Thermo-Economic Operation Analysis of SOFC–GT Combined Hybrid System for Application in Power Generation Systems

This study investigated the combination of the direct and indirect hybrid systems in order to develop a combined hybrid system. In the proposed system, a direct solid oxide fuel cell (SOFC) and gas turbine (GT) hybrid system and an indirect fuel cell cycle were combined and exchanged the heat through a heat exchanger. Several electrochemical, thermal, and thermodynamic calculations were performed in order to achieve more accurate results; then, beside the parametric investigation of the abovementioned hybrid system, the obtained results were compared to the results of direct and indirect hybrid systems and simple GT cycle. Results indicate that the efficiency of the combined hybrid system was between those of the direct and indirect hybrid systems. The electrical efficiency and the overall efficiency of the combined hybrid system were 43% and 59%, respectively. The generation power in the combined hybrid system was higher than that of both other systems, which was the only advantage of using the combined hybrid system. The generation power in the combined hybrid system was higher than that of the direct hybrid system by 16%; accordingly, it is recommended to be used by the systems that are supposed to have high generation power.