Evaluation of thermal response and performance of PHC energy pile: Field experiments and numerical simulation

► We performed TRTs for PHC energy piles with 3U- and W- shaped heat exchangers. ► We successfully predicted the monitored thermal behaviors in TRTs by 3D FE analyses. ► We evaluated thermal resistances of energy piles from TRT simulations. ► Thermal performance of the PHC energy pile in Korea was estimated to be efficient. ► Longer pipe was estimated to be beneficial not for base load but for peak load. This paper presents an experimental and numerical study on evaluation of thermal response and performance of prototype precast-high strength concrete (PHC) energy pile. Short-term field thermal response tests (TRTs) were conducted for the PHC energy piles installed in partially saturated weathered granite soil deposit, in which two types of heat exchangers were considered: W and 3U-shaped heat exchangers. The TRTs were successfully simulated by three-dimensional finite element analyses employing quasi-steady-state convective heat transfer boundary condition. The numerical model was applied to simulate 3-day TRTs, and the simulation results were used for assessing effective thermal conductivity and thermal resistance. Besides, continuous and intermittent operation simulations of the energy piles were performed, and for the results of performance analyses, discussion was made to evaluate energy efficiency of the prototype PHC piles.