Why use salt as a thermal storage medium?

Depending on its composition, liquid salt can be used as a storage medium at temperatures up to 750 °C without pressure. Solar salt, for example, has been used for decades in concentrated solar thermal power plants at temperatures up to 550 °C. Salt is therefore a market-ready, cost-effective storage and transfer material with high storage capacity, making it ideal for a wide range of applications in electricity generation and industrial heating processes.

Unlike water, salts remain single-phase—that is, completely liquid—at high temperatures and without pressure. Although they have only about one-third of the heat storage capacity of water, they are chemically stable. Compared to solid-state storage systems, the liquid salt here also serves as the thermal transfer medium—thereby simplifying the heat transfer process by reducing the number of system components. 

Nitrate and nitrite salts are chemically and physically stable up to 550 °C. They are primarily used as storage media and heat transfer fluids for steam power plants and industrial heating processes. The thermal properties of three typical salts are shown below: