Electrolyzer system and operating method

Abstract

The invention relates to an electrolyzer system (1), comprising at least two electrolysis units (10) which are connected in series, wherein each electrolysis unit has one pole (10a) and one other pole (10b), insulating elements (12), grounded end plates (12a), and a supply unit (14) which is connected to a first and a last electrolysis unit (10) of the at least two electrolysis units (10) connected in series and is configured to supply the at least two electrolysis units (10) with electrical power, one of the poles (16, 18) of the supply unit being grounded via a grounding switch (20). The electrolyzer system (1) is characterized in that the electrolyzer system (1) has a protective device (22), said protective device (22) being configured to measure a fault current between a grounded end plate (12a) and the grounded pole (16, 18) and, if the fault current exceeds a limit value, to open the grounding switch (20).

Description

[0001] ELECTROLYSIS SYSTEM AND OPERATING PROCEDURES

[0002] Description

[0003] The invention relates to an electrolyzer system and an operating method for such a system.

[0004] Electrolyzers are high-tech devices that play a crucial role in the energy transition. Using electricity, they split water into its components, producing hydrogen in the process. This climate-neutral hydrogen is intended to play a central role in the future economic system. It serves as an energy carrier in new gas-fired power plants when solar and wind power are unavailable. Furthermore, hydrogen can replace carbon in industry, thus avoiding large quantities of climate-damaging carbon dioxide. It is produced in specialized machines called electrolyzers. This technology is of great importance for the energy transition and is being further developed to meet the increasing demand for green hydrogen.

[0005] Hydrogen can be produced economically if larger plants are built decentrally. This decentralized approach has several advantages:

[0006] Economies of scale: Larger plants benefit from economies of scale because they can operate more efficiently. When several such plants are distributed across the country, hydrogen production becomes more cost-effective overall.

[0007] Grid stability: Decentralized power plants can help improve grid stability. They can utilize surplus electricity from renewable sources when demand is low and convert it into hydrogen. This relieves pressure on the electricity grid and prevents overloads.

[0008] Regional value creation: Decentralized plants create jobs and boost the regional economy. They can also help revitalize rural areas by establishing new industries.

[0009] Flexibility: Decentralized systems are more flexible and can be adapted to different locations. They can be placed near renewable energy sources or industrial consumers.

[0010] Problem statement: When scaling up electrolyzer systems, multiple electrolysis stacks are often designed in series. Each electrolysis stack is individually equipped with insulating elements. Over time, metal ions diffuse from the grounded end plates of the electrolysis stacks through these insulating elements into the electrodes, causing the insulating properties of the insulators to deteriorate over time.

[0011] Furthermore, it is common practice to ground one pole of the supply to the electrolysis stacks in order to have a defined potential in order to avoid corrosion.

[0012] This leads to the problem that a short circuit can occur between the grounding of one of the supply poles and a reduced-resistance insulator, potentially damaging the stacks and posing a danger to people in the vicinity. EP 4401 283 A1, a subsequently published prior art document, describes an electrolyzer system in which fuses are located between the electrolysis stacks and at the grounding point. These fuses are triggered when a ground fault occurs. However, this may be too late, resulting in damaged components and high replacement costs.

[0013] In DE 10 2020 121 593 A1, a fault current is measured between a solar generator and an earth connection in the middle of the electrolysis stacks. In the event of a high fault current, the connection between the solar generator and the electrolyzer is interrupted, thus breaking the circuit to earth.

[0014] This problem is solved by the electrolyzer system of the main claim and the operating method of the dependent claim. Further developments according to the invention are the subject of the dependent claims.

[0015] The main claim describes an electrolyzer system comprising at least two electrolysis units connected in series, each electrolysis unit having a first and a second pole, insulating elements, and grounded end plates. The electrolyzer system further describes a power supply unit connected to a first and a last electrolysis unit of the at least two electrolysis units connected in series and configured to supply electrical power to the at least two electrolysis units, one of the poles of the power supply unit being grounded via a grounding switch.

[0016] The electrolyzer system is characterized by a power supply unit with a protective device configured to measure a fault current between a grounded end plate and the grounded pole and, if the fault current exceeds a threshold, to open the grounding switch. The electrolyzer system comprises at least two electrolysis units, also called electrolysis stacks. These are connected in series. This allows the system to operate at a higher DC voltage, thus reducing costs. For system safety, each electrolysis unit, or rather the poles of each electrolysis unit, are individually equipped with insulating elements installed between the electrodes and the end plates. In electrolysis stacks, the end plates primarily serve to exert pressure on the stack, ensuring that the stacks remain sealed and the pressure within the stacks is maintained.

[0017] To supply the electrolysis units, the electrolyzer system also includes a power supply unit. This unit can be, for example, a rectifier that draws AC power from a power grid. Another option is a DC / DC converter that converts electrical power, such as that provided by a renewable energy source, into electrical power usable by the electrolysis units in terms of voltage and current.

[0018] For this purpose, the supply unit is connected to one pole of the first electrolysis unit and the other pole of the last electrolysis unit in the series.

[0019] Furthermore, one of the poles of the supply unit is grounded via an earthing switch, so that a defined earth potential is present at this pole.

[0020] The electrolyzer system is characterized by the inclusion of a protective device. This protective device is configured to measure a fault current. This fault current is measured between a grounded termination plate and the grounded terminal of the power supply unit. More precisely, the protective device is configured to measure a fault current between each of the grounded termination plates in the electrolyzer system and the grounded terminal of the power supply unit. Furthermore, the protective device is configured to open the grounding switch when a fault current exceeds a threshold value. Opening the grounding switch effectively prevents a short circuit between the grounded terminal and a grounded termination plate, which, in the event of a short circuit, would damage electrolysis units and, in extreme cases, could even create an ignition source.In particular, a short circuit is prevented because the fault current increases gradually before a short circuit occurs. Therefore, if the earthing switch is opened even at a fault current that does not yet damage the system, a short circuit is effectively prevented, thus avoiding catastrophic damage to the electrolyzer system. According to one embodiment, the electrolyzer system is configured to open the earthing switch only if the fault current exceeds the threshold for a predetermined period, exceeds the threshold a predetermined number of times within a predetermined period, or if an integrated value of the fault current exceeds a threshold over a predetermined period.

[0021] An effect can occur where a fault current exceeding the threshold value is present only briefly. In this case, the protective device would trip, disconnecting the ground. This embodiment addresses this issue. By incorporating a temporal component, such as the presence of the fault current for a predetermined period, exceeding the fault current threshold a predetermined number of times within a period, or an integrated fault current value (the integral of the measured fault current over a predetermined time interval or duration), it is possible to prevent a short-term effect from triggering the protective device and consequently disconnecting the ground from one pole of the electrolyzer system's power supply unit.

[0022] According to one embodiment, the electrolyzer system is configured to perform an insulation resistance measurement when the earthing switch has been opened, with the earthing switch being closed again when the insulation resistance measured during the insulation resistance measurement exceeds an insulation resistance threshold.

[0023] It is possible for a fault current to occur that results from causes other than the degradation of insulation elements. In such cases, it may be economically viable and safe to continue operating the electrolysis system. To differentiate between an insulation fault and other faults, this embodiment automatically performs an insulation resistance measurement when the earthing switch has been opened due to an impermissible fault current. If the insulation resistance measurement reveals an excessively low insulation resistance, the earthing switch remains open, and safety measures from other embodiments of the present invention are implemented.

[0024] According to one embodiment of the electrolyzer system, the protective device is further configured to terminate the supply to the electrolysis units from the power supply unit after the earthing switch opens, optionally after a predetermined time has elapsed, if the fault current exceeds a threshold value. In this embodiment, it is advantageously described that the supply to the electrolysis units from the power supply unit is terminated when the fault current exceeds a threshold value. This is done to prevent other damage to equipment or personal injury caused by deteriorating insulation of an electrolysis unit.

[0025] According to one embodiment of the electrolyzer system, the protective device is further configured to perform an insulation resistance measurement to earth at regular intervals or as instructed, and to temporarily open the earthing switch for the insulation resistance measurement.

[0026] Insulation resistance measurements measure the insulation resistance of the electrolyzer system to ground potential. This measurement is useful for preventing potential ground currents that could harm people nearby and for detecting damage to the electrolyzer system early. To perform the insulation resistance measurement, it is necessary to open a grounding switch on the power supply unit; otherwise, the measurement will yield an inaccurate result. The insulation resistance measurement can be performed either regularly, for example, every morning, or on demand, as described in the preceding embodiment.

[0027] According to one embodiment of the electrolyzer system, the threshold value is 100 mA.

[0028] This embodiment specifies the fault current threshold at which the earthing switch opens and potentially triggers further actions. Here, the threshold is set at 100 mA, as little to no damage or hazards are expected at this fault current, and the chance of a short circuit is low. However, other threshold values ​​are also conceivable. Higher values ​​such as 150 mA, 200 mA, or 1 A, as well as all intermediate values, are possible. It is also conceivable to define a range, such as 100 mA to 150 mA, and for the protective device to activate if the fault current remains within this range for a defined period.

[0029] According to one embodiment of the electrolyzer system, the threshold value is 30 mA.

[0030] In this embodiment, the threshold value of the fault current, above which the earthing switch opens and further steps may be initiated, is specified. Here, the threshold is set at 30 mA, as little to no damage or hazards occur at this fault current, and the chance of a short circuit is low. However, other threshold values ​​are also conceivable. Higher values ​​such as 50 mA, 75 mA, 100 mA, or 1 A, or lower values ​​such as 10 mA or 20 mA, as well as all intermediate values, are possible. It is also conceivable that a range exists, for example, from 30 mA to 50 mA, and the protective function of the protective device is triggered if the fault current remains within this range for a defined period of time.

[0031] According to one embodiment of the electrolyzer system, the positive and negative poles of the power supply unit are connected to each other via a discharge resistor and a discharge switch, and the protection device is configured to close the discharge switch when the fault current exceeds the threshold, the earthing switch is open, and the power supply unit has stopped supplying power.

[0032] If an excessive fault current is detected by the protective device and the supply unit terminates the power supply to the electrolysis units, it is advisable to discharge residual voltages in the electrolyzer system for maintenance purposes and to prevent accidents. According to the invention, this is achieved via a discharge switch that discharges the terminals of the power supply unit through a resistor acting as a discharge resistor. This process may sometimes require a longer duration, as electrolysis units exhibit high capacitive properties and because it is essential to prevent triggering electrochemical processes within the electrolyzer by excessively high discharge currents, which could damage one or more of the electrolysis units.

[0033] In one embodiment, a fuse is arranged in series with the earthing switch, which trips at a fault current higher than the threshold value. Fuses typically trip faster than devices that first measure, then process the measurement data, and subsequently open switches. Therefore, to protect the components of the protective device, the power supply unit, and the electrolysis unit, a fuse can be arranged in series with the earthing switch. In the event of an extremely high fault current, i.e., a short circuit to earth with high current values, this series connection protects the protective device and other system components from excessive currents.

[0034] Another aspect of the invention is an operating method for the electrolyzer system according to one of the preceding embodiments, comprising the steps of: supplying the at least two electrolysis units with electrical power via the power supply unit; measuring and monitoring a fault current between a grounded end plate of one of the at least two electrolysis units and a grounded terminal of the power supply unit when the fault current exceeds a threshold value; and opening the grounding switch. This aspect of the invention represents an operating method for the electrolyzer system described above. The method begins with supplying the at least two electrolysis units with electrical power via the power supply unit. This step illustrates the normal operation of the electrolyzer system.The fault current between a grounded end plate of an electrolysis unit and a grounded terminal of the power supply unit is measured and monitored continuously or at specific intervals. If the fault current exceeds a threshold, the grounding switch opens, effectively preventing a short circuit between the grounded end plate and the grounded terminal of the power supply unit. If the fault current does not exceed the threshold, the electrolyzer system continues operating according to the first two steps of the procedure.

[0035] According to one embodiment, the operating method includes a signal indicating that the fault current is increased or the grounding of the electrolysis unit is deteriorated if an average value of the fault currents over a period of time is higher than an average value of the fault currents over a previous period.

[0036] In this embodiment, the operating procedure is supplemented by a preventative maintenance system. It checks whether the average value of the fault current measured over a period is higher than the average value of the fault currents in a previous period. This allows for the determination of a trend in the measured fault currents and consequently whether the insulation of one or more insulating elements is deteriorating. If there is a trend indicating that the average value of the fault current measured over a period is higher than the average value of the fault currents in a previous period, the plant operator is notified, or signaled, that a deterioration in the insulation properties of one or more insulating elements is likely and that maintenance or inspection is required.

[0037] According to one embodiment, the operating procedure further includes a termination of the supply to the electrolysis units by the supply unit when the fault current exceeds the threshold and the earthing switch is open.

[0038] In this embodiment, it is advantageously described that the supply unit terminates the power supply to the electrolysis units when the fault current exceeds a threshold. This is done to prevent further damage to equipment or personal injury caused by deteriorating insulation in one of the electrolysis units. According to one embodiment, the operating procedure also includes a notification that a fault current has exceeded the threshold.

[0039] Automatic restart of the electrolyzer system is not provided, as the insulation of the electrolysis units must be checked before restarting to prevent the fault current from becoming large and causing a short circuit. Therefore, it is advantageous for the operator or maintenance company of the electrolyzer system to be notified if a fault current exceeds the threshold. This allows the fault to be rectified, preventing damage and reducing costs.

[0040] According to one embodiment, the operating method further includes a regular opening of the grounding switch in order to measure an insulation resistance to the earth of the electrolyzer system.

[0041] Insulation resistance measurements measure the insulation resistance of the electrolyzer system to earth. This is useful to prevent potential earth currents that could harm people nearby and to detect damage to the electrolyzer system. This insulation resistance measurement also serves to verify the readings of the residual current measurement after extended operating times and as a criterion for authorizing the electrolyzer system's power supply unit to be switched on. For the insulation resistance measurement, it is necessary to open an earthing switch on the power supply unit; otherwise, the measurement will yield an inaccurate result.

[0042] According to one embodiment, the operating procedure further includes closing the discharge switch when the fault current exceeds the threshold, the earthing switch is open, and the supply unit has terminated the supply.

[0043] If an excessive fault current is detected by the protective device and the supply unit terminates the power supply to the electrolysis units, it is advisable to discharge residual voltages in the electrolyzer system for maintenance purposes and to prevent accidents. According to the invention, this is achieved via a discharge switch that discharges the terminals of the power supply unit through a resistor acting as a discharge resistor. This process may sometimes require a longer duration, as electrolyzer units exhibit high capacitive properties, and it is essential to prevent electrochemical processes within the electrolyzer from being triggered by excessively high discharge currents, which could damage one or more of the electrolyzer units.

[0044] The invention is illustrated below with reference to the figures, where Fig. 1 represents an electrolyzer system according to the invention.

[0045] Fig. 2 shows an electrolyzer system according to the invention in one embodiment, and

[0046] Fig. 3 shows a flowchart of an operating process according to the invention.

[0047] The characters are explained in detail below.

[0048] Figure 1 shows an electrolyzer system 1 according to the invention. For clarity, not all individual electrolysis units 10 are labeled. Five electrolysis units 10, which can be identically configured, are shown as examples. Each electrolysis unit 10 is provided with a pole 10a and a pole 10b, wherein one of the poles 10a, 10b is suitable for connecting a positive electrode and the other pole 10a, 10b is suitable for connecting the negative electrode. The poles 10a, 10b supply the electrolysis unit 10 with electrical power. Each electrolysis unit 10 is provided with insulating elements 12 and grounded end plates 12a. The insulating elements 12 are arranged between the end plates 12a and the poles 10a, 10b of the respective electrolysis unit 10. The electrolysis units 10 are connected in series with one another.This means that an electrolysis unit 10 is connected to a neighboring electrolysis unit 10 via one of its poles 10a, 10b. For example, electrolysis unit 10 is connected to the neighboring electrolysis unit 10 at its negative pole via its positive pole.

[0049] A power supply unit 14 is provided to supply the electrolysis unit 10 with electrical power. The power supply unit 14 is equipped with two terminals 16 and 18, which are intended for supplying a load with direct current. Terminal 16 of the power supply unit 14 is connected to terminal 10a of the electrolysis unit 10. For example, this is the first electrolysis unit 10 in the series connection of the majority of the electrolysis units 10. Terminal 18 is connected to the corresponding terminal of the last electrolysis unit 10 in the series connection of the majority of the electrolysis units 10. In this way, the circuit of the power supply unit 14 in the series connection of the electrolysis units 10 is closed.

[0050] The terminal 18 of the power supply unit 14 is connected to earth via a grounding switch 20. The defined earth potential via the grounding switch 20 reduces corrosion on the electrolysis units 10. For example, grounding the positive terminal of the power supply unit 14 prevents corrosion because it sets the potential of the end plates 12a relative to the electrolysis units 10 relative to earth such that the end plates 12a always have a positive potential relative to the electrolysis units 10. The grounding switch 20 is controlled by a protective device 22 and can be opened and closed by the protective device 22. The protective device 22 is configured to measure a fault current between a grounded end plate 12a of the electrolysis unit 10 and the grounded terminal. If the fault current exceeds a threshold value, the protective device 22 controls the grounding switch 20 to open it.Furthermore, the protective device 22 is configured to measure the insulation resistance of the electrolyzer system 1 to earth. For this purpose, the protective device 22 controls the earthing switch 20 to open it, thus enabling such an insulation resistance measurement.

[0051] Figure 2 shows an electrolyzer system 1 according to the invention in one embodiment. For the sake of clarity, only the differences from the electrolyzer system 1 shown in Figure 1 are described.

[0052] In Fig. 2, the terminals 16 and 18 of the power supply unit 14 are connected via a discharge resistor 24 and a discharge switch 26. The discharge switch 26 is controlled by the protective device 22. If the fault current measured by the protective device 22 exceeds a threshold value, the earthing switch 20 opens, and the power supply to the power supply unit 14 is interrupted by the protective device 22, the discharge switch 26 closes. The remaining DC voltage between terminals 16 and 18 of the power supply unit 14 is discharged via the discharge resistor 24 in such a way that the DC voltage is discharged continuously, in other words, in a controlled and slow manner, to prevent damage to the electrolysis unit 10.

[0053] Figure 3 shows an operating procedure for an electrolyzer system 1 according to the invention. The procedure is generally started when the electrolyzer system 1 is put into operation. In step S10, the supply unit begins to provide electrical power to the at least two electrolysis units. The procedure continues in step S20 with the measurement and monitoring of a fault current between a grounded terminal 12, an electrolysis unit, one of the at least two electrolysis units 10, and a grounded pole 20 of the supply unit 14.

[0054] In step S30, it is checked whether the measured fault current exceeds a threshold value. If the measured fault current does not exceed a threshold value, the procedure returns to step S20 and thus to measuring and monitoring the fault current. If the measured fault current exceeds the threshold value, the procedure continues with step S40. In step S40, the earthing switch 20 is opened by a control signal from the protective device 22. The procedure now continues with step S50. In step S50, the electrolysis unit 10 can be shut down by the power supply unit 14.

[0055] In step S60, several actions can be performed. Each of the following actions can be performed, only some of the listed actions can be performed, or only one of the actions can be performed. In step S60, it is possible to send a notification that a fault current has exceeded the threshold value. This notification can be sent in many ways, for example, via a radio link, a higher-level control unit, or other conceivable communication channels. Furthermore, in step S60, it is possible to close the discharge switch 26 to discharge the system via the discharge resistor 24.

[0056] Reference symbol list

[0057] 1 Electrolyzer system

[0058] 10 Electrolysis units

[0059] 10a Pol

[0060] 10b Pol

[0061] 12 insulating element

[0062] 12a End plate

[0063] 14 supply units

[0064] 16 pole

[0065] 18 poles

[0066] 20 earthing switches

[0067] 22 Protective device

[0068] 24 discharge resistor

[0069] 26 discharge switches

Claims

Claims:

1. Electrolyzer system (1) comprising: at least two electrolysis units (10) connected in series, each electrolysis unit having one pole (10a) and another pole (10b), insulating elements (12) and grounded end plates (12a), comprising: a power supply unit (14) connected to a first and a last electrolysis unit (10) of the at least two electrolysis units (10) connected in series and configured to supply the at least two electrolysis units (10) with electrical power, wherein one of the poles (16, 18) of the power supply unit is grounded via a grounding switch (20), characterized in that the electrolyzer system (1) has a protective device (22), wherein the protective device (22) is configured to measure a fault current between a grounded end plate (12a) and the grounded pole (16, 18) and, if the fault current exceeds a threshold value, to trip the grounding switch (20) to open.

2. Electrolyzer system according to claim 1, wherein the earthing switch (20) is opened only if the fault current exceeds the threshold value for a predetermined period, exceeds the threshold value a predetermined number of times in a predetermined period, or an integrated value of the fault current exceeds a threshold value for a predetermined period.

3. Electrolyzer system according to claim 1 or 2, wherein when the earthing switch (20) has been opened, an insulation resistance measurement is carried out, wherein the earthing switch (20) is closed again when the insulation resistance measured during the insulation resistance measurement exceeds an insulation resistance threshold.

4. Electrolyzer system according to claim 1, 2 or 3, wherein the protective device (22) is further configured to terminate the supply to the electrolysis units (10) by the supply unit (14) when the fault current exceeds a threshold and after the opening of the earthing switch (20), optionally after a predetermined period of time.

5. Electrolyzer system according to one of the preceding claims, wherein the protective device (22) is further configured to perform an insulation resistance measurement to earth at regular intervals or as instructed and to open the earthing switch (20) for the insulation resistance measurement.

6. Electrolyzer system according to one of the preceding claims, wherein the threshold is 100 mA.

7. Electrolyzer system according to one of the preceding claims, wherein the threshold is 30 mA.

8. Electrolyzer system according to any one of the preceding claims 2 to 7, wherein the poles (16, 18) of the supply unit (14) are connected to each other via a discharge resistor (24) and a discharge switch (26) and wherein the protective device (22) is configured to close the discharge switch (24) when the fault current exceeds the threshold, the earthing switch (20) is open and the supply unit (14) has terminated the supply.

9. Electrolyzer system according to one of the preceding claims, wherein a fuse is arranged in series with the earthing switch (20) which trips at a fault current higher than the threshold value.

10. Operating method for the electrolyzer system according to one of the preceding claims, comprising the steps of: Supplying (S10) the at least two electrolysis units with electrical power by the supply unit, Measuring and monitoring (S20) a fault current between an earthed end plate of an electrolysis unit of at least two electrolysis units and an earthed pole of the supply unit, if the fault current exceeds a threshold value, opening the earthing switch (S40).

11. Operating method according to claim 10, wherein, If an average value of the fault currents over a period is higher than an average value of the fault currents over a previous period, signal that the fault current is increased or the grounding of the electrolysis unit is deteriorated.

12. Operating method for the electrolyzer system according to claim 10, the method further comprising: Termination (S50) of the supply to the electrolysis units by the supply unit (22) when the fault current exceeds the threshold and the earthing switch (20) is open.

13. Operating method for the electrolyzer system according to claim 10 or 12, the method further comprising: Notify (S60) that a fault current has exceeded the threshold.

14. Operating method for the electrolyzer system according to one of the preceding claims, the method further comprising: Regularly opening the grounding switch to measure the insulation resistance to the earth of the electrolyzer system.

15. Operating method for the electrolyzer system according to one of claims 10 to 14, the method further comprising: Closing (S60) of the discharge switch when the fault current exceeds the threshold, the earthing switch is open and the supply unit has terminated the supply.

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