Apparatus and method for controlling a fuel cell

• US 20070042243A1
• Filed: 08/17/2005
• Published: 02/22/2007
• Est. Priority Date: 08/17/2005
• Status: Active Grant

• Current Assignee: Emergent Power Inc. (Plug Power Inc.)
• Original Assignee: Relion Incorporated (Plug Power Inc.)
• Inventors: Bai, Lijun, Hernick, Mark, Lott, David
• Granted Patent: US 7,722,972 B2
• Time in Patent Office: Days
• US Class Current: 320/101
• CPC Class Codes: H01M 8/04067 Heat exchange or temperature measuring elements, thermal insulation, e.g. heat pipes, heat pumps, fins
• CPC Class Codes: H01M 8/04119 with simultaneous supply or evacuation of electrolyte; Humidifying or dehumidifying
• CPC Class Codes: H01M 8/04238 Depolarisation
• CPC Class Codes: H01M 8/04365 of other components of a fuel cell or fuel cell stacks
• CPC Class Codes: H01M 8/04529 of the electrolyte
• CPC Class Codes: H01M 8/04559 of fuel cell stacks
• CPC Class Codes: H01M 8/04589 of fuel cell stacks
• CPC Class Codes: H01M 8/04679 of fuel cell stacks
• CPC Class Codes: H01M 8/04731 of other components of a fuel cell or fuel cell stacks
• CPC Class Codes: H01M 8/04753 of fuel cell reactants
• CPC Class Codes: H01M 8/0485 of the electrolyte
• CPC Class Codes: H01M 8/0488 of fuel cell stacks
• CPC Class Codes: H01M 8/0491 of fuel cell stacks
• CPC Class Codes: H01M 8/0494 of fuel cell stacks
• CPC Class Codes: H01M 8/04992 characterised by the implementation of mathematical or computational algorithms, e.g. feedback control loops, fuzzy logic, neural networks or artificial intelligence
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

An apparatus and method for controlling a fuel cell which has an anode and a cathode includes first and second circuitry which are utilized, to selectively short the anode to the cathode and further is useful in measuring the rate of voltage recovery following shorting, and which can be utilized as a predictor of appropriate fuel cell hydration and can be further utilized to adjust the operational conditions of the fuel cell.

Claims

1. An apparatus for controlling a fuel cell which has an anode and a cathode, comprising:

first circuitry for selectively shorting the anode to the cathode so as to simultaneously increase a current and decrease a voltage output of the fuel cell; and

second circuitry for measuring the rate of voltage recovery following shorting, and wherein the rate of voltage recovery is employed, at least in part, to control and/or monitor the operation of the fuel cell.

2. An apparatus as claimed in claim 1, and wherein the fuel cell requires an amount of hydration to produce the voltage and current output, and wherein the rate of voltage recovery is predictive of the amount of hydration of the fuel cell.

3. An apparatus as claimed in claim 1, and wherein the fuel cell further comprises a gas diffusion layer which is juxtaposed relative to one of the anode or the cathode, and wherein the rate of voltage recovery is predictive of the amount of hydration in the gas diffusion layer.

4. An apparatus as claimed in claim 1, and wherein the fuel further comprises a gas diffusion layer which is juxtaposed relative to the cathode, and which permits oxygen to diffuse therethrough, and wherein the rate of voltage recovery is predictive of the an oxygen diffusion rate and/or oxygen concentration at the cathode.

5. An apparatus as claimed in claim 1, and wherein the fuel cell in operation has an operating temperature, and wherein the voltage recovery rate is employed, at least in part, to control the operating temperature.

6. An apparatus as claimed in claim 1, and wherein the fuel cell, in operation, has an operating temperature, and wherein the fuel cell further comprises a source of air which is supplied in an amount to the fuel cell to control the operating temperature, and wherein the voltage recovery rate is employed, at least in part, to control the amount of air supplied to the fuel cell.

7. An apparatus as claimed in claim 1, and wherein the fuel cell, in operation, has a voltage and current output which is supplied to a load, and wherein the voltage recovery rate is employed, at least in part, to control the voltage and current output of the fuel cell.

8. An apparatus as claimed in claim 1, and wherein the first circuitry selectively shorts the anode to the cathode according to a shunting duty cycle and a frequency, and wherein the voltage recovery rate is employed, at least in part, to adjust the shunting duty cycle and the frequency.

9. An apparatus as claimed in claim 1, and wherein the fuel cell has a bleed duty cycle, and a frequency, and wherein the voltage recovery rate is employed, at least in part, to adjust the bleed duty cycle and the frequency.

10. An apparatus as claimed in claim 2, and wherein the first circuitry selectively shorts the anode to the cathode according to a duty cycle, and frequency, and wherein the duty cycle, and frequency is selectively adjusted, based, at least in part, upon the amount of hydration of the fuel cell as predicted by the rate of voltage recovery.

11. An apparatus as claimed in claim 1, and wherein the rate of voltage recovery is predictive of the operational hydration of the fuel cell, and wherein the first circuitry further comprises:

a voltage sensor coupled in voltage sensing relation relative to the fuel cell;

a current sensor coupled in current sensing relation relative to the fuel cell; and

a controller electrically coupled with the anode and cathode of the fuel cell, and with the voltage and current sensors, and wherein the controller selectively electrically shorts the anode to the cathode based, at least in part, upon the operational hydration of the fuel cell as predicted, at least in part, by the rate of voltage recovery.

12. An apparatus as claimed in claim 11, and wherein the controller electrically shorts the anode to the cathode according to a duty cycle and a frequency, and wherein the duty cycle and the frequency of the electrical shorting is adjusted by the controller, at least in part, in response to the operational hydration of the fuel cell.

13. An apparatus as claimed in claim 12, and wherein the controller decreases the frequency of the electrical shorting of the anode of the fuel cell, to the cathode thereof, if the operational hydration of the fuel cell exceeds a predetermined threshold.

14. An apparatus as claimed in claim 13, and wherein the controller decreases the duration of the electrical shorting of the anode of the fuel cell, to the cathode thereof, if the operational hydration of the fuel cell exceeds a predetermined threshold.

15. An apparatus as claimed in claim 1, and wherein the fuel cell has a voltage recovery rate as defined by a first line, which has a first slope, when the fuel cell is optimally hydrated, and wherein the fuel cell has a voltage recovery rate, as defined by a second line, which has a slope which is about 20% to about 200% greater than the first line, when the fuel cell is operationally dehydrated.

16. An apparatus as claimed in claim 15, and wherein fuel cell has a voltage recovery rate, as defined by a third line, and which has a slope of less than about 20% to about 80% of the first line, when the fuel cell is excessively hydrated.

17. An apparatus for controlling a fuel cell which has a voltage and current output, comprising:

a controller which is operably coupled with the fuel cell, and which periodically increases the current output of the fuel cell; and

circuitry electrically coupled with the controller, and which is further disposed in voltage and current sensing relation relative to the fuel cell, and wherein the fuel cell, when optimally hydrated, has a rate of voltage recovery following the periodic reduction of the voltage output of the fuel cell, by the controller, and which is defined by a first line having a slope, and wherein the circuitry determines the operational hydration of the fuel cell based, at least in part, upon the relative comparison of the rate of voltage recovery of the fuel cell to the slope of the first line.

18. An apparatus as claimed in claim 17, and wherein the periodic reduction of the voltage output of the fuel cell results in a simultaneous increase in a current output of the fuel cell, and wherein the periodic reduction in the voltage output of the fuel cell by the controller is defined by a duty cycle, and wherein the duty cycle is adjusted, at least in part, upon the rate of voltage recovery of the fuel cell, as defined by a second line, being greater than the slope of the first line.

19. An apparatus as claimed in claim 18, and wherein the periodic reduction of the voltage output of the fuel cell, by the controller, is defined by a duty cycle, and wherein the duty cycle is adjusted, at least in part, upon the rate of voltage recovery of the fuel cell, as defined by a third line, being less than the slope of the first line.

20. An apparatus as claimed in claim 18, and wherein the fuel cell is operationally dehydrated when the slope of the second line is about 20% to about 200% greater than the first line.

21. An apparatus as claimed in claim 19, and wherein the fuel cell is excessively hydrated when the slope of the third line is less than about 20% to about 80% of the first line.

22. An apparatus as claimed in claim 20, and wherein the frequency of the periodic shorting increases when the fuel cell is operationally dehydrated.

23. An apparatus as claimed in claim 19, and wherein the frequency of the periodic shorting decreases when the fuel cell is excessively hydrated.

24. An apparatus as claimed in claim 17, and wherein the fuel cell membrane has a membrane electrode diffusion assembly which has an integral gas diffusion layer, and wherein the gas diffusion layer, when optimally operationally hydrated, allows an amount of oxygen to pass therethrough, and wherein the rate of voltage recovery is predictive of the oxygen concentration and diffusion rate at the gas diffusion layer.

25. An apparatus as claimed in claim 17, and wherein the fuel cell has an anode and a cathode, and wherein the controller selectively electrically shorts the anode to the cathode, to substantially effect the periodic increase in the current output of the fuel cell.

26. An apparatus as claimed in claim 25, and further comprising:

a voltage sensor electrically coupled with the anode and cathode of the fuel cell; and

a current sensor electrically coupled with the anode and cathode of the fuel cell, and wherein the controller measures the voltage and the current produced by the fuel cell immediately after the periodic electrical shorting of the anode to the cathode, and wherein the rate of recovery of the voltage immediately after the periodic electrical shorting of the anode to the cathode is predictive of the operational hydration of the fuel cell.

27. An apparatus as claimed in claim 26, and wherein the controller is configured, at times, to electrically short the anode of the fuel cell, to the cathode thereof, according to a duty cycle and frequency, and wherein the controller selectively adjusts the duty cycle and frequency of the electrical shorting based, at least in part, upon the hydration of the fuel cell as predicted by the voltage recovery rate.

28. An apparatus as claimed in claim 27, and wherein fuel cell, when operational, has a voltage and current output, and wherein the duty cycle and frequency are selectively adjusted so as to adjust the voltage and current output of the fuel cell.

29. An apparatus as claimed in claim 17, and wherein the voltage recovery rate is employed, at least in part, to control an operating temperature of the fuel cell.

30. An apparatus as claimed in claim 17, and wherein the voltage recovery rate is employed, at least in part, to control a source of air which is supplied to the fuel cell.

31. A method for controlling a fuel cell, comprising:

providing a fuel cell which has an anode and a cathode, and which produces electrical power having a current and voltage output;

periodically electrically shorting the anode of the fuel cell to the cathode of the fuel cell to increase the current output of the fuel cell;

measuring a rate of voltage recovery experienced by the fuel cell in timed relation to the electrical shorting; and

determining the amount of the hydration of the fuel cell from the measured rate of voltage recovery.

32. A method as claimed in claim 31, and wherein the step of determining the amount of hydration of the fuel cell further comprises:

determining an operational hydration for the fuel cell and which will produce an optimal sustainable voltage and current output, and wherein the optimal sustainable voltage and current output is defined by a first line having a first slope; and

wherein the rate of voltage recovery experienced by the fuel cell in timed relation relative to the electrical shorting is defined by a second line having a second slope;

determining whether the second slope is greater than, or less than the first slope; and

selectively adjusting the periodic electrical shorting of the anode to the cathode of the fuel cell based at least in part upon whether the second slope is greater than, or less than the first slope.

33. A method as claimed in claim 32, and wherein the step of selectively adjusting the electrical shorting of the anode to the cathode further comprises:

providing a controller which is electrically coupled with fuel cell;

implementing a duty cycle and frequency for the periodic electrical shorting by utilizing the controller; and

adjusting the duty cycle and frequency of the periodic electrical shorting, at least in part, by reference to whether the second slope is greater than or less than the first slope.

34. A method as claimed in claim 32, and wherein the fuel cell includes a gas diffusion layer which is juxtaposed relative to the cathode, and wherein the method further comprises:

determining an oxygen concentration at the gas diffusion layer from the measured voltage recovery rate.

35. A method as claimed in claim 32, and wherein the fuel cell has an operational temperature, and wherein the method further comprises:

controlling the operating temperature of the fuel cell from the measured voltage recovery rate.

36. A method as claimed in claim 32, and further comprising:

adjusting the periodic electrical shorting of the anode to the cathode of the fuel cell by reference to the determined amount of hydration of the fuel cell so as to selectively adjust the voltage and current output of the fuel cell.

37. A method for controlling a fuel cell, comprising:

providing a fuel cell which has a first membrane electrode diffusion assembly, and wherein the first membrane electrode diffusion assembly has an anode, a cathode, and a gas diffusion layer;

providing a source of fuel to the anode side of the first membrane electrode diffusion assembly, and providing a source of an oxidant to the cathode side of the first membrane electrode diffusion assembly, and wherein the fuel cell produces a voltage and current output when supplied with the sources of fuel and oxidant;

providing a voltage sensor which is electrically coupled in voltage sensing relation relative the first membrane electrode diffusion assembly;

providing a current sensor which is electrically coupled in current sensing relation relative to the first membrane electrode diffusion assembly;

providing a controller which is electrically coupled with the first membrane electrode diffusion assembly, and which is configured to periodically electrically short the anode to the cathode thereof, and which substantially increases the current output of the first membrane electrode diffusion assembly;

previously determining an optimal sustainable voltage and current output for a substantially identical second membrane electrode diffusion assembly;

measuring a rate of voltage recovery of the second membrane electrode diffusion assembly which is producing the optimal sustainable voltage and current output immediately following the electrical shorting of the second membrane electrode diffusion assembly, and wherein the optimal sustainable voltage and current output is indicative of an optimal hydrated state for the second membrane electrode diffusion assembly;

periodically electrically shorting the anode to the cathode of the first membrane electrode diffusion assembly;

measuring a rate of the voltage recovery of the first membrane electrode diffusion assembly immediately following the periodic electrical shorting of the anode to the cathode thereof;

determining whether the rate of recovery of the voltage of the first membrane electrode diffusion assembly immediately following the periodic electrical shorting is greater than or less than the voltage recovery rate as experienced by the substantially identical second membrane electrode diffusion assembly;

predicting the operational hydration of the first membrane electrode diffusion assembly, based, at least in part, upon whether the voltage recovery rate of the first membrane electrode diffusion assembly is greater or less than the voltage recovery rate as experience by the substantially identical second membrane electrode diffusion assembly; and

adjusting the frequency and duration of the periodic electrical shorting of the first membrane electrode diffusion assembly to optimize both the operational hydration of the first membrane electrode diffusion assembly, and the electrical current and voltage output thereof.

38. A method as claimed in claim 37, and wherein the method further comprises:

adjusting an operational temperature of the fuel cell by reference to the voltage recovery rate as determined for the first membrane electrode diffusion assembly.

39. A method as claimed in claim 37, and further comprising:

adjusting a bleed duty cycle of the fuel cell by reference to the voltage recovery rate as determined for the first membrane electrode diffusion assembly.

40. A method as claimed in claim 37, and further comprising:

determining an oxygen diffusion rate and/or concentration at the gas diffusion layer by reference to the voltage recovery rate as determined for the first membrane electrode diffusion assembly.

41. A method as claimed in claim 37, and further comprising:

providing a source of air which is supplied to the cathode of the fuel cell; and

controlling the volume of air delivered to the cathode of fuel cell by reference to the voltage recovery rate as determined for the first membrane electrode diffusion assembly.