DEVICE FOR PROVIDING HYDROGEN

Description

[0001] The invention relates to a device for providing hydrogen, wherein the device includes an electrolysis unit for generating the hydrogen. The invention also relates to a method for operating such a device.

[0002] Due to progressive climate change, increasingly stringent political regulations are being introduced regarding permissible CO2 emissions into the atmosphere. Particularly in the transportation sector, efforts are therefore underway to find alternatives to conventional fossil fuels (diesel, gasoline, natural gas, etc.). One possible approach is the use of battery-powered vehicles with electric drives. In this system, previously generated electrical energy is stored in batteries and used to power electric motors. However, the degree of CO2 reduction depends heavily on the method of electricity generation and the energy input required for battery production. For commercial vehicles in particular, purely battery-electric operation is currently not economically viable, primarily due to the poor weight / size-to-storage-capacity ratio.Suitable batteries would therefore be too large and / or too heavy, which would unduly restrict the transport capacity.

[0003] Another possibility is the use of hydrogen to power vehicles. The hydrogen can be used, for example, as fuel in modified combustion engines or converted into electrical energy in a fuel cell, which in turn can be used to power electric motors. Hydrogen can be stored, for example, in liquid form in suitable low-temperature tanks or in gaseous form at sufficiently high pressures in pressure vessels. This already makes it possible to achieve similarly long ranges for commercial vehicles as with conventional powertrains. Electrolysis is a known method for producing hydrogen. In this process, water is split into hydrogen (H₂) and oxygen (O₂) using electrical energy. Various types of electrolysis units, known as electrolyzers, are known, which differ in their design.At the output of an electrolysis unit, hydrogen is provided at a specific pressure (regardless of the design).

[0004] There are various approaches to further processing the hydrogen at the electrolyzer outlet. In EP 2 067 992 A1, the hydrogen is compressed using a hydraulically driven piston compressor and stored in a pressure vessel. The output pressure of the piston compressor can be adjusted by changing the pumping speed of a pump in the hydraulic drive. In KR 102 094 706 B1, the hydrogen from an electrolyzer is temporarily stored in a storage tank. From there, the hydrogen can be extracted and, for example, compressed using a compressor. In EP 3 428 317 A1, the hydrogen produced in an electrolyzer is stored in storage tanks. These storage tanks are designed as constant-pressure storage systems, incorporating a hydraulically driven piston to compress the hydrogen to a specific pressure level.

[0005] In hydrogen production, the CO2 reduction also depends on the type of electricity generation used to supply the electrolysis unit.

[0006] It is therefore particularly advantageous to use renewable energy sources, such as wind power or photovoltaics, to supply energy to the electrolysis unit. Unlike conventional energy sources, especially fossil fuels, electricity generation from these sources is generally not constant, but rather highly dependent on prevailing environmental conditions. With wind turbines, electricity generation varies with wind speed and is therefore inherently not constant. With photovoltaic systems, electricity generation varies with solar radiation, which is also typically not constant due to factors such as clouds or shading. If the electrolysis unit is directly connected to the respective energy source, then the electrical power supply to the electrolysis unit also fluctuates depending on the fluctuations in the energy source's electricity generation.However, a fluctuating power supply to an electrolysis unit is undesirable because it leads to pressure fluctuations of the produced hydrogen at the electrolysis unit's outlet. These pressure fluctuations, in turn, negatively affect the durability and consequently the lifespan of the electrolysis unit.

[0007] It is therefore an object of the invention to provide a device for supplying hydrogen by means of an electrolysis unit, which enables the longest possible service life of the electrolysis unit even in the case of fluctuating energy supply to the electrolysis unit.

[0008] The problem is solved with the device mentioned above by providing a reciprocating compressor for compressing the hydrogen produced by the electrolysis unit, by providing the reciprocating compressor with at least one automatic suction valve, by providing a lifting gripper to selectively hold the suction valve in an open position, by providing an electrically controllable actuator for actuating the lifting gripper, and by providing a control unit for controlling the actuator, wherein the control unit is configured to control the actuator in such a way that an output pressure of the hydrogen at the output of the electrolysis unit or a differential pressure between an anode and a cathode of the electrolysis unit can be adjusted to a predetermined setpoint.If the electrolysis unit has a proton exchange membrane between the anode and the cathode, then the differential pressure can be a differential pressure across the proton exchange membrane. This allows, for example, a desired setpoint for the output pressure to be set relatively quickly via the control of the lifting gripper, even in the case of a fluctuating power supply to the electrolysis unit, which previously led to a fluctuating output pressure.

[0009] The setpoint can be, for example, a fixed numerical value, or the control unit can include a function for determining the setpoint based on at least one other parameter, preferably time. This allows a constant output pressure or differential pressure to be set, regardless of any fluctuations in the power supply. Alternatively, a specific time profile for the output pressure or differential pressure can be set. This can be advantageously implemented, for example, when the electrolysis unit is switched off or the power supply is interrupted, in order to reduce the output pressure relatively slowly and in a controlled manner to a specific pressure.

[0010] Preferably, a measuring unit is provided for determining an actual value of the outlet pressure or the differential pressure, and the control unit is configured to use the determined actual value to regulate the outlet pressure or the differential pressure to the specified setpoint. The measuring unit preferably comprises at least one sensor and / or a calculation model, wherein the calculation model is preferably stored in the control unit. For example, a pressure sensor can be provided as the sensor for detecting an actual value of the hydrogen outlet pressure at the outlet of the electrolysis unit. The pressure sensor can be arranged in a connecting line that links the outlet of the electrolysis unit to the piston compressor. A differential pressure sensor can also be provided for detecting an actual value of the differential pressure.

[0011] The control unit is preferably designed to determine a manipulated variable for the actuator from the measured actual value and the specified setpoint, and to control the actuator with this manipulated variable. For this purpose, it is advantageous if the control unit includes a suitable controller, such as a PL controller or PID controller, for determining the manipulated variable. This allows for the implementation of a closed control loop, enabling very precise control of the output pressure or differential pressure.

[0012] Additionally or alternatively, the control unit can also contain a function for determining a manipulated variable for the actuator based on the specified setpoint. The control unit can be configured to derive a manipulated variable for the actuator from this function and control the actuator with the determined manipulated variable. This allows for a simpler (feedforward) control system compared to (feedback) control. The function can be considered known or can be determined through experimentation.

[0013] Preferably, an electrical energy source is provided to supply energy to the electrolysis unit and / or the reciprocating compressor. This allows, for example, the entire device to be powered by a single energy source. Particularly preferably, the energy source comprises a renewable energy generation device connected to the electrolysis unit and / or the reciprocating compressor, the energy generation device preferably being a photovoltaic system or a wind turbine. This allows a renewable energy carrier to be used for hydrogen production, which is advantageous for environmental reasons. Since renewable energy generation devices generally produce energy that is not constant over time due to environmental conditions, the control or regulation of the output pressure or differential pressure according to the invention is particularly advantageous because, for example, it allows for...Fluctuations can be quickly and easily corrected.

[0014] The actuator is preferably designed as a pneumatic, hydraulic, or electromagnetic actuator. Due to its short response time, an electromagnetic actuator is particularly advantageous for reacting as quickly as possible to rapid pressure fluctuations.

[0015] It is advantageous if at least one self-acting suction valve is designed as a ring valve, wherein the ring valve preferably has several annular valve openings and several annular valve elements that can be actuated by the lifting gripper. This design has already proven successful in previous compressors.

[0016] The reciprocating compressor can preferably also be designed as a double-acting reciprocating compressor and / or as a multi-stage reciprocating compressor. By selecting a suitable design of the reciprocating compressor, the device can be flexibly adapted to different operating conditions.

[0017] The electrolysis unit can, for example, be supplied directly by a renewable energy generation device with electrical energy that is not constant over time, and the control unit can regulate the output pressure or the differential pressure to a predetermined, for example constant, setpoint.

[0018] If the electrolysis unit is deactivated or its electrical power supply is interrupted, the control unit can reduce the output pressure to a predetermined value, for example, according to a predefined time function. This allows the output pressure to be lowered slowly, which is advantageous for the long-term reliability of the electrolysis unit.

[0019] The present invention is described below with reference to Figur 1 This is explained in more detail, and it shows, by way of example, schematically and without limitation, an advantageous embodiment of the invention. It shows Fig.1 a device for providing hydrogen in an exemplary embodiment of the invention.

[0020] The in Fig.1 The illustrated device 1 comprises an electrolysis unit 2 for generating hydrogen H₂ and a reciprocating compressor 3 for compressing the hydrogen H₂ generated by the electrolysis unit 2. Furthermore, a control unit 4 is provided for controlling the device 1. The control unit 4 comprises suitable hardware and / or software. Such control units 4 are known in the prior art, therefore no further description is given here. Fig.1 The control unit 4 is designed, by way of example, to control the electrolysis unit 2 and the piston compressor 3. However, this is only an example, and a separate electrolysis control unit 4a for the electrolysis unit 2 and a separate compressor control unit 4b for the piston compressor 3 could also be provided, as shown in Fig.1 As indicated, the control units 4a and 4b can communicate with each other in a suitable manner to exchange sensor signals and / or control signals, which will be described in more detail below. However, within the scope of the invention, it would also be sufficient if only one compressor control unit 4b were provided to control the piston compressor 3. This depends essentially on the choice of the operating parameter of the electrolysis unit 2, which will be set in more detail below.

[0021] In the illustrated example, an electrical energy source 13 is provided to supply energy to the electrolysis unit 2 and the reciprocating compressor 3. The energy source 13 here includes, by way of example, a renewable energy generation device 13a, which is connected to the electrolysis unit 2 and to a drive unit AE of the reciprocating compressor 3. In an advantageous embodiment, the energy generation device 13a includes, for example, a photovoltaic system, as shown in Fig.1 as indicated. Alternatively or additionally, the energy generation unit 13a could also include a (not shown) wind turbine or another suitable renewable energy generation unit 13a.

[0022] The design and function of a reciprocating compressor 3 are well known, which is why the reciprocating compressor 3 in Fig.1 This is only a schematic representation. In a known manner, a reciprocating compressor 3 has a number of cylinders Z, in each of which a piston K can be moved back and forth in an oscillating stroke H between a top dead center and a bottom dead center. Fig.1 The illustration shows a single cylinder Z as an example; of course, the reciprocating compressor 3 can also have multiple cylinders Z. In the illustrated example, the piston K is driven by a piston rod KS, which is connected to a crosshead KK.

[0023] The crosshead KK, in turn, is connected to a (schematically indicated) crank mechanism. The crank mechanism comprises a crankshaft KW and a connecting rod P for each piston K. The crankshaft KW is driven by a suitable drive unit AE, for example, an electric motor. The drive unit AE is supplied with electrical energy from the same energy source 13 as the electrolysis unit 2. Of course, the drive unit AE of the piston compressor 3 could also be supplied with drive energy from a separate energy source. The crosshead KK is connected to the crankshaft KW via the connecting rod P and is driven by it. The crosshead supports the lateral force generated by the connecting rod P against the housing of the reciprocating compressor 3, so that the piston rod KS performs an essentially pure oscillating motion, which is as free as possible from lateral forces.The piston compressor 3 could also be designed without a crosshead KK, in which case the drive of the piston K is directly via the connecting rod P.

[0024] A compression chamber KR is provided in cylinder Z, which is bounded on one side by the movable piston K and on the other by a wall of the piston compressor 3, for example, by a cylinder head ZK. At least one suction valve 5 and at least one pressure valve 8 are provided in the area of ​​the compression chamber KR for gas exchange. Contrary to the arrangement shown, several suction valves 5 and / or several pressure valves 8 could, of course, also be provided. A radial arrangement on cylinder Z would also be possible. During an expansion stroke of the piston K, the compression medium, here the hydrogen H₂ produced by the electrolysis unit 2, is drawn in through the open suction valve 5 and flows into the compression chamber KR. During a subsequent compression stroke of the piston K, the compression medium is compressed.When a defined pressure is reached, the pressure valve 8 opens and the compression medium can flow through it. The compressed compression medium can then be supplied, for example, to a suitable storage device (not shown) or to a consumer (not shown), such as a fuel cell.

[0025] The reciprocating compressor 3 has at least one automatic suction valve 5, which opens automatically during an expansion stroke of the piston K due to the pressure conditions and closes automatically during a compression stroke of the piston K. Thus, no external energy, such as an actuator, is required for valve actuation. Furthermore, a lifting gripper 6 is provided, which allows the suction valve 5 to be selectively held in an open position, independent of the prevailing pressure conditions. The suction valve 5 is preferably designed as a ring valve, wherein the ring valve preferably has several annular valve openings 5a and several annular valve elements 5b. The valve elements 5b seal the valve openings 5a when the ring valve 5 is closed. In this case, the lifting gripper 6 preferably has several lifting gripper fingers that can actuate the valve elements 5b through the valve openings 5a.Ring valves of this type are known in the prior art, therefore no more detailed description is given here.

[0026] Furthermore, an electrically controlled actuator 7 is provided for actuating the lifting gripper 6. The actuator 7 can be designed, for example, as a pneumatic, hydraulic, or electromagnetic actuator, with electromagnetic actuation being preferred due to its short switching times. The pressure valve 8 is located in Fig.1 The pressure valve 8 is only shown schematically and can, for example, be designed as a self-acting valve, analogous to the suction valve 5. In this case, the valve elements would open towards the side facing away from the compression chamber KR at a certain pressure ratio. Alternatively, another suitable valve could of course be provided as the pressure valve 8, for example a non-self-acting valve that can be actuated by a suitable actuator.

[0027] Contrary to the embodiment shown, the reciprocating compressor 3 can also be designed, for example, as a double-acting reciprocating compressor. In this case, a first compression chamber KR is provided in the cylinder Z on the side of the piston K facing away from the crankshaft (as in Fig.1 (as shown) and additionally, a second (not shown) compression chamber KR is provided on the side of the piston K facing the crankshaft. The second compression chamber KR naturally also includes at least one intake valve and one pressure valve for gas exchange.

[0028] The reciprocating compressor 3 could, of course, also be designed as a multi-stage compressor. In this case, several cylinders Z are provided in compression chambers KR with different compression ratios. The pressure valve of a first compression chamber would be connected to the suction valve of a subsequent second compression chamber. The compression medium, here hydrogen H₂, would then be compressed in several stages to a desired final pressure. Both double-acting reciprocating compressors and multi-stage compressors are known in the prior art. A combination of a double-acting reciprocating compressor and a multi-stage compressor would also be conceivable. In this case, it is advantageous if at least the first compressor stage connected to the outlet of the electrolysis unit 2 has an automatic suction valve 5 with a lifting gripper and actuator 7.

[0029] The control unit 4 (or the compressor control unit 4b) is configured to control the actuator 7 such that the hydrogen output pressure p1 at the outlet of the electrolysis unit 2 or the differential pressure Δp between an anode and a cathode of the electrolysis unit 2 can be set to a predetermined setpoint. If the electrolysis unit 2 has a PEM electrolyzer 2a with a proton exchange membrane between the anode and the cathode, then the differential pressure Δp is preferably a differential pressure Δp across the proton exchange membrane 11. During operation of the device 1, the reciprocating compressor 3 is preferably operated at a fixed constant speed. For this purpose, the control unit 4 (or the compressor control unit 4b) can control the drive unit AE of the reciprocating compressor 3 accordingly.

[0030] Preferably, a setpoint for the operating parameter is specified, for example, a setpoint pressure p1_setpoint for the hydrogen H₂ at the outlet of the electrolysis unit 2 or a setpoint pressure difference Δp_setpoint for the differential pressure Δp at the membrane 11. The control unit 4 can use the specified setpoint to control or regulate the actuator 7. This makes it possible, for example, to set a constant output pressure p1 of the hydrogen H₂ at the outlet of the electrolysis unit 2 or a constant pressure difference Δp at the membrane 11 by controlling the at least one suction valve 5 via the lifting gripper 6. This ensures that the output pressure p1 or the pressure difference Δp remains constant even with fluctuating energy input from the energy source 13, for example, the photovoltaic system 13a.Normally, a fluctuating energy supply would lead to pressure fluctuations of the output pressure p1, which, however, has a detrimental effect on the durability of the electrolysis unit 2, in particular a membrane 11, as mentioned at the beginning.

[0031] The setpoint can be, for example, a fixed numerical value, such as a target outlet pressure p1_setpoint in the range of 15 bar to 40 bar, or a predefined target differential pressure Δp_setpoint. At full load of electrolysis unit 2, the target outlet pressure p1_setpoint can be, for example, in the range of 30 bar. At partial load, the target outlet pressure p1_setpoint can be, for example, in the range of 25 bar. Furthermore, it can also be advantageous to maintain the outlet pressure p1 at a fixed value after electrolysis unit 2 has been deactivated. This can be beneficial for a rapid restart of electrolysis unit 2.

[0032] Control unit 4 can also contain a function for determining the setpoint as a function of at least one other parameter, e.g., as a function of time. This allows, for example, the output pressure p1 to be reduced in a controlled manner from an initial value to a second, lower value when electrolysis unit 2 is deactivated, using a time-based ramp function. This prevents an abrupt pressure drop at the output of electrolysis unit 2 after it is switched off, which could potentially have a detrimental effect on the long-term durability of electrolysis unit 2.

[0033] To implement a (feedback) control system, a determination unit is preferably provided for determining an actual value p1_actual of the output pressure p1 or an actual value Δp_actual of the differential pressure Δp. In this case, the control unit 4 is preferably configured to use the determined actual value to control the output pressure p1 or the differential pressure Δp to the specified setpoint.

[0034] The detection unit can include at least one sensor and / or a calculation model, the calculation model preferably being stored in the control unit 4. As described in Fig.1 As shown, for example, a pressure sensor 10a can be provided to detect the actual value p1_ist of the output pressure p1 of the electrolysis unit 2. The pressure sensor 10a could, for example, be located directly at the output of the electrolysis unit 2 and / or be part of the electrolysis unit 2. The pressure signal detected by the pressure sensor 10a could then be transmitted to the control unit 4 and processed by it to control the actuator 7.

[0035] If a separate electrolysis control unit 4a and a separate compressor control unit 4b are provided, then the sensor signal from the pressure sensor 10a could, for example, be transmitted to the electrolysis control unit 4a and from there to the compressor control unit 4b. Direct transmission of the sensor signal to the compressor control unit 4b would also be possible. This last option is particularly advantageous if an existing electrolysis unit 2 is retrofitted with a compressor 3 for pressure regulation, because in this case, access to the electrolysis control unit 4a may not be possible.

[0036] As in Fig.1 As shown, the output of the electrolysis unit 2 can be connected to the piston compressor 3 via a connecting line L, in particular to a suction line of the piston compressor 3. The generated hydrogen H₂ can then be supplied to the at least one automatic suction valve 5 of the piston compressor 3 via the connecting line L. The pressure sensor 10a can then, for example, be arranged in the connecting line L. If necessary, further devices 12, for example filters, can also be arranged between the output of the electrolysis unit 2 and the inlet of the piston compressor 3, as shown in Fig.1The pressure sensor 10a could, in this case, be arranged upstream of the filter 12 or downstream of it in the direction of flow. Generally, within the scope of the invention, the output pressure p1 is understood to be the pressure at any point in the connecting line L between the output of the electrolysis unit 2 and the inlet of the piston compressor 3.

[0037] Alternatively or additionally to the pressure sensor 10a, it can also be advantageous to use a differential pressure sensor 10b to detect the actual value Δp_actual of the differential pressure Δp across the diaphragm 11. This makes it possible not only to regulate the output pressure p1, but also, for example, to maintain a constant differential pressure Δp across the diaphragm 11. This is advantageous because the diaphragm 11 of the electrolyzer 2a is relatively sensitive to excessive pressure differences between the anode and cathode sides. Either a suitable sensor can be used as the differential pressure sensor 10b, or two pressure sensors can be used, from whose difference the differential pressure Δp of interest is determined, for example, by the control unit 4.

[0038] Alternatively or additionally to any sensors, the detection unit could also include a calculation model for determining an actual value. This calculation model could, for example, be stored in the control unit 4, e.g., in the form of a mathematical function, a characteristic curve, or a characteristic map. The calculation model could be known, for example, specified by the manufacturer of electrolysis unit 2. Alternatively, it could also be determined empirically, e.g., through experiments. Using the calculation model, the actual value p1_ist of the output pressure p1 or the actual value Δp_ist of the differential pressure Δp can be calculated from other available quantities. For example, it would be conceivable that the output pressure p1 of the hydrogen H₂ at the outlet of electrolysis unit 2 could be determined from an electrical measurement, e.g., from the current, voltage, or power of electrolysis unit 2.The electrical quantities can be measured relatively easily using suitable measuring devices.

[0039] The measuring device for recording the electrical quantity (current, voltage, power) could, for example, be integrated into electrolysis unit 2 as an integral component of electrolysis unit 2. In this case, the measured quantity could be transmitted to control unit 4 (e.g., electrolysis control unit 4a) and used by control unit 4 as an input variable in the calculation model. As an output variable, control unit 4 could, for example, determine the actual value p1_actual of the output pressure p1 at the outlet of electrolysis unit 2.

[0040] Alternatively, a separate (not shown) measuring device for recording the electrical quantity (current, voltage, power) could be provided, which is not part of the electrolysis unit 2. The separate measuring device could, for example, be arranged on a supply line through which the electrolysis unit 2 is supplied with electrical energy from the energy source 13. The quantity recorded by the separate measuring device could then be transmitted to the control unit 4 (in this case, for example, the compressor control unit 4b) and used by the control unit 4 as an input variable in the calculation model. The variant with the separate measuring device can also advantageously be used for retrofitting an existing electrolysis unit 2.

[0041] The control unit 4 can determine a suitable manipulated variable S1 for the actuator 7 from the determined actual value (for example, the actual value p1_actual of the output pressure p1 or the actual value Δp_actual of the differential pressure Δp) and the specified setpoint (for example, a constant setpoint p1_target of the output pressure p1 or a constant setpoint Δp_target of the differential pressure Δp) and control the actuator 7 with the determined manipulated variable S1. To determine the manipulated variable S1, a suitable controller, e.g., a P1 controller or PID controller, is preferably provided in the control unit 4. The type of manipulated variable S1 depends on the specific design of the actuator 7 and can, for example, be an electrical current or an electrical voltage. Depending on the control variable S1, the actuator 7 then adjusts the lifting gripper 6, preferably steplessly, to actuate the suction valve 5 in order to regulate the output pressure p1 or the differential pressure Δp.

[0042] In principle, a feedback control system is not necessary; a feedforward control system could also be used. For example, control unit 4 could contain a function for determining the manipulated variable S1 for actuator 7, based on a predefined setpoint (e.g., based on the setpoint p1_setpoint of the output pressure p1 or the setpoint Δp_setpoint of the differential pressure Δp). Control unit 4 can then use the function to determine the manipulated variable S1 for actuator 7 based on the setpoint and control actuator 7 with the determined manipulated variable S1. This function could, for example, be a mathematical function, a characteristic curve, or a characteristic map stored in control unit 4. The function can either be known or a suitable function can be determined, for example, through experimentation.

[0043] The electrolysis unit 2 can, for example, be supplied directly—that is, without any intervening electrical loads or storage devices—by a renewable energy generation unit 13a with a variable electrical energy supply. The control unit 4 can regulate the output pressure p1 or the differential pressure Δp to a predetermined, for example, constant, setpoint, as described. If the electrolysis unit 2 is deactivated or its electrical power supply is interrupted, the control unit 4 can also reduce the output pressure p1 to a fixed value, for example, according to a predetermined time function. This allows the output pressure p1 to be reduced in a controlled manner from a full-load pressure of approximately 30 bar to a defined lower pressure within a predetermined time when the electrolysis unit 2 is switched off.If the electrolysis unit 2 is only switched off temporarily, then the output pressure p1 could, for example, be kept at a relatively high value by appropriate control of the actuator 7, which is in the range of the output pressure p1 before the switch-off.

Claims

1. A device (1) for providing hydrogen (H2), wherein an electrolysis unit (2) for producing hydrogen (H2) is provided in the device (1), characterized in that a reciprocating piston compressor (3) for compressing the hydrogen (H2) produced by the electrolysis unit (2) is provided, that the reciprocating piston compressor (3) has at least one automatic intake valve (5), that a unloader (6) is provided to selectively hold the intake valve (5) in an open position, that an electrically actuable actuator (7) is provided for actuating the unloader (6) and that a control unit (4) is provided for controlling the actuator (7), the control unit (4) being designed to actuate the actuator (7) in such a way that an outlet pressure (p1) of the hydrogen (H2) at the outlet of the electrolysis unit (2) or a differential pressure (Δp) between an anode and a cathode of the electrolysis unit (2) can be adjusted to a predetermined target value (p1_target, Δp_target).

2. The device (1) according to claim 1, characterized in that the electrolysis unit (2) comprises a proton exchange membrane (11) between the anode and the cathode and that the differential pressure (Δp) is a differential pressure (Δp) at the proton exchange membrane (11).

3. The device (1) according to either claim 1 or claim 2, characterized in that the target value (p1_target, Δp_target) is a fixed numerical value or that a function for determining the target value (p1_target, Δp_target, Δp_target) on the basis of at least one further variable, preferably time, is stored in the control unit (4).

4. The device (1) according to any one of claims 1 to 3, characterized in that a determination unit for determining an actual value (p1_actual, Δp_actual) of the outlet pressure (p1) or the differential pressure (Δp) is provided and that the control unit (4) is designed to use the determined actual value (p1_actual, Δp_actual) to control the outlet pressure (p1) or the differential pressure (Δp) to the predetermined target value (p1_target, Δp_target).

5. The device (1) according to claim 4, characterized in that the determination unit has at least one sensor (10a, 10b) and / or that the determination unit has a calculation model, wherein the calculation model is preferably stored in the control unit (4).

6. The device (1) according to either claim 4 or claim 5, characterized in that the at least one sensor comprises a pressure sensor (10a) for recording an actual value (p1_actual) of the outlet pressure (p1) of the hydrogen (H2) at the outlet of the electrolysis unit (2), wherein the pressure sensor (10a) is preferably arranged in a connecting line (L) which connects the outlet of the electrolysis unit (2) to the piston compressor (3) and / or that the at least one sensor has a differential pressure sensor (10b) for recording an actual value (Δp_actual) of the differential pressure (Δp).

7. The device (1) according to any one of claims 4 to 6, characterized in that the control unit (4) is designed to determine a manipulated variable (S1) for the actuator (7) from the determined actual value (p1_actual, Δp_actual) and the predetermined target value (p1_target, Δp_target) and to actuate the actuator (7) using the determined manipulated variable (S1), wherein the control unit (4) preferably has a controller, for example a PI controller or PID controller, for determining the manipulated variable (S1).

8. The device (1) according to any one of claims 1 to 7, characterized in that a function for determining a manipulated variable (S1) on the basis of the predetermined target value (p1_target, Δp_target) is stored in the control unit (4) and that the control unit (4) is designed to determine a manipulated variable (S1) for the actuator (7) from the function and to actuate the actuator (7) using the determined manipulated variable (S1).

9. The device (1) according to any one of claims 1 to 8, characterized in that the electrical energy source (13) is provided for supplying energy to the electrolysis unit (2) and / or the reciprocating piston compressor (3).

10. The device (1) according to claim 9, characterized in that the energy source (13) comprises a regenerative energy generation apparatus (13a) which is connected to the electrolysis unit (2) and / or to the reciprocating piston compressor (3), wherein the energy generation apparatus (13a) preferably comprises a photovoltaic system or a wind turbine.

11. A method for operating a device (1) according to any one of claims 1 to 10, characterized in that hydrogen (H2) is produced by the electrolysis unit (2), that the hydrogen (H2) produced is fed to the reciprocating piston compressor (3) via the at least one intake valve (5) and is compressed by the reciprocating piston compressor (3), that a target value (p1_target, Δp_target) is predetermined for the outlet pressure (p1) or for the differential pressure (Δp) and that the control unit (4) actuates the actuator (7) in order to set the target value (p1_target, Δp_target).

12. The method according to claim 11, characterized in that a fixed numerical value is used as the target value (p1_target, Δp_target) or that the target value (p1_target, Δp_target) is determined from a function on the basis of at least one further variable, preferably time.

13. The method according to either claim 11 or claim 12, characterized in that, during operation of the device (1), an actual value (p1_actual, Δp_actual) of the outlet pressure (p1) or of the differential pressure (Δp) is determined and that the control unit (4) determines a manipulated variable (S1) for the actuator (7) from the actual value (p1_actual, Δp_actual) and the target value and actuates the actuator (7) using the determined manipulated variable (S1), wherein the manipulated variable (S1) is determined by a controller, preferably a PI controller or PID controller.

14. The method according to either claim 11 or claim 12, characterized in that a manipulated variable (S1) for the actuator (7) is determined from a function of the manipulated variable (S1) on the basis of the predetermined target value (p1_target, Δp_target) and that the control unit (4) controls the actuator (7) using the determined manipulated variable (S1).

15. The method according to any one of claims 11 to 14, characterized in that the electrolysis unit (2) is directly supplied with a temporally non-constant electrical energy by a regenerative energy generation apparatus (13a) and that the control unit (4) controls the outlet pressure (p1) or the differential pressure (Δp) to a predetermined target value (p1_target, Δp_target).

16. The method according to any one of claims 11 to 14, characterized in that the electrolysis unit (2) is deactivated or an electrical energy supply to the electrolysis unit (2) is interrupted and that the control unit (4) reduces the outlet pressure (p1) to a specified value in accordance with a predetermined time function.

17. The method according to any one of claims 11 to 16, characterized in that the reciprocating piston compressor (3) is operated at a fixed constant speed.