Experimental characterization of a direct methane flame solid oxide fuel cell power generation unit

A direct flame solid oxide fuel cell unit was designed and built in this work for potential combined heat and power generation. The direct combination of a methane flat flame and a solid oxide fuel cell (SOFC) in a simple, "no-chamber" setup was implemented. Direct flame fuel cell experiments were performed using an anode-supported planar SOFC with 50-mm-long square anode and 30-mm-long square cathode. At the SOFC anode, a multi-element diffusion flame burner with an outlet of 55 mm by 55 mm square provided methane/air rich flames for various equivalence ratios and flow rates. The maximum power generated by the direct flame fuel cell unit reached 0.35 W with the power density of 388 W/m² at the equivalence ratio of 1.2. The unit was operated for 3 hours at the equivalence ratio of 1.1 at a fixed voltage of 0.4 V with the current deteriorating from 0.29 A to 0.25 A. The system efficiency of the power generation unit was analyzed by considering the combustion efficiency, the fuel utilization efficiency and the SOFC electrical efficiency. The fuel utilization efficiency was found to be the dominant factor of the total efficiency.