JP2008146877A - Fuel cell system, and impurities accumulation amount estimation method of fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To estimate an amount of impurities accumulated at an anode side by permeating an electrolyte film from a cathode side, in a fuel cell system using a dead-end system. <P>SOLUTION: The fuel cell system is provided with a means of estimating an amount of impurities accumulated at an anode side by permeating an electrolyte membrane from a cathode side, and a means of purging the impurities at the instant their amount reaches a given value. The means of estimating an amount of the impurities can carry out estimation of the impurities by preliminarily finding a relation of a current density of a fuel cell and a rate at which the impurities are accumulated, and detecting a current density for each given period of time. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel cell system and a method for estimating the amount of accumulated impurities in a fuel cell system.

  The fuel cell has a structure in which an anode and a cathode are arranged with an electrolyte membrane interposed therebetween. When a reactive gas is supplied to each electrode, an electrochemical reaction occurs between the electrodes to generate an electromotive force. Specifically, the reaction occurs when hydrogen (fuel gas) is in contact with the anode and oxygen (oxidant gas) is in contact with the cathode.

  Generally, air taken in from outside air by a compressor is supplied to the cathode. On the other hand, hydrogen stored in a high-pressure hydrogen tank is supplied to the anode. One of the methods for supplying hydrogen to the anode is a so-called dead end system (see, for example, Patent Document 1). In this system, the operation is performed with the downstream of the hydrogen flow path blocked, and an amount of hydrogen corresponding to the consumed hydrogen is supplied to the anode.

  In the case of a dead-end fuel cell system, the amount of impurities that accumulate in the fuel gas flow path increases with time. Specifically, nitrogen contained in the air supplied to the cathode permeates the electrolyte membrane and accumulates on the anode side. For this reason, the fuel cell system disclosed in Patent Document 1 is provided with a purge valve that periodically discharges impurities from the flow path of the fuel gas. When the voltage of the fuel cell is lower than a predetermined value, the voltage is recovered by opening this purge valve.

JP-T-2004-536436

  However, in the fuel cell system described in Patent Document 1, purging may be performed even if the voltage drops due to a cause other than the above. The reason will be described in detail below.

In the fuel cell, when hydrogen is supplied to the anode, H ₂ → 2H ⁺ + 2e ⁻ is supplied to the anode.
The above reaction takes place and H ⁺ is produced. Then, this H ⁺ passes through the electrolyte membrane and moves to the cathode side, and then (1/2) O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O with oxygen supplied to the cathode.
Cause the reaction. That is, between both electrodes,
H ₂ + (1/2) O ₂ → H ₂ O
As a result of this electrochemical reaction, an electromotive force is generated in the fuel cell.

  In order for the above reaction to proceed smoothly, it is necessary to ionize the hydrogen gas while maintaining the electrolyte membrane in an appropriate wet state. Therefore, reaction gases such as fuel gas and oxidant gas are usually supplied to the fuel cell in a state containing water vapor. Here, when the moisture in the reaction gas decreases and the electrolyte membrane dries, the electrochemical reaction does not proceed smoothly, and the output of the fuel cell decreases. On the other hand, when the reaction gas contains excessive moisture, water condensation occurs, and the flow path of the reaction gas is blocked by the condensed water. Thereby, the supply of the reaction gas to the fuel cell is hindered, and the electrochemical reaction does not proceed smoothly. Accordingly, in this case as well, the output of the fuel cell decreases as described above.

  As described above, the voltage of the fuel cell also decreases for reasons other than the gas permeating from the cathode side to the anode side through the electrolyte membrane. Therefore, in the method of monitoring the output voltage as in Patent Document 1 and performing the purge when this value decreases, the purge is performed even though almost no impurities are accumulated on the anode side. was there. Further, even when impurities are accumulated, there is a problem that it is difficult to obtain a stable voltage because purging is performed after the output voltage is lowered.

  On the other hand, there is also a fuel cell system in which the timing for opening the purge valve is not determined according to the monitored voltage value of the fuel cell, but is opened at regular time intervals. However, in this case, if purging is performed before impurities accumulate on the anode side, high-concentration hydrogen will be discharged. For this reason, problems such as a reduction in fuel consumption and an increase in the size of a device for diluting hydrogen to a concentration below the flammable limit have occurred.

  The present invention has been made in view of these problems. That is, an object of the present invention is to estimate the amount of impurities that permeate the electrolyte membrane from the cathode side and accumulate on the anode side in the fuel cell system using the dead end system.

  Other objects and advantages of the present invention will become apparent from the following description.

According to a first aspect of the present invention, there is provided a fuel cell system including a fuel cell capable of operating in a state in which a fuel gas is supplied to an anode and an oxidant gas is supplied to a cathode, and a downstream side of the anode is closed.
Having means for estimating the amount of impurities accumulated on the anode side from the cathode side;
The means for estimating the amount of the impurity obtains in advance a relationship between the current density of the fuel cell and the speed at which the impurity accumulates, detects the current density of the fuel cell every predetermined time, and detects the current density. And means for estimating the amount of accumulated impurities from the relationship.

It is preferable that the first aspect of the present invention further includes a purge means for discharging impurities from the anode to the outside when the estimated amount of impurities reaches a predetermined value.
In this case, it is preferable to change the predetermined value according to the current density of the fuel cell.

According to a second aspect of the present invention, there is provided a fuel cell system including a fuel cell that can be operated in a state in which a fuel gas is supplied to an anode and an oxidant gas is supplied to a cathode, and a downstream side of the anode is closed.
Having means for estimating the amount of impurities accumulated on the anode side from the cathode side;
The means for estimating the amount of impurities obtains in advance a relationship between the power generation amount of the fuel cell and the speed at which the impurities accumulate, detects the power generation amount of the fuel cell every predetermined time, and generates the power generation amount. And means for estimating the amount of accumulated impurities from the relationship.

The second aspect of the present invention preferably further includes a purge means for discharging impurities from the anode to the outside when the estimated amount of impurities reaches a predetermined value.
In this case, it is preferable to change the predetermined value according to the current density of the fuel cell.

According to a third aspect of the present invention, a fuel cell is provided which supplies fuel gas to the anode and oxidant gas to the cathode, and can be operated in a state where the downstream side of the anode is closed. An impurity accumulation amount estimation method for estimating the amount of impurities accumulated on the anode side through the membrane,
Determining the relationship between the current density of the fuel cell and the rate at which the impurities accumulate;
And detecting the current density of the fuel cell every predetermined time and estimating the accumulated amount of impurities from the current density and the relationship.

According to a fourth aspect of the present invention, there is provided a fuel cell which can be operated in a state where a fuel gas is supplied to an anode and an oxidant gas is supplied to a cathode, and a downstream side of the anode is closed. An impurity accumulation amount estimation method for estimating the amount of impurities accumulated on the anode side through the membrane,
Determining the relationship between the amount of power generated by the fuel cell and the rate at which the impurities accumulate;
Detecting the amount of power generated by the fuel cell every predetermined time, and estimating the amount of accumulated impurities from the amount of generated power and the relationship.

  According to the present invention, it is possible to estimate the amount of impurities that have permeated the electrolyte membrane from the cathode side and accumulated on the anode side.

  FIG. 1 is a configuration diagram of a fuel cell system according to the present embodiment. In addition, this fuel cell system is applicable to various uses, such as a vehicle-mounted type and a stationary type.

  As shown in FIG. 1, a fuel cell system 1 includes a fuel cell 2 that is supplied with hydrogen as a fuel gas and air as an oxidant gas to generate an electromotive force, and a compressor that supplies compressed air to the fuel cell 2. 3, a humidifier 4 that recovers moisture contained in the oxidant off-gas discharged from the fuel cell 2 and humidifies the air supplied to the fuel cell 2, and the pressure of the air supplied from the compressor 3 to the fuel cell 2 An air pressure adjusting valve 5 for adjusting the pressure, a hydrogen tank 6 for storing dry hydrogen in a high pressure state, a hydrogen pressure adjusting valve 7 for adjusting the pressure of hydrogen supplied from the hydrogen tank 6 to the fuel cell 2, and the fuel cell 2 A purge valve 8 that purges the discharged fuel off-gas and a current density measuring means 9 that measures the current density of the fuel cell 2 are provided.

  The purge valve 8 constitutes a purge means in the present invention. In the fuel cell system 1, the fuel off gas discharged from the fuel cell 2 can be purged by opening the purge valve 8.

  Hydrogen is supplied to the anode (not shown) by a dead end system. That is, when the purge valve 8 is closed, the fuel off-gas flow path 10 is closed, and hydrogen is supplied only from the hydrogen tank 6. According to such a dead end system, the supplied hydrogen is completely consumed by the reaction in the fuel cell 2. Only the consumed hydrogen is newly supplied to the anode. In the present invention, a fuel cell that can be operated with the downstream side of the anode closed is a state in which the downstream side of the gas flow path formed in the anode surface is structurally (permanently) closed. It can be a fuel cell. In addition, a discharge flow path for discharging the fuel off gas to the outside of the fuel cell is formed on the downstream side of the anode, and the on-off valve provided in the discharge flow path is closed, so that the downstream of the anode (temporarily) ) It may be a closed fuel cell.

  The fuel gas supplied to the anode is not limited to hydrogen. For example, a reformed gas generated by a reforming reaction of a hydrocarbon-based compound can be used as a hydrogen source supplied to the anode. In this case, as the hydrocarbon compound, natural gas mainly composed of methane, alcohol such as methanol, gasoline, or the like is used. A catalyst and temperature suitable for the reforming reaction are selected according to the type of hydrocarbon compound used. As a result, a hydrogen-rich reformed gas containing hydrogen, carbon dioxide, and water is generated.

  As described above, since the fuel cell system 1 employs the dead end method for supplying hydrogen to the anode, the operation is performed in a state where the flow path 10 of the fuel off gas is closed. On the other hand, the air flow path 11 is operated in an open state. For this reason, impurities diffused from the cathode side tend to accumulate on the anode side via an electrolyte membrane (not shown). Therefore, with the passage of time, nitrogen contained in the air supplied to the cathode (not shown) permeates the electrolyte membrane and accumulates downstream of the anode side channel (channel 10 in the example of FIG. 1). (Exists). Here, since the hydrogen pressure is adjusted to be a predetermined value by the hydrogen pressure regulating valve 7, if the impurity concentration in the fuel off-gas increases, the hydrogen partial pressure relatively decreases. As a result, in the downstream of the anode-side flow path, a state in which hydrogen is deficient (hereinafter referred to as hydrogen deficiency) is entered, and the output voltage of the fuel cell decreases.

  Therefore, in this embodiment, the amount of impurities that permeate the electrolyte membrane from the cathode side and accumulate on the anode side is estimated, and purge is performed when this amount reaches a predetermined value. By doing so, purging is not performed in a state where almost no impurities are accumulated on the anode side. Accordingly, it is possible to avoid problems such as a reduction in fuel consumption due to the discharge of high concentration of hydrogen and an increase in the size of a device for diluting hydrogen to a concentration below the flammability limit. In addition, since the purge is performed without waiting for the output voltage to decrease, a stable voltage can be obtained.

  Specifically, the amount of impurities accumulated on the anode side can be estimated as described below.

  First, a map of the relationship between the current density of the fuel cell and the rate at which impurities accumulate on the anode side is created. This relationship can be obtained, for example, by CFD analysis.

  FIG. 2 shows an example of the above relationship. As can be seen from this figure, the smaller the current density of the fuel cell, the slower the impurity accumulation rate. The relationship between the current density of the fuel cell and the accumulation of impurities will be described in detail below.

  In the anode side flow path, the gas is transported by the flow from the upstream to the downstream of the fuel cell and the diffusion. Here, transport by flow is proportional to the flow rate and concentration of the gas. The gas flow rate is proportional to the flow path length and the current density of the fuel cell. On the other hand, transport by diffusion is proportional to the concentration gradient and the diffusion coefficient. The concentration gradient is inversely proportional to the channel length.

  Therefore, when the current density is constant, the longer the flow path length, the more dominant the transport by flow. On the other hand, when the channel length is shortened, the influence of transport due to diffusion is increased by increasing the concentration gradient instead of the influence of transport due to the flow. The transport by diffusion becomes more dominant as the flow path length is shorter.

FIG. 3 is an example showing the relationship between the flow path length and the gas moving speed when the current density is 0.1 A / cm ² . As shown in this figure, when the flow path length is short, the gas moving speed by diffusion is larger than the moving speed by flow. On the other hand, as the flow path length increases, the movement speed due to diffusion decreases, and instead the movement speed due to flow increases. This indicates that when the flow path length is short, gas migration from downstream to upstream may occur due to diffusion, and an effect of mitigating the accumulation of impurities downstream and lack of hydrogen is expected. Is done.

  Next, the relationship between the current density and the moving speed is considered with the flow path length being constant. FIG. 4 shows an example in which the flow path length is 10 cm. As shown in this figure, as the current density increases, the gas moving speed due to the flow also increases. On the other hand, the gas moving speed by diffusion remains constant even when the current density changes. When the current density is small, the gas moving speed by diffusion is larger than the moving speed by flow. Therefore, it is expected that the accumulation of impurities downstream is suppressed by the gas moving from the downstream to the upstream. However, as the current density increases, the moving speed due to the flow increases, so that the gas flows from upstream to downstream.

  FIG. 5 shows the gas distribution in the anode-side flow path. The horizontal axis is the distance from the inlet of the flow path, and the vertical axis is the ratio of impurities contained in the fuel off gas. When the impurity ratio is 1, hydrogen is not contained, and therefore no electrochemical reaction occurs.

  As can be seen from FIG. 5, at any current density, the ratio of impurities increases with increasing distance from the inlet of the flow path, that is, downstream. This tendency becomes more prominent as the current density increases. This is presumably because, as the current density becomes smaller, the movement of gas due to diffusion becomes dominant, so that the distribution of gas in the entire flow path is averaged due to the movement of impurities from downstream to upstream.

  FIG. 6 shows the actual reaction area ratio of hydrogen after a predetermined time has elapsed from time t = 0. Regardless of the current density, the actual reaction area ratio of hydrogen decreases with time. This is because the proportion of impurities increases with time, and the area in which hydrogen reacts relatively decreases. However, the degree of change depends on the magnitude of the current density, and the smaller the current density, the more difficult the substantial reaction area ratio decreases.

  In summary, if the flow path length is constant, the smaller the current density, the more dominant the gas movement is due to diffusion. For this reason, the smaller the current density, the more the gas distribution in the flow channel is averaged, and the lower the substantial reaction area ratio of hydrogen is. That is, the smaller the current density, the slower the impurity accumulation rate downstream. Here, since the current density correlates with the power generation amount, it can be said that the smaller the power generation amount, the slower the impurity accumulation rate. Moreover, this is as shown in FIG. Therefore, in the conventional method in which purging is performed when the voltage of the fuel cell becomes lower than a predetermined value, there is a problem that control becomes difficult because the degree of voltage drop differs depending on the difference in current density.

  In this embodiment, the amount of impurities that have permeated the electrolyte membrane from the cathode side and accumulated on the anode side is estimated, and purge is performed when this amount reaches a predetermined value. According to this method, purging can be performed at an appropriate timing as compared with the conventional method.

  Next, the predetermined value in the present embodiment will be described.

  For example, in FIG. 6, if the amount of impurities when the hydrogen real reaction area ratio is 0.8 is set to a predetermined value, the time until the real area ratio becomes 0.8 is set for each current density curve. Corresponds to the time to reach a predetermined value. In the present embodiment, the map shown in FIG. 2 can be obtained by using the reciprocal of this time as the accumulation rate of impurities at each current density.

  The predetermined value can be constant regardless of the value of the current density, but can also be changed according to the value of the current density. For example, in FIG. 6, when the amount of impurities when the substantial reaction area ratio is 0.8 is set to a predetermined value, the time until the intersection of each current density curve and the straight line A reaches the predetermined value. It becomes. On the other hand, when the predetermined value is changed in accordance with the value of the current density, the intersection point between each current density curve and the curve B is the time until the predetermined value is reached. Since the curve B is closer to the actual amount of impurities, it can be purged at a more appropriate timing. Therefore, it is possible to suppress the discharge of hydrogen together with the impurities, and to improve fuel efficiency.

  After setting a predetermined value and creating a map of the relationship between the current density of the fuel cell and the accumulation rate of impurities on the anode side, the amount of impurities accumulated on the anode side is estimated as shown in FIG. The timing for purging is determined.

In the flowchart of FIG. 7, the start is immediately after purging. Thus, the accumulation amount to Q ₁ impurity at this point, can be zero.

  First, the current density of the fuel cell is detected at a predetermined time interval (Δt) (step 101). In the fuel cell system 1 of FIG. 1, it can be detected by the current density measuring means 9. The current density is obtained, for example, by measuring the current for each cell constituting the fuel cell 2 and dividing this by the cell area. Moreover, you may obtain | require by measuring the electric current of the whole cell.

  Next, an accumulation rate v is obtained from the detected current density using a map of the relationship between the current density and the impurity accumulation rate (step 102).

  From the time interval Δt and the accumulation speed v, an accumulation amount Δq that has increased since the start is obtained (step 103). However, Δq = v × Δt.

With increased accumulation amount [Delta] q, it estimates the current accumulation amount Q ₂ (step 104). However, Q ₂ = Q ₁ + Δq.

Then, the storage amount Q ₂ to which the resulting determines whether or not reach the predetermined value QL (step 105). If Q ₂ > QL, the routine proceeds to step 106 where purge is performed. Then, Q ₂ = Q ₁ = 0 and the process returns to the start and the above steps are repeated. On the other hand, if Q ₂ > QL is not satisfied, the value of Q ₁ is updated from zero to Q ₂ , and the process returns to step 101.

According to the above steps, purging is not performed in a state where almost no impurities are accumulated on the anode side. Further, the purge can be performed at an appropriate timing without waiting for the output voltage to decrease. In order to perform this in the fuel cell system 1 of FIG. 1, the data detected by the current density measuring means 9 is sent to the control device 12, and the control device 12 performs the processing of steps 101 to 105 described above. If it is determined that Q ₂ > QL, the purge valve 9 may be opened to perform the purge.

  FIG. 8 shows the relationship between the current density and the accumulated amount of impurities in the fuel cell and the purge timing. As shown in this figure, since the accumulated amount of impurities increases with the passage of time, purging may be performed when the accumulated amount reaches a predetermined value.

  In FIG. 8, when the current density changes, a difference appears in the degree of change in the amount of accumulated impurities. That is, when the current density increases, the degree of change in the accumulation amount increases, and when the current density decreases, the degree of change in the accumulation amount decreases. FIG. 9 shows an example of determining the purge timing by changing the predetermined value according to the current density value.

In the flowchart of FIG. 9, the start is immediately after purging. Thus, the accumulation amount to Q ₁ impurity at this point, can be zero.

  First, the current density of the fuel cell is detected at a predetermined time interval (Δt) (step 201). In the fuel cell system 1 of FIG. 1, it can be detected by the current density measuring means 9.

  Next, using the map of the relationship between the current density and the impurity accumulation rate, the accumulation rate v is obtained from the detected current density, and the predetermined value QL is determined (step 202).

  From the time interval Δt and the accumulation speed v, an accumulation amount Δq increased from the start time is obtained (step 203). However, Δq = v × Δt.

With increased accumulation amount [Delta] q, it estimates the current accumulation amount Q ₂ (step 204). However, Q ₂ = Q ₁ + Δq.

Then, the storage amount Q ₂ to which the resulting determines whether or not reach the predetermined value QL (step 205). If Q ₂ > QL, the routine proceeds to step 206 where purge is performed. Then, Q ₂ = Q ₁ = 0 and the process returns to the start and the above steps are repeated. On the other hand, if Q ₂ > QL is not satisfied, the value of Q ₁ is updated from zero to Q ₂ , and the process returns to step 201.

  According to the above steps, a predetermined value is set according to the value of the current density, and the purge is performed when the accumulated amount (existence amount) of impurities reaches the predetermined value. Therefore, the purge timing is made more appropriate. be able to. Therefore, it is possible to prevent excessive accumulation of impurities or discharge of hydrogen together with the impurities, and to obtain a stable output and high fuel efficiency.

  FIG. 10 shows the relationship between the current density and impurity accumulation amount of the fuel cell and the purge timing. As shown in this figure, the degree of change in the amount of accumulated impurities varies depending on the value of current density. Therefore, by changing the predetermined value according to the value of the current density and performing the purge when the accumulated amount reaches the predetermined value, the purge can be performed at an appropriate timing according to the operation state of the fuel cell.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

  For example, in the above embodiment, the relationship between the current density and the impurity accumulation rate is obtained, the current density of the fuel cell is detected at predetermined time intervals, and the impurity accumulation rate is determined from the obtained value and the above relationship. Asked. On the other hand, in the present embodiment, the power generation amount of the fuel cell may be used instead of the current density.

  That is, in the fuel cell system 1 of FIG. 1, a power generation amount measuring unit is provided instead of the current density measuring unit 9, and the power generation amount of the fuel cell is detected at predetermined time intervals. The amount of power generation is obtained, for example, by determining the value of current flowing through each cell constituting the fuel cell 2. Further, the current value flowing through the entire cell may be obtained. On the other hand, the relationship between the power generation amount and the impurity accumulation rate is obtained in advance, and the impurity accumulation rate is obtained from this relationship and the value of the detected power generation amount. Then, when the accumulation amount estimated from the accumulation speed reaches a predetermined value, the same effect as described above can be obtained by performing the purge. In this case, the purge can be performed at a more appropriate timing by changing the predetermined value in accordance with the power generation amount, as described above. The specific operation can be performed according to the flowcharts shown in FIGS. However, the current density in these figures is replaced with the amount of power generation.

  Further, the accumulated amount of impurities obtained by the present invention can be reflected not only in the purge but also in the supply of the reaction gas and the power generation control of the fuel cell.

It is a block diagram of the fuel cell system in this Embodiment. It is a figure which shows the relationship between the current density of a fuel cell, and the speed | rate which an impurity accumulates on the anode side. It is a figure which shows the relationship between flow path length and the moving speed of gas. It is a figure which shows the relationship between a current density and the moving speed of gas. It is a figure which shows distribution of the gas in the flow path by the side of an anode. It is a figure which shows the time-dependent change of the real reaction area ratio of hydrogen. In this Embodiment, it is a figure which shows an example of the operation | movement which determines the timing of purge. It is an example which shows the relationship between the current density and impurity accumulation amount of a fuel cell, and the timing of purge. In this Embodiment, it is a figure which shows an example of the operation | movement which determines the timing of purge. It is an example which shows the relationship between the current density and impurity accumulation amount of a fuel cell, and the timing of purge.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell system 2 Fuel cell 3 Compressor 4 Humidifier 5 Air pressure regulating valve 6 Hydrogen tank 7 Hydrogen pressure regulating valve 8 Purge valve 9 Current density measuring means 10, 11 Flow path 12 Control device

Claims (8)

In a fuel cell system including a fuel cell that can be operated with a fuel gas supplied to an anode and an oxidant gas supplied to a cathode and the downstream side of the anode being blocked,
Having means for estimating the amount of impurities accumulated on the anode side from the cathode side;
The means for estimating the amount of the impurity obtains in advance a relationship between the current density of the fuel cell and the speed at which the impurity accumulates, detects the current density of the fuel cell every predetermined time, and detects the current density. And a means for estimating the amount of accumulated impurities from the relationship.   2. The fuel cell system according to claim 1, further comprising purge means for discharging impurities from the anode to the outside when the estimated amount of impurities reaches a predetermined value.   The fuel cell system according to claim 2, wherein the predetermined value is changed according to a current density of the fuel cell. In a fuel cell system including a fuel cell that can be operated with a fuel gas supplied to an anode and an oxidant gas supplied to a cathode and the downstream side of the anode being blocked,
Having means for estimating the amount of impurities accumulated on the anode side from the cathode side;
The means for estimating the amount of impurities obtains in advance a relationship between the power generation amount of the fuel cell and the speed at which the impurities accumulate, detects the power generation amount of the fuel cell every predetermined time, and generates the power generation amount. And a means for estimating the amount of accumulated impurities from the relationship.   5. The fuel cell system according to claim 4, further comprising purge means for discharging impurities from the anode to the outside when the estimated amount of impurities reaches a predetermined value.   6. The fuel cell system according to claim 5, wherein the predetermined value is changed according to a current density of the fuel cell. Fuel gas is supplied to the anode and oxidant gas is supplied to the cathode, respectively, and a fuel cell that can be operated in a state where the downstream side of the anode is closed is provided. An impurity accumulation amount estimation method for estimating the amount of impurities accumulated in
Determining the relationship between the current density of the fuel cell and the rate at which the impurities accumulate;
A method for estimating an accumulated amount of impurities in a fuel cell system, comprising: detecting a current density of the fuel cell every predetermined time and estimating the accumulated amount of impurities from the current density and the relationship. Fuel gas is supplied to the anode and oxidant gas is supplied to the cathode, respectively, and a fuel cell that can be operated in a state where the downstream side of the anode is closed is provided. An impurity accumulation amount estimation method for estimating the amount of impurities accumulated in
Determining the relationship between the amount of power generated by the fuel cell and the rate at which the impurities accumulate;
A method for estimating an accumulated amount of impurities in a fuel cell system, comprising: detecting a power generation amount of the fuel cell every predetermined time, and estimating the accumulated amount of impurities from the generated power amount and the relationship.

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