Method for operating a fuel cell system

Abstract

A method for operating a fuel cell system (2), comprising the steps of determining (100) an electrical power of an electrically operated component (4) of the fuel cell system (2) at at least one defined operating point of the fuel cell system (2), comparing (200) the determined electrical power of the electrically operated component (4) with the electrical power of an electrically operated component (4) of a reference fuel cell system (2') at at least one defined operating point, ascertaining (300) a difference between the determined electrical power of the electrically operated component (4) of the fuel cell system (2) and the determined electrical power of the electrically operated component (4) of the reference fuel cell system (2'), and adjusting (400) the determined electrical power of the electrically operated component (4) of the fuel cell system (2) by the ascertained difference.

Description

[0001] Description

[0002] title

[0003] Method for operating a fuel cell system

[0004] The present invention relates to a method for operating a fuel cell system, a fuel cell system and a motor vehicle comprising such a fuel cell system.

[0005] State of the art

[0006] Hydrogen-based fuel cell systems are considered a mobility concept of the future, as they emit only water as exhaust and allow for fast refueling times. However, there is still potential for optimization regarding the efficiency and lifespan of fuel cell systems.

[0007] In particular, the diffusion of nitrogen and water vapor into the anode compartment of fuel cells poses a disadvantage with regard to the efficiency and lifespan of fuel cell systems. Nitrogen and water vapor reduce the cell voltage of the fuel cells and thus the stack voltage of a fuel cell system. High nitrogen and water vapor concentrations in the anode circuit can also lead to stack degradation. This occurs not only as nitrogen diffuses into the anode compartment but also as a small amount of nitrogen introduced into the anode compartment via hydrogen recirculation within the hydrogen reservoir. Appropriate gas handling units, especially recirculation pumps, are used for this recirculation.

[0008] To reduce the inert gas content within the anode compartment, fuel cell systems typically have so-called purge valves, which allow the gas mixture containing inert gas to be removed from time to time.

[0009] To ensure optimal operating conditions for a fuel cell system and to avoid possible damage, it must be ensured that the inert gas content in the anode compartment remains within a certain range.

[0010] Models are known for monitoring and controlling the current inert gas concentration within an anode compartment, based on experimental measurements. However, these models, developed specifically for one fuel cell system, cannot be accurately transferred to other fuel cell systems. This is due, in particular, to differing system components, varying operating conditions, or wear, ultimately leading to a significant loss of accuracy in the developed models.

[0011] Disclosure of the invention

[0012] The invention relates, according to a first aspect, to a method with the features of the independent method claim, and according to a second aspect, to a fuel cell system with the features of the independent system claim. Further features and details of the invention will become apparent from the respective dependent claims, 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 system according to the invention, and vice versa, so that the disclosure relating to the individual aspects of the invention always includes, or allows for, reciprocal reference.

[0013] The inventive method and fuel cell system serve in particular to optimize a model for detecting and controlling the current inert gas content within an anode compartment. In particular, the application of the inventive method allows for the determination and compensation of system-related deviations, thus guaranteeing fast and accurate detection and control of the current inert gas content within the anode compartment. This not only improves the efficiency and reliability of a fuel cell system but also significantly extends its service life. Furthermore, the specific inventive design of the method and fuel cell system achieves these advantages in a structurally simple and cost-effective manner.Within the scope of the invention, it has been recognized that by determining a constant offset between a fuel cell system and a reference system, the required accuracy for adapting a fuel cell system to detect and control a current inert gas content within an anode space of the fuel cell system can already be achieved.

[0014] The inventive method for operating a fuel cell system comprises the steps of determining an electrical power of an electrically operated component of the fuel cell system at at least one defined operating point of the fuel cell system, comparing the determined electrical power of the electrically operated component with the electrical power of an electrically operated component of a reference fuel cell system at at least one defined operating point, determining a difference between the determined electrical power of the electrically operated component of the fuel cell system and the electrical power of the electrically operated component of the reference fuel cell system, and adjusting the determined electrical power of the electrically operated component of the fuel cell system by the determined difference.

[0015] Current electrical power can be measured, for example, using a power meter or by determining it using a current or voltage meter. Within the scope of the invention, a defined operating point of the fuel cell system and the reference fuel cell system can be understood, in particular, as a defined or definable state of a fuel cell system and a reference fuel cell system in which the fuel cell system and the reference fuel cell system are operated under specific, defined operating conditions.

[0016] The method according to the invention can be used in particular in fuel cell-powered motor vehicles. However, use in other fuel cell-powered means of transport, such as cranes, ships, rail vehicles, aircraft, or even stationary fuel cell-powered objects, is also conceivable.

[0017] It is also understood that, during the adjustment, a distinction is preferably made between a positive and a negative difference, such that the difference in power is added if the power of the reference system is greater and subtracted if the power of the reference system is less. The values ​​for the electrical power of the fuel cell system and the reference fuel cell system can preferably be stored on a storage unit or a system control unit. Before an adjustment of the determined electrical power of the fuel cell system by the calculated difference, as provided for in the invention, the difference can also be adjusted, for example, if the conditions at the defined operating points should differ at least partially between the fuel cell system and the reference fuel cell system.It is also understood that, for a meaningful comparison, the electrically driven component of the fuel cell system and the electrically driven component of the reference fuel cell system are the same electrical components, i.e., for example, a recirculation pump of an anode circuit in both cases. Adjustment can advantageously be achieved using valves for supplying hydrogen or for removing excess inert gas or water, or by adjusting the cooling temperature.

[0018] With regard to the particularly effective use of the method in question, especially in terms of saving operating time and computing power, it may be advantageous to perform the method during the commissioning of the fuel cell system and at regular intervals before and / or during the operation of the fuel cell system. These regular intervals could, for example, be fixed time intervals of one week or one month, or they could be adapted to the operating times of the fuel cell system in question.

[0019] With a view to optimizing achievable performance while simultaneously ensuring gentle operation, it can advantageously be further provided that, after adjusting the determined electrical power of the electrically operated component of the fuel cell system by the calculated difference, an anode compartment hydrogen and / or inert gas concentration model is applied to operate the fuel cell system under optimized conditions. Preferably, the anode compartment hydrogen and / or inert gas concentration model is used to determine the current inert gas content within the anode compartment based on the adjusted determined electrical power of the electrically operated component of the fuel cell system and to adjust it as needed. Nitrogen, as an inert gas, not only reduces the cell or...Stack voltage, and thus the efficiency of a fuel cell system, is not only affected, but it also contributes to cell degradation and therefore to a reduction in the lifespan of fuel cell systems. As mentioned, adjustments can advantageously be made using valves for supplying hydrogen or removing excess inert gas or water, or by adjusting the cooling temperature.

[0020] With a view to determining the nitrogen content as accurately as possible for rapid and proactive optimization of achievable performance while simultaneously ensuring gentle operation, it can advantageously be further provided that the anode compartment hydrogen concentration model is generated based on the reference fuel cell system. In this way, the anode compartment hydrogen concentration model can preferably be supplied with the necessary data via the reference fuel cell system.

[0021] As part of a particularly precise and error-free adaptation of a fuel cell system to a reference model, it can advantageously be further provided that the electrical power of the electrically driven component of the fuel cell system is determined for a plurality of different defined operating points of the fuel cell system, wherein the electrical power of the electrically driven component of the fuel cell system is recorded for at least three different defined operating points. Preferably, the operating points used differ sufficiently from one another.

[0022] With a view to determining the nitrogen content within an anode circuit as simply, quickly, and reliably as possible, it can also be advantageous if the electrically operated component of the fuel cell system is a gas supply unit of the fuel cell system, preferably a recirculation pump of the anode path of the fuel cell system. It has been recognized within the scope of the invention that the electrical power of a gas supply unit of an anode circuit, such as a recirculation pump, correlates very sensitively with the nitrogen content within the gas mixture of the anode circuit.

[0023] In the context of a particularly precise and error-free adaptation of a fuel cell system to a reference model, it can also be provided that the at least one defined operating point or the plurality of different defined operating points have constant conditions, wherein preferably the at least one defined operating point or the plurality of different defined operating points are constant at least with regard to one or more of the following parameters:

[0024] - Cooling temperature of the fuel cell system and the reference fuel cell system,

[0025] - Temperature of the gas mixture at an inlet of the electrically operated component of the fuel cell system and the reference fuel cell system,

[0026] - Temperature of the electrically operated component of the

[0027] fuel cell system and the reference fuel cell system,

[0028] - Pressure within an anode circuit of the fuel cell system and the reference fuel cell system, particularly at the inlet of the electrically driven component, - Rotational speed of the electrically driven component of the fuel cell system and the reference fuel cell system,

[0029] - Operating current of the fuel cell system and the reference fuel cell system,

[0030] - Hydrogen concentration of the gas mixture within the anode circuit of the fuel cell system and the reference fuel cell system.

[0031] The hydrogen concentration of the gas mixture within the anode circuit can preferably be determined indirectly, or brought to a reproducible value, by removing the gas mixture present in the anode circuit before the process is carried out, e.g., via a drain valve and a purge valve. Alternatively, instead of ensuring constant conditions, a corresponding adjustment or conversion, or the like, can be performed if the conditions at the defined operating points differ between the fuel cell system and the reference fuel cell system.

[0032] Within the scope of the invention, it can advantageously be provided that individual, several, or all mandatory and / or optional steps of the method according to the invention can be carried out in the proposed sequence, but also in a different sequence. In particular, individual, several, or all mandatory and / or optional steps of the method according to the invention can be carried out repeatedly, e.g., cyclically.

[0033] It is further understood that individual, several or all of the obligatory and optional steps of the method according to the invention can also be implemented by a computer and carried out automatically by a system control unit.

[0034] The invention also relates to a fuel cell system, in particular for carrying out a method described above. The fuel cell system according to the invention comprises an anode path comprising an anode, an anode gas supply line and an anode gas return line, a cathode path comprising a cathode, a cathode gas supply line and a cathode gas return line, an electrically operated component, and a processing unit for determining the electrical power of the electrically operated component and for comparing the determined electrical power of the electrically operated component with the electrical power of an electrically operated component of a reference fuel cell system.for determining the difference between the electrical power output of the electrically operated component of the fuel cell system and the electrical power output of the reference fuel cell system, and for adjusting the electrical power output of the fuel cell system by the determined difference, as well as a control unit for applying an anode compartment hydrogen and / or inert gas concentration model to operate the fuel cell system under optimized conditions. As mentioned, this adjustment can advantageously be made using valves for supplying hydrogen or for removing excess inert gas or water. The fuel cell system thus exhibits the same advantages as those already described in detail with regard to the method according to the invention.

[0035] With a view to a fast and accurate determination of the electrical power of the electrically operated component, it may be advantageous to provide a sensor unit for acquiring data to determine the electrical power of the electrically operated component.

[0036] With a view to determining the inert gas content within an anode circuit as simply, quickly, and reliably as possible, it can also be advantageous if the electrically operated component is designed in the form of a gas supply unit, preferably in the form of a recirculation pump for the anode path of the fuel cell system. It has been recognized within the scope of the invention that the electrical power of a gas supply unit of an anode circuit, such as a recirculation pump, correlates very sensitively with the nitrogen content within the gas mixture of the anode circuit. The invention also relates to a motor vehicle comprising a fuel cell system as described above. Thus, the motor vehicle according to the invention has the same advantages as those already described in detail with regard to the inventive method and the inventive fuel cell system.

[0037] Further advantages, features, and details of the invention will become apparent from the following description, in which exemplary embodiments of the invention are described in detail with reference to the drawings. The features mentioned in the claims and in the description can each be essential to the invention individually or in any combination.

[0038] They show:

[0039] Fig. 1 shows a schematic representation of the individual steps of a method according to the invention for operating a fuel cell system and

[0040] Fig. 2 shows a schematic representation of a fuel cell system according to the invention in a first embodiment.

[0041] Fig. 1 shows a schematic representation of the individual steps of a method according to the invention for operating a fuel cell system 2.

[0042] As can be seen in Fig. 1, the method according to the invention comprises the steps of determining 100 an electrical power of an electrically operated component 4 of the fuel cell system 2 at at least one defined operating point of the fuel cell system 2, comparing 200 the determined electrical power of the electrically operated component 4 with the electrical power of an electrically operated component 4 of a reference fuel cell system 2' at at least one defined operating point, determining 300 a difference between the determined electrical power of the electrically operated component 4 of the fuel cell system 2 and the electrical power of the electrically operated component 4 of the reference fuel cell system 2', and adjusting 400 the determined electrical power of the fuel cell system 2 by the determined difference.

[0043] The procedure is preferably carried out during the commissioning of the fuel cell system 2 and at regular intervals before and / or during the operation of the fuel cell system 2.

[0044] After adjusting the determined electrical power of the fuel cell system 2 by the determined difference, an anode compartment hydrogen and / or inert gas concentration model can then be applied to operate the fuel cell system 2 under optimized conditions, preferably using the anode compartment hydrogen and / or inert gas concentration model based on the adjusted determined electrical power of the electrically operated component 4 of the fuel cell system 2. For this purpose, input parameters such as temperatures, pressures and the fuel cell operating current can be used for the model, so that a current nitrogen content within the anode compartment can be determined and adjusted if necessary.

[0045] The anode space hydrogen and / or inert gas concentration model is advantageously generated on the basis of the reference fuel cell system 2'.

[0046] Determining the electrical power of the electrically operated component of the fuel cell system 2 can also be done for a plurality of different defined operating points of the fuel cell system 2, e.g. for at least three different defined operating points.

[0047] The electrically operated component of the fuel cell system 2 is also preferably a gas supply unit of the fuel cell system 2, e.g. a recirculation pump of the anode path of the fuel cell system 2.

[0048] Fig. 2 shows a schematic representation of a fuel cell system 2 according to a first embodiment of the invention. As can be seen in Fig. 2, the fuel cell system 2 according to the invention comprises an anode path comprising an anode 8, an anode gas supply line 12 and an anode gas return line 16, a cathode path comprising a cathode 10, a cathode gas supply line 14 and a cathode gas discharge line 18, and an electrically operated component 4 in the form of a gas delivery unit, in particular in the form of a recirculation pump.Furthermore, the fuel cell system 2 comprises a sensor unit 20 for acquiring data to determine the electrical power of the electrically operated component 4, a processing unit 22 for determining the electrical power of the electrically operated component 4, and a control unit 24 for applying an anode compartment hydrogen and / or inert gas concentration model to operate the fuel cell system 2 under optimized conditions. The sensor unit 20, the processing unit 22, and the control unit 24 can be connected to each other and to the rest of the fuel cell system 2, for example, via a control line. Alternatively, wireless control can also be provided.

[0049] The hydrogen introduced via the hydrogen reservoir 11 is fed into the anode via the hydrogen supply system 9 (with metering valve and injection pump) and under pressure control via the pressure sensor 13. Excess hydrogen can be returned to the anode 8 via the anode gas return line 16, with water being added or removed as needed via the arrangement of water reservoirs 6. Finally, excess water can be drained via the drain valves 5b.

[0050] Excess nitrogen and water vapor can also be discharged from the anode circuit via the purge valve 5a and the discharge line 7, whereby a hydrogen content in the cathode gas discharge line 18 can be registered via the hydrogen sensor 15.

[0051] Finally, a cooling system 17 and an electrical system 19 for converting the generated energy are arranged on the fuel cell system 2.

Claims

Claims 1. Method for operating a fuel cell system (2), comprising the steps: - Determining (100) an electrical power of an electrically operated component (4) of the fuel cell system (2) at at least one defined operating point of the fuel cell system (2), - Comparing (200) the determined electrical power of the electrically operated component (4) with the electrical power of an electrically operated component (4) of a reference fuel cell system (2') at at least one defined operating point, - Determining (300) a difference between the determined electrical power of the electrically operated component (4) of the fuel cell system (2) and the electrical power of the electrically operated component (4) of the reference fuel cell system (2') and - Adjusting (400) the determined electrical power of the electrically operated component of the fuel cell system (2) by the determined difference.

2. Method according to claim 1, characterized in that the method is carried out during system commissioning of the fuel cell system (2) and at regular intervals before and / or during the operation of the fuel cell system (2).

3. Method according to claim 1 or 2, characterized in that, after adjusting (400) the determined electrical power of the electrically operated component of the fuel cell system (2) by the determined difference, an anode compartment hydrogen and / or inert gas concentration model is applied to operate the fuel cell system (2) under optimized conditions, preferably by means of the Anode space hydrogen and / or inert gas concentration model based on the adapted determined electrical power of the electrically operated component of the fuel cell system (2) determines the current inert gas content within the anode space and adjusts it as needed.

4. Method according to claim 3, characterized in that the anode space hydrogen and / or inert gas concentration model is generated on the basis of the reference fuel cell system (2').

5. Method according to one of the preceding claims, characterized in that the determination (100) of the electrical power of the electrically operated component of the fuel cell system (2) is carried out for a plurality of different defined operating points of the fuel cell system (2), wherein the electrical power of the electrically operated component of the fuel cell system (2) is recorded for at least three different defined operating points.

6. Method according to one of the preceding claims, characterized in that the electrically operated component of the fuel cell system (2) is a gas supply unit of the fuel cell system (2), preferably a recirculation pump of the anode path of the fuel cell system (2).

7. Method according to one of the preceding claims, characterized in that the at least one defined operating point or the plurality of different defined operating points have constant conditions, wherein preferably the at least one defined operating point or the plurality of different defined operating points are constant at least with respect to one or more of the following parameters: - Cooling temperature of the fuel cell system (2) and the reference fuel cell system (2'), - Temperature of the gas mixture at an inlet of the electrically operated component (4) of the fuel cell system (2) and the reference fuel cell system (2'), - Temperature of the electrically operated component (4) of the fuel cell system (2) and the reference fuel cell system (2'), - Pressure within an anode circuit of the fuel cell system (2) and the reference fuel cell system (2'), particularly at the inlet of the electrically operated component (4), - Rotational speed of the electrically driven component (4) of the fuel cell system (2) and the reference fuel cell system (2'), - Operating current of the fuel cell system (2) and the reference fuel cell system (2'), - Hydrogen concentration of the gas mixture within the anode circuit of the fuel cell system (2) and the reference fuel cell system (2').

8. Fuel cell system (2), in particular for carrying out a method according to any one of claims 1 to 7, comprising: - an anode path comprising an anode (8), an anode gas supply line (12) and an anode gas return line (16), - a cathode path comprising a cathode (10), a cathode gas supply line (14) and a cathode gas discharge line (18), - an electrically operated component (4), - a processing unit (22) for determining (100) an electrical power of the electrically operated component (4), for comparing (200) the determined electrical power of the electrically operated component (4) with the electrical power of an electrically operated component (4) of a reference fuel cell system (2'), for determining (300) a difference between the determined electrical power of the electrically operated component (4) of the fuel cell system (2) and the determined electrical power of the electrically operated component (4) of the reference fuel cell system (2') and for adjusting (400) the determined electrical power of the fuel cell system (2) by the determined difference, and - a control unit (24) for applying an anode compartment hydrogen and / or inert gas concentration model to operate the fuel cell system (2) under optimized conditions.

9. Fuel cell system (2) according to claim 8, characterized in that a sensor unit (20) is provided for recording data for determining (100) an electrical power of the electrically operable component (4).

10. Fuel cell system (2) according to claim 8 or 9, characterized in that the electrically operable component (4) is designed in the form of a gas conveying unit, preferably in the form of a recirculation pump of the anode path of the fuel cell system (2).

11. Motor vehicle comprising a fuel cell system (2) according to any one of claims 8 to 10.

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