Progetto SWS-Heating - D3.3 Complete characterisation of SWS - RE-69/24

The present deliverable 3.3 refers to the activities performed in the framework of Task 3.3 of the project, mainly focused on the equilibrium (thermodynamic) and kinetic (dynamic) characterization of the most efficient adsorbent composite materials (SWSs) developed in the course of the project, whose synthesis process optimization was reported in D3.2. As already anticipated in previous activities, the most attractive embedded salt selected according to the operating boundary conditions, is the lithium chloride (LiCl). Furthermore, mainly for mechanical stability reasons, the identified matrices are commercially available mesoporous silica gels. The first part of the D3.3 is then dedicated to the equilibrium characterization and sorption heat analysis of the optimal composites developed. This experimental analysis is necessary to define the achievable thermodynamic performance of the composite sorbent, in terms of energy storage density that can be reached under the operating boundary conditions typical of a seasonal TES. The characterization was divided in adsorption and desorption equilibrium isobars by means of thermogravimetric apparatus to investigate the adsorption properties at evaporation and condensation temperatures typical of the adsorption (dicharging) and desorption (charging) conditions previously identified. Once this equilibrium curves were measured, the sorption heat under the expected adsorption jumps, which will occur during the discharging phase, were characterized by means of a coupled thermogravimetric and differential scanning calorimetry (TG-DCS) apparatus, operating under pure water vapour conditions. The results were then properly analysed to define the achievable TES density at material level. The results demonstrated that the sample employing 30 wt.% of salt embedded in round-shaped mesoporous silica gel can achieve up to 0.7 GJ/m3 storage density, according to the different operating boundary conditions investigated. Differently, the one using 35 wt.% of LiCl, can overcome the target of 1.0 GJ/m3.