Exploring Conditions That Enhance Durability and Performance of a Tubular Solid Oxide Fuel Cell Fed with Simulated Biogas

Abstract

Tubular solid-oxide fuel cells (t-SOFCs) fed directly with biogas, an equiproportioned mixture of CH 4 and CO 2 produced by fermentation of organic waste, are subject to nonuniform thermal stresses due to internal dry reforming in the anode entrance region coupled with structure exfoliation due to coking, resulting eventually in cell rupture. The integral t-SOFC is of practical interest, although many laboratory studies are conducted in differential button cells. Guided by mechanistic understanding and a robust thermodynamic model, the operating temperature and biogas feed composition were explored experimentally in order to enhance durability and performance of the t-SOFC. Thus, a temperature of 900 °C, a feed CH 4 /CO 2 ratio of 45/55, and a fuel utilization ≥25% were found to be optimal. The cell durability, performance, efficiency, and outlet gas composition at open-circuit voltage (OCV) as well as at different loads were found to be in accord with a thermodynamic analysis and mechanistic understanding based on a set of four independent overall reactions (ORs). It is shown that the OCV is independent of the chosen electrodic OR. In addition to single-tube experiments, a 5-tube SOFC pilot-unit was preliminarily tested as a step toward scale-up of this promising renewable energy technology.

A conceptual review of sustainable electrical power generation from biogas

“…The overpotential should be decreased to improve SOFC efficiency 111 . For example, the selection of optimum operating conditions was empirically found to be 900°C as operating temperature for SOFC, 45/55 CH 4 /CO 2 as biogas feed composition, and higher than 25% as fuel utilization for tubular SOFC 112 …”

A Brief Review on Recent Advancement of Anode Materials for Biogas-Fed Solid Oxide Fuel Cells (SOFCs)

“…Solid-oxide fuel cells (SOFCs), with its fuel flexibility, can use biogas directly and with little pre-treatment. SOFCs employ both CH4 and CO2 contained in biogas to create a syngas (CO+ H2) combination with a higher energy content, which further are oxidized to produce electricity, via internal dry reforming [5].…”