Granted Patent B2

US 7,166,378 · App. 10/703,930 · Granted Jan 23, 2007

Abstract

Claims (62)

1. A method usable with a fuel cell stack, comprising:

providing a fuel flow to the stack;

changing a rate of the fuel flow;

observing a response of at least one cell voltage of the stack to the changing of the rate; and

regulating an efficiency of the stack based on the observation.

2. The method of claim 1 , wherein the changing the rate of the fuel flow comprises:

decreasing the rate by a predetermined amount.

3. The method of claim 2 , wherein the predetermined amount comprises a predetermined percentage of the fuel flow before the decrease.

4. The method of claim 1 , wherein the observing comprises:

measuring said at least one cell voltage of the stack, said at least one cell voltage being associated with at least one cell designed be more sensitive to the change in rate than cells of the stack other than said at least one cell.

5. The method of claim 1 , wherein the observing comprises:

measuring said at least one cell voltage of the stack after the change in rate.

6. The method of claim 5 , wherein the observing further comprises:

determining if one of said at least one cell voltage is below a predetermined cell voltage threshold.

7. The method of claim 6 , wherein the regulating comprises:

increasing the rate if the one cell voltage is below the predetermined cell voltage threshold.

8. The method of claim 6 , wherein the regulating comprises:

repeating the decreasing of the rate until the one cell voltage is below the predetermined cell voltage threshold.

9. The method of claim 1 , wherein the observing comprises:

determining if a predetermined number of said at least one cell voltage is below a predetermined cell voltage threshold.

10. The method of claim 9 , wherein the regulating comprises:

increasing the rate if the predetermined number of said at least one cell voltage is below the predetermined cell voltage threshold.

11. The method of claim 9 , wherein the regulating comprises:

repeating the decreasing of the rate until the predetermined number of said at least one cell voltage is below the predetermined cell voltage threshold.

12. The method of claim 1 , wherein the observing comprises:

determining a standard deviation of said at least one cell voltage.

13. The method of claim 12 , wherein the regulating comprises:

increasing the rate if the standard deviation is above a predetermined threshold.

14. The method of claim 12 , wherein the regulating comprises:

repeating the decreasing of the rate until the standard deviation is above a predetermined threshold.

15. A method comprising:

selecting a group of one or more fuel cells of a fuel cell stack;

monitoring one or more cell voltages of the group;

determining from said one or more cell voltages whether the fuel cell stack is failing to consume substantially all of a fuel flow that is being provided to the stack; and

adjusting the fuel flow until said one or more cell voltages indicate that the fuel cell stack is consuming substantially all of the fuel flow that is being provided to the stack.

16. The method of claim 15 , wherein the adjusting comprises:

decreasing fuel flow to the stack until said one or more cell voltages indicate that the fuel cell stack is consuming substantially all of the fuel flow that is being provided to the stack.

17. The method of claim 15 , wherein the adjusting comprises:

decreasing the fuel flow that is being provided to the stack until said one or more cell voltages indicate that the fuel cell stack is being deprived of fuel.

18. The method of claim 17 , wherein the adjusting further comprises:

subsequently increasing the fuel flow that is being provided to the fuel cell stack until said one or more cell voltages indicate that the fuel cell stack is consuming substantially all of the fuel flow.

19. The method of claim 15 , wherein the determining comprises:

determining if at least one voltage of said one or more cell voltages decreases below a predetermined cell voltage threshold.

20. The method of claim 15 , wherein the determining comprises:

determining if at least a predetermined number of said one or more cell voltages decrease below a predetermined cell voltage threshold.

21. The method of claim 15 , wherein the determining comprises:

determining a standard deviation among said one or more cell voltages.

22. The method of claim 15 , wherein the adjusting comprises:

adjusting the fuel flow by predetermined increments.

23. The method of claim 15 , wherein the monitoring comprises:

interacting with a cell voltage monitoring circuit.

24. A method comprising:

determining from said one or more cell voltages of a fuel cell stack whether at least one of said one or more cell voltages is substantially equal to a cell threshold voltage indicative that a cell is being starved of fuel; and

in response to the determining, adjusting a fuel flow to the fuel cell stack until at least one of said one or more cell voltages is substantially equal to the cell threshold voltage.

25. The method of claim 24 , wherein the adjusting comprises:

decreasing the fuel flow until at least one of said one or more said voltages is less than the cell threshold voltage.

26. The method of claim 24 , wherein the adjusting comprises:

decreasing the fuel flow until at least one of said one or more cell voltages is substantially equal to the cell threshold voltage.

27. The method of claim 24 , wherein the adjusting comprises:

increasing a fuel flow to the fuel cell stack in response to at least one of said one or more cell voltages being below the cell threshold voltage.

28. The method of claim 24 , wherein the cell threshold voltage is indicative of an abrupt cell voltage decrease due to the fuel flow being insufficient.

29. The method of claim 24 , wherein the cell threshold voltage comprises a voltage in the range of −0.5 voltage to 0.5 volts.

Assignments (8)