METHOD FOR OPERATING A SYSTEM FOR ELECTROLYSIS, AND SYSTEM FOR ELECTROLYSIS

Abstract

A method for operating a system for electrolysis in order to obtain at least one gaseous electrolysis product, in which system at least one electrolysis device is electrically connected to a power converter by means of a direct-voltage circuit, the power converter being connected to an alternating-voltage circuit in order to supply the at least one electrolysis device with electrically energy for the operation of the at least one electrolysis device, the power converter being operated by means of zero crossing control. The invention further relates to a system of this type.

Claims

1-16. (canceled)

17. A method for operating a system for electrolysis to obtain at least one gaseous electrolysis product, in which system at least one electrolysis device is electrically connected to a power converter by means of a direct-voltage circuit, wherein the power converter is connected to an alternating-voltage circuit in order to supply the at least one electrolysis device with electrical energy for its operation, wherein the power converter is operated by means of a vibration package control.

18. The method according to claim 17, wherein a full-wave control or a half-wave control is used in the vibration package control.

19. The method according to claim 17, wherein a full-wave control is used in the vibration package control, and wherein a voltage range of 70% to 100% of the input voltage is used as the output voltage.

20. The method according to claim 17, wherein the alternating-voltage circuit is electrically connected to a power supply grid by means of a transformer.

21. The method according to claim 19, wherein the transformer is operated using a tap changer (111).

22. The method according to claim 20, wherein the transformer is operated using an on-load tap changer or a no-load tap changer as a tap changer.

23. The method according to claim 20, wherein a voltage range of 90% to 110% is used in the transformer with the tap changer.

24. The method according to claim 20, in which a public power supply grid or an island grid is used as power supply grid.

25. The method according to claim 17, wherein a voltage provided for the at least one electrolysis device is adapted, in particular increased, as a function of a previous operating time.

26. The method according to claim 25, wherein the voltage provided for the at least one electrolysis device is adapted as a function of a previous operating time in order to achieve a nominal capacity (ultimately corresponds to the extraction rate) of the electrolysis device for the gaseous electrolysis product, even in the case of degradation over the service life.

27. The method according to claim 17, wherein one or more gaseous electrolysis products are discharged and, in particular, stored and/or purified.

28. The method according to claim 17, wherein one or more stacks of the at least one electrolysis device are switched on and/or off as required.

29. The method according to claim 17, wherein the system is used for water electrolysis to obtain hydrogen and/or for carbon dioxide electrolysis to obtain carbon monoxide and/or for co-electrolysis to obtain synthesis gas and/or for chlorine-alkali electrolysis to obtain chlorine.

30. The method according to claim 17, wherein the system is used for low-temperature electrolysis and/or for medium-temperature electrolysis and/or high-temperature electrolysis.

31. A system for electrolysis to obtain at least one gaseous electrolysis product, with at least one electrolysis device and one power converter, wherein the at least one electrolysis device is electrically connected to the power converter via a direct-voltage circuit, wherein the power converter is electrically connectable or connected to an alternating-voltage circuit in order to supply the at least one electrolysis device with electrical energy for its operation, wherein the system is configured to operate the power converter by means of a vibration package control.

32. A system for electrolysis to obtain at least one gaseous electrolysis product, with at least one electrolysis device and one power converter, wherein the at least one electrolysis device is electrically connected to the power converter via a direct-voltage circuit, wherein the power converter is electrically connectable or connected to an alternating-voltage circuit in order to supply the at least one electrolysis device with electrical energy for its operation, wherein the system is configured to operate the power converter by means of a vibration package control, wherein the system is configured to perform the method according to claim 17.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0027] FIG. 1 schematically shows a system according to the invention in a preferred embodiment.

[0028] FIG. 2 schematically shows the operation of a vibration package control as used in the context of the present invention.

[0029] FIG. 3 schematically shows voltage curves for the operation of an electrolysis device that may be part of a system according to the invention.

DETAILED DESCRIPTION OF THE DRAWING

[0030] FIG. 1 schematically shows a system 100 according to the invention in a preferred embodiment. The system 100 is used for electrolysis and has a transformer 110, an alternating-voltage circuit 120, a power converter or inverter 130, a direct-voltage circuit 140 and, for example, two electrolysis devices 150 and 160. It goes without saying that even only one electrolysis device can be provided, or that even more electrolysis devices can be provided.

[0031] The transformer 110 has a tap changer 110, for example an on-load tap changer, and is electrically connected on the input side (or corresponding terminals) to a power supply grid 200 and on the output side (or corresponding other terminals) to the alternating-voltage circuit 120. The alternating voltage provided by the power supply grid 200 can thus be transformed down by means of the transformer 110, wherein the transformation ratio can be changed by using the tap changer 111.

[0032] The alternating-voltage circuit 120 is then electrically connected to the power converter 130 or corresponding terminals or input terminals of the power converter 130. The power converter 130 in turn is electrically connected to the direct-voltage circuit 140 via corresponding connections or output connections. The power converter 130 also has a control unit 131 by means of which semiconductor switches provided in the power converter can be activated accordingly, i.e., opened and closed, in order to rectify the alternating voltage. The electrolysis devices 150 and 160 are in turn electrically connected to the direct-voltage circuit 140.

[0033] In this way, electrical energy for operating the system 100 or the electrolysis devices 150, 160 comprised thereof can be provided by means of the power supply grid 200. By way of example, the electrolysis device 150 is designed for water electrolysis, in which water a is supplied and split into a plurality of stacks (only indicated) and hydrogen b and oxygen c are obtained and discharged as gaseous electrolysis products and optionally stored. It is also conceivable to (further) clean the gaseous electrolysis product, for example by drying and/or removing other gases. The electrolysis device 160 may have the same design or may also be different. As already mentioned at the outset, the specific type of electrolysis device is less relevant to the present invention; rather, the operation of the power converter 130 and possibly of the transformer 110 is important.

[0034] As mentioned, for operating the system 100, the power converter 130 or the semiconductor switches contained therein are controlled, in particular by means of the control unit 131, in such a way that the semiconductor switches always switch at or near a zero crossing of the relevant, applied vibration of the alternating voltage. The power converter 130 is thus operated by means of a vibration package control. The exact switching time does not have to be exactly at the zero crossing but can instead be up to 5% or up to 10% (relative to a period duration of the oscillation) before or after, for example.

[0035] In this way, feedback into the alternating-voltage circuit 120 and thus into the transformer 110 as well as the power supply grid 200 are prevented. A filter for reducing such undesired harmonics or feedback, as was previously necessary and shown in dashed lines in FIG. 1, cf. reference sign 115, is thus no longer necessary.

[0036] FIG. 2 schematically shows a control of the power converter with the vibration package control and thus its operation, as used in the context of the present invention. For this purpose, a voltage V is plotted over a time t, and vibrations or waves of the alternating voltage as they are present at the input of the power converter are shown.

[0037] For this purpose, t.sub.0 shows a vibration package duration of three full or whole vibrations here by way of example; t.sub.E, a switch-on duration of two full or whole vibrations here by way of example. It is hereby only switched at zero crossings, i.e., e.g., at t=0, t=t.sub.E or t=t.sub.0, so that no undesired harmonics can occur. In addition, this is only switched in the case of whole vibrations.

[0038] FIG. 3 shows schematic and purely exemplary or generic voltage curves for the operation of an electrolysis device, which can be part of a system according to the invention and is shown as an example in FIG. 1. For this purpose, a voltage V is applied above a current density I (instead, this can also be a density of hydrogen).

[0039] Curve V1 represents the relationship between the necessary voltage V and the current density I achieved therewith at the beginning of the service life of the electrolysis device, whereas curve V2 represents the corresponding relationship at the end of its service life. It can be seen that as the service life increases, an increasingly higher voltage is required here in order to achieve the same current density; the difference between the start and end of the service life is denoted here by ΔV.

[0040] Absolute values of the voltages usually vary in practice depending on the electrolysis technology and the number of cells in the stack of an electrolysis device. In this respect, as mentioned, only exemplary or generic curves are shown here. A slope also varies depending on electrolysis technology, insofar as they are likewise shown here only by way of example or generically.

[0041] However, by means of the above-described system and the proposed operation of such a system, it is possible to change the voltage applied to the electrolysis device and thus, for example, to select a lower voltage at the beginning of the service life, which is increased more and more over time in order to keep the current direction and thus also the production rate constant (if possible).