Electrolyzer cell stack system

• US 7,353,085 B2
• Filed: 09/21/2004
• Issued: 04/01/2008
• Est. Priority Date: 09/22/2003
• Status: Active Grant

• Current Assignee: Hydrogenics Corporation (Cummins Incorporated)
• Original Assignee: Hydrogenics Corporation (Cummins Incorporated)
• Inventors: Vale, Michael, Rusta-Sallehy, Ali
• Primary Examiner(s): Picard; Leo
• Assistant Examiner(s): Garland; Steven R.
• Application Number:
  US10/944,878
• Publication Number:
  US 20050197743A1
• Time in Patent Office: 1,288 Days
• Field of Search: 700/299, 700/300, 204/228.6, 429 22- 24
• US Class Current: 700/299
• CPC Class Codes: C25B 15/02 Process control or regulation
• CPC Class Codes: H01M 8/04007 related to heat exchange
• CPC Class Codes: H01M 8/04589 of fuel cell stacks
• CPC Class Codes: H01M 8/04701 Temperature
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

As an electrochemical cell stack gets older the internal resistances within the stack rise overtime as the materials that the stack is made of degrade. Consequently, an old and “worn” electrochemical cell stack draws less current at the same stack voltage and operating temperature as a new stack. When the current draw falls the electrochemical reaction rates also fall, as less energy is available to drive the electrochemical reactions. However, if the operating temperature of an older stack is controllable raised the current draw by an electrolyzer cell stack also rises, which in turn causes the reaction rates to rise again. Accordingly, in some embodiments, a balance-of-plant system is operable to regulate the current draw of an electrolyzer cell stack by first manipulating the operating temperature of the same electrolyzer cell stack.

Claims

1. A balance-of-plant system, suited for regulating the operating temperature of an electrolyzer cell stack having at least one electrolyzer cell, comprising:

a controller having a computer program readable code means for changing the operating temperature of the electrolyzer cell stack as a result of a current draw measurement, the computer program readable code means including;

instructions for monitoring the operating temperature;

instructions for monitoring the current draw associated with the electrolyzer cell stack; and

instructions for changing the operating temperature of the electrolyzer cell stack as a result of the current draw measurement.

2. A balance-of-plant system according to claim 1, wherein the instructions for changing the operating temperature of the electrolyzer cell stack as a result of the current draw measurement further comprises:

instructions for determining whether or not the current operating temperature is above a first threshold; and

instructions for initiating an emergency shut-down procedure if the current operating temperature is above the first threshold.

3. A balance-of-plant system according to claim 1, wherein the instructions for changing the operating temperature of the electrolyzer cell stack as a result of the current draw measurement further comprises:

instructions for determining whether or not the current operating temperature is above a first threshold;

instructions for providing a warning signal if the current operating temperature is above the first threshold; and

,

instructions for raising the operating temperature by a pre-set amount if the current operating temperature is below the first threshold.

4. A balance of plant system according to claim 3, wherein the instructions for raising the temperature include instructions for signaling balance-of-plant elements to increase the temperature by the pre-set amount.

5. A balance-of-plant system according to claim 3, wherein the instructions for changing the operating temperature of the electrolyzer cell stack as a result of the current draw measurement further comprises instructions for lowering the operating temperature if the current operating temperature is above the first threshold.

6. A balance of plant system according to claim 5, wherein the instructions for lowering the temperature include instructions for signaling balance-of-plant elements to decrease the temperature.

7. A balance-of-plant system according to claim 3, wherein the instructions for changing the operating temperature of the electrolyzer cell stack as a result of the current draw measurement further comprises:

instructions for determining whether or not the current operating temperature is above a second threshold; and

,

instructions for initiating an emergency shut-down procedure if the current operating temperature is above the second threshold.

8. A balance-of-plant system according to claim 1, wherein the computer program readable code means further comprises:

instructions for determining whether or not the current draw is above a first threshold; and

,

instructions for lowering the operating temperature if the current draw is above the first threshold.

9. A balance-of-plant system according to claim 1, wherein the computer program readable code means further comprises:

instructions for determining whether or not the current draw is below a first threshold; and

,

instructions for raising the operating temperature if the current draw is below the first threshold.

10. A balance-of-plant system according to claim 9, wherein the computer program readable code means further comprises:

instructions for determining whether or not the current draw is above a second threshold; and

,

instructions for lowering the operating temperature if the current draw is above the second threshold.

11. A balance-of-plant system according to claim 9, wherein the computer program readable code means further comprises:

instructions for determining whether or not the operating temperature is above a second threshold; and

instructions for providing a warning signal if the current operating temperature is above the second threshold; and

,

instructions for raising the operating temperature by a pre-set amount if the current operating temperature is below the second threshold.

12. A balance-of-plant system according to claim 11, wherein the instructions for changing the operating temperature of the electrolyzer cell stack as a result of the current draw measurement further comprises instructions for lowering the operating temperature if the current operating temperature is above the second threshold.

13. A balance-of-plant system according to claim 11, wherein the instructions for changing the operating temperature of the electrolyzer cell stack as a result of the current draw measurement further comprises:

instructions for determining whether or not the current operating temperature is above a third threshold; and

,

instructions for initiating an emergency shut-down procedure if the current operating temperature is above the third threshold.

14. A balance-of-plant system according to claim 1, wherein the controller is comprised of at least one of a centralized control system and a distributed control system.

15. An electrolyzer cell stack module comprising a controller for changing the operating temperature of the electrolyzer cell stack as the stack ages to compensate for degradation of the components of the electrolyzer cell stack, wherein as the current draw decreases for a fixed voltage, the operating temperature increases, and the controller has instructions for:

determining by how much a current draw has decreased below a first level as a result of component degradation;

calculating a temperature increase that will increase the current draw back to the first level; and

signaling balance-of-plant elements to increase the temperature as calculated.

16. A method of regulating the operating temperature of an electrolyzer cell stack having at least one electrolyzer cell, comprising:

monitoring the operating temperature;

monitoring the current draw associated with the electrolyzer cell stack; and

,

changing the operating temperature of the electrolyzer cell stack as a result of current draw measurements.

17. A method according to claim 16 further comprising:

determining whether or not the current operating temperature is above a first threshold;

providing a warning signal if the current operating temperature is above the first threshold; and

,

raising the operating temperature by a pre-set amount if the current operating temperature is below the first threshold.

18. A method according to claim 17 further comprising:

lowering the operating temperature if the current operating temperature is above the first threshold.

19. A method according to claim 17 further comprising:

determining whether or not the current operating temperature is above a second threshold; and

,

initiating an emergency shut-down procedure if the current operating temperature is above the second threshold.

20. A method according to claim 16 further comprising:

determining whether or not the current draw is below a first threshold; and

,

raising the operating temperature if the current draw is below the first threshold.

21. A method according to claim 20 further comprising:

determining whether or not the operating temperature is above a second threshold;

providing a warning signal if the current operating temperature is above the second threshold; and

,

raising the operating temperature by a pre-set amount if the current operating temperature is below the second threshold.

22. A method according to claim 21 further comprising:

lowering the operating temperature if the current operating temperature is above the second threshold.

23. A method according to claim 21 further comprising:

determining whether or not the current operating temperature is above a third threshold; and

,

initiating an emergency shut-down procedure if the current operating temperature is above the third threshold.