COBALT OXIDE-BASED STRUCTURED THERMOCHEMICAL REACTORS/HEAT EXCHANGERS FOR SOLAR THERMAL ENERGY STORAGE IN CONCENTRATED SOLAR POWER PLANTS

Based on the characteristics of the oxide redox pair system Co3O4/CoO as a thermochemical heat storage medium and the advantages of porous ceramic structures like honeycombs and foams in heat exchange applications, the idea of employing such ceramic structures coated with or manufactured entirely from a redox material like Co3O4, has been implemented. Thermo-Gravimetric Analysis (TGA) experiments have demonstrated that laboratory-scale Co3O4-coated, redox-inert ceramic foams and honeycombs exhibited repeatable, cyclic reduction-oxidation operation within the temperature range 800-1000 degrees C, employing all the redox material incorporated, even at loading levels exceeding 100 wt% loading percentages. To further improve the volumetric heat storage capacity, monolithic porous ceramic foams made entirely of Co3O4 were manufactured, together with analogous pellets. Such porous structures were also capable of cyclic reduction oxidation, exploiting the entire amount of Co3O4 used in their manufacture. In this perspective, "open" porous structures like the ones of ceramic foams seem to have significant advantages in addressing problems associated with cyclic expansion-contraction that could be detrimental to structural integrity.