Yaw bearings for wind turbines

Abstract

To provide a yaw system for a wind turbine, in particular, a gliding yaw bearing for the wind turbine and the wind turbine including the yaw system.SOLUTION: A gliding yaw bearing system used for a wind turbine includes: a first bearing assembly configured to be mounted to a tower (2) of the wind turbine; and a second bearing assembly configured to be mounted to a nacelle of the wind turbine. In the gliding yaw bearing system, an upwind part of the second bearing assembly is different from a downwind part of the second bearing assembly. The wind turbine including a gliding yaw bearing, or specifically a direct-driven wind turbine is also disclosed.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to a yaw system for a wind turbine, in particular to a sliding yaw bearing for a wind turbine, and to a wind turbine including such a yaw system. [Background technology]

[0002] Modern wind turbines are generally used to supply electricity to the power grid. This type of wind turbine generally includes a tower and a rotor arranged on the tower. The rotor, which typically includes a hub and a number of blades, is adapted to rotate under the influence of wind on the blades. Said rotation generates a torque that is usually transferred via the rotor shaft to a generator, either directly ("direct drive") or using a gearbox. In this way, the generator produces electricity that can be supplied to the power grid.

[0003] Most wind turbines include a yaw system that is used to orient the rotor of the wind turbine into the prevailing wind direction.

[0004] Yaw systems perform this rotation of the nacelle by means of a yaw drive, which usually includes multiple (electric or hydraulic) motors with appropriate gearboxes for driving gears (pinions) that mesh with an annular gear or gear ring mounted on the nacelle or wind turbine tower. Thus, the nacelle, with the wind turbine rotor mounted thereon, can rotate into and out of the wind direction about the longitudinal axis of the tower. The rotatable connection between the wind turbine tower and the nacelle is called the yaw bearing.

[0005] Typically, once the rotor is aligned with the wind, the yaw system maintains the position by means of braking (e.g., hydraulic brake calipers and / or electric brakes on the yaw motor). If the rotor is misaligned with the wind during operation, the yaw system rotates the nacelle to reach the proper alignment with the wind. In certain circumstances, the yaw system can also be used to point the wind turbine rotor out of the wind, for example in certain stormy conditions.

[0006] Yaw bearings may be roller or gliding type. Roller yaw bearings are generally disposed between an inner ring and an outer ring and may include balls or rolling elements to reduce friction between the rings. Because friction between the inner ring and the outer ring is very low, yaw systems with roller bearings may require constant operation of the yaw motor and braking system to maintain the yaw direction. As a result, the braking system and yaw motor are generally large. Additionally, roller bearings are relatively expensive compared to other bearings, especially large yaw roller bearings.

[0007] Planing or sliding yaw bearings form an alternative to roller yaw bearings and are known to be used in large wind turbines because they are cheaper than roller yaw bearings and can withstand high axial and radial loads. Planing or sliding yaw bearings can include an annular gear or gear ring configured to be fixed to the tower, and the frame of the nacelle can be stationary and sliding in its yaw motion. A lubricant, for example oil or grease, can be applied between the annular gear and the frame of the nacelle to allow the frame to rotate relative to the annular gear. The lubricant reduces friction between the annular gear and the frame of the nacelle and avoids wear of the annular gear and / or the frame. Furthermore, sliding or gliding surfaces can be provided between the annular gear and the frame to avoid direct contact between them.

[0008] An example of a sliding yaw bearing is disclosed in US Pat. No. 7,458,776. Summary of the Invention

[0009] In one aspect, a gliding yaw bearing system for use with a wind turbine is provided. The gliding yaw bearing system includes a first bearing assembly configured to be mounted to a tower of a wind turbine and a second bearing assembly configured to be mounted to a nacelle of the wind turbine. A windward side of the second bearing assembly is different from a leeward side of the second bearing assembly.

[0010] According to this aspect, a sliding yaw bearing is provided that accounts for the asymmetric mass distribution in the wind turbine, resulting in bending loads that are primarily or always in the same direction. In particular, in a direct drive wind turbine, the wind turbine rotor and generator are positioned relative to the tower and the yaw system. Thus, the windward and leeward parts of the yaw bearing are subjected to different loads. The bearing assembly mounted on the nacelle rotates with the nacelle as the wind changes and the yaw system operates. Thus, it is possible to define parts of the bearing assembly that are mounted on the nacelle, which are always subjected to bending loads in the same direction. The loads on the windward and leeward parts are different, and thus the parts of the bearing assembly mounted on the nacelle can be adapted to the different loads.

[0011] Non-limiting examples of the present disclosure are described below with reference to the accompanying drawings. [Brief description of the drawings]

[0012] [Figure 1] 1 is a perspective view of a known wind turbine; [Diagram 2] FIG. 2 is a simplified internal view of a nacelle of the wind turbine according to FIG. 1. [Figure 3A] FIG. 1 illustrates a schematic of how loads may be different for a direct drive wind turbine compared to a wind turbine with a gearbox. [Figure 3B] FIG. 1 illustrates a schematic of how loads may be different for a direct drive wind turbine compared to a wind turbine with a gearbox. [Figure 4] FIG. 1 illustrates a schematic diagram of a yaw system according to an example. [Figure 5A] 1A to 1C are schematic diagrams illustrating different examples of yaw systems. [Figure 5B] 1A to 1C are schematic diagrams illustrating different examples of yaw systems. [Figure 6] FIG. 2 shows a schematic diagram of a bearing assembly that may form part of a yaw bearing. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] In these figures, the same reference numbers are used to indicate corresponding elements.

[0014] FIG. 1 illustrates a perspective view of an example of a wind turbine 1. As illustrated, the wind turbine 1 includes a tower 2 extending from a support surface 3, a nacelle 4 attached to the tower 2, and a rotor 5 coupled to the nacelle 4. The rotor 5 includes a rotatable hub 6 and at least one rotor blade 7 coupled to the hub 6 and extending outwardly from the hub 6. For example, in the illustrated example, the rotor 5 includes three rotor blades 7. However, in alternative embodiments, the rotor 5 may include more or less than three rotor blades 7. Each rotor blade 7 may be spaced apart from the hub 6 to facilitate rotation of the rotor 5 and to allow kinetic energy to be converted from the wind into usable mechanical energy and subsequently electrical energy. For example, the hub 6 may be rotatably coupled to a generator 10 ( FIG. 2 ) disposed within or forming part of the nacelle 4 to enable the generation of electrical energy.

[0015] FIG. 2 illustrates a simplified internal view of an example nacelle 4 of the wind turbine 1 of FIG. 1. As illustrated, a generator 10 may be disposed within the nacelle 4. In general, the generator 10 may be coupled to the rotor 5 of the wind turbine 1 to generate electrical power from rotational energy generated by the rotor 5. For example, the rotor 5 may include a main rotor shaft 8 coupled to a hub 6 for rotation therewith. The generator 10 may then be coupled to the rotor shaft 8 such that rotation of the rotor shaft 8 drives the generator 10. For example, in the illustrated embodiment, the generator 10 includes a generator shaft 11 rotatably coupled to the rotor shaft 8 via a gearbox 9.

[0016] It will be appreciated that the rotor shaft 8 , gearbox 9 and generator 10 may generally be supported within the nacelle 4 by a bedplate or support frame 12 disposed on top of the wind turbine tower 2 .

[0017] The nacelle 4 is rotatably coupled to the tower 2 via a yaw system 20. The yaw system includes a yaw bearing (not visible in FIG. 2) having two bearing components configured to rotate relative to one another. The tower 2 is coupled to one of the bearing components and the bedplate or support frame 12 of the nacelle 4 is coupled to the other bearing component. The yaw system 20 includes an annular gear 21, a plurality of yaw drives 22 having motors 23, a gearbox 24, and a pinion 25 that meshes with the annular gear to rotate one of the bearing components relative to the other.

[0018] The yaw system 20 can be used to orient the nacelle 4 and rotor 5 during operation to align with the prevailing wind direction. In certain situations, such as high wind conditions, the yaw system can be used to rotate the nacelle 4 out of the wind direction.

[0019] Figures 3A and 3B show diagrammatically how loads may be different for a direct drive wind turbine compared to a wind turbine with a gearbox. In both Figures 3A and 3B, a wind turbine is disclosed with the wind turbine rotor on the windward side of the tower.

[0020] Upwind wind turbines have the rotor facing the wind on the front side of the tower. The basic advantage of the upwind design is to avoid the windshield behind the tower. The vast majority of wind turbines have this design. Downwinders have the rotor located on the downwind side of the tower. They have the theoretical advantage that they can be built without a yaw drive mechanism if the rotor and nacelle have a suitable design to passively follow the nacelle to the wind.

[0021] FIG. 3A discloses a wind turbine 100 similar to the wind turbine 1 of FIGS. 1 and 2. The wind turbine rotor includes a hub 6 and a number of blades 7. The rotor shaft connected to the hub 6 forms a "low speed shaft" of a gearbox 9. The output shaft or "high speed shaft" of the gearbox 9 is configured to drive a generator 10. Both the gearbox 9 and the generator 10 are housed within a nacelle 4. The nacelle 4 is rotatably mounted to a tower 2 via a yaw bearing system 20.

[0022] Although other components may be housed within the nacelle, the gearbox 9 and generator 10 are typically the heaviest components. The rotor 5 with its hub 6 and blades 7 forms an additional heavy component. The resulting centre of gravity CG is shown diagrammatically in FIG. 3A. The centre of gravity may be located upwind of the central axis of the tower 2. The tower 2 is therefore subject to bending loads (mass M M The bending moment due to the mass is considered to be a negative moment in this diagram.

[0023] During operation, under wind load, the additional wind moment M WThis wind load moment is not constant. Negative moment M M (positive) moment M relative to W Depending on the magnitude of M, the tower (and yaw system) may sometimes experience positive bending loads, i.e. W -M M >0 may be received.

[0024] Thus, in some cases the tower and yaw system are subjected to negative bending moments and in other cases to positive bending moments.

[0025] 3B shows diagrammatically a direct-drive wind turbine 200. In contrast to the wind turbine 100, the rotor 5 directly drives the rotor of the generator 10. The generator 10 can be located in front of the nacelle 4, i.e. on the upwind side of the nacelle 4, and partially or completely in front of the nacelle. The resulting bending moment M M is the bending moment M in Figure 3A. M Therefore, the wind load M W Even if a large positive bending moment occurs during operation due to the load on the tower 2, the resulting moment is still negative. As a result, in a direct drive wind turbine, the tower 2 and yaw system 20 may be subject to negative bending loads at all times.

[0026] FIG. 4 illustrates a schematic of a yaw system according to an example. FIG. 4 illustrates a planing yaw bearing system for use with a wind turbine, including a first bearing part 50 configured to be mounted to a tower 2 of the wind turbine and a second bearing part 40 configured to be mounted to a nacelle 4 of the wind turbine. The windward part 40A of the second bearing part is different from the leeward part 40B of the second bearing part. The planing yaw bearing illustrated herein is particularly suitable for direct drive wind turbines, but may also be used in wind turbines having a gearbox.

[0027] Specifically, in this example, the second bearing assembly may be configured to be able to support higher bending loads on the windward side of the nacelle.

[0028] The second bearing portion 40 may be attached to a nacelle frame 44 or a bed plate. In the particular example of Figure 4, the wind turbine rotor and generator may be located on the windward side of the tower 2. At the windward side 40A, the nacelle frame 44 has a tendency to be pushed down due to the mass of the windward generator and wind turbine rotor. At the downwind side, the nacelle frame has a tendency to be pulled upward for the same reason.

[0029] The second bearing portion 40 may include a plurality of nacelle gliding pads 47, 49. The first bearing portion 50 may include a plurality of tower gliding pads 53. The nacelle and tower gliding pads 47, 49, 53 form a gliding assembly such that the nacelle can slide or slide on the tower when the yaw drive acts on the annular gear. A lubricant may be provided between the first and second bearing portions.

[0030] In this particular example, the first bearing portion includes an annular disc 50 having a tower gliding pad 53. The tower gliding pad 53 may be attached to an upper surface of the disc 50. The pad may be, for example, screwed to the upper surface of the disc 50.

[0031] The annular disc 50 includes a top axial runner surface, a bottom axial runner surface, and a radial runner surface. The second bearing part may include a caliper that partially surrounds the second bearing component. The second bearing part may also include a top axial runner surface, a bottom axial runner surface, and a radial runner surface. In use, the top axial runner surface of the first bearing part may face the top axial runner surface of the second bearing part. Similarly, the bottom axial runner surface and the radial runner surface may be opposite each other.

[0032] The second bearing part 40 may include a number of calipers 45, 46. The calipers may be formed by brackets with a substantially L-shaped cross section that can be attached to the nacelle frame 44. They may be attached, for example, using screws. Shapes other than L-shaped may also be used, for example brackets with a C-shaped cross section, as well as any other shape for partially containing or limiting the movement of the disk 50.

[0033] In this particular example, the calipers 45, 46 include a bottom gliding pad 49 configured to contact the bottom of the disc 50. The caliper 46 may include a radial gliding pad 47 configured to contact the radial surface of the disc. In this particular example, the radial gliding pad 47 attached to the caliper establishes contact with the inner radial surface of the annular disc 50.

[0034] The radial gliding pads may be wedge shaped in some examples.

[0035] The number and configuration of calipers 46 may be different in the leeward portion than the calipers 45 in the windward portion. Due to the loads described above, the calipers 46 may be subjected to higher loads than the calipers 45 in the windward portion. The calipers 46 may have a larger cross section than the calipers 45. Additionally or alternatively, the number of calipers in the leeward portion may be greater than in the windward portion. The caliper density, i.e., the number of calipers per unit of length along the circumference of the tower, may be higher in the leeward portion.

[0036] Additionally or alternatively, the material of caliper 45 may be different than the material of caliper 46, for example being of a higher grade having higher tensile and yield strengths.

[0037] Additionally or alternatively, the caliper 45 on the windward side may include a mechanism for increasing friction between the first and second bearing parts. In particular, a bottom pad 49 of the caliper 45 may be pressed towards the annular disc 50. The mechanism 43 may include, for example, a spring 44 that presses the bottom pad 49 in contact with the bottom of the annular disc 50 to increase friction. Additionally or alternatively, a pneumatic or hydraulic mechanism for increasing friction may be used. At the windward side, friction on the bottom side of the annular disc may be relatively low due to the aforementioned loads.

[0038] The same or similar friction increasing mechanism may be included on the leeward side relative to the upper pad. Bending moments due to the mass tend to separate the first and second bearing assemblies on both the leeward and upwind sides. The friction increasing mechanism described above may be useful. The leeward and downwind phenomena apply to the upwind wind turbine rotor. The opposite is true for the downwind wind turbine rotor.

[0039] In some examples, the number of nacelle planing pads may be greater on the leeward side of the second bearing portion than on the windward side of the second bearing portion. In some examples, the material of the nacelle planing pads is different on the windward side of the second bearing portion than on the leeward side of the second bearing portion. For example, the material of the nacelle planing pads on the leeward side may be of a higher grade, i.e., have a higher strength or resistance than the nacelle planing pads on the windward side.

[0040] In this example, the annular disc may include gear teeth 21 on a radial surface of the disc 50 .

[0041] In one aspect of the disclosure, a direct drive wind turbine is provided that includes a tower 2, a nacelle 4 rotatably mounted to the tower 2, and a sliding yaw bearing system 20 according to any of the examples disclosed herein. The direct drive wind turbine 200 may further include a wind turbine rotor and a generator operatively connected to the wind turbine rotor, where the wind turbine rotor and the generator are located on the upwind side of the tower.

[0042] In one aspect of the disclosure, a direct drive wind turbine is provided having a tower, a nacelle rotatably mounted to the tower via a sliding yaw bearing, a wind turbine rotor, and a generator operatively connected to the wind turbine rotor, the generator and the wind turbine rotor disposed on a first side of the nacelle, the sliding yaw bearing including a first bearing portion coupled to the tower and including a plurality of tower sliding pads, and a second bearing portion coupled to the nacelle and including a plurality of nacelle sliding pads, the second bearing assembly configured to support a higher load on the second side of the nacelle.

[0043] In an example, the number and / or type of nacelle sliding pads are different on the first and second sides of the nacelle.

[0044] The number of nacelle sliding pads can be varied by changing the number of calipers on the first and second sides of the nacelle, as shown in the previous example. Additionally or alternatively, the angle segment covered by each caliper can also be varied.

[0045] In some examples, the first bearing portion may include a disk including the tower sliding pads. In these examples, the second bearing portion may include a plurality of calipers including the nacelle sliding pads. The calipers may include bottom sliding pads configured to contact the bottom of the disks.

[0046] In the alternative, the first bearing portion attached to the tower may include a caliper and the second bearing portion may include an annular disc partially surrounded by the caliper.

[0047] The pads shown in any of the examples disclosed herein may be connected to either the first bearing part (mounted to the tower) or the second bearing part (mounted to the nacelle), or part may be connected to the first bearing part and another part may be connected to the second bearing part.

[0048] In yet some further examples, the caliper mounted on the nacelle may carry both bottom and top sliding pads. In such examples, both the top and bottom sliding pads may vary, i.e., both the top and bottom sliding pads may have an asymmetric configuration. The number, size and material of the sliding pads may vary around the circumference of the tower.

[0049] 5A and 5B show schematic diagrams of different examples of the yaw system 20. FIG.

[0050] The yaw system may include an annular gear 21 coupled to the tower 2 and a plurality of yaw drives 22 coupled to the nacelle frame 44. The yaw drive 22 includes a motor and a pinion 25 for meshing with the annular gear 21. Rotation of the pinion can rotate the pinion relative to the annular gear 21. In this example, the annular gear 21 is coupled to a first bearing portion. Thus, the first bearing portion can rotate relative to the second bearing portion.

[0051] The yaw drive 22 in the example of Figure 5A is located inside the tower. The ring gear 21 is also located inside the tower.

[0052] 5B shows diagrammatically a yaw system 20 with an external yaw drive 22, where the pinion 25 engages with an annular gear 21 coupled to the tower 2. A first bearing part includes a guide plate with the annular gear 21 and is connected to the tower 2. The yaw drive 22 is external in this example in the sense that it is outside the outer periphery of the tower 2.

[0053] In some of these examples, the gliding plate may be integrally formed with at least one of the ring gear 21 or the tower 2. In some examples, the gliding plate may be formed by several pieces or segments.

[0054] In some examples, the nacelle frame 44 may include a number of mounting holes 28 that fit over the yaw drive 22. In some examples, the ring gear 21 may be connected, for example welded or fastened, to the planing plate. The ring gear 21 and the planing plate may form an integral part.

[0055] In all examples disclosed herein, the sliding yaw bearing includes three general surfaces covered with a number of sliding pads. These sliding pads are in sliding contact with a steel disc with gear teeth that form the sliding disc / gear rim. The teeth may be located on the inner or outer cylindrical surface of the disc, although the arrangement of the sliding pads as well as their exact number and location vary widely among existing designs.

[0056] The pads in any of these examples may be made from a polymer plastic such as polyoxymethylene plastic (POM), polyethylene terephthalate (PET), or polyamide (PA).

[0057] 6 shows diagrammatically a bearing assembly which may form part of the yaw bearing. The bearing assembly may be mounted to a nacelle, in particular to a bedplate or frame of the nacelle.

[0058] The bearing assembly may include a number of mounting holes 28 on a flange located on the outside diameter of the tower. As previously described, the yaw drive may be mounted in these holes. The bearing assembly in this example has a different number of nacelle gliding pads 53 on one side than the other. Also, in some examples, the pad material may be different on opposing sides (forward or aft, upwind or downwind) as well.

[0059] In a further aspect of the disclosure, a direct drive wind turbine is provided having a tower, a nacelle rotatably mounted to the tower via a sliding yaw bearing, a wind turbine rotor, and a generator operatively connected to the wind turbine rotor, the generator and the wind turbine rotor are disposed on the windward side of the nacelle, the sliding yaw bearing is coupled to the tower and includes a disk with an annular gear including a plurality of sliding pads, and a plurality of calipers mounted to the nacelle, the calipers partially surrounding the disk with the annular gear, and the calipers are disposed differently on the windward side of the nacelle and the leeward side of the nacelle.

[0060] The yaw bearing system according to all the examples shown herein includes a sliding pad, in particular they all include a bottom sliding pad, an upper sliding pad, and a radial sliding pad. In some examples including sliding pads, the radial sliding pad may not be used, only the upper and the lower sliding pads. In some examples, the upper and lower sliding pads may be made of different materials since they may be subjected to different loads. In particular, a first material may be used for the upper sliding pad on the leeward side and the bottom sliding pad on the windward side, and a second material may be used for the bottom sliding pad on the leeward side and the upper sliding pad on the windward side.

[0061] This specification uses examples to disclose the invention, including preferred embodiments, and also enables one of ordinary skill in the art to practice the invention, including making and using any device or system and performing any incorporated method. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those of ordinary skill in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the language of the claims, or if they include equivalent structural elements that do not differ substantially from the language of the claims. Those of ordinary skill in the art can mix and match aspects from the various embodiments described above, as well as other known equivalents for each such aspect, to construct further embodiments and techniques according to the principles of the present application. When reference numerals related to the drawings are placed within parentheses in the claims, these reference numerals are merely for enhancing the clarity of the claims, and should not be construed as limiting the scope of the claims. [Explanation of symbols]

[0062] 1. Wind Turbine 2. Tower 3 Support surface 4. Nacelle 5 Rotor 6 Hub 7 Rotor Blades 8 Main rotor shaft 9 Gearbox 10. Generator 11 Generator shaft 12 Support frame 20 Yaw system, sliding yaw bearing system 21 Annular gear, gear teeth 22 External yaw drive 23 Motor 24 Gearbox 25 Pinion 28 Mounting holes 40 Second bearing part 40A Windward 40B Downwind 43 Mechanism 44 Nacelle frame, spring 45 Caliper 46 Caliper 47 Nacelle sliding pad, radial sliding pad 49 Nacelle sliding pad, bottom sliding pad 50 annular disc, first bearing part 53 Tower Slide Pad 100 Wind Turbines 200 Direct Drive Wind Turbine

Claims

1. A sliding yaw bearing system (20) for use in a wind turbine (1), comprising: a first bearing part (50) configured to be mounted on a tower (2) of the wind turbine (1); a second bearing part (40) configured to be mounted in a nacelle (4) of the wind turbine (1); Including, The windward portion (40A) of the second bearing portion (40) is different from the leeward portion (40B) of the second bearing portion (40), The leeward portion (40B) of the second bearing portion (40) is configured to support higher bending loads in the longitudinal direction of the tower (2).

2. The planing yaw bearing system (20) of claim 1, wherein the second bearing portion (40) includes a plurality of nacelle planing pads (47, 49).

3. A sliding yaw bearing system (20) for use in a wind turbine (1), comprising: a first bearing part (50) configured to be mounted on a tower (2) of the wind turbine (1); a second bearing part (40) configured to be mounted in a nacelle (4) of the wind turbine (1); Including, The windward portion (40A) of the second bearing portion (40) is different from the leeward portion (40B) of the second bearing portion (40), The second bearing portion (40) includes a plurality of nacelle gliding pads (47, 49); A planing yaw bearing system (20) wherein the number of nacelle planing pads (47, 49) is greater in the leeward portion (40B) of the second bearing portion (40) than in the windward portion (40A) of the second bearing portion (40).

4. A sliding yaw bearing system (20) for use in a wind turbine (1), comprising: a first bearing part (50) configured to be mounted on a tower (2) of the wind turbine (1); a second bearing part (40) configured to be mounted in a nacelle (4) of the wind turbine (1); Including, The windward portion (40A) of the second bearing portion (40) is different from the leeward portion (40B) of the second bearing portion (40), The second bearing portion (40) includes a plurality of nacelle gliding pads (47, 49); A planing yaw bearing system (20), wherein the material of the nacelle planing pads (47, 49) is different between the leeward portion (40B) of the second bearing portion (40) and the windward portion (40A) of the second bearing portion (40).

5. A sliding yaw bearing system (20) for use in a wind turbine (1), comprising: a first bearing part (50) configured to be mounted on a tower (2) of the wind turbine (1); a second bearing part (40) configured to be mounted in a nacelle (4) of the wind turbine (1); Including, A planing yaw bearing system (20) wherein a windward portion (40A) of the second bearing portion (40) is different from a leeward portion (40B) of the second bearing portion (40). The first bearing portion (50) includes an annular disk (50) having a tower sliding pad (53), the annular disk (50) including gear teeth (21) on a radial surface of the disk (50).

6. 6. The planing yaw bearing system (20) of claim 5, wherein the tower planing pad (53) is attached to an upper surface of the disk (50).

7. A sliding yaw bearing system (20) for use in a wind turbine (1), comprising: a first bearing part (50) configured to be mounted on a tower (2) of the wind turbine (1); a second bearing part (40) configured to be mounted in a nacelle (4) of the wind turbine (1); Including, The windward portion (40A) of the second bearing portion (40) is different from the leeward portion (40B) of the second bearing portion (40), The second bearing portion (40) includes a plurality of calipers (45, 46).

8. 8. The planing yaw bearing system (20) according to claim 7, wherein the number of the calipers (45, 46) and / or the size of the calipers (45, 46) are different in the windward portion (40A) and the leeward portion (40B).

9. 9. The planing yaw bearing system (20) of claim 7 or 8, wherein the caliper (45, 46) includes a bottom sliding pad (49) configured to contact a bottom of the disc (50).

10. 10. The sliding yaw bearing system (20) according to any one of claims 7 to 9, wherein the calipers (45, 46) include radial sliding pads (47) configured to contact radial surfaces of the discs (50).

11. 11. The planing yaw bearing system (20) of claim 10, wherein said radial sliding pads (47) are wedge-shaped.

12. 12. The planing yaw bearing system (20) according to any one of claims 7 to 11, wherein the caliper (45) on the windward side (40A) includes a mechanism (43) for increasing friction between the first bearing part (50) and the second bearing part (40).

13. A wind turbine (1; 200) comprising a tower (2), a nacelle (4) rotatably mounted on the tower (2), and a planing yaw bearing system (20) according to any one of claims 1 to 12.

14. The wind turbine of claim 13, wherein the wind turbine (1) is a direct drive wind turbine (200).

15. The center of gravity of the rotor (5) and the nacelle (4) of the wind turbine (1) is located on the upwind side of the central axis of the tower (2); 15. The wind turbine according to claim 13 or 14, wherein the rotation axis of the rotor (5) is oriented with respect to the longitudinal axis of the tower (2) in such a way that wind load moments due to wind loads occurring during operation of the wind turbine (1) are positive moment and bending moments caused by the weight of the rotor (5) and the nacelle (4) are negative moment.

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