Apparatus and method for controlling variable power conditions in a fuel cell

• US 10,044,055 B2
• Filed: 10/14/2009
• Issued: 08/07/2018
• 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: Wilkinson, David P., Lam, Alfred
• Primary Examiner(s): Cano, Milton I
• Assistant Examiner(s): Stuckey, Philip A
• Application Number:
  US13/124,480
• Publication Number:
  US 20110269039A1
• Time in Patent Office: 3,219 Days
• 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 electrode having an anode inner face fluidly communicable with a fuel;

a cathode electrode having a cathode inner face ionically communicable with and physically separated from the anode inner face, and having a cathode 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 having a planar face positioned near at least one selected electrode surface comprising at least one of the anode inner face and the cathode inner face, each of the at least one selected electrode surface being planar, the at least one movable guard being configured to slide into a directly adjacent position that is directly adjacent to and covers a first portion of an active area of the at least one selected electrode surface, while leaving a second portion of the active area uncovered, thereby reducing the active area of the at least one selected electrode surface to an effective active area corresponding to the uncovered second portion, wherein the active area consists of a surface area and is at least a portion of an electrocatalyst-bearing surface area of the at least one selected electrode surface,

wherein the planar face of the at least one movable guard is configured to substantially prevent the fuel, the oxidant, or the electrolyte from directly contacting the covered first portion of the active area such that the covered first portion of the active area does not contribute significantly to a power output of the fuel cell and the 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 electrodes and comprising a frame defining an electrolyte chamber in between the anode and the cathode electrodes, 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 planar face of the at least one movable guard is movable within the frame to block at least part of the anode and cathode inner faces from ionically communicating with each other.

4. A fuel cell as claimed in claim 1 wherein the planar face of the at least one movable guard is selected from a group consisting of:

a solid plate, a perforated plate, and a diaphragm shutter.

5. A fuel cell system comprising:

a fuel cell as claimed in claim 1;

an actuator movably connected to the at least one movable 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 planar face of the at least one movable guard into a position corresponding to a desired effective active area and consequent power output.

6. A fuel cell system as claimed in claim 5 wherein the desired effective active area is selected, and the actuator controller is programmed to control the actuator to move the at least one movable guard in response to varying load conditions on the fuel cell to produce a selected current density.

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

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

9. A method for controlling an active area of a fuel cell comprising an anode, a cathode, and at least one movable guard ,the anode having an anode inner face fluidly communicable with a fuel;

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

the at least one movable guard having a planar face positioned near at least one selected electrode surface comprising at least one of the anode inner face and the cathode inner face, each of the at least one selected electrode surface being planar;

the method comprising;

sliding the at least one movable guard into a directly adjacent position that is directly adjacent to and covers a first portion of an active area of the at least one selected electrode surface, while leaving a second portion of the active area uncovered, thereby reducing the active area of the at least one selected electrode surface to an effective active area corresponding to the uncovered second portion, wherein the active area consists of a surface area and is at least a portion of an electrocatalyst-bearing surface area of the at least one selected electrode surface, wherein the planar face of the at least one movable guard is configured to substantially prevent the fuel, the oxidant, or the electrolyte from directly contacting the covered first portion of the active area such that the covered first portion of the active area does not contribute significantly to a power output of the fuel cell and the power output of the fuel cell is reduced.

10. A method as claimed in claim 9, wherein the effective active area is a first effective active area, and the method further comprises:

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

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

11. A method as claimed in claim 10, further comprising:

monitoring a varying load on the fuel cell; and

moving the at least one movable guard in response to the varying load to produce a substantially constant current density in the fuel cell while maintaining a constant fuel concentration.

12. A method as claimed in claim 9, wherein the effective active area is a first effective active area, and the method further comprises:

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

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

13. A method as claimed in claim 12, further comprising:

monitoring a varying load on the fuel cell; and

moving the at least one movable guard in response to the varying load to produce a substantially constant voltage in the fuel cell while maintaining a constant fuel concentration.

14. A method as claimed in claim 9, further comprising:

monitoring voltage in multiple active areas; and

moving the at least one movable guard to block one or more of the multiple active areas that has a voltage that deviates from a selected level.