Adaptive purge control to prevent electrode redox cycles in fuel cell systems

• US 7,846,600 B2
• Filed: 09/21/2006
• Issued: 12/07/2010
• Est. Priority Date: 09/21/2006
• Status: Active Grant

• Current Assignee: Bloom Energy Corporation
• Original Assignee: Bloom Energy Corporation
• Inventors: Gottmann, Matthias
• Primary Examiner(s): Ryan; Patrick
• Assistant Examiner(s): Lewis; Ben
• Application Number:
  US11/524,241
• Publication Number:
  US 20080075985A1
• Time in Patent Office: 1,538 Days
• Field of Search: 429/13, 429/21, 429/407, 429/429, 429/430, 429/431, 429/432, 429/444
• US Class Current: 429/432
• CPC Class Codes: H01M 2004/8684 Negative electrodes
• CPC Class Codes: H01M 2008/1293 Fuel cells with solid oxide electrolytes
• CPC Class Codes: H01M 8/04201 Reactant storage and supply, e.g. means for feeding, pipes
• CPC Class Codes: H01M 8/04231 Purging of the reactants
• CPC Class Codes: H01M 8/04559 of fuel cell stacks
• CPC Class Codes: H01M 8/04746 Pressure; Flow
• CPC Class Codes: H01M 8/04753 of fuel cell reactants
• CPC Class Codes: H01M 8/04791 Concentration; Density H01M8/04828 takes precedence
• CPC Class Codes: H01M 8/04798 of fuel cell reactants
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

A method of operating a fuel cell system during a fuel outage or shortage includes detecting an open circuit voltage (OCV) of the fuel cell system, and providing a reducing purge gas flow to anode electrodes of fuel cells of the fuel cell system when the OCV approaches, reaches or falls below a threshold value below which oxidation of the anode electrodes occurs.

Claims

1. A method of operating a fuel cell system during a fuel outage or shortage, comprising:

detecting an open circuit voltage (OCV) of the fuel cell system;

providing a reducing purge gas flow to anode electrodes of fuel cells of the fuel cell system when the OCV approaches, reaches or falls below a predetermined threshold value, or reaches or falls below a detected threshold value below which oxidation of the anode electrodes occurs; and

terminating the purge gas flow to the anode electrodes when the OCV increases above the threshold value.

2. The method of claim 1, further comprising intermittently providing the purge gas flow to the anode electrodes a plurality of times when the OCV approaches, reaches or falls below the predetermined threshold value or reaches or falls below the detected threshold value.

3. The method of claim 1, wherein the purge gas flow is provided to the anode electrodes when the OCV approaches the predetermined threshold value.

4. The method of claim 1, wherein the purge gas flow is provided to the anode electrodes when the OCV reaches the predetermined or the detected threshold value.

5. The method of claim 1, wherein the purge gas flow is provided to the anode electrodes when the OCV falls below the predetermined or the detected threshold value.

6. The method of claim 1, wherein the purge gas flow comprises at least one of hydrogen, forming gas and carbon monoxide.

7. The method of claim 1, wherein the fuel cells comprise solid oxide fuel cells.

8. The method of claim 1, wherein the OCV is detected by an operator and the purge gas flow is turned on by the operator when the OCV reaches or falls below the detected threshold value.

9. The method of claim 1, wherein the OCV is detected by a control system and the purge gas flow is turned on by the control system when the OCV reaches or falls below the detected threshold value.

10. The method of claim 1, wherein the purge gas flow is provided to the anode electrodes when the OCV approaches, reaches or falls below a predetermined threshold value.

11. The method of claim 1, wherein the purge gas flow is provided to the anode electrodes when the OCV approaches, reaches or falls below the threshold value which corresponds to a plateau in a plot of OCV versus time.

12. The method of claim 1, further comprising storing a liquid, gel or solid purge material and evaporating the purge material to provide the purge gas flow.