Effect of Steam on the Performance of an IT-SOFC/GT Hybrid System

The performance of an intermediate-temperature solid oxide fuel cell (IT-SOFC) and a gas turbine (GT) hybrid system fueled with gasified wood chips is analyzed. The effects of steam on the thermodynamic performances of reformer, fuel cell, gas turbine and hybrid system are studied. The results show that the system electrical efficiency can reach up to 59.24% at design condition, and it demonstrates excellent performance. As the steam increases, the reforming temperature decreases, which leads to CH₄ reforming reaction equilibrium constant decreases, and the reaction will be suppressed. The water gas shift reaction equilibrium constant increases with the decrease of the temperature. But the total amount of H₂ shows a decreasing trend. With the steam increases, the fuel cell electrode and ohmic polarization losses increase, Nernst potential decreases, the output power and electrical efficiency show a decreasing trend. And then the hybrid system output power and electrical efficiency decrease. The electrical efficiency decreases from 61% to 56.91%. In consideration of operation security of reformer, fuel cell stack and the hybrid system, maintaining a high value of the steam is very important.