Hydrogen fuel cell with multiple current collection points

Abstract

The invention relates to a hydrogen fuel cell comprising: two end plates; -at least one unit cell arranged between said end plates; -two current collection plates, each comprising a current collection point, the collection plates being respectively interposed between one of the end plates and the at least one unit cell. According to the invention, the number of collection points in each of the collection plates is greater than or equal to 3, and the fuel cell comprises control means for controlling the collection points, the control means being configured to enable selective opening / closing of the collection points from which current can be collected.

Description

1. Technical Field

[0001] The field of the invention is that of hydrogen fuel cells. More particularly, the invention relates to improvements in such fuel cells, and in particular to the collection of the electrical current generated during the operation of such fuel cells.

[0002] Fuel cells of this type can be used in many areas wherever it is necessary to generate electrical energy, in particular in an autonomous manner, such as in vehicles (cars, vans, trucks, buses, trains, ships, aircraft, etc.), generators, etc. 2. Background Technology

[0003] The principle of fuel cells has been known for many years. They are used, in particular, in the aerospace sector, and are also being developed in numerous projects by various car manufacturers.

[0004] Hydrogen fuel cells are based on Figure 1 The principle shown in FIG2 is used to generate electrical energy through a chemical reaction between hydrogen (H2) and oxygen (O2). The chemical reaction is described by the following formula:

[0005] [Chemical formula 1] H2-->2H + +2e -

[0006] O2+4H + +2e - -->2H2O

[0007] ____________________

[0008] H2+1 / 2O2-->H2O; Δ r H<0

[0009] Optional Δ r H < 0 simply means that the reaction is exothermic.

[0010] The reaction takes place in the so-called active zone of the electrolyte membrane electrode assembly (MEA), i.e., between the anode, which receives hydrogen from the tank, and the cathode, which receives oxygen (O2) from the outside air. + A stack of exchanged membranes.

[0011] like Figure 1 As shown, fuel hydrogen (H2) is introduced (F1) into the fuel cell to contact the anode A. A portion of the hydrogen enters (F2) to the anode A, where the hydrogen molecules are separated into electrons e - and ions H passing through the electrolyte E toward the cathode C + The cathode C contacts the air introduced from the outside (F3), and the oxygen molecules O2 (F4) in the air react with the ions H +and electronic - Combined to produce (F5) water (H2O). This water (F6) and unused air (F7) are exhausted.

[0012] Therefore, the anode A is the element that undergoes oxidation: H2 → 2H + +2e - , and the cathode C is the element that undergoes reduction: O2+4H + +4e - →2H2O. Electron e - The current circulates between the anode A and the cathode C (F8), thereby generating a current E, which is used to drive the motor and / or charge the battery pack.

[0013] The reaction is exothermic and the various components of the fuel cell can heat up quickly. Therefore, the entire system must be cooled. Therefore, the mechanical parts must be designed to be supplied with a cooling or heat transfer liquid.

[0014] Figure 2 The structure of a fuel cell utilizing this chemical reaction is shown in FIG.

[0015] The current collecting plate 24 is interposed between each of the end plates 231 and 232 and the unit cell 22 ( Figure 2 Only one of the two collecting plates 24 is visible).

[0016] Figure 3 The components that form a unit cell 22 are shown in detail in an exploded view. A unit cell 22 comprises two types of plates, either bipolar or unipolar, with an electrolyte membrane positioned between them. Unipolar plates are the first and last plates in the unit cell stack. They generally have the same design as bipolar plates, but the input ends are sealed, preventing the plates from receiving either gas. Thus, a unit cell includes a cathode unipolar plate that does not receive hydrogen, and an anode unipolar plate that does not receive oxygen.

[0017] The bipolar plate, stacked between two monopolar plates, is formed by assembling two metal halves 31 and 32 (an anode half 31 and a cathode half 32), which can be welded, brazed, or glued together. The space between the two halves is defined by forming the two halves to define two zones 33 and 34 for receiving a cooling liquid and channels for circulating hydrogen and oxygen (extracted from air), respectively. An MEA membrane 35 is inserted between the halves.

[0018] According to the prior art, each collector plate 24 includes one or two current collection points 25. Due to the reduced number of collection points 25, each draws a significant amount of current. To withstand this current, the collection points 25 must be sufficiently large. Since the collector plates 24 are made of copper, their manufacture inevitably results in significant copper consumption, which constitutes a significant cost. Furthermore, oversized collection points also result in losses, adversely affecting the fuel cell's output power.

[0019] Due to the small number of collection points, the current flow inside the unit cell is uneven. This can lead to the formation of hot spots. As a result, the temperature and humidity levels inside the unit cell are uneven, which affects the operation of the fuel cell and reduces its durability.

[0020] There is therefore a need for a new method for producing such fuel cells to improve their operation and / or efficiency. 3. Summary of the Invention

[0021] The present invention satisfies at least part of this need through a novel hydrogen fuel cell comprising:

[0022] - two end plates;

[0023] - at least one unit cell disposed between the end plates;

[0024] - two current collecting plates, each comprising a current collecting point, wherein the collecting plates are respectively interposed between one of the end plates and the at least one unit cell.

[0025] According to the present invention, the number of collecting points on each of the collecting plates is greater than or equal to 3, and the fuel cell comprises a control device for controlling the collecting points, wherein the control device is configured to enable selective opening / closing of the collecting points from which current can be collected.

[0026] In other words, the present invention relates to the use of collecting plates in a hydrogen fuel cell, each collecting plate comprising at least three current collecting points, and to the use of control means in a hydrogen fuel cell for selectively opening / closing the collecting points from which current can be collected.

[0027] Thus, according to the invention, the collection point at which the current generated by the fuel cell is tapped off can be chosen, which offers a number of advantages, in particular:

[0028] - by the position of the collecting points and the selection of open and closed collecting points, the current of one or more unit cells in the fuel cell can be homogenized in the plate;

[0029] -The temperature in the fuel cell can be better regulated and hot spots can be avoided. The humidity level in the fuel cell can also be better regulated, thereby improving the durability of the fuel cell;

[0030] - Increasing the number of collection points allows reducing their cross-section and, consequently, the consumption of raw materials;

[0031] -Control of the collection point allows for more calibrated dimensions, thus reducing the cross section, which helps reduce losses and increase the output of the fuel cell.

[0032] The number of collecting points on each of the collecting plates can be determined in particular according to the size of the active surface of the at least one unit cell, or according to the size of each active surface if more than one unit cell is present.

[0033] According to a particular embodiment, the collection points are substantially evenly distributed around the perimeter of the collection plate.

[0034] In particular, the number of collecting points on each of the collecting plates may be equal to four, the four collecting points on each of the collecting plates being arranged close to the four corners of the collecting plates.

[0035] The control device for controlling the collecting point can in particular be configured to enable opening / closing of the collecting point taking into account the current stage of life of the at least one unit battery.

[0036] The control device for controlling the collecting point may also be configured to enable opening / closing of the collecting point taking into account at least one usage condition and / or operating condition of the fuel cell.

[0037] In this case, the opening / closing of the collection points may be performed according to a predetermined control law based on the power to be delivered by the fuel cell and / or based on operating conditions.

[0038] The fuel cell as described above can be used in various applications. In particular, the fuel cell is used in at least one application belonging to the following group of applications:

[0039] - mobile vehicles;

[0040] - Commercial vehicles;

[0041] - Bus or truck;

[0042] -train;

[0043] -Boat;

[0044] - Aircraft;

[0045] -dynamo.

[0046] The invention also relates to a method for controlling a fuel cell as described above, said method comprising the step of selectively opening / closing one or more collecting points on each of said collecting plates from which current can be collected.

[0047] According to a particular embodiment, the selective opening / closing of one or more collection points from which current can be collected takes into account the current stage of life of the at least one unit cell.

[0048] According to another particular embodiment (which may or may not be combined with the previous one), the selective opening / closing of one or more collection points from which current can be collected takes into account at least one use condition and / or operating condition of the fuel cell.

[0049] In this case, in particular, the selection of the one or more collection points can be performed according to a predetermined control law which is based on the power to be delivered by the fuel cell and / or on operating conditions. 4. Description of the Figures

[0050] Other features and advantages of the invention will become more apparent upon reading the following description of exemplary embodiments—intended as simple, illustrative and non-limiting examples—and the accompanying drawings, in which:

[0051] [ Figure 1 ]: Figure 1 It has been described in the previous sections showing the general principles of fuel cells;

[0052] [ Figure 2 ]: Figure 2 It has been described in the foregoing section that the structure of a fuel cell is shown, the fuel cell comprising a stack of unit cells;

[0053] [ Figure 3 ]: Figure 3 As described in the previous section, the components are shown in the form of an exploded view. Figure 2 Components of the unit cell shown;

[0054] [ Figure 4 ]: Figure 4 The structure of a fuel cell including a collecting plate according to the present invention is shown;

[0055] [ Figure 5 ]、[ Figure 6 ]、[ Figure 7 ]、[ Figure 8 ]、[ Figure 9 ]、[ Figure 10 ]: Figures 5 to 10 Different examples of collecting plates according to the invention are shown;

[0056] [ Figure 11 ]: Figure 11 depicts a diagram showing a control device for controlling a collection point of a fuel cell according to the present invention;

[0057] [ Figure 12C ]、[ Figure 12B ]、[ Figure 12C ]、[ Figure 12D ] shows that Figure 11 Four examples of choices made by the control device;

[0058] [ Figure 13 ]、[ Figure 14 ]: Figure 13 and Figure 14 The different current densities generated in the unit cell by the open collecting point are shown. 5. Specific Implementation Methods

[0059] 5.1 Main Components of Hydrogen Fuel Cells

[0060] Reference Figure 4 The fuel cell according to the present invention generally includes at least one unit cell 22, which is located between a first end plate 231 and a second end plate 232. The fuel cell may include a single unit cell 22, but preferably includes a plurality of unit cells 22, which are stacked on each other between the two end plates 231 and 232.

[0061] The fuel cell generally further includes a first collecting plate and a second collecting plate 24. The first collecting plate 24 is located between the first end plate 231 and one or more unit cells 22. The second collecting plate 24 is located between the second end plate 232 and one or more unit cells 22. Figure 4 In the figure, only the first collecting plate is visible.

[0062] Each of the collecting plates 24 comprises current collecting points 25, and according to the principles of the present invention, the number of current collecting points 25 is greater than or equal to 3. These collecting plates will be described in more detail below.

[0063] The fuel cell comprises or is connected to control means for controlling the collection points (or 25), wherein these control means are configured to be able to selectively open / close the collection points 25 from which current can be collected. These control means will be described in more detail below.

[0064] 5.2 Collection Board

[0065] Reference Figures 5 to 10, present some illustrative and non-limiting examples of collection plates 24 according to the present invention.

[0066] like Figure 5 、 Figure 6 and Figure 7 As shown, the collecting plate 24 may include three collecting points 25. In this case, two collecting points 25 may be located on one side of the collecting plate 24 near two opposite corners, while another collecting point 25 is located on the other side of the collecting plate 24, for example, near one of the corners (see FIG. Figure 6 and Figure 7 ) or essentially in the middle (see Figure 5 ).

[0067] Figure 8 An embodiment is shown in which the collection plate 24 includes four collection points 25 located near the corners of the collection plate 24 , two collection points 25 located on one side of the collection plate 24 and two collection points 25 located on the other side of the collection plate 24 .

[0068] Preferably, the collecting plates 24 comprise four collecting points 25. However, they may comprise more collecting points.

[0069] Figure 9 By way of example, a collection plate 24 is shown comprising six collection points 25 , four of which are located near the four corners of the collection plate 24 and two of which are located approximately in the middle of opposite sides of the collection plate 24 .

[0070] Figure 10 By way of example, a collecting plate 24 is shown comprising five collecting points 25 , three collecting points 25 being evenly distributed on one side of the collecting plate 24 and two further collecting points being evenly distributed on the opposite side of the collecting plate 24 .

[0071] In the same fuel cell, the number and distribution of the collecting points on the first collecting plate and the second collecting plate are the same, but the number and distribution of the collecting points on the first collecting plate and the second collecting plate may be different from each other.

[0072] The number of collecting points is preferably an even number, but may alternatively be an odd number.Ideally, the collecting points are evenly distributed around the perimeter of the collecting plate.

[0073] In a hydrogen fuel cell, each unit cell includes an active surface. This surface is the area where chemical reactions occur, resulting in the generation of electrical current. The number of collection points on each collector plate can be determined by the size of the active surface, but this is not a mandatory requirement.

[0074] 5.3 Control device

[0075] As mentioned above, the fuel cell comprises or is connected to a control device for controlling the collection point.

[0076] These control means are configured to be able to selectively open / close the collection points 25 from which the current can be collected. In other words, they can select the collection points 25 from which the current generated by the fuel cell will be collected.

[0077] According to a first method, a control device for controlling the collection points is configured to selectively open / close the collection points at different stages of the life of one or more unit cells of the fuel cell. In this case, while the fuel cell is still operating, the collection points to be opened / closed can be selected during stages when the fuel cell needs to meet different requirements, and / or the collection points to be opened / closed can be selected based on changes in current concentration in the fuel cell, which changes are based on changes in the fuel cell over time.

[0078] Therefore, it is also possible to produce fuel cells with different current densities depending on the application using the same fuel cell structure.

[0079] According to the second method (which can of course be combined with the first method), the control device for controlling the collection points is configured to selectively open and close the collection points during the fuel cell's operation, depending on the fuel cell's usage and operating conditions. In this case, the collection points to be opened and closed can be selected in real time according to the phases in which the fuel cell needs to generate more or less current. Thus, the current density in the unit cells of the fuel cell can be varied during its operation.

[0080] Figure 11 A general example diagram of a control device for controlling a collection point is shown.

[0081] The control device includes a control unit 31 (e.g., a microprocessor or microcontroller) and a set of switches 321, 322, 323, 324, wherein each switch is connected to a collection point 331, 332, 333, 334 on the collection plate 33 to control its opening or closing. The control unit 31 is programmed to open / close each collection point as needed by sending appropriate opening / closing signals to the switch, thereby ensuring that each collection point is selectively opened / closed.

[0082] The control program executed by the control device (which can be stored in a memory provided for this purpose and, if necessary, modified by updating) implements one or more control laws that can take into account, in particular, medium- and long-term aspects, i.e. the evolution of the fuel cell over its lifetime, and / or short-term, instantaneous or quasi-instantaneous aspects, such as power demand or current operating conditions.

[0083] In particular, when the opening / closing of the collecting points is performed in real time, it is performed according to a predetermined control law that is based on the power to be delivered by the fuel cell and / or on the operating conditions.

[0084] The control device receives a series of sensor-based information 34 or reference data, such as statistical data on the behavior of the fuel cell during its lifetime, e.g.

[0085] - Immediate demand for electricity;

[0086] - Preset operating modes (e.g. "Economy" or "Sport");

[0087] - the temperature of the fuel cell and / or other vehicle components;

[0088] - external conditions, such as humidity and outside temperature;

[0089] - Management of water produced by fuel cells;

[0090] - life stage or age of the fuel cell;

[0091] - Specific information about the fuel cell, such as aging in specific areas;

[0092] …….

[0093] 12A to 12D Four specific examples are shown:

[0094] - Figure 12A In the context of fuel cell aging management, the current is concentrated in area 41, corresponding to the upper right area of the fuel cell. In this case, only the collection point 332 with the corresponding switch 322 is active. The current is thus directed to the nearest collection point, so that part of the current does not have to pass through the fuel cell to other collection points, risking losses and / or interference.

[0095] - Figure 12B : Selective use of half the catalyst surface, region 42 corresponding to the upper portion of collecting plate 33. This approach, for example, allows for optimized water management, particularly in accordance with humidity conditions. In this case, only switches 321 and 322 are closed, allowing the current to be collected at collection points 331 and 332 close to region 42 where the current is concentrated.

[0096] - Figure 12C: In the context of fuel cell aging management, it is clear that the lower right portion has become less functional or inoperative, and current concentration exists mainly in area 43. In this case, only switches 321, 322, and 323 are closed, so the current is collected at collection points 331, 332, and 333 close to area 44 where the current is concentrated;

[0097] - Figure 12D : In this configuration, the entire surface 44 of the collecting plate 33 is used, which corresponds to a balanced use, for example for new fuel cells and / or high power demand. All switches are closed and all collecting points are used.

[0098] If the fuel cell includes multiple active areas that can be selectively activated, the selection of the collection points will also take into account the locations of these active areas.

[0099] 5.4 Current density

[0100] The selective opening / closing of the different collection points 25 makes it possible to vary the current density in one or more unit cells 22 of the fuel cell.

[0101] Therefore, from Figure 13 As can be seen in FIG, two collecting points 25 are arranged on two opposite sides of the collecting plate 24 and at two corners facing each other. O A current density distribution 26 can be generated. Figure 14 As can be seen in FIG, two collecting points 25 arranged on two opposite sides of the collecting plate 24 and at two diametrically opposite corners O Another current density distribution 26 may be generated.

[0102] Thus, a variety of current density distributions can be created depending on the number of open collection points and their location around the collection plate 24 .

[0103] 5.5 Advantages

[0104] The implementation of the present invention has the following advantages in particular:

[0105] - by the position of the collecting points and the selection of open and closed collecting points, the current of one or more unit cells in the fuel cell can be homogenized in the plate;

[0106] -The temperature in the fuel cell can be better regulated and hot spots can be avoided. The humidity level in the fuel cell can also be better regulated, thereby improving the durability of the fuel cell;

[0107] - Increasing the number of collection points allows reducing their cross-section and, consequently, the consumption of raw materials;

[0108] -Control of the collection point allows for more calibrated dimensions, thus reducing the cross section, which helps reduce losses and increase the output of the fuel cell.

Claims

1. A hydrogen fuel cell, comprising: - two end plates; - at least one unit cell disposed between the end plates, the at least one unit cell being configured to generate electric current; - two current collecting plates, each of which comprises a current collecting point, wherein the collecting plates are respectively interposed between one of the end plates and the at least one unit cell, It is characterized in that the number of collection points on each of the collection plates is greater than or equal to 3, And the fuel cell comprises a control device for controlling the collection points, wherein the control device is configured to enable selective opening / closing of the collection points from which the current can be collected.

2. The hydrogen fuel cell according to claim 1, wherein: The at least one unit cell has an active surface, and the number of collecting points on each of the collecting plates is determined according to the size of the active surface.

3. The hydrogen fuel cell according to claim 1 or 2, wherein: The collection points are substantially evenly distributed around the perimeter of the collection plate.

4. The hydrogen fuel cell according to claim 1, wherein The number of collecting points on each of the collecting plates is equal to four, and the four collecting points on each of the collecting plates are arranged close to the four corners of the collecting plates.

5. The hydrogen fuel cell according to any one of claims 1 to 4, wherein The control means for controlling the collecting point are configured to enable opening / closing of the collecting point taking into account the current stage of life of the at least one unit battery.

6. The hydrogen fuel cell according to any one of claims 1 to 4, wherein The control device for controlling the collecting point is configured to enable opening / closing of the collecting point taking into account at least one usage condition and / or operating condition of the fuel cell.

7. The hydrogen fuel cell according to claim 6, wherein: The opening / closing of the collection points is performed according to predetermined control laws based on the power to be delivered by the fuel cell and / or on operating conditions.

8. Use of a fuel cell according to any one of claims 1 to 7 for at least one application belonging to the following group of applications: - mobile vehicles; - Commercial vehicles; - Bus or truck; -train; -Boat; - Aircraft; -dynamo.

9. A method for controlling a fuel cell according to any one of claims 1 to 7, the method comprising the step of selectively opening / closing one or more collecting points on each of the collecting plates from which current can be collected.

10. The method according to claim 9, wherein: Selectively opening / closing one or more collection points from which current can be collected takes into account the current stage of the life of the at least one unit battery.

11. The method according to claim 9 or 10, wherein: Selectively opening / closing one or more collection points from which current can be collected takes into account at least one usage condition and / or operating condition of the fuel cell.

12. The method according to claim 11, wherein The selection of the one or more collection points is performed according to a predetermined control law based on the power to be delivered by the fuel cell and / or on operating conditions.

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