Characteristics and energy performance of novel MicroPCM C50 energy pile in cooling mode

Abstract

Energy piles utilize geothermal energy via integrated geothermal heat exchangers (GHEs), which can sustain structural loads while also harvesting geothermal energy to meet the building's heating and cooling requirements. In the study, we report a systematic investigation of the Microencapsulated Phase Change Material (MicroPCM) C50 energy pile, from characterizing the material properties of the MicroPCM C50 concrete to analyzing the energy performance of the MicroPCM C50 based energy piles. Through integrating the MicroPCM into structural concrete, MicroPCM C50 concrete is manufactured and its properties, such as mechanical compressive strength and thermal conductivity, are characterized. With measured material properties implemented into a numerical model of the MicroPCM C50 energy pile, the energy performance when the energy pile works in the cooling mode is assessed. Our results suggest that (1) incorporating MicroPCM into C50 concrete specimens (up to 5 wt%), will dramatically reduce the compressive strength of C50 concrete; (2) Thermal conductivity and heat capacity of C50 concrete specimens are improved as mass fraction increases from 1 to 3 wt%, while reduced as mass fraction increases from 3 to 5 wt% (maximum at 3 wt%); (3) When considering both the mechanical and thermal performance of the energy pile, the energy pile with W shape GHE and 1 wt% MicroPCM addition is the best option for this scenario, followed by the energy pile with U shape GHE and 1 wt% MicroPCM, which will collect around 5% more geothermal energy, compared to normal concrete energy pile, and meanwhile retain a high level of mechanical strength. Our results will provide support for the design and optimization of the MicroPCM C50 energy piles toward real-world applications.