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Special Issue "Geothermal Energy: Delivering on the Global Potential"

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A special issue of Energies (ISSN 1996-1073).

Deadline for manuscript submissions: closed (30 April 2014)

Special Issue Editor

Guest Editor
Prof. Dr. Paul Younger, FREng

School of Engineering University of Glasgow Room 623, James Watt Building (South), Glasgow G12 8QQ, Scotland
Website | E-Mail
Interests: geothermal energy; resource evaluation; development; performance assessment

Special Issue Information

Dear Colleagues,

After decades of being largely the preserve of countries in volcanic regions, interest in geothermal energy—for both heat and power applications—is now spreading worldwide, as it is one of the few renewables that offers baseload and despatchable energy with minimal emissions. This Special Issue of Energies will explore the latest developments in technology to enable the diffusion of geothermal energy through far more of the globe. While papers concerning volcanogenic geothermal systems are welcomed, we would particularly welcome those that offer insights also applicable to mid-enthalpy resources elsewhere. The issue will encompass:

  • novel geothermal resource exploration and characterisation techniques
  • more efficient geothermal power cycles, especially binary systems
  • evaluation methodologies for geothermal energy as a renewable heat resource
  • monitoring, modeling and other performance assessment methodologies for operational geothermal systems
  • explorations of the future of geothermal energy, such as EGS at one end of the enthalpy spectrum and supercritical systems at the other

We welcome papers on primary, blue-skies research, as well as cutting-edge exemplars from industrial practice that can be used to encourage sustainable development and performance of geothermal energy systems worldwide.

Prof. Dr. Paul Younger, FREng
Guest Editor

Submission

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Energies is an international peer-reviewed Open Access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1400 CHF (Swiss Francs).

Abstract Proposal Deadline: 15 December 2013
Full Manuscript Deadline: 15 March 2014

Print Edition available!
A Print Edition of this Special Issue is available here.

Hardcover: 54.00 CHF*
Pages: 30, 400
*For contributing authors or bulk orders special prices may apply.
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Keywords

  • development
  • EGS
  • energy
  • exploration
  • geothermal
  • heat
  • monitoring
  • modeling
  • power
  • renewable
  • resource
  • supercritical

Published Papers (20 papers)

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Editorial

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Open AccessEditorial Geothermal Energy: Delivering on the Global Potential
Energies 2015, 8(10), 11737-11754; doi:10.3390/en81011737
Received: 8 October 2015 / Accepted: 9 October 2015 / Published: 19 October 2015
Cited by 2 | PDF Full-text (666 KB) | HTML Full-text | XML Full-text
Abstract
Geothermal energy has been harnessed for recreational uses for millennia, but only for electricity generation for a little over a century. Although geothermal is unique amongst renewables for its baseload and renewable heat provision capabilities, uptake continues to lag far behind that of
[...] Read more.
Geothermal energy has been harnessed for recreational uses for millennia, but only for electricity generation for a little over a century. Although geothermal is unique amongst renewables for its baseload and renewable heat provision capabilities, uptake continues to lag far behind that of solar and wind. This is mainly attributable to (i) uncertainties over resource availability in poorly-explored reservoirs and (ii) the concentration of full-lifetime costs into early-stage capital expenditure (capex). Recent advances in reservoir characterization techniques are beginning to narrow the bounds of exploration uncertainty, both by improving estimates of reservoir geometry and properties, and by providing pre-drilling estimates of temperature at depth. Advances in drilling technologies and management have potential to significantly lower initial capex, while operating expenditure is being further reduced by more effective reservoir management—supported by robust models—and increasingly efficient energy conversion systems (flash, binary and combined-heat-and-power). Advances in characterization and modelling are also improving management of shallow low-enthalpy resources that can only be exploited using heat-pump technology. Taken together with increased public appreciation of the benefits of geothermal, the technology is finally ready to take its place as a mainstream renewable technology, exploited far beyond its traditional confines in the world’s volcanic regions. Full article

Research

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Open AccessArticle 3D Geothermal Modelling of the Mount Amiata Hydrothermal System in Italy
Energies 2014, 7(11), 7434-7453; doi:10.3390/en7117434
Received: 29 May 2014 / Revised: 6 October 2014 / Accepted: 6 November 2014 / Published: 17 November 2014
Cited by 4 | PDF Full-text (2298 KB) | HTML Full-text | XML Full-text
Abstract
In this paper we build a subsurface model that helps in visualizing and understanding the structural framework, geology and their interactions with the Mt. Amiata geothermal system. Modelling in 3D provides the possibility to interpolate the geometry of structures and is an effective
[...] Read more.
In this paper we build a subsurface model that helps in visualizing and understanding the structural framework, geology and their interactions with the Mt. Amiata geothermal system. Modelling in 3D provides the possibility to interpolate the geometry of structures and is an effective way of understanding geological features. The 3D modelling approach appears to be crucial for further progress in the reconstruction of the assessment of the geothermal model of Mt. Amiata. Furthermore, this model is used as the basis of a 3D numerical thermo-fluid-dynamic model of the existing reservoir(s). The integration between borehole data and numerical modelling results allows reconstructing the temperature distribution in the subsoil of the Mt. Amiata area. Full article
Open AccessArticle Seismic Velocity/Temperature Correlations and a Possible New Geothermometer: Insights from Exploration of a High-Temperature Geothermal System on Montserrat, West Indies
Energies 2014, 7(10), 6689-6720; doi:10.3390/en7106689
Received: 23 June 2014 / Revised: 25 September 2014 / Accepted: 7 October 2014 / Published: 17 October 2014
Cited by 2 | PDF Full-text (3375 KB) | HTML Full-text | XML Full-text
Abstract
In 2013, two production wells were drilled into a geothermal reservoir on Montserrat, W.I. (West Indies) Drilling results confirmed the main features of a previously developed conceptual model. The results confirm that below ~220 °C there is a negative correlation between reservoir temperature
[...] Read more.
In 2013, two production wells were drilled into a geothermal reservoir on Montserrat, W.I. (West Indies) Drilling results confirmed the main features of a previously developed conceptual model. The results confirm that below ~220 °C there is a negative correlation between reservoir temperature and seismic velocity anomaly. However, above ~220 °C there is a positive correlation. We hypothesise that anomalous variations in seismic velocity within the reservoir are controlled to first order by the hydrothermal mineral assemblage. This study suggests a new geophysical thermometer which can be used to estimate temperatures in three dimensions with unprecedented resolution and to indicate the subsurface fluid pathways which are the target of geothermal exploitation. Full article
Open AccessArticle Geothermal Potential Evaluation for Northern Chile and Suggestions for New Energy Plans
Energies 2014, 7(8), 5444-5459; doi:10.3390/en7085444
Received: 31 March 2014 / Revised: 4 August 2014 / Accepted: 13 August 2014 / Published: 22 August 2014
Cited by 2 | PDF Full-text (816 KB) | HTML Full-text | XML Full-text
Abstract
Chile is a country rich in natural resources, and it is the world’s largest producer and exporter of copper. Mining is the main industry and is an essential part of the Chilean economy, but the country has limited indigenous fossil fuels—over 90% of
[...] Read more.
Chile is a country rich in natural resources, and it is the world’s largest producer and exporter of copper. Mining is the main industry and is an essential part of the Chilean economy, but the country has limited indigenous fossil fuels—over 90% of the country’s fossil fuels must be imported. The electricity market in Chile comprises two main independent systems: the Northern Interconnected Power Grid (SING) and the Central Interconnected Power Grid (SIC). Currently, the primary Chilean energy source is imported fossil fuels, whereas hydropower represents the main indigenous source. Other renewables such as wind, solar, biomass and geothermics are as yet poorly developed. Specifically, geothermal energy has not been exploited in Chile, but among all renewables it has the greatest potential. The transition from thermal power plants to renewable energy power plants is an important target for the Chilean Government in order to reduce dependence on imported fossil fuels. In this framework, the proposed study presents an evaluation of the geothermal potential for northern Chile in terms of power generation. The El Tatio, Surire, Puchuldiza, Orriputunco-Olca and Apacheta geothermal fields are considered for the analysis. The estimated electrical power is approximately 1300 MWe, and the energy supply is 10,200 GWh/year. This means that more than 30% of the SING energy could be provided from geothermal energy, reducing the dependence on imported fossil fuels, saving 8 Mton/year of CO2 and supplying the mining industry, which is Chile’s primary energy user. Full article
Open AccessArticle Geothermal Power Growth 1995–2013—A Comparison with Other Renewables
Energies 2014, 7(8), 4802-4812; doi:10.3390/en7084802
Received: 4 April 2014 / Revised: 15 July 2014 / Accepted: 16 July 2014 / Published: 24 July 2014
Cited by 3 | PDF Full-text (1408 KB) | HTML Full-text | XML Full-text
Abstract
Based on global statistical data the current status of deep geothermal resource utilization for electricity generation is presented. Particular attention is paid to growth rates. The rates are compared with those of other renewable energies (biomass, hydro, solar photovoltaic (PV), wind). Whereas wind
[...] Read more.
Based on global statistical data the current status of deep geothermal resource utilization for electricity generation is presented. Particular attention is paid to growth rates. The rates are compared with those of other renewable energies (biomass, hydro, solar photovoltaic (PV), wind). Whereas wind and solar PV exhibit annual growth rates of 25%–30% since 2004, geothermal growth is only about 5% per year. Geothermal electricity production (in TW∙h/yr) was higher until 2011 than from solar PV, but is now clearly falling behind. So far the global geothermal electricity generation is provided nearly entirely by hydrothermal resources, which exist only under specific geologic conditions. Further development (=increasing production capacity) based on this resource type alone will therefore hardly accelerate to two-digit (>10% per year) growth rates. Faster growth can only be achieved by using the ubiquitous petrothermal resources, provided that the key problem will be solved: establishing a universally applicable technology. This would enable to create, at any requested site, feasible and efficient deep heat exchangers for enhanced geothermal systems (EGS) power plants—irrespective of the local subsurface conditions. Goals and challenges of this technology are addressed. Full article
Open AccessArticle On the Design and Response of Domestic Ground-Source Heat Pumps in the UK
Energies 2014, 7(7), 4532-4553; doi:10.3390/en7074532
Received: 30 April 2014 / Revised: 7 July 2014 / Accepted: 9 July 2014 / Published: 15 July 2014
Cited by 3 | PDF Full-text (1013 KB) | HTML Full-text | XML Full-text
Abstract
The design and response of ground source heat pumps coupled to vertical closed loop arrays in UK domestic applications are investigated in this article. Two typical UK house types are selected as the vehicle for the study and a detailed dynamic thermal modelling
[...] Read more.
The design and response of ground source heat pumps coupled to vertical closed loop arrays in UK domestic applications are investigated in this article. Two typical UK house types are selected as the vehicle for the study and a detailed dynamic thermal modelling method is used to arrive at time-series heating demands for the two houses. A new empirical heat pump model is derived using experimental data taking into account the deteriorating performance of the heat pump during periods of light load. The heat pump model is incorporated into an existing numerical ground model and completed with a classical effectiveness type heat exchange model of the closed loop array. The model is used to analyse array sizing and performance over an extended time period, as well as sensitivity of the design to soil conductivity and borehole heat exchanger resistance and sensitivity to over-sizing and part-load behavior of the heat pump. Results show that the UK’s standard for ground source design (the Microgeneration Certification Scheme) may lead to under-estimated array sizes and that heating system over-sizing and deleterious part-load heat pump performance can add up to 20% to the electrical consumption of these systems. Full article
Open AccessArticle Thermoeconomic Analysis of Hybrid Power Plant Concepts for Geothermal Combined Heat and Power Generation
Energies 2014, 7(7), 4482-4497; doi:10.3390/en7074482
Received: 11 April 2014 / Revised: 20 May 2014 / Accepted: 1 July 2014 / Published: 14 July 2014
Cited by 8 | PDF Full-text (317 KB) | HTML Full-text | XML Full-text
Abstract
We present a thermo-economic analysis for a low-temperature Organic Rankine Cycle (ORC) in a combined heat and power generation (CHP) case. For the hybrid power plant, thermal energy input is provided by a geothermal resource coupled with the exhaust gases of a biogas
[...] Read more.
We present a thermo-economic analysis for a low-temperature Organic Rankine Cycle (ORC) in a combined heat and power generation (CHP) case. For the hybrid power plant, thermal energy input is provided by a geothermal resource coupled with the exhaust gases of a biogas engine. A comparison to alternative geothermal CHP concepts is performed by considering variable parameters like ORC working fluid, supply temperature of the heating network or geothermal water temperature. Second law efficiency as well as economic parameters show that hybrid power plants are more efficient compared to conventional CHP concepts or separate use of the energy sources. Full article
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Open AccessArticle Deep Geothermal Energy Production in Germany
Energies 2014, 7(7), 4397-4416; doi:10.3390/en7074397
Received: 5 May 2014 / Revised: 17 June 2014 / Accepted: 23 June 2014 / Published: 9 July 2014
Cited by 11 | PDF Full-text (2082 KB) | HTML Full-text | XML Full-text
Abstract
Germany uses its low enthalpy hydrothermal resources predominantly for balneological applications, space and district heating, but also for power production. The German Federal government supports the development of geothermal energy in terms of project funding, market incentives and credit offers, as well as
[...] Read more.
Germany uses its low enthalpy hydrothermal resources predominantly for balneological applications, space and district heating, but also for power production. The German Federal government supports the development of geothermal energy in terms of project funding, market incentives and credit offers, as well as a feed-in tariff for geothermal electricity. Although new projects for district heating take on average six years, geothermal energy utilisation is growing rapidly, especially in southern Germany. From 2003 to 2013, the annual production of geothermal district heating stations increased from 60 GWh to 530 GWh. In the same time, the annual power production increased from 0 GWh to 36 GWh. Currently, almost 200 geothermal facilities are in operation or under construction in Germany. A feasibility study including detailed geological site assessment is still essential when planning a new geothermal facility. As part of this assessment, a lot of geological data, hydraulic data, and subsurface temperatures can be retrieved from the geothermal information system GeotIS, which can be accessed online [1]. Full article
Open AccessArticle Thermal-Economic Modularization of Small, Organic Rankine Cycle Power Plants for Mid-Enthalpy Geothermal Fields
Energies 2014, 7(7), 4221-4240; doi:10.3390/en7074221
Received: 23 April 2014 / Revised: 18 June 2014 / Accepted: 22 June 2014 / Published: 2 July 2014
Cited by 9 | PDF Full-text (1648 KB) | HTML Full-text | XML Full-text
Abstract
The costs of the surface infrastructure in mid-enthalpy geothermal power systems, especially in remote areas, could be reduced by using small, modular Organic Rankine Cycle (ORC) power plants. Thermal-economic criteria have been devised to standardize ORC plant dimensions for such applications. We designed
[...] Read more.
The costs of the surface infrastructure in mid-enthalpy geothermal power systems, especially in remote areas, could be reduced by using small, modular Organic Rankine Cycle (ORC) power plants. Thermal-economic criteria have been devised to standardize ORC plant dimensions for such applications. We designed a modular ORC to utilize various wellhead temperatures (120–170 °C), mass flow rates and ambient temperatures (−10–40 °C). A control strategy was developed using steady-state optimization, in order to maximize net power production at off-design conditions. Optimum component sizes were determined using specific investment cost (SIC) minimization and mean cashflow (MCF) maximization for three different climate scenarios. Minimizing SIC did not yield significant benefits, but MCF proved to be a much better optimization function. Full article
Open AccessArticle Estimating Limits for the Geothermal Energy Potential of Abandoned Underground Coal Mines: A Simple Methodology
Energies 2014, 7(7), 4241-4260; doi:10.3390/en7074241
Received: 30 April 2014 / Revised: 7 June 2014 / Accepted: 17 June 2014 / Published: 2 July 2014
Cited by 5 | PDF Full-text (514 KB) | HTML Full-text | XML Full-text
Abstract
Flooded mine workings have good potential as low-enthalpy geothermal resources, which could be used for heating and cooling purposes, thus making use of the mines long after mining activity itself ceases. It would be useful to estimate the scale of the geothermal potential
[...] Read more.
Flooded mine workings have good potential as low-enthalpy geothermal resources, which could be used for heating and cooling purposes, thus making use of the mines long after mining activity itself ceases. It would be useful to estimate the scale of the geothermal potential represented by abandoned and flooded underground mines in Europe. From a few practical considerations, a procedure has been developed for assessing the geothermal energy potential of abandoned underground coal mines, as well as for quantifying the reduction in CO2 emissions associated with using the mines instead of conventional heating/cooling technologies. On this basis the authors have been able to estimate that the geothermal energy available from underground coal mines in Europe is on the order of several thousand megawatts thermal. Although this is a gross value, it can be considered a minimum, which in itself vindicates all efforts to investigate harnessing it. Full article
Open AccessArticle Geothermal Power Plant Maintenance: Evaluating Maintenance System Needs Using Quantitative Kano Analysis
Energies 2014, 7(7), 4169-4184; doi:10.3390/en7074169
Received: 14 May 2014 / Revised: 18 June 2014 / Accepted: 23 June 2014 / Published: 1 July 2014
Cited by 2 | PDF Full-text (1745 KB) | HTML Full-text | XML Full-text
Abstract
A quantitative Kano model is used in this study to identify which features are preferred by top-level maintenance engineers within Icelandic geothermal power plants to be implemented in a maintenance tool or software. Visits were conducted to the largest Icelandic energy companies operating
[...] Read more.
A quantitative Kano model is used in this study to identify which features are preferred by top-level maintenance engineers within Icelandic geothermal power plants to be implemented in a maintenance tool or software. Visits were conducted to the largest Icelandic energy companies operating geothermal power plants. Thorough interviews with chiefs of operations and maintenance were used as a basis for a quantitative Kano analysis. Thirty seven percent of all maintenance engineers at Reykjavik Energy and Landsvirkjun, responsible for 71.5% of the total energy production from geothermal resources in Iceland, answered the Kano questionnaire. Findings show that solutions focusing on (1) planning maintenance according to condition; (2) shortening documentation times; and (3) risk analysis are sought after by the energy companies but not provided for the geothermal sector specifically. Full article
Open AccessArticle The Marsili Volcanic Seamount (Southern Tyrrhenian Sea): A Potential Offshore Geothermal Resource
Energies 2014, 7(7), 4068-4086; doi:10.3390/en7074068
Received: 18 April 2014 / Revised: 9 June 2014 / Accepted: 10 June 2014 / Published: 26 June 2014
Cited by 5 | PDF Full-text (3527 KB) | HTML Full-text | XML Full-text
Abstract
Italy has a strong geothermal potential for power generation, although, at present, the only two geothermal fields being exploited are Larderello-Travale/Radicondoli and Mt. Amiata in the Tyrrhenian pre-Apennine volcanic district of Southern Tuscany. A new target for geothermal exploration and exploitation in Italy
[...] Read more.
Italy has a strong geothermal potential for power generation, although, at present, the only two geothermal fields being exploited are Larderello-Travale/Radicondoli and Mt. Amiata in the Tyrrhenian pre-Apennine volcanic district of Southern Tuscany. A new target for geothermal exploration and exploitation in Italy is represented by the Southern Tyrrhenian submarine volcanic district, a geologically young basin (Upper Pliocene-Pleistocene) characterised by tectonic extension where many seamounts have developed. Heat-flow data from that area show significant anomalies comparable to those of onshore geothermal fields. Fractured basaltic rocks facilitate seawater infiltration and circulation of hot water chemically altered by rock/water interactions, as shown by the widespread presence of hydrothermal deposits. The persistence of active hydrothermal activity is consistently shown by many different sources of evidence, including: heat-flow data, gravity and magnetic anomalies, widespread presence of hydrothermal-derived gases (CO2, CO, CH4), 3He/4He isotopic ratios, as well as broadband OBS/H seismological information, which demonstrates persistence of volcano-tectonic events and High Frequency Tremor (HFT). The Marsili and Tyrrhenian seamounts are thus an important—and likely long-lasting-renewable energy resource. This raises the possibility of future development of the world’s first offshore geothermal power plant. Full article
Open AccessArticle Determining the Maximum Depth of Hydrothermal Circulation Using Geothermal Mapping and Seismicity to Delineate the Depth to Brittle-Plastic Transition in Northern Honshu, Japan
Energies 2014, 7(5), 3503-3511; doi:10.3390/en7053503
Received: 1 May 2014 / Revised: 19 May 2014 / Accepted: 22 May 2014 / Published: 23 May 2014
Cited by 2 | PDF Full-text (1391 KB) | HTML Full-text | XML Full-text
Abstract
This paper defines the maximum possible vertical extent of hydrothermal circulation in granitic crust, and thus the maximum depth within which geothermal reservoirs can be encountered. To evaluate prospective geothermal fields we constructed a geothermal database in northern Honshu, Japan that includes 571
[...] Read more.
This paper defines the maximum possible vertical extent of hydrothermal circulation in granitic crust, and thus the maximum depth within which geothermal reservoirs can be encountered. To evaluate prospective geothermal fields we constructed a geothermal database in northern Honshu, Japan that includes 571 points of thermal data of existing wells and hot springs. Depth-temperature curves were normalized by the Activity Index for three-dimensional extrapolation and a depth contour map of the 380 °C isotherm was plotted as an assumed brittle-plastic transition for granitic crust. Shallower-depth anomalies of the brittle-plastic transition on this map are closely coincident with the Quaternary volcanoes and their prospective geothermal fields. It should be noted that the bottom of the spatial distribution of seismicity in the volcanic fields shows strong correlation to the 380 °C isotherm. This result indicates reliability of the subsurface three-dimensional thermal map and suggests that the 380 °C isotherm strongly constrains the bottom surface of seismicity, fracturing and hydrothermal convection in granitic crust. Full article
Open AccessArticle Implications of Spatial Variability in Heat Flow for Geothermal Resource Evaluation in Large Foreland Basins: The Case of the Western Canada Sedimentary Basin
Energies 2014, 7(4), 2573-2594; doi:10.3390/en7042573
Received: 13 February 2014 / Revised: 28 March 2014 / Accepted: 10 April 2014 / Published: 22 April 2014
Cited by 5 | PDF Full-text (2693 KB) | HTML Full-text | XML Full-text
Abstract
Heat flow and geothermal gradient of the sedimentary succession of the Western Canada Sedimentary Basin (WCSB) are mapped based on a large thermal database. Heat flow in the deep part of the basin varies from 30 mW/m2 in the south to high
[...] Read more.
Heat flow and geothermal gradient of the sedimentary succession of the Western Canada Sedimentary Basin (WCSB) are mapped based on a large thermal database. Heat flow in the deep part of the basin varies from 30 mW/m2 in the south to high 100 mW/m2 in the north. As permeable strata are required for a successful geothermal application, the most important aquifers are discussed and evaluated. Regional temperature distribution within different aquifers is mapped for the first time, enabling a delineation of the most promising areas based on thermal field and aquifer properties. Results of previous regional studies on the geothermal potential of the WCSB are newly evaluated and discussed. In parts of the WCSB temperatures as high as 100–210 °C exist at depths of 3–5 km. Fluids from deep aquifers in these “hot” regions of the WCSB could be used in geothermal power plants to produce electricity. The geothermal resources of the shallower parts of the WCSB (>2 km) could be used for warm water provision (>50 °C) or district heating (>70 °C) in urban areas. Full article
Open AccessArticle Differences in Public Perceptions of Geothermal Energy Technology in Australia
Energies 2014, 7(3), 1555-1575; doi:10.3390/en7031555
Received: 26 November 2013 / Revised: 13 February 2014 / Accepted: 27 February 2014 / Published: 14 March 2014
Cited by 6 | PDF Full-text (236 KB) | HTML Full-text | XML Full-text
Abstract
In Australia, geothermal energy technology is still considered an emerging technology for energy generation. Like other emerging energy technologies, how the public perceive the technology and under what conditions they are likely to accept or oppose the technology, remains relatively unknown. In response,
[...] Read more.
In Australia, geothermal energy technology is still considered an emerging technology for energy generation. Like other emerging energy technologies, how the public perceive the technology and under what conditions they are likely to accept or oppose the technology, remains relatively unknown. In response, this exploratory research utilised online focus groups to identify: (1) the extent of agreement with geothermal technology before and after information, including media reports focusing on a range of the technology’s attributes; and (2) how the characteristics of individuals with different levels of agreement vary. After information, within the sample of 101 participants, fewer reported being unsure, the minority disagreed and the majority agreed. Overall, the preference was for projects to be located away from communities. Participants that disagreed or were unsure, were more likely to report lower subjective knowledge of the technology, lower perceived benefits and higher risks, and were less likely to believe people in their community would have the opportunity to participate in consultation. These characteristics suggest there are advances to be made by analyzing what contributes to different levels of acceptance. The findings also suggest that the location of projects will be an important consideration and that the conditions of acceptance are likely to vary amongst community members. Full article
Open AccessArticle Temperatures and Heat Flows in a Soil Enclosing a Slinky Horizontal Heat Exchanger
Energies 2014, 7(2), 972-987; doi:10.3390/en7020972
Received: 20 November 2013 / Revised: 22 January 2014 / Accepted: 12 February 2014 / Published: 24 February 2014
Cited by 8 | PDF Full-text (558 KB) | HTML Full-text | XML Full-text
Abstract
Temperature changes and heat flows in soils that host “slinky”-type horizontal heat exchangers are complex, but need to be understood if robust quantification of the thermal energy available to a ground-source heat pump is to be achieved. Of particular interest is the capacity
[...] Read more.
Temperature changes and heat flows in soils that host “slinky”-type horizontal heat exchangers are complex, but need to be understood if robust quantification of the thermal energy available to a ground-source heat pump is to be achieved. Of particular interest is the capacity of the thermal energy content of the soil to regenerate when the heat exchangers are not operating. Analysis of specific heat flows and the specific thermal energy regime within the soil, including that captured by the heat-exchangers, has been characterised by meticulous measurements. These reveal that high concentrations of antifreeze mix in the heat-transfer fluid of the heat exchanger have an adverse impact on heat flows discharged into the soil. Full article

Review

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Open AccessReview National Deployment of Domestic Geothermal Heat Pump Technology: Observations on the UK Experience 1995–2013
Energies 2014, 7(8), 5460-5499; doi:10.3390/en7085460
Received: 25 July 2014 / Accepted: 13 August 2014 / Published: 22 August 2014
Cited by 7 | PDF Full-text (1233 KB) | HTML Full-text | XML Full-text | Correction
Abstract
Uptake of geothermal heat pump technology in the UK and corresponding development of a domestic installation industry has progressed significantly in the last decade. This paper summarizes the growth process and reviews the research that has been specifically concerned with conditions in the
[...] Read more.
Uptake of geothermal heat pump technology in the UK and corresponding development of a domestic installation industry has progressed significantly in the last decade. This paper summarizes the growth process and reviews the research that has been specifically concerned with conditions in the UK. We discuss the driving forces behind these developments and some of the supporting policy initiatives that have been implemented. Publically funded national trials were completed to assess the performance and acceptance of the technology and validate design and installation standards. We comment on both the technical and non-technical findings of the trials and the related academic research and their relevance to standards development. A number of technical issues can be identified—some of which may be particular to the UK—and we suggest a number of research and development questions that need to be addressed further. Current national support for the technology relies solely on a tariff mechanism and it is uncertain that this will be effective enough to ensure sufficient growth to meet the national renewable heat target in 2020. A broader package of support that includes mandatory measures applied to future housing development and retrofit may be necessary to ensure long-term plans for national deployment and decarbonization of heat are achieved. Industry needs to demonstrate that efficiency standards can be assured, capital costs reduced in the medium-term and that national training schemes are effective. Full article
Open AccessReview Geophysical Methods for Monitoring Temperature Changes in Shallow Low Enthalpy Geothermal Systems
Energies 2014, 7(8), 5083-5118; doi:10.3390/en7085083
Received: 15 May 2014 / Revised: 15 July 2014 / Accepted: 22 July 2014 / Published: 11 August 2014
Cited by 9 | PDF Full-text (1611 KB) | HTML Full-text | XML Full-text
Abstract
Low enthalpy geothermal systems exploited with ground source heat pumps or groundwater heat pumps present many advantages within the context of sustainable energy use. Designing, monitoring and controlling such systems requires the measurement of spatially distributed temperature fields and the knowledge of the
[...] Read more.
Low enthalpy geothermal systems exploited with ground source heat pumps or groundwater heat pumps present many advantages within the context of sustainable energy use. Designing, monitoring and controlling such systems requires the measurement of spatially distributed temperature fields and the knowledge of the parameters governing groundwater flow (permeability and specific storage) and heat transport (thermal conductivity and volumetric thermal capacity). Such data are often scarce or not available. In recent years, the ability of electrical resistivity tomography (ERT), self-potential method (SP) and distributed temperature sensing (DTS) to monitor spatially and temporally temperature changes in the subsurface has been investigated. We review the recent advances in using these three methods for this type of shallow applications. A special focus is made regarding the petrophysical relationships and on underlying assumptions generally needed for a quantitative interpretation of these geophysical data. We show that those geophysical methods are mature to be used within the context of temperature monitoring and that a combination of them may be the best choice regarding control and validation issues. Full article
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Open AccessReview Gamma-ray Spectrometry in Geothermal Exploration: State of the Art Techniques
Energies 2014, 7(8), 4757-4780; doi:10.3390/en7084757
Received: 30 April 2014 / Revised: 23 June 2014 / Accepted: 7 July 2014 / Published: 24 July 2014
Cited by 8 | PDF Full-text (975 KB) | HTML Full-text | XML Full-text
Abstract
Gamma-ray spectrometry is a surveying technique that allows the calculation of the heat produced during radioactive decay of potassium, uranium, and thorium within rock. Radiogenic heat producing rocks are often targets for geothermal exploration and production. Hence, refinements in gamma-ray spectrometry surveying will
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Gamma-ray spectrometry is a surveying technique that allows the calculation of the heat produced during radioactive decay of potassium, uranium, and thorium within rock. Radiogenic heat producing rocks are often targets for geothermal exploration and production. Hence, refinements in gamma-ray spectrometry surveying will allow better constraint of resources estimation and help to target drilling. Gamma-rays have long half-lengths compared to other radiation produced during radiogenic decay. This property allows the gamma-rays to penetrate far enough through media to be detected by airborne or ground based surveying. A recent example of ground-based surveying in Scotland shows the ability of gamma-ray spectrometry to quickly and efficiently categorize granite plutons as low or high heat producing. Some sedimentary rocks (e.g., black shales) also have high radiogenic heat production properties and could be future geothermal targets. Topographical, atmospheric and spatial distribution factors (among others) can complicate the collection of accurate gamma-ray data in the field. Quantifying and dealing with such inaccuracies represents an area for further improvement of these techniques for geothermal applications. Full article

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Open AccessCorrection Correction: Rees, S. and Curtis, R. National Deployment of Domestic Geothermal Heat Pump Technology: Observations on the UK Experience 1995–2013. Energies 2014, 7, 5460–5499
Energies 2014, 7(9), 6224; doi:10.3390/en7096224
Received: 27 August 2014 / Accepted: 1 September 2014 / Published: 25 September 2014
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Abstract We have found the following error in the publishing history of this article which was recently published in Energies [1].[...] Full article

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