Ground source heat pump (GSHP) systems, while renowned for their efficiency as renewable energy sources, can experience soil heat imbalance issues during prolonged use. Solar-coupled ground source heat pump (SGSHP) systems have been introduced to mitigate these imbalances by incorporating solar energy to enhance the overall system performance. However, SGSHP systems often face economic challenges because of their high initial and operational costs, thus making them less suitable for use in large-scale heating applications. To address these challenges, this study examines how underground pipe spacing impacts the thermal performance and the economic viability of both GSHP and SGSHP systems. Numerical simulations were conducted using fork models with pipe spacings of 4 m, 4.6 m, and 5.2 m. A comprehensive annual simulation was conducted to evaluate thermal characteristics in the subsurface and at ground level. During the secondary heating phase, spatial temperature variations at 49.5 m below surface were systematically examined alongside surface thermal patterns through cloud visualization and scatter plot analysis. The results revealed that increasing the underground pipe spacing reduces soil heat accumulation, improves the thermal balance, and enhances the heat transfer efficiency for both systems. Economically, pipe spacings of up to 4.6 m maintain cost-effectiveness for GSHP systems, but greater spacings lead to diminished economic performance and extended payback periods. This study provides actionable insights for pipe spacing optimization in the design of both GSHP and SGSHP systems and offers a practical pathway toward improved thermal efficiency and economic feasibility.
Han et al. (Thu,) studied this question.