JP2010129417A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system which enables suitable retention of humidification efficiency of a humidifier. <P>SOLUTION: The fuel cell system 1 is equipped with; a fuel cell stack 10 to generate electricity with hydrogen and air supplied to the same; a moisture-replaceable hollow fiber film 32d; a humidifier 32 to humidify air which goes to the fuel stack 10 through moisture exchange between air going to the fuel cell stack 10 and humid cathode offgas exhausted from the fuel cell stack 10 by way of the hollow fiber film 32d and; an ECU 60 to control a system operation condition so that the cathode offgas moisture introduced to the humidifier 32 does not become less than 100%. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel cell system including a humidifier.

  A fuel cell such as a polymer electrolyte fuel cell (PEFC) is required to function as a proton exchange membrane by making an electrolyte membrane constituting the fuel cell wet. Therefore, for example, between a humid cathode off gas discharged from the cathode of the fuel cell and air toward the cathode of the fuel cell by a humidifier loaded with a hollow fiber membrane having moisture exchange properties (moisture exchange membrane). There has been proposed a technique for making the electrolyte membrane wet by exchanging moisture and humidifying the air toward the cathode (see Patent Documents 1 and 2).

  The hollow fiber membrane having such a water exchange property has fine continuous pores communicating with the inside and outside of the membrane. In the state where moisture is retained in the fine continuous pores, for example, when the air to be humidified flows inside the hollow fiber membrane toward the cathode, and when a humid cathode off gas flows outside the hollow fiber membrane, Water (water vapor) in the off gas flows into the continuous pores. When flowing in this way, moisture moves through the continuous pores into the hollow fiber membrane and then into the air flowing through the hollow fiber membrane. As a result, the air flows through the hollow fiber membrane and flows toward the cathode. Is humidified.

JP-A-6-132038 JP-A-8-273687

  However, when the flow rates of air and cathode offgas increase or the cathode offgas humidity decreases, moisture does not move well from the cathode offgas to the fine continuous pores, and the moisture retained in the continuous pores. However, it moves (evaporates) to air or cathode off gas, and the amount of water in the continuous pores decreases. As a result, the hollow fiber membrane approaches a dry state (dry-up state).

  In such a state where the moisture content of the continuous pores is reduced, the air toward the cathode is not suitably humidified, that is, the humidification efficiency in the humidifier is greatly reduced. As a result, the electrolyte membrane of the fuel cell cannot be maintained in a good wet state, the function as a proton exchange membrane is reduced, the power generation performance of the fuel cell is reduced, the electrolyte membrane is electrolyzed, and the fuel The battery deteriorates and its durability is lowered.

  In addition, once the hollow fiber membrane is in a dry-up state, it is not possible to recover the state in which the moisture is sufficiently retained in the fine continuous voids only by passing the humid cathode off gas, and the humidifier is Decomposition and, for example, a treatment such as immersing the hollow fiber membrane in deionized water is necessary, which is troublesome.

  Then, this invention makes it a subject to provide the fuel cell system which can maintain the humidification efficiency of a humidifier suitably.

  As means for solving the above-described problems, the present invention includes a fuel cell that generates electric power when a reaction gas is supplied, and a moisture-exchangeable moisture exchange membrane, and the fuel cell via the moisture-exchange membrane. Moisture exchange is performed between the reaction gas toward the fuel cell and the humid off-gas discharged from the fuel cell, and the humidity of the off-gas introduced into the humidifier is 100%. The fuel cell system is characterized by comprising operating condition control means for controlling system operating conditions so as not to become less than the above.

  According to such a fuel cell system, the operating condition control means controls the system operating condition so that the humidity of the off gas introduced into the humidifier does not become less than 100% (becomes 100% or more). Thus, since the humidity of the off gas introduced into the humidifier does not become less than 100%, the water retained in the fine continuous pores of the moisture exchange membrane does not move to the off gas. That is, the moisture in the continuous pores is not reduced (vaporized), and the moisture exchange membrane is not in a dry state (dry up state). Therefore, it is not necessary to disassemble the humidifier.

  Thereby, the reaction gas which goes to a fuel cell can be favorably humidified with the off gas whose humidity does not become less than 100% through the moisture exchange membrane, and the humidification efficiency of the humidifier can be suitably maintained. Since the well-humidified reaction gas is supplied to the fuel cell, the electrolyte membrane is maintained in a wet state and functions suitably as a proton exchange membrane. Therefore, the power generation performance of the fuel cell does not deteriorate and the fuel cell does not deteriorate.

  A pressure sensor for detecting the pressure of the off-gas introduced into the humidifier; and a temperature sensor for detecting the temperature of the off-gas introduced into the humidifier. The humidity of the off gas introduced into the humidifier is estimated based on the pressure of the off gas to be detected and the temperature of the off gas detected by the temperature sensor.

  According to such a fuel cell system, the operating condition control means estimates the humidity of the offgas introduced into the humidifier based on the offgas pressure detected by the pressure sensor and the offgas temperature detected by the temperature sensor. To do. The operating condition control means can control the system operating condition based on the estimated humidity.

  In addition, a flow rate sensor that detects a flow rate of the reaction gas before humidification introduced into the humidifier is provided, and the operation condition control unit is configured to detect the offgas pressure detected by the pressure sensor and the offgas detected by the temperature sensor. The humidity of the off gas introduced into the humidifier is estimated based on the temperature, the flow rate of the reaction gas before humidification detected by the flow sensor, and a predetermined relational expression.

  According to such a fuel cell system, the operating condition control means includes the off-gas pressure detected by the pressure sensor, the off-gas temperature detected by the temperature sensor, and the flow rate of the reaction gas before humidification detected by the flow sensor. Based on a predetermined relational expression (equation (3) in the embodiment described later), the humidity of the off-gas introduced into the humidifier is estimated. The operating condition control means can control the system operating condition based on the estimated humidity.

  The operating condition control means controls at least one of an output current of the fuel cell, a flow rate of off gas introduced into the humidifier, and a pressure of off gas introduced into the humidifier. To do.

  According to such a fuel cell system, the system operating condition that is at least one of the output current of the fuel cell, the flow rate of the off gas introduced into the humidifier, and the pressure of the off gas introduced into the humidifier is controlled. Therefore, the humidity of the off gas introduced into the humidifier can be prevented from becoming less than 100%.

  ADVANTAGE OF THE INVENTION According to this invention, the fuel cell system which can maintain the humidification efficiency of a humidifier suitably can be provided.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 to 5.

≪Configuration of fuel cell system≫
A fuel cell system 1 according to this embodiment shown in FIG. 1 is mounted on a fuel cell vehicle (moving body) (not shown). The fuel cell system 1 includes a fuel cell stack 10, an anode system that supplies and discharges hydrogen (fuel gas and reaction gas) to and from the anode of the fuel cell stack 10, and air that contains oxygen with respect to the cathode of the fuel cell stack 10. A cathode system for supplying and discharging (oxidant gas, reaction gas), a power consumption system for consuming the generated power of the fuel cell stack 10, an accelerator pedal 51, and an ECU 60 (Electronic Control Unit, electronic control for electronically controlling them) Device).

<Fuel cell stack>
The fuel cell stack 10 is a stack formed by stacking a plurality of (for example, 200 to 400) solid polymer type single cells 11, and the plurality of single cells 11 are connected in series. The single cell 11 includes an MEA (Membrane Electrode Assembly) and two conductive separators sandwiching the MEA. The MEA includes an electrolyte membrane (solid polymer membrane) made of a monovalent cation exchange membrane or the like, and an anode and a cathode (electrode) that sandwich the membrane.

  The anode and cathode are mainly composed of a conductive porous material such as carbon paper, and contain a catalyst (Pt, Ru, etc.) for causing an electrode reaction in the anode and cathode.

  Each separator is formed with a groove for supplying hydrogen or air to the entire surface of each MEA, and through holes for supplying and discharging hydrogen or air to all single cells. It functions as a passage 12 (fuel gas passage) and a cathode passage 13 (oxidant gas passage).

When hydrogen is supplied to each anode via the anode flow path 12, the electrode reaction of Formula (1) occurs, and when air is supplied to each cathode via the cathode flow path 13, Formula (2) Thus, a potential difference (OCV (Open Circuit Voltage), open circuit voltage) is generated in each single cell. Next, when the OCV becomes equal to or higher than the predetermined OCV, the VCU 42 described later is controlled, and when the current is taken out, the fuel cell stack 10 generates power.
Therefore, the amount of oxygen consumed at the cathode accompanying power generation can be calculated based on the output current of the fuel cell stack 10 and the equation (2).
2H ₂ → 4H ⁺ + 4e ⁻ (1)
O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O (2)

Further, such a fuel cell stack 10 self-heats when it generates power.
That is, as the output current of the fuel cell stack 10 increases, the amount of water generated by electrode reaction at the cathode (water vapor) increases, but the amount of self-heating increases, and the temperature of the cathode offgas discharged from the cathode channel 13 (cathode). Therefore, the saturated water vapor pressure of the cathode offgas containing the generated water increases, and the (relative) humidity of the cathode offgas decreases.

On the other hand, when the output current of the fuel cell stack 10 decreases, the generated water (water vapor) due to the electrode reaction at the cathode decreases, but the temperature of the cathode offgas discharged from the cathode flow path 13 (cathode) decreases. As a result, the saturated water vapor pressure of the cathode offgas containing becomes lower, and the (relative) humidity of the cathode offgas becomes higher.
Note that when the output current is reduced, the amount of self-heating is reduced, and the fuel cell stack 10 is rapidly cooled by the refrigerant passing through the fuel cell stack 10 and the radiator. descend.

<Anode system>
The anode system includes a hydrogen tank 21. The hydrogen tank 21 is connected to the inlet of the anode flow path 12 via a pipe 21 a so that the hydrogen in the hydrogen tank 21 is supplied to the anode flow path 12. The pipe 21a is provided with a shut-off valve that is opened and closed by the ECU 60 and a pressure reducing valve (both not shown) for reducing the hydrogen pressure to a predetermined pressure.

  The outlet of the anode channel 12 is connected to a diluter 34 described later via a pipe 21b. The anode off gas containing unconsumed hydrogen discharged from the anode flow path 12 (anode) is discharged to the diluter 34.

<Cathode system>
The cathode system includes a compressor 31, a humidifier 32, a back pressure valve 33, a diluter 34, a mass flow sensor 35, a temperature sensor 36, and a pressure sensor 37.
The compressor 31 is connected to the inlet of the cathode channel 13 via a pipe 31a, a humidifier 32, and a pipe 32a. When the compressor 31 operates according to a command from the ECU 60, the air containing oxygen is taken in and supplied to the cathode channel 13. The compressor 31 operates using the fuel cell stack 10 and / or a battery 44 described later as a power source.

  The cathode channel 13 is connected to the diluter 34 via a pipe 32b, a humidifier 32, a pipe 32c, a back pressure valve 33, and a pipe 33a. The humid cathode off gas discharged from the cathode channel 13 (cathode) is discharged to the diluter 34 through the pipe 32b and the like.

  The humidifier 32 includes a plurality of hollow fiber membranes 32d having moisture exchangeability (moisture permeability), and air to be humidified toward the cathode flow path 13 and the humid cathode through the hollow fiber membranes 32d. Water is exchanged with the off gas to humidify the air toward the cathode channel 13.

  The hollow fiber membrane 32d is formed of polyimide or the like and has fine continuous pores that communicate between the inside and the outside of the hollow fiber membrane 32d. The hollow fiber membrane 32d is assembled in the humidifier 32 after water is sufficiently retained in the continuous pores by impregnation with deionized water or the like, and can be suitably humidified with cathode off gas It is in.

  The back pressure valve 33 is constituted by, for example, a butterfly or the like, and its opening degree is controlled by the ECU 60. For example, when the opening of the back pressure valve 33 is reduced, the pressure of the air in the cathode channel 13 and the pressure of the cathode offgas introduced into the humidifier 32 are increased.

  The diluter 34 dilutes hydrogen in the anode off-gas introduced from the anode system with the cathode off-gas introduced from the pipe 33a, and has a dilution space inside. The diluted gas is discharged out of the vehicle through the pipe 34a.

  The mass flow sensor 35 is provided at the intake port of the compressor 31. The mass flow sensor 35 detects the mass flow rate (g / min) of air sucked into the compressor 31 and outputs it to the ECU 60.

  The temperature sensor 36 is provided in the pipe 32b. The temperature sensor 36 detects the temperature of the cathode off gas introduced into the humidifier 32 and outputs it to the ECU 60.

  The pressure sensor 37 is provided in the pipe 32b. The pressure sensor 37 detects the pressure of the cathode off gas introduced into the humidifier 32 and outputs it to the ECU 60.

<Power consumption system>
The power consumption system includes a motor 41, a VCU 42 (Voltage Control Unit), a current sensor 43, and a battery 44. The motor 41 is connected to the output terminal of the fuel cell stack 10 via the VCU 42, and the battery 44 is connected to the VCU 42.

The motor 41 is an electric motor serving as a power source for the fuel cell vehicle.
The VCU 42 controls the generated power (output current, output voltage) of the fuel cell stack 10 and charging / discharging of the battery 44 in accordance with a command from the ECU 60, and has built-in electronic circuits such as a DC / DC chopper and a DC / DC converter. is doing.

  The battery 44 stores surplus generated power of the fuel cell stack 10 and regenerative power from the motor 41, or discharges the charged power and assists the fuel cell stack 10 when the generated power of the fuel cell stack 10 is small. To do. Such a battery 44 includes, for example, a plurality of lithium ion secondary batteries.

  The current sensor 43 is a sensor that detects a current value (output current) of the fuel cell stack 10 and is provided at an appropriate position. The current sensor 43 is configured to output the detected current value to the ECU 60.

<Accelerator pedal>
The accelerator pedal 51 is a pedal that the driver steps on to accelerate the fuel cell vehicle, and is disposed at the foot of the driver's seat. The accelerator pedal 51 outputs the depression amount (accelerator opening) to the ECU 60.

<ECU>
The ECU 60 is a control device that electronically controls the fuel cell system 1 and includes a CPU, ROM, RAM, various interfaces, electronic circuits, and the like, and controls various devices according to programs stored therein. However, various processes are executed.

<ECU-humidity calculation function>
The ECU 60 has a function of calculating (estimating) the relative humidity (off-gas humidity) of the cathode off-gas introduced into the humidifier 32 based on the equation (3). The ECU 60 has a function of determining whether or not the off-gas humidity is 100% or less.

In the equation (3), the generated water amount a (g / min) is the amount of water vapor generated in the fuel cell stack 10 along with power generation, and the current value input from the current sensor 43 and the electrode reaction equation (2 ).
The water vapor recovery rate α is the recovery rate of water vapor in the cathode off-gas in the humidifier 32 (0.5 to 0.7 (50 to 70%)), and the specifications of the humidifier 32 (the material and membrane of the hollow fiber membrane 32d) It is a fixed value depending on the thickness, the size of continuous pores, etc.), and is obtained by a preliminary test or the like.

The off gas pressure (Pa) is the pressure (total pressure) of the cathode off gas introduced into the humidifier 32 and is detected by the pressure sensor 37.
The saturated water vapor pressure (Pa) is the saturated water vapor pressure of the cathode off gas introduced into the humidifier 32. The saturated water vapor pressure (Pa) is calculated based on the cathode offgas temperature input from the temperature sensor 36 and a saturated water vapor pressure curve.

The air gas mass (g / min) is the mass of a gas obtained by removing water vapor from the cathode off-gas introduced into the humidifier 32 (this is called air gas). The air gas mass (g / min) is input from the mass flow sensor 35 and the mass flow rate of oxygen consumed in the fuel cell stack 10 during power generation from the dry air (humidity 0%) sucked into the compressor 31. Is calculated by subtracting.
Note that the mass flow rate of the consumed oxygen is calculated based on the current value of the fuel cell stack 10 and the above equation (2). Here, for the sake of simple explanation, the air sucked into the compressor 31 is dry air (humidity 0%).
However, if the humidity of the inhaled air can be detected by the humidity sensor, the moisture content (g / min) in the air is calculated based on this, and the moisture in the off-gas introduced into the humidifier 32 is calculated. What is necessary is just to correct | amend the quantity.

Next, how the equation (3) is derived will be described.
The mixing ratio of the cathode offgas introduced into the humidifier 32 (ratio of the mass of water vapor contained in the cathode offgas (wet air) and the mass of air gas (dry air) excluding water vapor from the cathode offgas) is “chemical According to the engineering essay, Haruo Hamada, published in 1982, it is given by equation (4) and transformed into equation (5). In formula (5), “18” is the molecular weight of water, and “29” is the molecular weight of air gas. Then, Expression (5) is transformed into Expression (6) and further Expression (7).

Next, in equation (8) obtained from equations (4) and (7), solving for off-gas humidity yields equation (9).
Here, if the humidification amount in the humidifier 32 is b (g / min), the water vapor mass (g / min) in the cathode off-gas is given by a + b (g / min), and thus is transformed into equation (10). The

On the other hand, the humidification amount b (g / min) is given by Equation (11), and when this is solved for the humidification amount b (g / min), Equation (12) is obtained.

Then, when Expression (12) is substituted into Expression (10), Expression (3) is obtained.

<ECU-Operating condition control function>
The ECU 60 (operating condition control means) has a function of operating the fuel cell system 1 in a normal mode in which the fuel cell system 1 is normally operated or in a humidity increasing mode in which the humidity of the cathode off gas introduced into the humidifier 32 is increased. .

[Normal mode]
Specifically, in the normal mode, the ECU 60 controls the VCU 42 while supplying hydrogen and air to the fuel cell stack 10 in response to the accelerator opening and the like (the amount of power generation required). It is designed to generate electricity.

[Humidity increase mode]
In the humidity increase mode, the ECU 60 has a function of controlling system operating conditions so that the off-gas humidity calculated based on the equation (3) increases. Specific control contents will be described later.

≪Operation of fuel cell system≫
Next, with reference to FIG. 2, the operation of the fuel cell system 1 will be described together with the flow of a program (flow chart) set in the ECU 60. In the initial state, the fuel cell system 1 operates in the normal mode, and the fuel cell stack 10 normally generates power based on the power generation request amount from the opening degree of the accelerator pedal 51 and the like.

In step S101, the ECU 60 determines (estimates) whether the current off-gas humidity calculated based on the equation (3) is 100% or less.
If it is determined that the current off-gas humidity is 100% or less (Yes in S101), the process of the ECU 60 proceeds to step S103. On the other hand, when it determines with the present off gas humidity not being 100% or less (S101 * No), the process of ECU60 progresses to step S102. However, the determination threshold value is not limited to 100%, but may be 100% or more and may be lower than a determination threshold value (105% in this case) in step S104 described later.

<Normal mode>
In step S102, the ECU 60 causes the fuel cell system 1 to operate in the normal mode. Thereafter, the processing of the ECU 60 proceeds to step S101.

<Humidity increase mode>
In step S103, the ECU 60 operates the fuel cell system 1 in the humidity increase mode so that the off-gas humidity calculated based on the equation (3) increases.

Specifically, the ECU 60 (A) controls the VCU 42 to reduce the output current of the fuel cell stack 10 and reduce the self-heat generation amount of the fuel cell stack 10, thereby reducing the temperature of the cathode offgas, A method of lowering the saturated water vapor pressure (Pa), (B) a method of lowering the rotation speed of the compressor 31 and lowering the mass of air gas (g / min) introduced into the humidifier 32, and (C) reducing the opening of the back pressure valve 33. Then, at least one method of increasing the cathode offgas pressure and decreasing the saturated water vapor pressure (Pa) is employed. Incidentally, when the saturated water vapor pressure (Pa) is lowered, the water vapor partial pressure rises.
In the method (C), when the cathode offgas pressure (total pressure) is increased, the water vapor partial pressure is also increased, so that the offgas humidity is increased. Further, when the temperature of the cathode offgas is lowered, the saturated water vapor pressure is greatly lowered and the offgas humidity is raised. Therefore, it is preferable to select the method (A).

  In step S104, the ECU 60 determines (estimates) whether or not the current off-gas humidity calculated based on the equation (3) is 105% or more. Humidity 105% is a switching threshold value that is determined to be switchable from the humidity increase mode to the normal mode, and is obtained by a preliminary test or the like. However, the switching threshold is not limited to 105% and may be changed as appropriate.

When it is determined that the current off-gas humidity is 105% or higher (S104 / Yes), the process of the ECU 60 proceeds to step S102 and shifts from the humidity increase mode to the normal mode.
On the other hand, when it is determined that the current off-gas humidity is not 105% or higher (S104, No), the process of the ECU 60 proceeds to step S103 and is continuously operated in the humidity increase mode.

≪Effect of fuel cell system≫
According to such a fuel cell system 1, the following effects are obtained.
When the off-gas humidity is 100% or less (S101 / Yes), the system is operated in the humidity increase mode (S103) and the off-gas humidity is increased, so that the off-gas humidity does not become less than 100%. This makes it difficult for the water retained in the continuous pores of the hollow fiber membrane 32d to vaporize (evaporate), and the humidification efficiency of the humidifier 32 is suitably maintained. Therefore, the air toward the cathode can be suitably humidified through the hollow fiber membrane 32d, the electrolyte membrane constituting the MEA can be maintained in a wet state, and the power generation performance of the fuel cell stack 10 is not deteriorated. Moreover, it does not deteriorate.

≪Operation example of fuel cell system≫
Next, an operation example of the fuel cell system 1 will be described with reference to FIGS.
As shown in FIG. 3, when the cathode off-gas humidity decreases to 100% (S101 / Yes), when the output current of the fuel cell stack 10 is decreased by the VCU 42, the self-heating amount of the fuel cell stack 10 decreases, As a result, the cathode offgas temperature decreases. As a result, the saturated water vapor pressure of the cathode off gas decreases, and the cathode off gas humidity calculated by the equation (3) increases.
When the output current (power) of the fuel cell stack 10 is reduced in this way, it is preferable to discharge the battery 44 and rotate the motor 41 so as to assist the shortage. Thereby, the drive feeling of the fuel cell vehicle is not lowered.

  Next, as shown in FIG. 4, when the cathode off-gas humidity is reduced to 100% (Yes in S101), the rotational speed of the compressor 31 is reduced and the flow rate of the air gas introduced into the humidifier 32 is reduced. The cathode off-gas humidity calculated in 3) increases.

  Next, as shown in FIG. 5, when the cathode offgas humidity is reduced to 100% (S101 / Yes), if the back pressure valve 33 is opened and the pressure of the cathode offgas is increased, the calculation is performed using equation (3). The cathode off-gas humidity is increased.

As mentioned above, although one Embodiment of this invention was described, this invention is not limited to this, For example, it can change as follows in the range which does not deviate from the meaning of this invention.
In the above-described embodiment, the configuration in which the moisture exchange membrane is the hollow fiber membrane 32d is exemplified, but other plate-like and spiral moisture exchange membranes may be used, for example.

  In the above-described embodiment, the present invention is applied to the humidifier 32 that humidifies the air toward the cathode flow path 13 with the cathode off-gas. However, for example, the humidifier humidifies the hydrogen toward the anode flow path 12 with the anode off-gas. You may apply. In this case, the flow rate of hydrogen toward the anode channel 12 may be controlled by, for example, a flow rate control valve made of butterfly or the like.

  In the above-described embodiment, the configuration in which the pressure sensor 37 is provided in the pipe 32b is illustrated, but other configurations, for example, in the pipe 31a and the pipe 32a may be used. In the case of this configuration, the pressure of the cathode off gas introduced into the humidifier 32 may be calculated in consideration of the pressure loss of the humidifier 32 and the fuel cell stack 10.

  In the above-described embodiment, the configuration in which the mass flow sensor 35 is provided at the intake port of the compressor 31 is exemplified, but other configurations, for example, may be provided in the pipe 32b.

  In the above-described embodiment, the case where the fuel cell system 1 is mounted on a fuel cell vehicle has been exemplified. However, for example, a fuel cell system mounted on a fuel cell moving body such as a motorcycle, a train, and a ship may be used. In addition, the present invention may be applied to a stationary fuel cell system for home use or a fuel cell system incorporated in a hot water supply system.

It is a figure which shows the structure of the fuel cell system which concerns on this embodiment. It is a flowchart which shows operation | movement of the fuel cell system which concerns on this embodiment. It is a time chart which shows one operation example of the fuel cell system concerning this embodiment. It is a time chart which shows one operation example of the fuel cell system concerning this embodiment. It is a time chart which shows one operation example of the fuel cell system concerning this embodiment.

Explanation of symbols

1 Fuel Cell System 10 Fuel Cell Stack (Fuel Cell)
11 Single cell (fuel cell)
31 Compressor 32 Humidifier 32d Hollow fiber membrane (moisture exchange membrane)
33 Back pressure valve 35 Mass flow sensor 36 Temperature sensor 37 Pressure sensor 43 Current sensor 60 ECU (Operating condition control means)

Claims (4)

A fuel cell that generates electricity by supplying reactive gas;
It has a moisture exchangeable moisture exchange membrane, and through the moisture exchange membrane, exchanges moisture between the reaction gas heading to the fuel cell and the humid off-gas discharged from the fuel cell, and heads to the fuel cell. A humidifier for humidifying the reaction gas;
Operating condition control means for controlling system operating conditions so that the humidity of the off-gas introduced into the humidifier is not less than 100%;
A fuel cell system comprising: A pressure sensor for detecting the pressure of off-gas introduced into the humidifier;
A temperature sensor for detecting the temperature of off-gas introduced into the humidifier;
With
The operating condition control means estimates the humidity of the offgas introduced into the humidifier based on the offgas pressure detected by the pressure sensor and the offgas temperature detected by the temperature sensor. The fuel cell system according to claim 1. A flow sensor for detecting the flow rate of the reaction gas before humidification introduced into the humidifier,
The operating condition control means is based on the off-gas pressure detected by the pressure sensor, the off-gas temperature detected by the temperature sensor, the flow rate of the reaction gas before humidification detected by the flow sensor, and a predetermined relational expression. The fuel cell system according to claim 2, wherein the humidity of the off-gas introduced into the humidifier is estimated. The operating condition control means controls at least one of an output current of the fuel cell, a flow rate of off-gas introduced into the humidifier, and a pressure of off-gas introduced into the humidifier. The fuel cell system according to any one of claims 1 to 3.

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