Enhancing ground source heat pump performance: The role of phase change material integrated grouts in subsurface temperature control

Ground source heat pump (GSHP) systems are increasingly being adopted for heating and cooling applications. However, their continuous operation can lead to thermal imbalances in the ground, which may impact overall system performance. This study investigates the thermal performance of a coaxial ground heat exchanger (CGHE) in a GSHP system, using different grouting materials: reference grout, enhanced grout, micro-encapsulated phase change material (MEPCM) grout, and shape-stabilized phase change material (SSPCM) grout. The effects of these grouts on the heat exchange efficiency and ground temperature variation are analyzed. Additionally, the integration of phase change materials (PCMs) into grouts is examined for its potential to improve thermal performance. Results show that the thermal conductivity of grout has a significant influence on system performance, affecting heat transfer. Among the grouts tested, the SSPCM-integrated grout outperformed others, achieving an average specific power of 5.72 kW/m for cooling and 4.06 kW/m for heating. Furthermore, the ground temperature with PCM-integrated grouts fluctuated between 20 °C and 23 °C, compared to 19 °C to 25 °C with ordinary grouts. Hence, PCM integration in grouts can enhance the stability of source and sink temperatures. • Sub-surface temperature fluctuations due to the continuous operation of GSHP system is studied. • PCM integrated grout is analyzed through numerical simulations with coaxial ground heat exchangers. • Reduction in subsurface temperature fluctuations is observed with PCM-added grouts. • Shape-Stabilized PCM outperformed in GSHP systems with a coaxial ground heat exchanger.