Method for operating a hydrogen production plant, and hydrogen production plant

Abstract

The invention relates to a method for operating a hydrogen production plant (10) having a plurality of electrolysis devices (11), which are designed to generate hydrogen from water with the aid of an electric current, wherein the electrolysis devices (11) preferably form a plurality of cascades (12) connected in parallel, each cascade consisting of electrolysis devices (11) connected in series, the electrolysis devices (11) are supplied with water via a water circuit (13) in order to produce hydrogen, and the electrolysis devices (11) are supplied with electric power from an electric power source or an electric voltage source in order to produce hydrogen. In order to check whether there is a hydrogen leak in an electrolysis device (11), the following steps of a safety routine are carried out: a defined electrical input variable is supplied to the electrolysis device (11) to be checked; an actual electrical output variable which is based on the defined electrical input variable is detected at the electrolysis device (11) to be checked; the actual output variable detected at the electrolysis device (11) to be checked is compared with a target output variable; and a hydrogen leak or the probability of a hydrogen leak at the electrolysis device (11) is inferred on the basis of the comparison of the actual output variable with the target output variable.

Description

[0001] 1 / 29 PB06260

[0002] Quest One GmbH

[0003] Methods for operating a hydrogen production plant and hydrogen production plant

[0004] The invention relates to a method for operating a hydrogen production plant and a hydrogen production plant.

[0005] DE 10 2017 108 413 A1 discloses an electrolysis device with a cell stack comprising several cell stack elements, wherein the cell stack elements of the cell stack form several electrolysis cells. Furthermore, the electrolysis device known from this prior art has a force application unit by which a force can be exerted on the cell stack to compress the cell stack elements of the cell stack in a fluid-tight manner. The force application unit has opposing end plates between which the cell stack is arranged and compressed. The force application unit also includes compression devices comprising spring elements and struts, wherein the spring force of the spring elements presses the end plates against each other, compressing the cell stack. Connections are provided on the end plates of the electrolysis device, namely water supply connections, water discharge connections, and hydrogen connections.Water is supplied to the electrolysis device via the water inlet connections, while water and oxygen are removed from the electrolysis device via the water outlet connections. The hydrogen connections are used to remove or pass through the hydrogen produced during electrolysis from the electrolysis device.

[0006] In a hydrogen production plant, several electrolysis devices are installed, wherein the electrolysis devices are expediently connected in series in the respective cascade, forming at least one cascade, preferably several parallel cascades.

[0007] 20.08.2025 2 / 29 PB06260

[0008] The electrolysis units of a hydrogen production plant are connected to a water circuit within the plant, which supplies the electrolysis units with hydrogen for hydrogen production. For hydrogen production, the electrolysis units, which are connected to an electrical current or voltage source within the hydrogen production plant, are supplied with electrical power by this source.

[0009] During the operation of a hydrogen production plant, a hydrogen leak can occur at an electrolysis unit, particularly at an electrolysis cell. This can lead to hydrogen escaping, either together with oxygen, into the water discharged from the electrolysis unit via the water drain connections, or alternatively into the environment, specifically into a process chamber housing the electrolysis unit. When hydrogen enters the water along with oxygen, this is known as an H₂-in-O₂ leak.

[0010] Hydrogen is an explosive gas. It becomes ignitable when mixed with oxygen. Therefore, for safety reasons, it is essential to monitor whether a hydrogen leak from an electrolysis unit or electrolysis cell could allow hydrogen to enter a process chamber of the hydrogen production plant or, along with the oxygen produced during hydrogen production, reach the water side of the plant. Hydrogen sensors can be used for this purpose, measuring the hydrogen concentration in the process chamber or in the area of ​​an oxygen separator, which separates the oxygen from the water in the hydrogen production plant's water circuit.

[0011] 20.08.2025 3 / 29 PB06260

[0012] If a hydrogen sensor detects an unacceptably high hydrogen concentration in the process room or in the area of ​​an oxygen separator, it can be concluded that there is a hydrogen leak in the hydrogen production plant.

[0013] However, it is not yet reliably possible to attribute a hydrogen leak to an electrolysis device of the hydrogen production plant or even to an electrolysis cell of an electrolysis device of the hydrogen production plant.

[0014] WO 2018 / 193 067 A1 discloses an electrolysis device with multiple electrolysis cells, wherein each electrolysis cell has at least one contact element that is distinct from a connection element for a power supply. The at least one contact element of the respective electrolysis cell serves to detect an individual cell parameter in order to identify a fault operating condition based on the individual cell parameter.

[0015] EP 3 336 947 B1 discloses a hydrogen compression device comprising a proton-conducting membrane, an anode, and a cathode. The hydrogen compression device includes a detector configured to detect hydrogen crossover through the proton-conducting membrane. This is achieved by detecting an electric current flowing between the anode and the cathode when an electrical voltage is applied to both and the flow paths of the hydrogen compression device are sealed at the anode and the cathode.

[0016] WO 03 / 096 459 A1 discloses a method for detecting a gas leak in a fuel cell.

[0017] 20.08.2025 4 / 29 PB06260

[0018] There is a need, particularly when a hydrogen leak is detected in a hydrogen production plant, to trace it back to an electrolysis unit, preferably an electrolysis cell within the electrolysis unit. However, it should also be possible to reliably verify, in other operating situations of a hydrogen production plant, whether a hydrogen leak exists in an electrolysis unit, especially in an electrolysis cell within the electrolysis unit.

[0019] The object of the invention is to provide a method for operating a hydrogen production plant that makes it possible to check whether a hydrogen leak exists in an electrolysis device of a hydrogen production plant. Furthermore, there is a need for a corresponding hydrogen production plant.

[0020] This problem is solved by a method for operating a hydrogen production plant according to claim 1 and a hydrogen production plant according to claim 18.

[0021] According to the invention, the following steps of a safety routine are performed to check whether a hydrogen leak is present in at least one electrolysis device: The electrolysis device to be checked is supplied with a defined electrical input. An actual electrical output variable, dependent on the defined electrical input variable, is measured at the electrolysis device. The actual output variable measured at the electrolysis device is compared with at least one target output variable. Depending on the comparison of the actual output variable with the at least one target output variable, a conclusion is drawn about a hydrogen leak or the probability of a hydrogen leak at the respective electrolysis device.

[0022] 20.08.2025 5 / 29 PB06260

[0023] The invention makes it possible to check whether a hydrogen leak or a probability of a hydrogen leak exists in an electrolysis device, and, if necessary, to locate the site of the hydrogen leak or the probability more precisely.

[0024] The method according to the invention can be applied to a hydrogen production plant with a plurality of electrolysis devices. However, it can also be applied to hydrogen production plants with only one electrolysis device. The method according to the invention can be used to identify a hydrogen leak and / or to locate a hydrogen leak. Localization can mean identifying a specific electrolysis device or even identifying a specific electrolysis cell within an electrolysis device. The term "safety routine" is to be understood broadly and can also include purposes of predictive maintenance and maintenance recommendations—for example, when or which electrolysis device should be replaced.

[0025] The defined electrical input can be interpreted as an excitation signal or pulse. The actual electrical output can be interpreted as a response signal or system response.

[0026] The electrical input and output variables can be point-like or quasi-point-like quantities. They can also be time-related. For example, a constant or variable voltage pulse can be used as the electrical input. The output variable can conveniently be the time course over a predefined time interval. Alternatively or additionally, the start and end of the output variable can be limited by exceeding and / or falling below defined threshold values. The target output variable can be, for example, an empirically determined expected value of an output variable.

[0027] Actual and / or target output variables can, in particular, be voltage gradients (rate of decrease of the applied voltage).

[0028] 20.08.2025 6 / 29 PB06260

[0029] Preferably, the safety routine is performed automatically, on a timer, and / or event-driven basis. In particular, the safety routine is performed on a timer after a defined operating time of the hydrogen production plant or the respective electrolysis device to be checked has been reached.Alternatively, or preferably additionally, the safety routine is then carried out in an event-driven manner when the hydrogen production plant or the respective electrolysis device to be checked is switched from a production operation to a shutdown operation or is in shutdown operation, and / or when the hydrogen production plant or the respective electrolysis device to be checked is switched from a production operation to a standby operation or is in standby operation, and / or when a hydrogen sensor either in the area of ​​an oxygen separator of the water circuit of the hydrogen production plant or in a process room accommodating the electrolysis devices of the hydrogen production plant detects a hydrogen concentration that is greater than a limit value, and / or when a pressure sensor in a hydrogen discharge line of the hydrogen production plant detects a pressure drop that is greater than a limit value.The time-controlled and / or event-controlled execution of the safety routine is particularly preferred in order to check whether a hydrogen leak is present at a respective electrolysis device of the hydrogen production plant.

[0030] The safety routine can be triggered automatically. However, it can also be triggered manually, for example, if maintenance personnel are on site and the hydrogen production plant is in maintenance mode.

[0031] Standby operation refers to a state of the hydrogen production plant in which at least the hydrogen lines of the hydrogen production plant are under operating pressure and water continues to circulate through the water circuit, but essentially no hydrogen is being produced. The water typically has a temperature close to the target operating temperature, preferably above 50°C. From standby operation

[0032] 20.08.2025 7 / 29 PB06260 The hydrogen production plant can be returned to production operation within a period of less than 5 minutes.

[0033] Shutdown operation refers to a state of the hydrogen production plant in which the hydrogen lines are depressurized, meaning they are no longer under operating pressure, and no water is circulating through the water circuit. Hydrogen is not produced in this state. The water typically reaches ambient temperature. Before hydrogen production can be resumed, a start-up routine must be performed, during which, among other things, the water is heated back to the target operating temperature before full hydrogen production capacity is available again.

[0034] Preferably, at least one target output variable for the respective electrolysis device under test depends on the age or operating hours of the device. This takes into account the fact that, for example, the expected target output variable shifts with increasing age. This prevents false detection of a hydrogen leak. Alternatively or additionally, the target output variable can be made dependent on pressure cycles, temperature cycles, or shutdown cycles (number of shutdowns).

[0035] Preferably, a defined electrical voltage signal is used as the defined electrical input variable applied to the electrolysis device under test, wherein the actual electrical output variable recorded at the electrolysis device under test is preferably a time-dependent measurement of an electrical voltage signal over a specific period of time, and wherein the target electrical output variable can be an empirically determined target output variable based on historical operating data or a variable dependent on the actual output variables of other electrolysis devices. This is particularly preferred for reliably verifying whether a hydrogen leak is present in an electrolysis device.

[0036] 20.08.2025 8 / 29 PB06260 or a probability of hydrogen leakage that is greater than a threshold.

[0037] The electrical voltage signal used as the defined electrical input is preferably a DC voltage signal. In particular, the electrical voltage signal can be identical to the operating voltage of the electrolysis device. The electrical input then corresponds to the operating voltage provided by a rectifier (or another DC voltage source). The operating voltage can, in particular, be the voltage of a DC intermediate circuit of the electrolysis device. The operating voltage of the electrolysis device is variable between a lower threshold corresponding to a minimum load and an upper limit corresponding to a maximum load (nominal load).

[0038] To carry out the procedure, the electrical voltage signal used as a defined electrical input quantity is expediently kept at the same voltage level for a defined period of time - for example, 30 minutes at 60% of the nominal load.

[0039] If the operating voltage of the electrolysis device, which is already present, is used as the voltage signal, additional means for feeding in the electrical voltage signal used as a defined electrical input quantity can be dispensed with.

[0040] The electrolysis devices can have permanently installed means for measuring the individual cell voltages (individual cell voltage measurement). Individual cell voltages allow, for example, conclusions to be drawn about the degradation state of a cell. Advantageously, these permanently installed means are also used to measure the actual electrical output variable according to the invention. This eliminates the need for additional measuring devices, such as a temporarily attached potentiostat.

[0041] 20.08.2025 9 / 29 PB06260

[0042] Preferably, an individual actual electrical output variable is recorded at each electrolysis cell of the respective electrolysis device under test. This actual output variable is then compared with at least one target output variable to determine whether or not hydrogen leakage has occurred at that specific electrolysis cell, or the probability of such leakage. The target electrical output variable for each electrolysis cell of the respective electrolysis device under test is preferably an expected value determined empirically or theoretically beforehand.

[0043] Alternatively or additionally, the actual output values ​​of the other electrolysis cells, or a value dependent on the actual output values ​​of the other electrolysis cells in this electrolysis device under test, can be used. In other words, it is possible either to make a relative comparison between the actual values ​​of the individual electrolysis cells of an electrolysis device and, if the actual value of one electrolysis cell deviates from the actual value of the other electrolysis cells, to infer a hydrogen leak or a leakage probability. Alternatively, the comparison of the actual value of an electrolysis cell can also be made with the previously determined, empirically or theoretically derived expected value as the target value in order to infer a hydrogen leak or a leakage probability. A combination of both approaches is possible.

[0044] The actual electrical output variable is preferably recorded over a time range of at least 30 seconds and up to 600 seconds.

[0045] This design allows for the determination of hydrogen leakage or the probability of such hydrogen leakage for individual electrolysis cells.

[0046] Preferably, the safety routine is executed for one of the cascades of the hydrogen production plant, while the other cascades are used for hydrogen production. This has the advantage that, while the safety routine is being executed, the hydrogen production plant can continue to be used for hydrogen production in those cascades where the safety routine is not performed.

[0047] 20.08.2025 10 / 29 PB06260

[0048] In a further advantageous embodiment of the invention, the method can also include repeating one or more steps of the safety routine, for example, by deliberately performing these steps under different environmental conditions. This allows testing to determine whether a similar (or differing) behavior of an electrolysis device or cell also occurs under varying environmental conditions. This can improve the predictive accuracy of a fault or fault probability. Examples of environmental conditions that can be varied include different pressures, different temperatures, or different flow rates on the water side, i.e., of process water in the process water circuit, or different pressures on the hydrogen side, i.e., in the hydrogen lines.For example, the steps of the safety routine can be performed once at a first temperature and a second time at a second temperature lower than the first. The results of the first run are then compared with the results of the second run of the safety routine to determine or further improve the assessment of leakage or leakage probability. Preferably, an increased leakage probability is inferred precisely when the results of both runs yield the same or at least qualitatively comparable results. If multiple runs under different environmental conditions lead to different results, this may indicate that causes other than leakage are responsible for the deviant behavior of an electrolysis device (or an electrolysis cell).

[0049] Preferred embodiments of the invention are set forth in the dependent claims and the following description. Exemplary embodiments of the invention are explained in more detail with reference to the drawing, without being limited thereto. The drawing shows:

[0050] 20.08.2025 11 / 29 PB06260

[0051] Fig. 1 is a schematic representation of a hydrogen production plant according to the invention with several electrolysis devices to illustrate the process according to the invention.

[0052] Fig. 2 shows actual output variables recorded at electrolysis cells of an electrolysis device.

[0053] Fig. 3 Target output variables dependent on the age or operating hours of the electrolysis device,

[0054] Fig. 4 is a diagram illustrating a further development of the method according to the invention.

[0055] Fig. 1 schematically shows a hydrogen production plant 10 with several electrolysis devices 11, which are set up to produce hydrogen H2 from water H2O using electric current. In the embodiment shown in Fig. 1, the electrolysis devices 11 are arranged in three parallel cascades 12, each consisting of two electrolysis devices 11 connected in series. The number of parallel cascades 12 and the number of electrolysis devices 11 per cascade 12 are purely illustrative.

[0056] The electrolysis devices 11 are supplied with water via a water circuit 13 of the hydrogen production plant 10 for hydrogen production. Furthermore, the electrolysis devices 11 are connected to an electrical current source or voltage source (not shown) of the hydrogen production plant 10 to supply the electrolysis devices 11 with electrical power for hydrogen production.

[0057] The basic structure of an electrolysis device 11 is known. An electrolysis device 11 has several cell stack elements arranged to form a cell stack, the cell stack being arranged and pressed between end plates. The end plates of the electrolysis devices 11 have at least one water supply connection.

[0058] 20.08.2025 12 / 29 PB06260 A water drain connection and at least one hydrogen connection are provided, wherein water H2O can be supplied to the respective electrolysis device 11 via the water supply connection, and wherein water H2O and oxygen O2 can be discharged from the respective electrolysis device 11 via the respective water drain connection. As already described, the water is supplied via the water circuit 13, wherein the water circuit 13 has a pump 14 for conveying the water and an oxygen separator 15 for separating the oxygen O2 from the water H2O. Hydrogen H2 produced during electrolysis by the respective electrolysis device 11 can be discharged via the at least one hydrogen connection, wherein the produced hydrogen H2 can be stored in a hydrogen tank 16 or discharged otherwise.

[0059] As previously explained, each electrolysis device 11 has a cell stack consisting of cell stack elements, which are bipolar plates and membranes, in particular polymer exchange membranes. The cell stack elements of a cell stack of an electrolysis device 11 form several electrolysis cells. If a membrane of an electrolysis cell of an electrolysis device 11 fails, hydrogen can escape from the cathode-side hydrogen side of the respective electrolysis cell to the anode-side water side of the respective electrolysis cell. This hydrogen, along with the oxygen (O2) produced during electrolysis, can then be carried away from the respective electrolysis device 11 via the discharged water (H2O) and enter the oxygen separator 15. A mixture of hydrogen (H2) and oxygen (O2), which is explosive, can then accumulate in the oxygen separator 15.

[0060] Furthermore, as a result of a hydrogen leak at an electrolysis device 11, for example due to defective seals in the electrolysis device 11, the produced hydrogen H2 can enter a process chamber in which the electrolysis devices 11, in particular the entire hydrogen production plant 10, are located.

[0061] 20.08.2025 13 / 29 PB06260 is arranged, whereby an explosive mixture of hydrogen H2 and oxygen O2 can then form in the process room.

[0062] To check whether there is a hydrogen leak at an electrolysis device 11 of a hydrogen production plant 10, the following steps of a safety routine are carried out for the respective electrolysis device 11 to be checked:

[0063] The respective electrolysis device 11 to be tested is supplied with a defined electrical input quantity (excitation quantity).

[0064] The defined electrical input variable is preferably a defined electrical voltage signal applied to the electrolysis device 11 under test, specifically to its electrical current connections, via which the electrolysis device 11 under test is connected to an electrical voltage source or electrical current source of the hydrogen production plant 10. This electrical voltage signal can be a constant voltage with a defined voltage level, applied to the electrolysis device 11 under test for a defined period of time. However, the defined electrical voltage signal applied as an electrical input variable to the electrolysis device 11 under test can also change over time according to a predetermined pattern.The magnitude of the voltage signal applied as an electrical input to the electrolysis device 11 to be tested can correspond to the magnitude of an operating voltage or only to a defined percentage of the operating voltage.

[0065] The electrolysis device 11 to be tested is subjected to the defined electrical input quantity over a defined time interval of several minutes, in particular over a time interval of 5 to 60 minutes or 5 to 50 minutes or 5 to 40 minutes or 5 to 30 minutes or 5 to 20 minutes 20.08.2025 14 / 29 PB06260 or 5 to 10 minutes or 10 to 60 minutes or 10 to 50 minutes or 10 to 40 minutes or 10 to 30 minutes or 10 to 20 minutes or 20 to 60 minutes or 20 to 50 minutes or 20 to 40 minutes or 20 to 30 minutes or 30 to

[0066] 60 minutes or 30 to 50 minutes or 30 to 40 minutes or 40 to 60 minutes or 40 to 50 minutes or 50 to 60 minutes.

[0067] During the application of the defined electrical input quantity to the electrolysis device 11 under test and / or immediately after the defined electrical input quantity has been applied to the electrolysis device 11 under test and subsequently switched off, an actual electrical output quantity, dependent on the defined electrical input quantity, is recorded at the electrolysis device 11 under test.

[0068] This actual electrical output variable of the electrolysis device 11 under test can be acquired either as a whole or individually at the electrolysis cells of the respective electrolysis device 11 under test. Fig. 1 shows that actual output variables acquired at the electrolysis devices 11 are fed via a signal line 17 to a control unit 18, which further processes the actual output variables.

[0069] The actual output value is preferably recorded over a time range of at least 30 seconds and up to 600 seconds.

[0070] Preferably, the electrical voltage signal passively generated at each electrolysis cell of the electrolysis device 11 to be tested is recorded as the actual electrical output variable for the respective electrolysis device 11 to be tested, which forms in response to the application of the defined electrical input variable to the electrolysis device 11.

[0071] 20.08.2025 15 / 29 PB06260

[0072] The actual output variable or variables recorded at the respective electrolysis device 11 to be checked are compared with a respective target output variable, whereby this comparison of the respective actual output variable and the stored target output variable takes place in the control unit 18.

[0073] As already explained, a corresponding target output variable can be compared with a corresponding actual output variable for the electrolysis device 11 as a whole or for each of the electrolysis cells of the respective electrolysis device 11.

[0074] Depending on the comparison of the respective actual output variable with the respective target output variable, a conclusion is drawn about a hydrogen leakage or the probability of a hydrogen leakage at the respective electrolysis device 11.

[0075] The safety routine by which a hydrogen leakage or the probability of a hydrogen leakage at a respective electrolysis device 11 is carried out preferably automatically, namely in a time-controlled and / or event-controlled manner, via the control unit 18.

[0076] If the safety routine is performed on a timer, it is carried out after the hydrogen production plant 10 has reached a defined operating time or age, in particular after the respective electrolysis device 11 of the hydrogen production plant 10 has reached a defined operating time or age. This makes it possible to subject an electrolysis device 11 to a safety routine whenever it has reached a defined number of operating hours of hydrogen production.

[0077] 20.08.2025 16 / 29 PB06260

[0078] If the safety routine is event-driven, it can be executed in this manner, in particular, when the hydrogen production plant 10 or the respective electrolysis device 11 to be checked is switched from hydrogen production operation to shutdown mode and / or when the hydrogen production plant 10 or the respective electrolysis device 11 is in shutdown mode. Alternatively or additionally, the safety routine is executed in an event-driven manner when the hydrogen production plant 10 or the respective electrolysis device 11 to be checked is switched from hydrogen production operation to standby mode and / or when the hydrogen production plant 10 or the respective electrolysis device 11 is in standby mode. Other events are possible.

[0079] Preferably, the safety routine at each electrolysis device 11 is executed in an event-driven manner when an impermissibly high hydrogen concentration is detected by a hydrogen sensor, for example, in a process chamber housing the electrolysis devices 11 or in the area of ​​the oxygen separator 15. Figure 1 shows a hydrogen sensor 19 installed in the area of ​​the oxygen separator 15, which detects the hydrogen concentration there. If the detected hydrogen concentration exceeds a limit value, the control unit 18 can automatically trigger the execution of the safety routine.

[0080] Another event that triggers the automatic execution of the safety routine is the signal from a pressure sensor 20, which is located in a hydrogen discharge line 21 leading to the hydrogen tank 16 and measures the pressure in the hydrogen discharge line 21. If the control unit 18 determines, based on the measurement signal provided by the pressure sensor 20, that the pressure drop in the hydrogen discharge line 21 is greater than a limit value, the control unit 18 can again automatically trigger the execution of the safety routine.

[0081] 20.08.2025 17 / 29 PB06260

[0082] As already explained above, to carry out the safety routine on a respective electrolysis device 11, a defined electrical input quantity, namely a defined electrical input voltage, is applied to it, wherein preferably for each electrolysis cell of the electrolysis device 11 a developing time course of an electrical voltage signal is measured as the actual output quantity.

[0083] The defined electrical input voltage is applied to the respective electrolysis device 11 via the electrical current source or electrical voltage source, which is connected to connection elements of the electrolysis device 11 for its electrical energy supply and from which the electrolysis device 11 is supplied with electrical power during hydrogen production operation.

[0084] The measurement of the actual output variable, namely the developing time course of the electrical voltage signal at preferably each of the electrolysis cells of the electrolysis device 11, is carried out via contact elements of the respective electrolysis cell, which are different from a connection element for the power supply (individual cell voltage measurement).

[0085] Fig. 2 shows the time course of actual output variables 22a, 22b, 22c and 22d measured at electrolysis cells of an electrolysis device 11, wherein these actual output variables are each the time course of an electrical voltage V measured at the respective electrolysis cell of the electrolysis device 11.

[0086] The actual output variables 22a, 22b, 22c and 22d of Fig. 2 are formed in response to a constant electrical voltage applied to the electrolysis device 11 as an input variable, which is present at the respective electrolysis device 11 until time t1 and is switched off at time t1.

[0087] 20.08.2025 18 / 29 PB06260

[0088] In Fig. 2, it is shown that for the electrolysis device 11 under test, the actual output variable 22c of one electrolysis cell of the electrolysis device 11 under test deviates by more than a limit value from the actual output variables 22a, 22b and 22d of the other electrolysis cells of the electrolysis device 11 under test.

[0089] Accordingly, in Fig. 2, each of the actual output variables 22a, 22b, 22c, and 22d of a respective electrolysis cell of the electrolysis device 11 under test is compared with the actual output variables 22a, 22b, 22c, and 22d of the other electrolysis cells of the electrolysis device 11 under test. Thus, in Fig. 2, the actual output variables of the other electrolysis cells of the electrolysis device 11 under test are used as the target output variable for one electrolysis cell, or alternatively, an average of the actual output variables. In contrast, it is also possible to use a target output variable based on historical operating data, i.e., one determined empirically.

[0090] Preferably, the respective target output variable with which an actual output variable is compared is dependent on the age or the operating hours of the respective electrolysis device 11 or of the electrolysis cells thereof, if the target output variable has been empirically determined and is stored in the control unit 18.

[0091] Figure 3 shows several different target output variables 23a, 23b, 23c, and 23d, which depend on the age of the respective electrolysis device 11 or its electrolysis cells. Corresponding target output variables 23a, 23b, 23c, and 23d can be stored in the control unit 18.

[0092] 20.08.2025 19 / 29 PB06260

[0093] The individual electrolysis units 11 installed in the hydrogen production plant 10 may have different operating hours or different ages, particularly if, for example, one or more electrolysis units 11 have already been replaced due to a defect. In this case, the individual electrolysis units 11, and thus their electrolysis cells, have different ages and therefore different operating hours. The control unit 18 then stores target output variables 23a, 23b, 23c, and 23d that depend on the age or operating hours.

[0094] When the control unit 18 detects a hydrogen leak or a probability of a hydrogen leak exceeding a threshold value, it can automatically generate a signal that triggers maintenance or a replacement of the respective electrolysis unit 11. This signal can be stored in the control unit 18 and kept ready for retrieval. Alternatively or additionally, a shutdown event can be triggered, shutting down at least the affected electrolysis unit, or a cascade comprising this electrolysis unit, or a sub-branch comprising this electrolysis unit. This makes it possible to prevent a fault and (only) take the leakage-prone electrolysis unit out of service as a precaution, without shutting down the entire hydrogen production plant.In other words, continued partial operation is possible. This eliminates or at least reduces the risk of an emergency shutdown due to a malfunction.

[0095] That is, if the control unit 18 concludes that there is a hydrogen leak or a probability of a hydrogen leak that exceeds a limit value, the control unit 18 can also automatically shut down or shut down the hydrogen production plant 10, at least partially.

[0096] 20.08.2025 20 / 29 PB06260

[0097] Alternatively or additionally, the control unit 18 can transmit a corresponding signal, for example via the internet, to a higher-level control unit. The recorded actual electrical output variables from the electrolysis device 11, together with their respective electrical input variables, can also be transmitted to a higher-level control unit to create a database and thus provide target output variables for the electrolysis devices 11 based on that database.

[0098] As already explained, the respective safety routine at each electrolysis device 11 is preferably executed in a time-controlled and / or event-controlled manner. When the electrolysis devices 11 are arranged in several cascades 12, as shown in Fig. 1, the safety routine is preferably executed for one of the cascades 12 of the hydrogen production plant 10, while the other cascades 12 of the hydrogen production plant 10 are used for hydrogen production. This is advantageous in order to use the hydrogen production plant 10 continuously for hydrogen production and thus avoid restricting its availability through a safety routine.

[0099] Figure 4 illustrates different operating scenarios for the hydrogen production plant 10 of Figure 1 over time t. During time interval At1, all cascades 12 of the hydrogen production plant 10 are used for hydrogen production. At time t2, i.e., at the end of time interval At1, the control unit 18 automatically triggers a hydrogen leakage test for the hydrogen production plant 10, for example, event-driven, by the control unit 18 determining, for example, at time t2, that the hydrogen concentration measured by the hydrogen sensor 19 is greater than a limit value. Then, during time interval At2, as shown in Figure 4, a safety routine is executed at the electrolysis devices 11 of one of the cascades, for example, the upper cascade shown in Figure 1, while the other cascades, i.e., the middle cascade 12 and the lower cascade 12 in Figure 1, continue to be used for hydrogen production.If it is found that at one of the electrolysis devices 11 of the cascade 12 checked during the time period At2 ei-.

[0100] 20.08.2025 21 / 29 PB06260 If a hydrogen leak is detected or the probability of a hydrogen leak exceeds a threshold, cascade 12 can be shut down or taken out of service for hydrogen production. However, if it is determined that no hydrogen leak is detected at any of the electrolysis devices 11 of the inspected cascade 12, or that the probabilities are less than a threshold, the respective cascade 12 can be restarted for hydrogen production after the time interval At2.

[0101] Following the time interval At2, the safety routines for the electrolysis devices 11 of another cascade are carried out during the time interval At3, for example in Fig. 1 for the middle cascade 12, while the lower cascade 11 continues to be operated, i.e., continues to be used for hydrogen production, and depending on whether a hydrogen leak was detected at an electrolysis device 11 of the upper cascade 12 or not, the upper cascade 12 is either put back into operation for hydrogen production or remains shut down.Similarly, during the time interval At4, the lower cascade 12 of electrolysis devices 11 can be subjected to the safety routine, whereby during the time interval At5, i.e., after completion of the execution of the safety routines in all cascades 12, depending on the result of the safety routines, either all electrolysis devices 11 of all cascades 12 are used for hydrogen production or only a subset of the cascades 12.

[0102] Depending on the result of the safety routine, the hydrogen production plant 10 can therefore be shut down completely or only partially. Furthermore, it is possible to initiate the replacement or maintenance of individual electrolysis devices 11, and in particular preventively, before a fault occurs.

[0103] Furthermore, in the event of a fault – in particular an H2-in-O2 fault – it is possible to identify the cascade with at least one faulty electrolysis device 11 by temporarily partially shutting down individual cascades, and then to perform the safety routine only in the cascade with the faulty electrolysis device 11. The cascade with the faulty electrolysis device 11 can be identified in particular by the fact that the hydrogen concentration in the O2 separator 15, which is measured via the H2 sensor 19, is higher when the cascade with the faulty electrolysis device 11 is operating, and the measured hydrogen concentration is lower when the cascade with the faulty electrolysis device 11 is temporarily taken out of service.Only after identifying the faulty cascade can the aforementioned safety routine then be performed for all electrolysis devices 11 in the faulty cascade to identify the faulty electrolysis device 11. The safety routine therefore does not need to be performed for all electrolysis devices 11 in all cascades. This results in significant time savings in identifying the faulty electrolysis device, particularly in large systems with several dozen, a shock (5 dozen), a large (12 dozen), or more electrolysis devices 11.

[0104] The invention further relates to the hydrogen production plant 10 with the multiple electrolysis devices 11 and the control unit 18, which is configured to automatically execute the method according to the invention. For this purpose, the control unit 18 has data interfaces for exchanging data with the components involved in carrying out the method according to the invention, for example, with the electrolysis cells of the electrolysis devices 11, where the actual output variables are recorded, and with the hydrogen sensor 19. Furthermore, the control unit 18 has a processor for data processing and a memory for data storage. In addition, program modules are implemented in the control unit 18 that serve to carry out the method according to the invention.

[0105] 20.08.2025 23 / 29 PB06260

[0106] Reference symbol list

[0107] 10 hydrogen production plants

[0108] 11 Electrolysis device

[0109] 12 Cascade

[0110] 13 Water cycle

[0111] 14 Pump

[0112] 15 Water treatment plant

[0113] 16 hydrogen storage

[0114] 17 Signal line

[0115] 18 Control unit

[0116] 19 Hydrogen sensor

[0117] 20 pressure sensor

[0118] 21 Hydrogen discharge line

[0119] 22a Actual output value

[0120] 22b Actual output value

[0121] 22c Actual output value

[0122] 22d Actual output value

[0123] 23a Target output variable

[0124] 23b Target output value

[0125] 23c Target output value

[0126] 23d Target output value

[0127] August 20, 2025

Claims

24 / 29 PB06260 Claims 1. A method for operating a hydrogen production plant (10) with several electrolysis devices (11) configured to produce hydrogen from water using electric current, wherein the electrolysis devices (11) preferably form at least one cascade (12) of electrolysis devices (11) connected in series, preferably several cascades (12) connected in parallel, each consisting of electrolysis devices (11) connected in series, wherein the electrolysis devices (11) are supplied with water via a water circuit (13) of the hydrogen production plant (10) for hydrogen production, wherein the electrolysis devices (11) are supplied with electrical power from an electric current source or electric voltage source for hydrogen production, characterized in that, in order to check whether a hydrogen leakage is present at at least one electrolysis device (11),The following steps of a safety routine are performed: the respective electrolysis device (11) to be checked is supplied with a defined electrical input quantity; an actual electrical output quantity, dependent on the defined electrical input quantity, is recorded at the respective electrolysis device (11); the actual output quantity recorded at the respective electrolysis device (11) to be checked is compared with at least one respective target output quantity; depending on the comparison of the actual output quantity with the at least one target output quantity, a conclusion is drawn about a hydrogen leakage or the probability of a hydrogen leakage at the respective electrolysis device (11). August 20, 2025 25 / 29 PB06260 2. Method according to claim 1, characterized in that the safety routine is carried out automatically, in a time-controlled manner and / or in an event-controlled manner.

3. Method according to claim 2, characterized in that the safety routine is carried out in a time-controlled manner after reaching a defined operating time of the hydrogen production plant (10) or the respective electrolysis device (11) to be checked.

4. Method according to claim 2 or 3, characterized in that the safety routine is then carried out in an event-controlled manner when the hydrogen production plant (10) or the respective electrolysis device (11) to be checked is switched from a production operation to a shutdown operation or is in a shutdown operation.

5. Method according to one of claims 2 to 4, characterized in that the safety routine is then carried out in an event-controlled manner when the hydrogen production plant (10) or the respective electrolysis device (11) to be checked is switched from a production operation to a stand-by operation or is in stand-by operation.

6. Method according to one of claims 2 to 5, characterized in that the safety routine is then carried out in an event-controlled manner when a hydrogen sensor (19) in the area of ​​an oxygen separator (15) of the water circuit (13) of the hydrogen production plant (10) and / or in a process room accommodating the electrolysis devices (11) detects a hydrogen concentration that is greater than a limit value. August 20, 2025 26 / 29 PB06260 7. Method according to one of claims 2 to 6, characterized in that the safety routine is then carried out in an event-controlled manner when a pressure sensor (20) in a hydrogen discharge line (21) of the hydrogen production plant (10) detects a pressure drop that is greater than a limit value.

8. Method according to one of claims 1 to 7, characterized in that the at least one target output variable for the respective electrolysis device (11) to be checked depends on the age or operating hours of the electrolysis device (11) to be checked.

9. Method according to one of claims 1 to 8, characterized in that the safety routine is carried out for one of the cascades (12) of the hydrogen production plant (10), while the other cascades (12) of the hydrogen production plant (10) are used for hydrogen production.

10. Method according to one of claims 1 to 9, characterized in that when a hydrogen leak or the probability of a hydrogen leak at the respective electrolysis device (11) is inferred to be greater than a limit value, a signal is generated which triggers a shutdown event, maintenance and / or replacement of the respective electrolysis device (11).

11. Method according to one of claims 1 to 10, characterized in that a defined electrical voltage signal is used as the defined electrical input quantity with which the respective electrolysis device (11) to be tested is supplied. August 20, 2025 27 / 29 PB06260 12. Method according to one of claims 1 to 11, characterized in that the electrical actual output variable, which is detected at the respective electrolysis device (11) to be checked, is a time course of an electrical voltage signal.

13. Method according to one of claims 1 to 12, characterized in that the electrical target output variable of the respective electrolysis device (11) to be tested is an empirically determined target output variable based on historical operating data.

14. Method according to one of claims 1 to 12, characterized in that the electrical target output variable of the respective electrolysis device (11) to be checked is a target output variable which depends on the actual output variables of the other electrolysis devices (11).

15. Method according to one of claims 1 to 14, characterized in that an individual electrical actual output variable is recorded at preferably each electrolysis cell of the respective electrolysis device (11) to be checked, which is compared with a target output variable in order to conclude, depending on the comparison of the respective actual output variable with the respective target output variable, that there is a hydrogen leakage or the probability of a hydrogen leakage at the respective electrolysis cell of the respective electrolysis device (11) of the hydrogen production plant (10). August 20, 2025 28 / 29 PB06260 16. Method according to claim 15, characterized in that the actual output variables of the other electrolysis cells or a variable dependent on the actual output variables of the other electrolysis cell of this electrolysis device (11) to be tested are used as the electrical target output variable of an electrolysis cell of the respective electrolysis device (11).

17. Method according to one of claims 1 to 16, characterized in that the respective actual electrical output variable is detected during the application of the defined electrical input variable to the electrolysis device (11) to be tested and / or immediately after the application of the defined electrical input variable to the electrolysis device (11) to be tested and the subsequent switching off of the same.

18. Hydrogen production plant (10) with several electrolysis devices (11) which are set up to produce hydrogen from water using electric current, wherein the electrolysis devices (11) preferably form at least one cascade (12) of electrolysis devices (11) connected in series, preferably several cascades connected in parallel of electrolysis devices (11) connected in series, and with a control unit which is set up to carry out the method according to one of claims 1 to 17. August 20, 2025

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