Review of organic and inorganic waste-based phase change composites in latent thermal energy storage: Thermal properties and applications

Systematization and analysis of standalone waste materials that can serve as phase change materials (PCMs), and composites consisting of commercially available PCMs combined with organic and inorganic waste materials is presented. Within the conducted review research, obtained thermal properties of so far investigated wastederived PCMs were presented, assessing, among other, their latent heat storage capacity, thermal conductivity, and thermal and cyclic stability. Refined coconut oil and Allanblackia oil exhibited exceptional thermal and cyclic stability along with high values of latent heat, amounting 105 kJ kg- 1 and 81 kJ kg- 1, respectively. In some cases incorporation of waste materials significantly improved thermal properties, e.g. the addition of carbonized waste tire rubber to dodecyl alcohol increased its thermal conductivity to 0.431 W m- 1K- 1, representing an increase by a factor of 2.3. This enhancement led to a 17.2 % reduction in heating times and a 20 % reduction in cooling times compared to using pure PCM. Besides providing extensive data on thermophysical properties of phase change composites, the study provides a comprehensive overview of their applications, economic feasibility, and environmental implications. This extensive review shows the potential of waste-derived PCMs to contribute to a circular economy by repurposing waste materials for sustainable energy solutions and reducing environmental impacts. The findings indicate that while valorising wastes or by-products as latent thermal energy storage materials is feasible, more research efforts are required towards potential commercialization.