Subsurface utilization in the tropical regions as a heat sink for ground source heat pumps (GSHPs) leads to thermal buildup in the long term, resulting in the decreased energy performance. However, the applicability of the GSHP in these regions has never been investigated based on the predicted heat sink temperature over a lifetime. This study aimed to evaluate the energy performance of a large-scale GSHP system in representative building models in Thailand based on operating conditions derived from a predicted 50-year heat sink temperature. The proposed system combines a GSHP and an air-source heat pump (ASHP), and, in one scenario, the GSHP also supplies hot water. The results confirm that the combined system achieves a higher efficiency than that of an ASHP system alone, and GSHP supplying hot water realizes substantial energy-saving. However, limitations on the annual GSHP operation hours are essential, resulting in low energy-saving performance for cooling dominated facilities. Further improvements are expected by mitigating the thermal interactions among each borehole heat exchanger.
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