Comparative performance assessment of pressurized solid oxide fuel cell / gas turbine hybrid systems considering various design options

This study aims at presenting important aspects in developing the pressurized SOFC/GT hybrid system, such as different types of system configurations, characteristics of matching between SOFC and GT and effects of design constraints. Assorted system configurations, depending on component design technologies, are analyzed and their performances are comparatively evaluated. Various options considered are internal and external reforming processes, reforming steam supply methods and reforming heat sources. Performances are examined in terms of matching of cell temperature and turbine inlet temperature. Performance limitation caused by practical matching of those parameters under additional constraints on the cell stack (temperature difference at the cell) is investigated. Performances of the hybrid systems are also compared with those of the SOFC only systems under identical constraints and the extent of performance enhancement is evaluated. In order for the system to reach a comparable level of efficiency with internal reforming, the system having external reforming requires both high operating temperature of the cell and large temperature difference at the cell. With a practical design constraint, the internally reformed system is more efficient and this superiority becomes increasingly evident as the constraint becomes more severe.