Fuel cell system for performing normal and abnormal shut-down processes

1. A fuel cell system comprising:

a fuel cell;

a first heat medium path through which a first heat medium for cooling the fuel cell flows;

a first flow control device configured to flow the first heat medium in the first heat medium path;

an abnormality detector configured to detect an abnormality; and

a controller configured to control the first flow control device in an abnormal shut-down process to flow the first heat medium in the first heat medium path until a temperature of the fuel cell after shut-down of power generation reaches a first temperature lower than a second temperature of the fuel cell which is reached in a normal shut-down process,

wherein the normal shut-down process is different from the abnormal shut-down process performed after the abnormality detector detects the abnormality.

2. The fuel cell system according to claim 1 ,

wherein the controller is further configured to control at least one of an operation time and an operation amount of the first flow control device in order for the temperature of the fuel cell to reach the first temperature in the abnormal shut-down process.

3. The fuel cell system according to claim 1 ,

wherein the controller is further configured to permit the fuel cell system to re-start an operation under a higher-temperature condition of the fuel cell, after the normal shut-down process than the abnormal shut-down process.

4. The fuel cell system according to claim 1 ,

wherein the controller is further configured to increase an operation amount of the first flow control device to be larger than an average operation amount during a power generation operation, regardless of a temperature of the fuel cell, in the abnormal shut-down process.

5. The fuel cell system according to claim 4 ,

wherein the controller is further configured to cool the fuel cell by controlling the operation amount of the first flow control device based on the temperature of the fuel cell in the normal shut-down process, and

wherein the controller is further configured to increase the operation amount of the first flow control device to be larger than an average operation amount during a power generation operation, regardless of the temperature of the fuel cell, in the abnormal shut-down process.

6. The fuel cell system according to claim 4 ,

wherein the controller is further configured to perform a first cooling step of controlling the operation amount of the first flow control device based on the temperature of the fuel cell and a second cooling step of increasing the operation amount of the first flow control device to be larger than the average operation amount during a power generation operation, regardless of the temperature of the fuel cell, in the abnormal shut-down process.

7. The fuel cell system according to claim 1 , further comprising:

a hydrogen generator further configured to supply a hydrogen-containing gas supplied to the fuel cell, using a raw material,

wherein the controller is further configured to continue a cooling operation of the fuel cell in the abnormal shut-down process at least until a material purge process of the hydrogen generator terminates.

8. The fuel cell system according to claim 1 ,

wherein the fuel cell system is further configured to perform a pressure compensation operation for supplying a gas to a reactant gas path in the fuel cell sealed, a pressure in the reactant gas path having been decreased, after the shut-down of the power generation of the fuel cell, and

wherein the controller is further configured to set a number of times of the pressure compensation operation more in the abnormal shut-down process than in the normal shut-down process.

9. The fuel cell system according to claim 1 , further comprising:

a heat accumulator further configured to store a second heat medium for recovering exhaust heat from the fuel cell;

a second heat medium path through which the second heat medium flows; and

a bypass path through which the second heat medium which has recovered the exhaust heat from the fuel cell flows so as to bypass the heat accumulator,

wherein the controller is further configured to switch to the bypass path through which the second heat medium flows so as to bypass the heat accumulator, in a cooling operation of the fuel cell in the abnormal shut-down process.

10. The fuel cell system according to claim 1 , wherein the controller is further configured to perform the abnormal shut-down process when the abnormality detector detects a component failure or a gas leakage abnormality.

11. The fuel cell system according to claim 1 , wherein:

the abnormal shut-down process includes a first abnormal shut-down process performed in response to a detection of a first abnormality which does not require a maintenance operation by a user to re-start an operation of the fuel cell system, and a second abnormal shut-down process performed in response to a detection of a second abnormality which requires the maintenance operation, and

the controller is further configured to control the first flow control device in the second abnormal shut-down process to flow the first heat medium until the temperature of the fuel cell reaches a third temperature lower than a fourth temperature which is reached in the first abnormal shut-down process.

12. The fuel cell system according to claim 11 , wherein the controller is further configured to permit the fuel cell system to re-start the operation under a higher-temperature condition of the fuel cell in the first abnormal shut-down process than in the second abnormal shut-down process.

13. The fuel cell system according to claim 11 ,

wherein the controller is further configured to increase the operation amount of the first flow control device to be larger than an average operation amount during a power generation operation, regardless of a temperature of the fuel cell, in the second abnormal shut-down process.

14. The fuel cell system according to claim 13 ,

wherein the controller is further configured to cool the fuel cell by controlling the operation amount of the first flow control device based on a temperature of the fuel cell in the first abnormal shut-down process, and

wherein the controller is further configured to increase the operation amount of the first flow control device to be larger than the average operation amount during a power generation operation, regardless of the temperature of the fuel cell, in the second abnormal shut-down process.

15. The fuel cell system according to claim 13 ,

wherein the controller is further configured to perform, in the second abnormal shut-down process, a first cooling step of controlling the operation amount of the first flow control device based on the temperature of the fuel cell, and a second cooling step of increasing the operation amount of the first flow control device to be larger than the average operation amount during a power generation operation, regardless of the temperature of the fuel cell.

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

a hydrogen generator further configured to generate a hydrogen-containing gas supplied to the fuel cell, using a raw material,

wherein the controller is further configured to continue a cooling operation of the fuel cell in the second abnormal shut-down process at least until a material purge process of the hydrogen generator terminates.

17. The fuel cell system according to claim 11 ,

wherein the fuel cell system is further configured to perform a pressure compensation operation for supplying a gas to a reactant gas path in the fuel cell sealed, a pressure in the reactant gas path having been decreased, after the shut-down of the power generation of the fuel cell, and

wherein the controller is further configured to set a number of times of the pressure compensation operation more in the second abnormal shut-down process than in the first abnormal shut-down process.

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

a heat accumulator configured to store a second heat medium for recovering exhaust heat from the fuel cell;

a second heat medium path through which the second heat medium flows; and

a bypass path through which the second heat medium which has recovered the exhaust heat from the fuel cell flows so as to bypass the heat accumulator,

wherein the controller is further configured to switch to the bypass path through which the second heat medium flows so as to bypass the heat accumulator, in a cooling operation of the fuel cell in the second abnormal shut-down process.

19. The fuel cell system according to claim 11 ,

wherein the first abnormality is at least one of a temperature abnormality of the first heat medium and an abnormality of the first flow control device.

20. The fuel cell system according to claim 11 ,

wherein the second abnormality is one or more of a component failure, a gas leakage abnormality and an excessive temperature increase abnormality of the controller.

21. The fuel cell system according to claim 1 , further comprising:

a hydrogen generator including a reformer configured to generate a hydrogen-containing gas through a reforming reaction using a raw material, a combustor further configured to heat the reformer, and a combustion air supplier further configured to supply combustion air to the combustor, wherein

the controller is further configured to control the first flow control device in the abnormal shut-down process to flow the first heat medium until the temperature of the fuel cell reaches the first temperature and control the combustion air supplier in order for the reformer to be cooled with an amount equal to an amount of cooling in the normal shut-down process, in an abnormal shut-down process performed after the abnormality detector detects an abnormality which is associated with the fuel cell and is other than an abnormality associated with the hydrogen generator.

22. The fuel cell system according to claim 21 ,

wherein the controller is further configured to control the combustion air supplier and the first flow control device in order for the reformer and the fuel cell to be cooled with an amount equal to an amount of cooling in the normal shut-down process, in an abnormal shut-down process performed after the abnormality detector detects a first abnormality which does not require a maintenance operation by a user to re-start an operation of the fuel cell system, is associated with the fuel cell system and is other than the abnormality associated with the hydrogen generator, and

wherein the controller is further configured to control the first flow control device in order for the temperature of the fuel cell to reach the first temperature and control the combustion air supplier in order for the reformer to be cooled with the amount equal to amount of cooling in the normal shut-down process, in an abnormal shut-down process performed after the abnormality detector detects a second abnormality which requires the maintenance operation, is associated with the fuel cell system and is other than the abnormality associated with the hydrogen generator.

23. The fuel cell system according to claim 1 or 21 , further comprising:

a hydrogen generator including a reformer configured to generate a hydrogen-containing gas through a reforming reaction using a raw material,

a combustor configured to heat the reformer, and

a combustion air supplier configured to supply combustion air to the combustor,

wherein the controller is further configured to control the combustion air supplier in order for the reformer to be cooled with a higher amount than in the normal shut-down process and control the first flow control device in order for the temperature of the fuel cell to reach the second temperature, when the abnormality detector detects the abnormality associated with the hydrogen generator.

24. The fuel cell system according to claim 23 ,

wherein the controller is further configured to control the combustion air supplier and the first flow control device in order for the reformer to be cooled with an amount equal to an amount of cooling in the normal shut-down process and the temperature of the fuel cell reaches the second temperature, in an abnormal shut-down process performed after the abnormality detector detects a first abnormality which does not require a maintenance operation by a user to re-start an operation of the fuel cell system and is associated with the hydrogen generator, and

wherein the controller is further configured to control the first flow control device in order for the reformer to be cooled with a higher amount than in the normal shut-down process and control the first flow control device in order for the temperature of the fuel cell to reach the second temperature, in an abnormal shut-down process performed after the abnormality detector detects a second abnormality which requires the maintenance operation and is associated with the hydrogen generator.

25. The fuel cell system according to claim 1 ,

wherein the controller is further configured to control the first flow control device in order for the temperature of the fuel cell after shut-down of power generation to reach the first temperature in an abnormal shut-down process performed after the abnormality detector detects a device failure, a gas leakage abnormality, or a temperature increase abnormality of the controller.

26. The fuel cell system according to claim 25 ,

wherein the first heat medium is cooling water,

the fuel cell system further comprising:

a cooling water tank for storing the cooling water; and

a cooling water tank water level detector for detecting a level of the cooling water stored in the cooling water tank, and

wherein the device failure is a failure of the cooling water tank water level detector.

27. The fuel cell system according to claim 25 , further comprising:

a condensed water tank for storing condensed water generated by condensation of steam contained in an off-fuel-gas and/or an off-oxidizing-gas which is exhausted from the fuel cell; and

a condensed water tank water level detector for detecting a level of the condensed water stored in the condensed water tank,

wherein the device failure is a failure of the condensed water tank water level detector.

28. The fuel cell system according to claim 25 , further comprising:

a first flow detector for detecting a flow rate of the fuel gas flowing through a fuel gas supply path,

wherein the device failure is a failure of the first flow detector.

29. The fuel cell system according to claim 25 , further comprising:

a second flow detector for detecting a flow rate of the oxidizing gas flowing through an oxidizing gas supply path,

wherein the device failure is a failure of the second flow detector.

30. The fuel cell system according to claim 25 , further comprising:

a third flow detector for detecting a flow rate of the first heat medium flowing through the first medium path,

wherein the device failure is a failure of the third flow detector.

31. The fuel cell system according to claim 25 , further comprising:

a temperature detector for detecting a temperature of the first heat medium flowing through the first heat medium path,

wherein the device failure is a failure of the temperature detector.

32. The fuel cell system according to claim 25 , further comprising:

a voltage transducer for supplying electricity generated in the fuel cell to a power load,

wherein the device failure is a failure of the voltage transducer.

33. The fuel cell system according to claim 25 , further comprising:

a package in which the fuel cell is accommodated; and

a ventilation fan disposed inside of the package,

wherein the device failure is a failure of the ventilation fan.

34. The fuel cell system according to claim 25 , further comprising:

a fuel gas path through which the fuel gas flows,

wherein the gas leakage abnormality is a pressure abnormality in the fuel gas path.

35. The fuel cell system according to claim 25 , further comprising:

an oxidizing gas path through which the oxidizing gas flows,

wherein the gas leakage abnormality is a pressure abnormality in the oxidizing gas path.

36. The fuel cell system according to claim 25 , further comprising:

a package in which the fuel cell is accommodated,

wherein the gas leakage abnormality is an abnormality of a concentration of a combustible gas.

37. The fuel cell system according to claim 1 , wherein the controller is further configured to control the first flow control device in order for a temperature of the fuel cell at an end of cooling the fuel cell by the first heat medium in the abnormal shut-down process to become lower than a temperature of the fuel cell at an end of cooling the fuel cell by the first heat medium in the normal shut-down process.

38. The fuel cell system according to claim 1 , wherein:

the controller includes a processor and a memory storing a program, and

the program, when executed by the processor, causes the controller to control the first flow control device in the abnormal shut-down process to flow the first heat medium in the first heat medium path until the temperature of the fuel cell after shut-down of power generation reaches the first temperature lower than the second temperature of the fuel cell which is reached in the normal shut-down process.

39. The fuel cell system according to claim 1 , wherein the abnormality is one of a gas leakage abnormality, and a temperature increase abnormality of the controller.