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Finite Element Modeling of Thermal Insulation Effects in a Borehole Thermal Energy Storage

  • Author / Creator
    Lee, Jungjin
  • A recent application of borehole thermal energy storage (BTES) technology to residential properties in Canada shows a significant reduction in the use of natural gas thereby saving energy consumption and reducing the generation of greenhouse gases. However, due to the construction principles of the BTES, the systems are not thermally insulated on the sides and the bottom. Hence, almost all injected heat into a single borehole dissipates into surrounding ground over the night when heat injection stops. In order to minimize thermal energy dissipation, construction of thermal insulation barrier using expanded perlite aggregate (EPA) was proposed to reduce the heat flow and increase the efficiency by providing a soilcrete thermal insulation layer around the BTES system. The initial research proposed to utilize jet grouting technology for construction of the EPA mixed soilcrete thermal insulation layer. However, due to the nature of the jet grouting technology, the construction process of jet grouting is lengthy and therefore expensive for this application. Besides, the high buoyancy forces exerted created potential risks of aggregate segregation. To improve constructability and to mitigate the risks of aggregate segregation, this research proposes to employ one pass deep trenching method construction of the soilcrete thermal insulation layer.the risks of aggregate segregation, this research proposes to employ one pass deep trenching method construction of the soilcrete thermal insulation layer. Full-scale numerical models using two finite element analysis (FEA) software: Abaqus and Temp/W were developed to investigate the effectiveness of the soilcrete insulation layer constructed with one pass deep trenching method. The numerical model provides theoretical evidence for the application of soilcrete thermal insulation layer in reducing the thermal energy loss and thereby improving the efficiency of the system. The FEA modeling results showed that the thermal insulating soilcrete successfully entrapped more thermal energy within the system compared to the system without thermal insulation and reduced the annual average heat flux up to 46 % with three-meter thickness insulation barrier.

  • Subjects / Keywords
  • Graduation date
    2017-11:Fall 2017
  • Type of Item
    Thesis
  • Degree
    Master of Science
  • DOI
    https://doi.org/10.7939/R3TQ5RT5Q
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.
  • Language
    English
  • Institution
    University of Alberta
  • Degree level
    Master's
  • Department
    • Department of Civil and Environmental Engineering
  • Specialization
    • Mining Engineering
  • Supervisor / co-supervisor and their department(s)
    • Liu, Victor (Mining Engineering)
    • Apel, Derek (Mining Engineering)
  • Examining committee members and their departments
    • Hall, Robert (Mining Engineering)