Modelling and Performance Assessment of a Ground-Coupled Ammonia Heat Pump System: The EMPEC Ustka Case Study

This study evaluates the feasibility of using a ground-coupled ammonia heat pump as a heat source for the district heating system in Ustka, Poland. A three-dimensional transient thermal model of a 122-borehole field was developed in ANSYS 2023 R1 using local geological data and hourly meteorological inputs. Three extraction loads—0.50, 0.75, and 1.00 MW—were analysed, together with regeneration periods of one month (August) and six months following the heating season. Ground temperatures were assessed across all geological layers down to 250 m. The simulations show that each of the tested loads leads to a noticeable and lasting reduction in ground temperature. For 1.00 MW, the temperature in the main heat-exchange layers remains more than 2 K below the initial value even after six months of regeneration. At 0.75 MW the deficit is smaller but still persists in the layers that dominate heat transfer. Even the 0.50 MW scenario does not return to thermal balance: the active layers stay more than 1 K cooler after the regeneration period, indicating cumulative long-term cooling. Although the model includes standard engineering simplifications, the large-scale thermal behaviour is consistent across all scenarios. The analysis shows that the analysed GSHP (ground-source heat pump) configuration cannot serve as a primary heat source for the Ustka network in the analysed configuration. Alternative low-emission solutions, such as air-source heat pumps supported by renewable electricity, are more suitable for this site.