Demonstration of a highly efficient solid oxide fuel cell power system using adiabatic steam reforming and anode gas recirculation

Solid oxide fuel cells (SOFCs) are being developed for a wide variety of applications because of their high efficiency over a wide range of power levels. Applications for SOFCs include 1–2 kW residential combined heat and power applications, 100–250 kW systems for distributed generation and grid extension, and megawatt-scale power plants utilizing coal. This paper reports on the development of a highly efficient, small-scale SOFC power system operating on methane. The system uses adiabatic steam reforming of methane and anode gas recirculation to achieve high net electrical efficiency. The heat and water required for the endothermic reforming reaction are provided by the recirculated anode gas emerging from the SOFC stack. Although the single-pass fuel utilization is only about 55%, because of the anode gas recirculation the overall fuel utilization is up to 93%. The demonstrated system achieved net power output of 1650–2150 W with a maximum net LHV efficiency of 0.566 at 1720 W. Overall system efficiency could be further improved to over 0.60 with use of properly sized blowers.

► Tested high-efficiency SOFC power system with steam reforming and anode recycle.
► Off-stack, adiabatic steam reforming used to maximize SOFC performance.
► System produced 1.7 kW at 57% net LHV efficiency on sulfur-free methane.
► All heat and water for steam reforming reaction provided by the hot anode tail gas.