DE102016116214A1 - Method for operating and ensuring a frost start capability of a fuel cell vehicle - Google Patents

Abstract

The invention relates to a method for operating and ensuring a frost-start capability of a fuel cell assembly of a fuel cell vehicle, wherein the fuel cell assembly is operable in a period of time under relatively dry operating conditions and in a period of relatively humid operating conditions, wherein the fuel cell assembly enables more efficient operation under wet operating conditions in dry operating conditions wherein, assuming a comparatively long trip of the fuel cell vehicle, the fuel cell assembly is operated under wet operating conditions during a travel while underway, and the fuel cell assembly for ensuring its frost start capability during a period of time during and / or after the drive is operated under dry operating conditions.
For ensuring the frost-start capability of the fuel cell assembly, the fuel cell assembly may: timed before or in time just prior to quitting the ride; in time after the end of the journey and in time before a cold start following the journey; and / or operated in time prior to or immediately before the subsequent cold start of the fuel cell assembly in a period of time under dry operating conditions.

Description

The invention relates to a method for operating and ensuring a frost-start capability of a fuel cell assembly of a fuel cell vehicle, wherein the fuel cell assembly is operable in a period of time under comparatively dry operating conditions and in a period under relatively humid operating conditions. Furthermore, the invention relates to a control unit, in particular an engine control unit, and / or a fuel cell vehicle, wherein an operating method according to the invention can be carried out or carried out by the control unit and / or the fuel cell vehicle.

A fuel cell of a fuel cell assembly of a fuel cell system uses an electrochemical reaction of a hydrogen-containing (H, H ₂ ) fuel with oxygen (O, O ₂ ) to form water for generating electrical energy. For this purpose, the fuel cell contains as a core component at least one so-called membrane electrode assembly (MEA, Membrane Electrode Assembly), which is a structure of an ion-conducting or proton-conducting membrane and electrodes arranged on both sides of the membrane, an anode electrode and a cathode electrode. In addition, gas diffusion layers (GDL) can be arranged on both sides of the membrane-electrode assembly on the sides of the electrodes facing away from the membrane.

In general, the fuel cell is formed by means of a plurality of arranged in a stack (English stack) membrane electrode assemblies, wherein add their electrical power in an operation of the fuel cell. Bipolar plates, also called flux field plates or separator plates, are usually arranged between the individual membrane electrode units, which supply and usually also supply the membrane electrode units, ie a supply of the individual cells of the fuel cell, with the operating media, the so-called reactants serve a cooling of the fuel cell. In addition, the bipolar plates provide for a respective electrically conductive connection to the respective adjacent membrane-electrode units.

In an operation of the individual cells of the fuel cell (single cell: membrane electrode assembly and an associated anode space bounded by a bipolar plate and an associated cathode space bounded by a second bipolar plate), the fuel, a so-called anode operating medium, via an anode side open flow field of the bipolar plates supplied to the anode electrodes, where an electrochemical oxidation of H ₂ to 2H ^{+ occurs} with a release of electrons (2e ^- ) (H ₂ => 2H ⁺ + 2e ^- ). Through the membranes or electrolytes of the membrane-electrode units, which gas-tightly separate and electrically isolate the respective reaction spaces (anode space-cathode space pairs of the individual cells), a water-bound or anhydrous transport of the protons (H ⁺ ) formed by the anode electrodes ( (composite) anode of the fuel cell) in the anode spaces of the single cells to the cathode electrodes ((composite) cathode of the fuel cell) in the cathode spaces of the single cells.

The electrons provided at the anode are fed via electrical lines and an electrical load (electric traction motor, compressor, air conditioning et cetera) of the cathode. An oxygen-containing cathode operating medium is supplied to the cathode electrodes of the cathode via a cathode field open flow field of the bipolar plates, wherein an electrochemical reduction of O ₂ to 2O ^2- takes place under a recording of electrons (½O ₂ + 2e ^- => O ^2- ). At the same time, the oxygen anions (O ^2- ) formed on the cathode electrodes react with the protons transported through the membranes or electrolytes to form water (O ^2- + 2H ⁺ => H ₂ O).

A fuel cell vehicle describes a vehicle, which is operated or operated to a large extent by an electrical energy of a fuel cell or a fuel cell stack of a fuel cell assembly of the vehicle. Optionally, an energy store, in particular a rechargeable battery, may assist the fuel cell assembly to provide an electrical (traction) motor of the vehicle which generates torque for propulsion of the vehicle and, optionally, an electrical consumer with electrical energy. With increasing mass production capability of the fuel cell vehicles, general issues of comfort are coming to the fore.

In the fuel cell assembly, an air mass flow supplied to the fuel cell is humidified for reaction by a humidifier. One reason for the humidification of the air mass flow is, inter alia, that an efficiency of the fuel cell with a humidity of a membrane of the humidifier, which in turn is influenced by an inlet moisture of the air mass flow, increases. However, a wet operation of the fuel cell assembly, in which a high efficiency can be achieved, is not always possible because the fuel cell assembly is no longer frost startable in humid or wet operating conditions. For this purpose, the fuel cell stack must be relatively dry.

Since the moisture from the fuel cell stack can be conveyed out only comparatively slowly, moist operation with subsequent drying of the fuel cell stack is not possible without further information, without converting too much electrical energy for this purpose. In addition, in wet operating conditions liquid water occurs at a cathode outlet, which leads to an increase in a cooling requirement (condensation enthalpy). Therefore, if there is a risk of frost during driving, dry operating conditions are selected for a total operating time of the fuel cell assembly, with the disadvantage of a lower efficiency of the fuel cell assembly

The DE 10 2007 044 760 A1 discloses a method of automatically selecting an operating mode for a fuel cell vehicle, wherein at least one first operating mode and a second operating mode are established, the first and second operating modes taking into account a current calendar date and / or taking into account a weather forecast obtained from a data network; or set under consideration of a current ambient air pressure. A first operating mode is a summer mode and a second operating mode is a winter mode.

The DE 11 2007 002 603 T5 teaches a fuel cell system having a fuel cell and a controller for driving the fuel cell. The controller controls performing a normal operation and a dry operation of the fuel cell, wherein in dry operation, a water content of the fuel cell is reduced compared to the normal operation. The controller executes the dry operation before a predicted instruction of a system stop, so that a water content of the fuel cell is reduced at a time of system stop compared to the normal operation.

It is an object of the invention to provide a method for operating and ensuring a frost-start capability of a fuel cell assembly of a fuel cell vehicle, which enables operation of the fuel cell assembly under the risk of frost even in wet operating conditions for increasing fuel cell unit efficiency. Furthermore, a corresponding control unit, in particular a corresponding engine control unit, and / or a corresponding fuel cell vehicle should be specified.

The object of the invention is a method for operating and ensuring a frost-start capability of a fuel cell assembly of a fuel cell vehicle, wherein the fuel cell assembly is operable in a period of time under comparatively dry or wet operating conditions and in a period under relatively humid operating conditions; and by means of a control unit, in particular an engine control unit, and / or a fuel cell vehicle; solved according to the independent claims. Advantageous developments, additional features and / or advantages of the invention will become apparent from the dependent claims and the following description.

In the method according to the invention, the fuel cell assembly allows more efficient operation under wet / wet operating conditions (hereinafter only wet conditions, but this term is intended to encompass the term wet operating conditions) than when in dry operating conditions a comparatively long trip of the fuel cell vehicle is to be operated, the fuel cell assembly is operated in a period during the journey under wet operating conditions, and the fuel cell unit is operated for ensuring its frost start capability in a period during and / or after the trip under dry operating conditions. This is preferably determined, if possible, for each trip individually.

The comparatively long journey should be understood to mean a travel time which is comparatively long in terms of time and / or a relatively long travel distance (route) in space. Ensuring the frost-start capability of the fuel cell unit should, of course, relate to a cold start of the fuel cell unit following the journey, whereby this cold start can take place in the medium term (several hours to several days) or long term (many days to well over several weeks) after the fuel cell unit has been switched off. - According to the invention results in an increase in efficiency (efficiency) of the fuel cell assembly.

In one embodiment, for ensuring the frost-start capability of the fuel cell assembly, the fuel cell assembly: timed before or in time just prior to quitting the ride; in time after the end of the journey and in time before a cold start following the journey; and / or operated in time prior to or immediately before the subsequent cold start of the fuel cell assembly in a period of time under dry operating conditions.

In one embodiment, frost information is used to ensure the frost-start capability of the fuel cell assembly, by which a statement can be made as to whether time at and / or after stopping the fuel cell Fuel cell unit is expected to have a temperature at which the fuel cell aggregate can at least partially freeze. Such information is, for example, a temperature, in particular an outside temperature, of a space-time range in which the fuel cell assembly or the fuel cell vehicle is located after it has been driven, while the fuel cell assembly is switched off.

In one embodiment, for ensuring the frost-start capability of the fuel cell assembly to the temperature, in particular an outside temperature, frost information: from a current season, a current climate, a current weather, a current date, a current time, a current location, a current Temperature, a predicted temperature, a predicted location, a predicted time, a predicated date, a predicted weather, a predicted climate and / or an upcoming season of the fuel cell vehicle closed.

The temperature may be, for example: a temperature measured, determined and / or calculated by the fuel cell vehicle; be a temperature obtained from the fuel cell vehicle, for example from a short-term, medium-term or long-term weather or climate forecast; and / or a temperature determined from short-term, medium-term or long-term weather data et cetera; et cetera. In this case, the temperature represents in particular an outside temperature, wherein the temperature is possibly predicted.

In one embodiment, the frost information and / or temperature for ensuring the frost-start capability of the fuel cell assembly is a measure of the time / time: from which fuel cell assembly is operated while operating at wet operating conditions; from which / on which the fuel cell unit is no longer operated at wet operating conditions while driving; from which fuel cell unit is operated while driving in dry operating conditions; from which / on which the fuel cell unit is no longer operated in dry operating conditions while driving; in which the fuel cell unit is operated after the trip in dry operating conditions; and / or in which / from which the fuel cell assembly starts autonomously and is operated under dry operating conditions or is dried without batch operation. - The temperature, even at higher temperatures, is generally an influencing factor. Thus, because of cooling, it is preferable to select dry operating conditions when the outside temperature is comparatively high.

In one embodiment, the comparatively long journey (travel time and / or travel distance (route)) of the fuel cell vehicle is determined by an input (destination, route, estimated duration et cetera) into a device or a device of the fuel cell vehicle set up for this purpose; by an input to a navigation device (fuel cell vehicle, smartphone, external navigation device et cetera); and / or due to parameters learned by the fuel cell vehicle.

In one embodiment, the fuel cell assembly is operated in time prior to reaching its destination for ensuring the frost-start capability of the fuel cell assembly under dry operating conditions; or the fuel cell aggregate is operated primarily or substantially until it reaches its destination at wet operating conditions, if it allows temperature and / or frost information.

Ensuring the Froststartfähigkeit via the frost information or on the temperature, in particular the outside temperature. In the presence of such (positive) frost information or such optionally predicted (possibly negative) temperature (as, for example, positive frost information), there is a certain / high probability of frost in the environment of the fuel cell vehicle. The fuel cell assembly therefore needs a fuel cell stack that has been dried to some extent for a renewed cold start.

In one embodiment, upon premature termination or interruption of travel to ensure the frost-start capability of the fuel cell assembly: shutdown of the fuel cell assembly is extended in time; there is a turn on the fuel cell assembly time extended or premature; or the fuel cell aggregate is during a Shutdown phase switched on; wherein the fuel cell assembly is operable or operated at dry operating conditions, wherein the fuel cell stack is not necessarily in operation.

In one embodiment, in the event of premature termination or interruption of travel: in the event of frost or frost to be expected at short notice, switching off the fuel cell assembly is prolonged in time; or in the case of no expected frost, the fuel cell unit is switched on in a time-prolonged or premature manner, or the fuel cell unit is switched on during a decommissioning phase; wherein the fuel cell assembly is operable or operated under dry operating conditions.

A period of time for operating the fuel cell assembly at dry operating conditions is substantially or substantially the same as a time until a fuel cell stack of the fuel cell assembly is mainly or substantially dried for a frost start. In embodiments of the method of operation, an enumeration point, an arbitrary plurality of enumeration points or all enumeration points can be realized by an enumeration. In embodiments of the invention, the method of operation is performed only at a certain probability for frost. If this probability does not exist (Sommer et cetera), the operating procedure can be obsolete.

The invention is explained in more detail below with reference to exemplary embodiments with reference to the attached schematic and not to scale drawing. Sections, elements, components, units, schemes and / or components that have identical, univocal or analogous training and / or function are in the description of the figures (see below), the list of reference numerals, the patent claims and in the figures of the drawing with the same Reference number marked. A possible, in the description (description of the invention (see above), figure description) not explained, not shown in the drawing and / or not final alternative, a static and / or kinematic reversal, a combination et cetera to the embodiments of the invention or a component , a scheme, a unit, a component, an element or a portion thereof, the list of reference numerals can be further removed.

In the invention, a feature (unit, component, section, element, component, function, etc.) may be positively, that is, present, or negative, that is, absent, with a negative feature not explicitly explained as a feature, if not It is important that it is absent. A feature of this specification may be applied not only in a specified manner and / or manner, but also in a different manner and / or manner (isolation, summary, substitution, addition, isolation, et cetera). In particular, it is possible to replace, add or omit a feature in the claims and / or the description based on a reference numeral and a feature assigned thereto, or vice versa, in the description, the list of reference numerals, the patent claims and / or the drawing. In addition, a feature in a claim can be interpreted and / or specified in more detail.

The features of this specification are also interpretable as optional features (given the (mostly unknown) state of the art); that is, each feature can be considered as an optional, arbitrary, or preferred, that is, as a non-binding, feature. Thus, a detachment of a feature, possibly including its periphery, from an embodiment possible, this feature is then transferable to a generalized inventive concept. The absence of a feature (negative feature) in one embodiment demonstrates that the feature is optional with respect to the invention. Furthermore, in the case of a type term for a feature, a generic term for the feature is also readable (possibly further hierarchical structure into subgenus, section et cetera), whereby, for example, taking into account equality and / or equivalence, a generalization of one or this feature is possible. - In the merely exemplary figures show:

1 a simplified block diagram of an embodiment of a fuel cell assembly of a fuel cell system according to the invention;

2 a simplified block diagram of an embodiment of a cathode supply of the fuel cell assembly according to the invention;

3 a flow diagram of a first embodiment of a method according to the invention for operating the fuel cell assembly;

4 a flowchart of a second embodiment of the operating method for the fuel cell assembly according to the invention; and

5 a flowchart of a third embodiment of the operating method for the fuel cell assembly according to the invention.

The invention is based on embodiments of methods for operating and ensuring a frost-start capability of a fuel cell assembly 1 a fuel cell system of a fuel cell vehicle (passenger car, passenger transport vehicle, bus, ATV (English All Terrain Vehicle), motorcycle, commercial vehicle, (heavy) truck, construction vehicle, construction machine, special vehicle, rail vehicle) explained in more detail. Here is the fuel cell aggregate 1 in a period of time under comparatively dry operating conditions and in a period of time under comparatively humid operating conditions, the fuel cell unit 1 allows more efficient operation (increased efficiency) at wet operating conditions than under dry operating conditions.

In the drawing, only those portions of the fuel cell assembly 1 of the fuel cell vehicle, which are necessary for an understanding of the invention. In particular, attention is drawn to a representation of a periphery of the fuel cell assembly 1 , Sensors, electronic, electrical and power electrical devices and / or facilities et cetera been largely waived. Although the invention has been described and illustrated in detail by preferred embodiments, the invention is not limited by the disclosed embodiments. Other variations can be deduced therefrom without departing from the scope of the invention.

The 1 shows a fuel cell aggregate 1 a fuel cell system according to a preferred embodiment of the invention. The fuel cell aggregate 1 is preferably part of the vehicle, not shown in detail, in particular a motor vehicle or an electric vehicle (fuel cell vehicle), which preferably has an electric traction motor, which or by a fuel cell 10 of the fuel cell aggregate 1 can be supplied with electrical energy. The fuel cell system differs from the fuel cell aggregate 1 In particular by not shown power electrical, electrical and electronic devices and / or devices (converter, battery, inverter et cetera), an engine control unit (English ECU, Engine Control Unit) et cetera, which the fuel cell assembly 1 not included.

The fuel cell aggregate 1 includes as a core component the fuel cell 10 or a fuel cell stack 17 , Which or which preferably a plurality of stacked individual fuel cells 11 , below as single cells 11 designated, wherein the fuel cell stack 17 in a preferably fluid-tight stack housing 16 is housed (fuel cell 10 ). Every single cell 11 includes an anode compartment 12 and a cathode compartment 13 , wherein the anode compartment 12 and the cathode compartment 13 from a membrane (part of a membrane-electrode assembly 14 , see below), preferably an ion-conductive polymer electrolyte membrane, spatially and electrically separated from each other (see detail).

The anode rooms 12 and the cathode rooms 13 the fuel cell 10 each have a catalytic electrode (part of the respective membrane-electrode unit 14 , see below), that is, an anode electrode and a cathode electrode, each of which catalyzes a partial reaction (see above) of a fuel cell reaction. The anode electrode and the cathode electrode each comprise a catalytic material, for example platinum, which is preferably supported on an electrically conductive carrier material with a comparatively large specific surface, for example a carbon-based material.

A structure of a membrane and the associated electrodes is also called a membrane-electrode unit 14 designated. Between two such membrane-electrode units 14 (in the 1 is only a single membrane electrode assembly 14 indicated) is further a bipolar plate 15 arranged (in the 1 again merely indicated), which supply of operating media 3 . 5 into a relevant anode compartment 12 a first single cell 11 and a respective cathode compartment 13 a directly adjacent second single cell 11 serves and which, moreover, an electrically conductive connection between the two directly adjacent individual cells 11 realized.

Between a bipolar plate 15 and a directly adjacent anode electrode of a membrane-electrode assembly 14 is an anode room 12 and between a cathode electrode of the same membrane-electrode assembly 14 and a second bipolar plate directly adjacent thereto 15 is a cathode compartment 13 a single cell 11 (Anode space-cathode space pair 12 / 13 ) educated. Optionally, gas diffusion layers between the membrane-electrode assemblies 14 and the bipolar plates 15 be arranged. In the fuel cell 10 or in the fuel cell stack 17 So are membrane electrode units 14 and bipolar plates 15 alternately arranged or stacked (fuel cell stack 17 ), taking between the individual cells 11 a flow field for a cooling medium 7 / 8th is integrated.

To supply the fuel cell 10 or the fuel cell stack 17 with the operating media 3 . 5 has the fuel cell aggregate 1 or the fuel cell system on the one hand an anode supply 20 and on the other hand, a cathode supply 30 on.

The anode supply 20 includes an anode supply path 21 , which is a supply of an anode operating medium 3 , a fuel 3 , for example hydrogen 3 or a hydrogen-containing gas mixture 3 , in the anode rooms 12 the fuel cell 10 serves. For this purpose, the anode supply path connects 21 a fuel storage 23 or fuel tank 23 with a Anode input of the fuel cell 10 , The anode supply 20 further includes an anode exhaust path 22 , which is an anode exhaust 4 from the anode chambers 12 through an anode output of the fuel cell 10 through. An established anode operating pressure on an anode side of the fuel cell 10 is preferably by means of an actuating means 24 in the anode supply path 21 adjustable.

In addition, the anode supply points 20 preferably a fuel recirculation line 25 on which the anode exhaust path 22 with the anode supply path 21 fluid mechanically connects. A recirculation of the anode operating medium 3 , that is, the actually preferred to be fueled fuel 3 , is often set up, the most over-stoichiometric anode operating medium 3 the fuel cell 10 to be returned and used. In the fuel recirculation line 25 Preferably, a conveyor, such as a compressor, or a conveyor device is arranged, by means of which a recirculation can be realized and / or a recirculation rate can be set.

The cathode supply 30 includes a cathode supply path 31 which is the cathode spaces 13 the fuel cell 10 a cathode operating medium 5 for example, oxygen 5 or an oxygen-containing gas mixture 5 , preferably air 5 , feeds, which in particular from the environment 2 is sucked. The cathode supply 30 further includes a cathode exhaust path 32 , which is a cathode exhaust 6 , in particular an exhaust air 6 , from the cathode rooms 13 the fuel cell 10 dissipates and feeds this or this optionally provided exhaust device.

For a promotion and compression of the cathode operating medium 5 is at / in the cathode supply path 31 preferably at least one cathode compressor 33 arranged. In embodiments, the cathode compressor 33 as a cathode compressor driven exclusively or also by an electric motor 33 designed, the drive (also) by means of an electric motor 34 or a drive 34 takes place, which preferably with a corresponding power electronics 35 Is provided.

The cathode compressor is preferred 33 as an at least electrically driven turbocharger 33 (English ETC, Electric Turbo Charger) trained. The cathode compressor 33 can also be characterized by a in the cathode exhaust path 32 arranged cathode turbine 36 optionally with variable turbine geometry, be supported by means of a common shaft or a transmission. The cathode turbine 36 represents an expander, which is an expansion of the cathode exhaust gas 6 and thus a lowering of the fluid pressure causes (increase efficiency fuel cell 10 ).

The cathode supply 30 may according to the illustrated embodiment, a wastegate 37 or a Waste Management 37 which or which the cathode supply path 31 or a cathode supply line with the cathode exhaust path 32 or a cathode exhaust pipe connects, so a cathode-side bypass for the fuel cell 10 represents. The wastegate 37 allows an operating pressure of the cathode operating medium 5 short term in the fuel cell 10 reduce without the cathode compressor 33 shut down. One in the wastegate 37 arranged adjusting means 38 or as a wastegate 38 trained actuating means 38 allows adjustment of a volume flow of the fuel cell 10 optionally immediate cathode operating medium 5 ,

All adjusting means 24 . 38 (, 51 . 52 (see below)) of the fuel cell assembly 1 can be designed as controllable, controllable or non-controllable valves, flaps, throttles, apertures et cetera. For insulation of the fuel cell 10 from the surroundings 2 or another object may be at least one further corresponding actuating means in the anode supply 20 and / or the cathode supply 30 , for example on / in an anode path 21 . 22 or a line of the anode path 21 . 22 , and / or on / in a cathode path 31 . 32 or a line of the cathode path 31 . 32 be arranged.

The fuel cell aggregate 1 further preferably comprises a humidifier 39 on. The humidifier 39 On the one hand, this is on / in the cathode supply path 31 arranged it from the cathode operating medium 5 can be flowed through. On the other hand, the humidifier 39 such on / in the cathode exhaust path 32 arranged it from the cathode exhaust 6 can be flowed through. The humidifier 39 is in the cathode supply path 31 preferably downstream of the cathode compressor 33 and upstream of a cathode input of the fuel cell 10 , and in the cathode exhaust path 32 between a cathode output of the fuel cell 10 and the on / in the cathode exhaust path 32 provided cathode turbine 36 arranged. A moisture transmitter of the humidifier 39 preferably has a plurality of membranes, which are often formed either flat or in the form of hollow fibers, optionally as a hollow fiber body.

Various further details of the fuel cell system or of the fuel cell aggregate 1 or the fuel cell 10 / of the fuel cell stack 17 , the anode supply 20 and / or the cathode supply 30 are in the 1 not shown for reasons of clarity. So can the humidifier 39 from the cathode supply path 31 (please refer 2 , Humidifier bypass 50 , Adjusting means 51 . 52 ) and / or the cathode exhaust path 32 be bypassed by means of a bypass (adjusting means). There may also be a turbine bypass on the cathode exhaust pathway 32 be provided, which is the cathode turbine 36 bypasses (adjusting means).

Furthermore, at / in the anode exhaust path 22 and / or cathode exhaust path 32 a water separator be installed, by means of which a from the relevant partial reaction of the fuel cell 10 resulting product water condensable and / or separable and optionally in a water collector for storing is derivable. Furthermore, the anode supply 20 alternatively or additionally to the cathode supply 30 analog humidifier 39 exhibit. Furthermore, the anode exhaust path 22 in the cathode exhaust path 32 or vice versa, the anode exhaust gas 4 and the cathode off-gas 6 optionally can be removed via the common exhaust device. Moreover, in embodiments, the cathode operating medium 5 a on / in the cathode supply path 31 flow through the provided intercooler.

The fuel cell aggregate 1 further comprises a in the 1 exemplified and greatly simplified cooling medium supply 40 , which is a cooling circuit 40 includes, in which the fuel cell 10 is integrated heat transfer. The cooling circuit 40 includes a cooling medium supply path 41 , which of the fuel cell 10 a comparatively cool, that is tempered, cooling medium 7 supplies, and further a cooling medium discharge path 42 that of the fuel cell 10 a comparatively warm cooling medium 8th dissipates. A promotion of the in the cooling circuit 40 circulating cooling medium 7 / 8th is preferably carried out by means of at least one electric motor driven cooling medium pump in the cooling circuit 40 , The cooling medium 7 / 8th , especially water 7 / 8th , a water-alcohol mixture 7 / 8th or a water-ethylene glycol mixture 7 / 8th is coolable by a radiator or main vehicle radiator in the cooling circuit, which usually has an air blower. An essentially anhydrous cooling medium 7 / 8th is of course applicable.

It is an object of the invention, operating conditions of the fuel cell assembly 1 depending on various parameters to set or change such that a humid or wet and thus more efficient operation of the fuel cell assembly 1 can be made possible, while still a frost-resistant fuel cell later 1 or fuel cell system (dry operating conditions) is obtained. In the following, the term wet or relatively humid operating conditions (wet operating conditions) is mentioned, the term wet or comparatively wet operating conditions (wet operating conditions) should thereby also be encompassed.

The parameters to which the operating conditions are particularly intended to be adjusted are, for example, the following. A route length and / or a period of time, also referred to as travel, a route to be traveled with the fuel cell vehicle, which by an input in a device set up for it (device of the fuel cell vehicle, navigation device, smartphone et cetera) and / or due to parameters learned by the fuel cell vehicle is determined. A frost information, by means of which a statement can be made as to whether a temperature, in particular an outside temperature or ambient temperature, is to be expected, at which the fuel cell aggregate can at least partially freeze. And possibly at least one weather datum or weather data along a route of the fuel cell vehicle (season, climate, weather, calendar date, time, location, temperature, current and / or due to a prediction).

As in 2 is shown, is a control or regulation of the humidifier 39 by means of a humidifier bypass 50 possible, by which comparatively dry cathode operating medium 5 (Mass air flow 5 ) around the humidifier 39 can be passed (adjusting means 51 open, adjusting means 52 partly open (partial humidification) or completely closed). As a result, a relative humidity at the cathode input of the fuel cell 10 essentially be varied directly. A design of the humidifier 39 is preferably such that at one end of its lifetime in a design point of the humidifier 39 a total air mass flow 5 through the humidifier 39 can flow through (humidifier bypass 50 closed). Thus, for its lifetime as well as for load points other than the design point, it is possible to humidify the air mass flow 5 with the same humidifier 39 to increase.

The designations A to L for the 3 to 5 are as follows: A: Ride begins, B: Ride destination with travel time greater than the drying time of the fuel cell stack 17 inter alia, to ensure frost start capability, C: Yes (+), D: outside temperature <T _critical for cooling, E: Yes (+), F: Moist operation (wet operating conditions) of the fuel cell 10 to increase efficiency until the expected remaining travel time equal to the drying time of the fuel cell stack 17 G, setting of dry operating conditions (dry operating conditions) for drying the fuel cell stack 17 , H: Ride ends, J: No (-), K: Dry operation (dry operating conditions) of the fuel cell 10 , L: No (-).

According to the invention, see the 3 , as well as the 4 and 5 , setting of comparatively humid operating conditions (humid operating conditions) of the fuel cell assembly takes place 1 if, for example, according to the navigation device at a start of the journey (box A) from a comparatively long journey (route: driving time or distance) is assumed (box B: destination with driving time greater than the drying time of the fuel cell stack 17 , C: +) and related outdoor temperatures (during travel and / or at the destination (Box D, E: +) (see also below).) A humid operation (humid operating conditions) of the fuel cell will take place 10 to increase efficiency until a presumed remaining travel time substantially equal to a drying time of the fuel cell stack 17 is (box F).

Corresponds (only 3 ) the expected remaining travel time substantially the drying time of the fuel cell stack 17 , switching to comparatively dry operating conditions (dry operating conditions, box G) takes place before reaching a travel destination (box H) to ensure a frost-startable fuel cell assembly 1 , - If this (C: + and / or E: +) is not possible (J: - and / or L: -), ( 3 to 5 ) adjusting comparatively dry operating conditions (dry operating conditions) of the fuel cell assembly 1 (Box K).

The designations M and N for the 4 , without the designations G and H, are in addition to the above: M: premature end of travel, N: to dry the fuel cell stack 17 , Extension of the connection, extension / premature start-up or switch-on during decommissioning. The designations O to S for the 5 without the terms G, H and N, are in addition to above: O: weather data / weather forecast to expect frost in the next few hours? P: Yes (+), Q: To dry the fuel cell stack 17 , Extension of shutdown, R: No (-), S: For drying the fuel cell stack 17 , Extension / early activation or switch-on during decommissioning.

If the fuel cell vehicle prematurely ends or stops, see 4 and 5 (Box M), may be an extension of the switched on or the switching off of the fuel cell assembly 1 (Shut-down, wake-up, box N, box Q), an extension or early departure strategy (wake-up, shut-down, box N, box S) or power-on during shutdown (wake-up, box N) , Box S) to the wet fuel cell stack 17 to dry again (preferably in conjunction with a current outside temperature). This is the fuel cell unit 1 operated naturally in dry operating conditions or the fuel cell aggregate 1 dried without batch operation.

If, for example, see 3 to 5 , in the navigation device, a destination is entered, resulting in a certain time (box A). If this travel time is greater than the time that the fuel cell system takes, the fuel cell stack 17 again to dry (box B), the fuel cell stack can 17 for a part driving time which is preceding in time, they are operated wetter and thus at a higher efficiency (C: +, box D, E: +, box F). Before the destination, the operating conditions of the fuel cell unit 1 changed (box G, (boxes M, N or boxes M, O, S, Q)) that the fuel cell stack 17 or an entire system (fuel cell system) reaches a specified (membrane) humidity again before reaching the destination, which guarantees a frost-start capability of the entire system.

Should during operation with increased relative cathode inlet humidity (air mass flow 5 ) the journey is interrupted prematurely (box M), the fuel cell stack can 17 via the departure strategy are also placed in a frost start capable state, but this has a wake of the fuel cell system or a premature startup result (box N, box S / Q). Switching on during the decommissioning of the fuel cell system can also be used here (wake-up, time-delayed, automated start of the fuel cell system, for example, shortly before freezing for conditioning components with respect to frost start, for example liquid water discharge or drying, box N, box S), around the fuel cell stack 17 bring into a frost start capable state (also caster of the fuel cell system), which is preferred.

A decision as to which procedure should be extended can be made dependent on weather data or a weather forecast (see 5 , Box O). The weather data include in particular the outside temperature (s) along the route. If a local outside temperature during the trip along the planned route is not below zero degrees Celsius, it may make sense to only extend / prematurely end the journey (Wake-up, R: -, box S) or on Turn on during the Decommissioning (Wake-up, R: -, Box S) in order to obtain a frost-resistant fuel cell system. Presumption here: the shutdown of the fuel cell vehicle is only a short rest, the journey continues and in the near future, no frost is suspected. If the temperatures are near or below zero degrees Celsius, freezing of the fuel cell system is possible within the near future. In this case, an extension of the shutdown can make sense (shut-down, P: +, box Q).

In addition, the outside temperature (s) should be for cooling the fuel cell 10 or the fuel cell stack 17 be considered (each box B). At high outside temperatures, a higher humidity in the fuel cell 10 for increasing liquid water in / on the fuel cell stack 17 lead, so that a necessary cooling capacity through the cooling medium supply 40 would rise. If necessary, this additional cooling capacity can not be applied by a cooling system, so that the fuel cell stack can be used at higher outside temperatures 17 dry or under dry operating conditions must be operated (L: -, box K).

LIST OF REFERENCE NUMBERS

1

Fuel cell aggregate of the fuel cell system

2

Environment, air

3

Fluid, operating medium, reactant, in particular anode operating medium, actual fuel, preferably hydrogen or hydrogen-containing gas mixture, inflowing

4

Fluid, exhaust possibly including liquid water, in particular anode exhaust, outflowing

5

Fluid, operating medium, reactant, in particular cathode operating medium, preferably (ambient) air, flowing

6

Fluid, exhaust gas optionally including liquid water, in particular cathode exhaust gas, preferably exhaust air, outflowing

7

Fluid, cooling medium, cooling water (water, water-alcohol mixture, water-ethylene glycol mixture), inflowing

8th

Fluid, cooling medium, cooling water, outflowing

10

Fuel cell of the fuel cell unit 1 or the fuel cell system

11

Single cell with an anode electrode of the anode of the fuel cell 10 and a cathode electrode of the cathode of the fuel cell 10 , Single fuel cell

12

Anode compartment of a single cell 11

13

Cathode space of a single cell 11

14

Membrane electrode unit with preferably a polymer electrolyte membrane and an anode electrode and a cathode electrode and optionally in each case a carrier therefor

15

Bipolar plate, flow field plate, separator plate

16

Stack housing of the fuel cell 10

17

Fuel cell stack of the fuel cell 10 , Cell stack

20

Fuel cell supply, anode supply, anode circuit of the fuel cell

10

or the fuel cell stack 10

21

Path, supply path, flow path, anode supply path

22

Path, exhaust path, flow path, anode exhaust path

23

Fuel storage, fuel tank with anode operating medium 3

24

Adjusting means, (on) controllable, (controllable), not controllable, in particular valve, flap, throttle, aperture et cetera

25

Fuel recirculation line

30

Fuel cell supply, cathode supply, cathode circuit of the fuel cell 10 or the fuel cell stack 10

31

Path, supply path, flow path, cathode supply path

32

Path, exhaust path, flow path, cathode exhaust path

33

(second) fluid / air conveyor, compressor, cathode compressor, compressor, pump with the motor 34

34

Motor, electric motor, drive with electric motor, possibly including gearbox

35

Electronics, in particular power electronics for the motor 34

36

Turbine with optionally variable turbine geometry, cathode turbine, expander, possibly an exhaust gas turbocharger

37

Wastegate, Waste Management

38

Adjustment means, (on) controllable, (controllable), not controllable, in particular valve, flap, throttle, aperture et cetera, optionally wastegate

39

Humidifier, humidity transmitter with humidity transmitter

40

Fuel cell supply, cooling medium supply, cooling circuit of the fuel cell

10

or the fuel cell stack 10

41

Path, inlet path, flow path, cooling medium inlet path

42

Path, drain path, flow path, cooling medium drain path

50

Humidifier bypass

51

Adjusting means, (on) controllable, (controllable), not controllable, in particular valve, flap, throttle, aperture et cetera

52

Adjusting means, (on) controllable, (controllable), not controllable, in particular valve, flap, throttle, aperture et cetera

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

• DE 102007044760 A1 [0009]
• DE 112007002603 T5 [0010]

Claims (10)

Method for operating and ensuring a frost-start capability of a fuel cell assembly ( 1 ) of a fuel cell vehicle, wherein the fuel cell assembly ( 1 ) is operable in a period of time under relatively dry operating conditions and in a period of time under relatively humid operating conditions, the fuel cell assembly ( 1 ) allows a more efficient operation in wet operating conditions than in dry operating conditions, characterized in that, if it can be assumed that the fuel cell vehicle has been running for a relatively long time, the fuel cell assembly ( 1 ) is operated in a period during the journey under wet operating conditions, and the fuel cell assembly ( 1 ) is operated for ensuring its frost-start capability in a period during and / or after the trip under dry operating conditions. Operating method according to claim 1, characterized in that for ensuring the frost-start capability of the fuel cell assembly ( 1 ), the fuel cell aggregate ( 1 ): before or just before the end of the journey; in time after the end of the journey and in time before a cold start following the journey; and / or temporally before or in time directly before the following cold start of the fuel cell assembly ( 1 ) is operated in a period under dry operating conditions. Operating method according to claim 1 or 2, characterized in that for ensuring the frost-start capability of the fuel cell assembly ( 1 ) a frost information is used, by which a statement can be made about whether time at and / or after switching off the fuel cell assembly ( 1 ) a temperature at which the fuel cell aggregate ( 1 ) can at least partially freeze. Operating method according to one of claims 1 to 3, characterized in that for ensuring the frost-start capability of the fuel cell assembly ( 1 ) to the temperature, in particular an outside temperature, as frost information: from a current season, a current climate, a current weather, a current date, a current time, a current location, a current temperature, a predicted temperature, a predicted location, a predicted time, a predicated date, a predicted weather, a predicted climate, and / or a coming season of the fuel cell vehicle. Operating method according to claim 3 or 4, characterized in that the frost information and / or temperature for ensuring the frost-start capability of the fuel cell assembly ( 1 ) is a measure of the time / duration: from which / with which the fuel cell aggregate ( 1 ) is operated while driving at wet operating conditions; from which / on which the fuel cell aggregate ( 1 ) is no longer operated at wet operating conditions while driving; from which / with which the fuel cell aggregate ( 1 ) is operated while driving in dry operating conditions; from which / on which the fuel cell aggregate ( 1 ) is no longer operated under dry operating conditions while driving; in which / with which the fuel cell aggregate ( 1 ) is operated after the trip in dry operating conditions; and / or in which / from which the fuel cell aggregate ( 1 ) starts automatically and is operated under dry operating conditions. Operating method according to one of claims 1 to 5, characterized in that determining the comparatively long travel of the fuel cell vehicle is carried out: by an input to a device designed for this purpose or a device of the fuel cell vehicle set up for this purpose; is done by an input to a navigation device; and / or due to parameters learned by the fuel cell vehicle. Operating method according to one of claims 1 to 6, characterized in that the fuel cell assembly ( 1 ) before reaching its destination for ensuring the frost-start capability of the fuel cell assembly ( 1 ) is operated under dry operating conditions; or the fuel cell aggregate ( 1 ) is operated in time to reach its destination in humid operating conditions, if it allows a temperature and / or frost information. Operating method according to one of claims 1 to 7, characterized in that at a premature end or an interruption of the drive to ensure the frost-start capability of the fuel cell assembly ( 1 ): a shutdown of the fuel cell assembly ( 1 ) is extended in time; turning on the fuel cell assembly ( 1 ) is prolonged or premature; or the fuel cell aggregate ( 1 ) is turned on during a decommissioning phase; wherein the fuel cell aggregate ( 1 ) is operated under dry operating conditions. Operating method according to one of claims 1 to 8, characterized in that in case of premature termination or interruption of the journey: in case of frost or a short-term to expected frost, a shutdown of the fuel cell assembly ( 1 ) is extended in time; or in the case of no expected frost, switching on the fuel cell assembly ( 1 ) is prolonged or premature, or the fuel cell aggregate ( 1 ) is turned on during a decommissioning phase; wherein the fuel cell aggregate ( 1 ) is operated under dry operating conditions. Control unit, in particular engine control unit, and / or fuel cell vehicle, characterized in that by the control unit and / or the fuel cell vehicle, an operating method according to one of claims 1 to 9 is feasible or carried out.

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