Central Research Institute of electric Power Industry (CRCIEPI) has developed original SOFC performance evaluation method and applied to a wide variety of cells. Based on the SOFC performance evaluation method, a new SOEC performance evaluation method has been developed this time. By this evaluation method, the difference between the open circuit voltage and the cell voltage can be expressed by the internal resistance loss (measured value), the fuel electrode overvoltage, the oxygen electrode overvoltage, and the Nernst loss.

In this study, cell performance before and after the CO₂ direct electrolysis test was compared by SOFC and SOEC evaluation methods and clarification of cell degradation factor by CO₂ direct electrolysis.