US-12618167-B2 - Method for operating an electrolysis system, and electrolysis system

US12618167B2US 12618167 B2US12618167 B2US 12618167B2US-12618167-B2

Abstract

An electrolysis system includes at least one electrolyzer for generating hydrogen and oxygen as products, and at least two downstream compressors for compressing at least one of the products produced in the electrolyzer. A method of operating the electrolysis system in a part-load operation of the electrolyzer that is optimized in terms of efficiency and is also cost-effective. During the part load operation of the electrolyzer, a first group of compressors is operated in part-load operation, while the compressor(s) of a second group can be switched on or off individually for full-load operation.

Inventors

Dirk Wall
Sven Schumann

Assignees

Siemens Energy Global GmbH & Co. KG

Dates

Publication Date: 20260505
Application Date: 20230707
Priority Date: 20220728

Claims (7)

1 . A method for operating an electrolysis system with at least one electrolyzer for generating hydrogen and oxygen as products, and a plurality of downstream compressors for compressing at least one of the products generated in the electrolyzer, the method comprising: operating the electrolyzer in a part-load operation; and while operating the electrolyzer in the part-load operation, operating a first group of the downstream compressors in part-load operation, and individually switching on and off one or more compressors in a second group of the downstream compressors; wherein each of the one or more compressors in the second group of the downstream compressors is independently operated in a manner exclusively selected from a group consisting of being switched off and being turned on to operate at full load; and wherein the first group of the downstream compressors includes a plurality of compressors and a number of compressors in the first group is smaller than a number of compressors in the second group.
2 . The method according to claim 1 , which comprises setting the first group of compressors to the part-load operation by way of a variable frequency drive.
3 . The method according to claim 1 , which comprises operating the at least two downstream compressors in a parallel-connected arrangement.
4 . The method according to claim 1 , which comprises exclusively employing the first group and the second group of compressors for compressing the hydrogen produced in the electrolyzer.
5 . An electrolysis system, comprising: at least one electrolyzer for generating hydrogen and oxygen as products; a plurality of compressors connected downstream of said at least one electrolyzer and configured for compressing at least one of the products generated in said at least one electrolyzer; a controller configured, in a part-load operation of said at least one electrolyzer, to operate a first group of the downstream compressors in part-load operation, and to individually switch on and off one or more compressors in a second group of the downstream compressors; wherein each of the one or more compressors in the second group of the downstream compressors is independently operated in a manner exclusively selected from a group consisting of being switched off and being turned on to operate at full load; and wherein the first group of the downstream compressors includes a plurality of compressors and a number of compressors in the first group is smaller than a number of compressors in the second group.
6 . The electrolysis system according to claim 5 , configured for executing the method according to claim 1 .
7 . The electrolysis system according to claim 5 , wherein said compressors are at least one of piston compressors or screw compressors.

Description

FIELD AND BACKGROUND OF THE INVENTION The invention relates to a method for operating an electrolysis system comprising at least one electrolyzer for generating hydrogen and oxygen as products, and at least two downstream compressors for compressing at least one of the products which is generated in the electrolyzer. The invention further relates to an electrolysis system which is appropriate for executing the method. An electrolysis system is a device which initiates a substance conversion by means of electric current (electrolysis). In line with the wide range of different electrochemical electrolysis processes, there is also a multiplicity of electrolysis systems, including, for example, an electrolysis system for water electrolysis. Nowadays, hydrogen is produced from water, for example by means of proton exchange membrane (PEM) electrolysis, or alkaline electrolysis. By means of electrical energy, electrolysis systems produce hydrogen and oxygen from an infeed of water. This process is executed in an electrolysis stack, which is comprised of multiple electrolysis cells. Water is introduced as an educt into the electrolysis stack, to which a DC voltage is applied, and, further to the throughflow thereof in the electrolysis cells, two fluid streams are discharged, comprised of water and gas bubbles (O2 or H2). Further to liquid-gas separation, hydrogen and oxygen are retrieved as products, which can then be compressed in a subsequent step. In alkaline electrolysis, in general, a small number of stacks (1 or 2) are connected in series, and form an electrolysis unit. In a PEM electrolyzer, multiple stacks or modules are connected in series, and form a module series. An electrolysis unit is formed of a number of module series. In the event of a part-load operation of the electrolysis system, there is a distinction between the part-load behavior of the electrolyzers and of the downstream compressors. The part-load efficiency, mass flow and operating behavior of electrolyzers assume a substantially continuous characteristic. On the compression side, for part-load mass flows, it is customary for individual compressors to be switched on and off, potentially resulting in stages or step changes in efficiency. This issue occurs, in particular, as the size of systems increases. For the resolution of this issue, costly options are available, including variable frequency drives for compressors, which enable a continuous adjustment of compressor capacity. A compressor drive system for controlling gas pressure in a pressurized volume of gas connected to the compressor is described e.g. in EP 0 085 285 A1. An AC power drive is directly coupled to the compressor, which is driven at the same speed as the drive. The pressure in the volume of gas is detected by pressure capture means, which are connected to a frequency converter. The converter simultaneously varies the amplitude and frequency of the drive voltage which is supplied to the drive. This variation is executed in response to volumetric pressure changes, thus forming a control loop. Although, by means of a frequency converter, the part-load behavior of compressors can be improved and adapted to the part-load behavior of electrolysis, this solution is associated with very high costs. SUMMARY OF THE INVENTION The fundamental object of the invention is therefore the provision of a part-load operation of the electrolysis system which is optimized with respect to efficiency and is also cost-effective. According to the invention, this object is fulfilled by a method for operating an electrolysis system comprising at least one electrolyzer for generating hydrogen and oxygen as products, and at least two downstream compressors for compressing at least one of the products which is generated in the electrolyzer, wherein, in a part-load operation of the electrolyzer, a first group of compressors is operated in part-load operation, whereas one or more compressors in a second group can be switched on or off individually for full-load operation. According to the invention, this object is moreover fulfilled by an electrolysis system which is appropriate for executing the method, comprising at least one electrolyzer for generating hydrogen and oxygen as products, at least two downstream compressors for compressing at least one of the products which is generated in the electrolyzer, and a control unit which is configured, in a part-load operation of the electrolyzer, to operate a first group of compressors in part-load operation, whereas one or more compressors of a second group are switched on or off individually for full-load operation. Advantages and preferred configurations described hereinafter with respect to the method can be appropriately applied to the electrolysis system. The invention proceeds from the consideration whereby the design rating and control of compressors is attuned, in a cost-effective manner, to load variations in the electrolysis process, wherein not all