Comparison of traditional and ambient air-assisted ground source heat pump systems using different bore field configurations

While ground source heat pump systems offer an energy-efficient means of generating local renewable energy for buildings, they also face challenges, such as ground thermal imbalance and the spatial requirements of the bore field. These problems can be addressed by optimizing the bore field configuration and coupling the system with complementary energy sources. This study explores the relationship between the bore field configuration and the long-term performance of an ambient air-assisted hybrid ground source heat pump system. The hypothesis was that utilizing ambient air as a supplementary heat source effectively reduces the significance of the bore field configuration on the techno-economic performance of the system. Understanding this relationship can aid in designing more efficient systems. This paper presents quantitative effects of bore field layout and borehole spacing on the performance of AAA-GSHP systems, using several different performance metrics. The analysis encompassed various bore field configurations assessed for a traditional and an ambient air-assisted ground source heat pump system using dynamic energy simulations for a 50-year period with IDA ICE software. A key finding was that utilizing ambient air as an additional heat source highly effectively mitigates the effects of the bore field layout and spacing on the techno-economic performance of the system. By decreasing borehole spacing from 15 m to 5 m, the required land area was reduced by 89 % while simultaneously achieving a 25 % higher share of renewable energy production compared to the traditional solution. Depending on the bore field configuration, the ambient air-assisted system achieved a 0–31 % lower levelized cost of energy, 2–52 % lower CO₂ emissions, and a 9–58 % higher share of renewable energy production compared to the traditional system. The achieved benefits were particularly substantial with configurations where numerous boreholes were concentrated in a small land area. On average, 40 % of the thermal energy from the ambient air was charged in the bore field, while the remaining portion was utilized directly in the evaporator. The conversion of a traditional system to an ambient air-assisted system can be achieved with a technically straightforward solution that leverages existing technology, increasing the initial investment by only 6 %. The ambient air-assisted ground source heat pump system shows significant potential for applications with a year-round heating demand and limited land area for bore hole installation.