Molten chloride salt technology for next-generation CSP plants: An economically competitive future scenario using Fe-based alloys with corrosion control

Kurzfassung

MgCl2-KCl-NaCl is one of the most promising chloride-salt mixtures for thermal energy storage (TES) in next-generation CSP plants with the advantages of low melting point (~383 °C), high thermal stability (stable at 800 °C), low vapor pressure (~ 1 kPa at 800 °C), and low cost (<0.35 USD/kg) [1]. With the chloride-TES and the advanced supercritical carbon dioxide (sCO2) Brayton power cycle, the next-generation (Gen3) concentrating solar power (CSP) plants could have a high thermal to electric efficiency of >50 % with >700 °C operating temperatures [2]. However, the high corrosivity of molten chloride salt to commercial Fe-Cr-Ni alloy results in the cost of chloride-TES using Ni-based alloys being several times higher than commercial nitrate-TES. It impedes the application of chloride-TES [2-5]. Our previous work showed that with the protection of corrosion inhibitor Mg. the corrosion of Fe-Cr-Ni can be significantly mitigated in molten chloride salt at 700 °C [6]. In this work, the possibility of using Fe-based alloys as the main structural materials for the hot and cold parts of the chloride-TES system is investigated.