Molten salt-based nanocomposites for thermal energy storage: Materials, preparation techniques and properties

Amongst various alternative energy storage and energy-producing technologies that have been developed and introduced in the past years, advanced heat transfer technologies are constantly growing popular. The efficiency of these systems is exclusively determined by the heat transfer fluid and its chemical and thermophysical properties. The application frequency of various mixtures of inorganic salts, which offer stability in a greater temperature range than organic compounds, is increasing over time. The most important properties such as the specific heat capacity, along with the thermal conductivity, viscosity, or the melting point can be significantly influenced by a well-designed addition of nanomaterials to the base fluid, leading to a formation of a multi-phase composite system often called nanofluid. Apart from the various energy-storage technologies, preparation techniques, and theoretical fundamentals, this review is aimed at a clear summarization of the up to date described molten salt-based composites with enhanced thermophysical properties, including the most important and often overlooked influencing factors such as the input materials, preparation techniques, and measurement conditions. • State of the art of nanocomposites consisting of molten mineral salts and suitable nanomaterials. • Key properties and application features of the molten salt systems summarized. • Most frequent preparation techniques of the systems described. • Influence of nanomaterial addition into the systems discussed and outcomes generalized. • Inconsistency in published results and in methodology revealed.