Thermal characterization of HITEC molten salt for energy storage in solar linear concentrated technology

The enhancement in the storage systems developed by solar thermoelectric centrals brings to this renewable energy a considerable efficiency increase. This improvement propitiates the design of storage fluids with lower melting point and higher thermal stability such as molten salt mixtures. This research has broadly studied the HITEC mixture composed by 53 mass% KNO3 + 40 mass% NaNO2 + 7 mass% NaNO3, with the aim to improve the existing solar salt used as energy storage fluid in CSP plants and focus the thermal properties obtained for application in solar linear concentrated technology. HITEC molten salt shows better physicochemical properties than the binary solar salt (60 % NaNO3 + 40 % KNO3), due to its lower melting point which can improve the work temperature range in commercial solar plants. The tested properties studied by differential scanning calorimeter and thermogravimetric analyser were melting points, heat capacities and thermal stability, mainly. This proposed mixture could be used as heat transfer fluid in solar linear concentrated technology extending the work range temperature between 130 and 550 °C. Results conclude that the main challenge in nitrite salts lies in the need to protect the sample above 350 °C with inert gas, to prevent oxidation of nitrite by oxygen.