontal open-loop collector
Open-loop collectors such as the type used for heat-pump sources such as lakes, rivers and
estuary/sea are uncommon in Ireland. Water is taken from the source, heat extracted from it
and the cooled water is returned to the source either downstream or at some distance from
the extraction point. Though a real possibility as a source of energy, this type of collector has
not been installed frequently in Ireland. Surface water temperatures generally vary between 5
– 15ºC and are strictly seasonally dependent.
One of the obvious ways of utilizing such a collector is in conjunction with water supply for an
urban area where the heat pump is connected to the water supply.
An example of an horizontal open-loop open collector is located in Tramore, Co. Waterford
where a small reservoir of 500,000L is used to supply 60kW of heat for the nearby purpose
built Civic Offices.
3.2.3
Vertical borehole open-loop collectors
Open-loop collectors are the most commonly used systems in shallow boreholes in Ireland at
present. Groundwater utilised as a heat pump source is accessed in much the same way as for
normal water supplies and it is possible to utilize the same for both. In Ireland these types of
collectors tend to be used where there is an available high yield aquifer or locally enhanced
water temperatures/warm springs. Good examples of these systems in operation are in
operation at Mallow swimming pool using a warm spring source and a recent installation in
County offices at Tullamore, Co. Offaly using a groundwater source from a gravel aquifer.
Installation has been completed on the new UCC Art Museum open-loop, heat pump system.
Drilling there produced such high volumes of water at around 12.5 - 13ºC that 30% of the
heating and cooling of the gallery will be provided from this source (Section 4.3).
Open-loop systems can also be installed in deep boreholes such as that at Southampton, UK
(Southampton City 2000) and can be very effective (Section 4.5). In the case of Southampton
the connection of the deep aquifer source to the sea results in the system extracting saline
water from the aquifer. The disposal of such water can be a problem but in Southampton,
they are fortunate to be able to discharge directly back into the sea which is effectively
infiltrating into the aquifer. In other areas using open loop borehole source, where there are
saline or other mineral rich waters at depth, may pose disposal problems. This can be avoided
by re-injecting into the aquifer through another borehole at some distance away and
effectively re-circulating the water. This system is used in one installation in the Paris Basin
where saline waters from 2,500m are extracted at 70ºC. After passing through the heat
exchanger the water is re-injected at depth at a temperature of 40ºC a distance of 1km away
(Section 4.5).
3.2.4
Vertical borehole closed-loop collectors
The more common types of these collectors are usually considered to be collectors placed in
boreholes to a maximum of 50m. These are commonly used in Switzerland where there is very
little space and flat ground in which to place a horizontal collector. They are an option in the
Irish situation where there insufficient space such as in cities etc., e.g. the Green Building,
18
Geothermal Energy Resource Map of Ireland
Temple Bar, Dublin. However they are not the preferred option in Ireland as they are more
expensive to install and, if they are not properly planned, they can result in over-cooling of the
ground in the area of the borehole, to a point where it is very difficult to replace the lost heat.
Deeper boreholes can be used in effectively
the same manner though the scale of the
heat recharge required needs to be
accurately modelled to ensure economic
viability. The current drilling on the Aachen
project in Germany will provide a very timely
test of this technology as drilling started in
June 2004. The proposed target depth at
Aachen (Pape et al. 2002, Gashnitz, 2002) is
2,500m in Lower Palaeozoic sediments. The
results of this project will be extremely useful
in the assessment of the best application of
deep borehole heat exchanger systems to the
Irish situation, as Lower Palaeozoic sediments
are likely to be one of the predominant rock
types encountered in the Irish sub-surface at
similar depths. This is especially the case in
the
Fig. 10. Vertical borehole closed-loop collector
midlands, north midlands and Co. Clare regions where there is greatest potential for deep
geothermal resources in Ireland. One of the concerns with this type of installation is that
though no water is brought to surface, the area around the collector needs a constant heat
flow and good porosity and permeability may be necessary to ensure replenishment of the
heat locally around the collector. It is interpreted that the most significant porosity and
permeability in Lower Palaeozoic aged sediments in Ireland is fault/fracture related (section 7).
3.3
Heat-pump technology
Ground source heat pumps (GSHPs) are based on the same principle as refrigerators. GSHP
systems are known by many different names, such as geothermal, ground-coupled, or
GeoExchange systems.
Currently there are many different models of heat-pumps being installed in Ireland by
approximately 12 different companies. Mostly these companies are providing quality
products with tried and tested technology. However heat-pump system design and
installation is complex requiring a broad understanding of issues such as sizing and load
calculations and sometimes unique solutions. The experience in many EU states is that
without proper certification / accreditation of both equipment and installer, failure of heatpump systems due to improper installation and usage results in a slump in the take-up of this
valuable renewable resource. This is due to very rapid growth in the sector attracting
unqualified installers and damaging the reputation of this tried and tested technology. It is for
this reason that SEI has funded a recently
19
Geothermal Energy Resource Map of Ireland
completed study of the issues surrounding
the promotion of heat-pump technology.
This study was undertaken by Arsenal
Research, Austria (Boesworth, 2004) and it is
hoped will provide a blueprint for how best
to
tackle
the
issue
of
certification/accreditation
while
also
encouraging and promoting heat-pump
usage in Ireland. Once accreditation of both
heat-pumps and installation companies is in
place there is much that can be done in
building awareness and familiarity with
heat-pump technology so it becomes a
regular option in all construction projects.
Fig. 11. Modern heat exchange system
3.3.1
Residential heat-pumps – proper sizing and installation
Much information is available on the Internet explaining and advertising heat pumps. The
following is a heat-pump ‘Technology Profile’ from the US, Federal Energy Management
Program (FEMP) which is a concise and easily understood summary of some widely accepted
criteria relevant to heat pump installation.
Heat pump sizing
There are three reasons that a heat pump needs to be properly sized:
•
Cost - Large equipment is more expensive than small equipment. If the system is too large, it will
cost more. If the heat pump is undersized for heating, supplemental heat will operate too often and
increase the electric bill.
•
Durability - Most wear and tear on a compressor occurs when it starts up. Oversized equipment
cycles on and off more quickly than properly sized equipment.
•
Efficiency - Oversized equipment has shorter "on" times, which means a greater portion of "on"
time is spent getting started--an inefficient part of the heat pump cycle.
Load calculations
The only way to properly size a heat pump is to carry out heating and cooling load calculations and then
match the equipment to the calculated loads. These load calculations should take the following into
account:
•
The dimensions of floors, basement walls, above-ground walls, windows, doors and ceilings.
•
The energy efficiency of these components (insulation, window types, air tightness, etc.).
Local weather factors
Loads should be calculated for a cold winter day (but not the coldest on record) and a hot summer day
(but not the hottest on record).
If using the heat pump for heating only, there is only need for a heat load calculation. If requiring both
heating and cooling, there is a need for both heating and cooling load calculations. It is necessary to
ensure with the contractor that the heating and cooling loads have been calculated, not guessed. There
are a number of methods of doing this.
Load calculation methods
There are several widely accepted methods of calculating heating and cooling loads. The most popular
are based on methods and data developed by the American Society of Heating, Cooling and Airconditioning Engineers, called ASHRAE. One of the best is called Manual J: Load Calculation developed
20
Geothermal Energy Resource Map of Ireland
by the Air Conditioning Contractors of America (ACCA). Most major manufacturers provide forms that
help contractors size their heating equipment. If the forms are based on ASHRAE or Manual J the
contractor will probably do a good job of estimating sizing requirements.
Room-by-room load calculations
Load calculations should be done for each "room" in the house, because each has its own heating and
cooling requirement. It's the only way contractors know how much heating or cooling to deliver to each
room. Otherwise, they can only guess at requirements and deliver incorrect amounts of heating or
cooling. Areas that are open to each other are treated as one "room." For example, one "room" could
include kitchen, family and dining areas.
Insulation
Insulation is the first step in plans for installation of a heat-pump system. Preference is a purpose built
construction with modern insulation standards. However if attempting to retro-fit a heat-pump system
it is important to upgrade insulation and windows and to reduce the air leakage from the building in
order to reduce winter heating requirements.
3.3.2
Some practical aspects of residential heat-pump systems
A closed-loop heat-pump system contains a water and glycol antifreeze/refrigerant mix (CFC
refrigerant HCFC 22 is used in US as it is the best refrigerant but this is not legal in Ireland). A
15.5kW output heat pump requires a 3.5kW pump. The heat-pump unit needs to be housed in
a weather proofed area. While in operation the heat-pump system is generally inaudible
outside the room. Once installed and checked the unit is virtually maintenance free. If just
used for heating it will be turned off during the summer. It is often the case that when it is
turned on again in the autumn the pump may stick but this is easily corrected. It is
recommended that a one year follow-up visit is built into any installation contract to deal with
settling in problems. Maintenance once a year requires a refrigerant and circuit check as well
as normal running current. 45ºC is the maximum running temperature advised for the
thermostat with most residential heat-pumps.
Where the thermostat is pushed higher on a
continuous basis, the result is inefficient
operation and overcooling of the collector
area leading to an extended shutdown period
to allow the collector area to return to normal
temperatures. The preferred heating system
to use in conjunction with ground source
heat pumps is a ground floor slab,
approximately 10cm thick with heavy
insulation underneath, with radiators upstairs
if required. It is worth noting that the
concrete limit temperature is 45º C and above
this there is a likelihood of shrinkage cracks.
Fig. 12. The benefits of geothermal energy.
3.3.3
Co-efficient of performance (COP) and CO2 savings
The co-efficient of performance (COP) is the ratio between the energy required to run the
system and the output of the system. COP values of 3-4 are normal for most efficient systems.
The higher the COP the more efficient the system. Percentage reductions in CO2 emissions are
21
Geothermal Energy Resource Map of Ireland
usually around 45%. Table 1 gives the average values of CO2 emission for different energy
sources. This table is extracted from the United Kingdom ‘Energy Consumption Guide 19 –
Energy use in Offices’ from the Energy Efficiency – Best Practice Programme. A copy of this
document is provided in the Appendix XII. Details of individual systems in Ireland including
output, COP and CO2 saving are included in Table 2. CO2 saving in the table where calculated
are based on the average values quoted in Table 1.
Fuel
Gas
Oil
Coal
Electricity average
kgC/kWh
0.052
0.069
0.081
0.127
kg CO2/kWh
0.19
0.25
0.30
0.46
Table 1: Carbon dioxide emissions
(after United Kingdom ‘Energy Consumption Guide 19)
22
Geothermal Energy Resource Map of Ireland
Table 2: Large GSHP installations in Ireland
23
Geothermal Energy Resource Map of Ireland
4
Current geothermal exploitation - Ireland and international
The options for geothermal energy cover a wide range of industrial, residential, agricultural
and leisure uses. Some of the uses are covered on the Lindal diagram below.
Fig. 13. Exploitation options for warm and hot water, from Lindall (1973).
The range of optimum usage is determined partly by the temperature and also the quantity
and chemistry of the water being recovered in the case of an open-loop system. The range of
uses for geothermal energy is varied even within the lower range of temperatures that are
more applicable in terms of Irish resources. Large low temperature (<20ºC) potential is
present for residential, horticultural (reducing seed germinating time through soil warming)
and aquaculture uses. Spas and swimming pools can benefit from temperatures >20ºC as
well as many other uses as above. It is unlikely that Ireland will ever generate electricity from
geothermal energy though there is good potential for temperatures between 50 – 100ºC at
depth in parts of Ireland’s sub-surface.
4.1
Ground source heat-pump usage in Ireland
4.1.1
History of GSHP in Ireland
Ground Source Heat Pumps (GSHPs) have been in use in Ireland for many years. As in many
countries, poor technology, training and installation, allied to lack of understanding of the
need for proper insulation, lead to the creation of a poor impression of the technique in
Ireland in the 1980s (B. Connor pers. comm. 2004). Also, as in these other countries, a second
wave of take-up has been taking place. In those countries where governments have
24
Geothermal Energy Resource Map of Ireland
supported the development the second wave has been exceptionally successful. See Arsenal
report on ‘Campaign for Take-off for Renewable Heat Pumps in Ireland’ (Boesworth 2004).
Fig.14. Collector site preparation, house site Kinsale. Fig.15.Heat
exchange
set-up,
house
site
Killavullen
4.1.2
Current GSHP usage in Ireland
There are now over a thousand domestic ground source heat-pump units installed in Ireland,
whilst a number of successful larger units are operating in office blocks, university buildings,
housing units, etc. There is successful exploitation of ground source by horizontal loops, of
shallow aquifers in urban heat islands by vertical boreholes, and of one warm spring by a
borehole. Information on the larger units currently installation and under installation is
provided as Table 1.
Fig. 16. Tralee Motor Tax office
Fig. 17. Heat Exchanger
4.2
Surface water source heat-pumps
There are very few examples of the exploitation of surface water bodies as heat sources in
Ireland, either open-loop or closed loop systems. In Navan, Co. Meath a 30kW closed-loop
system uses a stream as its source, whilst in Tramore, Co. Waterford the new Civic Offices use
an open-loop system (Section 4.2.1). An interesting exploitation of the open sea as a heating
and cooling source is seen at Stockholm in Sweden (Section 4.2.2). This holds great potential
for Ireland.
25
Geothermal Energy Resource Map of Ireland
4.2.1
Tramore Civic Offices
Tramore Civic Offices, Co Waterford, make use of a mains water supply adjacent to the site.
They constructed a 500,000 litre reservoir, through which the mains water flows. Some of this
water is piped in an open-loop to heat exchanger. In a three stage operation the heat is
transferred to the glycol fluid and then through the main heat exchanger to the radiator
circulating water, this
maintains the potable mains water separate
from the heat exchange operation. Water is
normally taken over a range from 5°C to 12°C,
about 2°C of heat is removed and the system
is rated at 60kW. Since the water in the
reservoir is constantly being renewed, it is
difficult to over cool the water in the
reservoir. The Tramore example represents
an excellent model development where such
buildings are located next to a high volume
mains supply.
Fig. 18. Tramore Civic Office
Fig. 19. The collector reservoir
Fig. 20. The heat exchange room
4.2.2
City of Stockholm
The city of Stockholm uses the Baltic Sea to supply 180MW (total capacity), in what is thought
to be the worlds largest heat pump facility in the world, to its district-heating customers
(Lindroth 2004, Axima 2004). A total of 6 large heat pumps (30MW each) are used with a COP
of 3.75.
26
Geothermal Energy Resource Map of Ireland
Fig. 21. The City of Stockholm.
Fig. 22. Sea Water Heat Pump Facility
The incoming seawater to the plants is drawn through an open loop system in large quantities
from different levels between surface and 15.5 m depth (depending on the time of year).
Large quantities are used in order to keep the temperature low. This helps to maximize the
efficiency of the system and also minimize the impact on the environment. Outgoing water is
discharged close to the surface. Passing the heat exchangers, the water is cooled while the
salinity remains unchanged. When discharged back into the sea, the water forms a layer
located deeper than the point of discharge. This layer must be well separated from the intake
layer in order to avoid a recirculation of water.
Additionally in Stockholm the heat stored in treated waste-water (+15°C) is recovered by heat
pumps by Stockholm Energy and added into the district heating system.
4.3
Shallow borehole source (open loop) heat-pumps
Besides GSHP, shallow boreholes with open loop heat-pump sources are the most
common form of larger scale geothermal installation in Ireland. Generally the depth of
the boreholes used in these systems is between 30m and 50m and so far tend they to
be located in areas with shallow aquifers as in Cork city or with locally enhanced
groundwater temperatures or warm springs as at Mallow swimming pool.
4.3.1
UCC Art Museum
The UCC Art Museum in Cork city is a 3 storey, 23.5m high building due for completion in
summer 2004 (Sikora & Allen 2004). The size and water production capacity of the UCC aquifer
as such that it is possible to obtain 200kW of heating / cooling, whereas a normal heat
exchanger would need 4,000m of pipe collector to attain this output. Drilling beside the Lee
on the UCC campus obtained 20litres/sec (only 10 litres/sec was required to run the heatpump). Temperature profiles were obtained from surface to 15m. The water will extracted
also be used for process water in the building. The pH of the water is 7.2 and chlorides are <20
(negligible), hardness is low. There is virtually no evidence of saline intrusion and therefore a
brazed stainless steel plate heat exchanger is adequate. If saline water was present, titanium
plates and hi-performance rubber gaskets would be required, which would increase the
equipment cost by a factor of four. The UCC project has two heat-pump units installed – one
as a backup. Installation of the system was completed in less than three months.
27
Geothermal Energy Resource Map of Ireland
Fig.23.The UCC Arts Museum Building.
Fig. 24. One of the two wellheads yielding 10 l/s
4.3.2
Mallow swimming pool
Following Michael O’Brien’s (1987) UCC ME thesis study on the geothermal potential in the
Mallow region, a successful application for funding from the Thermie programme led to a
drilling and temperature project. One of the boreholes drilled in Mallow to 75m now provides
heat for the municipal swimming pool. The source of the warm water was found to be rising
from depth along a fault / fracture. The water is at 19.5°C and is boosted by conventional
means at the pool. With a COP of 4, it is a very efficient system and the payback period of 11.5
years has long been passed.
Fig. 25 & 26. Mallow swimming pool and part of the heating system
4.4
Intermediate and deep borehole source heat-pumps/heat exchangers
4.5
Deep geothermal heat-pumps/heat exchangers
28
Geothermal Energy Resource Map of Ireland
Deep geothermal heat exchangers (GHE) consist of only one well with an outer steel casing
sealed at the base and an open, carbon fibre reinforced
production pipe which is run inside the outer pipe. The
water flows in a self-contained cycle down the annular
space heating up against the rock wall and is pumped
to surface through the production pipe. There is no risk
of corrosion because the water circulation is self
contained. The water circulating in the enclosed pipe
system consists of 300m3 fresh water without any toxic
additives. Mechanical units such as pumps are installed
at surface where they are accessible for maintenance.
The electricity consumption of the pumps, with an
installed capacity of 3kW, is low because of the artesian
principle of the GHE. With an output of 250 to 750kW
the capacity of GHE is lower than the dual system. GHE
is suitable for large buildings with an effective area
between 4,000 and 20,000 m2 and for local heat
networks.
The economy of a geothermal heating plant is
determined by the market value of heat, how the
project is financed and the period of operation. The drilling costs account for about two thirds
of the total investment cost of a GHE. The period of operation is assumed to be at least 40
years. The economic efficiency of GHE will improve with time when compared with the rising
cost of fossil fuel (oil/gas prices).
The only GHE in the European Union is an abandoned dual well system in Prenzlau, NE
Germany. Another system operates in Switzerland.
4.5.1
Paris Basin
Paris is situated on a Mesozoic sedimentary basin, where
warm water circulates at depth through porous Dogger
Limestone. Some 41 geothermal developments exploit this
deep resource. Most are open systems with re-injection of
the extracted water after some of the heat has been
removed. In a typical installation in the Paris Basin, saline
waters at 80ºC are pumped up from a depth of 2,500m
arriving at the surface at 70ºC. After the removal of 30°C
heat they are re-injected at 40ºC, via inclined boreholes to
the original aquifer, a distance of 1km away at depth.
Some of the early installations experienced severe problems
with corrosion of the pipe-work by the saline waters.
Advances in technology how now largely overcome this.
29
Geothermal Energy Resource Map of Ireland
Fig. 27. Low enthalpy geothermal plant, Paris
4.5.2
Southampton
Following the oil crisis of the seventies, Southampton was identified as a possible deep aquifer
location for geothermal energy exploitation. The deep borehole scheme was launched in
1986, tapping 76°C water from the porous Sherwood Sandstone Formation at a depth of
2000m. The saline water produced is suitable for discharge into the adjacent sea. The scheme
continues to develop and currently supplies more than 20 major consumers including the
Civic centre, apartment blocks, hotels, a hospital, a college and a superstore. It delivers
annually 30,000 MWh of heat, 4,000 MWh of electricity, whilst an integrated CHP plant saves
over 10,000 tonnes of CO2 emissions.
30
Geothermal Energy Resource Map of Ireland
Fig. 28. Southampton district heating flowchart
4.5.3
Aachen
Aachen University of Technology (RWTH Aachen), Germany is in the process of installing a
deep geothermal heat exchanger (GHE) to provide geothermal energy for heating and cooling
of its students’ service centre Super C. A deep GHE is a single well system where water
circulates in a self-contained cycle in the annulus and the central production pipe of the well.
Super C is the first purpose built project of its kind. Similar projects exist in Switzerland and
southern Germany, however compared to Super C all other projects have been ‘boreholes of
opportunity’ that were drilled for other purposes. The amount of available calibrated data
from the other sites is basically zero, so this is the first project where all data will be monitored
and then subsequently used for duplicating the project elsewhere. In that sense this project is
very innovative.
Drilling commences in July 2004, and is expected to take 60-90 days to complete depending
on bedrock characteristics, expected to be Carboniferous / Devonian limestones overlying
older siltstones and sandstones, with a temperature gradient of 30º/km depth. The borehole
diameter will be 64cm at the surface and 19cm at the base. The borehole will be cored using a
hybrid drill bit that acts as a open hole and coring bit at the same time. The building itself will
be built on top of the drill site and is expected to be finished in late 2005.
The GHE of Aachen will reach a depth of 2,500m and will provide a maximum of 480 kW at a
temperature of at least 70˚C over a period of 30 to 40 years. In winter the geothermal energy
will be used cascade-like in radiators, ceiling heating panels as well as in the floor heating of
the building. In summer an adsorption air cooling machine will use the geothermal energy.
The estimated energy production of this GHE will be about 625 MWh/a supplying 80% of total
heat consumption. This is equivalent to an annual reduction of CO2 emissions in the order of
340t. Peak load and backup supply will be provided by a district heating network.
The total budget for the GHE is €5.1m including drilling and installation of the heating and
cooling system in the building. Funding is provided by the European Union Life III (€2m) and
the Federal State of North Rhein-Westphalia (€1.4m). Aachen University is providing the
balance of funding (€1.7m). GHE projects are marginally economic at present. Local drilling
costs, local energy costs for space heating, local subsidies and tax environment and level of
investment will affect the economic viability of geothermal projects wherever they are
located.
31
Geothermal Energy Resource Map of Ireland
Fig. 29. Deep GHE system
Fig. 30. Architects drawing of proposed Super-C building at Aachen
4.6
Enhanced Geothermal or Hot Dry Rock (HDR)Systems
This system is based on drilling one or more boreholes into 5km deep crystalline rock, with
little permeability, where temperatures of up to 250°C may be expected. In order to allow
water to circulate around the borehole, the rock is artificially fractured by explosive, chemical
or hydraulic means.
Heat is extracted by pumping water through an engineered heat exchanger connecting two
or more wells. This heat exchanger is a volume of hot dry rock with enhanced permeability,
which is fabricated by hydraulic stimulation. This involves pumping high pressure water into
the pre-existing fracture system that is present in all rocks to varying degrees. The high
pressure water opens the stressed natural fractures and facilitates micro-slippage along them.
When the water pressure is released, the fractures close once more but the slippage that
occurred prevents them from mating perfectly again. The result is a million-fold permanent
increase in permeability along the fracture systems and a heat exchanger that can be used to
extract energy. Sometimes sand is pumped into the fractures to keep the walls apart.
In a typical system, an initial borehole is sunk into the hot rock mass and a hydraulic
stimulation is performed. A three dimensional micro-seismic network deployed on the surface
and in nearby wells is used to record "acoustic emissions" (i.e. small noises) caused by the
slipping fractures. The network records the locations of the acoustic emissions while pumping
continues over several weeks. In this way, the progress of the stimulation is monitored and the
size and shape of the growing heat exchanger is mapped. A second well is then drilled into
the margin of the heat exchanger 500 metres or more from the first well. Now water can be
pumped through the underground heat exchanger and in superheated form it can be
returned to the surface. There it can have its energy extracted before being re-injected to go
around the loop again.
Experimental systems have been developed in Los Alamos, Nevada, USA; Otterbach, Basel,
Switzerland; Soultz-sous-Forêts, France; Urach, Germany; Cornwall and England as well as
many in Japan and New-Zealand etc.
32
Geothermal Energy Resource Map of Ireland
Fig. 31. Fig. 9. Diagrammatical cross-section
for HDR
Water is injected into a borehole and
circulated through a "heat exchanger" of
hot cracked rock several kilometres below
the surface. The water is heated through
contact with the rock and is then returned
to the surface through another borehole
where it is used to generate electricity. The
water is then re-injected into the first
borehole to be reheated and used again.
Enhanced Geothermal Systems are as yet still in the experimental stage and research is
ongoing to improve the success rate and reduce the cost of these types of systems.
33
Geothermal Energy Resource Map of Ireland
4.6.1
Basel
A HDR rock project is currently underway at Basel in Switzerland (Häring 2001). Well DHM-1 at
Otterbach in 1999 reached 1,537m with an overall geothermal gradient of 42°C/km, which is
above the world average of 30°C/km, was encountered. Well DHM-2 commenced in 2001 and
has reached 2,755m with a temperature of 127ºC and a geothermal gradient of 38°C/km.
Drilling will continue to a final planned depth of 5km, with a target rock temperature of 200ºC.
A reservoir will then be developed and pumping tests carried out. The project is expected to
cost €45 million and to be operational in 2008. At a flow rate of 70 l/s, the power output is
expected to be 3 MW electricity and 20 MW thermal.
Fig. 32. Details of the Swiss Deep Mining drilling at Basle, both current and expected.
Switzerland is looking at developing a number of other sites and has prepared a feasibility
map.
34
Geothermal Energy Resource Map of Ireland
Fig. 33. Potential deep heat mining sites in Switzerland. Based on logistics, heat distribution and
geology
4.6.2
Soultz-sous-Forêts
This is the site of the European Deep Geothermal Energy Programme pilot project, situated on
the western edge of the Rhine Graben structure, in north-west France, close to the German
and Swiss borders. In 1987, the first well was drilled to about 3.9km and after some
experimentation, including a successful 4-month circulation test, it was decided to drill three
further wells to a depth of 5km, one an injection well and two production wells.
35
Geothermal Energy Resource Map of Ireland
Fig. 34. Left: The European HDR-project is situated in Soultz-sous-Forêts, France, at the western border
of the Rhine Graben..
Fig 35. Right: Aerial view to the platform of GPK2/3/4 with the actual drilling
activities. A part of the GPK1 platform is seen in the background.
36
Geothermal Energy Resource Map of Ireland
At present the programme is continuing to
develop these wells at 5km depth and
successful stimulation experiments have
been carried out at 4.4-5km depth.
Fig 36. Diagrammatical cross-section for Soultzsous-Forêts, France
4.6.3
Los Alamos
This was the original HDR project and work started at Fenton Hill, Nevada, USA in 1974. The
first well was drilled into granite to a depth of 2.9km, finding water at 197°C. A second well
was drilled and hydraulic fracturing allowed a connection to be made between them.
Pumping tests over 75 days showed a significant thermal drawdown from 175°C to 85°C. After
further fracturing, a reservoir was established which could maintain a temperature of 149°C
after a 286 day heat extraction flow test.
Further work in the early 1980s, with Japanese and German involvement, included the drilling
of new boreholes to depths of up to 4.4km, locating temperatures of 327°C, and extensive
fracturing and water injection work. In the mid 1990s, continuous production tests were
carried out under commercial operating conditions which showed that the system was
reliable, resilient and flexible. Later development appears to have passed back to the Federal
Government.
4.7
Application of deep geothermal heat exchangers in Ireland
The geothermal gradient throughout Ireland varies from 10-15˚C/km in the south to 2530˚C/km (see section 6) in the north which is similar to Northern Germany where the Aachen
Project is located. The location of a GHE plant in Ireland will be dictated by the customer
demand for heat. GHE is suitable for large buildings with an effective area between 4,000 and
20,000m2. The School of Nursing at University College Dublin with an effective area of 5,084m2
37
Geothermal Energy Resource Map of Ireland
was selected as a comparative site to Aachen and was chosen for economic modelling for GHE
in the Irish context. The Health Science Complex is expected to have a floor area of 20,000m2.
Using the base design model for the building the energy use was Thermal 198 kWh/m2/yr (or
Gas 220 kWh/m2/yr) and Electricity 113 kWh/m2/yr. The Irish University benchmarks, provided
by Sustainable Energy Ireland, suggest that the average energy performance is 253 kWh/m2.
The annual energy use cost for gas/thermal is €30,000 for the School of Nursing. This covers
space heating and does not include water heating for catering. The estimated cost of drilling
the deep borehole and installing the heat exchanger is €2.5m. Therefore a building with an
effective area in excess of 20,000m2 will be required to justify the capital cost and significant
grant aid would be required.
Out of a total of 5,000m2 the areas with full mechanical extraction are limited to less than 25%
of the footprint. A short heating season of 3024 heating hours per annum for the building was
calculated (14 hours X 6 days X 36 weeks). This effectively precludes the possibility of CHP
where the rule of thumb suggests 4,500 operating hours are necessary for cost-effective
application. The heating system will have four separate radiator circuits. Heating in large
spaces will be controlled using motorised valves responding to room temperature sensors.
The entire heating system will be controlled using a building management system to match
the heating demand of the building. The temperature of hot water for catering purposes is set
at 60˚C. The GHE plant can deliver water at 70˚C at surface.
38
Geothermal Energy Resource Map of Ireland
5
Warm springs data collation and modelling
For this study the majority of data on warm springs have been collated from previous
monitoring of warm springs in the Republic of Ireland. Data for Northern Ireland will be added
to this database during the forthcoming CSA Group INTERREG study. Most of the monitoring
in the Republic of Ireland was carried out by the GSI and Minerex in the warm springs areas of
west Dublin/south Meath and the north Cork/Mallow area (Burdon 83a, Wright Pers comm.
2004). Some additional data for these areas have been added from more recent work in the
Mallow area by the Cork County Energy Agency and additional check monitoring has also
been carried out by the CSA Group. A summary of all data available to date on the warm
springs is presented in Appendix I and has been modelled in conjunction with regional
groundwater temperatures on Maps No. 6A – 8B in Appendix VI. The modelled data are based
on the maximum temperature obtained at each monitoring site. Where data are available
over a period of time the variation in temperature at that site is presented graphically in
Appendix II. Later monitoring of the so called ‘tepid springs’ (temperatures from 9º-12ºC) was
also carried out by C. R. Aldwell (1992) but are not detailed here as these temperatures are
very close to regional groundwater temperatures.
The warm spring data have been modelled together with temperatures from boreholes
compiled in the rest of this study (section 6) in order to place the warm springs data in context.
It should be noted that, in an attempt to produce a regional surface water temperature map,
broad areas in which no data was available under the scope of this study have been assigned
moderate values based on the nearest groundwater temperature measurement available.
These groundwater temperatures have been obtained from the borehole monitoring
programmes undertaken by CSA and earlier workers as discussed and present a single
temperature reading. Therefore there is considered to be a probable error of 2-3ºC due to the
seasonal variation.
Fig. 37. Lady’s Well, Mallow.
Fig. 38. St. Gorman’s Well, Enfield.
As is known from earlier work there are two main areas of warm spring occurrence in Ireland
(Burdon 1983a). These are the west Dublin/south Meath or north Leinster warm springs,
(Maps 7A & 7B) and the north Cork/Mallow springs (Maps 8A & 8B). When modelled with
regional groundwater temperature, the two areas stand out as relative ‘Hot Spots’ (Maps 6A –
6B). Some more moderate warm temperatures are seen in the Kingscourt area of
Cavan/Monaghan and in west Co. Limerick.
Additional groundwater temperature
measurement is necessary in order to present a more detailed and comprehensive review of
the potential for warm springs in Ireland but the data included here present an useful broad
39
Geothermal Energy Resource Map of Ireland
estimate of the more significant variations in groundwater temperature in relation to warm
spring occurrence.
Variations in chemistry and physical characteristics as well as pH, Electrical conductivity (EC),
and discharge rates of springs have been monitored sporadically in warm springs in Ireland. In
some cases vegetation can be used as an indicator of chemistry and year round activity of
warm springs. Details of studies carried out on several of the warm springs in Ireland are
contained in many of the Aldwell publications (1992) and also Burdon (1983b), and O’Brien
(1987).
5.1.1
Geological modelling
In contrast to the increase in geothermal gradients, discussed below in Section 7 of this report,
from south to north in Ireland, warm springs are more confined to the south and east of the
country and are rare north of the Iapetus Suture. An exception to this is the Kingscourt outlier,
which also shows the enhanced temperatures. The two main areas of warm spring occurrence
are the north Leinster and Mallow areas discussed below.
5.1.1.1
North Leinster warm springs:
A summary of the warm springs and boreholes form the north Leinster area is included on
Table 3 and details are included in Appendices I and II and locations in Appendix VI. Details of
the modelling of the temperatures at these sites is included on map no’s. 7A and 7B in
Appendix VII. The north Leinster warm spring area is comprised of two separate clusters of
warm spring occurrence that can be traced from the north of Dublin city (St Margaret’s Spring)
to Enfield in County Meath. This group of warm springs is located parallel to the major
Carboniferous basin controlling fault referred to as the Blackrock – Rathcoole Fault and show a
range of maximum temperatures from 14ºC at Bride’s well to 24.8ºC at Kilbrook springs. This
fault juxtaposes younger limestones against the older Leinster Granite in south County Dublin.
Although the warm springs are located somewhat north of this fault and indeed are seen to
continue to the west where there is little evidence of the Blackrock – Rathcoole Fault at
surface, this fault is considered to exert a controlling influence on the distribution of the
springs and is, in fact, the probable deep heat source for the springs in that area. It is
interpreted that deeply circulating groundwater is heated at depth and transferred rapidly to
the surface along deep penetrating structures parallel to this Carboniferous Basin controlling,
Blackrock – Rathcoole Fault.
40
Geothermal Energy Resource Map of Ireland
BH/Spring ID
County
Easting
Northing
Area/Group
Surface
Elevation (m)
BH Surf Date
Temp ºC
Depth
(m)
Air Temp Water
ºC
Source
SG-4
Meath
274037
244193
Ballynakill / Enfield
80
18.9
2003-2004
1.5
12.70
BH
SG-7
Meath
274036
244194
Ballynakill / Enfield
80
Louisa Bridge Warm Sp.
Bride’s Well Warm Spring
Kildare
Meath
299500
289230
236450
242680
Leixlip
Calgath / Kilcock
50
85
17.7
2003-2004
1.5
12.70
BH
17
14
03/09/1981
09/06/1982
surf
surf
NA
NA
Nat sp
Nat sp
St. Patrick’s Well No.1
Kildare
294150
231890
Ardrass
Celbridge
Upr
/ 70
14.5
10/09/1981
surf
NA
Nat sp
Kilbrook Warm Spring
Kildare
281460
242200
Kilbrook/ Enfield
80
24.7
21/07/1982
surf
NA
Nat sp
Dysart Warm Spring
Kildare
279240
238140
Dysart / Enfield
85
14.9
05/08/1982
surf
NA
Nat sp
St. Gorman’s Warm Spring
Meath
274010
244120
Ballynakill / Enfield
80
22.5
27/04/1982
surf
NA
Nat sp
Ardanew Spring
Meath
273460
248870
13
28/08/1981
surf
NA
Nat sp
St. Margaret’s Sp. No.1
Dublin
312790
243770
Castlerickard
Longwood
St Margaret's
70
19.1
21/07/1982
surf
NA
Nat sp
Sunday’s Well Warm Sp.
Kildare
287650
227340
Carrigeen / Clane
70
13.1
10/01/1982
surf
NA
Nat sp
Macetown Spring
Dublin
305170
241830
Macetown middle / 60
Mulhuddart
16
16/07/1981
surf
NA
Nat sp
St. Edmondsbury Spring
Dublin
304780
236190
St. Edmondsbury
Lucan
/ 20
16.9
24/05/1982
surf
NA
Nat sp
Clonee Spring
Meath
302900
241630
Loughsallagh
Dunboyne
/ 60
15.2
10/08/1981
surf
NA
Nat sp
St. Margaret’s Sp. No.2
Dublin
312860
243960
St Margaret's
70
16
03/09/1981
surf
NA
Nat sp
St. Patrick’s Well No.2
Kildare
293970
231790
Ardrass
Lower
Celbridge
/ 60
12.8
10/09/1981
surf
NA
Nat sp
Kemmin’s Mill Spring
Meath
289880
243340
Kemmin's Mill / Kilcock 90
14.6
18/01/1982
surf
NA
Nat sp
Meath Hill BH/Drumcondrath
Meath
288000
290000
North Meath
13.5
NA
NA
NA
BH
St. Gormans GT well / SG 8
Kingscourt Co. Co BH
Meath
Cavan
274030
282220
244194
296960
Enfield
Kingscourt
21.4
15.4
04/04/1989
Jan-04
60
Surf
NA
12.00
BH
Artesian
BH
/ 70
35
Table 3. North Leinster warm springs and boreholes
41
Geothermal Energy Resource Map of Ireland
The exact distribution of springs is dependent on surface conditions and the distribution of
permeable / fractured rock and /or gravel aquifers at surface. The complexity of fracture
patterns and other features allowing permeability and porosity means there is potential for
additional warm spring discovery but exact prediction is difficult. As a result of this study it
is interpreted that potential for additional warm spring / groundwater occurrence along
the line of the Blackrock - Rathcoole fault as described is good. Additional groundwater
temperature monitoring in this area is recommended wherever boreholes are available.
Deeper geothermal gradient and temperature in the Dublin/Meath/Kildare area shows
much variation both with depth and laterally. It is possible that the presence of warm
springs in the area is altering the geothermal gradients there, causing some
unpredictability due to the springs acting as a local heat sink.
5.1.1.2
North Munster region/Mallow Area warm springs
A summary of the warm springs and boreholes form the north Munster region (centred on
the Mallow area) is included on Table 4 and details are included in Appendices I and II and
locations in Appendix VI. Details of the modelling of the temperatures at these sites is
included on map no’s. 8A and 8B in Appendix VII. The warm springs in the Mallow area
and in the more recently identified eastward extension to Glanworth, lie along an east
northeast trending Killarney-Mallow thrust fault. Temperatures in this area vary between
13ºC at Marybrook spring, Newmarket, Co. Cork (typical of groundwater temperatures in
the area) to 23.5 at the County Council borehole north of Glanworth, Co. Cork.
Fig. 39. Logging the warm borehole at the Cork County Council reservoir site at Glanworth.
This fault marks the northern limit of the more intensely developed Variscan fault
structures in the region. It is believed that this thrust is connected to the basal thrust of
the Variscan front and therefore is relatively deeply penetrating. Though the structures are
very different to those in the Dublin/Meath area, similarity exists in the effect of this major
fault allowing rapid transfer of water warmed at depth to the surface. Attempts to test
water temperatures at depth in this area have recorded a slowly increasing temperature
with depth and therefore low geothermal gradient at depths below the springs at Mallow
and Ballynagoul to the west. Drilling and temperature monitoring near the springs in
Mallow in work carried out in the 1980s by O’Brien (1987) and later F. X. Murphy (Murphy
and Brück, 1989), confirmed that the warm waters were confined to narrow fault structures
and outside of these areas temperatures and geothermal gradients are lower than is
recorded in most of the rest of Ireland.
42
Geothermal Energy Resource Map of Ireland
Fig. 40. Munster Warm Springs model, after Brück et al. 1983. The front face of the block is a fault
zone.
43
Geothermal Energy Resource Map of Ireland
BH/Spring ID
County
Easting
Northing
Area/Group
Max.
Water
Temp ºC
14
Date
Depth
(m)
Newcastlewest
Surface
Elevation
(m)
60
Water Source
surf
Air
Temp
ºC
NA
St. Bridget’s Well
Limerick
126500
132600
26/11/1985
Ballintona Meelin (1)
Cork
128300
Ballintona Meelin (1)
Cork
128300
112400
Meelin
195
13.7
112400
Meelin
195
14.8
30/08/1983
surf
NA
Nat sp
04/10/1986
surf
NA
Nat sp
Trinity Well
Cork
129900
107700
Newmarket
155
15.2
04/10/1986
surf
NA
Nat sp
Gneevegullia
Tobergal
Kerry
111600
98400
Gneevegullia
Limerick
131500
127900
Newcastlewest
205
17.5
26/07/1986
surf
NA
Nat sp
60
14
04/10/1986
surf
NA
Nat sp
Cregan’s/Sconces Well
Limerick
126600
131300
Lady’s Well/Mallow
Cork
156200
98600
Newcastlewest
60
14
12/03/1987
surf
NA
Nat sp
Mallow
50
22.1
surf
NA
Nat sp
Ballintona 1
Cork
128300
Ballintona 2
Cork
128300
112400
Meelin/Newmarket
195
13.75
surf
NA
Nat sp
112400
Meelin/Newmarket
195
14.8
surf
NA
Nat sp
Trinity Well
Cork
Marybrook
Cork
129900
107700
Newmarket
155
15.2
surf
NA
Nat sp
143000
104600
N Mallow/Newmarket
85
13
surf
NA
Nat sp
Carraundulkeen
Kerry
111600
98400
Gneevegullia
205
17.5
surf
NA
Nat sp
St. Bridget’s Well
Limerick
126500
132600
Newcastlewest
70
14
surf
NA
Nat sp
Cregan’s Well
Limerick
126600
131300
Newcastlewest
60
14
surf
NA
Nat sp
Camas/Sconces Well
Limerick
128100
128800
S of Newcastlewest
60
13
surf
NA
Nat sp
Tobergal
Limerick
131500
127900
S of Newcastlewest
60
14
surf
NA
Nat sp
Knocksouna 4
Limerick
156600
127600
W Kilmallock/Kilmallock
70
16.1
surf
NA
Nat sp
Ballynagoul 1
Limerick
154800
126000
Kilmallock
60
17
surf
NA
Nat sp
Ballynagoul 2
Limerick
154800
126000
Kilmallock
60
15.7
surf
NA
Nat sp
Garrane
Limerick
153800
128400
Kilmallock
65
13
surf
NA
Nat sp
Glanworth/Johnstown
Cork
177750
111100
Glanworth
112
22.9
12/02/2004
32.78
11.00
BH
Glanworth/Curraghoo
Cork
176150
106850
Glanworth
47
13.1
12/02/2004
5
11.00
BH artesian
Ballintona Waterworks
Cork
283200
122580
Newmarket
184
13.9
06/03/2004
Surface
NA
BH
Knocksouna Spring
Cork
156776
127663
Kilmallock
68
13.2
07/03/2004
Surface
9.20
Nat Sp
Table 4. Munster warm springs and boreholes
44
26/11/1985
Nat sp
Geothermal Energy Resource Map of Ireland
Fig. 41. Knocksouna Hill and Rising.
Fig. 42. Knocksouna Rising 13.2ºC
The presence of low geothermal gradients combined with warm spring development in the
south of Ireland may have some relationship in that the occurrence of hydrothermal activity in
the present day faults in the area, results in increasing the transmission of heat to the surface,
thereby cooling the surrounding rocks. Again, as in the Dublin area, there may be potential for
additional warm spring occurrence along the continuation of the Killarney-Mallow Thrust fault
to the west. Other parallel thrust faults both within the Devonian to the south or thrusts
which define the location of isolated Devonian sub-crop to the north, as on the northern side
of the Galty mountains, are also considered to have some potential, though there are no
currently known occurrences. It is also worth noting that in broad terms silica rich rocks, of
which the Devonian in the Cork and Kerry area are mostly comprised, have higher heat
conductivity than limestone. There is also interpreted to be a thicker continental crust in the
area of Variscan deformation in the south due to the compressional faulting. It is postulated
that these two factors play a large role in the occurrence of lower temperatures and
geothermal gradients in this area.
45
Geothermal Energy Resource Map of Ireland
6
Borehole temperature monitoring and data collation
The data compiled in the current study consists of new data from CSA’s monitoring
programme, together with data from previous studies as listed above and a number of other
sources in the mineral exploration industry.
A review of the existing data borehole availability for geothermal monitoring was initiated
through a number of sources within the mineral exploration industry and government
administration departments. A schedule of access to data through each of these sources was
drawn up. Companies and individuals included in the search for new information are included
in Table 5 below. This was followed by a review of all data available on mineral exploration
drilling in Ireland in order to plan a programme of temperature monitoring of any boreholes
available at that time.
In some cases there was data on temperature logging already available in the company’s
records and these data are dealt with in Section 6.2.
All data were reviewed to identify boreholes that had been recorded as open / capped, usually
for testing purposes or for the later resumption of drilling. This indicated the possible
availability of the site for testing in the programme of monitoring carried out in this study by
the CSA Group.
46
Geothermal Energy Resource Map of Ireland
Organisation
Type
Company/section
Contact person
Comments
DCMNR
GSI – Groundwater section
GSI – Geothermal
GSI – Open file
GSI – Drilling
EMD
PAD
Database
Noranda/Minco
Asarco
Pasminco
Anglo
Mineral Estates Ire.
Westland/Ennex/
Riotinto
Rio Algom
Navan Resources
CMF
Glencar
Ballinalack Mins
Billiton
Ivernia/Rath-North
Lisheen
Tara Mines
Arcon
Irish Gypsum
Priority
Irish Drilling
Drilling 2000
Dunnes Water Services
Minerex
Eugene Daly
TES
TCD
G. Wright
G. Wright
K. Verbruggen & PG O'Connor
T. McIntyre
P. Gardiner
N. Murphy
R. Goodman/J. Kelly
D. Blaney
R. Goodman
R. Goodman
K. Henderson
P. Harrisson
M. Boland
D. Blaney
J. Kelly /M. King
V. Williams
J. Colthurst
K. Harrington
J. Kelly
(Previously) E. Doyle
J. Kelly
L. Fusciardi
M. Holdstock
A. Bowden
Received data
Received data
Received data
No info available
Data on Web
Received data
Received data
Received data
Have data
Have data
Received data
Received data
Data at GSI
Received data
No info available
Data at GSI
Received data
Received data
No info available
Data at GSI
No info available
Received data
Received data
Received data
Data at GSI
Received data
Received data
Received data
Received data
Data @ GSI
Received data
Received data
Received data
Received data
Received data
Received data
Data with GSI
Data with GSI
Received data
CSA Group
Mineral Expl.
Mining
Diamond drilling
Water drilling
Environmental
Universities
County Councils
T. Cummins
M. Mahon
N. Conroy
B. Dunne
C. Shine
E. Daly
S. Finlay
P. Johnston
Dr. A. Phillips (Deceased 2003)
UCD
Dr. I. Sommerville
UCC
Dr. Bettie Higgs
UCG
(previously K. Barton)
UCG
M. Feely
Cork City Council
M. O'Brien
Table 5. Sources of new data
47
Geothermal Energy Resource Map of Ireland
6.1
Equipment
Based on the number of boreholes that were recorded as open on the borehole logs the
decision was taken to conduct a programme of borehole testing. The equipment for the
previous programme in 1983 was no longer in an usable condition. The following equipment
was acquired: temperature probe, metal detector, hand-held thermometer and a GPS unit.
6.1.1
Temperature probe
A 1000m GeoRemediation temperature probe was purchased for borehole testing (cost €6,357
including 2 free repairs). The reasonable cost, simplicity and portability were the deciding
factors in the choice of probe. The probe is also adaptable for a longer depth capability (max
1500m) if necessary and has the capacity for the addition of a motorised winding mechanism
which would be necessary in deeper boreholes. Simple electronic readout system on the
GeoRemediation probe meant very easy field operation and therefore less operator training
time and potential for error.
Fig. 43. The temperature probe
Fig. 44. Temperature readout
6.1.2
Other equipment
A metal detector was purchased to locate some of the boreholes with metal casing, recorded
as buried under 30 – 60cm of soil/till and also in some cases where the boreholes were more
than 12 years old and land use was likely to have changed on the interim. The metal detector
chosen was the Whites AF 350 at a cost of €539.00. This model is normally used for
underground pipe and cable detection and was considered appropriate for the planned
programme. Locating old boreholes by this method proved a difficult process and only 3
boreholes were ultimately found by the metal detector.
A hand-held thermometer, with a 2 metre cable was purpose built and purchased for testing
surface water/spring temperatures. This was of particular use in the programme as access was
obtained to test groundwater temperatures in the underground workings at mines and also
for temperature testing of springs. A basic hand GPS unit was purchased to aid location of the
boreholes and to record positions for use in the database. A plumb-line was also acquired.
48
Geothermal Energy Resource Map of Ireland
Fig. 45. The metal detector
Fig. 46. The hand-held thermometer at Kingscourt.
6.2
Borehole results
A thorough review of the available data and contact within the interested parties described
above produced a final list of 104 boreholes though only a total of 50 of these turned out to be
accessible in the field (see results section 6.2). Each of these (104) sites was followed up in
order to obtain information on exact field locations, borehole condition and summary
geology. This data search included a detailed trawl through the GSI’s Open File Catalogue
(available digitally through the GSI Public access office at Beggars Bush, Haddington Rd.
Dublin 4).
Fig. 47. Field trials with the GeoRemediation temperature probe. G. Ll. Jones (left) and Róisín Goodman
(right) with the John and Kenneth Broderick of the field crew at a Rathangan borehole.
Many of the boreholes monitored in this study, and some from earlier work, are detailed below
to present an overview of how the results were treated. Note that this section is best read in
conjunction with the data from the boreholes as detailed in Appendix III, and also preferably
with access to the digital temperature and geothermal gradients maps which accompany this
report on CD. Logs of the borehole temperatures and geothermal gradients are included as
Appendix IV and hard copy of the maps are included in Appendices VI - IX.
49
Geothermal Energy Resource Map of Ireland
6.2.1
Procedure for modelling temperature and geothermal gradient
Data from all sources, PAD, Minerex, CSA, Imperial College London and Tara Exploration were
combined to produce a single borehole database with a series of parameters for each
borehole, including borehole ID, location/co-ordinates, depth tested, basal temperature,
surface temperature (where available and otherwise assumed to be 10ºC), depth (20-100m
intervals), temperature (20-100m intervals), geothermal gradient (20-100m intervals) and
finally inflection point in the geothermal gradient profile, where applicable. All data were
converted to degrees Celsius and the geothermal gradients are measured in ºC/km. The final
raw data used for modelling are included in Appendix III. There is an approximate maximum
of 150m elevation difference between the boreholes used in this study, however no elevation
correction has been applied and the depths used in modelling are depths from ground
surface. This causes some distortion in the geothermal profile (a maximum of 4.75ºC) but is
considered to give more useful results in assessment of the expected temperature at specific
depths in any area of interest.
6.2.1.1
Extrapolation of measured data
Data from each borehole were examined and it became apparent that there was much
variation in geothermal gradient with depth. In most boreholes the geothermal gradient
increased with depth but in others it decreased. The geology of the boreholes was examined
where possible in order to identify a lithological correlation with changes in geothermal
gradient (described for individual boreholes below). This was necessary in order to identify
the influencing factors in geothermal gradient for modelling and also to identify a reliable
geothermal gradient in a given borehole that could be used to extrapolate temperatures at
depth for that area. After examination of the data a final set of boreholes was chosen that was
considered suitable for extrapolation at depth. Boreholes were rejected from the database
where either no geothermal gradient was observed or where there was a sudden change from
high gradients at shallow levels to very low gradients at depth and also where the gradient
varied widely over short intervals. These features of geothermal gradient were normally seen
in boreholes less than 300m deep or in the shallower parts of deep boreholes and are
considered to be the influence of the infiltration of cold surface water into deeper groundwater. For this reason it was decided that data from boreholes less than 300m would not be
used in the modelling for deeper levels. Also only data from boreholes over 500m deep is
used to extrapolate to depths greater than 1,000m.
Of particular note in demonstrating the difficulty of extrapolating geothermal gradients, is the
Mart borehole in the Mallow warm spring area, where the geothermal gradient and
temperatures dropped off dramatically below the warm spring water at the top. Though
temperatures were relatively high a negative geothermal gradient was recorded. This shows
also the restricted nature of the warm spring source at Mallow and seems to confirm that the
source is a narrow fracture or fault zone. This was due to the borehole passing through the
fault related warm aquifer into the colder rocks below.
A number of different methods of extrapolation were tested. Generally it was observed that
simple extrapolation of the geothermal gradient to depth resulted in an underestimation of
the geothermal gradient as in many cases the geothermal gradient was observed to increase
with depth. However this increase was not consistent and is partly the result of the
fluctuations in the flow of groundwater in areas of karst and fractures. It was not therefore
possible to quantify the rate of change of geothermal gradient with depth and as a result the
deepest reliable gradient (i.e. well defined over 100m or more) was used to calculate
50
Geothermal Energy Resource Map of Ireland
temperatures at depth. The final database was then transferred to a series of data sheets
corresponding to different depth levels for later modelling.
6.2.1.2
Influence of geology
The detailed geology of the boreholes provides some explanation for the observed variations
in geothermal gradient in a borehole and there are a number of lithologies seen to repeatedly
correspond with these variations. Short explanations of the most important of these
lithologies are described in the Glossary in Appendix XI. It should be noted however that
these lithologies often have only localised influence related to local alteration or fracturing
confined to this unit. Some specific influences of important lithologies are listed below but
caution is advised in applying broad regional influences to these lithologies.
•
•
•
•
The distribution of the available boreholes, means that most of the data apply to
Carboniferous limestones and associated lithologies. There are significant areas of
older metamorphic and igneous rocks with little or no data.
The Shaley Pales act as a local aquifer in the Navan area in comparison to the Pale Beds
or the Basal Sandstones.
Naul Formation: Lower Naul Formation shows higher geothermal gradients than
Upper Naul Formation.
All the following units Waulsortian Limestone, Ballysteen Formation and Ballymartin
Formations act as local aquifers when compared with the Basal Sandstones.
There are a number of additional observations that emerge from the current study:
• Deep aquifers and structures increase the throughput of deeply circulating water to
shallower levels and therefore potentially provide a source of warmer water.
• Shallow aquifers tend to result in lower geothermal gradients due to the effect of
rapid infiltration of cold surface water to depth.
• Temperature and geothermal gradient variation is more controlled by fracturing and
karst than lithology. This is also true of near surface groundwater.
• It is confirmed that there are no primary aquifers in the Carboniferous with all porosity
and permeability resulting from either fracturing and / or karst with some minor
dissolution.
6.2.2
Boreholes monitored by CSA
Despite removal / blockage of many of the borehole collars as a result of building /
reclamation and changes in land use, access was gained to a total of 50 boreholes. However
as 7 of these were dry due to de-watering around the Lisheen mine and monitoring was
possible in a total of 43 boreholes. 11 of the boreholes monitored were blocked at shallow
depths (30-50m) and were therefore not deep enough to provide data for deep modelling.
Data from a total of 32 boreholes gave sufficient data to be used in modelling and summaries
of these boreholes are included as Table 6. After analysis 9 of these boreholes were
considered as providing reliable data on temperature and geothermal gradients that could be
extrapolated and provide estimates of temperature at depths of 500m and greater. A detailed
analysis of all boreholes studied in this and previous studies are presented in Appendix V.
51
Geothermal Energy Resource Map of Ireland
BH ID
County
Easting Northing
Elevation
(m)
BH Surface
Temp ºC
Total
BH Base
depth Temp ºC
tested
(m)
455
18.2
Water
Air
table Temp ºC
depth
(m)
7.3
13
00-468-5
Tipperary
178991
132194
130
14
01-541-03
Galway
184800
208115
40
13.4
810
28.8
1.5
Data
Source
CSA
11
CSA
Meath
311259
260000
80
10.4
665
21.7
2.3
8
CSA
1226-28
Westmeath
249816
226347
100
13.2
329
17.3
14
12.4
CSA
1439-2
Meath
277309
265088
70
12.9
244
17.2
0
13.8
CSA
1439-3
Meath
279687
270029
80
10
525
22.5
2.5
10.5
CSA
1450-1
Meath
299772
253822
100
13
580
23.7
4.3
9.5
CSA
1629-66
Kildare
276044
225601
80
12.8
159.8
14.78
0.6
NA
CSA
1629-67
Kildare
275974
225471
80
13
156
14.7
0.6
NA
CSA
2872-1
Limerick
132604
154180
10
14.5
128
14.8
14.5
NA
CSA
3245-113
Kilkenny
228671
172014
120
12.9
108.4
13.1
16.94
14.94
CSA
3245-128
Kilkenny
228195
172257
120
14
163
13.5
30.57
16.8
CSA
3248-1
Roscommon
187846
260013
60
13.7
342
13.8
4.3
12.7
CSA
BCDR-1
Offaly
231382
220489
60
13.8
269
17.8
5.3
12.9
CSA
Kilkenny
227583
172511
120
12.7
234.1
16.5
35
14
CSA
Offaly
249339
235626
80
12.5
54.6
14.1
1.5
13.8
CSA
GY-227
Kilkenny
227601
171242
120
13.4
77
12.3
23.1
14
CSA
HB-63
Kildare
276367
223873
80
12.4
457
19.2
17
12.5
CSA
02-1453-10
CW-DOB-1
DG-4
Johnstown
Mitchelstown
test 2
LK-1389
Cork
177750
111100
112
22.8
42.28
23.5
32.08
approx.
11
CSA
Tipperary
221836
167193
130
13.4
225
14.6
129.5
14.3
CSA
LKE-1411
Tipperary
220698
168486
130
14.3
270
15.3
50.2
14.1
CSA
LKE-1429
Tipperary
220280
167205
130
14
221.7
14
117.8
16.7
CSA
NC-10
Offaly
253939
228980
70
13.5
116
13.7
0
14.5
CSA
PA-98-01
Offaly
246561
216619
PButler Clare
Clare
165564
170142
RND-1
Kildare
294400
232150
SG-4
Meath
274037
12.6
322.1
18.4
4
13.6
CSA
80
15
100
13.7
8.7
11.8
CSA
10
537.8
20.5
0
8.6
CSA
244193
80
18.9
41
21.9
1.5
12.7
CSA
Meath
274036
244194
80
17.7
180
22.3
1.5
12.7
CSA
S'mines K well 2
Tipperary
184161
171113
70
12.9
45.5
12.7
7.5
13.3
CSA
TW-10
Kilkenny
226634
172365
120
13.2
76.3
12.8
33.25
16.2
CSA
Louth
311192
278636
30
13.1
100
13.9
0.9
NA
CSA
Cork
153000
114600
13.5
30
13.4
14.60
CSA
SG-7
Water Well
Louth 1
Ballinageeagh
/Charleville 2
Table 6. Boreholes tested by CSA and summary results
52
Geothermal Energy Resource Map of Ireland
6.2.3
Boreholes monitored by mineral exploration companies
Some of the companies involved in mineral exploration in Ireland have collected temperature
data in drill-holes in Ireland as part of other down-hole surveys in boreholes particularly in
surveys to measure the angle of dip and the azimuth of a borehole. Some of this data has
been accessed through mining companies such as Outokumpu (now-Boliden) based in Navan,
Co. Meath and other data from Arcon, Galmoy, Co. Kilkenny. This data has been incorporated
into the database and has provided valuable additional temperature data. Data from 8
boreholes drilled and monitored by Outokumpu have been incorporated into the database
details of which are included in Appendices III, IV and V. A summary is included in Table 7
below.
BH ID
County
NO1595
NO1256
NO1617
3488-13
580-6
134-2
NO1350
NO1630
NO1588
Meath
Meath
Meath
Galway
Meath
Meath
Meath
Inclination
Approx.90
Approx.90
Approx.90
Approx.90
Approx.90
Approx.90
Approx.90
Approx.90
70-90
Easting
Northing
281082
280991
282196
133373
210229
167814
282706
281081
282133
265057
262517
271446
143924
268059
219581
265247
265057
266345
Depth
Bottom
Data Source
Hole Temp
C
1241
1550
981
774
391
658
1188
1263
1068
38
49.6
32
22.7
18.5
21
36
38.5
38.8
Outokumpu
Outokumpu
Outokumpu
Outokumpu
Outokumpu
Outokumpu
Outokumpu
Outokumpu
Outokumpu
Table 7: Boreholes monitored by Outokumpu and summary results
6.2.4
Boreholes monitored by oil exploration companies
This database consists of data from 11 boreholes in the Republic of Ireland (including 3 new
boreholes drilled since the last review) and also temperature data from 14 deep oil exploration
boreholes from Northern Ireland.1 These boreholes are up to 2800m in depth and provide
vital information in assessing the real temperatures and gradients to be expected at depth in
the Irish sub-surface (oil company reports PAD and DETI 1970-2001).
Typically oil borehole logs solely record bottom-hole temperatures (BHT) which permit the
calculation of an average geothermal gradient only. Therefore subtle variations in
temperature with depth are not available and it is not possible to calculate different gradients
for different geological units. However, much additional down-hole survey data is available
for the boreholes and a review of the results of these surveys, for boreholes drilled in the
Republic of Ireland, is presented below.
The review concentrated on the drilling records and electric logs to identify zones with water
flows, mud losses and porosity at depth. Any indicators of permeability and porosity at depth
are significant in the context of deep aquifer extraction of geothermal energy. The well
records for the following boreholes were reviewed: Ballyragget, Trim No.1, Doonbeg, McNean
No.2, Drumkeeran South No.1, Timahoe 1b, MacNean No. 1, Dowra 1, Meelin No.1, Dowra 2
1
A more detailed review of the Northern Ireland data is planned in a separate project which will result in an
updated map to be completed in early 2005.
53
Geothermal Energy Resource Map of Ireland
and Thur Mountain. A summary of the results for these boreholes are included in Table 8 and
details of the temperature data for these boreholes are included in Appendix III.
Borehole ID
County
Easting
Northing
Elevation
(m)
Surf
Temp
ºC
Depth
(m)
Temp
ºC
Data
Source
McNean No.1
Cavan
204650
237250
66.2
10
1650
Dowra No.1
Cavan
206498
327033
119
10
1830
Trim No. 1
Meath
280850
248960
81.5
10
1821
Ballyragget No.1 Kilkenny
244470
166250
64.8
10
1132
Doonbeg No.1
Clare
96340
163800
20.8
10
3266
Meelin No.1
Cork
126920
113200
248.8
10
1690
Drumkeeran 1
Leitrim
188850
319300
252
10
2510
McNean 2
Cavan
206100
337700
60.96
10
1514
Dowra No. 2
Cavan
206494
327031
118.8
10
1342
Thur Mountain
Cavan
200336
327031
137
10
1431
Table 8: Oil exploration boreholes (Republic of Ireland) summary results
57.2
51.6
30
31.1
38.8
33.8
19.4
57.2
45
45.5
PAD
PAD
PAD
PAD
PAD
PAD
PAD
PAD
PAD
PAD
6.2.4.1
Porosity and permeability measurements
A summary of the various significant parameters for these boreholes is included on Table 9.
Significant freshwater flows of about 24,000l (150 barrels) per hour occur in fractured
limestone, sandstones and dolomites at several intervals between 100m and 750m in all of the
wells. The moderate to fair porosity and permeability at these depths is predominantly due to
vugs and fractures in limestone. Matrix porosity from wireline logs and core is about 2% in
limestone. Occasionally sandstone in the Namurian can have porosities up to 15% above
750m. Sometimes dolomite has matrix porosities of 2% with a significant secondary vug and
fracture porosity with associated sulphur rich water flows. Most of the well logs show no
matrix porosity in any formation below 750m.
Only three of the wells indicated some porosity and permeability below 1,200m. The most
significant is 10% porosity in dolomite within the Waulsortian Limestone at 1,634m in Meelin
No.1 in Co. Cork. Five per cent porosity in the Old Red Sandstone at 1,500m in the NW
Carboniferous Sedimentary Basin is recorded in three wells. The porosity is a combination of
poor matrix porosity combined with vug porosity. The core permeability is poor at 0.22md2
but flowing water was recorded which indicates some permeability.
The following points are most significant:
• There is considerable potential to intersect significant aquifers between 100m and
750m in wells drilled in the Carboniferous Limestone that may, given certain
geological conditions, constitute a hot spring source.
• Where fractured vugular dolomite is associated with evaporites there is potential for
some porosity and permeability at depths below 1,000m.
• Sandstone below 1,200m can, in rare circumstances, have porosities of up to 5% and
sufficient permeability to support saltwater flows of up to 1,000l/hr (6bbls/hr).
• Given all of the above, the potential for deep aquifer extraction of geothermal heat in
Ireland needs to be further investigated, perhaps by re-entry into a suitable candidate
well.
2
md = millidarcies, measurement of permeability
54
Geothermal Energy Resource Map of Ireland
Well /
Borehole ID.
Depth
Rock Type
Porosity
(Ø)
Ballyragget
477 –
681m
Trim No. 1
558m
2% matrix 28,000l/h (180
+ vugs & bbls**/hr)
fractures
0.82%
Down to 633m
No
Doonbeg
0–
784m
1514m
15%
Yes
1613m
Fractured
Limestone &
Dolomite
Fractured
Limestone &
Dolomite
Namurian
Sandstone
Old
Red
Sandstone
Sandstone
Timahoe 1b
233m
Limestone
McNean
No. 1
McNean
No. 1
Dowra
1379m
Sandstone
1648m
211m
Old
Red Poor matSandstone
rix + vugs
Dolomite
Dowra
1238m
Sandstone
Meelin
117m
Meelin
649m
Limestone
cavernous
Dolomite
Meelin
Dowra 2
1649m
215m
Thur
Mountain
Thur
Mountain
59m
McNean
No. 2
Drumkeeran
277m
Dolomite
Fractured
Limestone
Fractured
Limestone /
Fault
Water Flow
18,300l/h (115
bbls/hr)
2%
wireline
5%
wireline
Perme
ability
(k)
Yes
No
Yes
5% sonic
5%
15-20%
10%
Nil
Nil
1,000l/h (6
bbls/hr)
Saltwater flow
160,000l/h
(1,000 bbls/hr)
Saltwater flow
80,000l/h (500
bbls/hr)
29,000l/h (130
bbls/hr)
10,000l/h (60
bbls/hr)
1,600-6,400l/h
(10-40 bbls/hr)
>6,400l/h
(>40bbls/hr)
Yes
Yes
Yes
Remarks
No Ø* below
681m
No wall cake
indicates no
k
No Ø below
762m
Drill
Stem
Test
(DST)
tight
Lost
circulation
65k ppm salt
water flow
DST mud +
salt water
Sulphur
water flow
0.22m
d
Yes
Yes
Freshwater
Yes
H2S 20ppm
Yes
Water influx
Yes
Water influx
* Ø = Symbol for porosity **bbl (barrels) = 40 gallons = 159 litres
Table 9: Porosity and permeability measurements for oil exploration boreholes in
the Republic of Ireland
6.2.5
Data for Northern Ireland
Bottom hole temperatures from 12 boreholes from Northern Ireland have been included in
the modelled data. Although details of these boreholes have not yet been seen they will be
examined as part of the separate INTERREG study on Northern Ireland. They are: Annaghmore
No. 1, Ballymacilroy No. 1, Ballytober No.1, Big Dog No. 1, Glenoo No. 1, Killary Glebe No. 1,
55
Geothermal Energy Resource Map of Ireland
Lang-ford Lodge, Larne No. 2, Newmill No.1, Owengarr No. 1, Portmore No. 1, and Slisgarrow
No. 1.
6.2.6
Imperial College monitoring programme
A series of temperature readings was taken in 18 boreholes in the early 1970s in a study
carried out by Imperial College London (Wheildon in Burdon 1983a). These readings were
taken in various exploration boreholes for the mineral and oil exploration industry. Data were
included in the study carried out by Minerex and the data have been reviewed again for this
study. Many of the boreholes were shallow and after reviewing the data a final group of 12
boreholes was included in the present study and used in modelling the data. These are
summarised in Table 10. A final 6 were used for deep modelling.
CSA BH ID
IMP 1
D1 IGS-P
Portmore
582
Bottom hole
Temperature
ºC
35.4
IMP11
R10
IBM014/9
Tulla 2
T1 1670/44
Tulla
167
13.1
Avoca
482
18.1
Sixmilebridge
490
17.7
Sixmilebridge
222
13
IMP12
IMP15
Old BH ID
Location
Depth
(m)
Adare
540
18.4
IMP3
R13
IBM019/1
R14
IBM019/2
R5
IBM025/2
M7 LX19/1
Mt. Mary
151
12.9
IMP4
SH4
Shrule
283
15.1
IMP5
M15 DM9
Moate
495
20.5
IMP6
M9 L1
Ballydoogan
230
12.9
IMP7
M10
IBM9/179
R8
IBM017/1
Killimor
613
22.2
Ennis
132
13
IMP16
IMP17
IMP9
Data Source
Imperial
College
Imperial
College
Imperial
College
Imperial
College
Imperial
College
Imperial
College
Imperial
College
Imperial
College
Imperial
College
Imperial
College
Imperial
College
Imperial
College
Table 10. Imperial College London boreholes used in this study.
Details of the geology of these boreholes was not accessed but, as only bottom hole
temperatures were available, it is not possible to review variations in the geothermal gradients
in these holes. The bottom hole temperatures are included on table 10.
56
Geothermal Energy Resource Map of Ireland
7
Data modelling for temperature & geothermal gradient
7.1
Temperature and geothermal gradient maps
A series of maps has been produced to present the settings, locations and variations in
temperatures and geothermal gradients throughout Ireland and is included as Appendices VI IX. Appendix V includes maps showing infrastructure, summary geology, gravel and rock
aquifers and location plans of warm springs and boreholes (Map No’s. 1–5). In Appendix VII,
Map No’s. 6A–8B, show warm springs and shallow (<10m) groundwater and some detail of the
Mallow and North Leinster areas. Also in Appendix VII map No’s. 9A – 13B show modelled
temperatures (from measured and calculated data) at five levels 100m, 500m, 1,000m, 2,500m
and 5,000m. These maps include a version with summary geology near surface.
Maps showing modelled geothermal gradients (from measured and calculated data) are
included as Map No’s. 14A–17A in Appendix VIII. It should be noted that below 1,000m no
significant changes in geothermal gradient have been modelled due to scarcity of measured
data at those depths. The distribution of temperatures in relation to geology and the
influencing factors is discussed below in each category.
Map No’s. 18A–21B in Appendix VIII, show modelled data for measured temperatures and
geothermal gradients (no calculated values are included) for all levels with significant data
distribution. These maps are useful for comparison with the calculated data and show the
present data distribution. Modelled heat flow data are included as Map No. 21 in Appendix X.
The modelled geothermal gradients at 500m, 1,000m and 2,500m are included in Appendix
VIII, Map No’s. 14A – 17A and show a similar regional pattern as for the temperature maps.
It should be noted that all maps produced for this study are potential maps only and cannot
be used as definitive measurements of temperature and gradient except at the point where
readings are taken. For this reason a set of maps modelling only the measured temperatures
and gradients are included in Appendix IX.
7.1.1
Data modelling techniques
Data obtained during the geothermal data review and collection has been modelled using
grid modelling software within a Geographic Information System (GIS). The GIS software used
is Mapinfo and the grid modelling software used is a Mapinfo add-in, Vertical Mapper.
A grid is made up of regularly spaced square cells arranged over a given area. Each cell has a
node, which is a point located at its centre. Each cell can be assigned a value and a colour
representing the value. If there are several cells between two known locations the change in
colour indicates how the values change between the locations.
57
Geothermal Energy Resource Map of Ireland
Fig. 48a, b & c. Point dataset, grid created over dataset and modelled surface generated from grid.
Typically, the gridding process begins by overlaying an array of grid nodes over the original
point file. This can be visualized as a regularly spaced point file arranged in the form of a grid.
Each grid node is then attributed with an estimated value based upon the values of the
surrounding points. This grid is then displayed as a coloured image, where the colours reflect
the estimated node values. Various mathematical methods can be employed to determine
the calculated values for the grid nodes using the values assigned to the original points (data).
There are a wide variety of techniques available to model and visualise spatial data within
Mapinfo, including
•
•
•
•
•
•
Triangulation with Smoothing
Inverse Distance Weighting
Natural Neighbour (simple and advanced)
Rectangular
Kriging
Custom Point Estimation
Some interpolation techniques produce more reasonable surfaces when the distribution of
points is truly random. Other techniques work better with point data that is regularly
distributed. Highly clustered data, such as the geothermal data for the springs and boreholes,
presents problems for many interpolation techniques. The geothermal data is a particularly
difficult dataset for modelling purposes due to the highly variable distribution of the data
points. The data points fall primarily within two data clusters (North Leinster and the Mallow
area) with scattered data points outside these two regions. In addition, parts of the country
had no data available.
58
Geothermal Energy Resource Map of Ireland
Fig. 49. Highly clustered dataset.
To model such a clustered dataset, it was decided to conduct the initial modelling using
natural neighbour interpolation, inverse distance weighting and kriging, to determine which
modelling technique would give the best solution.
Natural neighbour interpolation creates a network of natural neighbour
regions using the original data. This creates an area of influence for each
data point that is used to assign new values to overlying grid cells
With inverse distance weighting, the original data points lying within a
prescribed radius of a new grid node are weighted according to their
distance from the node and then averaged to calculate the new grid cell
value.
Kriging is a geostatistical interpolation technique that considers both
the distance and the degree of variation between known data points
when estimating values in unknown areas.
Fig. 50. Comparison of modelling techniques for clustered data.
Following initial results, it was determined that natural neighbour interpolation was best
suited to model the datasets and all detailed modelling was conducted using this method.
7.2
Shallow geothermal modelling
The top 300m of bedrock in Ireland has had a history of low sea level and therefore low
groundwater levels during glaciation and this has allowed the development of karst structures
in limestone, opening up fractures in the top 200m – 300m of bedrock. This karstification is
somewhat sporadic and is more in evidence in some of the units in the limestone succession,
in particular the Waulsortian unit and parts of the overlying Upper Limestone units especially
in the northwest part of the midlands. Limestone and therefore karstification is not so
common in the south of the country and groundwater movement there is more confined to
fracturing and faults. In the south also the presence of the Kiltorcan Sandstone Fm (E. Daly
pers. com. 2004) accounts for a large proportion of reliable aquifers. The Kiltorcan contains
remnant primary porosity, coupled with later fracturing, resulting in relatively good porosity
and permeability. It is however the case that no classic aquifers exist in the bedrock of the
Republic of Ireland. In Northern Ireland the much younger, Triassic aged, Sherwood
59
Geothermal Energy Resource Map of Ireland
Sandstone is a known aquifer and has true potential as an aquifer at depth. Details of this
potential in the Sherwood Sandstone will be dealt with in the separate study on Northern
Ireland. Overall, shallow depth groundwater temperatures and gradients are difficult to
predict.
7.2.1
Temperature and geothermal gradient modelling at 100m
The results of temperature modelling at 100m are included on Map No’s. 9A and 9B. The
borehole temperature map at 100m depth has been modelled from measured temperatures
in 94 boreholes in 22 counties throughout the Republic of Ireland and Northern Ireland. Data
from Northern Ireland are not complete and have been based on the deeper oil exploration
boreholes only. They will be updated by any available data from mineral exploration
boreholes and other available data sources in the later INTERREG study. The general range of
temperatures is from 10ºC – 13ºC with a low value of 10ºC in the south of the country and also
the north central midlands area and a spot high maximum of 22.3ºC in the Enfield/north
Leinster area. Regionally the highest temperatures are in Northern Ireland where
temperatures of 13.5ºC in north Antrim are interpreted at 100m from deep drilling there,
though no direct measurements at shallow levels are available for this area. The high
temperature in the Enfield area is in a borehole (SG-7) adjacent to the St. Gorman’s Spring and
indicates the continuation of warm temperatures to depth below the spring. This is a
phenomenon not seen in drilling of the Mallow warm spring area where the feeder structure
for the warm water there is interpreted as more narrow and restricted and therefore harder to
locate. Data in Northern Ireland and north Leinster at this level reflect to some degree the
higher temperatures and geothermal gradients seen at depth in these areas, thus showing a
significant change from the temperature distribution seen in the map of warm spring and
shallow ground-water. Underground temperature readings at Lisheen mine gave values from
12º – 15ºC at 150m depth though there was evidence of rapid run-off from surface down open
boreholes and along the decline. Data presented in this study show that there is no major
regional feature influencing groundwater temperature variation at 100m depth. Local
variations, caused by karst and fracture controlled aquifers allowing rapid run-off infiltration to
this depth, predominantly control groundwater temperature patterns.
7.3
Intermediate (100-1,000m) and deep (1,000-5,000m) modelling
Some details on the factors influencing local variation in temperature and gradient for each
borehole are discussed in Appendix V.
7.3.1
Intermediate (100-1,000m) and deep (1,000-5,000m) geothermal and
geological modelling
Data Modelling for geothermal gradients in Ireland’s subsurface is based on temperature
readings from 75 boreholes between 300m and 2,300m depth throughout Ireland. Another
set of data has been produced from 49 boreholes that extend to a minimum of 500m depth.
Details of the borehole locations, total depth and temperature range are included as Appendix
III. Data on many other boreholes <300m deep are available and have been modelled at 100m
only but have not been included in deeper modelling for a number of reasons as discussed in
section 6 above.
Two sets of modelled data have been produced. The first uses the measured temperature data
from boreholes >300m deep and extrapolates those data to 1,000m. A second set of data was
produced in a similar way but only using boreholes >500m deep and those data were
extrapolated to 5,000m. During modelling at each level the data sets were compared with the
data available from actual readings at those levels. Comparison of these data sets for each
60
Geothermal Energy Resource Map of Ireland
level shows reasonable correlation and therefore the extrapolated data is considered a reliable
indication of expected temperatures. Where no data is available extrapolation of data has
been a simple calculation based on the deepest reliable geothermal gradient and temperature
measured in the borehole. It should be noted that, in some cases where geothermal gradients
are measured in deep boreholes, the gradient is seen to increase with depth. In a given set of
borehole gradient measurements this is observed in 40% of cases. However the opposite is
also observed in 30% of cases. The controls on these changes in geothermal gradient are
complex and critically dependent on local conditions i.e. lithology, porosity and permeability
and fracturing/structure. Therefore, for the purpose of this study, an average geothermal
gradient, calculated from the deepest reliable geothermal gradient and temperature in the
borehole, is used to extrapolate values for the deeper levels.
It should be noted also that in similar modelling of geothermal gradients in Belgium by
Vanderberghe and Fock (1989) a strict limit was placed on the depth to which data from a
borehole would be extrapolated. This has not been applied in this study (once the borehole
was >300 or 500m) as the distribution of data is insufficient to give any meaningful estimate of
geothermal gradient at depth without extrapolation of most boreholes available.
7.3.2
Intermediate (100-1,000m) and deep (1,000-5,000m) structural modelling
In a regional context, geothermal gradients in Ireland show an increase from south to north at
all levels. An exception to this is the west of County Clare where the highest geothermal
gradients in the south of Ireland are located. Additionally this trend is also evident in
measured temperature data from the deeper boreholes. This regional trend is interpreted to
be associated with the main structural divisions in the Irish subsurface as identified from
geological studies. The major feature influencing groundwater temperature variation at
depth is the presence of the major northeast-southwest structural feature, the Iapetus Suture,
running approximately from Dublin to Limerick. The Iapetus Suture is the term given to a
deep crustal structural feature crossing the Irish midlands and marking the line of the collision
between two crustal plates which were previously separated by an ocean. The position and
different characteristics of these plates has impacted on their subsequent geological history
and is also seen to mark a change in the geothermal properties of these areas. The effects of
this feature will be discussed below.
Another trend seen to be significant in the data, is an east-west trend to the south of the
Iapetus Suture which is seen in both the North Leinster and North Munster warm spring data
sets. This is Variscan in origin and its associated structures are interpreted to be generally eastwest deep penetrating faults. To the north of the Iapetus Suture a subtle north-south trend
emerges which is interpreted to be associated with a much later tectonic event of circa.
Triassic age. This is seen in the Kingscourt area, Co. Cavan where there are enhanced
temperatures (15ºC) near surface. The same structure at Kingscourt may continue north to the
Lough Neagh area in Northern Ireland where there are high temperatures at depth. No deep
data is available for the Kingscourt area. This hypothesis will be followed up in additional data
analysis for the INTERREG project for Northern Ireland.
7.3.3
Temperature and geothermal gradient modelling at 500m
The results of temperature modelling at 500m are included on Map No’s. 10A and 10B. The
borehole temperature map at 500m depth has been modelled from measured and calculated
temperatures in 75 boreholes in counties throughout the Republic of Ireland and Northern
Ireland. The modelled data have been produced from boreholes that reached 500m, together
with temperatures calculated from geothermal gradients in boreholes that reached 300m.
61
Geothermal Energy Resource Map of Ireland
The measured temperatures only at 500m was compared with modelled data at 500m
including both measured and data calculated from geothermal gradients at 300m. It was
considered that there was good correlation between the two plotting methods, but that the
latter data set gave more detail and therefore this was used as the final map for the 500m
level.
At 500m depth a number of hot-spots are present in the data namely in west Clare, northwest
Cavan, north Antrim and east Tyrone where values range from 25ºC - 27ºC. Generally more
elevated values are present throughout the midlands as compared with the west and south
where values are mostly in the range of 17ºC - 19ºC. There is some degree of bias due to the
relative abundance of data in the more central areas. However despite this bias, it is
interpreted that there is some division in deep geothermal activity, from the colder
temperatures and lower geothermal gradients in the south to the warmer temperatures and
higher geothermal gradients in the north, across a line from Dublin to Limerick coincident
with the Iapetus Suture. This feature has some effect at shallow levels but becomes better
defined at deeper levels. Although the suture is over 460million years old it had a long-lived
influence on sedimentation patterns and can still be seen in deep geophysical profiles of the
sub-surface of Ireland (Jacob et al. 1985). Later structural movements in the south of Ireland
have resulted in an east-west overprint of earlier Caledonian aged northeast-southwest
structures. This east-west trend, related to the Variscan deformation, resulted in the formation
of a number of deep inclined faults in the south of the country which control the presence of
warm springs in the Cork area. It is interpreted that the thickening of the sediments in the
south, as a result of compressional faulting during the Variscan, resulted in the presence of
lower geothermal gradients due to the thickened crust there. It is postulated here that some
component of this low geothermal gradient in the south is also the higher conductivity of the
quartz rich sediments here allowing rapid transfer of the near surface heat to the atmosphere.
This is in contrast to the Northern Ireland where the interpreted presence of thinned crust
underlying the Antrim flood basalts seems to control the higher geothermal values seen there.
In the vicinity of the Iapetus Suture in the midlands there are zones of anomalous warmer or
colder temperatures and associated variations in geothermal gradient. Again the distribution
of boreholes available for testing has produced some bias in the data. A zone of enhanced
geothermal gradients was previously interpreted by Phillips (2001) to lie along the trend of the
suture zone where it is linked with Paleogene age fault activity in the area. In this study cooler
zones along the suture trend are interpreted to be the result of the presence of
fractured/jointed and/or karstified development, allowing localised rapid infiltration of cold
water from the surface deep into the groundwater, where it reduces the groundwater
temperatures for that area. Warmer anomalous zones are interpreted to be caused by the
presence of deep penetrating faults (similar to the situation with warm springs development)
causing localised warming. It should be noted that the latter areas therefore hold some
potential for surface warm spring occurrence. The presence of warmer temperatures in some
areas of thick limestone cover in the midlands, especially in Westmeath and through Offaly
into east Galway, may be the result of an insulating effect of the limestones (which have lower
heat conductivity than quartz rich sediments) and associated shale cover there.
7.3.4
Temperature and geothermal gradient modelling at 1,000m
The results of temperature modelling at 1,000m are included on Map No’s. 11A and 11B. The
borehole temperature map at 1,000m depth has been modelled from measured and
calculated temperatures in 72 boreholes in counties throughout the Republic of Ireland and
Northern Ireland. The modelled data have been produced from boreholes that reached
1,000m together with temperatures calculated from geothermal gradients in boreholes that
62
Geothermal Energy Resource Map of Ireland
reached 300m. Some similar patterns of warmer temperatures and geothermal gradients as
seen at 500m are also seen at this level, as some of the data have been directly extrapolated
from the data at 500m depth.
Again the areas showing the higher geothermal gradients are in the Antrim, northwest
Cavan/Fermanagh and Clare areas. The latter area shows a broader anomalous zone that
extends into southeast Galway than is seen on the temperature map. This is reflected also in
the heat flow measurement on the Galway granite (Map 21). Generally at 1,000m gradients in
the south of the country are 10ºC – 15ºC/km and range from 20ºC – 30ºC north of the Iapetus
Suture line. Highs of around 35ºC/km are recorded in the more anomalous zones and
represent the areas of most potential in any further investigation and testing of deep
geothermal gradients across the Republic of Ireland and Northern Ireland.
The presence of the Iapetus Suture becomes more strongly defined at this depth and
generally creates a separation between the north and south midlands. Temperature ranges
between 22ºC – 28ºC to the south to 37ºC – 46ºC to the north of this line. There are still some
zones of anomalously low temperatures in the midlands which may be the result of deep
circulation of cold groundwater from surface along fractures. The extrapolation of shallow
boreholes to depth is also an influencing factor here.
In the case of borehole 580-6 (Co. Longford) which intersected thin limestone cover overlying
Lower Palaeozoic lithologies, it records cooler temperatures (20ºC) and lower geothermal
gradients than areas with thicker limestone cover (eg. 109-Ballinalack temperature 25ºC). This
seems to indicate that when un-karstified/un-fractured, areas with limestone cover can have
higher than average geothermal gradients. In the Strokestown borehole BB-82-4, located
west of the inlier where there is a deep penetrating fault (defining the edge of the Lower
Palaeozoic) in close proximity to the borehole, temperatures in the limestones are locally
enhanced (21ºC). This is also seen in the Navan and Kildare areas where there are deep
penetrating faults controlling the edge of Lower Palaeozoic Inliers. Cooler temperatures in the
east Clare/southeast Galway area may be related to the presence of Lower Palaeozoic Inliers
with similar effects to those seen on the east side of the Strokestown Inlier. However it should
be noted that as there are very little measured data available. In the Lower Palaeozoic any
interpretation concerning the geothermal conditions in these rocks must be treated with
caution. The observations above seem to indicate that the temperatures seen at depth in the
Irish subsurface are to some extent controlled by the thermal conductivity of the lithologies
despite the more significant input of deep penetrating faults. Data on thermal conductivities
of different rock types show that limestone has a significantly lower conductivity than quartz
rich sediments and dolomite and therefore may retain heat longer. Table 11 gives average
thermal conductivity values for the common rock types present in Ireland. However the use of
this data must be cautious due to the variability within sediment and rock sequences.
Lithology type
Limestone
Sandstone
Calcareous sandstone
Shale
Mudstone
Dolerite
Volcanics
Dolomite
Average Conductivity Wm-1k-1
3.066
4.645
4.025
2.423
2.676
2.133
2.895
4.0
63
Geothermal Energy Resource Map of Ireland
Quartzite
4.0
Table 11. Average thermal conductivity values (Brück & Barton 1984)
7.3.5
Temperature and geothermal gradient modelling at 2,500m
The results of temperature modelling at 2,500m are included on Map No’s. 12A and 12B. The
borehole temperature map at 2,500m depth has been modelled from 2 measured and 47
calculated temperatures in 49 boreholes in counties throughout the Republic of Ireland and
Northern Ireland. The modelled data have been produced from the 2 boreholes that reached
2,500m, together with temperatures calculated from geothermal gradients in boreholes that
reached 500m. As most of the temperatures used in this modelling are calculated, more
caution must be used in the interpretation. The map shows a similar division in temperature
values across the Iapetus Suture from Dublin to Limerick with ‘hot-spots’ in the Kildare, Navan
and north Cavan areas in the Republic of Ireland and in the east Tyrone and north Antrim areas
of Northern Ireland. Temperatures vary from a range of 28ºC to 45ºC in the south to a range of
64ºC to 97ºC in the north (with a max of 101ºC). Caution must be applied in this data
modelling as most measured data are from the Carboniferous, while at a depth of 2,500m in
the midlands the predominant rock-type interpreted is Lower Palaeozoic in age and is a more
quartz rich, sedimentary sequence compared to the limestones of the Carboniferous.
7.3.6
Temperature and geothermal gradient modelling at 5,000m
The results of temperature modelling at 5,000m are included on Map No’s. 13A and 13B. The
borehole temperature map at 5,000m depth has been modelled with temperatures calculated
only from geothermal gradients in boreholes that reached 500m. The unavailability of data at
depths below 2,500m means the data used in this map are of necessity only an indication of
the possible temperatures that may be encountered at this depth. The patterns of ‘hot spots’
are the same as for the map for 2,500m, since the data on the 5,000m map are extrapolated
from the data at 2,500m. At 5,000m the background temperatures in the south are in the
range of 60ºC – 75ºC while in the north they are interpreted to reach 100ºC – 150ºC, with a
possible maximum of 180ºC.
64
Geothermal Energy Resource Map of Ireland
8
Geothermal database – User’s Manual
This section describes the structure of the database, how to search the database and gives
examples of information that can be accessed. A guide is also provided for downloading
geothermal data sets for viewing with Mapinfo Proviewer.
Modelled dataset maps completed as part of the geothermal study have been made available
for viewing using Mapinfo Proviewer. Report maps are also provided as JPEG images and .pdf.
To view the modelled datasets using Proviewer, it is necessary to download Proviewer from
the Mapinfo website. Proviewer is a free to download software package which allows you to
open, query and print maps and datasets prepared using the full version of Mapinfo.
To download the software you will need to visit the Mapinfo website, register with Mapinfo
and download the Proviewer software at no cost. Full installation instructions are provided on
the Mapinfo website. You may need administrator privileges to install the software to your PC.
If you do not have these privileges or are unsure, please contact your IT manager. The
Proviewer installer is approximately 35Mb so use of a broadband connection is recommended.
When you have installed Proviewer, you can download, view, query and print the data and
maps for each of the modelled datasets. A brief description of how to use Proviewer is
outlined below, but a .pdf manual for using Proviewer is available for download from the
Proviewer download page.
8.1
Downloading a geothermal dataset
Choose the dataset you wish to download and right click on the link and save the .zip file to a
folder on your computer. Right click on the .zip file and select the “Extract to Folder . . . “
option. This extracted folder will contain all the necessary files to open the map and datasets
for the map you have downloaded.
65
Geothermal Energy Resource Map of Ireland
Fig. 51. Extracting datafiles etc. from a downloaded zip file.
66
Geothermal Energy Resource Map of Ireland
8.2
Viewing the dataset using Proviewer
Launch Proviewer from the Start menu. When you launch Proviewer, an Open Mapinfo
Tables and Workspaces dialog box will automatically open.
Find and open the folder containing the extracted files from the downloaded .zip file and
select the file ending .WOR (or .wor). This is the Mapinfo Workspace. When you select and
open this file, all the datasets and the window for printing the map will open.
Fig. 52. The Open Mapinfo Tables or Workspaces dialog box. The Workspace file ends with .wor
67
Geothermal Energy Resource Map of Ireland
A Layout window will open last. The Layout window can be used for viewing and printing.
You can zoom in and out using the Zoom In and Zoom Out tools. Choose the appropriate
printer and page setting for printing. The default page size is A3.
Fig. 53. The Workspace will open with the Layout Window uppermost. This window is used for viewing
the map or printing.
68
Geothermal Energy Resource Map of Ireland
8.3
Querying the datasets
To query the data, minimise the Layout window and a Map window containing the image in
the Layout can be seen.
Fig. 54. Minimising the Layout window reveals the active map window.
The contents of the Map window are stored in the Layout window for printing.
IF YOU MOVE OR RESCALE THE MAP WINDOW, THE LAYOUT WINDOW WILL CHANGE AND
YOU WILL NOT BE ABLE TO PRINT THE MAP AS SET UP BY CSA. THE ORIGINAL LAYOUT CAN BE
RESTORED BY CHOOSING CLOSE ALL FROM THE FILE MENU AND REOPENING THE
WORKSPACE.
The Map window can be resized by dragging the bottom right hand corner or using the
Maximise button on the window bar. You can also zoom in and out using the Zoom In and
Zoom Out tools on the tool bar. A variety of tools are available
69
Geothermal Energy Resource Map of Ireland
Fig. 55 Mapinfo Proviewer tools. See Users Guide or Proviewer
Help files for more information on each tool
Information can be obtained from the datasets included within the map using the Info Tool.
Clicking on a datapoint or area will produce a list of all datapoints on all layers in the map.
Clicking on any item in the info list will display all the data for the item selected from the list.
Fig. 56. Map window resized and enlarged using zoom in tool. Information on individual spring
retrieved from dataset using the Info Tool.
70
Geothermal Energy Resource Map of Ireland
9
Current Irish geothermal resources
This section includes comments on the potential in surface water and all groundwater
geothermal resources in Ireland. For a definition of source types and categories see section
3.1.
9.1
Shallow soil and sediment (0-3m) geothermal resources - GSHP
There is a very large resource country-wide of warm, moist soil conditions. This is ideal for
exploitation by rural isolated housing which have enough ground available. Even in urban
areas, office blocks, etc. can usually access an adjacent area of lawn or car park to lay down the
required loop length.
9.1.1
The future for GSHP in Ireland
9.1.1.1
Summary of Arsenal Research Report
The Arsenal report (see Boesworth 2004, Appendix XII) highlights the key items that are
needed for the GSHP market to be successfully developed. These are:
•
The availability of the heat pump technology. Educated retailers and
accredited installers able to offer heat pump heating technology are essential
•
Trained installers, which requires an organized training scheme for installers,
(plumbers, electricians and drillers), retailers, after-sales personnel and service
technicians. This allows for all market players to reach a proper standard.
•
General Acceptance. It is crucial that heat pumps offered on the market are of a
high quality and installed properly with follow-up and maintenance. If the heat
pumps do not work satisfactorily or are not of adequate/offered quality, the
market will once again suffer major setbacks, and market penetration will be
diminished.
General acceptance among the decision makers, engineers,
technicians, politicians, architects, constructors, housing councils, trustees,
landlords, tenants and electric companies is vital.
•
Economic incentives. Is it economically favourable or profitable to install heat
pumps in comparison to other heating alternatives? Heat pump installations need
to have a payback period on the initial investment (including the heat pump and
the heat source) of not longer than 7 years. Various incentives are important in
“kick-starting” the system.
•
Awareness amongst end-users produces a self developing and ongoing market
where there is a "market pull" from the end users asking for a better heating
system. There need to be large scale information campaigns on heat pumps,
giving the end users, easily obtainable and understandable information.
•
Political decisions. Legislative initiatives should require efficient renewable
heating systems to benefit over non-renewable heating systems. Standards and
regulations should be set out controlling the maximum amount of CO2 emissions
allowed from new buildings. Balancing the unit size against the energy
requirements of the building is also crucial.
In summary, the technology is available in Ireland, but not all installers have certified
equipment. Some installers are experienced, but few are properly trained. There is an
71
Geothermal Energy Resource Map of Ireland
opportunity to develop general acceptance, and this must be done during a relatively
short window of opportunity, before another market confidence collapse occurs. If this is
done, there will be a strong growth in geothermal energy exploitation, which will save
the country many tonnes in CO2 emission and many euro in fossil energy purchasing.
9.2
Surface water resources
Defined to include all surface water bodies such as lakes, rivers and estuaries / seas, surface
water sources for open-loop systems are not commonly used in Ireland or Europe in general.
However the potential for the use of sea-water, as demonstrated in Stockholm (Lindroth 2004)
is considerable in suitably environmentally sound conditions.
Open bodies of water provide large resources of water from which, even at normal
temperatures, a couple of degrees of heat can be withdrawn and concentrated. The
exploitation of the warm Gulf Stream waters along the south and west coasts, represents a
major resource for exploitation in Ireland.
9.3
Shallow (0-100m) groundwater geothermal resources
It is the case that shallow vertical boreholes with closed-loop systems are an option that is not
commonly used in Ireland due to the general availability of space. However, open-loop
systems in boreholes are very suitable to Irish conditions due to the good aquifers available
throughout the country and also the presence of some warm springs. These are already used,
as in the Mallow and UCC Art Gallery mentioned above, but there are extensive untapped
resources both in existing borehole and surface water supplies and in un-quantified gravel
aquifers.
9.3.1
Warm springs geothermal resources
To date the only utilisation of warm spring occurrence in Ireland is at the Mallow swimming
pool, where a purpose drilled borehole taps groundwater at 19.6ºC which is circulated
through a heat pump system providing much of the heat for the public swimming pool.
Proven potential exists in the St Gorman’s Well warm spring at Hotwell House, Enfield, Co.
Meath (Brück et al. 1983) and efforts are currently underway to assess the means to exploit this
known potential (Wilkinson pers. comm. 2004). The recently discovered Glanworth warm
groundwater anomaly is currently the subject of a proposal for development by the Cork
County Energy Agency (CCEA) and UCC in conjunction with Cork County Council as part of
future plans for housing in the area.
Fig. 57. Hotwell House.
Fig. 58. St. Gorman’s Well April 2004
72
Geothermal Energy Resource Map of Ireland
It is felt that the current level of information in relation to warm spring occurrence and
potential is somewhat sporadic and needs a more planned approach. It is considered that
groundwater temperatures need to be monitored in a more systematic way in order that a
representative data base can be created on a county-by-county basis. In this way resources
can be more accurately assessed, protected and utilization optimised and this is especially
important in the case of the Mallow and the north Leinster areas, which should be targeted to
increase use of this unique source.
9.3.2
Shallow (0-50m) gravel aquifer geothermal resources
Assessment of the buried gravels in the Lee Valley in Cork has taken place in a number of
studies carried out at UCC by A. Allen with T. Davis (2003) and D. Melenic (2002). Data
modelled by Tara Davis (see poster details in Appendix XII) shows the location and geometry
of the gravels in the Lee Valley from boreholes drilled for geotechnical purposes. An
interpreted cross section shows the vertical thickness of the gravels from 10-30m deep.
Current planned usage of the gravels for large heat-pump installations in a number of new
county council and UCC developments in the city confirm this as a large and valuable resource
(pers. comm.. M. O’Brien, Cork City Council & A. Allen, UCC, 2004). The phenomenon of buried
valley gravels is one that is not unique to the Cork area but from what is known about their
origins there is more potential for their location in river valleys in the south and southwest
coastal areas than in other coastal areas. Outside of the Cork area, other gravel aquifers
throughout the country including the palaeo-channels in the midlands have not been fully
quantified in terms of their geothermal resource potential. However there is detailed local
data available for gravel deposits throughout parts of Ireland which can be accessed through
the Groundwater Section of the GSI which could be incorporated into local more detailed
studies on areas of potential gravel aquifer source geothermal energy.
9.3.3
Urban Heat Island Effect geothermal resources
Areas with gravel aquifer resources underlying large urban areas may have additional
geothermal potential, due to the Urban Heat Island (Sweeney 1987). Recent studies have
shown the potential for development in Dublin (Ball 1991) and Cork (Allen et al. 2003 & Davis
2003), where groundwater has been measured at up to 13ºC or 14ºC respectively. Elsewhere
in the country however, these resources have not yet been assessed. The O’Reilly Building in
Trinity College, Dublin and the UCC Arts Museum in Cork are two of the recent cases of Urban
Heat Island Effect utilised in the country. Currently the O’Reilly Building system is out of
commission due to building works at the site, but Ball (1991) shows there to be more potential
in the area (see Table 12). The Cork shallow gravel aquifer systems with their urban heat island
effect yield very large water volumes with temperatures up to 13ºC. Cork City Council is
progressive in developing this resource.
1.
2.
3.
4.
5.
Site
Flow
ESB Offices Block B,
Fitzwilliam St.
Royal
College
of
Surgeons – Link Bdg
Royal
College
of
Surgeons – Old Bdg
Royal
College
of
Surgeons – Millen Ho.
Premium Investments,
6.1
l/s
1.5
l/s
4.5
l/s
8 l/s
2.7
Temperature
16ºC
Heating / COP
Cooling
202kW
4.2
4.2 years
14ºC
40kW
4.1
17.8 years
14ºC
145kW
4.1
5.4 years
14ºC
220kW
4.2
14ºC
76kW
4.3
73
Pay-back
19 years
Geothermal Energy Resource Map of Ireland
6.
7.
2 Dawson St
Bord Gais,
Pearse St.
Irish Life,
George’s Quay
l/s
2.9
l/s
30 l/s
14ºC
80kW
4.2
14ºC
1008kW / 4
756 kW
“3.2” years extra
over oil boiler
Table 12. From Ball (1990) The possible development of seven sites in south central Dublin
9.4
Other shallow geothermal resources
The use of some specially designed conductive cement material such as Enercret (2004) which
has high heat conductivity can be very beneficial in providing geothermal solutions in large
construction projects with space restrictions. Enercret can be used in the construction of piles
or other sub-surface structures and if installed with closed loop heat-pump collectors can be
very effective in combining structural components of building with renewable energy.
Among other possible applications of heat-pump technology is the use of landfill as a heat
source for a heat-pump collector, since this is really a bio-source of energy it is not discussed
here.
9.5
Shallow (0-100m) bedrock aquifer geothermal resources
Large shallow bedrock aquifers in Waulsortian limestone and dolomite and in Kiltorcan
Sandstone are generally considered vulnerable aquifers and often comprise a vital part of local
water supplies. It is therefore considered from this study that the geothermal resource
contained in these aquifers should only be exploited in conjunction with providing a local
water source that is either already in place or is planned for an area. Vertical boreholes can
exploit all of these sources, either with open or closed-loop systems. Closed-loop systems
have the advantage that they have no other impact on aquifers apart from the heat
withdrawn.
9.6
Intermediate (100-1,000m) and deep (1,000-5,000) groundwater geothermal
resources
The presence of aquifers in Ireland is largely dependent on fracturing and/or dolomitization
(pers. comm.. E. Daly 2004), both of which are sporadically developed and are not generally
predictable from stratigraphy. The prediction of fracture density and dolomitization resulting
in increased porosity and permeability is dependent on local data density. For instance, it has
been calculated in parts of Tipperary where fracturing is intense that a borehole density of 1
borehole per 10m would be necessary in order to create a predictive model of fracture
distribution. The same may be true for deeper levels. Hydrogeological investigation in Ireland
has shown that aquifers are dependent on both lithology and fracture density. This becomes
more complex when, at depth, the presence of fracturing can result in either an increase or
decrease in local temperature and geothermal gradient. This can occur because fracturing can
either increase connectivity to surface and therefore result in infiltration of cooler surface
water or allow circulation of water from deeper levels thereby increasing temperatures.
The relatively young sedimentary basin in the northeast of Northern Ireland is unique in the
Irish context both for the age of rocks and for the geothermal gradients recorded there. These
high geothermal gradients compare well similar age basins in the south of England and parts
of France and Belgium. These geothermal gradients in Northern Ireland are the highest
encountered in this study and are considered reliable as they have been measured in a
number of deep boreholes.
74
Geothermal Energy Resource Map of Ireland
9.7
Enhanced Geothermal Systems or Hot Dry Rock resources
Previously known as Hot Dry Rock (HDR), Enhanced Geothermal Systems (EGS) (see Sections
3.1.7 & 4.5) have never been previously considered in the Irish context due to perceived low
geothermal gradients and/or lack of predictability of these geothermal gradients. Considering
the temperature constraints on developments using EGS this is a valid concern for the time
being.
9.7.1
Potential for Enhanced Geothermal or Hot Dry Rock Systems in Ireland
From the data reviewed in this study it is felt that considerable uncertainty remains in
estimating temperatures at depths of 2,000m or greater. However, results of this review
indicate a number of areas with the potential for high temperatures up to >150ºC at a depth
of 5,000m. These areas are the north-western part of Cavan / southwest Fermanagh, and
northern Antrim / Londonderry. Measured data in both these areas show temperatures of
57ºC in Cavan at 2,000m and 63ºC in Antrim at 1,500m depth, indicating overall geothermal
gradients between 24ºC/km and 35ºC/km. In parts of north County Meath there are
geothermal gradients between 25 and 30ºC/km at 1500m depth, which is also encouraging.
Additional data in these areas is required to confirm potential for EGS/HDR before any deep
drilling for exploitation is attempted. It is recommended that all drilling in these areas is
monitored closely in order to confirm these gradients and increase data coverage. It is likely
that deep drilling will continue in parts of the Antrim / Londonderry area of interest and
special attention should be given to any opportunities for temperature monitoring in this
area.
As EGS technology develops, it is likely that in the future, it will become of greater interest to
Ireland.
9.7.2
Heat flow in the continental crust
9.7.2.1
Regional tectonic setting
In general, Ireland is considered to be tectonically stable. The only evidence of tectonism in
recent times has been rare, small earthquakes in the Irish Sea basin. Except for small warm
spring areas there are no strongly geothermally active regions. However recent work in the
Irish Sea confirms the presence of some previous geothermal activity in the Irish Sea basin.
Ongoing work indicates the presence of a palaeo hot-spot which may have been active during
pre-Quaternary times (Section 3.1.4 above). This palaeo hot-spot has been postulated as
possibly influencing the distribution of river systems draining westward across Ireland and
resulting in the formation of the so called ‘palaeo-channels’ in the Irish midlands (Hardy, 2003).
9.7.2.2
Heat flow data for Ireland
Heat flow data for Ireland as compiled and illustrated on Map 21A & B is derived from the work
of Brock and Burdon (1984, 1988a,b, 1989). It shows a similar distribution as that seen in the
geothermal gradient maps and the temperature maps at depth in the Irish sub-surface.
However some areas, such as the granites in Galway, east Leinster and Donegal areas, may
have higher geothermal gradients than modelled in the temperature maps as there were no
available deep boreholes for those areas. Maps 21A & 21B show that heat flow values are low
in the south and high in the north, with relatively higher flow rates in Galway, Dublin and
Cavan-Donegal. These findings are compatible with the geothermal gradient maps.
75
Geothermal Energy Resource Map of Ireland
10
Technical summary and conclusions
10.1
10.1.1
•
•
•
•
10.1.2
•
•
•
•
•
10.1.3
•
•
•
•
Shallow geothermal
Soil (0-2m)
Ireland’s temperate climate results in relatively stable soil temperatures of between
9.5ºC and 12ºC at depths of 30 – 150cm.
Frequent rain recharge results in Ireland having very suitable conditions for the use of
ground source heat pumps. The soil moisture is constantly being recharged by run-off
which maintains the heat and conductivity, thus warming the area around the heatpump collectors.
Thick soil cover in Ireland also simplifies the logistical aspects of ensuring the
geothermal collector is not easily damaged.
One-off houses have adequate space for geothermal collectors. This provides a real
option for renewable energy usage in rural Ireland and small housing developments.
Surface water
The exploitation of surface water as a geothermal resource is not significantly
developed in Ireland. However there are a few small projects using reservoirs and
rivers.
The abundance of small lakes, particularly in the north midlands, is considered to be a
neglected energy source which could potentially be exploited using heat-pump
technology, subject to environmental impact review. Many of the small lakes referred
to are located adjacent to single dwellings and could be exploited domestically.
Streams, lakes and rivers in Ireland have as yet unquantified potential as energy
sources as a centralised database of surface water is not yet available.
Few examples of large heat pump collectors in sea water exist, though the Stockholm
example provides a very interesting demonstration of the technology. The provision
of 180MW of heating and 60MW of cooling capacity, should be of special interest to
Ireland, located in the Gulf Stream.
Large flow-rate, mains water supply can be tapped as a high volume heat source, e.g.
Tramore Civic Offices.
Shallow (0-50m) gravel aquifers
It has been identified through numerous recent studies that large gravel bodies are
often rich aquifers with strong potential for geothermal exploitation. Because of high
water volumes this is possible even in areas without enhanced water temperatures.
Again, Ireland is fortunate in having a temperate-wet climate continuously recharging
large stores of relatively warm water in the subsurface.
Areas currently being exploited such the Cork Buried Valleys (e.g. UCC Art Museum)
provide a very important demonstration of the potential of this resource. The
marginal raising of groundwater temperature, due to the urban heat island effect, also
improves the economics of this resource exploitation.
Studies on ‘palaeo-channel’ gravel aquifers in the midlands of Ireland indicate similar
potential to the buried channels of south Co. Cork and therefore significant potential
resources, if linked to suitable development opportunities.
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Geothermal Energy Resource Map of Ireland
10.1.4
•
•
•
Urban Heat Island Effect resources
In the Dublin city area the utilisation of the ‘Urban Heat Island Effect’ has been
demonstrated successfully (Ball 1991).
No volume calculation of gravels with potential for Urban Heat Island Effect resources
has been attempted to date, as detailed local information is required for each urban
area.
Cork and Dublin shallow gravel aquifers provide excellent opportunities for
exploitation of this geothermal resource.
10.1.5
Warm springs
In summary for this study groundwater is defined as having temperatures over 12ºC in the
south of the country and over 11ºC in the north of the country. This is related to climatic
variation from south to north. The data used for modelling the distribution of warm springs in
Ireland is compiled from sources involved with monitoring warm springs at various periods
during the past 23 years. There is an error of up to 2ºC in the temperature from place to place
due to thermometer accuracy and variation in the time of year at which monitoring took
place. Only the maximum recorded temperature value at each warm spring/groundwater has
been modelled in order to present an estimate of regional variation in surface water
temperature and the location of enhanced temperatures (Map 6A). Data on Warm springs in
Northern Ireland has not been compiled in this study but will be included in the new
INTERREG study being conducted by the CSA Group to review the geothermal resources in
Northern Ireland. An updated map based on this study will also be provided to SEI on
completion of the study in March 2005.
The following points present the main aspects of warm spring potential in Ireland.
• Warm spring and enhanced shallow ground water temperatures vary from just above
normal groundwater temperatures to a maximum of 23.5ºC, as observed in a borehole
at Glanworth Co. Cork.
• This study has confirmed that the areas with the most abundant warm springs are the
Mallow area in north Co. Cork and the Dublin/Meath/Kildare area (Map 4). There is
surprisingly little development of this known source of geothermal energy. Only at
Mallow swimming-pool is there current usage. This area of utilization should be
actively encouraged.
• Recent drilling (by Cork County Council) for local water supply, in the Glanworth area,
has encountered elevated temperatures in a well-known regional aquifer there, thus
extending eastward the known areas of warm springs from the Mallow area.
• Although warm springs are primarily located in the south of Ireland new data from this
study has shown that elevated shallow groundwater temperatures are present at
Navan Co. Meath and at Kingscourt Co. Cavan, which indicate some potential for warm
springs in the north midlands.
• Geological control is considered critical in the distribution of warm springs and can be
used to explain their occurrence and distribution, though prediction is often complex
(Map 6B & C).
• Of most importance in the distribution of warm springs is the presence of deep
tapping structures such as the Carboniferous Basin controlling, Blackrock-Rathcoole
fault at the north side of the Leinster Granite in south Co. Dublin (Map 7A) and the
thrust fault at the north side of the Devonian in Mallow (Map 8A & B).
77
Geothermal Energy Resource Map of Ireland
•
The north-south fault controlling the Kingscourt Inlier has some warm spring
potential.
10.1.6
Shallow (0-100m) bedrock aquifers
There are very few examples of vertical borehole closed-loop systems in Ireland, except for the
Green Building in Temple Bar, Dublin. However in order to provide an estimate of the likely
temperatures that are present in bedrock modelling of the temperatures at 100m is presented
on Map 9A & B.
The following points are relevant;
• There is some overlap of this category with warm springs and localised enhancement
of bedrock groundwater temperatures will result from proximity to warm springs (Map
6A, B & C).
• These aquifers are generally the same aquifers which provide the local water resources
throughout Ireland and therefore are best assessed in conjunction with county water
protection schemes.
• As with gravel aquifers Ireland’s temperate climate and reliable rainfall results in large
quantities of relatively warm water (>10ºC) at shallow depths of between 30 and 50m.
Ireland is therefore ideal for the use of heat-pumps on high-yield aquifers.
• The shallow aquifer map of Ireland (Map 3) provides a compilation of the more
significant shallow bedrock aquifers more detailed bedrock aquifer resource maps are
available on the GSI website (www.gsi.ie).
• As with gravel aquifers, shallow rock aquifers can provide large quantities of water and
for this reason elevated temperatures are not critical in their use as heat pump
sources.
10.2
10.2.1
•
•
•
•
•
•
•
Medium (100-1,000m) to deep (1,000-5,000m) geothermal
Data
Temperature data from a total of 40 new boreholes has been added to the geothermal
database
The field programme carried out with this study accessed 50 new boreholes. 32 of
these boreholes gave data that were considered reliable and are included in data
modelling for this study. Data on an additional 11 deep boreholes drilled in oil
exploration programmes throughout Ireland (drilled since the previous study) and also
an additional 8 boreholes monitored by mineral exploration companies during work
programmes have also been incorporated.
Only boreholes deeper than 300m have been found in this study to give reliable
geothermal data for extrapolation to depth.
Spot decreases in geothermal gradient have been interpreted as reflecting the
presence of localised karstification causing rapid transfer of cold surface water to deep
parts of an aquifer.
This study has also confirmed high gradients in the west Clare region.
The relative absence of data in the west and northwest has resulted in inconclusive
estimates of the geothermal gradients there.
Caution must be applied when extrapolating geothermal gradients below areas with
warm springs as the high surface gradient results in an apparent low geothermal
gradient at depth.
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Geothermal Energy Resource Map of Ireland
•
•
10.2.2
•
•
10.2.3
•
•
•
•
•
•
•
•
•
The distribution of boreholes considered in this study is biased towards the areas
underlain by Carboniferous aged rocks, resulting in poor data distribution in older rock
particularly in coastal areas in the southwest, west and northwest.
A more detailed analysis of the data from Northern Ireland will be included in a new
study being by the CSA Group reviewing the geothermal potential of the INTERREG
area of Northern Ireland and the surrounding counties in the Republic of Ireland. An
updated map based on this study will be provided to SEI on completion of the study in
March 2005.
Geology
Data indicates that the presence of Lower Palaeozoic rocks at relatively shallow (5001000m) depths below surface results in lower geothermal gradients as seen in the
southeast Galway and east Clare area (Map 14B & 15B).
From this study it is apparent that there is still a relationship between the present day
areas of high heat flow and the location of mineral deposits which record the palaeoheat flow. i.e. the same fault structures are still penetrating deeply into the crust.
Geothermal gradient and temperature variation
The CSA study having reviewed and analysed previous work on geothermal potential
and updated this with new data has confirmed the regional variation in the
geothermal gradient from an average of 10-15ºC/km in the south of the country to
and average of 25-30ºC/km in the north of the country (Maps 11 – 13).
The highest recorded geothermal gradient at 1000m in the republic is 28.4ºC/km and
is located in the vicinity of north Co. Meath in the Navan area (Map 11A & B).
Areas with abundant warm springs ex. Mallow, show an initial rapid increase in
temperature downward which then drops off rapidly with depth and results in lower
than average geothermal gradients.
A preliminary analysis of data from Northern Ireland has been included in this study
and indicates that the highest geothermal gradients in both the Republic of Ireland
and Northern Ireland are located in the Lough Neagh to Ballycastle/Antrim area. This
is interpreted as the result of thinned crustal rocks underlying the Antrim Flood
basalts.
When fractured or karstified the Waulsortian limestone records cold temperatures
unless adjacent to large deep faults, as karst/fracturing as relatively cold surface water
can penetrate deep into the ground water.
Carboniferous rocks acts as good insulators and geothermal gradients are relatively
low in the Carboniferous where fracturing is absent. This results in the presence of
relative cold areas in the Carboniferous even in the more northerly parts of the
Carboniferous basin where the geothermal gradient is higher.
The abundance of deep penetrating and more recent faults in the south of the country
results in the continuous leaking of heat to the surface and therefore low geothermal
gradients.
There needs to be a critical combination of fractures/karst/porosity and lithologies to
result in high geothermal gradients.
In this study CSA has recalculated geothermal gradients for some of the boreholes
included in earlier studies and obtained higher values than previously. Note: in
previous studies often an overall geothermal gradient was used whereas, in fact,
gradients often increase or decrease downward.
79
Geothermal Energy Resource Map of Ireland
•
•
•
From this study it is interpreted that at 2,500m depth from surface there is a predicted
temperature of 50°C generally north of the Limerick-Dublin line with ‘hot-spots’ in the
region of 80°C in Co. Clare, the east midlands and north Co. Cavan (Map 12A & B).
The results of this study indicate that the best potential for medium and deep
geothermal resources in the Republic of Ireland are in the Clare/Galway area, east
midlands and northwest midlands where temperatures of 40°C - 60°C are recorded at
a depth of 1,000m.
Granodiorites in Carlingford in Co. Louth and south Co. Down have been identified as
having the highest radioactivity levels of granites in Ireland and therefore have the
potential of high geothermal gradients at depth. However no data was available to
test this hypothesis with this study. These are considered to be prospective areas for
high temperatures.
10.2.4
Heat flow
Heat flow density is a measure of the actual amount of heat flowing in a given area and thus
gives a value which combines the thermal conductivity of the area with whether or not there
is a heat source in that area. Heat flow density measurements from 4 sites have been added to
a previous database and modelled. As expected modelling of the heat flow density data
(Maps 21A & 21B) in this study show a good correlation with modelled geothermal gradients
(Maps 14 – 17). Heat flow can change with depth and can also result in lower geothermal
gradients where it results in high transmissivity of heat to the surface resulting in more rapid
cooling of the surface of the crust. Therefore data on measurements of heat flow need to be
applied with caution.
10.3
•
•
•
Enhanced Geothermal Systems or Hot Dry Rock
There may be potential for exploitation by Enhanced Geothermal Systems of deep
geothermal resources in Ireland and this will become apparent as more temperature
data are collected. Deep Carboniferous and more recent sedimentary basins, as found
in Northern Ireland are critical in the search for deep geothermal resources
Clearly definable geological controls are difficult to evaluate in relation to geothermal
gradients within deeper levels of the sub-surface in Ireland.
Extrapolation of borehole data from boreholes >500m depth indicates that at 5,000m
depth the predicted temperatures are >100°C north of the Limerick-Dublin line or the
Iapetus Suture (Map 13A & B).
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Geothermal Energy Resource Map of Ireland
11
Non-technical conclusions
11.1
General
Information on geothermal potential in Ireland is now more accessible and is directly usable
by diverse groups including:
County Councils and regional authorities
Government strategic/spatial planning professionals
Engineers/architects
Industry
Agriculture
Community Groups
Environmentally aware individuals
11.2
11.2.1
•
•
•
11.2.2
•
•
11.2.3
•
•
11.2.4
•
11.2.5
•
Shallow geothermal
Soil
One-off houses have adequate space for heat-pump collectors to provide a real option
for geothermal energy usage in rural Ireland and small housing developments.
The use of ground source heat-pumps for office blocks or apartment blocks is
considered to have very good potential in Ireland. The Tralee Tax Office is seen as a
flagship example of this usage.
The use of ground source heat-pump borehole collectors also has specific potential
where space is a premium e.g.; The Green Building, Temple Bar, Dublin.
Surface Water
Streams, lakes and rivers in Ireland have as yet un-quantified potential as energy
sources since a centralised database of surface water is not yet available.
Few examples of large heat pump collectors in sea water exist, though an example at
Stockholm provides a useful demonstration of the technology. This should be of
special interest to Ireland, located in the warm waters of Gulf Stream
Shallow gravel aquifers and Urban Heat Island Effect
Cork and Dublin shallow gravel aquifers provide excellent opportunities for
exploitation of this resource.
Studies on gravel aquifers in the midlands of Ireland indicate similar potential to the
buried gravels of south Co. Cork and therefore significant potential resources may
exist.
Warm springs
This study has confirmed that the areas with the most abundant warm springs are the
Mallow area in north Co. Cork and the Dublin/Meath/Kildare area. There is surprisingly
little development of this source of geothermal energy. Mallow swimming-pool is the
only example of current usage of this resource.
Shallow bedrock aquifers
There is good potential for the utilization of shallow bedrock aquifers and much data is
already available through water resource/protection studies.
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Geothermal Energy Resource Map of Ireland
11.3
Medium to deep geothermal
•
The results of measurements and modelling from the 94 boreholes, indicate that the
best proven potential for medium and deep geothermal resources in the Republic of
Ireland are in the northeast (Navan area) and northwest midlands where temperatures
of up to 40°C - 60°C are either recorded at a depth of 1,000m. Modelling of
extrapolated or calculated data also shows potential for these temperatures at 1,000m
in the west Clare and east midlands areas.
• From this study it is also interpreted that at 2,500m depth from surface there is
potential for temperatures of 60°C generally north of the Limerick-Dublin line with
‘hot-spots’ in the region of 80°C in Co. Clare, the east midlands and north Co. Cavan.
At 5,000m depth values greater than 100°C are predicted north of the Limerick-Dublin
line.
Medium to deep geothermal resources are also referred to as geothermal heat exchanger
(GHE) systems. GHE technology is appropriate to the exploitation of geothermal energy
resources in Ireland. The principal cost is the drilling of a deep borehole. Aachen University will
commence drilling a deep geothermal borehole this year and financial information on the cost
of this operation will be available when the well is completed in the autumn.
11.4
Enhanced Geothermal Systems or Hot Dry Rock
There may be potential for the exploitation of Enhanced Geothermal Systems (previously
known as Hot Dry Rock) resources in Ireland and this will become apparent as more
temperature data are collected. The best sites will probably be west Clare, Navan, and
northwest Cavan with possibilities in the Kildare area along the line of the Iapetus Suture.
Deep geothermal technology includes dual well systems (production and injection well
<3000m), hot dry rock (<3,000m) and deep geothermal heat exchangers (<3,000m). Hot dry
rock and dual well technology (HDR) requires a combination of favourable geological
conditions and large local heat consumption (approx 10MW) in the proximity of the plant.
Deep hot rock with some degree of initial permeability is required for HDR. In Japan HDR is
associated with the margins of hydrothermal fields. In Europe HDR is associated with areas
such as the Rhine Graben where the regional stresses tend to be low, allowing stimulation and
circulation to be carried out at relatively moderate pressures. The HDR Soultz project
(http://www.soultz.net/) is located in the Rhine Graben where higher temperatures can be
encountered at shallower depth, a relatively low minimum stress gradient is likely and the
probability of finding joints / faults at depth, which are already partially open, is high.
Investigations in Ireland have not identified a site with this combination as yet, although
geothermal anomalies in the Lough Neagh area combined with Tertiary faulting in Northern
Ireland is worthy of further investigation. The concept is to make an artificial hot aquifer by
drilling two boreholes into deep rocks, then fracturing the rock between them so water can
percolate from one to the other. Cold water is pumped down one borehole and extracted hot
from the other. Hot dry rock can work but it is expensive and failure is common. All of the
European HDR projects are in the drilling phase and surface heat exchange facilities are not
yet in place.
Deep geothermal heat exchange (GHE) does not require specific geological conditions in the
subsurface and could be applied more readily than HDR in Ireland. The local consumer
potential determines the location of the deep geothermal heat exchanger. The economic
benefit of geothermal power plants results from the long term stability and predictability of
heat production costs and from the decoupling from rising costs of fossil fuels. With the
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Geothermal Energy Resource Map of Ireland
establishment of an international emissions trading scheme an additional commercial upside
potential exists.
11.5
Relevant Irish legislation
It is not clear how Geothermal Energy should be treated within the existing Irish fiscal and
regulatory framework. There is no doubt that French legislative set-up was important in
ensuring the success of the geothermal developments of the Paris and Alsace Basins. In
Germany geothermal energy, along with coal-bed methane and coal mine methane, is a
resource according to German mining law and geothermal projects are considered to be a
branch of the mining industry. An application for a scientific licence for exploration and
economic production of geothermal energy is made to the mining authorities. In the
Philippines exploration for geothermal energy is handled in the same way as oil exploration,
exploration licences are offered and production licences are granted. In Ireland the
responsible Department could be the Department of Communications, Marine and Natural
Resources. There are two divisions within the Department that might be responsible, the
Petroleum Affairs Division and the Exploration and Mining Division. Further research is
required to establish the appropriate fiscal and regulatory regime for the exploitation of
geothermal energy.
83
Geothermal Energy Resource Map of Ireland
12
Geothermal energy potential – recommendations for increased use
There is significant potential for the development of Irish sources of geothermal energy in the
following areas.
• Private housing – heating / cooling using shallow horizontal or vertical heat
exchangers
• Offices / utilities / industrial / agricultural enterprises – heating / cooling using shallow
or deep vertical heat exchangers/urban heat islands
• In particular the requirements of hospitals, breweries, creameries and industry for both
heating and cooling capacity should be emphasised
• Warm springs and urban district heating systems (potential Glanworth)
• Heat pump collectors in sea water
• Combination of geothermal energy with other energy sources, eg. solar
• (Industrial)
• Deep drilling options similar to Southampton and Aachen
• Enhanced geothermal or hot dry rock systems considered a strategic option for the
future
12.1
Recommended Actions
In order for geothermal energy to be successfully exploited, there needs to be initiatives in
several areas.
12.1.1
Heat-pump technology recommended actions
Whether this is in the area of shallow soil, water, heat island or shallow aquifer, it needs
government intervention and support (Boesworth 2004).
This includes the areas of;
• Standards of equipment
• Training of technicians
• Grants to encourage its usage
• Tax penalties to discourage its neglect
• Planning requirements to maximise its usage as has been initiated in Cork County
development plan (linked to grants system)
• The flagship developments should be highlighted as good practice, e.g. Tralee motor
tax office, UCC Arts Museum and the Green Building Temple Bar
Additionally
• The exploitation of surface water as a heat-pump source is considered an area where
there is much potential which needs assessment and coordination of efforts currently
ongoing. The exploitation of sea-water, as demonstrated by the successful Stockholm
scheme, should be particularly targeted.
• As it was not possible within the scope of this study to quantify the potential for
‘Urban Heat Island Effect’ resources in smaller cities and urban areas of Ireland it is
recommended that all Urban District Councils undertake a review of these resources in
their own area and consider routine temperature monitoring of all boreholes drilled in
their jurisdiction.
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Geothermal Energy Resource Map of Ireland
•
•
12.1.2
•
•
•
•
12.1.3
•
•
•
It is recommended that the County Councils work, perhaps in conjunction with the
GSI, to undertake routine monitoring of temperature to help to map the potential of
large gravel aquifers as heat sources on a countywide basis.
There is an urgent need for County Councils and local utility providers to be familiar
with the economic potential of elevated temperatures in high volume aquifers, as is
demonstrated by the situation in Glanworth, Co. Cork and the need for protection of
these resources within the planning guidelines.
Statutory perspective recommended actions
Requirements include the compulsory training of technicians, certification of
equipment, and education of end-users.
Requirement for enhanced building standards, inclusion of renewable energy in all
planning applications,
Setting in place of incentives such as grants, VAT exemptions, tax credits, CO2 emission
penalties, etc.
Education of the industry and of the public through large publicity and education
campaigns
Public awareness recommended actions
Increased public awareness is needed to accelerate uptake of geothermal exploitation,
this requires a sustained information campaign.
Interaction on the issues by SEI, GSI and GAI is required in order to provide public
access to information.
An enhanced profile for geothermal energy within the GSI is also recommended for
the furthering of the utilization of this resource.
12.1.4
Medium to deep geothermal exploitation recommendations
In this study, areas of the country have been identified where deep heat is more readily
accessible. One or more sites should be selected where a deep borehole can be drilled to
access this heat and investigate the parameters of its extraction in an Irish context. This will
involve the detailed study of the geology of the location and an assessment of the best
manner of engineering the borehole. It will be necessary to adapt the operation as it
progresses in response to the drilling conditions encountered.
There is an urgent need for a number of deep test boreholes to determine the existence of
permeability and the availability of warm water at those sites, with identified highest potential
and matching energy needs.
The choice of a university campus in Ireland as a demonstration geothermal project is
recommended because of the significant research potential in the area of geology, geophysics
and engineering that a deep borehole would provide. Research and development funding in
geology, geophysics and engineering would contribute to the grant aid needed to achieve the
drilling of the geothermal borehole.
One cost effective solution may be to examine the possible use of about 10 abandoned
onshore deep oil exploration wells in Ireland.
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Geothermal Energy Resource Map of Ireland
13
References, Bibliography and Further Reading
Aldwell, C.R. 1981a. Notes on Conference: Heat pumps for Hot Water, UCG, 24 April 81
Geological Survey of Ireland Internal Report
Aldwell, C.R. 1981b. Groundwater Heat Pumps. December-81, Conference Paper
Aldwell, C.R. 1982. Groundwater as a conveyor of energy. Subject 4 of symposium held at BRGM
Orleans, Nov. 1982 11pp.
Aldwell, C. R. 1984. Geothermal Investigations and Potential Development in Ireland.
Geological Survey of Ireland Internal Report. 33pp.
Aldwell, C.R. 1990. The Second Phase of Geothermal Investigations in Ireland 1986-89
Geological Survey of Ireland Internal Report, 34pp.
Aldwell, C.R. ~1992. Low Temperature Geothermal Resources in Ireland 10pp.
Aldwell, C.R. ~1992. Low Temperature Geothermal Energy in Ireland 7pp.
Aldwell, C.R. 1996. Mallow Springs, County Cork, Ireland. Environmental Geology, 27, 82-84.
Aldwell, C.R. 1998. Visit to Portugal 14-18 March 1998. Geological Survey of Ireland Internal
Report., 12pp
Aldwell, C.R. & Burdon, D.J. 1978. Proposed Geothermal Project for Ireland. January-78
Geological Survey of Ireland Internal Report
Aldwell, C.R. & Burdon, D.J. 1980. Hydrogeothermal Conditions in Eire.
International Geological Congress, Conference Paper.
September-80
Aldwell, C.R. & Burdon, D.J. 1984. Energy potential of Irish ground-waters. Transcript of
presentation to the Geol. Soc. 79pp.
Aldwell, C.R., Burdon, D.J. & Peel, S. 1985. Heat Extraction from Irish Groundwater. September85, International Association of Hydrogeologists, Congress Paper, Cambridge.
Aldwell, C.R. & Burdon, D.J. 1986. Energy potential of Irish ground-waters. Quarterly Journal of
Engineering Geology, London, 19, 133-141.
Allen, A. & Milenic, D. 2003. Low enthalpy geothermal energy resources from groundwater in
fluvioglacial gravels of buried valleys. Applied Energy. 74, 9-19.
Allen, A., Milenic, D. & Sikora, P. 2003. Utilisation of the urban ‘heat island’ effect on shallow
gravel aquifers as a source of low enthalpy hydro-geothermal energy. European
Geothermal Congress, Hungary, 2003. 8pp.
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Geothermal Energy Resource Map of Ireland
Andreescu, M. Burst, D., Demetrescu, C., Ene, M. & Polonic, G. 1989. On the geothermal regime
of the Moesian Platform and Getic Depression. Tectonophysics, 164, Amsterdam, p281286.
Bach, B. & Péter, T. Quality of heat pump systems through high-quality training schedules.
European Geothermal Congress, Hungary, 2003, 5pp.
Bäckstrom, A. & Henkel, H. 2004. Fracture frequency in three dimensions for assessment of
geothermal energy resources in crystalline rocks. Abstract 26th Nordic geological Winter
eeting, Uppsala, p153.
Ball, D. 1991. The investigation to determine the extent and usability of groundwater in the
centre of Dublin as a means to reduce consumption of energy derived from the
combustion of fossil fuels. ERA report to Dept. of Energy. 266pp.
Balling, N., Kristiansen, Breiner, N., Poulsen, K. D., Rasmussen, R. & Saxov, S. 1981. Geothermal
Measurements & Sub-Surface Temperature Modelling in Denmark. Geoskrifter 16,
Aarhus. 172pp.
Blackwell, J. & Connor, B. 1994. Mallow / Kilmallock Spa Tourism Development Plan
Jonathan Blackwell and Associates with Contour plan Consultancy and Brian P Connor
and Associates, December-94.
Boesworth, R. 2004a. Campaign for take-off for renewable heat pumps in Ireland.
Unpublished Arsenal Research report to Sustainable Energy Ireland, April 2004. 139pp.
Boesworth, R. 2004b. Campaign for the take-off of a sustainable heat pump market in Ireland.
Geothermal Association of Ireland Newsletter 7, May 2004, p8-10.
Boissavy, C. 1997. Geothermal Energy in Europe. European Geologist magazine, 5, p33-39.
Brock, A. 1979. Geothermal Energy in Ireland. Report to National Board of Science and
Technology, 68pp.
Brock, A. 1989. Heat flow measurements in Ireland. Tectonophysics, 164, p231-236.
Brock, A. & Barton, K. J. 1982. Third six monthly report on the progress of work carried out by
University College Galway under EEC contract EG-A-1-022-EIR (H), 8pp.
Brock, A. & Barton, K. J. 1984. Equilibrium Temperature and Heat Flow Density Measurements
in Ireland. Final Report on EEC contract EG-A-1-022-EIR (H), 115pp.
Brock, A. & Barton, K. J. 1988a. Temperature, Heat Flow and Heat Production Studies in
Ireland. Periodic Report for the period from July 1987 to December 1987, EEC contract EN3G0065-IRL (GDF) 6pp.
Brock, A. & Barton, K. J. 1988b. Temperature, Heat Flow and Heat Production Studies in
Ireland. Periodic Report for the period from January 1988 to June 1988, EEC contract EN3G0065-IRL (GDF), 18pp.
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Brock, A. & Barton, K. J. 1989. Temperature, Heat Flow and Heat Production Studies in Ireland.
Periodic Report for the period from July 1988 to December 1988, EEC contract EN3G-0065-IRL
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