DE102016206495A1 - Motor vehicle and method for operating a motor vehicle - Google Patents

Abstract

The technology disclosed here comprises a motor vehicle and a method for operating a motor vehicle, wherein the motor vehicle has at least one cryogenic pressure vessel, at least one fuel cell and at least one electrical storage device. The method comprises the steps of: 1) determining a future life of the motor vehicle; and 2) changing the state of charge of the storage device as a function of the determined service life of the motor vehicle before the start of the service life.

Description

The technology disclosed herein relates to a motor vehicle and a method for operating a motor vehicle, wherein the motor vehicle has at least one cryogenic pressure vessel, at least one fuel cell and at least one high-voltage storage.

Cryogenic pressure vessels are known in the art. Cryogenic pressure vessels are used, for example, for motor vehicles, in which a pressurized gaseous fuel is stored in the liquid or supercritical state of aggregation. The pressure vessels therefore require extremely good thermal insulation in order to prevent the unwanted heat input into the cryogenically stored medium as much as possible. Therefore, highly effective insulation sheaths (eg vacuum envelopes) are provided. For example, the EP 1 546 601 B1 such a pressure vessel.

Despite good thermal insulation, the stored fuel heats up slowly with a longer service life. At the same time, the pressure in the pressure vessel rises slowly. If a limit pressure is exceeded, the fuel must escape via suitable safety devices in order to avoid damage to the cryogenic pressure vessel, which can also be referred to as blow-off. For this purpose, pressure-operated relief valves are used, which allow a gradual escape of the medium. Downstream of the relief valves, for example, a so-called blow-off management system or boil-off management system (hereinafter BMS) can be used. The term "blowing off" here comprises the outflow of fuel into the environment and, alternatively or additionally, the conversion of the fuel by a chemical reaction, for example in a catalytic converter or in a fuel cell.

The DE 102 021 72 A1 discloses a fuel cell system in which the boil-off gas is supplied to a fuel cell in a phase of non-use of the motor vehicle. The energy converted by the fuel cell system during non-use can be stored in a battery. When the battery is fully charged, the energy produced by the fuel cell during the non-use phase of the motor vehicle must be converted by other electrical loads without meaningfully utilizing this converted energy.

It is an object of the technology disclosed herein to reduce or eliminate the disadvantages of the prior art solutions. In particular, it is an object of the technology disclosed herein to further improve the efficiency of the fuel cell system. Other objects arise from the beneficial effects of the technology disclosed herein. The object (s) is / are solved by the subject matter of claim 1. The dependent claims are preferred embodiments.

The technology disclosed here relates to a method for operating a motor vehicle, wherein the motor vehicle has at least one cryogenic pressure vessel, at least one fuel cell and at least one high-voltage accumulator.

The at least one fuel cell serves to provide the energy for at least one drive machine for locomotion of the motor vehicle. It is preferably a fuel cell with a proton exchange membrane (PEM). As a rule, several fuel cells are combined to form a fuel cell stack or stack.

The cryogenic pressure vessel may store fuel in the liquid or supercritical state. A supercritical state of aggregation is a thermodynamic state of a substance which has a higher temperature and a higher pressure than the critical point. The critical point denotes the thermodynamic state in which the densities of gas and liquid of the substance coincide, that is, it is single-phase. While one end of the vapor pressure curve in a p-T diagram is indicated by the triple point, the critical point represents the other end. For hydrogen, the critical point is 33.18 K and 13.0 bar. A cryogenic pressure vessel is particularly suitable for storing the fuel at temperatures significantly below the operating temperature (meaning the temperature range of the vehicle environment in which the vehicle is to be operated) of the motor vehicle, for example at least 50 Kelvin, preferably at least 100 Kelvin or At least 150 Kelvin below the operating temperature of the motor vehicle (usually about -40 ° C to about + 85 ° C). The fuel may be, for example, hydrogen, which is stored at temperatures of about 34 K to 360 K in the cryogenic pressure vessel. The cryogenic pressure vessel may in particular comprise an inner container which is designed for max. Operating pressures (MOPs) up to about 350 barü (= overpressure relative to the atmospheric pressure), preferably up to about 500 barü, and particularly preferably up to about 700 barü. The fuel is stored in the inner container. An outer container encloses the inner container.

The pressure vessel can be used in a motor vehicle, for example, with compressed ("compressed natural gas" = CNG) or liquefied (LNG) natural gas or with hydrogen.

The electrical storage device serves to store electrical energy. The electrical storage device may be, for example, a traction battery and / or a starter battery. Preferably, the electrical storage device is a high-voltage storage. A high-voltage storage is a memory device with a rest voltage of more than 60 volts.

• – Ermitteln einer zukünftigen Standzeit des Kraftfahrzeuges; und
• – Verändern des Ladezustandes der Speichereinrichtung in Abhängigkeit von der ermittelten Standzeit des Kraftfahrzeuges vor Beginn der Standzeit.

The method disclosed here comprises the steps:

• - Determining a future life of the motor vehicle; and
• - Changing the state of charge of the memory device as a function of the determined service life of the motor vehicle before the beginning of the service life.

The state of charge (SoC) of the storage device indicates what percentage of the storage device is loaded. It is thus a measure of the additional charge capacity and the amount of electrical energy that can be given by the storage device.

The service life is the duration of the inactive phase of the motor vehicle. So the phase of non-use and in particular a longer time interval during which the motor vehicle actively receives no instruction from the driver, which requires the operation of the fuel cell or the motor vehicle. The service life is in particular the parking time or parking time of the motor vehicle. Concerning. the blow-off management is particularly important the parking of the vehicle over a longer period. During such a lifetime i. d. R. no vehicle component - except the components of the fuel cell system including the cryogenic pressure vessel system - active energy from the fuel cell. In other words, the service life is a period of time in which the fuel cell system could remain switched off with regard to other electrical consumers of the motor vehicle if fuel that was not to be discharged were to be disposed of.

The service life is preferably determined taking into account at least one navigation information, at least one user input and / or at least one user information.

The user, e.g. As the driver, for example, enter the life of the motor vehicle manually. Furthermore, it can be provided that the service life is determined on the basis of user information, for example from calendar entries of the vehicle driver. If an appointment of two hours is entered in the calendar at the place of storage, the motor vehicle assumes a service life of two hours.

Preferably, the method disclosed here may comprise the step of identifying the vehicle driver, for example by means of the vehicle key, the driver preselected profile (eg driver settings stored in the motor vehicle), the mobile telephone, etc.

Navigation information can be, for example, a former parking location of the motor vehicle and / or a route destination at which the motor vehicle is parked. However, navigation information can also be determined independently of a route navigation, for example based on calendar entries and / or on the basis of correspondence to reservations, etc. If, for example, a parking space for a parking space for long-term parkers at an airport was reserved, then it is possible to determine without entering the route destination in that the motor vehicle is soon en route to the long-term parking space. By way of example, the motor vehicle can recognize from the actually traveled route whether the driver is actually also on the way to the airport.

On the way to the Abstellort (eg., Long-term parking) then the state of charge of the storage device is adjusted accordingly. On the basis of the information about the storage location (eg long-term parking space), the control of the motor vehicle can deduce that a comparatively long service life (eg greater than 7 days) is probable. Accordingly low, the max. Charging state or limit state of charge can be selected at the beginning of the service life and accordingly a lot of drive power can be delivered on the way to the parking lot of the electrical storage device to the electric traction motor. Thus, the memory device can be discharged to the parking of the motor vehicle to the extent that the auszublasendem fuel during the service life in the fuel cell converted electrical energy can be stored in the electrical storage device.

Also, the user can communicate directly to the parking place the motor vehicle, without having to start a route navigation. Direct input of the service life by the user is to be regarded here as a determination of the service life.

Preference can be stored in an electronic memory earlier Abstellorte of the motor vehicle and each of the earlier lives at these former Abstellorten. In other words, a database is created which shows how long the motor vehicle has lasted on average at the various previous or has been turned off. Preferably, the future service life for this Abstellort can be determined from belonging to a previous Abstellort earlier service life. In other words, the method disclosed herein is an adaptive method that generates future life based on previous life.

Preferably, in addition to the service life, the exact time and the driver can be saved. In addition to navigation information, it is particularly advantageous to simultaneously use user information to determine the future service life. If, for example, the address of a fitness center is entered as the place of parking, it is possible, for example, to determine a service life specifically for the vehicle driver if different drivers train for different lengths of time.

According to the method disclosed here, the state of charge of the storage device can be changed as a function of at least one state variable of the pressure vessel. Preferably, the state variables inner container internal pressure and inner container temperature can be used for this purpose. However, it is also possible to use other variables characterizing the fill level of the pressure vessel which, for example, make it possible to estimate whether and how much fuel has to be blown off. Besides the direct measurement of the density of the fuel, the para / ortho ratio (especially in the case of hydrogen), the current heat input into the tank or the quality of the insulating vacuum are also conceivable. In particular, historical pressure buildup curves are useful to predict the current pressure buildup behavior and thus the expected blowdown rate in a particular time interval.

According to the method disclosed here, the state of charge of the storage device can be changed such that the storage device at the beginning of the service life has a charge state that is below a maximum state of charge or limit state of charge at the beginning of the service life, wherein the maximum state of charge is determined by the service life of the motor vehicle and additionally preferably by at least one state variable of the pressure vessel.

• – Ermitteln der Menge an abzublasenden Brennstoff, die während der Standzeit aus dem Druckbehälter abzublasen ist; und
• – Ermitteln des Grenz Ladezustands den die Speichereinrichtung zu Beginn der Standzeit aufweisen darf, wobei der Grenz-Ladezustand aus der Menge an abzublasenden Brennstoff approximiert wird.

In one embodiment, different service lives can be assigned only fixed limit charge states. Such an algorithm is relatively simple. Preferably, however, the amount of the pressure vessel to be blown off can also be taken into account. Particularly preferably, the method comprises the steps:

• - Determining the amount of fuel to be discharged, which is to be blown out of the pressure vessel during the service life; and
• - Determining the limit state of charge which the storage device may have at the beginning of the service life, wherein the limit state of charge is approximated from the amount of fuel to be discharged.

• – Betreiben der mindestens einen Brennstoffzelle während der Standzeit, wenn der Druck in dem Druckbehälter über einem Druckbehältergrenzdruck liegt; und
• – Speichern der mit der mindestens einen Brennstoffzelle während der Standzeit generierten elektrischen Energie in der mindestens einen Speichereinrichtung.

Preferably, the method disclosed herein may comprise the steps of:

• - Operating the at least one fuel cell during the service life, when the pressure in the pressure vessel is above a pressure vessel boundary pressure; and
• - Storing the generated with the at least one fuel cell during the lifetime electrical energy in the at least one storage device.

The motor vehicle disclosed herein further includes at least one controller configured to perform the method disclosed herein. In other words, the control unit is operatively connected to the components listed here, that the controller can control these components according to the method disclosed herein.

In other words, the technology disclosed herein relates to a pressure vessel management system that is very accurate in predicting how long a lossless life will be, or which blowoff losses are expected over time, due to the known temperature and pressure in the inner vessel. By using navigation information (eg, driving home, driving to the airport), it can be predicted with some probability that after driving a longer parking time follows. Preferably, the driver can tell the system directly by means of a user interface which parking times the driver plans in the near future. Likewise, the system can be designed to be adaptive and can draw conclusions about the temporal and / or local behavior of the past on the future (eg: Wednesday's regular visit to the steakhouse, where 2.5 hours are parked there). Preferably, due to the predicted for the end of the journey pressure vessel condition and the expected or communicated by the driver parking time a discharge rate is calculated, which is converted by the fuel cell into electricity. If the predicted free storage capacity of the battery (= electrical storage unit) is exceeded, the battery is previously correspondingly emptied in order to be able to absorb the largest possible proportion of the electrical energy that will be produced by the fuel cell through the conversion of blow-off hydrogen. Advantageously, the blow-off losses can thus be reduced. One a higher proportion of the blow-off hydrogen can thus be used by the vehicle.

The technology disclosed herein will now be explained with reference to the schematic figures, wherein

1 schematically components of the motor vehicle disclosed here, and

2 schematically shows a flowchart of the method disclosed here.

The 1 schematically shows components of the motor vehicle disclosed here. The cryogenic pressure vessel 100 for storing fuel comprises an inner container 101 and an outer container 102 , The pressure vessel 100 is over the line 130 with a variety of fuel cells 200 fluidly connected, which are combined into a fuel cell stack. The electrical storage device 300 is connected via corresponding electrical lines to the pantographs of the fuel cell stack. The electrical storage device 300 is configured to store the electrical energy generated by the at least one fuel cell. The control unit 400 is with electrical modules of the storage device 300 , the fuel cell stack and the pressure vessel connected, for example via a communication bus.

The control unit is in particular designed to control or regulate the state of charge of the storage battery based on a determined future service life and optionally based on a state variable of the pressure vessel.

The 2 schematically shows a possible flowchart of the technology disclosed here. The process starts with step S100. First of all, the future service life or parking duration (hereinafter simplifying: parking duration) of the motor vehicle is determined, for example by user input. In step S300 it is then judged whether during the parking period the pressure in the pressure vessel rises to a value which is above the limit pressure at which fuel is discharged from the pressure vessel in order to avoid damaging the pressure vessel. If it is predicted that the pressure in the pressure vessel during the parking time will not be greater than the limit pressure, the following subprocesses S400 to S600 will not run through.

However, if the predicted pressure in the pressure vessel is higher than the limiting pressure, then it is determined in step S400 how much fuel is likely to have to be blown off. The amount of fuel to be discharged results from the state variables of the pressure vessel, z. B. pressure and temperature in the pressure vessel, and the service life. The calculation is based on previously known thermodynamic calculation methods and is therefore not described in detail here. In step S500 it is determined how much electrical energy can be generated from the fuel to be discharged by the fuel cells. The electrical energy is directly related to the efficiency of the fuel cells in the operating point, in which the fuel cells are operated during the blow-off process. Based on the amount of electrical energy generated in the fuel cells during the parking period, then the limit state of charge is selected. The limit state of charge of the storage device is the state of charge, which ensures that all the electrical energy which is generated during the parking period from the fuel to be discharged can be stored in the storage device. In step S 700, the current state of charge of the memory device is then changed, for example by adjusting the hybridization strategy. In order to bring the state of charge to a value below the limit state of charge, for example, more electrical energy is taken from the storage device than the at least one fuel cell supplies to the storage device.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 1546601 B1 [0002]
• DE 10202172 A1 [0004]

Claims (7)

Method for operating a motor vehicle, wherein the motor vehicle has at least one cryogenic pressure vessel, at least one fuel cell and at least one electrical storage device, comprising the steps: - Determining a future life of the motor vehicle; and - Changing the state of charge of the memory device as a function of the determined service life of the motor vehicle before the beginning of the service life. The method of claim 1, wherein the service life is determined taking into account at least one navigation information, at least one user input and / or at least one user information. A method according to claim 1 or 2, wherein earlier Abstellorte the motor vehicle and each of the earlier lives are stored at these former Abstellorten, and wherein the future life is determined from the earlier lives. Method according to one of the preceding claims, wherein the state of charge of the storage device is changed in dependence on at least one state variable of the pressure vessel. Method according to one of the preceding claims, wherein the state of charge of the memory device is changed such that the memory device at the beginning of the service life has a state of charge, which is below a limit state of charge, the limit state of charge is determined by the life of the motor vehicle and preferably additionally by at least one state variable of the pressure vessel. Method according to one of the preceding claims, wherein the amount of fuel to be blown is determined, which is to be blown out of the pressure vessel during the service life; and wherein from the amount of fuel to be blown off the state of charge is determined, which the storage device may have at the beginning of the service life. Motor vehicle comprising: - at least one cryogenic pressure vessel ( 100 ) for storing fuel; At least one fuel cell ( 200 ) fluidly connected to the cryogenic pressure vessel; At least one electrical storage device ( 300 ) configured to store the electrical energy generated by the at least one fuel cell; and - at least one control unit ( 400 ), which is designed to carry out a method according to one of the preceding claims.

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