D 3.2 "Synthesis and structural/morphological characterisation of new sorbents"

The main aim of Task 3.2 was the identification of composite sorbents compositions, based on porous matrixes and inorganic salts, to achieve storage energy densities suitable for seasonal thermal energy storage applications according to the boundary conditions defined in the D3.1. This activity was performed systematically, starting from the identification of commercially available porous structures and inorganic salts, whose potential sorption capacities could be in line with the requested operating conditions. These materials were firstly analysed to evaluate their morphological and structural characteristics, paying specific attention to the features of the porous structures, which affect the space available for the inorganic salt embedding, representing a critical parameters for the achievable overall sorption capacity. Subsequently, the dry impregnation method was applied to the identified porous structures and inorganic salts, to obtain composite sorbents with different amounts of embedded salts. A first check of the overall adsorption capacity, which reflects on the achievable thermal energy storage density, was performed to drive the selection of the most promising samples. The full characterization of the thermodynamic and dynamic performance will be then completed in the Task 3.3 and reported in D3.3. The most attractive composites were then thoroughly characterized from the structural and morphological point of view, to validate the achievement of proper composite composition, confirming the correct salt distribution inside the pores and the crystallinity of the deposited salt phases. The obtained results showed that, due to the large amount of salt used to enhance the sorption storage capacity, the applied synthesis procedure was not enough to obtain a reliable composite structure. Accordingly, the procedure was improved by varying the thermal treatment procedure after the impregnation phase. Different approaches were experimentally analysed, giving the opportunity to solve the highlighted issue and obtaining composite sorbents with high amount of embedded salts, with a homogeneous distribution inside the porous structure. Once the lab-scale process for the composite sorbents synthesis was properly optimized, the first scale-up design of a batch synthesis process to produce large amount of materials was designed. It will be then used for the manufacturing of theoptimized SWS to be tested in the demo sites during the second half of the project. The designed process will be fully implemented and tested in the course of Task 3.3 and 3.4.