PRESSURE REDUCER FOR A HYDROGEN SUPPLY SYSTEM

Abstract

The present development relates to a hydrogen supply system and a pressure reducer (20) for a hydrogen supply system (8), wherein the pressure reducer (20) comprises: - a galvanic cell (30) having an anode (23), a cathode (24) and a membrane (25) arranged between the anode (23) and the cathode (24), - a high-pressure side (21) in flow connection with the anode (23) and which can be coupled to a hydrogen storage device (10), - a low-pressure side (22) which is in flow connection with the cathode (24) and which can be coupled to a consumer (6).

Description

Technical area

[0001] The present development relates to a hydrogen supply system, in particular for the fuel cell of a motor vehicle, and a pressure reducer provided therefor. background

[0002] Hydrogen storage in motor vehicles, for example, to supply a fuel cell, typically occurs at a comparatively high pressure. The pressure level in a hydrogen tank can reach several hundred bar. Therefore, one or more pressure reducers must be provided in the hydrogen supply system, which fluidically connects the hydrogen tank to the fuel cell, to supply the fuel—i.e., the gaseous hydrogen—to the fuel cell at a predetermined pressure level.

[0003] For example, EP 3 214 684 B 1 discloses a fuel cell system, wherein a supply valve is provided for supplying the anode gas into an anode system of a fuel cell system and a purge valve is provided for discharging an exhaust gas from the anode system.

[0004] In contrast, the present development is based on the task of providing a pressure reducer, specifically designed for a hydrogen supply system, that can be operated particularly simply, cost-effectively, and energy-efficiently. The pressure reducer should demonstrate stable long-term operation and enable particularly efficient fuel cell operation from an energy perspective. Advantageous designs

[0005] This object is achieved with a pressure reducer, a hydrogen supply system, and a motor vehicle according to the features of the independent patent claims. Advantageous embodiments are the subject of dependent patent claims.

[0006] According to a first aspect, a pressure reducer for a hydrogen supply system is provided. The pressure reducer comprises a galvanic cell. The galvanic cell comprises an anode and a cathode, as well as a membrane arranged between the anode and the cathode. The pressure reducer further comprises a high-pressure side, by means of which the pressure reducer can be coupled to a hydrogen storage device in flow communication. The high-pressure side is further in flow communication with the anode. The pressure reducer, in particular its galvanic cell, further comprises a cathode, which forms a low-pressure side or is arranged on or in a low-pressure side of the pressure reducer. The low-pressure side can be coupled to a consumer, for example in the form of a fuel cell.

[0007] In simple terms, the pressure reducer comprises or forms a concentration cell. The membrane arranged between the anode and cathode, or which electrically insulates the anode and cathode from each other, is permeable to protons. In this respect, the operation of the pressure reducer is designed so that the highly pressurized hydrogen supplied via the high-pressure side is oxidized at the anode, and the protons or hydrogen nuclei created by oxidation diffuse through the membrane to the cathode. There, the protons or hydrogen nuclei can recombine or reduce to form hydrogen molecules with the electrons provided. The hydrogen molecules thus recombined are present on the cathode side at a significantly lower pressure than on the high-pressure side.

[0008] The use of a galvanic cell, especially a concentration cell, as a pressure reducer has the particular advantage of creating a current flow through the galvanic cell, namely between the anode and cathode. This current can be used to generate electrical energy. Furthermore, by regulating the current flow between the anode and cathode, the recombination rate of hydrogen on the cathode side can be precisely regulated, thus allowing a pressure gradient across the membrane to be precisely adjusted.

[0009] Thus, the pressure reducer proposed here can be implemented essentially without mechanically actuated components and can be controlled purely electrically to regulate the pressure on the low-pressure side. At the same time, electrical energy can be generated from the pressure gradient between the cathode and anode, thereby improving the energy efficiency of the entire hydrogen supply system. The pressure reducer, in particular the current flowing from cathode to anode, can not only be regulated via a control element or a converter but can also be fed into a motor vehicle's electrical system, for example. The energy efficiency of the motor vehicle can be improved or increased in this way.

[0010] According to a further embodiment of the pressure reducer, the membrane is designed to be permeable to protons. The membrane is typically designed to be electrically insulating. In this way, the anode and cathode can be electrically isolated from each other. At the same time, hydrogen nuclei, i.e., protons, can diffuse from the high-pressure side, namely the anode, through the membrane to the low-pressure side, i.e., the cathode. The membrane between the anode and cathode represents a mechanical barrier to the diffusion of the protons. At the same time, it creates an electrical separation between the anode and cathode.

[0011] According to a further embodiment of the pressure reducer, the anode and cathode can be electrically connected to each other in a controllable manner, forming a closed circuit. They can also be permanently connected to each other via the closed circuit. By interrupting the circuit and / or by regulating the current flow through the circuit, the concentration of recombined or reduced hydrogen on the cathode side can be regulated.

[0012] If, for example, the anode and cathode are not electrically connected because the circuit is interrupted, no electrons are available on the cathode side, which could allow the protons diffusing through the membrane to recombine into hydrogen. This would result in a comparatively low hydrogen partial pressure on the cathode side. Similarly, a hydrogen pressure level on the cathode side of the pressure reducer can be adjusted by throttling the current flow or by regulating or controlling the current flow through the closed circuit.

[0013] According to a further embodiment of the pressure reducer, it comprises an electronic control circuit. The electronic control circuit comprises a controller, a control element controllable by the controller, and a pressure sensor coupled to the low-pressure side and connected to the controller via signaling. The pressure sensor serves to measure a hydrogen partial pressure on the low-pressure side of the pressure reducer. The pressure sensor can be arranged, in particular, between the low-pressure side of the pressure reducer and a supply for the consumer. The pressure sensor can be used to detect the pressure level on the low-pressure side of the pressure reducer.

[0014] The pressure sensor is signal-coupled to the controller. The controller is designed to compare the pressure level that can be determined or measured using the pressure sensor with a previously set or predetermined pressure level and, accordingly or based on a comparison, to control a control element by means of which, for example, the current flow through the closed circuit between the anode and cathode can be regulated. For example, if the pressure on the low-pressure side is lower than a predetermined target pressure, the current flow can be increased by changing the electrical resistance, in particular by lowering the electrical resistance in the closed circuit. This in turn leads to a higher recombination rate of hydrogen on the cathode side.Consequently, by reducing the electrical resistance in the closed circuit between anode and cathode, the hydrogen partial pressure on the cathode side can be increased.

[0015] Similarly, increasing the electrical resistance in the closed circuit between anode and cathode can reduce the current flow and thus the recombination rate of hydrogen on the cathode side, thereby reducing the hydrogen partial pressure on the cathode side.

[0016] According to a further embodiment, the galvanic cell of the pressure reducer comprises a so-called concentration cell, or the galvanic cell forms such a concentration cell. The concentration cell can comprise two essentially identically constructed half-cells, namely an anode-side and a cathode-side half-cell, which differ only in terms of hydrogen concentration. In particular, the membrane arranged between the anode and cathode sides can be of identical design.

[0017] The voltage tapped at the anode and cathode sides can be described, in particular, by the so-called Nernst equation. The voltage generated between the cathode and anode can be determined, in particular, as proportional to the logarithm of the quotient between the hydrogen pressure on the high-pressure side and the hydrogen pressure on the low-pressure side.

[0018] In practical applications, the hydrogen pressure on the anode side can be up to approximately 700 bar. The hydrogen pressure on the cathode side can, for example, be in the range of less than 100 bar, less than 50 bar, less than 20 bar, and approximately in the range of 10 bar. In this way, a significant electrical power can be tapped between the cathode and the anode, which is in the range of several kilowatts if approximately 1 g / s of hydrogen is supplied to the consumer from the low-pressure side of the pressure reducer.

[0019] According to a further embodiment of the pressure reducer, the membrane is provided with or coated with a catalytic layer. The membrane can, in particular, comprise or essentially consist of a precious metal, such as platinum or similar metals. By or by means of a catalytic layer on at least one side of the membrane, the oxidation and / or reduction or recombination processes for the formation of protons and molecular oxygen on the cathode and anode sides can be improved and accelerated.

[0020] According to a further embodiment of the pressure reducer, it comprises several such galvanic cells arranged in the form of a cell stack. For example, the cathode of a first galvanic cell can be electrically connected to the anode of a second galvanic cell.

[0021] Furthermore, the cathode of the second galvanic cell can be electrically connected to the anode of a third galvanic cell. Such an electrical series connection of several galvanic cells or concentration cells makes it possible to increase the voltage tapped at opposite end plates of a galvanic cell stack through the series connection. The number of galvanic cells or concentration cells can be varied as desired to tap a desired voltage at the end plates.

[0022] In order to utilize the voltage that can be tapped at opposite end plates of the cell stack, the control element, which is provided in the circuit between the anode and cathode, can, for example, have a DC converter.

[0023] According to a further embodiment, one or more cooling elements can be provided or formed between adjacent cells of the cell stack. By means of such cooling elements, through which a cooling medium can flow, for example, the thermal energy released during oxidation and / or reduction can be dissipated from the cell stack. Such cooling elements can be arranged, in particular, between individual galvanic cells or concentration cells of the cell stack provided here. The cooling elements can typically be designed to be electrically conductive, such that they enable, for example, an electrically conductive connection between the anode of a first cell and the cathode of another, for example, a second cell.

[0024] According to a further aspect, the present development finally relates to a hydrogen supply system, in particular for the fuel cell of a motor vehicle. The hydrogen supply system comprises a hydrogen storage device with at least one hydrogen tank. The hydrogen supply system further comprises a previously described pressure reducer, which is fluidically coupled to the hydrogen storage device. Downstream of the pressure reducer, a hydrogen consumer, such as a fuel cell, is typically provided, which can typically be brought into fluid communication with the low-pressure side of the pressure reducer.

[0025] Using the hydrogen supply system, the hydrogen in the hydrogen tank, which is under comparatively high pressure, can be supplied to the hydrogen consumer at a significantly lower pressure level. At the same time, electrical energy can be recovered or generated from the pressure difference between the high-pressure and low-pressure sides of the pressure reducer.

[0026] Finally, a motor vehicle, such as a passenger car, a delivery van, or a small van, is envisioned. The motor vehicle has a fuel cell and a hydrogen supply system as described above. The hydrogen supply system is fluidly connected to the fuel cell.

[0027] Since the hydrogen supply system, and thus the motor vehicle, has a pressure reducer as described above, all features, advantages and effects described above with regard to the pressure reducer also apply equally to the hydrogen supply system and to the motor vehicle; and vice versa. Short description of the characters

[0028] Further objectives, features, and advantageous embodiments of the present development are explained in the following description of an exemplary embodiment. Herein: Fig. 1 a schematic representation of a motor vehicle, Fig. 2 Block diagram of the hydrogen supply system of the motor vehicle, Fig. 3 a block diagram of the pressure reducer, which comprises several galvanic cells and Fig. 4 an isolated representation of a single galvanic cell of the pressure reducer. Detailed description

[0029] The Fig. The motor vehicle 1 schematically illustrated in Figure 1 comprises a motor vehicle body 2 and an interior 3 functioning as a passenger cell. The motor vehicle is provided with a drive 4, which typically comprises an electric motor. The drive 4 can be supplied with electrical power, in particular, by a hydrogen consumer 6, for example in the form of a fuel cell 7. Typically, the motor vehicle 1 is provided with a rechargeable battery (not shown), by means of which the electrical power generated by the fuel cell 7 can be at least buffered or stored. The motor vehicle 1 further comprises a hydrogen storage unit 10 and a hydrogen supply system 8, by means of which the hydrogen stored in the hydrogen storage unit 10 can be supplied to the fuel cell 7, and thus to the consumer 6.

[0030] An exemplary example of a hydrogen supply system 8 is shown in Fig. 2. The hydrogen supply system serves to supply hydrogen from the hydrogen storage unit 10 to the fuel cell 7, and thus to the hydrogen consumer 6. The hydrogen supply system 8 comprises the hydrogen storage unit 10. The hydrogen storage unit 10 has several tanks 11, 12, which are connected approximately parallel in terms of flow. The hydrogen tank 11 is provided with an adjustable valve 13. The hydrogen tank 12 is provided with another adjustable valve 14. Downstream of the two valves 13, 14, the associated lines open into a common hydrogen supply 15, which is in flow connection with the high-pressure side 21 of a pressure reducer 20.

[0031] The pressure reducer 20 has a low-pressure side 22 downstream, via which a low-pressure line 16 leads to the consumer 6, for example, the fuel cell 7. A pressure sensor 42 is provided on the low-pressure side 22 of the pressure reducer 20, or in fluid communication with the low-pressure line 16. This sensor serves to measure the hydrogen partial pressure in the low-pressure line 16 downstream of the pressure reducer 20.

[0032] The sensor 42 is provided with a signaling controller 41, which in turn is coupled to a control element 40. The control element 40 can, for example, comprise or have a DC converter. However, the control element 40 can also provide a variable and / or adjustable ohmic resistor, by means of which, for example, a current in a circuit 29 can be regulated. The DC converter 40 can, for example, be electrically coupled to a low-voltage electrical system 5, such as a 12V electrical system of the motor vehicle.

[0033] Electrical power can be transmitted from the electrical circuit 29 to the on-board electrical system 5 of the motor vehicle 1 and / or stored in a battery via the control element 40. The electrical circuit 29 is closed by the pressure reducer 20. The electrical circuit 29 typically contacts opposite end plates 33, 34 of a cell stack 32 of several galvanic cells 30, 30', 30" of the pressure reducer 20.

[0034] The pressure reducer 20 has at least one Fig. 4 shows an exemplary galvanic cell 30. This cell has an anode 23, a cathode 24, and a membrane 25 arranged between the anode 23 and the cathode. The membrane 25 can have a catalytic layer 27 on the side of the cathode 24 or facing the cathode 24. Likewise, the membrane 25 can have a further catalytic layer 26, for example a coating of a precious metal, such as platinum, facing the anode 23.

[0035] The anode 23 is in fluid communication with the high-pressure side 21 of the pressure reducer 20. Thus, hydrogen gas at comparatively high pressure can be supplied to the anode 23. In the region of the anode, oxidation of the molecular hydrogen occurs, resulting in a type of oxidation and / or splitting of the hydrogen molecules into protons and electrons. The protons can diffuse through the membrane 25 to the cathode 24. There, the protons can recombine with electrons flowing through the circuit 29, which can be tapped at the anode 23, so that hydrogen is again produced at the cathode 24.

[0036] The rate of hydrogen production or recombination on the cathode side depends on the current flow through circuit 29, which connects anode 23 and cathode 24. Cathode 24 is located on the low-pressure side. From there, the recombined or reduced molecular hydrogen can be fed to the low-pressure line 16.

[0037] The Fig. 4, the isolated galvanic cell 30 is a concentration cell 31 or has such a concentration cell 31. In the block diagram of the Fig. 3, several such concentration cells 31 are provided. There, an example is shown in a series connection of three galvanic cells 30, 30', 30" or three concentration cells 31, 31', 31". The cathodes 24 and anodes 23 of all cells 30, 30', 30", 31, 31', 31" of the cell stack 32 formed in this way are each fluidically connected in parallel with regard to the gas flow. This means that all anodes 23 of the respective cells 30, 30', 30" are fluidically coupled to the high-pressure side 21. All cathodes 24 of the individual cells 30, 30', 30" are fluidically connected to the low-pressure side 22. The respective anodes 23 and cathodes 24 are fluidically connected in parallel with one another.

[0038] Electrically, the individual cells 30, 30', 30" are connected in series. As particularly in Fig. As shown in Figure 3, for example, the anode 23 of a first cell 30 can be electrically connected to the cathode 24 of another cell 30', so that the electrons released on the side of the anode 23 of the first cell 30 can flow to the cathode 24 of the adjacent cell 30'.

[0039] In the block diagram of the Fig. 3, individual cooling elements 35 are further provided and arranged between the electrically interconnected cells 30, 30', 30". The cooling elements 35 can be designed to be electrically conductive so that they do not impede the flow of electrons through the cell stack 32 and, in particular, promote this as much as possible. A coolant can flow through the individual cooling elements 35. They can, for example, be integrated into a cooling circuit 6. A total of several cooling elements 35 can be provided for a cell stack 32, each of which is arranged between adjacent cells 30, 30', 30".

[0040] In this way, the thermal energy released in the area of ​​a cell 30 can be dissipated in a controlled manner. Individual cooling elements 35 can be connected in parallel to one another in terms of flow. They can all be connected to a common inlet 37. Downstream, the individual cooling elements 35 can be connected to an outlet 38. The coolant circuit 36 ​​can also be provided with a separate pump, such as a circulation pump, to regulate or control the coolant flow through the coolant circuit 36.

[0041] Overall, the pressure reducer 20 can recover electrical energy from the pressure difference between the high-pressure side 21 and the low-pressure side 22 at the pressure reducer 20. This electrical energy can be supplied to the motor vehicle, in particular to the on-board electrical system 5 of the motor vehicle 1, via the control element 40, for example, via a DC converter. If necessary, a battery can be charged.

[0042] The illustrated embodiments merely show possible configurations of the development, for which numerous further variants are conceivable within the scope of the development. The exemplary embodiments shown are in no way to be interpreted as limiting the scope, applicability, or configuration options of the development. This description merely shows the person skilled in the art one or several possible implementations of an exemplary embodiment. Thus, a wide variety of modifications can be made to the function and arrangement of the described elements without departing from the scope of protection defined by the following claims or their equivalents. List of reference symbols 1 motor vehicle 2 Motor vehicle body 3 Interior 4 Drive 5 On-board network 6 consumers 7 Fuel cell 8 Hydrogen supply system 10 hydrogen storage units 11 Tank 12 tanks 13 Valve 14 Valve 15 Hydrogen supply 16 Line 20 pressure reducers 21 High pressure side 22 Low pressure side 23 Anode 24 Cathode 25 membrane 26 catalytic layer 27 catalytic layer 29 Circuit 30 galvanic cell 31 Concentration cell 32 cell stacks 33 End plate 34 End plate 35 Cooling element 36 Coolant circuit 37 Inlet 38 Process 40 control element 41 Control 42 Sensor 43 Control loop QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] EP 3 214 684

[0003]

Claims

[1] Pressure reducer (20) for a hydrogen supply system (8) comprising: - a galvanic cell (30) having an anode (23), a cathode (24) and a membrane (25) arranged between the anode (23) and the cathode (24), - a high-pressure side (21) in flow connection with the anode (23) and which can be coupled to a hydrogen storage device (10), - a low-pressure side (22) which is in flow connection with the cathode (24) and which can be coupled to a consumer (6). [2] Pressure reducer (20) according to claim 1, wherein the membrane (25) is designed to be permeable to protons. [3] Pressure reducer (20) according to one of the preceding claims, wherein the anode (23) and the cathode (24) are controllably electrically connectable to one another to form a closed circuit (29). [4] Pressure reducer (20) according to claim 3, further comprising an electronic control circuit (43) with a controller (41), a control element (40) controllable thereby and a pressure sensor (42) coupled to the low-pressure side (22) and signal-connected to the controller. [5] Pressure reducer (20) according to one of the preceding claims, wherein the galvanic cell (30) comprises or forms a concentration cell (31). [6] Pressure reducer (20) according to one of the preceding claims, wherein the membrane (25) is provided or coated with a catalytic layer (26, 27). [7] Pressure reducer (20) according to one of the preceding claims, wherein the pressure reducer comprises a plurality of galvanic cells (30, 30', 30") arranged in the form of a cell stack (32). [8] Pressure reducer (20) according to claim 7, wherein a cooling element (35) is arranged between adjacent cells (30, 30', 30") of the cell stack (32). [9] Hydrogen supply system (8) comprising: - a hydrogen storage device (10) with at least one hydrogen tank (11, 12) and - a pressure reducer (20) according to one of the preceding claims, which is fluidly coupled to the hydrogen storage device (10). [10] Motor vehicle (1) with a drive (4), a fuel cell (7) and with a hydrogen supply system (8) according to claim 9, which is fluidically connected to the fuel cell (7).

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