Life cycle analysis on phase change materials for thermal energy storage.

Abstract: Sustainable energy sources and utilization is a large area of interest and the developments are moving fast. Recently, thermal energy storage in the form of phase change materials other than water have caught more interest and a need of analysis for the entire life cycle of the materials have appeared. Previous work in the area shows that health and safety aspects of the products’ life cycle have been neglected and comparisons between different phase change materials other than water are sparsely researched. The objectives for this report are to compare three different phase change material intended for thermal energy storage in a life cycle analysis point of view with both environmental and health and safety aspects. A screening process of materials was subsequently performed in order to find suited materials given the objective (Octadecane, Xylitol and Manganese Nitrate Hexahydrate), taking into consideration the relevance in the scientific community amongst other criteria. The life cycle is in this work bounded from cradle to grave without recycling and for a thermal energy storage heating system operating in Scandinavian climates assuming 52 cycles per year. The results indicate that Octadecane are preferable in terms of global warming potential over 100 years (ca 4.5 kg CO2/kg Octadecane produced) and Xylitol more preferable in terms of cumulative energy demand (ca 21.5 MJ per kg Xylitol produced) and energy payback time (1.17 years). The health and safety aspects are difficult to evaluate in terms of working conditions and ecotoxicity but a simple scale have been put to use to give an overview of the health risk associated with each material. In the health and safety aspects Xylitol also show the most promise but further development of a methodology for evaluating these terms are recommended.