TAILORED MICROSTRUCTURED CERAMICS FOR THERMOCHEMICAL ENERGY STORAGE

Concentrated solar (CS) for power generation (CSP), coupling CS to high-temperature industrial processes, and harnessing thermal energy from industrial waste heat streams requires advanced thermal energy storage technologies that operate at high temperatures (500 to 1200 °C). A promising solution is reversible thermochemical gas-solid reactions based on metal oxides, carbonates etc., where endothermic reactions are used for heat storage and the reverse reaction is used for heat output, e.g. 𝑀𝑂𝑥(𝑠) +𝛥𝐻 ? 𝑀𝑂(𝑥-𝛿)(𝑠)+ 𝛿2𝑂2(𝑔). The advantages of such gas-solid thermochemical systems compared with phase-change and sensible heat storage are: (1) higher and tunable operation temperature ranges relevant to industrial process integration and high- efficiency air Brayton or sCO2 cycles for CSP; (2) high storage densities (chemical + sensible) over 1000 kJ/kg, (3) potentially cheaper storage media cost, leading to lower overall plant cost. However, low-cost storage materials with advanced chemical and mechanical properties produced from flexible, sustainable manufacturing practices must be developed. Our objective is to develop and commercialize high-performance thermochemical energy storage materials to accelerate integration of CS technologies and utilization of industrial waste heat. We will develop storage materials with hierarchical micro-/macrostructures to overcome current challenges associated with gas- solid thermochemical systems, namely, limitations in reaction rates, heat and mass transfer, storage capacity, operation temperature range, and mechanical/structural properties. In the Phase I project, microstructured materials were produced using a novel thermally and chemically- controlled liquid-fed aerosol manufacturing route developed by the applicant small business, using precursors dissolved or dispersed in a liquid solvent which is sprayed into a high-temperature reactor to produce product particles. Aerosol-generated perovskites (ABO3 oxides with dopants, e.g., Fe, Mg, Bi, Sr, Al) were shown to possess a micron-scale porous structure in comparison to materials produced using conventional synthesis methods. The materials display stable redox activity after 100 deep redox cycles between 500 and 1175 °C; uniform phase and chemical composition; tunable operation temperature ranges and storage enthalpies controlled by doping; and a fast response to rapid thermal cycling (250 °C/min), demonstrating the potential of aerosol technology to deliver materials with the required morphological and chemical properties. In Phase II the applicant small business and project partners will further develop these materials and integrate them into larger, high surface area macrostructures. Underpinning the project will be the experimental and computational elucidation of material properties on the atomic scale and their effect on rate and performance capabilities, which will guide material optimization efforts. The designed materials will be agglomerated into stable, high-surface area macrostructures (granular particulates and porous foams), which can be integrated into thermochemical energy storage applications ranging from CSP with integrated solids to concentrated solar thermochemical fuel synthesis. The project is also supported by subsystem-level modeling and technoeconomic analysis of a generic storage configuration, to refine application-specific development goals and assess performance / cost benefits going forward to scaled-up material manufacturing and pilot storage system testing. We envisage that the commercial thermochemical energy storage materials developed in this project will have significant impact for decarbonization of the US industrial and energy sectors in applications including next-generation concentrated solar thermochemical energy storage, industrial thermal process heating, and zero-carbon solar fuel production.