Fuel cell system

• US 20050244686A1
• Filed: 12/03/2003
• Published: 11/03/2005
• Est. Priority Date: 12/03/2002
• Status: Active Grant

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Kamihara, Tetsuya
• Granted Patent: US 7,931,994 B2
• Time in Patent Office: Days
• US Class Current: 429/415
• CPC Class Codes: H01M 8/04097 with recycling of the reactants H01M8/04119, H01M8/04104 take precedence
• CPC Class Codes: H01M 8/04104 Regulation of differential pressures
• CPC Class Codes: H01M 8/04223 during start-up or shut-down; Depolarisation or activation, e.g. purging; Means for short-circuiting defective fuel cells
• CPC Class Codes: H01M 8/241 with solid or matrix-supported electrolytes
• CPC Class Codes: H01M 8/2457 with both reactants being gaseous or vaporised
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

A fuel cell system which includes: a fuel cell (1); a supply system (Sc) for supplying fuel gas to the fuel cell (1); a recirculation system (Rc) for recirculating unused fuel gas from the fuel cell (1), in which the fuel gas therein may contain nitrogen; a purge valve (8) for purging nitrogen contained in the fuel gas in the recirculation system (Rc); and a controller (100) for adjusting a valve opening of the purge valve (8) so that a nitrogen concentration of the fuel gas in the recirculation system (Rc) is kept constant.

Claims

1. A fuel cell system comprising:

a fuel cell for generating power from fuel gas supplied thereto;

a supply system for supplying fuel gas to the fuel cell;

a recirculation system for recirculating unused fuel gas from the fuel cell, the fuel gas in the recirculation system containing nitrogen;

a purge valve for purging nitrogen contained in the fuel gas in the recirculation system; and

a controller for adjusting a valve opening of the purge valve so that a nitrogen concentration of the fuel gas in the recirculation system is kept constant.

2. The fuel cell system according to claim 1,

wherein the controller reduces the valve opening of the purge valve if a flow rate of the fuel gas passing through the purge valve is more than a threshold set in accordance with operation conditions of the fuel cell system and the valve opening of the purge valve, and increases the valve opening of the purge valve if the flow rate of the fuel gas passing through the purge valve is less than the threshold.

3. The fuel cell system according to claim 2,

wherein the threshold is set larger as the valve opening of the purge valve becomes larger.

4. The fuel cell system according to claim 2, further comprising:

a temperature sensor for detecting temperature of the fuel gas passing through the purge valve,

wherein the threshold is set lower as the temperature of the fuel gas detected by the temperature sensor rises.

5. The fuel cell system according to claim 2, further comprising:

a pressure sensor for detecting pressure of the fuel gas in the supply system,

wherein the threshold is set lower as the pressure of the fuel gas detected by the pressure sensor drops.

6. The fuel cell system according to claim 1,

wherein a flow rate of the fuel gas passing through the purge valve is obtained from a difference between a supply rate of the fuel gas supplied from the supply system and a consumption rate of the fuel gas consumed by the fuel cell.

7. The fuel cell system according to claim 6, further comprising:

an ejector provided in the recirculation system, to which the supply system is connected; and

a pressure sensor for detecting supply pressure of the fuel gas supplied to the ejector,

wherein the supply rate of the fuel gas is calculated based on the supply pressure detected by the pressure sensor.

8. The fuel cell system according to claim 7, further comprising:

a temperature sensor for detecting a temperature of the fuel gas upstream of the ejector,

wherein the supply rate of the fuel gas is calculated based on the temperature of the fuel gas detected by the temperature sensor and the supply pressure thereof detected by the pressure sensor.

9. The fuel cell system according to claim 6, further comprising:

a fuel pressure regulator for the fuel gas supplied to the fuel cell;

a valve opening sensor for detecting a valve opening of the fuel pressure regulator; and

a pressure sensor for detecting pressure of the fuel gas upstream of the fuel pressure regulator,

wherein the supply rate of the fuel gas is calculated based on the valve opening of the fuel pressure regulator detected by the valve opening sensor, and the pressure of the fuel gas upstream of the fuel pressure regulator detected by the pressure sensor.

10. The fuel cell system according to claim 9, further comprising:

a temperature sensor for detecting temperature of the fuel gas upstream of the fuel pressure regulator,

wherein the supply rate of the fuel gas is calculated based on the valve opening degree of the fuel pressure regulator detected by the valve opening sensor, the pressure of the fuel gas upstream of the fuel pressure regulator detected by the pressure sensor, and the temperature of the fuel gas detected by the temperature sensor.

11. The fuel cell system according to claim 6, further comprising:

an ammeter for detecting an output current of the fuel cell,

wherein the consumption rate of the fuel gas is calculated based on the output current detected by the ammeter.

12. The fuel cell system according to claim 6, further comprising:

an ammeter for detecting an output current of the fuel cell; and

a pressure sensor for detecting pressure of the fuel gas upstream or downstream of the fuel cell,

wherein the controller is provided with a unit for obtaining a variation rate of the pressure of the fuel gas detected by the pressure sensor, and

wherein the consumption rate of the fuel gas is calculated based the output current detected by the ammeter and the variation rate of the pressure of the fuel gas given by the unit of the controller.