Wind turbines and how they are constructed

Abstract

The wind turbine comprises a first cover (2) defining a high pressure region (3), pressurizing means (4) for increasing the pressure in the high pressure region (3), a generator (6) having a stator (7) and an outer rotor (8), the stator (7) being mounted in a fixed position relative to the first cover (2), the stator (7) comprising at least one inlet opening (9, 10) opening into the high pressure region (3) so as to allow air from the high pressure region (3) to enter the stator (7) for cooling the generator (6), and a rotor (8) mounted on the stator (7). The second cover (11) or the hollow section (33) of the stator (7) extends axially into the receiving opening (12) of the first cover (2), sealing means (13) are arranged between the first cover (2) and either the second cover (11) or the hollow section (33) to seal the high pressure region (3), the rotation axis (14) of the outer rotor (8) extends through the high pressure region (3), and the inlet openings (9, 10) are arranged at a shorter distance from the rotation axis (14) than the second cover (2) or the hollow section (33).

Description

[Technical Field]

[0001] The present invention relates to a wind turbine comprising a first cover defining a high pressure region, pressurizing means for increasing the pressure in the high pressure region, and a generator having a stator and an external rotor, the stator being mounted in a fixed position relative to the first cover and comprising at least one inlet opening opening into the high pressure region, thereby allowing air from the high pressure region to enter the stator and cool the generator.Furthermore, the present invention relates to a method for constructing a wind turbine.

[0002] As wind turbine efficiency and power density increase, effective methods for cooling generator components are becoming increasingly important. One advantageous approach for cooling is to provide cooling channels in the generator's stator and use increased pressure on one side of the channels to force air through these channels. Depending on the channel geometry and the desired airflow, a relatively low pressure increase, e.g., 10 to 100 millibars, or even as little as 100 millibars, may be sufficient. However, it is also possible to force air through the cooling channels using greater pressures, e.g., several bars. Depending on the desired pressure, it may be sufficient to use, for example, multiple fans as a pressurizing means. At higher pressures, the use of a compressor may be advantageous. The pressurizing means may be driven by an electric motor or directly, for example, by the wind turbine rotor.

[0003] To adequately cool the stator, it may be advantageous to use multiple cooling channels. Typically, a separate connection, such as a duct or pipe, is required to supply air to each cooling channel. Therefore, using direct cooling with multiple cooling channels increases the weight of components installed at the top of the tower and can require a significant amount of installation space.

[0004] The present invention is therefore based on the problem of providing a simplified approach for direct cooling, which makes it possible in particular to reduce the complexity of the cooling system and thus the cost, weight and / or required installation space.

[0005] This problem is solved by the wind turbine discussed at the beginning, in which a second cover or hollow section of the stator attached to the stator extends axially into the receiving opening of the first cover, sealing means are arranged between the first cover and either the second cover or hollow section to seal the high pressure area, the rotation axis of the outer rotor extends through the high pressure area, and the inlet opening is arranged at a shorter distance from the rotation axis than the second cover or hollow section.

[0006] The use of a second cover or hollow section in conjunction with a sealing means allows the high-pressure region to extend directly to one or more inlet openings in the stator. Separate piping to surround the high-pressure region is not required. This is particularly advantageous when using a fairly large opening, such as a central inlet opening in the stator, and / or a large number of inlet openings, such as cooling channels distributed around the circumferential direction of the stator.

[0007] The second cover can be formed, for example, from metal or plastic, particularly reinforced plastic. Preferably, there is no contact between the rotor and the second cover during normal operation. Therefore, a relatively low-cost material can be used for the second cover. However, in some cases, it may be advantageous to use the second cover as a rotor stop under extreme operating conditions, or to use the second cover as a bearing, or to attach a bearing to the second cover. In these use cases, it may be advantageous to use a stronger material for the second cover.

[0008] The Young's modulus of the sealing means may be at least 2, 5 or 10 times less than the Young's modulus of the first cover and / or second cover or hollow section, thereby allowing clamping of the sealing means between the first cover and second cover or hollow section without substantially deforming the clamping components.

[0009] Preferably, there is no contact between the sealing means and the rotor or other components that move relative to the first cover during normal operation of the wind turbine, which may increase the lifespan of the sealing means compared to using sealing means located between parts with relative movement, such as between the first cover and the rotor.

[0010] The first cover may in particular extend beyond the sealing means into the vicinity of the rotor, and a further cover attached to the rotor may then substantially close off the area including the sealing means, leaving only a small gap in the first cover, thus protecting the sealing means from weather and other external influences that may increase wear and tear and consequently reduce the lifespan of the sealing means.

[0011] The pressurizing means may in principle be or comprise a compressor, for example to enable a relatively high pressure above atmospheric pressure in the high pressure region, for example 1 bar or several bars. However, it has been found that when using the wind turbine design of the present invention, a relatively low increase in pressure in the high pressure region, for example a few tens of millibars, for example 20 mbar to 200 mbar, or even a few hundred millibars, for example 200 mbar to 2 bar, can still allow a sufficient air flow through the generator. The pressurizing means may therefore be, for example, a fan that pushes additional air from the region around the wind turbine into the high pressure region.

[0012] It may be advantageous to draw air from a relatively protected area, for example from the bottom side of the nacelle of the wind turbine. In the wind turbine according to the invention, a relatively large high pressure area can be used, for example the entire interior of the nacelle.

[0013] Additional means for filtering and / or drying the supplied air may be used in conjunction with the pressurization means to avoid or at least reduce the introduction of particles and / or fluids into the generator, for example into the cooling channels.

[0014] The axis of rotation is typically a virtual axis, and therefore preferably no axis extends through the high pressure region. The outer rotor may be disposed around the outer periphery of the stator and pivotally mounted relative to the stator.

[0015] In this document, directions are defined relative to the axis of rotation: the axial direction is parallel to the axis of rotation, and the local coordinate system is defined by the radial and circumferential directions relative to the axis of rotation.

[0016] When describing the connection or attachment of components to one another, particularly in the context of wind turbines, any technique for connecting the components may be used, such as connection by bolting, gluing, threaded connections, etc.

[0017] The sealing means may be formed by a flap made of an elastic material, in particular rubber, which is attached to the first cover and is elastically bent in the axial direction from an initial state by the second cover or hollow section, or the flap is attached to the second cover or hollow section and is elastically bent in the axial direction from an initial state by the first cover.

[0018] The resilience or restoring force of the flaps causes them to be pushed radially against the components to which they are not attached, resulting in very good sealing of the high pressure area.

[0019] The use of rubber or similar materials can be advantageous because these elastic materials can have a long lifespan. Ideally, the materials and other means for protecting the sealing means are selected so that the sealing means can have a lifespan of about 30 years. At the end of such a period, it is usually necessary to carry out major maintenance and / or refurbishment of the wind turbine, and therefore the use of seals does not increase, or at least does not increase significantly, the maintenance requirements of the wind turbine.

[0020] The flap may in particular be substantially ring-shaped. The flap may be attached to either the first cover or the second cover or the hollow section before assembling the wind turbine, in particular before an assembly step involving inserting the second cover or the hollow section into the receiving opening.

[0021] If the flap is attached to the first cover and the inner diameter of the flap in its initial state is smaller than the outer diameter of the second cover or hollow section, inserting the second cover or hollow section into the receiving opening will deform the flap, thereby applying prestress that improves sealing of the gap between the first and second covers or hollow sections. The same effect can be achieved if the outer diameter of the flap is attached to the second cover or hollow section and the outer diameter of the flap in its initial state is larger than the diameter of the receiving opening.

[0022] The stator may have a stator plate at its axial end opposite a hub carrying the rotor blades of the wind turbine, with the at least one inlet opening being formed by a respective hole in the stator plate. Additionally or alternatively, a second cover may be attached to the stator plate. The stator plate may be used, for example, to attach the stator to other components. By using the holes in the stator plate opposite the hub as inlet openings, it is possible, for example, to use the entire interior space of the nacelle adjacent to the stator plate as a high-pressure zone.

[0023] The first cover can be the canopy of the wind turbine's nacelle. In this case, for example, it is possible to draw air through the floor of the nacelle and / or use the interior of the nacelle as a high-pressure area. Cool air can be supplied to any openings in the stator that open into the interior of the nacelle. This allows for easy supply of multiple cooling channels in the stator with minimal technical complexity.

[0024] The stator, in particular the stator plate, may further comprise at least one outlet opening through which air entering the stator from the inlet opening or at least one of the inlet openings can exit the wind turbine, each outlet opening being coupled to a respective duct extending from the outlet opening to an outer surface of the wind turbine, in particular to the outer surface formed by the first cover.

[0025] This design allows the air heated during generator cooling to be delivered from the wind turbine in a controlled manner, while avoiding the build-up of counter pressure that would reduce cooling efficiency. The described arrangement requires a relatively small amount of piping, as the ducts can be fed directly to the exterior surface.

[0026] In a wind turbine according to the invention, it is particularly preferred if the number of outlet openings, and therefore the number of ducts, is less than the number of inlet openings, since the inlet openings do not require additional ducts or piping, for example by merging cooling channels supplied by several inlet openings into a single outlet opening.

[0027] The outlet openings may be arranged radially within the second cover or hollow section, with respective ducts extending through the high-pressure region and designed to separate the air flowing from the respective outlet openings from the air in the high-pressure region. This may be advantageous, for example, to provide free space outside the second cover or hollow section, which may be used, for example, for a rotor brake.

[0028] The wind turbine may include a further cover formed by or attached to the rotor, axially overlapping the end section of the first cover and positioned radially outward of the end section, the end section including the receiving opening. The use of the further cover may provide sufficient protection for the sealing means from weather and other external influences.

[0029] The further cover is preferably ring-shaped with an additional end wall at the end opposite the stator, which extends radially towards the first cover, leaving a relatively small gap.

[0030] The first cover may form a flange surrounding the receiving opening, which may be positioned particularly close to the side wall of the rotor, leaving only a small gap, and in particular, when combined with an end wall of the further cover extending toward the first cover, a labyrinth seal is obtained that can better protect the sealing means from weather and other external influences.

[0031] The second cover or hollow section can pass through the rotor opening in the axial sidewall of the rotor, and the axial section of the second cover or hollow section on the side of the axial sidewall opposite the stator can have a larger diameter than the rotor opening. Preferably, the second cover or hollow section extends just outside the hole and has a cover wall that runs approximately parallel to the rotor sidewall. This arrangement can be considered an additional labyrinth seal that further reduces the introduction of dirt and fluids into the rotor's interior space.

[0032] In principle, the part or hollow section of the second cover placed in the rotor can have a diameter greater than the rotor opening, but it may be advantageous to keep the diameter of the second cover or hollow section smaller than the diameter of the rotor opening in the rotor, for example to avoid competing for installation space with the rotor brake.

[0033] The stator may have at least one hollow interior space bounded at its axial ends by two stator plates. A stator body, which may be formed from a plurality of segments, may be arranged along the periphery of the stator plates and connect the stator plates. The stator plates may have central openings and be attached to a central support structure passing through the respective central openings.

[0034] The axial end of the stator facing the hub carrying the rotor blades of the wind turbine may comprise at least one further opening, which allows at least a portion of the air entering the stator through the inlet opening or at least one of the inlet openings to leave the stator and enter an air gap arranged radially between the outer surface of the stator and the inner surface of the rotor, thereby improving cooling of rotor and stator parts adjacent to the air gap, such as for example the rotor magnets and / or the stator windings.

[0035] The further opening may in particular be formed by a further stator plate which forms that end of the stator and defines the interior space of the stator, so that the air flow can pass along the end of the stator, in particular along the further stator plate, before entering the air gap, and thus in particular cool the end coils of the stator windings.

[0036] The second cover may include a cover opening that connects the high-pressure region to the rotor's interior space, allowing air to flow from the high-pressure region into an air gap located radially between the stator's outer surface and the rotor's inner surface. This may provide an additional or alternative method for cooling components adjacent to the air gap. Air may flow along the stator plate before entering the air gap, thereby specifically cooling the end coils of the stator windings.

[0037] The stator, in particular the stator body forming the radially outer surface of the stator, may comprise at least one radial opening connected to at least one of the outlet or outlet openings to allow air to exit the air gap via the radial opening and the outlet opening. This feature is particularly useful when air is supplied to the air gap via both axial ends, as air can be removed from the air gap via the radial opening while still cooling the stator body.

[0038] The stator may include at least one fan for moving air from the or at least one of the radial openings to the or at least one of the outlet openings. The use of a fan allows for a large air flow within the air gap while maintaining a relatively low pressure within the air gap.

[0039] Additionally or alternatively, the stator may comprise at least one braking means, preferably attached to the stator plate, designed to frictionally contact at least one surface of the rotor, preferably a brake disc of the rotor, when the braking means is activated. For example, the brake disc may form the aforementioned side wall of the rotor. The braking means may, for example, have a clamp-like structure for clamping a radially inner section of the brake disc.

[0040] In some use cases, it may be desirable to have both the brake means and the second cover extending through an opening in the rotor sidewall. Typically, it is advantageous to leave only a small gap between the second cover and the radially inner surface of the sidewall. However, the brake means is advantageously disposed radially between the sidewall and the second cover. To minimize the distance between the inner surface of the sidewall and the second cover in angular segments where the brake means is not present, the radial position of the second cover may be retracted closer to the axis of rotation in radial segments with the brake means and then in radial segments without the brake means.

[0041] In addition to the wind turbine, the present invention also relates to a method for constructing a wind turbine, the method comprising: - providing a generator having a stator and an external rotor, and a first cover having a receiving opening, wherein a sealing means formed by a flap made of elastic material, in particular rubber, is attached on the one hand to the first cover and on the other hand to a second cover, the second cover being attached to the stator or to a hollow section of the stator; - placing the stator in a fixed position relative to the first cover by inserting the open end of the second cover or hollow section into a receiving opening in the first cover, thereby elastically bending the flaps in the axial direction and forming a high pressure region defined by the first cover and either the second cover or hollow section; - attaching a hub to the rotor for carrying rotor blades of the wind turbine; - attaching the rotor blades to the hub.

[0042] After the first step, further steps may be performed in any order. The method may in particular be used to build a wind turbine according to the invention. Additionally or alternatively, any of the features described with respect to the wind turbine may be introduced into the method with the above advantages and vice versa.

[0043] The cover and the stator may in particular be attached to a carrying structure, for example the carrying structure of a nacelle. The described components may in particular be arranged at the top of a tower.

[0044] Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings, which, however, are merely principle sketches designed for illustrative purposes only and are not intended to limit the invention. The drawings show: [Brief explanation of the drawings]

[0045] [Figure 1] 1 is a detailed view of an exemplary embodiment of a wind turbine according to the present invention; [Figure 2] 1A-1C illustrate intermediate steps in an exemplary embodiment of a method for constructing a wind turbine according to the present invention. [Figure 3] 3 is a detailed view of an exemplary embodiment of a wind turbine according to the invention obtained from a construction according to FIG. 2; [Figure 4] 5A-5C show intermediate steps in a further exemplary embodiment of a method for constructing a wind turbine according to the invention; [Figure 5] 5 is a detailed view of an exemplary embodiment of a wind turbine according to the invention obtained from a construction according to FIG. 4. [Figure 6] 2 is a detailed view of a further exemplary embodiment of a wind turbine according to the present invention;

[0046] 1 shows a wind turbine 1 having a first cover 2 forming the housing of a nacelle 18 of the given example, and a generator 6 having a stator 7 and a rotor 8 connected to a hub 16 that carries the blades 17 of the wind turbine 1. In this example, the components described are mounted on top of a tower 32. The internal support structure for mounting the stator 7, cover 2, and various other components is not shown for the sake of clarity and simplicity.

[0047] The stator 7 and therefore the generator 6 are cooled using a direct cooling approach, where air is introduced into the stator 7 through inlet openings 9, 10 and leaves the stator through outlet openings 19, 20. To achieve uniform and efficient cooling, it is advantageous to use multiple inlet openings 9, 10 spaced around the periphery of the stator 7. To supply air individually to each of these openings 9, 10 would require fairly elaborate piping. Therefore, in the wind turbine 1 a different approach is used to supply air to the inlet openings 9, 10.

[0048] In the wind turbine 1, a common, fairly large high pressure area 3 is used to supply air to all inlet openings 9, 10. This is achieved by mounting the stator 7 in a fixed position relative to the first cover 2 and by using a second cover 11 that is attached to the stator 7, more specifically in this example to a stator plate 15, and that extends axially into the receiving openings 12 in the first cover 2. Sealing means 13 are arranged between the first cover 2 and the second cover 11 to seal the high pressure area 3.

[0049] In this example, air is drawn from the area below the nacelle 18 via pressurization means 4 into the high pressure area 3, as shown by arrows 5. This is advantageous because this area is somewhat protected from the weather and therefore the drawn-in air is already relatively dry. Additional means (not shown) for filtering and / or drying the air are preferably used in conjunction with the pressurization means 4.

[0050] In this example, the air is drawn over a relatively large area, with the main restriction to the air flow being caused by the diameter of the cooling channels through the stator 7, so the use of a fan or other relatively simple pressurization means 4 may be sufficient. However, in principle, it would also be possible to use a compressor to further increase the pressure in the high pressure region 3 if more intense cooling of the stator 7 were required.

[0051] The above approach creates a large high pressure region 3 that extends across the axis of rotation 14 of the rotor 8. No separate ducts or pipes are required to feed the inlet openings 9, 10, thus reducing the weight and cost of the wind turbine 1 and potentially freeing up installation space within the nacelle 18 for other components.

[0052] In this example, the second cover 11 is formed as a separate part from the stator 7 and may be connected to the stator 7, and in this example in particular to the stator plate 15, for example by bolting, screwing or gluing it to the stator 7. However, in an alternative embodiment it is also possible to use a hollow section of the stator 7 itself extending into the receiving opening 12 instead of the second cover 11.

[0053] In this example, the sealing means 13 is formed by a flap made of an elastic material, for example rubber. The advantages of this design are explained with further reference to Figure 2, which shows an intermediate state of a method for constructing the wind turbine 1. Only small relevant sections are shown, comprising, on the one hand, the end section of the second cover 11, or the hollow section 33 of the stator 7 opposite the hub 16, and, on the other hand, the end section of the first cover 2 forming the receiving opening 12.

[0054] 1 and 2, in this example, before the second cover 11 or hollow section 33 is introduced into the receiving opening 12, the sealing means 13 is already attached to the first cover 2, for example by gluing, bolting or screwing, as indicated by arrow 34 in Fig. 2. In its initial state 36, the flap forming the sealing means 13 is approximately ring-shaped, the inner circumference of the flap being smaller than the outer circumference of the second cover 11 or hollow section 33.

[0055] When the second cover 11 or hollow section 33 is introduced into the receiving opening 12, the flap is bent from its initial state 36 to its final state 37, as indicated by arrow 35. In the final state 37, the elasticity of the flap generates a restoring force that presses the flap against the outer surface of the second cover 11 or hollow section 33, thus ensuring a very tight sealing of the high pressure area 3.

[0056] Figure 3 shows a detailed view of the wind turbine resulting from the structure according to Figure 2. In addition to the explicit visualization of the final state 37 of the sealing means 13, the only change compared to the wind turbine 1 shown in Figure 1 is the use of a separate component, namely a brake disc 38, to form the side wall 28 of the rotor 7. The use of such a brake disc 38 will be explained below with reference to Figure 6.

[0057] Figure 4 shows the same step in a slightly modified method for constructing a slightly modified wind turbine 1. In this case, the sealing means 13 is attached to the second cover 11 or hollow section 33. The sealing means 13 is formed by a ring-shaped flap extending to an outer diameter that is larger than the diameter of the receiving opening 12. The flap is thus bent from an initial state 36 to a final state 37, as indicated by arrow 35 in Figure 4, and the restoring force generated by the elasticity of the flap presses the sealing means 13 against the inner surface of the first cover 2, thus ensuring a very tight sealing of the high-pressure area 3, as described above.

[0058] Figure 5 shows a detailed view of the wind turbine obtained from the structure according to figure 4. Apart from the different shape and positioning of the sealing means 13 in the final state 37, the wind turbine shown in figure 5 is identical to the wind turbine shown in figure 3.

[0059] Returning to Figure 1, the stator 7, and more particularly the stator plate 15 used in this example, further comprises outlet openings 19, 20 through which the air entering the stator through the inlet openings 9, 10 can leave the wind turbine. In order to allow controlled removal of the air heated by cooling the stator 7, as indicated by arrows 30, 31, ducts 21, 22 can be used to keep that air separated from the air in the high pressure region 3 and to supply the air to the outer surface 23 of the wind turbine 1, and more particularly of the first cover 2.

[0060] In principle, the outlet openings 19, 20 may alternatively be arranged at a larger radius than the second cover 11, thus allowing the air outside the high-pressure region 3 to be discharged directly. However, it has been found that even in these cases it is usually necessary to use some kind of duct to avoid heating of the rotor 8 by the air that has passed through the stator 7. Therefore, in most use cases it is advantageous to feed the duct 21 through the high-pressure region 3, since this avoids competing for installation space with components inside the rotor, such as the rotor brake.

[0061] To ensure a long service life of the sealing means 13, the sealing means 13 is protected from weather and other external influences by a combination of a flange 26 of the first cover 2 surrounding the receiving opening 12 and a further cover 24 attached to the rotor 8 and overlapping an end section 25 of the first cover 2, more specifically the flange 26, as shown in Figure 1. The resulting arrangement, shown in Figure 1, can be considered a labyrinth seal, thus enabling a strong limitation of the amount of fluid and / or dirt introduced into the area of ​​the sealing means 13 without requiring frictional contact between the first cover 2 and the rotating component.

[0062] In Figure 1, the second cover 11 widens in the axial section 29 after passing through a rotor opening 27 in the axial side wall 28 of the rotor. This configuration also allows a kind of labyrinth seal to be formed between the area of ​​the seal 13 and the interior space of the rotor, thus further limiting the amount of fluid and dirt that can be introduced into the interior of the rotor 8 and / or the area of ​​the stator 7 via the gap between the further cover 24 and the first cover 2 and the gap between the side wall 28 and the second cover 11.

[0063] Figure 6 shows a detailed view of a further wind turbine in which modified airflow may be used compared to the example shown in Figure 1 to improve cooling of components near the air gap 41 of the magnets 40 off the rotor 6 and the stator windings (not shown), for example. As most of the relevant features have already been described in the previous example, the following discussion will focus on some key differences of the implementation shown in Figure 6 with respect to Figure 1 and some implementation details not shown or described in the previous example.

[0064] In Figure 6, two separate paths are used to supply air to the air gap 41, indicated by arrows 39. To provide a first path, the axial end of the stator 7 facing the hub is provided with a further opening 43, which allows at least part of the air that enters the stator 7 via the inlet openings 9, 10 to leave the stator 7 and enter the air gap 41. The further opening 43 is formed in this example by a further stator plate 42.

[0065] To provide a second path, the second cover 11 has a cover opening 44 connecting the high pressure region 3 to the interior space of the rotor 6 to allow air to flow from the high pressure region 3 to the air gap 41.

[0066] As the air gap 41 is supplied with air from both axial ends of the stator, a stator body 49 forming the radial outer surface of the stator 7 has radial openings 47 connected to the outlet openings 19 to allow air to leave the air gap 41 via the radial openings 47 and the outlet openings 19. A fan 50 is used to draw air inwards and expel the air via ducts 22.

[0067] In the exemplary embodiment, only a single bearing 48 at the distal end of the rotor is used to support the rotor. In alternative embodiments, for example, bearings can be used at both ends of the rotor.

[0068] The stator comprises braking means 45, which in the example according to Fig. 6 are attached to the stator plate 15. The braking means 45 are designed to come into frictional contact with the brake discs 38 of the rotor when the braking means 45 are activated. As shown diagrammatically in Fig. 6, parts 46 of the braking means can extend beyond the brake discs 38 when the braking means 45 are activated, for example to clamp the brake discs 38 from both sides. This can result in a circumferential overlap between the second cover 11 and the braking means 45. In Fig. 6, parts of the braking means 45 are therefore hidden behind the second cover 11. The shape of the second cover 11 can therefore be selected to accommodate the presence of the braking means 45, for example by providing a cavity for accommodating part of the braking means 45.

[0069] Although the present invention has been described in detail with reference to preferred embodiments, the invention is not limited to the disclosed examples, and those skilled in the art can derive other variations therefrom without departing from the scope of the invention.

Claims

1. A wind turbine comprising a first cover (2) defining a high pressure region (3), pressurizing means (4) for increasing the pressure in said high pressure region (3), a generator (6) having a stator (7) and an outer rotor (8), said stator (7) being mounted in a fixed position relative to said first cover (2), said stator (7) comprising at least one inlet opening (9, 10) opening into said high pressure region (3) so as to allow air from said high pressure region (3) to enter said stator (7) for cooling said generator (6), and a second rotor (8) mounted on said stator (7). a cover (11) or a hollow section (33) of the stator (7) extending axially into the receiving opening (12) of the first cover (2), a sealing means (13) being arranged between the first cover (2) and either the second cover (11) or the hollow section (33) for sealing the high pressure area (3), a rotation axis (14) of the outer rotor (8) extending through the high pressure area (3), and the inlet openings (9, 10) being arranged at a shorter distance from the rotation axis (14) than the second cover (2) or the hollow section (33).

2. 2. The wind turbine according to claim 1, characterized in that the sealing means (13) is formed by a flap made of elastic material, in particular rubber, which is attached to the first cover (2) and is elastically bent in the axial direction from an initial state (36) by the second cover (11) or the hollow section (33), or the flap is attached to the second cover (11) or the hollow section (33) and is elastically bent in the axial direction from an initial state (36) by the first cover (2).

3. 3. Wind turbine according to claim 1 or 2, characterized in that the stator (7) comprises a stator plate (15) at its axial end opposite a hub (16) carrying the rotor blades (17) of the wind turbine (1), and the at least one inlet opening (9, 10) is formed by a respective hole in the stator plate (15) and / or the second cover (11) is attached to the stator plate (15).

4. Wind turbine according to any one of claims 1 to 3, characterized in that the first cover (2) is a canopy of a nacelle (18) of the wind turbine (1).

5. 5. Wind turbine according to any one of claims 1 to 4, characterized in that the stator (7), in particular the stator plate (15), further comprises at least one outlet opening (19, 20) through which air entering the stator (7) through the inlet openings (9, 10) or at least one of the inlet openings (9, 10) can exit the wind turbine (1), each outlet opening (19, 20) being connected to a respective duct (21, 22) extending from the outlet opening (19, 20) to an outer surface (23) of the wind turbine (1), in particular to an outer surface (23) formed by the first cover (2).

6. 6. The wind turbine according to claim 5, characterized in that the outlet openings (19, 20) are arranged radially in the second cover (11) or in the hollow section (33), and the respective ducts (21, 22) extend through the high pressure region (3) and are designed to separate the air flowing from the respective outlet openings (19, 20) from the air in the high pressure region (3).

7. 7. The wind turbine according to claim 1, further comprising a further cover (24) formed by or attached to the rotor (8), axially overlapping an end section (25) of the first cover (2) and arranged radially outward of said end section (25), said end section (25) comprising said receiving opening (12).

8. Wind turbine according to any one of claims 1 to 7, characterized in that the first cover (2) forms a flange (26) surrounding the receiving opening (12).

9. 9. The wind turbine according to claim 1, wherein the second cover (11) or the hollow section (33) passes through a rotor opening (27) in an axial side wall (28) of the rotor (8), and an axial section (29) of the second cover (11) or the hollow section (33) on a side of the axial side wall (28) opposite the stator (7) has a larger diameter than the rotor opening (27).

10. 10. Wind turbine according to any one of claims 1 to 9, characterized in that the hub (16) or the axial end of the stator (7) facing the hub (16), which carries the rotor blades (17) of the wind turbine (1), comprises at least one further opening (43), so that at least a part of the air entering the stator (7) through the inlet openings (9, 10) or at least one of the inlet openings (9, 10) can leave the stator (7) and enter an air gap (41) arranged radially between the outer surface of the stator (7) and the inner surface of the rotor (6).

11. 11. Wind turbine according to any one of claims 1 to 10, characterized in that the second cover (11) comprises a cover opening (44) connecting the high pressure area (3) to an internal space of the rotor (6) for allowing air to flow from the high pressure area (3) to an air gap (41) or to the air gap (41) arranged radially between the outer surface of the stator (7) and the inner surface of the rotor (6).

12. 12. Wind turbine according to claim 10 or 11, characterized in that the stator (7), in particular the radially outer surface of the stator (7) or a stator body (49) forming said radially outer surface, comprises at least one radial opening (47) connected to at least one of the outlet openings (19, 20) or the outlet openings (19, 20) in order to allow air to leave the air gap (41) via said radial opening (47) and said outlet openings (19, 20).

13. 13. Wind turbine according to any one of claims 1 to 12, characterized in that the stator comprises, on the one hand, at least one braking means (45), preferably attached to the stator plate (15), which is designed to come into frictional contact with at least one surface of the rotor (6), preferably a brake disc (38) of the rotor, when the braking means (45) is activated, and / or, on the other hand, at least one fan (50) for moving air from the or at least one of the radial openings (47) to the outlet openings (19, 20) or at least one of the outlet openings (19, 20).

14. A method for constructing a wind turbine (1), comprising: - providing a generator (6) having a stator (7) and an external rotor (8), and a first cover (2) having a receiving opening (12), with sealing means (13) formed by a flap made of elastic material, in particular rubber, attached on the one hand to said first cover (2) and on the other hand to a second cover (11), said second cover (11) being attached to said stator (7) or to a hollow section (33) of said stator (7); - placing the stator (7) in a fixed position relative to the first cover (2) by inserting the open ends of the second cover (11) or the hollow section (33) into the receiving openings (12) of the first cover (2), thereby elastically bending the flaps in the axial direction and forming a high pressure area (3) defined by the first cover (2) and either the second cover (11) or the hollow section (33); - attaching to said rotor (8) a hub (16) for carrying the rotor blades (17) of said wind turbine (1); - mounting rotor blades (17) on said hub (16); A method comprising:

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