Ultra High Efficient Power Generation With SOFC-Gas Turbine Systems: Different Options for 80%+ Efficiency Power Cycles

This work aims to design and simulate an ultra-high-efficient triple combined cycle for large-scale power generation, integrating an intermediate temperature Solid Oxide Fuel Cell (SOFC) with a gas turbine and a bottoming steam cycle. The power plant implements a large cathodic recirculation to preheat the air flow, while the inlet anodic stream is preheated by using steam produced in the heat recovery steam generator and anodic recirculation. System simulations are performed by using GS, a software developed and validated by Politecnico di Milano. State-of-the-art parameters are used for the SOFC, the H-class gas turbine and the steam cycle. Moreover, in order to identify the operating conditions that maximize the efficiency, a sensitivity analysis is performed on the compression ratio, the secondary fuel mass flow rate, the single-pass utilization factor and the cell voltage. The results show that the triple combined cycle may achieve an outstanding net electric efficiency of 84.4% (LHV basis). The sensitivity analysis indicates that adding secondary fuel to a supplementary burner ahead the gas turbine tends to decrease the system efficiency, while also adopting relatively low SOFC voltages (0.775V) or single-pass utilization factors (70%) it is possible to maintain the efficiency above 80%.