Compatibility of container materials for Concentrated Solar Power with a solar salt and alumina based nanofluid: A study under dynamic conditions

Thermal energy storage (TES) is an efficient solution for improving the dispatchability of Concentrated Solar Power (CSP) plants. A system, consisting of two tanks with Solar Salt (NaNO3 60% wt. and KNO3 40% wt.) is commonly used. However, the investment cost of this technology is very high, due to the huge amount of salts required (thousands of tons). A pronounced interest is evident for improving the thermophysical properties of molten salts by adding small amounts of nanoparticles in order to reduce the mass of molten salts at CSP. At the moment, the effect of nanoparticle addition on corrosion of container materials is poorly explored. In particular, there are no works regarding the dynamic effect of nanoparticles on the corrosivity of molten salts. In this work we present first ever dynamic corrosion tests for Solar salt doped with alumina nanoparticles (1% wt.). Carbon Steel A516 and SS347, used in double-tank system, were tested. Corrosion rates were 94.8 μm yr−1 and negligible respectively (1000 h, 385 °C). Detailed examination of construction materials revealed incorporation of nanoparticles into the corrosion layer and considerably lower corrosion rate as compared to the previously reported work on the nanoparticles-free Solar salt.The authors show gratitude to the Basque Government for funding this research under the frame of the program ELKARTEK0 15 (Grant agreement KK-2015/00100). It is also worth to mention our gratitude for the technical support to SQM, who are the nitrate salt providers for CSP applications worldwide. Finally, we would like to thank our colleagues Virginia Madina and Inigo Iparraguirre for their useful assessment in corrosion in molten salts and CSP technology issues. Angel G. Fernandez would like to acknowledge the financial support provided by CONICYT/FONDAP 15110019 “Solar Energy Research Center” SERC-Chile