Thermo-economic analyses of solid oxide fuel cell-gas turbine hybrids considering thermal cell gradients

Techno-Economic Optimization of SOC Design and Operating Conditions in a Solid Oxide Fuel Cell-Gas Turbine Hybrid System

“…For the system analysis, the cell stack is integrated into a GT and operated under pressurized conditions to identify the ideal operating pressure and fuel utilization factor. 16 The lowest cost of electricity is obtained for an operating pressure of 5 bar and a fuel utilization factor of 85%. In general, low operating pressures can lead to high flue gas exhaust temperatures, whereas high compression ratios limit fuel and air pre-heating, which then requires heat from the SOFC off-gas resulting in a reduction of the GT firing temperature.…”

“…14,15 The SOFC model with its optimized cell design is then integrated into a SOFC-GT hybrid system to identify the ideal system operating conditions with respect to economics. [16][17][18] This analysis allowed us to identify a Dresser Rand KG2-3G EF gas turbine with an ISO rating of 1.83 MW as suitable engine to support a ~10 MW SOFC-GT hybrid plant. For the GT, a model is developed that is able to predict the off-design performance based on compressor/turbine maps and corrections for the max.…”

Thermo-economic analysis of a solid oxide fuel cell-gas turbine hybrid with commercial off-the-shelf gas turbine

“…This work is building upon previous studies conducted by the authors, which include the optimization of the SOFC cell design with respect to thermal gradients and specific cell cost under SOFC-GT hybrid operating conditions [27] and the optimization of the SOFC-GT hybrid system design while considering thermal limitations within the SOFC [18]. The results suggest that it is favorable to operate the hybrid system at a pressure ratio of approximately 5 bar and that the operating point of the GT is rather unconventional when compared to commercial GTs due to the high air requirement of the SOFC, which determines the size of the GT rather than the GT's power output.…”

“…This synergy between the SOFC and GT allows the SOFC-GT hybrid to reach extremely high efficiencies. In this work, the same configuration as in [18] has been chosen to allow direct comparisons between the optimized case in [18] using a custom-designed GT and results from this work using a commercial off-the-shelf GT. In this design, an ejector recycles a portion of the anode off-gas back to the pre-reformer to avoid carbon deposition.…”

“…the anode off-gas from an SOFC) can result in a flow mismatch between the GT compressor and GT expander. This issue is eliminated and ignored with the use of custom-engineered GTs, an approach which is often adopted in simulation work concerned with the evaluation of the full thermodynamic potential of a technology [18,19]. However, GT vendors are not expected to offer GTs specifically designed for SOFC-GT hybrid applications.…”