High-temperature salt systems for thermal energy storage: A review of thermophysical data and the selection of application-relevant phase change materials

Latent heat thermal energy storage (LHTES) is essential for next-generation concentrated solar power (CSP) and industrial process-heat systems operating above 300 °C. This review consolidates and reconciles thermophysical and compatibility data for eutectic salts between 300 and 800 °C, addressing major sources of variability arising from non-standardized measurement methodology, impurity levels, and handling of hygroscopic salts. Quantitative ranges for melting temperatures, enthalpies of fusion, heat capacities, thermal conductivity, thermal stability, and corrosion behavior were extracted, harmonized, and complemented by an assessment of composite PCM (CPCM) concepts. A structured PCM-selection framework is developed to link property ranges with stability criteria, material compatibility, and application-specific operating windows. Across the evaluated systems, a temperature-band-based selection framework is applied to identify the most promising eutectic salt mixtures for latent heat thermal energy storage. Within the lower and intermediate temperature ranges considered in this study, chloride-based systems dominate, with NaCl KCl MgCl 2 and the binary KCl MgCl 2 eutectic showing the most consistent thermophysical behavior. NaCl CaCl 2 represents a relevant binary option in the mid-temperature range. At higher operating temperatures, carbonate-containing systems become increasingly favorable, with Na 2 CO 3 NaCl and Na 2 CO 3 K 2 CO 3 identified as the most promising candidates in the upper temperature ranges investigated. By unifying heterogeneous datasets and quantifying variability, this review provides a transparent evidence base for PCM selection and highlights priority gaps in high-temperature salt characterization. In addition, the review proposes pragmatic standardization steps for reporting thermophysical and compatibility data to improve comparability across future studies.