(498d) Kinetics of Manganese-Based Mixed Metal Oxide Redox Cycling for Solar Thermochemical Energy Storage

High-temperature thermochemical energy storage shows promise in aiding concentrating solar power plants in meeting variable, grid-scale electricity demand. In this work, manganese oxide-based mixed metal oxide particles have been designed and tested for thermochemical energy storage. Particles are designed for high energy storage capacity, flowability, and physical and chemical stability. We evaluate the effects of Al₂O₃, Fe₂O₃, and ZrO₂ in Mn₂O₃-based spray-dried particles in a TGA between 650°C and 1,200°C over six consecutive redox cycles. Results are compared with thermodynamic predictions from 400-1,400°C under oxidizing and reducing atmospheres. A mixture of 2:1 Fe₂O₃:Mn₂O₃ formed iron manganese oxide spinel (Fe₂MnO₄) on calcination, and demonstrated the highest thermochemical activity despite particle agglomeration and deformation. Conversely, zirconia was an inert support that does not react with manganese oxide. Differences in redox performance between materials with different Fe to Mn ratios have been attributed to ion diffusion and secondary phase formation.