Experimental studies for the cyclability of salt hydrates for thermochemical heat storage

Salt hydrates have promising potential as heat storage materials by use of their hydration/dehydration reaction. These hydration/dehydration reactions are studied in this paper for CuCl₂, CuSO₄, MgCl₂ and MgSO₄. During a hydration/dehydration reaction, the salt shrinks and expands as a result of the differences in densities of the phases. As a result, after the first dehydration cycle, the crystal is fractured into a pseudomorphic state that releases the water molecules more easily. The effect of fracturing is larger in case of hydrates with larger volumetric changes. In this study the performance of hydrates during cyclic loading is related to the pore water production and volume variations. On the basis of such data, it is concluded that CuCl₂ is the most promising heat storage material.