Shutdown and storage method for fuel cell system at below freezing temperatures

Patent metadata

Field	Value
Publication number	US-2017084939-A1
Application number	US-201615258141-A
Country	US
Kind code	A1
Filing date	Sep 7, 2016
Priority date	Sep 19, 2015
Publication date	Mar 23, 2017
Grant date	—

Abstract

Improved methods are disclosed for shutting down and storing a fuel cell system, particularly for below freezing temperature conditions. The methods comprise stopping power production from the fuel cell stack, monitoring the amount of energy remaining in an energy supply, monitoring the stack temperature, and repeatedly performing a predetermined warming operation if the stack temperature falls to a normal threshold temperature and if the amount of energy remaining exceeds a certain minimum amount. In the improved methods, when the amount of remaining energy is less than or equal to the minimum amount, a final warming operation is performed that differs from the predetermined warming operation.

First claim

What is claimed is:

1 . A method for shutting down and storing a fuel cell system, the fuel cell system comprising a fuel cell stack that is producing power and an energy supply for heating the fuel cell stack, the method comprising:
stopping power production from the fuel cell stack; monitoring the amount of energy remaining in the energy supply; monitoring the temperature of the fuel cell stack; repeatedly performing a predetermined warming operation if the stack temperature falls to a normal threshold temperature and if the amount of energy remaining exceeds a minimum amount; and performing a final warming operation if the stack temperature falls to the normal threshold temperature and if the amount of fuel remaining is less than or equal to the minimum amount; characterized in that the final warming operation differs from the predetermined warming operation.

2 . The method of claim 1 wherein the normal threshold temperature is less than 0° C.

3 . The method of claim 1 wherein the predetermined warming operation heats the stack to a predetermined target temperature, the final warming operation heats the stack to a final target temperature, and the predetermined target temperature is less than the final target temperature.

4 . The method of claim 1 wherein the predetermined warming operation heats the stack for a predetermined time period, the final warming operation heats the stack for a final time period, and the predetermined time period is less than the final time period.

5 . The method of claim 1 wherein the relative humidity of a reactant gas supplied to the fuel cell stack is lower during the final warming operation than during the predetermined warming operation.

6 . The method of claim 1 wherein the flow rate of a reactant gas supplied to the fuel cell stack is greater during the final warming operation than during the predetermined warming operation.

7 . The method of claim 1 wherein the pressure of a reactant gas supplied to the fuel cell stack is lower during the final warming operation than during the predetermined warming operation.

8 . The method of claim 1 wherein:
the predetermined warming operation comprises:
heating the stack for a predetermined time period; and
performing a predetermined purge after the predetermined time period;

the final warming operation comprises:
heating the stack for a final time period; and
performing a final purge after the final time period; and

wherein the final purge is longer than the predetermined purge.

9 . The method of claim 1 wherein the steps of performing the predetermined and the final warming operations are selected from the group consisting of producing power from the fuel cell stack and heating the fuel cell stack with an electric heater.

10 . A fuel cell system comprising:
a fuel cell stack; an energy supply for heating the fuel cell stack; apparatus for monitoring the amount of energy remaining in the fuel cell system; apparatus for monitoring the temperature of the fuel cell stack; and apparatus for performing predetermined and final warming operations; wherein the fuel cell system is configured to operate according to the method of claim 1 .

Assignees

• Daimler Ag
• Ford Motor Co
• Nissan Motor

Inventors

• Procter Michael
• Fukuyama Yosuke
• Fellows Richard
• Shiomi Takeshi

Classifications

• H01M8/04955

  Shut-off or shut-down of fuel cells · CPC title

• H01M8/0432

  Temperature; Ambient temperature · CPC title

• H01M8/24

  Grouping of fuel cells, e.g. stacking of fuel cells · CPC title

• H01M8/04619

  of fuel cell stacks · CPC title

• H01M2250/20

  Fuel cells in motive systems, e.g. vehicle, ship, plane · CPC title