Method for the predictive operation of a fuel cell or a high-voltage accumulator

Abstract

A method for the predictive operation of a fuel cell or a high-voltage accumulator, involving the steps of: detecting at least one external parameter, the at least one external parameter representing driving behavior data, navigation data and/or environmental data; and adjusting the at least one current desired fuel cell operating parameter on the basis of the at least one external parameter.

Claims

1. A method for predictive operation of a fuel cell of a vehicle by a control unit of the vehicle programmed to execute the method, the method comprising the steps of: detecting at least one external parameter with a vehicle sensor system, wherein the at least one external parameter represents driving behavior information and/or navigation information of the vehicle; predicting, by the control unit, at least one future value of at least one operating parameter of the fuel cell, based on the at least one external parameter, while the fuel cell is currently operated to power the vehicle according to at least one current setpoint for the operating parameter of the fuel cell; and adapting, by the control unit, the current setpoint for the operating parameter of the fuel cell, on the basis of the predicted future value of the operating parameter of the fuel cell.

2. The method as claimed in claim 1, wherein a setpoint operating parameter is the setpoint moisture content of the fuel cell, and the setpoint moisture content is reduced before the end of a journey.

3. The method as claimed in claim 2, wherein the setpoint moisture content and/or a duration of the reduction is adapted to take into account a predicted storage location of the fuel cell and/or the predicted ambient temperature.

4. The method as claimed in claim 1, wherein the setpoint moisture content is adapted to take into account a storage location of the fuel cell.

5. The method as claimed in claim 4, wherein before an end of a journey, the setpoint moisture content of the fuel cell is reduced if it is to be assumed that a frost start or cold start is to follow.

6. The method as claimed in claim 1, wherein a change in the at least one setpoint operating parameter is based on a predicted load range and a dynamic requirement.

7. The method as claimed in claim 1, wherein the fuel cell, and/or a fuel cell system comprising the fuel cell, functions itself as a buffer for moisture and/or cooling capacity for a predictive operating mode of the fuel cell.

8. The method as claimed in claim 7, wherein before predicted operation of the fuel cell in an upper load range for an uphill journey: the setpoint operating temperature of the fuel cell is lowered and/or additional cooling capacity which is not necessary for the instantaneous operation is made available and is buffered in a cooling system of the fuel cell system, and/or additional moisture which is not necessary for the instantaneous operation is introduced into the fuel cell and is buffered in the fuel cell.

9. The method as claimed in claim 1, wherein in the case of predicted operation in an upper load range of the fuel cell: the setpoint temperature of the fuel cell and/or a maximum nitrogen oxide partial pressure at the anode are/is reduced, and/or the setpoint moisture content of the fuel cell and/or the setpoint fuel partial pressure at the anode are/is increased, and/or in the case of predicted operation in a lower load range of the fuel cells the setpoint temperature of the fuel cell and/or the maximum nitrogen oxide partial pressure at the anode are/is increased, and/or the setpoint moisture content of the fuel cell and/or the setpoint fuel partial pressure at the anode are/is reduced.

10. The method as claimed in claim 1, wherein for the predictive operation of the fuel cell various operating modes are provided, wherein at least two operating modes in at least one characteristic curve differ for at least one setpoint operating parameter, and wherein the various operating modes are provided for various load ranges and various dynamic requirements, and wherein an operating mode of the fuel cell is selected as a function of a predicted load range and a predicted dynamic requirement.

11. The method as claimed in claim 1, wherein the at least one predicted operating parameter comprises a predicted load range and a predicted dynamic requirement.

12. The method as claimed in claim 1, wherein the at least one external parameter further presents environmental information.

13. A method for operating a motor vehicle by a control unit of the vehicle programmed to execute the method, wherein the method comprises: detecting at least one external parameter with a vehicle sensor system, wherein the at least one external parameter represents driving behavior information and/or navigation information of the vehicle; predicting, by the control unit, at least one future value of at least one operating parameter of the fuel cell, based on the at least one external parameter, while the fuel cell is currently operated to power the vehicle according to at least one current setpoint for the operating parameter of the fuel cell; and adapting, by the control unit, the current setpoint for the operating parameter of the fuel cell, on the basis of the predicted future value of the operating parameter of the fuel cell.

14. The method as claimed in claim 13, further comprising the step of: adapting a ratio of the setpoint capacity of the fuel cell to the setpoint capacity of a high-voltage accumulator as a function of the at least one external parameter.

15. The method as claimed in claim 14, wherein the ratio of the setpoint capacity of the fuel cell to the setpoint capacity of the high-voltage accumulator is adapted as a function of the operating mode of the fuel cell and/or of the storage location.

16. The method as claimed in claim 13, comprising the step of: reducing consumption and/or switching off at least one energy consumer.

17. The method as claimed in claim 16, wherein an energy consumer is a passenger-compartment air conditioning system of the vehicle, and in the case of predicted operation in an upper load range, a capacity of the passenger-compartment air conditioning can already be reduced or switched off before operation in the upper load range, with the result that more cooling capacity can be fed to the at least one fuel cell.

18. The method as claimed in claim 13, wherein the at least one predicted operating parameter comprises a predicted load range and a predicted dynamic requirement.

19. The method as claimed in claim 13, wherein the at least one external parameter further presents environmental information.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic overview of various operating modes; and

(2) FIG. 2 shows, by way of example, a simplified detail of a multi-dimensional operating characteristic diagram of a fuel cell.

DETAILED DESCRIPTION OF THE DRAWINGS

(3) FIG. 1 shows various operating modes of a fuel cell as a function of the load range and the dynamic requirement made on the fuel cell.

(4) M100 is an operating mode for a lower load range and a lower dynamic requirement such as occur, for example, in the town cycle with a steady driving style. The driver may, for example, also have preselected an environmentally protective ECO mode of the motor vehicle by means of the driving experience switch, in which mode high dynamic requirements for the vehicle are attenuated or prohibited. In this operating mode it is desired that the fuel cell tends to be operated at relatively high temperatures, since the fuel cell operates more efficiently at relatively high temperatures. The temperature characteristic curve therefore tends to exhibit higher temperatures than the temperature characteristic curves of other operating modes. This is possible, since pronounced changes in temperature of the fuel cell are not expected owing to the low dynamic requirements. In addition, the average operating temperature of the fuel cell which results during the continuous operation in the lower load range is sufficiently far away from any temperatures which would be critical for the operation of the fuel cell.

(5) The fuel cell is operated in the lower partial load range at which the nitrogen enrichment is not yet a strong factor. It is therefore permissible to permit comparatively high nitrogen values in this operating mode. In other words, comparatively high characteristic curves are provided for the maximum nitrogen partial pressure in the operating mode M100. The consumption of fuel can therefore be advantageously reduced. The increased recirculation has a positive effect on the water balance of the fuel cell. With respect to the moisture content, a relatively high moisture content is aimed at in the operating mode M100 at which, however, the formation of liquid water in the fuel cell can yet be reliably avoided.

(6) In the operating mode M200, the motor vehicle and the fuel cell are operated continuously in the upper load range. Here, for example a journey on a freeway is assumed. The dynamic requirement is low in this operating mode. For example, the vehicle is always kept at a constant speed with a cruise controller. The operating temperature of the fuel cell is already closer to the maximum temperature of the fuel cell in this load range compared to the operating mode M100. Since there is no risk of pronounced changes in the operating temperature, damage to the fuel cell can also be ruled out in the operating mode M200. The boundary for the maximum nitrogen content in the anode can also be comparatively high in the operating mode M200, which provides the above-mentioned advantages.

(7) M300 denotes an operating mode in which a high dynamic requirement occurs in the lower load range. For example this occurs in the town cycle when the driver adopts a sporty driving style with many load changes. In this mode, for example the water management of the fuel cell may tend to be critical compared to the other operating parameters. The temperature and the nitrogen partial pressure at the anode are generally not critical. The formation of liquid water should be avoided here, for example, by corresponding lambda control, i.e. the control of the supplied quantity of oxidizing agent to the actually required quantity of oxidizing agent. Alternatively or additionally, the operating temperature of the fuel cell can also be increased, as a result of which the moisture content drops.

(8) If the driver drives his motor vehicle on a freeway with many load jumps, (i.e. as sporty driving style) or if such a journey is predicted, the controller M400 changes into the operating mode M400. High operating temperatures usually occur in the upper load range. In addition, changes in temperature are possible owing to load jumps. In the operating mode M400, comparatively low temperature characteristic curves are therefore provided. As it were, comparatively low characteristic curves can be implemented for the maximum nitrogen partial pressure, which can have a positive effect on the capacity of the fuel cell. The moisture content characteristic curve has high values compared to the corresponding characteristic curves of other operating modes. As a result, drying out of the MEA can be at least delayed.

(9) Generally, the controller should be designed to reduce the temperature and/or the moisture content of the fuel cell in the case of a predicted moisture content above a first moisture content threshold value. Conversely, the controller should increase the moisture content if drying out of the fuel cell is predicted, in particular in the operating mode M400.

(10) The operating mode M500 constitutes operation with a medium dynamic requirement in the medium load range. The characteristic curve profiles which are set here are also selected if the operation of the fuel cell cannot be assigned unambiguously to any of the above-mentioned operating modes. These characteristic curves are optimized to the effect that they can be used for all load ranges and all dynamic requests.

(11) FIG. 2 shows a schematic sectional view of the profile of the temperature characteristic curve for various operating modes plotted against the instantaneous capacity. It is possible to differentiate the required instantaneous setpoint capacity, which depends, for example, on the instantaneous positive gradient and the position of the accelerator pedal, from the previously discussed continuous lower, medium and upper load range. A fuel cell which is operated in the upper load range can have a medium instantaneous setpoint capacity, for example for an instance, for example if one truck overtakes another truck on a freeway. For a specific instantaneous capacity Px, for example a low temperature characteristic curve can be provided in the operating mode M400 than in the operating mode M500. As it were, a comparatively high temperature characteristic curve can be provided for the operating mode M100.

(12) The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.