Degradation Analysis of SOFC Performance for Long-Term Operation with High Fuel Utilization

Abstract

In a NEDO’s project from FY2020 to FY2024, Central Research Institute of Electric Power Industry (CRIEPI) has operated three types of SOFC stacks, which are developed by KYOCERA, MORIMURA SOFC TECHNOLOGY (MST), and DENSO in order to clarify the technical issues for high efficiency and toughness of SOFC stacks and establish the method for degradation diagnosis of SOFC stacks. Each SOFC stack has been operated with the high fuel utilization (Uf = 80 and 85%) as a severe condition for high-efficiency and degradation factors for SOFC durability have been analyzed by using the electrode polarization model which we have developed. Analysis results until now showed that dominant degradation factor was increase of cathode overvoltage or IR loss as same as that in the previous term. Moreover, thermal property testing has been conducted to apply the effect of temperature to our polarization model. It was clarified that internal resistance and electrode resistance coefficients can be expressed by Arrhenius equation.

Evaluation of Electrolytic Characteristics with a Single Cell Developed as SOFC

“…It is required for developing the cell performance evaluation which can be adapted under various temperature conditions to determine the temperature dependence of the apparent activation energies in Equation [4], [5], and [6] in advance. The cell temperature was changed from 680 to 775 °C (680, 700, 725, 750, and 775 °C) and performance evaluation in co-electrolysis mode in TABLE I (a) was conducted at each cell temperature (Figure 3(a)).…”

“…Central Research Institute of Electric Power Industry (CRIEPI) has developed the original performance evaluation method of SOFC and evaluated many types of SOFC cell stacks from manufacturers in Japan for many years (3,4). This method can divide into various resistance factors which are the internal resistance (IR) loss, the fuel electrode overvoltage, the oxygen electrode overvoltage, and the Nernst loss.…”

Degradation Analysis of SOFC Performance for Long-Term Operation with High Fuel Utilization (2)

“…Central Research Institute of Electric Power Industry (CRIEPI) has operated three types of SOFC stacks, which are developed by KYOCERA, MORIMURA SOFC TECHNOLOGY (MST) and DENSO, and investigated their long-term durability in this project. CRIEPI has developed the electrode polarization model for SOFC performance which is able to express the SOFC performance such as Nernst loss (η ne ), anode overvoltage (η a ), cathode overvoltage (η c ), and internal resistance (IR) loss (η ir ) under various conditions with high prediction accuracy (2)(3)(4)(5)(6). In this study, we report the current status of the performance for two types of SOFC stacks as flattened tubular stacks (KYOCERA) and planar stacks (MST) which have been operated with the high fuel utilization (U f = 80 and 85 %) as a severe condition for high efficiency, and the degradation analysis of their performances.…”