The storage of fluctuating renewable energy is critical to increasing its utilization. In this study, we investigate an energy conversion and storage system with high energy density, called the chemical looping solid oxide cell (CL-SOC) system, from the integrated perspectives of redox kinetics and system design. The proposed system generates electricity, reproduces hydrogen, and stores it via metal oxide redox reactions in combination with a standard pressure fluidized bed reactor and a reversible solid oxide cell (SOC). We conducted redox kinetic analyses of Fe supported on an Fe-doped calcium titanate carrier in redox reaction using the modified shrinking core model and determined the scale of a fluidized bed reactor by developing the numerical Kunii–Levenspiel reactor model. Furthermore, the SOC redox system was modeled to estimate the round-trip efficiency and the system cost. The CL-SOC system achieved a stable hydrogen charge and discharge rate operation (i.e., constant redox reaction rate) in the fluidized bed reactor. It also achieved the reduction of system cost compared to the conventional high-pressure hydrogen storage system. In addition, the levelized cost of storage, including electricity costs, was calculated, and the advantage was also discussed. In this way, this study describes the integrated method of the CL-SOC system evaluation, which will provide a guide for material and system design.

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400 ppm of CO 2 was captured with Ru/K 2 CO 3 on K-β″ alumina at 30 °C and was transformed into CH 4 successfully when the temperature was increased to 300 °C. K-β″ alumina was employed as the support material, and K + ions were designed to access Ru particles and induce the activation of adsorbed CO 2 . By the promotional effect, the K-β″ alumina-supported catalyst displayed a lower methanation temperature (120 °C) than the γ-Al 2 O 3 -supported one (150 °C). The K-β″ alumina-supported catalysts also exhibited high CH 4 selectivity (79%) and highly stable cyclic properties throughout the tests. Diffuse reflectance infrared Fourier transform spectroscopy revealed that K + in K-β″ alumina actively intervenes in the formation of intermediates (CO 3 2− and CO). The promotion in reactions will be due to σ → π K backdonation and can assist in their reactions to other intermediates (formate and carbonyl) at 120 °C. This implies that promotion of CH 4 intermediates' formation was aided by the conduction of K + in K-β″ alumina.

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