Techno-economic analysis of a swimming pool heating system retrofitting through a dual source heat pump

The European energy policies are aiming to the electrification of the heating sector as it is considered one of the solutions indicated for the decarbonization of the energy system. Heat pumps represent the most promising and widely adopted solution. However, there are some inherent technological problems to heat pumps, such as evaporator frosting for air-source heat pumps and ground thermal drift for ground source heat pumps. From this perspective a dual-source (air-geothermal) heat pumps represents a promising solution to overcome those challenges. GEOFIT H2020 project aims at developing a wide range of smart solutions for the retrofitting of thermal systems based on shallow and deep geothermal source. In this paper, the retrofitting of a gas boiler based system for the heating of a swimming pool in Galway (Ireland) with a dual-source heat pump with active regeneration of the soil is presented. Firstly, a swimming pool model developed in TRNSYS environment was validated through experimental campaign data retrieved by the Galway demo site. The baseline system composed by a gas boiler was simulated, then a reference retrofit solution composed by a dual source heat pump and an analogous system with a reduced design size were proposed and simulated for a long-term period (20 years). The analysis showed that a relevant primary energy saving is achievable and that the ground thermal drift is mitigated through the active ground heat regeneration. The techno-economic analysis revealed that the proposed system could have a replicability in retrofit solutions, especially in those with a seasonal inbalance where only heating loads are required during the whole year. Considering the current and foreseen increase of the fossil fuel costs, the economic competitiveness will be more favourable.