A Numerical Investigation of the Thermal Stresses of a Planar Solid Oxide Fuel Cell

Abstract

A typical operating temperature of a solid oxide fuel cell (SOFC) is quite high above 750 °C and affects the thermomechanical behavior of the cell. Thermal stresses may cause microstructural instability and sub-critical cracking. Therefore, a joint analysis by the computational fluid dynamics (CFD) and computational structural mechanics based on the finite element method (FEM) was carried out to analyze thermal stresses in a planar SOFC and to predict potential failure locations in the cell. A full numerical model was based on the coupling of thermo-fluid model with the thermo-mechanical model. Based on a temperature distribution from the thermo-fluid model, stress distribution including the von Mises stress, shear stress as well as the operating principal stress were derived in the thermo-mechanical model. The FEM calculations were performed under different working conditions of the planar SOFC. The highest total stress was noticed at the lower operating voltage of 0.3 V, while the lowest total stress was determined at the voltage of 0.7 V. The obtained stress distributions allowed a better understanding of details of internal processes occurring within the SOFC and provided helpful guidance in the optimization of a new SOFC design.

Numerical study of detecting crack initiation in a planar solid oxide fuel cell

“…During the last two decades, the attention to SOFC has been drawn and the number of the experimental and numerical research papers has been increased considerably. [4][5][6][7][8][9][10] Unfortunately, the high-temperature operation of SOFCs has several drawbacks such as limited material selection, accelerated morphological and chemical degradation, and enhanced diffusion of components and impurities between adjacent layers and on the surface. Most researchers nowadays focus on the thermal stress inside the SOFC, [11][12][13][14] They studied the delamination and degradation of SOFCs electrode/electrolyte estimated by calculating the stresses generated within the different layers of the cell.…”

“…However, this technology still faces many challenges such as cost reduction and an extended lifetime operation. During the last two decades, the attention to SOFC has been drawn and the number of the experimental and numerical research papers has been increased considerably 4‐10 . Unfortunately, the high‐temperature operation of SOFCs has several drawbacks such as limited material selection, accelerated morphological and chemical degradation, and enhanced diffusion of components and impurities between adjacent layers and on the surface.…”

System Level Exergy Assessment of Strategies Deployed for Solid Oxide Fuel Cell Stack Temperature Regulation and Thermal Gradient Reduction

“…While fuel cell degradation is mainly attributed to the materials and catalyst physicochemical properties and fuel contaminations, 2,3 it is also strongly linked to the thermal instability and stress. 4,5 The latter is particularly important in SOFC case operating at elevated temperatures (700-900 o C) with a high temperature gradients across stack dimensions.…”

Modeling the Mechanical Integrity of Generic Solid Oxide Cell Stack Designs Exposed to Long‐term Operation

“…and Pianko‐Oprych et al. also made an extensive study on planar SOFC stack involving computational fluid dynamics together with structural mechanics shedding light on the transient thermal behavior of the stack and the correlation between stress and operational voltage in the SOFC .…”

“…Similarly, Greco et al showed that the probability of failure of the cells in an operating stack decreases over time due to relaxation of stresses, and the probability of failure peaks at the shifts between operation point [7]. Peksen et al and Pianko-Oprych et al also made an extensive study on planar SOFC stack involving computational fluid dynamics together with structural mechanics shedding light on the transient thermal behavior of the stack [4] and the correlation between stress and operational voltage in the SOFC [14].…”