ELECTROLYSIS SYSTEM FOR BREAKING DOWN WATER INTO HYDROGEN AND OXYGEN, AND A METHOD FOR OPERATING THE ELECTROLYSIS SYSTEM

Abstract

An electrolysis system for breaking down water into hydrogen and oxygen using at least two electrolysis modules, each electrolysis module having at least two electrolytic cells, an electrolytic cell having an anode compartment and a cathode compartment, the anode compartment being separated from the cathode compartment by a proton exchange membrane, and a switching device, which is compatible with direct current, being arranged electrically in parallel with at least one electrolysis module. The electrolysis system is operated by the at least two electrolysis modules. When the available electrical power decreases, at least one switching device is closed. At least one electrolysis module is bridged by the switching device. The number of electrolysis modules which are then operated is reduced by the number of bridged electrolysis modules. When the available electrical power increases, at least one switching device is opened.

Claims

1.-13. (canceled)

14. An electrolysis system for decomposition of water to afford hydrogen and oxygen, comprising: at least two electrolysis modules, wherein each electrolysis module comprises at least two electrolysis cells, wherein an electrolysis cell comprises an anode space and a cathode space and the anode space is separated from the cathode space by a proton-exchange membrane, wherein at least one direct current-capable switching apparatus is arranged electrically in parallel with at least one electrolysis module and wherein the switching apparatus in a closed state has a lower electrical resistance than the electrolysis module.

15. The electrolysis system as claimed in claim 14, wherein the electrolysis cells are arranged electrically connected in series.

16. The electrolysis system as claimed in claim 14, wherein the electrolysis modules are arranged electrically connected in series.

17. The electrolysis system as claimed in claim 14, wherein a pressure plate is arranged between two electrolysis modules and the pressure plate is electrically connected to the electrolysis modules.

18. The electrolysis system as claimed in claim 17, wherein the switching apparatus is electrically connected to two pressure plates which delimit at least one electrolysis module.

19. The electrolysis system as claimed in claim 14, wherein the switching apparatus comprises an encapsulated switching apparatus.

20. The electrolysis system as claimed in claim 14, wherein the switching apparatus comprises a vacuum interrupter.

21. A process for operating an electrolysis system for decomposition of water to afford hydrogen and oxygen, comprising: providing at least two electrolysis modules, wherein each electrolysis module comprises at least two electrolysis cells, wherein an electrolysis cell comprises an anode space and a cathode space and the anode space is separated from the cathode space by a proton-exchange membrane, wherein at least one direct current-capable switching apparatus is arranged electrically in parallel with at least one electrolysis module and wherein the switching apparatus in a closed state has a lower electrical resistance than the electrolysis module, operating at least two electrolysis modules, closing at least one switching apparatus in case of a fall in available electrical power and bridging at least one electrolysis module via the switching apparatus, operating a number of electrolysis modules which is reduced by the number of bridged electrolysis modules, and opening at least one switching apparatus in case of an increase in the available electrical power.

22. The process as claimed in claim 21, wherein opening the switching apparatus commutates direct current flow from the switching apparatus into the electrolysis module.

23. The process as claimed in claim 22, wherein the switching apparatus is operated with an arc voltage of at least 100 V during commutation.

24. The process as claimed in claim 21, wherein electrical current in the switching apparatus or in an electrolysis module is in a range from 2 kA to 10 kA.

25. The process as claimed in claim 21, wherein at least two electrolysis modules are bridged in parallel with a switching apparatus.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG. 1 is a schematic diagram of an electrolysis system comprising four electrolysis modules with three switching apparatuses in an open position;

[0025] FIG. 2 is an electrolysis system comprising four electrolysis modules with two switching apparatuses, one in the open position and one in the closed position.

DETAILED DESCRIPTION OF INVENTION

[0026] FIG. 1 shows an electrolysis system 1 comprising four electrolysis module 2. Each electrolysis module 2 comprises a plurality of electrolysis cells 3. The electrolysis cells 3 are arranged between two pressure plates 4. The pressure plates 4 press the electrolysis cells, which especially comprise a proton exchange membrane, together. The pressure plates 4 arranged at the edge of the electrolysis system 1 are electrically connected via an electrical connection 5. The electrolysis modules B, C and D of the electrolysis system 1 have three switching apparatuses 6 arranged in parallel with them. The switching apparatuses 6 are electrically connected in parallel to the electrolysis modules 2. In this example is switching apparatus 6 bridges and electrolysis module 2. Accordingly every switching apparatus 6 is electrically connected to the pressure plates 4 which delimit an electrolysis module 2.

[0027] In this example the electrolysis, in particular the decomposition of water to afford hydrogen and oxygen, is carried out in all electrolysis modules 2 since all switching apparatuses 6 are open. The electrolysis is carried out with direct current. The switching apparatuses 6 are therefore in the form of direct current switching apparatuses. A diode 8 is serially connected in the forward direction to the switching element. The polarity and a protective voltage for the stack are thus advantageously maintained.

[0028] In this example the electrolysis system 1 is operated under full load. If the electrical power in the grid decreases, especially as a result of little wind and little sunshine, at least one switching apparatus 6 may be closed. This allows the electrolysis modules B, C and D to be modularly switched off/bridged. In this example the electrolysis module A is always operated during operation of the electrolysis system 1. If the other modules are now switched off as a function of the available electrical power, the electrolysis module A may be operated at a constant power density. Accordingly and advantageously, no electrolysis modules/electrolysis cells 3 are operated at partial load. It is particularly advantageous to bridge the electrolysis modules one after another. In particular, module A may initially be bridged for a specified duration. Module B or module C may subsequently be bridged for a similar duration. This ensures that the modules are uniformly operated and subjected to uniform load. The bridging prevents rapid aging of the electrolysis cells 3. It is further ensured that the quality of the product gas, in particular of the hydrogen, remains constant.

[0029] FIG. 2 likewise shows an electrolysis system 1 having four electrolysis modules 2. The electrolysis modules are in turn delimited by pressure plates 4, wherein the pressure plates 4 press the electrolysis cells 3 together. In this example two switching apparatuses 6 are arranged in parallel with the electrolysis module 2. A switching apparatus 6 is arranged in parallel with the electrolysis module B. A further switching apparatus is arranged in parallel with the electrolysis modules C and D. A low-ohm resistor 9 is connected in series with the switching element. A further low-ohm resistor 9 is connected in series with a diode 8. It is likewise possible to employ only low-ohm resistors 9 without diode 8. The polarity and a protective voltage for the stack are advantageously maintained by means of the diode and/or the low-ohm resistor.

[0030] The switching apparatus 6 which bridges the electrolysis modules C and D is closed in this example. Thus in this example the electrolysis system is operated at partial load. The electrolysis modules A and B are each operated at constant electrical power. Partial load operation is achieved by closing the switching apparatus 6 to effect electrical bridging of the electrolysis modules C and D. If the available electrical power in the electrical grid increases again, the switching apparatus 6 may in turn be opened. The switching apparatus 6 is particularly advantageously in the form of a vacuum tube, in particular in the form of a low-voltage vacuum tube. Also suitable but not shown in the drawing are encapsulated gas switching paths analogous to a live tank or dead tank, such as are employed in high-voltage technology. This prevents an open arc being formed upon commutation of the current. This is desirable since gases at risk of explosion, in particular hydrogen, are formed in the electrolysis modules.

[0031] Both exemplary embodiments show four electrolysis modules 2. This is a simplified representation. It is likewise within the spirit of the invention for a greater number of electrolysis modules to be serially connected. It is likewise possible to arrange further staggered arrangements of the switching apparatuses 6 in order on the one hand to provide a sufficient quantity of switching apparatuses 6 and on the other hand to prevent too great a quantity of switching apparatuses 6.

[0032] Although the invention has been more particularly illustrated and described in detail via working examples the invention is not limited by the disclosed examples. Variations thereof may be derived by those skilled in the art without departing from the scope of protection of the invention such as is defined by the claims which follow.

LIST OF REFERENCE NUMERALS

[0033] 1 Electrolysis system [0034] 2 Electrolysis module [0035] 3 Electrolysis cell [0036] 4 Pressure plate [0037] 5 Electrical connection [0038] 6 Switching apparatus [0039] 7 Electrical conduit [0040] 8 Diode [0041] 9 Electrical resistor [0042] A Electrolysis module A [0043] B Electrolysis module B [0044] C Electrolysis module C [0045] D Electrolysis module D