Fuel Cell Systems

Abstract

To efficiently perform ion exchange treatment of a cooling liquid in a fuel cell system.SOLUTION: A fuel cell system comprises: a fuel cell stack; a cooling liquid circulation path which is connected to the fuel cell stack, and in which a cooling liquid circulates; an ion exchanger which performs ion exchange treatment for the cooling liquid; and a control circuit. The control circuit performs: a first operation in which the temperature of the cooling liquid is increased by generating power with the use of the fuel cell stack; and a second operation in which the ion exchange treatment is performed for the cooling liquid by the ion exchanger after the first operation.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The technology disclosed in this specification relates to a fuel cell system.

[0002] Patent Document 1 discloses a fuel cell system. In general, a fuel cell system has a coolant circulation passage. A coolant flows through the coolant circulation passage to cool the fuel cell stack. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-277407 A Summary of the Invention [Problem to be solved by the invention]

[0004] Ions may dissolve in the coolant in a fuel cell system, causing the insulation of the coolant to deteriorate. If the insulation of the coolant deteriorates excessively, current leaks through the coolant in the fuel cell stack. For this reason, in a fuel cell system, an ion exchange process is periodically performed to remove the ions dissolved in the coolant using an ion exchanger. By performing the ion exchange process, the insulation of the coolant can be restored. This specification proposes a technology for efficiently performing an ion exchange process on the coolant in a fuel cell system. [Means for solving the problem]

[0005] The fuel cell system disclosed in this specification includes a fuel cell stack, a coolant circulation path connected to the fuel cell stack and through which a coolant circulates, an ion exchanger that performs an ion exchange process on the coolant, and a control circuit, the control circuit configured to perform a first operation of increasing the temperature of the coolant by generating electricity using the fuel cell stack, and a second operation of performing the ion exchange process on the coolant using the ion exchanger after the first operation.

[0006] In this fuel cell system, after the temperature of the coolant is increased by the first operation, an ion exchange process is performed on the coolant by the second operation. Since the ion exchange process can be performed while the temperature of the coolant is high, the ions dissolved in the coolant can be efficiently removed from the coolant. Therefore, the insulating properties of the coolant can be restored in a short time. [Brief description of the drawings]

[0007] [Figure 1] 1 is a circuit diagram of a fuel cell system 10. [Diagram 2] FIG. 2 shows a container for housing the fuel cell system 10. [Diagram 3] FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The fuel cell system 10 shown in FIG. 1 is a stationary fuel cell system. For example, the fuel cell system 10 is housed in a container 10a shown in FIG. 2. As shown in FIG. 1, the fuel cell system 10 has a fuel cell stack 20, a hydrogen gas supply system 30, an oxygen gas supply system 40, a cooling system 50, and a control circuit 70. The fuel cell stack 20 is composed of a plurality of stacked fuel cell cells. The hydrogen gas supply system 30 supplies hydrogen gas to the fuel cell stack 20. The oxygen gas supply system 40 supplies oxygen gas to the fuel cell stack 20. The hydrogen gas and oxygen gas supplied to the fuel cell stack 20 react with each other in each fuel cell in the fuel cell stack 20. As a result, a voltage is output between output terminals 20a, 20b of the fuel cell stack 20. The cooling system 50 cools the fuel cell stack 20 by flowing a coolant through the fuel cell stack 20. The control circuit 70 controls each part of the fuel cell system 10.

[0009] The cooling system 50 has a coolant circulation path 52 connected to the fuel cell stack 20. A coolant flows in the coolant circulation path 52. The coolant circulation path 52 has a cooling flow path 52a, an ion exchange flow path 52b, and a heat dissipation flow path 52c. The cooling flow path 52a is configured to pass through the fuel cell stack 20. Although not shown, the cooling flow path 52a is branched into a plurality of paths in the fuel cell stack 20, and each of the branched paths is arranged along each fuel cell. The fuel cell stack 20 is cooled by the coolant flowing in the cooling flow path 52a. A pump 60 is installed in the cooling flow path 52a. The pump 60 sends out the coolant in the cooling flow path 52a from the upstream side to the downstream side. The upstream end of the cooling flow path 52a is connected to the downstream end of the ion exchange flow path 52b and the downstream end of the heat dissipation flow path 52c. The downstream end of the cooling flow path 52a is connected to the upstream end of the ion exchange flow path 52b and the upstream end of the heat dissipation flow path 52c via a three-way valve 54. The three-way valve 54 switches the connection state between a state in which the coolant flows from the cooling flow path 52a to the ion exchange flow path 52b and a state in which the coolant flows from the cooling flow path 52a to the heat dissipation flow path 52c. The three-way valve 54 is controlled by a control circuit 70. A radiator 58 is installed in the heat dissipation flow path 52c. The radiator 58 cools the coolant by dissipating heat from the coolant flowing in the heat dissipation flow path 52c to the outside air. A part of the ion exchange flow path 52b branches into a first flow path 52b1 and a second flow path 52b2. An ion exchanger 56 is installed in the second flow path 52b2. The ion exchanger 56 is an ion exchanger that uses an ion exchange resin or the like. The ion exchanger 56 performs an ion exchange process on the coolant flowing in the second flow path 52b2.

[0010] When the fuel cell system 10 is operated to generate electricity, the control circuit 70 supplies hydrogen gas from the hydrogen gas supply system 30 to the fuel cell stack 20 and supplies oxygen gas from the oxygen gas supply system 40 to the fuel cell stack 20. This causes the fuel cell stack 20 to generate electricity. Furthermore, during the power generation operation, the control circuit 70 operates the pump 60 while the three-way valve 54 is in a state in which the coolant flows from the cooling flow path 52a to the heat dissipation flow path 52c. This causes the coolant to circulate through the annular flow path formed by the cooling flow path 52a and the heat dissipation flow path 52c. Furthermore, the control circuit 70 operates the radiator 58. Therefore, the coolant cooled by the radiator 58 is supplied to the fuel cell stack 20 by the cooling flow path 52a. This causes the fuel cell stack 20 to be cooled.

[0011] In addition, the control circuit 70 periodically performs a maintenance operation. As shown in FIG. 3, in the maintenance operation, the control circuit 70 performs an output check operation and an ion exchange operation. The output check operation is an operation for checking whether or not an appropriate output voltage is obtained in the fuel cell stack 20. The ion exchange operation is an operation for recovering the insulation of the coolant in the coolant circulation path 52. Impurity ions (e.g., metal ions, chloride ions, etc.) are dissolved into the coolant from each part of the fuel cell system 10 (e.g., the piping of the coolant circulation path 52, etc.). Therefore, the concentration of the impurity ions in the coolant increases over time. When the concentration of the impurity ions in the coolant increases, the insulation of the coolant decreases. When the insulation of the coolant becomes excessively low, a current may leak through the coolant. Therefore, the control circuit 70 periodically performs an ion exchange operation to recover the insulation of the coolant.

[0012] In the output check operation, the control circuit 70 performs power generation in the fuel cell stack 20 in the same manner as in the power generation operation described above. That is, the control circuit 70 performs power generation in the fuel cell stack 20 by supplying hydrogen gas from the hydrogen gas supply system 30 to the fuel cell stack 20 and supplying oxygen gas from the oxygen gas supply system 40 to the fuel cell stack 20. As shown in FIG. 3, in the output check operation, a relatively high output voltage is output between the output terminals 20a and 20b. The control circuit 70 measures the output voltage in the output check operation. This checks whether the output voltage is a normal value or not. In addition, during the output check operation, the control circuit 70 circulates the coolant through the circulation flow path formed by the cooling flow path 52a and the heat dissipation flow path 52c to cool the fuel cell stack 20. Since the temperature of the fuel cell stack 20 has risen due to power generation, the coolant is heated by the fuel cell stack 20. Therefore, the temperature of the coolant rises during the output check operation. The control circuit 70 continues the output check operation until the temperature of the coolant becomes 60° C. or higher. Note that the radiator 58 may or may not be operated during the output check operation.

[0013] The control circuit 70 performs an ion exchange operation after the output confirmation operation. In the ion exchange operation, as shown in FIG. 3, the control circuit 70 reduces the output voltage of the fuel cell stack 20. That is, during the ion exchange operation, power is generated in the fuel cell stack 20 so that a low output voltage is output. The control circuit 70 also switches the three-way valve 54 so that the coolant flows from the cooling flow path 52a to the ion exchange flow path 52b. Therefore, in the ion exchange operation, the coolant circulates through the circulation flow path formed by the cooling flow path 52a and the ion exchange flow path 52b. Therefore, the coolant flows through the second flow path 52b2 of the ion exchange flow path 52b. The ion exchanger 56 converts impurity ions in the coolant flowing through the second flow path 52b2 into protons (H + ) or hydroxide ion (OH - ) to remove impurity ions from the coolant. Therefore, the concentration of impurity ions in the coolant decreases during the ion exchange operation, and the insulating properties of the coolant are restored.

[0014] The efficiency of ion exchange in the ion exchanger 56 improves as the temperature of the coolant increases. In the above-mentioned maintenance operation, the ion exchange operation is carried out after the temperature of the coolant is raised in the output confirmation operation. Therefore, the ion exchange operation can be started when the temperature of the coolant is high. This allows ion exchange to be performed efficiently in the ion exchange operation. Therefore, the insulating properties of the coolant can be restored in a short time, and the ion exchange operation can be completed in a short time. Therefore, in the fuel cell system of the embodiment, the time for the maintenance operation (i.e., the time during which the fuel cell system 10 cannot be used) can be shortened.

[0015] In the above embodiment, power generation was performed in which a low output voltage was output from the fuel cell stack 20 during the ion exchange operation. Therefore, the temperature of the coolant is less likely to drop during the ion exchange operation. This allows the ion exchange to be performed more efficiently. However, if the drop in the temperature of the coolant is not a significant problem, power generation in the fuel cell stack 20 may be stopped during the ion exchange operation.

[0016] Although the embodiments have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or drawings achieves multiple objectives simultaneously, and achieving one of the objectives itself has technical utility. [Explanation of symbols]

[0017] 10: Fuel cell system 20: Fuel cell stack 30: Hydrogen gas supply system 40: Oxygen gas supply system 50: Cooling system 52: Coolant circulation path 52a: Main flow path 52b: Ion exchange channel 52c: Heat radiation flow path 56: Ion exchanger 58: Radiator 60: Pump 70: Control circuit

Claims

1. 1. A fuel cell system comprising: A fuel cell stack; a coolant circulation path connected to the fuel cell stack, through which a coolant circulates; an ion exchanger for performing an ion exchange process on the cooling liquid; A control circuit, having The cooling liquid circulation path is a cooling passage provided with the fuel cell stack; A heat dissipation flow path; an ion exchanger flow path provided with the ion exchanger; Equipped with The control circuit, a first operation of increasing a temperature of the cooling liquid by generating electricity using the fuel cell stack while circulating the cooling liquid through the cooling flow path and the heat dissipation flow path in a state where the ion exchanger flow path is closed; a second operation of performing the ion exchange process on the cooling liquid by the ion exchanger while circulating the cooling liquid through the cooling flow path and the ion exchanger flow path in a state where the heat dissipation flow path is closed after the first operation; 4. The method according to claim 1, Fuel cell system.

2. The fuel cell system according to claim 1 , wherein in the second operation, power is generated by the fuel cell stack at an amount of power generation that is lower than that in the first operation.

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