APPARATUS AND METHOD FOR CONTROLLING VARIABLE POWER CONDITIONS IN A FUEL CELL

• US 20110269039A1
• Filed: 10/14/2009
• Published: 11/03/2011
• Est. Priority Date: 10/15/2008
• Status: Active Grant

• Current Assignee: National Research Council Canada, University of British Columbia
• Original Assignee: National Research Council Canada, University of British Columbia
• Inventors: Lam, Alfred, Wilkinson, David P.
• Granted Patent: US 10,044,055 B2
• Time in Patent Office: Days
• US Class Current: 429/428
• CPC Class Codes: H01M 8/04186 of liquid-charged or electrolyte-charged reactants
• CPC Class Codes: H01M 8/04276 Arrangements for managing the electrolyte stream, e.g. heat exchange
• CPC Class Codes: H01M 8/04582 of the individual fuel cell
• CPC Class Codes: H01M 8/04611 of the individual fuel cell
• CPC Class Codes: H01M 8/04932 of the individual fuel cell
• CPC Class Codes: H01M 8/08 Fuel cells with aqueous electrolytes
• CPC Class Codes: H01M 8/1011 Direct alcohol fuel cells [DAFC], e.g. direct methanol fuel cells [DMFC]
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

A fuel cell comprises an anode having an inner face and an outer face fluidly communicable with a fuel; a cathode having an inner face ionically communicable with and physically separated from the anode inner face, and having an outer face fluidly communicable with an oxidant; and at least one movable guard movable over at least one of the anode outer face, cathode outer face, anode inner face, and cathode inner face. The guard has a structure sufficient to block at least part of one or more of the anode'"'"'s communication with the fuel, the cathode'"'"'s communication with the oxidant, and the ionic communication between the anode and cathode thereby reducing a maximum potential active area of the fuel cell to an effective active area of the fuel cell.

Claims

1. A fuel cell comprising:

an anode having an inner face and an outer face fluidly communicable with a fuel;

a cathode having an inner face ionically communicable with and physically separated from the anode inner face, and having an outer face fluidly communicable with an oxidant, the cathode inner face being ionically communicable with the anode inner face by an electrolyte; and

at least one movable guard movable over at least one of the anode outer face, cathode outer face, anode inner face, and cathode inner face;

the guard having a structure sufficient to block at least part of one or more of the anode'"'"'s communication with the fuel, the cathode'"'"'s communication with the oxidant, and the ionic communication between the anode and cathode thereby reducing a maximum potential active area of an electrode surface to an effective active area of the electrode surface, such that a power output of the fuel cell is reduced.

2. A fuel cell as claimed in claim 1 further comprising a spacer assembly in between the anode and cathode and comprising a frame defining an electrolyte chamber in between the anode and the cathode, the electrolyte chamber for containing a liquid electrolyte that provides ionic communication between the anode and cathode inner faces.

3. A fuel cell as claimed in claim 2 wherein the guard is movable within the frame to block at least part of the inner faces of the anode and cathode from ionically communicating with each other.

4. A fuel cell as claimed in claim 1 wherein the guard structure is selected from a group consisting of:

a solid plate, a perforated plate, a shuttered gate having multiple movable slats, and a diaphragm shutter.

7. A fuel cell as claimed in claim 1 wherein the guard is movable to cover the outer surface of the cathode.

8. A fuel cell as claimed in claim 1 wherein at least one guard covers at least one of the anode and cathode outer surfaces, and is composed of an electrically conductive material such that the guard functions as a current collector.

9. A fuel cell system comprising:

a fuel cell as claimed in claim 1;

an actuator movably connected to the guard; and

an actuator controller communicative with the actuator and having a memory programmed with steps and instructions to control the actuator to move the guard into a position corresponding to a desired effective active area and consequent power output.

10. A fuel cell system as claimed in claim 9 wherein the desired effective active area is selected to produce a selected current density, and the controller is programmed to control the actuator to move the guard in response to varying load conditions on the fuel cell to produce a selected current density and consequently a constant selected voltage and power density of the fuel cell.

11. A fuel cell as claimed in claim 1 further comprising an ionically conducting membrane in between the anode and cathode, and the guard is movable over only at least one of the anode outer face and cathode outer face.

12. A fuel cell as claimed in claim 1 further comprising a porous separator in between the anode and cathode.

14. A fuel cell as claimed in claim 1 wherein the fuel cell is a passive fuel cell.

15. A fuel cell as claimed in claim 1 wherein the fuel cell is an active fuel cell.

5. A fuel cell comprising:

an anode having an inner face and an outer face fluidly communicable with a fuel;

a cathode having an inner face ionically communicable with and physically separated from the anode inner face, and having an outer face fluidly communicable with an oxidant;

at least one diffusion barrier each covering one or both of the anode and cathode outer faces; and

at least one movable guard movable over at least one of the diffusion barrier, anode outer face, cathode outer face, anode inner face, and cathode inner face;

the guard having a structure sufficient to block at least part of one or more of the anode'"'"'s communication with the fuel, the cathode'"'"'s communication with the oxidant, and the ionic communication between the anode and cathode thereby reducing a maximum potential active area of an electrode surface to an effective active area of the electrode surface, such that a power output of the fuel cell is reduced.

6. A fuel cell as claimed in claim 5 wherein the guard structure is a perforated plate and the diffusion barrier has openings alignable with perforations in the perforated plate.

22. A fuel cell as claimed in claim 5 wherein the guard is movable to cover the outer surface of the cathode.

23. A fuel cell as claimed in claim 5 wherein the fuel cell is a passive fuel cell.

24. A fuel cell as claimed in claim 5 wherein the fuel cell is an active fuel cell.

13. A fuel cell as claimed in 1 further comprising a lateral diffusion barrier in between the anode and cathode or integrated into one or both of the anode and cathode.

16. A method for controlling an active area of a fuel cell comprising an anode having an inner face and an outer face fluidly communicable with a fuel;

a cathode having an inner face ionically communicable with and physically separated from the anode inner face, and having an outer face fluidly communicable with an oxidant; and

at least one movable guard movable over at least one of the anode outer face, cathode outer face, anode inner face, and cathode inner face;

the method comprising;

moving the guard to block at least part of one or more of the anode'"'"'s communication with the fuel, the cathode'"'"'s communication with the oxidant, and the ionic communication between the anode and cathode such that a maximum potential active area of an electrode surface is reduced to an effective active area of the electrode surface such that a power output of the fuel cell is reduced.

17. A method as claimed in claim 16 further comprising:

determining a load on the fuel cell at a particular fuel concentration;

moving the guard to a position corresponding to an effective active area that produces a selected current density in the fuel cell for the determined load at the particular fuel concentration.

18. A method as claimed in claim 17 further comprising monitoring a varying load on the fuel cell and moving the guard in response to the varying load to produce a substantially constant current density in the fuel cell while maintaining a constant fuel concentration.

19. A method as claimed in claim 16 further comprising:

determining a load on the fuel cell at a particular fuel concentration;

moving the guard to a position corresponding to an effective active area that produces a selected voltage of the fuel cell for the determined load at the particular fuel concentration.

20. A method as claimed in claim 19 further comprising monitoring a varying load on the fuel cell and moving the guard in response to the varying load to produce a substantially constant voltage in the fuel cell while maintaining a constant fuel concentration.

21. A method as claimed in claim 16 further comprising monitoring voltage in multiple active areas, and moving the guard to block one or more active areas that has a voltage that deviates from a selected level.