Reactant recirculation system utilizing pressure swing for proton exchange membrane fuel cell

Abstract

To minimize the wastage of supplied reactant, fuel cells need to be operated in either dead-end or recirculation modes. A fuel cell operating in a dead-end mode is not durable without periodic purging because of flooding; therefore, a little reactant is unavoidably wasted. Conventional recirculation systems employ mechanical pumps or ejectors as their recirculation devices, but they have drawbacks originating from the inherent properties of pumps and ejectors. This paper proposes a pumpless reactant recirculation system, the pressure swing recirculation system, which utilizes pressure swings produced by the reactant supply and consumption. This system requires only two check valves and a fluid control device, and operates by alternating between the equivalent flow-through and dead-end modes. The proposed system was applied for both anode and cathode of a PEMFC. A single cell was operated in dead-end and pressure swing recirculation modes for comparative analyses. The resultant cell performances in the dead-end mode deteriorated rapidly because of flooding, while those in the pressure swing recirculation using high-purity reactants were stable and durable over 10h. The experimental results demonstrated that the pressure swing operation could expel the product water from the cell, and operations over 10h were achievable as long as the purity of the supplied reactants was high enough.