Conventional piles embedded with geothermal loops, referred to as energy piles, have been successfully used as heat exchangers for the ground source heat pump system. For heating-dominated regions, it is cruc. ••The thermal performance of energy piles for underground solar. According to the International Energy Agency, buildings are responsible for almost 40% of total final energy consumption in the European Union, out of which 80% is du. 2.1. Mathematical formulationFig. 2 shows a schematic diagram of the energy pile-solar collector coupled system to be modeled in this study. It consists of a flat-plate solar co. In the following interpretation of the numerical results, the focus is put on the inlet-outlet temperature difference (Tin-Tout), the rate of solar energy storage per unit of pile lengt. A total of seven cases were analyzed to study the evolution of the thermal performance of the system with varying solar irradiance and ambient air temperature, as.