Towards a high fuel utilization and low degradation of micro-tubular solid oxide fuel cells

This work evaluates the relevance of the carrier gas in the performance of micro-tubular SOFCs and describes its role in improving the fuel cell efficiency of these systems. Initial dual operation mode analyses revealed a strong influence of the carrier gas flow on the fuel cell degradation rate, showing a higher degradation rate when low fuel utilization (FU) conditions were employed under low total flow conditions. These experiments evidenced that a suitable fuel-to-carrier gas ratio must be satisfied in order to avoid mass transport limitations. A decrease of this relation, accomplished in this case by an increase in the amount of gas carrier flow (high total flow conditions), allowed to reduce the degradation rate even at high fuel utilization conditions (80%), breaking the limitations traditionally observed for this technology. This approach improves system efficiency –in terms of fuel consumption– while decreases the degradation rate.