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Double Ended Fuel Cell Stack And Fuel Cell System With Restrictive Flow Field Plate Port Sizing

IP.com Disclosure Number: IPCOM000198794D
Publication Date: 2010-Aug-16
Document File: 28 page(s) / 1M

Publishing Venue

The IP.com Prior Art Database

Related People

George A. Skinner: INVENTOR

Abstract

Fuel cell stacks and fuel cell systems with flow field plates with restrictive port sizes and multiple fuel cell stack reactant inlets and outlets are disclosed.

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DOUBLE ENDED FUEL CELL STACK AND FUEL CELL SYSTEM WITH RESTRICTIVE FLOW FIELD PLATE PORT SIZE

BACKGROUND

  Technical Field
5 The present disclosure relates to fuel cell stacks and fuel cell systems with flow field plates with restrictive port sizes and multiple fuel cell stack reactant inlets and outlets.

Description of the Related Art

         Fuel cells convert fuel and oxidant to electricity and reaction product. In a proton exchange membrane ("PEM") fuel cells, a membrane electrode assembly ("MEA") consisting of a PEM (also known as an ion-exchange membrane) interposed between an anode gas diffusion layer ("GDL") (also known in the art as a fluid distribution layer or fluid diffusion layer) and cathode GDL. An anode electrocatalyst is typically disposed at the interface between the PEM and the anode GDL. A cathode electrocatalyst is typically disposed at the interface between the PEM and the cathode GDL. The MEA is then interposed between an anode flow field plate and a cathode flow field plate to form a fuel cell assembly. The anode and cathode flow field plates allow access of reactants to the MEA by providing a flow field, typically in the form of flow field channels on the surface of the flow field plate. The anode and cathode flow field plates also act as current collectors, and provide structural support for the adjacent anode and cathode.

         At the anode, fuel, typically in the form of hydrogen gas, either from a pure hydrogen source or reformate, reacts at the anode electrocatalyst in the presence of the PEM to form hydrogen ions and electrons. At the cathode, oxidant reacts at the cathode electrocatalyst in the presence of the PEM to form anions. The PEM isolates the fuel stream from the oxidant stream and facilitates the migration of the hydrogen ions from the anode to the cathode where they react with anions formed at the cathode. The electrons

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pass through an external circuit, creating a flow of electricity. The net reaction product is water. The anode and cathode reactions in hydrogen PEM fuel cells are shown in the following equations:

H2 → 2H+ + 2e- (1)

                  ½O2 + 2H+ + 2e- → H2O (2) Each individual fuel cell in a fuel cell stack will produce a potential or voltage of approximately 0.67 volts, depending on the operating conditions. Where a greater potential is required, individual fuel cells may be coupled to form a fuel cell stack. In a fuel cell stack, the individual fuel cells are stacked in a stacking direction so that the individual fuel cells are physically and electrically coupled. Thus, in a fuel cell stack, a single flow field plate may serve both as the anode flow field plate via one side of the flow field plate for a particular fuel cell in the fuel cell stack and also serve as the cathode flow field plate via the opposite side of the flow field plate, for an adjacent fuel cell in the fuel cell stack.

         Each flow field plate typically has a first aperture that serves as a plate fuel inlet p...