JP2003059517A - Gas humidity determining method for solid polymer fuel cell, control device for solid polymer fuel cell and solid polymer fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably obtain a high cell output as much as possible while securely restraining within a given allowance instability of cell output due to excess of gas humidity in a solid polymer fuel cell. SOLUTION: With the solid polymer fuel cell adjusting absolute humidity xa, xb of fuel gas F or oxidant gas with a humidity adjustment means 4, 5, a corresponding absolute humidity xm is found when an index parameter σbecomes equal to a set threshold σm in correlation with the index parameter indicating variation of vibrational fluctuation of the cell output v and adjusted absolute humidity x by the humidity adjustment means 4, 5, and this corresponding absolute humidity xm is to be targeted absolute humidity xam, xbm in humidity adjustment by the humidity adjustment means 4, 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention supplies a fuel gas containing hydrogen gas to one gas diffusion electrode (fuel electrode) sandwiching a solid polymer electrolyte membrane, and the other gas diffusion electrode (oxygen electrode). The present invention relates to a solid polymer fuel cell in which an oxygen gas-containing oxidant gas is supplied to the gas diffusion electrode and the absolute humidity of the fuel gas or the oxidant gas supplied to these gas diffusion electrodes is adjusted by a humidity adjusting means. The present invention relates to a gas humidity determination method for a fuel cell, a solid polymer fuel cell control device used for implementing the gas humidity determination method, and a polymer electrolyte fuel cell.

[0002]

2. Description of the Related Art In a polymer electrolyte fuel cell, the fuel gas supplied to a gas diffusion electrode as a fuel electrode and the oxidant gas supplied to a gas diffusion electrode as an oxygen electrode are in a state of low humidity with insufficient absolute humidity. If so, the solid polymer electrolyte membrane dries and the proton conductivity of the electrolyte membrane decreases, leading to a decrease in battery output, and conversely, those fuel gas and oxidant gas have too high absolute humidity and excessive humidity. In this state, the water content in the gas is condensed in the electrode part, and the condensed water interferes with the gas flow in the electrode part, so that the gas diffusivity of the electrode is lowered and the battery output is destabilized. And, in particular, the destabilization of the battery output (specifically, the oscillatory fluctuation of the battery output as shown in FIG. 4) promotes the deterioration of the device and becomes a factor of reducing the service life of the battery.

For this reason, in the polymer electrolyte fuel cell, it is necessary to adjust the absolute humidity of the fuel gas and the oxidant gas supplied to the gas diffusion electrode to the optimum one. When the membrane resistance value of the electrolyte membrane becomes larger than the threshold value, the amount of humidification to the target gas is increased, and when the membrane resistance value of the electrolyte membrane is smaller than the threshold value and the output voltage of the battery becomes smaller than the threshold value, An adjustment method for reducing the amount of humidification has been proposed (see Japanese Patent Application Laid-Open No. 11-162490).

As another method, the target gas is humidified for a predetermined time each time the output voltage of the battery drops to a threshold value.
Alternatively, an adjustment method has also been proposed in which humidification for a target gas is alternately turned on and off each time the output voltage of the battery drops to a threshold value (Japanese Patent Laid-Open No. 11-1914).
23).

[0005]

However, these conventional adjustment methods still lack the function of optimizing the absolute humidity of the fuel gas and the oxidant gas supplied to the gas diffusion electrode.
For this reason, it is still difficult to obtain a stable battery output as high as possible while reliably stopping the instability of the battery output due to excessive gas humidity, which causes a decrease in service life, within a certain allowable limit. There was a problem.

[0006] Further, as a result of research, compared to the case where pure hydrogen gas is used as the fuel gas supplied to the fuel electrode, a mixed gas containing hydrogen gas (generally, a reformed gas produced by reforming raw fuel) When using a mixed gas having a low hydrogen gas concentration, the battery output v becomes lower under the same gas humidity conditions as shown in FIG. It was found that destabilization of hydrogen gas is likely to occur. Therefore, when using a mixed gas containing hydrogen gas as the fuel gas, remove the contained gas other than hydrogen gas (carbon dioxide gas, etc.) It is also possible to improve the cell output and stabilize it by supplying it to the fuel electrode after converting the gas to pure hydrogen gas, but in this case, it is necessary to add a device to remove the contained gas other than hydrogen gas. for Overall structure of the pond has greatly increased system cost while large, also This has been also a factor that prevents the generalization of a polymer electrolyte fuel cell according to the diversification of uses fuel gas.

In view of the above situation, the main object of the present invention is to allow a certain degree of instability of the battery output due to the excessive gas humidity, which causes a reduction in service life, by adopting a rational humidity adjustment method. The point is to ensure that the battery output is as high as possible while being reliably stopped within the limit.

[0008]

[1] The invention according to claim 1 relates to a method for determining gas humidity of a polymer electrolyte fuel cell,
The feature is that the fuel gas containing hydrogen gas is supplied to one gas diffusion electrode sandwiching the solid polymer electrolyte membrane, and the oxidant gas containing oxygen gas is supplied to the other gas diffusion electrode to diffuse these gases. Regarding a polymer electrolyte fuel cell in which the absolute humidity of the fuel gas or oxidant gas supplied to the electrode is adjusted by the humidity adjusting means, a predetermined index variable indicating the magnitude of the oscillatory fluctuation of the cell output and the adjustment by the humidity adjusting means Corresponding absolute humidity is obtained when the index variable becomes equal to the set threshold value in correlation with the absolute humidity, and this corresponding absolute humidity is set as the target absolute humidity in the humidity adjustment by the humidity adjusting means.

That is, according to this method, destabilization of the battery output due to excessive humidity of the target gas (fuel gas or oxidant gas) occurs in the form of oscillatory fluctuation of the battery output as described above. Since the corresponding absolute humidity when the index variable becomes equal to the set threshold value on the correlation between the predetermined index variable showing the magnitude of the fluctuation and the absolute humidity adjusted by the humidity adjusting means is the target absolute humidity in the humidity adjustment, this target absolute By adjusting the absolute humidity of the target gas to the target absolute humidity by the humidity adjusting means under the humidity setting, destabilization of the battery output due to excessive gas humidity, which is a factor of decreasing the service life, becomes a certain allowable limit (above). The maximum amount of water within that range can be stably replenished from the target gas to the electrolyte membrane while ensuring that the battery output is as high as possible. It is possible to obtain the Joteki.

Further, according to this method, it is possible to cope with the use of various fuel gases by simply obtaining the corresponding absolute humidity when the index variable becomes equal to the set threshold value on the above correlation for the fuel gas used. Therefore, when a mixed gas such as a reformed gas is used as the fuel gas, it is not necessary to additionally equip a removing means for removing the contained gas other than the hydrogen gas. The cost can be reduced, and the versatility of the polymer electrolyte fuel cell can be promoted by diversifying the fuel gas used.

[2] The invention according to claim 2 specifies an embodiment suitable for carrying out the invention according to claim 1, and is characterized in that a plurality of types of test fuel gas having different hydrogen gas concentrations are provided. For each of the above, the corresponding absolute humidity is calculated in advance, and based on the correspondence relationship between these multiple corresponding absolute humidity and the hydrogen gas concentration of each test fuel gas, actual use according to the hydrogen gas concentration of the fuel gas actually used The point is that the corresponding absolute humidity for the fuel gas is obtained and the corresponding absolute humidity for the actually used fuel gas is set as the target absolute humidity in the humidity adjustment by the humidity adjusting means.

That is, the corresponding absolute humidity when the index variable becomes the set threshold value (that is, the destabilization of the battery output due to the excessive gas humidity is surely stopped within a certain allowable limit, and the battery output as high as possible is stabilized. The absolute humidity of the target gas that can be obtained differs depending on the hydrogen gas concentration of the fuel gas as described above, but according to the above method, the corresponding absolute value for each of the plurality of types of test fuel gas having different hydrogen gas concentrations is obtained. Based on the correspondence between the humidity and the hydrogen gas concentration of each test fuel gas, the corresponding absolute humidity of the actually used fuel gas corresponding to the hydrogen gas concentration of the fuel gas actually used is calculated. It is necessary to grasp the correlation (correlation between the index variable and the adjusted absolute humidity) for the fuel gas used in the calculation of the corresponding absolute humidity for Ku, can support the use of various fuel gas just know the above relationship for the test fuel gas, in this respect, it is possible to facilitate the implementation of the gas humidity determining method according to claim 1.

[3] The invention according to claim 3 relates to a controller for a polymer electrolyte fuel cell used for carrying out the gas humidity determining method according to claim 2, which is characterized in that hydrogen gas concentrations are different from each other. Storage means for storing the correspondence relationship between the corresponding absolute humidity and the hydrogen gas concentration of each test fuel gas for each of a plurality of types of test fuel gas, and a concentration detecting means for detecting the hydrogen gas concentration of the fuel gas actually used And the corresponding absolute humidity for the actually used fuel gas in accordance with the hydrogen gas concentration detected by the concentration detecting means based on the corresponding relationship stored in the storage means, and the corresponding absolute humidity for the actually used fuel gas is obtained. And a gas humidity determining means for setting the humidity to a target absolute humidity in the humidity adjustment by the humidity adjusting means.

That is, according to this configuration, the gas humidity determining means stores the corresponding absolute humidity of the actually used fuel gas in the storage means according to the detected hydrogen gas concentration of the actually used fuel gas. Corresponding relationship between the corresponding absolute humidity for each fuel gas and the hydrogen gas concentration) is obtained automatically, and the obtained corresponding absolute humidity is automatically set as the target absolute humidity in the humidity adjustment by the humidity adjusting means. Since the setting is performed, as the implementation of the gas humidity determination method according to claim 2, the operator manually sets the corresponding absolute humidity of the actually used fuel gas according to the detected hydrogen gas concentration of the actually used fuel gas based on the corresponding relationship. Compared to the case where the calculated absolute humidity is set as the target absolute humidity by manual operation, it is possible to use various fuels in the practical use of polymer electrolyte fuel cells. Scan correspondence to the use of a can be enhanced more effectively.

In the practice of the invention according to claim 3, the automatic setting of the target absolute humidity as described above by the gas humidity determining means is carried out only in an initial setting according to the fuel gas used in actual use of the fuel cell. Alternatively, it may be performed at any time depending on the change in the hydrogen gas concentration in the fuel gas used.

Further, the hydrogen gas concentration detection of the fuel gas by the concentration detection means is replaced with the detection of the hydrogen gas concentration itself,
The detection mode may be one in which the concentration of the contained gas other than hydrogen gas in the fuel gas is detected and the hydrogen gas concentration in the fuel gas is determined based on the detection result.

[4] The invention according to claim 4 relates to a polymer electrolyte fuel cell, which is characterized in that a fuel gas containing hydrogen gas is supplied to one gas diffusion electrode sandwiching a polymer electrolyte membrane, Further, the battery output is detected in the configuration in which the oxygen gas-containing oxidant gas is supplied to the other gas diffusion electrode and the absolute humidity of the fuel gas or the oxidant gas supplied to these gas diffusion electrodes is adjusted by the humidity adjusting means. Based on the output detection means and the battery output detected by the output detection means, the humidity adjustment output of the humidity adjustment means is set so that a predetermined index variable indicating the magnitude of the oscillatory fluctuation of the battery output becomes equal to the set threshold value. It is provided with a control means for automatic adjustment.

That is, according to this configuration, the destabilization of the battery output due to excessive humidity of the target gas (fuel gas or oxidant gas) occurs in the form of oscillatory fluctuation of the battery output, whereas the output detection means According to the invention according to claim 1, the humidity adjusting output of the humidity adjusting means is automatically adjusted based on the detected battery output by the device 1 so that the predetermined index variable indicating the magnitude of the fluctuation of the battery output becomes equal to the set threshold value. In terms of contrast, the absolute humidity of the target gas is adjusted to the corresponding absolute humidity when the index variable becomes equal to the set threshold on the above correlation,
As a result, similarly to the invention according to claim 1, the destabilization of the battery output due to the excessive gas humidity, which causes the reduction of the service life, is reliably stopped within a certain allowable limit (the limit corresponding to the above-mentioned set threshold). However, it is possible to stably obtain a battery output as high as possible by stably replenishing the electrolyte membrane with the maximum amount of water within the range from the target gas.

Further, according to this structure, it is possible to cope with the use of various fuel gases only by the control of automatically adjusting the humidity adjusting output of the humidity adjusting means on the basis of the output of the detection battery. Similar to the invention described above, when a mixed gas such as a reformed gas is used as the fuel gas, it is not necessary to additionally equip a removing means for removing the contained gas other than the hydrogen gas, and the overall size of the battery and the device can be reduced. The cost can be reduced, and the versatility of the polymer electrolyte fuel cell can be promoted by diversifying the fuel gas used.

[5] The invention according to claim 5 specifies an embodiment suitable for carrying out the invention according to claim 4, and is characterized in that the solid polymer electrolyte membrane is sandwiched between the solid polymer electrolyte membrane and the solid polymer electrolyte membrane. And a configuration in which a large number of cells including the other gas diffusion electrode are stacked in a state of being electrically connected in series to form a battery stack, the output voltage of a part of the representative cells of the large number of cells is The point is that the output is detected by the output detection means.

That is, the fluctuation of the output voltage of the battery stack tends to be relatively slow, averaged by the series connection of a large number of cells, as compared with the fluctuation of the output voltage of the individual cells. When the output voltage of a part of the representative cells of the large number of cells is set as the detection target output of the output detection means as compared with the case where the output voltage of the battery stack is set as the detection target output of the output detection means, the output detection means It is possible to increase the control sensitivity in the above-mentioned control that automatically adjusts the humidity adjustment output based on the detection output of, and is suitable when high-sensitivity control is required. If the cell in the portion where the fluctuation of (3) easily occurs is set to the representative cell described above, it is possible to perform control with higher sensitivity.

In the practice of the invention according to claims 1 to 5, the absolute humidity is adjusted by the humidity adjusting means to supply the fuel gas supplied to the gas diffusion electrode serving as the fuel electrode and the gas diffusion electrode serving as the oxygen electrode. Either the embodiment for both the oxidant gas or the embodiment for only one of the fuel gas and the oxidant gas may be adopted.

In the practice of the invention according to claims 1 to 5, the humidity adjusting means may be either one that adjusts the absolute humidity of the target gas by humidification or one that adjusts it by dehumidification. Either of them may be adopted depending on the humidity condition before the adjustment of the fuel gas or the oxidant gas.

If the humidity adjusting means is capable of both adjusting the absolute humidity by humidifying and adjusting the absolute humidity by dehumidifying, the change of the humidity condition before adjustment of the target gas and the change of the target absolute humidity are performed. It is possible to further improve the responsiveness to the above.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] FIG. 1 shows a polymer electrolyte fuel cell, 1 is a cell stack formed by stacking a large number of cells 2, and 3 is a reforming treatment of raw fuel Fi. A reforming device for generating the reformed gas F, 4 is a fuel side humidity controller for the reformed gas F as a fuel gas, and 5 is an oxygen side humidity controller for the air A as an oxidant gas.

The cells 2 forming the battery stack 1 are shown in FIG.
As shown in FIG. 2, the solid polymer electrolyte membrane 6 is sandwiched between the gas diffusion electrode 7 as a fuel electrode (anode) and the gas diffusion electrode 8 as an oxygen electrode (cathode) to form a membrane sandwiching body 9, and the membrane sandwiching is performed. The body 9 is further configured to be sandwiched by gas-impermeable separators 10 having a large number of grooves 10a and 10b used as reaction gas flow paths formed on both surfaces.

Further, each electrode 7, 8 has a structure in which gas-permeable catalyst layers 7b, 8b are provided on the surface of the electrode bodies 7a, 8a made of a porous material on the electrolyte side. As schematically shown in FIG. 3, in the fuel electrode 7, the reformed gas F as the fuel gas is passed through the groove 10a of the separator 10 facing the fuel electrode 7 to diffuse the reformed gas F to the electrolyte membrane 6 side. Under the catalytic action of the catalyst layer 7b and the proton (H ⁺ ) conduction action of the electrolyte membrane 6, the anodic reaction shown in the following (Equation 1) proceeds, and at the oxygen electrode 8, the groove 10b of the separator 10 facing the oxygen electrode 8 faces. The air A as the oxidant gas is passed through the air to diffuse the air A to the side of the electrolyte membrane 6 and the catalytic action of the catalyst layer 8b and the proton (H ⁺ from the side of the fuel electrode 7 through the electrolyte membrane 6). ) Under conduction, The to cathode reaction proceeded, the power supplied to the load side with electrons e- flow in the external circuit 11 associated with these reactions.

H ₂ → 2H ⁺ + 2e- (Equation 1) 1 / 2O ₂ + 2H ⁺ + 2e- → H ₂ O (Equation 2)

A separator 10 for partitioning the flow path of the reformed gas F as the fuel gas and the flow path of the air A as the oxidant gas is formed of a conductive material (for example, expanded graphite) to form a large number of cells 2. By stacking them, a battery stack 1 in which the cells 2 are electrically connected in series is formed, and a required potential difference on the load side is obtained between both ends of the battery stack 1.

The solid polymer electrolyte membrane 6 has proton conductivity in a wet state, such as a perfluorocarbon sulfonic acid membrane or a polystyrene cation exchange membrane having a sulfonic acid group as a cation conductive membrane. Any of various materials can be used, and a porous carbon thin plate can be cited as a typical example of the electrode bodies 7a and 8a, and a platinum-based catalyst layer can be cited as a typical example of the catalyst layers 7b and 8b. Can be mentioned.

The reformer 3 desulfurizes the raw fuel Fi and then reacts it with steam in the presence of a catalyst to produce an intermediate reformed gas rich in hydrogen gas containing carbon monoxide gas (steam reforming treatment). Then, the carbon monoxide gas in the intermediate reformed gas is reacted with steam in the presence of a catalyst to form carbon dioxide gas (CO shift treatment), and further, in the intermediate reformed gas after the CO shift treatment. The carbon monoxide gas remaining in the above is selectively oxidized by a catalytic action to finally produce a reformed gas F mainly composed of hydrogen gas and carbon dioxide gas from which carbon monoxide gas is almost removed. .

Depending on the raw fuel Fi, the reformed gas F
There may be a small amount of other gas (for example, nitrogen gas) other than hydrogen gas and carbon dioxide gas.

The fuel-side humidity controller 4 humidifies or dehumidifies the reformed gas F as a fuel gas generated by the reformer 3 to the fuel electrode 7 of each cell 2 in the cell stack 1 to modify it. The absolute humidity xa of the quality gas F is adjusted, and the humidity controller 5 on the oxygen side also humidifies or dehumidifies the air A as an oxidant gas while sending it to the oxygen electrode 7 of each cell 2 in the battery stack 1. The humidity control units 4 and 5 adjust the absolute humidity xb of the air A. The humidity control units 4 and 5 store the water W in the sealed containers 12a and 12b and the heater 13a that heats the stored water W in the container. 13b and coolers 13a ', 13 for cooling the stored water W in the container by exchanging heat with the cooling water C.
b ′, gas introduction pipes 14a, 14b having a spiral structure with a tip opened in the reservoir water W at the bottom of the container, and gas delivery pipes 15a, 1b having a tip opened in the container space above the reservoir water W.
5b and.

In other words, in these humidity controllers 4 and 5, the stored water W whose temperature is adjusted by the heaters 13a and 13b or the coolers 13a 'and 13b' and the target gas F and A for humidity adjustment and the gas introduction pipe 14a having a spiral structure are provided. , 14b are heat-exchanged during passage through the pipes, and then the target gases F and A are introduced into the gas introduction pipes 14
a and 14b are discharged from the tips of the stored water W into a bubbling process, and the bubbling process humidifies or dehumidifies the target gases F and A in a dew-point-controlled adjustment mode for bringing the target gases F and A into a water vapor saturated state at a predetermined temperature. The absolute humidity xa, xb of the target gas F, A is adjusted. Then, the reformed gas F and the air A after the humidity adjustment, which accumulates in the space inside the container on the stored water W, are taken out from the containers 12a, 12b through the gas delivery pipes 15a, 15b and sent to the battery stack 1.

Reference numerals 16a and 16b denote temperatures t of the gases F and A on the stored water W in the humidity controllers 4 and 5 as humidity adjusting means.
A temperature sensor for detecting a and tb, and 18a for each humidity controller 4,
As the set values corresponding to the target absolute humidity xam, xbm in the humidity adjustment of No. 5, the target temperatures tam, tbm of the gases F, A in the water vapor saturated state after humidity adjustment (in other words, corresponding to the target absolute humidity xam, xbm) Dew point temperature) is a setting means, and 18 is a temperature sensor 16a, 16b.
Heater 13 in each of the humidity controllers 4 and 5 based on the detection information of
a, 13b heating output, or coolers 13a ', 13
By adjusting the cooling output of b ′, the temperatures ta and tb of the gases F and A in the water vapor saturated state after the humidity adjustment become the target temperatures tam and tbm set by the setting means 18a (in other words, , So that the absolute humidity xa, xb of the gas F, A after the humidity adjustment becomes the target absolute humidity xam, xbm).

Va and vb are coolers 13a 'and 13a
It is a valve for adjusting the supply amount of the cooling water C to b ', and the cooling output of the coolers 13a' and 13b 'to the stored water W in the container is adjusted by adjusting the cooling water supply amount by these valves va and vb.

On the other hand, as to the setting of the target temperatures tam and tbm, as shown in FIG. 4, the hydrogen gas concentration of the fuel gas (pure hydrogen gas or reformed gas) and the absolute values adjusted by the humidity controllers 4 and 5 are used. While the output voltage v of the cell 2 changes depending on the humidity x (xa or xb), the magnitude of the oscillatory fluctuation of the output voltage v tends to change.
As shown in FIG. 5, for each of the plurality of types of test fuel gas F1 to F3 having different hydrogen gas concentrations, the output voltage v
On the correlation between the index variable σ (standard deviation in this example) that indicates the magnitude of the oscillatory fluctuation of and the absolute humidity x (xa or xb) adjusted by the humidity controllers 4 and 5, the index variable σ is equal to the set threshold σm. Then, the corresponding absolute humidity xm1 to xm3 is calculated.

Then, based on the corresponding relationship K between the corresponding absolute humidity xm1 to xm3 of each of the test fuel gases F1 to F3 and the hydrogen gas concentration of each of the test fuel gas F1 to F3, the fuel gas F actually used is used. The corresponding absolute humidity xm of the actual fuel gas according to the hydrogen gas concentration d of
Then, the corresponding absolute humidity xm is calculated as the target absolute humidity (xam or xbm) in the humidity adjustment by the humidity controllers 4 and 5.
As described above, the dew point temperature corresponding to the calculated corresponding absolute humidity xm is set by the setting means 18a as the target temperature (tam or tbm).

That is, by carrying out this setting operation for each of the fuel gas F and the oxidant gas A, a battery which is generated in the form of an oscillatory fluctuation of the output voltage v in the operation of the solid polymer electrolyte fuel cell having the above-mentioned structure. A battery which is as high as possible by reliably stopping the destabilization of the output within a certain allowable limit and steadily replenishing the electrolyte membrane with the maximum amount of water from the supply gas F, A to the electrodes 7, 8 within that range. Make the output stable.

In this example, the standard deviation σ used for the index variable is defined by the following (formula 3). When the average of the amplitude X (random variable) of the oscillatory fluctuation of the output voltage v is written as E (X), σ = E [X−E (X)] ² square root (Equation 3)

[Second Embodiment] In the first embodiment, the target temperature tam, which is set as the target absolute humidity xam, xbm,
Although an example in which tbm is set manually is shown, instead of this, a concentration detecting means 17 (shown by a broken line in FIG. 1) for detecting the hydrogen gas concentration d of the reformed gas F sent from the reformer 3. In addition to the above, the controller 18 is provided with a storage means 18m for storing the correspondence K for a plurality of test fuel gases F1 to F3 as shown in FIG.

Further, in the controller 18, the corresponding absolute humidity of the actually used fuel gas F corresponding to the hydrogen gas concentration d detected by the concentration detecting means 17 based on the correspondence K stored in the storing means 18m. xm is calculated, and the corresponding absolute humidity xm for this actually used fuel gas F is made to be the target absolute humidity (xam or xbm) in the humidity adjustment by the humidity adjusters 4 and 5. The corresponding dew point temperature is set to the target temperature (tam to tb).
m) is provided with a gas humidity determining means 18n that is automatically set, thereby automating the setting of the target temperatures tam and tbm as the setting of the target absolute humidity xam and xbm.

[Third Embodiment] As shown in FIG. 7, in the solid polymer electrolyte fuel cell shown in the first embodiment, an output detecting means 19 for detecting the output voltage v of a representative cell of a large number of cells 2 is provided. Set up.

Further, the controller 18 sets the index variable σ (standard deviation similar to the above) indicating the magnitude of the oscillatory fluctuation of the output voltage v based on the output voltage v detected by the output detecting means 19. Humidifier 4, so that it becomes equal to the threshold σm
The humidity adjustment output of No. 5 (that is, the heating output of the heaters 13a and 13b or the cooling output of the coolers 13a 'and 13b') is automatically adjusted.

In other words, by the automatic adjustment of the humidity adjustment output, the index variable σ for the actually used fuel gas F shown in FIG.
And absolute humidity x (xa to x
The absolute humidity (xa to xb) of the target gases F and A is adjusted to the corresponding absolute humidity xm when the index variable σ becomes equal to the set threshold value σm in correlation with b), and as a result, similar to the first embodiment. In addition, while reliably destabilizing the instability of the battery output that occurs in the form of oscillatory fluctuation of the output voltage v within a certain allowable limit, the maximum amount of moisture within that range is supplied to the gas F supplied to the electrodes 7, 8. , A to the electrolyte membrane in a stable manner to obtain a battery output as high as possible in a stable manner.

The standard deviation σ used for the index variable in the third embodiment is the output voltage v between each time point during battery operation and a time point that is a fixed time before the time point.
Is calculated with respect to the vibrational fluctuation of.

[Other Embodiments] Next, other embodiments will be listed.

As the raw fuel Fi, natural gas, propane,
Various fuels such as kerosene and biogas can be used, and the oxidant gas A is not limited to air but may be oxygen gas-containing gas other than air or pure oxygen gas.

Absolute humidity x of fuel gas F and oxidant gas A
The method of adjusting a and xb is not limited to the bubbling method shown in the above-described embodiment, and for adjustment by humidification, a spray method of spraying the humidifying water on the target gas, a target gas by permeating the humidifying water through the membrane. A membrane humidification method,
Various humidification methods such as ultrasonic humidification method in which the water for humidification is misted by ultrasonic waves and supplied to the target gas can be adopted.For adjustment by dehumidification, the target gas is cooled by the cooling coil to condense the moisture in the gas. Coil system,
Membrane dehumidification method that removes the moisture in the target gas through the membrane.
Various dehumidifying methods such as a hygroscopic method for removing the moisture in the target gas by the hygroscopic material can be adopted.

In the above-described embodiment, the absolute humidity xa and xb of the fuel gas F and the oxidant gas A are controlled by the humidity controllers 4 and 5 capable of both adjusting the absolute humidity by humidifying and adjusting the absolute humidity by dehumidifying. Although an example of adjustment was shown, a humidifier that only adjusts the absolute humidity by humidification and a dehumidifier that only adjusts the absolute humidity by dehumidification are separately installed in the supply path for the target gas The absolute humidity of the target gas may be adjusted by a device or a dehumidifier.

Further, when the absolute humidity of the fuel gas F or the oxidant gas A before humidity adjustment is always lower than the target absolute humidity xam, xbm, only the absolute humidity is adjusted by humidification. However, conversely, if the absolute humidity of the fuel gas F or the oxidant gas A before the humidity adjustment is always higher than the target absolute humidity xam, xbm, only the absolute humidity adjustment by dehumidification is necessary. May be configured to perform.

In the above-described embodiment, an example has been shown in which the humidity is adjusted so that the index variable σ becomes the set threshold value σm for both the fuel gas F and the oxidant gas A. Humidity adjustment may be performed on only one of the fuel gas F and the oxidant gas A, and in some cases, the humidification process or dehumidification process itself on either the fuel gas F or the oxidant gas A may be performed. May be omitted.

The index variable is not limited to the above-mentioned standard deviation σ, but various variables can be adopted as long as they can show the magnitude of the oscillatory fluctuation of the battery output, and the simple average of the amplitude in the oscillatory fluctuation of the battery output can be adopted. The value may be used as an index variable.

Further, in order to perform the humidity adjustment in such a manner that the index variable σ becomes the set threshold value σm, in each of the above-described embodiments, the output voltage v of the representative cell of the large number of cells 2 is oscillated. Although the index variable indicating the magnitude of the fluctuation is used, the index variable indicating the magnitude of the oscillatory fluctuation of the output voltage of the battery stack 1 may be used in some cases.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a fuel cell showing a first embodiment.

FIG. 2 is an exploded perspective view showing a cell structure.

FIG. 3 is a diagram showing a power generation principle of a fuel cell.

FIG. 4 is a graph showing the relationship between hydrogen gas concentration, adjusted absolute humidity, and battery output.

FIG. 5 is a graph showing the correlation between index variables and adjusted absolute humidity.

FIG. 6 is a block diagram of a controller showing a second embodiment.

FIG. 7 is a configuration diagram of a fuel cell showing a third embodiment.

[Explanation of symbols]

1 Battery Stack 2 Cell 4, 5 Humidity Adjusting Means 6 Electrolyte Membrane 7 Gas Diffusion Electrode (Fuel Electrode) 8 Gas Diffusion Electrode (Oxygen Electrode) 17 Concentration Detection Means 18 Control Means 18m Storage Means 18n Gas Humidity Determination Means 19 Output Detection Means A Oxidizer gas F Fuel gas (actual fuel gas) F1 to F3 Test fuel gas K Correspondence between absolute humidity and hydrogen gas concentration v Battery output (cell output voltage) xa Fuel gas adjusted absolute humidity xb Oxidizer gas Adjusted absolute humidity xm1 to xm3 Correspondence absolute humidity for test fuel gas xm Correspondence absolute humidity for used fuel gas xam Fuel gas target absolute humidity xbm Oxidant gas target absolute humidity σ Index variable σm Setting threshold

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiroshi Yamakawa             1-1-1 Hama, Amagasaki City, Hyogo Prefecture Co., Ltd.             Kubota Technology Development Laboratory F-term (reference) 2G004 ZA01                 2G060 AA08 AB02 AE19 AF09 EB07                       HC02 HC13 HC19 HC21 HE05                       KA04                 5H026 AA06 CC03                 5H027 AA06 KK31 KK52

Claims (5)

[Claims] 1. A fuel gas containing hydrogen gas is supplied to one of the gas diffusion electrodes sandwiching a solid polymer electrolyte membrane, and
Regarding the polymer electrolyte fuel cell in which the oxygen gas-containing oxidant gas is supplied to the other gas diffusion electrode and the absolute humidity of the fuel gas or oxidant gas supplied to these gas diffusion electrodes is adjusted by the humidity adjusting means. Corresponding absolute humidity when the index variable becomes equal to the set threshold value on the correlation between the predetermined index variable indicating the magnitude of the vibrational fluctuation of the and the absolute humidity adjusted by the humidity adjusting means, A method for determining a gas humidity of a polymer electrolyte fuel cell, which sets a target absolute humidity in the humidity adjustment by the humidity adjusting means. 2. The above-mentioned corresponding absolute humidity is obtained for each of a plurality of types of test fuel gas having different hydrogen gas concentrations, and the correspondence relationship between the plurality of corresponding absolute humidity and the hydrogen gas concentration of each test fuel gas is set. Based on the above, the corresponding absolute humidity of the actually used fuel gas according to the hydrogen gas concentration of the actually used fuel gas is obtained, and the corresponding absolute humidity of this actually used fuel gas is the target for the humidity adjustment by the humidity adjusting means. The method for determining gas humidity of a polymer electrolyte fuel cell according to claim 1, wherein absolute humidity is used. 3. A controller for a polymer electrolyte fuel cell used for carrying out the method for determining gas humidity according to claim 2, wherein the measures are taken for each of a plurality of types of test fuel gas having different hydrogen gas concentrations. Storage means for storing the correspondence between the absolute humidity and the hydrogen gas concentration of each test fuel gas, a concentration detection means for detecting the hydrogen gas concentration of the fuel gas actually used, and the correspondence stored in the storage means. Based on the relationship, the corresponding absolute humidity of the actually used fuel gas according to the hydrogen gas concentration detected by the concentration detecting means is obtained, and the corresponding absolute humidity of the actually used fuel gas is the target in the humidity adjustment by the humidity adjusting means. A control device for a polymer electrolyte fuel cell, which is provided with a gas humidity determining means for setting an absolute humidity. 4. A fuel gas containing hydrogen gas is supplied to one of the gas diffusion electrodes sandwiching the solid polymer electrolyte membrane, and
A solid polymer fuel cell in which oxygen gas-containing oxidant gas is supplied to the other gas diffusion electrode, and the absolute humidity of the fuel gas or oxidant gas supplied to these gas diffusion electrodes is adjusted by a humidity adjusting means, Based on the output detecting means for detecting the battery output and the battery output detected by the output detecting means, the humidity adjusting means is set so that a predetermined index variable indicating the magnitude of the oscillatory fluctuation of the battery output becomes equal to a set threshold value. And a control means for automatically adjusting the humidity adjustment output of the polymer electrolyte fuel cell. 5. A structure in which a large number of cells each including the solid polymer electrolyte membrane and one of the gas diffusion electrodes sandwiching the solid polymer electrolyte membrane are electrically connected in series to form a battery stack. The output voltage of a part of the representative cells of the large number of cells is the detection target output of the output detection means.
The polymer electrolyte fuel cell described.