Method for manufacturing fuel cells with different power outputs, and corresponding fuel cells

Abstract

The invention relates to a method for manufacturing several types of fuel cells, having different power outputs according to the types of cells, the cells having a stack of plates each comprising first channels for the circulation of reactive gases, dihydrogen and air respectively, and second channels for the circulation of a heat-transfer fluid, a proton-exchange membrane being inserted between two adjacent plates, according to which method: - plates of a single format are obtained; - at least two types of membrane are obtained, having at least two membrane formats each having different dimensions; - the plates are assembled with a first one of said membrane formats, so as to produce a first type of fuel cell, having a first power output; - the plates are assembled with a second one of said membrane formats, so as to produce a second type of fuel cell, having a second power output, so as to have several types of cells, having different power outputs, from identical plates and membranes specific to each type of cell, each cell of a given type of cell using membranes of the same formats, intended for said type of cell.

Description

[0001] DESCRIPTION

[0002] TITLE: Process for manufacturing fuel cells of different powers, and corresponding fuel cells.

[0003] 1. Field of the invention

[0004] The field of the invention is that of hydrogen fuel cells. More specifically, the invention relates to the improvement of such fuel cells, and in particular of the bipolar and monopolar plates of which they are made.

[0005] Such plates, and therefore such batteries, find applications in many fields, whenever it is necessary to produce electrical energy, particularly autonomously, for example in vehicles (cars, utility vehicles, trucks, buses, trains, boats, aircraft, etc.), generator sets, etc.

[0006] In particular, the invention relates to the manufacture of batteries delivering power adapted to a given application or need, efficiently and economically.

[0007] 2. Prior art

[0008] The principle of the fuel cell has been known for many years. It has been implemented in the space sector, and numerous projects have also been developed by various car manufacturers.

[0009] A hydrogen fuel cell is based on the principle illustrated in Figure 1, and produces electrical energy by a chemical reaction between hydrogen (H2) and oxygen (O2). This chemical reaction is described by the equations below:

[0010] [Chem 1] H2-> 2H + + 2nd

[0011] O2+ 4 H + + 2nd -> 2H2O

[0012] Hz + 1 / 202 -> HzO A r H < 0

[0013] The optional term A rH < 0 only indicates that the reaction is exothermic.

[0014] This reaction occurs in what is called an active zone of an assembly of an electrolyte membrane and electrodes (MEA), i.e. a stack of membranes allowing the exchange of H ions. + , placed between an anode, receiving dihydrogen from a reservoir, and a cathode receiving dioxygen (O2) from the outside air.

[0015] As illustrated in Figure 1, the fuel, dihydrogen (H2), is introduced (Fl) into the cell, to come into contact with the anode A. A part of the dihydrogen enters (F2) the anode A, in which the dihydrogen molecules are separated into electrons e" and H ions +which pass through the electrolyte E towards the cathode C. The latter is in contact with the air brought from outside (F3) whose oxygen O2 molecules (F4) combine with the H ions + and the electrons e" to produce (F5) water (H2O). This water (F6) and the unused air (F7) are evacuated.

[0016] Anode A is therefore the element in which oxidation occurs: H2 ->2H + + 2nd _ , and the cathode C is the element in which the reduction occurs: O2 + 4H + + 4th _ -> 2H2O. The electrons e" circulate (F8) between the anode A and the cathode C, producing an electric current E, which is used to drive an electric motor and / or charge a battery.

[0017] This reaction is exothermic, and the various components of the battery can heat up quickly. The entire system must therefore be cooled. The design of the mechanical parts must therefore be adapted to be supplied with coolant, or heat transfer fluid.

[0018] The structure of a fuel cell, implementing this chemical reaction, is illustrated in Figure 2. The cell 21 consists of a stack of cells 22, placed between two end plates 23i and 232.

[0019] The constituent elements of a 22 cell are detailed, exploded, in Figure 3. It comprises two plates, bipolar or monopolar, between which is placed an electrolyte membrane. The monopolar plates are the first and last plates in the cell stack. They generally have the same design as a bipolar plate, but inlets are closed so that the plate does not receive one of the gases. The cell thus comprises a monopolar cathode plate not receiving dihydrogen and a monopolar anodic plate not receiving dioxygen.

[0020] The bipolar plates, stacked between the two monopolar plates, are formed by the assembly of two metal half-plates 31, 32 (one anode half-plate 31 and one cathode half-plate 32), which can be welded, brazed or glued. A space between the two metal half-plates is defined by the forming of these to define on the one hand zones 33, 34 receiving a cooling liquid and on the other hand channels allowing the circulation of gases, respectively dihydrogen and dioxygen (extracted from the air). MEA membranes 35 are interposed between the half-plates.

[0021] The plates are designed to be assembled to form a battery with a defined power output. Battery design is complex and specific. The designer of each plate must design it specifically to deliver the required power.

[0022] Depending on the application, different power levels may be required. Therefore, it is necessary to design a plurality of suitable plates. This design requires precise characterization of the shapes and dimensions of the plate and its various elements, particularly the channels, to obtain the required intensity at the battery terminals in the most efficient way possible. It is then necessary to develop specific tooling to manufacture each plate. This is expensive and complex.

[0023] 3. Main characteristics of the invention

[0024] The invention proposes a solution for simplifying the manufacture of batteries of different powers, or intensities, at constant voltage, and for reducing manufacturing costs, in the form of a method for manufacturing several types of fuel cells, delivering different powers according to said types of cells, said fuel cells having a stack of plates each comprising first channels for circulating reactive gases, respectively dihydrogen and air, and second channels for circulating a heat transfer fluid, a proton exchange membrane being interposed between two neighboring plates.

[0025] The invention implements the following steps: plates of a single format are obtained; at least two types of membrane are obtained having at least two membrane formats each having different dimensions; said plates are assembled with a first of said membrane formats, so as to produce a first type of fuel cell, delivering a first power; said plates are assembled with a second of said membrane formats, so as to produce a second type of fuel cell, delivering a second power, so as to have several types of cells, delivering different powers, from identical plates and membranes specific to each type of cell, each cell of a given type of cell using membranes of the same formats, intended for said type of cell.

[0026] Thus, plates of a single format and at least two membrane formats, each having different dimensions, are used, and said plates are assembled with one of said membrane formats, so as to produce at least two types of fuel cell, delivering different powers, from identical plates. In this way, it is possible to have several types of cells, and therefore to efficiently adapt the cell used according to the needs, using a single type of plate, only by varying the membrane format. It is thus quick and simple to produce several types of cells, without having to design and produce different types of plates, which is complex and expensive. In addition, economies of scale are obtained in the manufacture of these plates intended for several cell powers.

[0027] Each type of battery is equipped, for all of these plates, with the same type of membrane (the type of membrane only varies from one battery to another). This achieves an industrial gain, by reducing the complexity and production cost of several types of batteries.

[0028] According to a particular embodiment, the first channels and the second channels of said plates extend in orthogonal directions (DI, D2), respectively according to the length and the width of said plate, and at least two of said types of membrane have identical heights covering all of said first channels over part of their length.

[0029] Thus, each type of battery uses all of the first channels, or reactant channels, over all or part of their length, depending on the power required. Depending on the type of battery, the membrane may not cover all of the second channels carrying the heat transfer fluid.

[0030] The term "membrane height" is used to refer to the distance in the direction in which the first channels extend.

[0031] According to a particular embodiment, said first channels all have the same pattern along the direction D1. The geometry of the channels of the plates is thus adapted to allow optimized use of the same plate for each membrane format, in particular formats using the entire height of the plate.

[0032] Of course, other formats and other dimensions are possible, depending on the needs. To implement the method efficiently, it is desirable that said plates are designed so as to ensure a substantially constant diffusion of said reactive gases and said heat transfer fluid in an area coinciding with the membrane used, whatever the surface of the latter.

[0033] According to a particular implementation, said first and / or said second channels follow a path defining undulations in a corrugation plane substantially perpendicular to the main plane of said plate.

[0034] In other words, the plate, and in particular its active surface, that is to say the surface ensuring the exchange of protons, located opposite the membrane, is defined in three dimensions, and no longer according to a plane. It has undulations, or "hollows" and "bumps", determined in such a way as to optimize the pressure of said gases and / or the flow rate of said heat transfer fluid.

[0035] According to a particular embodiment, said first channels extend in a direction orthogonal to the direction of said second channels.

[0036] In particular, said channels may extend parallel to the length and width of the plate respectively, crossing each other and following the undulations.

[0037] According to another aspect, which may where appropriate be implemented independently of the first, said channels have a variable section.

[0038] This makes it possible in particular to optimize the pressure of said gases and / or the current density delivered by said plate.

[0039] In particular, said minimum section may correspond to the locations where one of said first channels crosses one of said second channels.

[0040] The invention also relates to fuel cells manufactured according to the method described above.

[0041] Some of these batteries have a first predetermined power, corresponding to a first membrane format covering a maximum active surface area of ​​said plates. Other batteries may have a second predetermined power, corresponding to a second membrane format with a surface area less than said maximum active surface area of ​​said plates.

[0042] In particular, these batteries may belong to the group comprising membranes having: a second format covering substantially 75% of said active surface; or a third format covering substantially 50% of said active surface; or a fourth format covering substantially 25% of said active surface.

[0043] In particular, when said first channels have a pattern repeated at least twice, each of said membrane formats can cover a distinct number of patterns.

[0044] 4. list of figures

[0045] Other characteristics and advantages of the invention will appear more clearly on reading the following description of an example of implementation, given as a simple illustrative and non-limiting example, and the appended figures among which:

[0046] [Fig 1]: Figure 1, already described in the preamble, illustrates the general principle of a fuel cell;

[0047] [Fig 2]: Figure 2, already described in the preamble, shows the structure of a fuel cell, comprising a stack of cells;

[0048] [Fig 3]: Figure 3, already described in the preamble, presents the constituent elements of a cell of Figure 2, exploded;

[0049] [Fig 4]: Figure 4 schematically illustrates the main elements of a bipolar plate of the cell of Figure 3;

[0050] [Fig 5A], [Fig 5B]: Figures 5A and 5B illustrate respectively the path of the gas flow (dihydrogen or air) and the path of the heat transfer fluid, following undulations (only a portion of the half-plate is shown);

[0051] [Fig 6]: Figure 6 is another view of a portion of the half-plate, showing the undulations in the two orthogonal directions defined by the channels;

[0052] [Fig 7]: Figure 7 schematically illustrates an example of undulation;

[0053] [Fig 8]: Figure 8 illustrates the variation of the section of a gas channel;

[0054] [Fig 9]: Figure 9 illustrates an example of a plate allowing the implementation of the invention; [Fig 10A]: Figure 10A illustrates a first use of the plate of Figure 9, in which the membrane covers 100% of the active surface;

[0055] [Fig 10B]: Figure 10B illustrates a first use of the plate of Figure 9, in which the membrane covers 75% of the active surface;

[0056] [Fig 10C]: Figure 10C illustrates a first use of the plate of Figure 9, in which the membrane covers 50% of the active surface;

[0057] [Fig 10D]: Figure 10D illustrates a first use of the plate of Figure 9, in which the membrane covers 25% of the active surface;

[0058] [Fig 11]: Figure 11 illustrates the method of the invention, in the form of a block diagram.

[0059] 5. Description of a particular embodiment

[0060] 5.1 Method of the invention

[0061] The invention is therefore based on a completely new approach to the design and manufacture of fuel cells. According to the prior art, the person skilled in the art develops a specific plate design for the required power, and in particular for the active part of the plate, opposite which the membrane allowing proton exchange will be placed.

[0062] According to the invention, on the other hand, a single plate is provided and several (at least two) membrane sizes can be placed between two plates. Thus, it is possible to easily manufacture several batteries, of different powers, from a single type of plate.

[0063] Thus, according to a particular embodiment: plates of a single rectangular format are obtained, the first channels and the second channels of which extend in orthogonal directions (DI, D2), respectively according to the length and the width of said plate; at least two types of membrane are obtained, corresponding to at least two membrane formats each defined by a height and a length, the heights being identical for all the types of membrane and chosen so as to cover all of said first channels, and the lengths being different according to the types of membranes.

[0064] As illustrated in the example of Figure 9, there are plates 90, represented in a simplified manner, and comprising first channels 91 transporting the reactants and second channels 92 transporting the heat transfer fluid, and orthogonal to the first channels 91. In this figure, the first channels 91 extend horizontally in the direction D1, and the second channels 92 orthogonally, in the direction D2.

[0065] These channels, and at least the first channels 91, advantageously have a repeated pattern (undulations and / or sections, as illustrated below). Thus, the first channels follow the same curves.

[0066] It is also possible to predict that a pattern is repeated, on the first channels, in the direction D1, and that the zones, here 4 in number, include an integer number of patterns.

[0067] Preferably, each pattern allows for optimized fluid distribution in the channels, and it is therefore desirable that each type of stack uses an integer number of patterns (i.e., the membranes cover an integer number of patterns).

[0068] Furthermore, regardless of the type of batteries, and therefore the format of the membrane, the preferred approach of the invention provides for exploiting all of the available reagents. Thus, advantageously, the membrane covers all of the reagent channels (i.e. it extends over the entire height, in the direction D2), as illustrated in Figures 10A to 10D.

[0069] The plate 90 can be cut into four portions 901, 902, 903 and 904, in the direction D1, which are identical or similar. It can be provided that each zone is optimized in terms of fluid distribution (and therefore efficiency in terms of power production), it is possible to use several types of membranes covering one or more portions: figure 10A: the membrane 101 covers the 4 portions (100% of the active surface); figure 10B: the membrane 102 covers 3 portions (75% of the active surface); figure 10C: the membrane 103 covers 2 portions (50% of the active surface); figure 10D: the membrane 104 covers only 1 portion (25% of the active surface).

[0070] This provides four battery powers from a single plate, i.e. without the need to design specific plates or specific tools.

[0071] The manufacturing method of the invention, according to one implementation, is illustrated in the figure

[0072] 11. Plates (El) are manufactured in a single dimension and format. Membranes of different dimensions are also manufactured, in this example in three distinct formats (E2A, E2B and E2C). Depending on the required power. The selected plates and membranes (E3A, E3B and E3C) are then assembled to manufacture batteries of different power levels: PA, PB or PC.

[0073] This approach goes against the habits of those skilled in the art, who have always developed plates and batteries for maximum power, that is to say by exploiting 100% of the active surface. It is not obvious for those skilled in the art to decide to exploit only a portion of the active surface.

[0074] Of course, it is important that the plates used are as efficient as possible. One of the difficulties in designing fuel cells, and these plates in particular, is the optimization and homogenization of the path of this coolant, which is generally imposed by what has been designed for the circulation of gases from the anode and cathode parts.

[0075] A particular embodiment of plates suitable for implementing the invention is described below.

[0076] 5.2 Main elements of a bipolar plate

[0077] Different types of channels are known for the circulation of gases, including straight channels, parallel to each other, serpentine or zigzag, extending over an active part of the plate.

[0078] The efficiency of these plates is not perfect. Despite the designers' efforts, there are significant variations in gas pressure, particularly oxygen, in the active surface, and an uneven distribution of the heat transfer fluid, particularly partial in the middle of the plate. This introduces thermal inhomogeneity, notably the presence of hot spots.

[0079] As a result, this introduces an inhomogeneity in the creation of the electric current in the plate.

[0080] Such plates are also difficult to manufacture and assemble. In particular, they have poor rigidity along their length, which leads to the use of relatively thick, therefore heavy, strips and requires the use of manufacturing techniques that are not well-suited to mass production, such as brazing or multiple welds. There is therefore a need for a new approach to the production of such plates, to enable production that is more suited to series production requirements and / or to improve their efficiency.

[0081] For information purposes, the main aspects of a bipolar plate are described below. As illustrated schematically in the example in Figure 4, there are several essential zones in a bipolar plate: active zone AZ: this is the location where the reaction takes place, consisting of many channels. One of the design difficulties of these plates is the need to provide a homogeneous distribution of the gas and not to overfeed or underfeed the channels. The surface area of ​​the active zone of the plate is the same as that of the active zone of the MEA;

[0082] Homogenization zone HZ: location in which the flows mix to supply the channels of the active zone with the same quantity of gas / coolant. It is similar to a funnel, going from a flow inlet towards the start of the active zone;

[0083] ABP anti-bypass zone: an anti-bypass zone is necessary for mechanical reasons such as good retention of the AME and / or good compression of the seal. It is then necessary to avoid a bypass effect for the gases, which could induce drops in gas pressure, and therefore the efficiency of the entire system;

[0084] M-manifolds: Manifolds are sizing elements, including inlets and outlets for each gas and the refrigerant. Generally, their position and dimensions define the overall dimensions of the plate;

[0085] Inlets I: The inlets are what allow the gas and refrigerant to go from the headers to the gas or refrigerant side of the plate;

[0086] G-guide interfaces: elements helping to hold the stack in position during the stacking process;

[0087] V measuring electrodes: allowing a pin or special device to be connected between the anode and the cathode to take measurements;

[0088] Data matrix: allowing precise identification of the plate. It can include a serial number, a supplier identification number, a time, a manufacturing date, etc. Its dimensions are generally 4x4 or 5x5 mm;

[0089] Poka-Yoke: mechanical element which constrains the positioning of the half-plates;

[0090] Welds: holding the half-plates together, they can be waterproof or simply intended to reinforce the structure.

[0091] 5.3 Three-dimensional (3D) topology

[0092] The invention therefore proposes, according to a particular embodiment, a new approach to bipolar or monopolar plates, according to which the active zone thereof, that is to say substantially the zone opposite the membrane, allows the flows of gas and heat transfer fluid to move in the three dimensions of space.

[0093] More specifically, as illustrated by Figures 5A and 5B, respectively representing the path of the gas flow (dihydrogen or air) and the path of the heat transfer fluid, the channels 51 intended for the gas and the channels 52 intended for the heat transfer fluid extend in orthogonal directions DI, D2, respectively according to the length and width of the plate, and intersect. In addition, these channels have undulations in both directions, the surface of the active part therefore not being flat, but having "hollows" and "bumps", as can be seen in particular in Figure 6.

[0094] This approach presents, compared to the prior art according to which the channels extend in a plane, the plane defined by the plate, can present numerous advantages, depending on the implementations: improvement of thermal convection, making it possible to reduce the flow rate and / or improve the efficiency of the system; better rigidity of the plate and / or weight saving, making it possible to reduce the thickness of the strip; improvement of electrical contact and reduction of electrical contact resistance; facilitation of the assembly of the battery, and in particular of the alignment of the cells with each other, making it possible in particular to avoid sealing problems; homogenization of the partial pressure of oxygen along the active surface; homogenization of the creation of current and improvement of the current density.

[0095] Figure 7 schematically illustrates an example of a ripple, characterized by its length, or period, P and its radius R, or maximum height of the ripple. Of course, the shape of the ripple may be different from that illustrated.

[0096] The inventors determined, taking into account in particular the tangency constraints of the fluid channels, a difference between the radius R and the period P less than or equal to 20% was effective, so as not to make the couple (radius; half-period) too strong and to obtain a balance between undulations that are too pronounced and undulations that are too tenuous, for example: R = P ± 20%.

[0097] As an indication, the dimensions can be of the order of:

[0098] %P: between 8 and 12 mm;

[0099] A: Between 16 and 24 mm.

[0100] As illustrated in Figure 7, for example, we can implement a radius R of 20 mm and a half-period of 10 mm.

[0101] More generally, the dimensions of the half-plate can be of the order of: length: between 250 and 350 mm; width: between 150 and 200 mm.

[0102] The number of gas channels is, for example, between 50 and 100, and the number of heat transfer fluid channels between 50 and 100.

[0103] 5.4 variable section channels

[0104] According to another aspect of the invention, which can, if necessary, be implemented independently of the 3D topology described above, the cross-section of the channels is varied. Indeed, the inventors have found that the active zones according to the prior art, which have channels for conveying fluids of constant cross-section, introduce heating and generate inhomogeneous partial pressures. In addition, this is detrimental to the rigidity of the plate.

[0105] To overcome these problems, gas channels are provided in particular whose section varies periodically, as illustrated by figure 8, in which it can be seen that, along the path 81 of the fluid, the section of the channel varies between a maximum section S ma x 82 and a minimum section Smin 83. This makes it possible in particular to improve the rigidity of the plate, to obtain better thermal convection, to balance the partial pressures and / or to obtain better electrical contact.

[0106] According to one embodiment, the maximum section S max corresponds to a location where the maximum height H of the gas channel 84 and the minimum section Smin at a location where the gas channel 84 crosses a heat transfer fluid channel 85 (crossing, or "crosschannel" in English), the height being reduced to the minimum height h.

[0107] The ratio between H and h is preferably between 2 and 3, and for example such that H = 2.5 * h.

[0108] For simplification, we consider that the width L of the channel, which varies little, is constant. Thus, the section S max is approximately L * H, and the section Smin is approximately (H - h) * L.

[0109] We therefore preferably choose a section variation ratio S max / Smin between 1.5 and 2, for example around 1.6.

[0110] It should be noted that this figure 8 illustrates a portion of a half-plate, and therefore a half-section of the channels which are obtained by assembling two half-plates, to form a complete plate. The ratios, however, obviously remain the same. As an indicative example, the dimensions can be of the order of:

[0111] H: between 0.2 and 0.35 mm; h: between 0.1 and 0.15 mm;

[0112] L: between 0.5 and 1.3 mm.

[0113] The lines defining the undulations and / or the variable sections can in particular be defined by the finite element method, so as to maximize one or more criteria, and in particular: optimization of the fluid distribution in said channels; optimization of the rigidity of each plate; limitation of the thickness of a battery cell, formed by a first bipolar plate, a membrane and a second bipolar plate.

[0114] These plots preferably have a channel pattern repeated several times, as illustrated in Figure 9.

[0115] 5.5 Manufacturing and assembly The approach of the invention makes it possible to manufacture half-plates from thinner strips than those conventionally used, for example 316L stainless steel with a double carbon coating, with a thickness of 0.075 mm. This makes it possible to produce batteries requiring less material, and therefore less heavy and less expensive.

[0116] Of course, the three-dimensional shape, the half-plates with corrugations in two orthogonal directions (corresponding to the directions of the channels) and / or the presence of channels with variable sections require special care during the production of the half-plates, for example by stamping or molding. A preferred manufacturing method is hydroforming, which has many advantages, such as precision in the repeatability of the process, elasticity after forming, homogeneity of the wall thickness, efficiency of the contact zones, adaptability...

[0117] On the other hand, this shape and / or the reduced thickness of the strips can allow a simpler and more reliable assembly of the two half-plates forming each plate, in particular for the joining of the half-plates, for example by welding, and for the assembly of the plates to form a stack.

[0118] The invention thus makes it possible to obtain highly efficient plates and batteries, suitable for numerous applications, for example in motor vehicles, and more generally in any type of vehicle or means carrying fuel cells.

Claims

DEMANDS 1. A method for manufacturing several types of fuel cells, delivering different power outputs depending on said types of cells, said cells having a stack of plates each comprising first circulation channels for reactive gases, respectively dihydrogen and air, and second circulation channels for a heat transfer fluid, a proton exchange membrane being interposed between two adjacent plates, characterized in that: plates of a single format are obtained; at least two types of membrane are obtained, each having at least two membrane formats, each having different dimensions; said plates are assembled with a first of said membrane formats, so as to produce a first type of fuel cell, delivering a first power output;said plates are assembled with a second of said membrane formats, so as to produce a second type of fuel cell, delivering a second power, so as to have several types of fuel cells, delivering different powers, from identical plates and membranes specific to each type of fuel cell, each fuel cell of a given type of fuel cell using membranes of the same formats, intended for said type of fuel cell.

2. A method for manufacturing fuel cells according to claim 1, characterized in that the first channels and the second channels of said plates extend along orthogonal directions (DI, D2), respectively along the length and width of said plate, and in that at least two of said types of membrane have identical widths covering all of said first channels over a part of their length.

3. Method for manufacturing fuel cells according to any one of claims 1 and 2, characterized in that said first channels all have the same pattern along the direction Dl.

4. Method for manufacturing fuel cells according to any one of claims 1 to 3, characterized in that said plates are designed so as to ensure a substantially constant diffusion of said reactive gases and said heat transfer fluid in an area coinciding with the membrane used, regardless of the surface area of ​​the latter.

5. Method for manufacturing fuel cells according to any one of claims 1 to 4, characterized in that said first and / or second channels follow a path defining undulations in a plane of undulation substantially perpendicular to the main plane of said plate.

6. A method for manufacturing fuel cells according to any one of claims 1 to 5, characterized in that said channels have a variable cross-section between a maximum cross-section (S max ) and a minimum section (S min ), said minimum section (S m in) corresponding to the locations where one of said first channels crosses one of said second channels.

7. Fuel cell manufactured according to the process of any one of claims 1 to 6.

8. Fuel cell according to claim 7, characterized in that it has a first predetermined power, corresponding to a first membrane format covering a maximum active area of ​​said plates.

9. Fuel cell according to claim 7, characterized in that it has a second predetermined power, corresponding to a second membrane format with a surface area less than said maximum active surface of said plates.

10. Fuel cell according to claim 9, characterized in that it belongs to the group comprising membranes having: a second format covering substantially 75% of said active surface; or a third format covering substantially 50% of said active surface; or - a fourth format covering substantially 25% of said active surface.

11. Fuel cell according to any one of claims 7 to 10, characterized in that, said first channels have a pattern repeated at least twice, each of said membrane format covers a distinct number of patterns.

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