JP2016038973A - Fuel battery system and control method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air cooling type fuel battery system in which electrolyte and an electrode at the anode electrode side can be suppressed from being dried.SOLUTION: An air cooling type fuel battery system A has a fuel battery stack 10 for generating power through an electrochemical reaction between oxidant gas and fuel gas. The fuel battery stack has a membrane electrode assembly 20, a fuel gas flow path 30a which is provided to one side of the membrane electrode assembly and through which the fuel gas flows, and an oxidant gas flow path 40a which is provided to the other side of the membrane electrode assembly and through which the oxidant gas flows. The flow direction of the fuel gas in the fuel gas flow path and the flow direction of the oxidant gas in the oxidant gas flow path are opposite to each other. The cooling type fuel battery system for cooling the fuel battery stack with cooling gas has a water storage unit 68 for condensing water component in cathode off-gas flowing out from the oxidant gas flow path and storing the condensed water, and a water supply unit 69 for supplying the water stored in the water storage unit to the entrance of the fuel gas flow path.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fuel cell system and a control method for the fuel cell system.

  The fuel cell stack includes a fuel cell stack that generates electric power by an electrochemical reaction between the oxidant gas for power generation and the fuel gas. An air-cooled fuel cell system that includes a passage and a cooling oxidant gas passage through which a cooling oxidant gas flows is known in which a fuel cell stack is cooled with a cooling oxidant gas (see, for example, Patent Document 1). ).

  In Patent Document 1, each single cell of a fuel cell stack is provided on a membrane electrode assembly, a fuel gas flow passage through which fuel gas flows provided on one side of the membrane electrode assembly, and on the other side of the membrane electrode assembly. And a power generation oxidant gas flow path through which the power generation oxidant gas flows. The fuel gas passage is formed by connecting the fuel gas flow passages of the single cells of the fuel cell stack in parallel, and the oxidant gas passage for power generation is connected by connecting the power generation oxidant gas flow passages of the single cells in parallel. Is formed. The flow direction of the fuel gas in the fuel gas flow path and the flow direction of the oxidant gas for power generation in the power generation oxidant gas flow path are perpendicular to each other. The flow direction of the power generation oxidant gas in the power generation oxidant gas flow passage is the same as the flow direction of the cooling oxidant gas in the cooling oxidant gas flow passage.

  The air-cooled fuel cell system has a simpler structure than the water-cooled fuel cell system, has fewer pipes and accessory equipment, can occupy less space, weight and cost, and is easy to maintain. It has the advantages such as. For this reason, research and development have been conducted on air-cooled fuel cell systems.

JP 2006-252934 A

  However, the air-cooled fuel cell system has characteristics that the cooling efficiency is low and the cooling effect is small as compared with the water-cooled fuel cell system. Therefore, in the air-cooled fuel cell system, there may be a portion where the temperature does not sufficiently decrease in a situation where the amount of heat generation is large as in the case of high output operation. For example, in the region near the outlet of the oxidant gas flow passage, the oxidant gas heated by the heat generated by the power generation of the fuel cell is concentrated, so that the temperature is not sufficiently lowered. As a result, the membrane electrode assembly in that region Becomes relatively hot. Here, if the membrane electrode assembly is at a low temperature, the water generated at the cathode electrode diffuses to the anode electrode side through the electrolyte, and the electrolyte and electrode on the anode electrode side are moistened. However, since the membrane / electrode assembly becomes relatively high in temperature, the water produced at the cathode electrode evaporates, making it difficult to diffuse to the anode electrode side through the electrolyte. It will dry greatly compared to the side. As a result, the electrochemical reaction is lowered due to a decrease in the ionic conductivity of the electrolyte, and the power generation efficiency is lowered. A technique for suppressing drying of the electrolyte and electrodes on the anode electrode side is desired.

  According to one aspect of the present invention, a fuel cell stack that generates electric power by an electrochemical reaction between an oxidant gas and a fuel gas is provided. The fuel cell stack includes a membrane electrode assembly, and a membrane electrode assembly. A fuel gas flow passage that is provided on one side and through which the fuel gas flows; and an oxidant gas flow passage that is provided on the other side of the membrane electrode assembly and through which the oxidant gas flows. The fuel gas flow path and the oxidant gas flow path are formed so that the flow direction of the fuel gas and the flow direction of the oxidant gas in the oxidant gas flow path are opposite to each other. An air-cooled fuel cell system in which a stack is cooled with a cooling gas, wherein the water storage unit condenses moisture in the cathode offgas flowing out from the oxidant gas flow passage and stores the condensed water, Air-cooled fuel cell system including a water supply unit, a for supplying stored in the storage unit water inlet of the fuel gas flow passage is provided.

  According to another aspect of the present invention, a fuel cell stack that generates electric power by an electrochemical reaction between an oxidant gas and a fuel gas is provided. The fuel cell stack includes a membrane electrode assembly, and a membrane electrode assembly. A fuel gas flow passage that is provided on one side and through which the fuel gas flows; and an oxidant gas flow passage that is provided on the other side of the membrane electrode assembly and through which the oxidant gas flows. The fuel gas flow path and the oxidant gas flow path are formed so that the flow direction of the fuel gas and the flow direction of the oxidant gas in the oxidant gas flow path are opposite to each other. A control method of an air-cooled fuel cell system in which a stack is cooled with a cooling gas, wherein water in the cathode offgas flowing out from the oxidant gas passage is condensed and condensed water is discharged by a water storage unit. The state of the fuel cell stack is detected by the storage unit, and the amount of water supplied from the water storage unit to the inlet of the fuel gas passage is determined by the water supply unit based on the state of the fuel cell stack. A method for controlling an air-cooled fuel cell system is provided.

  In the air-cooled fuel cell system, drying of the electrolyte and electrodes on the anode electrode side can be suppressed.

It is a block diagram of a fuel cell system. It is a fragmentary sectional view which shows the structure of a fuel cell single cell. It is a fragmentary sectional view which shows the connection position of the water supply part of another Example. It is a figure which shows the map of the relationship between an output electric current value and an output voltage value, and threshold temperature. It is a figure which shows the map of the relationship between an output electric current value and an output voltage value, and the flow volume of water. It is a figure which shows the map of the relationship between an output electric current value and an output voltage value, and the increment of water. It is a timing chart explaining water supply control. It is a flowchart which shows the routine of water supply control. It is a block diagram of the fuel cell system of another Example. It is a block diagram of the fuel cell system of another Example.

  Referring to FIG. 1, the fuel cell system A includes a fuel cell stack 10. The fuel cell stack 10 includes a plurality of fuel cell single cells stacked in the stacking direction. Each single fuel cell includes a membrane electrode assembly 20. The membrane electrode assembly 20 includes a membrane electrolyte, an anode electrode formed on one side of the electrolyte, and a cathode electrode formed on the other side of the electrolyte.

  The anode electrode and the cathode electrode of the single fuel cell are electrically connected in series, and constitute an electrode of the fuel cell stack 10. The electrode of the fuel cell stack 10 is electrically connected to the inverter 12 via the DC / DC converter 11, and the inverter 12 is electrically connected to the motor generator 13. Further, the fuel cell system A includes a capacitor 14, and this capacitor 14 is electrically connected to the above-described inverter 12 via a DC / DC converter 15. The DC / DC converter 11 is for increasing the voltage from the fuel cell stack 10 and sending it to the inverter 12, and the inverter 12 is for converting the direct current from the DC / DC converter 11 or the capacitor 14 into an alternating current. It is. The DC / DC converter 15 is for reducing the voltage from the fuel cell stack 10 or the motor generator 13 to the battery 14 or increasing the voltage from the battery 14 to the motor generator 13. In the fuel cell system A shown in FIG. 1, the battery 14 is composed of a battery.

  Further, as shown in FIG. 2, the fuel cell single cell has a fuel gas flow passage 30 a provided on one side of the membrane electrode assembly 20 for supplying fuel gas to the anode electrode, and a membrane electrode junction. An oxidant gas flow path 40a for supplying an oxidant gas to the cathode electrode provided on the other side of the body 20 and a cooling gas flow path 50a for supplying a cooling gas to the single fuel cell are formed. ing. By connecting the fuel gas flow passage 30a, the oxidant gas flow passage 40a, and the cooling gas flow passage 50a of the plurality of fuel cell single cells in parallel or in series, respectively, the fuel cell stack 10 includes the fuel gas passage 30, the oxidant. A gas passage 40 and a cooling gas passage 50 are formed.

  The fuel gas flow passage 30a and the oxidant gas flow passage 40a extend on both sides of the membrane electrode assembly 20 in parallel with each other. Then, the flow of the fuel gas in the fuel gas flow passage 30a and the flow in the oxidant gas flow passage 40a are such that the inlet 30ai of the fuel gas flow passage 30a and the outlet 40ao of the oxidant gas flow passage 40a are adjacent to each other. The flow of oxidant gas is set. Specifically, the flow direction of the fuel gas in the fuel gas flow passage 30 a and the flow direction of the oxidant gas in the oxidant gas flow passage 40 a are opposite to each other on both sides of the membrane electrode assembly 20. In addition, a fuel gas flow passage 30a and an oxidant gas flow passage 40a are formed. Accordingly, the fuel gas flowing on the anode electrode side of the membrane electrode assembly 20 and the oxidant gas flowing on the cathode electrode side of the membrane electrode assembly 20 flow in directions facing each other. At this time, it can be said that the fuel gas in the fuel gas flow passage 30a and the oxidant gas in the oxidant gas flow passage 40a form a counter flow. At this time, the flow directions of the respective gases do not have to be mutually opposite directions (directions facing each other) in a strict sense, and may be generally opposite to each other with a slight intersection. In the embodiment shown in FIGS. 1 and 2, the inlet 30ai of the fuel gas flow passage 30a and the outlet 40ao of the oxidant gas flow passage 40a are generally adjacent to each other, and the inlet of the fuel gas passage 30 and the outlet of the oxidant gas passage 40 are Are generally adjacent. Further, the outlet 30ao of the fuel gas flow passage 30a and the inlet 40ai of the oxidant gas flow passage 40a are generally adjacent to each other.

  The cooling gas flow passage 50 a and the oxidant gas flow passage 40 a extend in parallel with each other in the fuel cell stack 10. In the embodiment shown in FIG. 2, the cooling gas flow passage 50a is arranged such that the flow direction of the cooling gas in the cooling gas flow passage 50a and the flow direction of the oxidant gas in the oxidant gas flow passage 40a are opposite to each other. Is preferably formed. That is, it is preferable that the cooling gas in the cooling gas flow passage 50a and the oxidant gas in the oxidant gas flow passage 40a form a counter flow in the above-described meaning. In this case, since the region near the outlet 40ao of the oxidant gas flow passage 40a having a relatively high temperature and the region near the inlet 50ai of the cooling gas flow passage 50a having a relatively low temperature are adjacent, the oxidant gas flow passage 40a. The membrane electrode assembly 20 in the vicinity of the outlet 40ao can be efficiently cooled, and drying of the cathode electrode in the vicinity and the electrolyte on the cathode electrode side can be effectively suppressed.

  A fuel gas supply pipe 31 is connected to the inlet of the fuel gas passage 30, and the fuel gas supply pipe 31 is connected to a fuel gas source 32. In the embodiment shown in FIG. 1, the fuel gas is formed from hydrogen gas and the fuel gas source 32 is formed from a hydrogen tank. In the fuel gas supply pipe 31, in order from the upstream side, the shutoff valve 33, the regulator 34 for adjusting the pressure of the fuel gas in the fuel gas supply pipe 31, and the fuel gas from the fuel gas source 32 are supplied to the fuel cell stack 10. A fuel gas injector 35 for supply is arranged. On the other hand, an anode off gas pipe 36 is connected to the outlet of the fuel gas passage 30. When the shutoff valve 33 is opened and the fuel gas injector 35 is opened, the fuel gas in the fuel gas source 32 is supplied into the fuel gas passage 30 in the fuel cell stack 10 via the fuel gas supply pipe 31. The At this time, the gas flowing out from the fuel gas passage 30, that is, the anode off gas flows into the anode off gas pipe 36. An anode off gas control valve 37 for controlling the amount of anode off gas flowing in the anode off gas pipe 36 is disposed in the anode off gas pipe 36.

  An oxidant gas supply pipe 41 is connected to the inlet of the oxidant gas passage 40, and the oxidant gas supply pipe 41 is connected to an oxidant gas source 42. In the embodiment shown in FIG. 1, the oxidant gas is formed from air and the oxidant gas source 42 is the atmosphere. A gas cleaner 43 is disposed in the oxidant gas supply pipe 41. On the other hand, the outlet of the oxidant gas passage 40 is connected to the inlet of the cathode offgas pipe 45, and the outlet of the cathode offgas pipe 45 communicates with the atmosphere. A blower 44 and a radiator 46 are disposed in the cathode off gas pipe 45. In this case, the inlet of the blower 44 is connected to the oxidant gas passage 40, and the outlet of the blower 44 is connected to the radiator 46. When the blower 44 is driven, the oxidant gas is drawn into the oxidant gas supply pipe 41 and supplied to the oxidant gas passage 40 in the fuel cell stack 10 through the oxidant gas supply pipe 41. At this time, the gas flowing out from the oxidant gas passage 40, that is, the cathode off-gas flows into the cathode off-gas pipe 45, is sucked into the blower 44, is discharged from the blower 44, is radiated by the radiator 46, and the temperature is lowered. Then, it is exhausted as it is. In another embodiment (not shown), the outlet of the cathode offgas pipe 45 is connected to an anode offgas diluter, and the cathode offgas whose temperature has been lowered by the radiator 46 is used for dilution of the anode offgas. In still another embodiment (not shown), a compressor is disposed in the oxidant gas supply pipe 41 instead of the blower 44, and when the compressor is driven, the oxidation in the fuel cell stack 10 is performed via the oxidant gas supply pipe 41. It is supplied into the agent gas passage 40.

  The fuel cell system A further condenses the moisture in the cathode offgas flowing out from the oxidant gas flow passage 40a, and stores a water storage unit 68 that stores the condensed water, and water stored in the water storage unit 68. And a water supply unit 69 for supplying the fuel gas flow passage 30a to the inlet. In the embodiment shown in FIG. 1, a branch pipe 61 branched from the cathode offgas pipe 45 is connected in the middle of the cathode offgas pipe 45, and a water storage unit 68 and a water supply unit 69 are arranged in the branch pipe 61. The branch pipe 61 is connected to the fuel gas supply pipe 31 downstream of the fuel gas injector 35, and the water supply section 69 supplies the water stored in the water storage section 68 to the fuel gas supply pipe 31. In another embodiment, as shown in FIG. 3, the branch pipe 61 is connected to the inlet of the fuel gas passage 30, and the water supply unit 69 supplies the water stored in the water storage unit 68 to the inlet of the fuel gas passage 30. To do.

  In the embodiment shown in FIG. 1, the water storage unit 68 includes a control valve 62 that controls the amount of cathode offgas flowing from the cathode offgas pipe 45 into the branch pipe 61, a condenser 63 that condenses moisture in the cathode offgas, A water tank 64 for storing the water condensed by the condenser 63 and an exhaust valve 67 provided in the exhaust pipe 61a for discharging the cathode off gas from which moisture has been removed by the condenser 63 to the outside are provided. In the embodiment shown in FIG. 1, the control valve 62 is a three-way valve disposed at the inlet of the branch pipe 61. In this case, the control valve 62 communicates the cathode offgas pipe 45 with the branch pipe 61 or separates it from the branch pipe 61. In another embodiment (not shown), the control valve 62 is a two-way valve provided in the branch pipe 61. In still another embodiment (not shown), the condenser 63 and the water tank 64 are integrated. On the other hand, the water supply unit 69 removes ionic impurities contained in the water stored in the water storage unit 68 and the water stored in the water storage unit 68 into the fuel gas supply pipe 31. And a supply water injector 66 for injecting. In another embodiment not shown, the ion exchanger 65 is omitted.

  When the cathode offgas pipe 45 is communicated with the branch pipe 61 by the control valve 62 and the exhaust valve 67 is opened, a part or all of the cathode offgas flows from the cathode offgas pipe 45 into the branch pipe 61 and flows into the cathode offgas. The water inside is condensed by the condenser 63. The condensed water is stored in the water tank 64, and the cathode off-gas after the moisture is removed is discharged to the outside from the exhaust pipe 61a or used for dilution of the anode off-gas. From the water stored in the water tank 64, ionic impurities are removed by the ion exchanger 65, and the water is sent to the fuel gas supply pipe 31 by the supply water injector 66. In another embodiment (not shown), the control valve 62 is not used, the water storage unit 68 and the water supply unit 69 are disposed in the cathode offgas pipe 45, and the outlet of the cathode offgas pipe 45 is connected to the fuel gas supply pipe 31. Thus, the entire amount of the cathode off-gas is exhausted from the exhaust valve 67 through the water storage unit 68 at all times.

  A cooling gas supply pipe 51 is connected to the inlet of the cooling gas passage 50, and the cooling gas supply pipe 51 is connected to a cooling gas source 52. In the embodiment shown in FIG. 1, the cooling gas is formed from air and the cooling gas source 52 is formed from the atmosphere. A cooling gas blower 54 is disposed in the cooling gas supply pipe 51. On the other hand, the outlet of the cooling gas passage 50 is connected to the inlet of the cooling gas discharge pipe 53, and the outlet of the cooling gas discharge pipe 53 communicates with the atmosphere. When the cooling gas blower 54 is driven, the cooling gas is supplied into the cooling gas passage 50 in the fuel cell stack 10 through the cooling gas supply pipe 51. At this time, the cooling gas flowing out from the cooling gas passage 50, that is, the exhaust cooling gas, flows into the cooling gas discharge pipe 53 and is exhausted as it is. In another embodiment (not shown), the outlet of the cooling gas supply pipe 51 is connected to an anode off gas diluter, and the cooling gas is used for dilution of the anode off gas. In yet another embodiment not shown, a compressor is used in place of the cooling gas blower 54. Thus, the fuel cell system A of the embodiment shown in FIG. 1 is an air-cooled type.

  The electronic control unit 70 is composed of a digital computer and includes a ROM (read only memory) 72, a RAM (random access memory) 73, a CPU (microprocessor) 74, an input port 75 and an output port 76 which are connected to each other by a bidirectional bus 71. It comprises. A pressure sensor 81 for detecting the pressure in the fuel gas supply pipe 31 is attached to the fuel gas supply pipe 31 between the fuel gas injector 35 and the fuel cell stack 10. Further, a temperature sensor 82 for detecting the temperature of the single fuel cell, that is, the cell temperature in the vicinity thereof is attached to the outlet of the oxidant gas flow passage 40a of the fuel cell stack 10, that is, the vicinity of the inlet of the fuel gas flow passage 30a. It is done. Further, an output sensor 83 that detects an output current value and an output voltage value is attached to the fuel cell stack 10. Further, a water amount sensor 84 for measuring the amount of water in the water tank is attached to the water tank 64. The cell temperature, the output current value, and the output voltage value of the fuel cell stack 10 can be regarded as the state of the fuel cell stack 10, and the temperature sensor 82 and the output sensor 83 are regarded as a detection unit that detects the state of the fuel cell stack 10. be able to. Output signals from the pressure sensor 81, the temperature sensor 82, and the output sensor 83 are input to the input port 75 via the corresponding AD converter 77. On the other hand, the output port 76 is connected to the shut-off valve 33, the regulator 34, the fuel gas injector 35, the anode off-gas control valve 37, the blower 44, the cooling gas blower 54, the control valve 62, the exhaust valve 67, and the supply water injector via the corresponding drive circuit 78. 66 is electrically connected.

By the way, when the fuel cell stack 10 is to generate power, the shutoff valve 33 and the fuel gas injector 35 are opened, and hydrogen gas is supplied to the fuel cell stack 10. Further, the blower 44 is driven and air is supplied to the fuel cell stack 10. As a result, an electrochemical reaction (H ₂ → 2H ⁺ + 2e ⁻ , (1/2) O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O) occurs in the single fuel cell, and electric energy is generated. The generated electrical energy is sent to the motor generator 13. As a result, the motor generator 13 is operated as an electric motor for driving the vehicle, and the electric vehicle is driven. On the other hand, for example, when the vehicle is braked, the motor generator 13 operates as a regenerative device, and the electrical energy regenerated at this time is stored in the capacitor 14.

  In the fuel cell system A shown in FIG. 1, when power is to be generated, for example, the target current value and target of the fuel cell stack 10 according to the load of the motor generator 13 and the amount of power stored in the battery 14 represented by the amount of depression of the accelerator pedal, for example. A voltage value is obtained. Next, the fuel gas amount and the oxidant gas amount necessary for setting the output current value and the output voltage value of the fuel cell stack 10 to the target current value and the target voltage value, that is, the target fuel gas supply amount and the target oxidant gas supply, respectively. A quantity is required. Next, the regulator 34 and the fuel gas injector 35 are controlled so that the amount of fuel gas sent to the fuel cell stack 10 becomes the target fuel gas supply amount, and the amount of oxidant gas sent to the fuel cell stack 10 becomes the target oxidant gas supply. The blower 44 is controlled so as to be the quantity. As described above, power generation in the fuel cell system A is controlled.

  On the other hand, in the fuel cell system A shown in FIG. 1, the amount of cooling gas supplied by the cooling gas blower 54 is controlled so that the cooling gas temperature representing the temperature of the fuel cell stack 10 is maintained within a preset target temperature range. Is done. Specifically, the amount of cooling gas necessary to maintain the cooling gas temperature within a predetermined target temperature range, that is, the target cooling gas amount is calculated. Next, the cooling gas blower 54 is controlled so that the cooling gas amount becomes the target cooling gas amount. As described above, the cooling in the fuel cell system A is controlled.

  However, in the situation where the air-cooled fuel cell system generates a large amount of heat as in high output operation, the cell temperature near the outlet 40ao of the oxidant gas flow passage 40a, that is, near the cathode electrode side outlet becomes too high, and the membrane electrode There is a possibility that moisture evaporates from the cathode electrode side of the bonded body 20 and the anode side on the opposite side is greatly dried. If it becomes so, the electrochemical reaction in the membrane electrode assembly 20 will fall, and the output of the fuel cell stack 10 will fall. Therefore, in the embodiment shown in FIG. 1, when the cell temperature in the vicinity of the outlet 40ao of the oxidant gas flow passage 40a becomes higher than a preset threshold temperature, the water stored in the water storage unit 68 is supplied at a predetermined flow rate. It is made to send out from the supply part 69 toward the inlet 30ai of the fuel gas flow path 30a. That is, it is possible to avoid drying of the anode electrode side of the membrane electrode assembly 20 by replenishing moisture from the inlet 30ai of the fuel gas flow passage 30a, that is, the anode electrode side inlet. As a result, the electrochemical reaction in the vicinity of the anode electrode entrance in the membrane electrode assembly 20 can be maintained, and a decrease in the output of the fuel cell stack 10 can be prevented. In addition, in each cell, the in-plane distribution of the electrochemical reaction in the membrane electrode assembly 20 can be made uniform. Furthermore, since the vicinity of the anode inlet having a high temperature, that is, the vicinity of the cathode electrode outlet is cooled by the supply of moisture, the in-plane distribution of the temperature in the membrane electrode assembly 20 can be made uniform. Further, since the membrane electrode assembly 20 is cooled and the evaporation of water is reduced, the cathode electrode and the electrolyte on the cathode electrode side can be moistened with moisture.

Here, the threshold temperature T0 in the vicinity of the outlet 40ao of the oxidant gas flow passage 40a, that is, in the vicinity of the cathode electrode side outlet is determined as follows. As the output current value of the fuel cell stack 10 increases, the amount of heat generation increases, and as the output voltage value decreases, the amount of heat generation increases. Therefore, the cell temperature easily rises. As a result, a situation in which moisture evaporates from the cathode electrode side of the membrane electrode assembly 20 and the anode side on the opposite side greatly dries easily occurs. Therefore, in order to cope with this, the threshold temperature T0 is set so that the threshold temperature T0 decreases as the output current value increases, and the threshold temperature T0 decreases as the output voltage value decreases. In other words, the threshold temperature T0 is set such that the lower the output current value, the higher the threshold temperature T0, and the higher the output voltage value, the higher the threshold temperature T0. Accordingly, in at least one of the case where the output current value is large and the output voltage value is small, the water stored in the water storage unit 68 is quickly supplied from the water supply unit 69 to the fuel gas flow passage at a predetermined flow rate. It can be sent toward the entrance of 30a. That is, at least one of the output current value is large and the output voltage value is small, and a case where water is likely to be insufficient on the anode electrode side of the membrane electrode assembly 20 is detected at an early stage. Moisture can be quickly replenished from the inlet 30ai to the anode side. Such a threshold temperature T0 is set in advance as a function of the output current value and the output voltage value. For example, the output current value I (I ₁ ,..., I _n ) and the output voltage value V (V ₁ ,..., V _m ) and a threshold temperature T 0 (T 0 ₁₁ ,..., T 0 _mn ) are stored in advance in the ROM 72 in the form of a map. In another embodiment, the threshold temperature T0 is preset as a function of the target current value and the target voltage value. In this case, compared with the case where the output current value and the output voltage value are used, a case where water is likely to be insufficient on the anode electrode side of the membrane electrode assembly 20 is detected earlier, and the inlet 30ai of the fuel gas flow passage 30a is detected. Thus, water can be replenished more rapidly from the anode side. In yet another embodiment, the threshold temperature T0 is a constant value.

Further, the flow rate Q of water supplied from the water supply unit 69 is determined as follows. As the output current value of the fuel cell stack 10 increases, the amount of heat generation increases, and as the output voltage value decreases, the amount of heat generation increases. Therefore, the cell temperature easily rises. As a result, the amount of water deficient on the anode electrode side of the membrane electrode assembly 20 increases. Therefore, in order to cope with this, the flow rate Q is set so that the flow rate Q increases as the output current value increases, and the flow rate Q increases as the output voltage value decreases. In other words, the flow rate Q is set so that the flow rate Q decreases as the output current value decreases, and the flow rate Q decreases as the output voltage value increases. Thereby, in the case of at least one of a large output current value and a small output voltage value, a sufficient amount of water can be sent from the water supply unit 69 toward the inlet of the fuel gas flow passage 30. it can. That is, it detects at least one of a large output current value and a small output voltage value, and a case where a large amount of water is likely to be insufficient on the anode electrode side of the membrane electrode assembly 20. A sufficient amount of moisture can be replenished from the inlet 30ai to the anode side. Such a flow rate Q is set in advance as a function of the output current value and the output voltage value. For example, the output current value I (I ₁ ,..., I _n ) and the output voltage value V (V ₁ ) shown in FIG. ,..., V _m ) and the flow rate Q (Q ₁₁ ,..., Q _mn ) are stored in advance in the ROM 72 in the form of a map. In another embodiment, the flow rate Q is preset as a function of the target current value and the target voltage value. In yet another embodiment, the flow rate Q is a constant flow rate.

The flow rate Q is set based on the output current value and the output voltage value. However, depending on the actual state of the fuel cell stack 10, there may be a situation where the flow rate Q is not sufficient. Therefore, in the embodiment of FIG. 1, the flow rate Q is increased by a predetermined increment according to such a situation. The increment ΔQ that increases the flow rate Q is determined in the same way as the flow rate Q. That is, the increment ΔQ is set so that the increment ΔQ increases as the output current value increases, and the increment ΔQ increases as the output voltage value decreases. In other words, the increment ΔQ is set such that the smaller the output current value, the smaller the increment ΔQ, and the larger the output voltage value, the smaller the increment ΔQ. Such increment ΔQ is preset as a function of the output current and the output voltage value, for example, the output current value I shown in FIG. _{6 (I 1, ..., I} n) and an output voltage value V (V ₁ ,..., V _m ) and increments ΔQ (ΔQ ₁₁ ,..., ΔQ _mn ) are stored in advance in the ROM 72 in the form of a map. In another embodiment, the increment ΔQ is preset as a function of the target current value and the target voltage value. In yet another embodiment, the increment ΔQ is a constant amount.

  Next, control for supplying moisture of the cathode off-gas to the inlet of the fuel gas passage 30, that is, water supply control will be described with reference to FIG.

  Water in the water tank 64 is generated in the condenser 63 as the cathode off gas flows through the condenser 63. In other words, the cathode offgas pipe 45 is communicated with the branch pipe 61 by the control valve 62, the exhaust valve 67 is opened, and the cathode offgas flows into the branch pipe 61, thereby generating water in the water tank 64. The On the other hand, the cathode offgas pipe 45 is separated from the branch pipe 61 by the control valve 62, the exhaust valve 67 is closed, and the cathode offgas does not flow into the branch pipe 61, thereby stopping the generation of water in the water tank 64. The

  In FIG. 7, X indicates that the cell temperature T measured by the temperature sensor 82 is higher than the threshold temperature T0. However, the threshold temperature T0 is calculated from the map shown in FIG. 4 based on the output current value I and the output voltage value V detected by the output sensor 83. When it is detected at time t1 that the cell temperature T is higher than the threshold temperature T0, the supply water injector 66 is activated, and water in the water tank 64 is injected into the fuel gas supply pipe 31 at a flow rate Q = Qa. Is done. However, the initial flow rate Qa is calculated from the map shown in FIG. 5 based on the output current value I and the output voltage value V detected by the output sensor 83. Thereby, water in the water tank 64 is supplied to the inlet of the fuel gas passage 30 and flows into the inlet on the anode electrode side of the membrane electrode assembly 20. As a result, moisture is replenished to the anode electrode side, and the cell temperature T starts to decrease. At this time, for example, when the amount of water in the water tank 64 detected by the water amount sensor 84 is equal to or greater than the threshold amount of water P0, the cathode offgas pipe 45 is separated from the branch pipe 61 by the control valve 62, and the exhaust valve 67 is closed (not shown). The maintained state is maintained. As a result, the anode off gas does not flow into the condenser 63, and condensed water is not generated in the condenser 63. That is, use of water from the water tank 63 (injection by the supply water injector 66) is performed, and generation of water in the water tank 63 (generation of condensed water by the condenser 63) is not performed.

  After a lapse of a predetermined time Δts from time t2, that is, from time t1, the cell temperature T is measured by the temperature sensor 82. When it is detected that the cell temperature T measured by the temperature sensor 82 is higher than the threshold temperature T0, the flow rate Q of water injected from the feed water injector 66 is increased by an increment ΔQ, and the water tank 64 Water is injected into the fuel gas supply pipe 31 at a flow rate Q = Qb (= Qa + ΔQ). However, the increment ΔQ is calculated from the map shown in FIG. 6 based on the output current value I and the output voltage value V detected by the output sensor 83. Thereby, the water in the water tank 64 is supplied to the inlet of the fuel gas passage 30 at the increased flow rate Qb and flows into the inlet on the anode electrode side of the membrane electrode assembly 20. As a result, moisture is further replenished to the anode electrode side, and the cell temperature T further decreases. At this time, the water amount P in the water tank is reduced by the water injection at the times t1 to t2, and is reduced from the original water amount P0 to the water amount Pa, for example. That is, since the amount of water in the water tank 64 detected by the water amount sensor 84 is less than the threshold amount of water P0, the cathode offgas pipe 45 is communicated with the branch pipe 61 by the control valve 62, and the exhaust valve 67 is opened (illustrated). ) As a result, the anode off gas flowing into the condenser 63 flows in, and condensed water is generated in the condenser 63 and stored in the water tank 64. That is, the use of water from the water tank 63 (injection by the supply water injector 66) and the generation of water in the water tank 63 (generation of condensed water by the condenser 63) are performed simultaneously.

  Thereafter, the same process is repeated until the cell temperature T measured by the temperature sensor 82 becomes equal to or lower than the threshold temperature T0. Here, a case where the cell temperature T becomes the threshold temperature T0 at time t4 will be described.

  After a lapse of a predetermined time Δts from time t3, that is, from time t2, the cell temperature T is measured by the temperature sensor 82. When it is detected that the cell temperature T measured by the temperature sensor 82 is higher than the threshold temperature T0, the flow rate Q of the water jetted from the feed water injector 66 is further increased by the increment ΔQ, and the water tank 64 Is injected into the fuel gas supply pipe 31 at a flow rate Q = Qc (= Qb + ΔQ). As a result, the water in the water tank 64 is supplied to the inlet of the fuel gas passage 30 at the increased flow rate Qc, and flows into the inlet on the anode electrode side of the membrane electrode assembly 20. As a result, moisture is further replenished to the anode electrode side, and the cell temperature T further decreases. At this time, the amount P of water in the water tank fluctuates between a decrease due to water injection at times t2 to t3 and an increase due to condensation of moisture in the anode off-gas flowing into the condenser 63. For example, the amount P decreases from the amount Pa of water. The amount of water becomes Pb (<Pa). That is, since the amount of water in the water tank 64 detected by the water amount sensor 84 is less than the threshold amount of water P0, the cathode offgas pipe 45 is communicated with the branch pipe 61 by the control valve 62, and the exhaust valve 67 is kept open. Is done.

  After a lapse of a predetermined time Δts from time t4, that is, from time t3, the cell temperature T is measured by the temperature sensor 82. When it is detected that the cell temperature T measured by the temperature sensor 82 is equal to or lower than the threshold temperature T0, the feed water injector 66 is stopped. That is, the flow rate Q of water becomes zero. At this time, the amount P of water in the water tank fluctuates between a decrease due to water injection at time t3 to t4 and an increase due to condensation of moisture in the anode off gas flowing into the condenser 63. For example, the amount P decreases from the amount Pb of water. Pc (<Pb). That is, since the amount of water in the water tank 64 detected by the water amount sensor 84 is less than the threshold amount of water P0, the control valve 62 and the exhaust valve 67 are also used after the supply water injector 66 is stopped to replenish the water in the water tank 64. The valve open state is maintained. As a result, the anode off gas is introduced into the condenser 63, the moisture in the anode off gas is condensed, and the water amount P in the water tank 64 increases. However, it is determined whether the water amount P of the water tank 64 has reached the threshold water amount P0 every time the predetermined time Δts has elapsed. Thereafter, for example, at time t5, when the water amount P in the water tank 64 reaches the threshold water amount P0, the cathode offgas pipe 45 is separated from the branch pipe 61 by the control valve 62, and the exhaust valve 67 is closed. In another embodiment, the control valve 62 can have an intermediate opening (for example, 50%, etc.), and is opened at an intermediate opening at the time t1 to t4.

  FIG. 8 shows a control for supplying the cathode off-gas moisture to the anode electrode side in the fuel cell system A of FIG. 1, that is, a water supply control routine. This routine is executed by interruption at regular intervals.

   Referring to FIG. 8, in step 100, state data of the fuel cell stack 10 is acquired. The state data includes an output current value and an output voltage value detected by the output sensor 83 and a cell temperature T detected by the temperature sensor 82. In the subsequent step 101, it is determined whether or not the cell temperature T is higher than the threshold temperature T0. If the cell temperature T is less than or equal to the threshold temperature T0, the process ends. When the cell temperature T is higher than the threshold temperature T0, the water in the water tank 64 is injected from the supply water injector 66 toward the inlet of the fuel gas passage 30 at a flow rate Q. In the following step 103, it is determined whether or not the water in the water tank 64 is less than the threshold water amount P0. If the water in the water tank 64 is greater than or equal to the threshold water amount P0, the process proceeds to step 105. When the water in the water tank 64 is less than the threshold water amount P0, in step 104, the cathode offgas pipe 45 is communicated with the branch pipe 61 by the control valve 62, and the exhaust valve 67 is opened. Then, after a predetermined time Δts has elapsed in step 105, it is determined in step 106 whether or not the cell temperature T is equal to or lower than a threshold temperature T0. If the cell temperature T is less than or equal to the threshold temperature T0, the process proceeds to step 108. When the cell temperature T is higher than the threshold temperature T0, the increment ΔQ is calculated from the map of FIG. 6 in step 107, and the flow rate Q of the water injected from the feed water injector 66 is increased by the increment ΔQ. Thereafter, steps 102 to 107 are repeated until the cell temperature T becomes equal to or lower than the threshold temperature T0. When the cell temperature T is equal to or lower than the threshold temperature T0, in step 108, the cathode offgas pipe 45 is communicated with the branch pipe 61 by the control valve 62, and the state is maintained when the exhaust valve 67 is opened. On the other hand, when the cathode offgas pipe 45 is separated from the branch pipe 61 by the control valve 62 and the exhaust valve 67 is not opened, the cathode offgas pipe 45 is communicated to the branch pipe 61 by the control valve 62. Is opened. Thereafter, in step 109, water is accumulated in the water tank 64 until the water in the water tank 64 becomes equal to or greater than the threshold water amount P0. Thereafter, when the water in the water tank 64 reaches the threshold water amount P0 or more, the cathode offgas pipe 45 is separated from the branch pipe 61 by the control valve 62 in step 110, and the exhaust valve 67 is closed.

Next, another embodiment of the fuel cell system A will be described with reference to FIG.
In the fuel cell system A shown in FIG. 9, the outlet of the cathode offgas pipe 45 is connected to the inlet of the cooling gas passage 50, that is, the outlet of the oxidant gas passage 40 is connected to the inlet of the cooling gas passage 50, and the cathode offgas is cooled. 1 is different from the fuel cell system A shown in FIG. 1 in that it flows through the cooling gas passage 50 as gas. At this time, the same effect as the fuel cell system A shown in FIG. 1 can be obtained, and the cooling gas blower 54 can be omitted, and the power required for the operation of the cooling gas blower 54, the space occupied by the cooling gas blower 54, and the cost of the cooling gas blower 54 can be reduced. Can be reduced.

  In another embodiment (not shown), a three-way valve is provided in the vicinity of the outlet of the cathode offgas pipe 45 so that the cathode offgas of the target cooling gas amount among the cathode offgas is supplied to the cooling gas passage 50, Alternatively, a part is supplied to the cooling gas passage 50 and the rest is exhausted to the outside. In still another embodiment (not shown), the outlet of the exhaust pipe 61 a is connected to the inlet of the cooling gas passage 50 in addition to the outlet of the cathode offgas pipe 45.

Next, still another embodiment of the fuel cell system A will be described with reference to FIG.
The fuel cell system A shown in FIG. 10 is different from the fuel cell system A shown in FIG. 9 in that the branch pipe 61 is branched from the cooling gas discharge pipe 53 and the exhaust cooling gas is supplied to the branch pipe 61. In this case, as compared with the fuel cell system A shown in FIG. 9, the temperature of the cathode offgas given to the condenser 63 by passing through the cooling gas passage 50 is higher. 46a is additionally provided. Also in this case, the same effect as the fuel cell system A of FIG. 9 can be obtained.

A fuel cell system 10 fuel cell stack 30a fuel gas flow path 40a oxidant gas flow path 50a cooling gas flow path 68 water storage section 69 water supply section 82 temperature sensor 83 output sensor

Claims (5)

A fuel cell stack that generates electric power by an electrochemical reaction between an oxidant gas and a fuel gas is provided. The fuel cell stack is provided on one side of the membrane electrode assembly and the membrane electrode assembly, and the fuel gas flows. A fuel gas flow path; and an oxidant gas flow path that is provided on the other side of the membrane electrode assembly and through which an oxidant gas flows. The flow direction of the fuel gas in the fuel gas flow path and the oxidant gas The fuel gas flow passage and the oxidant gas flow passage are formed so that the flow directions of the oxidant gas in the flow passage are opposite to each other, and the air cooling in which the fuel cell stack is cooled with a cooling gas. Fuel cell system,
A water storage unit for condensing moisture in the cathode offgas flowing out from the oxidant gas flow passage and storing the condensed water;
A water supply unit for supplying water stored in the water storage unit to an inlet of the fuel gas flow path;
With
Air-cooled fuel cell system.   The fuel cell stack further includes a cooling gas flow path through which the cooling gas flows, an outlet of the oxidant gas flow path is connected to an inlet of the cooling gas flow path, and the cathode offgas serves as the cooling gas. The air-cooled fuel cell system according to claim 1, wherein the air-cooled fuel cell system flows through the flow passage.   The cooling gas flow path is formed so that the flow direction of the cathode off-gas in the cooling gas flow path and the flow direction of the oxidant gas in the oxidant gas flow path are opposite to each other. The air-cooled fuel cell system described. A detector for detecting a state of the fuel cell stack;
The said water supply part controls the quantity of the water supplied to the inlet_port | entrance of the said fuel gas channel | path from the said water storage part based on the state of the said fuel cell stack. Air-cooled fuel cell system. A fuel cell stack that generates electric power by an electrochemical reaction between an oxidant gas and a fuel gas is provided. The fuel cell stack is provided on one side of the membrane electrode assembly and the membrane electrode assembly, and the fuel gas flows. A fuel gas flow path; and an oxidant gas flow path that is provided on the other side of the membrane electrode assembly and through which an oxidant gas flows. The flow direction of the fuel gas in the fuel gas flow path and the oxidant gas The fuel gas flow passage and the oxidant gas flow passage are formed so that the flow directions of the oxidant gas in the flow passage are opposite to each other, and the air cooling in which the fuel cell stack is cooled with a cooling gas. A control method for a fuel cell system,
The water storage unit condenses moisture in the cathode offgas flowing out from the oxidant gas flow passage and stores the condensed water,
The detection unit detects the state of the fuel cell stack,
Based on the state of the fuel cell stack, the water supply unit controls the amount of water supplied from the water storage unit to the inlet of the fuel gas flow passage.
Control method of air-cooled fuel cell system.

Images