Fuel cell having interdigitated flow channels and water transport plates

• US 20010004501A1
• Filed: 12/08/2000
• Published: 06/21/2001
• Est. Priority Date: 12/17/1999
• Status: Active Grant

• Current Assignee: Audi AG (Volkswagen AG)
• Original Assignee: UTC Fuel Cells, LLC (Doosan Corporation)
• Inventors: Yi, Jung S., Puhalski, Jonathan
• Granted Patent: US 6,780,533 B2
• Time in Patent Office: Days
• US Class Current: 429/34
• CPC Class Codes: H01M 8/04089 of gaseous reactants
• CPC Class Codes: H01M 8/04097 with recycling of the reactants H01M8/04119, H01M8/04104 take precedence
• CPC Class Codes: H01M 8/04156 with product water removal
• CPC Class Codes: H01M 8/04291 Arrangements for managing water in solid electrolyte fuel cell systems H01M8/04119 takes precedence
• CPC Class Codes: H01M 8/1007 with both reactants being gaseous or vaporised H01M8/12 takes precedence
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

The present invention is a fuel cell power plant that includes a fuel cell having a membrane electrode assembly (MEA), which is disposed between an anode support plate and a cathode support plate, and porous water transport plates adjacent the anode and cathode support plates. The porous water transport plates have interdigitated flow channels for the reactant gas streams to pass therethrough and conventional flow channels for a coolant stream to pass therethrough. The fuel cell power plant also has means for creating a pressure differential between the reactant gas streams and the coolant stream such that the pressure of the reactant gas streams is greater than the coolant stream. Incorporating the interdigitated flow channels into the porous water transport plates and operating the fuel cell at a pressure differential allows the coolant water to saturate the water transport plates thereby forcing the reactant gases into the anode and cathode support plate. This, in turn, increases the mass transfer of such gases into the support plates, thereby increasing the electrical performance of the fuel cell. Current densities of about 1.6 amps per square meter are achieved with air stochiometries of not over 2.50.

Claims

1. A fuel cell power plant, comprising:

a fuel cell comprising an anode support plate including a porous substrate layer having an interdigitated passageway for a fuel reactant gas stream to enter therein and exit therefrom, a cathode support plate including a porous substrate layer having an interdigitated passageway for an oxidant gas stream to enter therein and exit therefrom, and a membrane electrode assembly disposed between said support plates, said membrane electrode assembly comprising a polymer electrolyte membrane disposed between two catalysts;

a first porous water transport plate adjacent to said cathode support plate, said first porous water transport plate having a passageway for a coolant stream to pass therethrough, and an interdigitated passageway for an oxidant gas stream to enter therein and exit therefrom;

a second porous water transport plate adjacent to said anode support plate, said second porous water transport plate having a passageway for a coolant stream to pass therethrough, and an interdigitated passageway for a fuel reactant stream to enter therein and exit therefrom;

means for creating a predetermined pressure differential between said oxidant gas stream and said coolant stream such that the pressure of said oxidant gas stream is greater than the pressure of said coolant stream; and

means for creating a predetermined pressure differential between said fuel reactant gas stream and said coolant stream such that the pressure of said fuel reactant gas stream is greater than the pressure of said coolant stream.

2. A fuel cell power plant according to

claim 1

wherein:

said cathode support plate comprises a porous, hydrophilic substrate layer, and a partially hydrophobic diffusion layer disposed between said substrate layer and said membrane electrode assembly;

said anode support plate includes a porous, hydrophilic substrate layer, but does not include a diffusion layer;

said water transport plates are hydrophilic; and

the pressure of said oxidant gas stream is between about 1.0 psig and about 1.5 psig above the pressure of said coolant stream.

3. A fuel cell power plant, comprising:

(a) a fuel cell comprising an anode support plate and a cathode support plate and a membrane electrode assembly disposed between said anode and cathode support plates, said membrane electrode assembly comprising a polymer electrolyte membrane disposed between two catalysts, one of said support plates comprising a substrate layer having pores therein and having an interdigitated passageway for a reactant gas stream to enter therein and exit therefrom;

(b) a porous water transport plate adjacent to said one support plate, said porous water transport plate having a passageway for a coolant stream to pass therethrough; and

(c) means for creating a predetermined pressure differential between said reactant gas stream and said coolant stream such that the pressure of said reactant gas stream is greater than the pressure of said coolant stream.

4. The fuel cell power plant of

claim 3

wherein both said support plates comprise a porous substrate layer having an interdigitated passageway for a reactant gas stream to enter therein and exit therefrom and wherein said fuel cell power plant further comprises:

(d) a porous water transport plate adjacent to each of said support plates, said porous water transport plates each having a passageway for a coolant stream to pass therethrough; and

(e) means for creating a predetermined pressure differential between each said reactant gas stream and said coolant stream such that the pressure of each said reactant gas stream is greater than the pressure of said coolant stream.

5. A fuel cell power plant, comprising:

(a) a fuel cell comprising an anode support plate and a cathode support plate and a membrane electrode assembly disposed between said anode and cathode support plates, said membrane electrode assembly comprising a polymer electrolyte membrane disposed between two catalysts, said support plates each comprising a substrate layer having pores therein;

(b) a porous water transport plate adjacent to one of said support plates, said porous water transport plate having a passageway for a coolant stream to pass therethrough and an interdigitated passageway for a reactant gas stream to enter therein and exit therefrom; and

(c) means for creating a predetermined pressure differential between said reactant gas stream and said coolant stream such that the pressure of said reactant gas stream is greater than the pressure of said coolant stream.

6. The fuel cell power plant of

claim 5

wherein said porous substrate layer within one of said support plates is hydrophilic.

7. the fuel cell power plant of

claim 6

wherein the pores within said hydrophilic substrate layer of said cathode support plate have a diameter such that when the pressure differential between said oxidant reactant gas stream and said coolant stream is equal to said predetermined pressure differential, a greater percentage of the pores contain oxidant gas rather than coolant.

8. The fuel cell power plant of

claim 6

wherein at least 50% of the pores within said hydrophilic substrate layer have a diameter (D) that is equal to or greater than 30/P, wherein D is measured in microns and P is said predetermined pressure differential measured in pounds per square inch.

9. The fuel cell power plant of

claim 6

wherein said hydrophilic porous substrate layer is a porous carbon substrate layer comprising a metal oxide, a metal hydroxide or a metal oxyhydroxide wherein said metal is selected from the group consisting of tin, aluminum, niobium, ruthenium, tantalum, titanium, zinc, zirconium, and mixtures thereof, thereby rendering said porous carbon substrate layer hydrophilic.

10. The fuel cell power plant of

claim 5

wherein said predetermined pressure differential between said reactant gas stream and said coolant stream is about 0.5 psi to 10 psi.

11. The fuel cell power plant of

claim 10

wherein said predetermined pressure differential between said reactant gas stream and said coolant stream is about 1.0 psi to 3 psi.

12. The fuel cell power plant of

claim 11

wherein said predetermined pressure differential between said reactant gas stream and said coolant stream is about 2.0 psi to 2.5 psi.

13. The fuel cell power plant of

claim 5

wherein said porous substrate layer within one of said support plates is hydrophobic.

14. The fuel cell power plant of

claim 5

wherein said support plate further comprises a diffusion layer disposed between said substrate layer and said membrane electrode assembly.

15. The fuel cell power plant of

claim 14

wherein said diffusion layer has critical surface energy equal to or less than about 30 dyne per centimeter.

16. The fuel cell power plant of

claim 5

wherein one of said support plates does not include a diffusion layer.

17. The fuel cell power plant of

claim 5

wherein both said support plates comprise a porous substrate layer and wherein said fuel cell power plant further comprises a porous water transport plate adjacent to each said support plate.

18. The fuel cell power plant of

claim 17

wherein both said porous water transport plates have a passageway for a coolant stream to pass therethrough and an interdigitated passageway for a reactant gas stream to enter therein and exit therefrom and wherein said fuel cell power plant further comprises means for creating a predetermined pressure differential between each said reactant gas stream and said coolant stream such that the pressure of each said reactant gas stream is greater than the pressure of said coolant stream.

19. A method of operating a fuel cell power plant comprising:

(a) a fuel cell comprising an anode support plate and a cathode support plate and a membrane electrode assembly disposed between said anode and cathode support plates, said membrane electrode assembly comprising a polymer electrolyte membrane disposed between two catalysts, said support plates each comprising a substrate layer having pores therein;

(b) a porous water transport plate adjacent to one of said support plates, said porous water transport plate having a passageway for a coolant stream to pass therethrough and an interdigitated passageway for a reactant gas stream to enter therein and exit therefrom; and

(c) means for creating a predetermined pressure differential between said reactant gas stream and said coolant stream such that the pressure of said reactant gas stream is greater than the pressure of said coolant stream;

said method comprising;

flowing hydrogen-containing gas adjacent said anode support plate;

flowing air at substantially atmospheric pressure through said interdigitated passageway;

controlling the flow rate of air to maintain an oxidant stochiometry of 250% or less;

operating said fuel cell at a maximum current density of at least 1.6 amps per square centimeter in response to a corresponding electrical load across said fuel cell; and

operating said fuel cell at current densities of less than 1.6 amps per square centimeter in response to related electrical loads across said fuel cell.

20. A method of operating a PEM fuel cell system comprising a plurality of fuel cells, each having a cathode support plate, an anode support plate, a membrane electrode assembly disposed between said support plates, interdigitated oxidant flow channels on the cathode side of said membrane electrode assembly, and fuel flow channels on the anode side of said membrane electrode assembly, said method comprising:

flowing hydrogen-containing gas through said fuel flow channels;

flowing air at substantially atmospheric pressure through said oxidant flow channels;

controlling the flow rate of air to maintain an oxidant stochiometry of 250% or less;

operating said fuel cell at a maximum current density of at least 1.6 amps per square centimeter in response to a corresponding electrical load across said fuel cell; and

operating said fuel cell at current densities of less than 1.6 amps per square centimeter in response to related electrical loads across said fuel cell.

21. A method of

claim 20

wherein said controlling and operating steps comprise:

operating said fuel cell at a maximum current density of at least 1.5 amps per square centimeter while controlling said flow rate to maintain a stochiometry of about 167% or less.