Salt-metal systems as new storage materials with enhanced thermal conductivity for thermal energy storage (SaltMe)

• Applicants: Professor Dr.-Ing. Antonio M. Hurtado; Privatdozent Dr. Michael Müller, since 4/2023
• Subject Area: Thermodynamics and Kinetics as well as Properties of Phases and Microstructure of Materials
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 497349462

Molten salt systems find application in many important industrial sectors such as metallurgy, nuclear and solar energy or as electrolytes. Solar thermal power plants are a promising area for the use of salts. In recent decades, solar thermal power plants have increasingly been used as an alternative form of electricity generation on an industrial scale in energy technology plants. This technology requires the development of powerful thermal energy storage and heat transfer systems. Molten salt systems fulfil various criteria of energy storage technologies, e.g. high enthalpy of fusion, high heat capacity and low price. On one hand, the variation of the different types of salts allows to find the temperature range for the application in different industrial processes and to create efficient thermal storage systems. On the other hand, salt systems also have disadvantages and limitations, such as low thermal conductivity, high corrosiveness and decomposition at high temperatures.In this project, mixtures of pure metals and molten salts (so-called metal salt systems) will be studied, which can increase the thermal conductivity of molten salts as a heat transfer medium. Furthermore, the addition of pure metals can significantly reduce the corrosion of these materials. For economic and technical reasons, combined molten metal salts are selected from chloride salts (Li, Na, K, Mg, Ca // Cl) and corresponding metals (Li, Na, K, Mg, Ca). Binary metal salt mixtures are limited and are not suitable for technical application conditions that require lower temperatures of the phase transitions. Nevertheless, due to their lower complexity, they are suitable for proving the basic hypotheses. In multicomponent systems the melting temperature can be significantly reduced. But there is very limited information about such systems in literature. Theoretically, the thermal conductivity of these metal salt systems should be increased significantly due to homogeneity and nonmetal-metal transitions. The thermodynamic and thermophysical properties of metal-salt mixtures will be studied to discover the correlations of these properties with nonmetal-metal transitions. To fit the main parameters of new salt mixtures to the requirements of CSP a great variety of possible combinations will be considered. To reliably solve this task, a universally consistent thermodynamic database needs to be developed. CALPHAD modelling will be combined with thermochemical analysis.

• DFG Programme: Research Grants
• Ehemaliger Antragsteller: Dr. Dmitry N. Sergeev, until 4/2023