Fuel cell arrangement for an H2 / O2 fuel cell

Abstract

Fuel cell arrangement (10) for an H2 / O2 fuel cell (16), comprising: - an anode (26) at which H2 (14) is oxidized during operation and which is connected to an H2 inlet (48) for supplying H2 (14) to the anode (26), wherein a valve (58) with a valve seat (62) and a valve element (60) is arranged in the H2 inlet (48), which valves cooperate in a closed position to interrupt an inflow of H2 (14) from the H2 inlet (48) to the anode (26), - a cathode (30) at which O2 (28) is reduced during operation and which is connected to an O2 inlet (50) for supplying O2 (28) to the cathode (30), wherein a differential pressure control device (52) for controlling a differential pressure between the H2 inflow (48) and the O2 inflow (50) is arranged between the H2 inflow (48) and the O2 inflow (50), wherein the differential pressure control device (52) has a fluid connection (52) between the H2 inflow (48) and the O2 inflow (50), in which a deflection force (F A ) deflectable membrane (56) is arranged for closing the fluid connection (54), wherein a pin (64) is coupled to the deflectable membrane (56) and the valve element (60) in such a way that the pin (64) presses the valve element (60) away from the valve seat (62) in the opening direction when the membrane (56) is deflected in the direction of the H2 inflow (48).

Description

[0001] The invention relates to a fuel cell arrangement for a hydrogen / oxygen fuel cell.

[0002] In a fuel cell, chemically stored energy is converted into electrical energy, with one reactant being oxidized and the other being reduced. In a hydrogen / oxygen fuel cell (H2 / O2 fuel cell), hydrogen (H2) is oxidized by releasing electrons at an anode, while oxygen (O2) is reduced by accepting electrons at a cathode. Through this redox reaction, the chemical energy stored in the reactants is converted into electrical energy at the anode or cathode, where it can be tapped and used.

[0003] Document DE 10 2005 006 357 A1 discloses a fuel cell system with a fuel cell unit, wherein a metering unit is provided for metering a quantity of substance for at least one electrode. The metering unit has at least two metering elements connected in parallel, of which the first metering element is designed as a control element for controlling the flow cross-section of the second metering element.

[0004] An example of use is the use of electrical energy to power motor vehicles, where the efficiency of converting chemically bound energy into electrical energy is up to 60%.

[0005] When using such H2 / O2 fuel cells, the hydrogen is provided for the application in a hydrogen tank with a pressure of approximately 350 bar to 700 bar.

[0006] Fig. 4 shows an exemplary fuel cell arrangement as is known from the prior art and can be used for powering motor vehicles.

[0007] The fuel cell arrangement 10 in Fig. 4 has a hydrogen tank 12 that provides hydrogen 14 for a redox reaction in an H2 / O2 fuel cell 16. To prevent uncontrolled escape of the hydrogen 14 from the hydrogen tank 12 in the event of a fault, a shut-off valve 18 is arranged directly downstream of the hydrogen tank 12. The hydrogen 14 is stored in the hydrogen tank 12 at a high pressure of approximately 350 bar to 700 bar. This high-pressure hydrogen 14 is reduced by a pressure reducer 20 to a lower pressure level in the medium pressure range of approximately 10 bar to 70 bar. Within this pressure level, the hydrogen 14 is fed to an anode 26 of the H2 / O2 fuel cell 16 via lines 22 and a hydrogen metering valve 24. The targeted addition of hydrogen 14 takes place via the hydrogen metering valve 24. At the anode 26, the hydrogen 14 is at a low pressure in a range of approximately 0.8 bar to 4 bar.The pressure gradient from the medium pressure to the low pressure sets a hydrogen mass flow in the hydrogen metering valve 24. The pressure in the anode 26, which forms a closed volume, is regulated by filling this volume with a defined mass flow of hydrogen 14. This establishes a defined pressure of the hydrogen 14 in the volume of the area of ​​the anode 26.

[0008] The hydrogen 14 reacts in the H2 / O2 fuel cell 16 with oxygen 28, which is supplied to a cathode 30 of the H2 / O2 fuel cell 16. The oxygen 28 is supplied to the cathode 30 via a separate supply unit 32, which ensures that sufficient oxygen 28 is available in this area at a defined pressure.

[0009] On the anode 26 side, the reaction of hydrogen 14 with oxygen 28 causes the concentration of hydrogen 14 to decrease over time. To ensure that there is always sufficient hydrogen 14 available to operate the H2 / O2 fuel cell 16, the hydrogen 14 is recirculated within the area of ​​the anode 26. This can be done, for example, by a gas blower 34 or an ejector. The hydrogen 14 is returned from an outlet 36 of the anode 26 to an inlet 38 of the anode 26. This results in gas exchange within the anode 26, whereby unused hydrogen 14 from the volume in the anode 26 can be used for the reaction with oxygen 28.

[0010] If there is no longer enough hydrogen 14 in the volume of the anode 26, the gas is removed from the volume through a drain valve 40. The hydrogen metering valve 24 meters new hydrogen 14 to the anode 26. It is important that a defined pressure is maintained on the side of the anode 26. This is because a pressure difference is required for the reaction of the hydrogen 14 with the oxygen 28 between the anode 26 and the cathode 30. At the same time, care must be taken to ensure that a diaphragm 42 arranged between the anode 26 and the cathode 30 is not damaged if the pressure difference between the anode 26 and the cathode 30 is too high.

[0011] To regulate this pressure difference, the pressure on the anode side and the cathode side is measured by sensors 44. Using a control algorithm, an electronic control unit 46 adjusts the hydrogen metering valve 24 so that the pressure in the anode 26 is regulated within a predefined range and the required pressure difference between the anode 26 and the cathode 30 for the reaction of hydrogen 14 and oxygen 28 is present.

[0012] The precise control of this pressure in the anode 26 and the required pressure difference between the anode 26 and the cathode 30 has therefore been achieved so far by a complex control system consisting of sensors 44, electronic control unit 46 and one or more electrohydraulic hydrogen metering valves 24.

[0013] The object of the invention is to propose a fuel cell arrangement which is simplified in this respect.

[0014] This object is achieved with a fuel cell arrangement having the combination of features of claim 1.

[0015] Advantageous embodiments of the invention are the subject of the dependent claims.

[0016] A fuel cell assembly for an H2 / O2 fuel cell comprises an anode, at which H2 is oxidized during operation, and which is connected to an H2 inlet for supplying H2 to the anode. A valve having a valve seat and a valve element is arranged in the H2 inlet, which cooperate in a closed position to interrupt an inflow of H2 from the H2 inlet to the anode. Furthermore, the fuel cell assembly comprises a cathode, at which O2 is reduced during operation, and which is connected to an O2 inlet for supplying O2 to the cathode.A differential pressure control device for controlling a differential pressure between the H2 inflow and the O2 inflow is arranged between the H2 inflow and the O2 inflow. The differential pressure control device has a fluid connection between the H2 inflow and the O2 inflow, in which a diaphragm is arranged to close the fluid connection. The diaphragm can be deflected by a deflection force acting due to a pressure difference between the H2 inflow and the O2 inflow. A pin is coupled to the deflectable diaphragm and the valve element in such a way that, upon deflection of the diaphragm in the direction of the H2 inflow, the pin pushes the valve element away from the valve seat in the opening direction.

[0017] The described fuel cell arrangement can regulate the differential pressure between the H2 inflow and the O2 inflow, and thus between the anode and cathode, with only one component, namely the differential pressure control device, and without additional sensors. The system is robust and compact, and an electrical control unit is also unnecessary, as the system can be constructed purely mechanically.

[0018] The differential pressure control device, which thus provides an improved hydrogen dosing valve, works as follows: The pressure in the O2 inlet to the cathode acts on the deflectable membrane, so that its position changes depending on the pressure difference between the H2 inlet and the O2 inlet. As the membrane changes position, the pin coupled to the membrane presses on the valve element, changing the position of the valve element and releasing a cross-section at the valve seat. The supply of hydrogen from the H2 inlet to the anode is controlled depending on the resulting cross-section.

[0019] The mass of hydrogen supplied to the anode therefore results from the force balance between the pressure acting in the H2 inflow and the pressure acting in the O2 inflow, and the pressure surfaces on the valve element or valve seat. This design allows a constant pressure difference to be maintained during operation of the fuel cell assembly.

[0020] Preferably, a second deflectable membrane for closing the fluid connection is arranged in the fluid connection at a distance from the membrane which can be deflected by the deflection force acting due to the pressure difference between the H2 inflow and the O2 inflow, which forms a first membrane.

[0021] Preferably, the first membrane closes the fluid connection to the H2 inflow, wherein the second membrane closes the fluid connection to the O2 inflow.

[0022] In an advantageous embodiment, the arrangement of the spaced-apart first and second membranes in the fluid connection forms a pressure transmission volume which is filled with a pressure transmission fluid which transmits the deflection force exerted by the pressure difference between the H2 inflow and the O2 inflow from the second membrane to the first membrane.

[0023] The pressure at the cathode inlet, i.e., in the O2 inlet, acts on the second membrane in the cathode region. The greater the pressure in the cathode region, the more the second membrane is deformed and acts on the pressure-transmitting fluid in the pressure-transmitting volume. The pressure-transmitting fluid further acts on the first membrane at the H2 inlet, i.e., in the anode region. From the other side of the first membrane, the pressure in the anode region, i.e., in the H2 inlet, acts on the first membrane, so the position of the first membrane depends on the pressure difference between the cathode inlet, i.e., the O2 inlet, and the pressure in the anode region, i.e., in the H2 inlet.

[0024] Preferably, the first membrane and the second membrane have different effective areas for absorbing the deflection force. The dependence of the position of the first membrane on the pressure difference between the H2 inflow and the O2 inflow can thus be adjusted by adjusting the ratios of the effective areas of the two membranes.

[0025] Advantageously, a first effective area of ​​the first diaphragm is smaller than a second effective area of ​​the second diaphragm. This makes it possible to achieve a sufficiently large deflection of the first diaphragm, thus lifting the valve element from the valve seat, even with small pressure differences between the H2 inflow and the O2 inflow.

[0026] Preferably, the valve comprises a compression spring arranged in the H2 inlet, which exerts a spring force on the valve element, biasing the valve element in a closing direction toward the valve seat. The arrangement of the compression spring allows the valve element to be securely held in the closed position on the valve seat. The pressure of the hydrogen acting in the H2 inlet thus acts in the same direction as the spring force of the compression spring, so that the valve element is securely held in the valve seat by the forces of both the flowing hydrogen and the compression spring.

[0027] Preferably, an actuator is provided to regulate the spring force of the compression spring. By providing such an actuator, it is possible to additionally adjust the force balance. This allows the pressure difference between the cathode and anode to be regulated to be additionally adjusted.

[0028] For example, the actuator is formed by a controllable piezo actuator. In an alternative embodiment, it is possible to form the actuator by a controllable electromagnetic actuator. However, in another possible embodiment, it is conceivable to form the actuator by a controllable electric motor having a spindle.

[0029] Advantageous embodiments of the invention are explained in more detail below with reference to the accompanying drawings, in which: Fig. 1 a schematic overview of a fuel cell arrangement with a fuel cell and a hydrogen metering valve; Fig. 2 a schematic detailed representation of a part of the fuel cell arrangement from Fig. 1 in a first embodiment; Fig. 3 a schematic detailed representation of a partial area of ​​the fuel cell arrangement from Fig. 1 in a second embodiment; and Fig. 4 a schematic overview of a fuel cell arrangement with hydrogen dosing valve from the prior art.

[0030] Fig. 1 shows an overview of a fuel cell arrangement 10 having an H2 / O2 fuel cell 16 comprising an anode 26 and a cathode 30. Hydrogen 14 is oxidized in the anode 26, while oxygen 28 is reduced in the cathode 30. A hydrogen tank 12 is provided to supply the anode 26, which stores the hydrogen 14 under high pressure. Via lines 22, in which a shut-off valve 18 and a pressure reducer 20 are arranged, the hydrogen 14 is supplied to a hydrogen metering valve 24, which adjusts the pressure of the hydrogen 14 in an H2 inlet 48 to the anode 26 and thus in the anode 26 itself. Oxygen 28 is supplied to the cathode 30 via an O2 inlet 50.

[0031] An inlet 38 of the anode 26 is connected to an outlet 36 of the anode 26 via a gas blower 34 to enable recirculation of the hydrogen 14. Once a large portion of the hydrogen 14 has been consumed by the reaction between hydrogen 14 and oxygen 28, the consumed gas can be released from the anode 26 via a vent valve 40. The hydrogen metering valve 24 then meters fresh hydrogen 14 to the anode 26 via the H2 inlet 48.

[0032] The hydrogen dosing valve 24 is designed as a differential pressure control device 52 which controls a pressure difference Δp between the H2 inflow 48 and the O2 inflow 50.

[0033] The structure of a first embodiment of the differential pressure control device 52 is shown in greater detail in a representation of the fuel cell arrangement 10 in Fig. 2 shown.

[0034] The differential pressure control device 52 has a fluid connection 54 between the H2 inlet 48 and the O2 inlet 50. A first membrane 56 is arranged in the fluid connection 54, which is acted upon by a pressure difference Δp between the H2 inlet 48 and the O2 inlet 50 and a deflection force F acting thereby. A can be deflected from its position.

[0035] A passive valve 58 is arranged in the H2 inlet 48, which has a valve element 60 and a valve seat 62. In a closed position, the valve seat 62 and the valve element 60 interact, so that the valve 58 is closed.

[0036] A pin 64 is coupled to the first membrane 56 and the valve element 60. As soon as the first membrane 56 deflects toward the H2 inlet 48, the first membrane 56 presses the pin 64 onto the valve element 60, causing it to lift off the valve seat 62 and the valve 58 to open. This releases the H2 inlet 48 to the anode 26, allowing hydrogen 14 to flow to the anode 26.

[0037] A second membrane 66 is arranged in the fluid connection 54 at a distance from the first membrane 56, the position of which can also be changed by the pressure difference Δp.

[0038] The first membrane 56 closes the fluid connection 54 to the H2 inlet 48, while the second membrane 66 closes the fluid connection 54 to the O2 inlet 50. Due to the spaced arrangement of the two membranes 56, 66 in the fluid connection 54, a pressure transmission volume 68 is formed in the fluid connection 54, wherein this pressure transmission volume 68 is filled with a pressure transmission fluid 70. If the second membrane 66 is now deflected towards the H2 inlet 48 due to the pressure difference Δp between the H2 inlet 48 and the O2 inlet 50, the pressure transmission fluid 70 transmits the deflection force F acting thereby. A from the second membrane 66 to the first membrane 56, which thus opens the valve 58.

[0039] The greater the pressure in the O2 inlet 50, the more the second membrane 66 is deformed and the more this deformation acts on the pressure transfer fluid 70 in the pressure transfer volume 68. The pressure transfer fluid 70 also acts on the first membrane 56 in the area of ​​the H2 inlet 48. From the side of the H2 inlet 48, the pressure in the area of ​​the anode 26 acts on the first membrane 56, so that the position of the first membrane 56 depends on the pressure difference Δp between the O2 inlet 50 and the H2 inlet 48. The dependence of the position of this first membrane 56 on the pressure difference Δp can be determined via the ratios of effective areas A W of the membranes 56, 66 can be adjusted constructively. For example, if the first membrane 56 has a smaller effective area A W than the second membrane 66, even a small pressure difference Δp causes a relatively large deflection of the first membrane 56 and thus a rapid opening of the valve 58.

[0040] This is because the position change of the first membrane 56 causes the pin 64 to press on the valve element 60, thereby changing the position of the valve element 60 relative to the valve seat 62 and thus opening a cross-section. The supply of hydrogen 14 to the anode 26 is controlled depending on the resulting cross-section.

[0041] In addition, the valve 58 has a compression spring 72 arranged in the H2 inlet and a spring force F F on the valve element 60, whereby the valve element 60 is preloaded in a closing direction onto the valve seat 62. Due to the spring force F F the preload of the valve element 60 can be adjusted so that the deflection force F A which is required to lift the valve element 60 from the valve seat 62 can be influenced.

[0042] The amount of hydrogen supplied to the anode 26 therefore results from the balance of forces between the pressure prevailing in the O2 inlet 50, the pressure prevailing in the H2 inlet 48, the effective areas A W on the valve element 60 and the valve seat 62 as well as the spring force F F the compression spring 72, which holds the valve element 60 in its position and which acts on the valve element 60 from the side opposite the pin 64.

[0043] This force balance can be used to set a constant pressure difference Δp between the anode 26 and the cathode 30 during operation of the fuel cell 16.

[0044] Fig. 3 shows a schematic representation of a second embodiment of the fuel cell assembly 10, which is essentially constructed in the same way as the first embodiment, which is shown in Fig.2. In the second embodiment, only an additional actuator 74 is provided, which determines the spring force F F of the compression spring 72. The force balance can therefore be influenced by the additional actuator 74, which can be implemented, for example, as a piezo actuator, an electric motor with a spindle, or an electromagnet. This allows the pressure difference Δp to be controlled between the cathode 30 and the anode 26 to be additionally adjusted.

Claims

[1] Fuel cell assembly (10) for an H2 / O2 fuel cell (16), comprising: - an anode (26) at which H2 (14) is oxidized during operation and which is connected to an H2 inlet (48) for supplying H2 (14) to the anode (26), wherein a valve (58) with a valve seat (62) and a valve element (60) is arranged in the H2 inlet (48), which valves cooperate in a closed position to interrupt an inflow of H2 (14) from the H2 inlet (48) to the anode (26), - a cathode (30) at which O2 (28) is reduced during operation and which is connected to an O2 inlet (50) for supplying O2 (28) to the cathode (30), wherein a differential pressure control device (52) for controlling a differential pressure between the H2 inflow (48) and the O2 inflow (50) is arranged between the H2 inflow (48) and the O2 inflow (50), wherein the differential pressure control device (52) has a fluid connection (52) between the H2 inflow (48) and the O2 inflow (50), in which a deflection force (F A ) deflectable membrane (56) is arranged for closing the fluid connection (54), wherein a pin (64) is coupled to the deflectable membrane (56) and the valve element (60) in such a way that the pin (64) presses the valve element (60) away from the valve seat (62) in the opening direction when the membrane (56) is deflected in the direction of the H2 inflow (48). [2] Fuel cell arrangement (10) according to claim 1, characterized by that in the fluid connection (54) at a distance from the deflection force (F A) deflectable membrane (56) which forms a first membrane (56), a second deflectable membrane (66) is arranged to close the fluid connection (54). [3] Fuel cell arrangement (10) according to claim 2, characterized by that the first membrane (56) closes the fluid connection (54) to the H2 inlet (48), wherein the second membrane (66) closes the fluid connection (54) to the O2 inlet (50). [4] Fuel cell arrangement (10) according to one of claims 2 or 3, characterized by that by arranging the first and second membranes (56, 66) spaced apart from one another in the fluid connection (54), a pressure transmission volume (68) is formed which is filled with a pressure transmission fluid (70) which transmits the deflection force (F A ) from the second membrane (66) to the first membrane (56). [5] Fuel cell arrangement (10) according to claim 4, characterized by that the first membrane (56) and the second membrane (66) have different effective areas (A W ) to absorb the deflection force (F A ). [6] Fuel cell arrangement (10) according to claim 5, characterized by that a first effective area (A W ) of the first membrane (56) is smaller than a second effective area (A W ) of the second membrane (66). [7] Fuel cell arrangement (10) according to one of claims 1 to 6, characterized by that the valve (58) has a compression spring (72) which is arranged in the H2 inlet (48) and has a spring force (F F ) on the valve element (60), which biases the valve element (60) in a closing direction onto the valve seat (62). [8] Fuel cell arrangement (10) according to claim 6, characterized by that an actuator (74) for regulating the spring force (F F ) of the compression spring (72). [9] Fuel cell arrangement (10) according to claim 8, characterized by that the actuator (74) is formed by a controllable piezo actuator, a controllable electromagnetic actuator or by a controllable electric motor with spindle.

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