Charging and discharging tests of a composite of CaCl2 and vermiculite for thermochemical adsorption energy storage

Thermal Energy Storage plays a crucial role in increasing the flexibility of energy systems and facilitating the integration of renewable energy sources, particularly in the building sector. Salt hydrates combined in composite materials are the most suitable medium for thermochemical adsorption energy storage. This promising technology is characterised by higher energy density compared to sensible and latent heat energy storage systems. In this work, the charging and discharging behaviour of a composite material consisting of vermiculite and CaCl2 is evaluated through experimental tests. The aim is to obtain relevant results for the design of an innovative thermal energy storage prototype in the context of the European project ECHO. A thermogravimetric evaluation was performed through employment of a thermobalance. The instrument measured the mass of water adsorbed and released by the material during the different phases, and possible deliquescence problems could be detected. The discharging and charging cycles were investigated using a small lab-scale setup. The hydration of the composite occurred in a closed-loop system, while the circuit was opened during dehydration. The assessed air temperature lift between inlet and outlet of the material allowed the quantification of the power released in the discharging process. The findings of this research provide useful information regarding the thermal performance and efficiency of the vermiculiteCaCl2 composite as a candidate for thermochemical adsorption energy storage, thus contributing to the development and spread of these systems.