Experimental Study, Modelling and Design of High-Temperature Ground Thermal Energy Storage for Achieving Energy Efficient Building Energy Systems

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A key technology in energy efficiency and conservation is a thermal energy storage system. It often helps to reduce the mismatch between demand and supply of thermal energy in a system, thereby improving its efficiency. Thus, a ground thermal energy storage (GTES), readily available under a building, backyard or front yard, can play an important role in the future to combat climate change, reduce fossil fuel consumption, and increase renewable energy utilization. The technology can also be extended to communities through district heating systems, as is the case at the one-of-a-kind Drake Landing Solar Community in Okotoks, Alberta. Here, 90% of residential space heating needs for 52 houses have been met since 2007 by retrieving solar energy stored during the summer season from a high-temperature (up to 80°C) ground thermal energy store. The equivalent reduction is approximately 39 GJ of heating energy (or 1,050 m3 of natural gas) and 2 tonnes of greenhouse gas emissions per home, per year. In order to widely use such technology in Canada and the world, a reliable tool is required to simulate and design an optimized system in the most energy- and cost-efficient way. The proposed research will develop such a reliable and powerful computer software tool. The software program will have the capability to simulate the complex nature of coupled heat and water movement in the ground, as well as phase change process of phase change materials (PCMs) around ground heat exchangers, such that an appropriate sizing of a ground thermal energy storage system can be achieved - that is, it will be able to match the demand (e.g., heating for buildings) and supply (e.g., solar energy from solar collectors) of thermal energy over a typical service life of 20 years or longer. To meet this objective, experiment and modeling work will be required to validate or model the theory of coupled heat and moisture movement in soils and soil thermal properties. Once developed and validated, all the models will be implemented into a computer program for studying different GTES systems, including ground source heat pump (GSHP), hybrid GSHP, and high-temperature GTES systems.