Numerical Analysis of Optimal Design and Operation of Solar-Assisted Geothermal Heat Pump System

This study aimed to solve the problem of performance degradation in geothermal heat pump (GSHP) systems caused by a drop in ground temperature due to heating and cooling imbalances in climatic conditions with high heating loads. To this end, a solar-assisted geothermal source heat pump system (SAGHP) utilizing solar energy as an auxiliary heat source was proposed. A numerical analysis model was established based on thermodynamic equations between system components. A numerical analysis tool was developed and validated using actual measurement data. The tool was used to quantitatively analyze system performance based on design variables (solar collector area, thermal storage capacity) and operating variables (source transition temperature). The analysis revealed that excessive collector area led to performance degradation due to over-storage. When the thermal storage capacity or transition temperature was too low or too high, efficiency decreased due to repeated heat source transition or unused solar heat. When optimal conditions were applied, power consumption was reduced by an average of 25.0% compared to GSHP operation alone, and a reduction effect of 28.5% was confirmed based on a three-year average. The SAGHP specific numerical analysis tool developed in this study enables iterative analysis based on a simple input model, significantly reducing the time required for modeling and analysis. Since it was calibrated using actual measurement data, precise performance analysis is possible under conditions similar to actual operating conditions. This enables analysis considering various operating conditions and can be effectively utilized for establishing optimal design and operating strategies. This study confirmed the potential for performance improvement in hybrid regenerative heat source systems and provides practical design and operating guidelines for SAGHP to achieve zero-energy buildings.