Fabrication and operational experiences of a 6 kW molten carbonate fuel cell stack

An MCFC stack consisting of 20 unit cells with an effective electrode area of 3,000 cm2 was prepared and operated to verify the performance and reliability of the cells. All the porous cell components such as anode, cathode and matrix including electrolyte sheets were manufactured by the tape casting method. Hard-rail type separator made with AISI 316 L stainless steel was used for separating fuel and oxidant gases and conducting electricity between unit cells as well. When fuel gas (H2: CO2: H2O = 72: 18: 10) and oxidant gas (Air: CO2 = 70: 30) were supplied at a flow rate of 40% utilization to the stack at 650 °C, the output power of the stack was measured as 7.6 kW at its peak time. This was much higher than the design value of 6 kW. In addition to this high performance, the standard deviation of cell voltage among 20 unit cells was a mere 3 mV. The stack showed little performance decay up to 1,800 hours of operation time. After an unexpected thermal cycle due to the failure of the pre-heater for fuel gas around 2,000 hours, however, the decay rate became larger accordingly with operating time. The total operation time reached 5,600 hours including 4,800 hours under load in which a total of 23,202 kWh was generated. The evaluation of the stack was quite satisfactory in general except for the difficulty in temperature control under full load.