Measuring thermo-physical properties of phase change materials (PCM) in a consistent and reliable manner is essential for system layout of thermal energy storages and correspondingly material selection. Only if basic properties are assessed in a comparable way a selection process leads to the top candidate for any given application and thus enhances market penetration of renewable energy sources coupled with thermal energy storage. In this study, we focus on differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) as basic assessment techniques and develop consistent measurement procedures to create a database with comparable results. We show consistency of the measured results through analysis of coefficient of variation (CV), being in the mean 1.69%, 0.05%, 0.06% and 4.00% for enthalpy, melting onset, melting peak and maximum operating temperature, respectively. Overall, 23 PCM have been measured with the presented methodology, which was mainly possible due to the reduced measurement and preparation time per PCM compared to standard techniques, while achieving similar accuracy and precision.

Interest in phase change materials keeps on rising as thermal energy storage grows in popularity in the scientific community as a promising complement for renewable energies in the future. Extending the possibilities beyond pure compounds, the use of mixtures (especially eutectics) widens the range of suitable phase change materials (PCM) available in the market. However, a precise knowledge of the mixtures’ phase behavior is required, making phase diagrams the most appropriate tools to follow. The aim of this work is to collect and analyze published literature concerning the phase diagrams of fatty acid esters mixtures, which constitute promising candidates as PCM due to their attractive properties, such as high latent heat, chemical stability and the possibility of extracting them from vegetable and animal oils. The topic appears as a still open scientific field, where further studies need to be performed to complete, complement and perfect the currently available information.

Latent heat storage units for refrigeration processes are promising as alternatives to water/glycol-based storage due to their significantly higher energy densities, which would lead to more compact and potentially more cost-effective storages. In this study, important thermophysical properties of five phase change material (PCM) candidates are determined in the temperature range between −22 and −35 °C and their compatibility with relevant metals and polymers is investigated. The goal is to complement existing scattered information in literature and to apply a consistent testing methodology to all PCMs, to enable a more reliable comparison between them. More specifically, the enthalpy of fusion, melting point, density, compatibility with aluminum, copper, polyethylene (PE), polypropylene (PP), neoprene and butyl rubber, are experimentally determined for 1-heptanol, n-decane, propionic acid, NaCl/water mixtures, and Al(NO₃)₃/water mixtures. The results of the investigations reveal individual strengths and weaknesses of the five candidates. Further, 23.3 wt.% NaCl in water stands out for its very high volumetric energy density and n-decane follows with a lower energy density but better compatibility with surrounding materials and supercooling performance. The importance of using consistent methodologies to determine thermophysical properties when the goal is to compare PCM performance is highlighted.