DE102020203357A1 - Method for flushing fuel cells, fuel cell assemblies, and vehicles with such a fuel cell assembly - Google Patents

Abstract

The invention relates to a method for flushing fuel cells (5), wherein a plurality of fuel cells (5) are operated together in a fuel cell arrangement (3), the fuel cells (5) being arranged so that they can be flushed at least partially independently of one another , and wherein flushing processes for the fuel cells (5) are coordinated in time.

Description

The invention relates to a method for flushing fuel cells, a fuel cell arrangement, and a vehicle with such a fuel cell arrangement.

In order to permanently guarantee the functionality of a fuel cell, in particular to prevent deterioration in performance parameters of the fuel cell, it must be regularly flushed with a gas, in particular an inert gas or an educt gas, in particular hydrogen. In particular, undesirable substances, in particular also product water, are discharged from the fuel cell. In particular, the anode of the fuel cell must be rinsed. When purging, the output voltage at the electrical output of the fuel cell first collapses, and then suddenly increases again. In particular, this results in a voltage increase, also referred to as a peak. This peak is associated with electromagnetic emissions that have a broad, but low-frequency spectrum. The corresponding electromagnetic emission can - especially in water - be transmitted very far. If several fuel cells are combined with one another to form a fuel cell arrangement, the emission power can increase even further. This is particularly disadvantageous for fuel cells that are used in submarines (submarines), since the corresponding electromagnetic emissions can be used for reconnaissance and localization of the submarines. If necessary, conclusions can also be drawn about a performance state of the respective submarine, possibly also about the type or even the identity of the submarine, from the flushing behavior of the fuel cells detected in this way.

The invention is based on the object of creating a method for flushing fuel cells, a fuel cell arrangement and a vehicle with such a fuel cell arrangement, the disadvantages mentioned being at least reduced, preferably avoided.

The object is achieved in that the present technical teaching is provided, in particular the teaching of the independent claims and the embodiments disclosed in the dependent claims and the description.

The object is achieved in particular by creating a method for purging fuel cells, wherein a plurality of fuel cells are operated together in a fuel cell arrangement, the fuel cells being arranged - and in particular connected in such a way in terms of flow technology - that they are at least partially, in particular at least in groups or can be rinsed individually, independently of one another. Flushing processes for the fuel cells are coordinated in time. This meant in particular that the flushing processes for the fuel cells - in particular individually or in groups - are coordinated with one another. By suitably coordinating the flushing processes with one another, it is possible to reduce the emitted electromagnetic power and / or at least largely suppress the transmission of a signature, preferably to avoid which would otherwise draw conclusions, in particular about the performance status, the type or even the identity of the fuel cell arrangement and thus could possibly give to a vehicle equipped with the fuel cell arrangement, in particular a submarine.

The flushing processes are preferably coordinated in time, i.e. in particular coordinated with one another, that the electromagnetic radiation power of the fuel cell arrangement is reduced - due to the flushing peaks - and / or in such a way that a signature when the electromagnetic emission is emitted is at least largely suppressed, preferably avoided will.

A fuel cell is understood here to mean, in particular, a structurally integrated arrangement, in particular spatial and electrical series connection, of a plurality of galvanic cells. Such a fuel cell is also referred to as a fuel cell stack or fuel cell stack, or just a stack for short. The galvanic cells of such a fuel cell stack have common fluidic inlets and outlets, in particular with an integrated flow guide, so that they can only be flushed together, that is to say at the same time.

In contrast, a fuel cell arrangement is to be understood in particular as an arrangement of a plurality of such fuel cells which are electrically interconnected with one another, in particular in order to be able to apply a higher voltage and / or a higher power than a single such fuel cell. The individual fuel cells of the fuel cell arrangement can be connected to one another electrically in series or electrically in parallel. It is also possible that some fuel cells of the plurality of fuel cells are electrically connected in series with one another, while other fuel cells of the plurality of fuel cells are electrically connected in parallel with one another. In particular, the fuel cells can be electrically connected in series with one another in groups, with different fuel cell groups being electrically connected in parallel with one another.

The fuel cells are preferably flushed in a time-controlled or state-dependent manner. In the case of a time-controlled flushing of a fuel cell, it is assigned a flushing interval, that is to say a time interval between two flushing processes, a flushing process being carried out after each such flushing interval has elapsed. It is possible for the flushing interval to be determined as a function of the load; in particular, it is possible for the flushing interval to be shorter when the power output of the fuel cell is higher than when the power output is lower. A state-dependent purging of a fuel cell is preferably controlled by at least one cell parameter, in particular performance parameter, of the fuel cell in comparison to a threshold value. An electrical cell voltage of the fuel cell is particularly preferably monitored, a flushing process being initialized when the cell voltage falls below a predetermined voltage limit value as a threshold value.

The flushing processes can be coordinated over time, in particular, by adapting the flushing intervals of the fuel cells as required, or by suitably adapting the corresponding threshold value in the case of state-dependent flushing. It is also possible for flushing processes to be brought forward or delayed in order to time-coordinate the flushing processes of the individual fuel cells or fuel cell groups with one another.

According to a further development of the invention, it is provided that the fuel cells are at least partially flushed at different times. In particular, a high electromagnetic radiation power of the fuel cell arrangement can thus be avoided.

The fuel cells are preferably flushed in groups at different times, or all fuel cells are flushed at different times. In particular, the flushing processes of the fuel cells are coordinated, that is to say coordinated with one another, that the fuel cells are flushed at least partially, in particular in groups, or also as a whole, at different times. In particular, the flushing processes are coordinated, that is to say coordinated with one another, so that simultaneous flushing of all fuel cells is avoided.

According to a further development of the invention, it is provided that the fuel cells - individually or in groups - are assigned time windows for purging. This represents a particularly efficient possibility of flushing the fuel cells at least partially, in particular in groups, at different times and thus in any case avoiding flushing of all fuel cells at the same time. In particular, different time windows for purging are preferably assigned to different fuel cells of the plurality of fuel cells, individually or in groups. In this way, the flushing processes are divided over the various time windows so that simultaneous flushing is avoided. According to one embodiment, the time windows can overlap with one another; However, simultaneous start times and in particular simultaneous end times for the time windows are preferably avoided in order to keep the electromagnetic radiation power low. The time windows particularly preferably do not overlap with one another.

According to a preferred embodiment, the time windows can be assigned to the fuel cells centrally, in particular by a central control device. According to another embodiment, however, it is also possible that the time slots are assigned decentrally, in particular through communication from control devices assigned to the individual fuel cells or fuel cell groups, which are connected to one another in a data-transferring manner, preferably via a bus system, in particular analogous to a CAN protocol.

It is particularly preferred that rinsing processes of different fuel cells or fuel cell groups are immediately lined up in time. This advantageously contributes to equalizing the power applied by the fuel cell arrangement. At any point in time, certain, momentarily purged fuel cells fail in terms of performance. The sequencing of flushing processes is therefore particularly advantageous when flushing processes of different fuel cells or fuel cell groups connected in parallel are carried out immediately in a row, since the power applied by the parallel connection remains constant under otherwise identical conditions.

According to a further development of the invention, it is provided that fuel cells connected electrically in series are flushed at the same time, that is to say in particular together. Since the flushing of a single fuel cell in a string of fuel cells connected electrically in series leads to the voltage of this string dropping to zero, it makes sense to flush the fuel cells connected in series all at the same time and together in order to reduce the voltage failure to one to limit the period of time as small as possible. In particular, all fuel cells electrically connected in series with one another within a fuel cell group are preferably flushed at the same time, the number of those in the group connected in series with one another Fuel cells is smaller than a total number of all fuel cells in the fuel cell arrangement.

According to a further development of the invention, it is provided that the flushing intervals, that is to say the time intervals between two flushing processes, for the fuel cells, in particular for the individual fuel cells or fuel cell groups, are determined by a random generator. In this way, in particular, the emission of an electromagnetic signature can be avoided, which would enable information about the type of fuel cell arrangement or even about the identity of the fuel cell arrangement, and possibly also about its current performance status. If the purging intervals are determined by a random generator, they are neither meaningful for the current load of the fuel cell arrangement, nor are they determined in any way by the type or the identity of the fuel cell arrangement.

Random flushing can advantageously also be used in the case of only one fuel cell, that is to say if a fuel cell arrangement or a power generator does not comprise a plurality of fuel cells but only a single fuel cell. In this case, too, there are the advantages of avoiding the emission of an electronic signature and concealing the current load, the type and / or the identity of the fuel cell.

According to a further development of the invention, it is provided that a total power to be generated in the partial load operation of the fuel cell arrangement is distributed unevenly, that is to say inhomogeneously, to the fuel cells or fuel cell groups. The total output is therefore inhomogeneously, that is to say unevenly, applied by the various fuel cells or fuel cell groups, in particular applied in unequal parts. Thus, the overall performance state of the fuel cell arrangement can no longer be reliably determined, in particular on the basis of the electromagnetic signature resulting from the flushing, in particular since the flushing intervals for the individual fuel cells do not result in a uniform picture of the performance state.

In a preferred embodiment, the uneven distribution of the total power to be applied to the fuel cells or fuel cell groups is changed over time, in particular varied. The total power to be generated is therefore dynamically unevenly distributed over the fuel cells or fuel cell groups. This also makes it difficult to determine a load condition based on the electromagnetic emission.

The fact that the total power to be generated is distributed unevenly over the fuel cells or fuel cell groups means in particular that the individual fuel cells or fuel cell groups do not provide the same proportions of the total power to be generated that are assigned to them, but rather that the power of certain fuel cells or fuel cell groups is increased compared to an even distribution of the total power , at the same time the output of other fuel cells or fuel cell groups is reduced accordingly. This is possible in particular under partial load, since here the individual fuel cells are not operated at their maximum output or nominal output, so that there is room for increasing the output of individual fuel cells.

According to a development of the invention, it is provided that flushing processes for the fuel cells are initialized as a function of a threshold value, the threshold value being varied over time. In this way, particularly in the case of load-controlled flushing processes, a false load can be simulated or confusion about the actual load state can be created.

In particular, a flushing process can be initialized as a function of a partial pressure of oxygen or a charge air pressure, this preferably being done in such a way that the flushing interval is shortened or lengthened as a function of the load, in particular as a function of the partial pressure or boost pressure. A higher partial pressure of oxygen or a higher charge air pressure corresponds to a higher load, a lower partial pressure of oxygen or charge air pressure corresponds to a lower load. With a higher load, the flushing interval is shortened accordingly, with a lower load it is lengthened. If a threshold value for the shortening or lengthening of the flushing interval is now changed, the correspondingly resulting flushing interval quasi simulates a load that deviates from the actual current load.

If the flushing processes are initialized by the cell voltage, in particular in such a way that a flushing process is carried out when the cell voltage falls below a certain voltage limit value, this voltage limit value is preferably changed as a threshold value. This also simulates a load that deviates from the actual current load.

The fact that a flushing process is being initialized does not mean that the flushing process will be carried out immediately. Rather, a purging request is preferably triggered, the purging process then being released to the fuel cell at a specific point in time; is particularly preferred A time window for the flushing process is assigned to the fuel cell accordingly.

The object is also achieved by creating a fuel cell arrangement which has a plurality of fuel cells. The fuel cells are arranged in such a way that they can be purged at least partially independently of one another. The fuel cell arrangement also has a flushing control which is set up to time-coordinate flushing processes for the fuel cells, that is to say in particular to coordinate them with one another. In connection with the fuel cell arrangement, the advantages that have already been explained above in connection with the method are realized in particular. In particular, the fuel cell arrangement is set up to carry out a method according to the invention or one of the previously described embodiments of the method.

In particular, the flushing control is set up to time-coordinate the flushing processes for the fuel cells in such a way that an electromagnetic radiation power of the fuel cell arrangement during flushing, in particular when a flushing process is ended, is reduced, preferably suppressed, and / or so that an emission of a signature, in particular could indicate a load state, a type and / or an identity of the fuel cell arrangement, is at least largely suppressed, preferably avoided.

The flushing control is preferably designed as a central, in particular a higher-level control device, or implemented in a decentralized manner, in particular through the individual fuel cells interacting with one another.

According to a further development of the invention, it is provided that each fuel cell or each group of fuel cells, also referred to as a fuel cell group, is assigned a control device to the plurality of fuel cells, the control devices being connected to one another in a data-transferring manner and set up to time-coordinate the flushing processes for the fuel cells . In this case, the flushing control is designed to be decentralized and in particular has the plurality of control devices or is formed by the plurality of control devices - in particular in cooperation with one another. In this way, the rinsing processes can be controlled very flexibly.

According to a further development of the invention, an alternative embodiment provides that the flushing control is designed as a central control device which is operatively connected to the individual fuel cells or fuel cell groups in order to time-coordinate the flushing processes for the fuel cells. In this case, the flushing control is designed centrally, in particular as a higher-level control device. It is thus possible, in particular, to also include higher-level aspects in the operation of the fuel cell arrangement in the control of the flushing processes.

According to a further development of the invention it is provided that at least two fuel cells of the plurality of fuel cells in a flushing group are directly adjacent to each other and are arranged in such a way that electromagnetic fields emitted by the fuel cells of the same flushing group at least mutually weaken, preferably cancel one another, with the fuel cells of the same flushing group at the same time be rinsed together. In this way, the electromagnetic radiation during flushing is preferably reduced to a particularly great extent, preferably completely avoided. In particular, the at least two fuel cells of a flushing group can be arranged alternately next to one another in an inverted geometric arrangement, so that the electrical and magnetic fields occurring during the flushing process are aligned in opposite directions.

If an uneven number of fuel cells are arranged next to each other within the flushing group, the intensity of the individual flushing processes is preferably distributed unevenly over the fuel cells of the flushing group in such a way that the electromagnetic fields are at least largely canceled out: For example, if three fuel cells are arranged in a row next to each other, the medium strong and the two outer ones with a weaker intensity so that the outer fields aligned in the same direction add up in such a way that together they at least largely, preferably completely, compensate for the more pronounced central field. This principle can of course be generalized to other uneven numbers of fuel cells.

If, on the other hand, an even number of fuel cells are arranged together in a flushing group, the fuel cells can each be flushed in pairs with the same intensity, so that the electromagnetic fields that arise in pairs at least largely, preferably completely, compensate one another.

The fuel cell arrangement preferably has a plurality of flushing groups. The different rinsing groups are preferably rinsed at different times, that is, not at the same time.

According to a preferred embodiment of the fuel cell arrangement, at least one fuel cell, preferably each fuel cell, Associated with a capacitor which is electrically connected to the fuel cell in such a way that it reduces, preferably prevents, the electromagnetic radiation generated during purging. A capacitance as high as possible is preferably chosen for the capacitor. Such a capacitor is preferably assigned to each fuel cell or each fuel cell group.

The object is finally also achieved by creating a vehicle which has a fuel cell arrangement according to the invention or a fuel cell arrangement according to one of the exemplary embodiments described above. In connection with the vehicle, the advantages already mentioned above in connection with the method and the fuel cell arrangement are realized in particular.

The fuel cell arrangement is preferably set up to supply a drive of the vehicle with energy.

The vehicle is preferably designed as a ship, in particular as a submarine (submarine). The advantages mentioned here are realized in a very special way, in particular since submarine location and / or reconnaissance, in particular reconnaissance of a momentary load, type and / or identity of the submarine is made difficult or impossible.

Advantageously, by means of the method proposed here, in the fuel cell arrangement proposed here and in the vehicle proposed here, a flushing process in the area of the so-called Schumann resonance and its integral dividers and harmonics is avoided. The lightning detection takes place at this frequency, whereby the fuel cell arrangement could otherwise be detected with the aid of the lightning detection system.

The invention is explained in more detail below with reference to the drawing.

• 1 eine schematische Darstellung eines Ausführungsbeispiels eines Fahrzeugs mit einem Ausführungsbeispiel einer Brennstoffzellenanordnung, und
• 2 eine schematische Detaildarstellung eines weiteren Ausführungsbeispiels einer Brennstoffzellenanordnung.

Show:

• 1 a schematic representation of an embodiment of a vehicle with an embodiment of a fuel cell arrangement, and
• 2 a schematic detailed illustration of a further exemplary embodiment of a fuel cell arrangement.

1 shows a schematic representation of an exemplary embodiment of a vehicle 1 , which is designed here in particular as a ship, in particular as a submarine, wherein the vehicle 1 an embodiment of a fuel cell assembly 3 having. The fuel cell assembly 3 has a plurality of fuel cells 5 which are arranged so that they can be flushed at least partially independently of one another. Preferably all fuel cells 5 each can be rinsed independently of one another. The fuel cell assembly 3 also has a flush control 7th on that is set up to flush the fuel cells 5 to coordinate in terms of time, in particular to coordinate them.

By coordinating the flushing processes over time, it is possible to generate an electromagnetic radiation output from the fuel cell arrangement 3 Advantageously, at least to reduce during purging, preferably to avoid electromagnetic radiation, and / or to reduce the emission of a signature, preferably to avoid, from which conclusions may otherwise be drawn about a current load state, a type and / or an identity of the fuel cell arrangement 3 or the vehicle 1 could be drawn. The temporal coordination of the flushing processes makes it difficult or prevents in particular a location and / or reconnaissance of the vehicle 1 .

In the context of an advantageous embodiment of a method for flushing the fuel cells 5 are these together in the fuel cell arrangement 3 operated, with flushing processes for the fuel cells 5 coordinated in terms of time, in particular coordinated with one another.

In the exemplary embodiment shown here, the fuel cells are 5 divided into two fuel cell groups, namely a first fuel cell group 9 and a second fuel cell group 11 . The fuel cells 5 each fuel cell group 9 , 11 are electrically connected in series with each other. The two fuel cell groups 9 , 11 are electrically connected in parallel to each other.

In a preferred embodiment, it is possible for fuel cells that are electrically connected in series with one another 5 rinsed together at the same time. This is based on the idea that the fuel cell group 9 , 11 , one of which is a fuel cell 5 is flushed, anyway nothing to the overall performance of the fuel cell arrangement 3 can contribute.

Preferably the fuel cells 5 at least partially, in particular in groups, rinsed at different times. It is also possible for all fuel cells 5 flushed at different times.

Preferably the fuel cells 5 - individually or in groups - assigned time slots for flushing.

In a preferred embodiment, flushing intervals, that is to say time intervals between two flushing processes, are used for the fuel cells 5 - individually or in groups - determined by a random generator.

A total power to be generated by the fuel cell arrangement is preferably 3 in partial load operation unevenly on the fuel cells 5 distributed. This distribution of the total power is particularly preferably varied over time.

Flushing processes for the fuel cells are preferred 5 as a function of a threshold value, in particular a load threshold value and / or a voltage threshold value, initialized, the threshold value being varied over time.

The flush control 7th can be designed centrally and / or decentrally.

In particular, it is possible that every fuel cell 5 - or any fuel cell group 9 , 11 - a separate control device 13th is assigned, the control devices 13th - in a manner not explicitly shown here - are operatively connected to one another in a data-transferring manner and are set up to carry out the flushing processes for the fuel cells 5 to coordinate in time. The flush control 7th In this case, it is designed in a decentralized manner.

The flush control 7th but can also be a central control device 15th have or as a central control device 15th be trained. The central control device 15th is then - in a way not explicitly shown here - with the individual fuel cells 5 or with the fuel cell groups 9 , 11 Operationally connected to the flushing processes for the fuel cells 5 to coordinate in time.

2 shows a schematic detailed illustration of a further exemplary embodiment of a fuel cell arrangement 3 . Identical and functionally identical elements are provided with the same reference symbols in the figures, so that in this respect reference is made to the preceding description. In this further exemplary embodiment, there are two fuel cells here by way of example 5 together in a rinsing group 17th arranged. More than two fuel cells can also be used 5 together in a rinsing group 17th be arranged. The ones in the rinsing group 17th arranged fuel cells 5 are arranged immediately adjacent to one another. They are also arranged so that they stand out from the fuel cells 5 same flushing group 17th emitted electromagnetic fields at least weaken each other when the fuel cells 5 same flushing group 17th be rinsed together at the same time. Accordingly, fuel cells are preferred 5 same flushing group 17th simultaneously flushed with each other in order to weaken the emitted electromagnetic emission, preferably to eliminate it.

und magnetische Felder B für die beiden Brennstoffzellen 5 dargestellt, wobei anhand der Pfeilrichtungen deutlich wird, dass sowohl die elektrischen Felder $\stackrel{\rightharpoonup }{E}$

als auch die magnetischen Felder $\stackrel{\rightharpoonup }{B}$

einander entgegengerichtet sind, sodass sie sich gegenseitig zumindest abschwächen, vorzugsweise wechselseitig aufheben. Insbesondere werden die beiden in der Spülgruppe 17 angeordneten Brennstoffzellen 5 bevorzugt gleichzeitig mit gleicher Intensität gespült, sodass auch die einander entgegengerichteten elektrischen Felder $\stackrel{\rightharpoonup }{E}$

und magnetischen Felder B zeitgleich auftreten und gleiche - allerdings entgegengerichtete - Feldstärken aufweisen.In 2 are electric fields here $\stackrel{\rightharpoonup }{\mathrm{E.}}$

and magnetic fields B for the two fuel cells 5 shown, whereby it is clear from the directions of the arrows that both the electric fields $\stackrel{\rightharpoonup }{\mathrm{E.}}$

as well as the magnetic fields $\stackrel{\rightharpoonup }{\mathrm{B.}}$

are opposite to each other, so that they at least weaken each other, preferably cancel each other out. In particular, the two are in the rinsing group 17th arranged fuel cells 5 preferably flushed at the same time with the same intensity, so that the opposing electrical fields $\stackrel{\rightharpoonup }{\mathrm{E.}}$

and magnetic fields B occur at the same time and have the same - albeit oppositely directed - field strengths.

The fuel cell arrangement preferably has 3 a plurality of such flushing groups 17th on. The different flush groups 17th are preferably rinsed at different times.

Claims (11)

Method for flushing fuel cells (5), wherein - A plurality of fuel cells (5) are operated together in a fuel cell arrangement (3), wherein - The fuel cells (5) are arranged so that they can be flushed at least partially independently of one another, and wherein - Flushing processes for the fuel cells (5) are coordinated in time. Procedure according to Claim 1 , characterized in that the fuel cells (5) are at least partially flushed at different times. Method according to one of the preceding claims, characterized in that the fuel cells (5) - individually or in groups - are assigned time windows for purging. Method according to one of the preceding claims, characterized in that fuel cells (5) connected electrically in series are flushed at the same time. Method according to one of the preceding claims, characterized in that flushing intervals for the fuel cells (5) are determined by a random generator. The method according to any one of the preceding claims, characterized in that a total power to be applied in partial load operation of the Fuel cell arrangement (3) is distributed unevenly over the fuel cells (5). Method according to one of the preceding claims, characterized in that flushing processes for the fuel cells (5) are initialized as a function of a threshold value, the threshold value being varied over time. Fuel cell arrangement (3), with a plurality of fuel cells (5) which are arranged in such a way that they can be flushed at least partially independently of one another, and with a flushing control (7) which is set up to schedule flushing processes for the fuel cells (5) to coordinate. Fuel cell assembly (3) according to Claim 8 , characterized in that a) each fuel cell (5) or fuel cell group (9, 11) of the plurality of fuel cells (5) is assigned a control device (13), the control devices (13) being operatively connected to one another in a data-transmitting manner and being set up to carry out the flushing processes to coordinate in time for the fuel cells (5) or fuel cell groups (9, 11), and / or that b) the flushing control (7) is designed as a central control device (15) which is connected to the individual fuel cells (5) or fuel cell groups (9, 11) is operatively connected in order to time-coordinate the flushing processes for the fuel cells (5) or fuel cell groups (9, 11). Fuel cell arrangement (3) according to one of the Claims 8 or 9 , characterized in that at least two fuel cells (5) of the plurality of fuel cells (5) in a flushing group (17) are immediately adjacent to each other and are arranged in such a way that electromagnetic fields emitted by the fuel cells (5) of the same flushing group (17) are $\left(\stackrel{\rightharpoonup }{\mathrm{E.}},\stackrel{\rightharpoonup }{\mathrm{B.}}\right)$

at least mutually weaken, the fuel cells (5) of the same flushing group (17) being flushed at the same time. Vehicle (1), with a fuel cell arrangement (3) according to one of the Claims 8 until 10 .

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