Superconducting Cable System

Abstract

The present invention provides a superconducting cable system designed to facilitate long distance superconductivity, the cable system including at least one inner cryostat containing a supply of cryogenic fluid, and at least one superconductor extending longitudinally of the inner cryostat and in thermal communication with the cryogenic fluid, the inner cryostat including a liquid crystal polymer.

Description

[Technical field]

[0001] The present invention relates to a superconducting cable system that utilizes at least one liquid crystal polymer cryostat. [Background technology]

[0002] The current state of the art in high temperature superconductor (HTS) power cable design involves the use of metal alloy cryostats, typically corrugated tubing adapted from industrially relevant uses such as liquid nitrogen gas (LNG) transportation solutions, to host the HTS power cable, deliver the pressurized cryogenic fluid, and cool the HTS materials.

[0003] Metal alloys are not thermally efficient and are not electrical insulators. This creates challenges in the design and reliability of cryostat systems and HTS power cables. A conventional cross section of an HTS power cable system includes an inner corrugated tube concentrically disposed within an outer corrugated tube. The metal alloy cryostat is designed to mechanically resist external mechanical loads and support the HTS power cable and cryogenic fluid within the inner corrugated tube. Corrugated profile tubing is subject to deficiencies in the performance of the metal alloy, including its coefficient of thermal expansion (CTE), causing the metal alloy to shrink in both longitudinal and radial dimensions. These corrugations in the inner corrugated tube cause significant pressure loss in the flow of the cryogenic fluid, resulting in a shortened longitudinal length of the HTS power cable system until repressurization of the cryogenic fluid is required.

[0004] Due to metal alloy properties, HTS power cables must include a separate dielectric insulation, typically from polypropylene laminated paper (PPLP) with liquid nitrogen (LN2) or equivalent with a layer thickness proportional to the dielectric strength of PPLP&LN2 and the HTS power cable voltage. Alternatively, the dielectric may be added to the outside of the corrugated cryostat using a conventional insulation such as cross-linked polyethylene (XLPE). The need for HTS power cables to have a separate dielectric insulation layer presumes that, since HTS power cables have a larger outer diameter, in many embodiments the inner corrugated tube must have a larger diameter to host the HTS power cable and contain sufficient cryogenic fluid to achieve the target mass flow rate for cooling the HTS material.

[0005] In summary, the major design issues and inefficiencies associated with modern HTS power cable systems include: Limited or single functional layers within the cable system, e.g. separate dielectric insulation over the conductors and metal cryostats for containing vacuum and cryogenic fluids; Corrugated metal cryostats lead to heat ingress and turbulence in the liquid cryogenic fluid, resulting in more heat generation and higher accumulated pressure drop over shorter distances, requiring more pressurized points on the HTS power cable system, resulting in higher friction coefficient of the cryogenic fluid and heat generation; · Higher radiative heat intrusion due to the larger diameter of the cryostat required to host multilayer HTS conductors; -The rate of thermal contraction and expansion increases with temperature changes. · complex manufacturability and associated costs; Non-corrugated steel cryostats have reliability and associated mobilization issues, and are more complex to install.

[0006] There are currently no long-distance HTS power cables in operation. The longest is currently a project under development at 12 km, which uses the conventional HTS power cable arrangement described using a corrugated steel cryostat. Shorter HTS power cable runs can use extruded aluminum tubes or stainless steel inner cryostat smoothbore tubes, or lined corrugated cryostats. Smoothbore stainless steel cryostats are the most common technology for terrestrial particle accelerators or LNG transport pipes. These are typically installed with rolling or expansion devices to accommodate thermal contraction.

[0007] Alternatively, Invar (FeNi36) is a nickel-iron alloy known for its extremely low CTE, allowing for a smoothbore solution without having to accommodate thermal expansion upon cooling. Common metal alloys such as stainless steel and aluminum have thermal expansion / contraction coefficients that are too high, requiring multiple bellows-based expansion joints to compensate for the longitudinal contraction of the metal tubes when filled with cryogenic fluids. These joints reduce reliability by introducing failure points and thermal leak paths into the system.

[0008] The metal alloys and carbon fiber composites traditionally used are electrical and thermal conductors. Therefore, insulating layers are required which increase the overall size of the cryostat. Thermal-hydraulic performance and cost are adversely affected.

[0009] All smoothbore metal cryostats cannot be manufactured continuously and need to be welded into straight sections of about 12 meters. They cannot be wound into coils for transportation. This increases the cost of manufacturing, transporting and deploying systems such as these. Carbon fiber thermoset cryostats cannot be wound due to their high stiffness.

[0010] Corrugated metal cryostats introduce additional turbulence and friction with the liquid cryogenic fluid, which generates more heat and results in higher accumulated pressure drops over shorter distances, requiring more pressurized points on the HTS power cable system. Long-distance SCS with corrugated ICs is not technically feasible.

[0011] Carbon fiber thermoset composites, when subjected to cryogenic environments, are known to develop cracks within the material. These cracks could represent permeable leaks of cryogenic liquid into the vacuum chamber, disrupting SCS operations.

[0012] Thus, at present, existing technology makes long-range SCS deployments (i.e., 100 km long) economically and technically unfeasible.

[0013] SUMMARY OF THE PRESENT EMBODIMENT It is therefore an object of the present invention to overcome the above-mentioned deficiencies of the prior art by providing an improved superconducting cable system capable of operating over long distances without significant performance degradation. Summary of the Invention

[0014] According to a first aspect of the present invention, a superconducting cable system is provided, comprising at least one inner cryostat, a supply of cryogenic fluid into a lumen of the at least one inner cryostat, and at least one superconductor extending longitudinally of the at least one inner cryostat and in thermal communication with the cryogenic fluid, the at least one inner cryostat comprising a liquid crystal polymer.

[0015] Preferably, the liquid crystal polymer comprises a thermotropic liquid crystal polymer.

[0016] Preferably, the liquid crystal polymer comprises an aromatic ester, which comprises aromatic dicarboxyl repeat units, and / or aromatic hydroxycarboxyl repeat units, and / or repeat units derived from aromatic diols, aromatic amides and / or non-aromatic monomers.

[0017] Preferably, the liquid crystal polymer comprises at least one filler.

[0018] Preferably, the at least one filler is selected from zirconium tungstate, chopped glass fibers, chopped PTFE fibers, chopped carbon fibers, chopped liquid crystal polymer fibers, carbon nanofibers, aramid nanofibers, nanotubes, boron nitride and graphene nanoparticles.

[0019] Preferably, the one or more fillers comprise between 0.1% and 40% by volume of the liquid crystal polymer.

[0020] Preferably, the liquid crystal polymer has a viscosity of 10e -6 / C.

[0021] Preferably, the liquid crystal polymer has a viscosity of 1×10 when measured in nitrogen gas at room temperature. -12 cm 3 .cm / cm 2 3. It has a transmittance of less than 1 / s / bar.

[0022] Preferably, the liquid crystal polymer has a dielectric strength between 0 kV / mm and 40 kV / mm.

[0023] Preferably, the liquid crystal polymer has a failure strain at break between 1% and 20%.

[0024] Preferably, the liquid crystal polymer has a minimum use temperature between 4 and 90 degrees Kelvin.

[0025] Preferably, the liquid crystal polymer has a thermal conductivity of less than 0.5 W / mk.

[0026] Preferably, the liquid crystalline polymer has a yield strength of greater than 25 MPa.

[0027] Preferably, the liquid crystal polymer has a stiffness between 1 GPa and 100 GPa.

[0028] Preferably, the at least one superconductor is retained within the lumen of the at least one inner cryostat.

[0029] Preferably, the cable system includes a first inner cryostat and a second inner cryostat surrounding the first inner cryostat.

[0030] Preferably, the second inner cryostat comprises a liquid crystal polymer.

[0031] Preferably, the first inner cryostat and / or the second inner cryostat include a smooth bore.

[0032] Preferably, the cable system includes an outer cryostat that encapsulates at least one inner cryostat.

[0033] Preferably, the cable system includes a centralizer positioned between the outer cryostat and the at least one inner cryostat.

[0034] Preferably, the cable system includes one or more thermal and / or electrical insulating layers.

[0035] Preferably, one or more of the layers comprises a thermal insulator comprising one or more of an aerogel, a nanoporous insulator, a solid insulator, a layered composite insulator, a multi-layer insulator, an insulating blanket, and a vacuum.

[0036] Preferably, the superconductor comprises a multi-phase superconductor.

[0037] Preferably, the superconductor comprises a plurality of separate superconducting elements.

[0038] Preferably, the superconducting elements are arranged coaxially with and electrically insulated from at least adjacent superconducting elements.

[0039] Preferably, the superconducting elements are arranged in a circular array coaxial with the at least one inner cryostat.

[0040] Preferably, the cryogenic fluid comprises liquid hydrogen, liquid nitrogen, liquid helium and / or any other suitable cryogen.

[0041] According to a second aspect of the present invention, a cryogen conduit is provided that includes at least one inner cryostat and a supply of cryogenic fluid within a lumen of the at least one inner cryostat, the at least one inner cryostat including a liquid crystal polymer.

[0042] Preferably, the liquid crystal polymer comprises a thermotropic liquid crystal polymer.

[0043] Preferably, the liquid crystal polymer comprises an aromatic ester, which comprises aromatic dicarboxyl repeat units, and / or aromatic hydroxycarboxyl repeat units, and / or repeat units derived from aromatic diols, aromatic amides and / or non-aromatic monomers.

[0044] Preferably, the liquid crystal polymer has a viscosity of 10e -6 / C.

[0045] Preferably, the liquid crystal polymer has a viscosity of 1×10 when measured in nitrogen gas at room temperature. -12 cm 3 .cm / cm 2 3. It has a transmittance of less than 1 / s / bar.

[0046] Preferably, the liquid crystal polymer has a dielectric strength between 0 kV / mm and 40 kV / mm.

[0047] Preferably, the liquid crystal polymer has a failure strain at break between 1% and 20%.

[0048] Preferably, the liquid crystal polymer has a minimum use temperature between 4 and 90 degrees Kelvin.

[0049] Preferably, the liquid crystal polymer has a thermal conductivity of less than 0.5 W / mk.

[0050] Preferably, the liquid crystalline polymer has a yield strength of greater than 25 MPa.

[0051] Preferably, the liquid crystal polymer has a stiffness between 1 GPa and 100 GPa.

[0052] Preferably, the cryogen conduit includes a first inner cryostat and a second inner cryostat surrounding the first inner cryostat.

[0053] Preferably, the second inner cryostat comprises a liquid crystal polymer.

[0054] Preferably, the first inner cryostat and / or the second inner cryostat include a smooth bore.

[0055] The present invention will now be described with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0056] [Figure 1] 1 shows a perspective view of a superconducting cable system according to a first embodiment of the present invention. [Diagram 2] 2 shows a perspective view of a superconducting cable system according to a second embodiment of the present invention. [Diagram 3] 1 shows a perspective view of a superconducting cable system according to a third embodiment of the present invention. [Figure 4] FIG. 13 shows a perspective view of a superconducting cable system according to a fourth embodiment of the present invention. [Diagram 5] FIG. 13 shows a perspective view of a superconducting cable system according to a fifth embodiment of the present invention. [Figure 6] FIG. 13 shows a perspective view of a superconducting cable system according to a sixth embodiment of the present invention. [Figure 7] FIG. 13 shows a perspective view of a superconducting cable system according to a seventh embodiment of the present invention. [Figure 8] 1 shows a perspective view of a cryogen conduit according to an embodiment of the present invention. [Figure 9] 1 illustrates a perspective view of an alternative embodiment of a cryogen conduit in accordance with the present invention; [Figure 10] 13 shows a perspective view of a further alternative embodiment of a cryogen conduit according to the present invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0057] Referring now to Figure 1 of the accompanying drawings, there is shown a superconducting cable system, generally designated 10, providing long distance superconducting capability for use while avoiding or significantly reducing problems associated with applications such as those of superconducting technology as detailed above.

[0058] The cable system 10 includes a superconductor 12, which may be of any known suitable material, and may include a single component or multiple components, such as an array or arrangement of superconducting ribbons. The superconductors 12 may be configured to conduct single or multi-pole direct current (DC) or single or multi-phase alternating current (AC), and may be physically arranged on concentric axes (e.g., a tri-axial arrangement for a three-phase system) or adjacent axes (a tri-ad arrangement for a three-phase system). In the case of AC systems, so-called high temperature superconductors (HTS) or other conductive materials or neutral conductors may be added, and in the case of AC or DC systems, one or more forms of magnetic shielding layers may be added, as illustrated in the embodiments described later in this specification.

[0059] The superconductor 12 extends longitudinally within a central lumen of an internal cylindrical cryostat 14 which, in use, is at least partially filled with a cryogenic fluid (cryoagent) 16, e.g., liquid hydrogen, nitrogen, helium, although it is envisioned that any other liquid, gaseous or multi-phase cryogen, or combination of cryogens may be utilized. The superconductor 12 is thus in thermal communication with the cryogen 16 to maintain the required cryogenic temperature required for superconductivity. In the illustrated embodiment, the superconductor 12 is in direct contact with the cryogen 16 to establish thermal communication, although it is also possible that indirect contact between the superconductor and the cryogen may provide the required thermal communication, as shown in later embodiments. The operating temperature of the cryogen 16 may vary depending on the operating requirements and / or conditions of the cable system 10, or additional or alternative parameters; for example, if liquid nitrogen is used as the cryogen 16, the operating temperature may be in the range of 67° K to 77° K at operating pressures between 0 bar and 25 bar. However, it should be understood that these are example parameters and that lower or higher temperatures and / or pressures may be used. It should also be understood that the superconductor 12 may be, for example, eccentrically disposed, or extend helically, or the like, yet still extend longitudinally relative to the entire length of the cable system 10.

[0060] The cable system 10 further includes a thermal insulation layer 18 surrounding the inner cryostat 14, and an outer cryostat 20 surrounding and encapsulating the aforementioned components. A vacuum annulus 22 is defined between the inner cryostat 14 and the outer cryostat 20 to provide additional thermal insulation. A vacuum is drawn within the vacuum annulus 22 to reduce thermal convection within the cable system 10, and in the illustrated embodiment may be in the range of between 1-1000 Pa, although alternative vacuum levels may be used, e.g., hard or soft vacuum. To physically maintain the correct position of the inner cryostat 14 concentrically or otherwise with the outer cryostat 20, a centralizing element 24 may be provided within the vacuum annulus 22, preferably to ensure a uniform vacuum annulus 22. The outer cryostat 20 provides environmental protection for the cable system 10, reducing heat loss, avoiding the penetration of contaminants such as particulate matter, and providing structural containment against the surrounding environment, which may be, for example, a body of water that exerts significant pressure on the outer cryostat 20. The outer cryostat 20 is preferably a multi-layered structure including a smooth bore steel pipe or a corrugated steel jacket for environmental protection. Alternatively, the outer cryostat 20 may include a polymeric pipe with one or more optional electrical insulation layers (not shown) and / or a permeation barrier layer, which may be, for example, metallic. The centralizing element 24 may be of any suitable shape, configuration, and material, and in the illustrated embodiment is helical in shape to extend around the periphery of the annulus 22. Finally, the cable system 10 may be provided with an external ballast 26 to ensure that the cable system 10 is deployed underwater, such as in a subsea application, and that the cable system 10 sinks to the ocean floor.

[0061] The primary function of the inner cryostat 14 is to contain the cryogen 16 and facilitate thermal communication between the superconductor 12 and the cryogen 16, which in the embodiment of Figure 1 is accomplished by direct contact with the cryogen 16 as the superconductor 12 is disposed within the lumen of the cryostat 14. The cryostat 14 must also provide structural integrity to the pressurized cryogen 16, act as a dielectric insulator for the cable system 10 from the superconductor 12, act as a thermal insulator to minimize heat ingress from the outside, and act as a permeable barrier between the cryogen 18 and the vacuum annulus 22.

[0062] Additionally, to facilitate ease of design and transportation while minimizing the cost of the cable system 10, the inner cryostat 14 should have a low coefficient of thermal expansion (CTE) so that it can be wound on a reel and manufactured in long lengths, e.g., 1 km or more, and preferably 10 km or more, avoiding or reducing the use of conventional bellows-based expansion joints.

[0063] To achieve this performance and manufacturing characteristics, the inner cryostat 14 is constructed from liquid crystal polymers (LCPs). LCPs are quite different from conventional polymers. They have properties including low melt viscosity, fast cycle times for molding, very low mold shrinkage, excellent mechanical properties, solvent resistance, excellent barrier properties, low water absorption, low coefficient of thermal expansion, excellent thermal stability, low flammability, etc. Thus, numerous applications have been explored, such as high strength and high modulus fibers, precision molded miniature components, and films that exhibit excellent barrier properties.

[0064] Compared to monomeric liquid crystals, polymeric liquid crystals can exhibit similar behavior and can be classified into thermotropic and lyotropic LCPs. Several well-known classes of polymers, including polyesters, polyethers, and polyamides, can exhibit liquid crystal phases. According to the different mesogen positions in the polymer, LCPs can be defined as main chain, side chain, and hybrid LCPs, with more complex structures possible. Aromatic rings are the most common units used in LCPs.

[0065] Main-chain thermotropic LCPs are the most important group of LCPs. They consist of mesogenic groups incorporated into the polymer backbone and, when prepared without flexible spacers, are usually known as fully aromatic thermotropic LCPs. They form an LC phase when melted, which allows for improved processing due to their relatively low viscosity in the molten state.

[0066] Polyesters are an important group within this class of polymers. Particularly suitable LCPs have a basic structure comprising one or more aromatic ester repeat units, which may have a general molecular structure comprising a substituted or unsubstituted 6-membered aryl group, or alternatively a substituted or unsubstituted 6-membered aryl group fused to a substituted or unsubstituted 5-membered or 6-membered aryl group, or a substituted or unsubstituted 6-membered aryl group bonded to a substituted or unsubstituted 5-membered or 6-membered aryl group. The molecular structure may have one or more side groups. Exemplary aromatic ester repeat units are aromatic dicarboxyl repeat units, aromatic hydroxycarboxyl repeat units, and combinations thereof. The aromatic units may be in an amount of 60 mol.% to 99.9 mol.%.

[0067] The aromatic dicarboxyl repeating unit can be derived from aromatic dicarboxylic acid.Suitable aromatic dicarboxylic acids are terephthalic acid, diphenyl ether-4,4'-dicarboxylic acid, bis(4-carboxyphenyl)ether, bis(4-carboxyphenyl)butane, bis(4-carboxyphenyl)ethane, bis(3-carboxyphenyl)ether, bis(3-carboxyphenyl)ethaneisophthalic acid, 2,6-naphthalenedicarboxylic acid, 1,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 4,4'-dicarboxybiphenyl.

[0068] Aromatic hydroxycarboxyl repeating units can be derived from aromatic hydroxycarboxylic acids, such as 4-hydroxybenzoic acid, 4-hydroxy-4'-biphenylcarboxylic acid, 2-hydroxy-6-naphthoic acid, 2-hydroxy-5-naphthoic acid, 3-hydroxy-2-naphthoic acid, 2-hydroxy-3-naphthoic acid, 4'-hydroxyphenyl-4-benzoic acid, 3'-hydroxyphenyl-4-benzoic acid, 4'-hydroxyphenyl-3-benzoic acid and alkyl, alkoxy, aryl and halogen substituents.Exemplary aromatic hydroxycarboxylic acids are 4-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid.

[0069] Repeat units may also be derived from aromatic diols and alkyl, alkoxy, aryl, and halogen substituents. Exemplary aromatic diols are 4,4'-biphenol and hydroquinone. Repeat units such as those derived from aromatic amides or aromatic amines may also be used. Any repeat unit may be variously substituted with alkyl, alkoxy, aryl, and halogen substituents.

[0070] The LCP may contain numerous other monomeric repeat units such as dicarboxylic acids, aliphatic or cycloaliphatic hydroxycarboxylic acids, amides, amines, or diols.

[0071] Examples of suitable commercially available LCPs are Vectra® from Celanese Corporation, Laperos® from Polyplastics Co. Ltd., Xydar® from Solvay, Sumikausper™ from Sumitomo Chemical, Siveras™ from Toray Industries Inc., Ueno LCP® from Ueno Fine Chemicals Industry, Ltd., and Vicryst® from Kingfa. Optional fillers may be added to the LCP to modify the mechanical, chemical, thermal, and / or dielectric properties of the LCP. Fillers such as these include, for example, zirconium tungstate (ZrW 2 O 8 ), glass and / or polytetrafluoroethylene (PTFE) and / or short carbon fibers, boron nitride and graphene nanoplatelets, and the fillers may constitute up to 20% by volume of the final LCP used to manufacture the inner cryostat 14.

[0072] The inner cryostat 14 is typically manufactured via an extrusion process into a smooth bore tube using a selected LCP and optional filler compounds to meet the requirements of the inner cryostat 14 and improve the techno-economic feasibility of long distance HTS power cables. Providing a smooth bore defining the inner lumen minimizes drag on the cryogen 16, thereby increasing the operating length of the cable system 10. Additional manufacturing processes for the inner cryostat 14 include, but are not limited to, pultrusion, tape laying, tape or filament winding, fiber placement, waving, braiding, injection molding, thermoforming, compression molding, roll forming, and melt kneading.

[0073] Intermediate or inner or outer layers (not shown), typically metallic or other composite layers, can be preferentially co-extruded with the inner cryostat 14 to improve its technical performance. Other manufacturing methods to include these layers with the inner cryostat 14 are, but are not limited to, spraying, adhesive bonding, welding, thermal bonding, tape laying, wrapping.

[0074] The use of LCP for the inner cryostat 14 allows for the extrusion of an inner smooth bore with controllable, preferential / neutral CTE in the longitudinal and radial directions. This avoids the requirement for a thermal expansion device (not shown) and reduces system pressure losses compared to conventional corrugated cryostats. LCP has low thermal conductivity, high dielectric strength and low permeability, facilitating a reduction in the number of insulation layers and overall size reduction of the cryostat 14, and thus the optional entire cable system 10, compared to state-of-the-art alternatives.

[0075] LCPs are preferentially manufactured into smoothbore tubing by long or continuous extrusion, an inexpensive manufacturing process, and their thermoplastic composition is tailored to have a combination of properties that allow the LCP to be wound on a reel for storage and transport, thereby minimizing costs.

[0076] An example, but non-limiting, thermoplastic compound of the LCP is engineered with fillers to have a high failure strain (>3.5%), strength of 200 MPa, and stiffness of 10 GPa at break. This combination of properties allows an inner cryostat 14 formed from this LCP to be wound on a reel for storage and transport with a minimum bend radius (MBR) of 0.5 to 9 m depending on the diameter of the inner cryostat 14.

[0077] In general, the LCP, including the optional modifying filler, is selected to impart the following properties to the inner cryostat 14: [Table 1]

[0078] 2, a second embodiment of a superconducting cable system in accordance with the present invention is shown and generally designated 110. In this second embodiment, like components are given like reference numerals and perform like functions unless otherwise noted.

[0079] The cable system 110 includes a superconductor 112 consisting of an inner superconducting element 112a, a first coaxial superconducting element 112b surrounding the inner element 112a and separated therefrom by an insulating layer 128, and a second coaxial superconducting element 112c surrounding the first coaxial superconducting element 112b and separated therefrom by an insulating layer 128. This arrangement is selected to conduct three-phase AC current. Of course, it will be understood that unipolar or biaxial bipolar DC conductors (not shown) can be used as an alternative. The superconductor 112 is coaxially disposed within the lumen of an inner cryostat 114 comprising a liquid crystal polymer as described hereinabove, which contains a cryogen 116 such that the superconductor 112 within the cryogen is encapsulated to establish thermal communication therebetween. A thermal insulation layer 118 surrounds the inner cryostat 114 and may be a layer of any suitable form including, for example, one or more of an aerogel, a nanoporous insulator, a layered composite insulator, a multi-layer insulator, or an insulating blanket.

[0080] The outer cryostat 120 surrounds the insulated inner cryostat 114 by a vacuum annulus 122, which is defined between the inner cryostat 114 and the outer cryostat 120 and provides additional thermal insulation. To physically maintain the precise location of the inner cryostat 114 concentrically or otherwise with the outer cryostat 120, centralizing elements 124 may be provided within the vacuum annulus 122 to ensure a uniform vacuum annulus area.

[0081] 3 illustrates a third embodiment of a superconducting cable system in accordance with the present invention, generally designated 210. In this third embodiment, like components are given like reference numerals and perform like functions unless otherwise indicated.

[0082] The cable system 210 includes a superconductor 212 in a three-core, three-axis configuration including a first superconducting element 212a, a second superconducting element 212b, and a coaxial third superconducting element 212c arranged in a circular array to facilitate three-phase AC. The superconductor 212 is disposed longitudinally within the lumen of an inner cryostat 214 that includes a liquid crystal polymer as described hereinabove, which contains a cryogen 216 that surrounds the superconductor 212 and establishes thermal communication therebetween. A thermal insulation layer 218 surrounds the inner cryostat 214 and may be a layer of any suitable form as described hereinabove.

[0083] The outer cryostat 220 surrounds the insulated inner cryostat 214 by a vacuum annulus 222 defining a vacuum annulus therebetween, within which a centralizing element 224 may be provided.

[0084] 4 illustrates a fourth embodiment of a superconducting cable system in accordance with the present invention, generally designated 310. In this fourth embodiment, like components are given like reference numerals and perform like functions unless otherwise indicated.

[0085] The cable system 310 includes a superconductor 312 in tubular form that is positioned longitudinally around and in thermal communication with an exterior surface of a first inner cryostat 314, the inner cryostat 314 comprising a liquid crystal polymer as previously described herein. The inner cryostat 314 contains a cryogen 316 that is in thermal communication with the superconductor 312 through the inner cryostat 314, which contains the pressurized cryogen 316 and provides structural integrity that acts as a permeability barrier.

[0086] The cable system 310 further includes a second inner cryostat 330, which surrounds the first inner cryostat 314 and again includes a liquid crystal polymer of suitable composition. However, the second inner cryostat 330 may be formed from any suitable alternative material, for example, where the second inner cryostat 330 is not subject to internal pressurization, and internal pressurization may occur solely within the first inner cryostat 314. The second inner cryostat 330 may have a design and dimensions suitable for lower structural and mechanical requirements, and the insulation may not provide sufficient dielectric strength, but merely provide light mechanical protection for the superconductor. Thus, an additional electrical and / or mechanical layer 328 may be provided between the superconductor 312 and the second inner cryostat 330.

[0087] A thermal insulation layer 318 outwardly surrounds the second inner cryostat 330 and may be of any suitable form as previously described herein. The outer cryostat 320 surrounds the insulated inner cryostats 314 and 330 by a vacuum annulus 322 defining therebetween, within which a centralizing element 324 may be provided. An optional ballast 326 may be provided, preferably around the exterior surface of the outer cryostat 320.

[0088] 5 illustrates a fifth embodiment of a superconducting cable system in accordance with the present invention, generally designated 410. In this fifth embodiment, like components are given like reference numerals 328 and perform like functions unless otherwise stated.

[0089] 4, but includes a three-phase coaxial superconductor 412 in tubular form positioned longitudinally around and in thermal communication with an outer surface of a first inner cryostat 414, the inner cryostat 414 comprising a liquid crystal polymer as previously described herein. The superconductor 412 consists of a tubular inner superconducting element 412a, a first tubular coaxial superconducting element 412b surrounding the inner element 412a and separated therefrom by an insulating layer 428, and a second tubular coaxial superconducting element 412c surrounding the first coaxial superconducting element 412b and separated therefrom by a further insulating layer 428. This arrangement is selected to conduct three-phase AC current.

[0090] An inner cryostat 414 contains a cryogen 416, which is in thermal communication with the superconductor 412 via the inner cryostat 414. The cable system 410 further includes a second inner cryostat 430, which surrounds the first inner cryostat 314 and again comprises a liquid crystal polymer or other suitable material of suitable composition. A thermal insulation layer 418 surrounds the second inner cryostat 430 and may be of any suitable form. An outer cryostat 420 surrounds the insulated inner cryostats 414 and 430 by a vacuum annulus 422 defining a vacuum annulus therebetween, and within which a centralizing element 424 may be provided.

[0091] 6 illustrates a sixth embodiment of a superconducting cable system in accordance with the present invention, generally designated 510. In this sixth embodiment, like components are given like reference numerals and perform like functions unless otherwise indicated.

[0092] The cable system 510 includes a single-phase superconductor 512 that is positioned longitudinally around and in thermal communication with an exterior surface of a first inner cryostat 514, the inner cryostat 514 including a liquid crystal polymer as previously described herein. Of course, the single-phase superconductor 512 may be replaced with a multi-phase superconductor in various previous embodiments as previously described herein. The inner cryostat 514 contains a cryogen 516, which is in thermal communication with the superconductor 512 via the inner cryostat 514.

[0093] The cable system 510 further includes a second inner cryostat 530 that surrounds the first inner cryostat 514 and again includes a liquid crystal polymer of suitable composition, or other material depending on the operational functionality of the second inner cryostat 530. The second inner cryostat 530 defines a second lumen that contains a second supply of cryogen 516 to provide improved thermal performance. The second supply may include a different cryogen 516 than that contained within the first inner cryostat 514. An electrical and / or mechanical layer 528 may be provided between the superconductor 512 and the second inner cryostat 530.

[0094] A thermal insulation layer 518 surrounds a second inner cryostat 530, and an outer cryostat 520 surrounds the insulated inner cryostats 514 and 530 by a vacuum annulus 522 defining a vacuum annulus therebetween and incorporating a centralizing element 524.

[0095] 7 illustrates a seventh embodiment of a superconducting cable system according to the present invention, generally designated 610. In this seventh embodiment, like components are given like reference numerals and perform like functions unless otherwise indicated.

[0096] The cable system 610 includes a single-phase superconductor 612 of any suitable form that extends longitudinally, preferably coaxially, within the lumen of a first inner cryostat 614 filled with a cryogen 616. As such, the superconductor 612 is in direct thermal communication with the cryogen 616 to maintain the necessary cryogenic temperatures required for superconductivity. Of course, the single-phase superconductor 612 may be replaced with a multi-phase superconductor as previously described herein.

[0097] The cable system 610 further includes a second inner cryostat 630 that surrounds the first inner cryostat 614 and again comprises a liquid crystal polymer of suitable composition. The second inner cryostat 630 defines a second lumen that contains a second supply of cryogen 616 to provide improved thermal performance, which may be the same as or different from the cryogen 616 contained within the first inner cryostat 614 and may be maintained at a different temperature. A thermal insulation layer 618 surrounds the second inner cryostat 630 and an outer cryostat 620 surrounds the insulated inner cryostats 614 and 630 by a vacuum annulus 622 that defines a vacuum annulus therebetween and incorporates a centralizing element 624.

[0098] 8 illustrates an embodiment of a cryogen conduit, generally designated 710, in accordance with an additional aspect of the present invention, as previously described herein, but which is devoid of any superconductor and utilizes the general design and material properties of the superconducting cable systems of the present invention for the primary or combined purpose of transporting cryogenic fluid(s), such as, but not limited to, liquid nitrogen, liquid hydrogen, liquid helium, etc. This transport may include one or more supply paths or loops, and optionally, return paths or loops, such as those described later herein with reference to the embodiment of FIG. 9. Like components are given like reference numbers and perform like functions unless otherwise noted.

[0099] Cryogen conduit 710 includes an inner cryostat 714 filled with cryogen 716, the inner cryostat 714 comprising a liquid crystal polymer as previously described herein. A thermal insulation layer 718 surrounds the inner cryostat 714, and an outer cryostat 720 surrounds the insulated inner cryostat 714 by a vacuum annulus 722 defining therebetween a vacuum annulus and incorporating a centralizing element 724.

[0100] 9 illustrates a second embodiment of a cryogen conduit in accordance with the present invention, generally designated 810. In this embodiment, like components are given like reference numerals and perform like functions unless otherwise noted.

[0101] The cryogen conduit 810 includes a first inner cryostat 814, which includes a liquid crystal polymer as previously described herein, and contains a cryogen 816. The cryogen conduit 810 further includes a second inner cryostat 830, which surrounds the first inner cryostat 814 and again includes a liquid crystal polymer of suitable composition. The second inner cryostat 830 defines a second lumen that contains a second supply of cryogen 816, which acts as an initial cooling layer, thus providing improved thermal performance. The second supply may include a different cryogen 816 than that contained within the first inner cryostat 814. Alternatively, the second inner cryostat 830 may define a cryogen return path. A thermal insulation layer 818 surrounds a second inner cryostat 830, and an outer cryostat 820 surrounds the insulated inner cryostats 814 and 830 by a vacuum annulus 822 defining a vacuum annulus therebetween and incorporating a centralizing element 824.

[0102] 10 illustrates an alternative embodiment of a cryogen conduit in accordance with the present invention, generally designated 910. In this embodiment, like components are given like reference numbers and perform like functions unless otherwise noted.

[0103] Cryogen conduit 910 includes an inner cryostat 914, which includes a liquid crystal polymer as previously described herein, and contains a cryogen 916. The inner cryostat may be provided with one or more insulating layers (not shown) as previously described herein, and is intended for use in transporting liquid cryogen.

[0104] It is also envisioned that the superconducting cable system of the present invention may be used in a combined capacity to provide both superconductivity and / or transport of liquid cryogen through one or more of the internal cryostats, as illustrated in the embodiment of Figures 1-7. Such transport may include a cryogen supply path defined by one internal cryostat and a cryogen return path defined by another internal cryostat, or two separate cryogen supply paths for separate cryogens. This function may occur while the cable system is operational and transmitting superconducting electricity, or while the superconducting function is inactive and therefore only transporting one or more cryogens. It should thus be understood that the materials, operating parameters, and functions described above with respect to the superconducting cable system may be embodied in the cryogen conduit embodiment of the present invention illustrated in Figures 8-10.

[0105] Thus, the use of at least one internal cryostat formed from a liquid crystal polymer within a superconducting cable system or cryogen conduit facilitates the realization of long distance superconducting and cryogenic fluid transportation with optimal structural characteristics for the application, as well as a cheaper life cycle than current potential alternatives.

Claims

1. 1. A superconducting cable system comprising: at least one internal cryostat; a supply of cryogenic fluid into a lumen of the at least one internal cryostat; and at least one superconductor extending longitudinally of the at least one internal cryostat and in thermal communication with the cryogenic fluid, the at least one internal cryostat comprising a liquid crystal polymer.

2. The superconducting cable system of claim 1 , wherein the liquid crystal polymer comprises a thermotropic liquid crystal polymer.

3. 3. The superconducting cable system according to claim 1, wherein the liquid crystal polymer comprises an aromatic ester, and the aromatic ester comprises an aromatic dicarboxyl repeating unit, and / or an aromatic hydroxycarboxyl repeating unit, and / or a repeating unit derived from aromatic diols, aromatic amides and / or non-aromatic monomers.

4. The superconducting cable system of claim 1 , wherein the liquid crystal polymer includes at least one filler.

5. 10. The superconducting cable system of claim 1, wherein the at least one filler is selected from zirconium tungstate, chopped glass fibers, chopped PTFE fibers, chopped carbon fibers, chopped liquid crystal polymer fibers, carbon nanofibers, aramid nanofibers, nanotubes, boron nitride, and graphene nanoparticles.

6. 6. The superconducting cable system according to claim 5, wherein the one or more fillers constitute 0.1 to 40% by volume of the liquid crystal polymer.

7. The liquid crystal polymer is 10e －６ 2. The superconducting cable system of claim 1, wherein the superconducting cable system has a thermal expansion coefficient of less than 1 / C.

8. The liquid crystal polymer is 1×10 －１２ cm ３ . cm / cm ２ 10. The superconducting cable system of claim 1, having a permeability of less than 1000 psi / s / bar.

9. 2. The superconducting cable system according to claim 1, wherein the liquid crystal polymer has a dielectric strength between 0 kV / mm and 40 kV / mm.

10. 10. The superconducting cable system of claim 1, wherein the liquid crystal polymer has a failure strain at break of between 1% and 20%.

11. 2. The superconducting cable system of claim 1, wherein the liquid crystal polymer has a minimum use temperature between 4 and 90 degrees Kelvin.

12. 10. The superconducting cable system of claim 1, wherein the liquid crystal polymer has a thermal conductivity of less than 0.5 W / mK.

13. The superconducting cable system of claim 1 , wherein the liquid crystal polymer has a yield strength greater than 25 MPa.

14. 2. The superconducting cable system according to claim 1, wherein the liquid crystal polymer has a stiffness between 1 and 100 GPa.

15. The superconducting cable system of claim 1 , wherein said at least one superconductor is retained within a lumen of said at least one inner cryostat.

16. 10. The superconducting cable system of claim 1, comprising a first inner cryostat and a second inner cryostat surrounding said first inner cryostat.

17. The superconducting cable system of claim 1 , wherein the second internal cryostat comprises a liquid crystal polymer.

18. The superconducting cable system according to claim 1 , wherein the first inner cryostat and / or the second inner cryostat comprises a smooth bore.

19. The superconducting cable system of claim 1 including an outer cryostat enclosing said at least one inner cryostat.

20. A cryogen conduit including at least one inner cryostat, a supply of cryogenic fluid within a lumen of said at least one inner cryostat, said at least one inner cryostat comprising a liquid crystal polymer.

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