"Experiment, Modelling and Simulation of High-Temperature Ground Thermal Storage 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 and improves the system's efficiency. Thus, a ground thermal energy store, 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, since 2007 80% of residential space heating needs for 52 houses have been met 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 72 GJ of heating energy (or 1920 m3 of natural gas) and 3.6 tonnes of greenhouse gas emissions per home, per year. In order to widely use such technology in Canada or 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, 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, 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 30 to 50 years or longer. To meet this objective, experiment and modelling work will be required to validate or model the theory of coupled heat and moisture movement in soils, soil thermal conductivity and ground heat exchangers. Once developed and validated, all the models will be implemented into a computer program for modelling the heat exchange between a ground heat exchanger system and the ground. The software should be able to predict and remedy any potential problems, such as dry out of ground, which would degrade the thermal performance of the system.