Solid Oxide Fuel Cell/Gas Turbine Hybrid System Studies

Abstract

Power generation systems based on SOFCs provide a highly efficient alternative to traditional systems. In the present study a sensitivity analysis with cell operating temperature, pressure ratio and fuel utilization as system parameters is performed on a SOFC-GT system fed by Hydrogen and Methane. Exergy losses in different system components and their dependence on system operating parameters and fuel chemistry are investigated in detail. In the considered ranges system efficiency increased with both cell operating temperature and fuel utilization. A flat optimum with pressure ratio was found for Hydrogen (2.5) and Methane (5). The main causes of high losses in the system are found to be very different for Hydrogen and Methane which leads to different optimization strategies.
Following the optimizations comparable system exergy efficiencies were obtained with Hydrogen (76.2%) and Methane (78%). Electrical efficiencies were 74.6% and 80.9% with Hydrogen and Methane respectively. An additional study of a SOFC system without a gas turbine was also undertaken with 4 fuels (Methane, Hydrogen, Methanol and Ammonia). It was observed that it is possible to achieve a high system efficiency by minimizing the excess heat left due to the removal of the gas turbine and utilizing it completely for internal reforming of the fuel. An electrical efficiency of 73.3% was achieved with Methane without the gas turbine.