Performance characteristics of a solid oxide fuel cell/gas turbine hybrid system with various part-load control modes

The purpose of this study is to compare the part-load performance of a solid oxide fuel cell/gas turbine (SOFC/GT) hybrid system in three different control modes: fuel-only control, rotational speed control, and variable inlet guide vane (VIGV) control. While the first mode maintains a constant air supply and reduces the supplied fuel to achieve part-load operation, the other modes are distinguished by the simultaneous controls of the air and fuel supplied to the system. After the performance analysis of a SOFC/GT hybrid system under part-load operating conditions, it was concluded that the rotational speed control mode provided the best performance characteristics for part-load operations. In spite of worse performance than the rotational speed control mode, the VIGV control mode can be a good candidate for part-load operation in a large-scale hybrid system in which the rotational speed control is not applicable. It was also found that, in spite of a relatively small contribution to the total system power generation, the gas turbine plays an important role in part-load operation of a SOFC/GT hybrid system.