In the building heating/cooling sector, resorting to the use of renewable energy is difficult, as there is a strong seasonal difference between the periods of greater demand for thermal energy compared to those of greater supply. To effectively address this misalignment, a possible solution is to use seasonal storage systems; in this context, underground thermal storage systems (ATES – Aquifer Thermal Energy Storage systems) have significant potential.
This report describes the results and methodologies adopted to investigate the pre-feasibility and sustainability of ATES systems and promote their development on the national territory, since no ATES project currently exists in Italy despite the geological characteristics being rather favorable.
Based on the geological characteristics and the availability of data, sites have been identified in Italy on which accurate 3D simulations can be carried out with the aim to investigate the evolution of temperature and pressure fields following the installation of ATES systems.
For the site defined as “Lombardy Area”, the fluid dynamic simulations started in 2020 were completed using two calculation codes (GeoSIAM and FeFlow): based on different methods, the numerical results were validated and their applicability to the study of ATES systems assessed. An HT-ATES (high temperature) system was hypothesized in which the excess heat produced by a biomass power plant is accumulated underground and extracted in subsequent periods; various options of the industrial thermal storage process were evaluated to investigate the effect of the different temperature of the injected water and the effect of different distances between the wells. The analyzes made it possible to define the optimal condition for the implementation of an ATES project.
For the site called “Areale Roma”, geological and fluid dynamic numerical simulations were carried out aimed at demonstrating the feasibility of an LT-ATES (low temperature) system in an area with a high population density. Two different configurations were analyzed: the first assuming a single pair of wells and the second assuming five pairs of wells in order to evaluate the possible interferences between them.
The results of the numerical simulations prove that the methodologies adopted by the GeoSIAM and FeFlow codes are suitable for ATES applications.