Method for improving decline behavior of humidity transmitter in fuel cell assembly

Abstract

The invention relates to an operating method (100) for a fuel cell assembly (1), in particular of a fuel cell vehicle, said operating method (100) comprising a humidity transmitter anti-aging routine (101), by means of which an aging behavior of a humidity transmitter (36), in particular a gas-to-gas humidifier (36), of the fuel cell assembly (1) is influenced, in this way, aging of the humidity transmitter (36) is slowed down.

Description

Technical Field

[0001] The invention relates to a method for operating a fuel cell unit, in particular a fuel cell vehicle, a fuel cell unit, a fuel cell system and a fuel cell vehicle. Background Art

[0002] In a low-temperature polymer electrolyte fuel cell of a fuel cell unit (stationary or mobile) of a fuel cell system, such as a fuel cell vehicle, two reactants of two operating media are electrochemically converted into electrical energy and heat. Here, the fuel cell includes at least one membrane electrode unit (MEA: Membrane Electrode Assembly). Usually, the fuel cell is constructed with a plurality of membrane electrode units arranged in a stack and bipolar plates arranged between them (a fuel cell stack or a fuel cell group having a plurality of individual fuel cells (monocells)). Summary of the invention

[0003] Task Proposal

[0004] In order to operate such a fuel cell stack efficiently and with low decay, the membranes of the membrane electrode units must be adequately humidified. To ensure this requirement, a humidity transmitter, in particular an air-to-air humidifier, is often used on the cathode side of the fuel cell stack. The humidity transmitter uses the moist exhaust gas of the fuel cell stack to humidify the dry intake air of the fuel cell stack. The object of the present invention is to provide a method for operating a fuel cell stack with low decay.

[0005] Invention Disclosure

[0006] The object of the present invention is achieved by an operating method (i.e., operating strategy) for a fuel cell assembly, in particular a fuel cell assembly of a fuel cell vehicle, and by means of a fuel cell assembly, a fuel cell system or a fuel cell vehicle. Advantageous developments, additional features and / or advantages of the present invention are revealed in the dependent claims and the following description.

[0007] The operating method according to the invention comprises a humidity transmitter anti-aging routine, by means of which the aging behavior of a humidity transmitter, in particular an air-to-air humidifier, of the fuel cell assembly can be influenced or influenced, so that the aging of the humidity transmitter can be slowed down or slowed down. By means of the humidity transmitter anti-aging routine, at least one operating parameter of the fuel cell assembly can be adjusted, so that the aging of the humidity transmitter is slowed down by low-degradation operation of the humidity transmitter.

[0008] This can be any operating parameter, as long as it is suitable for slowing down the aging behavior and for low-degradation operation of the humidity transmitter. This can be, in particular, an operating parameter of the cathode supply of the fuel cell assembly. Additionally or alternatively, operating parameters of the anode supply of the fuel cell assembly and / or operating parameters of the coolant supply can also be used. Furthermore, additionally or alternatively, other operating parameters of the fuel cell assembly can also be used.

[0009] Low-degradation operation of the humidity transmitter can be ensured by supplying the humidity transmitter with at least a sufficient amount of water over a certain period of time. The amount of water in the certain period of time is selected such that irreversible drying or drying out of the humidifier membrane of the humidity transmitter substantially does not occur. The water in question is in particular present as water vapor (gaseous and / or aerosolized water).

[0010] The humidity transmitter anti-aging routine can select operating parameters and / or set values ​​for the operating parameters such that the humidifier membrane of the humidity transmitter is kept substantially permanently moist by the cathode exhaust medium. Alternatively or additionally, wet-dry cycles of the humidity transmitter can be avoided. Alternatively or additionally, the water activity at the cathode outlet of the fuel cell unit can be influenced in a targeted manner.

[0011] The water activity at one / the outlet of the cathode can be influenced so that it does not fall below or does not fall significantly below a certain limit value. Preferably, the value of the water activity is about or greater than 1. In particular, the limit values ​​that should not be fallen below are: 1±0.01; 1±0.02; 1±0.03; 1±0.04; 1±0.05; 1±0.075; 1+0.1; 1+0.125; 1+0.15; 1+0.175 or 1+0.2.

[0012] Furthermore, at least one operating parameter of the fuel cell assembly can be selected and / or adjusted such that the water activity does not fall below or does not fall significantly below a limit value. Insignificant and / or short-term falls below can be neglected. Furthermore, during operation of the fuel cell assembly, the at least one operating parameter can be a stoichiometry, a pressure and / or a temperature, in particular at / in the cathode.

[0013] By means of the humidity transmitter anti-aging routine in the operating method, the at least one operating parameter can be adjusted in such a way that the low-degradation operation of the humidity transmitter is maintained as far as possible. That is, the at least one operating parameter is adjusted in such a way that the low-degradation operation is maintained or is only interrupted briefly. The low-degradation operation of the humidity transmitter can only be interrupted if a priority signal is present, for example due to a request to the fuel cell stack or by a fuel cell unit, a fuel cell system or a fuel cell vehicle. Subsequently, the regeneration mode of the humidity transmitter can be set by the humidity transmitter anti-aging routine.

[0014] If the water activity falls below a limit value at any or all times, the low-decay operation of the humidity transmitter is interrupted for a defined duration. The defined duration can be determined based on the water storage capacity of the humidifier path upstream of the humidity transmitter. Such a determination can take into account, for example, the duration, the loss of humidity transmitter water / the required amount of water, etc.

[0015] After the water activity falls below the limit value, the humidity transmitter can be operated in a regeneration mode, in which more humid conditions are set in the humidity transmitter (recovery). After the end of this specific period and, if necessary, after the end of the regeneration mode, the humidity transmitter should be set to low-degradation operation again within the operating method, if possible; or, if no humidity transmitter anti-aging routine is required, a conventional reference method should be set.

[0016] In a first step of the humidity transmitter anti-aging routine, the water activity in the cathode supply, in particular downstream of the fuel cell stack, can be ascertained. In this case, the water activity can be ascertained, for example, at the cathode outlet, at the inlet into the humidity transmitter or, if necessary, also between them. In a second step of the humidity transmitter anti-aging routine following the first step, it can be checked whether the ascertained water activity is less than or greater than a limit value for the water activity.

[0017] In the case of a water activity below a limit value for the water activity, operating parameters of the fuel cell unit, the fuel cell stack and / or the cathode supply are changed so that more humid conditions are set in the cathode supply downstream of the fuel cell stack. Such operating parameters are in particular the stoichiometry in the cathode, the pressure in the cathode and / or the cathode supply, and / or the temperature in the fuel cell stack, the cathode and / or the cathode supply.

[0018] In a third step of the humidity transmitter anti-aging routine, following the second step, the stoichiometry in the cathode can be adjusted, in particular reduced. In a fourth step of the humidity transmitter anti-aging routine, following the second or third step, the pressure in the cathode supply or in the cathode can be adjusted, in particular reduced. In a fifth step of the humidity transmitter anti-aging routine, following the second, third or fourth step, the temperature of the fuel cell stack, the temperature in the cathode supply and / or the temperature of the humidity transmitter can be adjusted, in particular reduced.

[0019] In an embodiment, a reference operation of the operating method of the fuel cell unit can be performed with modifications by the humidity transmitter anti-aging routine, that is, the reference operation is performed only slightly modified according to the humidity transmitter anti-aging routine (if necessary), i.e., the current operation of the fuel cell unit without the humidity transmitter anti-aging routine.

[0020] Furthermore, the humidity transmitter anti-aging routine can be executed as a separate reference operation of the fuel cell unit. That is, the humidity transmitter anti-aging routine is designed as a separate reference operation routine in addition to the actual reference operation. Furthermore, the humidity transmitter anti-aging routine can be executed during operation of the fuel cell unit or in a stationary state. In this case, the humidity transmitter anti-aging routine can be executed at at least one predetermined time point (time control). BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Below, the present invention is explained in more detail based on the embodiment with reference to the attached schematic and not to scale drawings. In the present invention, a feature can be configured as positive (i.e., existing) or negative (i.e., not existing). In this specification, a negative feature is not explicitly explained as a feature unless it is emphasized that it does not exist according to the present invention. That is, the invention actually made and not constructed by the prior art is to omit the feature. The absence of a feature (negative feature) in an embodiment indicates that the feature is optional. In the only exemplary drawings of the drawing part:

[0022] Figure 1 A simplified block diagram shows one embodiment of a fuel cell unit for a fuel cell system of a fuel cell vehicle, and

[0023] Figure 2 A possible flow chart of the method for operating a fuel cell unit according to the invention is shown, which method includes the humidity transmitter anti-aging routine according to the invention. DETAILED DESCRIPTION

[0024] By means of a method for operating a fuel cell assembly 1, in particular for a fuel cell vehicle (see Figure 2 The fuel cell unit 1 is preferably a fuel cell unit of a low-temperature polymer electrolyte fuel cell system of a fuel cell vehicle (ie, a motor vehicle having a fuel cell stack 10, a fuel cell unit 1 or a fuel cell system).

[0025] In the drawings, only those parts of the fuel cell system that are necessary for understanding the invention are shown ( Figure 1 : Fuel cell unit 1). Although the invention has been described and illustrated in more detail by means of preferred embodiments, the invention is not limited to the disclosed embodiments. Other variations can be derived therefrom without departing from the scope of protection of the invention. In particular, the invention can also be applied to other mobile or stationary fuel cell units 1 or fuel cell systems.

[0026] Figure 1A fuel cell unit 1 is shown according to an exemplary embodiment, which has at least one, in particular a plurality of electrochemical individual fuel cells 11 (single cells 11) bundled into a fuel cell stack 10, which are installed in a preferably fluid-tight stack housing 16. Each single cell 11 comprises an electrode chamber 12 designed as an anode chamber 12 and an electrode chamber 13 designed as a cathode chamber 13, which are separated from each other spatially and electrically by the membrane of a membrane electrode unit 15.

[0027] A bipolar plate 14 is arranged between two directly adjacent membrane electrode units 15, 15, each containing an associated anode chamber 12 and cathode chamber 13, which serves in particular to conduct / discharge the operating medium 3, 5 into the anode chamber 12 of a first single cell 11 and into the cathode chamber 13 of a second single cell 11 directly adjacent thereto, and also to realize an electrically conductive connection between these single cells 11, 11. The cathode chamber 13 and, if necessary, its common inflow region or its electrodes form the cathode of the fuel cell stack 10, and the anode chamber 12 and, if necessary, its common inflow region or its electrodes form the anode of the fuel cell stack 10.

[0028] In order to supply the fuel cell stack 10 with its actual operating medium 3 (anode operating medium, actual fuel) and 5 (cathode operating medium, usually air), the fuel cell unit 1 has an anode supply device 20 and a cathode supply device 30. The anode supply device 20 comprises in particular: a fuel reservoir 23 for the anode operating medium 3 (inflow); an anode supply path 21 with a shut-off / metering valve 27 and an injector 24; an anode exhaust gas path 22 for the anode exhaust gas medium 4 (usually outflowing into the environment 2); preferably, a fuel recirculation line 25 with a fluid conveying device 26 located therein; a water separator and a water container if necessary.

[0029] The cathode supply device 30 includes, in particular: a cathode supply path 31 for a cathode operating medium 5 (usually flowing in from the environment 2), preferably having a fluid conveying device 33; a cathode exhaust gas path 32 for a cathode exhaust gas medium 6 (usually flowing out into the environment 2), preferably having a turbine 34, in particular for the fluid conveying device 33; preferably, a humidity transmitter 36, in particular an air-to-air humidifier 36; if necessary, a stacked bypass 35 (waste gate 35) on the cathode side between the cathode supply path 31 and the cathode exhaust gas path 22, having a bypass valve 135; if necessary, a water separator and, if necessary, a water container.

[0030] In addition, the cathode supply device 30 (not shown) may have an air filter upstream of the fluid delivery device 33, may have a charge air cooler downstream of the fluid delivery device 33, and may have a pressure holding valve downstream of the cathode in the cathode exhaust path 32. A humidity transmitter 36 is provided between the cathode supply path 31 and the cathode exhaust path 22, wherein the stack bypass 35 is arranged upstream of the humidity transmitter 36 with respect to the cathode supply path 31 ( Figure 1 ) or downstream, and is arranged downstream of the humidity transmitter 36 with respect to the cathode exhaust path 22 ( Figure 1 ) or upstream.

[0031] The fuel cell unit 1 also includes a cooling medium supply device 40 of a thermal system, in particular a fuel cell vehicle, through which the fuel cell stack 10 can preferably be connected to the cooling circuit for temperature control by means of its bipolar plate 14 (cooling medium path 43) in a heat transfer manner. The cooling medium supply device 40 includes a cooling medium inflow path 41 and a cooling medium outflow path 42. The delivery of the cooling medium 7 (inflow) and 8 (outflow) circulating in the cooling medium supply device 40 is preferably carried out by means of at least one cooling medium delivery device 44. In addition to the fuel cell unit 1, the fuel cell system also includes peripheral system components, such as a controller, which can be a controller of the fuel cell vehicle itself.

[0032] In the humidity transmitter 36, a humidifier membrane is used to transfer water from the exhaust gas side (32, 6) to the operating medium side (31, 5), whereby a mass transport occurs from the exhaust gas side (32, 6) to the operating medium side (31, 5) due to the partial pressure difference of the water on both sides. With increasing degradation of the humidifier membrane, the performance capacity or the transfer rate of water in the humidity transmitter 36 decreases, thereby reducing the humidification performance of the humidity transmitter 36. The degree and rate of degradation are decisively influenced by the number and degree of humidity cycles in the humidity transmitter 36.

[0033] Currently, also refer to Figure 2 , within the scope of operating method 100 or operating strategy for fuel cell unit 1, humidity transmitter anti-aging routine 101 is explained in more detail for counteracting the operation-dependent degradation of humidity transmitter 36, in particular of air-to-air humidifier 36. In other words, humidity transmitter anti-aging routine 101 is intended to substantially ensure low-degradation operation (i.e., anti-aging operation) of humidity transmitter 36.

[0034] That is, the aging of the humidity transmitter 36 in the cathode supply device 30 of the fuel cell unit 1 of the fuel cell system should be slowed down by the humidity transmitter anti-aging routine 101 for the fuel cell unit 1 or the fuel cell system according to the present invention, compared to the same humidity transmitter 36 in the same cathode supply device 30 of the same fuel cell unit 1 of the same fuel cell system without such an anti-aging routine 101.

[0035] In order to realize the operation of the humidity transmitter 36 and the fuel cell stack 10 at a higher relative humidity, it is preferably necessary to adjust at least one operating parameter of the fuel cell unit 1, in particular at least one operating parameter in the cathode supply device 30. Of course, it is feasible to adjust another operating parameter, such as an operating parameter of the anode supply device 20, an operating parameter of the coolant supply device 40, etc., in addition or alternatively, as long as the water balance on the cathode side can be influenced by the operating parameter.

[0036] An important and generally known characteristic variable for achieving a stable water balance in a fuel cell assembly 1 is the water activity a at the cathode outlet. K This parameter relates the current mass fraction of water (liquid and gaseous) to the mass fraction of the gas phase of water (which is saturated). K ≤1, the water activity of the discharged cathode exhaust medium 6 is equivalent to the relative humidity. K At values ​​>1, there is a supersaturated cathode exhaust medium 6, so that a portion of the water is present in liquid form at the cathode outlet.

[0037] If the exhaust side of the humidity transmitter 36 is supplied with a K <1, this can lead to drying or even drying up of the humidifier membrane of the humidity transmitter 36 and thus to water shortage in the fuel cell stack 10 (membrane of the membrane electrode assembly 15). K A water activity of <1 results in a decrease in the measured relative humidity at the cathode inlet. K The greater the drop, the faster the relative humidity at the cathode outlet and therefore also at the cathode inlet via the humidity transmitter 36 drops.

[0038] In the prior art, the operating method (i.e., operating strategy) of the fuel cell unit 1 does not directly take into account the degradation of the humidity transmitter 36. If the humidity transmitter 36 has degraded, the system parameters of the cathode supply device 30 are not explicitly adjusted in view of this degradation. In addition, dynamic effects, such as water storage effects, etc., are not taken into account in the conventional operating method.

[0039] The present invention (i.e., humidity transmitter anti-aging routine 101) aims to improve the degradation behavior of humidity transmitter 36 by selecting an operating parameter (air system parameter), in particular in cathode supply device 30, such that low-degradation operation of humidity transmitter 36 can be ensured. In this case, at least one operating parameter of fuel cell unit 1 is adjusted in order to maintain this low-degradation operation as far as possible.

[0040] When selecting at least one such operating parameter, the aging behavior of the humidity transmitter 36 is explicitly taken into account. This is achieved, for example, by deliberately avoiding wet-dry cycles. K should be chosen not to fall below a certain limit value (e.g. a K ≈ / =1). Based on this limit value, at least one operating parameter (pressure, temperature, stoichiometry) in the operation of the fuel cell assembly 1 should be selected such that this limit value is not fallen below.

[0041] If the temperature drops below the upper limit, for example because the requirements of the humidity transmitter anti-aging routine 101 conflict with the service life or efficiency requirements of the fuel cell stack 10 of the fuel cell unit 1, a temporary drop below the upper limit may occur, for example when utilizing the dynamic storage effect of the humidifier path of the cathode supply device 30. In order to prevent the humidifier membrane from drying out excessively or even drying out, a regeneration mode should be operated after a certain period of time, in which the humidified conditions in the humidity transmitter 36 are set again for a certain period of time (intermittent operation).

[0042] In the following, it will be explained how the reference operation (also referred to as reference operation) of the fuel cell unit 1 can be carried out in a modified manner by means of the humidity transmitter anti-aging routine 101 of the operating method 100. Figure 2 Of course, other embodiments are also applicable, in which, in particular, different priority rankings of operating parameters can be adopted and / or other operating parameters can be applied.

[0043] In the first step 111 of the humidity transmitter aging protection routine 101, the current water activity a at the cathode outlet is obtained. K This can be achieved based on a water balance. Here, the amount of water produced at the cathode outlet can be estimated by subtracting the diffusion mass flow from the cathode to the anode of the fuel cell stack 10 from the sum of the supplied water and the water produced in the fuel cell stack 10. Based on this balance, the water activity a can be calculated. K Alternatively, the water activity a upstream or at the inlet of the humidity transmitter 36 can also be determined. K .

[0044] In the second step 121 of the humidity transmitter anti-aging routine 101, the water activity a is checked. K Is it less than ( Figure 2 :121+) or greater than ( Figure 2 : 121-) water activity a K If the water activity a K Greater than the limit value ( Figure 2 :121-), then the unchanged reference operation 110 of the fuel cell unit 1 can be continued. If the water activity a K Less than the limit value ( Figure 2 : 121+), the reference operation of the fuel cell unit 1 is continued by changing the humidity transmitter anti-aging routine 101.

[0045] In order to maintain a minimum water activity at the cathode outlet or at the humidity transmitter inlet or in between by the humidity transmitter anti-aging routine 101, the operating parameters of the cathode supply device 30 (stoichiometry (e.g., the third step 131 of the humidity transmitter anti-aging routine 101), pressure (e.g., the third step 131 of the humidity transmitter anti-aging routine 101) and / or temperature (e.g., the fourth step 141 of the humidity transmitter anti-aging routine 101)) must be coordinated with each other. It is easy to imagine that the stoichiometry in the cathode or the stoichiometry of the cathode and the pressure in the cathode supply device 30 or the pressure of the cathode are adjusted first, because they can only be changed in the cathode supply device 30.

[0046] In addition to at least one of the above measures (stoichiometry, pressure), the temperature of the fuel cell stack 10 or the cathode supply device 30 or the humidity transmitter 36 can preferably be reduced to avoid further drying or even drying out of the humidifier membrane. In addition, it is also possible to only reduce the temperature, i.e. without adjusting the stoichiometry or pressure. In general, the water activity a K , stoichiometry, pressure, temperature and / or other operating parameters can, for example, be measured, detected, sensed, diagnosed (artificial intelligence, KI) and / or, or determined via a model (physically, based on artificial intelligence or hybridly).

[0047] If, for example, for certain operating points or operating ranges of the fuel cell assembly 1 a water activity below a K If the limit value of , then the stoichiometry in the cathode can be reduced, for example. In addition, for certain operating points or operating ranges, the pressure in the cathode supply device 30 can also be reduced or, if necessary, increased. In addition, for certain operating points or operating ranges, the temperature in the cathode supply device 30 can also be reduced.

[0048] If permanent adaptation of at least one operating parameter is not possible or is not desired, for example due to the requirements of the fuel cell stack 10, a regeneration operation can be requested via the humidity transmitter anti-aging routine 101 (e.g., the fifth step 151 of the humidity transmitter anti-aging routine 101), in which operating conditions of the fuel cell stack 10 are achieved at a higher relative humidity, at least for a period of time.

[0049] This can be achieved, for example, by temporarily adapting parameters or operating the fuel cell stack 10 at a higher load, wherein more water is produced. By intermittent operation, excessive drying or even drying out can be prevented by a storage effect in the cathode supply device 30 .

[0050] This provides an operating strategy or operating method 100 which reduces the degradation rate of the humidity transmitter 36 (in particular the gas-to-gas humidifier 36 ) from the outset, reacts to changing ambient and operating conditions, and / or adapts during the operating time of the fuel cell system.

Claims

1. A method (100) for operating a fuel cell unit (1), in particular a fuel cell vehicle, It is characterized in that The operating method (100) comprises a humidity transmitter anti-aging routine (101), by which the aging behavior of the humidity transmitter (36), in particular the air-to-air humidifier (36), of the fuel cell unit (1) is influenced, so that the aging of the humidity transmitter (36) is slowed down.

2. The operating method (100) according to the preceding claim, It is characterized in that At least one operating parameter of the fuel cell assembly (1) is adjusted by the humidity transmitter anti-aging routine (101) so that the aging of the humidity transmitter (36) is slowed down by low-degradation operation of the humidity transmitter (36).

3. The operating method (100) according to any one of the preceding claims, It is characterized in that The low-fade operation of the humidity transmitter (36) is ensured by supplying the humidity transmitter (36) with at least a sufficient amount of water over a certain period of time.

4. The operating method (100) according to any one of the preceding claims, It is characterized in that The humidity transmitter anti-aging routine (101) selects operating parameters and / or sets the values ​​of the operating parameters so that: The humidifier membrane of the humidity transmitter (36) is kept substantially permanently moist by the cathode exhaust medium (6); thereby avoiding wet-dry cycles of the humidity transmitter (36); and / or Targetedly influence the water activity (a) at the cathode outlet of the fuel cell unit (1) K ).

5. The operating method (100) according to any one of the preceding claims, It is characterized in that Affects the water activity at one / the outlet of the cathode (a K ), so that it does not fall below or does not fall significantly below a determined limit value, Select and / or adjust at least one operating parameter of the fuel cell unit (1) so that the water activity (a K ) is not lower than or not significantly lower than the said limit value; and / or During operation of the fuel cell assembly (1), the at least one operating parameter is, in particular, the stoichiometry, the pressure and / or the temperature at / in the cathode.

6. The operating method (100) according to any one of the preceding claims, It is characterized in that The at least one operating parameter is adjusted by the humidity transmitter anti-aging routine (101) in the operating method (100) so that the humidity transmitter (36) is maintained as low-degradation operation as possible.

7. The operating method (100) according to any one of the preceding claims, It is characterized in that · at any or necessarily lower water activity (a K ), interrupting the low-decay operation of the humidity transmitter (36) for a determined duration, the determined duration is determined based on the water storage capacity of a humidifier path upstream of the humidity transmitter (36), and / or · Below the water activity (a K ), the humidity transmitter (36) is operated in a regeneration mode in which more humid conditions are set in the humidity transmitter (36).

8. The operating method (100) according to any one of the preceding claims, It is characterized in that In a first step (111) of the humidity transmitter anti-aging routine (101), a water activity (a) is determined in a cathode supply device (30), in particular downstream of the fuel cell stack (10). K ),and In a second step (121) of the humidity transmitter anti-aging routine (101) following the first step (111), the determined water activity (a K ) is less than or greater than the water activity (a K ) limit value.

9. The operating method (100) according to any one of the preceding claims, It is characterized in that In water activity (a K ) is less than the water activity (a K ) limit value, The operating parameters of the fuel cell unit (1), the fuel cell stack (10) and / or the cathode supply device (30) are changed so that a more humid condition is set in the cathode supply device (30) downstream of the fuel cell stack (10).

10. The operating method (100) according to any one of the preceding claims, It is characterized in that In the humidity transmitter anti-aging routine (101), In a third step (131) following the second step (121), the stoichiometry in the cathode is adjusted, in particular reduced, In a fourth step (141) following the second or third step (121, 131), the pressure in the cathode supply device (30) or in the cathode is adjusted, in particular reduced, and / or In a fifth step (141) following the second, third or fourth step (121, 131, 141), the temperature of the fuel cell stack (10), the temperature in the cathode supply device (30) and / or the temperature of the humidity transmitter (36) are adjusted, in particular reduced.

11. The operating method (100) according to any one of the preceding claims, It is characterized in that The reference operation of the operating method (100) of the fuel cell unit (1) is carried out in a modified manner by means of the humidity transmitter anti-aging routine (101), · executing the humidity transmitter anti-aging routine (101) as the fuel cell assembly (1)'s own reference operation, and / or · Executing the humidity transmitter anti-aging routine (101) during operation or in a stationary state of the fuel cell assembly (1).

12. A fuel cell unit (1), a fuel cell system or a fuel cell vehicle, It is characterized in that The operating method (100) for a fuel cell assembly (1) according to any one of the preceding claims can be carried out and / or is carried out by the fuel cell assembly (1), the fuel cell system or the fuel cell vehicle.

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