JP5504932B2 - Method for predicting mechanical deterioration of solid polymer electrolyte membrane used in fuel cell, and deterioration prediction apparatus - Google Patents

Description

  The present invention relates to a technique for predicting mechanical deterioration due to swelling / shrinkage of a solid polymer electrolyte membrane used in a fuel cell.

  A fuel cell that generates electricity by an electrochemical reaction between a fuel gas and an oxidant gas has attracted attention as an energy source. This fuel cell includes a solid polymer fuel cell using a solid polymer membrane (solid polymer electrolyte membrane) as an electrolyte membrane. Conventionally, various techniques for predicting the lifetime of a solid polymer electrolyte membrane have been proposed for fuel cells.

  For example, Patent Document 1 listed below includes a step of alternately repeating an open circuit standing test and a crossover amount measurement, and a step of obtaining an integrated amount of fluorine discharged from the fuel cell until the crossover amount reaches a predetermined value. And a step of calculating a discharge rate of fluorine discharged in the power generation test, and a step of calculating the lifetime of the polymer membrane based on the accumulated amount and discharge rate of fluorine. The life prediction test method is described. According to this method, the lifetime due to chemical degradation of the solid polymer electrolyte membrane can be predicted.

JP 2007-311027 A JP 2009-26567 A

  However, in the technique described in Patent Document 1, mechanical deterioration of the solid polymer electrolyte membrane is not taken into account when the lifetime of the polymer membrane is predicted.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a technique for predicting mechanical deterioration of a solid polymer electrolyte membrane used in a fuel cell. In this specification, the term “fuel cell” means a “solid polymer fuel cell” using a solid polymer electrolyte membrane as an electrolyte membrane.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

[Application Example 1]
A method for predicting mechanical deterioration of a solid polymer electrolyte membrane used in a fuel cell,
Based on the stress-strain curve of the solid polymer electrolyte membrane, a rupture energy calculation step for calculating the rupture energy until the solid polymer electrolyte membrane is plastically deformed to break,
When the solid polymer electrolyte membrane swells / shrinks, for one cycle of the swelling / shrinkage, a plastic absorption energy calculation step of calculating plastic absorbed energy absorbed by plastic deformation of the solid polymer electrolyte membrane;
A cycle number calculating step of calculating the number of cycles of swelling / shrinking until the solid polymer electrolyte membrane breaks based on the breaking energy and the plastic absorption energy;
A method comprising:

  As is well known, the solid polymer electrolyte membrane has an intrinsic elastic coefficient, and the stress applied to the solid polymer electrolyte membrane is below the elastic limit and the amount of strain is in the elastic region. In the case of (elastic strain), by removing the stress, the solid polymer electrolyte membrane contracts to its original shape by elastic deformation. However, when the stress applied to the polymer electrolyte membrane exceeds the elastic limit and the amount of strain reaches the plastic region, the polymer electrolyte membrane plastically deforms (plastic strain), and the stress is removed and contracts. However, only the elastic strain is recovered, and the plastic strain remains as a permanent strain in the solid polymer electrolyte membrane. That is, plastic absorption energy is absorbed and accumulated in the solid polymer electrolyte membrane by plastic deformation. Further, the stress applied to the solid polymer electrolyte membrane reaches the breaking stress, that is, the strain applied to the solid polymer electrolyte membrane reaches the breaking strain, and the total of the plastic absorbed energy accumulated in the solid polymer electrolyte membrane. When rupture energy is reached, the solid polymer electrolyte membrane breaks.

  By the way, in the fuel cell, water (generated water) is generated by power generation, that is, an electrochemical reaction between the fuel gas and the oxidant gas. For this reason, the solid polymer electrolyte membrane provided in the fuel cell repeatedly swells and contracts by repeatedly starting and stopping the fuel cell. At this time, the swelling amount (strain amount) of the solid polymer electrolyte membrane exceeds the elastic limit, reaches the plastic region, and undergoes plastic deformation. Then, plastic absorption energy is accumulated in the solid polymer electrolyte membrane. When the solid polymer electrolyte membrane provided in the fuel cell swells, that is, when power is generated by the fuel cell, the amount of distortion always reaches the plastic region.

  In the method of Application Example 1, based on the breaking energy of the solid polymer electrolyte membrane and the plastic absorption energy, in other words, by dividing the breaking energy by the plastic absorption energy, the solid polymer electrolyte membrane is obtained. The number of cycles until the rupture breaks is roughly calculated. The mechanical deterioration of the solid polymer electrolyte membrane used in the fuel cell can be predicted by comparing the calculated number of cycles with the actual number of swelling / shrinking cycles. In the method of Application Example 1, the plastic absorption energy for each cycle of swelling / shrinking of the solid polymer electrolyte membrane is substantially equal.

[Application Example 2]
A method described in Application Example 1,
The stress-strain curve is a stress-strain curve measured for the solid polymer electrolyte membrane in a humidified environment,
The plastic absorption energy calculation step includes:
Obtaining a shrinkage amount εd in the planar direction of the solid polymer electrolyte membrane in a dry environment;
Obtaining a swelling amount εw in the planar direction of the solid polymer electrolyte membrane in the humidified environment;
Obtaining a strain amount εb of the solid polymer electrolyte membrane at a yield point with reference to the stress-strain curve in the humidified environment;
Obtaining a yield stress Sb of the solid polymer electrolyte membrane with reference to the stress-strain curve in the humidified environment;
Calculating the plastic absorption energy E by the following equation:
Including methods.
E≈ (εw−εd−εb) × Sb

  By the method of Application Example 2, mechanical degradation of the solid polymer electrolyte membrane used in the fuel cell can be estimated relatively easily and approximately. In this application example, the temperature and humidity in the “dry environment” and the “humidified environment” can be arbitrarily set. By adapting these values to the environment in which the fuel cell is used, mechanical deterioration of the solid polymer electrolyte membrane used in the fuel cell can be predicted with higher accuracy.

[Application Example 3]
A method according to application example 1 or 2,
The solid polymer electrolyte membrane is a solid polymer electrolyte membrane used in a state where pressure is applied to the surface of the solid polymer electrolyte membrane,
The cycle number calculating step uses the correction coefficient determined based on the water content of the solid polymer electrolyte membrane in a state where the pressure is applied to the surface of the solid polymer electrolyte membrane, and the plastic absorption Correcting energy or the number of cycles,
Method.

  A fuel cell is generally configured by sandwiching a membrane electrode assembly formed by joining an anode and a cathode on both sides of a solid polymer electrolyte membrane, respectively, with a current collector plate. That is, in the fuel cell, the solid polymer electrolyte membrane is used in a state where pressure is applied to the surface thereof. For this reason, the swelling amount of the solid polymer electrolyte membrane actually provided in the fuel cell is smaller than when no pressure is applied to the surface of the solid polymer electrolyte membrane. Therefore, according to the method of Application Example 3, mechanical deterioration of the solid polymer electrolyte membrane in a state where it is actually used in a fuel cell can be predicted with relatively high accuracy. The correction coefficient can be obtained experimentally or analytically.

[Application Example 4]
A deterioration prediction device for predicting deterioration of a solid polymer electrolyte membrane provided in a fuel cell,
A storage unit for storing the number of cycles of swelling / shrinking until the solid polymer electrolyte membrane breaks when the solid polymer electrolyte membrane swells / shrinks by repeated starting and stopping of the fuel cell;
An activation count section for counting the number of activations of the fuel cell;
A deterioration prediction unit that predicts mechanical deterioration of the solid polymer electrolyte membrane based on the number of cycles and the number of activations;
A deterioration prediction apparatus comprising:

  In the deterioration prediction apparatus of the application example 4, for example, the number of cycles obtained by the method of the application example 3 described above is stored in the storage unit. In the deterioration prediction apparatus of Application Example 4, mechanical deterioration of the solid polymer electrolyte membrane provided in the fuel cell can be predicted based on the number of cycles and the number of activations. For example, by calculating the difference between the number of activations and the number of cycles, or by calculating the quotient of the number of activations and the number of cycles, the solid polymer electrolyte membrane provided in the fuel cell is broken until it breaks. The remaining life and the degree of mechanical degradation of the solid polymer electrolyte membrane can be predicted and estimated.

[Application Example 5]
In the deterioration prediction device according to application example 4,
Based on the prediction result by the deterioration prediction unit, the display unit displays the degree of mechanical deterioration of the solid polymer electrolyte membrane and at least one of the remaining life until the solid polymer electrolyte membrane breaks.
Deterioration prediction device.

  In the deterioration prediction device of Application Example 5, when the fuel cell user views the display unit, at least the degree of mechanical deterioration of the solid polymer electrolyte membrane provided in the fuel cell and the remaining life until breakage are provided. One can be visually recognized. The display form of the display unit may be analog display or digital display.

[Application Example 6]
The deterioration prediction apparatus according to Application Example 4 or 5, further comprising:
A parameter value acquisition unit for acquiring a parameter value used for predicting chemical degradation of the solid polymer electrolyte membrane;
The deterioration prediction unit further predicts chemical deterioration of the solid polymer electrolyte membrane based on the acquired parameter value.
Deterioration prediction device.

  With the deterioration prediction apparatus of Application Example 6, it is possible to predict the chemical deterioration of the solid polymer electrolyte membrane as well as the mechanical deterioration of the solid polymer electrolyte membrane provided in the fuel cell. Furthermore, it is possible to predict chemical deterioration of a membrane electrode assembly including a solid polymer membrane by appropriately selecting parameter values acquired by the parameter value acquisition unit. Various parameter values can be applied as the parameter value. Examples of the parameter value include the concentration of a predetermined gas or ion contained in the exhaust gas discharged from the anode or cathode of the fuel cell, the voltage between the anode and the cathode in the fuel cell (so-called cell voltage), and the like. Can be mentioned.

[Application Example 7]
In the deterioration prediction device according to application example 6,
Based on the prediction result by the deterioration prediction unit, the display unit displays at least one of the degree of chemical deterioration of the solid polymer electrolyte membrane and the remaining life of the solid polymer electrolyte membrane,
Deterioration prediction device.

  In the deterioration prediction device of Application Example 7, the user of the fuel cell looks at the display unit so that the degree of chemical deterioration of the solid polymer electrolyte membrane provided in the fuel cell and the remaining lifetime of the solid polymer electrolyte membrane At least one of them can be visually recognized.

[Application Example 8]
The deterioration prediction apparatus according to any one of Application Examples 4 to 7, further comprising:
When the prediction result by the deterioration prediction unit is a prediction result to replace the solid polymer electrolyte membrane, a warning unit that issues a warning prompting replacement of the solid polymer electrolyte membrane,
Deterioration prediction device.

  With the deterioration prediction device of Application Example 8, it is possible to prompt the user of the fuel cell to replace the solid polymer electrolyte membrane provided in the fuel cell. For example, a warning lamp or a warning buzzer can be used as the warning unit.

  The present invention does not necessarily have all the various features described above, and may be configured by omitting some of them or combining them appropriately. Further, the present invention is not limited to the above-described configuration as the deterioration prediction device, and various aspects such as a computer program that realizes this, a recording medium that records the program, and a data signal that includes the program and is embodied in a carrier wave. Can be realized. In addition, in each aspect, it is possible to apply the various additional elements shown above.

  When the present invention is configured as a computer program or a recording medium on which the program is recorded, the entire program for controlling the operation of the above-described degradation prediction apparatus may be configured, or only a part that performs the function of the present invention. It is good also as what comprises. The recording medium includes a flexible disk, a CD-ROM, a DVD-ROM, a magneto-optical disk, an IC card, a ROM cartridge, a punch card, a printed matter on which a code such as a barcode is printed, a computer internal storage device (RAM or Various types of computer-readable media such as a memory such as a ROM and an external storage device can be used.

It is explanatory drawing which shows schematic structure of the degradation prediction apparatus 100 as one Example of this invention. 4 is a flowchart showing a flow of operation processing of the degradation prediction apparatus 100. It is explanatory drawing for showing the outline | summary of the prediction method of the mechanical deterioration of the solid polymer electrolyte membrane of a present Example. It is a flowchart which shows the flow of calculation of the allowable cycle number in a present Example. It is explanatory drawing which shows typically the dimension in the various conditions of a solid polymer electrolyte membrane, respectively. It is explanatory drawing which shows the stress-strain curve of the solid polymer electrolyte membrane as an example of a modification.

Hereinafter, embodiments of the present invention will be described in the following order based on examples.
A. Configuration of deterioration prediction device:
B. Deterioration prediction device operation processing:
C. Prediction method for mechanical degradation of solid polymer electrolyte membrane:
D. Variations:

A. Configuration of deterioration prediction device:
FIG. 1 is an explanatory diagram showing a schematic configuration of a deterioration prediction apparatus 100 as an embodiment of the present invention. The deterioration prediction apparatus 100 is provided in parallel with a fuel cell system (not shown) including a fuel cell (solid polymer fuel cell). In a fuel cell, water (product water) is generated by power generation, that is, an electrochemical reaction between a fuel gas and an oxidant gas. For this reason, the solid polymer electrolyte membrane provided in the fuel cell repeatedly swells and contracts by repeatedly starting and stopping the fuel cell. In addition, the solid polymer electrolyte membrane provided in the fuel cell undergoes chemical degradation over time. Therefore, as will be described later, the deterioration prediction apparatus 100 predicts, for example, mechanical deterioration of the solid polymer electrolyte membrane included in the fuel cell, or predicts chemical deterioration of the solid polymer electrolyte membrane or the membrane electrode assembly. Or Note that these deterioration prediction methods will be described in detail later.

  As shown in the figure, the deterioration prediction device 100 includes an activation number counting unit 10, a parameter value acquisition unit 20, a storage unit 30, a deterioration prediction unit 40, a display unit 50, and a warning unit 60.

  The activation number counting unit 10 counts the number of activations of the fuel cell every time a fuel cell (not shown) is activated. Note that the activation count unit 10 is provided with a reset operation unit (for example, a reset button) (not shown). Then, the reset operation part is provided when the membrane electrode assembly provided in the fuel cell, that is, when the solid polymer electrolyte membrane is replaced, or when the fuel cell is replaced, the accumulated fuel cell. It is operated by the user to reset the number of activations to 0 (zero). Then, the activation number counting unit 10 resets the number of activations of the fuel cell to 0 (zero) when the reset operation unit is operated.

  The parameter value acquisition unit 20 acquires various parameter values used for predicting chemical deterioration of the solid polymer electrolyte membrane or the membrane electrode assembly from the fuel cell system. Examples of the parameter value include the concentration of a predetermined gas or ion contained in the exhaust gas discharged from the anode or cathode of the fuel cell, the voltage between the anode and the cathode in the fuel cell (so-called cell voltage), and the like. Can be mentioned.

  The storage unit 30 stores various data used for predicting mechanical deterioration of the solid polymer electrolyte membrane and chemical deterioration of the solid polymer electrolyte membrane and the membrane electrode assembly. For example, when the solid polymer electrolyte membrane swells or contracts due to repeated start and stop of the fuel cell as one of data used to predict the mechanical deterioration of the solid polymer electrolyte membrane, the storage unit 30 In addition, an allowable cycle number that is a cycle number of swelling / shrinkage allowed until the solid polymer electrolyte membrane is broken is stored. This allowable cycle number is calculated in advance by a method described later.

  As will be described later, the deterioration predicting unit 40 is provided in the fuel cell on the basis of the above-described allowable cycle number and the fuel cell activation count counted by the activation frequency counting unit 10 with reference to the storage unit 30. Predict mechanical degradation of solid polymer electrolyte membranes. Further, the deterioration predicting unit 40 predicts chemical deterioration of the solid polymer electrolyte membrane or the membrane electrode assembly based on various parameter values acquired by the parameter value acquiring unit 20. For example, the deterioration prediction unit 40 determines the presence or absence of pinholes in the solid polymer electrolyte membrane due to chemical deterioration based on the concentration of the constant gas discharged from the anode or cathode of the fuel cell described above, The chemistry of the solid polymer electrolyte membrane is determined based on the concentration of predetermined ions discharged from the anode or cathode (for example, if the solid polymer electrolyte membrane is a so-called fluorine-based solid polymer electrolyte membrane). The deterioration of the electrode (catalyst layer) in the membrane electrode assembly can be predicted based on the cell voltage.

  The display unit 50 displays the degree of mechanical deterioration of the solid polymer electrolyte membrane and the degree of chemical deterioration of the solid polymer electrolyte membrane based on the prediction result by the deterioration prediction unit 40. The user of the fuel cell can visually recognize the degree of mechanical deterioration and the degree of chemical deterioration of the solid polymer electrolyte membrane by looking at the display unit 50. The display form of the display unit 50 may be analog display or digital display.

  The warning unit 60 issues a warning that prompts replacement of the solid polymer electrolyte membrane when the prediction result by the deterioration prediction unit 40 is a prediction result for replacing the solid polymer electrolyte membrane. As the warning unit 60, for example, a warning lamp or a warning buzzer can be used. This warning unit 60 can prompt the user of the fuel cell to replace the solid polymer electrolyte membrane.

B. Deterioration prediction device operation processing:
FIG. 2 is a flowchart showing a flow of operation processing of the degradation prediction apparatus 100. This process is executed every time the fuel cell is started.

  When the fuel cell is activated, the degradation predicting apparatus 100 counts the number of activations of the fuel cell by the activation number counting unit 10 (step S100). Then, the deterioration prediction device 100 refers to the storage unit 30 by the deterioration prediction unit 40 and determines whether or not the number of activations of the fuel cell is larger than the allowable number of cycles (step S110). When the number of start-ups of the fuel cell is larger than the allowable number of cycles (step S110: YES), the deterioration prediction device 100 gives a warning to the user to replace the solid polymer electrolyte membrane by the warning unit 60. (Step S150). For example, a warning lamp is turned on or blinked, or a warning buzzer is sounded. This is because when the number of start-ups of the fuel cell is larger than the allowable number of cycles, it is considered that the solid polymer electrolyte membrane has undergone mechanical deterioration that is inappropriate for continued use.

  On the other hand, when the number of activations of the fuel cell is equal to or less than the allowable number in step S110 (step S110: NO), the degradation predicting apparatus 100 causes the parameter value acquisition unit 20 to chemically degrade the solid polymer electrolyte membrane. Various parameter values used for prediction are acquired (step S120). Then, the deterioration prediction device 100 refers to the storage unit 30 by the deterioration prediction unit 40, and based on the acquired various parameter values, the solid polymer electrolyte membrane is chemically deteriorated to an extent unsuitable for continuous use. It is determined whether or not there is (step S130). As described above, the parameter value may be, for example, the concentration of a predetermined gas or ion contained in the exhaust gas discharged from the anode or cathode of the fuel cell, or the voltage between the anode and cathode in the fuel cell. (So-called cell voltage).

  In step S130, as described above, the deterioration predicting unit 40, for example, determines the pinholes of the solid polymer electrolyte membrane due to chemical deterioration based on the concentration of constant gas discharged from the anode or cathode of the fuel cell. Based on the concentration of predetermined ions discharged from the anode or cathode of the fuel cell (for example, fluorine ions when the solid polymer electrolyte membrane is a so-called fluorine-based solid polymer electrolyte membrane) Thus, chemical degradation of the solid polymer electrolyte membrane can be predicted, or degradation of the electrode (catalyst layer) in the membrane electrode assembly can be predicted based on the cell voltage.

  If it is determined that the solid polymer electrolyte membrane has undergone chemical degradation that is unsuitable for continued use (step S130: YES), the degradation prediction device 100 causes the warning unit 60 to notify the user. Then, a warning to replace the solid polymer electrolyte membrane is issued (step S150). In step S150, the warning method based on the mechanical deterioration of the solid polymer electrolyte membrane and the warning method based on the chemical deterioration may be the same method or different method steps.

  In step S130, when the solid polymer electrolyte membrane has not undergone chemical degradation that is unsuitable for continued use (step S130: NO), the degradation predicting apparatus 100 displays the solid polymer electrolyte on the display unit 50. The predicted remaining life of the film is displayed (step S140).

  In the present embodiment, the display unit 50 includes a predicted remaining life about the mechanical deterioration of the solid polymer electrolyte membrane based on step S110 and a predicted remaining life about the chemical deterioration of the solid polymer electrolyte membrane based on step S130. Were to be displayed separately. The predicted remaining life for the mechanical degradation of the solid polymer electrolyte membrane based on step S110 is, for example, calculating the difference between the number of times the fuel cell is started and the allowable number of cycles described later, or the number of times the fuel cell is started and the allowable number of cycles. Or the quotient of. In addition, the predicted remaining life for the chemical degradation of the solid polymer electrolyte membrane based on step S130 is the parameter value when no chemical degradation occurs in the solid polymer electrolyte membrane, and the chemical degradation of the solid polymer electrolyte membrane. It is calculated by comparison with the parameter value in the case where this occurs.

  Thereafter, the deterioration prediction device 100 determines whether or not the operation of the fuel cell has been stopped (step S160). When the operation of the fuel cell is stopped (step S160: YES), the deterioration prediction device 100 ends the operation. On the other hand, when the operation of the fuel cell is not stopped (step S160: NO), the deterioration predicting apparatus 100 returns the process to step S120.

C. Prediction method for mechanical degradation of solid polymer electrolyte membrane:
FIG. 3 is an explanatory diagram for illustrating an outline of a prediction method for mechanical deterioration of the solid polymer electrolyte membrane of the present embodiment, which is performed by the deterioration prediction unit 40 in the deterioration prediction apparatus 100 described above. The stress-strain curve (SS curve) of the solid polymer electrolyte membrane was shown. In the illustrated stress-strain curve, the stress is assumed to be constant in the plastic region even when the amount of strain of the solid polymer electrolyte membrane increases in order to facilitate understanding.

  As shown in FIG. 3A, when the solid polymer electrolyte membrane is further distorted beyond the elastic limit due to swelling, and the amount of strain of the solid polymer electrolyte membrane reaches a rupture strain in the plastic region, as shown in FIG. The electrolyte membrane breaks. In FIG. 3A, the area surrounded by the stress-strain curve, that is, the area indicated by hatching is the rupture energy until the solid polymer electrolyte membrane is plastically deformed to break. .

  As is well known, the solid polymer electrolyte membrane has an intrinsic elastic coefficient, and the stress applied to the solid polymer electrolyte membrane is below the elastic limit and the amount of strain is in the elastic region. In the case of (elastic strain), by removing the stress, the solid polymer electrolyte membrane contracts to its original shape by elastic deformation. For example, in FIG. 3B, the elastic strain of the solid polymer electrolyte membrane from point O to point A in the elastic region returns to point O by removing the stress applied to the solid polymer electrolyte membrane.

  However, when the stress applied to the polymer electrolyte membrane exceeds the elastic limit and the amount of strain reaches the plastic region, the polymer electrolyte membrane plastically deforms (plastic strain), and the stress is removed and contracts. However, only the elastic strain is recovered, and the plastic strain remains as a permanent strain in the solid polymer electrolyte membrane. For example, in FIG. 3B, the solid polymer electrolyte membrane plastically deformed by swelling as point O → point A → point B in FIG. 3B returns only to point C even if the stress is removed and contracted. That is, plastic absorption energy is absorbed and accumulated in the solid polymer electrolyte membrane by plastic deformation. When the solid polymer electrolyte membrane provided in the fuel cell swells, that is, when power is generated by the fuel cell, the amount of distortion always reaches the plastic region.

  In the example shown in FIG. 3B, when the solid polymer electrolyte membrane swells and then contracts (point O → point A → point B → point C), as shown with an arrow in the figure, In the locus, the line segment OA and the line segment BC are parallel to each other, and the area of the parallelogram OABC indicated by hatching is expressed as a plastic absorption energy for one cycle of swelling / shrinkage of the solid polymer electrolyte membrane. Accumulated in the polymer electrolyte membrane. When the solid polymer electrolyte membrane repeats swelling / shrinking for a plurality of cycles and the total of the plastic absorption energy accumulated in the solid polymer electrolyte membrane reaches the breaking energy, the solid polymer electrolyte membrane breaks.

  Therefore, in this example, the breaking energy of the solid polymer electrolyte membrane shown in FIG. 3A is used as the plastic absorption energy for one cycle of swelling / shrinkage of the solid polymer electrolyte membrane shown in FIG. The number of cycles of swelling / shrinking until the solid polymer electrolyte membrane breaks is roughly calculated. In the present embodiment, the plastic absorption energy for each cycle of swelling / shrinking of the solid polymer electrolyte membrane is approximately equal.

  Then, the allowable number of cycles is calculated by multiplying the calculated number of cycles by a correction coefficient W described later. As described above, the allowable number of cycles is determined when the solid polymer electrolyte membrane is actually provided in the fuel cell, and the solid polymer electrolyte membrane swells / shrinks due to repeated starting and stopping of the fuel cell. The number of cycles of swelling / shrinking allowed before the solid polymer electrolyte membrane breaks. For this reason, the correction coefficient W is set in consideration of the state in which the solid polymer electrolyte membrane is actually provided in the fuel cell. The correction coefficient W will be described later.

  FIG. 4 is a flowchart showing a flow of calculation of the allowable cycle number in the present embodiment. FIG. 5 is an explanatory view schematically showing dimensions of the solid polymer electrolyte membrane under various conditions. In addition, each dimension typically shown in FIG. 5 represents the dimension of the plane direction of a solid polymer electrolyte membrane, respectively.

  FIG. 5A shows the dimensions of the solid polymer electrolyte membrane cut out in an environment of room temperature (for example, 25 (° C.)) and normal humidity (for example, relative humidity: 50 (%)). In addition, according to Japanese Industrial Standard, normal humidity means the range whose relative humidity is 45-85 (%).

  FIG. 5B shows the dimensions of the solid polymer electrolyte membrane when contracted (dried). In FIG. 5 (b), a membrane / electrode assembly is produced by forming an anode and a cathode on both surfaces of the solid polymer electrolyte membrane shown in FIG. 5 (a), respectively. The dimensions of the solid polymer electrolyte membrane in which the solid polymer electrolyte membrane is contracted and the expansion and contraction of the solid polymer electrolyte membrane are constrained by thermocompression bonding of the gas diffusion layers on both sides of the body, respectively. Indicated. The amount of shrinkage of the solid polymer electrolyte membrane in this dry environment is defined as the amount of shrinkage εd. The value of the amount of contraction εd varies depending on, for example, the environmental conditions from which the solid polymer electrolyte membrane is cut out and the conditions for thermocompression bonding of the gas diffusion layer described above.

  FIG. 5C shows the dimensions of the solid polymer electrolyte membrane during swelling. In FIG. 5 (c), the solid polymer membrane shown in FIG. 5 (a) is not restrained from expanding and contracting under the operating environment of the fuel cell, that is, in a humid environment (humid environment). The dimensions of the solid polymer electrolyte membrane are shown.

  FIG. 5D shows the dimensions of the solid polymer electrolyte membrane during swelling. In FIG. 5 (d), the expansion and contraction of the solid polymer electrolyte membrane is constrained (see FIG. 5 (b)), and in the operating environment of the fuel cell, that is, in the humidified environment (humid environment). The dimensions of the solid polymer electrolyte membrane are shown. As can be seen from a comparison between FIG. 5 (b) and FIG. 5 (d), the dimensions (FIG. 5 (d)) of the solid polymer electrolyte membrane with its expansion and contraction restricted are as shown in FIG. 5 (d). The size of the solid polymer electrolyte membrane (FIG. 5B) is almost equal. The virtual swelling amount that should have been swollen if the expansion and contraction of the solid polymer electrolyte membrane in which the expansion and contraction is constrained is not constrained is defined as the swelling amount εw in the humidification environment.

  In the calculation of the allowable number of cycles in the present embodiment, as shown in FIG. 4, first, the shrinkage amount εd in the dry environment shown in FIG. 5B is acquired (step S200). And the swelling amount (epsilon) w in the humidification environment shown in FIG.5 (d) is acquired (step S210). Moreover, the stress-strain curve in the said humidified environment is acquired (step S220). These are acquired experimentally in advance. Note that the order of steps S200 to S220 can be arbitrarily changed.

  Next, referring to the stress-strain curve in the humidified environment, the yield strain εb, which is the amount of strain of the solid polymer electrolyte membrane at the yield point, and the yield stress, which is the stress of the solid polymer electrolyte membrane at the yield point Sb is acquired (step S230). For example, in the stress-strain curve shown in FIG. 3B, the point A is the yield point, the strain amount at the point A is the yield strain εb, and the stress at the point A is the yield stress Sb. Then, based on the stress-strain curve in the humidified environment, the breaking energy (see FIG. 3A) of the solid polymer electrolyte membrane is calculated (step S240). Note that the order of step S230 and step S240 may be interchanged.

Next, the plastic absorption energy E for one cycle of swelling / shrinking of the solid polymer electrolyte membrane by starting and stopping of the fuel cell is calculated (step S250). In this embodiment, the plastic absorption energy E is calculated by the following formula (1).
E≈ (εw−εd−εb) × Sb (1)

  For example, in FIG. 3B, the strain amount at point B corresponds to εw in the above equation (1), the strain amount at point A (yield point) corresponds to εb in the above equation (1), and at point O The amount of strain corresponds to (−εd) in the above equation (1), and the stress at point A (yield point) corresponds to Sb in the above equation (1). That is, (εw−εd−εb) in the above equation (1) corresponds to the length of the base of the parallelogram OABC depicted in FIG. Further, Sb in the above equation (1) corresponds to the height of the parallelogram OABC depicted in FIG. The plastic absorption energy E calculated in the above equation (1) corresponds to the area of the parallelogram OABC depicted in FIG.

  After step S250 in FIG. 4, the number of cycles until the solid polymer electrolyte membrane breaks is calculated (step S260). As described above, the number of cycles is calculated by dividing the rupture energy of the solid polymer electrolyte membrane calculated in step S240 by the plastic absorption energy E calculated in step S250. Then, the allowable cycle is calculated by multiplying the calculated cycle number by the correction coefficient W (step S270). The correction coefficient W is a value larger than 1. As described above, the allowable number of cycles is calculated using the correction coefficient W for the following reason.

  That is, when the solid polymer electrolyte membrane is actually provided in the fuel cell, the membrane electrode assembly including the solid polymer electrolyte membrane is sandwiched by the current collector plate, and pressure is applied to the surface of the solid polymer electrolyte membrane. Is added. For this reason, in the solid polymer electrolyte membrane actually provided in the fuel cell, the swelling amount εw in the humidified environment is applied to the surface of the solid polymer electrolyte membrane due to the effect of the pressure applied to the surface. It will be smaller than if not. This is because when the pressure is applied to the surface of the solid polymer electrolyte membrane, the moisture content of the solid polymer electrolyte membrane in a humidified environment is such that the pressure is applied to the surface of the solid polymer electrolyte membrane. This is because it is less than in the case of no. The number of cycles calculated in step S260 is a value when no pressure is applied to the surface of the solid polymer electrolyte membrane, and until the solid polymer electrolyte membrane actually provided in the fuel cell is broken. This is because the swelling / shrinking cycle number (allowable cycle number) is larger than the cycle number calculated in step S260.

  The correction coefficient W is determined based on the water content of the solid polymer electrolyte membrane in a state where pressure is applied to the surface of the solid polymer electrolyte membrane, and is expressed by a series developed by the reciprocal of the water content. be able to. Specifically, the correction coefficient W is approximately obtained by the following equation (2).

Here, a _j is a j-th order expansion function. The allowable cycle is calculated by the above flow.

  The allowable cycle stored in the storage unit 30 in the deterioration prediction apparatus 100, that is, the allowable cycle referred to in step S110 of the operation process of the deterioration prediction apparatus 100 shown in FIG. 2 is calculated by the above equation (2). The allowable number of cycles is multiplied by a predetermined safety factor (coefficient). This safety factor is, for example, in consideration of manufacturing errors and variations in solid polymer electrolyte membranes and fuel cells, before the solid polymer electrolyte membrane is mechanically deteriorated unsuitably for continued use. It is set so that a warning for replacing the solid polymer electrolyte membrane can be given to the user.

  According to the deterioration prediction apparatus 100 of the present embodiment described above, the remaining life until the solid polymer electrolyte membrane provided in the fuel cell breaks and the degree of mechanical deterioration of the solid polymer electrolyte membrane are predicted, Can be estimated. Moreover, according to the prediction method of the mechanical degradation of the solid polymer electrolyte membrane of a present Example, the mechanical degradation of the solid polymer electrolyte membrane used for a fuel cell can be estimated.

  Moreover, in the deterioration prediction apparatus 100 of the present embodiment, the chemistry of the solid polymer electrolyte membrane and the membrane electrode assembly including the solid polymer membrane is predicted along with the prediction of the mechanical deterioration of the solid polymer electrolyte membrane provided in the fuel cell. It is also possible to predict mechanical degradation.

D. Variations:
Although the embodiments of the present invention have been described above, the present invention is not limited to such embodiments, and can be implemented in various modes without departing from the scope of the present invention. For example, the following modifications are possible.

D1. Modification 1:
In the above embodiment, the stress-strain curve of the solid polymer electrolyte membrane shown in FIG. 3 is assumed to be constant in the plastic region even if the amount of strain of the solid polymer electrolyte membrane increases. The invention is not limited to this.

  FIG. 6 is an explanatory diagram showing a stress-strain curve of a solid polymer electrolyte membrane as an example of a modification. In the stress-strain curve of the solid polymer electrolyte membrane shown in FIG. 6, unlike the stress-strain curve of the solid polymer electrolyte membrane shown in FIG. 3, the strain amount of the solid polymer electrolyte membrane also in the plastic region. The stress increases with the increase. For the solid polymer electrolyte membrane having such a stress-strain curve, for example, when calculating the plastic absorption energy in the prediction of the mechanical deterioration of the solid polymer electrolyte membrane, for example, the strain amount at the yield point and the strain amount at the break point And the arithmetic mean of the stress at the yield point and the stress at the fracture point, respectively, and the plastic absorption energy may be calculated using these values. In addition, when the stress-strain curve is curved in the plastic region, the method for calculating the plastic absorption energy may be appropriately changed.

  Moreover, in the said Example, although the plastic absorption energy E shall be calculated approximately by said Formula (1), this invention is not limited to this. The plastic absorption energy E may be calculated by other methods or arithmetic expressions.

D2. Modification 2:
In the above embodiment, the display unit 50 in the deterioration prediction device 100 displays the degree of mechanical deterioration of the solid polymer electrolyte membrane and the degree of chemical deterioration of the solid polymer electrolyte membrane. Is not limited to this. The display unit 50 displays the degree of mechanical deterioration of the solid polymer electrolyte membrane and the degree of chemical deterioration of the solid polymer electrolyte membrane, or alternatively, the degree of mechanical deterioration of the solid polymer electrolyte membrane, In addition to displaying the degree of chemical degradation of the solid polymer electrolyte membrane, the remaining lifetime of the solid polymer electrolyte membrane may be displayed.

D3. Modification 3:
In the above embodiment, the deterioration prediction device 100 includes the parameter value acquisition unit 20, and the deterioration prediction unit 40 predicts chemical deterioration of the solid polymer electrolyte membrane included in the fuel cell, but this is omitted. You may make it do.

D4. Modification 4:
In the said Example, although the degradation prediction apparatus 100 shall be provided with the warning part 60, this invention is not limited to this. In the deterioration prediction apparatus 100, the warning unit 60 may be omitted.

D5. Modification 5:
In the said Example, although the degradation prediction apparatus 100 shall be provided with the display part 50, this invention is not limited to this. In the deterioration prediction apparatus 100, the display unit 50 may be omitted.

D6. Modification 6:
In the above embodiment, in step S110 of the operation process of the degradation predicting apparatus 100 shown in FIG. 2, when the number of activations is larger than the allowable number of cycles, the process proceeds to step S150. However, the present invention is not limited to this. I can't. In parallel with this, the process may proceed to step S120.

D7. Modification 7:
In the above embodiment, when calculating the allowable cycle number shown in FIG. 4, the allowable cycle number is calculated by multiplying the cycle number calculated in step S260 by the correction coefficient W in step S270. The invention is not limited to this. When calculating the plastic absorption energy in step S250, the amount of swelling of the solid polymer electrolyte membrane is calculated using a correction coefficient obtained in consideration of the state in which pressure is applied to the surface of the solid polymer electrolyte membrane. The plastic absorption energy may be corrected. In this case, the number of cycles equivalent to the allowable number of cycles calculated in step S270 is calculated in step S260.

D8. Modification 8:
In the above embodiment, when calculating the allowable number of cycles shown in FIG. 4, the correction coefficient W obtained by the above equation (2) is used in step S270. However, the present invention is not limited to this. Other correction coefficients may be used for calculating the allowable number of cycles. When evaluating the mechanical deterioration of a solid polymer electrolyte membrane that is not provided in a fuel cell, that is, a solid polymer electrolyte membrane in which no pressure is applied to the surface thereof (for example, a solid polymer electrolyte) In the case of performing an acceleration test on the mechanical deterioration of the film), the correction coefficient W in the above embodiment may be omitted.

DESCRIPTION OF SYMBOLS 100 ... Deterioration prediction apparatus 10 ... Start count count part 20 ... Parameter value acquisition part 30 ... Memory | storage part 40 ... Deterioration prediction part 50 ... Display part 60 ... Warning part

Claims (7)

A method for predicting mechanical deterioration of a solid polymer electrolyte membrane used in a fuel cell,
Based on the stress-strain curve of the solid polymer electrolyte membrane, a rupture energy calculation step for calculating the rupture energy until the solid polymer electrolyte membrane is plastically deformed to break,
When the solid polymer electrolyte membrane swells / shrinks, for one cycle of the swelling / shrinkage, a plastic absorption energy calculation step of calculating plastic absorbed energy absorbed by plastic deformation of the solid polymer electrolyte membrane;
A cycle number calculating step of calculating the number of cycles of swelling / shrinking until the solid polymer electrolyte membrane breaks based on the breaking energy and the plastic absorption energy;
A method comprising: The method of claim 1, comprising:
The stress-strain curve is a stress-strain curve measured for the solid polymer electrolyte membrane in a humidified environment,
The plastic absorption energy calculation step includes:
Obtaining a shrinkage amount εd in the planar direction of the solid polymer electrolyte membrane in a dry environment;
Obtaining a swelling amount εw in the planar direction of the solid polymer electrolyte membrane in the humidified environment;
Obtaining a strain amount εb of the solid polymer electrolyte membrane at a yield point with reference to the stress-strain curve in the humidified environment;
Obtaining a yield stress Sb of the solid polymer electrolyte membrane with reference to the stress-strain curve in the humidified environment;
Calculating the plastic absorption energy E by the following equation:
Including methods.
E≈ (εw−εd−εb) × Sb A deterioration prediction device for predicting mechanical deterioration of a solid polymer electrolyte membrane provided in a fuel cell,
The rupture energy until the solid polymer electrolyte membrane is plastically deformed and ruptured, derived from the stress-strain curve of the solid polymer electrolyte membrane, and the solid polymer electrolyte membrane swells / shrinks 1 Stores the number of cycles of swelling / shrinking until the solid polymer electrolyte membrane breaks , calculated based on the plastic absorption energy absorbed by plastic deformation of the solid polymer electrolyte membrane during the cycle A storage unit to
An activation count section for counting the number of activations of the fuel cell;
A deterioration prediction unit that predicts mechanical deterioration of the solid polymer electrolyte membrane based on the number of cycles and the number of activations;
A deterioration prediction apparatus comprising: The deterioration prediction apparatus according to claim 3 , further comprising:
Based on the prediction result by the deterioration prediction unit, the display unit displays the degree of mechanical deterioration of the solid polymer electrolyte membrane and at least one of the remaining life until the solid polymer electrolyte membrane breaks.
Deterioration prediction device. The deterioration prediction apparatus according to claim 3 or 4 , further comprising:
A parameter value acquisition unit for acquiring a parameter value used for predicting chemical degradation of the solid polymer electrolyte membrane;
The deterioration prediction unit further predicts chemical deterioration of the solid polymer electrolyte membrane based on the acquired parameter value.
Deterioration prediction device. The deterioration prediction apparatus according to claim 5 , further comprising:
Based on the prediction result by the deterioration prediction unit, the display unit displays at least one of the degree of chemical deterioration of the solid polymer electrolyte membrane and the remaining life of the solid polymer electrolyte membrane,
Deterioration prediction device. The degradation prediction apparatus according to any one of claims 3 to 6 , further comprising:
When the prediction result by the deterioration prediction unit is a prediction result to replace the solid polymer electrolyte membrane, a warning unit that issues a warning prompting replacement of the solid polymer electrolyte membrane,
Deterioration prediction device.

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