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Abstract

A multi-stage arrangement for the electrolyte material in a SOFC electrochemical power system. Multiple stages may be arranged in series, and each stage contains electrolyte elements which are constructed of a different material from the elements in previous and subsequent stages. A fuel gas admitted to the power system flows serially through each stage and is then exhausted from the power system. Upstream stages contain electrolyte elements made from an electrolyte material having low ion conductivity and high resistance. Subsequent stages contain electrolytes having progressively higher conductivity and progressively lower resistance. The fuel exhaust from an upstream stage is fed to the next downstream stage until the gas is exhausted from the final stage in the power system. Each stage operates at a progressively lower temperature than the previous stage. In a three-stage embodiment, a first stage has ZrO.sub.2, electrolyte material, a second stage has CeO.sub.2, and a third stage has Bi.sub.2 O.sub.3. The multi-stage fuel cell arrangement leads to a higher total power output for the same initial mass flow rate of fuel gases though the fuel cells.

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First Claim