Performance study of a solid oxide fuel cell and gas turbine hybrid system designed for methane operating with non-designed fuels

This paper presents an analysis of the fuel flexibility of a methane-based solid oxide fuel cell-gas turbine (SOFC-GT) hybrid system. The simulation models of the system are mathematically defined. Special attention is paid to the development of an SOFC thermodynamic model that allows for the calculation of radial temperature gradients. Based on the simulation model, the new design point of system for new fuels is defined first; the steady-state performance of the system fed by different fuels is then discussed. When the hybrid system operates with hydrogen, the net power output at the new design point will decrease to 70% of the methane, while the design net efficiency will decrease to 55%. Similar to hydrogen, the net output power of the ethanol-fueled system will decrease to 88% of the methane value due to the lower cooling effect of steam reforming. However, the net efficiency can remain at 61% at high level due to increased heat recuperation from exhaust gas. To increase the power output of the hybrid system operating with non-design fuels without changing the system configuration, three different measures are introduced and investigated in this paper. The introduced measures can increase the system net power output operating with hydrogen to 94% of the original value at the cost of a lower efficiency of 45%.

Research highlights▶ Mathematical models of all the components in the hybrid system are defined. Detailed thermal dynamic model of the SOFC developed in this paper includes convectional heat transfer between gas and solids as well as radiation and conduction between solid materials. Thus the SOFC model can be used to calculate the radial temperature gradients, which is the main source of stress. ▶ New design points are defined for the hybrid system operating with non-designed fuels. ▶ The performance of a methane-based hybrid system operating with non-designed fuels is discussed both at its design point and part-load conditions. ▶ Three possible measures are introduced and investigated to increase the power output of the hybrid system operating with non-designed fuel.