Fuel Cell Systems

Abstract

To provide a technique for surely initiating a plurality of fuel battery units.SOLUTION: A fuel battery system comprises a battery, a plurality of fuel battery units connected to the battery, and a controller for controlling the operation of the plurality of the fuel battery units. The controller is configured to execute activation processing to activate the plurality of fuel battery units. The activation processing comprises first processing of activating a part of the plurality of fuel battery units using power supplied from the battery, and second processing of activating at least one of the rest of the plurality of fuel battery units.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] Patent Document 1 discloses a fuel cell system. This fuel cell system includes multiple fuel cell units and a control device that controls their operation. The control device is configured to execute a start-up process to start up the multiple fuel cell units in response to a request from a user, for example. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-014177 A Summary of the Invention [Problem to be solved by the invention]

[0004] In order to start the fuel cell unit, it is necessary to supply an oxidizing gas (e.g., air containing oxygen gas) or a fuel gas (e.g., hydrogen gas) to the fuel cell unit. Therefore, when starting the fuel cell unit, a certain amount of power is required to operate the equipment that supplies these gases (hereinafter, this power may be referred to as "starting power"). In order to supply this starting power, the fuel cell system may further include a battery. In this case, in order to start multiple fuel cell units simultaneously, starting power needs to be supplied to each fuel cell unit, and a large amount of power is required to be output from the battery. However, depending on the state of the battery, it may not be possible to supply sufficient starting power to the multiple fuel cell units. For example, in extremely cold areas (e.g., below -20°C), if the battery is in an extremely low temperature state, the power that the battery can output decreases. Or, even if the SOC (State of Charge) of the battery is low, the power that the battery can output decreases. Under such specific conditions, it may not be possible to supply sufficient starting power to the multiple fuel cell units, and it may be impossible to start the multiple fuel cell units.

[0005] In view of the above circumstances, the present specification provides a technique for reliably starting up a plurality of fuel cell units. [Means for solving the problem]

[0006] The technology disclosed in this specification is embodied in a fuel cell system. The fuel cell system includes a battery, a plurality of fuel cell units connected to the battery, and a control device that controls the operation of the plurality of fuel cell units. The control device is configured to be able to execute a start-up process for starting up the plurality of fuel cell units. The start-up process includes a first process for starting up some of the plurality of fuel cell units using power supplied from the battery, and a second process for starting up at least one of the remaining plurality of fuel cell units after execution of the first process.

[0007] In the above-mentioned fuel cell system, when starting up the multiple fuel cell units, a start-up process including a first process and a second process can be executed. In the first process, only some of the multiple fuel cell units are started up using power supplied from the battery. Then, in the second process, at least one other of the multiple fuel cell units is started up. In this way, by selectively starting up at least some of the multiple fuel cell units at different timings, the start-up power to be output by the battery can be significantly reduced. This allows the multiple fuel cell units to be started up reliably. Note that at the stage where the second process is completed, some of the multiple fuel cell units may not have been started up. In this case, the start-up process may further include a third process or a fourth process for starting up at least one of the multiple fuel cell units after the second process is executed. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 shows a schematic configuration of an FC system 10 according to an embodiment. [Diagram 2] 10 is a flowchart showing an example of a special start process. [Diagram 3] 3 is a diagram for explaining the state of each FC unit FCU during the special startup process shown in FIG. 2. [Figure 4] 10 is a flowchart showing a modified example of the special starting process. [Diagram 5] 5 is a diagram for explaining the state of each FC unit FCU during the special startup process shown in FIG. 4. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] In one embodiment of the present technology, the start-up process may be executed under specific conditions. In this case, the specific conditions may include at least an ambient temperature being lower than a predetermined temperature. With this configuration, even if the battery temperature is relatively low and the battery's outputtable power is reduced, the multiple fuel cell units can be reliably started. However, in other embodiments of the present technology, the start-up process is not necessarily limited to only the specific conditions, and may not be executed under any conditions.

[0010] In addition to or instead of the above, the specific condition may include at least the battery SOC being lower than a predetermined value. With this configuration, even if the battery SOC is relatively low and the battery's outputtable power is reduced, the multiple fuel cell units can be reliably started.

[0011] In one embodiment of the present technology, the second process may further include starting at least one of the fuel cell units using power output by the fuel cell unit started by the first process. With this configuration, the fuel cell unit can be started by the second process without consuming power from the battery or while suppressing the amount of power consumption. Therefore, since the power to be supplied from the battery can be reduced when starting the multiple fuel cell units, the multiple fuel cell units can be reliably started even if the battery's outputtable power is reduced, for example.

[0012] In one embodiment of the present technology, in the first process, only one of the fuel cell units may be started. With this configuration, when starting the multiple fuel cell units, the power to be supplied from the battery can be further reduced.

[0013] In one embodiment of the present technology, in the second process, only one of the remaining fuel cell units may be started. With such a configuration, it is possible to reduce the start-up power required in the second process. Alternatively, in another embodiment of the present technology, in the second process, two or more of the remaining fuel cell units may be started simultaneously. With such a configuration, it is possible to shorten the time required to start the multiple fuel cell units. Note that, at the stage where the second process is completed, all of the multiple fuel cell units do not have to be started, and the start-up process may further include other processes executed subsequent to the second process, such as the third process described below.

[0014] In one embodiment of the present technology, the start-up process may further include a third process for starting at least one of the remaining fuel cell units after the second process is performed. That is, the multiple fuel cell units may be started sequentially by three or more processes. With this configuration, the number of fuel cell units to be started in each process can be reduced, thereby reducing the required start-up power. In addition, when a fuel cell unit after start-up is warmed up for a certain period of time, the power generated during the warm-up operation may become surplus power. In this regard, by reducing the number of fuel cell units started simultaneously, the power generated during the subsequent warm-up operation can be suppressed, and the generation of surplus power can be avoided or suppressed.

[0015] In some of the above-described embodiments, the number of fuel cell units started in the second process may be greater than the number of fuel cell units started in the first process. With this configuration, the startup power required in the first process, i.e., the power to be supplied from the battery, can be reduced, and more of the fuel cell units can be started in a short period of time.

[0016] In one embodiment of the present technology, in the second process, all of the remaining fuel cell units may be started simultaneously. With this configuration, the first process and the second process are executed, so that all of the fuel cell units can be started. In other words, it is possible to reduce the time required to start the multiple fuel cell units. EXAMPLES

[0017] A fuel cell system (hereinafter, FC (Fuel cell) system) 10 according to an embodiment will be described with reference to the drawings. The FC system 10 is a power generation system that is mounted on a fuel cell vehicle (e.g., an automobile, a bus, a truck, a train) or a stationary fuel cell device, and outputs electric power according to the required electric power. Note that the FC system 10 may also be mounted on various moving bodies other than a vehicle (e.g., a ship or an airplane).

[0018] As shown in Fig. 1, the FC system 10 includes a plurality of fuel cell units (hereinafter, FC units) FCU. For ease of explanation, the number of FC units FCU included in the FC system 10 is set to N (N is an integer equal to or greater than 2). That is, the plurality of FC units FCU include a first FC unit FCU1 to an NFC unit FCUN. Note that the number of FC units FCU included in the FC system 10 (i.e., N) is not particularly limited and can be changed as appropriate depending on the power required for the FC system 10.

[0019] As shown in FIG. 1, the FC system 10 further includes a system control device 12 and a battery 14. The system control device 12 is a control device that controls the operation of the multiple FC unit FCUs and the battery 14. The battery 14 is, for example, a lithium ion battery or a nickel hydrogen battery, and has multiple built-in secondary batteries. The system control device 12 is connected to each FC unit FCU so as to be able to communicate with them, and controls the operation of each FC unit FCU as described above. Similarly, the system control device 12 is connected to the battery 14 so as to be able to communicate with them, and controls the operation of the battery 14 as described above. The battery 14 is electrically connected to each FC unit FCU, and is configured to be able to supply power to each FC unit FCU. In this case, a converter that steps up or steps down the power may be provided between the battery 14 and each FC unit FCU, as necessary.

[0020] As shown in Fig. 1, each FC unit FCU includes a fuel cell unit control device (hereinafter, FC unit control device) 16, a fuel cell stack (hereinafter, FC stack) 18, a compressor 20, and a hydrogen supply valve 22. The FC unit control device 16 is connected to the system control device 12 so as to be able to communicate with it, and controls the operation of the FC stack 18, the compressor 20, and the hydrogen supply valve 22 based on instructions from the system control device 12. In this manner, the operation of each FC unit FCU is controlled by the corresponding FC unit control device 16. Note that the FC unit control device 16 is not necessarily required for each FC unit FCU. For example, the system control device 12 may directly control each of the components of each FC unit FCU, without going through the FC unit control device 16.

[0021] The FC stack 18 is, for example, a polymer electrolyte fuel cell, and has a structure in which multiple unit cells are stacked. As described above, the FC unit control device 16 controls the operation of the FC stack 18 based on instructions from the system control device 12. For example, the FC unit control device 16 controls the start of power generation by the FC stack 18 or the suspension of power generation. As an example, the FC unit control device 16 may monitor the operation of the FC stack 18 in each FC unit FCU.

[0022] The compressor 20 compresses air taken in from the outside and supplies it to the FC stack 18. Meanwhile, the hydrogen supply valve 22 is provided between the hydrogen tank 24 connected to the FC system 10 and the FC stack 18. As described above, the FC unit controller 16 controls the operation of the compressor 20 and the hydrogen supply valve 22 based on instructions from the system controller 12. For example, the FC unit controller 16 controls the compressor 20 to supply air containing oxygen gas to the FC stack 18. Similarly, the FC unit controller 16 controls the hydrogen supply valve 22 to adjust the amount of hydrogen gas supplied from the hydrogen tank 24 to the FC stack 18. The power required for the operation of the compressor 20 and the hydrogen supply valve 22 may be supplied from the battery 14 or from the FC unit FCU itself or another FC unit. The air and hydrogen gas that have completed power generation in the FC stack 18 are discharged from the FC stack 18 to the outside. In this case, the gas discharged from the FC stack 18 to the outside may contain unreacted hydrogen gas. Therefore, each FC unit FCU may further include a circulation path (not shown) so that unreacted hydrogen gas can be circulated to the FC stack 18. The compressor 20 is an example of a device that supplies air to each FC unit FCU. Also, hydrogen gas is an example of a fuel gas, and air is an example of an oxidizing gas. Although not particularly limited, the FC system 10 may further include a cooling system (not shown) that circulates cooling water to each FC unit FCU for cooling.

[0023] Next, an operation related to the start-up of the FC system 10 of this embodiment will be described. The start-up of the FC system 10 is executed by the system control device 12 and the FC unit control device 16 provided in each FC unit FCU. Usually, the system control device 12 simultaneously issues a start command to each FC unit FCU to start all the FC unit FCUs at the same time. At this time, the start-up power required to start each FC unit FCU is supplied from the battery 14. However, depending on the state of the battery 14, it may not be possible to supply sufficient start-up power to the multiple FC unit FCUs. For example, in extremely cold areas (for example, below -20°C), if the battery 14 is in an extremely low temperature state, the power that the battery 14 can output decreases. Alternatively, even if the SOC of the battery 14 is low, the power that the battery 14 can output decreases. Under such specific conditions, it may not be possible to supply sufficient start-up power to the multiple FC unit FCUs, and it may not be possible to start the multiple FC unit FCUs.

[0024] In regard to the above point, the FC system 10 of this embodiment is configured to execute a special start process described below when starting is required under a specific condition. The specific condition here may include, for example, that the ambient temperature of the FC system 10 is lower than a predetermined temperature. In addition, or instead, the specific condition may include that the SOC of the battery 14 is lower than a predetermined value. The specific condition is not limited to these, and various conditions that may reduce the power that can be output by the battery 14 may be set. However, in other embodiments of the present technology, the start process is not necessarily limited to only under a specific condition, and may not be executed under any condition. Hereinafter, the special start process will be described with reference to FIG. 2 and FIG. 3.

[0025] As shown in Fig. 2, when the system controller 12 detects a start-up operation (YES in step S10), the process proceeds to step S12 and subsequent steps (time T0 in Fig. 3). Here, the start-up operation refers to, for example, a user turning on the main switch of the FC system 10. On the other hand, when a start-up operation is not detected (NO in step S10), the system controller 12 returns to step S10 again. In other words, when a start-up operation is not detected, the system controller 12 repeats the process of step S10.

[0026] First, in step S12, the system control device 12 sets a parameter n to "1." This parameter n indicates the FC unit FCU to be started, and means that the n-th FC unit FCUn will be started in the processing of the subsequent steps S14 to S18. In this embodiment, since "1" is initially set to the parameter n, first only the first FC unit FCU1 is started.

[0027] In step S14, the system control device 12 issues a start command to the FC unit control device 16 of the first FC unit FCU1 (time T1 in FIG. 3). The FC unit control device 16, which has received the start command, starts processing to start the first FC unit FCU1. The compressor 20 starts operating, compressing air taken in from the outside and supplying it to the FC stack 18. At this time, the hydrogen supply valve 22 is also controlled to adjust the amount of hydrogen gas supplied to the FC stack 18. As a result, the first FC unit FCU1 starts generating power using the air supplied from the compressor 20 and the hydrogen gas supplied from the hydrogen tank 24. That is, the first FC unit FCU1 starts. In the processing of this step S14, power is supplied from the battery 14 to each component of the first FC unit FCU1, such as the compressor 20. That is, the starting power of the first FC unit FCU1 is supplied from the battery 14.

[0028] In step S16, a rapid warm-up operation is performed in the started first FC unit FCU1. The rapid warm-up operation is an example of a warm-up operation for warming up the FC stack 18, which is at a low temperature immediately after startup. In general, in a warm-up operation of the FC stack 18, power is generated with a lower power generation efficiency than during normal power generation, and the heat generated by power generation losses is used to increase the temperature of the FC stack 18. In contrast, in a rapid warm-up operation, for example, the amount of air supplied to the FC stack 18 is further restricted, and the power generation losses in the FC stack 18 are increased, thereby raising the temperature of the FC stack 18 in a shorter time.

[0029] In step S18, when the rapid warm-up operation of the first FC unit FCU1 is completed, a completion signal is sent from the FC unit control device 16 to the system control device 12. Note that the rapid warm-up operation may be completed when a predetermined time has passed, or may be completed based on the measured temperature of the FC stack 18. For example, the FC unit control device 16 may monitor the temperature of the FC stack 18 during the rapid warm-up operation, and determine that the rapid warm-up operation is completed when the temperature becomes equal to or exceeds a threshold value.

[0030] In step S20, the system controller 12 that has received the completion signal judges whether the set value of the parameter n is "N". If the set value of the parameter n is not "N", the system controller 12 proceeds to the process of step S22 and sets the parameter n to "n+1". Since the parameter n is set to "1" here, the parameter n is newly set to "2". Next, the system controller 12 returns to the process of step S14 and issues a start command to the second FC unit FCU2 (time T2 in FIG. 3). As a result, the second FC unit FCU2 is started, and a rapid warm-up operation is performed in the second FC unit FCU2 after starting. At this time, the start-up power of the second FC unit FCU2 is supplied from the first FC unit FCU1 that has already been started, as shown typically by the arrow in FIG. 3. The start-up power of the second FC unit FCU2 may be supplied from the battery 14 instead of or in addition to the first FC unit FCU1. Thereafter, the above-mentioned processing is repeated until the start-up and rapid warm-up operation of the NFC unit FCUN are completed, that is, until the processing of step S20 becomes YES (T3, . . . , TN in FIG. 3). At this time, as shown typically by the arrows in FIG. 3, the start-up power of the third FC unit FCU3 is supplied from the second FC unit FCU2 that has already been started. Note that the start-up power of the third FC unit FCU3 may be supplied from at least one of the battery 14 and the first FC unit FCU1 that has already been started, instead of or in addition to the second FC unit FCU2. In other words, the start-up power of the NFC unit FCUN may be supplied from the battery 14, or a part or all of it may be supplied from another FC unit FCU that has already been started. As a result, the start-up of all FC units FCU is completed at time TF in FIG. 3.

[0031] As shown in FIG. 3, according to the above-mentioned series of starting processes, first, as a first process, only the first FC unit FCU1 is started (time T1). Next, as a second process, only the second FC unit FCU2 is started (time T2). Thereafter, the same process is repeated (times T3, . . . , TN), and the multiple FC units FCU are started one by one in sequence. In this way, the starting process includes at least the first process and the second process, and by selectively starting at least some of the multiple FC units FCU at different timings, it is possible to limit the FC units FCU that are started simultaneously, and therefore it is possible to significantly reduce the starting power that the battery 14 should output. For example, even if the battery 14 is in an extremely low temperature state and the power that the battery 14 can output is reduced, the multiple FC units FCU can be started reliably. Note that the multiple FC units FCU do not necessarily need to be started one by one in sequence, and in another embodiment, two or more FC units FCUs may be started simultaneously.

[0032] In the FC system of this embodiment, when each FC unit FCU starts up, a rapid warm-up operation is performed as part of the operations related to the start-up. During rapid warm-up operation (or warm-up operation), power is generated in the FC stack 18, so if many FC units FCUs are started up simultaneously, there is a risk that a relatively large amount of power will be unnecessarily generated by the rapid warm-up operation. Regarding this point as well, by selectively starting up at least some of the multiple FC units FCUs at different times and limiting the FC units FCUs that start up simultaneously, it is possible to avoid the generation of excess power that would accompany the rapid warm-up operation.

[0033] In addition, if the power generated by the rapid warm-up operation of the FC unit FCU that was started earlier is supplied as startup power to the FC unit FCU that is started subsequently, it is possible to further reduce the startup power that should be output from the battery 14. In this case, after one or more FC units FCU have started, the system control device 12 may issue a startup command to the next FC unit FCU before the rapid warm-up operation is completed (i.e., before step S18 in FIG. 2).

[0034] Next, a modified example of the special start-up process will be described with reference to Figures 4 and 5. In this modified example, the start-up process includes a first process and a second process, in which the first FC unit FCU1 is started, and in the second process, the second FC unit FCU2 through the NFC unit FCUN are started simultaneously. Therefore, steps S24 to S30 shown in Figure 4 are the same as the first process described above, that is, steps S10 to S18 when n is set to "1" in step S12 in Figure 2.

[0035] As shown in FIG. 4, when the system controller 12 detects a start-up operation (YES in step S24), the system controller 12 proceeds to processing in step S26 and thereafter (time T0 in FIG. 5). On the other hand, when a start-up operation is not detected, the system controller 12 returns to step S24 again, and repeats the processing in step S24 until a start-up operation is detected. In step S26, the system controller 12 issues a start-up command to the FC unit controller 16 of the first FC unit FCU1 (time T1 in FIG. 5). The FC unit controller 16, which has received the start-up command, starts processing for starting the first FC unit FCU1. In the processing in step S26, the start-up power of the first FC unit FCU1 is supplied from the battery 14. In step S28, a rapid warm-up operation is performed in the started first FC unit FCU1. In step S30, when the rapid warm-up operation of the first FC unit FCU1 is completed, a completion signal is transmitted from the FC unit controller 16 to the system controller 12.

[0036] Next, in step S32, the system control device 12 simultaneously issues a start command to each of the FC unit control devices 16 from the second FC unit FCU2 to the NFC unit FCUN (time T2 in FIG. 5). Upon receiving the start command, each of the FC unit control devices 16 simultaneously starts processing to start up the second FC unit FCU2 through the NFC unit FCUN. In the processing of this step S32, the start-up power of each of the FC units FCU to be started is supplied from the first FC unit FCU1 that has already been started, as diagrammatically indicated by the arrows in FIG. 5. Note that part of the start-up power of each of the FC units FCU may be supplied from the battery 14 instead of the first FC unit FCU1.

[0037] In step S34, rapid warm-up operation is performed in the started second FC unit FCU2 through the NFC unit FCUN. In step S36, when the rapid warm-up operation is completed from the second FC unit FCU2 through the NFC unit FCUN, a completion signal is sent from each FC unit controller 16 to the system controller 12. As a result, at time TF in Fig. 5, startup is completed for all FC units FCU.

[0038] As shown in FIG. 5, according to the above-mentioned series of start-up processes, first, in the first process, only the first FC unit FCU1 is started (time T1). Next, in the second process, the second FC unit FCU2 through the NFC unit FCUN are started (time T2). That is, in the second process, all the remaining FC units FCU that were not started in the first process are started. Therefore, by adopting such a configuration, it is possible to reduce the time required to start all the FC units FCU included in the FC system 10. Also, in such a configuration, it is possible to supply the start-up power of each FC unit FCU from the first FC unit FCU1 that has already been started in the first process to each FC unit FCU that is started in the second process. Therefore, for example, even if the power that can be output from the battery 14 is reduced, it is possible to start a plurality of FC units FCU reliably.

[0039] The number of FC units FCU started in the first process is not limited to one. As another embodiment, the first process may start two or more FC units FCU simultaneously. Also, in the second process, all of the second FC unit FCU2 to the NFC unit FCUN do not necessarily need to be started simultaneously. As another embodiment, the second process may start at least two FC units FCU simultaneously. Even in these cases, although not particularly limited, the number of FC units FCU started in the second process may be greater than the number of FC units FCU started in the first process. Then, following the second process, the system control device 12 may further execute one or more processes for starting FC units FCUs that have not been started.

[0040] Although several specific examples 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 changes to the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical usefulness alone or in combination. [Explanation of symbols]

[0041] 10:FC system 12: System control device 14: Battery 16:FC unit control device 18:FC stack 20: Compressor 22: Hydrogen supply valve 24: Hydrogen tank FCU:FC unit FCU1: 1st FC unit FCU2: 2nd FC unit FCU3: 3rd FC unit FCUN: NFC Unit

Claims

1. A battery; a plurality of fuel cell units connected to the battery; a control device for controlling the operation of the plurality of fuel cell units; the control device is configured to be capable of executing a start-up process for starting up the plurality of fuel cell units; The start-up process includes: a first process of starting up some of the plurality of fuel cell units using power supplied from the battery; a second process of starting up at least one of the remaining fuel cell units after the first process is performed; The start-up process is executed under specific conditions, The specific conditions include at least an ambient temperature being lower than a predetermined temperature and an SOC of the battery being lower than a predetermined value. Fuel cell system.

2. 2. The fuel cell system according to claim 1, wherein the second process further includes starting up the at least one of the plurality of fuel cell units using power output by the fuel cell unit started by the first process.

3. 3. The fuel cell system according to claim 1, wherein in the first process, only one of the plurality of fuel cell units is started.

4. 4. The fuel cell system according to claim 1, wherein in the second process, only one of the remaining fuel cell units is started up.

5. 4. The fuel cell system according to claim 1, wherein in the second process, two or more of the remaining ones of the plurality of fuel cell units are started up simultaneously.

6. 6. The fuel cell system according to claim 1, wherein the start-up process further includes a third process for starting up at least one other of the remaining fuel cell units after the second process has been performed.

7. 7. The fuel cell system according to claim 5, wherein the number of the fuel cell units started up in the second process is greater than the number of the fuel cell units started up in the first process.

8. 8. The fuel cell system according to claim 1, wherein in the second process, all of the remaining ones of the plurality of fuel cell units are started up simultaneously.

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