Method of actuating fuel cell system and fuel cell system

Abstract

A method of actuating a fuel cell system equipped with a fuel cell is disclosed. The fuel cell system is supplied with reaction gases for generating electricity. The method includes the steps of: a first step for actuating the fuel cell in a low-temperature actuation mode to thereby warm up the fuel cell, if a low-temperature actuation condition is satisfied at a start-up of the fuel cell; and a second step for drying a membrane electrode assembly of the fuel cell, if a power generation capacity of the fuel cell is lower than a predetermined power generation capacity.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The aspects of the present invention will become more apparent by describing in detail illustrative, non-limiting embodiments thereof with reference to the accompanying drawings, in which:

FIG. 1 is a block diagram illustrating the configuration of a fuel cell system according to one aspect of the present invention;

FIG. 2A is a sectional view of a fuel cell shown in FIG. 1, illustrating a state before drying an MEA, and FIG. 2B is a sectional view of the fuel cell, illustrating a state after drying the MEA;

FIG. 3 is a graph showing a relation between temperature and output power of the fuel cell after the ignition IG is on;

FIG. 4 is a graph showing I-V curve (I-V characteristics) of the fuel cell;

FIG. 5 is a flow chart showing the manner of actuation of the fuel cell system;

FIG. 6 is a flow chart showing processes in an MEA drying mode of FIG. 5;

FIG. 7 is a graph showing a relation between pressure of hydrogen and output power of the fuel cell;

FIG. 8 is a graph showing a relation between the number of low-temperature actuations and output power of the fuel cell;

FIG. 9 is a time chart showing an example of operating the fuel cell system according to the present invention; and

FIG. 10 is a time chart showing an example of operating the conventional fuel cell system as a comparative example.

Claims

1. A method of actuating a fuel cell system equipped with a fuel cell, to which reaction gases are supplied for generating electricity, the method comprising the steps of: a first step for actuating the fuel cell in a low-temperature actuation mode to thereby warm up the fuel cell, if a low-temperature actuation condition is satisfied at a start-up of the fuel cell; anda second step for drying a membrane electrode assembly of the fuel cell, if a power generation capacity of the fuel cell is lower than a predetermined power generation capacity.

2. The method according to claim 1, wherein the second step includes a further step for elevating a temperature of the fuel cell to be higher than in a steady operation of the fuel cell.

3. The method according to claim 2, wherein the further step includes a cooling rate decreasing step for decreasing a cooling rate of the fuel cell to be lower than in the steady operation of the fuel cell.

4. The method according to claim 2, wherein the further step includes a gas pressure decreasing step for decreasing a pressure of the reaction gas to be supplied to the fuel cell to be lower than in the steady operation of the fuel cell.

5. The method according to claim 1, wherein the second step includes a step for lowering a humidity increase in the reaction gas to be supplied to the fuel cell than in a steady operation of the fuel cell.

6. The method according to claim 1, wherein the second step includes a flow rate increasing step for increasing a flow rate of the reaction gas to be supplied to the fuel cell to be higher than in a steady operation of the fuel cell.

7. The method according to claim 1, wherein the second step is continued until the power generation capacity of the fuel cell becomes equal to or higher than the predetermined power generation capacity.

8. A fuel cell system comprising: a fuel cell to which reaction gases are supplied for generating electricity;an electric motor connected to and driven by the fuel cell;an anode system for supplying and discharging hydrogen as a reaction gas to and from an anode of the fuel cell;a cathode system for supplying and discharging air containing oxygen as a reaction gas to and from a cathode of the fuel cell;means for actuating the fuel cell in a low-temperature actuation mode to thereby warm up the fuel cell, if a low-temperature actuation condition is satisfied at a start-up of the fuel cell; andmeans for drying a membrane electrode assembly of the fuel cell after the fuel cell is actuated in the low-temperature actuation mode and before an operation of the fuel cell is stopped, if a power generation capacity of the fuel cell is lower than a predetermined power generation capacity.

9. A fuel cell system according to claim 8, wherein the means for drying the membrane electrode assembly of the fuel cell elevates a temperature of the fuel cell to be higher than in a steady operation of the fuel cell.

10. A fuel cell system according to claim 9, wherein the means for drying the membrane electrode assembly of the fuel cell decreases a cooling rate of the fuel cell to be lower than in the steady operation of the fuel cell.

11. A fuel cell system according to claim 9, wherein the means for drying the membrane electrode assembly of the fuel cell decreases a pressure of the reaction gas to be supplied to the fuel cell to be lower than in the steady operation of the fuel cell.

12. A fuel cell system according to claim 9, wherein the means for drying the membrane electrode assembly of the fuel cell lowers a humidity increase in the reaction gas to be supplied to the fuel cell than in the steady operation of the fuel cell.

13. A fuel cell system according to claim 9, wherein the means for drying the membrane electrode assembly of the fuel cell increases a flow rate of the reaction gas to be supplied to the fuel cell to be higher than in the steady operation of the fuel cell.

14. A fuel cell system according to claim 8, wherein the membrane electrode assembly of the fuel cell is continuously dried until the power generation capacity of the fuel cell becomes equal to or higher than the predetermined power generation capacity.