JP2013161678A - Fuel cell storage method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell storage method capable of storing a solid polymer fuel cell after power generation is stopped using a simple device structure.SOLUTION: The method for storing a solid polymer fuel cell FC having plural laminated cells C constituted to nip a solid polymer electrolyte membrane 4 with a fuel electrode 3 and an oxygen electrode 5 after power generation is stopped comprises: a storage period measurement step of measuring a storage duration during which the solid polymer fuel cell FC is stored under a power generation stop state from a start of storing the fuel cell; a determination step of determining whether a length of the storage duration measured in the storage period measurement step reaches a setting period or not; a water supply step for supplying water to the solid polymer electrolyte membrane 4 when the length of the storage duration reaches to the setting period in the determination step; and a storage restarting step of restarting storage of the solid polymer fuel cell FC under the power generation stop state after completion of the power supply step.

Description

  The present invention relates to a storage method after stopping power generation of a polymer electrolyte fuel cell comprising a plurality of stacked cells in which a solid polymer electrolyte membrane is sandwiched between a fuel electrode and an oxygen electrode.

  A polymer electrolyte fuel cell is configured by stacking a plurality of cells each having a solid polymer electrolyte membrane sandwiched between a fuel electrode and an oxygen electrode. When the polymer electrolyte fuel cell is operated for power generation, fuel gas (hydrogen) is supplied to the fuel electrode, and oxygen-containing gas (oxygen (air)) is supplied to the oxygen electrode. The solid polymer electrolyte membrane plays a role of moving hydrogen ions generated at the fuel electrode to the oxygen electrode. In particular, a solid polymer electrolyte membrane used in a polymer electrolyte fuel cell exhibits good hydrogen ion conductivity in a moderately wet state, but cannot exhibit good hydrogen ion conductivity when the wet state is lowered. Therefore, it is important to maintain the solid polymer electrolyte membrane in an appropriate wet state in order to exhibit the performance of the solid polymer fuel cell. During the power generation operation of the polymer electrolyte fuel cell, water generated on the oxygen electrode side is diffused into the polymer electrolyte membrane, so that the wet state of the polymer electrolyte membrane is prevented from decreasing. Yes.

  When such a polymer electrolyte fuel cell is stopped after the power generation operation, a storage method in which the cell is isolated from the outside and sealed is generally performed. Therefore, since the solid polymer electrolyte membrane is kept in a certain wet state immediately after the power generation operation is stopped or within a predetermined period after it is stopped, even if the power generation operation is started again, the solid polymer electrolyte membrane is maintained. Is considered to exhibit a certain degree of hydrogen ion conductivity.

  However, if the storage period is prolonged after the power generation operation is stopped, water in the cell evaporates, and there is a problem that the wet state of the solid polymer electrolyte membrane gradually decreases. For example, the storage period may be extended by installing a polymer electrolyte fuel cell in a customer's dwelling unit or facility, performing a trial run, stopping it, and delivering the polymer electrolyte fuel cell to the customer. In the case where the vehicle is not operated for a long period of time due to the convenience of the customer (for example, the situation where the user has not yet entered a residence or facility), the customer may be absent for a long period of time. In addition, if a polymer electrolyte fuel cell is installed and commissioned in a built-up house and delivered to a home dealer, the polymer electrolyte fuel cell will be stopped at least until the built house is sold. It is also assumed that the suspension period will be prolonged.

  Patent Document 1 describes that a fuel cell that can maintain a wet state of a polymer electrolyte membrane even during a power outage and that can maintain excellent power generation characteristics even after a long time outage is described. Specifically, the fuel cell described in Patent Document 1 includes a reservoir that contains therein a liquid that can wet the solid polymer electrolyte membrane and supplies the liquid to the solid polymer electrolyte membrane. And even during the suspension of power generation operation, the solid polymer electrolyte membrane is always in contact with the liquid stored in the reservoir, so that the liquid permeates from the contact portion into the solid polymer electrolyte membrane, and the polymer electrolyte Go around the whole. Thereby, the solid polymer electrolyte membrane can always maintain a wet state.

JP 2011-14256 A

However, the method described in Patent Document 1 employs a configuration in which a reservoir tank is provided in the cell stack so that the solid polymer electrolyte membrane and the liquid contained in the reservoir are always in contact with each other. There is a problem of increasing the size.
Further, in the method described in Patent Document 1, since the solid polymer electrolyte membranes of all the cells to be stacked must be assembled so as to contact the reservoir, a highly accurate assembly technique is required, which increases the production cost. There is a problem of being connected.

  The present invention has been made in view of the above-mentioned problems, and its purpose is that when the power generation operation of the polymer electrolyte fuel cell is performed after the power generation is stopped and stored, the wet state of the solid polymer electrolyte membrane is good. It is in the point which provides the storage method of the fuel cell which can ensure that it is.

  In order to achieve the above object, the fuel cell storage method according to the present invention is characterized by a solid polymer fuel comprising a plurality of stacked cells each having a solid polymer electrolyte membrane sandwiched between a fuel electrode and an oxygen electrode. A storage method after stopping the power generation of the battery, a storage period measuring step of measuring a storage continuation period in which the polymer electrolyte fuel cell is stored in a power generation stopped state from the start of storage, and the storage period measuring step When determining whether or not the length of the storage continuation period measured in (2) has reached the set period, and when determining that the length of the storage continuation period has reached the set period in the determination step, There is a water supply step of supplying water to the solid polymer electrolyte membrane, and a storage resumption step of starting storage of the solid polymer fuel cell in a power generation stop state again after the water supply step is completed.

According to the above characteristic configuration, the wet state of the solid polymer electrolyte membrane can be enhanced by performing the water supply step at a predetermined timing while the solid polymer fuel cell is stored in a power generation stopped state. Moreover, the timing which performs a water supply process determines whether the length of the storage continuation period measured by the storage period measurement process reached the set period. That is, the wet state of the solid polymer electrolyte membrane can be increased by performing the above-mentioned water supply step at the timing when the storage continuation period becomes longer and the wet state of the solid polymer electrolyte membrane is reduced below a predetermined level. Therefore, even if the power generation operation of the polymer electrolyte fuel cell is resumed at any timing during the storage continuation period when the polymer electrolyte fuel cell is stored in a power generation stop state, the solid polymer electrolyte at that time It can be ensured that the wet state of the membrane is above a predetermined level.
Accordingly, a fuel cell storage method is provided that can ensure that the solid polymer electrolyte membrane is in a good wet state when the power generation operation of the polymer electrolyte fuel cell is performed after power generation is stopped and stored. it can.

  Another feature of the fuel cell storage method according to the present invention is that in the water supply step, water is supplied to the fuel electrode via a fuel gas supply path and to the oxygen electrode via an oxygen-containing gas supply path. By supplying at least one of the water supply, water is supplied to the solid polymer electrolyte membrane.

According to the above characteristic configuration, at least one of water supply to the fuel electrode via the existing fuel gas supply path and water supply to the oxygen electrode via the existing oxygen-containing gas supply path is performed. It is not necessary to install a special flow path for supplying water to the solid polymer electrolyte membrane. As a result, an increase in the size of the fuel cell can be suppressed.
In addition, when water is supplied to the fuel electrode and the oxygen electrode in the water supply step, in addition to the effect that the solid polymer electrolyte membrane can be humidified, the effect that the fuel electrode and the oxygen electrode can be cleaned is also obtained. For example, the fuel gas and the oxygen-containing gas supplied to the gas diffusion layer and the catalyst layer of the fuel electrode and the oxygen electrode during the power generation operation while the polymer electrolyte fuel cell is stopped and stored after the power generation operation. There is a possibility that the substances contained in the catalyst stay or deposit on the surfaces of the gas diffusion layer and the catalyst layer. In addition, microorganisms or the like suspended in the air may propagate on the surfaces of the gas diffusion layer and the catalyst layer. However, if the water supply process as in this characteristic configuration is performed, it can be expected that substances that have stayed or deposited in the gas diffusion layer and the catalyst layer and microorganisms that have survived and propagated will be washed away.

  Still another characteristic configuration of the fuel cell storage method according to the present invention is that the fuel gas when the solid polymer fuel cell is in a power generation operation when supplying water to the fuel electrode in the water supply step. When supplying water to the oxygen electrode by flowing water in a direction opposite to the flow direction of the fuel gas in the supply path, the oxygen-containing gas supply path when the solid polymer fuel cell is in power generation operation. The point is that water flows in the direction opposite to the flow direction of the oxygen-containing gas.

Both the fuel electrode and the oxygen electrode inside the cell are in a situation where foreign substances are likely to stay or deposit in the upstream part where fuel gas and oxygen-containing gas first flow into the fuel electrode and oxygen electrode during power generation operation. . Therefore, when water is supplied to the fuel electrode and the oxygen electrode, the flow direction of the fuel gas in the fuel gas supply path and the oxygen-containing gas in the oxygen-containing gas supply path when the polymer electrolyte fuel cell is operated for power generation If water is flowed in the same direction as the flow method, the washed-out foreign matter may diffuse from the upstream part toward the downstream part throughout the cell.
However, according to this characteristic configuration, the water flowing inside the fuel electrode and the oxygen electrode in the water supply process flows downstream from the part where the foreign substances are likely to stay or precipitate, so that the washed-out foreign substances diffuse throughout the cell. There is no end to it.

  Still another characteristic configuration of the fuel cell storage method according to the present invention is that the water pressure applied to the fuel electrode and the oxygen electrode when water is simultaneously supplied to the fuel electrode and the oxygen electrode in the water supply step. The pressure difference with the water pressure given to the point is adjusted within the set pressure difference.

  According to the above characteristic configuration, when water is supplied to the fuel electrode and the oxygen electrode at the same time, the solid polymer electrolyte membrane sandwiched between the fuel electrode and the oxygen electrode is subjected to water pressure from both the fuel electrode side and the oxygen electrode side. However, if the pressure difference between the water pressure applied to the fuel electrode and the water pressure applied to the oxygen electrode is adjusted within the set pressure difference, the height of the solid present in the intermediate portion between the fuel electrode and the oxygen electrode Since the water pressure from both sides of the molecular electrolyte membrane is almost balanced, problems such as deformation of the solid polymer electrolyte membrane due to water pressure do not occur.

  Still another feature of the fuel cell storage method according to the present invention is that in the water supply step, water prepared for use as cooling water for the cell during power generation operation of the polymer electrolyte fuel cell is It exists in the point supplied to a solid polymer electrolyte membrane.

  According to the above characteristic configuration, water to be supplied to the solid polymer electrolyte membrane need not be specially prepared. As a result, an increase in the size of the fuel cell can be suppressed.

  Still another characteristic configuration of the fuel cell storage method according to the present invention is that, in the water supply step, the heat discharged from the polymer electrolyte fuel cell is collected and stored, and the temperature is raised to a predetermined temperature to use the heat. The hot water provided from the exhaust heat recovery apparatus that can be supplied to the apparatus is supplied to the solid polymer electrolyte membrane.

  According to the above characteristic configuration, water to be supplied to the solid polymer electrolyte membrane need not be specially prepared. As a result, an increase in the size of the fuel cell can be suppressed. Furthermore, since hot water having a high temperature is supplied to the fuel electrode and the oxygen electrode, even if microorganisms or the like are alive on the surfaces of the gas diffusion layer and the catalyst layer, an effect of killing them can be expected.

  Still another characteristic configuration of the fuel cell storage method according to the present invention is to supply, to the solid polymer electrolyte membrane, water subjected to a treatment for reducing the concentration of an ionic substance contained in the water in the water supply step. There is in point to do.

  According to the above characteristic configuration, water having a low concentration of the ionic substance can be supplied to the solid polymer electrolyte membrane. Therefore, the solid polymer electrolyte membrane can be prevented from being contaminated by the ionic substance.

  Still another characteristic configuration of the fuel cell storage method according to the present invention is to supply the solid polymer electrolyte membrane with water subjected to a treatment for reducing the concentration of organic matter contained in the water in the water supply step. It is in.

  According to the above characteristic configuration, water having a low concentration of organic matter can be supplied to the solid polymer electrolyte membrane. Therefore, the solid polymer electrolyte membrane can be prevented from being contaminated by organic substances.

  Still another characteristic configuration of the fuel cell storage method according to the present invention is that, in the water supply step, water supplied to at least one of the fuel electrode and the oxygen electrode is vibrated by ultrasonic vibration generating means. is there.

  According to the above characteristic configuration, water supplied to at least one of the fuel electrode and the oxygen electrode can be vibrated by operating the ultrasonic vibration generating means in the water supply step. That is, the effect of cleaning at least one of the fuel electrode and the oxygen electrode can be enhanced by supplying water to at least one of the fuel electrode and the oxygen electrode while shaking water molecules by this ultrasonic vibration.

It is a figure explaining the structure of a fuel cell system. It is a flowchart which shows the storage method of a fuel cell. It is a figure explaining the water supply mechanism for performing a water supply process. It is a figure explaining the effect at the time of implementing the storage method of a fuel cell. It is a figure explaining the structure of another fuel cell system. It is a figure explaining another embodiment of a fuel cell.

<First Embodiment>
A configuration of a fuel cell system in which a fuel cell storage method according to the present invention is implemented will be described below with reference to the drawings.
FIG. 1 is a diagram illustrating the configuration of a fuel cell system. The fuel cell system includes a polymer electrolyte fuel cell FC (hereinafter simply referred to as “fuel cell FC”). The fuel cell FC includes a plurality of stacked cells C each having a solid polymer electrolyte membrane 4 sandwiched between a fuel electrode 3 and an oxygen electrode 5. In FIG. 1, only a single cell C is shown for simplicity. The fuel cell FC includes a cooling unit 6 that cools the fuel cell FC by recovering heat generated during power generation. In this embodiment, a water-cooled cooling unit 6 is provided. Specifically, the cooling unit 6 is supplied with water circulating in a recovered water circulation path 19 (to be described later) (hereinafter referred to as “recovered water”) to cool the fuel cell FC. The recovered water whose temperature has increased by passing through the cooling unit 6 flows into the heat exchanger 8 provided in the middle of the recovered water circulation path 19. Although details will be described later, in the heat exchanger 8, the recovered water exchanges heat with hot water flowing through the exhaust heat recovery path 25 and passes the exhaust heat recovered from the fuel cell FC to the hot water. Hot water is stored in the hot water storage tank 7 where heat is stored.

  The reformer 1 is supplied with a raw fuel containing hydrocarbons (for example, city gas containing methane), and water is supplied through a reforming water supply path 20 branched from the recovered water circulation path 19. . The reformer 1 performs steam reforming of the raw fuel by using the combustion heat provided from the combustor 2 provided therewith. The fuel gas mainly composed of hydrogen obtained by steam reforming in the reformer 1 is supplied to the fuel electrode 3 through the fuel gas supply path 14.

  In the fuel electrode 3, not all the supplied fuel gas is consumed in the power generation reaction. Therefore, fuel gas components such as hydrogen remain in the fuel electrode exhaust gas discharged from the fuel electrode 3. Therefore, fuel electrode exhaust gas is used as a combustion gas in the combustor 2. Specifically, the fuel electrode exhaust gas is supplied from the fuel electrode 3 to the combustor 2 through the fuel electrode exhaust gas passage 15. The combustion exhaust gas after being combusted in the combustor 2 is discharged to the outside through the combustion exhaust gas passage 16.

  The fuel electrode exhaust gas and the combustion exhaust gas contain moisture. Therefore, water recovery devices 21 and 22 are provided in the middle of the fuel electrode exhaust gas passage 15 and the combustion exhaust gas passage 16 for the purpose of recovering the moisture. The water recovery units 21 and 22 are configured by combining a condenser and a drain trap, for example. That is, the moisture contained in the fuel electrode exhaust gas and the combustion exhaust gas is condensed by the condenser, and the condensed water is taken out by the drain trap. The water taken out by the drain trap is recovered into the water recovery tank 10 and reused as water circulating in the recovered water circulation path 19.

  In this way, the recovered water flowing through the recovered water circulation path 19 contains the moisture contained in the fuel electrode exhaust gas and the moisture contained in the combustion exhaust gas. Is assumed to be included. Therefore, the fuel cell system of the present embodiment is configured such that the recovered water flowing through the recovered water circulation path 19 is processed by the water treatment device 9 provided in the middle of the recovered water circulation path 19. In the present embodiment, the water treatment device 9 includes an adsorbent 9a capable of adsorbing organic substances and the like present in the recovered water, and an ion exchange resin 9b capable of removing ions dissolved in the recovered water. The water treatment device 9 may be composed of only one of the adsorbent 9a and the ion exchange resin 9b, or may include other means. For example, a reverse osmosis membrane may be used in combination.

The ion exchange resin 9b replaces electrolyte ions dissolved in the recovered water (for example, salts and ammonia dissolved by ionization) with, for example, H ⁺ and OH ⁻ , so that the electrolyte contained in the recovered water is obtained. It functions to lower the concentration of (i.e., lower electrical conductivity). For example, the electrical conductivity of the recovered water flowing through the recovered water circulation path 19 on the downstream side of the water treatment device 9 is preferably about 1 μS / cm to 10 μS / cm.

  The adsorbent 9a is configured to include, for example, activated carbon, and adsorbs adsorbents such as organic substances (eg, siloxane, nonpolar or polar organic molecules, microorganisms, microbial secretions, oil, etc.) contained in the recovered water. Demonstrate the function. For example, the concentration of oil in the recovered water flowing through the recovered water circulation path 19 on the downstream side of the water treatment device 9 is preferably about 0.01 wtppm to 1 wtppm.

  The exhaust heat recovered from the recovered water in the heat exchanger 8 (that is, the exhaust heat recovered from the fuel cell FC) is given to the hot water flowing through the exhaust heat recovery path 25, and the hot water is stored in the hot water storage tank 7. In the present embodiment, the exhaust heat recovery device 12 that recovers the exhaust heat of the fuel cell FC includes a hot water storage tank 7 and an auxiliary heat source device 11. Specifically, the exhaust heat recovery device 12 has an exhaust heat recovery path 25 through which hot water stored in the hot water storage tank 7 circulates between the hot water storage tank 7 and the heat exchanger 8. The flow rate of hot water in the exhaust heat recovery path 25 is adjusted by the pump P2. The exhaust heat recovery device 12 also has a hot water circulation path 26 through which hot water stored in the hot water storage tank 7 is supplied to the heat utilization device 13 via the auxiliary heat source unit 11. The flow rate of hot water in the hot water circulation path 26 is adjusted by the pump P3. When the heat utilization device 13 is a floor heating device or the like that uses only the heat of hot water, the hot water after the heat is utilized by the heat utilization device 13 returns to the hot water storage tank 7 through the hot water circulation path 26. Alternatively, when the heat utilization device 13 is a hot water supply device that uses hot water itself, the hot water does not return to the hot water storage tank 7. The auxiliary heat source unit 11 is used when hot water required by the heat utilization device 13 is heated to a predetermined temperature and then supplied to the heat utilization device 13.

[Fuel cell power generation operation]
While the fuel cell FC is performing the power generation operation, the operation control device 27 causes the three-way valve V6 provided in the middle of the fuel gas supply path 14 to flow from the reformer 1 side to the fuel electrode 3 side. The valve is opened to supply fuel gas from the reformer 1 to the fuel electrode 3, and a three-way valve V7 provided in the middle of the oxygen-containing gas supply path 17 is passed from the air supply source side to the oxygen electrode 5 side. The valve is opened in such a direction that air is supplied to the oxygen electrode 5. As a result, a power generation reaction is performed in the cell C, and electric power is output to an electric load (not shown), an inverter (not shown), and the like.
The operation control device 27 opens the three-way valve V5 provided in the middle of the fuel electrode exhaust gas passage 15 from the fuel electrode 3 side to the combustor 2 side during the power generation operation of the fuel cell FC. The fuel electrode exhaust gas is supplied to the combustor 2. As a result, in the combustor 2, the hydrogen remaining in the fuel electrode exhaust gas is burned.
Further, the operation control device 27 opens the three-way valve V4 provided in the middle of the oxygen electrode exhaust gas passage 18 in a direction to flow from the oxygen electrode 5 side to the discharge side during the power generation operation of the fuel cell FC. The oxygen electrode exhaust gas is discharged to the outside.
The operation control device 27 supplies raw fuel to the reformer 1 when the reformer 1 generates fuel gas, operates the pump P1 provided in the recovered water circulation path 19, and recovers the recovered water circulation path. The reforming water is supplied to the reformer 1 by opening the valve V <b> 2 provided in the reforming water supply path 20 branched from 19. As described above, the reformer 1 is given the combustion heat generated in the combustor 2 to promote the steam reforming reaction.

[Stopping fuel cell power generation]
The operation control device 27 releases the electrical connection between the electric load, the inverter, and the like and the cell C of the fuel cell FC, and stops the output of the electric power obtained by the power generation in the fuel cell FC. For example, the operation control device 27 reduces the amount of fuel gas generated in the reformer 1 before stopping the output of the electric power obtained by the power generation in the fuel cell FC, thereby fuel to the fuel cell FC. The gas supply amount is decreased, and the air supply amount to the fuel cell FC is decreased. Thereafter, the operation control device 27 stops the supply of the fuel gas and air to the fuel cell FC, and also releases the electrical connection between the electric load, the inverter, and the like and the cell C of the fuel cell FC, so that the fuel cell FC The output of electric power obtained by power generation at is stopped. In this way, the operation control device 27 shifts the fuel cell FC to the power generation stop state.
In addition, the operation control device 27 closes the upstream side and the downstream side of the fuel electrode 3 and the upstream side and the downstream side of the oxygen electrode 5 during the step of shifting the fuel cell FC to the power generation stop state. A process of isolating the cell C of the battery FC from the outside is performed. For example, the operation control device 27 closes the upstream side of the fuel electrode 3 using the three-way valve V6, closes the downstream side of the fuel electrode 3 using the three-way valve V5, and closes the oxygen electrode 5 using the three-way valve V7. By closing the upstream side and closing the downstream side of the oxygen electrode 5 using the three-way valve V4, the cell C of the fuel cell FC can be isolated from the outside. In addition, while performing this isolation process, the cell C of the fuel cell FC may be sealed with an inert gas, raw fuel gas, water, or the like.

[Storage after stopping fuel cell power generation]
After the power generation operation is stopped, the fuel cell FC is stored in a state where the cell C is isolated from the outside as described above while the power generation is stopped. It is difficult to maintain a complete isolation state for a long time. Accordingly, moisture inside the cell C may escape to the outside while the fuel cell FC is stored. In that case, even if the solid polymer electrolyte membrane 4 of the cell C is wet at the time of stopping the power generation operation, moisture may subsequently escape from the solid polymer electrolyte membrane 4 of the cell C and the wet state may be lowered. There is.

In addition, when the operation of the fuel cell FC is restarted in a state where the wet state of the solid polymer electrolyte membrane 4 is lowered, the ionic conductivity of the solid polymer electrolyte membrane 4 is low, so that the output voltage is reduced. Problems arise.
Therefore, in the storage method of the fuel cell FC according to the present invention, water is supplied to the solid polymer electrolyte membrane 4 at an appropriate timing during storage after the power generation of the fuel cell FC is stopped, so that the solid polymer electrolyte membrane 4 is supplied. 4 to increase the wet state.
FIG. 2 is a flowchart showing a storage method of the fuel cell FC according to the present invention. In the present embodiment, the operation control device 27 starts the storage process control after stopping the power generation of the fuel cell FC. For example, the start timing of the storage process control is a timing at which the output of the power obtained by the power generation in the fuel cell FC is stopped and the cell C of the fuel cell FC is isolated from the outside.

  In step # 1, the operation control device 27 performs a storage period measuring step of measuring a storage continuation period in which the fuel cell FC is stored in a power generation stop state from the start of storage. In the present embodiment, the storage continuation period is started from the timing when the output of the power obtained by the power generation in the fuel cell FC is stopped and the cell C of the fuel cell FC is isolated from the outside. The longer the storage duration period, the higher the possibility that the moisture is released from the solid polymer electrolyte membrane 4 of the cell C and the wet state is lowered as described above.

  Next, the operation control device 27 performs a determination process for determining whether or not the length of the storage continuation period measured in the storage period measurement process has reached the set period (process # 2). When it is determined that the length of the storage continuation period has reached the set period, a water supply step of supplying water to the solid polymer electrolyte membrane 4 is performed (step # 3). These determination process and water supply process take into consideration that the wet state of the solid polymer electrolyte membrane 4 decreases if the storage continuation period becomes long, that is, the fuel cell FC after the storage continuation period reaches the set period. When the above operation is started again, it is performed in view of the problem that the output voltage decreases because the ionic conductivity of the solid polymer electrolyte membrane 4 is low. Therefore, the “setting period” used as a determination criterion in the determination process is such that even if moisture escapes from the solid polymer electrolyte membrane 4 of the cell C during the storage continuation period and the wet state of the solid polymer electrolyte membrane 4 decreases, This corresponds to a period in which the ionic conductivity of the solid polymer electrolyte membrane 4 is maintained at a level where the output voltage of the fuel cell FC is not greatly attenuated. This “setting period” can be set as appropriate for each fuel cell FC. Further, when the temperature is high and drying is promoted, the setting period is shortened. Also good.

  Drawing 3 is a figure explaining the water supply mechanism for performing a water supply process. In the present embodiment, in the water supply process, a water supply mechanism that supplies water, which is prepared for use as cooling water of the cell C during the power generation operation of the fuel cell FC, to the solid polymer electrolyte membrane 4 is employed. Specifically, in the water supply process, the operation control device 27 operates the pump P1 provided in the recovered water circulation path 19 to open the valve V1 and close the valve V2, and to the downstream side of the cooling unit 6 The three-way valve V <b> 3 provided in the valve is opened in a direction to flow the water supply passage 23, and the recovered water (cooling water) flows through the water supply passage 23. In addition, the operation control device 27 opens the three-way valve V5 in a direction to flow from the water supply path 23 side to the fuel electrode 3 side, supplies the recovered water to the fuel electrode 3, and sets the three-way valve V4 to the water supply path. The recovered water is supplied to the oxygen electrode 5 by opening the valve in the direction of flowing from the 23 side to the oxygen electrode 5 side. In addition, the operation control device 27 opens the three-way valve V6 in a direction that allows the three-way valve V6 to flow from the fuel electrode 3 side to the water discharge passage 24 side, and the recovered water that has flowed into the fuel electrode 3 passes through the three-way valve V6. A flow path to be discharged to the discharge path 24 is formed, and the three-way valve V7 is opened in a direction in which the three-way valve V7 flows from the oxygen electrode 5 side to the water discharge path 24 side. A flow path that is discharged to the water discharge path 24 via the three-way valve V7 is formed. Further, the operation control device 27 causes the three-way valve V8 provided in the middle of the recovered water circulation path 19 between the heat exchanger 8 and the water recovery water tank to flow from the water discharge path 24 side to the water recovery tank 10 side. The recovered water discharged to the water discharge passage 24 is returned to the recovered water circulation passage 19.

  Thus, in the water supply process, water is supplied to the fuel electrode 3 via the fuel gas supply path 14 and water is supplied to the oxygen electrode 5 via the oxygen-containing gas supply path 17. Although not shown, each of the fuel electrode 3 and the oxygen electrode 5 includes a gas diffusion layer and a catalyst layer, and the supplied recovered water passes through the gas diffusion layer and the catalyst layer to pass through the solid polymer electrolyte. The film 4 can be reached. Accordingly, by supplying water to the fuel electrode 3 via the fuel gas supply path 14 and supplying water to the oxygen electrode 5 via the oxygen-containing gas supply path 17, water to the solid polymer electrolyte membrane 4 is obtained. Can be supplied. As a result, the wet state of the solid polymer electrolyte membrane 4 can be increased. Note that how much water is supplied in the water supply process can be set as appropriate.

  As described above, when water is supplied to the fuel electrode 3 and the oxygen electrode 5 at the same time, the pressure difference between the water pressure applied to the fuel electrode 3 and the water pressure applied to the oxygen electrode 5 can be adjusted within a set pressure difference. preferable. For example, the water pressure applied to the fuel electrode 3 and the oxygen electrode 5 are adjusted by designing the apparatus in which the pressure loss between the three-way valve V3 and the fuel electrode 3 and the pressure loss between the three-way valve V3 and the oxygen electrode 5 are adjusted. The pressure difference with the water pressure given to can be adjusted within the set pressure difference. When water is supplied to the fuel electrode 3 and the oxygen electrode 5 simultaneously as in the present embodiment, the solid polymer electrolyte membrane 4 sandwiched between the fuel electrode 3 and the oxygen electrode 5 has a fuel electrode 3 side and an oxygen electrode. Water pressure is applied from both sides of the 5 side. However, if the pressure difference between the water pressure applied to the fuel electrode 3 and the water pressure applied to the oxygen electrode 5 is adjusted within the set pressure difference, the solid polymer present in the intermediate portion between the fuel electrode 3 and the oxygen electrode 5 Since the water pressure from both sides of the electrolyte membrane 4 is almost balanced, there is no problem that the solid polymer electrolyte membrane 4 is deformed by the water pressure. Such a set pressure difference is the same as the allowable pressure difference between the gas pressure applied to the fuel electrode 3 and the gas pressure applied to the oxygen electrode 5 during the power generation operation.

  When water is supplied to the fuel electrode 3 and the oxygen electrode 5 in the water supply step, in addition to the effect that the solid polymer electrolyte membrane 4 can be humidified, the effect that the fuel electrode 3 and the oxygen electrode 5 can be cleaned is also obtained. For example, while the fuel cell FC is stopped after power generation operation and stored, the fuel gas and the oxygen-containing gas supplied to the gas diffusion layer and the catalyst layer of the fuel electrode 3 and the oxygen electrode 5 during the power generation operation. Substances contained (for example, when the fuel gas and the oxygen-containing gas are humidified and then supplied to the fuel electrode 3 and the oxygen electrode 5, fluoride ions, chloride ions, sub-oxides contained in the humidified water) Nitrate ions, nitrate ions, phosphate ions, sulfate ions, sodium ions, potassium ions, ammonium ions, calcium, magnesium, etc.) may stay or deposit on the surfaces of the gas diffusion layer and the catalyst layer. In addition, microorganisms or the like suspended in the air may propagate on the surfaces of the gas diffusion layer and the catalyst layer. However, if the water supply process as in the present embodiment is performed, it can be expected that substances that have stayed or deposited in the gas diffusion layer and the catalyst layer and microorganisms that have survived and propagated will be washed away.

In particular, in the present embodiment, when water is supplied to the fuel electrode 3, the water flows in the direction opposite to the direction in which the fuel gas flows through the fuel gas supply path 14 when the polymer electrolyte fuel cell FC is in a power generation operation. When the water is supplied to the oxygen electrode 5, the water is supplied in a direction opposite to the flow direction of the oxygen-containing gas in the oxygen-containing gas supply passage 17 when the polymer electrolyte fuel cell FC is operated for power generation. ing.
In both the fuel electrode 3 and the oxygen electrode 5 inside the cell C, foreign matter stays or deposits in the upstream portion where the fuel gas and the oxygen-containing gas first flow into the fuel electrode 3 and the oxygen electrode 5 during the power generation operation. It is easy to do. Therefore, when water is supplied to the fuel electrode 3 and the oxygen electrode 5, the flow direction of the fuel gas in the fuel gas supply path 14 when the fuel cell FC is in a power generation operation and the oxygen content in the oxygen-containing gas supply path 17. If water is flowed in the same direction as the gas flow method, the washed-out foreign matter may diffuse from the upstream portion toward the downstream portion throughout the cell C.
However, in the present embodiment, the water flowing through the fuel electrode 3 and the oxygen electrode 5 inside the cell C in the water supply process flows downstream from the portion where the foreign matters are likely to stay or precipitate. It is discharged to the water discharge path 24 without being diffused throughout.

  Further, the recovered water supplied to the fuel electrode 3 and the oxygen electrode 5 in the water supply process is water that has been subjected to a treatment for reducing the concentration of the ionic substance by the ion exchange resin 9b of the water treatment device 9, and the water treatment device 9 It is the water which performed the process which reduces the density | concentration of organic substance with the adsorbent 9a. Therefore, water with a low concentration of impurities (ionic substances, organic substances, etc.) can be supplied to the fuel electrode 3 and the oxygen electrode 5 of the fuel cell FC.

  When the water supply process as described above is completed, the operation control device 27 performs a storage resumption process for starting storage of the polymer electrolyte fuel cell FC in the power generation stop state again after the completion of the water supply process (process # 4). . Specifically, the operation control device 27 closes the upstream side of the fuel electrode 3 by using the three-way valve V6, closes the downstream side of the fuel electrode 3 by using the three-way valve V5, and oxygen by using the three-way valve V7. By closing the upstream side of the electrode 5 and closing the downstream side of the oxygen electrode 5 using the three-way valve V4, the cell C of the fuel cell FC is isolated from the outside, and its state (that is, the power generation stopped state) maintain.

FIG. 4 is a diagram for explaining the effect when the storage method of the fuel cell FC according to the present invention is carried out. Specifically, FIG. 4 shows the average cell voltage output while the fuel cell FC is in operation. Note that the black circles in FIG. 4 indicate the transition of the average cell voltage since the start of operation immediately after the trial operation of the fuel cell FC. In FIG. 4, black triangles indicate the transition of the average cell voltage after the fuel cell FC is trial run, stored for 30 days with the power generation stopped, and then started. The white square marks in FIG. 4 indicate the average when the fuel cell FC is stored for 30 days with the power generation stopped after the test operation of the fuel cell FC, and then the water supply process is performed and then the operation is started. It is the transition of the cell voltage. This period of “30 days” is an example of the “set period” described above.
The three types of data shown in FIG. 4 are similar to the method for storing the fuel cell FC according to the present invention, as shown by the white square marks.

As shown in FIG. 4, the average cell voltage (initial value: black circle) from the start of operation immediately after the test operation of the fuel cell FC has been maintained at a very high value from the initial operation.
On the other hand, the average cell voltage (black triangle mark) after starting the operation after storing the fuel cell FC in the power generation stop state for 30 days shows a very low value from the initial operation, and the operation is performed for 30 hours. Even after the time has elapsed, the average cell voltage remains low. This is considered to be because the wet state of the solid polymer electrolyte membrane 4 was lowered during the long-term storage of the fuel cell FC while the power generation was stopped. As shown by the black triangles, the average cell voltage tends to increase slightly as the operation duration increases. This is because moisture generated in the cell C due to the power generation operation of the fuel cell FC is reduced. This is considered to be due to the fact that the wet state of the solid polymer electrolyte membrane 4 is increased by the moisture supplied into the cell C together with the fuel gas.

  In the data indicated by white squares similar to the storage method of the fuel cell FC according to the present invention, a relatively high average cell voltage can be indicated from the initial operation of the fuel cell FC. The average cell voltage at the initial stage of operation is a value much higher than the average cell voltage after 30 hours of operation indicated by black triangles. That is, the effect obtained by performing the water supply treatment to the solid polymer electrolyte membrane 4 as in the present invention is an effect that cannot be obtained simply by operating the fuel cell FC for a long time.

Second Embodiment
In the above embodiment, the example in which water prepared for use as the cooling water of the cell C during the power generation operation of the fuel cell FC is supplied to the solid polymer electrolyte membrane 4 has been described. It may be supplied to the electrolyte membrane 4. FIG. 2 is a diagram illustrating a configuration of a fuel cell system different from the first embodiment.

  In the fuel cell system shown in FIG. 2, a water supply path 23 for supplying water to the solid polymer electrolyte membrane 4 is configured to branch from a hot water circulation path 26. Specifically, a three-way valve V9 is provided between the hot water storage tank 7 and the auxiliary heat source machine 11 in the hot water circulation path 26, and hot water stored in the hot water storage tank 7 is either the auxiliary heat source machine 11 side or the water supply path 23. It is configured to be able to flow through. The water supply path 23 is connected to a three-way valve V5 provided in the middle of the fuel electrode exhaust gas path 15 and a three-way valve V4 provided in the middle of the oxygen electrode exhaust gas path 18.

  In the water supply process, the operation control device 27 operates the pump P3 provided in the hot water circulation path 26 and opens the three-way valve V9 in the direction of flowing the water supply path 23 to supply hot water to the water supply path 23. Shed. In addition, the operation control device 27 opens the three-way valve V5 in a direction to flow from the water supply path 23 side to the fuel electrode 3 side to supply hot water to the fuel electrode 3, and the three-way valve V4 is connected to the water supply path 23. The valve is opened in such a direction as to flow from the side to the oxygen electrode 5 side, and hot water is supplied to the oxygen electrode 5. Thus, the wet state of the solid polymer electrolyte membrane 4 can be enhanced by supplying water (hot water) to the solid polymer electrolyte membrane 4 in the water supply step. Furthermore, in the present embodiment, hot water stored in the hot water storage tank 7 having a relatively high temperature (for example, 45 ° C. or more) is supplied to the fuel electrode 3 and the oxygen electrode 5, so Even if it is alive on the surface of the gas diffusion layer and the catalyst layer of the pole 5, the effect of killing them can be expected.

<Another embodiment>
<1>
In the above embodiment, the example in which the fuel electrode 3 and the oxygen electrode 5 are simultaneously flown in the water supply process has been described, but the fuel electrode 3 and the oxygen electrode 5 may be flowed to only one of them.
Further, unlike the above embodiment, in the water supply process, water is flowed in the same direction as the flow direction of the fuel gas in the fuel gas supply path 14 when the polymer electrolyte fuel cell FC is in the power generation operation, and then to the oxygen electrode 5. When water is supplied, water may flow in the same direction as the flow direction of the oxygen-containing gas in the oxygen-containing gas supply path 17 when the polymer electrolyte fuel cell FC is in a power generation operation. In this case, the water supply path 23 is connected to the upstream side of the cell C of the fuel cell FC (that is, the side into which the fuel gas flows during power generation operation), and the water discharge path 24 is connected to the downstream side of the cell C of the fuel cell FC (that is, the side). And the oxygen-containing gas inflow side during power generation operation.

<2>
In the above embodiment, the configuration of the fuel cell system has been described with a specific example, but the configuration can be appropriately changed. For example, although a system configuration in which water collected from the fuel cell FC is reused as reforming water and cooling water has been shown, such a system configuration is not necessarily essential. 5 exemplifies a configuration in which hot water stored in the hot water storage tank 7 is supplied to the water supply path 23, hot water heated by the auxiliary heat source unit 11 is supplied to the water supply path 23. You may comprise as follows.

  Further, as shown in FIG. 6, a configuration in which an ultrasonic vibration generator 29 (an example of ultrasonic vibration generating means) is mounted on a housing 28 that accommodates the cell C of the fuel cell FC may be employed. In this case, if the operation control device 27 operates the ultrasonic vibration generator 29 in the water supply step, the water supplied to at least one of the fuel electrode 3 and the oxygen electrode 5 can be vibrated. That is, by supplying water to at least one of the fuel electrode 3 and the oxygen electrode 5 while shaking water molecules by this ultrasonic vibration, the effect of cleaning at least one of the fuel electrode 3 and the oxygen electrode 5 is enhanced. be able to.

<3>
In the embodiment described above, an operation for preventing freezing of water (that is, recovered water) prepared for use as the cooling water of the cell C may be performed. For example, a temperature sensor capable of detecting the outside air temperature and the temperature of the cooling water is provided, and the pump provided in the recovered water circulation path 19 when the operation control device 27 determines that the temperature detected by the temperature sensor is equal to or lower than the set temperature. By operating P1 and flowing the recovered water, freezing of the recovered water can be prevented. Furthermore, during this freeze prevention operation, if the recovered water is circulated through the same flow path as the water supply step (that is, the recovered water (cooling water) is supplied to the cell C via the water supply path 23). ), The effect of preventing the water remaining in the cell C (the fuel electrode 3, the solid polymer electrolyte membrane 4 and the oxygen electrode 5) from freezing can be obtained.

  INDUSTRIAL APPLICABILITY The present invention can be used for a storage method of a fuel cell that can be stored after stopping the power generation of the polymer electrolyte fuel cell using a simple device configuration.

3 Fuel electrode (cell C)
4 Solid polymer electrolyte membrane (cell C)
5 Oxygen electrode (cell C)
13 Heat Utilization Device 14 Fuel Gas Supply Path 17 Oxygen-Containing Gas Supply Path 29 Ultrasonic Vibration Generator (Ultrasonic Vibration Generation Means)
FC polymer electrolyte fuel cell

Claims (9)

A storage method after stopping the power generation of a polymer electrolyte fuel cell comprising a plurality of cells configured by sandwiching a polymer electrolyte membrane between a fuel electrode and an oxygen electrode,
A storage period measuring step of measuring a storage duration in which the polymer electrolyte fuel cell is stored in a power generation stop state from the start of storage; and
A determination step of determining whether or not the length of the storage continuation period measured in the storage period measurement step has reached a set period;
When it is determined that the length of the storage continuation period has reached the set period in the determination step, a water supply step of supplying water to the solid polymer electrolyte membrane,
A fuel cell storage method comprising: a storage restarting step of starting storage of the polymer electrolyte fuel cell again in a power generation stop state after completion of the water supply step.   In the water supply step, by performing at least one of water supply to the fuel electrode via a fuel gas supply path and water supply to the oxygen electrode via an oxygen-containing gas supply path, The fuel cell storage method according to claim 1, wherein water is supplied to the molecular electrolyte membrane. In the water supply step,
When supplying water to the fuel electrode, water flows in a direction opposite to the flow direction of the fuel gas in the fuel gas supply path when the solid polymer fuel cell is in a power generation operation,
3. When supplying water to the oxygen electrode, water flows in a direction opposite to the flow direction of the oxygen-containing gas in the oxygen-containing gas supply path when the polymer electrolyte fuel cell is in a power generation operation. The fuel cell storage method as described in 1.   In the water supply step, when water is simultaneously supplied to the fuel electrode and the oxygen electrode, a pressure difference between a water pressure applied to the fuel electrode and a water pressure applied to the oxygen electrode is adjusted within a set pressure difference. Item 4. A fuel cell storage method according to Item 2 or 3.   5. The water supply step supplies water, which is prepared for use as cooling water for the cells during power generation operation of the polymer electrolyte fuel cell, to the polymer electrolyte membrane. The method for storing a fuel cell according to Item.   In the water supply step, heat discharged from the polymer electrolyte fuel cell is recovered and stored, and hot water provided from an exhaust heat recovery device that can be heated to a predetermined temperature and supplied to a heat utilization device is supplied to the solid high fuel cell. The storage method of the fuel cell as described in any one of Claims 1-4 supplied to a molecular electrolyte membrane.   The fuel cell according to any one of claims 1 to 6, wherein in the water supply step, water subjected to a treatment for reducing the concentration of an ionic substance contained in water is supplied to the solid polymer electrolyte membrane. Storage method.   The method for storing a fuel cell according to any one of claims 1 to 7, wherein in the water supply step, water subjected to a treatment for reducing a concentration of an organic substance contained in water is supplied to the solid polymer electrolyte membrane. .   The fuel cell storage method according to any one of claims 1 to 8, wherein in the water supply step, water supplied to at least one of the fuel electrode and the oxygen electrode is vibrated by an ultrasonic vibration generating unit.

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