Fuel cell cooling system

Abstract

To provide a fuel cell cooling system that can improve the accuracy of temperature control. [Solution] The fuel cell system 1 includes a refrigerant-flow circuit having a radiator 3 and a fan 4 capable of cooling a refrigerant 2, and a plurality of fuel cell stacks 33 arranged in parallel with the radiator 3, a plurality of temperature detection units 42 provided for each of the plurality of fuel cell stacks 33 for detecting the temperature of the refrigerant 2 for cooling the fuel cell stacks 33, and a control unit 6 that performs duty cycle control of the fan 4 based on the detection results of the temperature detection units 42. The control unit 6 calculates an individual duty cycle for each fuel cell stack 33 based on the detection results of the temperature detection units 42, and calculates the duty cycle applied to the fan 4 by dividing the sum of the individual duty cycles by the total number of fuel cell stacks 33.

Description

Technical Field

[0001] The present invention relates to a technology for cooling a fuel cell stack using a refrigerant.

Background Art

[0002] In recent years, research and development on fuel cells that contribute to energy efficiency have been carried out to ensure that more people can access affordable, reliable, sustainable and advanced energy. Patent Document 1 describes a cooling system for fuel cells in which a plurality of fuel cell main bodies are arranged in parallel with a radiator.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of Invention

Problems to be Solved by the Invention

[0004] In the system described in Patent Document 1, the radiator is required to have performance capable of cooling all of the plurality of fuel cell main bodies. However, for example, when it is desired to cool one of the plurality of fuel cell main bodies, operating such a radiator may cause overcooling or increase power consumption. Therefore, it is desired to improve the accuracy of temperature management of fuel cells.

[0005] The present invention has been made in view of the above points, and an object thereof is to provide a fuel cell cooling system that can improve the accuracy of temperature management and can contribute to energy efficiency.

Means for Solving the Problems

[0006] To solve the aforementioned problems, the fuel cell cooling system of the present invention comprises a cooling unit capable of cooling a refrigerant, a plurality of fuel cells provided in parallel with the cooling unit, a refrigerant-flowable circuit, a plurality of temperature detection units provided for each of the plurality of fuel cells for detecting the temperature of the refrigerant used to cool the fuel cell, and a control unit that performs duty cycle control of the cooling unit based on the detection results of the temperature detection units, wherein the control unit calculates an individual duty cycle for each fuel cell based on the detection results of the temperature detection units, and calculates the duty cycle applied to the cooling unit by dividing the sum of the individual duty cycles by the total number of the plurality of fuel cells. [Effects of the Invention]

[0007] According to the present invention, it is possible to improve the accuracy of temperature control and, consequently, contribute to energy efficiency. [Brief explanation of the drawing]

[0008] [Figure 1] This figure schematically shows a fuel cell cooling system according to an embodiment of the present invention. [Modes for carrying out the invention]

[0009] <Fuel cell cooling system> Next, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. As shown in Figure 1, the fuel cell cooling system 1 according to an embodiment of the present invention is a system that cools a plurality of fuel cell stacks 33 using a refrigerant 2, and cools the refrigerant 2, which has been heated by such cooling, using a single radiator 3. The fuel cell cooling system 1 is applicable to vehicles (fuel cell vehicles), for example. The fuel cell cooling system 1 comprises a radiator 3, a fan 4, a plurality of fuel cell units 5, and a control unit 6. The radiator 3 and the fan 4 constitute an example of a cooling unit that cools the refrigerant 2 under the control of the control unit 6.

[0010] <Radiator and fan> The radiator 3 has a shape (such as multiple fins) that optimizes heat exchange between the refrigerant 2 circulating inside the radiator 3 and the outside air. The fan 4 operates based on a control signal from the control unit 6, blowing or sucking air onto the radiator 3 to improve the cooling efficiency of the refrigerant 2 circulating within the radiator 3.

[0011] <Fuel cell unit> Multiple fuel cell units 5 generate electricity through a chemical reaction that produces water from hydrogen and oxygen. The multiple fuel cell units 5 are connected in parallel to a single radiator 3 for the flow of refrigerant 2. The fuel cell units 5 will be described in detail later.

[0012] <Department Head> The control unit 6 is a so-called ECU (Electronic Control Unit) composed of a CPU (Central Processing Unit), ROM (Read-Only Memory), RAM (Random Access Memory), input / output circuits, etc. The control unit 6 controls the fan 4 and the multiple fuel cell units 5.

[0013] <Circuit (refrigerant flow path)> The fuel cell cooling system 1 includes an upstream flow path 11, a plurality of upstream parallel flow paths 12, a plurality of downstream parallel flow paths 13, and a downstream flow path 14 as the flow paths for the refrigerant 2. These flow paths constitute a circuit through which the refrigerant 2 circulates.

[0014] The upstream end of the upstream flow path 11 is connected to the downstream end of the radiator 3 in a way that allows refrigerant to flow. The downstream end of the upstream flow path 11 is connected to the upstream ends of the multiple upstream parallel flow paths 12 in a way that allows refrigerant to flow.

[0015] The plurality of upstream parallel flow paths 12 each correspond to one fuel cell unit 5, and are provided in parallel with the radiator 3. The upstream end of the upstream parallel flow path 12 is connected to the downstream end of the radiator 3 in a manner allowing coolant to flow therethrough. The downstream end of the upstream parallel flow path 12 is connected to the upstream end of the fuel cell unit 5 in a manner allowing coolant to flow therethrough.

[0016] The plurality of downstream parallel flow paths 13 each correspond to one fuel cell unit 5, and are provided in parallel with the radiator 3. The upstream end of the downstream parallel flow path 13 is connected to the downstream end of the fuel cell unit 5 in a manner allowing coolant to flow therethrough. The downstream end of the downstream parallel flow path 13 is connected to the upstream end of the radiator 3 in a manner allowing coolant to flow therethrough.

[0017] The upstream end of the downstream flow path 14 is connected to the downstream ends of the plurality of downstream parallel flow paths 13 in a manner allowing coolant to flow therethrough. The downstream end of the downstream flow path 14 is connected to the upstream end of the radiator 3 in a manner allowing coolant to flow therethrough.

[0018] <Detailed Configuration of Fuel Cell Unit> The fuel cell unit 5 includes a main flow path 21 and a sub flow path 22 as flow paths for the coolant 2. The main flow path 21 is a flow path for cooling a fuel cell stack 33 described later. The upstream end of the main flow path 21 is connected to the downstream end of the upstream parallel flow path 12 in a manner allowing coolant to flow therethrough. The downstream end of the main flow path 21 is connected to the upstream end of the downstream parallel flow path 13 in a manner allowing coolant to flow therethrough.

[0019] The sub flow path 22 is a bypass flow path of the main flow path 21. The upstream end of the sub flow path 22 is connected to the vicinity of the upstream end of the main flow path 21 in a manner allowing coolant to flow therethrough. The downstream end of the sub flow path 22 is connected to the vicinity of the downstream end of the main flow path 21 in a manner allowing coolant to flow therethrough.

[0020] The fuel cell unit 5 includes a valve 31, a pump 32, and a fuel cell stack 33 in order from the upstream side to the downstream side of the main flow path 21. Further, the fuel cell unit 5 includes an opening degree detection unit 41 and a temperature detection unit 42 as a sensor group.

[0021] <Valve> The valve 31 is provided at the branch portion between the main flow path 21 and the sub flow path 22. The valve 31 is configured to be switchable between an open state and a closed state described below based on a control signal from the control unit 6. Open state: a state in which the upstream side of the main flow path 21 relative to the valve 31, and at least one of the downstream side of the main flow path 21 relative to the valve 31 and the sub flow path 22 are opened to allow refrigerant to flow therethrough In the open state, the valve 31 is configured to be capable of adjusting the flow rate of the refrigerant 2 to the downstream side of the main flow path 21 relative to the valve 31 and the flow rate of the refrigerant 2 to the sub flow path 22 based on a control signal from the control unit 6. Closed state: a state in which the upstream side of the main flow path 21 relative to the valve 31, the downstream side of the main flow path 21 relative to the valve 31, and the sub flow path 22 are blocked to prevent refrigerant from flowing therethrough In the closed state, the valve 31 is configured to communicate the downstream side of the main flow path 21 relative to the valve 31 and the sub flow path 22 with each other to allow refrigerant to flow therethrough.

[0022] <Pump> The pump 32 operates based on a control signal from the control unit 6 to transport the refrigerant 2.

[0023] <Fuel Cell Stack (Fuel Cell)> The fuel cell stack 33 generates electric power using hydrogen supplied from a hydrogen tank (not shown) and oxygen. The fuel cell stack 33 is cooled by the refrigerant 2 flowing through the main flow path 21.

[0024] <Refrigerant Flow Direction> When the valve 31 is in the open state, the refrigerant 2 circulates in a closed circuit of radiator 3 → upstream flow path 11 → upstream parallel flow path 12 → main flow path 21 (or sub flow path 22) → downstream parallel flow path 13 → downstream flow path 14 → radiator 3 by the operation of the pump 32. The temperature of the refrigerant 2 rises by exchanging heat (absorbing heat) with the fuel cell unit 33 in the main flow path 21, and the temperature of the refrigerant 2 drops by exchanging heat (releasing heat) with external air in the radiator 3.

[0025] When valve 31 is closed, the refrigerant 2 circulates through a closed circuit consisting of the main flow path 21 and the sub-circuit 22 by the operation of pump 32.

[0026] <Opening degree detection unit> The valve opening detection unit 41 is a valve opening sensor that detects the opening degree of the valve 31 and outputs the detection result to the control unit 6. Here, the valve opening degree of the valve 31 is the opening degree toward the main flow path 21 side (fuel cell stack 33 side) in the open valve state described above. The larger the valve opening degree of the valve 31, the larger the flow rate of refrigerant 2 flowing toward the main flow path 21 side (fuel cell stack 33 side) and the smaller the flow rate of refrigerant 2 flowing toward the sub-flow path 22 side. The smaller the valve opening degree of the valve 31, the smaller the flow rate of refrigerant 2 flowing toward the main flow path 21 side (fuel cell stack 33 side) and the larger the flow rate of refrigerant 2 flowing toward the sub-flow path 22 side. The state in which the valve opening degree of the valve 31 is zero corresponds to the closed valve state described above.

[0027] <Temperature detection unit> The temperature detection unit 42 is a temperature sensor that detects the temperature of the refrigerant 2 upstream of the fuel cell stack 33 in the main flow path 21 and outputs the detection result to the control unit 6.

[0028] <Basic Control> The control unit 6 controls the valve 31 for each fuel cell unit 5 based on the detection result of the temperature detection unit 42, and also controls the pump 32 based on the detection result of the opening degree detection unit 41.

[0029] If the temperature of the refrigerant 2 detected by the temperature detection unit 42 is below the first predetermined temperature, the control unit 6 closes the valve 31 and operates the pump 32. In this state, the refrigerant 2 circulates through a closed circuit within the fuel cell unit 5, which is composed of the main flow path 21 and the sub-circuit 22, due to the operation of the pump 32. The refrigerant 2 heats up by exchanging heat (absorbing heat, cooling the fuel cell stack 33) with the fuel cell stack 33 in the main flow path 21.

[0030] If the temperature of the refrigerant 2 detected by the temperature detection unit 42 is above the first predetermined temperature, the control unit 6 opens the valve 31 and operates the pump 32. In this state, the refrigerant 2 circulates through a closed circuit by the operation of the pump 32: radiator 3 → upstream flow path 11 → upstream parallel flow path 12 → main flow path 21 (or sub-flow path 22) → downstream parallel flow path 13 → downstream flow path 14 → radiator 3 →… The refrigerant 2 heats up by exchanging heat with the fuel cell stack 33 in the main flow path 21 (absorbing heat, cooling the fuel cell stack 33), and cools down by exchanging heat with the outside air in the radiator 3 (dissipating heat).

[0031] <Opening degree tracking control> In this embodiment, the control unit 6 uses the maximum opening detected by the opening detection unit 41 of the multiple fuel cell units 5 to control the valves 31 of the fuel cell units 5 that are not at the maximum opening to be at the maximum opening. This control allows the pressure loss of the refrigerant 2 in the multiple fuel cell units 5 to be matched, and suppresses the occurrence of pulsation of the refrigerant 2 in the other fuel cell units 5 due to the opening and closing operation of the valve 31 at the maximum opening.

[0032] More specifically, the control unit 6 calculates the temperature difference between the temperature of the refrigerant 2 detected by the temperature detection unit 42 of the fuel cell unit 5 at its maximum opening and the temperature of the refrigerant 2 detected by the temperature detection unit 42 of the fuel cell unit 5 at a position other than the maximum opening. If the temperature difference (absolute value) is less than a predetermined value, the control unit 6 controls the opening of the valve 31 for each fuel cell unit 5 as described above.

[0033] If the temperature difference (absolute value) is greater than or equal to a predetermined value, the control unit 6 controls the valve 31 of the corresponding fuel cell unit 5 to its maximum opening, and then controls it to an opening based on the temperature of the refrigerant 2 detected by the temperature detection unit 42 of the corresponding fuel cell unit 5 (returning to normal control). This control suppresses the pulsation of the refrigerant 2 and prevents the cooled refrigerant 2 from flowing to the fuel cell unit 5 that does not require cooling.

[0034] The control unit 6 controls the valve 31 such that the closing speed of the valve 31 when returning to normal control is faster than the opening speed of the valve 31 when the valve 31 is at its maximum opening. This control suppresses the pulsation of the refrigerant 2 when returning the valve 31 to normal control.

[0035] The control unit 6 controls the closing speed of the valve 31 when returning the valve 31 to normal control, based on the temperature of the refrigerant 2 detected by the temperature detection unit 42 of the corresponding fuel cell unit 5. Specifically, the control unit 6 increases the closing speed of the valve 31 as the temperature of the refrigerant 2 decreases, and decreases the closing speed of the valve 31 as the temperature of the refrigerant 2 increases. This control suppresses overcooling of the fuel cell stack 33 while suppressing unnecessary power consumption.

[0036] The control unit 6 may be configured to adjust the amount of operation (e.g., rotational speed) of the pump 32 of the fuel cell unit 5 on which the opening degree tracking control is being performed, based on the maximum opening degree, in conjunction with the opening degree tracking control described above.

[0037] The control unit 6 may be configured to perform the aforementioned opening degree tracking control for fuel cell units 5 whose opening degree difference from the maximum opening degree is less than a predetermined opening degree difference, and not to perform the aforementioned opening degree tracking control for fuel cell units 5 whose opening degree difference from the maximum opening degree is greater than or equal to a predetermined opening degree difference. With such control, it is possible to suitably suppress the cooling of the fuel cell stack 33, which does not require cooling.

[0038] Furthermore, the control unit 6 may be configured to have a function for diagnosing abnormalities in multiple fuel cell units 5. In this case, the control unit 6 limits the amount of power generated by the fuel cell stack 33 in the fuel cell unit 5 diagnosed as abnormal, and sets the opening of the valve 31 to an opening that minimizes the refrigerant pressure loss (for example, an opening that is midway between the maximum and minimum openings). With this control, the refrigerant pressure loss in the fuel cell unit 5 diagnosed as abnormal can be fixed at a minimum, and the impact of such refrigerant pressure loss on other normal fuel cell units 5 (the pulsation effect of the refrigerant 2) can be suppressed.

[0039] <Fan control> In this embodiment, the function of the fan 4 is set to a specification that allows the refrigerant 2 to be cooled even when the refrigerant 2 becomes hot in all of the fuel cell units 5. The control unit 6 stops the fan 4 when none of the fuel cell units 5 require cooling by the cooling unit (operation of the fan 4), and operates the fan 4 when at least one of the fuel cell units 5 requires cooling by the cooling unit (operation of the fan 4). This control suppresses overcooling of the refrigerant 2 and unnecessary power consumption, and allows the refrigerant 2 to be cooled appropriately.

[0040] In this embodiment, the control unit 6 determines that the corresponding fuel cell unit 5 does not require the fan 4 to operate if the detection result of the temperature detection unit 42 is below a first predetermined temperature. The control unit 6 also determines that the corresponding fuel cell unit 5 requires the fan 4 to operate if the detection result of the temperature detection unit 42 is at or above the first predetermined temperature. In other words, the control unit 6 stops the fan 4 if all of the detection results of the temperature detection units 42 in multiple fuel cell units 5 are below the first predetermined temperature. The control unit 6 also activates the fan 4 if at least one of the detection results of the temperature detection units 42 in multiple fuel cell units 5 is at or above the first predetermined temperature.

[0041] Furthermore, the control unit 6 may be configured to stop the fan 4 when only one of the fuel cell units 5 requires the fan 4 to operate, and to operate the fan 4 when at least two of the fuel cell units 5 require the fan 4 to operate. Such control can suppress a decrease in operating efficiency due to overcooling of the fuel cell stack 33.

[0042] The control unit 6 calculates the individual duty cycle of the fan 4 for each fuel cell unit 5 that requires the fan 4 to operate, based on at least one of the detection results of the opening degree detection unit 41 and the temperature detection unit 42.

[0043] When using the detection result of the opening degree detection unit 41, the control unit 6 calculates the individual duty cycle such that the individual duty cycle increases as the opening degree of the valve 31 detected by the opening degree detection unit 41 increases. In other words, the control unit 6 calculates the duty cycle such that the individual duty cycle decreases as the opening degree of the valve 31 detected by the opening degree detection unit 41 decreases. Since the opening degree of the valve 31 is set based on the temperature of the refrigerant 2 detected by the temperature detection unit 42, the detection result of the opening degree detection unit 41 can be said to be a parameter related to the temperature of the refrigerant 2, similar to the detection result of the temperature detection unit 42.

[0044] When using the detection results of the temperature detection unit 42, the control unit 6 calculates the individual duty cycle such that the higher the temperature of the refrigerant 2 detected by the temperature detection unit 42, the larger the individual duty cycle. In other words, the control unit 6 calculates the individual duty cycle such that the lower the temperature of the refrigerant 2 detected by the temperature detection unit 42, the smaller the individual duty cycle. Here, it can be said that the control unit 6 calculates the individual duty cycle of the fuel cell unit 5, which does not require the operation of the fan 4, to be zero.

[0045] The control unit 6 calculates the duty cycle actually applied to the fan 4 using the following equation (1). [Duty cycle] = [Sum of individual duty cycles] / [Total number of fuel cell units 5] ...Formula (1) In the example shown in Figure 1, the total number of fuel cell units 5 is 4. The sum of the individual duty cycles is the sum of the individual duty cycles calculated assuming that cooling by the cooling unit is required, and is the sum of the individual duty cycles for each fuel cell unit 5 (fuel cell stack 33) that requires cooling. The control unit 6 controls the fan 4 duty cycle based on the calculated duty cycles. Such duty cycle control can be achieved by controlling the rotation speed of the fan 4, the operating time, and the rest time ratio. With such control, temperature management of multiple fuel cell stacks 33 can be performed with fewer radiators 3 (and fans 4). Furthermore, with such control, the accuracy of temperature management of the fuel cell stacks 33 can be improved.

[0046] In this embodiment, if the maximum temperature of the refrigerant 2 detected by the temperature detection units 42 of the multiple fuel cell units 5 is less than the second predetermined temperature (second predetermined temperature > first predetermined temperature), the control unit 6 calculates the duty cycle actually applied to the fan 4 using equation (1). Furthermore, if the maximum temperature of the refrigerant 2 detected by the temperature detection units 42 of the multiple fuel cell units 5 is equal to or greater than the second predetermined temperature, the control unit 6 calculates the duty cycle actually applied to the fan 4 using the following equation (2), even if there is only one fuel cell unit 5 that requires the operation of the fan 4. [Duty Ratio] = [Maximum Individual Duty Ratio] × [Number of Fuel Cell Units 5 that require Fan 4 to operate] / [Total Number of Fuel Cell Units 5] ... Equation (2) In equation (2), the duty cycle is calculated using only the maximum value of the individual duty cycles, without using any other individual duty cycles. This control allows for optimal cooling of the high-temperature refrigerant 2, protecting the overheated fuel cell stack 33 and improving the durability of the fuel cell stack 33.

[0047] Furthermore, if the maximum temperature of the refrigerant 2 detected by the temperature detection units 42 of the multiple fuel cell units 5 is equal to or greater than the second predetermined temperature, the control unit 6 calculates the duty cycle actually applied to the fan 4 using the following equation (3). [Duty cycle] = [Maximum value of individual duty cycles] ...Equation (3)

[0048] Furthermore, the control unit 6 may be configured to detect abnormalities in the fuel cell control system 1, and if an abnormality is detected, set the duty cycle of the fan 4 to an abnormal duty cycle (a predetermined fixed value). Here, the control unit 6 may be configured to set the duty cycle of the fan 4 to a fixed value when the output of the fuel cell unit 5 where an abnormality has been detected is limited and the opening degree of the valve 31 in the fuel cell unit 5 where an abnormality has been detected is greater than or equal to a predetermined opening degree. Also, if the output of the fuel cell unit 5 where an abnormality has been detected is not limited, or if the opening degree of the valve 31 in the fuel cell unit 5 where an abnormality has been detected is less than a predetermined opening degree, the control unit 6 may be configured to stop the fuel cell control system 1 and notify the abnormality and stoppage by image and / or sound through the display unit and / or sound output unit.

[0049] The duty cycle actually applied to fan 4 may be configured to be set in steps. For example, if A and a are constants and n is an integer greater than or equal to 0, the control unit 6 may be configured to adopt A+n·a as the duty cycle if the duty cycle calculated using any of the above equations (1), (2), or (3) is greater than or equal to A+n·a and less than A+(n+1)·a.

[0050] A fuel cell system 1 according to an embodiment of the present invention includes a cooling section (radiator 3 and fan 4) capable of cooling a refrigerant 2, a plurality of fuel cells (fuel cell stack 33) provided in parallel with the cooling section, a circuit through which a refrigerant can flow, a plurality of temperature detection units 42 provided for each of the plurality of fuel cells for detecting the temperature of the refrigerant used to cool the fuel cell, and a control unit 6 that performs duty cycle control of the cooling section based on the detection results of the temperature detection units 42. The control unit 6 calculates an individual duty cycle for each fuel cell based on the detection results of the temperature detection units 42, and calculates the duty cycle applied to the cooling section by dividing the sum of the individual duty cycles by the total number of fuel cells. Therefore, the fuel cell cooling system 1 can improve the accuracy of temperature control of the fuel cell.

[0051] The control unit 6 calculates the duty cycle when cooling of two or more fuel cells by the cooling unit is required. Therefore, the fuel cell cooling system 1 can suppress the decrease in operating efficiency caused by overcooling of the fuel cell.

[0052] The control unit 6 calculates the duty cycle when the temperature of the refrigerant 2 detected by one of the temperature detection units 42 is equal to or greater than a predetermined temperature (second predetermined temperature). Therefore, the fuel cell cooling system 1 can protect overheated fuel cells and improve the durability of the fuel cell stack.

[0053] The control unit 6 calculates the duty cycle based solely on the individual duty cycles based on the temperature of the refrigerant 2, which is the temperature of the refrigerant 2 detected by one of the temperature detection units 42, if the temperature of the refrigerant 2 is equal to or greater than the predetermined temperature. Therefore, the fuel cell cooling system 1 can suitably protect the overheated fuel cell and improve the durability of the fuel cell stack.

[0054] Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above and can be modified as appropriate without departing from the spirit of the invention. For example, the fuel cell cooling system 1 of the present invention can be applied to fuel cells other than those for fuel cell vehicles. Furthermore, the cooling unit is not limited to a radiator 3 and a fan 4. [Explanation of Symbols]

[0055] 1. Fuel cell cooling system 2 Refrigerant 3. Radiator (cooling unit) 4. Fan (cooling unit) 5. Fuel cell unit 6 Control Unit 31 valves 32 pumps 33. Fuel cell stack (fuel cell)

Claims

1. A refrigerant-circulating circuit having a cooling unit capable of cooling a refrigerant, and a plurality of fuel cells provided in parallel with the cooling unit, Each of the fuel cells is provided with a plurality of temperature detection units for detecting the temperature of the refrigerant used to cool the fuel cell, A control unit that performs duty cycle control of the cooling unit based on the detection result of the temperature detection unit, Equipped with, The control unit calculates an individual duty cycle for each fuel cell based on the detection result of the temperature detection unit, and then calculates the duty cycle applied to the cooling unit by dividing the sum of the individual duty cycles by the total number of fuel cells. A fuel cell cooling system characterized by the following features.

2. The control unit calculates the duty cycle when cooling of two or more fuel cells by the cooling unit is required. The fuel cell cooling system according to claim 1.

3. The control unit calculates the duty cycle when the temperature of the refrigerant detected by one of the temperature detection units is above a predetermined temperature. A fuel cell cooling system according to claim 1 or 2, characterized in that it is the same as described in claim 1.

4. The control unit calculates the duty cycle based solely on the individual duty cycles determined by the temperature of the refrigerant at or above the predetermined temperature, when the temperature of the refrigerant detected by one of the temperature detection units is above the predetermined temperature. The fuel cell cooling system according to claim 3.

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