To address thermal imbalance and ground temperature degradation in shallow geothermal heat pump (GSHP) systems in severely cold climates, this study analyzes a typical logistics building using an hourly dynamic load model. Multiyear simulations were conducted to investigate the coupling between building load variation and soil thermal response. The results indicate that with a cumulative heating load of 14.681 million kWh and cooling load of 6.3948 million kWh, annual heat extraction significantly exceeds heat rejection, causing ground temperature to decline by about 1 °C per year. Over five and ten years, the cumulative drops reached 2.65 °C and 4.71 °C, respectively, leading to a noticeable reduction in borehole heat exchanger performance and system COP. The study quantitatively evaluates ground temperature and heat exchange degradation, highlighting the key role of load imbalance. To mitigate long-term thermal deterioration, strategies such as load optimization, summer heat reinjection, and operational adjustments are proposed. The findings offer guidance for the design and sustainable operation of GSHP systems in cold regions.

Ground-source heat pump (GSHP) systems with medium-depth and deeply buried pipes in cold regions are highly important for addressing global climate change and the energy crisis because of their efficient, clean, and sustainable energy characteristics. However, unique geological conditions in cold climates pose serious challenges to the heat transfer efficiency, long-term stability, and adaptability of systems. This study comprehensively analyses the effects of various factors, including well depth, inner-to-outer tube diameter ratios, cementing material, the thermal conductivity of the inner tube, the flow rate, and the start–stop ratio, on the performance of a medium-depth coaxial borehole heat exchanger. Field tests, numerical simulations, and sensitivity analyses are combined to determine the full-cycle thermal performance and heat-transfer properties of medium-depth geological formations and their relationships with system performance. The results show that the source water temperature increases by approximately 4 °C and that the heat transfer increases by 50 kW for every 500 m increase in well depth. The optimization of the inner and outer pipe diameter ratios effectively improves the heat-exchange efficiency, and a larger pipe diameter ratio design can significantly reduce the flow resistance and improve system stability. When the thermal conductivity of the cementing cement increases from 1 W/(m·K) to 2 W/(m·K), the outlet water temperature at the source side increases by approximately 1 °C, and the heat transfer increases by 13 kW. However, the improvement effect of further increasing the thermal conductivity on the heat-exchange efficiency gradually decreases. When the flow rate is 0.7 m/s, the heat transfer is stable at approximately 250 kW, and the system economy and heat-transfer efficiency reach a balance. These findings provide a robust scientific basis for promoting medium-deep geothermal energy heating systems in cold regions and offer valuable references for the green and low-carbon transition in building heating systems.

Ground source heat pump systems are prone to long-term ground thermal imbalance in severe cold regions because seasonal heat extraction considerably exceeds summer heat rejection. To address this issue, this study proposes a proton exchange membrane fuel cell-assisted ground source heat pump system with cascade waste heat recovery for a heating-dominated industrial building in Changchun, Northeast China. A TRNSYS-based dynamic simulation model was developed by coupling the building load, PEMFC stack, vertical ground heat exchanger, water-source heat pump, thermal storage tank, battery storage, circulation pumps, and coordinated control modules. The recovered PEMFC waste heat was preferentially used for space heating and thermal storage and was further allocated for ground-side thermal compensation when required. Annual and ten-year simulations were conducted to evaluate the effects of PEMFC integration on ground-side temperature, soil thermal balance, heat pump power consumption, and seasonal coefficient of performance. The simulated annual heating and cooling demands were 516,721 and 99,538 kWh, respectively, confirming the strongly heating-dominated load profile of the case building. Compared with the reference GSHP system, the PEMFC-assisted system reduced the annual soil temperature drop from 1.24 °C to 0.37 °C. Over ten years, the final average soil temperature increased from 7.29 °C to 9.95 °C, corresponding to a 52.1% reduction in cumulative soil temperature decline. In addition, the winter heat pump power range decreased from 15.76–39.94 kW to 12.33–28.90 kW, while the average heating-season COP increased from 4.68 to 5.21. These results demonstrate that PEMFC waste heat recovery can serve not only as an auxiliary heating source but also as an active ground thermal compensation mechanism, thereby improving the long-term thermal sustainability and operational performance of GSHP systems in severe cold regions.