Salt Hydrate Phase Change Materials: Material Behaviour and Thermal Energy Storage Applications

This thesis has investigated the use of hydrated salt phase change materials (PCMs) for sustainable thermal energy storage. The research spanned theoretical foundations, extensive experimental characterization, and the development of practical composite systems, all aimed at addressing both energy efficiency and environmental sustainability. In the early chapters, the fundamental principles of thermal energy storage were established. A clear distinction was drawn between sensible and latent heat, with an emphasis on the advantages of latent heat storage during phase transitions. Salt hydrates were introduced as promising candidates due to their high energy density and favorable melting behavior. The theoretical discussion provided the necessary background for understanding the thermodynamic and crystallographic factors that influence the performance of these materials. The experimental work involved a suite of advanced characterization techniques. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and X-ray diffraction (XRD) were employed to evaluate the thermal stability, phase change behavior, and crystalline structure of the recycled salt hydrates. These methods yielded important insights into the melting mechanics, the role of water coordination, and the challenges posed by phase separation and corrosion. Despite these challenges, the overall performance of the salt hydrates confirmed their suitability as PCMs. A significant portion of this work focused on the development of composite systems to enhance the practical application of salt hydrates. By incorporating the salt hydrates into cementitious and vermiculite matrices, the research demonstrated improved handling and stability of the materials. This integration not only maintained the essential thermal properties but also enabled compatibility with building materials—a key step toward real-world implementation. Sustainability has been a core theme throughout this thesis. The use of recycled materials and the focus on reducing carbon emissions underscore the environmental benefits of adopting hydrated salt PCMs. While several technical challenges remain, the study has provided a robust framework for future efforts to optimize these materials. In particular, the promising results suggest that with further research—especially in areas such as long-term performance testing and advanced stabilization techniques—salt hydrate-based thermal batteries could become an integral component of next-generation energy systems. In conclusion, the work presented in this thesis demonstrates both the potential and the challenges of using hydrated salt PCMs for thermal energy storage. The findings contribute to a broader understanding of phase change materials and open up new possibilities for sustainable energy solutions. The insights gained here will serve as a valuable guide for future research and technological developments aimed at achieving efficient, durable, and environmentally friendly energy storage systems.