MoltenSalt

Molten salt, sometimes referred to as moltensalt, designates salt compounds that are liquid at elevated temperatures. Most commonly these are inorganic salts melted for use as heat transfer fluids or thermal energy storage media. To tailor melting points and stability, engineers often use eutectic mixtures, such as nitrate-based blends. Fluoride-based salts are also employed in specialized applications, notably certain nuclear and high-temperature systems. Chloride salts are studied as lower-cost options but tend to be more corrosive.

Key properties of molten salts include high boiling points, low vapor pressures, and substantial heat capacity, which together support operation at temperatures well above conventional fluids. Their chemical stability in the chosen temperature window minimizes phase changes and reduces vapor losses. Some molten salts are optimized for heat transfer, while others are designed for long-term thermal energy storage. The exact properties depend on composition, purity, and operating environment.

Applications include thermal energy storage for concentrated solar power plants, where salt is heated during the day and used to drive turbines when sunlight is unavailable; and nuclear engineering, where molten salts serve as coolant or fuel carriers in molten-salt reactors (MSRs). Research also explores high-temperature heat transfer in industrial processes and chemical synthesis. Because of their versatility, molten salts are a focus of energy storage and advanced reactor development.

Advantages include high energy density, low vapor pressure at operating temperatures, and the ability to operate at high temperatures depending on composition. They enable compact, efficient energy storage and high-temperature heat transfer. Challenges include corrosion of containment materials, salt decomposition or impurity accumulation, solidification if temperatures drop, and cost and handling risks associated with nitrate or fluoride chemistries. Material compatibility and system design are active areas of research.

Safety and regulation emphasize proper containment, materials resistant to salt corrosion, and protocols to mitigate oxidizing and toxic decomposition products. Environmental considerations focus on salt purity and potential leakage.