System for cooling a fuel cell of a motor vehicle and method for cooling a fuel cell

Abstract

The invention relates to a system (2) for cooling a fuel cell (4) of a motor vehicle, comprising a fluid-carrying coolant circuit of an air conditioning system (6), which has an expansion unit (12), a compressor (16), and a fluid-carrying line (20) through which the expansion unit (12) and compressor (16) are fluidly connected to one another, comprising a fluid-carrying coolant circuit of a fuel cell (8), which is thermally coupled to the fuel cell (4), and comprising a heat exchanger (10) in which the coolant circuit of the air conditioning system (6) and the coolant circuit of the fuel cell (8) can be thermally coupled to one another, wherein the heat exchanger (10) on the side of the coolant circuit of the air conditioning system (6) can be thermally coupled to a coupling section (22) of the coolant circuit of the air conditioning system (6), which coupling section is located downstream of the expansion unit (12) and upstream of the compressor (16). Furthermore, the invention comprises a method for cooling a fuel cell (4) by such a system (2).

Description

[0001] The invention relates to a system for cooling a fuel cell of a motor vehicle and a method for cooling a fuel cell.

[0002] Motor vehicles are known in which energy, particularly electrical energy, is generated for the operation of the vehicle using a fuel cell. When the fuel cell is in operation, it heats up.

[0003] For optimal operation of a motor vehicle's fuel cell, it is necessary that the fuel cell be operated within a specific temperature window. In particular, when the fuel cell is started up from a cooled state, for example, if it has not been in operation for an extended period, the fuel cell requires a certain amount of time to reach the temperature window in which it operates optimally. To ensure that the temperature window is reached more quickly, it is known from the prior art to equip the fuel cell with a separate heater.

[0004] To prevent the fuel cell from exceeding the specified temperature range, motor vehicles are known in which the fuel cell is assigned a fuel cell coolant circuit, in which a coolant is heated as it passes through the fuel cell and cooled downstream of the fuel cell. This requires additional energy to cool the coolant again after passing through or passing through the fuel cell.

[0005] An object of an embodiment of the invention is to propose a system for cooling a fuel cell and a method for cooling a fuel cell, in which energy consumption for cooling the fuel cell is at least reduced.

[0006] This object is achieved by a system for cooling a fuel cell of a motor vehicle with a fluid-carrying coolant circuit of an air conditioning system, which has an expansion unit, a compressor and a fluid-carrying line, by means of which the expansion unit and compressor are in fluid communication with one another, with a fluid-carrying coolant circuit of a fuel cell, which is thermally coupled to the fuel cell, and with a heat exchanger, in which the coolant circuit of the air conditioning system and the coolant circuit of the fuel cell can be thermally coupled to one another, wherein the heat exchanger on the side of the coolant circuit of the air conditioning system can be thermally coupled to a coupling section of the coolant circuit of the air conditioning system located downstream of the expansion unit and upstream of the compressor.

[0007] Because the air conditioning system's coolant circuit can be thermally coupled to the fuel cell's coolant circuit via the heat exchanger, heat can be transferred from the fuel cell's coolant circuit to the air conditioning system's coolant circuit. Because the air conditioning system's coolant circuit is located between the expansion unit and the compressor, a section of the air conditioning system's coolant circuit where the temperature of the air conditioning system's coolant circuit is very low can be fed to the heat exchanger.

[0008] This allows for energy-efficient use of an existing component to cool the fuel cell. This saves energy required for cooling the fuel cell.

[0009] Furthermore, it proves to be advantageous if the coolant circuit of the air conditioning system comprises an evaporator downstream of the expansion unit and upstream of the compressor and if the coupling section of the coolant circuit of the air conditioning system, to which the heat exchanger can be thermally coupled, is arranged on the side of the coolant circuit of the air conditioning system downstream of the evaporator and upstream of the compressor.

[0010] This ensures that the air conditioning system's coolant circuit is coupled to the fuel cell's cooling circuit via the heat exchanger at a point where the air conditioning system's coolant circuit has already fulfilled its actual function—namely, cooling, for example, a vehicle interior. In this case, the air conditioning system's coolant circuit, which may reach ambient temperature after cooling the vehicle interior, will be further heated.

[0011] After passing through the heat exchanger, i.e., before entering the compressor, the coolant circuit of the air conditioning system in the subject matter of the invention has a higher temperature before entering the evaporator than before entering the heat exchanger. This leads to a larger temperature difference (ΔT) between the ambient air and the coolant after passing through the compressor.

[0012] The air conditioning system's refrigerant circuit may include a condenser downstream of the compressor.

[0013] The flow direction of the refrigerant circuit of the air conditioning system includes a flow of the refrigerant from the expansion unit towards the evaporator, towards the compressor, towards the condenser, and back towards the expansion unit.

[0014] Furthermore, in one embodiment of the system, it is provided that the coolant circuit of the air conditioning system has a controllable first valve and a bypass line branching off from the fluid-carrying line via the controllable first valve, which bypass line is arranged downstream of the evaporator and upstream of the compressor, wherein the bypass line is connected in terms of flow parallel to the section of the fluid-carrying line of the coolant circuit of the air conditioning system located downstream of the evaporator and upstream of the compressor.

[0015] By providing an adjustable first valve, the coolant circuit of the air conditioning system between the evaporator and the compressor can take place either in the fluid-carrying line or in the bypass or in both.

[0016] In a further development of the latter embodiment, it proves to be advantageous if the coupling section of the coolant circuit of the air conditioning system, which can be thermally coupled to the heat exchanger, is formed by a coupling region of the fluid-carrying line, which is arranged downstream of the evaporator and upstream of the compressor, or if the coupling section of the coolant circuit of the air conditioning system, which can be thermally coupled to the heat exchanger, is formed entirely by the bypass line or by a coupling region of the bypass line.

[0017] This makes one of the two lines available, either the fluid-carrying line between the evaporator and compressor or the bypass line.

[0018] It proves to be advantageous if the coolant circuit of the fuel cell has a fluid-carrying line coupled to the heat exchanger and a conveying means, such as a pump, for circulating a heat exchange medium through the fluid-carrying line of the coolant circuit of the fuel cell, wherein the conveying means is arranged upstream of the heat exchanger and downstream of the fuel cell.

[0019] The conveying means may, for example, comprise a pump. The conveying means serves to circulate the heat exchange medium within the fuel cell's coolant circuit.

[0020] Embodiments of the system are conceivable in which the coolant circuit of the fuel cell is cooled exclusively via the heat exchanger by the coolant circuit of the air conditioning system.

[0021] In order to be able to limit the exceeding of a maximum temperature of the heat exchange medium within the coolant circuit of the fuel cell, it proves to be advantageous if the coolant circuit of the fuel cell has a controllable second valve and a cooling line branching off from the fluid-carrying line via the controllable second valve, which cooling line is arranged downstream of the fuel cell and upstream of the conveying means and in which a cooling element, such as a radiator, is arranged for cooling the heat exchange medium, wherein the cooling line is connected in terms of flow parallel to the section of the fluid-carrying line of the coolant circuit of the fuel cell located downstream of the fuel cell and upstream of the conveying means.

[0022] This allows the heat exchange medium to be fed exclusively or bypassing the cooling line through the controllable second valve, where it can be actively cooled by the cooling element. The cooling element can, for example, comprise a radiator.

[0023] Because the cooling line is arranged downstream of the fuel cell and upstream of the conveying means, the cooling line and the cooling element arranged thereon are positioned at a point in the coolant circuit of the fuel cell at which the heat exchange medium reaches its maximum temperature, namely after passing through and cooling the fuel cell.

[0024] The efficiency of the operation of the system can be increased if the system comprises at least one first temperature sensor which is arranged in the coolant circuit of the air conditioning system in or on the fluid-carrying line downstream of the evaporator and upstream of the controllable first valve, at least one second temperature sensor which is arranged in the fluid-carrying coolant circuit of the fuel cell in the region upstream of the fuel cell, and a control unit by means of which the controllable first valve can be controlled on the basis of the values ​​detected by the first temperature sensor and the second temperature sensor and by means of which the controllable second valve and / or the cooling element can be controlled on the basis of the values ​​detected by the second temperature sensor.

[0025] By providing the first temperature sensor and the second temperature sensor as well as the control unit, which has the temperatures measured by the temperature sensors as input variables, the bypass line and the cooling line can be switched on as required.

[0026] In a further development of the latter embodiment, it proves to be advantageous if the controllable first valve can be controlled by the control unit to release the bypass line that can be thermally coupled to the heat exchanger in order to transfer waste heat from the coolant circuit of the fuel cell to the coolant circuit of the air conditioning system, in particular if the temperature detected at the first temperature sensor is lower than the temperature detected at the second temperature sensor and / or if the controllable first valve can be controlled by the control unit to block the bypass line that can be thermally coupled to the heat exchanger, if the temperature detected at the first temperature sensor is greater than or equal to the temperature detected at the second temperature sensor and / or if the controllable second valve can be controlled by the control unit to release the cooling line and / or the cooling element for commissioning,to cool the temperature of the heat exchange medium by the cooling element, in particular when the temperature detected by the second temperature sensor reaches or exceeds a limit value stored in the control unit.

[0027] This can, for example, prevent heat from being transferred from the air conditioning system's coolant circuit to the fuel cell's coolant circuit. This can be detected if the temperature detected by the first temperature sensor is higher than the temperature detected by the second temperature sensor. In this case, the bypass is blocked by the first valve, preventing flow through the heat exchanger and preventing heat exchange between the air conditioning system's coolant circuit and the fuel cell's coolant circuit.

[0028] Because the second valve and / or the cooling element can be controlled via the control unit and the values ​​detected by the second temperature sensor, the cooling line can be activated by switching the controllable second valve when the second temperature sensor detects that a stored limit temperature has been reached or exceeded. Because the cooling element can be controlled by the control unit, it can only be activated when the stored limit temperature has been reached or exceeded. In all other cases, the cooling element can be deactivated. This allows for efficient energy savings.

[0029] Furthermore, the object is achieved by a method for cooling a fuel cell of a motor vehicle using a system with at least one of the aforementioned features, wherein thermal energy is transferred from the coolant circuit of the fuel cell to the coolant circuit of the air conditioning system by means of the heat exchanger, comprising the steps: a. Step 100: Detecting operation of the fuel cell; b. Step 101: Detecting a temperature of the coolant circuit of the air conditioning system upstream of the heat exchanger, in particular by the first temperature sensor, and detecting a temperature of the coolant circuit of the fuel cell upstream of the fuel cell, in particular by a second temperature sensor; c. Step 102: Switching or remaining the controllable first valve by the control unit in a release position in which the bypass line is released for the flow of fluid of the coolant circuit of the air conditioning system, if the temperature detected at the first temperature sensor is lower than the temperature detected at the second temperature sensor; and / or d. Step 103: Switching or remaining of the controllable first valve by the control unit in a blocking position in which the bypass line is blocked against the flow of fluid of the coolant circuit of the air conditioning system when the temperature detected at the first temperature sensor is greater than the temperature detected at the second temperature sensor.

[0030] If it is detected in step 102 that the temperature detected at the first temperature sensor is lower than the temperature detected at the second temperature sensor and the first valve is in a blocking position, the valve is switched to the release position in step 102. If the first valve is already in the release position, the first valve remains in the release position in step 102.

[0031] If it is determined in step 103 that the temperature at the first temperature sensor is greater than the temperature detected at the second temperature sensor, the first valve, if it is in the release position, is switched to the blocking position. If the first valve is already in the blocking position, the first valve remains in the blocking position in step 103.

[0032] When further developing the procedure, it proves advantageous if: e. Step 104: Comparing the temperature of the fuel cell coolant circuit detected by the second temperature sensor with a limit value stored in the control unit; f. Step 105: Switching or remaining in a release position of the control unit of the adjustable second valve, in which the cooling line is released for the flow of heat exchange medium of the coolant circuit of the fuel cell, when the temperature detected at the second temperature sensor reaches or exceeds the limit value stored in the control unit, and, if applicable, commissioning of the cooling element; and / or g. Step 106: Switching or leaving the controllable second valve in a blocking position by the control unit, in which the cooling line is blocked for the flow of heat exchange medium of the coolant circuit of the fuel cell, if the temperature detected at the second temperature sensor falls below the limit value stored in the control unit, and if necessary, deactivation of the cooling element.

[0033] If it is detected in step 105 that the temperature at the second temperature sensor reaches or exceeds the limit value stored in the control unit, the second valve, if it is in a blocking position, is switched to an enabling position. If the second valve is already in the enabling position, it remains in the enabling position in step 103.

[0034] The limit value stored in the control unit can include a threshold temperature at which the heat exchange medium, even before passing through the fuel cell, reaches a temperature so high that the difference between the temperature of the fuel cell and the temperature of the heat exchange medium is too small to ensure sufficient heat absorption by the heat exchange medium. This leads to the temperature of the fuel cell exceeding the temperature window in which the fuel cell operates optimally.

[0035] "If necessary, commissioning" means that the cooling element is put into operation in step 105 if it was previously out of operation. If the cooling element was already in operation, "if necessary, commissioning" is not necessary.

[0036] In step 106, the second valve, if it is in the release position, is moved to the blocking position when the temperature detected at the second temperature sensor falls below the limit value stored in the control unit. If the second valve is already in the blocking position at step 106, the controllable second valve remains in the blocking position.

[0037] "Deactivation of the cooling element, if any," means deactivating the cooling element if it was in operation when the second valve was moved from the release position to the blocking position. If the cooling element was already deactivated, the "deactivation of the cooling element, if any" step is not necessary.

[0038] Further features, details and advantages of the invention emerge from the appended patent claims, from the drawings and the following description of a preferred embodiment of the system and the method.

[0039] The drawing shows: Fig. 1 A schematic circuit diagram of an embodiment of the system according to the invention; Fig. 2 A schematic flow diagram of a method according to the invention.

[0040] Fig. Figure 1 shows a system, designated overall by reference numeral 2, for cooling a fuel cell 4 of a motor vehicle. The system 2 comprises a fluid-carrying coolant circuit of an air conditioning system 6. Furthermore, the system 2 comprises a fluid-carrying coolant circuit of a fuel cell 8. The coolant circuit of the air conditioning system 6 and the coolant circuit of the fuel cell 8 can be thermally coupled to one another via a heat exchanger 10.

[0041] In the Fig. 1, the coolant circuit of the air conditioning system 6 comprises an expansion unit 12, an evaporator 14, a compressor 16 and a condenser 18. Here, fluid of the fluid-carrying coolant circuit of the air conditioning system 6 flows from the heat exchanger 10 towards the evaporator 14, from there further towards the compressor 16 and from there further towards the condenser 18 back to the expansion unit 12.

[0042] The individual components are connected to each other by a fluid-carrying line 20.

[0043] In the Fig. In the embodiment shown in Figure 1, the heat exchanger 10 is connected via a coupling section 22 of the coolant circuit of the air conditioning system 6, which is arranged downstream of the evaporator 14 and upstream of the compressor 16.

[0044] In addition, the fluid-carrying coolant circuit of the air conditioning system 6 comprises a controllable first valve 24 and a bypass line 26 branching off from the fluid-carrying line 20 via the controllable first valve 24. The bypass line 26 forms the coupling section 22.

[0045] Downstream of the evaporator 14 and upstream of the first valve 24, the fluid-carrying coolant circuit of the air conditioning system 6 comprises a first temperature sensor 28.

[0046] In the Fig. In the embodiment of the system 2 shown in Figure 1, the coolant circuit of the fuel cell 8 comprises a fluid-carrying line 30 coupled to the heat exchanger 10 and a conveying means 32 through which a heat exchange medium can be conveyed through the fluid-carrying line 30 of the coolant circuit of the fuel cell 8. The conveying means 32 can, for example, comprise a pump.

[0047] Downstream of the heat exchanger 10, the coolant circuit of the fuel cell 8 includes a second temperature sensor 34. This is arranged directly upstream of a fuel cell 4. Downstream of the fuel cell 4, the coolant circuit of the fuel cell 8 includes a controllable second valve 36, which is arranged upstream of the conveying means 32. A cooling line 38 branching off from the fluid-carrying line 30 can be controlled via the second valve 36, to which the heat exchange medium can be fed to a cooling element 40. The cooling element 40 can comprise a radiator, for example. The heat exchange medium cooled thereby can be fed to the conveying means 32 after passing through the cooling element 40.

[0048] Fig. 2 shows a schematic flow diagram of an embodiment of the method according to the invention. With reference to the illustration according to Fig. 1 the procedure is described below: In a first step 100, it is detected that the fuel cell 4 is in operation. In a subsequent step 101, the temperature of the coolant circuit of the air conditioning system 6 upstream of the heat exchanger 10 is detected by the first temperature sensor 28. Furthermore, in step 101, the temperature of the coolant circuit of the fuel cell 8 upstream of the fuel cell 4 is detected by the second temperature sensor 34.

[0049] Based on the temperatures detected in step 101, in a step 102 the controllable first valve 24 is switched by a control unit 42 into or left in a release position, in which the bypass line 26 is released for the flow of fluid of the coolant circuit of the air conditioning system 6 if the detected temperature at the first temperature sensor 28 is lower than the detected temperature at the second temperature sensor 34. Alternatively, in a step 103 the controllable first valve 24 is switched by the control unit 42 into a blocking position and left there, in which the bypass line 26 is blocked against the flow of fluid of the coolant circuit of the air conditioning system 6 if the detected temperature at the first temperature sensor 28 is higher than the detected temperature at the second temperature sensor 34.

[0050] In the embodiment according to Fig.2, in a step 104, the temperature of the coolant circuit of the fuel cell 8 detected by the second temperature sensor 34 is compared with a limit value stored in the control unit 42.

[0051] Based on this, in a subsequent step 105, the controllable second valve 36 is switched to or left in a release position, in which the cooling line 38 is released for the flow of heat exchange medium of the coolant circuit of the fuel cell 8 when the temperature detected at the second temperature sensor 34 reaches or exceeds the limit value stored in the control unit 42. Furthermore, in step 105, the cooling element 40 can be activated if it was previously out of operation.

[0052] Alternatively, in a step 106, the controllable second valve 36 can be switched to a blocking position or remain in this position, in which the cooling line 38 is blocked from flowing heat exchange medium of the coolant circuit of the fuel cell 8 if the temperature detected at the second temperature sensor 34 falls below the limit value stored in the control unit 42. At the same time, an operating cooling element 40 can be deactivated.

[0053] The features of the invention disclosed in the above description, in the claims and in the drawings can be essential both individually and in any combination in the realization of the invention in its various embodiments within the scope of the following claims. List of reference symbols 2 systems 4 Fuel cell 6 Air conditioning coolant circuit 8 Fuel cell coolant circuit 10 heat exchangers 12 Expansion unit 14 evaporators 16 Compressor 18 Capacitor 20 fluid-carrying line 22 coupling section 24 first valve 26 Bypass line 28 first temperature sensor 30 fluid-carrying line 32 funding 34 second temperature sensor 36 second valve 38 Cooling line 40 Cooling element 42 Control unit 100-106 procedural steps

Claims

[1] System (2) for cooling a fuel cell (4) of a motor vehicle, comprising a fluid-carrying coolant circuit of an air conditioning system (6), which has an expansion unit (12), a compressor (16), and a fluid-carrying line (20) through which the expansion unit (12) and compressor (16) are in fluid communication with one another, comprising a fluid-carrying coolant circuit of a fuel cell (8), which is thermally coupled to the fuel cell (4), and comprising a heat exchanger (10) in which the coolant circuit of the air conditioning system (6) and the coolant circuit of the fuel cell (8) can be thermally coupled to one another, wherein the heat exchanger (10) on the side of the coolant circuit of the air conditioning system (6) can be thermally coupled to a coupling section (22) of the coolant circuit of the air conditioning system (6), which coupling section is located downstream of the expansion unit (12) and upstream of the compressor (16). [2] System (2) according to claim 1, characterized bythat the coolant circuit of the air conditioning system (6) comprises an evaporator (14) downstream of the expansion unit (12) and upstream of the compressor (16), and that the coupling section (22) of the coolant circuit of the air conditioning system (6), to which the heat exchanger (10) can be thermally coupled, is arranged on the side of the coolant circuit of the air conditioning system (6) downstream of the evaporator (14) and upstream of the compressor (16). [3] System (2) according to claim 1 or 2, characterized byin that the coolant circuit of the air conditioning system (6) has a controllable first valve (24) and a bypass line (26) branching off from the fluid-carrying line (20) via the controllable first valve (24), which bypass line is arranged downstream of the evaporator (14) and upstream of the compressor (16), wherein the bypass line (26) is connected in terms of flow parallel to the section of the fluid-carrying line (20) of the coolant circuit of the air conditioning system (6) lying downstream of the evaporator (14) and upstream of the compressor (16). [4] System (2) according to claim 3, characterized bythat the coupling section (22) of the coolant circuit of the air conditioning system (6), which can be thermally coupled to the heat exchanger (10), is formed by a coupling region of the fluid-carrying line (20), which is arranged downstream of the evaporator (14) and upstream of the compressor (16), or that the coupling section (22) of the coolant circuit of the air conditioning system (6), which can be thermally coupled to the heat exchanger (10), is formed entirely by the bypass line (26) or by a coupling region of the bypass line (26). [5] System (2) according to one of the preceding claims, characterized byin that the coolant circuit of the fuel cell (8) has a fluid-carrying line (30) coupled to the heat exchanger (10) and a conveying means (32), such as a pump, for circulating a heat exchange medium through the fluid-carrying line (30) of the coolant circuit of the fuel cell (8), wherein the conveying means (32) is arranged upstream of the heat exchanger (10) and downstream of the fuel cell (4). [6] System (2) according to claim 5, characterized byin that the coolant circuit of the fuel cell (8) has a controllable second valve (36) and a cooling line (38) branching off from the fluid-carrying line (30) via the controllable second valve (36), which is arranged downstream of the fuel cell (4) and upstream of the conveying means (32) and in which a cooling element (40), such as a radiator, is arranged for cooling the heat exchanger medium, wherein the cooling line (38) is connected in a fluidically parallel manner to the section of the fluid-carrying line (30) of the coolant circuit of the fuel cell (8) which is arranged downstream of the fuel cell (4) and upstream of the conveying means (32). [7] System (2) according to one of claims 3 to 6, characterized byat least one first temperature sensor (28) which is arranged in the coolant circuit of the air conditioning system (6) in or on the fluid-conducting line (20) downstream of the evaporator (14) and upstream of the controllable first valve (24), by at least one second temperature sensor (34) which is arranged in the fluid-conducting coolant circuit of the fuel cell (8) in the region upstream of the fuel cell (4), and by a control unit (42) by which the controllable first valve (24) can be controlled on the basis of the values ​​detected by the first temperature sensor (28) and the second temperature sensor (34) and by which the controllable second valve (36) and / or the cooling element (40) can be controlled on the basis of the values ​​detected by the second temperature sensor (34). [8] System (2) according to claim 7, characterized bythat the controllable first valve (24) can be controlled by the control unit (42) to release the bypass line (26) that can be thermally coupled to the heat exchanger (10) in order to transfer waste heat from the coolant circuit of the fuel cell (8) to the coolant circuit of the air conditioning system (6), in particular when the temperature detected at the first temperature sensor (28) is lower than the temperature detected at the second temperature sensor (34) and / or that the controllable first valve (24) can be controlled by the control unit (42) to block the bypass line (26) that can be thermally coupled to the heat exchanger (10) when the temperature detected at the first temperature sensor (28) is greater than or equal to the temperature detected at the second temperature sensor (34) and / or that the controllable second valve (36) can be controlled by the control unit (42) to release the cooling line (38) and / or the cooling element for commissioning,to cool the temperature of the heat exchange medium by the cooling element (40), in particular when the temperature detected at the second temperature sensor (34) reaches or exceeds a limit value stored in the control unit (42). [9] Method for cooling a fuel cell (4) of a motor vehicle using a system (2) according to one of the preceding claims 1 to 8, wherein thermal energy is transferred from the coolant circuit of the fuel cell (8) to the coolant circuit of the air conditioning system (6) by means of the heat exchanger (10), comprising the steps: a. Step 100: Detecting an operation of the fuel cell (4); b. Step 101: detecting a temperature of the coolant circuit of the air conditioning system (6) upstream of the heat exchanger (10), in particular by the first temperature sensor (28) and detecting a temperature of the coolant circuit of the fuel cell (8) upstream of the fuel cell (4), in particular by a second temperature sensor (34); c. Step 102: Switching or remaining the controllable first valve (24) by the control unit (42) in a release position in which the bypass line (26) is released for the flow of fluid of the coolant circuit of the air conditioning system (6) when the temperature detected at the first temperature sensor (28) is lower than the temperature detected at the second temperature sensor (34); and / or d. Step 103: Switching or remaining of the controllable first valve (24) by the control unit (42) in a blocking position in which the bypass line (26) is blocked against the flow of fluid of the coolant circuit of the air conditioning system (6) when the temperature detected at the first temperature sensor (28) is greater than the temperature detected at the second temperature sensor (34). [10] Method according to claim 9, characterized by : e. Step 104: comparing the temperature of the coolant circuit of the fuel cell (8) detected by the second temperature sensor (34) with a limit value stored in the control unit (42); f. Step 105: Switching or remaining of the controllable second valve (36) by the control unit (42) in a release position in which the cooling line (38) is released for the flow of heat exchange medium of the coolant circuit of the fuel cell (8) when the detected temperature at the second temperature sensor (34) reaches or exceeds the limit value stored in the control unit (42), and if necessary, commissioning of the cooling element (40); and / or g. Step 106: Switching or leaving the controllable second valve (36) in a blocking position by the control unit (42) in which the cooling line (38) is blocked from flowing through heat exchange medium of the coolant circuit of the fuel cell (8) when the temperature detected at the second temperature sensor (34) falls below the limit value stored in the control unit (42), and if necessary, decommissioning of the cooling element (40).

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