Optimizing the thermal performance of energy piles using response surface methodology

Abstract

Energy piles have been recently utilized as ground heat exchangers in ground source heat pump systems to improve the energy efficiency in the heating, ventilation and air conditioning (HVAC) systems for residential and commercial buildings. On top of the structural role of energy piles to transfer the mechanical loads of buildings to the ground, they are used to dissipate heat energy into the soil to reduce the consumption of energy and hence lower greenhouse gas emissions. In this study, eight factors affecting the thermal conductance of the energy piles are investigated to maximize the thermal performance of energy piles. These eight factors are the number of U-tubes, pile diameter, tube diameter, tube thickness, pile thermal conductivity, tube thermal conductivity, soil thermal conductivity, and velocity of circulated water in U-tubes. The significance of these factors is statistically evaluated, and the optimal values of the significant factors are obtained using response surface methodology. The results reveal that tube thickness, water velocity, and soil conductivity have an insignificant impact on thermal conductance of the energy piles, while other factors have a significant effect. This research may lay a foundation for future research in optimizing the thermal performance of energy piles and promoting their applications in practice.