386 / 2018-12-20 10:26:33

Utilization of multivalent metal oxides in thermochemical heat storage system

Solar energy; Metal oxide; Thermochemical heat storage

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Thermochemical heat storage of solar energy exploits the enthalpy effect of reversible chemical reactions for the storage of solar energy, to reconcile the inconsistency between the continuous electricity demand and the inherently intermittent availability of solar energy. Utilization of a pair of reduction-oxidation reactions of solid oxides of multivalent metals, with the advantages of high energy storage density, high reaction temperature, and evading additional reagent gas storage system by direct employing atmospheric oxygen as reactant, has attracted much attention. Up to now, the pairs of Co3O4/CoO, CuO/Cu2O, Mn3O4/Mn2O3, BaO2/BaO, and Fe2O3/Fe3O4 have been studied and proved promisingly appropriate for industrial application. The reaction temperature of Co3O4/CoO is suitable (~900 癈), and the energy storage density and the conversion rate are relatively high. The porous structure improves its recyclability, but it is expensive and potentially toxic. CuO/Cu2O has a higher reaction temperature (~1100 癈) than Co3O4/CoO and a lower price than other metal oxides. However, sintering is easy to occur in the heating process, and the re-oxidation process is incomplete. The temperature at which Mn3O4/Mn2O3 works is appropriate (~950 癈), and the low cost and nontoxicity benefits its wide application, although the energy storage density is not very satisfactory. BaO2/BaO exhibits high reversibility, but also presents low energy storage density. The low cost and high enthalpy of Fe2O3/Fe3O4 favor the promising prospect, while the high working temperature (~1400 癈) restricts its standalone application. Therefore, it is proposed to be used accompanying with proper partner.