Fuel cell system and method for starting a fuel cell system

Abstract

The invention relates to a method for starting up a fuel cell system, a first pressure difference between a first pressure and an ambient pressure is determined, the first pressure being present in an anode chamber of the fuel cell system connected to an anode of at least one fuel cell, a second pressure difference between a second pressure and the ambient pressure is determined, the second pressure being present in an anode chamber of the fuel cell system connected to an anode of at least one fuel cell, the second pressure is present in a cathode chamber of the fuel cell system connected to a cathode of at least one fuel cell, comparing the first pressure difference with a first threshold value, comparing the second pressure difference with a second threshold value, when the first pressure difference is higher than the ambient pressure by more than a first threshold and / or when the second pressure difference is higher than the ambient pressure by more than a second threshold, a pressure equalization is carried out between the anode chamber and the cathode chamber and fuel is supplied into the anode chamber.

Description

Technical Field

[0001] The invention relates to a fuel cell system and a method for starting or starting a fuel cell system. Background Art

[0002] Fuel cell systems are increasingly being used as energy converters, also in motor vehicles, for converting chemical energy stored in a fuel, such as hydrogen, together with oxygen, directly into electrical energy. A fuel cell system has an anode, a cathode and an electrolyte membrane arranged between the anode and the cathode. The fuel is oxidized at the anode and the oxygen is reduced at the cathode.

[0003] The cathode of a fuel cell is usually supplied with oxygen in such a way that the flow chamber connected to the cathode is supplied with ambient air. The ambient air contains the well-known nitrogen. In particular, when the fuel cell is out of operation or in a stationary state, when the anode and cathode are not supplied with reactants and the cell does not provide voltage, it may happen that nitrogen diffuses through the electrolytic membrane into the anode chamber connected to the anode. Nitrogen acts as an inert gas at the anode and in particular reduces the surface area of ​​the anode ready for reaction with the fuel. When starting up the fuel cell, the anode side is therefore typically first flushed with fuel to adjust a suitable gas concentration at the anode. This delays the start-up process of the fuel cell.

[0004] When the fuel cell is out of operation, the anode chamber is usually separated from the fuel supply by a valve, and the cathode chamber is separated from the surroundings by a shut-off valve. As a result, it can occur, in particular due to temperature changes, that pressures deviate from the surrounding pressure in the anode chamber and in the cathode chamber. If the pressure on the anode side and the cathode side exceeds the surrounding pressure, the flushing process requires a significant pressure increase in the anode chamber. This can lead to a pressure difference on the anode side and the cathode side, which results in a high mechanical load on the electrolytic membrane.

[0005] EP 2 026 396 B1 discloses a fuel cell system in which, during a shutdown process, the oxidizing gas supply is interrupted and the cathode is separated from the surroundings, while the anode continues to be supplied with fuel at a pressure greater than or equal to the surrounding pressure and greater than or equal to the pressure on the cathode side, and current is taken from the fuel cell by means of an electrical consumer in order to consume the oxidizing gas on the cathode and to supply the fuel to the cathode via the membrane. The purpose of this approach is to prevent the oxidizing gas from entering the cathode side in the static state. Summary of the invention

[0006] Based on this background, the invention provides a method for starting a fuel cell system having the features of claim 1 and a fuel cell system having the features of claim 7 .

[0007] According to a first aspect of the invention, a method for starting a fuel cell system comprises: determining a first pressure difference between a first pressure and an ambient pressure, the first pressure existing in an anode chamber of the fuel cell system connected to the anode of at least one fuel cell, determining a second pressure difference between a second pressure and an ambient pressure, the second pressure existing in a cathode chamber of the fuel cell system connected to the cathode of at least one fuel cell, comparing the first pressure difference with a first threshold value, comparing the second pressure difference with a second threshold value, and, if the first pressure difference is higher than the ambient pressure by more than the first threshold value and / or if the second pressure difference is higher than the ambient pressure by more than the second threshold value, performing a pressure balance between the anode chamber and the cathode chamber. If a pressure balance is required between the anode chamber and the cathode chamber, a further step is performed after the pressure balance, in which a fuel is supplied to the anode chamber and preferably also an oxidizing gas is supplied to the cathode chamber.

[0008] According to a second aspect of the present invention, a fuel cell system comprises: at least one fuel cell having an anode, a cathode and an electrolyte membrane located between the anode and the cathode; an anode chamber connected to the anode of the at least one fuel cell in a fluid-conducting manner, having an inlet and an outlet for gaseous fuel to pass through; a fuel supply connected to the inlet of the anode chamber; a cathode chamber connected to the cathode of the at least one fuel cell in a fluid-conducting manner, having an inlet and an outlet for oxidizing gas to pass through; a first shut-off valve, through which the inlet of the cathode chamber can be connected to the surrounding environment; a second shut-off valve, through which the outlet of the cathode chamber can be connected to the surrounding environment; a flushing valve, through which the anode chamber can be connected to the surrounding environment; a sensor system, the sensor system is configured to detect a first pressure in the anode chamber, a second pressure in the cathode chamber and a pressure of the surrounding environment; and a control device, the control device is connected to the sensor system, the fuel supply, the flushing valve and the first and / or second shut-off valve in a signal-conducting manner. The control device is configured to cause the fuel cell system to implement the method according to the first aspect of the present invention.

[0009] Features and advantages disclosed here in connection with the method are therefore also disclosed for the fuel cell system and vice versa.

[0010] The invention is based on the idea that, in preparation for startup, i.e. before the production of current with the fuel cell system, the pressure in the anode chamber and the cathode chamber is detected and compared with the ambient pressure. If one of the partial pressures deviates upward from the ambient pressure by more than a limit value or a threshold value, a pressure equalization is performed between the anode chamber and the cathode chamber. Thus, before the fuel is supplied to the anode chamber for flushing the anode chamber, the pressures in the anode chamber and the cathode chamber are adjusted to the same or substantially the same value.

[0011] The invention has the advantage that, by implementing a pressure balance when at least one partial pressure deviates upward from the ambient pressure by more than a limit value or a threshold value, a pressure difference between the anode chamber and the cathode chamber which overloads the electrolytic membrane is avoided when fuel is supplied for flushing the anode chamber. In addition, the pressure in the anode chamber which is built up by supplying fuel for flushing is reduced. This advantageously accelerates the start-up process.

[0012] Advantageous embodiments and developments emerge from the further dependent claims and from the description with reference to the drawings.

[0013] According to some embodiments, it can be provided that, in order to achieve pressure equalization between the anode chamber and the cathode chamber, the anode chamber and the cathode chamber are each connected to the surroundings in a fluid-conducting manner. The pressure equalization between the anode chamber and the cathode chamber is thus achieved by setting the surrounding pressure in both chambers. This provides the advantage that the pressure exceeds the surrounding pressure by the pressure equalization. This further facilitates and accelerates the supply of fuel and additionally reduces the load on the membrane.

[0014] According to some embodiments, it can be provided that the anode chamber is directly connected to the surroundings by opening the flushing valve or is connected to the inlet of the anode chamber, which is connected to the surroundings by opening at least one stop valve. The flushing valve can, for example, establish a connection for conducting fluid with an outlet section, which connects the cathode chamber to the surroundings. In this case, the gas discharged from the anode chamber is introduced into the surroundings via the outlet section or the anode chamber presents a pressure in the outlet section by opening the flushing valve, which pressure corresponds to the pressure of the surroundings. Alternatively, the flushing valve can establish a connection for conducting fluid with the inlet or supply line of the cathode chamber, and the cathode chamber can be connected to the surroundings by at least one stop valve, so that the anode chamber presents a pressure in the cathode chamber by opening the flushing valve, which pressure corresponds to the pressure of the surroundings after opening the corresponding stop valve.

[0015] According to some embodiments, it can be provided that the supply of fuel into the anode chamber is initiated when the anode chamber is connected to the surroundings in a fluid-conducting manner, so that gas is flushed out of the anode chamber into the surroundings.

[0016] According to some embodiments, it can be provided that the connection of the anode chamber to the conductive fluid of the surroundings is disconnected after a predetermined period of time has expired since the start of the pressure equalization. Thus, for example, the pressure balance can be controlled. Alternatively, it can be provided that the connection of the anode chamber to the conductive fluid of the surroundings is disconnected if the first pressure difference reaches a predetermined third threshold value. Thus, for example, a regulation of the pressure balance can be carried out. The third threshold value can, for example, correspond to the pressure of the surroundings or be slightly higher than the pressure of the surroundings.

[0017] According to some embodiments, it can be provided that the first and second threshold values ​​are respectively in the region between 10 mbar and 700 mbar. The threshold values ​​substantially represent the maximum permissible deviation from the ambient pressure. Independent of the specific values ​​of the first and second threshold values, the first and second threshold values ​​can, for example, be equal.

[0018] According to some embodiments, it can be provided that the control device is designed to open the flushing valve and the at least one shutoff valve for pressure compensation between the anode space and the cathode space, so that the anode space and the cathode space are each connected to the surroundings in a fluid-conducting manner.

[0019] According to some embodiments, it can be provided that the fuel supply part has a fuel source and at least one fuel supply valve, through which the fuel source can be connected to the anode chamber and the fuel supply valve is connected to the control device in a signal-conducting manner, wherein the control device is configured to open the at least one fuel supply valve to supply gaseous fuel to the anode chamber. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The invention is explained below with reference to the accompanying drawings. The accompanying drawings show:

[0021] Figure 1 : A schematic description of a hydraulic circuit diagram of a fuel cell system according to an embodiment of the present invention; and

[0022] Figure 2 : A flow chart of a method for starting a fuel cell system according to an embodiment of the present invention;

[0023] In the figures, the same reference symbols identify identical or functionally identical components, unless otherwise indicated. DETAILED DESCRIPTION

[0024] Figure 1 A fuel cell system 100 is shown as an example. Figure 1 As shown in FIG. 1 , the fuel cell system 100 includes at least one fuel cell 1 , a fuel supply 4 , a flushing valve 6 , an oxidizing gas supply 9 , a first shutoff valve 51 , a second shutoff valve 52 , a sensor system 7 and a control device 8 .

[0025] Fuel cell 1 Figure 1 1 is only schematically depicted and includes an anode 12, a cathode 14 and an electrolytic membrane 14 located between the anode 12 and the cathode 14. Oxidation of a gaseous fuel, such as hydrogen, is performed at the anode 12, and reduction of oxygen contained in an oxidizing gas, such as air, is performed at the cathode 14. Protons are exchanged between the anode 12 and the cathode 14 via the electrolytic membrane. Electrons released at the anode 12 during chemical reduction are used to provide voltage.

[0026] For obvious reasons, Figure 1In the purely schematic diagram, only one fuel cell 1 is described. Of course, a plurality of fuel cells 1 can be provided, which are preferably arranged as a so-called reactor and are electrically connected in series. In the following, for simplicity, reference is made only to the fuel cell 1. This embodiment is of course also applicable to the case where a plurality of fuel cells 1 are provided.

[0027] The anode 12 of the fuel cell 1 is connected in a fluid-conducting manner to an anode chamber 12A, which is provided for the passage of gaseous fuel. If a plurality of fuel cells 1 are provided, all of them are connected to the anode chamber 12A. The anode chamber 12A thus forms a kind of flow chamber in which the anode 12 is arranged. Figure 1 Schematically, the anode chamber 12A has an inlet 15A, through which gaseous fuel can be supplied to the anode chamber 12A by means of a fuel supply 4 explained below, and an outlet 15B, through which unconsumed fuel or generally gas can be discharged from the anode chamber 12A.

[0028] The cathode 14 of the fuel cell 1 is connected to a cathode chamber 14A in a fluid-conducting manner, which is provided for the passage of an oxidizing gas, for example air. If a plurality of fuel cells 1 are provided, all of them are connected to the cathode chamber 14A. The cathode chamber 14A thus forms a flow chamber in which the cathode 14 is arranged. Figure 1 Schematically shown, cathode chamber 14A has an inlet 16A, through which gaseous fuel can be supplied to cathode chamber 14A by means of an oxidizing gas supply 9 explained later, and an outlet 16B, through which gas and reduction products, especially water, can be drawn out from cathode chamber 14A.

[0029] The fuel supply 4 is generally designed to supply the anode chamber 12A and thus the anode 12 with a gaseous fuel. Figure 1 As shown by way of example in FIG. 1 , the fuel supply 4 can for this purpose have, in particular, a fuel source 41 , for example in the form of a gas cylinder, and at least one supply valve 42 , 43 , via which the fuel source 41 can be connected to the anode chamber 12A. Figure 1 4 shows a fuel supply unit 4 with a recirculation system, which has a suction jet pump 44, a recirculation fan 45 and a fuel metering valve 43A, which forms the fuel supply valve 43. Figure 1 Schematically shown in FIG. 4 , the pressure output port of the suction jet pump 44 is connected to the anode input port 15A, and the high-pressure input port of the suction jet pump 44 is connected to the fuel source 41, wherein the fuel metering valve 43A is arranged between the high-pressure input ports of the suction jet pump 44. A shut-off valve 42A, which also forms the fuel supply valve 42, may be arranged between the tank 41 and the fuel metering valve 43A.

[0030] The recirculation fan 45 is arranged in a recirculation line 48, which connects the outlet 15B of the anode chamber 12A to the suction inlet of the suction jet pump 44. The recirculation fan 45 is configured to convey gas, in particular unconsumed fuel, from the outlet 15B of the anode chamber 12A to the suction inlet of the suction jet pump 44.

[0031] As in Figure 1 It is also shown that a dehumidifier 46 can be arranged in the recirculation line 48 between the outlet 15B of the anode chamber 12A and the recirculation fan 45. The dehumidifier 46 is configured to extract water from the recirculated gas. The water accumulated in the dehumidifier 46 can be discharged from the dehumidifier 46, for example, via a drain valve 47.

[0032] The flushing valve 6 can be arranged, for example, in a flushing line 61 connected to the dehumidifier 46, such as in Figure 1 Generally, the flushing line 61 can be connected to the recirculation line 48 or connected to the output port 15B of the anode chamber 12A in a fluid-conducting manner in other ways. Figure 1 , the flushing line 61 can also be connected to the outlet line 3 leading to the surrounding environment E. The flushing valve 6 can be designed, for example, as a switchable valve, in particular a solenoid valve, and can be switched between an open state, in which a gas can flow through the flushing valve 61, and a closed state, in which the flushing valve closes the flushing line 61. The anode chamber 12A can thus be connected to the surrounding environment E via the flushing valve 6.

[0033] The oxidizing gas supply 9 is generally designed to supply the cathode space 14A with an oxidizing gas, in particular air. Figure 1 In the example shown in FIG. 1 , the oxidizing gas supply 9 can have a fan 91A for this purpose, which is arranged in a supply line 95 connected to the inlet 16A of the cathode chamber 14A and draws air from the surrounding environment E. The outlet 16B of the cathode chamber 14A is connected to the outlet line 3 via a lead-out line 96. Figure 1 It is shown in FIG. 1 that a recovery turbine 91B can be arranged in the discharge line 96 to assist in driving the fan 91A.

[0034] like Figure 1 In addition, it is shown by way of example that a humidifier 92 connected to the supply line 95 and the outlet line 96 can be provided, and the humidifier is configured to extract water from the gas flowing in the outlet line 96 and supply water to the oxidizing gas flowing in the supply line 95. The humidifier 92 can be optionally bypassed in the supply line 95 via a first bypass line 93, which can be blocked by a first bypass valve 93A.

[0035] The first stop valve 51 can be as Figure 1, in the supply line 95, in particular between the ventilator 91A and the optional humidifier 92. The first shut-off valve 51 can be configured, for example, as a switchable valve, in particular a solenoid valve, and can be switched between an open state and a closed state, in which the valve allows gas to flow through the supply line 95, and in which the valve closes the supply line 95. Therefore, the cathode chamber 14A can be connected to the surrounding environment E via the first shut-off valve 51.

[0036] The second stop valve 52 can be as shown in Figure 1 As shown in the figure, it is arranged in the outlet line 96, in particular, between the outlet line 3 or the turbine 91B provided if necessary and the optional humidifier 92. The second shut-off valve 52 can be configured as a check valve, which only allows flow in the direction of the surrounding environment E, as shown in Figure 1 As shown in the example. Alternatively, the second stop valve 52 can also be configured as a switchable valve, such as a solenoid valve. Therefore, the cathode chamber 14A can be connected to the surrounding environment E through the second stop valve 52.

[0037] As in Figure 1 It is also described in the specification that a second bypass line 94 may optionally be provided, which connects the supply line 95 and the discharge line 96 and can be blocked by a second bypass valve 94A.

[0038] The sensor system 7 may have a plurality of pressure sensors 71, 72, 73. Figure 1 As schematically described in FIG. 1 , the first pressure sensor 71 may be disposed at the anode chamber 12A to detect the first pressure present in the anode chamber 12A. Figure 1 , it is shown by way of example that the first pressure sensor 71 detects the first pressure directly in the anode chamber 12A. The first pressure sensor 71 can of course also detect the first pressure in the recirculation line 48, for example between the outlet 15B of the anode chamber 12A and the dehumidifier 46, or between the suction jet pump 44 and the inlet 15A of the anode chamber 12A. There can also be a plurality of pressure sensors in the recirculation line 48, for example between the outlet 15B of the anode chamber 12A and the dehumidifier 46 and between the suction jet pump 44 and the inlet 15A of the anode chamber 12A and / or in the anode chamber 12A itself to detect the pressure, wherein the first pressure is approximated by finding an average value of the detected pressures.

[0039] The second pressure sensor 72 may be disposed at the cathode chamber 14A to detect a second pressure existing in the cathode chamber 14A. Figure 1, the second pressure sensor 71 detects the second pressure directly in the cathode chamber 14A. The second pressure sensor 72 can of course also detect the second pressure in the supply line 95, for example, at the input port 16A of the cathode chamber 14A, or in the outlet line 96, for example, at the output port 16B of the cathode chamber 14A. There can also be multiple pressure sensors detecting the pressure at the input port 16A, at the output port 16B and / or in the anode chamber 12A itself, wherein the average value of the detected pressures is obtained as the second pressure.

[0040] The third pressure sensor 73 detects the ambient pressure existing in the surrounding environment E.

[0041] Generally speaking, the sensor system 7 is therefore designed to detect a first pressure in the anode space 12A, a second pressure in the cathode space 14A and the ambient pressure.

[0042] The control device 8 is Figure 1 , which are only described as blocks with symbols. The control device 8 is particularly designed as an electronic control device 8 and is therefore configured to generate and output output signals or control signals based on input signals. For example, the control device 8 can have a computing device, in particular a processor, such as a CPU, FPGA, ASIC or the like, and a data memory that can be read by the processor. The data memory can in particular have a non-volatile data storage medium, for example in the form of a hard disk, a flash memory, an SD memory or the like, and store software that can be executed by the processor and causes the control device to output output signals.

[0043] The control device 8 is connected to the sensor system 7, the fuel supply 4, in particular the fuel supply valves 42, 43, the flushing valve 6 and the first and / or second shut-off valves 51, 52 by signal transmission, for example, by wire through a BUS system or wirelessly through WIFI, Bluetooth or the like. The control device 8 is particularly configured to switch the valves 42, 43, the flushing valve 6, the first shut-off valve 51 and (if switchable) the second shut-off valve 52 of the fuel cell system 100. The control device 8 can also be connected to the drive device of the ventilator 91A and the drive device of the recirculation fan 45 to control the operation of these components. If present, the control device 8 can also be connected to the bypass valves 93A, 94A and the drain valve 47 and is configured to switch these valves 93A, 94A, 47.

[0044] When the fuel cell system 100 is started, the anode chamber 12A is usually flushed with gaseous fuel first to remove nitrogen or other undesirable substances accumulated in the anode chamber 12A during the static state. To this end, the control device 8 opens the flushing valve 6 and the fuel supply valves 42, 43, so that the fuel from the tank 41 flows into the anode chamber 12A and the gas in the anode chamber is led out of the anode chamber to the surrounding environment E via the flushing line 61. This process can lead to a significant pressure difference between the anode chamber 12A and the cathode chamber 14A depending on the pressure in the anode chamber 12A and the cathode chamber 14A.

[0045] exist Figure 2 The process of the method M for starting the fuel cell system 100 is described in an exemplary manner, and the method is exemplarily referred to in Figure 1 The fuel cell system 100 shown in FIG.

[0046] In step M1, control device 8 determines a first pressure difference between a first pressure prevailing in anode chamber 12A of fuel cell system 100 and the ambient pressure. For this purpose, control device 8 uses, for example, the first pressure detected by first pressure sensor 71 and the ambient pressure detected by third pressure sensor 73.

[0047] In step M2, control device 8 determines a second pressure difference between a second pressure and the ambient pressure, which is present in cathode chamber 14A of fuel cell system 100. To this end, control device 8 uses, for example, the second pressure detected by second pressure sensor 72 and the ambient pressure detected by third pressure sensor 73.

[0048] In step M3, the control device 8 compares the determined first pressure difference with a first threshold value for the first pressure. Figure 2 As described by the symbol "+", method M can either directly proceed to step M5 or first proceed to step M4. If the first pressure difference is lower than the ambient pressure or is exactly the first threshold value, as in Figure 2 As described by the symbol “-”, method M proceeds to step M4.

[0049] Step M4 is another comparison step in which the control device 8 performs a comparison between the second pressure difference and a second threshold value. The second threshold value may be equal to the first threshold value or may be a different value. Generally, the first and second threshold values ​​may be in the region between 10 mbar and 700 mbar, respectively.

[0050] If it is determined in step M4 that the second pressure difference is higher than the ambient pressure by more than a second threshold value, such as Figure 2In the method M, the method M proceeds to step M5. If it is determined in step M4 that the second pressure difference is higher than the ambient pressure by less than or exactly by the second threshold value, as in Figure 2 As described by the symbol “-” in the method M, the method M proceeds to step M6. As explained above and Figure 2 As can also be seen in , step M5 can also be performed independently of the comparison result of step M4. Step M5 is therefore performed when the first pressure difference exceeds the ambient pressure by more than a first threshold value and / or when the second pressure difference exceeds the ambient pressure by more than a second threshold value.

[0051] In step M5, pressure equalization is performed between the anode chamber 12A and the cathode chamber 14A. For this purpose, the anode chamber 12A and the cathode chamber 14A can be connected to the surroundings E, for example, in a fluid-conducting manner. The control device 8 can in particular activate the flushing valve 6 and at least one shut-off valve 51, 52. Figure 1 In the embodiment, the first stop valve 51 is switched to an open state. The anode chamber 12A is therefore connected to the surroundings E via the flushing line 61 and the outlet line 3, and the cathode chamber 14A is connected to the surroundings via the inlet line 95. In this way, the surrounding pressure or at least the approximate surrounding pressure can be set relatively smoothly not only in the anode chamber 12A but also in the cathode chamber 14A. The connection of the anode chamber 12A with the fluid-conducting environment E can be disconnected again after a predetermined time period has expired since the start of pressure equalization, for example, in that the control device 8 closes the flushing valve 6 and the at least one open stop valve 51, 52 after the time has expired. Alternatively, the control device 8 can continuously determine at least the first pressure difference, and when it reaches a predetermined third threshold value, the flushing valve 6 and the at least one open stop valve 51, 52 are switched to a closed state.

[0052] In step M6, fuel is supplied to the anode chamber 12A to flush the anode chamber. To this end, the control device 8 can, for example, switch at least one fuel supply valve 42, 43 so that a fluid-conducting connection is generated between the fuel source and the anode chamber 12A. The flow or pressure generated by the fuel in the anode chamber 12A can be controlled or adjusted, for example, by the opening of the metering valve 43A. If pressure balancing is performed in step M5, step M6 is implemented only after pressure balancing. Optionally, the supply M6 of fuel to the anode chamber 12A can be started by the control device 8, if the anode chamber 12A is connected to the surrounding environment E in a fluid-conducting manner, so that the gas is flushed out of the anode chamber 12A into the surrounding environment E.

[0053] Although the invention has been explained above by way of example with reference to exemplary embodiments, the invention is not restricted thereto but can be modified in many ways. In particular, combinations of the exemplary embodiments described above are also conceivable.

[0054] The fuel cell system 100 is not specifically limited to Figure 1 . For example, the flushing line 61 can also be connected to the inlet 16A of the cathode chamber 14A. In this way, via the switchable second shut-off valve 52, the anode chamber 12A can also be connected to the surrounding environment E via the flushing line 61, the outlet line 96 and the outlet line 3. Via the flushing valve 6, the anode chamber 12 can therefore be generally connected to the surrounding environment E via the cathode chamber 14A or directly.

Claims

1. A method (M) for starting a fuel cell system (100), comprising: determining (M1) a first pressure difference between a first pressure and an ambient pressure, the first pressure being present in an anode chamber (12A) of the fuel cell system (100) connected to an anode (12) of at least one fuel cell (1); Determining (M2) a second pressure difference between a second pressure and an ambient pressure, the second pressure existing in a cathode chamber (14A) of the fuel cell system (100) connected to a cathode (14) of the at least one fuel cell (1); comparing (M3) the first pressure difference with a first threshold; comparing (M4) the second pressure difference with a second threshold; If the first pressure difference is higher than the ambient pressure by more than the first threshold value and / or if the second pressure difference is higher than the ambient pressure by more than the second threshold value, performing (M5) pressure equalization between the anode chamber (12A) and the cathode chamber (14A); and Fuel is supplied (M6) to the anode chamber (12A).

2. The method (M) according to claim 1, wherein: In order to carry out (M5) a pressure equalization between the anode space (12A) and the cathode space (14A), the anode space (12A) and the cathode space (14A) are each connected to the surroundings (E) in a fluid-conducting manner.

3. The method (M) according to claim 2, wherein: The anode chamber (12A) is connected directly to the surrounding environment (E) by opening a flushing valve (6) or to an inlet (16A) of the anode chamber (14A), which is connected to the surrounding environment (E) by opening at least one shut-off valve.

4. The method (M) according to claim 2 or 3, wherein: When the anode chamber (12A) is fluidically connected to the surrounding environment (E), a fuel supply (M6) is activated into the anode chamber (12A), so that gas is flushed out of the anode chamber (12A) into the surrounding environment (E).

5. The method (M) according to any one of claims 2 to 4, wherein: The connection of the anode chamber (12A) to the fluid-conducting environment (E) is disconnected after a predetermined period of time has elapsed since the start of pressure equalization, or when the first pressure difference reaches a predetermined third threshold value.

6. The method (M) according to any one of the preceding claims, wherein: The first threshold value and the second threshold value are each located in the region between 10 mbar and 700 mbar.

7. A fuel cell system (100) comprising: At least one fuel cell (1) having an anode (12), a cathode (14) and an electrolyte membrane (14) located between the anode (12) and the cathode (3); an anode chamber (12A) fluidically connected to the anode (12) of the at least one fuel cell (12), the anode chamber having an inlet (15A) and an outlet (15B) for passage of a gaseous fuel; and a fuel supply portion (4) connected to the inlet (15A) of the anode chamber (12A); a cathode chamber (14A) fluidically connected to the cathode (14) of the at least one fuel cell (12), the cathode chamber having an inlet (16A) and an outlet (16B) for passage of an oxidizing gas; a first stop valve (51), via which the inlet (16A) of the cathode chamber (14A) can be connected to the surrounding environment (E); a second stop valve (52), via which the outlet (16B) of the cathode chamber (14A) can be connected to the surrounding environment (E); a flushing valve (6), via which the anode chamber (12A) can be connected to the surrounding environment (E); A sensor system (7) configured to detect a first pressure in the anode chamber (12A), a second pressure in the cathode chamber (14A), and an ambient pressure; and A control device (8) which is connected to the sensor system (7), the fuel supply (4), the flushing valve (6) and the first and / or the second shut-off valve (51, 52) in a signal-conducting manner and is configured to cause the fuel cell system (100) to implement a method (M) according to any one of the preceding claims.

8. The fuel cell system (100) according to claim 7, wherein: The control device (8) is configured to open the flushing valve (6) and at least one of the shut-off valves (51, 52) in order to implement (M5) pressure balance between the anode chamber (12A) and the cathode chamber (14A) so that the anode chamber (12A) and the cathode chamber (14A) are respectively connected to the surrounding environment (E) in a fluid-conducting manner.

9. The fuel cell system (100) according to claim 7 or 8, wherein: The fuel supply section (4) has a fuel source (41) and at least one fuel supply valve (42, 43), through which the fuel source (41) can be connected to the anode chamber (12A), and the fuel supply valve is connected to the control device (8) in a signal-conducting manner, wherein the control device (8) is configured to open the at least one fuel supply valve (41, 42) to supply gaseous fuel to the anode chamber (12A).

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