Thermodynamic assessment of SOFC-ICGT hybrid cycle: Energy analysis and entropy generation minimization

Hybrid power systems are being developed by the integration of fuel cell with conventional gas turbine. Integration of solid oxide fuel cell (SOFC) with gas turbine (GT) to form a hybrid cycle based power plant has been considered as this is known to be highly efficient primarily performance of SOFC being not limited to Carnot efficiency. In this article, a novel and optimal thermal integration of SOFC with intercooled-recuperated gas turbine has been presented. The novel contribution of this work is integration of blade cooled gas turbine model to a SOFC model. 1st and 2nd law thermodynamic analysis has been performed analyzing the influence of compression ratio (rp,c) and turbine inlet temperature (TIT) on hybrid plant specific work, hybrid efficiency, blade coolant requirement and entropy generation rate. The performance of hybrid system has been optimized by entropy generation minimization, for this purpose a constraint based algorithm has been developed, which is a function of recirculation ratio, mass of fuel and TIT, based on which gas composition at the anode exit stream has been examined. It has observed that the entropy generation first increases and then decreases as TIT increases. Furthermore, a unique performance contour has also been plotted for proposed hybrid cycle, which can be utilized by power plant designer. At TIT 1800K and rp,c 20, optimal efficiency has been achieved with entropy minimization of 8.05 W/K.