A numerical study to determine proper steam-to-fuel ratio in a biogas-fueled solid oxide fuel cell for different levels of biogas methane content

Abstract

It is vital to find the optimal quantity of water added to the fuel in a biogas-fueled Solid Oxide Fuel Cell (SOFC). An under-optimal water quantity can impede steam reforming reactions, while an over-optimal quantity of water (which is equivalent to reduced biogas portion) may reduce the performance of the fuel cell due to a shortage of fuel. Water production in electrochemical reactions and the carbon deposition constraint add to the complexity of water quantity optimization. The present work develops a 3D numerical model to simulate a direct biogas-fueled SOFC to find the optimal steam/biogas (S/C) ratio. Several biogas mixtures (CH4/CO2 ratios) are analyzed. For each mixture, a wide range of S/C ratios is evaluated in a wide range of voltages. It is found that the polarization curves corresponding to different S/C ratios intersect each other for a given biogas mixture. In other words, an S/C ratio can be optimal at some voltages and non-optimal at others. Based on power density maximization as an explicit criterion, the optimal S/C ratio is found to be 0.75 at low CH4 molar fractions (~50%) and 1.25 at high CH4 molar fractions (~75%).

Numerical and Thermodynamic Analysis of the Effect of Operating Temperature in Methane-Fueled SOFC

“…Thanks to these features, SOFCs provide fuel flexibility in energy production, effectively utilizing various fuel sources such as hydrogen, biogas, and methane. Experimental and numerical studies on the use of hydrocarbon-based fuels in SOFCs are documented in the literature [7][8][9][10][11][12][13]. Rath et al conducted a performance analysis of an anode-supported SOFC under various operating conditions.…”

Computational and Experimental Research on the Influence of Supplied Gas Fuel Mixture on High-Temperature Fuel Cell Performance Characteristics

“…There are several studies that have been carried out using the additional ANSYS Fluent SOFC module [14][15][16][17]. In this module, the electrolyte is represented as a pair of imaginary walls, called the "electrolyte surface," through which the movement of ions and electrons is simulated.…”

“…When analyzing publication activity from 2021 to 2024, it was revealed that the interest of researchers modeling SOFCs is aimed at studying the operation of a fuel cell using various types of organic and inorganic fuels, biofuels, and various agricultural and industrial wastes [12,14,16,27,38,39].…”