Numerical analysis of operating range and SOFC-off-gas combustor requirements of a biogas powered SOFC-MGT hybrid power plant

In the present study, a detailed numeric model of the hybrid power plant demonstrator being constructed at the DLR is presented. The model is used for an in-depth investigation of the operating limits using biogases with various methane contents. The influence of fuel cell operating limits, like the stack temperature, minimal cell voltage and maximal fuel utilization ratio, on the hybrid power plant operating range are discussed. While the results show a strong correlation between methane content and operating range, a power output reduction of 33% is still feasible for methane contents as low as 60 vol%. Furthermore, knowing the operating range of the hybrid power plant is crucial for the design of the plant components. Therefore, in a final step, the operating conditions for the fuel cell off-gas combustor are derived for the respective operating ranges.