Power maximization and load range extension of solid oxide fuel cell operation by water cooling

To be suitable for a wider range of applications, the capability of solid oxide fuel cell (SOFC) to be operable under various load conditions is needed. Under extreme load conditions, SOFC thermal management can become more difficult. In the present study, the thermal limiting load of the planar SOFC stack, and its enhancement using water cooling, are evaluated. Three-dimensional computational fluid dynamics (3D-CFD) modeling is conducted to simulate SOFC operation with wide-range operating conditions. It is found that current density of conventional SOFC is likely to be limited by thermal constraints, while that of water-cooled SOFC is much more robust against them, enabling the water-cooled SOFC to operate at much higher power densities. The maximum power of conventional SOFC can be enhanced by tuning air flow rate or inlet temperature, but those generally have trade-offs such as a higher parasitic loss. For the thermal constraints and operating conditions used in this study, the thermal limiting power density of water-cooled SOFC operating at 1023 K can be even higher than that of the conventional SOFC operating at 1123 K. Two methods to suppress overcooling in water-cooled SOFC operations at part-load are also proposed and evaluated.