A thermally self-sustaining miniature solid oxide fuel cell

A thermally self-sustaining miniature power generation device was developed utilizing a single-chamber solid oxide fuel cell (SOFC) placed in a controlled thermal environment provided by a spiral counterflow "Swiss roll" heat exchanger and combustor. With the single-chamber design, fuel/oxygen crossover due to cracking of seals via thermal cycling is irrelevant and coking on the anode is practically eliminated. Appropriate SOFC operating temperatures were maintained even at low Reynolds numbers (Re) via combustion of the fuel cell effluent at the center of the Swiss roll. Both propane and higher hydrocarbon fuels were examined. Extinction limits and thermal behavior of the integrated system were determined in equivalence ratio - Re parameter space and an optimal regime for SOFC operation was identified. SOFC power densities up to 420 mW/cm² were observed at low Re. These results suggest that single-chamber SOFC's integrated with heat-recirculating combustors may be a viable approach for small-scale power generation devices.