Fuel cell system and method of controlling the same

• US 20020106537A1
• Filed: 01/18/2002
• Published: 08/08/2002
• Est. Priority Date: 05/23/2000
• Status: Active Grant

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Saito, Kazuo
• Granted Patent: US 6,830,841 B2
• Time in Patent Office: Days
• US Class Current: 429/13
• CPC Class Codes: H01M 16/003 of fuel cells with other electrochemical devices, e.g. capacitors, electrolysers
• CPC Class Codes: H01M 8/04007 related to heat exchange
• 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 8/04156 with product water removal
• CPC Class Codes: H01M 8/04291 Arrangements for managing water in solid electrolyte fuel cell systems H01M8/04119 takes precedence
• CPC Class Codes: H01M 8/04298 Processes for controlling fuel cells or fuel cell systems
• CPC Class Codes: H01M 8/04313 characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
• 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 8/04753 of fuel cell reactants
• CPC Class Codes: H01M 8/04776 at auxiliary devices, e.g. reformer, compressor, burner
• CPC Class Codes: H01M 8/04835 of fuel cell reactants
• CPC Class Codes: H01M 8/0485 of the electrolyte
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

In a fuel cell system and its controlling method, the fuel cell system includes a stack 21 including fuel cells 11 each having a polymer electrolyte membrane 13, and a controller 61. The controller 61 is responsive to detected outputs of a displacement sensor 27 and a temperature sensor 27 and controls such that, when the polymer electrolyte membrane 13 is discriminated to remain in an excessively dry state, a shut-off valve 37 is applied with a “close” control signal to interrupt the supply of fuel gas to the stack 21 and, concurrently, a shut-off valve 41 is applied with an “open” control signal to allow air to be supplied to the stack 21 while applying a pump control signal to a pump 57 so as to maximize its rotational speed for thereby increasing the flow rate of pure water 59 to be circulated to the humidifier 35 from a pure water tank 55. Simultaneously, a timer of the controller 61 is operated to begin counting an incremental time. As a result, air is excessively humidified by the humidifier 35 and is supplied to the stack 21 via the shut-off valve 41.

Claims

1. A fuel cell system comprising:

a humidifier humidifying fuel gas and air;

a stack producing electric power by reacting the fuel gas humidified by the humidifier and the air humidified by the humidifier, including a plurality of fuel cells and fixed for free movement in a stacked direction thereof, each of the plurality of fuel cells having a polymer electrolyte membrane;

a displacement sensor detecting a displacement value in length of the stack in the stacked direction;

a temperature sensor detecting a temperature of the stack; and

a controller discriminating whether the polymer electrolyte membrane is in a dry state in response to the displacement value of the stack detected by the displacement sensor and the temperature of the stack detected by the temperature sensor, and controlling the humidifier, when the polymer electrolyte membrane is discriminated as in a dry state at a start of operation of the stack, to cause the polymer electrolyte membrane to be brought into a wet state.

2. A fuel cell system according to claim 1, wherein the controller controls the humidifier, when the polymer electrolyte membrane is discriminated as in the dry state at the start of operation, to supply the air through the humidifier to the stack for a predetermined time period while not supplying the fuel gas through the humidifier to the stack.

3. A fuel cell system according to claim 2, wherein the controller controls the humidifier, after only the air has been supplied to the stack through the humidifier for the predetermined time period, to supply the fuel gas and the air through the humidifier to the stack, while controlling the stack such that the electric power output from the stack is regulated to a limited value below a predetermined value until the polymer electrolyte membrane is determined as in a wet state.

4. A fuel cell system according to claim 1, wherein the humidifier includes a heater heating the fuel gas and the air, and the stack produces the electric power by reacting the fuel gas humidified and heated by the humidifier and the air humidified and heated by the humidifier.

5. A fuel cell system according to claim 4, wherein the controller controls the humidifier, when the polymer electrolyte membrane is discriminated as in the dry state at the start of operation, to supply the air through the humidifier to the stack for a predetermined time period while not supplying the fuel gas through the humidifier to the stack.

6. A fuel cell system according to claim 5, wherein the controller controls the humidifier, after only the air has been supplied to the stack through the humidifier for the predetermined time period, to supply the fuel gas and the air through the humidifier to the stack, while controlling the stack such that the electric power output from the stack is regulated to a limited value below a predetermined value until the polymer electrolyte membrane is determined as in a wet state.

7. A fuel cell system according to claim 1, wherein the controller controls the humidifier to supply the fuel gas and the air through the humidifier to the stack when the polymer electrolyte membrane is discriminated as in a wet state at the start of operation of the stack.

8. A fuel cell system according to claim 7, wherein the controller controls the humidifier to supply the fuel gas and the air through the humidifier to the stack, while controlling the stack such that the electric power output from the stack is regulated to a limited value below a predetermined value until the temperature of the stack exceeds a predetermined temperature.

9. A fuel cell system comprising:

humidifying means humidifying fuel gas and air;

a stack producing electric power by reacting the fuel gas humidified by the humidifying means and the air humidified by the humidifying means, including a plurality of fuel cells and fixed for free movement in a stacked direction thereof, each of the plurality of fuel cells having a polymer electrolyte membrane;

a displacement detecting means detecting a displacement value in length of the stack in the stacked direction;

temperature detecting means detecting a temperature of the stack; and

controlling means discriminating whether the polymer electrolyte membrane is in a dry state in response to the displacement value of the stack detected by the displacement detecting means and the temperature of the stack detected by the temperature detecting means, and controlling the humidifying means, when the polymer electrolyte membrane is discriminated as in a dry state at a start of operation of the stack, to cause the polymer electrolyte membrane to be brought into a wet state.

10. A method of controlling a fuel cell system provided with a humidifier humidifying fuel gas and air, and a stack producing electric power by reacting the fuel gas humidified by the humidifier and the air humidified by the humidifier, including a plurality of fuel cells and fixed for free movement in a stacked direction thereof, each of the plurality of fuel cells having a polymer electrolyte membrane, the method comprising:

detecting a displacement value in length of the stack in the stacked direction;

detecting a temperature of the stack;

discriminating whether the polymer electrolyte membrane is in a dry state in response to the displacement value of the stack detected by the displacement sensor and the temperature of the stack detected by the temperature sensor; and

controlling the humidifier, when the polymer electrolyte membrane is discriminated as in a dry state at a start of operation of the stack, to cause the polymer electrolyte membrane to be brought into a wet state.