Hydrated organic salts as materials for low-temperature thermochemical energy storage

Thermal energy storage (TES) is a key technology in a world where energy demand is increasingly predominant. A lot of energy in every kind of process is irremediably lost as heat, but TES systems may be the solution to catch and use it for other purposes, such as water warming. Methods to achieve this purpose can be divided into physical and chemical processes: the second ones (thermochemical energy storage) are particularly relevant because the correlated systems promise high energy density (cutting costs) and a negligible heat loss. To this purpose, nowadays several materials are studied; among these, it has been revealed that hydrated salts fit properly the characteristics to be thermochemical materials working at mid-low temperatures. Such materials, which should incorporate as much water molecules as possible, are based on performing a reversible dehydration/hydration process to store energy through the dehydration process (endothermic) and release it through the hydration one (exothermic). To the best of our knowledge, all the hydrated salts so far analysed are inorganic and often characterised by deliquescence issues. In this preliminary study, there are reported some hydrated organic salts that could be suitable as thermochemical materials, avoiding deliquescence phenomena by using insoluble or slightly soluble salts. Moreover, this study is focused on reactions characterised by a dehydration/hydration cycle that occurs at low temperature (ideally below 100°C).