Fuel Cell Systems

Abstract

To provide a technique for effectively using a plurality of coolers in a fuel cell system where each of a plurality of fuel cell stacks is individually equipped with each of the coolers.SOLUTION: A fuel cell system comprises a plurality of fuel cell stacks, a plurality of coolers, a coupling pipe, and a regulating valve. Each of the coolers individually corresponds to each of the fuel cell stacks so that each of the coolers cools the corresponding fuel cell stack. Each of the coolers has a radiator and a circulating passage. The circulating passage circulates a coolant between the radiator and the fuel cell stack. The coupling pipe couples the circulating passages of the plurality of coolers. The regulating valve regulates a flow rate of the coolant flowing in the coupling pipe. When the regulating valve is opened, the coolant is mixed in the plurality of coolers, thereby leveling a temperature of the coolant. The fuel cell stack at a high temperature can be cooled by using the plurality of coolers.SELECTED DRAWING: Figure 2

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] Patent Documents 1 and 2 disclose fuel cell systems equipped with multiple fuel cell stacks. Because the fuel cell stacks generate heat during power generation, the fuel cell system is equipped with a cooler that cools the multiple fuel cell stacks. The fuel cell system of Patent Document 1 is equipped with one common cooler for the multiple fuel cell stacks. Coolant supplied from the single cooler is distributed to the multiple fuel cell stacks. The fuel cell system of Patent Document 2 is equipped with coolers in the same number as the fuel cell stacks, and each cooler cools a corresponding fuel cell stack.

[0003] For ease of explanation, hereinafter, "fuel cell" will be abbreviated to "FC." That is, "fuel cell system" will be abbreviated to "FC system," and "fuel cell stack" will be abbreviated to "FC stack." [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2005-93349 A [Patent Document 2] JP 2020-136205 A Summary of the Invention [Problem to be solved by the invention]

[0005] As in the FC system disclosed in Patent Document 2, providing an individual cooler for each FC stack allows for precise control of the temperature of each FC stack. On the other hand, providing an individual cooler for each FC stack may result in a high load on only the cooler corresponding to the high temperature FC stack, despite the fact that the load on the cooler corresponding to the low temperature FC stack is small. This specification relates to a fuel cell system provided with an individual cooler for each of multiple FC stacks, and provides technology for effectively using multiple coolers. [Means for solving the problem]

[0006] The FC system disclosed in this specification includes multiple FC stacks, multiple coolers, a connecting pipe, an adjustment valve, and a controller. Each cooler corresponds to a respective FC stack individually, and each cooler cools its corresponding FC stack. Each cooler has a radiator and a circulation path. The circulation path circulates refrigerant between the radiator and the FC stack. The connecting pipe connects the circulation paths of the multiple coolers. The adjustment valve adjusts the flow rate of the refrigerant flowing through the connecting pipe. The controller adjusts the adjustment valve. Note that the adjustment valve may be a type that can continuously adjust the flow rate, or may be a switching type that simply switches between an open state and a closed state.

[0007] The above FC system can mix the refrigerants of multiple coolers through a connecting pipe. When a high-temperature FC stack and a low-temperature FC stack are present, mixing the refrigerants of the multiple coolers through a connecting pipe equalizes the refrigerant temperature and reduces the load on the cooler corresponding to the high-temperature FC stack. The FC system disclosed in this specification can make effective use of multiple coolers.

[0008] Details and further improvements of the technology disclosed in this specification are described in the following "Forms for Carrying Out the Invention". [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram of an FC system according to a first embodiment. [Diagram 2] FIG. 13 is a diagram showing an example in which a refrigerant flows through a connecting pipe. [Diagram 3] FIG. 11 is a block diagram of an FC system according to a second embodiment. [Figure 4] FIG. 11 is a block diagram of an FC system according to a third embodiment. [Diagram 5] FIG. 13 is a block diagram of an FC system according to a fourth embodiment. [Figure 6] FIG. 13 is a block diagram of an FC system according to a fifth embodiment. [Figure 7] FIG. 13 is a block diagram of an FC system according to a sixth embodiment. [Figure 8] FIG. 13 is a block diagram of an FC system according to a seventh embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] (First embodiment) An FC system 102 of the first embodiment will be described with reference to Figures 1 and 2. As mentioned above, "FC" is an abbreviation for "fuel cell." Figure 1 shows a block diagram of the FC system 102. A controller 4 and various electric devices (adjusting valve 41, boost converters 11a-11c, pumps 23a-23c, temperature sensors 24a-24c, etc.) are connected by communication lines, but the communication lines are not shown in the figure.

[0011] The FC system 102 has three FC stacks 10a, 10b, and 10c, and each FC stack generates power. In the following, when there is no need to distinguish between the FC stacks 10a-10c, they may be referred to as FC stack 10. Similarly, when there is no need to distinguish between the boost converters 11a-11c and the coolers 20a-20c (radiators 21a-21c, circulation paths 22a-22c, pumps 23a-23c, and temperature sensors 24a-24c), they may be referred to as the boost converter 11 and the cooler 20 (radiator 21, circulation path 22, pump 23, and temperature sensor 24).

[0012] Each FC stack 10 is accompanied by a boost converter 11. The boost converter 11 is connected to a power output end of the FC stack 10, and an output end of the boost converter 11 is connected to a system output end 3. The boost converter 11 boosts the DC power generated by the FC stack 10 and supplies it to the system output end 3. The power generated by the multiple FC stacks 10 is supplied to other devices from the system output end 3. Even if the output voltages of the multiple FC stacks 10 differ, the outputs of the multiple FC stacks 10 can be added together and supplied to the system output end 3 by adjusting the output voltage of the boost converter 11. When supplying power to an AC-driven device, an inverter is connected between the device and the system output end 3.

[0013] In the FC stack 10, fuel gas (hydrogen gas) reacts with air (oxygen) to generate electricity. The desired power is obtained by a controller 4 controlling the amounts of fuel gas and air supplied to the FC stack 10. The device that supplies the fuel gas and air to the FC stack 10 is not shown in the illustration.

[0014] The temperature of the FC stack 10 rises during power generation. The FC system 102 includes the same number of coolers 20 as the FC stacks 10, and each cooler 20 can individually cool the corresponding FC stack 10. The FC stack 10a is associated with the cooler 20a, and the FC stack 10b (10c) is associated with the cooler 20b (20c).

[0015] The cooler 20a is equipped with a radiator 21a that releases heat from the refrigerant, a circulation path 22a through which the refrigerant circulates between the radiator 21a and the FC stack 10a, a pump 23a that pumps the refrigerant, and a temperature sensor 24a. The circulation path 22a is divided into a supply path 221 that supplies the refrigerant from the radiator 21a to the FC stack 10a, and a return path 222 that returns the refrigerant from the FC stack 10a to the radiator 21a. The pump 23a is disposed in the supply path 221.

[0016] Temperature sensor 24a is placed in a location on return line 222 close to FC stack 10a (FC stack outlet for the coolant). Temperature sensor 24a measures the temperature of the coolant that has absorbed heat from FC stack 10a. The measurement value of temperature sensor 24a is treated as an approximation of the temperature of FC stack 10a. Controller 4 adjusts the flow rate of the coolant sent to FC stack 10a so that the measurement value of temperature sensor 24a (i.e., the temperature of FC stack 10a) is maintained within an acceptable range. The flow rate of the coolant is adjusted by the output of pump 23a.

[0017] The coolers 20a-20c have the same structure, so the explanation of the coolers 20b, 20c will be omitted. The cooler 20b adjusts the flow rate of the coolant supplied to the FC stack 10b based on the temperature sensor 24b (i.e., the temperature of the FC stack 10b). The cooler 20c adjusts the flow rate of the coolant supplied to the FC stack 10c based on the temperature sensor 24c (i.e., the temperature of the FC stack 10c). That is, the three coolers 20a-20c individually cool the corresponding FC stacks 10a-10c. For example, when the temperature of the FC stack 10a is the highest and the temperature of the FC stack 10c is the lowest, the flow rate of the coolant supplied to the FC stack 10a is the highest and the flow rate of the coolant sent to the FC stack 10c is the lowest. For example, as illustrated in FIG. 1, 30 L / s of coolant is supplied to the high-temperature FC stack 10a, and 20 L / s of coolant is sent to the low-temperature FC stack 10c. A refrigerant is sent to the medium-temperature FC stack 10b at a flow rate (25 L / s) intermediate between the two. The multiple coolers 20 are controlled by the controller 4. The unit [L / s] is an abbreviation for Litter / second.

[0018] The FC system 102 includes a plurality of coolers 20 each individually corresponding to a respective one of the plurality of FC stacks 10. Therefore, typically, the temperature of each FC stack 10 can be precisely adjusted.

[0019] The FC system 102 includes a connecting pipe 31 that connects the circulation paths 22 of the multiple coolers 20, and an adjustment valve 41 that adjusts the flow rate of the refrigerant flowing through the connecting pipe 31. The connecting pipe 31 is divided into a first segment pipe 311, a second segment pipe 312, and a third segment pipe 313. The first segment pipe 311 connects the circulation path 22a (supply path 221) of the cooler 20a to the circulation path 22c (return path 222) of the cooler 20c. The second segment pipe 312 connects the circulation path 22c (supply path 221) of the cooler 20c to the circulation path 22b (return path 222) of the cooler 20b. The third segment pipe 313 connects the circulation path 22b (supply path 221) of the cooler 20b to the circulation path 22a (return path 222) of the cooler 20a. The connecting pipe 31 connects the supply path 221 of one of the adjacent coolers 20 to the return path 222 of the other of the adjacent coolers 20. In other words, the connecting pipe 31 connects the circulation paths 22 of the multiple coolers 20 in sequence.

[0020] The flow rate of the refrigerant flowing through the connecting pipe 31 is adjusted by the adjustment valve 41. The controller 4 controls the adjustment valve 41. When the adjustment valve 41 is closed, as shown in FIG. 1, each cooler 20 is independent and the refrigerants do not mix with each other. The controller 4 compares the temperatures of all the FC stacks 10, and opens the adjustment valve 41 when the temperature difference between the maximum and minimum temperatures of the FC stacks 10 exceeds a predetermined temperature difference threshold. When the adjustment valve 41 is opened, a portion of the refrigerant coming out of the radiator 21a of the cooler 20a flows into the connecting pipe 31 (first segment pipe 311), and the remaining refrigerant flows to the FC stack 10a. The refrigerant flowing through the connecting pipe 31 (first segment pipe 311) flows into the circulation path 22c (return path 222) of the cooler 20c.

[0021] Since the circulation path 22c is connected in a ring shape, the same amount of refrigerant as the amount of refrigerant flowing into the return path 222 of the circulation path 22c flows from the supply path 221 of the circulation path 22c to the cooler 20b through the connecting pipe 31 (second segment pipe 312). Similarly, the same amount of refrigerant returns to the cooler 20a from the circulation path 22b (supply path 221) of the cooler 20b through the third segment pipe 313.

[0022] Figure 2 shows an example of refrigerant distribution when part of the refrigerant flows into connecting pipe 31. The thick arrows represent the flow of the refrigerant. In the following figures, the thick arrows also represent the flow of the refrigerant. In the case of Figure 2, it is assumed that FC stack 10a has the highest temperature and FC stack 10c has the lowest temperature. As in the case of Figure 1, 30 L / s, 25 L / s and 20 L / s of refrigerant flow into radiators 21a-21c, respectively. Part of the refrigerant (10 L / s) pushed out by pump 23a flows into connecting pipe 31, and the remainder (20 L / s) flows into FC stack 10a.

[0023] The refrigerant flows from the cooler 20a into the circulation path 22c of the cooler 20c at 10 L / s. The refrigerant flows into the radiator 21c at 20 L / s, of which a portion (10 L / s) flows from the circulation path 22c (supply path 221) to the circulation path 22b (return path 222) of the cooler 20b, and the remainder (10 L / s) flows to the FC stack 10c.

[0024] 10 L / s of refrigerant flows from the cooler 20c into the circulation path 22b (return path 222) of the cooler 20b. Of the 25 L / s of refrigerant that flows into the radiator 21b, a portion of it (10 L / s) flows from the circulation path 22b (supply path 221) to the circulation path 22a (return path 222) of the cooler 20a, and the remainder (15 L / s) flows to the FC stack 10b. 10 L / s of refrigerant flows from the cooler 20a to the cooler 20c, and the same amount of refrigerant returns from the cooler 20b to the cooler 20a.

[0025] When the regulating valve 41 opens, the refrigerant flows through the connecting pipe 31, and the refrigerants in the multiple coolers 20 mix together. Therefore, the temperatures of the refrigerant in the multiple coolers 20 are equalized. The temperature of the refrigerant flowing through the low-temperature FC stack 10c rises, and the temperature of the refrigerant flowing through the high-temperature FC stack 10a falls. The cooler 20a can effectively cool the FC stack 10a using not only the radiator 21a but also the capabilities of the radiators 21b and 21c of the other coolers. The FC system 102 of the embodiment includes multiple coolers 20 that are independent of each other, but when the temperature difference in the FC stack becomes large, the refrigerant is mixed in the multiple coolers 20, and the high-temperature FC stack 10 can be efficiently cooled. The FC system 102 can effectively utilize the multiple coolers 20.

[0026] The controller 4 opens the adjustment valve 41 when the temperature difference between the multiple FC stacks 10 exceeds a predetermined temperature difference threshold. The controller 4 also opens the adjustment valve 41 when shutting down the multiple fuel cell stacks. The refrigerant temperatures of the multiple coolers 20 are equalized during shutdown, and the temperatures of the multiple FC stacks 10 after the system is shut down are equalized.

[0027] (Second embodiment) Fig. 3 shows a block diagram of an FC system 202 of a second embodiment. The difference between the FC system 102 and the FC system 202 will be described. In the FC system 102, the connecting pipe 31 (first segment pipe 311) is connected to the circulation path 22a (supply path 221) downstream of the pump 23a. In the FC system 202 of the second embodiment, the connecting pipe 31 (first segment pipe 311) is connected to the circulation path 22a (supply path 221) upstream of the pump 23a. The other structure of the FC system 202 is the same as that of the FC system 102 of the first embodiment. The same effect can be obtained whether the connecting pipe 31 is connected to the circulation path 22a upstream of the pump 23a or connected to the circulation path 22a downstream.

[0028] Similarly, in the cooler 20b (20c), the connecting pipe 31 may be connected to the circulation path 22b (22c) upstream of the pump 23b (23c).

[0029] (Third embodiment) Figure 4 shows a block diagram of an FC system 302 of a third embodiment. The FC system 302 has an adjustment valve 42 instead of the adjustment valve 41 of the FC system 102. The adjustment valve 42 is placed at the branch point of the circulation path 22a (supply path 221) and the connecting pipe 31. The adjustment valve 42 adjusts the ratio of the refrigerant flowing through the connecting pipe 31 to the refrigerant supplied to the FC stack 10a. The adjustment valve 42 is controlled by the controller 4. By providing the adjustment valve 42 that adjusts the flow rate ratio at the branch point of the circulation path 22a and the connecting pipe 31, the flow rate of the refrigerant flowing through the connecting pipe 31 can be precisely controlled.

[0030] (Fourth embodiment) FIG. 5 shows a block diagram of an FC system 402 of a fourth embodiment. In the FC system 302 of the third embodiment, a control valve 42 is disposed at the branch point of the supply line 221 of the circulation line 22a and the connecting pipe 31. In the FC system 402 of the fourth embodiment, a control valve 42 is provided at the branch point of the return line 222 of the circulation line 22a and the connecting pipe 31. The control valve 42 adjusts the ratio of the refrigerant flowing in the connecting pipe 31 to the refrigerant returning to the radiator 21a. The control valve 42 is controlled by the controller 4. When the return line 222 is provided with the control valve 42, the direction in which the refrigerant flows in the connecting pipe 31 differs from that in the third embodiment. FIG. 5 shows an example of refrigerant distribution. A portion (10 L / s) of the 30 L / s refrigerant leaving the FC stack 10a flows to the connecting pipe 31 (third segment pipe 313), and the remaining refrigerant (20 L / s) returns to the radiator 21a.

[0031] The refrigerant coming out of the cooler 20a flows into the circulation path 22b (supply path 221) of the cooler 20b. The pump 23b pumps out the refrigerant at 15 L / s. The refrigerant flows through the FC stack 10b at 25 L / s, and a portion of that (10 L / s) flows from the cooler 20b to the cooler 20c through the second segment pipe 312.

[0032] The refrigerant coming out of the cooler 20b flows into the circulation path 22c (supply path 221) of the cooler 20c. The pump 23c pumps out the refrigerant at 10 L / s. 20 L / s of the refrigerant flows through the FC stack 10c, and a portion of that (10 L / s) returns from the cooler 20c to the cooler 20a through the first segment pipe 311. With the configuration in Fig. 5, it is possible to obtain the same effect as the FC system 302 in Fig. 4.

[0033] It should be noted that, in any one of the multiple coolers 20, the regulating valve 42 may be provided at the branch point of the circulation path 22 and the connecting pipe 31. This is because, if the flow rate of the connecting pipe 31 is determined by one regulating valve 42, the flow rates of all the segment pipes 311, 312, and 313 will be equal.

[0034] (Fifth embodiment) Fig. 6 shows a block diagram of an FC system 502 of a fifth embodiment. In addition to the configuration of the FC system 302 of the third embodiment, the FC system 502 has each cooler 20 having a bypass path 25 and a switching valve 43. The cooler 20a (20b, 20c) has a bypass path 25a (25b, 25c) and a switching valve 43a (43b, 43b). Since the coolers 20a-20c have the same structure, hereinafter, the bypass paths 25a-25c may be collectively referred to as the bypass path 25, and the switching valves 43a-43c may be collectively referred to as the switching valve 43.

[0035] The bypass path 25 connects the supply path 221 and the return path 222 of the circulation path 22 so that the refrigerant bypasses the FC stack 10. The connecting pipe 31 is connected to the circulation path 22 between the radiator 21 and the bypass path 25. The switching valve 43 switches the flow destination of the refrigerant leaving the radiator 21 to either the bypass path 25 or the FC stack 10.

[0036] The FC system 502 of the fifth embodiment is effective when the temperature of any one of the FC stacks 10 is much higher than the other FC stacks 10. For example, assume that the temperature of the FC stack 10a is higher than the other FC stacks 10b, 10c. The controller 4 controls the switching valve 43a in the cooler 20a corresponding to the FC stack 10a with the highest temperature, and sets the refrigerant destination to the FC stack 10a. The controller 4 controls the switching valves 43b, 43c in the coolers 20b, 20c of the other FC stacks 10b, 10c, and sets the refrigerant destination to the bypass paths 25b, 25c. Then, the controller 4 controls the adjustment valve 42 to distribute part of the refrigerant to the connecting pipe 31.

[0037] An example of the refrigerant flow is shown in Figure 6. 35 L / s of refrigerant flows through the radiator 21a. In the cooler 20a, part of the refrigerant (5 L / s) flows through the connecting pipe 31, and the remaining refrigerant (30 L / s) flows through the FC stack 10a.

[0038] 5 L / s of refrigerant flows through coolers 20b, 20c via connecting pipe 31. In coolers 20b, 20c, the entire amount of refrigerant flows through bypass paths 25b, 25c, and does not flow through FC stacks 10b, 10c. Therefore, the refrigerant flowing through connecting pipe 31 is not affected by the temperature of FC stacks 10b, 10b, and is rapidly cooled by radiators 21b, 21c. FC stack 10a is cooled by making full use of all of radiators 21a-21c.

[0039] 7 shows a block diagram of an FC system 602 of the sixth embodiment. In the FC system 602, a regulating valve 44 is provided instead of the regulating valve 42 of the FC system 502. That is, the regulating valve 42 that was provided in the supply path 221 in the FC system 502 is provided in the return path 222 in the FC system 602. The regulating valve 44 distributes part of the refrigerant flow that has left the FC stack 10a to the connecting pipe 31. The other configuration is the same as that of the FC system 502.

[0040] For example, assume that the temperature of FC stack 10a is higher than the other FC stacks 10b, 10c. The controller 4 controls the switching valve 43a so that the destination of the refrigerant leaving the radiator 21a is the FC stack 10a. The controller 4 controls the switching valve 43b (43c) in the cooler 20b (20c) so that the destination of the refrigerant is the bypass path 25b (25c). The controller 4 then controls the adjustment valve 44 so that some of the refrigerant flows into the connecting pipe 31.

[0041] FIG. 7 also shows an example of the flow of the refrigerant. Since the adjustment valve 44 is provided on the return line 222, the refrigerant that absorbs heat in the FC stack 10a is distributed to the radiator 21a and the other coolers 20b, 20c. In the example of FIG. 7, 30 L / s of refrigerant flows through the FC stack 10a, of which 20 L / s flows to the radiator 21a, and the remainder (10 L / s) flows through the connecting pipe 31 to the coolers 20b, 20c. The 10 L / s of refrigerant is also cooled by the radiators 21b, 21c of the coolers 20b, 20c. In the coolers 20b, 20c, the entire amount of refrigerant flows through the bypass paths 25b, 25c, and does not flow to the FC stacks 10b, 10c. Therefore, in the coolers 20b, 20c, the refrigerant is effectively cooled by the radiators 21b, 21c without being affected by the temperature of the FC stacks 10b, 10c.

[0042] The refrigerant cooled in the radiators 21b, 21c is returned to the circulation path 22a (supply path 221) of the cooler 20a through the connecting pipe 31, and flows to the FC stack 10a. In the example of Fig. 7, the refrigerant that absorbs heat in the FC stack 10a is distributed to all of the radiators 21a-21c and effectively cooled. The FC system 602 can effectively use multiple coolers 20 to intensively cool the high-temperature FC stack 10a.

[0043] (Seventh embodiment) Figure 8 shows a block diagram of an FC system 702 of the seventh embodiment. The FC system 702 has the following structure. In the cooler 20a, the connecting pipe 31 is connected to the circulation path 22a between the bypass path 25a and the FC stack 10a. In addition, the first segment pipe 311 of the connecting pipe 31 is connected to the circulation path 22a (supply path 221) downstream of the pump 23a. A switching valve 43a is disposed at the branch point of the bypass path 25a and the return path 222. The switching valve 43a switches the destination of the refrigerant coming out of the FC stack 10a to either the radiator 21a or the bypass path 25a.

[0044] In the cooler 20b, the connecting pipe 31 is connected to the circulation path 22b between the bypass path 25b and the FC stack 10b. In addition, the third segment pipe 313 of the connecting pipe 31 is connected to the circulation path 22b (supply path 221) upstream of the pump 23b. A switching valve 43b is disposed at the branch point of the bypass path 25b and the return path 222. The switching valve 43b switches the destination of the refrigerant coming out of the FC stack 10b to either the radiator 21b or the bypass path 25b. The structure of the cooler 20c is the same as that of the cooler 20b.

[0045] In the FC system 702, the FC stack 10 can be cooled by effectively utilizing multiple coolers 20.

[0046] The following points should be noted regarding the technology described in the embodiments: The FC system disclosed in this specification may have four or more FC stacks.

[0047] Although specific examples of the present invention have been described above in detail, 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 alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of these objectives is itself technically useful. [Explanation of symbols]

[0048] 102-702: fuel cell system 3: system output terminal 4: controller 10, 10a-10c: fuel cell stack 11, 11a-11c: boost converter 20, 20a-20c: cooler 21, 21a-21c: radiator 22, 22a-22c: circulation path 23, 23a-23c: pump 24, 24a-24c: temperature sensor 25, 25a-25c: bypass path 31: connecting pipe 41, 42, 44: regulating valve 43, 43a-43c: switching valve 221: supply path 222: return path 311, 312, 313: segment pipe

Claims

1. A plurality of fuel cell stacks; a plurality of coolers corresponding to the respective fuel cell stacks, each of the coolers having a radiator and a circulation path for circulating a coolant between the corresponding fuel cell stack and the radiator; A connecting pipe that connects the circulation paths of the plurality of coolers; an adjusting valve for adjusting a flow rate of the refrigerant flowing from the circulation path to the connecting pipe; A controller for adjusting the regulating valve; Equipped with each of the circulation paths includes a supply path for sending the coolant from the radiator to the fuel cell stack, and a return path for returning the coolant from the fuel cell stack to the radiator; Each of the coolers includes a bypass passage connecting the supply passage and the return passage, The connecting pipe connects the supply passage of one of the coolers to the return passage of another of the coolers, and is connected to the circulation passage between the bypass passage and the radiator. Fuel cell system.

2. the controller opens the regulating valve when a temperature difference between the plurality of fuel cell stacks exceeds a predetermined temperature difference threshold; or The controller opens the regulating valve when shutting down the plurality of fuel cell stacks. The fuel cell system according to claim 1 .

3. Each of the coolers has a switching valve that switches the flow destination of the coolant that has left the radiator between the bypass path and the fuel cell stack, The controller includes: controlling the switching valve to set the flow destination of the refrigerant of the cooler corresponding to the fuel cell stack having the highest temperature to the fuel cell stack, and set the flow destination of the refrigerant of the other coolers to the bypass path; 3. The fuel cell system according to claim 1, wherein the regulating valve is controlled so that a portion of the refrigerant flows through the connecting pipe.

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