JP5341624B2 - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To aim at simplification and weight-reduction of a fuel cell system including a fuel cell stack. <P>SOLUTION: In the fuel cell system 10, a first fuel cell stack 12 and a second fuel cell stack 14 are laminated. A first electrolyte contained in the first fuel cell stack 12 shows proton conductivity irrespective of it being a wet state or not. Meanwhile, a second electrolyte contained in the second fuel cell stack 14 shows proton conductivity when it is made wet. In this structure, when a fuel gas and an oxidant gas are supplied to the first fuel cell stack 12, these fuel gas and oxidant gas are exhausted from the first fuel cell stack 12 while moisture generated by an electrode reaction is contained. The fuel gas and the oxidant gas are cooled at a first inter-cooler 212 and a second inter-cooler 214 respectively and supplied to the second fuel cell stack 14 while a relative humidity is raised by cooling. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a fuel cell system including two types of fuel cell stacks having different electrolytes.

  As one type of fuel cell stack, a unit cell in which a solid polymer electrolyte membrane made of perfluorosulfonic acid polymer (for example, Nafion manufactured by DuPont, USA) is sandwiched between an anode side electrode and a cathode side electrode is well known. Has come to be.

  This type of solid polymer electrolyte membrane exhibits almost no proton conductivity in a dry state, and exhibits proton conductivity as it is wetted. In other words, during the operation of the fuel cell stack, it is necessary to impart moisture to the solid polymer electrolyte membrane, thereby maintaining the proton conductivity of the solid polymer electrolyte membrane. This is because when the proton conductivity of the solid polymer electrolyte membrane is lowered, it becomes difficult for protons to move from the anode side electrode to the cathode side electrode, so that the power generation characteristics of the fuel cell stack are lowered.

  Therefore, conventionally, a fuel cell system is constructed by attaching a humidifier to the fuel cell stack (see, for example, Patent Document 1). In this case, moisture is applied to the fuel gas supplied to the anode side electrode and the oxidant gas supplied to the cathode side electrode under the action of the humidifier. The moisture reaches the end face on the side facing the anode side electrode and the end face on the side facing the cathode side electrode in the solid polymer electrolyte membrane, so that the wet state of the solid polymer electrolyte membrane is maintained.

JP 2008-41466 A

  As understood from the above, in order to maintain power generation characteristics in a fuel cell stack including a solid polymer electrolyte membrane, it is necessary to attach a humidifier to keep the solid polymer electrolyte membrane in a wet state. In other words, it is essential to provide a humidifier in this type of fuel cell system.

  However, in this case, since the humidifier is present, the fuel cell system becomes large-scale, and it is difficult to simplify and reduce the weight.

  Further, a cooling medium such as cooling water or cooling oil is generally circulated inside the fuel cell stack. Here, the operating temperature of the fuel cell stack including the solid polymer electrolyte membrane is about 100 ° C., and the temperature of the cooling medium after cooling the fuel cell stack at such a temperature is about the same as the temperature of the atmosphere. There is no difference. Therefore, a large-area radiator is required to lower the cooling medium to such a temperature that the fuel cell stack can be cooled again.

  Such a large-area radiator is inevitably large in size and also heavy in weight. This also contributes to the simplification and weight reduction of the fuel cell system.

  The present invention has been made to solve the above-described problems, and does not require a humidifier. Further, the cooling means for lowering the temperature of the cooling medium can be miniaturized. For this reason, the configuration is simplified and the weight is reduced. An object of the present invention is to provide a fuel cell system that can be realized.

To achieve the above object, the present invention provides a first fuel cell stack including an electrolyte exhibiting proton conductivity regardless of whether or not it contains moisture, and proton conductivity as it is wetted. A fuel cell, an oxidant gas, and a cooling medium discharged from the first fuel cell stack are supplied to the second fuel cell stack. A fuel cell system,
Each of a fuel gas discharge port, an oxidant gas discharge port, and a coolant discharge port in the first fuel cell stack, and a fuel gas supply port, an oxidant gas supply port, and a coolant supply port in the second fuel cell stack First to third cooling means for cooling the fuel gas, the oxidant gas, and the cooling medium discharged from the first fuel cell stack are interposed in each pipe communicating with each of
After being discharged from the first fuel cell stack, the fuel gas, the oxidant gas, and the cooling medium cooled by each of the first to third cooling means are supplied to the second fuel cell stack. As supplied
It further has piping for returning the cooling medium discharged from the second fuel cell stack to the first fuel cell stack.

  The electrolyte in the first fuel cell stack exhibits proton conductivity regardless of whether it is wet or dry. For this reason, when fuel gas and oxidant gas are supplied to the first fuel cell stack, an electrode reaction occurs, and as a result, moisture is generated at the cathode side electrode. This moisture becomes water vapor when the temperature of the first fuel cell stack exceeds 100 ° C., the amount of water that has passed through the electrolyte and reached the anode side electrode becomes fuel gas, and the amount that remains on the cathode side electrode becomes oxidant gas. , Respectively, and discharged from the first fuel cell stack. That is, the fuel gas and the oxidant gas become a wet gas containing water vapor.

  The fuel gas and oxidant gas thus wetted are cooled by the first cooling means and the second cooling means, thereby increasing the relative humidity. In this state, the fuel gas and the oxidant gas introduced into the second fuel cell stack come into contact with each of the anode side electrode and the cathode side electrode included in the second fuel cell stack, so that the anode side Moisture is applied to the electrolyte sandwiched between the electrode and the cathode side electrode. As a result, the electrolyte exhibits proton conductivity.

  That is, according to the present invention, the electrolyte contained in the second fuel cell stack can be brought into a wet state without attaching a humidifier, thereby allowing the electrolyte to exhibit proton conductivity. Since the humidifier is not necessary in this way, the fuel cell system can be simplified and reduced in weight.

  In addition, the operating temperature of the first fuel cell stack including the electrolyte that does not require moisture for the development of proton conductivity is generally the operating temperature of the second fuel cell stack including the electrolyte that requires the water for expression of proton conductivity. It is hotter than For this reason, the temperature of the cooling medium exhausted by taking heat from the first fuel cell stack is higher than that of the atmosphere. In other words, the temperature difference between the cooling medium and the atmosphere is relatively large.

  For this reason, the efficiency of heat exchange in the third cooling means for cooling the cooling medium is increased. This means that a small size can be adopted as the third cooling means. This also contributes to simplification and weight reduction of the fuel cell system.

  The first fuel cell stack and the second fuel cell stack may be laminated together to form a composite stack. In this case, a partition member is interposed between the first fuel cell stack and the second fuel cell stack, and the fuel gas exhaust port of the first fuel cell stack, the oxidant gas exhaust are inserted into the partition member. All of the outlet and the cooling medium discharge port, and the fuel gas supply port, the oxidant gas supply port, and the cooling medium supply port of the second fuel cell stack may be formed. The fuel gas discharge port and the fuel gas supply port, the oxidant gas discharge port and the oxidant gas supply port, the cooling medium discharge port and the cooling medium supply port, What is necessary is just to make it connect with piping which interposed the cooling means.

  Thus, by stacking the first fuel cell stack and the second fuel cell stack to form a composite stack, the first fuel cell stack and the second fuel cell stack are compared with the case where they are individually installed. This makes it easy to install a fuel cell system.

  When the composite stack is configured as described above, the fuel gas supply port and the oxidant gas supply port in the first fuel cell stack and the fuel gas supply port and the oxidant gas supply in the second fuel cell stack, respectively. Each of the ports is located diagonally, and each of the fuel gas outlet and the oxidant gas outlet in the first fuel cell stack, and the fuel gas outlet and the oxidant gas outlet in the second fuel cell stack When each of the first and second fuel cell stacks is positioned diagonally, it becomes easy to circulate the fuel gas and the oxidant gas between the first fuel cell stack and the second fuel cell stack stacked on each other. This is because it is very easy to connect piping for communicating each supply port and each discharge port.

  In any case, a three-way valve is interposed in a pipe bridged from the cooling medium discharge port of the first fuel cell stack to the third cooling means, and one of the outlets of the three-way valve is connected to the cooling medium. It is preferable to connect to the pipe returning to the first fuel cell stack.

  That is, the three-way valve is disposed on the upstream side of the third cooling means. Therefore, in this case, by operating the three-way valve, the cooling medium that has become hot due to the heat taken from the first fuel cell stack is transferred to the first fuel cell stack without going through the third cooling means. It becomes possible to return to.

  In short, in this case, the high-temperature cooling medium is supplied again to the first fuel cell stack. For this reason, for example, the temperature of the first fuel cell stack can be quickly raised at the time of starting the first fuel cell stack.

  Further, the output of the first fuel cell stack is preferably set to ¼ to 〜 of the total output of the first fuel cell stack and the second fuel cell stack. Note that this does not mean that the output of the first fuel cell stack is always controlled to ¼ to ３ of the total output during operation of the fuel cell system. This means that the theoretical maximum output is set to 1/4 to 1/3 of the sum of the theoretical maximum outputs of the first fuel cell stack and the second fuel cell stack.

  By setting the output of the first fuel cell stack in this way, the temperature of the first fuel cell stack can be raised efficiently, for example, when the first fuel cell stack is started.

  Moreover, in this case, when the temperature of the second fuel cell stack is raised after the temperature of the first fuel cell stack has sufficiently increased, it is avoided that the temperature of the first fuel cell stack rises excessively. . In other words, it becomes easy to maintain the first fuel cell stack at a temperature suitable for power generation (operation).

  Apart from this, during the low output operation, the first fuel cell stack may be mainly operated. Thereby, it is avoided that the temperature of the first fuel cell stack is excessively lowered. That is, even in this case, the first fuel cell stack can be maintained at a temperature suitable for operation.

  In the present invention, a first fuel cell stack including an electrolyte exhibiting proton conductivity regardless of whether or not it contains moisture, and a first electrolyte including an electrolyte that exhibits proton conductivity when wetted. A fuel cell system comprising two fuel cell stacks, and a fuel gas supplied to the first fuel cell stack and discharged in a wet state by an electrode reaction of the first fuel cell stack, and The oxidant gas is supplied to the second fuel cell stack by increasing the relative humidity. As a result, proton conductivity develops in the electrolyte contained in the second fuel cell stack, so that the second fuel cell stack becomes ready for power generation.

  Thus, according to the present invention, it is possible to make the second fuel cell stack capable of generating electric power without providing a humidifier. In other words, a humidifier is not necessary. For this reason, the fuel cell system can be simplified and reduced in weight.

  Further, since the operating temperature of the first fuel cell stack is higher than the operating temperature of the second fuel cell stack, the temperature difference between the cooling medium discharged from the first fuel cell stack and the atmosphere. Is relatively large. Accordingly, since the efficiency of heat exchange in the third cooling means for cooling the cooling medium is increased, a small one can be adopted as the third cooling means. In combination with this, the fuel cell system can be further simplified and reduced in weight.

1 is a schematic overall configuration diagram of a fuel cell system according to an embodiment. 2 is an exploded perspective view of a first unit cell constituting a first fuel cell stack included in the fuel cell system. FIG. It is a whole front view which shows the end surface of the side contained in the adjacent 1st unit cell of the separator contained in a 1st unit cell, and facing a different kind of separator. It is a whole front view which shows the end surface of the side which faces the cathode side electrode of the said separator. It is a whole front view which shows the end surface of the side facing the anode side electrode of the said another kind of separator. It is a whole front view which shows the end surface at the side which faces the said separator contained in the adjacent 1st unit cell of the said another kind of separator. It is a schematic whole perspective view of the middle plate (partition member) interposed between the 1st fuel cell stack and the 2nd fuel cell stack. It is a schematic whole perspective view from another angle of the middle plate. It is a disassembled perspective view of the 2nd unit cell which comprises the 2nd fuel cell stack contained in the fuel cell system. It is a whole front view by the side of the 2nd fuel cell stack of the fuel cell system. FIG. 2 is a schematic overall system diagram of an electric system of the fuel cell system.

  Preferred embodiments of the fuel cell system according to the present invention will be described below in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic overall configuration diagram of a fuel cell system according to the present embodiment. The fuel cell system 10 includes a composite stack 15 configured by stacking a first fuel cell stack 12 and a second fuel cell stack 14 in the arrow X direction. A middle plate 16 as a partition member is interposed between the first fuel cell stack 12 and the second fuel cell stack 14.

  First, the first fuel cell stack 12 will be described.

  FIG. 2 is an exploded perspective view of the first unit cell 20 constituting the first fuel cell stack 12. The first unit cell 20 includes a first electrolyte / electrode assembly 26 formed by sandwiching a first electrolyte (not shown) between an anode side electrode 22 and a cathode side electrode 24, and a pair of separators 28, 30. It is configured by interposing between them. Reference numeral 32 is a gasket that supports the first electrolyte-electrode assembly 26.

  The first fuel cell stack 12 is formed by stacking a predetermined number of the first unit cells 20 configured as described above. That is, the separator 28 in the adjacent first unit cell 20 is superimposed on the separator 30 in the arbitrary first unit cell 20.

  On the lower left side of the separator 28, the gasket 32, and the separator 30 in FIG. 2, oxidant gas supply holes 34, 36, 38 for supplying an oxidant gas containing oxygen to the cathode side electrode 24 are formed in communication with each other. On the lower right side, fuel gas supply holes 40, 42, 44 for supplying a fuel gas containing hydrogen to the anode side electrode 22 are formed in communication with each other. On the other hand, on the upper left side, fuel gas discharge holes 46, 48, 50 for discharging the fuel gas are formed in communication with each other, and on the upper right side, an oxidant for discharging the oxidant gas. Gas discharge holes 52, 54, and 56 are formed in communication with each other. That is, the fuel gas supply holes 40, 42, 44 and the fuel gas discharge holes 46, 48, 50 are disposed diagonally to each other. Similarly, the oxidant gas supply holes 34, 36, 38 and the oxidant gas discharge holes 52, 54 and 56 are also arranged diagonally to each other. The communication direction of each hole is the arrow X direction.

  Further, between the oxidant gas supply holes 34, 36, 38 and the fuel gas discharge holes 46, 48, 50, and between the fuel gas supply holes 40, 42, 44 and the oxidant gas discharge holes 52, 54, 56. Are formed with cooling medium discharge holes 58, 60, 62 and cooling medium supply holes 64, 66, 68, respectively. That is, the cooling medium supply holes 64, 66, 68 and the cooling medium discharge holes 58, 60, 62 are provided so as to face each other.

  As shown in FIGS. 2 and 3, the cooling medium (abbreviated as “refrigerant” in the drawings) flows through the separator 28 on the end face of the adjacent first unit cell 20 facing the separator 30. The passage 70 is engraved as a groove shape. The cooling medium flows from the cooling medium supply hole 64 toward the cooling medium discharge hole 58 only through the cooling medium passage 70.

  Further, as shown in FIG. 4, an oxidant gas passage 72 through which the oxidant gas flows is provided on the end face of the separator 28 facing the cathode side electrode 24. The oxidant gas flows from the oxidant gas supply hole 34 toward the oxidant gas discharge hole 52 only through the oxidant gas passage 72.

  On the other hand, on the end surface facing the anode side electrode 22 in the separator 30, as shown in FIGS. 2 and 5, the fuel gas for flowing the fuel gas from the fuel gas supply hole 44 toward the fuel gas discharge hole 50. A passage 74 is provided. The fuel gas flows from the fuel gas supply hole 44 toward the fuel gas discharge hole 50 only through the fuel gas passage 74.

  In the separator 30, the end surface of the adjacent first unit cell 20 facing the separator 28 is a flat surface as shown in FIG. The flat surface covers the cooling medium passage 70 (see FIGS. 2 and 3) of the separator 30, so that the cooling medium passage 70 is covered.

  The first electrolyte constituting the first electrolyte / electrode assembly 26 interposed between the separators 28 and 30 is substantially the same regardless of whether the first electrolyte is wet or dry. Proton conductivity is shown. That is, the proton conductivity of the first electrolyte is not affected by the amount of water.

  Such a first electrolyte can be formed of, for example, a porous body impregnated with an inorganic acid such as sulfuric acid or phosphoric acid, or an organic acid. Alternatively, the first electrolyte may be configured by doping an organic polymer such as polybenzimidazole (PBI).

As another preferred example of the material of the first electrolyte, an acid salt such as CsHSO ₄ , Sn _0.95 Al _0.05 P ₂ O _7, an acid salt glass, or an ionic liquid having a structure represented by the following formula: The thing which impregnated the porous material can be mentioned.

  Further, the first electrolyte may be an ion conductive ceramic such as perovskite.

  The first electrolyte made of this kind of material exhibits good proton conductivity at a temperature generally exceeding 100 ° C., regardless of the amount of water.

  Both the cathode side electrode 24 and the anode side electrode 22 sandwiching the first electrolyte have a gas diffusion layer in which the oxidant gas or the fuel gas diffuses, and an electrode catalyst layer (both not shown) in which an electrode reaction occurs, The electrode catalyst layer therein faces the first electrolyte side. The structures of the cathode side electrode 24 and the anode side electrode 22 of this type are known, and thus detailed description thereof is omitted.

  In order to obtain the first fuel cell stack 12, a plurality of first unit cells 20 configured as described above are stacked, and current collector plates and tabs (not shown) having tab portions (see FIG. 1) 76 at both ends thereof are provided. A current collecting plate (not shown) having a portion 78 is provided. Further, an end plate 80 and a middle plate 16 are disposed outside the current collecting plate through insulating plates, respectively.

  The end plate 80 includes an oxidant gas supply port 82 communicating with the oxidant gas supply holes 34, 36, 38, a fuel gas supply port 84 communicating with the fuel gas supply holes 40, 42, 44, a cooling medium supply hole 64, Supply hollow tubes 88, 90, 92 having cooling medium supply ports 86 communicating with 66, 68 are provided.

  One middle plate 16 has a substantially rectangular parallelepiped shape as shown in FIGS. 7 and 8. 7 and 8, the end face 16a faces the first fuel cell stack 12 side, and the end face 16b faces the second fuel cell stack 14 side.

  In the end face 16a of the middle plate 16, a first oxidant gas receiving portion 94 communicating with the oxidant gas supply holes 34, 36, 38 is formed on the lower left side of FIGS. 7 and 8, and on the lower right side, A first fuel gas receiving portion 96 communicating with the fuel gas supply holes 40, 42, 44 is formed. Further, a fuel gas collective exhaust port 98 communicating with the fuel gas exhaust holes 46, 48, 50 is formed on the upper left side, and an oxidant gas collective exhaust communicating with the oxidant gas exhaust holes 52, 54, 56 is formed on the upper right side. An outlet 100 is formed.

  Further, a cooling medium collective discharge port 102 communicating with the cooling medium discharge holes 58, 60, 62 is formed between the first oxidant gas receiving portion 94 and the fuel gas collective discharge port 98, and the first fuel. A first cooling medium receiving unit 104 is formed between the gas receiving unit 96 and the oxidant gas collective discharge port 100.

  On the other hand, the end surface 16b of the middle plate 16 is positioned at the back surface of each of the first oxidant gas receiving portion 94, the first fuel gas receiving portion 96, the fuel gas collective discharge port 98, and the oxidant gas collective exhaust port 100. The second oxidant gas receiving unit 106, the second fuel gas receiving unit 108, the fuel gas collective supply port 110, and the oxidant gas collective supply port 112 are provided. Further, a cooling medium batch supply port 114 and a second cooling medium receiving portion 116 are provided at positions on the back surfaces of the cooling medium batch discharge port 102 and the first cooling medium receiving portion 104.

  As can be understood from FIGS. 7 and 8, the first oxidant gas receiver 94 and the second oxidant gas receiver 106, and the first fuel gas receiver 96 and the second fuel gas receiver 108 are separated from each other. Yes. Similarly, the fuel gas collective supply port 110 and the fuel gas collective discharge port 98, the oxidant gas collective supply port 112 and the oxidant gas collective exhaust port 100, the cooling medium collective discharge port 102, and the cooling medium collective supply port 114 are also connected. Are separated from each other.

  On one side surface 16 c of the middle plate 16, there are a hollow joint pipe 120 whose inside communicates with the cooling medium batch discharge port 102 and a hollow joint pipe 122 whose inside communicates with the cooling medium batch supply port 114. It is attached. In addition, on the side surface 16c, joint pipes 124 and 126, each of which communicates with the fuel gas collective discharge port 98 and the fuel gas collective supply port 110, are provided above the joint pipes 120 and 122, respectively.

  Similarly, hollow joint pipes 128 and 130 are attached to one side surface 16 d of the middle plate 16, each of which communicates with the oxidant gas collective discharge port 100 and the oxidant gas collective supply port 112. As will be described later, the joint pipes 120 and 122, the joint pipes 124 and 126, and the joint pipes 128 and 130 are connected to each other through pipes 132, 134, and 136. The coolant gas batch supply ports 114 communicate with each other, the fuel gas collective discharge ports 98 and the fuel gas collective supply ports 110 communicate with each other, and the oxidant gas collective discharge ports 100 and the oxidant gas collective supply ports 112 communicate with each other (see FIG. 1).

  The second fuel cell stack 14 has an insulating plate (not shown) and a tab portion 138 (see FIG. 1) (not shown) on the end surface 16b side (see FIGS. 7 and 8) of the middle plate 16 configured as described above. It is arranged via an electric plate.

  Here, an exploded perspective view of the second unit cell 140 constituting the second fuel cell stack 14 is shown in FIG. The same constituent elements as those constituting the first unit cell 20 are denoted by the same reference numerals.

  As can be understood from FIG. 9, the second unit cell 140 has a second electrolyte / electrode assembly 142 that employs a second electrolyte (not shown) instead of the first electrolyte as a set of separators 144, 146. It is configured in accordance with the first unit cell 20 except that it is interposed in between.

  As the second electrolyte constituting the second electrolyte / electrode assembly 142, a substance that exhibits high proton conductivity when in a wet state is selected. Suitable examples of this type of material include perfluorosulfonic acid polymers (for example, Nafion manufactured by DuPont, USA), sulfonated aromatic hydrocarbon polymers (for example, sulfonated polyethersulfone, And sulfonated polyetheretherketone).

  When the second electrolyte made of such a substance is in a wet state, it exhibits a high proton conductivity of about 0.1 S / cm at a relatively low temperature range of 100 ° C. or lower.

You may make it add the additive for improving a hygroscopic property and a water | moisture retention to a 2nd electrolyte. Preferable examples of such additives include particles of metal oxides such as TiO ₂ and silica. Further, for example, a strong acid group may be added to silica.

  The configurations of the separators 144 and 146 and the gasket 148 are the same as those of the separators 28 and 30 and the gasket 32 in the first unit cell 20, but the positions of the supply holes and the discharge holes are different. That is, in the second unit cell 140, the oxidant gas discharge holes 150, 152, 154 are formed to communicate with each other on the lower left side of the separator 144, the gasket 148, and the separator 146, and the fuel gas discharge holes 156, 158, 160 are formed in communication with each other. Further, fuel gas supply holes 162, 164, 166 are formed in communication with each other on the upper left side, and oxidant gas supply holes 168, 170, 172 are formed in communication with each other on the upper right side. Further, between the oxidant gas discharge holes 150, 152, 154 and the fuel gas supply holes 162, 164, 166, and between the fuel gas discharge holes 156, 158, 160 and the oxidant gas supply holes 168, 170, 172. Are formed with cooling medium supply holes 174, 176, 178 and cooling medium discharge holes 180, 182, 184, respectively.

  Of course, the oxidant gas supply holes 168, 170, 172 communicate with the oxidant gas collective supply port 112 (see FIGS. 8 and 9) of the middle plate 16, and the fuel gas supply holes 162, 164, 166 are of the middle plate 16. The fuel gas collective supply port 110 communicates. Similarly, the cooling medium supply holes 174, 176 and 178 communicate with the cooling medium batch supply port 114 of the middle plate 16. That is, the oxidant gas collective supply port 112, the fuel gas collective supply port 110, and the coolant supply batch supply port 114 of the middle plate 16 are the oxidant gas supply port, fuel gas supply port, and coolant supply in the second fuel cell stack 14. Acts as a mouth.

  The second oxidant gas receiver 106, the second fuel gas receiver 108, and the second cooling medium receiver 116 provided on the end surface 16b of the middle plate 16 are respectively provided with the oxidant gas discharge holes 150, 152, and 154. The fuel gas discharge holes 156, 158, 160 and the coolant discharge holes 180, 182, 184 communicate with each other.

  The second fuel cell stack 14 is formed by stacking a predetermined number of the second unit cells 140 configured in this manner, and ends with a current collector plate (not shown) having a tab portion 186 and an insulating plate at the end portion thereof. A plate 188 is arranged. The number of the first unit cells 20 and the second unit cells 140 is such that the output of the first fuel cell stack 12 is ¼ to the total output of the first fuel cell stack 12 and the second fuel cell stack 14. It is preferable to set to 1/3.

  As shown in FIG. 10, the end plate 188 has an oxidant gas discharge port 190 communicating with the oxidant gas discharge holes 150, 152, 154, and a fuel gas discharge port 192 communicated with the fuel gas discharge holes 156, 158, 160. Discharge hollow tubes 196, 198, and 200 having cooling medium discharge ports 194 communicating with the cooling medium discharge holes 180, 182, and 184 are provided.

  A back plate 202 is disposed outside the end plate 80 (see FIG. 1), and a back plate 204 is disposed outside the end plate 188 (see FIG. 10). The back plate 202 is formed with two through holes and two escape portions 205a and 205b, and the back plate 204 is also formed with two through holes and two escape portions 206a and 206b. Is done. The supply hollow tubes 88 and 90 and the discharge hollow tubes 196 and 198 are passed through the through holes, and the supply hollow tube 92 and the discharge hollow tube 200 are connected to the escape portion 205b or the escape portion. Interference with the back plates 202 and 204 is avoided by 206a.

  As shown in FIGS. 1 and 10, screw insertion holes 207 a to 207 d and 207 e to 207 h are formed through the vicinity of the four corners of the back plates 202 and 204. An end plate 80 interposed between the back plates 202 and 204 is formed by screwing nuts (not shown) into the thread portions of the tie rods 208a to 208d inserted into the screw insertion holes 207a to 207d and 207e to 207h. , Insulating plate, current collecting plate, first fuel cell stack 12, insulating plate, middle plate 16, insulating plate, current collecting plate, second fuel cell stack 14, insulating plate, current collecting plate and end plate 188 are tightened .

  In the above configuration, as shown in FIG. 1, a pipe 132 is bridged on the joint pipes 120 and 122, and a pipe 134 is bridged on the joint pipes 124 and 126. A pipe 136 is bridged between the joint pipes 128 and 130. A radiator 210, a first intercooler 212, and a second intercooler 214 as cooling means are interposed in the pipes 132, 134, and 136, respectively.

  Further, a pipe 216 is bridged from the discharge hollow tube 200 of the end plate 188 to the supply hollow tube 92 of the end plate 80. A branch pipe 218 is connected to the pipe 216 so as to branch from the pipe 216, and the branch pipe 218 is connected to the upstream side of the radiator 210 in the pipe 136 via a three-way valve 220.

  Of course, an oxidant gas supply source (for example, an air compressor) (not shown) is connected to the supply hollow tube 88 in which the oxidant gas supply port 82 is formed. Similarly, a fuel gas supply source (for example, a hydrogen cylinder) (not shown) is connected to the supply hollow tube 90 in which the fuel gas supply port 84 is formed.

  FIG. 11 schematically shows an electric system of the fuel cell system 10. The tab portions 76 and 138 are electrically connected to the input side of the motor 222 (external load), while the tab portions 78 and 186 are electrically connected to the output side of the motor 222. Further, switches 224 and 226 are interposed between the output side of the motor 222 and the signal lines connecting the tab portions 78 and 186, respectively. Of course, these switches 224 and 226 can be individually set to an on state or an off state.

  The fuel cell system 10 according to the present embodiment is basically configured as described above. Next, the function and effect will be described.

  When operating the fuel cell system 10, first, the three-way valve 220 is arranged so that the cooling medium flows only from the cooling medium batch discharge port 102 to only the cooling medium supply port 86, that is, only inside the first fuel cell stack 12. (See FIG. 1) is set. In addition, what is necessary is just to select cooling water, cooling oil, etc. as a cooling medium.

  In this state, the oxidant gas is supplied from the oxidant gas supply source and the fuel gas is supplied from the fuel gas supply source. Among them, part of the fuel gas flows through the fuel gas supply holes 40 and 42 of the first fuel cell stack 12 (first unit cell 20), and the fuel gas supply holes of the separator 30 shown in FIGS. After passing through 44, the fuel gas passage 74 is circulated. In the course of this distribution, hydrogen contained in the fuel gas comes into contact with the anode-side electrode 22 of the first electrolyte / electrode assembly 26. The fuel gas diffuses through the gas diffusion layer of the anode side electrode 22 and reaches the electrode catalyst layer.

  Hydrogen is separated into protons and electrons in the electrode catalyst layer. Here, the first electrolyte is made of a substance that exhibits proton conductivity regardless of whether or not it is wetted (whether or not moisture is present). For this reason, for example, even when the first fuel cell stack 12 is activated at an environmental temperature lower than 0 ° C., protons conduct through the first electrolyte and reach the electrode catalyst layer of the cathode-side electrode 24. . Further, the electrons reach the electrode catalyst layer of the cathode side electrode 24 after passing through the motor 222 (see FIG. 11).

  Excess fuel gas not involved in the reaction reaches the fuel gas discharge hole 50. Then, the surplus fuel gas that has not been introduced into the first unit cell 20 merges and flows through the fuel gas discharge holes 46, 48, 50 of the adjacent first unit cell 20 along the arrow X direction. Finally, the reacted and unreacted fuel gas reaches the fuel gas collective discharge port 98 of the middle plate 16.

  On the other hand, a part of the oxidant gas is introduced into the oxidant gas passage 72 from the oxidant gas supply hole 34 of the separator 28 shown in FIGS. Then, when flowing through the oxidant gas passage 72 of the separator 28, it contacts the cathode side electrode 24. The oxidant gas diffuses through the gas diffusion layer of the cathode side electrode 24 and reaches the electrode catalyst layer.

  As described above, in the electrode catalyst layer of the cathode-side electrode 24, there are protons that have reached through the first electrolyte and electrons that have reached through the external circuit. These protons and electrons react with oxygen contained in the oxidant gas to generate moisture.

  This moisture generation reaction is an exothermic reaction. Moreover, in the present embodiment, the output of the first fuel cell stack 12 is preferably set to about ¼ to ３ of the total output of the fuel cell system 10. For this reason, in the 1st fuel cell stack 12, said electrode reaction advances efficiently. As a result, the temperature of the first fuel cell stack 12 rises rapidly and reaches a temperature suitable for operation, that is, over 100 ° C.

  Thus, even if the environmental temperature is less than 0 ° C., the first fuel cell stack 12 can be easily raised to a temperature suitable for operation.

  While the temperature of the first fuel cell stack 12 rises, the coolant supplied from the coolant supply port 86 of the end plate 80 to the inside of the first fuel cell stack 12 passes through the coolant supply hole 64 of the separator 28. It reaches the cooling medium discharge hole 58 through the passage 70. The cooling medium cools the first unit cell 20 by taking heat from the first unit cell 20 during this period, and then circulates along the direction of the arrow X through the cooling medium discharge holes 60 and 62, It is discharged from the first fuel cell stack 12 through 16 cooling medium batch discharge ports 102.

  In the present embodiment, the coolant discharged from the first fuel cell stack 12 in this manner is returned to the coolant supply port 86 via the branch pipe 218 and the pipe 216 without passing through the radiator 210, The high temperature is supplied again to the first fuel cell stack 12. This also raises the temperature of the first fuel cell stack 12 quickly.

  As the temperature of the first fuel cell stack 12 exceeds 100 ° C., the moisture is generated as water vapor. The water vapor is entrained by the unreacted surplus oxidant gas, reaches the oxidant gas discharge hole 52, and merges with the surplus oxidant gas that has not been introduced into the first unit cell 20 to oxidize the gasket 32. The gas passes through the gas discharge hole 54 and the oxidant gas discharge hole 56 of the separator 30 through the oxidant gas discharge holes 52, 54, and 56 of the adjacent first unit cell 20 along the arrow X direction. Finally, the reacted and unreacted oxidant gas reaches the oxidant gas collective discharge port 100 of the middle plate 16 in a state containing water vapor.

  As described above, as the temperature of the first fuel cell stack 12 rises, the temperature of the oxidant gas rises due to heat transfer. This increases the amount of saturated water vapor in the oxidant gas. For this reason, the oxidant gas discharged from the oxidant gas collective discharge port 100 contains a large amount of water vapor. That is, the oxidant gas discharged from the first fuel cell stack 12 is a wet gas containing water vapor.

  The oxidant gas led out from the oxidant gas collective discharge port 100 to the pipe 136 through the joint pipe 128 reaches the second intercooler 214 and is cooled. This cooling increases the relative humidity of the oxidant gas.

  Part of the water vapor generated in the electrode catalyst layer of the cathode side electrode 24 passes through the first electrolyte, reaches the electrode catalyst layer of the anode side electrode 22, and is accompanied by the fuel gas supplied to the anode side electrode 22. Are discharged from the fuel gas discharge holes 46, 48 and 50. For this reason, the fuel gas that has reached the fuel gas collective discharge port 98 also becomes a wet gas containing water vapor.

  The fuel gas led out from the fuel gas collective discharge port 98 to the pipe 134 through the joint pipe 124 reaches the first intercooler 212 and is cooled. This cooling also increases the relative humidity of the fuel gas.

  The oxidant gas and the fuel gas whose relative humidity has increased in this way reach the oxidant gas collective supply port 112 and the fuel gas collective supply port 110 via the pipes 136 and 134 and the joint pipes 130 and 126, respectively. And it introduce | transduces into the oxidant gas supply holes 168, 170, 172, and the fuel gas supply holes 162, 164, 166 of the second fuel cell stack 14 (second unit cell 140), respectively, and circulates along the arrow X direction.

  As described above, in the second unit cell 140 (second fuel cell stack 14), the supply start position of the oxidant gas, the fuel gas, and the cooling medium is different from that of the first unit cell 20 (first fuel cell stack 12). That is, in the present embodiment, the oxidant gas supply port (oxidant gas batch supply port) in the second fuel cell stack 14 with respect to the oxidant gas supply port 82 and the fuel gas supply port 84 in the first fuel cell stack 12. 112) and the fuel gas supply port (fuel gas collective supply port 110) are located on the diagonal line, respectively, while the oxidant gas exhaust port (oxidant gas collective exhaust port 100) and fuel in the first fuel cell stack 12 respectively. The fuel gas discharge port 192 and the oxidant gas discharge port 190 in the second fuel cell stack 14 provided in the end plate 188 are positioned diagonally with respect to the gas discharge port (fuel gas batch supply port 110). It is. The middle plate 16 switches the flow direction of the oxidant gas, the fuel gas, and the cooling medium.

  A part of the fuel gas flows through the fuel gas supply holes 162 and 164 of the second fuel cell stack 14 (second unit cell 140), passes through the fuel gas supply holes 166 of the separator 146 shown in FIG. The fuel gas passage 74 is circulated. In the course of this circulation, water vapor contained in the fuel gas contacts the anode electrode 22 of the second electrolyte / electrode assembly 142. The fuel gas diffuses through the gas diffusion layer of the anode electrode 22 and reaches the electrode catalyst layer.

  At this time, an ionization reaction similar to that of the anode side electrode 22 in the first unit cell 20 occurs in the anode side electrode 22.

  On the other hand, part of the oxidant gas flows through the oxidant gas passage 72 of the separator 144 through the oxidant gas supply hole 168 of the second fuel cell stack 14 (second unit cell 140). In the course of this flow, water vapor contained in the oxidant gas contacts the cathode side electrode 24 of the second electrolyte / electrode assembly 142. The oxidant gas further diffuses through the gas diffusion layer of the cathode side electrode 24 and reaches the electrode catalyst layer.

  Each electrode catalyst layer of the cathode side electrode 24 and the anode side electrode 22 faces the second electrolyte. For this reason, moisture is imparted to the second electrolyte from both the fuel gas and the oxidant gas, which are wet gases reaching the electrode catalyst layer. Thereby, the 2nd electrolyte can be efficiently moistened. That is, the second electrolyte is wetted with the wet gas (fuel gas and oxidant gas) discharged from the first fuel cell stack 12.

  The second electrolyte wetted in this manner exhibits excellent proton conductivity. For this reason, it becomes easy for the proton generated in the anode side electrode 22 to conduct in the second electrolyte. In other words, protons start moving from the anode side electrode 22 toward the cathode side electrode 24.

  Thereafter, as in the first unit cell 20, in the cathode side electrode 24, the oxidant gas supplied to the cathode side electrode 24, the proton that has passed through the second electrolyte and reached the cathode side electrode 24, and the anode An electrode reaction occurs with electrons generated at the side electrode 22 and reaching the cathode side electrode 24 via an external circuit, and moisture is generated.

  That is, according to the present embodiment, it is possible to wet the second electrolyte without attaching a humidifier, and thereby make it possible to generate (operate) the second fuel cell stack 14. In other words, although the second fuel cell stack 14 that needs to wet the electrolyte for power generation is included, a humidifier becomes unnecessary. For this reason, simplification and weight reduction of the fuel cell system 10 can be achieved.

  As the electrode reaction described above occurs in the second fuel cell stack 14, the temperature of the second fuel cell stack 14 begins to rise. Further, although the fuel gas and the oxidant gas discharged from the first fuel cell stack 12 are cooled by the first intercooler 212 and the second intercooler 214, the second fuel cell stack 14 is at a higher temperature than the room temperature. To be supplied. Therefore, the temperature of the second fuel cell stack 14 rises efficiently.

  When it is confirmed that the second fuel cell stack 14 has risen to a predetermined temperature, the three-way valve 220 is switched to allow the coolant discharged from the first fuel cell stack 12 to flow to the radiator 210 side. The cooling medium is cooled by the radiator 210, passes through the joint pipe 122, reaches the cooling medium batch supply port 114 of the middle plate 16, and is introduced into the second fuel cell stack 14.

  Here, the operating temperature of the first fuel cell stack 12 exceeds 100 ° C. as described above. Therefore, the cooling medium discharged after cooling the first fuel cell stack 12 is higher in temperature than the atmosphere. For this reason, even if the radiator 210 is small, the temperature of the cooling medium can be lowered efficiently.

  That is, according to the present embodiment, a small radiator 210 can be employed. This also contributes to simplification and weight reduction of the fuel cell system 10.

  Furthermore, the cooling medium that has taken heat from the first fuel cell stack 12 and has reached a high temperature has a large amount of heat. If this amount of heat is used as a heating source, the fuel efficiency of the fuel cell system 10 can be improved.

  While the temperature of the second fuel cell stack 14 rises, the output of the first fuel cell stack 12 is suppressed to about ¼ to ３ of the total output of the fuel cell system 10. Therefore, it is kept at a substantially constant temperature. That is, the temperature of the first fuel cell stack 12 is prevented from rising excessively, and is maintained at a temperature suitable for the operation of the first fuel cell stack 12. For this reason, the power generation efficiency of the first fuel cell stack 12 is maintained in a high state.

  After the second fuel cell stack 14 reaches an appropriate operating temperature, that is, approximately 100 ° C., the switches 222, 226 shown in FIG. 11 are both turned on to energize the motor 222. When the output of the first fuel cell stack 12 is sufficient, such as during low power operation, the switch 226 is turned off and only the switch 224 is turned on. Nevertheless, when the required output is lower than the output of the first fuel cell stack 12, the surplus output of the first fuel cell stack 12 may be stored in the power storage device.

  Here, when the fuel cell system 10 is operated at a low output, the first fuel cell stack 12 may be a main output source. Thereby, it is avoided that the temperature of the first fuel cell stack 12 decreases excessively. That is, also in this case, the first fuel cell stack 12 is maintained at a temperature suitable for operation, and as a result, the power generation efficiency of the first fuel cell stack 12 is maintained at a high level.

  As described above, regardless of whether or not moisture is present (whether or not it is in a wet state), it is distributed to the first fuel cell stack 12 including the first electrolyte exhibiting proton conductivity and is wetted accordingly. The liquefied fuel gas and oxidant gas are circulated through the second fuel cell stack 14 including the second electrolyte that exhibits proton conductivity when wetted, so that a second humidifier is not provided. The fuel cell stack 14 can be brought into an operable state. For this reason, the fuel cell system 10 can be simplified and reduced in weight.

  Moreover, since the heat exchange efficiency of the radiator 210 for cooling the cooling medium discharged from the first fuel cell stack 12 is also improved, a small radiator 210 can be adopted. This also contributes to simplification and weight reduction of the fuel cell system 10.

  Further, since the cooling medium that has taken high heat from the first fuel cell stack 12 and has a high temperature has a large amount of heat, the fuel consumption as the fuel cell system 10 can be improved by using this amount of heat as a heating source. it can.

  Furthermore, with the configuration as described above, there is also an advantage that the temperatures of the first fuel cell stack 12 and the second fuel cell stack 14 can be increased efficiently.

  In the above-described embodiment, the first fuel cell stack 12 and the second fuel cell stack 14 are stacked via the middle plate 16, but the first fuel cell stack 12 and the second fuel cell are stacked. The stacks 14 may be provided apart from each other.

DESCRIPTION OF SYMBOLS 10 ... Fuel cell system 12 ... 1st fuel cell stack 14 ... 2nd fuel cell stack 16 ... Middle plate 20 ... 1st unit cell 22 ... Anode side electrode 24 ... Cathode side electrode 26 ... 1st electrolyte and electrode assembly 28, 30, 144, 146 ... separators 34, 36, 38, 168, 170, 172 ... oxidant gas supply holes 40, 42, 44, 162, 164, 166 ... fuel gas supply holes 46, 48, 50, 156, 158, 160 ... Fuel gas discharge holes 52, 54, 56, 150, 152, 154 ... Oxidant gas discharge holes 58, 60, 62, 180, 182, 184 ... Cooling medium discharge holes 64, 66, 68, 174, 176, 178 ... Cooling medium supply hole 70 ... Cooling medium passage 72 ... Oxidant gas passage 74 ... Fuel gas passages 76, 78, 138, 186 ... Tab portion 82 ... Oxidant gas Supply port 84 ... Fuel gas supply port 86 ... Cooling medium supply port 88, 90, 92 ... Supply hollow tube 98 ... Fuel gas collective discharge port 100 ... Oxidant gas collective exhaust port 102 ... Cooling medium collective exhaust port 110 ... Fuel Collective gas supply port 112 ... Oxidant gas collective supply port 114 ... Cooling medium collective supply port 120, 122, 124, 126, 128, 130 ... Fitting pipes 132, 134, 136, 216 ... Piping 140 ... Second unit cell 142 ... second electrolyte / electrode assembly 190 ... oxidant gas discharge port 192 ... fuel gas discharge port 194 ... cooling medium discharge port 196, 198, 200 ... discharge hollow tube 210 ... radiator 212 ... first intercooler 214 ... second Intercooler 218 ... Branch pipe 220 ... Three-way valve 222 ... Motor 224, 226 ... Switch

Claims (5)

A first fuel cell stack having an electrolyte exhibiting proton conductivity regardless of whether it contains water, or a second fuel cell stack having an electrolyte that exhibits proton conductivity when wetted A fuel cell system in which a fuel gas, an oxidant gas, and a cooling medium discharged from the first fuel cell stack are supplied to the second fuel cell stack,
Each of a fuel gas discharge port, an oxidant gas discharge port, and a coolant discharge port in the first fuel cell stack, and a fuel gas supply port, an oxidant gas supply port, and a coolant supply port in the second fuel cell stack First to third cooling means for cooling the fuel gas, the oxidant gas, and the cooling medium discharged from the first fuel cell stack are interposed in each pipe communicating with each of
After being discharged from the first fuel cell stack, the fuel gas, the oxidant gas, and the cooling medium cooled by each of the first to third cooling means are supplied to the second fuel cell stack. As supplied
The fuel cell system further comprising a pipe for returning the cooling medium discharged from the second fuel cell stack to the first fuel cell stack. The fuel cell system according to claim 1, wherein
The second fuel cell stack is stacked on the first fuel cell stack, and has a partition member interposed between the first fuel cell stack and the second fuel cell stack. And
The fuel gas discharge port of the first fuel cell stack, the oxidant gas discharge port and the cooling medium discharge port, the fuel gas supply port of the second fuel cell stack, the oxidant gas supply port, A fuel cell system, wherein all of the cooling medium supply port is formed in the partition member. The fuel cell system according to claim 2, wherein
Each of the fuel gas supply port and the oxidant gas supply port in the first fuel cell stack and each of the fuel gas supply port and the oxidant gas supply port in the second fuel cell stack are located on a diagonal line,
Each of the fuel gas outlet and the oxidant gas outlet in the first fuel cell stack and each of the fuel gas outlet and the oxidant gas outlet in the second fuel cell stack are located diagonally. A fuel cell system. The fuel cell system according to any one of claims 1 to 3,
Having said first fuel cell and the cooling medium three-way valve which is interposed from the outlet to a pipe that is bridged over the third cooling hand stages of the stack,
One of the three-way valve outlets is connected to the pipe for returning the cooling medium to the first fuel cell stack. In the fuel cell system according to any one of claims 1 to 4,
The fuel cell system, wherein an output of the first fuel cell stack is ¼ to ３ of a total output of the first fuel cell stack and the second fuel cell stack.

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