Reticulated porous perovskite structures for thermochemical solar energy storage

Abstract

The inherent capability of concentrated solar power (CSP) plants for sensible thermal energy storage ensures their continuous operation and is considered their most crucial competitive edge versus other renewable energy sources. The storage density of air-operated CSP plants can be significantly increased by hybridizing sensible with thermochemical storage of solar heat, exploiting reversible air–solid oxide reduction–oxidation reactions. Thermochemical storage-relevant-protocols testing of in-house manufactured lab-scale reticu-lated porous ceramic foams made entirely of CaMnO3 perovskite reveals fully reversible reduction-oxidation in up to 46 cycles between 300 and 1100 °C under air, without any deterioration of the foams’ structural integrity and exploitable endothermic/exothermic heat effects between 890 and 920 °C linked to an orthorhombic-to-cubic phase transition. Dilatometry experi-ments with CaMnO3 bars under identical cyclic conditions demonstrate the correlation of this phase transition to an increase in the thermal expansion coefficient but nevertheless, complete recovery of the initial specimen dimen-sions upon completion of a full heat-up/cooldown redox cycle. The possibility of shaping into sturdy reticulated porous ceramic structures which exhibit complete dimensional reversibility upon cyclic redox operation, combined with the low cost, earth abundance and environmentally benign character of the constituting elements, render such perovskite compositions extremely attractive for the manufacture of large-scale porous structured objects for exploitation in various thermochemical processes.