Compatibility tests between high temperature concrete and molten salts to be used for a thermal energy storage

Abstract

Solar Energy is an abundant resource and can be stored for use at any time of the day. One of the most efficient methods of storage is the thermal process at high temperature (> 400 °C) usual for solar concentrators using molten salts stored in two tanks. In order to reduce total storage costs, an alternative solution would be to store in a solid medium using concrete with thermal properties optimized as a storage medium. The present paper focuses on performing a compatibility evaluation, by analyzing at a laboratory scale, small concrete cubes uncoated and concrete cubes covered with protective refractory coatings that were put in contact with molten salts subject to a heating cycle up to 500°C. In this investigation, thermal cycles between 290 °C and 500 °C were tested by placing cubic samples (40x40x40 cm) in a bath with a ternary mixture of molten salts in a furnace to simulate loading and unloading cycles The results show that a good concrete mix (suitable binder, suitable aggregates, admixtures) is critical for good thermal performance and adequate durability.