Adaptive purge control to prevent electrode redox cycles in fuel cell systems
View Patent ↗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.
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.