JPH0896825A - Fuel cell power generating system - Google Patents

Abstract

PURPOSE: To operate a fuel cell power generating system at the optimum utilization factor of reaction gas so as to prevent accelerated cell performance deterioration caused by reaction gas diffusion failure and remarkably reduce cell performance deterioration. CONSTITUTION: Load current and voltage of a fuel cell 10 are measured with a measuring device 16, and the measured load current and voltage are recorded as a change with time by corresponding them to operation time. The change with time is compared with change with time of catalyst itself of the fuel cell 10 caused by deterioration, and the condition of the fuel cell 10 is evaluated with a record evaluation device 17. On a basis of the evaluated results, flow rates of fuel and air are controlled with a flow rate control device 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell power generator for stably and reliably operating a fuel cell body.

[0002]

2. Description of the Related Art A fuel cell is a device for directly converting the chemical energy of fuel into electrical energy.
In the structure of this fuel cell, a pair of porous electrodes are usually arranged with an electrolyte in between. The method of extracting the electric output is that one of the pair of electrodes is brought into contact with a gas fuel such as hydrogen and the other electrode is brought into contact with an oxidant such as oxygen, and the electrochemical reaction occurs, whereby the pair of electrodes is I try to extract electrical energy from the space.

The fuel and oxidant necessary to obtain electric energy from the fuel cell will be generically referred to as a reaction gas. The electrolyte sandwiched by the pair of electrodes includes a molten carbonate, an alkaline solution, an acidic solution, a polymer membrane, and the like. The principle of a fuel cell using phosphoric acid as an electrolyte as a typical fuel cell will be described.

FIG. 6 is a block diagram of a unit cell constituting a fuel cell. The electrolyte layer is referred to as the matrix layer 1, and is formed by molding a mineral powder such as a fibrous sheet or silicon carbide using a binder represented by polytetrafluoroethylene (PTFE).

The matrix layer 1 is a porous body composed of pores ranging from 1 micron or less to approximately 10 microns, and has a function of retaining phosphoric acid as an electrolyte. The anode electrode 2 and the cathode electrode 3 are carbonaceous porous electrodes. The anode electrode 2 and the cathode electrode 3 have a porous structure in order to efficiently diffuse the reaction gas necessary for the reaction into the electrode.

Further, these anode electrode 2 and cathode electrode 3 have a catalyst for accelerating the reaction, and the surface in contact with the matrix layer 1 is usually coated with a catalyst having platinum supported on carbon powder. The catalyst layers 4 and 5 are formed.

In the reaction of the fuel cell, a reaction gas, an electrolyte,
Three of the catalysts are needed. In each of the catalyst layers 4 and 5, a so-called three-phase interface composed of the reaction gas, phosphoric acid, and the gas, liquid, and solid of the catalyst is formed, and the electrochemical reaction necessary for the fuel cell proceeds here.

The fuel flow path 6 is a groove that serves as a path for a reaction gas containing hydrogen, and the air flow path 7 is a groove that serves as a path for an oxidant. The fuel or oxidant flows through the respective flow paths 6, 7,
Each of the catalyst layers 4, 5 diffuses in each of the electrodes 2, 3 having a porous structure.
The reaction proceeds by reaching the three-phase interface formed inside.

Hydrogen in the fuel diffuses in the holes of the anode 2 and reaches the three-phase interface formed in the catalyst layer 4 on the anode side. Here, hydrogen gas is dissociated into hydrogen ions and electrons by the action of a catalyst.

The reaction formula is H ₂ → 2H ⁺ + 2e (1)

Hydrogen ions move in the matrix layer 1 holding phosphoric acid and reach the three-phase interface formed in the catalyst layer 5 on the cathode 3 side. On the other hand, the electrons separated by the dissociation of hydrogen gas flow from the anode 2 to the external circuit,
Work through the power load and reach the three-phase interface in the cathode 3.

At the three-phase interface formed in the catalyst layer 5 on the cathode electrode 3 side, the hydrogen ions that have moved from the anode electrode 2 through the matrix layer 1 and the air flow path 7 to the cathode electrode 3 as an oxidant. Oxygen that has diffused inside and electrons that have worked in the external circuit are three-phase interfaces formed in the catalyst layer 5 on the cathode electrode 3 side, and the 4H + 4e + O ₂ → 2H ₂ O (2) The reaction proceeds.

Thus, the reaction in which hydrogen is oxidized to water and the chemical energy at this time is converted into electric energy, and the entire reaction of giving electric energy in an external electric load as a battery is completed.

Generally, a fuel cell is constructed by stacking a plurality of the above unit cells. This battery stack is usually called a stack. When stacking, the unit cells require a separator for ensuring an electrical connection path between the unit cells and for separating the fuel flow path 6 and the air flow path 7.

This separator is generally a thin gas-impermeable flat plate made of a carbon material, but depending on the battery structure, one having a groove in the separator, one having a function of storing phosphoric acid in the separator, or both of them. It has both.

[0016] These are due to the difference in structure in consideration of extending the life of the fuel cell. A gas manifold for flowing a reaction gas to each of the fuel flow path 6 and the air flow path 7 is attached to the stack, and has a structure capable of uniformly supplying each reaction gas to each unit cell.

Further, in order to prevent fuel and air from leaking from the edge portions of the electrodes 2 and 3 having the flow paths 6 and 7 and mixing with each other, the edge portions of the electrodes 2 and 3 have , Gas seals 8 and 9 called edge seals are provided.

In the fuel cell power generator, the reaction gas usually supplied to the stack flows in a larger amount than the theoretical reaction gas amount required for power generation. The value obtained by dividing the theoretical amount of reaction gas required for power generation by the amount of gas actually supplied to the stack is called the reaction gas utilization rate.

In the fuel cell power generation device, the smaller the amount of the reaction gas flowing in excess, that is, the higher the reaction gas utilization rate, the higher the efficiency of the device. From the viewpoint of cell performance, improvement of the reaction gas utilization rate can be enhanced by increasing the diffusivity of fuel or air in the anode 2 or the cathode 3.

On the other hand, from the viewpoint of operation, when the pressure is higher than the normal pressure, the partial pressure of the reaction gas is increased, and the operation can be performed at a high reaction gas utilization rate. As described above, in general, the reaction gas utilization rate of the stack is determined and operated in accordance with the performance of the power generator.

[0021]

The electrical output efficiency of the fuel cell depends on the performance of the output voltage of the cell, but also on the utilization rate of the reaction gas. The higher the reaction gas utilization rate, the higher the efficiency of the battery. By the way, in the reaction of the fuel cell, the reaction gas that has diffused through the pores of the catalyst proceeds at the three-phase interface in the catalyst layers 4 and 5.

That is, in order for the reaction gas to reach the reaction point, diffusion in the pores, dissolution in phosphoric acid, and diffusion in phosphoric acid are necessary. The actual three-phase interface is the catalyst layer 4, 5 is at the interface between the electrolyte membrane covering the surface of 5 and the catalyst.

This is because the reaction gas has the property of being dissolved in phosphoric acid, which allows the original gas, liquid,
It is possible to have a reaction interface larger than the three-phase interface made of solid, and to exhibit excellent reactivity.

By the way, phosphoric acid as an electrolyte is a liquid,
The anode 2 and the cathode 3 are porous bodies having small holes. In general, liquid has the property of penetrating into small pores. The force that works for this penetration is called capillary force. The smaller the pores, the stronger the capillary force is, and the larger the force of attraction, but the smaller the pores, the more time it takes for permeation.

Each of the catalyst layers 4 and 5 is subjected to a water repellent treatment for repelling the liquid so that the electrolyte does not excessively enter the pores at that time. The catalyst layers 4 and 5 maintain good gas diffusibility due to the water repellency.

On the other hand, in each of the catalyst layers 4 and 5, a large three-phase interface is required to promote the reaction. That is, it is required to form a larger three-phase interface by permeating a proper amount of phosphoric acid. Therefore, it is impossible to provide the catalyst layers 4 and 5 with water repellency that does not accept phosphoric acid.

At present, catalyst layers 4 and 5 having appropriate wettability with phosphoric acid have been developed so that the ability of the catalyst can be sufficiently brought out. However, the catalyst layers 4 and 5 have not been developed yet, because they can maintain appropriate wettability and can continue to bring out the ability of the catalyst. That is, since the catalyst layers 4 and 5 are required to have appropriate wettability, the permeation of phosphoric acid by the capillary force is allowed as the fuel cell is operated,
The pores in the catalyst layers 4 and 5 are filled with phosphoric acid.

FIG. 7 shows a characteristic deterioration curve of a typical fuel cell with time. The decrease in battery voltage is roughly divided into two factors. One of them is a decrease in the activity of the catalyst itself,
The other one is the deterioration of characteristics due to poor diffusion of the reaction gas due to the progress of wetting of the catalyst.

The pores in the catalyst layers 4 and 5 are indispensable for diffusion of the reaction gas as described above. The diffusivity of the reaction gas is far inferior when it is dissolved and diffuses in the liquid phase, as compared with when it proceeds to the reaction point in a gaseous state.

This is because the amount of gas that can be dissolved in the liquid phase is limited by the partial pressure of the dissolved gas in the gas phase, as indicated by Henry's law. In other words, the total diffusion rate is determined by the dissolution and diffusion of the reaction gas into phosphoric acid in the process until the reaction gas reaches the reaction point.

Therefore, the pores of the catalyst phases 4 and 5 are filled with phosphoric acid, resulting in poor diffusion. Since the reaction gas is dissolved in phosphoric acid and diffused, the diffusion rate is suppressed. By the way, this poor diffusion of the reaction gas does not occur from the initial operation of the fuel cell power generator. As shown in FIG. 7, for a while after the operation is started, the time range in which the deterioration of the characteristics due to the deterioration of the catalyst itself becomes the decrease of the battery voltage continues.

However, as the operation of the fuel cell power generator progresses, the reaction gas diffusion failure progresses, which affects the cell characteristics. Therefore, when the catalyst is operated for a while, it enters the voltage reduction region where the deterioration of the catalyst itself and the deterioration of the characteristics due to the progress of the defective diffusion of the reaction gas are combined to cause the decrease of the battery voltage.

The operating time until the voltage drop due to the reaction gas diffusion failure appears is different depending on the specifications of the battery and the operating method, and it is difficult to accurately predict the generation time during this period.

When a load is applied to take out electric energy from the fuel cell, it is caused by resistance polarization of loss due to electric resistance of the cell from thermodynamically-calculated logic voltage, reaction rate due to catalytic activity and magnitude of reaction amount. Active polarization of loss,
The cell voltage drops due to diffusion polarization of the loss due to the diffusion rate of the reaction gas to the reaction point.

The magnitude of the resistance polarization depends on the battery structure such as the thickness of the electrolyte. The magnitude of the diffusion polarization is that the reaction gas diffuses through diffusion paths such as pores in the catalyst layers 4 and 5,
It depends on the speed to the reaction point and the amount of reaction gas.

As described above, the catalyst layers 4 and 5 initially having a sufficient diffusion path are allowed to permeate phosphoric acid by capillary force during the operation, and the pores in the catalyst layers 4 and 5 are filled with phosphoric acid. By blocking the path of the reaction gas, the amount of the reaction gas reaching the reaction point per unit time decreases, and the diffusion polarization increases.

As a result, the voltage loss from the theoretical voltage of the battery increases, and the output voltage decreases even with the same load.
Now, in the fuel cell power generator, output control is adopted so as to obtain a target cell output. The output control is to control the operation so that the output of the battery, that is, the product of the current and the voltage taken out from the power generation device becomes constant.

In this control system, when the output obtained at a certain current becomes large due to the loss in the battery and the original output cannot be obtained at that current, the current is increased to obtain the current and voltage. The output is maintained by making the product the initial value.

Therefore, when the battery deteriorates with operation and the voltage drops, control is performed so that a larger current is gradually obtained to obtain the same battery output. When the current of the battery is increased, it is required that the amount of diffusion of the reaction gas to the reaction point also increases with the increased current.

Therefore, a larger amount of reaction gas is added to the catalyst layer 4,
It has to pass through 5 pores and reach the reaction point, ie the three-phase interface. However, in the catalyst layers 4 and 5, the pores are filled with phosphoric acid as described above, and the diffusion and alienation of the reaction gas proceeds with the operation of the battery.

Due to the increase of the load, the increase of the required reaction gas and the decrease of the gas diffusibility in the catalyst layers 4 and 5, a shortage of the reaction gas occurs in a part of the anode electrode 2 and the cathode electrode 3.

The shortage of the reaction gas not only causes the voltage of the battery to be remarkably lowered, but also the current is concentrated at the air inlet where the concentration of the reaction gas is high, particularly the oxygen concentration is high, and the temperature rises, or the fuel is insufficient. Produces a lack of protons in the electrolyte.

In particular, the lack of protons may cause electrolytic corrosion of carbon, which is a constituent material of the battery, by the reaction of C + 2H ₂ O → CO ₂ + 4H + 4e (3).

Such a phenomenon not only accelerates the deterioration of the battery characteristics with the operation of the battery, but also induces a reaction gas leak, which becomes a factor for alienating safety. Therefore, if the diffusivity of the reaction gas is left unattended and the battery is continuously operated under the condition that the reaction gas utilization rate is constant, not only the characteristics of the battery are accelerated, but also the battery may be damaged. .

Therefore, the present invention prevents the acceleration of the deterioration of the battery characteristics due to the poor diffusion of the reaction gas, and can operate at the optimum reaction gas utilization rate so that the deterioration of the battery characteristics can be suppressed as much as possible. The purpose is to provide.

[0046]

According to a first aspect of the present invention, in a fuel cell power generator for supplying a fuel containing hydrogen and an oxidant to a fuel cell and converting the fuel cell into an electric output, load current and voltage of the fuel cell are changed. The measuring means for measuring and the load current and voltage measured by the measuring means are recorded as a change with time corresponding to the operating time, and the change with time and a healthy change with time in the cell output of the fuel cell are compared. And a flow rate control means for controlling the flow rate of at least one of the fuel and the oxidant in accordance with the evaluation result of the record evaluation means. It is a power generator.

According to the second aspect, the record evaluation means records the change with time before the fuel cell is stopped and after the fuel cell is restarted,
It has a function of evaluating the state of the fuel cell by comparing this change with time and the sound cell output of the fuel cell with time.

According to a third aspect of the present invention, in a fuel cell power generator that supplies a fuel containing hydrogen and an oxidant to a fuel cell and converts it into an electric output, the load current, voltage, cell cooling water temperature, reaction of the fuel cell. Measurement calculation means for measuring or calculating the gas utilization rate to obtain fuel cell information, data standardization means for standardizing the fuel cell information obtained by this measurement calculation means, and standardization by this data normalization means A data recording means for recording the obtained data as a change with time of the fuel cell,
A record evaluation unit for evaluating the state of the fuel cell by comparing the time-dependent change of the fuel cell recorded in the data recording unit and the time-dependent change of the sound cell output of the fuel cell, and a record evaluation unit according to the diagnosis result of the record evaluation unit. And a flow rate control unit that controls the flow rate of at least one of the fuel and the oxidant, and a fuel cell power generation device that achieves the above object.

According to the fourth aspect of the present invention, in a fuel cell power generator for supplying a fuel containing hydrogen and an oxidant to a fuel cell and converting it into an electric output, voltages at two desired points with different load currents of the fuel cell are applied. A measuring means for measuring and a record evaluating means for receiving the voltage at two desired points having different load currents of the fuel cell measured by the measuring means and judging deterioration of the fuel cell based on the change with time of the slope of the voltage with respect to these load currents. And a flow rate control means for controlling each flow rate of fuel or air according to the evaluation result of the recording evaluation means.

According to a fifth aspect of the present invention, in a fuel cell power generator for supplying a fuel containing hydrogen and an oxidant to a fuel cell and converting the fuel cell into an electric output, a measuring means for measuring a load current and a voltage of the fuel cell, Depending on the load current measured by the measuring means, the fuel or oxidant is used at a reaction gas utilization rate slightly smaller than the critical reaction gas utilization rate at which the fuel or oxidant cannot be supplied to the three-phase interface of each current measured in advance. And a suitable reaction gas utilization rate control means for controlling the flow rate of at least one of the two.

[0051]

According to the present invention, the load current and voltage of the fuel cell are measured, and the measured load current and voltage are recorded as a change with time corresponding to the operating time. The state of the fuel cell is evaluated by comparing various cell output changes with time, and the flow rate of at least one of the fuel and the oxidant is controlled according to the evaluation result. That is,
By detecting the deterioration state and operating state of the fuel cell by measuring the load current and voltage of the fuel cell, and adjusting the reaction gas amount of the fuel or oxidant supplied to the fuel cell to an amount suitable for the situation of the fuel cell, Stabilize the characteristics of fuel cells.

According to the second aspect of the present invention, the change with time before and after the restart of the fuel cell is recorded, and the change with time and the sound cell output with time of the fuel cell are compared to determine the state of the fuel cell. By evaluating, it is possible to judge whether or not the cell voltage has dropped due to the start and stop of the fuel cell, by comparing the cell characteristics before and after the fuel cell is stopped, and it is possible to continuously evaluate the characteristics from the previous operation. It can be corrected to be possible.

According to claim 3, the load current of the fuel cell,
Measure or calculate the voltage, cell cooling water temperature, and reaction gas utilization rate, normalize the information of these fuel cells, and record them as changes over time in the fuel cell. Evaluate the state of the fuel cell by comparison,
The flow rate of at least one of the fuel and the oxidant is controlled according to the evaluation result. As a result, when power generation cannot always be performed under constant conditions, it is possible to evaluate the characteristic deterioration state of the fuel cell between different currents and operating conditions.

According to the fourth aspect, the voltage of two desired points having different load currents of the fuel cell is captured, and the deterioration of the fuel cell is captured by the change with time of the slope of the voltage with respect to each load current to evaluate the fuel cell. As a result, it is not necessary to standardize the current for evaluating the condition of the fuel cell, and it is possible to determine the deterioration due to the leakage of the fuel cell.

According to the fifth aspect, the load current and voltage of the fuel cell are measured, and according to the measured load current,
The flow rate of at least one of the fuel and the oxidant is controlled to a reaction gas utilization rate slightly smaller than the critical reaction gas utilization rate at which the fuel or the oxidant cannot be supplied to the three-phase interface of each current measured in advance. As a result, the reaction gas utilization rate adopted depending on the load current can be varied, and it is possible to cope with different sensitivity of the influence of the reaction gas utilization rate at each load current.

[0056]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a fuel cell power generator. The fuel cell 10 has a pair of porous electrodes sandwiching an electrolyte, and one of the pair of electrodes is contacted with a gaseous fuel such as hydrogen, and the other electrode is contacted with an oxidant such as oxygen such as air. An electrical energy is taken out from between a pair of electrodes by an electrochemical reaction caused by the contact.

The fuel and oxidant necessary to obtain electric energy from the fuel cell 10 are collectively referred to as the reaction gas as described above. An inverter 11 is connected to the fuel cell 10.

The fuel supply line 12 and the air supply line 13 of the fuel cell 10 are provided with flow rate adjusting valves 14 and 15, respectively. On the other hand, the measuring device 16
Has a function of measuring the load current of the fuel cell 10 and the voltage at that time.

The record evaluation device 17 receives the load current of the fuel cell 10 measured by the measuring device 16 and the voltage of the voltage at that time, and outputs the load current and voltage to the fuel cell 10.
It is recorded as a time-dependent change corresponding to the operating time of, and this time-dependent change is compared with the time-dependent change in the sound cell output of the fuel cell 10, that is, the time-dependent change due to the deterioration of the catalyst itself of the fuel cell 10. It has a function of evaluating the state of the fuel cell 10.

The flow rate control device 18 controls the flow rate control valves 14, 1 of the fuel or air according to the evaluation result of the recording evaluation device 17.
5 has a function of controlling at least one of the flow rate control valves 14 or 15.

The fuel cell power generator is equipped with auxiliary equipment such as a compressor, a blower, and a fuel reformer for sending out a reaction gas for power generation operation. These auxiliary machines usually do not have an excessive capacity in terms of maintaining high power generation efficiency. Nevertheless, in addition to ensuring the target power generation efficiency up to a predetermined operating time, a design is required that can predict deterioration of the fuel field 10 and maintain the rated output at the end of the battery life.

Next, the operation of the apparatus configured as described above will be described. The flow rate control device 18 is provided for each flow rate control valve 1
By controlling the opening degrees of 4 and 15, the reaction gas amount of the fuel and air supplied to the fuel cell 10 is set to a predetermined flow rate. That is, the amount of reaction gas supplied to the fuel cell 10 is
A predetermined reaction gas utilization rate is set according to the output of the fuel cell 10.

When the reaction gas of fuel and air is supplied to the fuel cell 10 in this manner, the fuel cell 10 brings one electrode into contact with a gaseous fuel such as hydrogen and the other electrode into contact with air such as oxygen. The electrochemical reaction caused by the reaction causes electric energy to be obtained from between the pair of electrodes.

In this state, the measuring device 16 is the fuel cell 1
The load current value of 0 and the voltage value at that time are measured and transmitted to the recording evaluation device 17. The record evaluation device 17 receives the load current value of the fuel cell 10 and the voltage value at that time transmitted from the measuring device 16, and changes the load current value and the voltage value with time according to the operating time of the fuel cell 10. To record as.

The recording / evaluating device 17 compares the recorded changes with time with the previously stored changes due to deterioration of the catalyst itself of the fuel cell 10, and the characteristics of the fuel cell 10 are not deviated from the deterioration of the catalyst itself. To monitor.

By the way, FIG. 2 is a diagram showing the relationship between the reaction gas utilization rate and the fuel cell voltage. Diffusion failure is fuel cell 1
The effect on the voltage of 0 will be described in detail. When the utilization rate of the reaction gas is increased, the diffusion rate of the reaction gas is decreased and the fuel cell voltage is decreased.

Thus, when the deterioration of the fuel cell 10 progresses, the reaction gas diffusion failure occurs, and the characteristic deteriorates, the reaction gas responsiveness of the initial cell voltage is lower than that of the reaction gas and the large voltage is used. It becomes a curve after the deterioration of the characteristics.

For example, the voltage of the fuel cell 10 of the fuel cell power generator operating at a reaction gas utilization rate of 80% is the initial voltage of the fuel cell 10 in which the cell voltage has dropped due to the deterioration of the characteristics due to defective diffusion of the reaction gas. In order to maintain it, it is sufficient to increase the amount of gas supplied to the fuel cell 10 and reduce the utilization rate of the reaction gas to operate at a little over 70%.

That is, the characteristic deterioration due to the poor diffusion of the reaction gas can be maintained at the voltage of the fuel cell 10 by adjusting the reaction gas utilization rate. Therefore, the flow rate control device 18 controls the opening degree of at least one flow rate control valve 14 or 15 of the fuel or air flow rate control valves 14 or 15 according to the evaluation result of the recording evaluation device 17 to control the fuel or air flow rate control valve 14 or 15. Adjust the air flow rate.

More specifically, if the result of the evaluation by the recording evaluation device 17 is that the voltage drop of the fuel cell 10 is on the voltage drop curve due to the deterioration of the catalyst itself, it was determined in advance by the initial design. The flow rate control valves 14 and 15 are operated so as to achieve the reaction gas utilization rate.

The actual voltage drop of the fuel cell 10 is monitored,
When the amount of decrease begins to deviate from the decrease in the voltage of the catalyst itself, the flow rate control device 18 controls the fuel cell 10 so that the cell voltage of the fuel cell 10 falls on a predetermined voltage deterioration curve of the catalyst itself. The flow rate control valves 14 and 15 are operated to increase the amount of reaction gas supplied to the fuel cell 10.

That is, the reaction gas utilization rate is determined by the fuel cell 10
It is lowered according to the deterioration situation. Thus, the first
In the embodiment, the load current and voltage of the fuel cell 10 are measured, and the measured load current and voltage are recorded as a change with time corresponding to the operating time. Since the state of the fuel cell 10 is evaluated by comparing with the change with time due to deterioration and the flow rate of the fuel or air is controlled according to the evaluation result, the state of the cell voltage drop of the fuel cell 10 is determined by the fuel cell power generation. It is possible to monitor while operating the device, and it is possible to quickly detect the occurrence of reaction gas diffusion failure.

By increasing the reaction gas, it is possible to prevent local concentration of the load of the fuel cell 10 due to poor diffusion of the reaction gas, and to maintain the power generation reaction utilizing the entire electrode surface.

On the other hand, the output voltage of the fuel cell 10 can be increased by increasing the reaction gas amount, and the output of the fuel cell 10 can be maintained without increasing the load current of the fuel cell 10.

Therefore, the deterioration of the fuel cell 10 progresses with time, and the characteristic deterioration due to the poor diffusion of the reaction gas in the catalyst layer starts as described above. If this is left unattended, local concentration of the fuel cell load will occur and the progress of deterioration will be accelerated.
There is also the danger of damage due to corrosion of the.

By operating the fuel cell 10 in a state in which deterioration of the fuel cell progresses and defective diffusion of the reaction gas occurs, and maintaining a predetermined power generation output by increasing the amount of reaction gas supplied to the fuel cell 10, Fuel cell 10 with no rise
Can be prevented from being locally deteriorated.

As described above, the change of the fuel cell 10 over time is detected, the state of the fuel cell 10 is detected, and the reaction gas required for the reaction is formed on the three-phase sea surface involved in the cell reaction according to the reaction gas diffusivity in the catalyst layer. The fuel cell 10 can be operated at an appropriate reaction gas utilization rate so that the fuel cell 10 can be quickly reached, and the characteristics of the fuel cell 10 can be stabilized.

Next, a second embodiment of the present invention will be described. The same parts as those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted. The record evaluation device 17 is used for the fuel cell 1.
It is assumed to have a function of evaluating the state of the fuel cell 10 by recording the changes over time before the stop of 0 and after the restart, and comparing the changes over time with the changes due to the deterioration of the catalyst itself of the fuel cell 10. .

That is, at times, the characteristics of the fuel cell 10 may be deteriorated due to its starting and stopping.
In some cases, this deterioration of the characteristics may be diagnosed and evaluated by the voltage decrease of the fuel cell 10 during a predetermined continuous operation time.

Further, it is possible to judge whether or not the cell voltage has dropped due to the start and stop of the fuel cell 10 by comparing the cell characteristics before the stop and after the restart so that continuous evaluation of the characteristics from the previous operation can be performed. In some cases, it may be necessary to correct it.

Therefore, the recording / evaluating apparatus 17 records the changes with time before the fuel cell 10 is stopped and after it is restarted, and compares the changes with time with the sound cell output changes with time of the fuel cell 10. By evaluating the state of No. 10, it is possible to determine whether or not the cell voltage has dropped due to the start and stop of the fuel cell 10 by comparing the cell characteristics before the fuel cell 10 is stopped and after the fuel cell 10 is restarted. It can be corrected so that continuous evaluation on characteristics can be performed.

Next, a third embodiment of the present invention will be described. The same parts as those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted. FIG. 3 is a block diagram of a recording evaluation system of the fuel cell power generator.

The measuring device 20 measures the load current I, the voltage V, the cell cooling water temperature T, the fuel flow rate and the air flow rate of the fuel cell 10, and the reaction gas utilization rate based on the fuel flow rate and the air flow rate. And has a function of obtaining information of the fuel cell 10.

The data standardization device 21 is the measuring device 2
It has the function of converting the load current I voltage V, the cell cooling water temperature T, and the reaction gas utilization rate information of the fuel cell 10 obtained by 0 into a predetermined temperature current and reaction gas utilization rate to standardize the data. are doing.

The data recording device 22 has a function of recording the data standardized by the data normalizing device 21 as a change with time of the fuel cell 10. Then, an evaluation device that evaluates the state of the fuel cell by comparing the time-dependent change of the fuel cell recorded in the data recording device 22 with the time-dependent change of the sound cell output of the fuel cell, and the evaluation result of the evaluation device A flow rate control device for controlling the flow rate control valves 14 and 15 is provided.

Next, the operation of the apparatus configured as described above will be described. In a state where the fuel cell 10 is supplied with a predetermined flow rate of fuel and air and electric energy is obtained between the pair of electrodes of the fuel cell 10, the measuring device 20 measures the load current I, the voltage V, the cell voltage of the fuel cell 10. The cooling water temperature T, the fuel flow rate and the air flow rate are measured, and the reaction gas utilization rate is calculated based on the fuel flow rate and the air flow rate to obtain the information of the fuel cell 10.

As described above, the load current I, the voltage V, the cell cooling water temperature T of the fuel cell 10 are measured, and the reaction gas utilization rate is obtained when the operating condition of the fuel cell differs depending on the necessity. However, this is performed to improve the monitoring accuracy of the fuel cell 10.

The load current I, the voltage V, the cell cooling water temperature T of the fuel cell 10 measured by the measuring device 20, and the calculated reaction gas utilization rate are shown in the data standardization device 21.
Be transmitted to.

This data standardization device 21 is used for the measuring device 2
The information of the load current I voltage V, the cell cooling water temperature T, and the reaction gas utilization rate of the fuel cell 10 obtained from 0 is converted into a predetermined temperature current and reaction gas utilization rate to standardize the data.

The data recording device 22 records the data standardized by the data normalizing device 21 as a change with time of the fuel cell 10. Then, this data recording device 22
The state of the fuel cell 10 is evaluated by comparing the time-dependent change of the fuel cell 10 and the time-dependent change of the healthy cell output of the fuel cell, and the flow rate control valves 14, 14 are evaluated according to the evaluation result.
The opening degree of 15 is controlled.

That is, when the voltage drop of the fuel cell 10 is on the voltage drop curve due to the deterioration of the catalyst itself,
The flow rate control valves 14 and 15 are operated so that the reaction gas utilization rate determined in advance by the initial design is achieved.

The actual voltage drop of the fuel cell 10 is monitored,
When the amount of decrease begins to deviate from the decrease in the voltage of the catalyst itself, the flow rate control device causes the flow rate control device to adjust the flow rate so that the cell voltage of the fuel cell 10 is on the predetermined voltage deterioration curve of the catalyst itself. The fuel cell 10 is operated by operating the control valves 14 and 15.
Increase the amount of reaction gas supplied to.

As described above, in the third embodiment,
The load current, voltage, cell cooling water temperature, and reaction gas utilization rate of the fuel cell 10 are measured or calculated, the information of the fuel cell 10 is standardized, and recorded as a change with time of the fuel cell 10,
Since the state of the fuel cell 10 is evaluated by comparing this time-dependent change with the sound cell output time-dependent change of the fuel cell 10, and the flow rates of fuel and air are controlled according to the evaluation result, it is always constant. When power cannot be generated under the conditions, it is possible to diagnose the state of deterioration of the characteristics of the fuel cell 10 between different currents and operating conditions.

By normalizing the data, not by standardizing the measurement of the characteristic change of the fuel cell 10 over time, it is possible to capture the timing at which the reaction gas amount is increased to prevent the characteristic acceleration of the fuel cell 10. You can easily.

Therefore, it is possible to grasp the state of the fuel cell 10 without affecting the operation of the fuel cell 10 by the change of the fuel cell 10 with time, whereby the detected state of the fuel cell 10, that is, in the catalyst layer. It is possible to operate at an appropriate reaction gas utilization rate that allows the reaction gas required for the reaction to reach the three-phase interface involved in the battery reaction promptly according to the reaction gas diffusivity.

Next, a fourth embodiment of the present invention will be described. FIG. 4 is a configuration diagram of the fuel cell power generator. The measuring device 30 has a function of measuring voltages at two desired points with different load currents of the fuel cell 10.

The evaluation device 31 receives two desired voltage points having different load currents of the fuel cell 10 measured by the measuring device 30, and determines the deterioration of the fuel cell 10 by the change with time of the slope of the voltage with respect to these load currents. It has the function to do.

The flow control device 32 has a function of controlling at least one flow control valve 14 or 15 of the fuel or air flow control valves 14 and 15 according to the evaluation result of the evaluation device 31.

With such a configuration, the measuring device 30
Measures the voltage at two desired points with different load currents of the fuel cell 10 and transmits it to the evaluation device 31. This evaluation device 31
Receives a desired voltage at two different load currents of the fuel cell 10 measured by the measuring device 30, and determines the deterioration of the fuel cell 10 based on the change over time in the slope of the voltage with respect to these load currents.

The flow rate control device 32 is the evaluation device 3
Each flow control valve of fuel or air according to the evaluation result of 1
4 and 15 are controlled. That is, in the case where the voltage drop curve due to the deterioration of the catalyst itself is present, each flow rate control valve 1 is controlled so that the reaction gas utilization rate determined in advance in the initial design is achieved.
The operation is performed by operating Nos. 4 and 15.

The actual voltage drop of the fuel cell 10 is monitored,
When the amount of decrease begins to deviate from the decrease in the voltage of the catalyst itself, the flow rate control device 18 controls the fuel cell 10 so that the cell voltage of the fuel cell 10 falls on a predetermined voltage deterioration curve of the catalyst itself. The flow rate control valves 14 and 15 are operated to increase the amount of reaction gas supplied to the fuel cell 10.

By the way, the measuring instrument 1 of the third embodiment described above.
Ideally, the load current of the fuel cell 10 measured by 6 and the voltage at that time are standardized with high accuracy.
When converting the battery voltage to another current, the current / voltage curve differs depending on the fuel cell state, so the battery state determination prediction of what kind of current / voltage curve should be used is included, which may increase the diagnostic error. is there.

In order to improve the accuracy, a method is used in which the cell voltage of different current is measured without changing the current and the deterioration of the fuel cell 10 is detected by the change with time of the slope with respect to the current.

In such a method, it is not necessary to standardize the current for diagnosing the condition of the fuel cell 10, and the deterioration due to the wetting of the fuel cell 10 can be caught. The slope of the battery voltage due to different currents always shows the same value as that due to the deterioration of the catalyst itself. However, when the reaction gas diffusion failure due to the wetting signal progresses, the inclination becomes large.

Therefore, the amount of the reaction gas is adjusted by controlling the flow rate of the suitable reaction gas so that the time-dependent change in the slope of the voltage with respect to the load current does not occur. As described above, in the fourth embodiment, the voltages at desired two points having different load currents of the fuel cell 10 are captured, and the deterioration of the fuel cell 10 is determined by the temporal change of the slope of the voltage for each load current. Therefore, when power generation cannot always be performed under constant conditions, characteristic deterioration of the fuel cell 10 can be diagnosed from cell voltages having different current values.

The timing at which the reaction gas amount is increased and acceleration of characteristic deterioration of the fuel cell 10 is prevented only by normalizing the data, not by standardizing the voltage measurement, of the characteristic change of the fuel cell 10 over time. Can be easily captured.

Therefore, the state of the fuel cell 10 can be grasped without affecting the operation of the fuel cell 10 by the change with time of the fuel cell 10, and the state of the fuel cell 10 detected by this, that is, in the catalyst layer It is possible to operate at an appropriate reaction gas utilization rate that allows the reaction gas required for the reaction to quickly reach the three-phase interface involved in the battery reaction according to the reaction gas diffusibility.

Next, a fifth embodiment of the present invention will be described. The same parts as those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted. FIG. 5 is a configuration diagram of the fuel cell power generator.

The measuring device 40 has a function of measuring the load current and voltage of the fuel cell 10. The suitable reaction gas utilization rate control device 41 is slightly smaller than the critical reaction gas utilization rate at which fuel or air cannot be supplied to the three-phase interface of each current measured in advance in accordance with the load current measured by the measuring device 40. It has a function of controlling the flow rate of at least one of fuel and air depending on the reaction gas utilization rate.

With such a configuration, the fuel cell 10 is supplied with a predetermined flow rate of fuel and air, and electric energy is obtained between the pair of electrodes of the fuel cell 10.
The measuring device 20 measures the load current and voltage of the fuel cell 10 and transmits the measured load current and voltage to the appropriate reaction gas utilization rate control device 41.

The suitable reaction gas utilization rate control device 41 is
Depending on the load current measured by the measurement device 40, the fuel or the reaction gas may be adjusted so that the reaction gas utilization rate is slightly smaller than the critical reaction gas utilization rate at which the fuel or air cannot be supplied to the three-phase interface of each current measured in advance. Air flow control valves 14,
One or both of 15 are controlled.

That is, when the voltage drop curve is due to the deterioration of the catalyst itself, the flow rate control valves 14 and 15 are adjusted so that the reaction gas utilization rate is determined in advance by the initial design.
To operate the car.

The actual voltage drop of the fuel cell 10 is monitored,
When the amount of decrease begins to deviate from the decrease in the voltage of the catalyst itself, the flow rate control device 41 causes each of the fuel cells 10 so that the cell voltage of the fuel cell 10 falls on a predetermined voltage deterioration curve of the catalyst itself. The flow rate control valves 14 and 15 are operated to increase the amount of reaction gas supplied to the fuel cell 10.

By the way, the amount of reaction gas fed into the three-phase interface of the fuel cell 10 increases as the load on the fuel cell 10 increases. Therefore, when the reaction gas is operated at a constant utilization rate, the larger the battery load is, the more the characteristics are deteriorated due to the influence of the poor diffusion of the reaction gas due to the progress of wetting of the catalyst layer.

On the other hand, when the load on the fuel cell 10 is small, it is possible to operate at a higher reaction gas utilization rate than when the load is large. Therefore, with the above configuration, the fuel cell 10 can be operated at an appropriate reaction gas utilization rate according to the current of the fuel cell 10. When the load is small, it is possible to increase the reaction gas utilization rate. On the contrary, when the load is large, the reaction gas utilization rate is decreased to operate.

That is, the proper reaction gas utilization rate control device 4
Reference numeral 1 denotes a reaction gas supplied to the fuel cell 10
Depending on the load current of 0, each flow rate is set so that the reaction gas amount is set to a reaction gas utilization rate that is slightly smaller than the critical reaction gas utilization rate at which the reaction gas cannot be supplied to the three-phase interface of each current measured in advance. The opening degree of the control valves 14 and 15 is controlled.

As a result, the reaction gas utilization factor adopted depending on the current can be varied, and the sensitivity of the reaction gas utilization factor to each current can be different.

Further, by inputting the difference in the influence of the cell deterioration due to the current to the appropriate reaction gas utilization rate control device 41 as comparison data in advance, the reaction gas is increased in accordance with the deterioration of the fuel cell 10 to accelerate the deterioration. Also in the case of prevention, it is possible to take into consideration the difference in deterioration due to current.

As described above, in the fifth embodiment,
The load current and voltage of the fuel cell 10 are measured, and the reaction is slightly smaller than the critical reaction gas utilization rate at which fuel or air cannot be supplied to the three-phase interface of each current measured in advance in accordance with the measured load current. Since the flow rate of at least one of fuel and air is controlled for the gas utilization rate,
The amount of reaction gas flowing on the surface of the fuel cell 10 can be suppressed, and the amount of loss of phosphoric acid carried out by the reaction gas can be reduced.

Further, the efficiency of auxiliary equipment such as a compressor, a blower, and a reformer required for power generation of the fuel cell 10 can be improved, and the power generation efficiency under low load can be increased. Therefore, by adjusting the reaction gas utilization rate according to the operating conditions of the fuel cell 10, it is not necessary to adjust the reaction gas required for the reaction to the three-phase interface involved in the cell reaction in the catalyst layer. It is possible to operate at an appropriate reaction gas utilization rate that does not cause excessive excess.

The present invention is not limited to the first to fifth embodiments described above, but may be modified as follows. For example, in the fuel cell power generator that adjusts the amount of reaction gas supplied to the fuel cell 10 according to the electric output as described above, when increasing the electric output, the reaction gas flow rate is adjusted before the increase of the electric load. Alternatively, when the electrical output is reduced, the electrical load may be reduced prior to the adjustment of the reaction gas flow rate.

[0122]

As described above in detail, according to the present invention, the optimum use of the reaction gas can be prevented so that the deterioration of the battery characteristics due to the poor diffusion of the reaction gas can be prevented and the deterioration of the battery characteristics can be suppressed as much as possible. A fuel cell power generator that can be operated at a high rate can be provided.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of a fuel cell power generator according to the present invention.

FIG. 2 is a diagram showing changes over time in a typical fuel cell.

FIG. 3 is a configuration diagram of a recording evaluation system showing a third embodiment of the fuel cell power generator according to the present invention.

FIG. 4 is a configuration diagram showing a fourth embodiment of a fuel cell power generator according to the present invention.

FIG. 5 is a configuration diagram showing a fifth embodiment of a fuel cell power generator according to the present invention.

FIG. 6 is a configuration diagram of a unit cell that constitutes a fuel cell.

FIG. 7 is a view showing a typical characteristic deterioration of a fuel cell.

[Explanation of symbols]

10 ... Fuel cell, 14, 15 ... Flow control valve, 16, 2
0, 30, 40 ... Measuring device, 17 ... Recording evaluation device, 18
... Flow rate control device, 21 ... Data standardization device, 22 ... Data recording device, 31 ... Evaluation device, 32 ... Flow rate control device, 4
1. Appropriate reaction gas utilization rate control device.

Claims (5)

[Claims] 1. A fuel cell power generator for supplying a fuel containing hydrogen and an oxidant to a fuel cell to convert the fuel cell into an electric output, and a measuring means for measuring a load current and a voltage of the fuel cell, and the measuring means. Recording and evaluating means for evaluating the state of the fuel cell by recording the measured load current and voltage as a change with time corresponding to the operating time, and comparing this change with time with a healthy change in cell output of the fuel cell. And a flow rate control means for controlling the flow rate of at least one of the fuel and the oxidant according to the evaluation result of the recording evaluation means. 2. The record evaluating means records a change with time before and after restarting the fuel cell, and compares the change with time with a sound change with time of a healthy cell output of the fuel cell. The fuel cell power generator according to claim 1, having a function of evaluating a state. 3. A fuel cell power generator for supplying a fuel containing hydrogen and an oxidant to a fuel cell to convert the fuel cell into an electric output, wherein the load current, voltage, cell cooling water temperature, and reaction gas utilization rate of the fuel cell are measured. A measurement calculation means for measuring or calculating the fuel cell information, a data standardization means for standardizing the fuel cell information obtained by the measurement calculation means, and a data standardization means for normalizing the fuel cell information. Data recording means for recording data as the time-dependent change of the fuel cell, and comparing the time-dependent change of the fuel cell recorded in the data recording means with the sound cell output time-dependent change of the fuel cell, A recording evaluation means for evaluating the state, and a flow rate control means for controlling the flow rate of at least one of the fuel and the oxidant according to the diagnosis result of the recording evaluation means are provided. Fuel cell power generation system, wherein the door. 4. A fuel cell power generator for supplying a fuel containing hydrogen and an oxidant to a fuel cell to convert the fuel cell into an electric output, and measuring means for measuring voltages at two desired points having different load currents of the fuel cell. Record evaluation means for receiving two desired voltage points having different load currents of the fuel cell measured by the measuring means, and determining deterioration of the fuel cell by aging of a slope of voltage with respect to these load currents; And a flow rate control means for controlling each flow rate of the fuel or the air according to the evaluation result of the recording evaluation means. 5. A fuel cell power generator for supplying a fuel containing hydrogen and an oxidant to a fuel cell to convert the fuel cell into an electric output, and a measuring means for measuring a load current and a voltage of the fuel cell, and the measuring means. Depending on the measured load current, the fuel or the oxidant is set to a reaction gas utilization rate slightly smaller than the critical reaction gas utilization rate at which the fuel or the oxidant cannot be supplied to the three-phase interface of each current measured in advance. And a suitable reaction gas utilization rate control means for controlling the flow rate of at least one of the two.