Comparative thermodynamic analysis on design performance characteristics of solid oxide fuel cell/gas turbine hybrid power systems

This paper presents analysis results for the hybrid power system combining a solid oxide fuel cell and a gas turbine. Two system layouts, with the major difference being the operating pressure of the fuel cell, were considered and their thermodynamic design performances were compared. Critical temperature parameters affecting the design performances of the hybrid systems were considered as constraints for the system design. In addition to energy analysis, exergy analysis has been adopted to examine the performance differences depending on system layouts and design conditions. Under a relaxed temperature constraint on the cell, the ambient pressure system exhibits relatively larger power capacity but requires both higher cell temperature and temperature rise at the cell for a given gas turbine design condition. The pressurized system utilizes the high temperature gas from the fuel cell more effectively than the ambient pressure system, and thus exhibits better efficiency. Under a restricted temperature constraint on the cell, the efficiency advantage of the pressurized system becomes manifested.