Design of High Specific Power Solid Oxide Fuel Cells

Abstract

The development of solid oxide fuel cells (SOFCs) has progressed from the early Electrolyte Supported Cell (ESC) to state-of-the-art Anode Supported Cell (ASC), which allows the implementation of thinner electrolyte layer (less than 10 micron) and reduction in the operating temperature (below 800°C). The various components of SOFC are constantly being optimized by many research groups to further improve the overall stack performance, including specific power, power density, thermal shock resistance, rapid start-up, and thermal cycling exposure.Precision Combustion, Inc. (PCI) has been working on an advanced electrochemical-based energy storage and power generator design for meeting aggressive specific-power and specific-energy targets required for mobile and transportation applications, such as all-electric propulsion of ground and air vehicles. The key drivers are an exceptionally power-dense solid oxide fuel cell design operating with energy-dense liquid fuels and a hybridized system architecture that maximizes component efficiencies for ultra-high system efficiency. This effort builds on PCI’s experience in developing groundbreaking SOFC generators for mobile and space applications.PCI has developed and demonstrated a novel design of fuel cells with high specific power, that also allows for direct internal reforming of methane and hydrocarbon fuels within a SOFC stack. The system consists of interconnected internal reforming Microlith® metal mesh catalysts strategically embedded within the solid oxide stack. The fuel cell configuration was optimized to reduce CTE mismatch and to improve area specific resistance. The resulting enhanced heat transfer design of the combined components offers the potential for higher overall system efficiency and system simplification as well as enables further compactness and weight reduction of the fuel cell while improving the conditions for long system life. The approach also offers the potential to operate with a wide range of input fuels (i.e., high hydrocarbons as well as various levels of CO2 and water in the fuel inlet) without forming carbon. Carbon formation within the stack system has been known to be detrimental to the performance and durability. Our approach allows for the operation of a modular, advanced SOFC stack for generating power directly from hydrocarbon fuels. Computational design, process simulation, and qualification testing were performed to validate the concept.In this presentation, the results from a breadboard SOFC stack system operation will be highlighted, including the power density, efficiency, and durability. An improvement in the performance as a result of the design advancement, which could improve the stack lifetime, will also be described. The carbon avoidance in the stack while operating with hydrocarbon fuels and with a low water requirement was confirmed. Sensitivity study of the concept to temperature, flow rate, and anode fuel composition was performed and will be highlighted. Finally, preliminary results from the fuel cell design optimization activities will be summarized.