Enhancing Fuel Cell/Gas Turbine Hybrid Power Systems via Reduced Fuel Utilization Within Indirect Internally Reforming (IIR) Fuel Cell Stacks

A system design process innovation is reported, in conjunction with a fuel cell/ gas turbine hybrid power system (HPS). Lowering cell stack fuel utilization increases system power generation and cost effectiveness. This occurs with minimal penalty to the system’s lofty efficiency. The cell stack produces more power at lower fuel utilizations, because reactant flows to the stack actually increase. The bottoming gas turbine also increases in power production, because a greater amount of unreacted fuel fires it. Since power generation installation cost is normalized per unit capacity rating (e.g., $/kW), increasing power production is a viable means of lowering capital costs. At lower cell stack fuel utilizations, enhanced regenerative effects within the HPS counteract the increasing prevalence of combustion. System efficiency thus remains stable. The adage that best system performance occurs at the highest cell stack fuel utilizations is based on “parallel plant” logic. The investigators have shown, however, that such reasoning is not necessarily applicable to these HPS designs (which incorporate indirect internal reformation). A process patent is pending.