ELECTROLYSIS SYSTEM AND METHOD OF OPERATION

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. § 119(a) and (b) to European Ser. No. 24/215,647 , filed Nov. 27, 2024, the entire contents of which are incorporated herein by reference.

BACKGROUND

Technical Field

The invention relates to an electrolysis system comprising one or more electrolysers, a header line for providing a continuous flow of a fluid, one or more power supplies to provide electrical energy to the one or more electrolysers for the electrolysis process and one or more liquid-based first cooling devices for cooling the one or more power supplies.

Background of the Invention

Electrolysis refers to the splitting of a chemical compound through the use of electric current. Electrolysis is carried out in an electrolyser. The process requires two electrodes (anode and cathode), a direct current source, and an electrolyte (e.g., pure water or an aqueous alkaline solution). Electrolysis is in particular economically crucial for hydrogen production due to its ability to generate hydrogen from water using renewable electricity sources such as wind or solar power. This process is pivotal in the transition towards sustainable energy systems, offering a clean and versatile energy carrier that can be used in various sectors, including transportation, industry, and energy storage. Additionally, electrolysis enables the production of hydrogen without carbon emissions, contributing to efforts in combating climate change and achieving carbon neutrality goals globally. Hydrogen (H₂) can be obtained by separation from compounds such as water by electrolysis. This process may be represented as 2H₂O→2H₂+O.

An electrolyser 2 typically 2 consists 2 of a series of cells, each containing an anode and a cathode in contact with a fluid, i.e., an electrolyte. Within these cells, the electrical energy passes through the electrolyte into the respective cathodes and anodes. During the electrolysis process utilizing a water containing electrolysis medium, hydrogen gas is generated at the cathode and oxygen gas at the anode. The liquid electrolyte ensures continuous ion conduction between the anode and cathode, enabling the electrochemical reactions.

The electrolysis process generates heat within the electrolyser during the electrolysis of the fluid used for the electrolysis, e.g. a process fluid which is topped up during the electrolysis process by means of a makeup fluid. This heat needs to be managed to prevent overheating, which can degrade the electrolyser's performance and lifespan, and risk unsafe operation. Similarly, the power supply for the electrolyser, e.g. a rectifier, plays an essential role by converting AC (alternating current) from the power source into DC (direct current) suitable for the electrolyser's operation. The power supply, in particular the rectifier, also regulates the supplied current to the electrolysis cells and so the rate of chemical conversion. This conversion process inherently generates heat due to electrical losses and resistance within the rectifier's components. Adequate cooling is essential to dissipate this heat and prevent the rectifier from overheating.

In current practice, both the electrolyser and its power supply often utilize individual closed-loop cooling systems that are interconnected through a shared open loop cooling system. Typically, the rectifier cooling demand is only a small fraction of that of the electrolyser stacks. The rectifier closed loop cooling system demands deionised water with conductivities preferably <1 microS/cm nominally for safety reasons. However, several significant drawbacks stem primarily from the traditional cooling system architecture. A central disadvantage is the high capital costs associated with using independent closed-loop cooling systems for each electrolyser module and power supply. Each rectifier cooling arrangement requires its own pumps, heat exchangers, and ion exchange beds to maintain operational conditions and ensure the reliability of the electrolysis process. It requires power, control cables and Instrument Air to be run to the unit. It requires an independent secondary cooling stream to be routed to it to cool the closed-loop system used through the rectifier (change to power source as per definition). This requires significant materials and consumes ongoing power resources to maintain functionality. The installation and maintenance of these separate cooling systems significantly escalate acquisition costs and complicate the overall design of the facility. Another critical drawback is the increased susceptibility to failures and associated operational disruptions. Each independent cooling system presents potential failure points such as pump failures, leaks in the cooling water lines, or issues with heat exchangers and ion exchange beds. These components require regular maintenance and occasional replacement, further increasing operating costs and tying up additional resources. Furthermore, the multitude of instruments such as conductivity sensors, pressure transmitters, and other monitoring devices significantly heightens system complexity. While these instruments are essential for monitoring the plant's condition and ensuring efficient and safe operation, they also represent potential points of failure and necessitate regular calibration and maintenance to maintain accuracy and reliability. Finally, the pumps and instruments add an incremental power load to the overall plant.

It is the object of the invention to improve the efficiency, reliability, and cost-effectiveness of electrolysis processes and systems.

SUMMARY

The object of the invention is achieved by an electrolysis system and a method of operating an electrolysis system as defined in the independent claims. Further and preferred embodiments of the invention are disclosed in the following description and in the dependent claims.

The invention is described in terms of multiple aspects, encompassing an electrolysis system and a method of operating an electrolysis system. The descriptions of each aspect complement one another, so that the descriptions for the system can also be understood as descriptions of the method, and vice versa.

According to the invention, the electrolysis system comprises one or more electrolysers, a header line for providing a continuous flow of a fluid used for the electrolysis, one or more power supplies to provide electrical energy to the one or more electrolysers for the electrolysis process, and one or more liquid-based first cooling devices for cooling the one or more power supplies. The one or more electrolysers are each fluidly connected to the header line to receive the fluid to perform the electrolysis of the fluid, wherein the first cooling devices are each fluidly connected to the header line, e.g., via inlet lines, to receive a continuous flow of the fluid as cooling medium, and the first cooling devices are each fluidly connected to the header line, e.g., via outlet lines, to return the fluid into the header line.

The invention provides an integrated electrolysis system that utilizes a fluid for both electrolysis and cooling of power supply units from the same source. After used for cooling in the one or more first cooling devices, the fluid provided to the one or more first cooling devices is returned from the one or more first cooling devices to the header line and may be reconditioned for further electrolysis and cooling.

The fluid provided by the header line and used for the electrolysis is preferably a process fluid or a make-up fluid. Make-up fluid is used to replenish the fluid consumed by the electrolysis process and other losses in the electrolyser, e.g. from evaporation or ion depletion. It preferably has a conductivity of less than 10 mS/cm. Process fluid refers to the electrolyte that circulates through the electrolysis cells and participates directly in the electrochemical reactions. Preferably, the fluid, in particular the make-up fluid, is demineralised water with a conductivity of <20 microS/cm, more preferably deionised water with conductivity of <2 microS/cm.

The term “electrolyser” as used herein can encompass individual electrolysis units, electrolysis stacks, or entire arrays of electrolysis stacks. An electrolysis stack refers to a series of individual electrolysis cells connected together to increase the production capacity within a single compact unit. An electrolysis array, on the other hand, consists of multiple electrolysis stacks arranged in parallel or series, further scaling up the production capability to meet higher industrial demands.

Each cooling device is assigned to a respective single power supply, e.g., a rectifier. However, it is also conceivable for a cooling device to cool multiple power supplies.

According to a further embodiment of the invention, downstream or upstream of the first cooling device a further (herein referred to as third) cooling device is provided to cool a transformer, wherein the further cooling device is configured to cool a closed-loop cooling circuit of the transformer. Preferably, the cooling medium of the closed-loop cooling circuit of the transformer comprises an oil. More preferred, the closed-loop cooling system of the transformer comprises an oil-based closed-loop circuit and a water-based closed-loop circuit. Thereby, the circulating oil, which is the primary cooling fluid for cooling the transformer, is re-cooled by the circulating water. The cooling water of the water-based circuit of the transformer is re-cooled by the fluid which flows through the third cooling device. As a result, oil contaminations in the (process) fluid are avoided.

According to a further embodiment of the invention, multiple rectifiers and/or transformers are arranged in parallel downstream of the first cooling device.

According to a further embodiment of the invention, the header line is connected to a conditioning unit to condition, e.g., to deionise, the flow of fluid into conditioned fluid supplied to the one or more electrolysers and the one or more first cooling devices. Both, the electrolyser and the first cooling device may utilize the conditioned fluid. Thus, there is no need for a separate conditioning unit for the cooling medium of the power supply, such as a conditioning unit to provide low-conductivity water. Instead, the central treatment unit for the fluid is sufficient, streamlining the system and enhancing efficiency. Preferably, the conditioning unit is configured to deionise the fluid. Furthermore and also preferred, the conditioning unit is configured to cool the fluid, in particular to re-cool the fluid.

According to a further embodiment of the invention, the header line comprises a first section for supplying the fluid to the one or more first cooling devices and the one or more electrolysers and a second section for receiving the fluid from the one or more first cooling devices, wherein the returned fluid is received in the second section only after the final supply of the fluid to the one or more first cooling devices and the one or more electrolysers in the flow direction of the fluid. This arrangement ensures that the first cooling devices and the electrolysers are not supplied with heated fluid.

According to a further embodiment of the invention, the return of the fluid from the first cooling device into the header line is arranged upstream the conditioning unit. The connection from the outlet of the first cooling device to the header line is positioned on the header line before the conditioning unit in the flow direction of the fluid within the header line. This ensures that the fluid is properly reconditioned before being circulated to the electrolysers and first cooling devices. By placing the return upstream of the conditioning unit, any changes in the fluid's properties caused by the cooling are corrected, maintaining the quality and effectiveness of the fluid for continuous and efficient operation.

According to a further embodiment of the invention, the one or more electrolysers are each connected to the header line through a respective supply line, and inlet lines of the one or more first cooling devices are connected to the supply lines at a diversion to divert at least part of the continuous flow of fluid from the supply lines into the first cooling devices. Preferably, the length of the supply line between the diversion and the electrolyser is less than 50 times the diameter of the supply line between the diversion and the electrolyser, preferably less than 10 times the diameter. When a particular electrolyser is not in operation and no fluid or conditioned fluid flows through it, the fluid or conditioned fluid still flows through the supply line and the diversion into the first cooling device of the power supply. Keeping the length of the supply line between the diversion and the electrolyser as short as possible minimizes the dead space between the diversion and the electrolyser where no fluid flow occurs when the electrolyser is inactive. This design helps maintain the quality of the fluid used for the electrolysis by reducing stagnant areas where contamination or degradation could occur. This embodiment helps to address issues encountered with electrolysis, specifically maintaining the low conductivity feed of the water to the electrolyser. Electrolysis typically requires water <2 microS/cm, preferably <1 microS/cm, more preferably <0.1 microS/cm. To ensure the water has the correct conductivity before restarting, purging is normally necessary, which wastes valuable water, delays the restart process, and increases production costs. However, this issue is effectively avoided with the proposed embodiment.

According to a further embodiment of the invention, the fluid used for the electrolysis is water. This electrolysis system described herein is particularly well-suited for the production of hydrogen (H₂) and oxygen (O₂). By using water as fluid for the electrolysis, the system facilitates the 2 electrolysis process 2 where water molecules are split into hydrogen and oxygen gases. Deionised Water may also be used as a makeup fluid. The efficient cooling mechanism, combined with the continuous flow of, in particular conditioned, fluid, ensures optimal performance and reliability of the electrolysis system, making it ideal for large-scale hydrogen and oxygen production.

According to a further embodiment of the invention, the header line is a recirculating header, wherein the recirculating header line comprises a first section for supplying the fluid to the one or more first cooling devices and the one or more electrolysers and a second section for receiving the fluid from the one or more first cooling devices, wherein the returned fluid is received in the second section only after the final supply, i.e., last supply, of the fluid to the one or more first cooling devices and the one or more electrolysers in the flow direction of the fluid. The header line is designed to recirculate or loop the fluid continuously through the electrolysis system. In a recirculating header configuration, the fluid flows through the header line and is distributed to the electrolysers and the cooling devices of the system, preferably after being conditioned into conditioned fluid. After passing through the cooling devices, the fluid is returned to the header line. This continuous loop ensures that the fluid is consistently available for electrolysis and cooling processes without interruption.

According to a further embodiment of the invention, the header line comprises or is connected to a buffer tank; wherein a cooling unit is arranged in the header line upstream the buffer tank. The cooling unit helps to regulate the temperature of the fluid, maintaining optimal conditions for the electrolysis process.

According to a further embodiment of the invention, the header line comprises a bypass arranged to allow the flow of fluid to bypass the conditioning unit and/or a bypass arranged to allow the flow of fluid to bypass a cooling unit upstream a buffer tank connected to the header line. By bypassing the conditioning unit, an even more precise control over the conditioning of the fluid may be achieved. The ability to bypass the cooler unit before the buffer tank allows for customized temperature regulation of the fluid entering the tank.

According to a further embodiment of the invention, the power supply is configured to provide direct current to the one or more electrolysers. Preferably, the power supply comprises or is a rectifier. A rectifier converts alternating current (AC) from a main power supply into direct current (DC), which is necessary for the electrolysis process. However, the power supply could also be other types of devices that provide direct current. For example, it could be a DC-DC converter, which converts one level of DC voltage to another, more suitable level for the electrolyser. Additionally, the power supply could be a battery or a solar power system with an inverter, providing sustainable and renewable energy for the electrolysis process.

According to a further embodiment of the invention, the first cooling device is adapted for direct liquid cooling of the power supply. Direct liquid cooling involves circulating a coolant directly in contact with the surface of electrical components. Direct liquid cooling shows enhanced heat dissipation efficiency. Liquids, typically water or specialized coolants, have higher heat capacity and thermal conductivity than air. By directly contacting the power supply, heat is efficiently transferred away from the components, maintaining lower operating temperatures. Using conditioned fluid, e.g. deionised water, is particularly advantageous because of its low conductivity and the ability to prevent electrical conductivity issues or short circuits, particularly when the cooling fluid interacts with electrical components or circuits.

According to a further embodiment of the invention, the electrolysis system comprises a liquid-based second cooling device adapted to cool the electrolyser by being fed with a flow of a cooling fluid, wherein the first cooling device of the power supply is adapted to operate independently of the cooling fluid supplied to the second cooling device. According to a further embodiment of the invention, the fluid is exclusively used as the cooling medium for the first cooling device. Using the fluid as the sole cooling medium for the first cooling device offers several significant benefits. It minimizes the overall system complexity by eliminating the need for separate cooling fluids for the power supply, and the system requires fewer pipelines, pumps, and other auxiliary components. This reduction in hardware not only simplifies installation and maintenance but also decreases the potential points of failure, thereby enhancing system reliability.

According to a further embodiment of the invention, the one or more first cooling devices solely rely on the fluid supplied from the header line for liquid cooling, without the need for an additional closed-loop cooling circuit to dissipate heat from the power supply. By eliminating the need for a separate closed-loop circuit, the number of components such as extra pumps, heat exchangers, and additional pipelines is reduced. The direct use of the fluid used for the electrolysis for cooling eliminates the need for separate treatment or conditioning of a distinct cooling medium.

The invention also relates to a method of operating an electrolysis system, in particular as described herein. The electrolysis system comprises an electrolyser, a header line providing a continuous flow of a fluid, a power supply electrically connected to the electrolyser to provide electrical energy to the electrolyser for the electrolysis process and a liquid-based first cooling device to cool the power supply. At least part of the continuous flow of fluid to the electrolyser is diverted into the first cooling device for cooling the power supply, wherein after passing the first cooling device, the fluid is returned into the header line.

According to a further embodiment of the invention, the fluid is conditioned into a conditioned fluid before being supplied to the electrolyser and the first cooling device.

According to a further embodiment of the invention, the flow of fluid into the first cooling device is maintained when the inflow of fluid into the respective electrolyser is blocked or when the electrolyser is inactive.

The described system and method are particularly relevant for water electrolysis but can also be applied to other electrolysis processes.

BRIEF DESCRIPTION OF THE FIGURES

The invention will now be described referring to an exemplary embodiment shown in the figures in which:

FIG. 1 schematically shows a layout of an electrolysis system according to a first embodiment of the invention; and

FIG. 2 details of the electrolysis system of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a schematic representation of the layout of an electrolysis system 1 for the electrolysis of water. The electrolysis system 1 comprises a cooling water supply 2, which provides a cooling fluid in a recirculating manner. The system further includes two electrolysers 3 adapted to perform water electrolysis by use of electrical current. The number of two electrolysers 3 is merely for illustration purposes; the system can, of course, be equipped with more or fewer electrolysers. Each electrolyser is assigned a power supply in the form of a rectifier 4. The rectifier 4 is connected to an alternating current source (not shown) via an electrical connection 5 and to the electrolyser 3 via an electrical connection 6. The electrolyser 3 is supplied with the direct current necessary for the electrolysis reaction via the electrical connection 6.

The rectifier 4 includes a first cooling device 7. The first cooling device 7 is based on a direct liquid cooling configuration to maximize the effective cooling of the rectifier's 4 electrical components. The electrolyser 3 includes a second cooling device 8, which serves to cool the electrolyser 3.

The second cooling device 8 is connected to the cooling water supply 2 via a cooling water inlet line 9 and is supplied with cooling fluid 10 through this line. The heat-dissipating cooling fluid 10 is discharged from the second cooling device 8 via a cooling water discharge line 11 and fed into a discharge line 12 of the cooling water supply 2.

For the purpose of electrolysis, the electrolysers 3 are supplied with deionised water (DIW) as fluid for the electrolysis from a recirculating header line 13. The header line 13 comprises two main sections 14 and 15. The first section 14 serves to supply the fluid used for the electrolysis to the electrolysers 3. The second section 15 serves to collect the heated fluid from the first cooling devices 7, condition the fluid, if necessary, and recirculate it back to the first section 14. The direction of the flow of fluid 18 in the recirculating header line 13 is indicated with arrows. The electrolysers 3 are each connected to the first section 14 via a supply line 16 through which the fluid is fed to the electrolyser 3.

After the last 17 supply line 16 in the direction of the flow of the fluid 18, the header line 13 transitions from the first section 14 into the second section 15, which includes a cooler unit 19 and a deionisation unit 20 for conditioning the fluid (deionised water), and a buffer tank 21. The cooler unit 19 and the deionisation unit together are referred to as the conditioning unit of the electrolysis system. The cooler unit 19 is used to re-cool the fluid and may include a filter to remove impurities and contaminants from the fluid, ensuring it remains clean and suitable for use in the electrolysers 3. The deionisation unit 20 removes ions from the fluid to maintaining its high purity and preventing any interference with the electrolysis process, i.e., the deionisation unit 20 finally conditions the fluid 18 into a conditioned fluid 22 (indicated by arrow). The conditioned fluid 22 then flows back into the first section 14 to be, again, fed into the electrolysers 3. The cooler unit 19 can be provided in the first section 14 or, as shown herein, in the second section 15.

The cooling devices 7 of the rectifiers (power supplies) 4 also operate on the basis of the fluid used for the electrolysis, in particular the make-up fluid used for the electrolysis, here deionised water (DIW). Inlet lines 23 of the liquid-based first cooling devices 7 of the power supplies 4 are fluidly connected to the first section 14 of the header line 13 via the supply line 16 for receiving fluid, e.g., conditioned fluid 22, as cooling medium. Outlet lines 24 of the liquid-based first cooling devices 7 of the power supplies 4 are fluidly connected to second section 15 of the header line 13 to discharge the heat-dissipating fluid from the first cooling device 7 and to feed it back into the header line 13.

If necessary, the flow of fluid returning from the first cooling devices 7 and recirculating into the second section 15 can bypass the deionisation unit 20 through a bypass line 27. This is particularly feasible when the fluid is sufficiently conditioned.

FIG. 2 is an enlarged view of section A from FIG. 1. As shown, the inlet line 23 of the first cooling device 7 is connected to the supply line 16 at a diversion 25. Thereby, part of the continuous flow of fluid from the first section 14 to the electrolyser 3 through the supply line 16 is diverted into the first cooling device 7. The diversion 25 is continuously open. This means that even when no fluid is flowing through electrolyser 3, a continuous flow of fluid, e.g., conditioned fluid, still passes through the first cooling device 7. The length 26 of the supply line 16 after the diversion 25 is kept as short as possible. Keeping the length of the supply line 16 between the diversion 25 and the electrolyser 3 as short as possible minimizes the dead space between the diversion 25 and the electrolyser 3 where no flow occurs though the electrolyser, e.g., when the electrolyser 3 is inactive.

REFERENCE NUMERALS

• • 1 electrolysis system
  • 2 cooling water supply
  • 3 electrolyser
  • 4 rectifier (power supply)
  • 5 electrical connection
  • 6 electrical connection
  • 7 first cooling device
  • 8 second cooling device
  • 9 cooling water inlet line
  • 10 cooling fluid
  • 11 cooling water discharge line
  • 12 discharge line
  • 13 header line
  • 14 first section
  • 15 second section
  • 16 supply line
  • 17 last supply line
  • 18 flow of fluid
  • 19 cooler unit
  • 20 deionisation unit
  • 21 buffer tank
  • 22 flow of conditioned fluid
  • 23 inlet line
  • 24 outlet line
  • 25 diversion
  • 26 length after diversion (dead space)
  • 27 bypass line

It will be understood that many additional changes in the details, materials, steps and arrangement of parts, which have been herein described in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. Thus, the present invention is not intended to be limited to the specific embodiments in the examples given above.