Bipolar plate for fuel cell

Abstract

The present invention relates to a bipolar plate (14) for a fuel cell, comprising a first face (18) and a second face, a first set of channels (26) extending over the first face and a second set of channels extending over the second face, the bipolar plate further comprising cooling units (30) comprising circulation ducts (36) formed by orifices passing through the thickness of the bipolar plate from the first face to the second face, the circulation ducts being configured to circulate a cooling fluid in the bipolar plate. The cooling units are surrounded by the first set of channels on the first face and by the second set of channels on the second face.

Description

[0001] TITLE: Bipolar plate for fuel cell

[0002] The present invention relates to a bipolar plate for a fuel cell, of the type comprising a first face and a second face, opposite to the first face, a first set of channels extending over at least a part of the first face and a second set of channels extending over at least a part of the second face, the bipolar plate further comprising at least one cooling unit, said cooling unit comprising at least one circulation duct formed by an orifice passing through the thickness of the bipolar plate from the first face to the second face, said circulation duct being configured to circulate a cooling fluid in the bipolar plate.

[0003] A fuel cell is a device that generates electricity through an electrochemical reaction between a fuel, in particular dihydrogen, more simply called hydrogen, and an oxidizer, in particular dioxygen, more simply called oxygen, often taken from the air.

[0004] For this purpose, a fuel cell typically comprises a series of elementary cells, usually called a "stack." Each elementary cell consists of a first and a second electrode, separated by a membrane. The first electrode, called the anode, is supplied with hydrogen, and the second electrode, called the cathode, is supplied with oxygen. Each elementary cell is further positioned between two bipolar plates. Each bipolar plate is connected on one side to the anode of an elementary cell and on the other side to the cathode of the next elementary cell. Each bipolar plate is thus configured to supply hydrogen to the anode on one side and oxygen to the cathode on the other.

[0005] Electricity production is accompanied by the production of water and heat. To ensure the cooling of the fuel cell, it is known to construct bipolar plates from two half-plates, a first half-plate and a second half-plate, assembled together, and to circulate a coolant between the two half-plates. More specifically, the two half-plates define on their inner surface a set of channels configured to circulate a coolant designed to prevent overheating of the fuel cell, while the outer surface of each half-plate is equipped with a set of channels to circulate hydrogen on one side and oxygen on the other. However, such a bipolar plate is not entirely satisfactory.The need for compatibility in the shape of the three channel assemblies complicates the design and manufacturing of the bipolar plate by increasing the number of parameters to consider and limiting the choice of channel geometry, thereby increasing the risk of hot spots in the fuel cell. Indeed, in order to manufacture each half-plate, for example by stamping, it is not possible to optimally choose the shape of the channel assemblies on both faces of each half-plate, which reduces the potential for optimizing the cooling and / or circulation of hydrogen or oxygen.

[0006] Furthermore, the coolant supplying the cooling channels is routed between the half-plates via the periphery of the bipolar plates, which reduces the overall cooling efficiency of each bipolar plate. The coolant heats up as it flows from one edge of the plate to the opposite edge, thus degrading cooling at the opposite edge.

[0007] The aim of the invention is therefore to overcome these disadvantages by proposing a bipolar plate which limits the appearance of hot spots and facilitates the design of the plate.

[0008] To this end, the invention relates to a bipolar plate for a fuel cell of the aforementioned type, in which said cooling unit is surrounded by the first set of channels on the first face and by the second set of channels on the second face.

[0009] The circulation of the cooling fluid through channels formed by through-holes eliminates the need for a third set of channels inside the bipolar plate, simplifying the design of the other two sets. Furthermore, the presence of these channels allows the bipolar plate to be manufactured as a single unit, thus eliminating the step of joining two half-plates together.

[0010] The cooling unit is surrounded by the channels of the first and second assemblies, which ensures cooling "at the core" of the bipolar plate, and not from an edge of it, so that the cooling of the entire bipolar plate is improved.

[0011] The bipolar plate according to the invention may further comprise one or more of the following features, considered alone or in any technically feasible combinations: - the bipolar plate comprises a plurality of cooling units distributed in the bipolar plate, said cooling units being preferably arranged at equidistances from each other;

[0012] - the cooling unit further includes a clamping orifice passing through the thickness of the bipolar plate from the first face to the second face, the orifice opening into the first face and into the second face and being intended to receive a clamping element;

[0013] - the cooling unit includes a plurality of circulation ducts;

[0014] - the circulation channels are distributed around the clamping orifice;

[0015] - the cooling unit comprises on the first face a first ring extending outward from the first face and extending between the channels of the first assembly and the circulation duct, and on the second face a second ring extending outward from the second face and extending between the channels of the second assembly and the circulation duct;

[0016] - the first set of channels comprises a plurality of baffles arranged one after the other in lines, and the second set of channels also comprises baffles arranged one after the other in columns, perpendicular to the lines; and

[0017] - the bipolar plate includes at its periphery at least two oblong lights, the channels of the first set opening into at least one of said oblong lights, the channels of the second set opening into at least one other of said oblong lights.

[0018] The invention also relates to a fuel cell of the type comprising at least one elementary cell formed of two electrodes separated by a membrane, each elementary cell being arranged between two bipolar plates as described above, the cooling units of said bipolar plates extending opposite each other.

[0019] According to an optional feature of the fuel cell, the fuel cell includes at least one seal, the seal extending between the cooling units of two bipolar plates arranged opposite each other, the seal hermetically separating the space between these two cooling units and the elementary cell arranged between said bipolar plates.

[0020] The invention will become clearer upon reading the following description, given solely by way of non-limiting example, and made with reference to the accompanying drawings, in which: Figure 1 is a schematic exploded perspective view of a fuel cell according to the invention; Figure 2 is a schematic perspective view of an elementary cell and two bipolar plates according to the invention, said elementary cell being arranged between said two bipolar plates; Figure 3 is a schematic cross-sectional view of the elementary cell and the bipolar plates along the axis lll-lll of Figure 2; Figure 4 is a schematic front view of a cooling unit for one of the bipolar plates of Figure 2; Figure 5 is a schematic perspective view of an elementary cell and two bipolar plates according to a second embodiment of the invention.said elementary cell being arranged between said two bipolar plates, and figure 6 is a schematic front view representation of a cooling unit of one of the bipolar plates of figure 5.

[0021] With reference to Figure 1, a fuel cell 10 is described comprising at least one elementary cell 12 and at least one bipolar plate 14.

[0022] According to one embodiment, the fuel cell 10 further comprises two monopolar end plates 16 intended to close the fuel cell 10.

[0023] Each elementary cell 12 is surrounded by two plates, either by two bipolar plates 14, or by one bipolar plate 14 and one monopolar end plate 16.

[0024] Thus, according to one embodiment, a fuel cell 10 successively comprises a monopolar end plate 16, an elementary cell 12, a bipolar plate 14 according to the invention, another elementary cell 12 and another monopolar end plate 16.

[0025] The fuel cell generates electricity through a reaction between a fuel, specifically dihydrogen (hereafter referred to simply as hydrogen), and an oxidant, specifically dioxygen (hereafter referred to simply as oxygen), usually obtained from the air. In addition to electricity, the reaction between hydrogen and oxygen produces water and heat.

[0026] For example, the fuel cell 10 generates an electrical power output roughly between 1 and 500 kW.

[0027] The fuel cell 10, for example, is configured to power transport devices including an electric motor such as a car, bus or boat.

[0028] In the example in Figure 1, the fuel cell 10 comprises a plurality of elementary cells 12; three elementary cells 12 are shown here. A set of elementary cells 12 is more commonly called a "stack." Each elementary cell 12 consists of two electrodes, a first and a second electrode, separated by a membrane.

[0029] The first electrode, called the anode, is supplied with hydrogen, and the second electrode, called the cathode, is supplied with oxygen. The reaction of hydrogen at the anode and the reaction of oxygen at the cathode produces a current flowing from the cathode to the anode. Electrodes are made, for example, of platinum or nickel.

[0030] The membrane is a solid membrane.

[0031] For example, the membrane is an ion-conducting membrane, meaning it can exchange protons or anions. The membrane allows the exchange of ions between the anode and the cathode while electrically insulating the anode from the cathode. The membrane is an electrical insulator.

[0032] Each elementary cell 12 is perforated to form at least one orifice 17 suitable for cooling the elementary cell 12. In the example of Figure 1, each elementary cell 12 comprises a plurality of orifices 17, in particular each elementary cell 12 comprises six orifices 17 in a central region and other orifices 17 at the periphery of the elementary cell 12.

[0033] Each elementary cell 12 is arranged between two bipolar plates 14, or between a bipolar plate 14 and a monopolar plate 16 for an elementary cell 12 placed at one end of the stack, also called the terminal elementary cell. Each bipolar plate 14 is then connected on one side to the anode of an elementary cell 12 and on the other side to the cathode of the next elementary cell 12. The fuel cell 10 is thus obtained by alternating between elementary cells 12 and bipolar plates 14.

[0034] All the bipolar plates 14 of the fuel cell 10 are identical and arranged parallel to each other.

[0035] The two monopolar end plates 16 are intended to close the stack. The monopolar end plates 16 have one face in contact with an elementary cell 12 and a free face 19. Thus, the monopolar end plates 16 are arranged at each end of the stack. In particular, one monopolar end plate 16 has one face in contact with the anode of a terminal elementary cell 12, and the other monopolar end plate 16 has one face in contact with the cathode of the other terminal elementary cell 12.

[0036] Furthermore, the monopolar end plates 16 are connected to a hydrogen source and an oxygen source (not shown) and are capable of supplying the entire fuel cell 10 with hydrogen and oxygen. The monopolar end plates 16 are also connected to a current collector (not shown). The current collector supplies electricity produced by the fuel cell 10 to the device to which the fuel cell 10 is connected. For example, the current collector powers an electric motor.

[0037] Figures 2 and 3 represent a single elementary cell 12 arranged between two identical bipolar plates 14, so we will now describe one of the bipolar plates 14 of this set.

[0038] In the example shown in Figure 2, the bipolar plate 14 has a rectangular shape. However, it is understood that other shapes are possible, for example, another polygonal shape.

[0039] The bipolar plate 14 comprises a first face 18 and a second face 20, opposite the first face 18, along a thickness direction of the bipolar plate 14. The thickness direction of the bipolar plate 14 corresponds to the direction in which the bipolar plates 14 and the elementary cells 12 are stacked in the stack of the fuel cell 10.

[0040] In the example of Figure 2, the first face 18 is attached to an anode of an elementary cell 12 not shown and the second face 20 is attached to the cathode of the elementary cell 12 included between the two bipolar plates 14.

[0041] In one variant, the first face 18 is attached to a cathode of an elementary cell 12 and the second face 20 is attached to an anode of another elementary cell 12.

[0042] The bipolar plate 14 is made from a single piece.

[0043] According to one embodiment, the bipolar plate 14 is made of at least one conductive metallic material. The bipolar plate 14 is, for example, made of copper or preferably aluminum.

[0044] Preferably, the bipolar plate 14 has a thickness between 0.5 mm and 2.5 mm depending on the material chosen to make the bipolar plate 14, measured along the thickness direction and corresponding to the distance separating the first face 18 from the second face 20.

[0045] The bipolar plate 14 has a periphery 22 and a central zone 24, also called the active zone, defined within the periphery 22.

[0046] The bipolar plate 14 comprises a first set of channels 26, a second set of channels 28 and at least one cooling unit 30. The second set of channels 28 is visible in Figure 3.

[0047] The bipolar plate 14 further includes at its periphery 22 at least two oblong lights 32A, 32B and at least one fixing hole 34. Similarly, each monopolar end plate 16 includes at least one cooling unit 30, at least two oblong lights 32A, 32B and at least one fixing hole 34.

[0048] However, each monopolar end plate comprises a unique set of channels, either the first set of channels 26 or the second set of channels 28.

[0049] According to one embodiment, all the elements of the bipolar plate 14 are engraved. For example, all the elements of the bipolar plate 14 are produced by stamping or embossing a plate, in particular a single-piece plate, corresponding to the desired dimensions for the bipolar plate 14.

[0050] The first and second sets of channels 26 and 28 of the bipolar plates 14, as well as at least one cooling unit 30, are advantageously formed, preferably simultaneously, by cold striking using a suitable punch.

[0051] This embodiment makes it possible in particular to form separate channels two by two in the plane of the first, respectively second, face 18, 20 of a distance of less than 1 mm, in particular less than 0.9 mm, or even less than 0.8 mm or 0.7 mm, in particular of the order of 0.6 mm.

[0052] This embodiment thus makes it possible to obtain the bipolar plates 14, in particular of one piece, in which the channels of the first and second sets of channels 26 and 28 are of possibly varied geometries and of finely controlled dimensions, in particular bipolar plates 14 of thin thickness, and this in a simple, fast and economical way.

[0053] A characteristic depth of the channels of the first set of channels 26 and / or the second set of channels 28 according to the thickness direction of the bipolar plate 14 is for example on the order of 0.4 mm or less, in particular on the order of 0.3 mm or less, in particular on the order of 0.2 mm.

[0054] As can be seen in the example in Figure 3, the channel depths of the first set 26 and the channel depths of the second set 28 of channels along the thickness direction of the bipolar plate 14 are advantageously strictly less than half the thickness of the bipolar plate 14 along this direction. This arrangement makes it possible to form first and second sets of channels 26 and 28 that are completely independent of each other within a single-piece plate.

[0055] The first set of channels 26 extends over at least part of the first face 18.

[0056] For example, the first set of channels 26 covers the central area 24 of the bipolar plate 14 on the first face 18. The shape and number of channels of the first set 26 in Figure 2 are given only as an example and it is understood that these may vary from one bipolar plate 14 to another.

[0057] In the example in Figure 2, the first set of channels 26 comprises a plurality of baffles 35, shown in detail in Figure 4, arranged one after the other in the form of lines 37, the baffles 35 covering the entire central area 24.

[0058] For example, the chicanes 35 are aligned one after the other so as to form a line 37 in a first direction and are arranged, in a second direction substantially perpendicular to the first direction, in a staggered pattern with respect to each other.

[0059] In other words, each chicane 35 of a first line 37 is arranged between two chicanes 35 of the line or lines 37 above or below said first line 37.

[0060] We understand from this example that two given lines 37 of chicanes 35 extending along the first direction and close to each other along the second direction delimit a channel of the first set of channels 26 extending along the first direction, the walls of this channel being discontinuous due to the spacing between the chicanes 35 of a given line 37.

[0061] The discontinuities in the walls of the channels in the first set of channels 26 allow the circulation of an anodic or cathodic gas between the channels of the first set of channels 26, in addition to the circulation of this gas within the channels themselves, which will be described later. In other words, as can be seen in Figure 4, the baffles 35 define, besides the directions of the lines 37, multiple additional directions for the circulation of the anodic or cathodic gas.

[0062] This arrangement therefore allows a particularly homogeneous distribution of this gas on the first face 18 as well as a better uniformization of the temperature of this gas from the cooling orifices 17. The electrochemical reaction which takes place in an elementary cell 12 bordered by the bipolar plate 14 therefore takes place in a particularly efficient and homogeneous manner.

[0063] According to another embodiment, the first set of channels 26 is formed by longitudinal channels extending from one end to the other of the central zone 24, the longitudinal channels being arranged parallel to each other.

[0064] In the example in Figure 2, the first set of channels 26 is configured to supply hydrogen to the anode of the attached elementary cell 12.

[0065] According to one variant, the first set of channels 26 is configured to supply oxygen to the cathode of the adjacent elementary cell 12. The channels of the first set 26 open into at least one oblong lumen 32A or 32B.

[0066] In the example in Figure 2, the channels of the first set 26 open into the oblong lights 32A.

[0067] The second set of channels 28 extends over at least part of the second face 20.

[0068] For example, the second set of channels 28 covers the central area 24 of the bipolar plate 14 on the second face 18.

[0069] In the example in Figure 3, the second set of channels 28 is configured to supply the cathode of the attached elementary cell 12 with oxygen.

[0070] According to one variant, the second set of channels 28 is configured to supply hydrogen to the anode of the attached elementary cell 12.

[0071] The channels of the second set 28 open into at least one other oblong light 32B distinct from the oblong light 32A into which the channels of the first set 26 open.

[0072] According to one variant, the channels of the second set 28 open into the oblong lights 32A.

[0073] According to one embodiment, the geometry of the channels of the second set 28 differs from the geometry of the channels of the first set 26. For example, the second set of channels 28 includes baffles 35 arranged one after the other in the form of columns, perpendicular to the lines 37, the baffles 35 covering the entire central area 24.

[0074] In the same way as before, the chicanes 35 are for example aligned one after the other so as to form a column in a first direction and are arranged, in a second direction substantially perpendicular to the first direction, in a staggered pattern with respect to each other.

[0075] As in the case of the first set of channels 26, it is understood from this example that two given columns of baffles 35 of the second set of channels 28 extending along the first direction of the columns and close to each other along the second direction delimit a channel of the second set of channels 28 extending along the first direction of the columns, the walls of this channel being discontinuous due to the spacing between the baffles 35 of a given column.

[0076] The discontinuities in the walls of the channels of the second set of channels 28 allow, as described previously, the circulation of an anodic or cathodic gas between the channels of the second set of channels 28, in addition to the circulation of this gas within the channels of the second set of channels 28. This arrangement therefore allows a particularly homogeneous distribution of this gas on the second face 20 as well as a better uniformization of the temperature of this gas from the cooling orifices 17.

[0077] The electrochemical reaction therefore takes place in a particularly efficient and homogeneous manner at the level of the electrochemical cell 12 bordered by the bipolar plate 14.

[0078] In particular, the determination of the geometry of the channels of the second set 28 is independent of the geometry of the channels of the first set 26.

[0079] In particular, in the case where the baffle columns 35 of the second set of channels 28 extend along an inclined direction, in particular perpendicular, to a direction along which the baffle lines 35 of the first set of channels 26 extend, the temperature on both sides of the bipolar plate 14 is particularly homogeneous.

[0080] The oblong lights 32A and 32B are configured to supply the channels of the first 26 and the second set 28 with fuel or oxidizer.

[0081] According to one embodiment, the oblong lights 32A configured to supply hydrogen to the bipolar plate 14 are arranged on the width of the bipolar plate 14 and the oblong lights 32B configured to supply oxygen to the bipolar plate 14 are arranged on the length of the bipolar plate 14.

[0082] The oxygen inlet flow rate and the hydrogen inlet flow rate into the oblong lights 32 and consequently into the channels are defined as a function of the oxygen and hydrogen source, the stack size and the channel parameters.

[0083] The oblong lights 32A into which open the channels intended to supply the elementary cells 12 with hydrogen are connected together and at least one monopolar end plate 16 includes an oblong light 32A connected to a hydrogen source.

[0084] According to one embodiment, the oblong lights 32A are connected to each other by watertight seals arranged in the orifices 17 at the periphery of the elementary cells 12 formed opposite the oblong lights 32A.

[0085] Preferably, the hydrogen supplied to the fuel cell 10 is completely consumed by the anodes of the elementary cells 12.

[0086] The oblong lumens 32B into which open the channels intended to supply the elementary cells 12 with oxygen are connected to each other and at least one monopolar end plate 16 includes an oblong lumen 32B connected to an oxygen source.

[0087] According to one embodiment, the oblong lights 32B are connected to each other by watertight seals arranged in the orifices 17 at the periphery of the elementary cells 12 formed opposite the oblong lights 32B.

[0088] At least one cooling unit 30 is located in the central area 24. In the example in Figure 2, the bipolar plate 14 comprises a plurality of cooling units 30.

[0089] In the example in Figure 2, the bipolar plate 14 comprises exactly six cooling units 30. The number and location of the cooling units 30 are given only as an example and may vary from one bipolar plate 14 to another.

[0090] Preferably, the arrangement of the cooling units 30 is configured to ensure the most homogeneous cooling possible in the fuel cell 10.

[0091] Preferably, the cooling units 30 are arranged at equidistant intervals from each other in the central area of ​​the bipolar plate.

[0092] For example, the set of cooling units 30 occupies between 10% and 25% of the surface area of ​​the central zone 24 of the bipolar plate 14.

[0093] With reference to Figure 1, the cooling units 30 are arranged opposite the orifices 17 of the central region of the elementary cells 12. In other words, each elementary cell 12 is drilled so that each of the cooling units 30 of the bipolar plates 14 is juxtaposed, on either side of each bipolar plate 14, with an orifice 17 in order to ensure fluidic communication between the cooling units 30 of the bipolar plates and the orifices 17 of the elementary cells 12 over the whole stack forming the fuel cell 10. This fluidic communication is ensured along the stacking direction of the fuel cell 10, corresponding to the thickness direction of a bipolar plate.

[0094] Each cooling unit 30 is surrounded by the first set of channels 26 on the first face 18 and by the second set of channels 28 on the second face 20.

[0095] In other words, the first set of channels 26 bypasses and surrounds each cooling unit 30 on the first face 18 and the second set of channels 28 bypasses and surrounds each cooling unit on the second face 20, as particularly visible in Figure 4.

[0096] With reference to Figure 4, a cooling unit 30 will now be described.

[0097] For example, the cooling unit 30 has a circular shape. Referring to Figure 4, the cooling unit 30 is surrounded on its first face 18 by a channel 50 extending circularly around it. This is because the baffles 35 located near the cooling unit 30 are cut to form the channel 50. This feature is not shown for clarity. Similarly, on its second face 20, which is not visible in Figure 4, the cooling unit 30 is surrounded by a channel extending circularly around it.According to the embodiment where the channel sets 26, 28 are formed by longitudinal channels, the cooling unit 30 is surrounded on the first face 18 on one side by a channel of the first set 26 extending along one half-perimeter of the cooling unit 30 and on the other side by another channel of the first set 26 extending along the other half-perimeter of the cooling unit 30. Similarly on the second face 20, the cooling unit 30 is surrounded on one side by a channel of the second set 28 extending along one half-perimeter of the cooling unit 30 and on the other side by another channel of the second set 28 extending along the other half-perimeter of the cooling unit 30.

[0098] The cooling unit 30 includes at least one circulation conduit 36 ​​for a cooling fluid.

[0099] The cooling unit 30 further includes a clamping orifice 38, a first ring 40, a second ring 42, a first recess 44 located on the first face 18 and a second recess 45 located on the second face 20 opposite the first recess 44.

[0100] According to one embodiment, the cooling unit 30 comprises a plurality of circulation ducts 36. The distribution of the circulation ducts 36 is configured to ensure the most homogeneous cooling possible around the cooling unit 30 as well as in the fuel cell 10.

[0101] In the example in Figure 4, the cooling unit 30 comprises exactly six circulation conduits 36, the circulation conduits 36 being distributed around the clamping orifice 38 along a circumference external to the clamping orifice 38. Each circulation conduit 36 ​​is arranged equidistant from the two circulation conduits 36 which are adjacent to it.

[0102] Each circulation conduit 36 ​​is formed by an orifice traversing the thickness of the bipolar plate 14 from the first face 18 to the second face 20. That is to say, the orifice forming the circulation conduit 36 ​​extends along the thickness direction of the bipolar plate 14 and opens into the first face 18, on the one hand, and into the second face 20, on the other hand.

[0103] Each circulation conduit 36 ​​preferably has a cylindrical shape, for example with a diameter approximately equal to 1 mm.

[0104] Each circulation conduit 36 ​​is configured to circulate a cooling fluid into the bipolar plate 14.

[0105] The diameter of each circulation pipe 36 is, for example, defined to generate turbulence for the circulating cooling fluid, thereby optimizing heat exchange. The cooling fluid is, for example, a dielectric coolant, which both conducts heat and acts as an electrical insulator.

[0106] Preferably, the flow rate of the cooling fluid in the circulation lines 36 is between 2 L / min and 30 L / min.

[0107] In a particular example, in which the fuel cell 10 generates an electrical power approximately equal to 1.3 kW, the flow rate of the cooling fluid in the circulation lines 36 is estimated to be about 5 L / min.

[0108] The circulation channels 36 of each monopolar end plate 16 are connected to a coolant source. Thus, through the ports 17 and the cooling units 30 in fluidic communication with each other, the coolant flows through the entire stack of elementary cells 12 from one monopolar end plate 16 to the other.

[0109] The clamping orifice 38 is formed by an orifice passing through the thickness of the bipolar plate 14 from the first face 18 to the second face 20. That is to say, the orifice forming the clamping orifice 38 extends along the thickness direction of the bipolar plate 14 and opens into the first face 18, on the one hand, and into the second face 20, on the other hand.

[0110] In the example of Figure 4, the clamping orifice 38 is located in the center of the cooling unit 30.

[0111] The clamping orifice 38 opens into the first recess 44 on the first face 18 and into the second recess 45 on the second face 20.

[0112] The clamping orifice 38 is designed to receive a clamping element. The clamping element allows the bipolar plates to be clamped together and ensures that the elementary cells 12 extending between the bipolar plates 14 are held in place.

[0113] The clamping element ensures that the entire fuel cell assembly 10 is held in place.

[0114] For example, the clamping element passes through all the elementary cells 12 and bipolar plates 14 and extends from one monopolar end plate 16 to another through the clamping orifices 38.

[0115] The clamping element is, for example, a screw-nut assembly or any other suitable device.

[0116] For example, the clamping orifice 38 has a diameter between 0.5 mm and 8 mm, for example approximately equal to 3 mm.

[0117] The first ring 40 extends outward from the first face 18 and extends between the channels of the first set 26 and the circulation conduits 36.

[0118] The height of the first ring 40 is greater than or equal to the height of the walls of the channels of the first set 26. Thus, the first ring 40 is configured to prevent the fluid, i.e. oxygen or hydrogen, circulating in the first set of channels 26 from entering the cooling unit 30 and to prevent the cooling fluid from entering the channels.

[0119] The second ring 42 projects out from the second face 20 and extends between the channels of the second set 28 and the circulation conduits 36.

[0120] The height of the second ring 42 is greater than or equal to the height of the walls of the channels of the second set 28. Thus, the second ring 42 is configured to prevent the fluid, i.e. oxygen or hydrogen, circulating in the second set of channels 28 from entering the cooling unit 30 and to prevent the cooling fluid from entering the channels.

[0121] The first ring 40 and the second ring 42 are configured to receive a gasket. The gasket thus surrounds the cooling unit 30.

[0122] Thus, the joint is disposed between the first ring 40 of a first bipolar plate 14 and the second ring 42 of a second bipolar plate 14 successive to the first bipolar plate through the orifice 17 of the elementary cell 12 disposed between said two bipolar plates 14.

[0123] The seal is configured to ensure a seal between the cooling unit 30 and the elementary cell 12 and prevents the penetration of the cooling fluid into the elementary cell 12.

[0124] The first impression 44 and the second impression 45 extend between the clamping orifice 38 and the circulation conduits 36.

[0125] The first cavity 44 and the second cavity 45 are configured to receive another seal. Thus, the seal is disposed between the first cavity 44 of a first bipolar plate 14 and the second cavity 45 of a second bipolar plate 14 successive to the first bipolar plate through the orifice 17 of the elementary cell 12 disposed between said two bipolar plates 14.

[0126] The seal is configured to ensure a seal between the circulation channels 36 and the clamping orifice 38 and prevents the penetration of the cooling fluid into the elementary cell 12.

[0127] According to one variant, the sealing is ensured by the association of two seals and a spacer, the spacer being disposed between the first cavity 44 of a first bipolar plate 14 and the second cavity 45 of a second bipolar plate 14 successive to the first bipolar plate through the orifice 17 of the elementary cell 12 disposed between said two bipolar plates 14. A first seal ensures the sealing at the level of the first cavity 44 between the cooling unit 30 of the first bipolar plate 14 and the spacer and a second seal ensures the sealing at the level of the second cavity 45 between the cooling unit 30 of the second bipolar plate 14 and the spacer.

[0128] In the orifices 17 of the elementary cell 12, the coolant therefore circulates between the two seals and / or the seal-spacer assemblies, the first being disposed between the first ring 40 of a bipolar plate 14 and the second ring 42 of another bipolar plate 14, and the seal being disposed between the first recess 44 of the bipolar plate 14 and the second recess 45 of the other bipolar plate 16, the two said bipolar plates framing said elementary cell 12.

[0129] Furthermore, the seals and / or the seal-spacer assemblies prevent contact between two successive bipolar plates 14 and thus prevent the occurrence of a short circuit in the fuel cell 10.

[0130] Each mounting hole 34 is configured to receive a clamping element, the clamping element preferably being identical to that received by the clamping holes 38 of the cooling units 30.

[0131] The clamping element allows the bipolar plates to be clamped together and ensures the retention of the elementary cells 12 extending between the bipolar plates 14.

[0132] For example, the clamping element passes through all the elementary cells 12 through certain orifices 17 at the periphery of the elementary cells 12 arranged opposite the fixing orifices 34 and passes through all the bipolar plates 14 through the fixing orifices 34.

[0133] The clamping element extends from one monopolar end plate 16 to another.

[0134] For example, each fixing hole 34 has a diameter between 0.5 mm and 8 mm, for example approximately equal to 3 mm.

[0135] According to one embodiment, the bipolar plate 14 comprises at least four fixing holes 34, each fixing hole 34 being located at a corner of the bipolar plate 14.

[0136] In the example of Figure 2, the bipolar plate 14 further includes mounting holes 34 along its length and width, each mounting hole 34 being located between two oblong slots 32A or 32B. In other words, the periphery 22 of the bipolar plate 14 comprises an alternation of mounting holes 34 and oblong slots 32A or 32B.

[0137] In one embodiment, the fuel cell 10 includes an embedded simulation system comprising at least one temperature sensor, the embedded simulation system being configured to determine the temperature profile of the entire fuel cell 10 during its use. With reference to Figures 5 and 6, a second embodiment of the invention will now be described.

[0138] Not all features similar to the first embodiment will be described here and will bear the same reference symbol. In the following, only features differing from the first embodiment will be detailed.

[0139] In this embodiment, the clamping orifice 38 receives a tubular retaining element 60 intended for fixing the bipolar plates 14 to each other, as well as to the elementary cell 12.

[0140] For readability reasons, in figure 5, only three tubular retaining elements 60 are shown.

[0141] As illustrated in Figure 5, each clamping orifice 38 is delimited at its periphery by an upper ring 62 and a lower ring 64.

[0142] In particular, the upper crown 62 is included in the upper bipolar plate 14 and the lower crown 64 is included in the lower bipolar plate 14.

[0143] Each crown 62, 64 comprises a plurality of spacers 66 projecting from a peripheral wall 65 of the crown 62, 64, towards the center of the orifice 38, as illustrated in Figure 6.

[0144] For example, each crown 62, 64 includes at least three spacers 66 that are angularly offset and distributed symmetrically around the orifice 38.

[0145] Each spacer 66, for example, forms a flexible fixing tab.

[0146] The tubular retaining element 60 is then inserted into the orifice 38, in contact with the spacers 66, which, by plastic deformation, ensure the fixing of the bipolar plates 14 and the elementary cell 12 to each other.

[0147] In addition, the tubular retaining element 60 is thus inserted into the orifice 38, away from the peripheral wall 65 of the crowns 62, 64.

[0148] Each spacer 66 then delimits, with the neighboring spacer 66, with the tubular retaining element 60 and with the peripheral wall 65, free spaces for the circulation of the cooling fluid.

[0149] In this embodiment, the free spaces for the circulation of the cooling fluid define the circulation channels 36 of the cooling fluid.

[0150] The dimensions of the defined free spaces, in particular the thickness of the defined free spaces, taken along a radial direction, are for example chosen so as to generate turbulence during the circulation of the cooling fluid in the free spaces in order to optimize heat exchange.

[0151] The characteristics of the bipolar plate 14 described above, regardless of the embodiment considered, make it possible to guarantee cooling limiting the appearance of hot spots in the fuel cell 10, to ensure a solid fixing and tightening between the bipolar plates 14 and to facilitate the design of the bipolar plates 14.

[0152] Thanks to the circulation ducts 36, the cooling units 30 ensure a compression of the thermal profile, in particular the temperature difference between the hottest point and the coldest point of the fuel cell 10 is about 3°C ​​to 4°C in an elementary cell 12 of a fuel cell 10 whereas this difference is 10°C in the prior art.

[0153] Furthermore, the clamping holes 38 located in the central area 24 reduce the distance between each clamping or fastening point, thus facilitating the assembly of the fuel cell 10 by ensuring a secure fit. Therefore, unlike the prior art, the monopolar end plates 16 do not need to be more rigid than the bipolar plates 14. Preferably, the monopolar end plates 16 are manufactured in the same way as the bipolar plates 14.

[0154] Finally, the cooling units 30, which can be formed, in particular, by hammering, and especially simultaneously with the channels of the first and second sets of channels 26, 28, eliminate the need to form a third set of channels for the circulation of the cooling fluid. Thus, the bipolar plate 14 is produced as a single unit, and the geometries of the first 26 and the second set 28 can be chosen independently of each other. This facilitates the production of the bipolar plate 14, which can be manufactured rapidly and cost-effectively on an industrial scale, with precisely controlled channel dimensions. The resulting bipolar plate 14 optimizes cell cooling and the homogeneity of the electrochemical reaction, thanks to the synergy between the first and second sets of channels 26, 28 and the cooling units 30.

Claims

DEMANDS 1. Bipolar plate (14) for a fuel cell (10) comprising a first face (18) and a second face (20), opposite the first face (18), a first set of channels (26) extending over at least a portion of the first face (18) and a second set of channels (28) extending over at least a portion of the second face (20), the bipolar plate (14) further comprising at least one cooling unit (30), said cooling unit (30) comprising at least one circulation conduit (36) formed by an orifice passing through the thickness of the bipolar plate (14) from the first face (18) to the second face (20), said circulation conduit (36) being configured to circulate a cooling fluid in the bipolar plate (14), characterized in that said cooling unit (30) is surrounded by the first set of channels (26) on the first face (18) and by the second set of channels (28) on the second side (20).

2. Bipolar plate (14) according to claim 1, comprising a plurality of cooling units (30) distributed in the bipolar plate, said cooling units (30) being preferably arranged at equidistances from each other.

3. Bipolar plate (14) according to claim 1 or 2, wherein the cooling unit (30) further comprises a clamping orifice (38) passing through the thickness of the bipolar plate (14) from the first face (18) to the second face (20), the orifice opening into the first face (18) and into the second face (20) and being intended to receive a clamping element.

4. Bipolar plate (14) according to any one of claims 1 to 3, wherein the cooling unit (30) comprises a plurality of circulation conduits (36).

5. Bipolar plate (14) according to claims 3 and 4, in which the circulation conduits (36) are distributed around the clamping orifice (38).

6. Bipolar plate (14) according to any one of claims 1 to 5, wherein the cooling unit (30) comprises on the first face (18) a first ring (40) projecting from the first face (18) and extending between the channels of the first assembly (26) and the circulation conduit (36), and on the second face (20) a second ring (42) extending outward from the second face (20) and extending between the channels of the second set (28) and the circulation conduit (36).

7. Bipolar plate (14) according to any one of claims 1 to 6, wherein the first set of channels (26) comprises a plurality of baffles (35) arranged one after the other in the form of lines (37), and the second set of channels (28) also comprises baffles (35) arranged one after the other in the form of columns, perpendicular to the lines (37).

8. Bipolar plate (14) according to any one of claims 1 to 7, comprising at its periphery at least two oblong lights (32A, 32B), the channels of the first set (26) opening into at least one of said oblong lights (32A), the channels of the second set (28) opening into at least one other of said oblong lights (32B).

9. Fuel cell (10) comprising at least one elementary cell (12) formed of two electrodes separated by a membrane, each elementary cell (12) being arranged between two bipolar plates (14) according to claims 1 to 9, the cooling units (30) of said bipolar plates (14) extending opposite each other.

10. Fuel cell (10) according to claim 9, comprising at least one seal, the seal extending between the cooling units (30) of two bipolar plates (14) arranged opposite each other, the seal hermetically separating the space between these two cooling units (30) and the elementary cell (12) arranged between said bipolar plates (14).

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