Potential Application of Renewable Eutectic Mixtures as Phase Change Materials for Thermal Energy Storage

Abstract

Many energies management and storage technologies use phase change materials (PCM) to increase process efficiency. Technologies such as solar thermal energy storage, passive temperature management in buildings, even the development of high-performance sportswear employ various types of PCM. Phase change materials can be classified according to the working temperature, their nature or the phase transition, highlighting the use of materials of renewable origin. There are different methodologies to modify the properties of PCM, among which the preparation of eutectic mixtures stands out. This is a technique that allows obtaining PCM with a lower melting temperature than that of the initial components. Considering the above, this work presents the thermal characterization of mixtures of palm stearin, hydrogenated palm stearin, beeswax, and paraffin wax in order to evaluate the heat storage potential of the resulting products. Mixing ratios of 80:20, 65:35, 50:50, 35:65 and 20:80 were evaluated. Melting and crystallisation temperatures and enthalpies and their solid and liquid heat capacities were measured by differential scanning calorimetry. The thermal stability of the mixtures was also determined by thermogravimetric analysis. From the results obtained, the PCM obtained by mixing beeswax and hydrogenated palm stearin, which presents its eutectic melting point for the mixture ratio of 50:50 with a temperature of 56 °C and an enthalpy of fusion of 264 kJ/kg, stands out.