Method for operating a fuel cell system, fuel cell stack, fuel cell system, computer program product and computer-readable storage medium

Abstract

The invention relates to a method for operating a fuel cell system (100) having at least one fuel cell stack (110) which has an inlet (111) for introducing fuel and an outlet (112) for discharging the degradation products, comprising: adjusting a hydrogen concentration at the outlet (112) and adjusting an oxygen-to-carbon ratio at the inlet (111), whereby a fuel consumption of the fuel cell system (100) is determined, wherein the fuel consumption of the fuel cell system (100) is proportional to a minimum hydrogen concentration at the outlet (112) and the minimum hydrogen concentration at the outlet (112) corresponds to the amount of hydrogen at which the fuel cell stack (110) is operated in a depletion-free manner. The invention further relates to a fuel cell stack, a fuel cell system, a computer program product and to a computer-readable storage medium.

Description

[0001] Description

[0002] title

[0003] Method for operating a Fuel cell stack.

[0004] The invention relates to a method for operating a fuel cell system, a fuel cell stack, a fuel cell system, a computer program product and a computer-readable storage medium.

[0005] State of the art

[0006] Solid oxide fuel cells (SOFCs) are made of solid materials and operate at high temperatures, enabling efficient energy conversion. SOFCs are used in a variety of applications, from stationary power generation systems to potential applications in vehicles. They are considered a promising technology for energy generation due to their efficiency and versatility.

[0007] According to the current state of the art, SOFC systems often have two actuators in the anode path, which allow the independent adjustment of two different system sizes. With this in mind, system sizes are usually selected that aim for safe and efficient operation of the SOFC system. While in previous years the fuel utilization of the stack and the oxygen-to-carbon ratio at the stack inlet were controlled, today's software variants are more focused on controlling the fuel utilization of the stack and the fuel utilization of the system. The widely varying gas quality worldwide poses a particular challenge for robust and efficient plant operation. Due to these gas quality fluctuations, as well as sensor tolerances and model errors, the control of an SOFC system can be subject to greater uncertainties.

[0008] Disclosure of the invention

[0009] A method for operating a fuel cell system, a fuel cell stack, a fuel cell system, a computer program product, and a computer-readable storage medium are proposed. Further features and details of the invention emerge from the subclaims, the description, and the drawings. Features and details described in connection with the method according to the invention naturally also apply in connection with the fuel cell stack according to the invention and / or in connection with the fuel cell system according to the invention and / or in connection with the computer program product according to the invention and / or in connection with the computer-readable storage medium according to the invention, and vice versa, so that with regard to the disclosure of the individual aspects of the invention, reference is and can always be made reciprocally.

[0010] According to the invention, a method is provided for operating a fuel cell system with at least one fuel cell stack, which has an inlet for introducing fuel and an outlet for removing the decomposition products, comprising:

[0011] - Setting a hydrogen concentration at the outlet,

[0012] - Setting an oxygen-to-carbon ratio at the inlet, thereby determining a fuel consumption of the fuel cell system, wherein the fuel consumption of the fuel cell system is proportional to a hydrogen concentration at the outlet and a minimum hydrogen concentration at the outlet corresponds to the amount of hydrogen at which the fuel cell stack is operated depletion-free.

[0013] In other words, according to the invention, a method for controlling a fuel cell system with a stack which has an inlet and an outlet for introducing and discharging fuel, wherein both the concentration of hydrogen of the fuel at the outlet and the ratio of oxygen to carbon of the fuel at the inlet are controllable, wherein this control results in a consumption of the fuel of the fuel cell system which depends on a minimum concentration of hydrogen at the outlet, which in turn corresponds to the amount of hydrogen which is necessary so that no depletion occurs in the stack.

[0014] A fuel cell stack can be understood as an arrangement of several individual cells connected in series or parallel. A stack is used, for example, to generate a higher voltage or power. In addition to cells, a fuel cell stack can comprise interconnects, end plates and fuel channels. Interconnects can be arranged between the individual cells and designed to conduct current from one cell to the next. Furthermore, they can be designed to create thermal insulation between the cells. Fuel channels can be designed to supply the cells with fuel (particularly natural gas) which is required for the reaction within the cells. End plates can be arranged at the ends of the stack and designed to hold the cells, and in particular other components, together.

[0015] The fuel cell stack and / or fuel cell system can be designed as a solid oxide fuel cell. These cells are made of solid materials and operate at high temperatures, enabling efficient energy conversion.

[0016] An inlet can be understood as an opening on the fuel cell stack, in particular on an end plate, which is suitable for supplying fuel to the fuel cell stack. The inlet can be provided with a valve, in particular a control valve, which is designed to control the volume flow of fuel into the fuel cell stack.

[0017] A fuel can be understood as a substance that is suitable for being consumed in an electrochemical reaction in the fuel cell stack with the release of energy, i.e., being converted into a degradation product. The fuel can comprise at least hydrogen, oxygen, and carbon. Furthermore, the fuel can comprise at least hydrogen, natural gas, biogas, a synthetically produced gas, or hydrocarbons. It will be clear to a person skilled in the art that the fuel in the fuel cell stack may only be partially converted, so that a mixture of fuel and degradation products generally results at the outlet. Provision can be made for at least a portion of this mixture to be returned to the inlet and, in particular, mixed with new fuel (also called recirculation). This means that intermediate products may also be present. E.g.Hydrogen can be an intermediate product produced during the reforming of methane and subsequently oxidized to water. Depending on the context, fuel or a degradation product can therefore refer to the starting product, the end product, or a mixture.

[0018] The outlet can be understood as an opening on the fuel cell stack, in particular on an end plate, which is suitable for removing fuel and / or degradation products from the fuel cell stack. The inlet can be provided with a valve, in particular a control valve, which is designed to control the volume flow of fuel into the fuel cell stack.

[0019] A degradation product can be one or more substances produced during the electrochemical process. The degradation product can include at least water, carbon dioxide, carbon monoxide, or nitrogen oxides.

[0020] A fuel cell system can comprise additional components compared to a fuel cell stack. In particular, it can be provided that a fuel cell system comprises means for returning the fuel from the outlet to the inlet. The means for returning can comprise a return line, a return valve, and a return flow controller. The return flow controller can be designed to control the return according to a recirculation rate and / or a recirculation volume flow. For this purpose, the return flow controller can, in particular, control the return valve accordingly. In the context of the invention, setting a hydrogen concentration at the outlet can be understood as transmitting a signal for setting the hydrogen concentration at the outlet to a controller and / or a control unit of the fuel cell system. For this purpose, a dedicated hydrogen concentration controller can, in particular, be provided.It can further be provided that a hydrogen concentration sensor is provided at the outlet, which is designed to measure the hydrogen concentration at the outlet. Alternatively or additionally, the hydrogen concentration can be determined based on a model. The hydrogen concentration sensor can be coupled to the hydrogen concentration controller to form a control loop. The hydrogen concentration controller can be designed to control at least one gas flow, in particular the volume flow of the fuel and / or a recirculation volume flow. For this purpose, the hydrogen concentration controller can control flow controllers provided for this purpose. It can be provided that the hydrogen concentration at the outlet is set at least to a minimum hydrogen concentration at the outlet and / or above it. This ensures that the fuel cell stack is always operated without depletion.

[0021] In the context of the invention, adjusting an oxygen-to-carbon ratio at the inlet can be understood as transmitting a signal for adjusting the oxygen-to-carbon ratio at the outlet to a controller and / or a control unit of the fuel cell system. For this purpose, a dedicated oxygen-to-carbon ratio controller can be provided. Furthermore, an oxygen-to-carbon sensor can be provided at the inlet, which is designed to measure the oxygen-to-carbon ratio at the inlet. Alternatively or additionally, the oxygen-to-carbon ratio can be determined based on a model. The oxygen-to-carbon sensor can be coupled to the oxygen-to-carbon ratio controller to form a control loop.The oxygen-to-carbon ratio controller can be designed to control at least one gas flow, in particular the fuel flow rate and / or a recirculation flow rate. For this purpose, the oxygen-to-carbon ratio controller can control flow controllers provided for this purpose. Particularly advantageously, it can be provided that adjusting the oxygen-to-carbon ratio at the inlet controls the recirculation flow rate, and adjusting the hydrogen concentration at the outlet controls the fuel flow rate.

[0022] The term fuel consumption refers to the amount of fuel required to sustain the electrochemical reaction within the cell, specifically to generate energy through the electrochemical reaction. This can be expressed as volume per unit time. Determining the fuel consumption of a fuel cell system means that the hydrogen concentration at the outlet and the oxygen-to-carbon ratio at the inlet, under otherwise constant conditions, determine the fuel consumption of the fuel cell system. In other words, the fuel consumption of a fuel cell system is a function of the hydrogen concentration at the outlet and the oxygen-to-carbon ratio at the inlet.

[0023] The process may be carried out at a constant current. A constant current can be determined and / or adjusted by appropriate control of the fuel cell system.

[0024] In particular, the fuel consumption of the fuel cell system can be expressed as

[0025] Fsys = f x H2Stk 0Ut min) where F Sys is the fuel consumption of the fuel cell system, xH2Stkoutmin is the minimum hydrogen concentration at the outlet and f is a function of the minimum hydrogen concentration at the outlet.

[0026] In the context of the invention, a minimum hydrogen concentration is understood to be the hydrogen concentration at which no depletion occurs during the electrochemical reaction and the fuel cell stack and / or the fuel cell system is operated depletion-free. In the context of the invention, the term depletion-free can be understood as an operating state of the fuel cell stack in which sufficient fuel is still available for the desired electrochemical reaction even at the end of the fuel cell stack. In the operating state, the fuel is consumed by the electrochemical reaction as it passes through the fuel cell stack, releasing electrical energy. Depletion-free in this context therefore means that the fuel within the fuel cell stack is not completely consumed.Depletion-free operation has the advantage that the fuel cell can generate a particularly large amount of energy and also increases its service life.

[0027] Overall, the method according to the invention offers the advantage of enabling robust and efficient operation of a fuel cell system, in particular an SOFC system, even in the context of widely varying natural gas quality and tightly specified stack limitations. Adjusting the hydrogen concentration at the outlet and the oxygen-to-carbon ratio at the inlet offers a relatively simple and thus precisely and reproducibly controllable variable in the fuel cell system. Due to its relationship with the fuel consumption of the fuel cell system, this simultaneously enables consistently depletion-free operation that can still be efficiently adjusted.

[0028] Within the scope of the invention, it may be advantageous for the hydrogen concentration at the outlet to be converted into the fuel consumption of the fuel cell system using an algorithm. In other words, it may be provided that the fuel consumption is determined from the hydrogen concentration at the outlet using a formula defined in a clear set of instructions, particularly in a software process. The algorithmic formulation allows for particularly fast and reliable control.

[0029] Within the scope of the invention, it is conceivable that a chemical equilibrium of the reaction in the fuel cell stack exists and / or is detected at the outlet. In other words, a state exists in the fuel cell stack in which the overall reaction appears to be at rest from the outside, i.e., no changes are detectable at the macroscopic level. The chemical equilibrium can be detected by a sensor that measures at least the concentration of a substance in the fuel and / or the degradation product, particularly over time.

[0030] Within the scope of the invention, it can be provided that the hydrogen concentration at the outlet is determined at least by the temperature at the outlet, by a hydrogen-to-carbon ratio, by the nitrogen-to-carbon ratio or the oxygen-to-carbon ratio at the outlet. It can be provided that the hydrogen-to-carbon ratio and / or the nitrogen-to-carbon ratio are assumed to be constant across the fuel cell stack and / or the fuel cell system. It can be provided that the temperature at the outlet is determined by a sensor and / or regulated by a temperature control device, which can in particular comprise a heating element and / or a cooling element. The temperature can be constant over time, in particular by the temperature control device.

[0031] It may be provided that the hydrogen concentration at the outlet, especially in chemical equilibrium, is calculated from f x H2pcs 0Ut ) = f (HC,NC,0C stkOut , T sktOut ) where x H2Stkout the hydrogen concentration at the outlet, HC the hydrogen-to-carbon ratio, NC the nitrogen-to-carbon ratio, 0C stkOut the oxygen-to-carbon ratio at the outlet and T sktOut represents the temperature at the stack exit.

[0032] It is also conceivable that the hydrogen-to-carbon ratio corresponds at least to the hydrogen-to-carbon ratio of a reference gas, in particular where the reference gas has a low hydrogen-to-carbon ratio, or is determined based on a model based on the ratio of the number of hydrogen atoms in moles of the fuel to the number of carbon atoms in moles of the fuel. Deriving the hydrogen-to-carbon ratio from a reference gas offers the advantage that no complex calculations are necessary for subsequent calculations. This allows for simple and efficient control. Different reference gases are suitable depending on the application.A reference gas with a low hydrogen-to-carbon ratio, which in other words corresponds to a worst-case scenario, i.e. the worst possible assumption under rationally conceivable circumstances, offers the advantage that the fuel cell stack and / or the fuel cell system is always operated without depletion, i.e. particularly robustly.

[0033] Alternatively or in addition, the hydrogen-to-carbon ratio can be determined using a model. This allows for a more precise determination, which can contribute to more efficient operation of the fuel cell system. In addition, the reference gas can be used to verify the plausibility of the model-based determination, which allows for particularly robust operation. The hydrogen-to-carbon ratio HC can also be modeled as where K H the hydrogen concentration, K c the carbon concentration and HHV Fueicorresponds to a factor of an empirical gas parameter correlation.

[0034] It is also conceivable that the nitrogen-to-carbon ratio corresponds at least to the nitrogen-to-carbon ratio of a reference gas, wherein in particular the reference gas has a high nitrogen-to-carbon ratio, or is determined model-based from the ratio of the number of nitrogen atoms in moles of the fuel and the number of carbon atoms in moles of the fuel.

[0035] Deriving the nitrogen-to-carbon ratio from a reference gas offers the advantage that no complex calculations are required for subsequent calculations. This allows for simple and efficient control. Different reference gases are suitable depending on the application. A reference gas with a high nitrogen-to-carbon ratio, which in other words corresponds to a worst-case scenario, i.e., the worst possible assumption under rationally conceivable circumstances, offers the advantage that the fuel cell stack and / or fuel cell system always operates depletion-free, thus being particularly robust. A high nitrogen-to-carbon ratio can lead to lower H2 concentrations with the same hydrogen-to-carbon ratio, temperature, and oxygen-to-carbon ratio.However, if experience shows that a low nitrogen-to-carbon ratio is to be expected, the reference gas can also have a low nitrogen-to-carbon ratio in order to achieve more efficient control.

[0036] Alternatively or in addition, the nitrogen-to-carbon ratio can be determined based on a model. This allows for a more precise determination, which can contribute to more efficient operation of the fuel cell system. In addition, the reference gas can be used to verify the plausibility of the model-based determination, which allows for particularly robust operation. The nitrogen-to-carbon ratio NC can also be modeled as where K N the nitrogen concentration, K c the carbon concentration and HHV Fueicorresponds to a factor of an empirical gas parameter correlation. Furthermore, the nitrogen-to-carbon ratio can be assumed to be zero for simplicity, further simplifying the process for operating the fuel cell system.

[0037] Within the scope of the invention, it is optionally possible for the hydrogen concentration at the outlet to be further determined by the oxygen-to-carbon ratio at the outlet, wherein in particular the hydrogen concentration at the outlet corresponds to the oxygen-to-carbon ratio at the outlet multiplied by a gas quality-dependent parameter. In other words, the oxygen-to-carbon ratio at the outlet OCc tk “ be determined from

[0038] OC st k out = z F Syswith z as a gas quality-dependent parameter. The oxygen-to-carbon ratio at the outlet can be determined by a sensor and / or adjusted by an oxygen-to-carbon controller.

[0039] Furthermore, it can be provided within the scope of the invention that at least one setting value of an oxygen-to-carbon ratio at the outlet, a fuel consumption of the fuel cell system or a volume flow of the fuel, in particular in the listed order, is determined from a setting value of the hydrogen concentration at the outlet.

[0040] In other words, the setting of the hydrogen concentration at the outlet can be done by setting at least one default value xH2stk 0Ut 0C stkout -> F Sys -> V Fuei with V Fueias the volume flow rate of the fuel. It may be provided that one or more actual values ​​corresponding to the specified values ​​are recorded by a corresponding sensor.

[0041] With regard to the present invention, it is conceivable that a recirculation rate is determined from the oxygen-to-carbon ratio at the inlet, wherein the recirculation rate corresponds in particular to the ratio of the oxygen-to-carbon ratio at the outlet, a volume flow of the fuel, and at least one fuel parameter to an oxygen ion flow. It can be provided that a minimum required recirculation rate is determined from a minimum oxygen-to-carbon ratio, which corresponds in particular to depletion-free operation. The recirculation rate r Agrcan be defined as

[0042] OC stk n V Fue iK c r Asr ■ with a gas parameter K c and an oxygen ion current V o ~. The oxygen ion current V o - can be a function of the supplied electrical current and can be determined analytically. The gas parameter K c can be derived from the calorific value of the fuel by empirical correlation.

[0043] Furthermore, it is conceivable that a recirculation volume flow is determined at least from the recirculation rate, a volume flow of the fuel, or a volume gas parameter. The recirculation volume flow V Agr can be defined as with as r Agr as, in particular, minimum, recirculation rate and K Das a gas parameter. The gas parameter can be determined in the same way as the gas parameter K c .

[0044] Within the scope of the invention, it may be advantageous that at least one recirculation rate or a recirculation volume flow, in particular in the listed order, is determined from a setting value of the oxygen-to-carbon ratio at the inlet and / or the volume flow of the fuel.

[0045] In other words, it can be provided that the setting of the oxygen-to-carbon ratio at the inlet is carried out by setting at least one default value It can be provided that one or more actual values ​​that correspond to the specified values ​​are recorded by a corresponding sensor.

[0046] Furthermore, a fuel cell stack according to the invention is proposed, comprising means for carrying out a method according to the invention.

[0047] This results in the same advantages with regard to a fuel cell stack according to the invention as have already been described with regard to a method according to the invention.

[0048] Furthermore, a fuel cell system according to the invention is proposed, comprising means for carrying out a method according to the invention.

[0049] This results in the same advantages with regard to a fuel cell system according to the invention as have already been described with regard to a method according to the invention and / or a fuel cell stack according to the invention.

[0050] Furthermore, a computer program product according to the invention is proposed, comprising instructions which, when the program is executed by a computer, in particular by a computing unit of a fuel cell system according to the invention, cause the computer to carry out a method according to the invention.

[0051] This results in the same advantages with regard to a computer program product according to the invention as have already been described with regard to a method according to the invention and / or a fuel cell stack according to the invention and / or a fuel cell system according to the invention.

[0052] Furthermore, a computer-readable storage medium is proposed, comprising instructions which, when executed by a computer, in particular by a processing unit of a fuel cell system according to the invention, cause the computer to execute a method according to the invention. Thus, with respect to a computer-readable storage medium according to the invention, the same advantages arise as have already been described with respect to a method according to the invention and / or a fuel cell stack according to the invention and / or a fuel cell system according to the invention and / or a computer program product according to the invention.

[0053] Further advantages, features, and details of the invention will become apparent from the following description, in which several embodiments of the invention are described in detail with reference to the drawings. The features mentioned in the claims and in the description may be essential to the invention individually or in any combination. These schematically show:

[0054] Figure 1 shows a fuel cell system and a fuel cell stack and

[0055] Figure 2 shows a relationship between a hydrogen concentration at the outlet and a fuel consumption of the fuel cell system.

[0056] In the following figures, identical reference numerals are used for the same technical features, even for different embodiments.

[0057] Figure 1 shows a fuel cell system 100 and a fuel cell stack 110. It can be seen that the fuel cell stack 110 has an inlet 111 for introducing fuel and an outlet 112 for removing the decomposition products. Furthermore, the fuel cell system 100 can have a computing unit 120 configured to execute a computer program product corresponding to a method according to the invention.

[0058] The fuel cell stack 110 according to the invention is designed to carry out a method according to the invention. This results in the same advantages with respect to a fuel cell stack 110 according to the invention as have already been described with respect to a method according to the invention.

[0059] According to the invention, a method is provided for operating a fuel cell system 100 with at least one fuel cell stack 110, which has an inlet 111 for introducing fuel and an outlet 112 for removing the decomposition products, comprising:

[0060] - Setting a hydrogen concentration at the outlet 112 and

[0061] - Setting an oxygen-to-carbon ratio at the inlet 111, whereby a fuel consumption of the fuel cell system 100 is determined, wherein the fuel consumption of the fuel cell system 100 is proportional to a hydrogen concentration at the outlet 112 and a minimum hydrogen concentration at the outlet 112 corresponds to the amount of hydrogen at which the fuel cell stack 110 is operated without depletion.

[0062] Overall, the method according to the invention offers the advantage of enabling robust and efficient operation of a fuel cell system 100, in particular an SOFC system, even in the context of widely varying natural gas quality and tightly specified stack limitations. Adjusting the hydrogen concentration at the outlet 112 and an oxygen-to-carbon ratio at the inlet 111 provides a relatively simple and thus precisely and reproducibly controllable variable in the fuel cell system 100. Due to the relationship with the fuel consumption of the fuel cell system 100, this simultaneously enables consistently depletion-free operation that can nevertheless be efficiently adjusted.

[0063] Figure 2 shows, by way of example, a relationship between the hydrogen concentration at outlet 112, plotted on the ordinate axis, and a percentage fuel utilization for power generation by the fuel cell system 100, plotted on the abscissa axis. If the current is constant, this means that fuel consumption decreases with increasing percentage utilization. Thus, fuel consumption decreases along the abscissa axis. The higher the fuel consumption, the higher the H2 concentration at outlet 112.

Claims

Claims 1. A method for operating a fuel cell system (100) with at least one fuel cell stack (110) having an inlet (111) for introducing fuel and an outlet (112) for removing the decomposition products, comprising: - Setting a hydrogen concentration at the outlet (112) and - Setting an oxygen-to-carbon ratio at the inlet (111), whereby a fuel consumption of the fuel cell system (100) is determined, wherein the fuel consumption of the fuel cell system (100) is proportional to a hydrogen concentration at the outlet (112) and a minimum hydrogen concentration at the outlet (112) corresponds to the amount of hydrogen at which the fuel cell stack (110) is operated without depletion.

2. Method according to claim 1, characterized in that the hydrogen concentration at the outlet (112) is converted into the fuel consumption of the fuel cell system (100) using an algorithm.

3. Method according to claim 1 or 2, characterized in that a chemical equilibrium of the reaction in the fuel cell stack (110) is present and / or detected at the outlet (112).

4. Method according to one of the preceding claims, characterized in that the hydrogen concentration at the outlet (112) is determined at least by the temperature at the outlet (112), by a Hydrogen-to-carbon ratio, by the nitrogen-to-carbon ratio or the oxygen-to-carbon ratio at the exit (112).

5. The method according to claim 4, characterized in that the hydrogen-to-carbon ratio corresponds at least to the hydrogen-to-carbon ratio of a reference gas, wherein in particular the reference gas has a low hydrogen-to-carbon ratio, or is determined model-based from the ratio of the number of hydrogen atoms in moles of the fuel and the number of carbon atoms in moles of the fuel.

6. The method according to claim 4, characterized in that the nitrogen-to-carbon ratio corresponds at least to the nitrogen-to-carbon ratio of a reference gas, wherein in particular the reference gas has a low nitrogen-to-carbon ratio, or is determined model-based from the ratio of the number of nitrogen atoms in moles of the fuel and the number of carbon atoms in moles of the fuel.

7. Method according to one of the preceding claims, characterized in that the hydrogen concentration at the outlet (112) is further determined by the oxygen-to-carbon ratio at the outlet (112), wherein in particular the hydrogen concentration at the outlet (112) corresponds to the oxygen-to-carbon ratio at the outlet (112) multiplied by an electrical current generated by the fuel cell system (100) and a gas quality-dependent parameter.

8. Method according to one of the preceding claims, characterized in that that from a setting value of the hydrogen concentration at the outlet (112) at least one setting value of an oxygen-to-carbon ratio at the outlet (112), a fuel consumption of the fuel cell system (100) or a volume flow of the fuel is determined, in particular in the listed order.

9. Method according to one of the preceding claims, characterized in that a recirculation rate is determined from the oxygen-to-carbon ratio at the inlet (111), wherein the recirculation rate corresponds in particular to the ratio of the oxygen-to-carbon ratio at the outlet (112), a volume flow of the fuel and at least one fuel parameter to an oxygen ion flow.

10. The method according to claim 9, characterized in that a recirculation volume flow is determined at least from the recirculation rate, a volume flow of the fuel or a volume gas parameter. 11 . Method according to one of the preceding claims, characterized in that at least one recirculation rate or a recirculation volume flow, in particular in the listed order, is determined from a setting value of the oxygen-to-carbon ratio at the inlet (111) and / or the volume flow of the fuel.

12. Fuel cell stack (110) comprising means for carrying out a method according to one of claims 1 to 11.

13. Fuel cell system (100) comprising means for carrying out a method according to one of claims 1 to 11.

14. Computer program product, comprising instructions which, when the program is executed by a computer, in particular by a Computing unit (120) of a fuel cell system (100) according to claim 13, causing it to carry out a method according to one of claims 1 - 11.

15. Computer-readable storage medium comprising instructions which, when executed by a computer, in particular by a computing unit (120) of a fuel cell system (100) according to claim 13, cause the computer to carry out a method according to one of claims 1 to 11.

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