Magnesium sulphate-silicone foam composites for thermochemical energy storage: Assessment of dehydration behaviour and mechanical stability

This paper assesses the mechanical stability and dehydration behaviour of a new composite material constituted by magnesium sulphate hepta-hydrate, used as filler at vary contents, and a porous silicone, used as matrix in order to evaluate its applicability in sorption thermal energy storage field. This new composite was developed to avoid the typical issues of salt hydrates such as swelling, agglomeration and corrosion issues occurring during hydration/dehydration process. A preliminary physical-mechanical characterization, by means of morphological and calorimetric analysis, was carried out to investigate the main properties of the composite foams. The morphological characterization showed that the foam pores were homogenously distributed and well interconnected to each other. Thermo-gravimetric dehydration tests, have demonstrated that the tested samples are able to exchange efficiently water. Static compression tests evidenced a high compression stability of the material, indicating a high flexibility of the cellular silicone structure. Furthermore, cyclic compression test was performed to evaluate the progressive loss of salt at increasing number of the cycles. After 50 cycles, a reduction of salt hydrate up to 13% was observed. This behaviour, that is potentially a critical factor in these composite structures, was studied for showing that the loss of the salt does not compromise considerably the sorption storage performance of the filled silicone foams. Eventually, the assessment of thermo-gravimetric characteristics and mechanical stability was performed on the MgSO4·7H2O silicone composite foam.