Concentrated solar power systems require effective high-temperature energy storage to deliver dispatchable electricity independent of solar availability. Thermochemical energy storage using metal oxide redox reactions offers a promising approach, with perovskite oxides emerging as leading candidates due to their structural versatility and cycling durability.
Perovskite oxides—compounds with the general formula ABO₃—can be systematically tuned by substituting elements at the A-site (lanthanum, barium, strontium, calcium) and B-site (cobalt, iron, manganese) positions. This compositional flexibility allows engineers to control reduction temperatures, oxygen exchange capacity, and reaction kinetics independently.
Cobalt- and iron-based perovskites operate efficiently at relatively low temperatures (300–500°C), enabling rapid charging and discharging cycles. They achieve reversible oxygen release-and-recovery of 0.25–0.50 moles per formula unit, supporting practical cycling performance. Calcium manganite compositions, conversely, operate at higher temperatures (700–1100°C) but demonstrate superior thermal stability and deliver total storage densities exceeding 800–1000 kJ/kg through combined sensible and chemical heat.
Experimental validation has progressed beyond laboratory thermogravimetric analysis into packed-bed reactors, fluidized beds, and directly irradiated granular-flow systems, confirming technical feasibility under realistic operating conditions. These demonstrations reveal that material performance under continuous cycling differs meaningfully from equilibrium predictions, introducing practical constraints on cycling speed and oxygen exchange depth.
Critical challenges remain. Scaling from laboratory samples to ton-scale reactor operation requires solving heat and mass transfer limitations. Kinetic performance degrades in packed configurations due to diffusional constraints. Material sintering and surface area loss during repeated heating cycles can reduce reactivity over extended operation.
Future development priorities include rational doping strategies to enhance low-temperature kinetics while maintaining high-temperature robustness, advanced reactor designs that minimize mass transfer resistance, and system-level demonstrations coupling solar receivers to storage and power generation. Commercial viability ultimately depends on cost-competitive manufacturing and demonstrated cycle life exceeding 10,000 full-depth discharge cycles.
