Cooling system for superconducting wind turbines

Abstract

A technique is described for wind power generators in which a coolant, such as liquid helium and / or helium gas, is applied to the superconducting magnets via thermally conductive flexible structures. These structures thermally couple the coolant flow channels to the magnets and / or to the thermally conductive structures (e.g. metal plates) to which the magnets are thermally coupled. The thermally conductive flexible structures can be positioned such that movement of the magnets relative to the cryogenic flow channels cooling the structures during heating and / or cooling of the magnets does not result in damage to the thermal connections between the channels and the magnets. The fixed base of the generator can house a cooling station and deliver the coolant to the rotating base via a suitable rotating union.

Description

[Background technology]

[0001]

[0001] A wind turbine converts the kinetic energy of the wind into electrical energy using a generator. A turbine typically includes fins or other structures connected to a rotor that are driven by the wind to rotate the rotor. The generator includes magnets housed within the rotor, the rotation of which produces an electrical current in an armature.

[0002]

[0002] Some wind turbines use powerful permanent magnets, others electromagnets. In the latter case, wind turbines may be equipped with superconducting magnets, which can be very efficient as a result of being able to pass electric current without losses. However, to operate in this way, superconducting materials must be cooled to low temperatures. Summary of the Invention [Means for solving the problem]

[0003]

[0003] According to some aspects, a wind turbine generator is provided comprising: a plurality of high temperature superconducting (HTS) magnets arranged in a loop; a plurality of thermally conductive flexible structures, each thermally coupled to one or more of the plurality of HTS magnets in the loop; and a gas flow path including an inlet portion extending radially outward from a central region of the loop, a peripheral portion connected to the inlet portion and thermally coupled to at least some of the plurality of thermally conductive flexible structures, and an outlet portion connected to the peripheral portion and extending radially inward to the central region of the loop.

[0004]

[0004] According to some aspects, a wind turbine generator is provided comprising a cooling system comprising: a rotating part having a gas inlet and a gas outlet, with a gas flow path connected between the gas inlet and the gas outlet; a fixed part having a gas outlet and a gas inlet and configured to supply cooled gas at the outlet; a rotary union connected between the rotating part and the fixed part, with a first flow path in fluid communication with the gas outlet of the fixed part and the gas inlet of the rotating part and a second flow path in fluid communication with the gas outlet of the rotating part and the gas inlet of the fixed part; and a plurality of thermally conductive flexible structures, each thermally coupled to at least a portion of the rotating part.

[0005] According to some aspects, a cooling system for a wind turbine generator is provided, the cooling system comprising: a fixed portion having a first inlet configured to receive refrigerant gas from a refrigerant supply source, a first outlet configured to supply gas to an input of a rotary union, and a second inlet configured to receive gas from a discharge of the rotary union, wherein a temperature of the gas at the first outlet is lower than a temperature of the gas at the second inlet, the fixed portion comprising: a cryostat; a thermal radiation shield disposed within the cryostat; a gas flow path provided within the thermal radiation shield and having a first inlet corresponding to the first inlet of the fixed portion, a first outlet corresponding to the first outlet of the fixed portion, and a second inlet corresponding to the second inlet of the fixed portion; a first plurality of cold heads thermally coupled to the gas flow path; a compressor coupled to the first plurality of cold heads thermally coupled to the gas flow path; a cold head coupled to the thermal shield; a compressor coupled to the cold head for the thermal shield; and a valve system coupled to the gas flow path and configured to direct the flow of gas through the gas flow path.

[0006]

[0006] According to some embodiments, a generator is provided comprising a plurality of high temperature superconducting (HTS) magnets arranged in a loop, a plurality of thermally conductive flexible structures, each thermally coupled to one or more of the plurality of HTS magnets in the loop, and a cooling flow path comprising an inlet portion, a peripheral portion connected to the inlet portion and thermally coupled to at least some of the plurality of thermally conductive flexible structures, and an outlet portion.

[0007]

[0007] According to some aspects, a wind turbine generator is provided comprising a cooling system comprising: a rotating portion having an inlet and an outlet with a cooling flow path connected between the inlet and the outlet; a fixed portion having an outlet and the inlet and configured to supply cooled gas at the outlet; a rotary union connected between the rotating portion and the fixed portion, the rotary union having a first flow path in fluid communication with the outlet of the fixed portion and the inlet of the rotating portion and a second flow path in fluid communication with the outlet of the rotating portion and the inlet of the fixed portion; and a plurality of thermally conductive flexible structures, each thermally coupled to at least a portion of the rotating portion.

[0008]

[0008] The above-described apparatus and method embodiments may be implemented in any suitable combination of the aspects, features, and acts set forth above or described in more detail below. These and other aspects, embodiments, and features of the present teachings will become more fully understood from the following description taken in conjunction with the accompanying drawings.

[0009]

[0009] Various aspects and embodiments are described with reference to the following figures. It should be appreciated that the figures are not necessarily drawn to scale. In these figures, identical or nearly identical components shown in various figures are represented by like numerals. For purposes of clarity, every component may not be labeled in every figure. [Brief description of the drawings]

[0010] [Figure 1]1 is a schematic diagram of a cooling station for a cooling system according to some embodiments. [Figure 2A]

[0011] FIG. 2 is a side view in schematic form of a portion of a turntable having a cooling system. [Figure 2B]

[0012] FIG. 2 is a front view of a portion of the turntable in schematic form illustrating a cooling scheme for the turntable utilizing a cooling system, according to some embodiments. [Diagram 3]

[0013] FIG. 2 is a diagram of magnet coils in a rotor excluding cooling system components according to some embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011]

[0014] As mentioned above, wind turbines may be equipped with superconducting magnets, which must be cooled to cryogenic temperatures so that the conductors in the magnets operate in the superconducting phase. As referred to herein, a superconductor or superconducting material is a material that exhibits zero electrical resistance below a critical temperature. This critical temperature may be on the order of a few Kelvin for some superconductors, but for a class of materials known as high temperature superconductors (HTS), the critical temperature may be as high as about 90K.

[0012]

[0015] However, cryogenic cooling of magnets in the rotating base of a generator (e.g., a wind turbine) presents several challenges. First, locating a refrigerator in the rotating base itself can be difficult and can result in reduced performance as a result of operating under centrifugal forces. For this reason, the coolant must typically be supplied from a fixed base and transported to the rotating stages. Second, the coolant must be transported between regions of the rotating base (e.g., from the center of the rotating base to the outer parts of the rotating base), but at the size and rotational speed of wind turbines, the centrifugal forces that might otherwise aid such transport are relatively small. Third, uniform cooling of the magnets can be difficult to achieve due to the difficulty of supplying the coolant to the magnets and the low magnet temperatures required for operation.

[0013]

[0016] The inventors recognize and fully understand cooling techniques for generators, such as wind turbine generators, in which a coolant, such as liquid helium and / or helium gas, is applied to a superconducting magnet via thermally conductive flexible structures. These structures thermally couple the coolant flow passages to the magnet and / or to the thermally conductive structures (e.g., thermally conductive surfaces or structures, such as metal plates) to which the magnet is thermally coupled. The thermally conductive flexible structures may be positioned such that movement of the magnet relative to the cryogenic flow passages cooling the structure during heating and / or cooling of the magnet does not result in damage to the thermal connection between the flow passages and the magnet. For example, the thermally conductive flexible structures may allow movement of the magnet during heating and / or cooling of the magnet, which avoids high stresses due to differential thermal contraction / expansion of the tube-magnet structure.

[0014]

[0017] The cooling systems described herein may be more thermally efficient than cooling systems in which the magnet is in a vessel where it is cooled to substantially the same operating temperature as the magnet itself. For example, the cooling techniques described herein may allow the vessel housing the magnet to be cooled to about 70-80K, while the magnet itself may be cooled to about 20K. Thus, the cooling techniques described herein may provide more efficient cooling as a result of having a relatively small cooling thermal envelope. Still further, the use of HTS magnets may be advantageous in that they allow for cooling via gas, obviating the need for liquid helium. In contrast, low temperature superconductor (LTS) magnets must operate at low temperatures and may require liquid helium.

[0015]

[0018] According to some embodiments, the cooling system may include a non-rotating stage in which a coolant (e.g., a source of gas such as compressed helium gas) is cooled to cryogenic temperatures (e.g., below 40K) and discharged through a rotating union to a rotating stage having inlet and outlet manifolds for supplying the coolant through flow paths proximate to the superconductor magnets (e.g., high temperature superconductor (HTS) coils) in the rotor. The coolant may carry heat away from the magnets via the thermally conductive flexible structures described above that thermally couple the coolant flow paths to the magnets and / or to plates (e.g., copper or aluminum plates) to which the magnets are thermally coupled.

[0016]

[0019] Various concepts related to cooling technologies for wind turbines and embodiments of such technologies are described in more detail below. It should be appreciated that the various aspects described herein may be implemented in any of numerous ways. Examples of specific implementations are provided herein for illustrative purposes only. In addition, the various aspects described in the following embodiments may be used alone or in any combination, and are not limited to the combinations expressly described herein.

[0017]

[0020] 1 is a schematic diagram of a cooling station for a cooling system, according to some embodiments. The cooling station may be a non-rotating or part of the cooling system and may be configured to direct a coolant through a rotary union to the rotating bed. The cooling station may also be configured to cool a gas to be used as a coolant to cryogenic temperatures. The rotary union and inlet / outlet manifolds that provide the coolant for cooling the magnets are shown in FIG. 1, but the rotating bed itself is only partially shown in FIG. 1, as described further below.

[0018]

[0021] In the example of FIG. 1, a cryocooler cold head 109 (also labeled CHI, CH2, CH3, and CH4) is located in or provided as part of a cryostat 102 that is vacuum insulated and includes a thermal shield 103. The cryocooler cold head located in the cryostat 102 serves to cool the helium circulating in the depicted closed loop circuit. In the example of FIG. 1, the cryocooler cold head is connected to room temperature compressors (labeled Cl, C2, C3, and C4) that drive the cryocooler cold head. The circuit shown in FIG. 1 receives gas, which may be at ambient temperature, from a source 101, which may be, for example, a compressed gas source, and directs the gas through the loop. Circulation in the loop is provided by a cryocooler blower (e.g., cryofan) 104 located in the cryostat 102. The gas in the circuit is cooled by cold head 109, and the cooled gas and / or the resulting cold liquid (hereafter "refrigerant") may be fed through rotary union 105 into the rotating platform (to the right of vertical dashed line 108, which marks the boundary between the stationary and rotating parts of the system). An inlet manifold 106 feeds the refrigerant to the magnets (not shown in FIG. 1). The refrigerant returning from the rotor is routed through outlet manifold 107, back through rotary union 105, and back to the closed loop cooling station. As a result, the refrigerant may circulate through the system by being cooled by the cold head, cooling the magnets in the rotor, back to the cryofan, then back to the cold head, and so on.

[0019]

[0022] Each of the cold heads CHI, CH2, CH3, and CH4 is coupled to a heat exchanger (depicted with jagged lines) for providing cooling to the refrigerant flow in the circuit. The refrigerant flow through the heat exchangers may circulate in series, parallel, or both series and parallel, as shown in the example of Figure 1. That is, in the example of Figure 1, one flow path passes through CHI and CH2 in series, and a parallel flow path passes through CH3 and CH4 in series. It will be appreciated that any number of cold heads may be included in the cooling system, and that four cold heads are shown merely by way of example.

[0020]

[0023] In some embodiments, one or more of the cold heads may include or be otherwise coupled to a heater configured to control the temperature of the gas flow in the circuit. During initial cooling of the magnets in the wind turbine generator, it may be beneficial to limit the temperature of the magnets to manage differential temperatures and thermal stresses in the magnets and associated structures (e.g., magnet housings). For example, the heater may be operated to limit the temperature difference between the magnet temperature and the cooling circuit temperature to less than 50 K during initial cooling to about 120 K, but below 120 K the magnets may be allowed to cool more freely.

[0021]

[0024] In some embodiments, the refrigerant flow in the circuit shown in Figure 1 may have a pressure between 10 and 30 bar, or may have a pressure between 15 and 25 bar, or may have a pressure of 20 bar (or about 20 bar). In some embodiments, the refrigerant flow in the circuit shown in Figure 1 may be cycled at an operating temperature between 10K and 30K, or at a temperature between 15K and 25K, or at a temperature of 20K (or about 20K).

[0022]

[0025] As mentioned above, a cryofan 104 installed in the cryostat provides refrigerant circulation around the cooling circuit depicted in FIG. 1. In some embodiments, the cooling circuit is filled with high purity helium gas from a source 101 comprising a high pressure cylinder, which is circulated around the circuit by the cryofan 104. According to some embodiments, each cold head 109 may be connected to a room temperature refrigerant compressor, for example, with a cold head motor located on the cryostat lid by a flexible hose. Some or all of the equipment for cooling the circulating refrigerant flow may be installed on a fixed part of the wind turbine, such as on the platform of the wind turbine nacelle, or may be otherwise connected to the platform of the wind turbine nacelle.

[0023]

[0026] According to some embodiments, the cryostat 102 may include a bypass valve to allow testing of its cooling characteristics without an external cooling circuit. In some embodiments, the cryostat 102 may include a circuit supply and / or return valve to allow for routing the inlet and outlet cold tubing close together outside the cryostat and placing them in mutual vacuum jacketed piping (VJL), which may reduce the heat load on the refrigerant flow.

[0024]

[0027] According to some embodiments, the cryostat heat shield 103 may be cooled to a temperature between the temperature of the circuit and room temperature. For example, the heat shield may be cooled to about 80 K, while the circuit is about 20 K. In some embodiments, the heat shield may be cooled by a small capacity pulse tube cryocooler, for example a Cryomech pulse tube PT90 with an air-cooled compressor and a capacity of 90 W at 80 K. Using a separate cryocooler to cool the heat shield may eliminate the need to use liquid nitrogen to cool the radiation shield of a cryostat installed in a wind turbine nacelle.

[0025]

[0028] 2A-2B show a cooling scheme for a turntable of a cooling system, according to some embodiments. The turntable of the cooling system may be located inside the rotor of a wind turbine, which may be housed within a stator. FIG. 2A shows a side view of the cooling scheme for the turntable and an example rotor superconducting magnet 205, and FIG. 2B shows a front view of the cooling scheme in the turntable with some of the rotor magnets. In each of FIGS. 2A and 2B, a helium inlet manifold 201 and an outlet manifold 202, respectively, are shown, which may correspond to the inlet manifold 106 and the outlet manifold 107, respectively, shown in FIG. 1. For clarity, only a single circulation loop from the inlet manifold to the outlet manifold is shown, although in general several such loops may be included, as described further below.

[0026]

[0029] As shown in FIG. 2B, the coolant flowing from the inlet manifold 201 flows in cooling channels (e.g., tubes having any desired or convenient cross-sectional shape) generally designated 207 (sometimes referred to herein as "channels") toward the rotor and then back to the outlet 202. In this exemplary embodiment, the coolant flows in radial channels from a central region (e.g., an area proximate to the rotor axis) outwardly, around a portion of the rotor's periphery, and back to the outlet manifold 202. This path is shown in FIG. 2A, where it can be seen that the channels 207 are thermally coupled to a cooling plate 203, which may be formed from or include a thermally conductive material. In this exemplary embodiment, the channels 207 are positioned behind the superconducting magnets 205 to cool the cooling plate 203 (e.g., a copper or aluminum plate) that is in thermal contact with one or more magnets. Cooling between the flow channels and the cooling plate can be achieved via thermally conductive flexible structures 206 shown in FIG. 2B, each disposed adjacent to a peripheral area of ​​the flow channels. Multiple cooling loops (such as those formed by flow channels 207a, 207b, 207c shown in FIG. 2B) may be provided, each providing cooling to one or more superconductor magnets via a thermally coupled flexible structure and cooling plate. Note that flow channel portions 207a, 207c are oriented substantially radially from a substantially central rotor region where inlet manifold 201 and outlet manifold 202 are disposed, toward the rotor and HTS magnets 205, and flow channel portion 207b is oriented along a substantially peripheral path.

[0027]

[0030] According to some embodiments, the structure 206 may be formed from a thermally conductive (e.g. metallic) radial tube, with the peripheral portion of the tube thermally coupled (e.g. attached by soldering or the like) to the cooling plate 203. According to some embodiments, one or more of the flexible structures 206 may be connected to the outer diameter of the coolant flow passage and to the cooling plate 203. In some embodiments, the structure 206 may be formed as a metallic adjustable plate that can expand or contract the space between the magnet and the coolant flow passage. This configuration may provide an improved thermal connection by eliminating bends and joints in the structure. The flexibility of the radial tube may be provided by a bellows structure and / or by bending of the tube. In the latter case, the bending may allow the magnet to move during cooling and heating, which avoids high stresses due to differential thermal contraction / expansion of the tube-magnet structure. According to some embodiments, one of the flexible structures 206 may cool multiple magnet coils (e.g. five coils). The coils may be connected to a common cooling plate or to multiple cooling plates to which the flexible structure is connected.

[0028]

[0031] According to some embodiments, the coolant flow path may pass through a sealed, insulated thermal feedthrough as it enters the evacuated thermal enclosure 204. Thus, the cooling plate 203, the HTS magnets 205, the thermally conductive flexible structure 206, and the cooling flow path portion 207b may be disposed within the evacuated thermal enclosure 204.

[0029]

[0032] In some cases, one or more of the coolant flow paths may be bent near the location of the cooling plate. In some cases, the coolant flow paths may be bent radially to lead to an outlet manifold located near the rotor axis. In one design, the rotor magnet may have 60 magnet coils and 12 parallel inlet and outlet tubes to provide series and parallel cooling of all the magnets. The number of radially running inlet and outlet channels may be varied to vary the cooling scheme. For example, a single radial inlet tube may be provided for two nearby magnet coils, with two radial outlet tubes returning the gas to the outlet manifold.

[0030]

[0033] According to some embodiments, the rotor's external and internal coolant flow paths and / or the inlet and outlet manifolds 201 and 202 may be placed in a vacuum jacket (VJL) to provide thermal insulation. The coolant flow paths and / or manifolds may be encased by multi-layer insulation (MLI) and may include getters (e.g., charcoal getters) to improve vacuum retention. In some cases, for example, a VJL for cryogenic helium transfer may operate for years after factory pumping without significant degradation of the insulating vacuum and without the need for re-pumping. In some cases, the vacuum vessel may include getters to extend operation at the design vacuum without the need for pumping.

[0031]

[0034] The cooling system described above, in which cold gas (e.g. helium) is applied only to the coil copper cooling plate, can provide a design with a heat shield in which a thermal vacuum envelope (vessel) around the magnet is maintained at a higher temperature, e.g. 70-80 K. The relatively lightweight envelope is suspended on the magnet support, but provides the necessary thermal resistance and differential temperature to the magnet temperature.

[0032]

[0035] In some embodiments, the heat load on the cooling system due to the current leads supplying current to the magnet 205 can be reduced by using hybrid type current leads, e.g., copper resistive current leads for temperatures in the range 300-70 K and HTS current leads for temperatures between 70-20 K. Partial exhaust from the cooling coil helium flow can be used to cool the copper current leads down to about 70 K, achieving the functionality of the HTS current leads with low heat load.

[0033]

[0036] FIG. 3 shows a diagram of magnet coils in a rotor excluding cooling system components, according to some embodiments. To illustrate the shape of the magnets in the coils, FIG. 3 shows a loop 305 of magnets. Each of the magnets may include a high temperature superconductor (HTS) such as REBCO (e.g., YBCO). In some embodiments, each of the magnets 305 may comprise a stack of HTS tape wound into a loop. In some embodiments, the magnets 305 may comprise a double pancake coil. In some embodiments, the magnets may be non-insulated HTS magnets.

[0034]

[0037] According to some embodiments, each of the magnets 305 may comprise one or more laminations of HTS wound into one or more turns as a racetrack spiral. If the magnet comprises multiple laminations of HTS, each lamination may be separated by a conventional (non-superconducting) conductor, such as steel. During a quench, the steel may allow current to flow between the turns of the magnet, thereby dissipating the current and reducing damage to the HTS.

[0035]

[0038] Having thus described several aspects of at least one embodiment of this invention, it will be appreciated that various alterations, modifications, and improvements will readily occur to those skilled in the art.

[0036]

[0039] Such changes, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and scope of the present invention. Moreover, while advantages of the present invention have been set forth, it should be appreciated that not all embodiments of the technology described herein include all of the advantages described. Some embodiments may not implement the features described herein as advantageous, and in some cases, one or more of the described features may be implemented to achieve further embodiments. Accordingly, the foregoing description and drawings are by way of example only.

[0037]

[0040] Various aspects of the invention may be used alone, in combination, or in various configurations not specifically described in the embodiments described above, and therefore its application is not limited to the details and configurations of components described in the above description or illustrated in the drawings. For example, aspects described in one embodiment may be combined in any manner with aspects described in other embodiments.

[0038]

[0041] In the claims, the use of ordinal numbers such as "first," "second," "third," etc. to modify claim elements does not, in and of itself, imply a priority, precedence, or order of one claim element over another, or the temporal order in which acts of a method are performed, but is merely used to distinguish one claim element having a particular name from other claim elements having the same name (other than the use of the ordinal number).

[0039]

[0042] The terms "approximately" and "about" may be used to mean, in some embodiments, within ±20% of a target value, and in some embodiments, within ±10% of a target value, and in some embodiments, within ±5% of a target value, and even in some embodiments, within ±2% of a target value. The terms "approximately" and "about" may include the target value. The term "substantially equal" may be used to refer to values ​​that are, in some embodiments, within ±20% of each other, and in some embodiments, within ±10% of each other, and in some embodiments, within ±5% of each other, and even in some embodiments, within ±2% of each other.

[0040]

[0043] The term "substantially" may be used to refer to values ​​that are within ±20% of a comparison scale in some embodiments, and within ±10%, and within ±5%, and even within ±2% in some embodiments. For example, a first direction that is "substantially" perpendicular to a second direction may refer to a first direction that is within ±20% of making a 90° angle with the second direction in some embodiments, and within ±10% of making a 90° angle with the second direction in some embodiments, and within ±5% of making a 90° angle with the second direction in some embodiments, and within ±2% of making a 90° angle with the second direction in some embodiments.

[0041]

[0044] Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of "including," "comprising," "having," "containing," "involving," and variations thereof herein are intended to encompass the items listed thereafter and equivalents thereof, as well as additional items.

Claims

1. 1. A cooling system for a wind turbine generator, comprising: a stationary part having a first inlet configured to receive refrigerant gas from a refrigerant supply source, a first outlet configured to supply gas to an input of a rotary union, and a second inlet configured to receive gas from a discharge of the rotary union, wherein a temperature of the gas at the first outlet is lower than a temperature of the gas at the second inlet; A cryostat and a thermal radiation shield disposed within the cryostat; a gas flow path disposed within the thermal radiation shield, the gas flow path having a first inlet corresponding to the first inlet of the stationary portion, a first outlet corresponding to the first outlet of the stationary portion, and a second inlet corresponding to the second inlet of the stationary portion; a first plurality of cold heads thermally coupled to the gas flow path; a compressor coupled to the first plurality of cold heads thermally coupled to the gas flow path; a cold head coupled to the thermal shield; a compressor coupled to the cold head for the heat shield; a valve system coupled to the gas flow path and configured to direct the flow of gas through the gas flow path;

2. 2. The cooling system of claim 1, wherein the gas flow path forms a loop such that gas entering the gas flow path through the second inlet is supplied to one or more of the first plurality of cold heads and cooled before being supplied to the first outlet of the fixed portion.

3. 2. The cooling system of claim 1, wherein the compressor is provided as a plurality of compressors, some of the plurality of compressors coupled to some of the first plurality of cold heads coupled to the gas flow path, and wherein each of the first plurality of cold heads is coupled to at least one compressor.

4. 2. The refrigeration system of claim 1, wherein the compressors are provided as a first plurality of compressors, each of the first plurality of compressors adapted to be coupled to a corresponding one of the first plurality of cold heads.

5. The cooling system of claim 1 , further comprising a rotary union having an inlet in fluid communication with the outlet of the stationary portion and having an outlet in fluid communication with the inlet of the stationary portion.

6. The cooling system of claim 1 , further comprising a helium bottle coupled to the first inlet of the fixed portion.

7. The cooling system of claim 2 , further comprising a rotary union having a first flow passage in fluid communication with the outlet of the stationary portion and having a second flow passage.

8. 8. The cooling system of claim 7, further comprising a rotary part having a gas inlet and a gas outlet with a gas flow path connected between the gas inlet and the gas outlet, wherein the rotary union is connected between the rotary part and a stationary part, the first flow path of the rotary union being in fluid communication with the outlet of the stationary part and the inlet of the rotary part, and the second flow path of the rotary union being in fluid communication with the discharge of the rotary part and the inlet of the stationary part.

9. a plurality of high temperature superconducting (HTS) magnets arranged in a loop; a plurality of thermally conductive flexible structures, each thermally coupled to one or more of the plurality of HTS magnets in the loop; A cooling channel comprising: entrance part, a peripheral portion coupled to the inlet portion and thermally coupled to at least some of the plurality of thermally conductive flexible structures; and a cooling channel having an outlet portion; A generator comprising:

10. the inlet portion extends radially outward from a central region of the loop; the outlet portion extending radially inward to a central region of the loop; The generator of claim 9.

11. 10. The generator of claim 9, further comprising one or more thermally conductive plates, each of the plurality of thermally conductive flexible structures thermally coupled to one or more of the plurality of HTS magnets in the loop via one or more of the one or more thermally conductive plates.

12. The generator of claim 9 , further comprising an inlet manifold coupled to the inlet portion of the cooling passages, and an outlet manifold coupled to the outlet portion of the cooling passages.

13. The generator of claim 12 further comprising a rotary union coupled to the inlet manifold and coupled to the outlet manifold.

14. the cooling channel is a first cooling channel; the peripheral portion of the first cooling channel is thermally coupled to a first of the plurality of thermally conductive flexible structures; The generator further comprises a second cooling flow path, the second cooling flow path comprising: an inlet portion extending radially outward from a central region of the loop; a peripheral portion coupled to the inlet portion of the second gas flow path and thermally coupled to a second subset of the plurality of thermally conductive flexible structures; an outlet portion connected to the peripheral portion of the second gas flow path and extending radially inward to the central region of the loop; The generator of claim 13.

15. The generator of claim 9 , wherein each HTS magnet in the loop comprises a stack of HTS tapes.

16. 10. The generator of claim 9, wherein each HTS magnet in the loop comprises a double pancake coil.

17. The generator of claim 9 , wherein the plurality of thermally conductive flexible structures each comprise a flexible radial tube.

18. 1. A cooling system comprising: a rotating portion having an inlet and an outlet with a cooling passage connected between the inlet and the outlet; a stationary portion having an outlet and an inlet and configured to provide cooled gas at the outlet; a rotary union coupled between the rotating portion and the stationary portion, the rotary union having a first flow path in fluid communication with the outlet of the stationary portion and the inlet of the rotating portion, and a second flow path in fluid communication with the outlet of the rotating portion and the inlet of the stationary portion; a plurality of thermally conductive flexible structures, each thermally coupled to at least a portion of the rotating portion; A wind power generator comprising:

19. The cooling passages of the rotating portion of the cooling system include: the inlet portion of the gas flow passage extends radially outward from a central region of the rotating portion; a peripheral portion of the gas flow passage connected to the inlet portion and thermally coupled to at least some of the plurality of thermally conductive flexible structures; 19. The wind turbine generator of claim 18, wherein the outlet portion of the gas flow path is connected to the peripheral portion and is configured to extend radially inward to the central region of the rotor portion.

20. 20. The wind turbine generator of claim 19, wherein the rotating portion comprises a plurality of high temperature superconducting (HTS) magnets arranged in a loop.

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