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Developing Geothermal Energy Research Capabilities at University College Dublin

2011, Hemmingway, Phil, Long, Michael (Michael M.)

Ireland has one of the highest energy dependencies in Europe and as such must adapt quickly to increase renewable energy exploitation levels in order to secure its energy future. A mix of renewable energy technology types (wind, solar, biomass, wave, tidal, geothermal) will be required in order to achieve Ireland’s national renewable energy generation targets. Geothermal (or ground source) energy can have a part to play in this mix. Over the last number of years the School of Civil, Structural & Environmental Engineering in University College Dublin has begun to develop shallow geothermal energy research capabilities in several areas of interest. Early studies involved the investigation of water chemistry and settlement issues at several sites on the Cork docklands. It was concluded that the chemical characteristics of the water contained in the aquifer could hinder the development of open loop geothermal systems in the area, and that settlement may be a potential concern in cases where open loop systems are installed due to the presence of highly compressible alluvium deposits. Subsequent work has involved the development, construction & performance validation of a thermal response testing rig for site thermal characterisation, installation of both domestic and commercial sized energy piles for research purposes and investigation of soil, rock and grout thermal properties using both steady-state and non-steady-state laboratory testing techniques. This paper gives a brief overview of the completed and ongoing work in the School of Civil, Structural & Environmental Engineering.

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Thermal response testing of compromised borehole heat exchangers

2012-03-19, Hemmingway, Phil, Long, Michael (Michael M.)

The results of five thermal response tests (TRTs) are presented. Three of the tests were carried out consecutively on the same borehole to illustrate the importance of allowing artificially imposed thermal gradients to dissipate prior to commencement or re-commencement of a test following testing issues. The two remaining tests carried out on separate boreholes confirm the results obtained by the first(uncompromised) of the initial three tests. The testing regime demonstrates the necessity of careful performance of TRT’s and shows the variation in costs/required borehole length which may occur if testing problems occur on site.

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Energy Foundations - Potential for Ireland

2011-03, Hemmingway, Phil, Long, Michael (Michael M.)

With one of the highest energy dependencies in the European Union, Ireland must adapt quickly to renewable energy technologies or risk paying the penalty in the form of high energy prices in years to come. Escalating energy costs have led to a renewed interest in alternative energy technologies and ground source energy is one such resource which is being increasingly considered. This paper presents some of the practical considerations of energy foundations, evidenced from the installation of a number of test energy piles. In addition, a preliminary feasibility study of an energy foundation system for a planned university administrative building and an overview of the current status of ground source energy technology in Ireland are presented. Building heating and cooling loads are estimated based on high building energy standards which the university hopes to implement in all building projects going forward. The proposed energy foundation system is shown to have the capacity to provide the heating and cooling base loads for the building

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Numerical and finite element analysis of heat transfer in a closed loop geothermal system

2013-08, Hemmingway, Phil, Tolooiyan, Ali

Analysis of the thermal regime created by a geothermal borehole heat exchanger is performed using a closed form radial heat flow equation, a geothermal borehole heat exchanger design tool and a finite element model. Climatic, heat exchanger construction and building load data are entered into the heat exchanger design tool in order to create a theoretical model along with thermal parameters from a number of geological formations. Output data from the design tool model are used in conjunction with the closed form radial heat flow equation to calculate the predicted temperature with respect to time and distance from the heat exchanger for the modelled ground formations. The output data from the design tool is also used to create a number of finite element method models against which the predictions calculated using the closed form radial heat flow equation can be compared. A good correlation between the temperatures predicted by the finite element models and the closed form equation calculations is observed. However when used within its recommended limiting conditions, the closed form equation is shown to slightly underestimate the temperature of the ground when compared to the finite element model predictions. The limiting conditions associated with the closed form equation are discussed in the context of the output from the finite element method models.

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Geothermal energy in small countries - laying the foundations for innovative development

2011-09-04, Hemmingway, Phil, Long, Michael (Michael M.)

Creation of an environment in which shallow geothermal energy can thrive will require a coherent approach and a high level of collaboration with professionals from countries that have developed technical expertise in the area. Implementation of regulations, standards and guidelines adapted from best practice in countries such as Switzerland, Germany and Sweden, in addition to understanding the mistakes and successes made by these countries, with respect to the development of their geothermal industries, will help small countries such as Ireland to develop a well-regulated market for the technology. This paper outlines and addresses some of the technical, regulatory and certification issues faced particularly by small countries in their efforts to develop a shallow geothermal energy industry, provides examples of best practice with regard to development in countries with established geothermal energy industries and presents proposed solutions to these issues / barriers using the existing situation in Ireland by way of example.

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Design and development of a low-cost thermal response rig

2012-08-01, Hemmingway, Phil, Long, Michael (Michael M.)

A thermal response test (TRT) is a controlled insitu test during which a known quantity of heat energy is injected into a closed loop heat-exchanger pipe while the heat dissipation rate into the surrounding ground is monitored. Results from a test can be interpreted to determine a number of ground thermal parameters with are vital design requirements for any medium to large scale ground source energy system. This paper describes the design and construction of a low cost TRT rig and compares the results obtained from a test using the constructed rig and a commercially built rig in order to evaluate the accuracy of the constructed equipment. The TRT rig is designed in accordance with the following principles: keep construction costs low, improve the cost-efficiency of TRT testing by incorporating remote data transmission capability and ensure attainment of sufficient accuracy to satisfy the design requirements of ground source energy systems. Analysis of data collected by the TRT rigs result in a calculated thermal conductivity of 1.9 W/mK in both cases. This value falls within the range expected for the tested geological formation and confirms the accuracy of both test rigs.