Numerical and experimental investigations into thermal aspects of geothermal energy piles

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Geothermal energy piles serve not only as structural support to buildings but also as ground heat exchangers for space heating and cooling. This innovative technology was pioneered in Europe and takes advantage of the moderate ground temperature to heat and cool buildings. It can generate savings in energy bills and effectively reduce carbon emissions at the same time. Such implementation has become increasingly popular worldwide over the last decade due to its environmental and economical benefits. In order to accurately predict the energy performance of this technology, it is very important to understand the heat transfer process taking place between the geothermal energy piles and the surrounding ground. The thermal properties of the ground have a significant impact on the heat transfer process and require a wide range of investigation, considering a large variety of soil types and conditions. This study investigates the heat transfer process of a geothermal energy pile installed at Monash University Clayton campus. The pile has a diameter of 600 mm and a length of 16 m. Numerical models were developed to simulate the thermal response tests (TRTs) carried out on the test pile and assess the thermal properties of the surrounding soils, by comparing the numerically predicted and experimental surrounding soil temperature responses at different depths. The numerical simulations were performed in both 2-dimension (2-D) and 3-dimension (3-D), thus, the capabilities of the two types of simulations were compared. Furthermore, this study investigates the pile thermal performance through a series of heating and cooling tests simulating different energy demands. The temperature responses of the pile and surrounding soils during these tests were also investigated. The surrounding soil temperature responses were numerically simulated using the best model (of 2-D and 3-D) used to simulate the TRTs, hence, to verify further the results of soil thermal properties and the accuracy of the numerical model used.