Design and Evaluation of Hydrogen Energy Storage Systems Using Metal Oxides

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.

Automated summary

This study investigates a high-energy density chemical looping solid oxide cell (CL-SOC) system for the storage of fluctuating renewable energy. Through simulation and analysis, it is found that this system achieves stable charge and discharge rates and reduces system cost.