Long-Term Evaluation of District-Scale Heat Pumps and Aquifer Thermal Energy Storage in Southern Europe

This study aims to assess the energy and environmental benefits of an aquifer thermal energy storage (ATES) system coupled with a water-to-water heat pump, installed in Rome within central Italy. The energy system is designed to supply a small-scale district heating and cooling network serving a district composed of various user types in the residential and tertiary sectors. It is proposed as an alternative to a conventional reference system, namely an air-to-water heat pump. The thermal behaviour of the wells within the aquifer is simulated using GeoSIAM, while TRNSYS 18 is employed to model the buildings and energy conversion systems. The two configurations are compared over the period from 2015 to 2023, first using annual average values for power grid efficiency and carbon dioxide emission factors, and then hourly data. The results show that the proposed system can support the decarbonization of the building sector by reducing annual electricity demand by 18%, thereby achieving primary energy savings and avoided emissions compared to the conventional setup. Linear regression models applied to the annual average scenario enabled forecasts up to 2030, confirming the long-term benefits of the proposed system, with primary energy savings and carbon dioxide emission avoidance of up to 7% and 24.1%, respectively, under the conservative scenario. These findings highlight the potential of ATES-based systems to support national and European strategic decarbonization objectives in the building sector in Southern Europe.