Cooling system for superconducting cable

Abstract

To provide means capable of expanding an application of a coolant for cooling the coolant to be used for cooling a conductor of a superconducting cable.SOLUTION: A cooling system for a superconducting cable at least comprises: a sub cooler 10 in which a first coolant 11 in a liquid state is stored and which cools a second coolant to be circulated in a superconducting cable A with the first coolant 11 in such a liquid state; a pump 20 which sucks the first coolant 12 in a gas state which is gasified in the sub cooler 10; and a cooling path 30 which is interposed between the sub cooler 10 and the pump 20 and in which a current lead D provided in a terminal connection part of the superconducting cable A is cooled with the first coolant 12 which is taken out of the sub cooler 10. Thus, heat intrusion from the current lead D in the terminal connection part can be suppressed and a heater 40 for preventing a failure of the pump 20 can be omitted or heating energy in the heater 40 can be saved.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a cooling system for a superconducting cable. [Background technology]

[0002] As a cooling means for the refrigerant used to cool the conductor of a superconducting cable, Patent Document 1 below discloses a subcooling system configured to store a portion of the refrigerant for cooling the conductor of the superconducting cable in a reserve tank, and to cool the refrigerant circulating through the superconducting cable with the refrigerant stored in the reserve tank (stored refrigerant). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-117026 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the subcooling system described in Patent Document 1, the refrigerant vaporized from the refrigerant stored in the reserve tank is simply liquefied again using a heat exchanger or the like and supplied to the reserve tank, or is discharged into the atmosphere.

[0005] Therefore, an object of the present invention is to expand the range of uses of refrigerants for cooling the conductors of superconducting cables. [Means for solving the problem]

[0006] The present invention, which has been made to solve the above-mentioned problems, is a cooling system for a superconducting cable, characterized by comprising at least a subcooler that stores a first refrigerant in a liquid state and uses this first refrigerant in a liquid state to cool a second refrigerant that is circulated within the superconducting cable, a pump that draws in the first refrigerant in a gaseous state that has evaporated within the subcooler, and a cooling path that is interposed between the subcooler and the pump and uses the first refrigerant taken out from the subcooler to cool current leads provided at termination connections of the superconducting cable. [Effects of the Invention]

[0007] According to the present invention, the refrigerant used to cool the conductor of the superconducting cable can also be used to cool the current leads connected to the superconducting cable, thereby contributing to improving the performance of the entire superconducting system. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram showing the overall configuration of a cooling system according to a first embodiment. [Figure 2] FIG. 10 is a schematic diagram showing the overall configuration of a cooling system according to a second embodiment. [Figure 3] FIG. 10 is a schematic diagram showing the overall configuration of a cooling system according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. [Example]

[0010] <1> Overall structure FIG. 1 shows an outline of the overall configuration of a cooling system according to a first embodiment of the present invention. The cooling system according to this embodiment is a system including a subcooling system for cooling a refrigerant for cooling a superconducting cable A in order to supply electric power in a superconducting state using the superconducting cable A. The cooling system according to this embodiment comprises a subcooler 10, a pump 20, a cooling path 30, a heater 40, a compressor 50 and a heat exchanger 60. Each part will be described in detail below.

[0011] <2> Subcooler The subcooler 10 is a member for cooling the refrigerant for cooling the superconducting cable A. In the present invention, the configuration of the subcooler 10 is not particularly limited. In this embodiment, a liquid refrigerant (a liquid first refrigerant 11) is contained inside the subcooler 10, and a pipe is arranged inside the subcooler 10 to carry the refrigerant (a second refrigerant C1 before cooling) used to cool the superconducting cable A. The second refrigerant C1 before cooling is taken out from one of the terminal connection parts B1 connected to both ends of the superconducting cable A, and returned to the other terminal connection part B2 via the subcooler 10, thereby making it possible for the second refrigerant cooled by the subcooler 10 to circulate within the superconducting cable A.

[0012] <2.1>First refrigerant / second refrigerant The first refrigerant is a refrigerant for cooling the second refrigerant in the subcooler 10 . The second refrigerant is a refrigerant for cooling the conductor in the superconducting cable A. In the present invention, the types of the first and second refrigerants are not particularly limited, but in this example, nitrogen is assumed.

[0013] <3> pump The pump 20 is a member for sucking and extracting the first refrigerant 12 in a gaseous state that has evaporated in the subcooler 10 from the subcooler 10 . In the present invention, the configuration of the pump 20 is not particularly limited. In this embodiment, a vacuum pump is used as the pump 20 .

[0014] <4> cooling path The cooling path 30 is a flow path for using the gaseous first refrigerant 12 extracted from the subcooler 10 to cool the current lead D provided at the terminal connection portion where the superconducting cable A is connected. It is possible that at least a part of the gaseous first refrigerant 12 extracted from the subcooler 10 may liquefy on its way through the cooling path 30. Therefore, in the present invention, there is no particular limitation as to whether the first refrigerant 12 used to cool the current leads D is in a gaseous state or a liquid state, and all modes are included. In this embodiment, of terminal connection parts B1 and B2 connected to both ends of a superconducting cable A, a cooling path 30 is installed so as to cool a current lead D provided at the other terminal connection part B2.

[0015] <4.1> Current leads In the present invention, the current lead D is a component provided at the terminal connection portion for connecting a superconducting cable, and is a component that constitutes a conductor for connecting and energizing a power source, which is the source of power supply, and various devices, which are the destinations of power supply. Current lead D is connected to a power cable at room temperature, and is therefore considered to be a part where a large amount of heat penetrates, which is one of the factors that maintain the superconducting state in a superconducting system. In the present invention, the shape and structure of the current lead D are not particularly limited. The number of current leads D for the terminal connection portion may be one or more.

[0016] <4.2> Cooling method for current leads In the present invention, the method of cooling the current leads D by the cooling paths 30 is not particularly limited. The cooling method for the current lead D using the cooling path 30 may be any of the following methods or a suitable combination of these methods. (1)Indirect cooling type This is a method of indirectly cooling the current lead D by wrapping a pipe constituting a cooling path 30 around a container such as a ceramic tube that houses the current lead D inside, which is in contact with an environment (such as the room temperature environment around the terminal connection) that is higher in temperature than the cryogenic environment required to maintain the superconducting state. (2)Direct cooling type This method involves forming a substantially closed space around the current lead D, which is in contact with an environment (such as the room temperature environment around the terminal connection) that is higher than the cryogenic environment required to maintain the superconducting state, and passing a gaseous first refrigerant 12 through this space via a cooling path 30 to directly cool the current lead D.

[0017] <5> Warmer The heater 40 is a member for heating the first refrigerant 12 in a gaseous state sucked by the pump 20 . In the present invention, the configuration of the heater 40 is not particularly limited. In this embodiment, a heater 40 is interposed between the pump 20 and the cooling path 30 . This is because the first refrigerant 12 in a gaseous state inside the subcooler 10 is at a low temperature, and if it is allowed to flow into the pump 20 as is, there is a risk that the pump 20 will break down.

[0018] <5.1> Omission of heater In the present invention, the addition of the heater 40 is not essential. For example, if the temperature of the first refrigerant 12 in a gaseous state immediately before flowing into the pump 20 has risen to a temperature that will not cause a breakdown of the pump 20 due to its use in cooling the current lead D, the heater 40 can be omitted.

[0019] <6> compressor The compressor is a component for compressing the first refrigerant 12 in a gaseous state. In the present invention, the configuration of the compressor 50 is not particularly limited. In this embodiment, the compressor 50 is interposed between the pump 20 and the heat exchanger 60, and the pressure of the first refrigerant 12 in a gaseous state is returned to normal pressure before being introduced into the heat exchanger 60. This is because the pressure of the gaseous first refrigerant 12 sucked by the pump 20 is increased to lower the melting point, thereby promoting liquefaction of the gaseous first refrigerant 12 in the heat exchanger 60.

[0020] <7> heat exchanger The heat exchanger 60 is a component for liquefying the gaseous first refrigerant 12 and returning it to the subcooler 10 . In the present invention, the type of heat exchanger 60 is not particularly limited, and any device may be used as long as it is capable of cooling and liquefying the first refrigerant 12 in a gaseous state pressurized by the compressor 50.

[0021] <8> summary As described above, the cooling system according to this embodiment provides at least the following advantageous effects. (1) Since heat intrusion from the current lead D can be suppressed at the terminal connection part, the cooling efficiency of the entire cooling system can be expected to improve. (2) By configuring the system so that the gaseous first refrigerant 12 drawn from the subcooler 10 is used to cool the current leads D and then returned to the subcooler 10, it is possible to omit the heater 40 used to prevent breakdown of the pump 20 or to reduce the heating energy required by the heater 40.

[0022] This makes it possible to provide a cooling system for superconducting cables with improved cooling efficiency compared to conventional systems, and ultimately to provide superconducting cable terminations with stable performance that contribute to a decarbonized society. This will contribute to Goal 7 of the Sustainable Development Goals (SDGs), "Ensure access to affordable, reliable, sustainable and modern energy for all" and Goal 9, "Build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation," which are international goals aimed at achieving a sustainable and better world by 2030 as set out in the 2030 Agenda for Sustainable Development adopted at the United Nations Summit in September 2015. [Example]

[0023] FIG. 2 shows an outline of the overall configuration of a cooling system according to a second embodiment. In the cooling system of this embodiment, a branch pipe 70 is newly provided between pump 20 and compressor 50 in the cooling system of embodiment 1, so that first refrigerant 12 in a gaseous state after being used to cool current leads D can be freely discharged into the atmosphere or supplied to utilization facilities installed in manufacturing plants, research institutes, medical facilities, various types of mobility, etc. that utilize the first refrigerant. For example, when liquid nitrogen is used as the liquid first refrigerant 11 stored in the subcooler 10, the gaseous first refrigerant 12 (nitrogen gas) after being used to cool the current lead D can be reused as a sealed gas to prevent food deterioration in a food factory. According to this embodiment, it is possible to obtain the effects obtained in the cooling system according to the first embodiment, and further expand the applications of the first refrigerant. [Example]

[0024] FIG. 3 shows an outline of the overall configuration of a cooling system according to a third embodiment. The cooling system of this embodiment is configured such that compressor 50 and heat exchanger 60 are excluded from the cooling system of embodiment 1, and the first refrigerant 12 in a gaseous state after being used to cool current lead D is discharged into the atmosphere or supplied to the utilization equipment described in embodiment 2. In this embodiment, the effects obtained in the cooling system according to the first embodiment (excluding the effect of using the first refrigerant 12 to cool the current lead D and then returning it to the subcooler 10) can be obtained, while the uses of the first refrigerant 12 can be further expanded. [Explanation of symbols]

[0025] 10: Subcooler 11: First refrigerant in liquid state 12: First refrigerant in gaseous state 20: Pump 30: Cooling path 40:Warmer 50: Compressor 60: Heat exchanger 70: Branch pipe A: Superconducting cable B1: One end connection B2: The other end connection C1: Second refrigerant before cooling C2: Second refrigerant after cooling D: Current lead

Claims

1. A cooling system for a superconducting cable, comprising: a subcooler containing a first refrigerant in a liquid state and cooling a second refrigerant circulated within the superconducting cable with the first refrigerant in the liquid state; a pump that draws the first refrigerant in a gaseous state that has evaporated in the subcooler; a cooling path interposed between the subcooler and the pump, for cooling a current lead provided at a terminal connection portion of a superconducting cable with the first refrigerant extracted from the subcooler; characterized by comprising at least Cooling system for superconducting cables.

2. a compressor that compresses the first refrigerant in a gaseous state that has passed through the cooling path; a heat exchanger that liquefies the first refrigerant in a gaseous state compressed by the compressor and supplies the liquefied first refrigerant to the subcooler; Further comprising:

2. The cooling system for a superconducting cable according to claim 1.

3. The compressor further includes a heater disposed between the cooling path and the compressor to heat the first refrigerant in a gaseous state.

3. The cooling system for a superconducting cable according to claim 2.

4. The system is characterized in that a part or all of the first refrigerant in a gaseous state that has passed through the cooling path is supplied to a utilization facility that utilizes the first refrigerant, such as a manufacturing factory, a research institute, a medical facility, or various types of mobility.

2. The cooling system for a superconducting cable according to claim 1.

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