Evaluation of ground source absorption heat pumps combined with borehole free cooling

• GSAHP with borehole free cooling is proposed to reduce the thermal imbalance.
• Unguarded heating and guaranteed cooling hours are comparatively simulated.
• Performance of GSAHP can be maintained at a high level by borehole free cooling.

Ground source absorption heat pumps (GSAHPs) extract less heat from the ground than ground source electrical heat pumps (GSEHPs) and therefore require fewer boreholes and can reduce the deterioration in heating performance. GSAHP integrated with borehole free cooling is proposed to reduce the thermal imbalance further and keep the heat pump system working efficiently for a longer period. Dynamic simulations of different applications in three typical cities are conducted in TRNSYS to investigate the potential of GSAHP + borehole free cooling. The results show that the soil temperature reduction for GSAHP can reach 6–7 °C after 10 years but can be reduced to 0–3 °C by floor radiation cooling, and the coefficient of performance (COP) and heating capacity can be kept at a high level. Moreover, the unguaranteed heating hours can be greatly reduced, while the guaranteed cooling hours are in the range of 800–1500 in different areas. Additionally, the primary energy efficiency of GSAHP with heating only is 95–120%, while that of the hybrid GSAHP + borehole free cooling can reach 111–156% in typical cities. The proposed system provides additional cooling and indoor comfort while also reducing the underground thermal imbalance, slowing the deterioration of soil temperature and system performance, improving the heating reliability, and reducing the system’s energy consumption.