JP2023137664A - fuel cell system - Google Patents

Abstract

To provide a fuel cell system capable of individually determining the presence/absence of internal leak in a humidifier.SOLUTION: The present invention relates to a fuel cell system comprising: a fuel cell; a supplier which supplies an oxygen containing gas to the fuel cell; a humidifier for humidifying the oxygen containing gas with moisture contained in a cathode off-gas exhausted from the fuel cell; a voltage sensor for measuring a voltage of the fuel cell; and a determination device for determining whether or not internal leak occurs in the humidifier. In the fuel cell system, the determination device includes: an acquisition section for acquiring a voltage value from the voltage sensor; a control section which performs control so as to generate power from the fuel cell in a state where the supply of the oxygen containing gas from the supplier is stopped; and a determination section which makes the determination on the basis of a change in the voltage value during the control.SELECTED DRAWING: Figure 5

Description

The present disclosure relates to fuel cell systems.

A fuel cell system is a system that generates electricity by supplying fuel gas and oxidant gas to a fuel cell having a fuel electrode (anode), an electrolyte membrane, and an oxygen electrode (cathode).

Furthermore, from the viewpoint of suppressing deterioration of fuel cells and improving safety, techniques for determining whether or not gas supplied to and discharged from a fuel cell is leaking from a gas flow path are being considered. For example, Patent Document 1 describes the total voltage of the fuel cell, the pressure in the anode flow path, the pressure in the cathode flow path, the oxygen concentration in the anode flow path, and the oxygen concentration in the cathode flow path with respect to the elapsed time after the fuel cell stops generating electricity. A method for determining a leakage abnormality in a fuel cell system is disclosed, which comprises determining a leakage abnormality in a flow path seal of the fuel cell system based on a change in state of at least one of the above.

Japanese Patent Application Publication No. 2013-171737

Furthermore, in fuel cell systems, it is known to use a humidifier that humidifies oxygen-containing gas supplied to the fuel cell with moisture contained in off-gas discharged from the cathode. If gas leakage (internal leakage) occurs in the humidifier, it becomes difficult to supply a sufficient amount of oxygen-containing gas to the fuel cell, and the power generation performance of the fuel cell may deteriorate.

The present disclosure has been made in view of the above circumstances, and its main purpose is to provide a fuel cell system that can individually determine whether there is an internal leak in a humidifier.

In order to solve the above problems, the present disclosure includes a fuel cell, a supply device that supplies an oxygen-containing gas to the fuel cell, and a supply device that supplies the oxygen-containing gas to a cathode off-gas discharged from the fuel cell. A fuel cell system comprising: a humidifier that humidifies the fuel cell; a voltage sensor that measures the voltage of the fuel cell; and a determination device that determines whether an internal leak is occurring in the humidifier. , the determination device includes: an acquisition unit that acquires a voltage value from the voltage sensor; a control unit that controls the fuel cell to generate power while the supply of oxygen-containing gas from the supply device is stopped; A fuel cell system is provided that includes a determination unit that makes the above determination based on a change in voltage value during control.

According to the present disclosure, the fuel cell is controlled to generate electricity while the supply of oxygen-containing gas is stopped, and based on the change in the voltage value during the control, it is determined whether an internal leak is occurring in the humidifier. Therefore, it is possible to individually determine whether there is an internal leak in the humidifier.

The present disclosure has the advantage that it is possible to provide a fuel cell system that can individually determine whether there is an internal leak in a humidifier.

1 is a schematic diagram illustrating the configuration of a fuel cell system according to the present disclosure. FIG. 3 is a diagram illustrating a mechanism in the present disclosure. 1 is a schematic cross-sectional view illustrating a fuel cell according to the present disclosure. FIG. 3 is a diagram illustrating a determination method of a determination unit in the present disclosure. FIG. 2 is a flow diagram illustrating processing of the determination device according to the present disclosure.

Hereinafter, the fuel cell system according to the present disclosure will be described in detail.
FIG. 1 is a schematic diagram illustrating the configuration of a fuel cell system according to the present disclosure. A fuel cell system 100 shown in FIG. 1 includes a fuel cell 10, a supply device 20 that supplies oxygen-containing gas to the fuel cell 10, and a supply device 20 that supplies the oxygen-containing gas to the fuel cell 10 by using water contained in cathode off gas discharged from the fuel cell 10. It includes a humidifier 30 that humidifies, a monitoring unit 40 that monitors the fuel cell, and an electronic control unit (ECU) 50. The monitoring unit has at least a voltage sensor that measures the voltage of the fuel cell. Further, the ECU 50 performs various controls of the fuel cell system, and also functions as a determination device to be described later.

In the fuel cell system 100, the ECU 50 controls the fuel cell 10 to generate electricity while the supply of oxygen-containing gas is stopped, and detects internal leakage in the humidifier 30 based on a change in the voltage value of the fuel cell 10 during the above control. Determine whether or not this is occurring.

The fuel cell system 100 also includes a cathode gas supply path 60A and a cathode gas discharge path 60B. A flow meter 61, an intercooler 62, and a three-way valve 63 are arranged upstream of the cathode gas supply path 60A (upstream of the humidifier 30). The flow meter 61 can measure the flow rate of oxygen-containing gas (cathode gas). The intercooler 61 allows heat exchange between the oxygen-containing gas supplied to the fuel cell 10 and the coolant. The three-way valve 62 also controls the ratio between the flow rate of the oxygen-containing gas that is humidified by the humidifier 30 and supplied to the fuel cell 10 and the oxygen-containing gas that is not humidified by the humidifier 30 and is supplied to the fuel cell 10. Can be adjusted. Note that the oxygen-containing gas that is not humidified by the humidifier 30 is supplied to the fuel cell 10 via the bypass flow path 60C.

Further, the fuel cell system 100 includes a pressure regulating valve 64 for adjusting back pressure on the downstream side of the cathode gas discharge path 60B (downstream side of the humidifier 30). Further, the fuel cell system 100 includes a monitoring unit 40 that monitors the fuel cell.

According to the present disclosure, the fuel cell is controlled to generate electricity while the supply of oxygen-containing gas is stopped, and based on the change in the voltage value during the control, it is determined whether an internal leak is occurring in the humidifier. Therefore, it is possible to individually determine whether there is an internal leak in the humidifier.

If anode gas (for example, hydrogen gas) is supplied while the supply of oxygen-containing gas is stopped, the oxygen-containing gas (cathode gas) remaining inside the fuel cell will be consumed and the fuel cell will continue to generate electricity. can be controlled. When the oxygen-containing gas inside the fuel cell is consumed, the internal pressure of the fuel cell decreases, so if there is no internal leak in the humidifier, the oxygen-containing gas remaining in the gas flow path will cause a pressure difference. and flows into the fuel cell only from the cathode gas inlet due to gas diffusion. On the other hand, if an internal leak occurs in the humidifier, oxygen-containing gas flows into the fuel cell not only from the cathode gas inlet but also from the cathode gas outlet. Therefore, if an internal leak occurs in the humidifier, power generation continues on both the cathode gas inlet side and the cathode gas outlet side of the fuel cell (fuel cell stack). As a result, as shown in FIG. 2, when an internal leak occurs in the humidifier, the voltage drop of the fuel cell becomes more gradual than when no internal leak occurs in the humidifier. In this way, the fuel cell system according to the present disclosure can individually determine whether there is an internal leak in the humidifier based on changes in voltage.

Note that the behavior of the voltage change during control, which will be described later, is considered to be different between a case where an internal leak occurs in the fuel cell and a case where an internal leak occurs in the humidifier. For example, if an internal leak has occurred in the fuel cell, the voltage value at the start of control by the control unit will be relatively low, and the transition of voltage change will also be considered to be on the relatively low voltage side. Therefore, even if an internal leak occurs in the fuel cell, it is possible to individually determine whether or not there is an internal leak in the humidifier based on the change in the voltage value.

1. Fuel Cell FIG. 3 is a schematic cross-sectional view illustrating a fuel cell in the present disclosure. The fuel cell (single cell) 10 shown in FIG. 3 is a membrane-electrode in which a cathode gas diffusion layer 1, a cathode catalyst layer 2, an electrolyte membrane 3, an anode catalyst layer 4, and an anode gas diffusion layer 5 are laminated in this order. It has a joined body (MEA) 11 and two separators 12 that sandwich the MEA 11. The fuel cell may be a single cell or a laminate in which a plurality of single cells are stacked.

Examples of the electrolyte membrane include fluorine-based electrolyte membranes such as perfluorosulfonic acid membranes and non-fluorine-based electrolyte membranes. Examples of non-fluorine electrolyte membranes include hydrocarbon electrolyte membranes. The thickness of the electrolyte membrane is, for example, 5 μm or more and 100 μm or less.

The cathode catalyst layer and the anode catalyst layer include, for example, a catalyst metal that promotes an electrochemical reaction, a base material that supports the catalyst metal, an electrolyte that has proton conductivity, and carbon particles that have electron conductivity. Examples of the catalyst metal include simple metals such as Pt (platinum) and Ru (ruthenium), and alloys containing Pt. Examples of the electrolyte include fluororesin. Furthermore, examples of the base material and the conductive material include carbon materials such as carbon. The thickness of the cathode catalyst layer and the anode catalyst layer is, for example, 5 μm or more and 100 μm or less, respectively.

The anode side gas diffusion layer and the cathode side gas diffusion layer may be electrically conductive members having gas permeability. Examples of the conductive member include carbon porous bodies such as carbon cloth and carbon paper, and metal porous bodies such as metal mesh and foam metal. The thicknesses of the anode side gas diffusion layer and the cathode side gas diffusion layer are, for example, 5 μm or more and 100 μm or less, respectively.

The separator may have a gas path on the surface facing the gas diffusion layer (the anode gas diffusion layer and the cathode gas diffusion layer). Examples of the material of the separator include metal materials such as stainless steel and carbon materials such as carbon composite materials. Note that this separator has electronic conductivity and also functions as a current collector for the generated electricity.

2. Supplier and Humidifier The supplier supplies oxygen-containing gas to the fuel cell. Air is generally mentioned as the oxygen-containing gas. An example of the supply device is an air compressor. Further, as shown in FIG. 1, the supply device 20 (air compressor) may include a compressor 20a, a motor 20b, and a turbine 20c. As the compressor 20a rotates, compressed oxygen-containing gas (air) is supplied to the fuel cell 10. Further, as the turbine 20c rotates, oxygen-containing gas (cathode off gas) discharged from the fuel cell 10 is discharged to the outside. For example, the ECU 50 can adjust whether or not the oxygen-containing gas is supplied and the supply amount by controlling the rotational speed of the motor 20b.

The humidifier humidifies oxygen-containing gas using moisture contained in off-gas discharged from the fuel cell. Specifically, the humidifier includes a moisture permeable member, and adds moisture in the off-gas to the oxygen-containing gas via the moisture permeable member. Examples of the moisture permeable member include hollow fibers and ion exchange membranes.

Here, since humidifiers using hollow fibers have a relatively large amount of internal leakage in normal times, systems are often designed with internal leakage of humidifiers in mind. On the other hand, in humidifiers that use ion exchange membranes, the amount of internal leakage is relatively small under normal conditions, but the amount of internal leakage increases rapidly in abnormal situations (for example, when the ion exchange membrane breaks). Therefore, the impact on the system is considered to be large. Therefore, when the humidifier has an ion exchange membrane, the benefit of the fuel cell system according to the present disclosure that it is possible to individually determine whether or not there is an internal leak in the humidifier can be further enjoyed.

Examples of the ion exchange membrane include fluorine-based electrolyte membranes such as perfluorosulfonic acid membranes and non-fluorine-based electrolyte membranes. Examples of non-fluorine electrolyte membranes include hydrocarbon electrolyte membranes.

3. Voltage Sensor The voltage sensor measures the voltage of the fuel cell. The voltage includes, for example, an open circuit voltage.

4. Determination Device (1) Configuration of Determination Device The fuel cell system according to the present disclosure includes a determination device that determines whether an internal leak has occurred in the humidifier. The determination device controls the fuel cell to generate electricity while the supply of oxygen-containing gas is stopped, and determines whether or not an internal leak has occurred in the humidifier based on a change in voltage during the control. It is configured as follows.

As described above, the electronic control unit (ECU) also functions as a determination device in the present disclosure, and includes a CPU (Central Processing Unit), a memory, and an input/output port for inputting and outputting various signals. The memory includes, for example, ROM (Read Only Memory), RAM (Random Access Memory), and rewritable nonvolatile memory. Various controls are executed by the CPU executing programs stored in the memory. The various controls performed by the ECU are not limited to processing by software, but can also be processed by dedicated hardware (electronic circuits).

The determination device includes an acquisition unit, a control unit, and a determination unit as processing blocks for realizing its functions. The acquisition unit is configured to acquire the voltage value of the fuel cell from the voltage sensor.

The control unit is configured to control the fuel cell to generate electricity while the supply of oxygen-containing gas from the supply device is stopped. For example, the control unit controls the supply device to stop the supply of the oxygen-containing gas, and to supply an anode gas such as hydrogen gas. Even if the supply of the oxygen-containing gas is stopped, the fuel cell continues to generate electricity using the oxygen-containing gas inside the fuel cell and the cathode gas flow path and the supplied anode gas.

Further, the control unit may perform advance control so that the fuel cell performs oxygen-deficient power generation before the above control. The advance control is performed, for example, by controlling the supply device so that the amount of oxygen-containing gas that is equal to or less than the minimum amount necessary for power generation is supplied to the fuel cell. By performing oxygen-deficient power generation, the amount of oxygen contained in the cathode off-gas can be reduced. By performing the above control after the preliminary control, it is possible to more clearly distinguish the voltage change of the fuel cell depending on whether there is an internal leak in the humidifier, and it is possible to more accurately determine whether or not there is an internal leak in the humidifier. can do.

The determination unit is configured to determine whether an internal leak is occurring in the humidifier based on a change in voltage value during control. As shown in FIG. 4A, for example, the determination unit determines the voltage value (v1) at a first time (t1) during control and the voltage value at a second time (t2) after the first time. If the difference (ΔV) from the value (v2) is less than the threshold value, it can be determined that an internal leak has occurred in the humidifier. The first time may be at the start of control (t=0) or may be after the start of control. It is preferable that the first time, the second time, and the threshold value be set by performing a preliminary test in advance and recorded in the memory.

In addition, if an internal leak occurs in the humidifier, as shown in Figure 2, the voltage change (voltage drop) during control will be gradual, but the oxygen inside the fuel cell and gas flow path will be consumed. As time goes on, there will be a lack of oxygen and power generation will no longer be possible. Therefore, when internal leakage occurs in the humidifier, a point (change point P) at which the voltage drop rate of the fuel cell rapidly changes is observed, as shown in FIG. 4(b). Therefore, when the change point P is observed, the determination unit can determine that an internal leak has occurred in the humidifier. In addition, when the change point P is observed, it is determined whether an internal leak has occurred in the humidifier based on the time from the start of control until the time when the change point P is observed (tp). You can. It is preferable that the amount of change in the voltage drop rate for defining the change point P and the time until the change point P is observed be set by performing a preliminary test in advance and recorded in the memory.

Further, the determination unit may determine whether an internal leak has occurred in the humidifier based on the time required for the voltage to drop to a predetermined voltage from the start of control. The predetermined voltage is preferably the lower limit voltage of the fuel cell. It is preferable that the "predetermined voltage" and "time" be set by conducting a preliminary test in advance and recorded in the memory.

(2) Processing executed by the determination device FIG. 5 is a flowchart illustrating the processing executed by the determination device according to the present disclosure. In step S1, control is performed to supply hydrogen gas while the supply of oxygen-containing gas is stopped. This allows the fuel cell to continue generating electricity. Then, in step 2, the open circuit voltage value of the fuel cell during the above control is obtained. Then, in step S3, if the amount of decrease (ΔV) in the open circuit voltage value during the predetermined time period during the above control is less than the threshold value, the process proceeds to step S4, where it is reported that an abnormality has occurred in the humidifier and processing is performed. finish.

Note that the present disclosure is not limited to the above embodiments. The above-mentioned embodiments are illustrative, and any configuration that has substantially the same technical idea as the claims of the present disclosure and provides similar effects is the present invention. within the technical scope of the disclosure.

10...Fuel cell 20...Supplier 30...Humidifier 40...Monitoring unit 50...ECU
100...Fuel cell system

Claims (1)

fuel cell and
a supply device that supplies oxygen-containing gas to the fuel cell;
a humidifier that humidifies the oxygen-containing gas with moisture contained in cathode off gas discharged from the fuel cell;
a voltage sensor that measures the voltage of the fuel cell;
A fuel cell system comprising: a determination device that determines whether an internal leak has occurred in the humidifier;
The determination device includes:
an acquisition unit that acquires a voltage value from the voltage sensor;
a control unit that controls the fuel cell to generate electricity while the supply of oxygen-containing gas from the supply device is stopped;
A fuel cell system comprising: a determination unit that makes the determination based on a change in voltage value during the control.