Method for filling a hydrogen tank of a motor vehicle having a fuel cell drive and motor vehicle

Abstract

The invention relates to a method for filling a hydrogen tank (2) of a motor vehicle (1) having a fuel cell drive, wherein the method has the following steps: (a) determining a first operating time point at which the motor vehicle (1) should be put into operation and a first operating location at which the motor vehicle (1) should be put into operation, (b) determining a predicted maximum ambient temperature (T u,max ) at the first operating location at the first operating time point, and (c) filling the hydrogen tank with hydrogen (3) until a tank pressure (p) in the hydrogen tank (2) reaches a maximum tank pressure (P max ) which is permissible at a tank temperature (T), wherein for the tank temperature (T) applies: tank temperature (T) = [maximum ambient temperature (T u,max ), maximum ambient temperature (T u,max ) + 10 K]. Furthermore, the invention relates to a motor vehicle (1) having a hydrogen tank (2), a fuel cell drive and a control system (5) for controlling the filling of the hydrogen tank (2), wherein the control system (5) is designed to carry out the method.

Description

BACKGROUND

[0001] The filling quantity of the hydrogen tank depends on the maximum tank pressure allowed in the hydrogen tank. The tank pressure, in turn, depends on the temperature of the hydrogen in the hydrogen tank. Thus, when the ambient temperature rises, the tank pressure increases.

[0002] Therefore, a motor vehicle having a hydrogen tank is usually not filled with the desired high filling quantity, for example the maximum filling quantity for the current ambient temperature, because the tank pressure would exceed the maximum allowed tank pressure when the temperature of the hydrogen rises, for example due to a rise in the ambient temperature.

[0003] Correspondingly, it is known to fill the hydrogen tank only to such an extent that the tank pressure itself remains below the maximum allowed tank pressure even at very high ambient temperatures. SUMMARY

[0004] According to a first aspect, the invention relates to a method for filling a hydrogen tank of a motor vehicle having a fuel cell drive, wherein the method has the following steps: (a) determining a first operating time point at which the motor vehicle is put into operation and a first operating location at which the motor vehicle is put into operation, (b) ascertaining a maximum ambient temperature predicted at the first operating time point at the first operating location, and (c) filling the hydrogen tank with hydrogen until the tank pressure in the hydrogen tank reaches the maximum allowed tank pressure at a tank temperature, wherein for the tank temperature it applies: tank temperature = [maximum ambient temperature, maximum ambient temperature + 10 K].

[0005] In particular, for the tank temperature it can apply: tank temperature = [maximum ambient temperature, maximum ambient temperature + 5 K] or tank temperature = [maximum ambient temperature, maximum ambient temperature + 2 K]. In other words, the hydrogen tank is filled only to such an extent that the tank temperature corresponds at least to the maximum ambient temperature and at most to the maximum ambient temperature plus 10 K, in particular plus 5 K and furthermore in particular plus 2 K.

[0006] According to this, by means of the method according to the invention it is possible to maximize the filling quantity of the hydrogen tank at the time of filling before the motor vehicle is later planned to be put into operation. By means of the method according to the invention, the hydrogen tank is thus filled to the maximum extent in consideration of the conditions at the later time of putting into operation. The range is thereby increased and the number of required filling processes is reduced.

[0007] For example, according to the method according to the invention, the motor vehicle can be filled in the evening or at night, wherein the first operating time is in the morning of the following day. Correspondingly, the night temperature is low and the hydrogen tank is not allowed to be filled to the maximum extent because otherwise the tank pressure would exceed the maximum allowed tank pressure at the temperature higher than at night in the morning of the following day.

[0008] However, with the aid of the predicted maximum ambient temperature it is not necessary to take into account an impossible and excessively high safety factor, i.e. a possible excessively high ambient temperature, in order to avoid the tank pressure exceeding the maximum permissible tank pressure.

[0009] Rather, it is sufficient to predict the ambient temperature at the first operating site, i.e. the place of use, and at the first operating time point, i.e. the time of use. Here, the safety factor can be 10 K, in particular 5 K or 2 K, higher than the predicted maximum ambient temperature.

[0010] The predicted maximum ambient temperature can be provided, for example, with the aid of known weather data or weather forecasts. Weather data or weather forecasts can be obtained, for example, via the Internet. Alternatively or additionally, ambient temperatures measured on the motor vehicle at this time and at this place a few days previously can be taken into account.

[0011] The first operating time point and the first operating site can be predefined manually, for example, by the vehicle user. This can be achieved with the aid of an input on the motor vehicle. Alternatively or additionally, this can be achieved with the aid of an interface of the motor vehicle to an external device of the vehicle user, for example a smartphone. The smartphone can have a calendar which can be read by the motor vehicle. Correspondingly, the motor vehicle can be set up to provide the first operating time point and the first operating site automatically on the basis of the data of the external device, for example the calendar of the smartphone. The first operating site can also be determined here with the aid of GPS data. Additionally or alternatively, the first operating time point and the first operating site can be predefined fixedly by the motor vehicle. Furthermore, it can be provided that the first operating time point and the first operating site are determined by the motor vehicle on the basis of the use profile of the motor vehicle. In other words, it can be provided that a learning algorithm is used by the motor vehicle with the aid of which the motor vehicle learns and determines the operating time point and the operating site of the vehicle user.

[0012] The maximum permissible tank pressure depends on the hydrogen tank. For example, the maximum permissible tank pressure can be 875 bar.

[0013] Preferably, the tank temperature corresponds to or substantially corresponds to the predicted maximum ambient temperature. Substantially corresponds to the predicted maximum ambient temperature includes a technical deviation of at most 1 K and / or a slight deviation. Thereby, the hydrogen tank can be filled to the greatest extent possible taking into account the predicted maximum ambient temperature, thus maximizing the range of the motor vehicle having a fuel cell drive.

[0014] Furthermore preferably, the method also has the following step: if it is determined that the tank pressure will exceed the maximum permissible tank pressure, the hydrogen tank is relieved of pressure. Thereby, a solution is provided for the scenario in which the tank pressure will exceed the maximum permissible tank pressure contrary to expectations. Damage to the hydrogen tank can thus be avoided.

[0015] For example, such a scenario can be that the weather and thus the actual ambient temperature at the first point in time of operation or before and / or at the first point of operation changes contrary to the prediction. Another exemplary scenario can be a shift or a maneuver of the scheduled point in time of operation. Then, the ambient temperature can rise above the predicted maximum ambient temperature and can also cause the tank pressure to rise above the allowed maximum tank pressure.

[0016] Here, preferably, it is determined whether the ambient temperature will exceed the tank temperature before the motor vehicle is put into operation in order to determine whether the tank pressure will exceed the allowed maximum tank pressure. Alternatively or additionally, the tank pressure can be actively monitored in order to determine whether an exceedance of the allowed maximum tank pressure is to be expected. Such a determination can be achieved, for example, by exceeding a limit of a predetermined tank pressure which is just below the allowed maximum tank pressure. Both determinations can react here to a possible change, for example the weather, or to an exceedance of the first point in time of operation without starting the motor vehicle.

[0017] Here, it can be that the pressure is unloaded by means of a fuel cell drive of the motor vehicle being put into operation in the case of the motor vehicle not moving. The motor vehicle can thus be adapted, for example, for a later operation. Alternatively or additionally, at least one seat heating device can be operated, the windshield and / or the rearview mirror can be defrosted and / or a software update can be installed. In this regard, the operation of the fuel cell drive with hydrogen from the hydrogen tank is included in the operation of the motor vehicle or the putting into operation of the motor vehicle. In order that the excess charged hydrogen can be efficiently utilized contrary to the prediction without exceeding the allowed maximum tank pressure.

[0018] Especially, here, preferably, the pressure unloading is achieved by means of the fuel cell drive being put into operation in order to charge the battery of the motor vehicle. Correspondingly, the excess charged hydrogen can be used in a simple and advantageous manner to reduce the tank pressure and to charge the battery of the motor vehicle.

[0019] Alternatively or additionally, it is preferred that the pressure unloading is achieved by means of the hydrogen gas being released from the hydrogen tank. For this purpose, the venting valve of the hydrogen tank can be used. The released hydrogen gas can be diluted with an air mass flow. This variant of the pressure unloading is particularly simple and thus does not require any complex control and programming.

[0020] Further alternatively or additionally preferably, the motor vehicle is an autonomously driving motor vehicle and the pressure relief is achieved by autonomously driving the motor vehicle. These drives can be empty drives and / or driving service drives. In the case of empty drives, the motor vehicle is driven without passengers. In the case of driving service drives, passengers are transported with the motor vehicle for a fee. To this end, the motor vehicle can have an interface for coupling with a driving service app, which can be installed on a smartphone, for example. The driving service app can be located on a smartphone of a passenger, for example, by means of which the passenger requests a driving service with the motor vehicle, which otherwise has too high a tank pressure. Correspondingly, an economic utilization of the overfilled hydrogen can be achieved.

[0021] Especially, when the motor vehicle is an autonomously driving motor vehicle, the hydrogen tank can be filled autonomously, in particular. In this case, the filling takes place completely automatically. The vehicle user of the autonomously driving motor vehicle then gives, for example, only when he wants to leave the house, in order for the motor vehicle to fill the hydrogen tank to the maximum automatically.

[0022] Furthermore preferably, a predicted second operating time point is determined, at which the motor vehicle is to be put into operation after the first operating time point, wherein a maximum ambient temperature is determined at the second operating time point, for example at the first operating site. Preferably, here a predicted second operating time point can be determined, at which the motor vehicle is to be put into operation after the first operating time point, and, if necessary, a second operating site, at which the motor vehicle is to be put into operation at the second operating time point, wherein a maximum ambient temperature is determined at the second operating site at the second operating time point. This can be meaningful if only a short run is planned or carried out at the first operating time point, at which the motor vehicle is started for the first time, during which only a small amount of hydrogen from the hydrogen tank is consumed and the second operating time point is significantly later, so that the temperature of the hydrogen can be higher at this second operating time point, so that the tank pressure can exceed the maximum permissible tank pressure. To this end, it can be provided that it is determined how much hydrogen will be consumed by the motor vehicle at the first operating time point of the first run.

[0023] Finally, it is also preferred that the hydrogen tank is filled with hydrogen in two time intervals alternating with one another, wherein in the first time interval hydrogen flows into the hydrogen tank until the hydrogen in the hydrogen tank reaches a maximum permissible temperature, and in the second time interval no hydrogen flows into the hydrogen tank, so that the hydrogen with the maximum permissible temperature in the hydrogen tank can cool down. The maximum permissible temperature can be in the range of 80 to 90°C, in particular 85°C, for example.

[0024] The first and second time intervals are thus alternating. Thereby it can be avoided that the allowed maximum temperature is exceeded. The second time interval can be accelerated by an active cooling of the hydrogen in the hydrogen tank. Alternatively and / or additionally, the hydrogen can be pre-cooled before flowing to the hydrogen tank, for example to a range of -20°C to -50°C, in particular to -40°C. In case of a respective pre-cooling, the intervalled filling can be cancelled if necessary.

[0025] According to a second aspect, the invention relates to a motor vehicle having a hydrogen tank, a fuel cell drive and a control system for controlling a filling of the hydrogen tank, wherein the control system is configured to carry out the method according to the first aspect of the invention. BRIEF DESCRIPTION OF DRAWINGS

[0026] The invention is explained in more detail below with reference to the drawings. All features derived from the claims, the description or the drawings, including structural details, are important for the invention, both individually and in any arbitrary combination. The drawings show schematically:

[0027] Figure 1 a perspective side view of an embodiment of a motor vehicle according to the invention during a filling, and

[0028] Figure 2 a graph of a method for filling a motor vehicle according to the invention. Figure 1

[0029] Elements having the same function and the same mode of action have the same reference signs in Figure 1 and Figure 2 , respectively. DETAILED DESCRIPTION

[0030] Figure 1 a perspective side view of an embodiment of a motor vehicle 1 according to the invention during a filling at a hydrogen filling station 6.

[0031] The hydrogen filling station 6 is connected to the motor vehicle 1 by means of a line and a filling gun. The hydrogen tank 2 of the motor vehicle 1 is filled with hydrogen 3 from the hydrogen filling station 6.

[0032] Furthermore, the motor vehicle 1 has a battery 4 and a control system 5. The battery 4 can be charged by means of the fuel cell drive and the hydrogen 3 from the hydrogen tank 2. The control system 5 is used to control the filling process.

[0033] Figure 2 a graph of a method for filling a motor vehicle 1 according to the invention. Figure 1

[0034] ​​The diagram shows the flow rate S of hydrogen 3 into the hydrogen tank 2 or in other words the filling of the hydrogen tank 2 with hydrogen 3, the temperature T of the hydrogen 3 in the hydrogen tank 2 and the tank pressure p of the hydrogen 3 in the hydrogen tank 2. Here, the time t of the filling process is plotted on the abscissa. The temperature T and the tank pressure p of the hydrogen are plotted on the ordinate.

[0035] In a first time interval I, hydrogen 3 is supplied to the hydrogen tank 2 by means of the flow rate S.1. Here, the tank pressure p and the temperature T of the hydrogen 3 increase, and when or before the temperature T reaches the permissible maximum temperature T max , the flow rate S.1 is interrupted and the filling process is paused.

[0036] This is followed by a second time interval II in which a waiting time t is waited for in order to allow the hydrogen 3 to cool. The cooling can be actively assisted.

[0037] Immediately after the second time interval II, there is again a first time interval I in which hydrogen 3 is supplied to the hydrogen tank 2 by means of the flow S.2 until the permissible maximum temperature T max is reached. This is again followed by a second time interval II.

[0038] This interval-based filling process continues until the tank pressure p is reached which corresponds to the permissible maximum tank pressure p u,max at the predicted maximum ambient temperature T max . Here, the predicted maximum ambient temperature T u,max is the temperature which prevails at the predicted first point in time of operation and at the predicted first point of location of operation.

[0039] An exemplary application scenario is explained in more detail below. The ambient temperature at 1 a.m. in the night is T u = 10°C. At this point in time, the motor vehicle 1 is to be filled. The motor vehicle 1 is then to be put into operation at 8 a.m. the following day.

[0040] In order to determine how much hydrogen 3 can be filled into the hydrogen tank 2, the maximum ambient temperature T u,max at 8 a.m. is predicted on the basis of a weather forecast for the point of location of operation of the motor vehicle 1. In the present example, T u,max = 20°C. In correspondence therewith, the hydrogen tank 2 can be filled with hydrogen 3 up to the permissible maximum tank pressure p max of, for example, 875 bar and a tank temperature of 20°C.

[0041] If the vehicle is now not put into operation at 8 a.m. contrary to the plan and it is determined that the ambient temperature T u will rise above the predicted maximum ambient temperature T u,max = 20°C, this will result in the tank pressure rising above the maximum tank pressure P max .

[0042] In order to avoid exceeding the maximum tank pressure p max For example, the motor vehicle 1 can be put into operation in order to charge the battery 4, in order to drive autonomously or in order to release hydrogen 2 from the hydrogen tank 3 by means of the exhaust valve.

Claims

1. A method for filling a hydrogen tank (2) of a motor vehicle (1) having a fuel cell drive, wherein The method has the following steps: (a) determining a first operating point in time at which the motor vehicle (1) should be put into operation and a first operating point in location at which the motor vehicle (1) should be put into operation, (b) determining a maximum ambient temperature (Tmax) predicted at the first operating site at the first operating time point, and u,max ), and (c) filling the hydrogen tank with hydrogen (3) until a tank pressure (p) in the hydrogen tank (2) reaches a maximum tank pressure (p max ) allowed at a tank temperature (T), wherein for the tank temperature (T) applies: tank temperature (T) = [maximum ambient temperature (T u,max , maximum ambient temperature (T u,max ) + 10 K], wherein the method further has the step of: if it is determined that the tank pressure (p) will exceed the allowed maximum tank pressure (P max ), then pressure-unloading the hydrogen tank (2), wherein the ambient temperature (T u ) is determined whether the tank pressure (p) will exceed an allowed maximum tank pressure (p max ) by ascertaining whether the ambient temperature (T u ) will exceed the tank temperature before the motor vehicle is put into operation.

2. The method as claimed in claim 1, characterized in that The tank temperature (T) corresponds to the predicted maximum ambient temperature (T u,max ).

3. The method as claimed in claim 1 or 2, characterized in that The pressure relief is achieved by putting a fuel cell drive into operation in order to charge a battery (4) of the motor vehicle (1).

4. The method as claimed in claim 1 or 2, characterized in that The pressure relief is achieved by releasing hydrogen (3) from the hydrogen tank (2).

5. The method as claimed in claim 1 or 2, characterized in that The motor vehicle (1) is a motor vehicle (1) that drives autonomously, and the pressure relief is achieved by the motor vehicle (1) driving autonomously.

6. The method as claimed in claim 1 or 2, characterized in that determining a predicted second operating time point at which the motor vehicle (1) is to be put into operation immediately after the first operating time point, wherein a maximum ambient temperature (T u,max ) predicted at the second operating time point is ascertained.

7. The method as claimed in claim 1 or 2, characterized in that The hydrogen tank (2) is filled with hydrogen (3) in two time intervals alternating with each other, wherein, in a first time interval, hydrogen (3) flows into the hydrogen tank (2) until the hydrogen (3) in the hydrogen tank (2) reaches an admissible maximum temperature (T max ) and, in a second time interval, no hydrogen (3) flows into the hydrogen tank (2) so that the hydrogen (3) in the hydrogen tank (2) having the admissible maximum temperature (T max ) can cool down.

8. Motor vehicle (1) with a hydrogen tank (2), a fuel cell drive and a control system (5) for controlling the filling of the hydrogen tank (2), wherein The control system (5) is designed to carry out the method as claimed in any one of claims 1 to 7.

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