Cooling system for an electrolysis device for producing hydrogen

Abstract

The invention relates to a cooling system for an electrolysis device for producing hydrogen, wherein the electrolysis device has at least one electrolysis stack (1) and at least one installation component, wherein the cooling system has at least two coolant circuits (2, 2') which are separate from one another, wherein a first coolant circuit (2) is designed only for cooling the electrolysis stack (1) of the electrolysis device, and a second coolant circuit (2') is provided only for cooling the installation component of the electrolysis device, and wherein the temperature of the coolant in the first coolant circuit (2) differs from the temperature of the coolant in the second coolant circuit (2').

Description

[0001] Cooling system for an electrolysis device for producing hydrogen

[0002] The invention relates to a cooling system for an electrolysis device for producing hydrogen.

[0003] Electrolysis devices, so-called electrolyzers, for the electrochemical production of hydrogen are known from the state of the art. Such electrolysis devices are generally based on alkaline electrolysis (AEL) or proton exchange membrane electrolysis (PEM). Electrolyzers typically comprise an electrolysis stack with several electrolysis cells connected in series. These cells are supplied with a cell voltage in the range of 1.5V - 2.5V DC and each has an anode compartment, a cathode compartment, and an ion-permeable separating layer.

[0004] In alkaline hydrogen electrolysis, a concentrated, approximately 30% potassium hydroxide solution is passed through the anode and cathode sections of the electrolysis cell. The product gases are separated from the potassium hydroxide solution in a gas separator. The operating temperature of the electrolysis cell is approximately 70°C to 95°C. The operating pressure can range from atmospheric pressure to 40 bar.

[0005] In proton exchange membrane hydrogen electrolysis, pure water is fed into the anode section of the electrolysis cell. Oxygen is produced at the anode, which is then removed from the stack along with the water and separated from the water in a separator vessel. Hydrogen is produced at the cathode and is also removed from the stack. The operating temperature is usually between 70°C and 80°C. The operating pressure can range from atmospheric pressure to 40 bar. An electrolyzer can preferably comprise an electrolysis stack with several, preferably 100 to 200 or more, electrolysis cells arranged in series. Depending on the design of the individual electrolysis cells and the entire stack, a typical electrolyzer for producing hydrogen has an efficiency of 70% to 80%, generating a high level of waste heat that must be removed from the system using suitable cooling equipment.For industrial plants designed for a power output in the range of over 10 MW to several hundred MW, cooling the plants requires considerable technical and financial effort.

[0006] The object of the invention is to reduce the effort for cooling industrial electrolysis devices for producing hydrogen and to provide a cooling system that enables reduced technical and financial effort for cooling industrial hydrogen electrolyzers.

[0007] These and other objects are achieved according to the invention with a cooling system according to claim 1.

[0008] A cooling system according to the invention is designed for an electrolysis device for generating hydrogen, wherein the electrolysis device comprises one or more electrolysis stacks and at least one system component. In particular, the electrolysis device can comprise a plurality of different system components that are cooled by the cooling system.

[0009] The electrolysis stack can comprise a plurality of individual electrolysis cells configured for alkaline hydrogen electrolysis and comprising an electrical anode, an electrical cathode, and a substantially ion-permeable and electrically insulating separating layer. The alkaline hydrogen electrolysis can comprise electrolysis using an aqueous potassium hydroxide solution (KOH) or aqueous sodium hydroxide solution (NaOH) as the medium. By applying a direct current (DC) voltage (VDC) between the anode and cathode, the product gases H2 and O2 are generated in the electrolysis cell. The system components can include at least one gas separator for separation and cooling, at least one gas purifier for purification, and / or at least one gas compressor for compression of the product gas.Furthermore, at least one electrical voltage supply, in particular an electrical rectifier for providing the direct voltage VDC required for electrolysis, can be provided as a system component.

[0010] These system components are characterized by the fact that their contribution to the electrolysis device's thermal losses is generally lower than the electrolysis stack's contribution to the electrolysis device's thermal losses, i.e., the waste heat. In other words, the electrolysis stack generates the majority of thermal losses compared to the system components.

[0011] For example, an electrolysis stack generates up to 80% of the waste heat from an electrolysis device, while the system components contribute only 20%. At the same time, the system components are typically designed to operate at a lower operating temperature than the electrolysis stack. For example, gas separators and gas purifiers can preferably operate at a temperature below 45°C, while an alkaline electrolysis stack is preferably operated at a temperature of approximately 80°C.

[0012] According to the invention, the cooling system has at least two separate coolant circuits, wherein a first coolant circuit is designed only for cooling the electrolysis stack, and a second coolant circuit is provided only for cooling the one or more system components of the electrolysis device, and wherein the temperature of the coolant in the first coolant circuit differs from the temperature of the coolant in the second coolant circuit.

[0013] In particular, it can be provided that the temperature of the coolant in the inlet of the first coolant circuit is higher than the temperature of the coolant in the inlet of the second coolant circuit. By separating the coolant circuits, it is achieved that the heat generated in the electrolysis stack is dissipated at a higher temperature level than the heat generated in the system components. According to the invention, it can be provided for this purpose that the first coolant circuit is operated at a inlet temperature in the range of approximately 50°C to approximately 80°C, preferably approximately 60°C. In contrast, the second coolant circuit can be operated at a inlet temperature in the range of approximately 30°C to approximately 50°C, preferably approximately 45°C.

[0014] This division into a first coolant circuit for the electrolysis stack with a high flow temperature, which however provides the largest share of the cooling capacity, and a second coolant circuit for the system components with a low flow temperature, which is essentially only used where low temperatures are actually required, results in a particularly efficient cooling system with a minimum of required cooling capacity and cooling surface.

[0015] According to the invention, it can further be provided that the cooling system comprises three or more different coolant circuits, which are operated at different flow temperatures and are designed to cool different system components. For example, a first coolant circuit can be designed to cool the electrolysis stack to a temperature of approximately 60°C, a second coolant circuit can be designed to cool the product gas post-treatment to approximately 45°C, and a third coolant circuit can be designed to cool the electrical components to approximately 30°C. An even finer subdivision of the temperature levels of the cooling system can also be provided according to the invention.

[0016] According to the invention, the coolant circuits can each be connected to a separate dry cooler system. The use of dry coolers allows for efficient heat dissipation in both hot and cold climates. Furthermore, the use of dry coolers avoids high water consumption and eliminates wastewater.

[0017] According to the invention, a mixture of water and glycol can be provided as the coolant in the coolant circuits. According to the invention, a heat exchanger for extracting thermal energy can be provided in one of the coolant circuits, preferably in the first coolant circuit with a high flow temperature. The heat exchanger can be designed, in particular, to extract thermal energy at a temperature level above 70°C. The generated waste heat can be used, for example, in a district heating network.

[0018] The invention further relates to an electrolysis device for producing hydrogen, comprising at least one electrolysis stack and at least one further system component, as well as a cooling system according to the invention for differentially cooling the electrolysis stack and the system component.

[0019] The invention further relates to the use of a cooling system according to the invention for cooling an electrolysis device having an electrolysis stack and at least one system component.

[0020] Further features of the invention emerge from the patent claims, the drawings and the following descriptions of the figures.

[0021] The invention will now be explained in more detail using a non-exclusive exemplary embodiment. Figure 1 shows a schematic block diagram of an embodiment of a cooling system according to the invention.

[0022] In Fig. 1, a cooling system according to the invention is arranged on an electrolysis device for generating hydrogen. The electrolysis device comprises an electrolysis stack 1 having a plurality of individual alkaline electrolysis cells connected in series. The electrolysis device 1 further comprises several system components. In this exemplary embodiment, the system components provided are an electrical rectifier 8 for generating the necessary direct voltage VDC, a gas separator 5 for separating and cooling the generated product gases H2 and O2, a gas purifier 6, and a gas compressor 7. In other, not shown exemplary embodiments of the invention, further electrolysis stacks 1 and further system components can be provided.

[0023] A cooling system is provided that has two separate coolant circuits 2, 2'. A first coolant circuit 2 is designed exclusively for cooling the electrolysis stack 1 and the electrolysis cells contained therein. A second coolant circuit 2' is provided exclusively for cooling the system components of the electrolysis device. Specifically, in this exemplary embodiment, the second coolant circuit 2' cools the rectifier 8, as well as the gas separator 5, the gas purifier 6, and the gas compressor 7.

[0024] The temperature of the coolant in the first coolant circuit 2 differs from the temperature of the coolant in the second coolant circuit 2'. Specifically, the temperature of the coolant in the flow of the first coolant circuit 2 is approximately 60°C, whereas the temperature of the coolant in the flow of the second coolant circuit 2' is approximately 45°C.

[0025] The coolant circuits 2, 2' are each connected to a separate dry cooler system 3, 3'. The dry cooler systems 3, 3' can be equipped with fin exchangers and fans to dissipate the waste heat to the environment and cool the coolant.

[0026] Pumps are arranged in the coolant circuits 2, 2' to pump the coolant through the cooling lines. A mixture of water and glycol is used as the coolant. The first coolant circuit 2 also includes a heat exchanger 4 for extracting thermal power Pth. This can be used, for example, to operate a district heating network.

[0027] The electrolysis device shown in this embodiment is designed as a large-scale industrial plant and has a capacity of approximately 100 MW, with a cooling capacity of approximately 18 MW to approximately 26 MW. However, the invention is not limited to the embodiment described here, but encompasses all devices and methods within the scope of the following patent claims.

Claims

Patent claims 1. Cooling system for an electrolysis device for producing hydrogen, wherein the electrolysis device has at least one electrolysis stack (1) and at least one system component, characterized in that - the cooling system has at least two separate coolant circuits (2, 2'), - wherein a first coolant circuit (2) is designed only for cooling the electrolysis stack (1) of the electrolysis device, and - a second coolant circuit (2') is provided only for cooling the system component of the electrolysis device, and wherein - the temperature of the coolant in the first coolant circuit (2) differs from the temperature of the coolant in the second coolant circuit (2').

2. Cooling system according to claim 1, characterized in that the first coolant circuit (2) is operated at a flow temperature in the range of approximately 50°C to approximately 80°C, preferably approximately 60°C.

3. Cooling system according to claim 1 or 2, characterized in that the second coolant circuit (2') is operated at a flow temperature in the range of approximately 30°C to approximately 50°C, preferably approximately 45°C.

4. Cooling system according to one of claims 1 to 3, characterized in that three or more coolant circuits (2, 2') are provided, which are operated with different flow temperatures and are designed to cool different system components.

5. Cooling system according to one of claims 1 to 4, characterized in that the coolant circuits (2, 2') are each connected to a separate dry cooler system (3, 3').

6. Cooling system according to one of claims 1 to 5, characterized in that a mixture of water and glycol is provided as the coolant of the coolant circuits (2, 2').

7. Cooling system according to one of claims 1 to 6, characterized in that in one of the coolant circuits (2, 2'), preferably in the first coolant circuit (2), a heat exchanger (4) for coupling out thermal energy is provided.

8. Cooling system according to claim 7, characterized in that the heat exchanger (4) is designed to extract thermal energy at a temperature level above 70°C.

9. Cooling system according to one of claims 1 to 8, characterized in that the system component comprises at least one gas separator (5) for separating and cooling the product gas.

10. Cooling system according to one of claims 1 to 9, characterized in that the system component comprises at least one gas cleaner (6) for cleaning the product gas.

11. Cooling system according to one of claims 1 to 10, characterized in that the system component comprises at least one gas compressor (7) for compressing the product gas.

12. Cooling system according to one of claims 1 to 11, characterized in that the system component comprises at least one electrical voltage supply, in particular an electrical rectifier (8) for providing the direct voltage required for electrolysis.

13. Electrolysis device for producing hydrogen, comprising at least one electrolysis stack (1) and at least one further system component, characterized in that a cooling system according to one of claims 1 to 12 is provided.

14. Use of a cooling system according to one of claims 1 to 12 for cooling an electrolysis device.

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