Thermomechanical performance analysis of MicroPCM-enhanced energy pile concrete: A multiscale numerical study and formulation design implications

Abstract

Energy pile is a form of pile foundation that combines load-bearing and heat exchange, marking a pivotal avenue for harnessing geothermal energy. Recent strides in research have highlighted the incorporation of microencapsulated phase change materials (MicroPCM) into energy piles due to their potential to amplify heat transfer efficiency. The thermomechanical behavior of phase change energy piles, however, becomes intricate owing to the dual impact of thermal and mechanical loads. Thus, a holistic multiscale analysis remains indispensable to grasp the repercussions of varied MicroPCM concentrations on the thermomechanical attributes of phase change concrete and the dominant mechanisms driving their thermo-mechanical performance. In the study, we propose an innovative multiscale numerical model to investigate the thermomechanical performance of MicroPCM-enhanced energy pile concrete, taking into account the randomly distributed MicroPCM particles and aggregate. The sensitivity analysis pinpointing the intrinsic determinants of phase change concrete was conducted to discern the pivotal contributors to its thermomechanical response. Core insights revealed that while MicroPCM addition might compromise the mechanical strength of concrete owing to its inherently weaker properties, it unquestionably bolsters the thermal characteristics of phase change concrete. The thermal conductivity of phase change concrete stands in inverse relation to its porosity and direct correspondence with its saturation level. Correlation evaluations ascertained that the thermal prowess of phase change concrete is predominantly swayed by saturation, followed by porosity, and lastly, MicroPCM content. This inquiry endeavors to elevate the heat transfer efficacy of energy piles by finetuning the formulation design of phase change concrete materials, shedding light on underlying mechanisms, and laying a robust foundation for the forthcoming adoption of MicroPCM energy piles.