DE102020106087A1 - Method for parking a fuel cell device, fuel cell device and motor vehicle assigned to a motor vehicle - Google Patents

Abstract

The invention relates to a method for switching off a fuel cell device (1) assigned to a motor vehicle with a main coolant cooler (3) integrated in a coolant circuit (4), comprising the steps: a) Predictive determination of a driving time until the end of the journey (Y), b) When it is reached a predetermined or predeterminable remaining driving time (11) closing a valve (8) to provide a coolant reservoir assigned to a bypass (9) to the coolant circuit (4), to which an additional coolant cooler (10) is assigned, c) cooling the coolant in the coolant reservoir by the additional coolant cooler (10) during the remaining driving time (11), d) At the end of the journey (Y) the fuel cell device (1) is switched off and the valve (8) is opened to introduce the coolant from the coolant reservoir (4) into the coolant circuit for condensation of the Humidity in a fuel cell, e) discharging the liquid water from the fuel cell. The invention also relates to a fuel cell device (1) and a motor vehicle with a fuel cell device (1).

Description

1. a) Prädiktive Bestimmung einer Fahrdauer bis zum Fahrtende,
2. b) Bei Erreichen einer vorgegebenen oder vorgebbaren Rest-Fahrdauer Schließen eines Ventils zum Bereitstellen eines einem Bypass zum Kühlmittelkreislauf zugeordneten Kühlmittelreservoirs, dem ein Zusatzkühlmittelkühler zugeordnet ist,
3. c) Abkühlen des im Kühlmittelreservoirs befindlichen Kühlmittels durch den Zusatzkühlmittelkühler während der Rest-Fahrdauer,
4. d) Bei Fahrtende Abstellen der Brennstoffzellenvorrichtung und Öffnen des Ventils zur Einbringung des Kühlmittels aus dem Kühlmittelreservoir in den Kühlmittelkreislauf zur Kondensation der Feuchte in einer Brennstoff-zelle,
5. e) Austragen des Flüssigwassers aus der Brennstoffzelle.

Die Erfindung betrifft weiterhin eine Brennstoffzellenvorrichtung sowie ein Kraftfahrzeug mit einer Brennstoffzellenvorrichtung.The invention relates to a method for shutting down a fuel cell device assigned to a motor vehicle with a main coolant cooler integrated in a coolant circuit, comprising the steps:

1. a) Predictive determination of a driving time until the end of the journey,
2. b) When a predetermined or predeterminable remaining driving time is reached, a valve is closed to provide a coolant reservoir assigned to a bypass to the coolant circuit, to which an additional coolant cooler is assigned,
3. c) Cooling of the coolant in the coolant reservoir by the additional coolant cooler during the remaining driving time,
4. d) At the end of the journey, the fuel cell device is switched off and the valve is opened to introduce the coolant from the coolant reservoir into the coolant circuit to condense the moisture in a fuel cell,
5. e) Discharge of the liquid water from the fuel cell.

The invention further relates to a fuel cell device and a motor vehicle with a fuel cell device.

Fuel cells are used to generate electrical energy from an electrochemical reaction in which hydrogen reacts with oxygen in a controlled manner. For this purpose, fuel cells have a complex structure with a membrane electrode arrangement, on one side of which the anode is formed and on the other side of which the cathode is formed, the electrodes being supplied with the necessary reactants via bipolar plates, for which purpose flow channels are formed in the plate body of the bipolar plates. In order to be able to dissipate the heat generated in the fuel cell, the bipolar plates also have lines for a coolant, which is pumped through the fuel cell and a main coolant cooler by means of a coolant pump, especially if for an increased power requirement, as is the case when fuel cell devices are used in one Motor vehicle is common, several fuel cells are combined to form a fuel cell stack.

In order to ensure ionic conductivity for hydrogen protons through the membrane of the membrane electrode arrangement, the presence of water molecules in the membrane is necessary. The fuel and / or the cathode gas is therefore humidified before they are fed to the fuel cell stack in order to bring about a moisture saturation of the membrane. It is problematic if, when the fuel cell system is started, there are frost conditions, that is to say conditions in which water freezes. This can result in the necessary flow channels for the reactant gases and product water being blocked by ice. In order to prevent this condition, it is known to dry the fuel cell stack when the fuel cell system is switched off, i.e. to drive out the liquid water, for which purpose cathode gas is introduced into the cathode chambers for a longer period of time by a compressor via the cathode air supply line. The disadvantage here is that the reduction of liquid water or relative humidity within the fuel cell stack takes place only slowly and thus the procedure for completely shutting down the fuel cell device can take a very long time, especially if vaporous water only condenses with a delay.

In the DE 10 2008 063 088 B4 describes a method for operating a fuel cell device in a vehicle, in which a control unit determines an anticipated end of journey time and a shutdown procedure begins so far before the end of the journey that the shutdown procedure is run through at the anticipated end of the journey.

the DE 10 2012 016 976 A1 also describes the problem that when a fuel cell device is switched off, water in vapor form condenses out at the operating temperature, specifically in an undirected manner in the area which first falls below the dew point. It is therefore proposed that a heat exchanger be actively cooled by the air conditioning system of a motor vehicle in order to force condensation there. The active cooling should take place after the reactant gases have been switched off, ie during and / or after the fuel cell device itself has been switched off, so that water vapor condenses in the area of the heat exchanger and water accumulation is prevented in critical areas. the DE 10 2014 217 780 A1 proposes to reduce the need for drying after parking a motor vehicle with a fuel cell device, to predict the end of the journey and to reduce the target moisture content of the fuel cell; also the DE 10 2018 209 431 A1 mentions the possibility of reducing the moisture content of a fuel cell device arranged in a motor vehicle when approaching the destination by feeding the cathode gas by means of a bypass switching element through a bypass around a humidifier to the cathode chambers.

In the DE 10 2015 211 476 A1 is used in a motor vehicle with a fuel cell device to reduce the conductivity of a Cooling liquid proposed to flow through a bypass to a heat exchanger during a phase in which the motor vehicle is parked and / or is being prepared for being parked, an ion exchanger being arranged in the bypass.

The object of the present invention is to provide a method with which the drying of a fuel cell of the fuel cell device can be shortened after it has been switched off. A further object is to provide an improved fuel cell device and an improved motor vehicle.

This object is achieved by a method with the features of claim 1, by a fuel cell device with the features of claim 9 and by a motor vehicle with the features of claim 10. Advantageous configurations with expedient developments of the invention are specified in the dependent claims.

The method described at the beginning is characterized in that, during normal operation of the fuel cell device, the coolant circuit is completely flowed through, including the bypass, which is included in the flow via the open valve. If it can now be seen that the remaining journey time is limited by approaching the destination and in particular falls short of a remaining journey time, the valve is closed and the coolant in the bypass is thereby separated as a coolant reservoir from the flow in the coolant circuit. This coolant is then cooled by the additional coolant cooler, so that after the end of the journey and the opening of the valve, the temperature in the coolant circuit can be suddenly reduced and condensation begins so that the liquid water can be discharged from the fuel cell. There are thus defined conditions for a restart of the fuel cell device, which avoid the problems with blockages of the flow channels, in particular in the case of a frost start.

The advantages of the method are particularly evident in the event of an impending start of frost, so that there is also the possibility that before step a), i.e. before the predictive determination of the driving time until the end of the journey, a predictive determination is made that the possibility of a subsequent restart is made a frost start is given. In this way, the implementation of the method and the associated effort and energy use can be saved if there is no threat of a frost start. The predictive determination can take place by evaluating the season, a weather forecast, an altitude or location information or actively by a user input.

It is also advantageous if in step d), that is, when the fuel cell device is switched off and the valve of the bypass is opened, a coolant pump assigned to the coolant circuit is operated with increased power when the valve is opened. Opening the valve causes the coolant retained in the coolant reservoir to be reintegrated into the coolant circuit, which is then operated overall with an increased volume. In order to be able to deliver the cooled coolant from the coolant reservoir of the bypass quickly into the fuel cell and to initiate the condensation, the coolant pump is operated with the increased power, whereby the time provided for this can be short from an interval between 3 and 12 seconds.

The discharge of the condensate is promoted and the time required for this is shortened if a compressor assigned to a cathode air supply line is used for step e), that is to say the discharge of the liquid water.

It is also advantageous if a temperature sensor assigned to the coolant circuit downstream of the fuel cell is used in order to detect the flow of the coolant originating from the coolant reservoir. The temperature sensor thus provides useful information as to when the coolant from the bypass has reached the fuel cell and has flowed through it, whereby this information can be used to switch the coolant pump and the compressor.

It is preferred if the remaining driving time is determined in such a way that the temperature in the coolant reservoir can be reduced to the ambient temperature, i.e. at least the option exists that the ambient temperature is reached without unforeseen influences on the driving time by flowing through the additional coolant cooler the wind. So no energy is required for active cooling.

The accuracy in determining the remaining driving time increases if the data from a navigation system is used to determine the driving time to the end of the journey as well as the expected speed and / or the expected power requirement and to derive the remaining driving time from this. The power requirement influences the heating of the coolant, while the speed via the airstream influences the cooling potential.

In order to be able to use the method even on short journeys, that is to say to limit the remaining travel time, there is the option of using a fan to cool the coolant in the coolant reservoir.

The above-mentioned advantages and effects also apply mutatis mutandis to a fuel cell device with a fuel cell stack having at least one fuel cell, which is integrated into a coolant circuit with a main coolant cooler, a bypass to a coolant reservoir being connected to the coolant circuit through a valve, to which an additional coolant cooler is assigned, in particular if the fuel cell device is assigned to a motor vehicle, since then, as intended, a frequent change of location is provided for the fuel cell device with the possibility that the fuel cell device is parked in the motor vehicle in places where there is the possibility of frost start conditions when starting again.

The features and combinations of features mentioned above in the description as well as the features and combinations of features mentioned below in the description of the figures and / or shown alone in the figures can be used not only in the respectively specified combination, but also in other combinations or alone, without the scope of the Invention to leave. Thus, embodiments are also to be regarded as encompassed and disclosed by the invention, which are not explicitly shown or explained in the figures, but which emerge and can be generated from the explained embodiments by means of separate combinations of features.

• 1 eine schematische Darstellung einer Brennstoffzellenvorrichtung mit einem zu einem Kühlmittelreservoir führenden Bypass in einem Kühlmittelkreislauf,
• 2 die zeitabhängige Darstellung des Temperaturverlaufs in dem Bypass nach dessen Füllen, und
• 3 die zeitabhängige Darstellung des Temperaturverlaufs (unterer Graph) in dem Kühlmittelkreislauf nach dem Brennstoffzellenstapel (dünne Linie) und nach dem Hauptkühlmittelkühler (dicke Linie) sowie die zeitabhängige Darstellung des Volumenstromes (oberer Graph) in dem Kühlmittelkreislauf.

Further advantages, features and details of the invention emerge from the claims, the following description of preferred embodiments and on the basis of the drawings. Show:

• 1 a schematic representation of a fuel cell device with a bypass leading to a coolant reservoir in a coolant circuit,
• 2 the time-dependent representation of the temperature profile in the bypass after it has been filled, and
• 3 the time-dependent representation of the temperature profile (lower graph) in the coolant circuit after the fuel cell stack (thin line) and after the main coolant cooler (thick line) as well as the time-dependent representation of the volume flow (upper graph) in the coolant circuit.

In the 1 is of a fuel cell device 1 the part required to explain the invention is shown, wherein the fuel cell device 1 in particular a device for cooling a plurality of in a fuel cell stack 2 comprises combined fuel cells, namely a main coolant cooler 3 .

Each of the fuel cells comprises an anode, a cathode and a proton-conductive membrane separating the anode from the cathode. The membrane is formed from an ionomer, preferably a sulfonated tetrafluoroethylene polymer (PTFE) or a polymer of perfluorinated sulfonic acid (PFSA). Alternatively, the membrane can be formed as a hydrocarbon membrane.

The anode can be supplied with fuel (eg hydrogen) via an anode compartment. In a polymer electrolyte membrane fuel cell (PEM fuel cell), fuel or fuel molecules are split into protons and electrons at the anode. The membrane lets the protons through, but is impermeable to the electrons. For example, the reaction takes place at the anode: 2H ₂ → 4H ⁺ + 4e ^- (oxidation / electron donation). While the protons pass through the membrane to the cathode, the electrons are conducted to the cathode or to an energy store via an external circuit.

The cathode gas (eg oxygen or air containing oxygen) can be fed to the cathode via a cathode compartment, so that the following reaction takes place on the cathode side: O ₂ + 4H ⁺ + 4e ^- → 2H ₂ O (reduction / electron uptake). Because in the fuel cell stack 2 several fuel cells are combined, a sufficiently large amount of cathode gas must be made available so that a large cathode gas mass flow is provided by a compressor.

In order to ensure ionic conductivity for hydrogen protons through the membrane, the presence of water molecules in the membrane is necessary. The fuel and / or the cathode gas is therefore humidified before they are fed to the fuel cell in order to bring about a moisture saturation of the membrane. In addition, the fuel cell becomes warm during operation, so that cooling of the fuel cell is necessary. There is also a coolant circuit 4th provided in the next to the main coolant radiator 3 also a coolant pump 5 is involved. The coolant circuit 4th can also be a thermostat 6th as well as a temperature sensor 7th be assigned to the downstream of the fuel cell stack in the embodiment shown 2 is arranged.

• Prädiktive Bestimmung einer Fahrdauer bis zum Fahrtende Y, so dass erkennbar ist, wann eine vorgegebene oder vorgebbare Rest-Fahrdauer 11 erreicht ist (Schnitt a)). Dann erfolgt das Schließen eines Ventils 8 zum Bereitstellen eines einem Bypass 9 zum Kühlmittelkreislauf 4 zugeordneten Kühlmittelreservoirs, dem mindestens ein Zusatzkühlmittelkühler 10 zugeordnet ist. Das im Kühlmittelreservoir befindliche Kühlmittel ist durch das geschlossene Ventil 8 nicht mehr in den Kühlmittelkreislauf 4 einbezogen, durchströmt also nicht mehr den Brennstoffzellenstapel 2 und wird dadurch nicht mehr mit Wärme beladen, so dass dessen Temperatur gegenüber dem restlichen Kühlmittel absinkt. Dies wird noch gefördert und beschleunigt durch den mindestens einen Zusatzkühlmittelkühler 10 in dem Bypass 9, der ein Abkühlen des im Kühlmittelreservoirs befindlichen Kühlmittels durch die Zusatzkühlmittelkühler 10 bewirkt während der Rest-Fahrdauer 11.

Because of that in the fuel cell stack 2 During operation of the water that is present and occurring, problems arise in the event of a frost start, namely when there are blockages of flow channels due to frozen water. To avoid these problems it is known to use the Fuel cell stack 2 in the event of an imminent start of frost, i.e. if the water can be expected to freeze predictively through the evaluation of the season, a weather forecast, an altitude and / or location or actively through a user input, drying can be carried out in the fuel cell stack 2 any water present is blown out. This blowing out is particularly effective when condensed water is present, so that a method for switching off a fuel cell device assigned to a motor vehicle 1 with one in a coolant circuit 4th integrated main coolant cooler 3 is provided, which includes the following steps:

• Predictive determination of a driving time until the end of the journey Y so that it can be seen when a given or predefinable remaining driving time 11 is reached (section a)). Then a valve closes 8th to provide a bypass 9 to the coolant circuit 4th associated coolant reservoir, the at least one additional coolant cooler 10 assigned. The coolant in the coolant reservoir is through the closed valve 8th no longer in the coolant circuit 4th included, so no longer flows through the fuel cell stack 2 and is no longer loaded with heat, so that its temperature drops compared to the rest of the coolant. This is further promoted and accelerated by the at least one additional coolant cooler 10 in the bypass 9 , the cooling of the coolant located in the coolant reservoir by the additional coolant cooler 10 causes during the remaining driving time 11 .

The rest of the driving time 11 is determined so that the temperature T1 in the coolant reservoir down to ambient temperature T2 can be lowered, so there is no active, energy-requiring cooling, which is nevertheless possible to shorten the cooling time by using a fan to cool the coolant in the coolant reservoir. These relationships are in 2 shown when the required remaining driving time is reached at X, within which the temperature drops T1 of the coolant in the bypass 9 through the additional coolant cooler 10 takes place in the direction of the ambient temperature T2 , but it is not necessary to achieve this in order to be able to use the advantages of the procedure.

At the end of the journey Y the fuel cell device is switched off 1 and opening the valve 8th for introducing the coolant from the coolant reservoir into the coolant circuit 4th . As a result, the coolant in the coolant circuit is suddenly cooled 4th flowing coolant, as shown in 3 is shown for the flow path after the main coolant cooler 3 and after the fuel cell stack 2 for condensation of moisture in a fuel cell. The introduction of the cooled coolant is accelerated by opening the valve 8th the coolant circuit 4th assigned coolant pump 5 is operated with increased power, i.e. the coolant from the bypass 9 is accelerated again to the normal flow rate. Then the coolant pump can 5 can be operated again with reduced or decreasing power. A control is made possible when the coolant circuit is connected to the downstream of the fuel cell 4th assigned temperature sensor 7th is used to detect the flow of the coolant originating from the coolant reservoir.

As soon as the moisture has condensed, it can be simplified as liquid water from the fuel cell or the entire fuel cell stack 2 are discharged, in particular by using the compressor assigned to the cathode supply air line for this method step, which compressor is not shown in the drawing itself.

A further refinement of the method uses a predictive determination for fine control before step a) as to whether there is the possibility of a frost start during a subsequent restart, that is to say whether the method is only carried out as required. There is also the possibility that the data from a navigation system can be used to determine the duration of the journey until the end of the journey Y as well as to determine the expected speed and / or the expected power requirement and from this the remaining driving time 11 derive so that the point in time X is off 2 can be determined with less uncertainty.

The fuel cell device suitable for carrying out the method 1 required in addition to the fuel cell stack having at least one fuel cell 2 in a coolant circuit 4th with a main coolant cooler 3 is integrated, in addition, only the coolant circuit 4th assigned valve 8th for the separation of a bypass 9 with a coolant reservoir to which an additional coolant cooler 10 assigned. This fuel cell device 1 can therefore be easily used in an automobile.

List of reference symbols

1

Fuel cell device

2

Fuel cell stack

3

Main coolant cooler

4th

Coolant circuit

5

Coolant pump

6th

thermostat

7th

Temperature sensor

8th

Valve

9

bypass

10

Auxiliary coolant cooler

11

Remaining driving time

T1

Coolant temperature in the bypass

T2

Ambient temperature

Y

Travelers

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was 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.

Patent literature cited

• DE 102008063088 B4 [0004]
• DE 102012016976 A1 [0005]
• DE 102014217780 A1 [0005]
• DE 102018209431 A1 [0005]
• DE 102015211476 A1 [0006]

Claims (10)

A method for shutting down a fuel cell device (1) assigned to a motor vehicle with a main coolant cooler (3) integrated in a coolant circuit (4), comprising the steps of: a) Predictive determination of a journey time to the end of the journey (Y), b) When a predetermined or predeterminable remaining driving time (11) is reached, a valve (8) is closed to provide a coolant reservoir assigned to a bypass (9) to the coolant circuit (4), to which an additional coolant cooler (10) is assigned, c) cooling of the coolant located in the coolant reservoir by the additional coolant cooler (10) during the remaining driving time (11), d) At the end of the journey (Y) the fuel cell device (1) is switched off and the valve (8) is opened to introduce the coolant from the coolant reservoir into the coolant circuit (4) to condense the moisture in a fuel cell, e) Discharge of the liquid water from the fuel cell. Procedure according to Claim 1 , characterized in that a predictive determination is made before step a) that there is the possibility of a frost start in the event of a subsequent restart. Procedure according to Claim 1 or 2 , characterized in that in step d) with the opening of the valve (8) a coolant pump (5) assigned to the coolant circuit (4) is operated with increased power. Method according to one of the Claims 1 until 3 , characterized in that a compressor assigned to a cathode air supply line is used for step e). Method according to one of the Claims 1 until 4th , characterized in that a temperature sensor (7) assigned to the coolant circuit (4) downstream of the fuel cell is used to detect the flow of the coolant from the coolant reservoir. Method according to one of the Claims 1 until 5 , characterized in that the remaining driving time (11) is determined so that the temperature (T1) in the coolant reservoir can be lowered to the ambient temperature (T2). Method according to one of the Claims 1 until 6th , characterized in that the data of a navigation system are used to determine the duration of the journey to the end of the journey (Y) as well as the expected speed and / or the expected performance requirement and to derive the remaining driving time (11) therefrom. Method according to one of the Claims 1 until 6th , characterized in that a fan is used to cool the coolant in the coolant reservoir. Fuel cell device (1) with a fuel cell stack (2) which has at least one fuel cell and which is integrated into a coolant circuit (4) with a main coolant cooler (3), the coolant circuit (4) being a bypass (9) to a valve (8) Coolant reservoir can be switched on, to which an additional coolant cooler (10) is assigned. Motor vehicle with a fuel cell device (1) according to Claim 9 .

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