Granted Patent B2

US 6,977,119 · App. 10/121,267 · Granted Dec 20, 2005

Abstract

Claims (55)

1. A fuel cell system, comprising:

a fuel cell having an anode chamber and a cathode chamber, wherein the anode chamber is in fluid communication with a hydrogen reservoir, wherein the cathode chamber has an inlet and an outlet;

wherein the cathode chamber comprises non-intersecting flow channels, the non-intersecting flow channels providing fluid communication between the cathode inlet and outlet;

the fuel cell having a first connection to an electrical load, the first connection comprising a first diode adapted to prevent current flow to the fuel cell;

a blower in fluid communication with the cathode inlet, the blower having an electronic connection to a controller, the blower being adapted to vary a flow of oxygen through the cathode chamber according to a control signal received from the controller;

a battery having a second connection to the electrical load, the second connection being in parallel with the first connection of the fuel cell to the load, the second connection comprising a second diode adapted to prevent current flow to the battery; and

wherein the controller maintains the flow of oxygen such that an output power capacity of the fuel cell is limited by the amount of oxygen flowed through the fuel cell.

2. The system of claim 1 , wherein the fuel cell comprises a polymer electrolyte membrane having an operating temperature in the range 20–100° C.

3. The system of claim 1 , wherein the fuel cell comprises a polymer electrolyte membrane having an operating temperature in the range 120–200° C.

4. The system of claim 1 , wherein the fuel cell comprises a dead-headed anode and a flow-through cathode.

5. The system of claim 4 , wherein the hydrogen reservoir comprises at least 90 wt % hydrogen, and wherein the flow of oxygen comprises air.

6. The system of claim 1 , wherein the anode chamber has an inlet and an outlet, and wherein the inlet and outlet are in fluid communication.

7. The system of claim 1 , wherein the hydrogen reservoir comprises a pressure regulator valve adapted to maintain a predetermined pressure of the reservoir.

8. A method of operating a fuel cell system, comprising:

connecting a fuel cell to an electrical load through a first diode adapted to prevent current back-flow to the fuel cell;

connecting a battery to the electrical load through a second diode adapted to prevent current back-flow to the battery;

providing the fuel cell with a first stoichiometric excess of hydrogen with respect to a stoichiometric hydrogen requirement of the electrical load; and

providing the fuel cell with a second stoichiometric excess of oxygen with respect to a stoichiometric oxygen requirement of the electrical load, wherein the second stoichiometric excess of oxygen is less that the first stoichiometric excess of hydrogen.

9. The method of claim 8 , further comprising:

maintaining an operating temperature of the fuel cell at a temperature in the range 20–100° C.

10. The method of claim 8 , further comprising:

maintaining an operating temperature of the fuel cell at a temperature in the range 120–200° C.

11. The method of claim 8 , further comprising:

dead-heading an anode chamber of the fuel cell; and

circulating air through the a cathode of the fuel cell.

12. The method of claim 8 , further comprising:

exhausting hydrogen from the fuel cell anode chamber; and

recirculating a portion of the exhausted hydrogen to an inlet of the anode chamber.

13. The method of claim 8 , further comprising:

varying a blower output according to a control signal to blow air through a cathode chamber of the fuel cell to provide the second stoichiometric excess of oxygen.

14. The method of claim 13 , further comprising:

measuring a voltage of the fuel cell; and

varying the control signal to increase the blower output when the fuel cell voltage falls below a predetermined threshold.

15. The method of claim 13 , further comprising:

measuring an oxygen content of a cathode exhaust stream; and

varying the control signal to increase the blower output when the oxygen content falls below a predetermined threshold.

16. A method of transient load response for a fuel cell system, comprising:

connecting a fuel cell to an electrical load through a first diode adapted to prevent current back-flow to the fuel cell;

connecting a battery to the electrical load through a second diode adapted to prevent current back-flow to the battery;

providing the fuel cell with an amount of hydrogen, the amount of hydrogen having a first stoichiometric excess over a hydrogen requirement of the electrical load,

operating a blower to supply the fuel cell with a flow of oxygen, the amount of oxygen having a second stoichiometric excess over an oxygen requirement of the electrical load;

applying a transient load increase to the fuel cell;

increasing the flow of oxygen during a response lag period;

starving the fuel cell of oxygen during the response lag period; and

supplying power from the battery to the electrical load during the response lag period.

17. The method of claim 16 , wherein the fuel cell comprises a dead-headed anode and a flow-through cathode.

18. The method of claim 16 , wherein the fuel cell comprises an anode chamber and a cathode chamber, the method further comprising:

exhausting hydrogen from the fuel cell anode chamber; and

recirculating a portion of the exhausted hydrogen to an inlet of the anode chamber.

19. The method of claim 16 , further comprising:

measuring a voltage of the fuel cell; and

increasing the flow of oxygen during the response lag period when the fuel cell voltage falls below a predetermined threshold.

20. The method of claim 16 , further comprising:

measuring an oxygen content of a cathode exhaust stream; and

increasing the flow of oxygen during the response lag period when the oxygen content falls below a predetermined threshold.

Assignments (8)