Cooling gas tanks for heat shields in superconducting machines

Abstract

Provides gas tank cooling for heat shields in superconducting machines. The generator includes a non-rotatable component supporting a field winding assembly and a rotatable component oriented to rotate relative to the non-rotatable component during operation of the generator. The generator further includes an armature winding assembly fixedly coupled to the rotatable component for rotation therewith during operation of the generator. The armature winding assembly includes a plurality of conductive coils. The generator further includes a heat shield surrounding the field winding assembly fixedly coupled to the stationary component, a cryocooler in thermal contact with the heat shield, and a gas tank adjacent to and in thermal contact with the heat shield, the gas tank containing a cooling gas configured to circulate therethrough to provide uniform cooling to the heat shield.

Description

[Technical Field]

[0001] TECHNICAL FIELD This disclosure relates generally to superconducting machines, and more particularly to a cooling system for cooling heat shields of superconducting machines. [Background technology]

[0002] Wind turbines are gaining attention as an environmentally safe and relatively inexpensive alternative energy source. A wind turbine typically includes multiple rotor blades coupled to the turbine's main shaft via a rotor hub. The rotor hub is positioned on a tubular tower or base. Utility-grade wind turbines (i.e., wind turbines designed to supply power to the utility grid) can have large rotors (e.g., greater than 100 meters in diameter). The rotor blades convert wind energy into rotational torque or force, which drives a generator rotatably coupled to the rotor.

[0003] Low-reactance machines (e.g., superconducting generators) are being considered for use in wind turbine installations, particularly offshore installations. These machines use a superconducting field winding and armature coil assembly, a cooling system, and nonmagnetic teeth positioned between the armature coils. In certain designs, superconducting generators differ from the configuration of conventional machines (e.g., conventional non-superconducting generators) in that they include an armature winding assembly that rotates within a superconducting field assembly, which in turn includes a cryostat with superconducting field coils inside the cryostat.

[0004] Additionally, superconducting machines typically include cryogenic cooling systems for cooling their various components, and the art is therefore continually seeking new and improved cooling systems for superconducting generators. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2021 / 006881 Summary of the Invention

[0006] Aspects and advantages of the present invention will be set forth in part in the description that follows, or will be obvious from the description, or may be learned by practice of the present invention.

[0007] In one aspect, the present disclosure is directed to a generator including a non-rotatable component supporting a field winding assembly and a rotatable component oriented to rotate relative to the non-rotatable component during operation of the generator. The generator further includes an armature winding assembly fixedly coupled to the rotatable component so as to rotate therewith during operation of the generator. The armature winding assembly includes a plurality of electrically conductive coils. The generator further includes a heat shield surrounding the field winding assembly fixedly coupled to the stationary component, a cryocooler in thermal contact with the heat shield, and a gas tank adjacent to and in thermal contact with the heat shield, the gas tank containing a cooling gas configured to circulate therethrough to provide uniform cooling to the heat shield.

[0008] In another aspect, the present disclosure is directed to a cooling system for a superconducting generator. The cooling system includes a heat shield for surrounding a field winding assembly fixedly coupled to a stationary component of the superconducting generator. The stationary component is oriented relative to the rotatable component during operation of the superconducting generator. The cooling system further includes a cryocooler in thermal contact with an outer surface of the heat shield via a bus bar. The cooling system further includes a gas tank in thermal contact with the heat shield, the gas tank including a toroidal shape and disposed on an inner surface radially inward of the heat shield, the gas tank containing a cooling gas configured to circulate therethrough to provide uniform cooling to the heat shield.

[0009] These and other features, aspects, and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. [Brief explanation of the drawings]

[0010] A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the following specification, which makes reference to the accompanying drawings. [Figure 1] 1 is a perspective view of an embodiment of a wind turbine having power generation according to the present disclosure; FIG. [Figure 2] 1 is a perspective interior view of an embodiment of a nacelle of a wind turbine having a superconducting generator according to the present disclosure. [Figure 3] 1 is a side view of a generator according to an aspect of the present invention; [Figure 4] 1 is a simplified schematic diagram of a superconducting generator of conventional construction, particularly showing the cooling system disposed with the generator's thermal shield; [Figure 5] FIG. 1 is a simplified schematic diagram of one embodiment of a cooling system for a heat shield of a superconducting generator according to the present disclosure, particularly showing the toroidal gas tank of the cooling system positioned with the heat shield of the generator. [Figure 6] FIG. 1 is a perspective view of one embodiment of a toroidal gas tank of a cooling system for a heat shield of a superconducting generator according to the present disclosure. [Figure 7] FIG. 1 is a perspective view of one embodiment of a toroidal gas tank of a cooling system for a heat shield of a superconducting generator according to the present disclosure. [Figure 8] FIG. 1 is a perspective view of one embodiment of a fixture assembly for a toroidal gas tank of a cooling system for a heat shield of a superconducting generator according to the present disclosure. [Figure 9] FIG. 10 is a simplified schematic diagram of yet another embodiment of a cooling system for a heat shield of a superconducting generator according to the present disclosure, particularly showing the toroidal gas tank of the cooling system positioned with the heat shield of the generator such that cooling gas circulates symmetrically in the four quadrants of the gas tank. [Figure 10] FIG. 10 is a simplified schematic diagram of yet another embodiment of a cooling system for a heat shield of a superconducting generator according to the present disclosure, particularly showing the toroidal gas tank of the cooling system positioned with the heat shield of the generator such that cooling gas circulates within the gas tank in a single loop. [Figure 11] FIG. 1 is a simplified schematic diagram of another embodiment of a cooling system for a heat shield of a superconducting generator according to the present disclosure, particularly showing the toroidal gas tank of the cooling system positioned with the heat shield of the generator such that cooling gas circulates within the gas tank in a single loop. [Figure 12] FIG. 1 is an interior perspective view of another embodiment of a cooling system for a heat shield of a superconducting generator according to the present disclosure, particularly showing a toroidal gas tank of the cooling system integrated with the heat shield of the generator. [Figure 13] FIG. 1 is a detailed internal view of a toroidal gas tank of a cooling system for a heat shield of a superconducting generator according to the present disclosure, particularly showing the toroidal gas tank of the cooling system integrated with the heat shield of the generator. [Figure 14] FIG. 2 is a partial perspective view of an embodiment of a toroidal gas tank of a cooling system for a heat shield of a superconducting generator according to the present disclosure. [Figure 15] FIG. 15 is a partial detailed view of the toroidal gas tank of FIG. 14. [Figure 16] 16A to 16D are diagrams showing examples of cross-sectional shapes of a toroidal gas tank of a cooling system for a heat shield of a superconducting generator according to the present disclosure. [Figure 17] 1 is a cross-sectional view of one embodiment of a toroidal gas tank of a cooling system for a heat shield of a superconducting generator according to the present disclosure, particularly showing the toroidal gas tank integrated into the end of the heat shield of the generator. [Figure 18] 1 is a cross-sectional view of another embodiment of a toroidal gas tank of a cooling system for a heat shield of a superconducting generator according to the present disclosure, particularly showing the toroidal gas tank welded to the inner surface of the heat shield.

[0011] Repeat use of reference characters in the present specification and drawings is intended to represent same or analogous features or elements of the invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] Reference will now be made in detail to embodiments of the present invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. Indeed, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For example, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention cover such modifications and variations as come within the scope of the appended claims and their equivalents.

[0013] Terms such as "coupled," "fixed," and "attached" refer to both direct coupling, fixing, or attachment, as well as indirect coupling, fixing, or attachment through one or more intermediate components or features, unless otherwise specified herein.

[0014] Conventional heat shields for superconducting generators have large temperature differences around the periphery of the shield, which reduces the efficiency of blocking radiation heat to the cold mass that the shield is intended to protect. This is because the cooling of the heat shield occurs at the top of the shield, while thermal energy (radiation and conduction) penetrates from the periphery of the shield.

[0015] Accordingly, the present disclosure is generally directed to a cooling system for a heat shield of a generator, such as a superconducting generator, that more effectively transfers heat, thereby creating a more uniform temperature distribution. In certain embodiments, for example, the cooling system of the present disclosure includes a toroidal-shaped heat shield for surrounding a field winding assembly fixedly coupled to a structural component of the superconducting generator, a cryocooler in thermal contact with an outer surface of the toroidal-shaped heat shield via a bus bar, and at least one gas tank in thermal contact with the heat shield. Furthermore, the gas tank may have a generally toroidal shape to reduce temperature differences around the periphery of the heat shield through circulation of cooling gas within the gas tank. Furthermore, in one embodiment, the bus bar thermally connecting the cryocooler to the heat shield may be positioned in an asymmetric position relative to the heat shield to promote gas circulation within the gas tank to maximize heat transfer, thereby providing a more uniform thermal temperature distribution that reduces radiative heat transfer to the cold mass.

[0016] Referring to the drawings, Figure 1 is a perspective view of a wind turbine 10. As previously mentioned, the present disclosure is directed to generators that are particularly suited for use with wind turbine 10, although it is not limited to such use. While Figure 1 depicts a "land-based" wind turbine 10 installation, it should be understood that the present invention is not limited to land-based wind turbines, but is equally applicable to "off-shore" (water-based) wind turbine installations with either fixed or floating foundations.

[0017] With further reference to FIG. 1 , wind turbine 10 includes a tower 12 extending from a support surface 14, a nacelle 16 mounted on tower 12, and a rotor 18 coupled to nacelle 16. Rotor 18 includes a rotatable hub 20 and at least one rotor blade 22 coupled to and extending outward from hub 20. For example, in the illustrated embodiment, rotor 18 includes three rotor blades 22. However, in alternative embodiments, rotor 18 may include more or fewer than three rotor blades 22. Each rotor blade 22 may be spaced apart relative to hub 20 to rotate rotor 18 and convert kinetic energy from wind into usable mechanical energy, and thus electrical energy. For example, hub 20 may be rotatably coupled to a generator (not shown) disposed within nacelle 16 to enable the generation of electrical energy.

[0018] 2, a perspective interior view of an embodiment of nacelle 16 having a superconducting generator 23 housed therein in accordance with the present disclosure is illustrated. Additionally, as shown, a support tube 41 is directly connected to hub 20 and supports armature winding assembly 24. Armature winding assembly 24 can therefore be considered a rotating component of generator 23 having a rotating first electromagnetic component configuration, such as superconducting field winding assembly 26, that rotates around stationary field assembly 26 having a second electromagnetic component configuration.

[0019] The stationary field assembly 26 includes superconducting coils 52, which may be a group of wires formed in a racetrack shape. Thus, in certain embodiments, the superconducting coils 52 are constrained to maintain the racetrack shape. Further, as shown, each superconducting coil 52 is supported in a recess / passage 50 within the casing 42, which may be conduction-cooled by cryogenic cooling tubes filled with a cryogenic material (e.g., helium, hydrogen, or neon) for the purpose of removing heat from the superconducting coils. As such, the casing 42 may be supported within a cryostat housing 36 (also referred to herein as a vacuum vessel) that is secured to a base tube 44.

[0020] Still referring to FIG. 2 , the superconducting coils 52 may be arranged side by side in an annular array extending around the casing 42. For example, in an embodiment, 36 coils may form an annular array of field windings that function as the stator field windings of the generator 23. Furthermore, in an embodiment, the superconducting coils 52 may each be formed of wire (NbTi or other superconducting material) helically wound around a racetrack shape that may include cooling conduits for a cryogen. The stationary field assembly 26 includes superconducting coil magnets 54 that are generated by passing current through the superconducting field coils 52, which are enclosed within the casing 42 and receive cryogen through cooling recesses / passages 50.

[0021] In additional embodiments, the cryogenic recondensers 38, 40 may be housed within the field coil assembly 26, except that the cryogenic coolant in the recondensers 38, 40 is at least partially elevated above the superconducting field windings to provide a gravity feed of cryogenic temperature to the windings. Alternatively, the recondensers 38, 40 may be mounted on top of the field coil assembly.

[0022] Referring now to FIG. 3 , a cross-section of an embodiment of a direct drive superconducting generator 23 is illustrated in which an annular rotating armature winding assembly 24 (“armature 24”) is radially inward of a stationary field assembly 26. It should be understood that the disclosure described herein can equally function with the armature winding assembly 24 disposed radially outward of the stationary field assembly 26. In particular, as illustrated, the armature 24 is essentially an inner annular ring configuration ( FIG. 4 ) that rotates within the stationary field assembly 26. The armature 24 includes conducting coils 52, e.g., coils or bars, arranged longitudinally on the inner cylindrical surface of the armature 24 along its length. The conducting coils 52 may have their opposing ends connected to one another by conductive end turns 28. The number and arrangement of end turns 28 between longitudinal conductive coils 52 depends on the phase of electricity being generated by conductive coils 52. The outer cylindrical surface of the armature winding is separated from the inner surface of static field assembly 26 by a narrow air gap, e.g., about 10-25 mm.

[0023] Referring generally to FIG. 3 , the armature 24 includes a cylindrical yoke or body 30 (referred to herein as “body”) that supports a conductive coil 52. Specifically, the conductive coil 52 is received within slots defined between adjacent teeth extending radially from the body 30. The body 30 and teeth may be of a layered laminate construction. The inner surface of the body 30 is fixed to a cylindrical housing 32 that rotates with the armature 24. Further, as shown, the stationary field winding assembly 26 may be supported by a field winding support disk 34. Furthermore, the field winding support disk 34 is attached to the end of a cryostat housing 36 that contains the superconducting coil 52 ( FIG. 2 ) of the field winding assembly 26. The housing 36 and its cooling components form a cryostat that cools the superconducting coil of the field winding.

[0024] The cryostat housing 36 insulates the superconducting coils 52 so that they can be cooled to temperatures near absolute zero, e.g., about 20 Kelvin (K), more preferably about 10 K, and even more preferably about 4 K. To cool the windings, the cryostat housing 36 can include one or more insulated conduits 46 for receiving liquid helium (He) or other similar cryogenic liquid (called a cryogen). A conventional two-stage recondenser 38 mounted in the upper region of the field coil assembly, on top of the field coil assembly, or on top of the tower 12 and above the field windings, uses a gravity feed to supply the cryogen, e.g., liquid He. A second recondenser 40 optionally supplies a second cooling liquid, e.g., liquid nitrogen or neon, to the inner heat shield of the cryostat housing 36 via conduit 48.

[0025] Referring now to FIG. 4 , various components of a simplified cooling system 102 schematic diagram for a superconducting generator 100 of conventional construction are illustrated. More specifically, as illustrated, the superconducting generator 100 generally includes the cooling system 102 arranged with the generator's 100 thermal shield 104, vacuum vessel 106, cold mass 108, and cryocooler 110. In such an embodiment, for example, the cold mass 108 may be a stationary component, such as the field winding assembly 26 about which the armature winding assembly 24 rotates. It should be understood that the toroid for the armature winding assembly, shown in FIG. 3 , has been omitted from FIGS. 4-9 to simplify the illustration and more clearly illustrate the details of the present disclosure. Further, by way of example, the vacuum vessel 106 may be a non-rotatable component supporting a field winding assembly, such as the stationary field assembly 26. Thus, in such an embodiment, the rotatable component may be oriented to rotate relative to the non-rotatable component during operation of the generator 100, as shown in FIG. 3 . In such a conventional configuration, the heat shield 104 blocks and / or blocks radiation (as indicated by arrows 114) from the vacuum vessel 106. Additionally, as shown, heat is removed to the cryocooler 110 via a thermal bus / bus bar 112, thereby blocking most radiant heat from the cold mass 108. Additionally, as shown, the thermal bus / bus bar(s) 112 in such a configuration are attached to the top of the heat shield 104 for connection to the cryocooler 110. The heat shield 104 also blocks heat conducted through structural components, such as those used to hold the stationary field assembly 26 in place.

[0026] Thus, in a conventional cooling system such as that shown in FIG. 4 , the heat shield 104 has a temperature (T) distribution around its circumference. Cooling is provided by the cryocooler 110 via a thermal bus / busbar 112 located on top of the heat shield 104 for efficient heat transfer. As a result, lower temperatures are observed near the thermal bus / busbar 112 and higher temperatures are observed farther away from the thermal bus / busbar 112. This results in a large temperature difference between the top and bottom of the heat shield 104, further resulting in radiative heat transfer from the heat shield 104 to the cold mass 108. This large temperature difference is undesirable because it imposes a high thermal load on the cold mass 108 and therefore reduces the operating margin of the superconducting field winding. As previously mentioned, it should be understood that the configuration of FIG. 4 is simplified relative to the field winding assembly 26 of FIG. 3 to better illustrate the operating principles of the cooling system.

[0027] Accordingly, the present disclosure is directed to an improved cooling system 200 that addresses the aforementioned problems. In particular, the cooling system 200 of the present disclosure reduces large temperature differences within the heat shield 104 by reducing the temperature of the hottest spot on the heat shield 104. For example, referring now to Figures 5-11, various components of an embodiment of an improved cooling system 200 for a superconducting generator 100 according to the present disclosure are illustrated.

[0028] In particular, as shown in FIGS. 5 and 9-11 , cooling system 200 includes a heat shield 204 configured to surround a stationary component 208, such as field winding assembly 26. As previously described, heat shield 204 is disposed between a cold mass, which may be stationary component 208, such as field winding assembly 26, and vacuum vessel 106, which may be a non-rotatable component supporting a field winding assembly, such as stationary field assembly 26. Thus, in such an embodiment, the rotatable component may be oriented to rotate relative to the non-rotatable component during operation of the generator. It should further be appreciated that vacuum vessel 106 may also be separate and distinct from stationary field assembly 26, except for structural components used to support the heat shield and cold mass within vacuum vessel 106.

[0029] 5 and 9-11 , the cooling system 200 also includes a cryocooler 210 in thermal contact with the heat shield 204. In particular, as shown in FIGS. 5 and 9-11 , the cryocooler 210 is in thermal contact with the heat shield 204 via a bus bar 212. Furthermore, in embodiments, as shown in FIGS. 5-7 and 9-11 , the cooling system 200 includes a gas tank 206 adjacent to and in thermal contact with the heat shield 204. Accordingly, in such embodiments, the gas tank 206 includes a cooling gas 213 configured to circulate therethrough to provide uniform cooling to the heat shield 204. For example, in one embodiment, the cooling gas 213 may be helium gas at a pressure, e.g., about 1 bar, although pressures greater than and less than 1 bar may also be utilized.

[0030] More specifically, as shown in FIGS. 6 and 7, in one embodiment, the gas tank 206 can have a generally toroidal shape 211, i.e., a shape similar to a donut. As described herein, a toroidal shape can include any three-dimensional shape having a surface of revolution with a central hole. Thus, a toroidal shape can have a square or rectangular cross-section (as shown in FIG. 7), as well as a circular or elliptical cross-section (as shown in FIG. 6). Furthermore, the gas tank 206 can be a single gas tank or can be divided to include multiple gas tanks 206. It will be understood that division into multiple tanks is possible without departing from the spirit of the present invention, provided that the multiple gas tanks 206 are each toroidal and connected to a heat shield.

[0031] Further, in one embodiment, the gas tank 206 may be constructed of any suitable material, such as steel, aluminum, and / or other suitable metals or metal alloys. Further, as shown in the illustrated embodiment, the gas tank 206 may be positioned radially inward of the heat shield 204, e.g., against the inner surface 214 of the heat shield 204. In an alternative embodiment, the gas tank 206 may be positioned radially outward of the heat shield 204, e.g., against the outer surface of the heat shield 204. Thus, as shown, in one embodiment, the gas tank 206 may extend around the entire inner circumference of the heat shield 204. It will be appreciated that physical contact between the gas tank 206 and the heat shield 204 thermally couples the two components, thereby allowing the gas tank 206 to participate in determining the temperature distribution around the circumference of the heat shield 204.

[0032] 8, the gas tank 206 may be secured to the heat shield 204 using any suitable means, such as via a fastening assembly 226. In particular, as shown, the fastening assembly 226 may include one or more brackets 228 that may be secured around and / or to the gas tank 206 and / or heat shield 204. Such brackets 228 may, in embodiments, be metal brackets, such as aluminum brackets, or may be any other suitable material in addition to aluminum.

[0033] 5 and 9, in embodiments, the bus bar 212 may be positioned substantially at the 12 o'clock position of the heat shield 204 such that the cooling gas 213 circulates symmetrically in the four quadrants (e.g., labeled I, II, III, and IV) of the gas tank 206, as indicated by arrows 216. Thus, in such embodiments, the symmetric gas circulation in all four quadrants reduces the temperature difference between the upper and lower locations 220, 222 of the heat shield 204.

[0034] 10, the bus bar 212 may be offset from the 12 o'clock position of the heat shield 204 so that the cooling gas 213 circulates within the gas tank 206 in a single loop 218. In such an embodiment, offsetting the bus bar 212 as shown disrupts the gas circulation pattern, thereby forcing gas circulation throughout the gas tank 206. Thus, in one embodiment, the single loop circulation increases heat transfer within the gas tank 206, reducing the temperature difference between the upper and lower locations 220, 222 and the overall temperature at the hot spot 224 on the heat shield 204 compared to the symmetrical configuration of FIG.

[0035] In particular, as shown, the bus bar 212 may be positioned in a first quadrant (e.g., labeled I in FIG. 10 ) of the heat shield 204 such that the cooling gas 213 circulates within the gas tank 206 in a gravity-driven clockwise direction. Thus, as shown, the first quadrant I generally refers to the quadrant between the 12 o'clock and 3 o'clock positions of the heat shield 204. Thus, by way of example, the bus bar 212 is positioned from approximately the 1 o'clock position to approximately the 2 o'clock position.

[0036] 11, in an embodiment, the bus bar 212 may be positioned in a fourth quadrant (e.g., labeled IV in FIG. 11) of the heat shield 204 such that the cooling gas 213 circulates within the gas tank 206 in a gravity-driven clockwise direction. Thus, as shown, the fourth quadrant generally refers to the quadrant between the 9 o'clock and 12 o'clock positions of the heat shield 204. Thus, by way of example, the bus bar 212 may be positioned from approximately the 10 o'clock position to approximately the 11 o'clock position.

[0037] 12-18, there is further illustrated an additional embodiment of the gas tank 206 described herein. Rather than being secured to the heat shield 204 via a fastening assembly 226, the gas tank 206 of FIGS. 12-18 is integral with the heat shield 204. In particular, as shown in FIGS. 12 and 13, the gas tank 206 is integrally formed with (or welded to) the heat shield 204, such as at one or more edges of the heat shield 204.

[0038] The integrated gas tank 206 can have a variety of configurations or shapes. For example, as shown in FIGS. 12-16A, the gas tank 206 may have a circular opening 228 defining a tank portion that receives the cooling gas 213, with an abutting flange 230 configured to align with a wall 232 (FIG. 13) of the heat shield 204. In a further embodiment, as shown in FIG. 16B, the gas tank 206 can include a circular opening 228 with opposing thickened edges 234 for connecting with the wall 232 (FIG. 13) of the heat shield 204. Similarly, as shown in FIG. 16C, the gas tank 206 can include a circular opening 228 with opposing thickened edges 234 for connecting with the wall 232 (FIG. 13) of the heat shield 204, but can also include a cutout 236 to reduce the overall material of the gas tank 206.

[0039] In a further embodiment, as shown in Figure 16D, the gas tank 206 can include a circular opening 228 recessed in a square or rectangular wall 238 for connecting with the wall of the heat shield 204 (Figure 13). In such an embodiment, as shown in Figures 17 and 18, the wall 238 of the gas tank 206 can be secured to the end of the heat shield 204 (Figure 17) or to an inner surface 242 of the heat shield 204 (Figure 18). In each of Figures 17 and 18, by way of example, the wall 238 of the gas tank 206 can be secured to the heat shield 204 using, for example, welding, as shown via weld joint 244.

[0040] Additionally, as shown in Figure 14, the gas tank 206 may be a monolithic tank formed from a single curved piece, for example, via extrusion. In contrast, as shown in Figure 15, the gas tank 206 may be formed from multiple segments 240 arranged circumferentially together. In such an embodiment, the segments 240 may be straight rather than curved, as shown.

[0041] The use of the gas tanks described herein provides various advantages, including improved thermal contact and mechanical stability.

[0042] Moreover, those skilled in the art will recognize the interchangeability of various features from different embodiments. Similarly, the various method steps and features described, and other known equivalents to each such method and feature, can be mixed and matched by those skilled in the art to construct additional systems and techniques in accordance with the principles of the present disclosure. Of course, it should be understood that not necessarily all such objects or advantages may be achieved in accordance with any particular embodiment. Thus, for example, one skilled in the art may implement the systems and methods described herein in a manner that achieves or optimizes one advantage or advantages as taught herein, without necessarily achieving other objects or advantages as may be taught or suggested herein.

[0043] Further aspects of the invention are provided by the subject matter of the following clauses. [Embodiment 1] A generator a non rotatable component supporting a field winding assembly; a rotatable component oriented to rotate relative to the non-rotatable component during operation of the generator; and an armature winding assembly fixedly coupled to the rotatable component so as to rotate therewith during operation of the generator, the armature winding assembly comprising a plurality of conducting coils; a thermal shield surrounding the field winding assembly fixedly coupled to the stationary component; and a cryocooler in thermal contact with the thermal shield; a gas tank adjacent to and in thermal contact with the thermal shield, the gas tank containing a cooling gas configured to circulate therein so as to provide uniform cooling to the thermal shield. [Embodiment 2] A generator as described in embodiment 1, wherein the gas tank has a toroidal shape. [Embodiment 3] A generator as described in any of the preceding embodiments, wherein the gas tank is positioned radially inward of the thermal shield. [Embodiment 4] A generator as described in any of the preceding embodiments, wherein the gas tank extends around an entire internal circumference of the thermal shield. [Embodiment 5] A generator as described in any of the preceding embodiments, wherein the stationary component comprises a vacuum vessel. [Embodiment 6] The generator of any of the preceding embodiments, wherein the cooling gas comprises cryogen gas. [Embodiment 7] A generator according to any of the preceding embodiments, wherein the cryocooler is in thermal contact with the thermal shield via a busbar. [Embodiment 8] A generator as described in embodiment 7, wherein the busbar is positioned at a substantially 12 o'clock position of the thermal shield such that the cooling gas circulates symmetrically in four quadrants of the gas tank. [Embodiment 9] A generator as described in embodiment 7 or 8, wherein the busbar is offset from a 12 o'clock position of the thermal shield such that the cooling gas circulates in the gas tank in a single loop. [Embodiment 10] The generator described in embodiment 9, wherein the busbar is positioned in a first quadrant of the thermal shield such that the cooling gas circulates in the gas tank in a clockwise direction that is driven by gravity, and the first quadrant is between the 12 o'clock position and a 3 o'clock position of the thermal shield. [Embodiment 11] A generator as described in embodiment 9 or 10, wherein the busbar is positioned in a fourth quadrant of the thermal shield such that the cooling gas circulates in the gas tank in a counterclockwise direction that is driven by gravity, and the fourth quadrant is between the 12 o'clock position and a 9 o'clock position of the thermal shield. [Embodiment 12] A generator according to any of the preceding embodiments, wherein the generator is a superconducting generator and the plurality of conducting coils are superconducting coils. [Embodiment 13] A cooling system for a superconducting generator, comprising: a thermal shield for surrounding a field winding assembly fixedly coupled to a stationary component of the superconducting generator, the stationary component oriented relative to a rotatable component during operation of the superconducting generator; and a cryocooler in thermal contact with an outer surface of the thermal shield via a busbar; and a gas tank in thermal contact with the thermal shield, the gas tank comprising a toroidal shape and being positioned radially inward of the thermal shield on an inner surface thereof, the gas tank containing a cooling gas configured to circulate therein so as to provide uniform cooling to the thermal shield. [Embodiment 14] A cooling system as described in embodiment 13, wherein the gas tank extends around an entire internal circumference of the thermal shield. [Embodiment 15] A cooling system as described in embodiment 13 or 14, wherein the fixed component includes a vacuum vessel. [Embodiment 16] A cooling system described in any of embodiments 13 to 15, wherein the cooling gas includes a cryogenic gas. [Embodiment 17] A cooling system described in any of embodiments 13 to 16, wherein the bus bar is positioned substantially at the 12 o'clock position of the heat shield so that the cooling gas circulates symmetrically in the four quadrants of the gas tank. [Embodiment 18] A cooling system described in any of embodiments 13 to 17, wherein the bus bar is offset from the 12 o'clock position of the heat shield so that the cooling gas circulates within the gas tank in a single loop. [Embodiment 19] A cooling system as described in embodiment 18, wherein the bus bar is positioned in a first quadrant of the heat shield so that the cooling gas circulates within the gas tank in a clockwise direction driven by gravity, and the first quadrant is between the 12 o'clock position and the 3 o'clock position of the heat shield. [Embodiment 20] A cooling system described in any of embodiments 13 to 19, wherein the bus bar is positioned in the fourth quadrant of the heat shield so that the cooling gas circulates within the gas tank in a counterclockwise direction driven by gravity, and the fourth quadrant is between the 12 o'clock position and the 9 o'clock position of the heat shield.

[0044] This specification uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems, and performing the incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements that do not differ substantially from the literal language of the claims. [Explanation of symbols]

[0045] 10: Wind turbine 12: Tower 14: Support surface 16: Nacelle 18: Rotor 20: Hub 22: Rotor blades 23: Superconducting generator / Direct drive superconducting generator 24: Armature winding assembly / Annular rotating armature winding assembly / Armature 26: Superconducting field winding assembly / Static field assembly 28: Conductive end turns 30: Body 32: Cylindrical housing 34: Field winding support disk 36: Cryostat housing 38, 40: Recondenser / Cryogenic recondenser 41: Support tube 42: Casing 44: Base tube 46: Insulating conduit 48: Conduit 50: Cooling recess / Cooling passage 52: Conductive coil 54: Superconducting coil magnet 100: Generator 102: Cooling system 104: Heat shield 106: Vacuum vessel 108: Cold mass 110: Cryocooler 112: Thermal bus / busbar 114: Arrow 200: Cooling system 204: Heat shield 206: Gas tank 208: Stationary part 210: Cryocooler 211: Toroidal shape 212: Busbar 213: Cooling gas 214: Inner surface 216: Arrow 218: Single loop 220: Upper position 222: Lower position 224: Hot spot 226: Fixing assembly 228: Circular opening / bracket 230: Abutting flange 232: Wall 234: Opposing thickened edges 236: Notch 238: Wall 440: Segment 242: Inner surface 244: Weld joint

Claims

1. A generator, a non-rotatable component supporting the field winding assembly; a rotatable component oriented to rotate relative to the non-rotatable component during operation of the generator; an armature winding assembly fixedly coupled to the rotatable component for rotation during operation of the generator, the armature winding assembly including a plurality of conductive coils; a heat shield surrounding the field winding assembly fixedly coupled to the non-rotatable component; a cryocooler in thermal contact with the heat shield; a gas tank adjacent to and in thermal contact with the heat shield, the gas tank containing a cooling gas configured to circulate therethrough to provide uniform cooling to the heat shield; Including, generator.

2. The generator of claim 1 , wherein the gas tank has a toroidal shape.

3. The generator of claim 1 , wherein the gas tank is located radially inward of the heat shield.

4. The generator of claim 1 , wherein the gas tank extends around the entire inner periphery of the heat shield.

5. The generator of claim 1 , wherein the non-rotatable component comprises a vacuum vessel.

6. The generator of claim 1 , wherein the cooling gas comprises a cryogenic gas.

7. The generator of claim 1 , wherein the cryocooler is in thermal contact with the heat shield through a bus bar.

8. 8. The generator of claim 7, wherein the busbar is positioned substantially at the 12 o'clock position of the heat shield so that the cooling gas circulates symmetrically in the four quadrants of the gas tank.

9. 8. The generator of claim 7, wherein the busbar is offset from the 12 o'clock position of the heat shield so that the cooling gas circulates within the gas tank in a single loop.

10. 10. The generator of claim 9, wherein the busbar is positioned in a first quadrant of the heat shield such that the cooling gas circulates within the gas tank in a gravity-driven clockwise direction, the first quadrant being between a 12 o'clock position and a 3 o'clock position on the heat shield.

11. 10. The generator of claim 9, wherein the busbar is positioned in a fourth quadrant of the heat shield such that the cooling gas circulates within the gas tank in a counterclockwise direction driven by gravity, the fourth quadrant being between the 12 o'clock position and the 9 o'clock position of the heat shield.

12. The generator of claim 1 , wherein the generator is a superconducting generator and the plurality of conductive coils are superconducting coils.

13. 1. A cooling system for a superconducting generator, comprising: a heat shield for surrounding the field winding assembly fixedly coupled to a stationary component of the superconducting generator, the stationary component being oriented relative to the rotatable component during operation of the superconducting generator; and a cryocooler in thermal contact with an outer surface of the heat shield via a bus bar; a gas tank in thermal contact with the heat shield, the gas tank including a toroidal shape; a gas tank disposed radially inward of the heat shield on its inner surface, the gas tank containing a cooling gas configured to circulate therein to provide uniform cooling to the heat shield.

14. The cooling system of claim 13 , wherein the gas tank extends completely around an inner periphery of the heat shield.

15. The cooling system of claim 13 , wherein the stationary component comprises a vacuum vessel.

16. The cooling system of claim 13 , wherein the cooling gas comprises a cryogenic gas.

17. 14. The cooling system of claim 13, wherein the bus bar is positioned substantially at the 12 o'clock position of the heat shield so that the cooling gas circulates symmetrically through the four quadrants of the gas tank.

18. 14. The cooling system of claim 13, wherein the bus bar is offset from the 12 o'clock position of the heat shield so that the cooling gas circulates within the gas tank in a single loop.

19. 20. The cooling system of claim 18, wherein the bus bar is positioned in a first quadrant of the heat shield such that the cooling gas circulates within the gas tank in a gravity-driven clockwise direction, the first quadrant being between a 12 o'clock position and a 3 o'clock position on the heat shield.

20. 20. The cooling system of claim 18, wherein the bus bar is positioned in a fourth quadrant of the heat shield such that the cooling gas circulates within the gas tank in a gravity-driven counterclockwise direction, the fourth quadrant being between a 12 o'clock position and a 9 o'clock position on the heat shield.

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