Fuel cell system

Abstract

To provide a new technique for starting a plurality of fuel cell stacks.SOLUTION: A fuel cell system comprises: a plurality of fuel cell stacks including a first fuel cell stack: an air supply system supplying air to each of the plurality of fuel cell stacks; a hydrogen supply system supplying hydrogen to each of the plurality of fuel cell stacks; and a controller controlling the air supply system and the hydrogen supply system to perform start processing starting the plurality of fuel cell stacks. The start processing includes: first processing of actuating the air supply system using power supplied from other than the plurality of fuel cell stacks to start the first fuel cell stack; and second processing of actuating a plurality of fuel cell stacks except the fuel cell stack using power supplied from the first fuel cell stack after starting the first fuel cell stack to start the plurality of fuel cell stacks except the fuel cell stack.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to a fuel cell system including a plurality of fuel cell stacks. [Background technology]

[0002] In fuel cell systems, high-voltage components are generally used when starting the fuel cell, and if a malfunction occurs in the high-voltage power supply in such a fuel cell system, it may be impossible to start the fuel cell.

[0003] Patent Document 1 discloses a fuel cell system that starts a fuel cell without the assistance of a high-voltage power supply when a malfunction occurs in the high-voltage power supply. In this fuel cell system, an emergency air supply device is detachably provided to supply air to the fuel cell stack in place of an air blower that requires a high-voltage power supply when the high-voltage power supply malfunctions. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-041808 Summary of the Invention [Problem to be solved by the invention]

[0005] Provided herein is a novel technique for starting up multiple fuel cell stacks. [Means for solving the problem]

[0006] This specification discloses a fuel cell system. In a first aspect, the fuel cell system includes a plurality of fuel cell stacks including a first fuel cell stack, an air supply system that supplies air to each of the plurality of fuel cell stacks, a hydrogen supply system that supplies hydrogen to each of the plurality of fuel cell stacks, and a control device that controls the air supply system and the hydrogen supply system to execute a startup process to start up the plurality of fuel cell stacks, the startup process including a first process of operating the air supply system with power supplied from a fuel cell stack other than the plurality of fuel cell stacks to start up the first fuel cell stack, and a second process of operating the air supply system with power supplied from the first fuel cell stack after starting up the first fuel cell stack to start up the plurality of fuel cell stacks excluding the first fuel cell stack.

[0007] According to the above configuration, a first fuel cell stack among the plurality of fuel cell stacks is started up by operating the air supply system with power supplied from a stack other than the plurality of fuel cell stacks. After the first fuel cell stack is started up, the air supply system is operated with power supplied from the first fuel cell stack, and the plurality of fuel cell stacks other than the first fuel cell stack are started up. In this way, the plurality of fuel cell stacks can be started up.

[0008] In a second aspect, in the first aspect, the air supply system may include a first air supplier and a second air supplier having a higher driving voltage than the first air supplier, and the first process may operate using the first air supplier, and the second process may operate using the second air supplier. According to the above configuration, the first fuel cell stack is started up using the first air supplier, which has a relatively low driving voltage. After the first fuel cell stack is started up, the second air supplier, which has a relatively high driving voltage, is operated using power supplied from the first fuel cell stack, and multiple fuel cell stacks other than the first fuel cell stack are started up. In this way, multiple fuel cell stacks can be started up using a relatively low voltage.

[0009] In a third aspect, in the second aspect described above, the second process may be initiated after the output power of the first fuel cell stack exceeds a predetermined threshold, and after the start of the second process, air may be supplied to the first fuel cell stack from the second air supplier instead of the first air supplier. According to the above configuration, when the output power of the first fuel cell stack exceeds a predetermined threshold and a relatively high drive voltage of the second air supplier becomes available, air is supplied to the first fuel cell stack from the second air supplier. Because the drive voltage of the second air supplier is higher than that of the first air supplier, the amount of air supplied from the second air supplier may be greater than the amount of air supplied from the first air supplier. This allows the first fuel cell stack to operate more efficiently.

[0010] In a fourth aspect, in any one of the first to third aspects, in the second process, the plurality of fuel cell stacks excluding the first fuel cell stack may be started at the same time. With the above configuration, the plurality of fuel cell stacks can be started up relatively quickly.

[0011] In a fifth aspect, in any one of the first to third aspects, in the second process, at least some of the fuel cell stacks excluding the first fuel cell stack may be started at different times. If the multiple fuel cell stacks are started at the same time using the output power of the first fuel cell stack, there may be a shortage of power to start the multiple fuel cell stacks. With the above configuration, at least some of the multiple fuel cell stacks are started at different times, which can prevent the above-mentioned power shortage from occurring. [Brief explanation of the drawings]

[0012] [Figure 1] 1 shows a plurality of fuel cell stacks that make up a fuel cell system. [Figure 2] 1 shows a schematic diagram of an air supply system, a hydrogen supply system, and a cooling system for each fuel cell stack. [Figure 3]1 shows a schematic diagram of an air supply system for a particular fuel cell stack. [Figure 4] 10 shows a flowchart of a startup process of the control device. [Figure 5] 4 shows a time chart for starting up each fuel cell stack in the first embodiment. [Figure 6] 10 shows a time chart for starting up each fuel cell stack in the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] (First Example) As shown in Fig. 1, the fuel cell system 2 of this embodiment includes a plurality of fuel cell stacks 10. Although three fuel cell stacks 10A to 10C are shown in Fig. 1, the number of fuel cell stacks is merely an example, and the number may be two, or four or more. The fuel cell system 2 of this embodiment is mounted on, for example, a fuel cell vehicle. Hereinafter, a fuel cell will be referred to as FC (short for Fuel Cell).

[0014] As shown in FIG. 2, each FC stack 10 is provided with an air supply system 20, a hydrogen supply system 30, and a cooling system 40. The air supply system 20 supplies air containing oxygen to the FC stack 10. The hydrogen supply system 30 supplies hydrogen gas containing hydrogen to the FC stack 10. In the FC stack 10, power is generated by a reaction between the oxygen contained in the air supplied from the air supply system 20 and the hydrogen contained in the hydrogen gas supplied from the hydrogen supply system 30. The FC stack 10 generates heat when generating power. Therefore, a cooling system 40 is provided to cool the FC stack 10. The FC system 2 also has a control device 50 for controlling the FC stack 10 and each of the systems 20, 30, and 40.

[0015] The air supply system 20 includes an air inlet path 21a, an air outlet path 21b, multiple valves 22a to 22c, an air compressor 24, and an air flow meter 26. Air flowing in through the air inlet path 21a is supplied to the FC stack 10 and then discharged to the outside through the air outlet path 21b. The air flow meter 26 is provided midway along the air inlet path 21a and can measure the flow rate of air flowing into the air inlet path 21a from the outside.

[0016] An air compressor 24 is provided downstream of the air flow meter 26. The air compressor 24 is a compressor that compresses the air that flows in through the air inflow path 21a and supplies the compressed air to the FC stack 10. The operation of the air compressor 24 is controlled based on the air flow rate measured by the air flow meter 26.

[0017] The plurality of valves 22a to 22c are valves for adjusting the amount of air supplied and for switching the air supply path.

[0018] The hydrogen supply system 30 includes a hydrogen tank 32 that stores hydrogen gas containing hydrogen, an intermediate pressure valve 34, and an injector 36. The hydrogen tank 32 is provided in common for each of the FC stacks 10A to 10C. When the intermediate pressure valve 34 is opened, the hydrogen gas flowing from the hydrogen tank 32 is supplied to the injector 36. The injector 36 adjusts the pressure of the hydrogen gas supplied to the FC stack 10.

[0019] The cooling system 40 includes a flow path 41 through which a liquid refrigerant (for example, water or LLC) flows, a water pump 42, a three-way valve 44, and a radiator 46. The water pump 42 discharges the refrigerant toward the FC stack 10. The three-way valve 44 adjusts the flow rate of the refrigerant flowing through the refrigerant flow path that passes through the radiator 46 and the refrigerant flow path that bypasses the radiator 46. The radiator 46 cools the refrigerant whose temperature has risen after passing through the FC stack 10.

[0020] 3, the air supply system provided in at least one of the multiple FC stacks 10 has a different configuration. FIG. 3 shows an FC stack 10A and an air supply system 20A provided in the FC stack 10A. The air supply system 20A further includes a blower 28 and a valve 29. The blower 28 is also a compressor, and compresses air that flows in from the air inflow path 21a and supplies the compressed air to the FC stack 10. The operation of the blower 28 is controlled based on the air flow rate measured by the air flow meter 26. The pressure ratio of the air compressor 24 (i.e., the ratio between the pressure of the air flowing out from the air compressor 24 and the pressure of the air flowing into the air compressor 24) is higher than the pressure ratio of the blower 28. Meanwhile, the drive voltage of the air compressor 24 is higher than the drive voltage of the blower 28. Valve 29 switches the air supply path between a blower path that passes through blower 28 and an air compressor path that passes through air compressor 24. Specifically, when valve 22a is closed and valve 29 is opened, air flows through the blower path. Conversely, when valve 29 is closed and valve 22a is opened, air flows through the air compressor path.

[0021] As described above, the pressure ratio of the air compressor 24 is higher than that of the blower 28, so when the air compressor 24 is used, the flow rate of air supplied to the FC stack 10A is higher than when the blower 28 is used (i.e., air can be supplied to the FC stack 10A more efficiently). However, because the drive voltage of the air compressor 24 is higher than the drive voltage of the blower 28, a high-voltage power supply with a relatively high voltage must be provided to drive the air compressor 24. In other words, a high-voltage power supply is required to start up the FC stack 10. To solve this problem, the control device 50 of the FC system 2 of the present application executes the following process shown in Figure 4.

[0022] The startup process executed by the control device 50 will be described with reference to Figure 4. The startup process is initiated, for example, when a switch of the FC vehicle is turned on.

[0023] 4, the control device 50 drives the hydrogen supply system 30 of the FC stack 10A. Specifically, the control device 50 opens the medium-pressure valve 34 and starts controlling the injector 36. As a result, the supply of hydrogen gas to the FC stack 10A starts.

[0024] In S12, the control device 50 switches the air supply path for supplying air from the air supply system 20A to the FC stack 10A to the blower supply path. Specifically, the control device 50 closes the valve 22a and opens the valve 29. As a result, the air that flows into the air inflow path 21a flows into the blower path.

[0025] In S14, the control device 50 starts the blower 28. Specifically, the control device 50 causes a low-voltage power supply (not shown) to supply power to the blower 28. As a result, the air that flows in from the air inflow path 21a is compressed by the blower 28, and the compressed air is supplied to the FC stack 10A. Note that the low-voltage power supply here may be a self-power supply (for example, a battery) provided in the fuel cell system 2, or an external power supply (including a commercial power supply).

[0026] When the processing of S14 is completed, both hydrogen gas and air are being supplied to the FC stack 10A. Therefore, the FC stack 10A starts generating power (i.e., is started up). As the supply of hydrogen gas and air increases, the output voltage of the FC stack 10A gradually increases up to a certain value (i.e., the upper limit of power generation power of the FC stack 10A).

[0027] In S16, the control device 50 monitors whether the output power of the FC stack 10A exceeds a threshold value. Here, the threshold value is set to the voltage required to drive the air compressor 24. In other words, the threshold value is set to a voltage higher than the drive voltage of the blower 28. If the output voltage of the FC stack 10A exceeds the threshold value (YES in S16), the control device 50 proceeds to S18.

[0028] In S18, the control device 50 starts the air compressor 24. Specifically, the control device 50 causes the FC stack 10A to supply power to the air compressor 24. As described above, at the stage of S18, the output voltage of the FC stack 10A is greater than the voltage required to drive the air compressor 24. As a result, the air compressor 24 is started appropriately.

[0029] In S20, the control device 50 switches the air supply path to the air compressor path. Specifically, the control device 50 closes valve 29 and opens valve 22a. As a result, the air flowing into air inflow path 21a flows into the air compressor path. Thereafter, for example, while the FC vehicle is running, air compressed by air compressor 24 is supplied to each of the FC stacks 10A to 10C. Although not shown, the control device 50 may cause the low-voltage power supply to stop supplying power to blower 28 after the air supply path has been switched to the air compressor path.

[0030] Next, a time chart of specific processing realized by the processing of FIG. 4 will be described with reference to FIG.

[0031] At time t1, the FC vehicle is switched on. In this case, the control device 50 activates the hydrogen supply system 30 of the FC stack 10A (S10 in FIG. 4), switches the air supply path to the blower path (S12), and starts the blower 28 (S14). As a result, at time t1, the FC stack 10A is activated by using the blower 28 (i.e., low-voltage power supply), and begins generating power. After time t1, as the total amount of air and hydrogen supplied to the FC stack 10A gradually increases, the output voltage also gradually increases.

[0032] At time t2, the output voltage of the FC stack 10A exceeds the threshold value (i.e., the voltage required to drive the air compressor 24) (YES in S16). In this case, the control device 50 drives the air compressor 24 by supplying the output voltage of the FC stack 10A to the air compressor 24 (S18) and switches the air supply path to the air compressor path (S20). As a result, from time t2 onwards, the FC stack 10A is activated by using the air compressor 24 (i.e., the FC stack 10A, which is a high-voltage power supply), and generates electricity. After time t2, the output voltage of the FC stack 10A also gradually increases as the total amount of air and hydrogen supplied to the FC stack 10A gradually increases. In particular, the flow rate of the air supplied from the air compressor 24 is greater than the flow rate of the air supplied from the blower 28. Therefore, the output voltage of the FC stack 10A is more likely to increase after time t2 when the air compressor 24 is activated than between time t1 and time t2 when the blower 28 is activated.

[0033] At time t3, the output voltage of the FC stack 10A increases to near its upper limit output voltage, and the start-up of the FC stack 10A is completed.

[0034] Thereafter, at time t4, the control device 50 continues to operate the air compressor 24 using power supplied from the FC stack 10A, supplying air to each of the FC stacks 10B, 10C excluding the FC stack 10A. The control device 50 also drives the hydrogen supply system 30 of each of the FC stacks 10B, 10C, supplying hydrogen gas to each of the FC stacks 10B, 10C. As a result, each of the FC stacks 10B, 10C enters an activated state at time t4 and begins generating power.

[0035] Then, at time t5, the output voltages of FC stacks 10B and 10C increase to near their upper limit output voltages, completing the startup of FC stacks 10B and 10C, and thus completing the startup of FC system 2. In this way, FC stacks 10B and 10C are started at the same time, so the startup of FC system 2 is relatively quick.

[0036] With the above configuration, the FC stack 10A is started by operating the blower 28 with power supplied from a low-voltage power supply other than the FC stacks 10A-10C (S10-S14 in FIG. 4). After the FC stack 10A is started, if the output voltage of the FC stack 10A exceeds the threshold (YES in S16), the air compressor 24 is operated with power supplied from the FC stack 10A, and the FC stacks 10B and 10C other than the FC stack 10A are started. In this way, multiple FC stacks 10A-10C can be started. In particular, the FC system 2 does not need to be equipped with a high-voltage power supply (other than the FC stack 10) for driving the air compressor 24 in order to start multiple FC stacks 10A-10C.

[0037] (Second Example) Next, a second embodiment will be described with reference to Fig. 6. The second embodiment differs from the first embodiment in the timing at which the FC stacks 10B and 10C are started up. The configuration of the FC system 2 is the same as that of the first embodiment. The processing until the start-up of the FC stack 10A is completed (i.e., times t11 to t13 in Fig. 6) is the same as that of the first embodiment.

[0038] At time t14, the control device 50 continues to operate the air compressor 24 using power supplied from the FC stack 10A to supply air to the FC stack 10B. The control device 50 also drives the hydrogen supply system 30 of the FC stack 10B to supply hydrogen gas to the FC stack 10B. As a result, the FC stack 10B enters an activated state at time t14 and begins power generation. At the stage t14, the FC stack 10C is not activated (i.e., it does not generate power).

[0039] Then, at time t15, the output voltage of the FC stack 10B increases to near its upper limit output voltage, and the start-up of the FC stack 10B is completed.

[0040] Thereafter, at time t16, the control device 50 continues to operate the air compressor 24 using power supplied from the FC stack 10A to supply air to the FC stack 10C. The control device 50 also drives the hydrogen supply system 30 of the FC stack 10C to supply hydrogen to the FC stack 10C. As a result, the FC stack 10C enters an activated state at time t16 and begins generating power.

[0041] Then, at time t17, the output voltage of the FC stack 10C increases to near its upper limit output voltage, and the start-up of the FC stack 10C is completed. This completes the start-up of the FC system 2.

[0042] In particular, in the second embodiment, the startup timing of FC stack 10B is different from the startup timing of FC stack 10C. With this configuration, it is possible to prevent an event such as a shortage of power to start up each of FC stacks 10B and 10C, which occurs when FC stacks 10B and 10C are started at the same timing.

[0043] Points to note regarding the above embodiment are as follows. The FC stack 10A corresponds to an example of a "first fuel cell stack" of the present technology. The blower 28 and the air compressor 24 correspond to an example of a "first air supplier" and a "second air supplier" of the present technology, respectively. The processes of S10 to S14 in FIG. 4 correspond to an example of a "first process" of the present technology. The processes of S18 and S20 in FIG. 4 correspond to an example of a "second process" of the present technology.

[0044] For example, a fan may be used instead of the blower 28. In this modification, the fan is an example of a "first air supplier."

[0045] Instead of the process of S16 in Fig. 4, it may be determined whether the startup of the FC stack 10A is complete. In this modification, the upper limit voltage of the FC stack 10A is an example of a "predetermined threshold value." In another modification, the air supply system 20A may not be equipped with the air compressor 24. In other words, only the blower 28 may be used to start up the FC stack 10A.

[0046] Although specific examples of the technology disclosed in this specification have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical utility either alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology exemplified in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of these objectives itself has technical utility. [Explanation of symbols]

[0047] 2: FC system, 10, 10A to 10C: FC stack, 20, 20A: air supply system, 21a: air inlet path, 21b: air outlet path, 22a to 22c, 29: valve, 24: air compressor, 26: air flow meter, 28: blower, 30: hydrogen supply system, 32: hydrogen tank, 34: medium pressure valve, 36: injector, 40: cooling system, 41: refrigerant flow path, 42: water pump, 44: three-way valve, 46: radiator, 50: control device

Claims

1. 1. A fuel cell system, comprising: a plurality of fuel cell stacks, including a first fuel cell stack; an air supply system that supplies air to each of the plurality of fuel cell stacks; a hydrogen supply system that supplies hydrogen to each of the plurality of fuel cell stacks; a control device that controls the air supply system and the hydrogen supply system to execute a startup process for starting up the plurality of fuel cell stacks; Equipped with The startup process includes: a first process of operating the air supply system with power supplied from a source other than the plurality of fuel cell stacks to start up the first fuel cell stack; a second process of operating the air supply system with power supplied from the first fuel cell stack after the first fuel cell stack has been started, thereby starting up the plurality of fuel cell stacks excluding the first fuel cell stack; Fuel cell system.

2. the air supply system includes a first air supplier and a second air supplier having a driving voltage higher than that of the first air supplier; In the first process, the first air supplier operates, 2. The fuel cell system according to claim 1, wherein the second air supplier operates in the second process.

3. the second process is initiated after the output power of the first fuel cell stack exceeds a predetermined threshold; 3. The fuel cell system according to claim 2, wherein after the second process is started, air is supplied to the first fuel cell stack from the second air supplier instead of the first air supplier.

4. 4. The fuel cell system according to claim 1, wherein in the second process, the plurality of fuel cell stacks excluding the first fuel cell stack are started up at the same time.

5. 4. The fuel cell system according to claim 1, wherein in the second process, at least some of the plurality of fuel cell stacks excluding the first fuel cell stack are started at different times.

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