Fuel Cell Systems

Abstract

To implement response performance improvement of power generation output and downsizing of a fuel cell system.SOLUTION: A fuel cell system 1 comprises: a fuel cell stack 10 for generating electricity using hydrogen and oxygen; and an air passage 31 connected to the fuel cell stack 10. The air passage 31 has a compressed air introduction port 32 to which house air or air for control is introduced. On the air passage 31 is provided a pressure reduction valve 33 between the compressed air introduction port 32 and the fuel cell stack 10.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE The present invention relates to a fuel cell system. [Background technology]

[0002] Fuel cell systems are known as systems that directly convert the chemical energy of fuel gas into electricity. The fuel cells in these fuel cell systems are capable of producing electrical energy with high power generation efficiency by electrochemically reacting hydrogen, which is the fuel, with oxygen, which is the oxidant. Fuel cells require a flow rate of air that corresponds to the required power output. To introduce air into the fuel cell, the fuel cell system is equipped with, for example, a blower. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-242964 A Summary of the Invention [Problem to be solved by the invention]

[0004] In this regard, there is a demand for improving the responsiveness of the power generation output of the fuel cell system to the required power generation output, and also for reducing the size of the fuel cell system.

[0005] The present invention has been made in consideration of the above points, and has an object to improve the responsiveness of the power generation output of a fuel cell system and to reduce the size of the system. [Means for solving the problem]

[0006] The fuel cell system according to the present invention comprises: a fuel cell stack that generates electricity using hydrogen and oxygen; an air flow path connected to the fuel cell stack; Equipped with The air flow path has a compressed air inlet through which facility air or control air is introduced, A pressure reducing valve is provided on the air flow path between the compressed air inlet and the fuel cell stack.

[0007] Alternatively, the fuel cell system according to the present invention comprises: a plurality of fuel cell stacks that generate electricity using hydrogen and oxygen; an air distribution channel that distributes air to the plurality of fuel cell stacks; Equipped with The air distribution flow path has a compressed air inlet into which facility air or control air is introduced, A pressure reducing valve is provided on the air distribution passage between the compressed air inlet and the plurality of fuel cell stacks. Effect of the Invention

[0008] According to the present invention, it is possible to improve the responsiveness of the power generation output of a fuel cell system and reduce the size of the system. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram showing the configuration of a fuel cell system according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a block diagram showing the configuration of a modified example of the fuel cell system shown in FIG. [Diagram 3] FIG. 3 is a block diagram showing the configuration of another modified example of the fuel cell system shown in FIG. [Figure 4] FIG. 4 is a block diagram showing the configuration of still another modified example of the fuel cell system shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will now be described with reference to the drawings. Fig. 1 is a block diagram showing the configuration of a fuel cell system 1 according to an embodiment of the present invention.

[0011] The fuel cell system 1 shown in Fig. 1 includes a fuel cell stack 10, a hydrogen supply system 20, and an oxygen supply system 30. Connected to the fuel cell stack 10 are a power supply device 2 for extracting current from the fuel cell stack 10, and a control device 70 for calculating an output command value and sending it to the power supply device 2. Connected to the control device 70 is an input unit 3. A required power generation amount required of the fuel cell system 1 is input to the control device 70 via the input unit 3. The control device 70 calculates an output command value based on the required power generation amount input from the input unit 3. The control device 70 also controls each part of the fuel cell system 1 based on the output command value and other information.

[0012] The fuel cell stack 10 generates electricity using hydrogen and oxygen. The fuel cell stack 10 has an anode electrode (fuel electrode) 11 and a cathode electrode 12. Hydrogen is supplied to the anode electrode 11 as a fuel gas. Air is supplied to the cathode electrode 12. The fuel cell stack 10 reacts hydrogen with oxygen in the air to produce water, and generates electricity from this reaction. This electricity is output from the fuel cell stack 10 as direct current.

[0013] Hydrogen is supplied to the anode electrode 11 by a hydrogen supply system 20. Air is supplied to the cathode electrode 12 by an oxygen supply system 30. The remainder of the hydrogen supplied to the anode electrode 11 is discharged from the fuel cell stack 10 as anode exhaust. The remainder of the air supplied to the cathode electrode 12 is discharged from the fuel cell stack 10 as cathode exhaust. In the illustrated example, the anode exhaust is supplied again to the anode electrode 11, and the cathode exhaust is discharged to the outside of the fuel cell system 1.

[0014] The hydrogen supply system 20 includes a hydrogen supply source 21, such as a hydrogen storage tank, and a hydrogen flow path 22. The hydrogen flow path 22 connects the hydrogen supply source 21 to the fuel cell stack 10. As a result, hydrogen from the hydrogen supply source 21 is supplied to the fuel cell stack 10 via the hydrogen flow path 22. A blower may be provided on the hydrogen flow path 22, and hydrogen from the hydrogen supply source 21 may be sent to the anode electrode 11 using the blower. The hydrogen supply source 21 may be located inside or outside the fuel cell system 1.

[0015] The oxygen supply system 30 includes an air flow path 31, and a pressure reducing valve 33 and a filter device 60 provided on the air flow path 31. The air flow path 31 connects an on-site air supply device 40 that is external to the fuel cell system 1 to the fuel cell stack 10. As a result, air from the on-site air supply device 40 is supplied to the fuel cell stack 10 via the air flow path 31. More specifically, the air flow path 31 has a compressed air inlet 32. The compressed air inlet 32 ​​is connected to the on-site air supply device 40. On-site air from the on-site air supply device 40 is introduced into the compressed air inlet 32. The compressed air inlet 32 ​​may be connected to a control air supply device instead of the on-site air supply device 40. In this case, control air from the control air supply device is introduced into the compressed air inlet 32.

[0016] The station air supply device 40 and the control air supply device may be known devices that supply station air or control air (also called factory air or instrument air). The station air supply device 40 and the control air supply device may be existing devices in the plant in which the fuel cell system 1 is installed, and may be used for purposes other than supplying compressed air to the fuel cell system 1. For example, the compressed air (station air, control air, factory air, instrument air) from the station air supply device 40 or the control air supply device may be used as driving air for various machines, or as cleaning air for cleaning equipment in the plant. The uses of the compressed air from the station air supply device 40 and the control air supply device are not limited to those described above.

[0017] In the illustrated example, a station air supply pressure gauge 51 is connected to the station air supply device 40. The station air supply pressure gauge 51 measures the pressure of compressed air provided from the station air supply device 40 to the air flow path 31. The station air supply pressure gauge 51 can be connected to a control device 70 in the fuel cell system 1, and can send information related to the measured pressure of the compressed air to the control device 70.

[0018] The pressure reducing valve 33 is disposed on the air flow path 31 between the compressed air inlet 32 ​​and the fuel cell stack 10. The pressure reducing valve 33 reduces the pressure of the compressed air provided from the station air supply device 40 or the control air supply device. Here, the pressure of the compressed air provided from the station air supply device 40 or the control air supply device is generally about 800 kPa to 4.5 MPa. In contrast, the pressure of the air preferably provided to the fuel cell stack 10 is, for example, about 2 kPa to 20 kPa. Thus, the pressure of the compressed air provided from the station air supply device 40 or the control air supply device is much higher than the pressure preferably provided to the fuel cell stack 10. Therefore, in the fuel cell system 1, the compressed air provided from the station air supply device 40 or the control air supply device is reduced in pressure using the pressure reducing valve 33 and then supplied to the fuel cell stack 10. The pressure reducing valve 33 reduces the pressure of the compressed air provided from the station air supply device 40 or the control air supply device to, for example, about 20 kPa to 30 kPa.

[0019] The filter device 60 removes moisture and impurities from the air introduced from the on-site air supply device 40 or the control air supply device to the fuel cell system 1. In the illustrated example, the filter device 60 is disposed on the air flow path 31, between the compressed air inlet 32 ​​and the pressure reducing valve 33.

[0020] As described above, in the fuel cell system 1 shown in FIG. 1, the oxygen supply system 30 does not include an air supply device such as a blower, and receives air supply from an existing device 40 installed in the place where the fuel cell system 1 is used. This allows the fuel cell system 1 to be made compact. In addition, in general, the indoor air supply device 40 and the control air supply device constantly generate indoor air and control air. Therefore, if the compressed air inlet 32 ​​of the fuel cell system 1 is connected to the indoor air supply device 40 or the control air supply device, air can be immediately supplied to the fuel cell stack 10. This contributes to improving the responsiveness of the power generation output of the fuel cell system 1. Note that, when the oxygen supply system 30 of the fuel cell system 1 includes a blower and supplies air to the fuel cell stack 10 using the blower, sufficient air cannot be supplied to the fuel cell stack 10 from the time the blower is started until the air volume of the blower reaches a desired air volume. This is a factor that hinders improvement of the responsiveness of the power generation output of the fuel cell system 1.

[0021] In the illustrated example, the oxygen supply system 30 further includes a buffer tank 34, a flow rate control valve 35, and a buffer tank pressure gauge 50. The buffer tank 34 is provided on the air flow path 31 between the pressure reducing valve 33 and the fuel cell stack 10, and stores air depressurized by the pressure reducing valve 33. The buffer tank 34 is connected to the buffer tank pressure gauge 50. The buffer tank pressure gauge 50 measures the pressure inside the buffer tank 34. The flow rate control valve 35 is provided on the air flow path 31 between the buffer tank 34 and the fuel cell stack 10. The flow rate control valve 35 adjusts the flow rate of air from the buffer tank 34 to the fuel cell stack 10. The flow rate control valve 35 adjusts the flow rate of the air in response to an output command value input to the power supply device 2 and a battery current measured by the power supply device 2. The flow rate control valve 35 controls the flow rate of the air, for example, by receiving a control signal from the control device 70.

[0022] The air reduced in pressure by the pressure reducing valve 33 is stored in the buffer tank 34, and the flow rate of air from the buffer tank 34 to the fuel cell stack 10 is adjusted by the flow control valve 35, thereby enabling air of the desired pressure and at the desired flow rate to be stably supplied to the fuel cell stack 10.

[0023] In the illustrated example, the oxygen supply system 30 further includes an auxiliary compressor 36, an auxiliary air flow path 37, and a flow rate control valve 38. The auxiliary compressor 36 may be a known compressor, and can generate compressed air of about 20 kPa to 30 kPa by compressing outside air, for example. The auxiliary air flow path 37 connects the auxiliary compressor 36 and the buffer tank 34, and introduces the compressed air from the auxiliary compressor 36 into the buffer tank 34. The auxiliary compressor 36 is started upon receiving a control signal from, for example, the control device 70. The flow rate control valve 38 controls the flow rate of air from the auxiliary compressor 36 to the buffer tank 34. The flow rate control valve 38 adjusts the flow rate of the air according to the battery current measured by the power supply device 2. The flow rate control valve 38 controls the flow rate of the air upon receiving a control signal from, for example, the control device 70.

[0024] By being able to introduce compressed air from the auxiliary compressor 36 into the buffer tank 34, even if for some reason sufficient compressed air is not available from the on-site air supply system 40 or the control air supply system, the buffer tank 34 can be filled with a sufficient amount of compressed air. Therefore, air at a desired pressure and at a desired flow rate can be more stably supplied to the fuel cell stack 10.

[0025] Next, the operation of the fuel cell system 1 shown in Fig. 1 will be described. First, the compressed air inlet 32 ​​of the fuel cell system 1 is connected to the on-site air supply device 40, and the on-site air supply device 40 starts supplying air to the buffer tank 34. At this time, air from which moisture and impurities have been removed by the filter device 60 is supplied to the buffer tank 34. Furthermore, when the required amount of power generation required of the fuel cell stack 10 is input from the input unit 3 to the control device 70, the control device 70 calculates an output command value based on the required amount of power generation and passes it to the power supply device 2. As a result, the supply of hydrogen from the hydrogen supply system 20 and the supply of air from the oxygen supply system 30 to the fuel cell stack 10 starts, and the fuel cell system 1 starts generating power.

[0026] While the fuel cell system 1 is generating power, the control device 70 obtains information about the pressure in the buffer tank 34 from the buffer tank pressure gauge 50. If the pressure is lower than a predetermined pressure, the control device 70 inputs a control signal to the auxiliary compressor 36 to start the auxiliary compressor 36.

[0027] Furthermore, while the fuel cell system 1 is generating power, the control device 70 adjusts the opening degree of the flow rate adjustment valve 35 based on the output command value input to the power supply device 2.

[0028] As a result of the above, a power generation output corresponding to the output command value determined by the control device 70 is obtained from the fuel cell stack 10.

[0029] The output command value is calculated as follows. First, the control device 70 performs a predetermined calculation on the required power generation amount input from the input unit 3. If the calculation result is equal to or less than a predetermined upper limit value and equal to or greater than a predetermined lower limit value, the control device 70 passes the calculation result to the power supply unit 2 as an output command value. On the other hand, if the calculation result is greater than the predetermined upper limit value, the control device 70 passes the predetermined upper limit value to the power supply unit 2 as an output command value. If the calculation result is less than a predetermined lower limit value, the control device 70 passes the predetermined lower limit value to the power supply unit 2 as an output command value. If the facility air supply unit 40 and the auxiliary compressor 36 are not operating normally, the control device 70 determines the output command value to be 0, as will be described later.

[0030] The upper limit value used in the calculation of the output command value is determined as follows. Usually, the upper limit value is set to the same value as the rated power output of the fuel cell stack 10. However, when the pressure in the buffer tank 34 obtained from the buffer tank pressure gauge 50 during power generation by the fuel cell system 1 is lower than a predetermined pressure, the fuel cell stack 10 cannot generate power at its rated power output because only a flow rate of air less than normal can be supplied from the buffer tank 31 to the fuel cell stack 10. For this reason, the control device 70 obtains a new upper limit value corresponding to the pressure measured by the buffer tank pressure gauge 50, and determines the output command value using this new upper limit value. Here, the new upper limit value is a value lower than the rated power output. For example, the new upper limit value is the maximum power output that the fuel cell stack 10 can output even if the pressure in the buffer tank 31 is the measured pressure. The new upper limit value is obtained by performing a predetermined calculation on the pressure measured by the buffer tank pressure gauge 50. This predetermined calculation is performed by the upper limit value calculation unit 71 of the control device 70.

[0031] When the new upper limit value is set, a new output command value is input from the control device 70 to the power supply device 2, and power generation is performed in the fuel cell stack 10 based on this new output command value. Since the new output command value is determined using a new upper limit value that is lower than the normal upper limit value, the maximum flow rate of air required for power generation by the fuel cell stack 10 is reduced. In this way, the upper limit value of the output set value input to the power supply device 2 is lowered when the pressure in the buffer tank 34 drops, so that the fuel cell system 1 can continue power generation even if the flow rate of air supplied from the buffer tank 34 to the fuel cell stack 10 (in other words, from the on-site air supply device 40 or the auxiliary compressor 36 to the buffer tank 34) drops. Note that if the amount of air supplied to the fuel cell stack 10 drops and the amount of air consumed by the fuel cell stack 10 becomes greater than the amount of air, the fuel cell system 1 cannot continue power generation and is therefore stopped for protection.

[0032] Also, while the fuel cell system 1 is generating power, the control device 70 obtains information on the pressure of the compressed air provided by the local air supply device 40 to the fuel cell system 1 from the local air supply pressure gauge 51. As a result, the control device 70 judges whether the local air supply device 40 is operating normally. Specifically, when the pressure measured by the local air supply pressure gauge 51 is extremely low, the control device 70 judges that the local air supply device 40 is not operating normally. Also, while the fuel cell system 1 is generating power, the control device 70 judges whether the auxiliary compressor 36 is operating normally. For example, when the control device 70 does not receive an operation signal from the auxiliary compressor 36, it judges that the auxiliary compressor 36 has broken down and is stopped. When the local air supply device 40 is not operating normally and the auxiliary compressor 36 is stopped, air cannot be supplied to the fuel cell stack 10. In this case, the control device 70 determines the output command value to be 0 and passes it to the power supply device 2. As a result, the operation of the fuel cell system 1 can be safely stopped.

[0033] The determination of whether the on-site air supply device 40 and the auxiliary compressor 36 are operating normally may be made based on the pressure in the buffer tank 34 obtained from the buffer tank pressure gauge 50. Specifically, if the pressure measured by the buffer tank pressure gauge 50 remains extremely low for a predetermined period of time, the control device 70 may determine that neither the on-site air supply device 40 nor the auxiliary compressor 36 are operating normally.

[0034] As described above, the fuel cell system 1 according to this embodiment includes a fuel cell stack 10 that generates electricity using hydrogen and oxygen, and an air flow path 31 connected to the fuel cell stack 10. The air flow path 31 has a compressed air inlet 32 ​​through which station air or control air is introduced. A pressure reducing valve 33 is provided on the air flow path 31 between the compressed air inlet 32 ​​and the fuel cell stack 10. With this fuel cell system 1, it is possible to reduce the size of the fuel cell system 1 compared to a case in which the fuel cell system 1 includes an air supply device such as a blower. In addition, the responsiveness of the power generation output of the fuel cell system 1 can be improved.

[0035] Furthermore, in the fuel cell system 1 according to this embodiment, a buffer tank 34 for storing air decompressed by the pressure reducing valve 33, and a flow rate adjustment valve 35 for adjusting the flow rate of air from the buffer tank 34 to the fuel cell stack 10 are provided on the air flow path 31 between the pressure reducing valve 33 and the fuel cell stack 10. With this fuel cell system 1, air at a desired pressure and at a desired flow rate can be stably supplied to the fuel cell stack 10.

[0036] Moreover, the fuel cell system 1 according to this embodiment further includes an auxiliary compressor 36 that introduces compressed air into the buffer tank 34. With this fuel cell system 1, even if for some reason sufficient compressed air cannot be obtained from the on-site air supply device 40 or the control air supply device, the buffer tank 34 can be filled with a sufficient amount of compressed air. Therefore, air at a desired pressure and at a desired flow rate can be more stably supplied to the fuel cell stack 10.

[0037] The fuel cell system 1 according to this embodiment further includes a control device 70 that calculates an output command value equal to or less than a predetermined upper limit based on the power generation amount required of the fuel cell stack 10 and a predetermined upper limit, and causes the fuel cell stack 10 to generate power at a power output corresponding to the output command value, and a pressure gauge 50 that measures the pressure in the buffer tank 34. When the pressure in the buffer tank 34 measured by the pressure gauge 50 is lower than the predetermined pressure, the control device 70 lowers the predetermined upper limit and calculates a new output command value, and causes the fuel cell stack 10 to generate power at a power output corresponding to the new output command value. In this case, even if the flow rate of air supplied from the buffer tank 34 to the fuel cell stack 10 (in other words, from the facility air supply device 40 or the auxiliary compressor 36 to the buffer tank 34) decreases, the fuel cell system 1 can continue to generate power.

[0038] The fuel cell system 1 according to this embodiment further includes a pressure gauge 50 for measuring the pressure in the buffer tank 34, an auxiliary compressor 36, and an auxiliary air flow path 37 for introducing the air compressed by the auxiliary compressor 36 into the buffer tank 34. The auxiliary compressor 36 is activated when the pressure in the buffer tank 34 measured by the pressure gauge 50 is lower than a predetermined pressure. Since the auxiliary compressor 36 can introduce compressed air into the buffer tank 34, the buffer tank 34 can be filled with a sufficient amount of compressed air even if sufficient compressed air cannot be obtained from the on-site air supply device 40 or the control air supply device for some reason. Therefore, air at a desired pressure and at a desired flow rate can be more stably supplied to the fuel cell stack 10.

[0039] The fuel cell system 1 according to this embodiment further includes a control device 70 that calculates an output command value based on the power generation amount required of the fuel cell stack 10 and causes the fuel cell stack 10 to generate power at a power generation output according to the output command value, and a pressure gauge 50 that measures the pressure in the buffer tank 34. The control device 70 stops the fuel cell system 1 when the pressure in the buffer tank 34 measured by the pressure gauge 50 remains lower than a predetermined pressure for a predetermined period of time. When the pressure in the buffer tank 34 measured by the pressure gauge 50 remains lower than a predetermined pressure for a predetermined period of time, the on-site air supply device 40 is not operating normally and the auxiliary compressor 36 is broken, so that air cannot be supplied to the fuel cell stack 10. In this case, the control device 70 stops the fuel cell system 1, thereby allowing the operation of the fuel cell system 1 to be safely stopped.

[0040] Next, a modified example of the fuel cell system according to the present embodiment will be described with reference to Fig. 2. The fuel cell system 1 of the modified example shown in Fig. 2 differs in that the buffer tank 34, auxiliary compressor 36, and flow rate control valve 38 are located upstream of the pressure reducing valve 33, and that the oxygen supply system 30 includes a check valve 61 for the purpose of preventing backflow of air to the on-site air supply facility 40 due to a change in the position of the auxiliary compressor. The other configurations are substantially the same as those of the fuel cell system 1 shown in Fig. 1. In the modified example shown in Fig. 2, the same parts as those in the embodiment shown in Fig. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0041] The fuel cell system 1 shown in FIG. 2 can also provide the same effects as those of the fuel cell system 1 shown in FIG.

[0042] Next, another modified example of the fuel cell system according to the present embodiment will be described with reference to FIG. 3. The fuel cell system 100 of the modified example shown in FIG. 3 differs in that it includes a plurality of fuel cell stacks 10A, 10B. The fuel cell system 100 of the modified example shown in FIG. 3 also differs in that its oxygen supply system 300 includes an air distribution channel 310 that distributes air to the plurality of fuel cell stacks 10A, 10B. The fuel cell system 100 of the modified example shown in FIG. 3 also differs in that its hydrogen supply system 200 includes a hydrogen supply source 21 and a plurality of hydrogen channels 22A, 22B. The other configurations are substantially the same as those of the fuel cell system 1 shown in FIG. 1. In the modified example shown in FIG. 3, the same parts as those in the embodiment shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0043] 3, the fuel cell system 100 of the modified example includes a first fuel cell stack 10A, a second fuel cell stack 10B, a hydrogen supply system 200, and an oxygen supply system 300. Power supply devices 2A, 2B for extracting current from the fuel cell stacks 10A, 10B are connected to the respective fuel cell stacks 10A, 10B. Each power supply device 2A, 2B is connected to a control device 70.

[0044] The required power generation amount required for the fuel cell system 100 is input to the control device 70 via the input unit 3. The control device 70 calculates output command values ​​for each of the fuel cell stacks 10A, 10B based on the required power generation amount input from the input unit 3. The control device 70 also controls each part of the fuel cell system 100 in the same manner as the control device 70 of the fuel cell system 1 shown in FIG.

[0045] The first fuel cell stack 10A and the second fuel cell stack 10B are configured in the same manner as the fuel cell stack 10 shown in FIG. 1. The hydrogen supply system 200 supplies hydrogen to the anode electrode 11 of the first fuel cell stack 10A and the anode electrode 11 of the second fuel cell stack 10B, respectively. The hydrogen supply system 200 includes a hydrogen supply source 21 and hydrogen flow paths 22A and 22B. The first hydrogen flow path 22A connects the hydrogen supply source 21 to the first fuel cell stack 10A. As a result, hydrogen from the hydrogen supply source 21 is supplied to the first fuel cell stack 10A via the first hydrogen flow path 22A. The second hydrogen flow path 22B connects the hydrogen supply source 21 to the second fuel cell stack 10B. As a result, hydrogen from the hydrogen supply source 21 is supplied to the second fuel cell stack 10B via the second hydrogen flow path 22B.

[0046] The oxygen supply system 300 supplies air to the cathode electrode 12 of the first fuel cell stack 10A and the cathode electrode 12 of the second fuel cell stack 10B. In the example shown in FIG. 3, the oxygen supply system 300 includes an air distribution passage 310 that distributes air to the first fuel cell stack 10A and the second fuel cell stack 10B, and a pressure reducing valve 33 provided on the air distribution passage 310. The air distribution passage 310 connects the station air supply device 40 or the control air supply device, which is outside the fuel cell system 100, to the multiple fuel cell stacks 10A and 10B. As a result, air from the station air supply device 40 or the control air supply device is supplied to the multiple fuel cell stacks 10A and 10B via the air distribution passage 310. More specifically, the air distribution passage 310 has a main passage 311 and a first branch passage 312 and a second branch passage 313 that are connected to the downstream end of the main passage 311. A compressed air inlet 32 ​​connected to the facility air supply unit 40 or a control air supply unit is provided at the upstream end of the main flow path 311. The downstream ends of the first branch flow path 312 and the second branch flow path 313 are connected to the first fuel cell stack 10A and the second fuel cell stack 10B, respectively.

[0047] The pressure reducing valve 33 is disposed on the air distribution flow path 310 between the compressed air inlet 32 ​​and the fuel cell stacks 10A, 10B. In the illustrated example, the pressure reducing valve 33 is disposed on the main flow path 311. The pressure reducing valve 33 reduces the pressure of the compressed air provided from the on-site air supply device 40 or the control air supply device.

[0048] 3, the oxygen supply system 300 does not include an air supply device such as a blower. This allows the fuel cell system 100 to be compact. In addition, since air is supplied from the on-site air supply device 40 or a control air supply device, the responsiveness of the power generation output of the fuel cell system 100 can be improved.

[0049] In the illustrated example, the oxygen supply system 300 further includes a buffer tank 34 and flow rate control valves 35A and 35B. The buffer tank 34 is provided on the air distribution flow path 310 between the pressure reducing valve 33 and the fuel cell stacks 10A and 10B, and stores air depressurized by the pressure reducing valve 33. In the illustrated example, the buffer tank 34 is disposed on the main flow path 311. The flow rate control valves 35A and 35B are provided on the air distribution flow path 310 between the buffer tank 34 and the fuel cell stacks 10A and 10B. In the illustrated example, the oxygen supply system 300 includes a first flow rate control valve 35A and a second flow rate control valve 35B. The first flow rate control valve 35A and the second flow rate control valve 35B are provided on the first branch flow path 312 and the second branch flow path 313, respectively. The first flow rate control valve 35A and the second flow rate control valve 35B adjust the flow rate of air from the buffer tank 34 to the first fuel cell stack 10A and the second fuel cell stack 10B, respectively. The flow rate control valves 35A, 35B adjust the flow rate of the air in accordance with an output command value input to the power supply devices 2A, 2B of the corresponding fuel cell stacks 10A, 10B, and / or a cell current measured in the power supply devices 2A, 2B of the corresponding fuel cell stacks 10A, 10B. The flow rate control valves 35A, 35B control the flow rate of the air in response to a control signal from the control device 70, for example.

[0050] The air decompressed by the pressure reducing valve 33 is stored in the buffer tank 34, and the flow rate of the air from the buffer tank 34 to each of the fuel cell stacks 10A, 10B is adjusted by the flow rate control valves 35A, 35B, so that air of a desired pressure can be stably supplied to each of the fuel cell stacks 10A, 10B at a desired flow rate. In the example shown in FIG. 3, the oxygen supply system 300 has the same number of flow rate control valves 35A, 35B as the branch paths 312, 313, but this is not limited to this. For example, the oxygen supply system 300 may have only one flow rate control valve 35. In this case, the flow rate control valve 35 may be provided on the main path 311 downstream of the buffer tank 34 (between the buffer tank 34 and the branch paths 312, 313). In this case, the flow rate control valve 35 can also adjust the flow rate of air from the buffer tank 34 to each of the fuel cell stacks 10A, 10B.

[0051] In the illustrated example, the oxygen supply system 300 further includes an auxiliary compressor 36, an auxiliary air flow path 37, and a flow rate control valve 38.

[0052] In the example shown in Fig. 3, the fuel cell system 100 includes two fuel cell stacks 10A, 10B, but is not limited to this. The fuel cell system 100 may include three or more fuel cell stacks 10. In this case, the air distribution channel 310 of the fuel cell system 100 may have branch channels in the same number as the fuel cell stacks 10, and a flow rate control valve 35 may be provided in each branch channel. In the example shown in Fig. 3, the fuel cell system 100 may have multiple hydrogen supply systems 20. In this case, one hydrogen supply system 20 may be provided for each fuel cell stack 10.

[0053] 4, a buffer tank 34, an auxiliary compressor 36, and a flow rate control valve 38 may be provided upstream of the pressure reducing valve 33. In this case, as shown in FIG. 4, the oxygen supply system 300 may include a check valve 61 for the purpose of preventing backflow of air to the on-site air supply facility 40.

[0054] Next, the operation of the fuel cell system 100 shown in Fig. 3 will be described. First, the compressed air inlet 32 ​​of the fuel cell system 100 is connected to the on-site air supply device 40, and the on-site air supply device 40 starts supplying air to the buffer tank 34. At this time, air from which moisture and impurities have been removed by the filter device 60 is supplied to the buffer tank 34. Furthermore, when a required amount of power generation required of the fuel cell system 100 is input from the input unit 3 to the control device 70, the control device 70 calculates an output command value based on the required amount of power generation and passes it to the power supply device 2. As a result, the supply of hydrogen from the hydrogen supply system 200 and the supply of air from the oxygen supply system 300 to the fuel cell stacks 10A, 10B starts, and the fuel cell system 100 starts generating power.

[0055] While the fuel cell system 100 is generating power, the control device 70 obtains information about the pressure in the buffer tank 34 from the buffer tank pressure gauge 50. If the pressure is less than a predetermined value, the control device 70 inputs a control signal to the auxiliary compressor 36 to start the auxiliary compressor 36.

[0056] In addition, while the fuel cell system 100 is generating power, the control device 70 adjusts the opening degree of the flow rate control valve 35A based on the output command value input to the power supply unit 2A, and adjusts the opening degree of the flow rate control valve 35B based on the output command value input to the power supply unit 2B.

[0057] As a result of the above, a power generation output corresponding to the output command value determined by the control device 70 is obtained from each of the fuel cell stacks 10A, 10B.

[0058] The output command value is calculated as follows. First, when the required power generation amount is input from the input unit 3, the control device 70 calculates the required power generation amount required for each fuel cell stack 10A, 10B, taking into consideration the rated power generation output of each fuel cell stack 10A, 10B. Next, the control device 70 performs a predetermined calculation on the required power generation amount required for the first fuel cell stack 10A. If the calculation result is equal to or less than a predetermined upper limit value and equal to or more than a predetermined lower limit value, the control device 70 passes the calculation result to the power supply device 2A as an output command value. On the other hand, if the calculation result is greater than the predetermined upper limit value, the control device 70 passes the predetermined upper limit value to the power supply device 2A as an output command value. If the calculation result is less than a predetermined lower limit value, the control device 70 passes the predetermined lower limit value to the power supply device 2A as an output command value. Similarly, the control device 70 performs a predetermined calculation on the required power generation amount required for the second fuel cell stack 10B. If the calculation result is equal to or less than a predetermined upper limit value and equal to or more than a predetermined lower limit value, the control device 70 passes the calculation result to the power supply device 2B as an output command value. On the other hand, if the calculation result is greater than a predetermined upper limit value, the control device 70 passes the predetermined upper limit value to the power supply unit 2B as an output command value. If the calculation result is smaller than a predetermined lower limit value, the control device 70 passes the predetermined lower limit value to the power supply unit 2B as an output command value. If the on-site air supply unit 40 and the auxiliary compressor 36 are not operating normally, as described below, the control device 70 determines the output command value to be 0.

[0059] The upper limit value used in the calculation of the output command value is determined as follows. Usually, the upper limit value used in the calculation of the output command value input to the power supply device 2A is set to the same value as the rated power output of the first fuel cell stack 10A. Also, the upper limit value used in the calculation of the output command value input to the power supply device 2B is set to the same value as the rated power output of the second fuel cell stack 10B. However, when the pressure in the buffer tank 34 obtained from the buffer tank pressure gauge 50 during power generation by the fuel cell system 100 is lower than a predetermined pressure, only a flow rate of air less than normal can be supplied from the buffer tank 31 to the fuel cell stacks 10A, 10B, and the fuel cell stacks 10A, 10B cannot generate power at their rated power output. For this reason, the control device 70 obtains new upper limit values ​​corresponding to the pressures measured by the buffer tank pressure gauge 50 for each of the fuel cell stacks 10A, 10B, and uses the new upper limit values ​​to determine the output command values ​​to be input to each of the power supply devices 2A, 2B. Here, the new upper limit value input to the power supply device 2A is a value lower than the rated power output of the first fuel cell stack 10A. Furthermore, the new upper limit value input to the power supply device 2B is a value lower than the rated power output of the second fuel cell stack 10B. For example, the new upper limit value is the maximum power output that each of the fuel cell stacks 10A, 10B can output even if the pressure inside the buffer tank 31 is the pressure measured above. The new upper limit value is determined by performing a predetermined calculation on the pressure measured by the buffer tank internal pressure gauge 50. This predetermined calculation is performed by the upper limit value calculation unit 71 of the control device 70.

[0060] When a new upper limit value is set, a new output command value is input from the control device 70 to the power supply devices 2A, 2B, and power generation is performed in the fuel cell stacks 10A, 10B based on this new output command value. Because the new output command value is determined using a new upper limit value that is lower than the normal upper limit value, the maximum flow rate of air required for power generation by the fuel cell stacks 10A, 10B is reduced. In this way, by lowering the upper limit value of the output set value input to the power supply device 2 when the pressure in the buffer tank 34 drops, the fuel cell system 100 can continue power generation even if the flow rate of air supplied from the buffer tank 34 to the fuel cell stacks 10A, 10B (in other words, from the on-site air supply device 40 or the auxiliary compressor 36 to the buffer tank 34) drops.

[0061] Furthermore, while the fuel cell system 100 is generating power, the control device 70 obtains information on the pressure of the compressed air provided by the local air supply device 40 to the fuel cell system 100 from the local air supply pressure gauge 51. As a result, the control device 70 determines whether the local air supply device 40 is operating normally. Specifically, if the pressure measured by the local air supply pressure gauge 51 is extremely low, the control device 70 determines that the local air supply device 40 is not operating normally. Furthermore, while the fuel cell system 100 is generating power, the control device 70 determines whether the auxiliary compressor 36 is operating normally. For example, if the control device 70 does not receive an operation signal from the auxiliary compressor 36, it determines that the auxiliary compressor 36 has broken down and is stopped. If the local air supply device 40 is not operating normally and the auxiliary compressor 36 is stopped, air cannot be supplied to the fuel cell stacks 10A, 10B. In this case, the control device 70 determines the output command value to be input to each of the power supply devices 2A, 2B to be 0, and passes it to the power supply devices 2A, 2B. This makes it possible to safely stop the operation of the fuel cell system 100.

[0062] The determination of whether the station air supply unit 40 and the auxiliary compressor 36 are operating normally may be made based on the pressure in the buffer tank 34 obtained from the buffer tank pressure gauge 50. Specifically, if the pressure measured by the buffer tank pressure gauge 50 remains extremely low, the control device 70 may determine that neither the station air supply unit 40 nor the auxiliary compressor 36 are operating normally.

[0063] As described above, the fuel cell system 100 according to the modified example includes a plurality of fuel cell stacks 10A, 10B that generate electricity using hydrogen and oxygen, and an air distribution passage 310 that distributes air to the plurality of fuel cell stacks 10A, 10B. The air distribution passage 310 has a compressed air inlet 32 ​​through which station air or control air is introduced. A pressure reducing valve 33 is provided on the air distribution passage 310 between the compressed air inlet 32 ​​and the plurality of fuel cell stacks 10A, 10B. This fuel cell system 100 can also be made smaller than a fuel cell system 100 that includes an air supply device such as a blower. In addition, the responsiveness of the power generation output of the fuel cell system 100 can be improved.

[0064] Furthermore, in the fuel cell system 100 according to the modified example, a buffer tank 34 capable of storing air decompressed by the pressure reducing valve 33, and flow rate control valves 35A, 35B for controlling the flow rate of air from the buffer tank 34 to each of the fuel cell stacks 10A, 10B are provided on the air distribution flow path 310 between the pressure reducing valve 33 and the multiple fuel cell stacks 10A, 10B. According to this fuel cell system 100, air at a desired pressure and at a desired flow rate can be stably supplied to each of the fuel cell stacks 10A, 10B.

[0065] Moreover, the fuel cell system 100 according to the modified example further includes an auxiliary compressor 36 that introduces compressed air into the buffer tank 34. With this fuel cell system 100, even if for some reason sufficient compressed air cannot be obtained from the on-site air supply device 40 or the control air supply device, it is possible to fill the buffer tank 34 with a sufficient amount of compressed air. Therefore, air at a desired pressure and at a desired flow rate can be more stably supplied to each of the fuel cell stacks 10A, 10B.

[0066] The above-described embodiments and modifications thereof are included within the scope and spirit of the invention, and are included in the scope of the invention and its equivalents as set forth in the claims. In addition, it is of course possible to combine the above-described embodiments and modifications thereof in part as appropriate within the spirit of the present invention. [Explanation of symbols]

[0067] 1,100: fuel cell system, 2: power supply device, 3: input section, 10, 10A, 10B: fuel cell stack, 11: anode electrode, 12: cathode electrode, 20, 20A, 20B: hydrogen supply system, 21: hydrogen supply source, 22: hydrogen flow path, 30, 300: oxygen supply system, 31: air flow path, 32: compressed air inlet, 33: pressure reducing valve, 34: buffer tank, 35, 35A, 35B: flow control valve, 36: auxiliary compressor, 37: auxiliary air flow path, 38: flow control valve, 40: indoor air supply device, 50: buffer tank pressure gauge, 51: indoor air supply pressure gauge, 60: filter device, 61: check valve, 70: control device, 71: upper limit value calculation section, 310: air distribution flow path, 311: main flow path, 312: first branch flow path, 313: second branch flow path

Claims

1. A fuel cell system, comprising: a fuel cell stack that generates electricity using hydrogen and oxygen; an air flow path connected to the fuel cell stack; Equipped with The air flow path has a compressed air inlet through which facility air or control air is introduced, the indoor air and the control air are air supplied from existing devices in a facility in which the fuel cell system is installed, a pressure reducing valve is provided on the air flow path between the compressed air inlet and the fuel cell stack; a buffer tank for storing air reduced in pressure by the pressure reducing valve, and a flow rate control valve for controlling the flow rate of air from the buffer tank to the fuel cell stack, the buffer tank being disposed on the air flow path between the pressure reducing valve and the fuel cell stack.

2. 2. The fuel cell system according to claim 1, further comprising an auxiliary compressor that introduces compressed air into the buffer tank.

3. A fuel cell system, comprising: a plurality of fuel cell stacks that generate electricity using hydrogen and oxygen; an air distribution channel that distributes air to the plurality of fuel cell stacks; Equipped with The air distribution flow path has a compressed air inlet into which facility air or control air is introduced, the indoor air and the control air are air supplied from existing devices in a facility in which the fuel cell system is installed, a pressure reducing valve is provided on the air distribution passage between the compressed air inlet and the plurality of fuel cell stacks; a buffer tank capable of storing air reduced in pressure by the pressure reducing valve, and a flow control valve for controlling the flow rate of air from the buffer tank to each fuel cell stack, the buffer tank being disposed on the air distribution path between the pressure reducing valve and the plurality of fuel cell stacks.

4. 4. The fuel cell system according to claim 3, further comprising an auxiliary compressor that introduces compressed air into the buffer tank.

5. a control device that calculates an output command value equal to or less than a predetermined upper limit value based on a required power generation amount required of the fuel cell stack and the predetermined upper limit value, and causes the fuel cell stack to generate power at a power generation output according to the output command value; A pressure gauge that measures the pressure in the buffer tank; Further comprising:

5. The fuel cell system according to claim 1, wherein, when the pressure in the buffer tank measured by the pressure gauge is lower than a predetermined pressure, the control device lowers the upper limit value, calculates a new output command value, and causes the fuel cell stack to generate power at a power generation output according to the new output command value.

6. A pressure gauge that measures the pressure in the buffer tank; An auxiliary compressor; an auxiliary air flow path that introduces air compressed by the auxiliary compressor into the buffer tank; Further comprising:

6. The fuel cell system according to claim 1, wherein the auxiliary compressor is activated when the pressure in the buffer tank measured by the pressure gauge is lower than a predetermined pressure.

7. a control device that calculates an output command value based on a required amount of power generation required of the fuel cell stack and causes the fuel cell stack to generate power at a power generation output according to the output command value; A pressure gauge that measures the pressure in the buffer tank; Further comprising:

7. The fuel cell system according to claim 1, wherein the control device stops the fuel cell system when the pressure in the buffer tank measured by the pressure gauge remains lower than a predetermined pressure for a predetermined period of time.

Images