Preparation and thermal properties of quaternary mixed nitrate with low melting point

• Heat transfer and storage medium for concentrating solar power.
• Melting point of quaternary mixed nitrate salts is lower than 90 °C.
• Other crucial thermophysical properties are very good.

Mixed molten salt is considered as a promising medium for both heat transfer and energy storage in solar thermal power because of its many advantages such as large heat capacity, low vapor pressure, low cost, wide range of temperature in application, etc. In order to obtain molten salt with lower melting point and higher decomposition temperature, a new kind of nitrate was prepared based on different mixing ratios of KNO3–NaNO3–LiNO3–Ca(NO3)2·4H2O. Experimental results show that the melting point of some molten salts can be down to below 90 °C with their decomposition temperature above 600 °C. The new kind of mixed molten salts has a lower melting point and wider usable temperature range. In addition, other thermal properties such as latent heat of melting, specific heat, density, viscosity, thermal conductivity and thermal stability are measured and analyzed, which are also not worse than that of commonly used mixed molten salt. Therefore, it is a promising medium for both heat transfer and energy storage in solar thermal power plants.