Mid term performance simulation of a dual source heat pump

Electrification of the heating sector is one of the solutions indicated for the decarbonization of the European energy system and the achievement of the 100% renewable targets for residential and tertiary purposes. Towards this aim, heat pumps represent the most promising and widely adopted solution. The GEOFIT project (H2020- 792210) aims to develop components, systems and tools for geothermal-based retrofitting solutions, among them, a key-role is played by geothermal heat pumps. Five demonstration plants will be installed in five European countries. The system that will be installed in in Galway, Ireland was modelled in TRNSYS environment. It consists in a geothermal heat pump that supplies hot water to a swimming pool. The whole borehole field, the heat pump, the hydraulic underground piping and the final user circuit were modelled. A dual source operating mode was analysed: a simple control logic was implemented to switch between ground source (exploited through the borehole field) and air source (exploited by an external dry heater). Finally, a regeneration mode was also considered in order to deliver energy from air to ground, storing heat during hot periods and re-using it during cold ones. A period of ten years was simulated to consider the effects on ground thermal drift. The results showed a relevant energy saving obtained through dual source mode if compared to the standard system supplied by a gas boiler.