Given the fact that there is a delay between the solar resource and its use, it might be interesting to use excess solar energy during the summer by doing a long-term thermal storage in order to restore the energy surplus during the heating periods. Solid/gas thermochemical systems are good candidates for inter-seasonal heat storage. They allow to get high energy densities (between 300 and 500 kWh.m-3 of solid reactant) and to prevent the heat losses (storage such as chemical potential). These systems are based on a cyclic process involving a reversible chemical reaction between a porous solid reactant and a reactive gas (couple SrBr2/H2O in our case). This reaction is endothermic in a way and exothermic in the other. A key point of solid/gas thermochemical systems is the design of the reactive bed and of the reactor, seat of the thermochemical reaction. This design must take into account two aspects that need to be optimized: the heat and mass transfers in the porous reactive bed and their energy density, which evolve antagonistically. For that different tools have been developed. On one hand, different models of reactive porous media crossed by a moist air flow have been developed. These models take into account the mass and heat transfers through the reactive porous bed. And on the other hand, characterizations of mass transfer in a reactive porous bed were performed. Using these tools, a prototype of thermochemical storage was designed and tested.
Thermochemical process for seasonal storage of solar energy: multiscale modeling and experiment of a prototype operating with moist air