Thermodynamic analysis of a combined gas turbine power system with a solid oxide fuel cell through exergy

This paper examines the exergetic performance of a high-temperature solid oxide fuel cell (SOFC) combined with a conventional recuperative gas turbine (GT) plant. Individual models are developed for each component, specifically for SOFC and a combustor that is located downstream of the cell stack. The exergy destruction and efficiency of each component are derived and presented. Furthermore, the overall system is analyzed and its exergy efficiency, as well as exergy destruction, is computed. An assessment of the cycle is performed for an actual system and the results for certain operating conditions are compared with past published results. The comparisons provide useful verification of the thermal simulations in the present work. Further outcomes indicate that increasing the turbine inlet temperature (TIT) results in decreasing the exergy and thermal efficiencies of the cycle, whereas it improves the total specific power output. Also, an increase in either TIT or compression ratio (r_p) leads to a higher rate of exergy destruction of the plant. A comparison between the GT-SOFC plant and a traditional GT cycle, based on identical operating conditions, is also made. The superior performance of a GT-SOFC, in terms of thermal and exergy efficiencies, over a traditional GT cycle is evident: 26.6% and 27.8% better exergetic and energetic performance, respectively, than a traditional GT plant. In this case, the exergy and thermal efficiencies of the integrated cycle become as high as 57.9% and 60.6%, respectively, at the optimum compression ratio.