Method for operating a fuel cell device, open-loop or closed-loop control device and fuel cell device

Abstract

The invention relates to a method for operating a fuel cell device, wherein, in at least one method step, at least one operating parameter of the fuel cell device is adjusted in order to achieve a predefined operating point of the fuel cell device. According to the invention, in at least one method step, the operating point to be adjusted is determined according to an electrical power parameter (14) of the fuel cell device.

Description

[0001] Description

[0002] Procedure for operating a Tax or

[0003] State of the art

[0004] A method for operating a fuel cell device has already been proposed, in which at least one operating parameter of the fuel cell device is adapted in at least one method step in order to achieve a predetermined operating point of the fuel cell device.

[0005] Disclosure of the invention

[0006] The invention is based on a method for operating a fuel cell device, wherein in at least one method step at least one operating parameter of the fuel cell device is adapted in order to achieve a predetermined operating point of the fuel cell device.

[0007] It is proposed that, in at least one method step of the method, the operating point to be set is determined as a function of an electrical performance parameter of the fuel cell device. The fuel cell device preferably comprises at least one electrochemical conversion unit with at least one fuel cell for converting a fuel by supplying oxygen and delivering electrical power. The operating point preferably comprises at least one variable or characteristic that describes or characterizes an operating state, efficiency, and / or effectiveness of the electrochemical conversion unit and / or the entire fuel cell device during fuel conversion.The operating point includes, for example, a temperature of the electrochemical conversion unit, a local fuel utilization of the electrochemical conversion unit, a system-wide fuel utilization of the fuel cell device, an air utilization of the electrochemical conversion unit, a composition of the fuel, or the like.

[0008] The fuel cell device preferably comprises at least one actuating unit for adjusting the at least one operating parameter. The operating parameter is, for example, a flow rate of the fuel, a flow rate of an oxygen-containing fluid, in particular ambient air or an industrial gas with a defined oxygen content, a recirculation rate of an exhaust gas resulting from the fuel, or the like. The fuel cell device preferably comprises a control or regulating device for controlling the actuating unit. The control or regulating device preferably adjusts the at least one operating parameter by means of the control unit depending on the operating point to be reached or maintained.

[0009] The electrical power parameter preferably describes an electrical power to be provided by the electrochemical conversion unit. The electrical power parameter can be in the form of electrical power, electrical current, or electrical voltage. The electrical power parameter can in particular be in the form of an absolute value or a relative value to a nominal power, a nominal current, or a nominal voltage of the electrochemical conversion unit. The electrical power parameter is preferably specified externally during the method. The electrical power parameter can be specified via a data interface of the control or regulating device and / or, in particular during a load change of a load supplied with electrical power by the fuel cell device, can be detected based on a change in an actual value of a variable dependent on the electrical power parameter.The fuel cell device preferably comprises at least one electrical energy buffer to counteract a change in the electrical power parameter on the part of the electrochemical conversion unit during a load change, in particular at least until the control or regulating device can initiate and / or complete an adjustment of the operating point. The data interface can be configured to specify the electrical power parameter by a control device of the load and / or an operator of the fuel cell device.

[0010] The control or regulating device preferably selects an operating point to be set from a plurality of predetermined operating points depending on the predetermined electrical power parameter. The operating point can be selected depending on the electrical power parameter using a table or by evaluating a mathematical function of the electrical power parameter. The control or regulating device preferably sets the operating point selected depending on the electrical power parameter as the setpoint for controlling or regulating the fuel cell device. The control or regulating device preferably sets the at least one operating parameter to achieve the selected operating point.

[0011] The inventive design advantageously allows for a controlled response to a change in the electrical power drawn by the fuel cell device. Advantageously, the risk of maintaining an operating point that is unfavorable for a given electrical power parameter can be minimized. In particular, the risk of overheating of the fuel cell device, in particular the electrochemical conversion unit, can be minimized.

[0012] It is further proposed that, in at least one method step of the method, the operating point is determined as a function of a spatial temperature profile of the fuel cell device. The spatial temperature profile preferably comprises a temperature profile through the electrochemical conversion unit, in particular from a fluid inlet to a fluid outlet of the electrochemical conversion unit. The fluid inlet can be provided for admitting the fuel and the fluid outlet for discharging the fuel-poor exhaust gas, or the fluid inlet is provided for admitting the oxygen-containing fluid and the fluid outlet is provided for discharging the oxygen-poor exhaust gas. The spatial temperature profile is preferably determined, in particular recorded or calculated, outside of regular operation, in particular during test operation, during maintenance operation and / or by means of a simulation of the fuel cell device.Preferably, possible candidates for the operating point are evaluated on the basis of their respective spatial temperature profile and, if the evaluation is positive, are stored in a memory of the control or regulating device. Preferably, a candidate for an operating point is only evaluated positively if the associated spatial temperature profile runs exclusively below and / or at a permissible temperature maximum of the electrochemical conversion unit. Preferably, the spatial temperature profile of a candidate for the operating point is checked with regard to at least one condition which is different from the permissible temperature maximum, for example with regard to a relationship to a further temperature reference, a maximum or minimum gradient of the temperature profile, a duration of a maximum of the spatial temperature profile or the like.Preferably, at least one operating point is determined for at least two different values, in particular for several permissible values, preferably for the majority of all permissible values, in particular for all permissible values, of the electrical power parameter and stored in the memory of the control or regulating device, in particular together with the respective value of the electrical power parameter. The configuration according to the invention advantageously allows the effect of an interaction between the operating point and the electrical power parameter on the fuel cell device, in particular on the electrochemical conversion unit, to be taken into account when selecting the operating point.

[0013] It is further proposed that the spatial temperature profile lies at least substantially exclusively below and / or at a nominal temperature profile of the fuel cell device at a nominal operating point for providing a nominal value of the electrical performance parameter. The nominal temperature profile is preferably a spatial temperature profile of an operating point, which is determined in particular as described in the previous paragraph and is referred to as the nominal operating point for differentiation. The nominal temperature profile lies in particular exclusively below and / or at the permissible maximum temperature. Preferably, the nominal temperature profile is used as a temperature reference for evaluating a respective spatial temperature profile of candidate operating points which are intended to provide a lower value of the electrical performance parameter than the nominal value.The term "essentially exclusively below and / or at the nominal value temperature profile" should be understood in particular to mean that the totality of all points of a spatial temperature profile at which this spatial temperature profile has a higher temperature than the nominal value temperature profile is less than 20%, preferably less than 10%, particularly preferably less than 5%, extremely preferably less than 1% of a maximum spatial extent of the electrochemical conversion unit along a line or along a flow direction of the fuel or the oxygen-containing fluid, from the fluid inlet to the fluid outlet. Preferably, the spatial temperature profile at each point has at most a temperature that is less than 110%, preferably less than 105%, particularly preferably less than 101%, extremely preferably less than or equal to 100% of a temperature of the nominal value temperature profile at this point.The design according to the invention advantageously minimizes the risk of overheating of the fuel cell device, in particular of the electrochemical conversion unit. In particular, a set of operating points can be defined that can advantageously be safely operated at different values ​​of the electrical performance parameter. In particular, an advantageously rapid change in the electrical performance parameter can be permitted by using the defined set of operating points.

[0014] It is further proposed that, in at least one method step of the method, the spatial temperature profile of the fuel cell device is detected by a sensor unit of the fuel cell device. Preferably, the spatial temperature profile of a candidate for the operating point is detected by means of the sensor unit. The sensor unit preferably comprises at least one sensor element for detecting a temperature of the electrochemical conversion unit. Preferably, the sensor unit comprises a plurality of sensor elements for detecting temperatures at different points of the electrochemical conversion unit. The at least one sensor element can be arranged in or on the electrochemical conversion unit. The at least one sensor element is preferably designed as a thermocouple.By means of the configuration according to the invention, the temperature profile can advantageously be recorded precisely and, in particular, the operating point dependent on the temperature profile can advantageously be specified precisely.

[0015] It is further proposed that the operating point be optimized with respect to the efficiency of the fuel cell device, given a given electrical performance parameter and a temperature restriction of the fuel cell device. The temperature restriction is preferably a comparison of the spatial temperature profile of a candidate for the operating point with the nominal temperature profile. Typically, several candidates for an operating point can be identified that are suitable for providing a given value of the electrical performance parameter and whose spatial temperature profile satisfies the temperature restriction.Preferably, from all candidates for the operating point at a given value of the electrical power parameter, the one that has the greatest possible efficiency, particularly with respect to a ratio of the electrical power provided by the fuel cell device to the chemical power of the fuel, is selected and stored in the memory of the control or regulating device, subject to temperature constraints. The inventive design assigns an advantageously high spatial temperature profile to the operating point, which is advantageously similar to the nominal temperature profile. As a result, temperature changes in the fuel cell device, particularly in the electrochemical conversion unit, can be advantageously kept low when the electrical power parameter changes.In particular, thermomechanical stresses and the risk of wear of the fuel cell device, in particular of the electrochemical conversion unit, can advantageously be kept low.

[0016] It is further proposed that in at least one method step of the method the electrical power parameter is changed by more than 15% / min in order to switch between two active operating states. Percentages of the electrical power parameter preferably relate to the nominal value of the electrical power parameter. The control or regulating device preferably changes the electrical power parameter at a maximum rate of change of more than 15% / min. In particular, the control or regulating device changes the electrical power parameter at a maximum rate of change of more than 25% / min, preferably by more than 35% / min, more preferably by more than 45% / min, particularly preferably by more than 50% / min. In at least one embodiment, the control or regulating device changes the electrical power parameter at a maximum rate of change of more than 100% / min, in particular more than 200% / min, particularly preferably more than 300% / min.A change in the electrical power parameter can be carried out by the control or regulating device continuously or in discrete steps. The rate of change of the electrical power parameter is preferably to be understood as average rates of change, which are formed, for example, by a total value of the change, in particular a difference between the target value and the starting value, a summation or integration over a time-dependent instantaneous value or the like, of the electrical power parameter divided by a total duration required to achieve the change. Due to the configuration according to the invention, the electrical power parameter can advantageously be quickly adapted to the electrical power drawn from the fuel cell device. Furthermore, a capacity, required installation space and / or costs of the energy buffer can advantageously be kept low.

[0017] It is further proposed that a supercapacitor of the fuel cell device be used as an electrical energy buffer during a load change. Alternatively or additionally, an accumulator is used as an energy buffer. The inventive design allows the use of a fuel cell device that is advantageously compact and cost-effective to manufacture.

[0018] Furthermore, a control or regulating device for a fuel cell device for carrying out a method according to the invention is proposed. The control or regulating device is provided for controlling or regulating the fuel cell device. The control or regulating device is preferably a unit with at least one control electronics unit. The term "control electronics" should be understood in particular as a unit with a processor unit and with a memory as well as with an operating program stored in the memory. The configuration according to the invention makes it possible to provide a control or regulating device with which the operation of a fuel cell device can be adapted advantageously reliably and advantageously quickly to a change in electrical power consumption.

[0019] Furthermore, a fuel cell device with at least one electrochemical conversion unit and with at least one control or regulating device according to the invention is proposed. The electrochemical conversion unit preferably comprises at least one fuel cell, preferably a stack of, in particular structurally identical, fuel cells, or a composite of several stacks of, in particular structurally identical, fuel cells. The at least one fuel cell is preferably designed as a high-temperature fuel cell, in particular a solid oxide fuel cell or a molten carbonate fuel cell. Alternatively, the fuel cell is a phosphoric acid fuel cell, a direct methanol fuel cell, or a polymer electrolyte membrane fuel cell.The fuel cell device preferably comprises at least one fuel feed unit or a fuel shut-off device for adjusting a flow rate of fresh fuel to the electrochemical conversion unit. The fuel feed unit or the fuel shut-off device is preferably controlled by the control or regulating device to adjust the operating parameter. The fuel cell device preferably comprises at least one electrical actuating unit, in particular an inverter or an adjustable resistor, for adjusting the electrical power parameter. The electrical actuating unit is preferably controlled by the control or regulating device to adjust the electrical power parameter. The fuel cell device preferably comprises the sensor unit for detecting the spatial temperature profile in the electrochemical conversion unit.The fuel cell device preferably comprises the electrical energy buffer, in particular a supercapacitor and / or an accumulator, for temporarily decoupling the electrical power parameter from the electrical power required by a load. The fuel cell device optionally comprises an afterburner for utilizing fuel residues in the fuel-lean exhaust gas, a desulfurizer and / or a reformer for processing the fuel, at least one heat exchanger for transferring heat from at least one of the exhaust gases, in particular an afterburner exhaust gas of the afterburner, to the oxygen-containing fluid and / or the fuel, and / or a recirculation line for feeding the fuel-lean exhaust gas back into the fuel. The design according to the invention makes it possible to provide a fuel cell device that can be switched on advantageously safely and quickly.

[0020] The method according to the invention, the control or regulating device according to the invention, and / or the fuel cell device according to the invention should not be limited to the application and embodiment described above. In particular, the method according to the invention, the control or regulating device according to the invention, and / or the fuel cell device according to the invention can have a number of individual elements, components, units, and method steps that differs from the number stated herein in order to fulfill a function described herein. Furthermore, in the value ranges specified in this disclosure, values ​​within the stated limits are also to be considered disclosed and can be used arbitrarily.

[0021] Drawings

[0022] Further advantages will become apparent from the following description of the drawings. The drawings illustrate an exemplary embodiment of the invention. The drawings, the description, and the claims contain numerous features in combination. Those skilled in the art will also expediently consider the features individually and combine them into useful further combinations.

[0023] They show:

[0024] Fig. 1 is a schematic representation of a fuel cell device according to the invention with a control or regulating device according to the invention, Fig. 2 is a schematic flow diagram of a method according to the invention and

[0025] Fig. 3 is a schematic diagram of various temperature profiles of the fuel cell device.

[0026] Description of the embodiment

[0027] Figure 1 shows a fuel cell device 12. The fuel cell device 12 preferably comprises at least one electrochemical conversion unit 30. The electrochemical conversion unit 30 comprises at least one fuel cell, preferably a plurality of fuel cells, which are particularly preferably arranged in at least one stack. For the sake of clarity, the electrochemical conversion unit 30 is functionally illustrated here as a single fuel cell. Particularly preferably, the at least one fuel cell, in particular all fuel cells of the electrochemical conversion unit 30, are designed as solid oxide fuel cells (SOFC). The electrochemical conversion unit 30, in particular each fuel cell of the electrochemical conversion unit 30, comprises at least one oxygen electrode 32 and at least one fuel electrode 34. The oxygen electrode 32 is provided for direct contact with an oxygen-containing fluid.The oxygen electrode 32 preferably emits an oxygen-poor exhaust gas. The fuel electrode 34 is designed for direct contact with a fuel. The fuel electrode 34 preferably emits a fuel-poor exhaust gas.

[0028] The fuel cell device 12 preferably comprises an electrical control unit 36, in particular an inverter, for adjusting an electrical power parameter 14 (see Fig. 2) of the fuel cell device 12, in particular an electrical current provided by the electrochemical conversion unit 30. The electrical control unit 36 ​​is preferably electrically connected to the oxygen electrode 32 and the fuel electrode 34. The fuel cell device 12 preferably comprises an electrical energy buffer 26. The electrical energy buffer 26 is preferably provided to temporarily maintain the electrical power parameter 14, in particular until an operating point change of the fuel cell device 12, independently of the electrical power consumed or requested by a load 38.The capacity of the electrical energy buffer 26 is preferably designed depending on the speed at which the electrical performance parameter 14 can be changed without risking damage and / or premature aging of the electrochemical conversion unit 30. In a particularly preferred embodiment, the electrical energy buffer 26 is a supercapacitor. Alternatively, the electrical energy buffer 26 is designed as an accumulator.

[0029] The fuel cell device 12 preferably comprises an oxygen delivery unit 40, in particular a fan, a blower, or a compressor, for delivering the oxygen-containing fluid to the oxygen electrode 32. The oxygen-containing fluid is particularly preferably ambient air, which is drawn in by the oxygen delivery unit 40. Alternatively, the oxygen-containing fluid is an industrial gas with a defined oxygen content. The oxygen delivery unit 40 is preferably arranged upstream of the oxygen electrode 32 with respect to the oxygen-containing fluid.

[0030] The fuel cell device 12 preferably comprises a fuel delivery unit 42, in particular a fan, a blower, or a compressor, for conveying the fuel to the fuel electrode 34. The fuel is preferably hydrogen and / or natural gas. Alternatively, the fuel comprises at least one hydrocarbon as a pure substance or as a mixture and / or ammonia. The fuel delivery unit 42 is arranged upstream of the fuel electrode 34 with respect to the fuel. The electrochemical conversion unit 30 is preferably provided to convert the fuel into the fuel-lean exhaust gas by supplying oxygen from the oxygen-containing fluid to provide the electrical power parameter 14.

[0031] Optionally, the fuel cell device 12 comprises a desulfurizer 44. The desulfurizer 44 is preferably arranged downstream of the fuel feed unit 42 and upstream of the electrochemical conversion unit 30 with respect to the fuel. Optionally, the fuel cell device 12 comprises a reformer 46 for reforming the fuel. The reformer 46 is preferably arranged downstream of the fuel feed unit 42 with respect to the fuel, in particular downstream of the desulfurizer 44, and upstream of the electrochemical conversion unit 30.

[0032] Preferably, the fuel cell device 12 comprises a recirculation line 48 and a recirculation conveying unit 50, in particular a fan, a blower or a compressor, arranged in or on the recirculation line 48, for recirculating the fuel-poor exhaust gas exiting from the fuel electrode 34 into the fuel upstream of the fuel electrode 34. A feed opening of the recirculation line 48 is preferably arranged upstream of the reformer 46 and downstream of the desulfurizer 44 with respect to the fuel.

[0033] The fuel cell device 12 preferably comprises an afterburner 52 for converting fuel residues contained in the fuel-lean exhaust gas. The afterburner 52 is preferably arranged downstream of the fuel electrode 34 with respect to the fuel-lean exhaust gas, and in particular downstream of a branch into the recirculation line 48. The afterburner 52 is preferably arranged downstream of the oxygen electrode 32 with respect to the oxygen-poor exhaust gas. The fuel cell device 12 preferably comprises at least one heat exchanger 54, 56 for transferring heat from an afterburner exhaust gas of the afterburner 52 exiting the afterburner 52 to the oxygen-containing fluid or to the fuel upstream of the electrochemical conversion unit 30.

[0034] The fuel cell device 12 comprises at least one control or regulating device 28. The control or regulating device 28 is preferably provided for controlling the oxygen delivery unit 40, the fuel delivery unit 42, and / or the recirculation delivery unit 50 in order to adjust a flow rate of the oxygen-containing fluid, the fuel, or a recirculated portion of the fuel-lean exhaust gas. The control or regulating device 28 is preferably provided for controlling the electrical actuating unit 36 ​​in order to adjust the electrical power parameter 14. The control or regulating device 28 is provided for carrying out a method 10, which is explained in more detail in the following Figure 2. The fuel cell device 12 optionally comprises at least one sensor unit 22 for detecting a spatial temperature profile 16, 18, 20 (see Figure 3) within the electrochemical conversion unit 30.The sensor unit 22 preferably comprises at least one sensor element, preferably a plurality of sensor elements, which is / are arranged in or on the electrochemical conversion unit 30. The at least one sensor element is preferably designed as a thermocouple. In an advantageously simple embodiment of the detection of the spatial temperature profile 16, 18, 20, the sensor unit 22 detects a temperature of the electrochemical conversion unit 30 at least at a fluid inlet 68 and at a fluid outlet 70 of the electrochemical conversion unit 30, and the control or regulating device 28 or an external computer system interpolates the temperature profile 16, 18, 20 between these points, in particular linearly.

[0035] Figure 2 shows the method 10 for operating the fuel cell device 12. The method 10 preferably includes a nominal operating point determination 58. In the nominal operating point determination 58, a nominal operating point is determined at which the fuel cell device 12 can provide a nominal value of the electrical performance parameter 14. Preferably, a nominal temperature profile 16 (see Fig. 3) of the electrochemical conversion unit 30 is determined at the nominal operating point. The nominal temperature profile 16 is detected, for example, by the sensor unit 22; alternatively, the nominal temperature profile 16 is determined by simulation.

[0036] The method 10 preferably comprises a further operating point determination 60. In the further operating point determination 60, at least one operating point is preferably determined that is suitable for providing a lower value of the electrical performance parameter 14. The operating point is determined as a function of a spatial temperature profile 18, 20 (cf. Fig. 3) of the electrochemical conversion unit 30 at this operating point. The spatial temperature profile 18, 20 is detected, for example, by the sensor unit 22; alternatively, the nominal temperature profile 16 is determined by simulation. Candidates for the operating point are preferably evaluated as a function of their respective spatial temperature profile 18, 20.An operating point is preferably evaluated positively if the spatial temperature profile 18, 20 of the operating point lies at least substantially exclusively below and / or at the nominal value temperature profile 16. If a temperature profile 76 (cf. Fig. 3) of a candidate for the operating point lies partially or completely above the nominal value temperature profile 16, the associated candidate for the operating point is preferably rejected. Of all the positively evaluated candidates, those are preferably preferred which have a lower maximum temperature value, in particular at the fluid outlet 70. Optionally, candidates whose temperature profile at the fluid outlet 70 has a temperature above a temperature setpoint are rejected. The temperature setpoint is preferably lower than a permissible maximum temperature 66 of the electrochemical conversion unit 30 (cf. Fig. 3). The temperature setpoint is preferably dependent on the electrical power parameter.Preferably, the temperature setpoint for operating points different from the nominal operating point is lower than for the nominal operating point. Optionally, the temperature setpoint decreases monotonically with the electrical power to be delivered by the operating point. From all positively evaluated candidates of the operating point for a given value of the electrical power parameter 14, the candidate that exhibits the greatest possible efficiency of the fuel cell device 12 is preferably selected. Preferably, for several values ​​of the electrical power parameter 14, at least one operating point is determined in each case depending on their spatial temperature profiles 18, 20 and stored in a memory of the control or regulating device 28.

[0037] The method 10 preferably comprises an operating point selection 62. During a load change or when the fuel cell device 12 is started, the control or regulating device 28 selects an operating point to be set, in particular suitable temperature boundary conditions, from the operating points stored in the memory of the control or regulating device 28 depending on a predetermined value of the electrical power parameter 14 of the fuel cell device 12.

[0038] The method 10 preferably comprises a control or regulating step 64. In the control or regulating step 64, the control or regulating device 28 adapts at least one operating parameter of the fuel cell device 12 in order to reach the operating point of the fuel cell device 12. The control or regulating device 28 preferably controls the oxygen delivery unit 40, the fuel delivery unit 42 and / or the recirculation delivery unit 50 in order to adapt a flow parameter as an operating parameter. The control or regulating device 28 preferably controls the electrical actuating unit 36 ​​in order to adapt an actual value of the electrical power parameter 14 to the predetermined value of the electrical power parameter 14. The electrical power parameter 14 is changed by the control or regulating device 28 by more than 15% / min in order to switch between two active operating states with different operating points.

[0039] Figure 3 shows a diagram in which the temperature 24 of the electrochemical conversion unit 30, in particular of the fuel electrode 34, is plotted over a spatial extent 78 of the electrochemical conversion unit 30, in particular of the fuel electrode 34. The spatial extent 78 considered in the method 10 preferably extends from the fluid inlet 68 of the electrochemical conversion unit 30 to the fluid outlet 70 of the electrochemical conversion unit 30. The spatial extent 78 considered in the method 10 preferably includes a spatial extent of the fluid inlet 68 and / or the fluid outlet 70.Between the fluid inlet 68 and an active zone of the fuel electrode 34 and / or between the active zone of the fuel electrode 34 and the fluid outlet 70, the electrochemical conversion unit 30 optionally has a transition region 72, 74, for example, for distributing the fuel among multiple fuel cells, for avoiding direct physical contact of the fuel cells with a housing of the electrochemical conversion unit 30 comprising the fluid inlet 68 and / or fluid outlet 70, or the like. The diagram shows, by way of example, the nominal temperature profile 16, the temperature profile 18 of an operating point for an average value of the electrical performance parameter 14, the temperature profile 20 of an operating point for an average value of the electrical performance parameter 14, and a temperature profile 76 of an impermissible operating point.The temperature profile 76 of the impermissible operating point is preferably not evaluated as positive, since a change to the impermissible operating point is likely to cause the temperature to overshoot to values ​​above the maximum temperature 66 at and / or in one of the transition regions 74. The temperature profile 76 of the impermissible operating point is optionally not evaluated as positive, since it lies above the nominal temperature profile 16, particularly in a region around the fluid inlet 68. The temperature profiles 16, 18, 20, 76 all run entirely below and / or partially at a permissible maximum temperature 66 of the electrochemical conversion unit 30.

Claims

Claims 1 . Method for operating a fuel cell device, wherein in at least one method step at least one operating parameter of the fuel cell device is adjusted in order to achieve a predetermined operating point of the fuel cell device, characterized in that in at least one method step the operating point to be set is determined as a function of an electrical power parameter (14) of the fuel cell device.

2. Method according to claim 1, characterized in that in at least one method step the operating point is determined as a function of a spatial temperature profile (16, 18, 20) of the fuel cell device.

3. Method according to claim 2, characterized in that the spatial temperature profile (18, 20) lies at least substantially exclusively below and / or at a nominal temperature profile (16) of the fuel cell device at a nominal operating point for providing a nominal value of the electrical power parameter (14).

4. Method according to claim 2 or 3, characterized in that in at least one method step the spatial temperature profile (16, 18, 20) of the fuel cell device is detected by a sensor unit (22) of the fuel cell device.

5. Method according to one of the preceding claims, characterized in that the operating point is optimized with respect to an efficiency of the fuel cell device at a predetermined electrical power parameter (14) and at a limitation of a temperature (24) of the fuel cell device.

6. Method according to one of the preceding claims, characterized in that in at least one method step the electrical power parameter (14) is changed by more than 15% / min in order to switch between two active operating states.

7. Method according to one of the preceding claims, characterized in that, during a load change, a supercapacitor of the fuel cell device is used as an electrical energy buffer (26).

8. Control or regulating device for a fuel cell device for carrying out a method according to one of the preceding claims.

9. Fuel cell device with at least one electrochemical conversion unit (30) and with at least one control or regulating device according to claim 8.

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