AU2014376966B2

AU2014376966B2 - Fuel cell unit

Info

Publication number: AU2014376966B2
Application number: AU2014376966A
Authority: AU
Inventors: Albert Hammerschmidt; Arno Mattejat
Original assignee: Siemens Energy Global GmbH and Co KG
Current assignee: Siemens Energy Global GmbH and Co KG
Priority date: 2014-01-09
Filing date: 2014-12-30
Publication date: 2017-05-25
Anticipated expiration: 2034-12-30
Also published as: KR101983887B1; EP3066710B1; WO2015104195A1; EP2894704A1; KR20160096175A; AU2014376966A1; EP3066710A1

Abstract

The invention relates to a fuel cell unit (2) having at least one chamber (6, 12, 14) through which a fluid can flow, which chamber is sealed off from the surroundings of the chamber by means of a primary seal (8). The invention further relates to a method for monitoring the fuel cell unit (2) for leakage. In order to enable space-saving monitoring of the fuel cell unit (2) for leakage, the primary seal (8) according to the invention is surrounded by a secondary seal (10) such that a monitoring chamber (16) is formed between the primary seal (8) and the secondary seal (10), which monitoring chamber is bounded by the primary seal (8) and the secondary seal (10) and is sealed off from the surroundings of the monitoring chamber by means of the secondary seal (10). In addition, according to the invention, a measurement variable of the monitoring chamber (16), in particular a pressure or a fuel concentration in the monitoring chamber (16), is measured by means of a measuring device such that the fuel cell unit (2) can be monitored for leakage in a simple manner.

Description

PCT/EP2014/079405 / 2013P19130WO 1

Description Fuel cell unit

The invention relates to a fuel cell unit having at least one chamber through which a fluid can flow, which chamber is sealed off from its surroundings by means of a primary seal. A fuel cell unit may be conceived of as an entity which comprises at least one fuel cell, preferably a plurality of fuel cells arranged stacked one on top of the other and/or disposed next to one another. In addition, at least one coolant chamber adjoining the at least one fuel cell can be part of the fuel cell unit.

Such a fuel cell unit is typically subdivided into a plurality of chambers through which different fluids (fuel, oxidizing agent or coolant) can flow. Said chambers are generally sealed off from one another or from their surroundings with the aid of seals in order to prevent the fluids from mixing with one another in an uncontrolled manner or to prevent an escape of the fluids into the environment. Leakages may nonetheless be present between the seals and components of the fuel cell unit against which the seals abut.

It can be critical for safety reasons if a fuel flowing through the fuel cell unit escapes into the environment due to a leak or mixes in an uncontrolled manner with an oxidizing agent flowing through the fuel cell unit. In this situation it is namely possible under certain conditions for the fuel to mix with the medium surrounding the fuel cell unit ("ambient medium") or with the oxidizing agent to form a potentially

PCT/EP2014/079405 / 2013P19130WO 2 explosive mixture, with the result that the risk of an explosion may exist.

By the fuel may be understood a substance whose stored energy can be converted in a redox reaction into usable, in particular electrical, energy. A suitable candidate for use as a fuel can be e.g. hydrogen or a hydrogen-containing substance such as e.g. methane or methanol. By the oxidizing agent may be understood a substance which is reduced in a redox reaction and in so doing oxidizes another substance (e.g. the fuel).

For example, oxygen in a gas mixture, such as e.g. air, or in pure form can be used as an oxidizing agent.

In order to prevent a potentially explosive mixture from forming, a powerful gas/air stream can be circulated around the fuel cell unit. In addition to such a circulating flow or, if the circulating flow is not possible e.g. for mechanical design reasons, alternatively thereto, the fuel cell unit can be monitored for leakage. A first known method for monitoring the fuel cell unit for leakage is to arrange sensors in the vicinity of the fuel cell unit so that an escape of the fuel from the fuel cell unit can be detected by means of said sensors. If leaking fuel is detected, a predetermined reaction can be triggered. Said predetermined reaction can comprise e.g. cutting off a supply of fuel to the fuel cell unit and/or purging the environment of the fuel cell unit with a purging gas, in particular with air or an inert gas. Purging with the purging gas can cause the fuel to be diluted to such an extent during its egress that no potentially explosive mixture is formed. 3 2014376966 31 Mar 2017

In a second known method, the fuel cell unit is arranged in a housing and an interior of the housing is monitored for leakage by means of a sensor or a pressure measuring device. With this method, too, if the fuel is detected, or in the event of an increase in pressure in the housing, a predetermined reaction can be triggered. In the second method, the predetermined reaction, analogously to the predetermined reaction in the first method, can include, among other measures, purging the housing with a purging gas and/or cutting off the fuel supply to the fuel cell unit.

The devices necessary for performing said methods require space. Thus, e.g. in the first method, numerous sensors are necessary, these being arranged as uniformly as possible around the fuel cell unit, in order to realize the shortest possible flow path from a possible leakage to the sensor and thereby to enable a leak to be detected at an early stage. Elements connected to the sensors, such as e.g. power/data lines, also require space. In the second method, the housing in particular, dimensioned in accordance with the fuel cell unit, requires a lot of space.

It is an object of the present invention to substantially overcome or at least ameliorate one or more of the above disadvantages, or at least provide a useful alternative.

It is an object of an embodiment of the present invention to disclose a fuel cell unit which can be monitored for leakage in a space-saving manner.

In a first aspect, the invention provides a fuel cell unit having at least one chamber through which a fluid can flow, said chamber being sealed off from its surroundings by means of a primary seal, wherein the primary seal is surrounded by a secondary seal such that a monitoring chamber is formed between the primary seal and the secondary seal, said monitoring chamber being bounded by the primary seal and the secondary seal and being sealed off from its surroundings by means of the secondary seal, and in that there is provided in the secondary seal an inspection opening by means of which the monitoring chamber is connected to its surroundings.

In a second aspect the present invention provides a method for leakage monitoring of a fuel cell unit as claimed in one of the preceding claims, wherein a measurement variable of the monitoring chamber, in particular a pressure or a fuel concentration in the monitoring chamber, is measured by means of a measuring device.

AH26( 12855996_ 1 ):KEH 4 2014376966 31 Mar 2017

In an embodiment, the monitoring chamber may be understood a chamber of the fuel cell unit which can be monitored by means of suitable measuring instruments in order to determine whether the at least one chamber of the fuel cell unit through which a fluid can flow has a leak. A primary seal, in an embodiment, refers to a seal which is provided for the purpose of sealing off the chamber through which the fluid can flow, in particular directly, from its surroundings.

In contrast, a secondary seal, in the present context, denotes an additional seal which is provided for the purpose of sealing off a different chamber than the chamber through which the fluid may flow, such as e.g. the monitoring chamber, from its surroundings.

Embodiments of the invention are based on the consideration that the fuel cell unit enables space-saving leakage monitoring through integration of the monitoring chamber in the fuel cell unit itself. This dispenses with the need to arrange the fuel cell unit in a housing or to provide a plurality of sensors arranged uniformly around the fuel cell unit in order to monitor the environment of the fuel cell unit.

Embodiments of the invention are further based on the consideration that if the at least one chamber through which fluid may flow has a leak, the fluid will initially enter a closed space, namely the monitoring chamber of the fuel cell unit which is sealed off by means of the secondary seal. It may be achieved by this means that the fluid, in particular the fuel, will not find its way into the environment of the fuel cell unit, and consequently may not come into contact with a potential ignition source, unless the secondary seal also has a leak in addition to the primary seal.

In order to dilute that part of the fuel that escapes from a chamber through which the fuel may flow, the monitoring chamber may be purged by means of a purging gas. Referred to internal volumes of typical housings for fuel cell units or referred to typical surrounding volumes of fuel cell units determined by constructional measures, the monitoring chamber has a small volume. A smaller volumetric flow may therefore be sufficient already for purging the monitoring chamber than for purging the housing or the environment of the fuel cell unit.

Preferably, the at least one fuel cell of the fuel cell unit comprises two collector plates. Beneficially, the collector plates delimit the fuel cell. Furthermore, the collector plates may be provided as mechanical carriers of components of the fuel cell.

AH26(12855996_1):KEH 5 2014376966 31 Mar 2017

Preferably, the at least one fuel cell has a membrane electrode assembly which is arranged between the collector plates of the fuel cell. By the membrane electrode assembly may be understood a unit consisting of two electrodes (an anode and a cathode) as well as at least one, in particular semipermeable, membrane arranged between the electrodes.

The at least one chamber through which a fluid may flow may be a fuel chamber through which a fuel may flow. In this case a leakage of the fuel chamber may be detectable based on a monitoring of the monitoring chamber. A fuel chamber may be conceived of as that space in which the fuel is oxidized. In this case the oxidation preferably takes place catalytically at the anode.

On the other hand, the at least one chamber through which the fluid may flow may also be an oxidizing agent chamber through which an oxidizing agent may flow. In this case a leakage of the oxidizing agent chamber may be detectable based on a monitoring of the monitoring chamber. An oxidizing agent chamber may be conceived of as that space in which the oxidizing agent is reduced. In this case the reduction preferably takes place catalytically at the cathode.

The at least one chamber through which the fluid mayflow may furthermore be a coolant chamber through which a coolant may flow. In this case a leakage of the coolant chamber may be detectable based on a monitoring of the monitoring chamber. By the coolant may be understood a substance or substance mixture for dissipating heat. Water, for example, may be used as a coolant.

The at least one chamber through which the fluid may flow may furthermore be a supply channel or a disposal channel through which the coolant, fuel or oxidizing agent may flow. This enables a leakage of the supply/disposal channel to be detected by means of a monitoring of the monitoring chamber. A supply channel may be conceived of as a conduit for delivering the coolant, fuel or oxidizing agent to the at least one fuel cell of the fuel cell unit. Analogously, a disposal channel may be conceived of as a conduit for discharging the coolant, fuel or oxidizing agent from the at least one fuel cell.

The collector plates of the at least one fuel cell may incorporate stamped impressions. The impressions may form e.g. groove-shaped structures which beneficially branch off at right angles from the supply/disposal channel and have openings for introducing the fluid transported in the supply/disposal channel into a chamber of the fuel cell unit that is provided therefor.

AH26(12855996_1):KEH 6 2014376966 31 Mar 2017

The fuel cell unit preferably comprises three of such supply channels. It makes sense if the fuel cell unit also comprises three of such disposal channels. A first of the three supply channels may allow the coolant to flow therethrough. A second of the three supply channels may allow the fuel to flow therethrough. The third of the three supply channels may allow the oxidizing agent to flow therethrough. It makes sense for the same arrangement to apply analogously to the three disposal channels.

In an embodiment the fuel cell unit may have a plurality, preferably at least nine, of such chambers through which a fluid may flow. It is beneficial if at least one of said plurality of chambers is a supply channel. Preferably, three of said plurality of chambers are supply channels. It is furthermore beneficial if at least one of said plurality of chambers is a disposal channel. Preferably, three of said plurality of chambers are disposal channels. At least one other of the plurality of chambers may be a coolant chamber. Furthermore, at least one other of said plurality of chambers may be a fuel chamber. In addition, at least one other of said plurality of chambers may be an oxidizing agent chamber.

Preferably, each fuel cell of the fuel cell unit has a fuel chamber and an oxidizing agent chamber. If the fuel cell unit comprises a plurality of fuel cells, a coolant chamber may be provided in each case between two neighboring fuel cells. A mutual heating of neighboring fuel cells may be reduced by this means.

It is preferable if the fuel cell unit, in an embodiment, has precisely three supply and precisely three disposal channels, and moreover irrespective of the number of its fuel cells. This is because a plurality, preferably all, of the fuel cells may be supplied simultaneously by means of a single supply channel with the fluid conveyed in said channel and the fluid may be disposed of from a plurality, preferably all, of the fuel cells by means of a single disposal channel. It is convenient if the three supply and three disposal channels form channel pairs, each consisting of one supply and one disposal channel. In this case a first of the three channel pairs may be provided for transporting the fuel, a second of the three channel pairs for transporting the oxidizing agent and a third of the three channel pairs for transporting the coolant.

In a preferred embodiment, at least one inspection opening is provided. The monitoring chamber may be connected to its surroundings, i.e. to the environment of the fuel cell unit, by means of the inspection opening. Beneficially, the inspection opening is arranged in the secondary seal.

AH26(12855996_1):KEH 7 2014376966 31 Mar 2017

This enables the monitoring chamber to be monitored from its surroundings or, as the case may be, from the environment of the fuel cell unit by means of a measuring device.

In a further preferred embodiment, at least one connecting port is provided. Preferably, the monitoring chamber is connected by means of the at least one connecting port to at least one further monitoring chamber of the fuel cell unit. This enables a mass transfer to take place between a plurality of monitoring chambers of the fuel cell unit. This in turn enables a simultaneous purging or monitoring of a plurality of such monitoring chambers to be implemented in a simple manner. Preferably, the connecting port is arranged in one of the collector plates of the at least one fuel cell.

Preferably, at least one measuring device, in particular a pressure measuring device or a gas sensor, is connected to the connecting port. By a gas sensor may be understood a device for detecting a gaseous substance, in particular for measuring a concentration of the gaseous substance. The measuring device may be connected to the connecting port indirectly, e.g. by way of pipework, or directly.

In an embodiment, the measuring device may be connected to an evaluation device, e.g. via a data line. The evaluation device in turn may be connected to an electrically controllable valve of a fuel supply line, e.g. via a further data line. Preferably, the evaluation device is disposed for controlling the valve of the fuel supply line. This enables the evaluation device to effect a closure of the fuel supply line. Furthermore, the evaluation device may also be connected to an electrically controllable valve of an oxidizing agent supply line and/or to an electrically controllable valve of a coolant supply line and be disposed for controlling said valve/valves.

This enables the evaluation device to effect a closure of the oxidizing agent supply line and/or coolant supply line.

It is also possible for a plurality of measuring devices to be connected to the connecting port. In this case the measuring devices may be connected to the connecting port in series or in parallel. The gas sensor may be utilized alternatively to the pressure measuring device or in addition to the pressure measuring device. Furthermore, a plurality of gas sensors may be used, e.g. a gas sensor for detecting the fuel and a gas sensor for detecting the oxidizing agent. A sensor for detecting the coolant may be used in addition.

AH26(12855996_1):KEH 8 2014376966 31 Mar 2017

In a preferred embodiment, the fuel cell unit has a plurality of such connecting ports. A pump may be connected on the input side to a first such connecting port. The pump may be connected to a second such connecting port on the output side. A circulation of an atmosphere of the monitoring chamber may be achieved with the aid of the pump. By connecting the pump to the first as well as to the second connecting port it is made possible to produce a closed circuit for the circulation of the atmosphere of the monitoring chamber. Thus, potential ignition sources do not come into direct contact with the atmosphere of the monitoring chamber.

Alternatively, a purging gas feed line may be connected to the first connecting port for the purpose of purging the monitoring chamber. In this case a purging gas discharge line via which the purging gas may be extracted by suction from the fuel cell unit is connected to the second connecting port. A gas that is inert in terms of reactivity with the fuel, e.g. nitrogen or a noble gas, may be used for purging the monitoring chamber.

In order, in the event of a leak being present, to counteract an escape of the fuel/oxidizing agent from a chamber through which the fuel/oxidizing agent may flow, the monitoring chamber, in an embodiment, may be subjected to a pressure by means of the purging gas, said pressure being greater than a pressure in the chamber through which the fuel/oxidizing agent may flow.

If an embodiment of the fuel cell unit has a plurality of fuel cells, the two connecting ports to which the pump is connected or to which the purging gas feed line and the purging gas suction extractor are connected are preferably connecting ports of different fuel cells. Said two connecting ports may be arranged in the region of corners of the fuel cell unit that are spatially diagonally opposite each other. This allows a uniform circulation or, as the case may be, a uniform purging of the monitoring chamber atmosphere.

The primary seal is preferably embodied as a sealing frame. Preferably, the secondary seal is also embodied as a sealing frame. A sealing frame may be conceived of as a seal, in particular a seal consisting of an elastomer, having a concentrically arranged opening. However, a welded seam embodied in a frame shape and serving as a seal may also be conceived of as a sealing frame. Preferably, the sealing frame is flat, as measured by its lateral dimensions. The sealing frame may have e.g. a rectangular shape. Alternatively, the sealing frame may be embodied in a ring shape (as an “O-ring”).

AH26(12855996_1):KEH 9 2014376966 31 Mar 2017

The primary/secondary seal may consist substantially of an injection-molded elastomer. Elastomers have a higher elasticity and deform to a greater extent than many other materials when subjected to pressure. As a result, when two components of the fuel cell unit that are to be sealed are pressed together, a high degree of leak tightness may be achieved by insertion of an elastomer seal as an intermediate layer.

Such a primary/secondary seal consisting of an injection-molded elastomer may be sprayed directly onto one of the collector plates of the fuel cell unit. An assembly of an embodiment of the fuel cell unit may be simplified as a result, since there is no need to place the seal into position on the collector plate.

Alternatively, however, the primary/secondary seal may also be embodied by means of a welded seam. If the fuel cell unit comprises a plurality of fuel cells, adjacent collector plates of two neighboring fuel cells are beneficially welded to one another. The primary/secondary seal may in particular be embodied by a welded seam which joins such adjacent collector plates that are welded to one another.

The invention further relates to a method for monitoring the fuel cell unit for leakage. A further object of an embodiment of the invention is to disclose a method by means of which the fuel cell unit may be monitored for leakage in a simple manner.

In an embodiment, the measuring device may be e.g. the aforementioned pressure measuring device or the aforementioned gas sensor. Preferably, the measuring device is connected to the aforementioned evaluation device. Beneficially, the measured measurement variable is compared by means of the evaluation device with a threshold value that is stored in the evaluation device. A maximum permissible value of the measurement variable may be used as a threshold value. The threshold value may be dependent on the type of fuel, oxidizing agent and/or ambient medium used. Thus, the threshold value may be e.g. a certain percentage of a lower explosion limit for a predetermined mixture composed of the fuel, the oxidizing agent and/or the ambient medium. Alternatively, however, the threshold value may also be e.g. a predetermined pressure, in particular a pressure dependent on a temperature of the fuel cell unit. A temperature sensor may be provided for determining the temperature of the fuel cell unit.

AH26(12855996_1):KEH ίο 2014376966 31 Mar 2017

Preferably, the electrically controllable valve of the fuel supply line is actuated by the evaluation device in such a way that the valve is closed as soon as the measurement variable exceeds the threshold value. In the event of a leak this may prevent the fuel concentration from increasing to an unacceptably high value.

It is furthermore preferable if the electrically controllable valve of the oxidizing agent supply line is actuated by the evaluation device in such a way that the valve is closed as soon as the measurement variable exceeds the threshold value. This may prevent a continuing consumption of the oxidizing agent in the event of a leak.

Since a redox reaction between the fuel and the oxidizing agent may no longer take place once the fuel supply line has been closed off, it follows that no waste heat is generated. For this reason it also makes sense for the electrically controllable valve of the coolant supply line to be actuated by the evaluation device in such a way that said valve is closed as soon as the measurement variable exceeds the threshold value.

Furthermore, a plurality of measuring devices may be used, e.g. a pressure measuring device as well as a gas sensor for detecting the fuel. Alternatively or in addition to the pressure measuring device, a gas sensor for detecting the oxidizing agent may be used. A plurality of different measurement variables may be determined by means of said plurality of measuring devices. Each of said plurality of measurement variables may be compared by the evaluation device with a different threshold value in each case. Preferably, the electrically controllable valves may be actuated by the evaluation device in such a way that one or more of the valves will be closed as soon as one of the plurality of measurement variables exceeds its associated threshold value. A two-stage method may be provided in order to accommodate special safety requirements. Thus, the fuel cell unit may be arranged e.g. in a housing, in particular an explosion-proof housing. In addition to the monitoring of the monitoring chamber, an interior of the housing may be monitored by means of the known methods described in the introduction.

The description of preferred embodiments presented in the foregoing contains numerous features, some of which are reproduced combined into groups in the individual dependent claims. Said features may, however, also preferably be considered individually and grouped

AH26(12855996_1):KEH 11 2014376966 31 Mar 2017 together to form further expedient combinations. In particular, said features may in each case be combined individually and in any desired suitable combination with the first aspect and/or the second aspect.

The above-described characteristics, features and advantages of embodiments of the invention, as well as the manner in which these are realized, will become clearer and more readily understandable in connection with the following description of the exemplary embodiments, which are explained in more detail with reference to the drawings. The exemplary embodiments serve to explain the invention and do not limit the invention to the combination of features disclosed therein, including not in respect of functional features. Furthermore, features of any exemplary embodiment that are suitable therefor may also be explicitly considered in isolation, removed from one exemplary embodiment, introduced into another exemplary embodiment to complement the latter and/or combined with any desired one of the claims.

In the figures:

The next page of the specification is - PAGE 16

AH26(12855996_1):KEH

PCT/EP2014/079405 / 2013P19130WO 12 elasticity and deform to a greater extent than many other materials when subjected to pressure. As a result, when two components of the fuel cell unit that are to be sealed are pressed together, a high degree of leak tightness can be achieved by insertion of an elastomer seal as an intermediate layer.

Such a primary/secondary seal consisting of an injection-molded elastomer can be sprayed directly onto one of the collector plates of the fuel cell unit. An assembly of the fuel cell unit can be simplified as a result, since there is no need to place the seal into position on the collector plate .

Alternatively, however, the primary/secondary seal can also be embodied by means of a welded seam. If the fuel cell unit comprises a plurality of fuel cells, adjacent collector plates of two neighboring fuel cells are beneficially welded to one another. The primary/secondary seal can in particular be embodied by a welded seam which joins such adjacent collector plates that are welded to one another.

The invention further relates to a method for monitoring the fuel cell unit for leakage. A further object of the invention is to disclose a method by means of which the fuel cell unit can be monitored for leakage in a simple manner.

This object is achieved by means of a method in which, according to the invention, a measurement variable of the monitoring chamber, in particular a pressure or a fuel

PCT/EP2014/079405 / 2013P19130WO 13 concentration in the monitoring chamber, is measured by means of a measuring device.

The measuring device can be e.g. the aforementioned pressure measuring device or the aforementioned gas sensor. Preferably, the measuring device is connected to the aforementioned evaluation device. Beneficially, the measured measurement variable is compared by means of the evaluation device with a threshold value that is stored in the evaluation device. A maximum permissible value of the measurement variable can be used as a threshold value. The threshold value can be dependent on the type of fuel, oxidizing agent and/or ambient medium used. Thus, the threshold value can be e.g. a certain percentage of a lower explosion limit for a predetermined mixture composed of the fuel, the oxidizing agent and/or the ambient medium. Alternatively, however, the threshold value can also be e.g. a predetermined pressure, in particular a pressure dependent on a temperature of the fuel cell unit. A temperature sensor can be provided for determining the temperature of the fuel cell unit.

Advantageously, the electrically controllable valve of the fuel supply line is actuated by the evaluation device in such a way that the valve is closed as soon as the measurement variable exceeds the threshold value. In the event of a leak this can prevent the fuel concentration from increasing to an unacceptably high value.

It is furthermore advantageous if the electrically controllable valve of the oxidizing agent supply line is actuated by the evaluation device in such a way that the valve

PCT/EP2014/079405 / 2013P19130WO 14 is closed as soon as the measurement variable exceeds the threshold value. This can prevent a continuing consumption of the oxidizing agent in the event of a leak.

Since a redox reaction between the fuel and the oxidizing agent can no longer take place once the fuel supply line has been closed off, it follows that no waste heat is generated. For this reason it also makes sense for the electrically controllable valve of the coolant supply line to be actuated by the evaluation device in such a way that said valve is closed as soon as the measurement variable exceeds the threshold value.

Furthermore, a plurality of measuring devices can be used, e.g. a pressure measuring device as well as a gas sensor for detecting the fuel. Alternatively or in addition to the pressure measuring device, a gas sensor for detecting the oxidizing agent can be used. A plurality of different measurement variables can be determined by means of said plurality of measuring devices. Each of said plurality of measurement variables can be compared by the evaluation device with a different threshold value in each case. Preferably, the electrically controllable valves can be actuated by the evaluation device in such a way that one or more of the valves will be closed as soon as one of the plurality of measurement variables exceeds its associated threshold value. A two-stage method can be provided in order to accommodate special safety requirements. Thus, the fuel cell unit can be arranged e.g. in a housing, in particular an explosion-proof

PCT/EP2014/079405 / 2013P19130WO 15 housing. In addition to the monitoring of the monitoring chamber, an interior of the housing can be monitored by means of the known methods described in the introduction.

The description of advantageous embodiments presented in the foregoing contains numerous features, some of which are reproduced combined into groups in the individual dependent claims. Said features can, however, also beneficially be considered individually and grouped together to form further expedient combinations. In particular, said features can in each case be combined individually and in any desired suitable combination with the device according to the invention and/or the method according to the invention.

The above-described characteristics, features and advantages of the invention, as well as the manner in which these are realized, will become clearer and more readily understandable in connection with the following description of the exemplary embodiments, which are explained in more detail with reference to the drawings. The exemplary embodiments serve to explain the invention and do not limit the invention to the combination of features disclosed therein, including not in respect of functional features. Furthermore, features of any exemplary embodiment that are suitable therefor can also be explicitly considered in isolation, removed from one exemplary embodiment, introduced into another exemplary embodiment to complement the latter and/or combined with any desired one of the claims.

In the figures:

PCT/EP2014/079405 / 2013P19130WO 16 FIG 1 FIG 2 FIG 3 FIG 4 FIG 5 FIG 6 shows a section through a fuel cell unit at right angles to a stacking direction of its fuel cells, shows a section through the fuel cell unit along the sectional plane II shown in FIG 1, shows a section through the fuel cell unit along the sectional plane III shown in FIG 1, shows a section through the fuel cell unit along the sectional plane IV shown in FIG 1, shows a circuit diagram for leakage monitoring of the fuel cell unit by means of a pump and a gas sensor, shows a circuit diagram for leakage monitoring of the fuel cell unit by means of a pressure measuring device, FIG 7 FIG 8 FIG 9 shows a circuit diagram for leakage monitoring of the fuel cell unit by means of a pump and a pressure measuring device, shows a circuit diagram for leakage monitoring of the fuel cell unit by means of a gas sensor, wherein a purging of a monitoring chamber is provided, shows a section through a further fuel cell unit at right angles to a stacking direction of its fuel cells, and

PCT/EP2014/079405 / 2013P19130WO 17 FIG 10 shows a section through the fuel cell unit from FIG 9 along the sectional plane X shown in FIG 9.

Elements depicted in Figures 1 to 10 are represented schematically. Furthermore, the elements are not necessarily shown true to scale. FIG 1 shows a section through a fuel cell unit 2 which comprises a plurality of fuel cells 4 arranged one on top of the other ("stacked"), wherein the fuel cells 4 are stacked perpendicularly to the drawing plane such that only one of the fuel cells 4 can be seen in FIG 1.

Each of the fuel cells 4 comprises a fuel chamber through which a fuel can flow, and also an oxidizing agent chamber through which an oxidizing agent can flow. A coolant chamber through which a coolant can flow is arranged in addition in each case between two fuel cells 4. All of the fuel, oxidizing agent and coolant chambers of the fuel cell unit are aligned parallel to one another. The section shown extends by way of example longitudinally through a fuel chamber 6, such that neither an oxidizing agent chamber nor a coolant chamber can be seen in FIG 1. A section running longitudinally through an oxidizing agent chamber or a coolant chamber would in principle appear exactly like the section shown in FIG 1, except that the oxidizing agent chamber or the coolant chamber would be depicted instead of the fuel chamber 6.

It can be seen from FIG 1 that the fuel chamber 6 is bounded by a primary seal 8 by means of which the fuel chamber 6 is sealed off from its surroundings. Furthermore, said primary seal 8 is surrounded by a secondary seal 10.

PCT/EP2014/079405 / 2013P19130WO 18

The fuel cell unit 2 comprises six channels 12, 14. Three of the six channels 12, 14 are supply channels 12. The three remaining of the six channels 12, 14 are disposal channels 14. One of the three supply channels 12 is provided for delivering the fuel to the fuel cells 4, while another of the three supply channels 12 is provided for delivering the oxidizing agent to the fuel cells 4. A further of the three supply channels 12 is provided for delivering the coolant to the fuel cells 4. Analogously, one of the three disposal channels 14 is provided for discharging the fuel from the fuel cells 4, while another of the three disposal channels 14 is provided for discharging the oxidizing agent from the fuel cells 4. A further of the three disposal channels 14 is provided for discharging the coolant from the fuel cells 4.

The channels 12, 14 are aligned perpendicularly to the drawing plane. Accordingly, the channels 12, 14 are aligned in the direction along which the fuel cells 4 are stacked ("stacking direction").

In the section shown, each of the six channels 12, 14 is bounded by a further primary seal 8 by means of which the respective channel 12, 14 is sealed off from its surroundings. Each of said further primary seals 8 is surrounded by the same secondary seal 10 which also surrounds the primary seal 8 by means of which the fuel chamber 6 is bounded and sealed off. A monitoring chamber 16 is formed between the primary seal 8 by means of which the fuel chamber 6 is sealed off, the primary seals 8 by means of which the channels 12, 14 are sealed off, and the secondary seal 10. Said monitoring chamber

PCT/EP2014/079405 / 2013P19130WO 19 16 is bounded by the primary seals 8 and the secondary seal 10 and sealed off from its surroundings by means of the secondary seal 10.

The primary seals 8 and also the secondary seal 10 are embodied in each case as rectangular sealing frames having a thickness of several hundred micrometers up to several millimeters. The secondary seal 10 is furthermore arranged at a distance of several millimeters from the primary seals 8.

Also shown in FIG 1 are three sectional planes II, III, IV which are oriented perpendicularly to the drawing plane and to which Figures 2 to 4 relate. Thus, FIG 2 relates to a section through the fuel cell unit 2 along the sectional plane II, while FIG 3 relates to a section through the fuel cell unit 2 along the sectional plane III. Further, FIG 4 relates to a section through the fuel cell unit 2 along the sectional plane IV.

Also indicated in FIG 1 are two connecting ports 18 which are arranged diagonally opposite each other and are disposed in collector plates of the fuel cell unit 2, the collector plates themselves not being depicted in FIG 1. A depiction of the collector plates, albeit from a different perspective, can be found e.g. in Figures 2 to 4. The monitoring chamber 16 of the illustrated fuel cell 4 is connected by means of said two connecting ports 18 to monitoring chambers 16 of the other fuel cells 4 of the fuel cell unit 2 and also to monitoring chambers 16 arranged between the fuel cells 4. FIG 2 shows a section through the fuel cell unit 2 from FIG 1 along the sectional plane II. Two of the fuel cells 4 of the

PCT/EP2014/079405 / 2013P19130WO 20 fuel cell unit 2 are shown by way of example. Also illustrated are a coolant chamber 20 arranged between the two fuel cells 4, a coolant chamber 20 arranged above the upper of the two fuel cells 4, and a coolant chamber 20 arranged below the lower of the two fuel cells 4.

In the stacking direction 22 or in the opposite direction, the fuel cell unit 2 has further fuel cells (not shown in FIG 2) as well as further coolant chambers arranged between said fuel cells .

Each of the fuel cells 4 of the fuel cell unit 2 comprises two collector plates 24 which bound the respective fuel cell 4 and are provided as mechanical carriers of components of the fuel cell 4. The collector plates 24 incorporate stamped impressions which form frame-shaped grooves. For clarity of illustration reasons the impressions of the collector plates 24 are not depicted. In addition, each of the fuel cells 4 has a membrane electrode assembly 26 which is arranged between its collector plates 24 and by means of which the oxidizing agent chamber 28 and the fuel chamber 6 of the respective fuel cell 4 are separated from one another.

Each of the fuel chambers 6, each of the oxidizing agent chambers 28 and each of the coolant chambers 20 of the fuel cell unit 2 is sealed off from its surroundings by means of a primary seal 8. Each of said primary seals 8 is surrounded by a secondary seal 10, such that monitoring chambers 16 are formed between the primary seals 8 and the secondary seals 10. The secondary seals 10 of the fuel cell unit 2 are furthermore arranged between two adjacent collector plates 24 in each case. The monitoring chambers 16 are bounded by the primary

PCT/EP2014/079405 / 2013P19130WO 21 seals 8 and the secondary seals 10 and sealed off from their surroundings by means of the secondary seals 10. In addition, the monitoring chambers 16 are bounded by two adjacent collector plates 24 in each case.

The primary seals 8 by means of which the coolant chambers 20 of the fuel cell unit 2 are sealed off are arranged in each case between adjacent collector plates 24 of neighboring fuel cells 4. In contrast, the primary seals 8 by means of which the fuel chambers 6 or the oxidizing agent chambers 28 are sealed off are arranged in each case between a collector plate 24 and a membrane electrode assembly 26.

Adjacent collector plates 24 of two neighboring fuel cells 4 are welded to one another at their impressions. Between the welded-together collector plates 24, the primary seals 8 and the secondary seal 10 are in each case embodied by means of a frame-shaped welded seam which joins such adjacent welded-together collector plates 24. The remaining primary seals 8 and secondary seals 10 consist of an injection-molded elastomer which is sprayed directly onto the collector plates 24. For the sake of simplicity all of the primary seals 8 are represented in the same way, irrespective of whether they consist of an elastomer or are formed by means of a welded seam. This applies analogously to the secondary seals 10. FIG 3 shows a section through the fuel cell unit 2 from FIG 1 along the sectional plane III. The section shown extends through the three supply channels 12 and in relation to the stacking direction 22 of the fuel cells 4 comprises the same portion of the fuel cell unit 2 as the section shown in FIG 2.

PCT/EP2014/079405 / 2013P19130WO 22

It can be seen from FIG 3 that the supply channels 12 are embodied such that the collector plates 24 of the fuel cell unit 2 in each case have a channel opening 30 for each of the three supply channels 12, which channel opening 30 is arranged congruently over/under one of the channel openings 30 of adjacent collector plates 24.

In addition, three primary seals 8 and one secondary seal 10 which surrounds the three primary seals 8 are located in each case between two adjacent collector plates 24. Between the three primary seals 8 and the secondary seal 10 there is formed a monitoring chamber 16 which is sealed off from its surroundings by means of the secondary seal 10 and is bounded by the three primary seals 8 and the secondary seal 10.

The supply channels 12 run in the stacking direction 22 of the fuel cells 4 and are bounded and sealed off perpendicularly to the stacking direction 22 by the primary seals 8 arranged between the collector plates 24.

The disposal channels 14 (not shown in FIG 3 (see FIG 1)) are embodied in a completely analogous way to the supply channels 12. A section through the disposal channels 14 along a sectional plane aligned parallel to the sectional plane III would in principle appear exactly like the section shown in FIG 3. FIG 4 shows a section through the fuel cell unit 2 from FIG 1 along the sectional plane IV, the section comprising the same portion of the fuel cell unit 2 in relation to the stacking direction 22 of the fuel cells 4 as the section shown in FIG 2.

PCT/EP2014/079405 / 2013P19130WO 23

In the section shown, each of the collector plates 24 has a connecting port 18, said connecting ports 18 of the collector plates 24 being arranged congruently one above the other. In addition, each of the collector plates 24 has a further connecting port 18 (not shown in FIG 4) which is arranged diagonally opposite its connecting port 18 shown in FIG 4 (cf. FIG 1 and the associated description).

All of the monitoring chambers 16 of the fuel cell unit 2 are connected to one another by means of the connecting ports 18, thereby enabling a mass transfer between the individual monitoring chambers 16. FIG 5 shows a circuit diagram for leakage monitoring of the fuel cell unit 2.

Three supply lines 32, 34, 36 and three disposal lines 40, 42, 44 are connected to the fuel cell unit 2. Each of said three supply lines 32, 34, 36 is connected to one of the three supply channels 12 from FIG 1 in each case, while each of said three disposal lines 40, 42, 44 is connected to one of the three disposal channels 14 from FIG 1 in each case. The supply/disposal channels 12, 14 themselves are not shown in FIG 5.

One of the three supply lines 32, 34, 36 is a fuel supply line 32 for supplying the fuel cell unit 2 with the fuel. Furthermore, another of the three supply lines 32, 34, 36 is a coolant supply line 34 for supplying the fuel cell unit 2 with the coolant. Another of the three supply lines 32, 34, 36 is

PCT/EP2014/079405 / 2013P19130WO 24 an oxidizing agent supply line 36 for supplying the fuel cell unit with the oxidizing agent.

Both the fuel supply line 32 and the coolant supply line 34 and also the oxidizing agent supply line 36 have an electrically controllable valve 38 in each case.

One of the three disposal lines 40, 42, 44 is a fuel disposal line 40 for removing the fuel from the fuel cell unit 2. Furthermore, another of the three disposal lines 40, 42, 44 i a coolant disposal line 42 for removing the coolant from the fuel cell unit 2. Another of the three disposal lines 40, 42, 44 is an oxidizing agent disposal line 44 for removing the oxidizing agent from the fuel cell unit 2.

In addition, a pump 46 is connected to the fuel cell unit 2 via a line system 48. On the input side, the pump 46 is connected to a first connecting port of the fuel cell unit 2, in particular to the bottommost fuel cell of the fuel cell unit 2. On the output side, the pump 46 is connected to a second connecting port of the fuel cell unit 2 arranged spatially diagonally opposite the first connecting port, in particular to the topmost fuel cell of the fuel cell unit 2. The connecting ports (see FIG 1 or FIG 4) themselves are not shown in FIG 5.

With the aid of the pump 46, an atmosphere of the interconnected monitoring chambers of the fuel cell unit 2 is circulated in a closed circuit.

Flow directions of the fuel/coolant/oxidizing agent in the supply/disposal lines 32, 34, 36, 40, 42, 44 or, as the case

PCT/EP2014/079405 / 2013P19130WO 25 may be, in the line system 48 are indicated by means of arrows in FIG 5. A gas sensor 50 is also connected to the pump 46 via the line system 48. The gas sensor 50 is disposed for measuring the fuel concentration present in the monitoring chambers. In the present exemplary embodiment the gas sensor 50 is arranged downstream of the pump 46, referred to the flow direction in the line system 48. Basically, the gas sensor 50 can also be arranged upstream of the pump 46.

The gas sensor 50 is connected to an evaluation device 54 via a data line 52. The evaluation device 54 in turn is connected via further data lines 52 to the electrically controllable valve 38 of the fuel supply line 32, the electrically controllable valve 38 of the coolant supply line 34 and the electrically controllable valve 38 of the oxidizing agent supply line 36. The evaluation device 54 is furthermore disposed for controlling said three valves 38. A fuel concentration present in the monitoring chambers is measured by means of the gas sensor 50 and transmitted to the evaluation device 54. The evaluation device 54 compares the fuel concentration with a threshold value that is stored in the evaluation device 54. The threshold value amounts for example to 20% of that fuel concentration as of which an explosive mixture ratio of a fuel/ambient air mixture is present (20% of the lower explosion limit of the fuel/ambient air mixture).

If a chamber of the fuel cell unit 2 through which the fuel can flow has a leak, the fuel concentration in the monitoring

PCT/EP2014/079405 / 2013P19130WO 26 chambers increases. As soon as the measured fuel concentration exceeds the threshold value, the electrically controllable valve 38 of the fuel supply line 32, the electrically controllable valve 38 of the coolant supply line 34 and the electrically controllable valve 38 of the oxidizing agent supply line 36 are actuated by the evaluation device 54 in such a way that the three valves 38 are closed.

An additional gas sensor, not shown in FIG 5, which is disposed for measuring the oxidizing agent concentration present in the monitoring chambers can also be connected to the pump 46 via the line system 48. Said additional gas sensor can in turn be connected to the evaluation device 54 via an additional data line. The oxidizing agent concentration present in the monitoring chambers can be measured by means of the additional gas sensor and transmitted to the evaluation device 54. If the oxidizing agent concentration in the monitoring chambers exceeds a predetermined threshold value stored in the evaluation device 54, the evaluation device 54 can actuate said valves 38 in such a way that the valves 38 are closed.

In addition, a further sensor, not shown in FIG 5, which is disposed for measuring the coolant concentration present in the monitoring chambers can be used. With the aid of said further sensor the monitoring chambers can be monitored in an analogous manner for a leakage of a chamber through which the coolant can flow.

The following description, discussed in connection with Figures 6 to 8, is essentially limited to the differences compared to the exemplary embodiment shown in FIG 5, to which

PCT/EP2014/079405 / 2013P19130WO 27 reference is made in respect of features and functions that remain the same. Components remaining substantially the same are generally labeled with the same reference numerals and features that are not mentioned are included in the following exemplary embodiments without being described again. FIG 6 shows an alternative circuit diagram for leakage monitoring of the fuel cell unit 2. In the exemplary embodiment in FIG 6, no pump is provided for circulating the atmosphere of the monitoring chambers. Furthermore, a pressure measuring device 56 is employed for monitoring the monitoring chambers in lieu of a gas sensor.

In the present exemplary embodiment, the pressure measuring device 56 is connected to that connecting port to which the pump 46 from FIG 5 is connected on the output side. Alternatively, the pressure measuring device 56 can be connected to that connecting port to which the pump 46 from FIG 5 is connected on the input side. In both cases it makes sense for the other connecting port in each case to be closed. A pressure prevailing in the monitoring chambers is measured by means of the pressure measuring device 56 and transmitted via a data line 52 to the evaluation device 54. The evaluation device 54 compares the pressure with a threshold value that is stored in the evaluation device 54. The threshold value is in this case a predetermined maximum pressure.

If a chamber of the fuel cell unit 2 through which the fuel/oxidizing agent can flow has a leak, the pressure prevailing in the monitoring chambers increases. If the coolant used is gaseous, a leakage of a chamber through which

PCT/EP2014/079405 / 2013P19130WO 28 the coolant can flow also leads to an increase in the pressure in the monitoring chambers.

As soon as the measured pressure exceeds the threshold value, the electrically controllable valve 38 of the fuel supply line 32, the electrically controllable valve 38 of the coolant supply line 34 and the electrically controlled valve 38 of the oxidizing agent supply line 36 are actuated by the evaluation device 54 in such a way that the three valves 38 are closed. FIG 7 shows a further circuit diagram for leakage monitoring of the fuel cell unit 2. In the present exemplary embodiment, a pressure measuring device 56 is used for monitoring the monitoring chambers in addition to the gas sensor 50 that is disposed for measuring the fuel concentration present in the monitoring chambers.

The pressure measuring device 56 is connected to the pump 46 via the line system 48, the pressure measuring device 56 being arranged upstream of the pump 46, referred to the flow direction in the line system 48. Basically, the pressure measuring device 56 can also be arranged downstream of the gas sensor 50. A pressure prevailing in the monitoring chambers is measured by means of the pressure measuring device 56 and transmitted to the evaluation device 54 via a data line 52.

Furthermore, a threshold value for the pressure is stored in the evaluation device 54 in addition to a threshold value for the fuel concentration. The threshold value for the pressure is a predetermined maximum pressure.

PCT/EP2014/079405 / 2013P19130WO 29

The evaluation device 54 compares the pressure transmitted by the pressure measuring device 56 as well as the fuel concentration transmitted by the gas sensor 50 with the respective associated threshold value.

If a chamber of the fuel cell unit 2 through which the fuel/oxidizing agent can flow has a leak, the pressure prevailing in the monitoring chambers increases. If the coolant used is gaseous and a chamber of the fuel cell unit 2 through which the coolant can flow has a leak, the pressure prevailing in the monitoring chambers likewise increases. By means of the pressure measuring device 56 it is therefore possible not only to detect a leakage of a chamber through which the fuel can flow, but also to detect a leakage of a chamber through which the oxidizing agent can flow and/or of a chamber through which the coolant can flow.

As soon as the pressure measured by the pressure measuring device 56 exceeds the threshold value, the electrically controllable valve 38 of the fuel supply line 32, the electrically controllable valve 38 of the coolant supply line 34 and the electrically controllable valve 38 of the oxidizing agent supply line 36 are actuated by the evaluation device 54 in such a way that the three valves 38 are closed.

In addition, the evaluation device 54 evaluates a time characteristic of the measured fuel concentration up to the time instant at which the valves 38 are closed. In particular, the evaluation device 54 checks the time characteristic for an increase in the fuel concentration immediately before the closing of the valves 38. By means of the evaluation it is possible to narrow down whether a cause for the closing of the

PCT/EP2014/079405 / 2013P19130WO 30 valves 38 is a leakage of a chamber through which the fuel has flowed or a leakage of a chamber through which the coolant/oxidizing agent has flowed. This enables a significant reduction to be achieved in an amount of effort required to remove the leak. The evaluation device 54 can additionally have an indicating element, such as e.g. a warning light, which provides information on whether the cause for the closing of the valves 38 is a leakage of a chamber through which the fuel has flowed.

If the pressure measuring device 56 fails due to a fault, the monitoring chambers can continue to be monitored for a leakage of a chamber through which the fuel can flow by means of the gas sensor 50. Furthermore, the monitoring chambers can continue to be monitored for a leakage in the above-described manner by means of the pressure measuring device 56 if the gas sensor 50 fails due to a fault. FIG 8 shows yet another circuit diagram for leakage monitoring of the fuel cell unit 2. In the exemplary embodiment in FIG 8, no pump is provided for circulating the atmosphere of the monitoring chambers. Instead, in the present exemplary embodiment, a purging gas feed line 58 is connected to that connecting port to which the pump 46 from FIG 5 is connected on the output side. A purging gas discharge line 60 is connected to that connecting port to which the pump 46 from FIG 5 is connected on the input side. Furthermore, a pressure measuring device 56 is used for monitoring the monitoring chambers in lieu of a gas sensor. A purging gas can be introduced into the interconnected monitoring chambers of the fuel cell unit 2 via the purging

PCT/EP2014/079405 / 2013P19130WO 31 gas feed line 58, while the purging gas can be extracted by suction from the monitoring chambers via the purging gas discharge line 60. The pressure measuring device 56 is connected to the purging gas discharge line 60. In order to siphon off the purging gas, a suction extractor device (not shown) is connected to the purging gas discharge line 60. Referred to a flow direction in the purging gas discharge line 60, the suction extractor device is arranged downstream of the pressure measuring device 56.

In an operating state of the fuel cell unit 2, the purging gas, which is inert in terms of reactivity with the fuel, is introduced into the monitoring chambers via the purging gas feed line 58. In the process the monitoring chambers are subjected to a pressure (purging gas pressure) which is greater than a pressure in the chambers through which the fuel/oxidizing agent can flow so as to counteract an escape of the fuel/oxidizing agent from the chambers through which the fuel/oxidizing agent can flow in the event of a leak being present. The purging gas is extracted from the monitoring chambers via the purging gas discharge line 60 by means of the suction extractor device.

In this exemplary embodiment, the threshold value stored in the evaluation device is a predetermined minimum pressure. If a chamber of the fuel cell unit 2 through which the fuel/oxidizing agent can flow has a leak, the purging gas flows from the monitoring chambers into said chamber and the purging gas pressure decreases. As soon as the purging gas pressure measured by the pressure measuring device 56 drops below the minimum pressure stored in the evaluation device 54, the electrically controllable valve 38 of the fuel supply line

PCT/EP2014/079405 / 2013P19130WO 32 32, the electrically controllable valve 38 of the coolant supply line and the electrically controllable valve 38 of the oxidizing agent supply line 36 are actuated by the evaluation device 54 in such a way that the three valves 38 are closed.

In the exemplary embodiments in Figures 5 to 8, monitoring of the monitoring chambers can be carried out both in an inoperative state and in an operating state of the fuel cell unit 2.

The following description, discussed in connection with FIG 9 and FIG 10, is essentially limited to the differences compared to the exemplary embodiment shown in Figures 1 to 4, to which reference is made in respect of features and functions that remain the same. Features that are not mentioned are included in the following exemplary embodiment without being described again. FIG 9 shows a section through a further fuel cell unit 2. Said further fuel cell unit 2 differs from the fuel cell unit 2 from FIG 1 in that the depicted fuel cell 4 of the further fuel cell unit 2 has an inspection opening 62 instead of connecting ports arranged in the collector plates. Said inspection opening 62 is arranged in the secondary seal 10. Furthermore, the monitoring chamber 16 is connected to its surroundings, i.e. to the environment of the further fuel cell unit 2, by means of the inspection opening 62.

Three sectional planes II, III, X oriented perpendicularly to the drawing plane are shown in FIG 9. A section through the further fuel cell unit 2 along the sectional plane II corresponds to the section shown in FIG 2, while a section

PCT/EP2014/079405 / 2013P19130WO 33 along the sectional plane III corresponds to the section shown in FIG 3. FIG 10 shows a section through the further fuel cell unit 2 from FIG 9 along the sectional plane X.

It can be seen from FIG 10 that an inspection opening 62 is arranged in each of the secondary seals 10, said inspection openings 62 being arranged one above the other. Since there are no connecting ports in the collector plates 24, the individual monitoring chambers 16 arranged between collector plates 24 are not connected to one another, but are separated from one another by the collector plates 24.

Individual monitoring of the separate monitoring chambers 16 is made possible by means of the arrangement of the inspection openings 62 shown in FIG 10, which in turn allows simple localization of a leakage.

An individual monitoring of the monitoring chambers 16 can be realized e.g. in that a suitable measuring device, in particular a gas sensor, is held to one of the inspection openings in order to determine whether some of the fuel/coolant/oxidizing agent enters the associated monitoring chamber 16. In this way it is possible to detect whether a leak is present at one of the primary seals abutting said monitoring chamber 16.

The further fuel cell unit 2 shown in FIG 9 and FIG 10 can furthermore be arranged in a housing (not shown) which can be monitored for leakage in the fuel cell unit 2 by means of a further measuring device. If a leak is detected by means of

PCT/EP2014/079405 / 2013P19130WO 34 the further measuring device, the above-described individual monitoring of the monitoring chambers 16 can be carried out.

In this case it makes sense to hold the measuring device to the individual inspection openings 62 in succession until that monitoring chamber 16 into which some of the fuel/coolant/oxidizing agent enters has been identified.

Alternatively, one measuring device in each case can be connected in a stationary arrangement to each of the inspection openings 62, thereby enabling simultaneous automatic monitoring of all of the monitoring chambers 16.

Although the invention has been illustrated and described in more detail on the basis of the preferred exemplary embodiments, the invention is not limited by the disclosed examples and other variations may be derived herefrom without leaving the scope of protection of the invention.

Claims

1. A fuel cell unit having at least one chamber through which a fluid can flow, said chamber being sealed off from its surroundings by means of a primary seal, wherein the primary seal is surrounded by a secondary seal such that a monitoring chamber is formed between the primary seal and the secondary seal, said monitoring chamber being bounded by the primary seal and the secondary seal and being sealed off from its surroundings by means of the secondary seal, and in that there is provided in the secondary seal an inspection opening by means of which the monitoring chamber is connected to its surroundings.

2. The fuel cell unit as claimed in claim 1, wherein the at least one chamber through which the fluid can flow is a fuel chamber through which a fuel can flow.

3. The fuel cell unit as claimed in claim 1 or 2, wherein the at least one chamber through which the fluid can flow is an oxidizing agent chamber through which an oxidizing agent can flow.

4. The fuel cell unit as claimed in one of the preceding claims, wherein the at least one chamber through which the fluid can flow is a coolant chamber through which a coolant can flow.

5. The fuel cell unit as claimed in one of the preceding claims, wherein the at least one chamber through which the fluid can flow is a supply channel or a disposal channel through which a coolant, fuel or oxidizing agent can flow.

6. The fuel cell unit as claimed in one of the preceding claims, wherein a plurality of such chambers through which a fluid can flow, of which at least one chamber is a fuel chamber, at least one chamber is an oxidizing agent chamber, at least one chamber is a coolant chamber, at least one chamber is a supply channel and at least one chamber is a disposal channel.

7. The fuel cell unit as claimed in one of the preceding claims, wherein at least one connecting port is provided by means of which the monitoring chamber is connected to at least one further monitoring chamber.

8. The fuel cell unit as claimed in claim 7, wherein at least one measuring device, in particular a pressure measuring device or a gas sensor, is connected to the connecting port.

9. The fuel cell unit as claimed in claim 8, wherein the at least one measuring device is at least one pressure measuring device or gas sensor.

10. The fuel cell unit as claimed in claim 8 or 9, wherein the measuring device is connected to an evaluation device, the evaluation device is connected to an electrically controllable valve of a fuel supply line and the evaluation device is disposed for controlling said valve.

11. The fuel cell unit as claimed in one of claims 7 to 10, wherein a pump is connected to a first such connecting port on the input side and to a second such connecting port on the output side.

12. The fuel cell unit as claimed in one of the preceding claims, wherein the primary seal and the secondary seal are in each case embodied as a sealing frame.

13. The fuel cell unit as claimed in one of the preceding claims, wherein the primary seal and the secondary seal substantially consist of an injection-molded elastomer or the primary seal and the secondary seal are in each case embodied by means of a welded seam.

14. A method for leakage monitoring of a fuel cell unit as claimed in one of the preceding claims, wherein a measurement variable of the monitoring chamber is measured by means of a measuring device.

15. The method as claimed in claim 14, wherein the measurement variable of the monitoring chamber is a pressure or a fuel concentration in the monitoring chamber.

16. The method as claimed in claim 14 or 15, wherein the measured measurement variable is compared with a threshold value by means of an evaluation device connected to the measuring device and an electrically controllable valve of a fuel supply line is actuated by the evaluation device in such a way that the valve is closed as soon as the measurement variable exceeds the threshold value.