JP2009238669A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact fuel cell system enabling to suppress power generation performance caused by dryness of a solid polyelectrolyte membrane under situations in which the solid polyelectrolyte membrane is apt to be dried. <P>SOLUTION: In the case the degree of the dryness of a solid polyelectrolyte membrane is estimated to go over a certain level by a membrane drying degree estimating means, a fuel cell is cooled by combination of cooling by a cooling medium circulated through a cooling medium circulation course and also by supplying liquid water to an air electrode by injecting the liquid water in the form of mist by water liquid supply means. Accordingly, in the case dryness of the solid polyelectrolyte membrane is estimated to go over a certain level by membrane dryness estimation means, by cooling with cooling medium circulated through the cooling medium circulation course and by liquid water supply means, not only the fuel cell is fully cooled but also the solid polyelectrolyte membrane is moisturized, which prevents reduction of the power generation performance caused by dryness of the solid polyelectrolyte membrane. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel cell system including a solid polymer fuel cell.

  The unit cell of the polymer electrolyte fuel cell has a configuration in which a solid polymer electrolyte membrane is sandwiched between a fuel electrode (hydrogen electrode, anode electrode) and an air electrode (oxygen electrode, cathode electrode). Power generation is performed by electrochemically reacting a supplied fuel gas (for example, hydrogen) and an oxidant gas (for example, air) supplied to the air electrode.

In a fuel cell system including such a polymer electrolyte fuel cell (hereinafter simply referred to as “fuel cell”), the fuel cell generates heat as power is generated, so that the fuel cell is cooled to a temperature suitable for operation. A cooling mechanism is provided. As the cooling mechanism, for example, a cooling mechanism that circulates a cooling medium and cools the fuel cell as described in JP 2003-109637 A (Patent Document 1) is generally used.
JP 2003-109637 A

  However, the cooling mechanism described in Patent Document 1 cannot prevent the solid polymer electrolyte membrane from being dried under the circumstances where the solid polymer electrolyte membrane is easily dried, and cannot prevent the power generation performance from being lowered. There was a point. On the other hand, when it is assumed that a fuel cell system including a fuel cell is mounted on a vehicle, there is a high demand for a compact fuel cell system as a whole.

  The present invention has been made in view of the above-described circumstances, and provides a compact fuel cell system capable of suppressing power generation performance due to drying of the solid polymer electrolyte membrane in a situation where the solid polymer electrolyte membrane is easily dried. The purpose is that.

  To achieve this object, a fuel cell system according to claim 1 is a fuel cell comprising a solid polymer electrolyte membrane, and a fuel electrode and an air electrode that sandwich the solid polymer electrolyte membrane from both sides. A fuel cell stack laminated with a separator interposed therebetween, a fuel gas supply means for supplying fuel gas to the fuel electrode, an oxidant gas supply means for supplying air taken from outside the system to the air electrode at normal pressure, and A refrigerant circulation path for circulating the refrigerant in the separator, a cooling means for cooling the refrigerant, a liquid water supply means for cooling the fuel cell by supplying atomized liquid water together with air to the air electrode, Membrane dryness estimating means for estimating the degree of dryness of the solid polymer electrolyte membrane, and when the degree of dryness of the solid polymer electrolyte membrane estimated by the membrane dryness estimation means is below a predetermined level The cooling of the fuel cell is performed by circulating the refrigerant cooled by the cooling means through the refrigerant circulation path, and the degree of dryness of the solid polymer electrolyte membrane estimated by the membrane dryness estimating means is predetermined. When the level is exceeded, cooling control means is provided that uses both cooling of the fuel cell by the refrigerant circulating in the refrigerant circulation path and cooling of the fuel cell by the liquid water supply means.

  The fuel cell system according to claim 2 is the fuel cell system according to claim 1, wherein water storage means for storing liquid water supplied to the air electrode by the liquid water supply means, and discharge from the air electrode in the fuel cell. A heat exchanger that cools the exhaust gas by heat exchange and condenses water from the exhaust gas to separate it as liquid water, water recovery means that recovers liquid water from the heat exchanger and returns the liquid water to the water storage means, A second refrigerant circulation path that circulates the refrigerant cooled by the cooling means as a refrigerant for cooling the heat exchanger.

  The fuel cell system according to claim 3 is the fuel cell system according to claim 1, wherein a cooling unit that cools the exhaust gas discharged from the air electrode in the fuel cell by heat exchange, and moisture accompanying cooling by the cooling unit. A water storage part for storing liquid water separated from the exhaust gas by the condensation of the water, a water storage means for storing liquid water supplied to the air electrode by the liquid water supply means, and a refrigerant cooled by the cooling means And a second refrigerant circulation path that circulates as a refrigerant for cooling the cooling section of the water storage means.

  According to the fuel cell system of the first aspect, the fuel gas is supplied to the fuel electrode of the polymer electrolyte fuel cell by the fuel gas supply means, while the air electrode is always supplied by the oxidant gas supply means. Pressure air is supplied. As a result, the fuel cell generates power by an electrochemical reaction between the fuel gas and air.

  According to the fuel cell system of claim 1, when the degree of drying of the solid polymer electrolyte membrane estimated by the membrane dryness estimating means is below a predetermined level, it is cooled by the cooling means by the cooling control means. The refrigerant is circulated in the separator of the fuel cell stack through the refrigerant circulation path to cool the fuel cell.

  On the other hand, when the degree of dryness of the solid polymer electrolyte membrane estimated by the membrane dryness estimating means exceeds a predetermined level, the cooling control means cools the liquid by circulating through the separator through the refrigerant circulation path, and the liquid water. The fuel cell is cooled in combination with cooling by supplying the liquid water to the air electrode by spraying the liquid water in a mist form with the supply means.

  Here, the cooling by the liquid water supply means is due to the latent heat of evaporation of the mist-like liquid water supplied to the air electrode, and the latent heat is taken away from the surface of the air electrode and the surrounding air. Evaporation of moisture can be prevented, and the solid polymer electrolyte membrane is moisturized together with a cooling effect.

  Therefore, when the degree of dryness of the solid polymer electrolyte membrane estimated by the membrane dryness estimation means exceeds a predetermined level, by combining cooling by the refrigerant circulating in the refrigerant circulation path and cooling by the liquid water supply means, Not only can the fuel cell be sufficiently cooled, but the solid polymer electrolyte membrane is moisturized, and it is possible to prevent a decrease in power generation performance due to drying of the solid polymer electrolyte membrane.

  Further, the liquid water sprayed (sprayed) to the air electrode by the liquid water supply means exhibits both the cooling action of the fuel cell (air electrode) and the moisturizing action of the solid polymer electrolyte membrane. In addition, the fuel cell system can be prevented from being enlarged and can be contained in a compact space.

  According to the fuel cell system of claim 2, in addition to the effect of the fuel cell system of claim 1, the following effect is obtained. Exhaust gas discharged from the air electrode in the fuel cell is cooled by heat exchange in a heat exchanger, and moisture in the exhaust gas is condensed and separated as liquid water. The liquid water separated in the heat exchanger is returned by the water recovery means to the water storage means for storing the liquid water supplied to the air electrode by the liquid water supply means. Thus, a system is constructed in which liquid water for cooling and moisturizing the fuel cell by the liquid water supply means is recovered from the exhaust gas discharged from the air electrode by the water recovery means and circulated.

  Here, according to the fuel cell system of the second aspect, since the second refrigerant circulation path for circulating the refrigerant for cooling the heat exchanger is provided, the cooling efficiency of the exhaust gas in the heat exchanger can be improved. Accordingly, the recovery efficiency of liquid water (condensed water) from the exhaust can be increased. Therefore, it is possible to prevent the amount of liquid water supplied to the air electrode of the fuel cell from the liquid water supply means from being insufficient to cool the fuel cell or to moisturize the solid polymer electrolyte membrane. As a result, it is possible to more effectively prevent a decrease in power generation performance.

  Further, the cooling of the refrigerant circulating in the second refrigerant circulation path is performed by the same cooling means as the cooling means for cooling the refrigerant circulating in the refrigerant circulation path for cooling the fuel cell. Therefore, there is no need to provide a dedicated cooling means for cooling the refrigerant for cooling the heat exchanger, the increase in the size of the fuel cell system can be suppressed, and it is possible to fit in a compact space. There is.

  According to the fuel cell system of claim 3, in addition to the effect of the fuel cell system of claim 1, the following effect is obtained. Exhaust gas discharged from the air electrode in the fuel cell is cooled by heat exchange in the cooling unit of the water storage means, and liquid water separated from the exhaust gas by condensation of water accompanying cooling by the cooling unit is also stored in the water storage means. It is stored in the part. The liquid water stored in the water storage section of the water storage means is used as liquid water supplied to the air electrode by the liquid water supply means.

  Therefore, the liquid water separated from the exhaust in the cooling part of the water storage means is stored and recovered in the water storage part of the water storage means, and the liquid water is reused as liquid water to cool and keep the fuel cell by the liquid water supply means. A circulatory system is constructed.

  Here, according to the fuel cell system of the third aspect, since the second refrigerant circulation path for circulating the refrigerant for cooling the cooling unit of the water storage means is provided, the cooling efficiency of the exhaust gas in the cooling unit is increased. Accordingly, the recovery efficiency of liquid water (condensed water) from the exhaust can be increased. Therefore, it is possible to prevent the amount of liquid water supplied to the air electrode of the fuel cell from the liquid water supply means from being insufficient to cool the fuel cell or to moisturize the solid polymer electrolyte membrane. As a result, it is possible to more effectively prevent a decrease in power generation performance.

  Further, the cooling of the refrigerant circulating in the second refrigerant circulation path is performed by the same cooling means as the cooling means for cooling the refrigerant circulating in the refrigerant circulation path for cooling the fuel cell. Therefore, there is no need to provide a dedicated cooling means for cooling the refrigerant for cooling the heat exchanger, the increase in the size of the fuel cell system can be suppressed, and it is possible to fit in a compact space. There is.

  Furthermore, the water storage means has both a function of separating liquid water from the exhaust discharged from the air electrode (cooling unit) and a function of storing the separated liquid water (water storage unit), so that the water is discharged from the air electrode. It is not necessary to separately provide a device for separating liquid water from the exhaust gas and a device for storing the separated liquid water. Therefore, there is an effect that it is useful for making the fuel cell system compact.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a block diagram showing an embodiment (first embodiment) of a fuel cell system 100 which is a fuel cell system of the present invention.

  In this fuel cell system 100, a fuel cell stack 40 and hydrogen gas as a fuel gas are supplied to a fuel electrode (hydrogen electrode, anode electrode) 13 (see FIG. 2) of each unit cell 10 (see FIG. 2) constituting the fuel cell stack 40. 2) and the air electrode (oxygen electrode, cathode electrode) 12 of each unit cell 10 constituting the fuel cell stack 40 (see FIG. 2). A unit cell by supplying atomized liquid water to the air electrode 12 of each unit cell 10 constituting the fuel cell stack 40, an air supply system 60 for supplying to the water cell, a water cooling system 120 that is a water cooling type cooling mechanism A water supply system 80 that cools and humidifies (humidifies) 10 and an exhaust system 110 that exhausts exhaust discharged from the fuel cell stack 40 (the air electrode 12 of each unit cell 10) to the outside of the system are provided.

  In the fuel cell system 100 shown in FIG. 1, the flow paths (air supply path 63, air discharge path 111) of air (supply air, exhaust) are represented by the thickest solid lines, and the hydrogen gas flow path (hydrogen gas) The supply flow path 51) is next represented by a thick solid line, the water flow path (water guide path 81a, water supply path 81b) is represented by a dotted line, and the path constituting the water cooling system 120 (cooling water circulation path 121a, cooling water circulation). The path 121b) is represented by a thick dotted line.

  The fuel cell stack 40 has a configuration in which a plurality of unit cells 10 (see FIG. 2) are stacked in the thickness direction via a conductive separator 20, and adjacent unit cells are electrically connected in series. .

  The hydrogen gas supply system 50 corresponds to a fuel gas supply means constituting the fuel cell system of the present invention, and is an electromagnetic valve (see FIG. 5) for adjusting the flow rate of hydrogen gas supplied from a hydrogen cylinder (not shown) serving as a hydrogen source. (Not shown) is connected to a hydrogen gas flow path (not shown) from a gas intake port 41 of the fuel cell stack 40 through a hydrogen gas supply flow path 51 including a hydrogen gas flow path. The hydrogen gas supply system 50 is configured so that unreacted hydrogen gas discharged from the fuel cell stack 40 can be circulated back to the hydrogen gas supply flow path via a path (not shown).

  The air supply system 60 is provided on the upstream side of an air supply path 63 that is an air supply path and an air flow path (not shown) in the fuel cell stack 40, and an air manifold to which an end portion on the outlet side of the air supply path 63 is connected. 62. In the air supply path 63, an outside air temperature sensor SE <b> 1, a filter 64, and an air fan 61 such as a sirocco fan or a turbo fan, in order from the side taking in air (outside air) from outside the system, in the direction in which the air flows. Is provided. The air supply system 60 corresponds to an oxidant gas supply means constituting the fuel cell system of the present invention.

  The air supply system 60 drives the air fan 61 to supply air taken from outside the system to the air flow path of the fuel cell stack 40 via the air supply path 63 and the air manifold 62.

  The exhaust system 110 includes an air discharge path 111 having one end connected to an exhaust manifold (not shown) provided on the downstream side of the air flow path in the fuel cell stack 40.

  On the path of the air discharge path 111, a condenser 112 as a heat exchanger and a filter 113 are provided in this order from the fuel cell stack 40 side toward the air (exhaust) flow direction. Exhaust gas that has passed is discharged outside the system.

  The condenser 112 cools the exhaust gas by heat exchange with cooling water circulating through a cooling water circulation path 121b described later, and separates and collects moisture contained in the exhaust gas by condensation. Exhaust gas discharged from the fuel cell stack 40 flows into the condenser 112, and water contained in the exhaust gas is separated as liquid water, collected by a water supply system 80 described later, and returned to the water tank 82. It is.

  The water cooling system 120 includes a cooling water circulation path 121a as a refrigerant circulation path for circulating cooling water as a refrigerant for cooling the fuel cell stack 40. The cooling water circulation path 121a guides cooling water into the separator 20 (see FIG. 2) in the fuel cell stack 40 and cools the fuel cell stack 40. The cooling water circulation path 121 a is provided with a circulation pump 123 that pumps the cooling water to the fuel cell stack 40. Further, in the cooling water circulation path 121a, a radiator 122 as a cooling means for cooling the cooling water and a circulation electromagnetic valve 124 are provided in order from the fuel cell stack 40 toward the downstream side (the direction in which the cooling water flows). It has been.

  Further, the water cooling system 120 includes a cooling water circulation path 121b as a second refrigerant circulation path for circulating cooling water as a refrigerant for cooling the condenser 112. This cooling water circulation path 121 b is provided so as to branch from the cooling water circulation path 121 a on the downstream side of the radiator 122, and to merge with the cooling water circulation path 121 a on the upstream side of the circulation pump 123 via the condenser 112. . The cooling circulation path 121b is provided with a circulation electromagnetic valve 125.

  The cooling water cooled by the radiator 122 is circulated through both the cooling water circulation path 121a and the cooling water circulation path 121b by pumping by the circulation pump 123, and cools (water-cools) the fuel cell stack 40 and the condenser 112, respectively. . In addition, as a refrigerant | coolant, it is not limited to a cooling water, The fluid (liquid, gas) which can become a various refrigerant | coolant can be used.

  As described above, the fuel cell system 100 of the present embodiment is configured so that the fuel cell stack 40 can be cooled by the water-cooling type cooling mechanism. Although details will be described later, the fuel cell system 100 of the present embodiment does not perform humidification until the situation where the fuel cell stack 40 becomes dry (that is, the situation where the solid polymer electrolyte membrane 11 is easily dried) occurs. The operation is performed by cooling with the cooling water circulating through the cooling water circulation path 121a (water-cooled non-humidifying operation).

  Moreover, since the fuel cell system 100 of this embodiment cools the condenser 112 with the cooling water which circulates through the cooling water circulation path 121b, the cooling efficiency of exhaust gas is high, and the recovery efficiency of moisture from the exhaust gas is also high.

  The water supply system 80 includes a water tank 82 as a water storage means, and a water supply path 81 b that is connected to the water tank 82 at one end side and supplies water stored in the water tank 82 to the fuel cell stack 40. Composed. The water supply path 81b in the water supply system 80 corresponds to the liquid water supply means constituting the fuel cell system of the present invention.

  The water tank 82 stores water for supplying water serving as cooling water and humidification water (humidity retention water) to the fuel cell stack 40. The water tank 82 is provided with a water level sensor SE4 (see FIG. 3) and a water temperature sensor (not shown).

  A filter 84, a water supply pump 85, a water supply electromagnetic valve 86, and a nozzle 83 serving as an outlet of water from the water supply path 81b are provided in the water supply path 81b from the water tank 81 side toward the water flow direction. It is provided in order.

  The tip of the nozzle 83 is directed to the air manifold 62, and the water guided from the water tank 82 via the water supply path 81b is jetted from the tip of the nozzle 83. The water jetted from the nozzle 83 toward the air manifold 62 is sent into the fuel cell stack 40 in the form of a mist by the flow of supply air flowing through the air supply system 60.

  The water sprayed in the form of mist flows into the air electrode 12 of each unit cell 10 (see FIG. 2), and acts as cooling water and humidification water (humidity retention water) for the fuel cell stack 40. That is, the fuel cell system 100 according to the present embodiment cools the fuel cell stack 40 (air electrode 12) by spraying liquid water, and can directly moisturize the solid molecular electrolyte membrane 11 (see FIG. 2). It is configured as a type of fuel cell system.

  As described above, the fuel cell system 100 according to the present embodiment can not only cool the fuel cell stack 40 by the water cooling system 120 described above but also can cool the fuel cell stack 40 by the water supply system 80.

  Although details will be described later, in the present embodiment, the cooling of the fuel cell stack 40 by the water cooling system 120 is basically used, and the fuel cell stack 40 is dry (that is, the solid polymer electrolyte membrane 11 is easily dried). When it occurs, the cooling by the water cooling system 120 and the cooling by the water supply system 80 are used in combination. With this configuration, it is possible to effectively prevent a decrease in power generation performance due to drying of the solid polymer electrolyte membrane 11.

  Further, as shown in FIG. 1, the water supply system 80 includes a water conduit 81 a that guides the water collected by the condenser 112 to the water tank 82. The water conduit 81a is a route in which one end side is connected to the condenser 112 and the other end side is connected to the water tank 82, and a recovery pump 88 is provided in the water conduit 81a. In addition, the water conduit 81a in this water supply system 80 corresponds to the water collection | recovery means which comprises the fuel cell system of this invention.

  As described above, the water supply system 80 supplies liquid water stored in the water tank 82 as cooling water and humidified water of the fuel cell stack 40 via the water supply path 81b, and exhaust gas discharged from the fuel cell stack 40. The water contained therein is condensed by the condenser 112 and separated as liquid water, and the water is returned to the water tank 82 through the water conduit 81a.

  Further, the water supply system 80 has a drainage channel 81 c that branches from the water supply channel 81 b and drains the water in the water supply channel 81. The drainage channel 81c is provided with a draining electromagnetic valve 87 that is opened when draining.

  When operating the fuel cell system 100 configured as described above, the air fan 61 is driven to supply outside air (air) taken from outside the system into the air flow path of the fuel cell stack 40, The water supply pump 85 of the supply system 80 is driven to supply water. On the other hand, a solenoid valve (not shown) in the hydrogen gas supply system 50 is adjusted to supply hydrogen gas into the hydrogen gas flow path of the fuel cell stack 40 as a predetermined pressure.

  As a result, an electrochemical water generation reaction (electrode reaction) with hydrogen and oxygen is performed in each unit cell 10 constituting the fuel cell stack 40, and the generated current flows to a load system (such as a motor) not shown. .

  During operation of the fuel cell system 100, the fuel cell stack 40 is cooled by the cooling water circulating in the cooling water circulation path 121a of the water cooling system 120. Further, each unit cell 10 can be cooled and humidified (humidified) by supplying mist liquid water to the fuel cell stack 40 by the water supply system 80.

  Further, as shown in FIG. 1, the fuel cell system 100 of the present embodiment further includes a control device 70 that controls the operation of the fuel cell system 100. The detailed configuration of the control device 70 will be described later with reference to FIG.

  Next, with reference to FIG. 2, the unit cell 10 which comprises the fuel cell stack 40 is demonstrated. FIG. 2 is a cross-sectional view schematically showing the unit cell 10. As shown in FIG. 2, the unit cell 10 includes a membrane electrode assembly (MEA) 15, an air flow path 16 provided on the air electrode 12 side of the membrane electrode assembly 15, and a membrane electrode joint. A hydrogen gas passage 17 provided on the fuel electrode 13 side in the body 15, an air passage 16, a conductive separator 20 disposed on the outer surface side of the hydrogen gas passage 17, and a sealing material 21. .

  The membrane electrode assembly 15 is a laminate composed of a solid polymer electrolyte membrane 11 and an air electrode 12 and a fuel electrode 13 that sandwich both surfaces of the solid polymer electrolyte 11. Examples of the solid polymer electrolyte membrane 11 include solid polymer electrolyte membranes applicable to solid polymer fuel cells such as Nafion (registered trademark: manufactured by DuPont) and Aciplex (registered trademark: manufactured by Asahi Kasei Co., Ltd.). Can be used.

  The air electrode 12 is composed of a catalyst layer 12a in contact with the solid polymer electrolyte membrane 11, and a diffusion layer 12b in contact with the surface of the catalyst layer 12a opposite to the solid polymer electrolyte membrane 11.

  The fuel electrode 13 includes a catalyst layer 13a that contacts the solid polymer electrolyte membrane 11, and a diffusion layer 13b that contacts the surface of the catalyst layer 13a opposite to the solid polymer electrolyte membrane 11.

  The catalyst layer 12 a is a layer that is in contact with the solid polymer electrolyte membrane 11 to promote an electrode reaction in the air electrode 12, and the catalyst layer of the fuel electrode 13 that is in contact with the other surface of the solid polymer electrolyte membrane 11. Together with 13a, the water generation reaction of oxygen and hydrogen is promoted. As the catalyst layers 12a and 13a, for example, a catalyst layer including a catalyst-supporting carbon in which a catalyst such as platinum is supported on carbon particles and an electrolyte can be employed.

  The diffusion layers 12b and 13b are composed of a porous base material such as carbon woven fabric or carbon paper capable of gas diffusion. For example, carbon cloth, carbon paper, non-woven fabric made of carbon fiber, etc. Can be used.

  The air flow path 16 is a flow path through which the air supplied by the air supply system 60 (see FIG. 1) flows, and the air flows from the upper side to the lower side (arrow A direction) and is discharged. On the other hand, the hydrogen gas channel 17 is a channel through which the hydrogen gas supplied by the hydrogen supply system 50 flows. Hydrogen gas is supplied to the hydrogen gas flow path 17 from a supply port (not shown), and circulates from the front side to the back side (perpendicular to the page), for example, and is discharged from a discharge port (not shown).

  By supplying air to the air channel 16 and supplying hydrogen gas to the hydrogen gas channel 17, an electrochemical reaction between oxygen and hydrogen occurs in the membrane electrode assembly 15. Although specific configurations of the air flow path 16 and the hydrogen gas flow path 17 are omitted, the flow paths 16 and 17 are made of a conductive material, and the membrane electrode assembly 15 (air electrode 12, The fuel electrode 13) and the separator 20 are electrically connected.

  Next, a control device 70 that is mounted on the fuel cell system 100 of the present embodiment and controls the operation of the fuel cell system 100 will be described with reference to FIG. FIG. 3 is a block diagram showing an electrical configuration of the control device 70.

  As shown in FIG. 3, the control device 70 includes a CPU 71 which is a central processing unit, a ROM 72 which is a non-rewritable nonvolatile memory storing a control program executed by the CPU 71, fixed value data, and the like, and a control program The CPU 73, the ROM 72, and the input / output port 75 connected to the RAM 73 via the bus line 74 are mainly configured.

  As shown in FIG. 3, the input / output port 75 includes an outside air temperature sensor SE 1 that detects the temperature of outside air taken from outside the system, a voltage sensor SE 2 that detects the output voltage of the fuel cell stack 40, and the fuel cell stack 40. A current sensor SE3 for detecting the output current and a water level sensor SE4 are connected.

  Also, the input / output port 75 includes a water supply pump 85 that supplies liquid water stored in the water tank 82 to the nozzle 83 via the water supply path 81b, and a water supply electromagnetic valve 86 that adjusts the opening of the water supply path 81b. The air fan 61 is connected.

  When the detection values of the sensors SE1 to SE3 are input via the input / output port 75, the CPU 71 of the control device 70 sets the voltage control values based on the detection values to be controlled (water supply pump 85, water supply electromagnetic valve 86, It outputs to the air fan 61) and controls the operation of each control object.

  The control device 70 includes other sensors included in the fuel cell system 100, other electromagnetic valves included in the fuel cell system 100 (for example, a water draining electromagnetic valve 87), fuel, and the like by wiring not shown. The CPU 71 is also connected to other pumps included in the battery system 100, an inverter included in a load system (not shown), and the like. The CPU 71 controls a control target (solenoid valve, pump, etc.) based on the input of detection values from each sensor. ), Various controls for operating the fuel cell system 100 are performed.

  Next, with reference to FIGS. 4A and 4B, operation control for the fuel cell system 100 having the above-described configuration will be described.

  FIG. 4A is a flowchart showing an operation control process executed in the control device 70. This operation control process is a process for controlling the operation of the fuel cell system 100, and is repeatedly executed periodically by the CPU 71 while the power of the control device 70 is turned on. A control program for executing this operation control process is stored in the ROM 72.

  As shown in FIG. 4A, in this operation control process, first, detection values of the sensors (sensors SE1 to SE3, etc.) are acquired (S1). After the process of S1, an air supply control process for performing control related to air supply to the air electrode 12 (for example, control of the rotational speed of the air fan 61) is executed (S2), and control related to hydrogen gas supply to the fuel electrode 13 is performed. A hydrogen gas supply control process for performing (for example, control of a supply amount adjusting electromagnetic valve not shown) is executed (S3).

  After the process of S3, a direct fountain control process for controlling the jet of liquid water from the nozzle 83 is executed (S4). The specific control in the direct fountain control process (S4) will be described later with reference to FIG.

  After execution of the direct fountain control process (S4), other control processes for controlling the operation of the fuel cell system 100 are executed (S5), and the operation control process is terminated. In the other control process (S21), for example, when the detected value of the outside air temperature sensor SE1 indicates that the outside air temperature is low, the water draining electromagnetic valve 87 is opened and water in the water supply channel 81 is drained. A freeze prevention process that is a process of pulling out from the drainage channel 81c is included.

  FIG.4 (b) is a flowchart which shows the direct fountain control process (S4) performed in the operation control process (FIG.4 (a)) mentioned above. In this direct fountain control process (S4), first, dry determination is performed to determine whether or not the fuel cell stack 40 is in a dry state (S41).

  As one of the dry determinations performed in the processing of S41, the outside air temperature indicated by the detection value of the outside air temperature sensor SE1, the output of the fuel cell stack 40 obtained from the detection value of the voltage sensor SE2 and the detection value of the current sensor SE3, and A decision based on is used.

  Here, FIG. 5 is a correlation diagram schematically showing the correlation between the outside air temperature, the output of the fuel cell stack 40, and the occurrence of a situation where the fuel cell stack 40 becomes dry. In the correlation diagram shown in FIG. 5, the vertical axis is an axis indicating the outside air temperature, and indicates that the outside air temperature is higher toward the upper side. On the other hand, the horizontal axis is an axis indicating the output of the fuel cell stack 40, and indicates that the output is higher toward the right side.

  In FIG. 5, the hatched area where the outside air temperature is high and the fuel cell stack 40 is on the high output side is an area (dry area) showing a situation where the fuel cell stack 40 is dry. That is, the fuel cell stack 40 is in a dry state when the outside air temperature is high and the fuel cell stack 40 has a high output.

  In the process of S41, based on the detected values of the outside air temperature sensor SE1, the voltage sensor SE2, and the current sensor SE3, when the current state is in the dry region, the fuel cell stack 40 becomes dry (that is, the solid polymer electrolyte membrane) 11 is determined to be easily dried).

  Further, for the dry determination, for example, the resistance value of the unit cell 10 located in the center may be used instead of the outside air temperature, current, and voltage. Note that, for example, when the fuel cell system 100 is started up or when the fuel cell stack 40 repeats a low load and no load, the resistance of the unit cell of the fuel cell may exceed the threshold value. It may be.

  Returning to FIG. After the process of S41, it is confirmed whether or not the fuel cell stack 40 is in a dry state (S42). When the fuel cell stack 40 is in a dry state as a result of the confirmation in the process of S42 (S42: Yes), supply of direct jet water, that is, the nozzle by opening the water supply electromagnetic valve 86 and driving the water supply pump 85 The liquid water is sprayed from 83 (S43), and this direct fountain control process (S4) is terminated.

  On the other hand, if the fuel cell stack 40 is not in a dry state as a result of the confirmation in S42 (S42: No), the direct fountain is not supplied (S44) and the direct fountain control process (S4) is performed. finish. In addition, when stopping the supply of direct jet water, the water supply electromagnetic valve 86 is closed and the water supply pump 85 is stopped.

  Therefore, according to this direct fountain control process (S4), if the situation where the fuel cell stack 40 becomes dry does not occur, the direct fountain is not supplied. In this case, the water cooling system 120 (cooling water circulation path 121a) The water-cooled and non-humidified operation is performed by cooling only with the cooling water circulating.

  On the other hand, when a situation occurs in which the fuel cell stack 40 becomes dry, in that case, liquid water is sprayed from the nozzle 83 (direct jet water supply), and cooling by the water cooling system 120 and the water supply system 80 are performed. The operation is used in combination with cooling by. In addition, the process of S41 in this direct fountain control process (S4) corresponds to the film | membrane dryness estimation means in this invention, and the process of S42-S44 corresponds to the cooling control means in this invention.

  As described above, according to the fuel cell system 100 of the present embodiment, when the situation where the fuel cell stack 40 becomes dry (that is, the situation where the solid polymer electrolyte membrane 11 is easily dried) occurs, An operation using both cooling by the system 120 and cooling by the water supply system 80 is performed.

  Here, the cooling by the water supply system 80 is caused by the latent heat of vaporization of the mist-like liquid water supplied to the air electrode 12. That is, the mist-like liquid water supplied to the air electrode 12 cools the air electrode 12 by removing latent heat from the surface of the air electrode 12 and the surrounding air, and thus evaporation of moisture from the solid polymer electrolyte membrane 11 is performed. Can be prevented. Therefore, the cooling by the water supply system 80 has not only a cooling function but also a function of retaining the solid polymer electrolyte membrane.

  Therefore, in a situation where the fuel cell stack 40 is dry, not only can the fuel cell stack 40 be sufficiently cooled by performing an operation in which the cooling by the water cooling system 120 and the cooling by the water supply system 80 are combined, but also the solid polymer The electrolyte membrane 11 is moisturized, and a decrease in power generation performance due to drying of the solid polymer electrolyte membrane 11 can be prevented.

  Further, according to the fuel cell system 100 of the present embodiment, the condenser 112 is cooled by the cooling water circulating in the cooling water circulation path 121b, so that the exhaust cooling efficiency is high and the moisture recovery efficiency from the exhaust is high. Therefore, a sufficient amount of liquid water stored in the water tank 82 can be secured, and the amount of direct jet water (liquid water sprayed from the nozzle 83) supplied by the water supply system 80 is the fuel cell stack 40. It is possible to prevent the amount from becoming insufficient for cooling the substrate or moisturizing the solid polymer electrolyte membrane 11. As a result, a decrease in power generation performance is more effectively prevented.

  Further, according to the fuel cell system 100 of the present embodiment, the direct fountain sprayed on the air electrode 12 by the water supply means 80 causes the cooling action of the fuel cell stack 40 (air electrode 12) and the solid polymer electrolyte membrane 11. It exhibits both the moisturizing action and the action. Therefore, the high output of the fuel cell stack 40 can be effectively extracted under a high temperature environment. Further, the cooling water circulating in the cooling water circulation path 121b (that is, cooling water for cooling the condenser 112) is combined with the cooling water circulating in the cooling water circulation path 121b (that is, cooling water for cooling the fuel cell stack 40) and the radiator. Since it is cooled by 122, there is no need to provide a dedicated cooling device for cooling the cooling water circulating in the cooling water circulation path 121b. Accordingly, an increase in size of the fuel cell system 100 is suppressed, and the fuel cell system 100 can be accommodated in a compact space.

  Next, a second embodiment will be described with reference to FIGS. In the first embodiment described above, moisture is condensed from the exhaust by the condenser 112 and the separated liquid water is stored in the water tank 82, whereas in the second embodiment, moisture is removed from the exhaust. A water trap tank 89 having both a function of condensing and separating as liquid water and a function of storing the separated liquid water are used. In addition, the same code | symbol is attached | subjected to the part same as above-described 1st Embodiment, and the description is abbreviate | omitted.

  FIG. 6 is a block diagram showing the fuel cell system 200 of the second embodiment. As shown in FIG. 6, in the fuel cell system 200 of the second embodiment, a water trap tank 89 as a water storage means that is a part of the water supply system 80 is provided between the fuel cell stack 40 and the air discharge path 111. Is provided. The specific configuration of the water trap tank 89 will be described later with reference to FIG.

  In the second embodiment, the cooling water circulation path 121 b used for cooling the condenser 111 in the first embodiment is used for cooling the water trap tank 89. Therefore, as shown in FIG. 6, the cooling water circulation path 121 b branches from the cooling water circulation path 121 a on the downstream side of the radiator 122, passes through the water trap tank 89, and on the upstream side of the circulation pump 123, the cooling water circulation path 121 a. It is provided to merge with. In the second embodiment as well, the cooling water circulation path 121b corresponds to the second refrigerant circulation path constituting the fuel cell system of the present invention.

  Note that the control device 70 that controls the operation of the fuel cell system 200 of the second embodiment executes a direct fountain control process (see FIG. 4B) as in the first embodiment described above, and performs a fuel cell stack. When the situation in which the fuel cell stack 40 becomes dry is not generated, the cooling by the water cooling system 120 and the cooling by the water supply system 80 are performed. The fuel cell system 200 is controlled so as to perform the operation using the fuel cell.

  FIG. 7 is a cross-sectional view schematically showing the water trap tank 89. As shown in FIG. 7, the water trap tank 89 has at least a power generation unit 40a (more specifically, each power cell 40a (more specifically, each unit cell 10 stacked below the fuel cell stack 40). It is a tray-shaped tank that receives the exhaust discharged from the air electrode 12) of the unit cell 10.

  As shown in FIG. 7, a hollow part 89 a as a cooling part is provided on the outer periphery of the water trap tank 89. The hollow portion 89a is provided with communication portions 89a1 and 89a2 communicating with the cooling water circulation path 121b. The communication portion 89a1 is connected to the radiator 122 side of the cooling water circulation path 121b, and the communication portion 89a2 includes a cooling portion. It is connected to the circulation pump 123 side in the water circulation path 121b. That is, the hollow part 89a of the water trap tank 89 becomes a part of the cooling water circulation path 121b and the cooling water cooled by the radiator 122 is circulated.

  Thus, the cooling water flows through the hollow portion 89 a provided on the outer periphery of the water trap tank 89, whereby the exhaust discharged from the fuel cell stack 40 is cooled inside the water trap tank 89. As a result, the moisture of the exhaust gas is condensed and stored as liquid water W in a space 89 b as a storage portion formed on the inner wall side of the water trap tank 89.

  On the bottom side of the space 89b in the water trap tank 89, a drain port 89c communicating with the water supply path 81b is formed. Therefore, when the water supply pump 85 is driven, the liquid water W stored in the space 89 b (that is, liquid water condensed from the exhaust gas) flows out from the drain port 89 c and is pumped to the nozzle 83 from the nozzle 83. The mist is injected toward the air manifold 62.

  The water trap tank 89 is formed with an opening 89 d communicating with the air discharge path 111, and the exhaust discharged from the fuel cell stack 40 finally passes through the opening 89 d to the air discharge path 111. And discharged.

  Note that a partition wall 89e having an opening on the bottom side of the space 89b is provided on the opening 89d side of the water trap tank 89. The partition wall 89e is provided with a butterfly valve 89f at a position corresponding to the opening 89d.

  The butterfly valve 89f is controlled by the control means 70 so as to be closed when the liquid water W stored in the space 89b is not full. Therefore, when the water trap tank 89 is not full, the exhaust discharged from the fuel cell stack 40 flows to the opening 89d through the opening between the partition wall 89e and the bottom of the space 89b.

  Therefore, when the butterfly valve 89f is closed, the exhaust is easily cooled by the cooling water flowing through the hollow portion 89a, and the condensation of moisture from the exhaust is promoted, contributing to an increase in the amount of stored water.

  On the other hand, the butterfly valve 89f is opened by the control of the control means 70 when the liquid water W stored in the space 89b is full, and the exhaust discharged from the fuel cell stack 40 mainly passes through the butterfly valve 89f. Then, it flows to the opening 89d. Therefore, when the trap tank 89 is full, the exhaust from the fuel cell stack 40 is mainly discharged from the butterfly valve 89f, thereby preventing the liquid water from overflowing from the water trap tank 89.

  The water trap tank 89 includes a water level sensor SE4 that detects the level of the liquid water W stored in the space 89b, a direct jet water temperature sensor (not shown) that detects the temperature of the liquid water W, and a hollow portion 89a. A sensor such as a cooling water temperature sensor (not shown) for detecting the temperature of the cooling water flowing through the pipe is provided.

  As described above, according to the fuel cell system 200 of the second embodiment, the function of condensing moisture from the exhaust gas and separating it as the liquid water W (hollow part 89a) and the function of storing the separated liquid water W ( Since the water trap tank 89 having both the space 89b) is used, it is not necessary to provide a condenser and a water tank separately. Therefore, the fuel cell system capable of preventing the solid polymer electrolyte membrane 11 from being dried and preventing the power generation performance from being lowered can be configured more compactly.

  As described above, the present invention has been described based on the embodiments, but the present invention is not limited to the above-described embodiments, and various improvements and modifications can be easily made without departing from the spirit of the present invention. It can be guessed.

  For example, in the first embodiment, the liquid water condensed from the exhaust by the condenser 112 is stored in the water tank 82 and used as the water to be supplied to the nozzle 83, but instead of this, or In addition, it is good also as a structure which stores the condensed water of a vehicle-mounted air conditioner in a tank, and utilizes this stored water as the water supplied to the nozzle 83. FIG.

  Further, in the second embodiment, the hollow portion 89a is provided on the outer periphery of the water trap tank 89, and the cooling water is circulated through the hollow portion 89a to condense the moisture in the exhaust gas. Alternatively, or in addition to this, the cooling water circulation path 121b may be passed through the inner peripheral side of the water trap tank 89 to condense the moisture in the exhaust.

  Moreover, in each said embodiment, when the quantity of the liquid water stored in the water tank 82 or the water trap tank 89 is small, the opening degree of the circulation electromagnetic valve 125 is raised and the cooling water which distribute | circulates the cooling water circulation path 121b. A configuration may be adopted in which the amount is increased or the amount of air supplied to the fuel cell stack 40 is reduced by lowering the rotational speed of the air fan 61.

  Further, in each of the above embodiments, the degree of drying of the solid polymer electrolyte membrane 11 (that is, whether or not it is in a dry state) is indirectly estimated based on parameters such as the outside air temperature and the output of the fuel cell stack. However, the degree of drying of the solid polymer electrolyte membrane 11 may be estimated by directly measuring the water content or resistance value of the solid polymer electrolyte membrane 11.

1 is a block diagram showing a first embodiment of a fuel cell system which is a fuel cell system of the present invention. FIG. It is sectional drawing which shows a unit cell typically. It is a block diagram which shows the electric constitution of a control apparatus. (A) is a flowchart which shows the operation control process performed in a control apparatus, (b) is a flowchart which shows the direct fountain control process performed in the operation control process of (a). FIG. 5 is a correlation diagram schematically showing the correlation between the outside air temperature, the output of the fuel cell stack, and the occurrence of a situation where the fuel cell stack becomes dry. It is a block diagram which shows the fuel cell system of 2nd Embodiment. It is sectional drawing which shows a water trap tank typically.

Explanation of symbols

10 Unit cell (fuel cell)
11 Solid polymer electrolyte membrane 12 Air electrode 13 Fuel electrode 40 Fuel cell stack 50 Hydrogen supply system (fuel gas supply means)
60 Air supply system (oxidant gas supply means)
81a Water conduit (water recovery means)
81b Water supply channel (liquid water supply means)
82 Water tank (water storage means)
89 Water trap tank (water storage means)
89a Hollow part (part of water storage means, cooling part)
89b Space (part of water storage means, water storage part)
100 Fuel cell system 112 Condenser (heat exchanger)
121a Cooling water circulation path (refrigerant circulation path)
121b Cooling water circulation path (second refrigerant circulation path)
122 Radiator (cooling means)
S41 Film dryness estimation means S42 to S44 Cooling control means

Claims (3)

A fuel cell stack in which a fuel cell configured to include a solid polymer electrolyte membrane and a fuel electrode and an air electrode that sandwich the solid polymer electrolyte membrane from both sides with a separator interposed therebetween;
Fuel gas supply means for supplying fuel gas to the fuel electrode;
Oxidant gas supply means for supplying air taken from outside the system to the air electrode at normal pressure;
A refrigerant circulation path for circulating the refrigerant in the separator;
Cooling means for cooling the refrigerant;
Liquid water supply means for cooling the fuel cell by supplying atomized liquid water together with air to the air electrode;
A membrane dryness estimating means for estimating the dryness of the solid polymer electrolyte membrane;
When the degree of dryness of the solid polymer electrolyte membrane estimated by the membrane dryness estimating means is below a predetermined level, the fuel cell is circulated by circulating the refrigerant cooled by the cooling means through the refrigerant circulation path. When the degree of drying of the solid polymer electrolyte membrane estimated by the membrane dryness estimating means exceeds a predetermined level, the cooling of the fuel cell by the refrigerant circulating in the refrigerant circulation path and the liquid And a cooling control unit that uses both the cooling of the fuel cell by the water supply unit. Water storage means for storing liquid water to be supplied to the air electrode by the liquid water supply means;
A heat exchanger for cooling the exhaust discharged from the air electrode in the fuel cell by heat exchange and condensing moisture from the exhaust to separate it as liquid water;
Water recovery means for recovering liquid water from the heat exchanger and returning it to the water storage means;
The fuel cell system according to claim 1, further comprising a second refrigerant circulation path that circulates the refrigerant cooled by the cooling means as a refrigerant for cooling the heat exchanger. A cooling unit that cools the exhaust gas discharged from the air electrode in the fuel cell by heat exchange; and a water storage unit that stores liquid water separated from the exhaust gas due to condensation of water accompanying cooling by the cooling unit. Water storage means for storing liquid water to be supplied to the air electrode by the liquid water supply means;
2. The fuel cell system according to claim 1, further comprising: a second refrigerant circulation path that circulates the refrigerant cooled by the cooling unit as a refrigerant that cools a cooling unit of the water storage unit.

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