PI: Animesh Kundu
University: Lehigh University

Chloride salts have been established as better candidates as high temperature heat transfer fluids for third generation concentrating solar power plants (CSP) because of their higher thermal stability at temperatures over 750°C . These plants have been projected at high temperatures (great than 700°C) to increase the production efficiency and reduce the levelized cost of electricity (LCOE) to 5¢/kWh. The extreme corrosive nature of the chloride salts towards metal pipes that would contain them in applications is the primary impediment for the commercialization. Binary and ternary chloride salts have been extensively studied in an effort to develop economically and technologically viable salt blends with favorable thermophysical and corrosion properties, but a feasible solution is yet to be realized.

In this exploratory effort, the thermophysical properties of quaternary chloride salt blends (LiCl-NaCl-KCl-CaCl2) will be systematically investigated in an effort to develop an economically feasible salt blend. The effect of the quaternary salt blends on stainless steel at temperatures greater than 750°C in presence of the inhibitor package will be investigated under various under various atmospheric conditions, including nitrogen, carbon dioxide, and air/moisture for prolonged time (about 100 hours). A secondary goal of this proposed effort is to investigate the effect of chloride salts on alumina ceramic castables under identical conditions as the metals. The alumina castable could potentially be utilized as a liner for containing the salts in a molten state at elevated temperatures in thermal energy storage tanks. The corrosion mechanism will be studied by systematic evaluation of the salts on the microstructure and interfaces of these materials by advanced analytical electron microscopy tools. We envision that the scientific insight gained will not only provide guidelines for tuning chloride salt formulations for developing economically/technologically viable solutions, but will also lead to strategies for enhancing the corrosion resistance of these materials by engineering the interfaces.