EP2274516A2

EP2274516A2 - Wind turbine comprising an air inlet assembly

Info

Publication number: EP2274516A2
Application number: EP08749404A
Authority: EP
Inventors: Thomas Feddern
Original assignee: Powerwind GmbH
Current assignee: Powerwind GmbH
Priority date: 2008-05-08
Filing date: 2008-05-08
Publication date: 2011-01-19
Also published as: WO2009135509A2; WO2009135509A3

Abstract

The invention relates to a wind turbine comprising a tower, a nacelle which is located at the upper end of the tower, is rotatably mounted in relation to the vertical tower axis and has an interior that is delimited by a housing, a rotor that is mounted rotatably in relation to the nacelle, runs transversally to the tower axis and can be made to rotate about the rotor axis by an air stream that impinges on the rotor in a flow direction running approximately parallel to the rotor axis, the nacelle housing having a convex or level flow conduction surface for an air stream flowing in the flow direction and an air inlet assembly located on the housing with an air inlet for supplying air to the interior. The air inlet assembly has a recess in the flow conduction surface extending towards the air inlet opening in the flow direction and the air inlet opening is located between a delimitation surface of the recess and the adjoining region of the flow conduction surface.

Description

WIND ENERGY SYSTEM WITH AIR INTAKE ASSEMBLY

The invention relates to a wind energy plant with a tower, a gondola arranged at the upper end of the tower, rotatably mounted with respect to the vertical tower axis and an inner space delimited by a housing, a rotor mounted rotatably with respect to a rotor axis extending transversely to the tower axis with respect to the nacelle, which can be displaced by an air flow in a direction of flow approximately parallel to the rotor axis in a rotation about the rotor axis, the nacelle housing having a convex or planar Strömungsleitfläche for an inflowing in the air flow direction, and arranged on the housing and an air inlet opening having air inlet assembly for supplying air to the interior.

Such wind turbines are known (DE 10 2004 046 700 A1). Due to the rotatable mounting of the nacelle on the tower, the rotor of the system is suitably rotated in the wind during operation, so that the wind flowing in a direction of flow onto the rotor causes the rotor to rotate. In a state of the art, usually The windward side of the nacelle is turned into the wind while a leeward runner would turn the rotor side of the nacelle to the leeward side (lee). After (windward runner) or before (leeward runner) the wind causes the rotor of the system to rotate, it flows around the nacelle housing essentially in the direction of flow along this usually streamlined outer surface. In particular, the outer or outer surface of the nacelle housing has one or more convex or planar flow guide surfaces for the air flow flowing in the wind direction or inflow direction along which the air flow is conducted around the nacelle.

The conversion of the obtained mechanical rotor energy into electrical energy via a coupled to the rotor and arranged in the nacelle generator of the wind turbine. In the conversion results in heat loss, the larger, the higher the power of the generator is. To ensure reliable operation of the system, therefore, a cooling of the generator is required. The cooling takes place via the supply of outside air into the interior via an arranged on the housing of the nacelle air inlet assembly and an air inlet opening of the air inlet assembly.

An advantageous arrangement of the air inlet opening is described for example in DE 10 2004 046 700 A1. Accordingly, an air gap between the tower and nacelle is provided, is sucked by the outside air from a fan arranged within the nacelle. This arrangement is advantageous because the air suction against the gravity direction takes place and therefore the air sucked contains less foreign particles such as raindrops, salt water drops, dust particles, etc., which can adversely affect the components to be cooled. The air sucked in by the fan flows around the components exposed in the nacelle interior to the intake air flow and thus ensures heat dissipation and thus cooling. Also, air intake arrangements in the form of Hutzen are known.

However, it has been found that in conventional wind turbines, especially at varying wind speed conditions, the air supply is not completely satisfactory. For example, the performance of the fan at high wind speeds, correspondingly higher generator power and correspondingly more dissipated heat must be controlled accordingly high. In view of the not completely satisfactory air supply of conventional wind turbines, the invention is therefore an object of the invention to provide an improved air supply into the nacelle interior.

This object is achieved by a development of the wind turbine of the type mentioned essentially in that the air inlet arrangement has a extending in the direction of flow towards the air inlet opening indentation in the flow guide and the air inlet opening between a boundary surface of the recess and the adjoining region of the Flow control surface is arranged.

In this case, the invention is based on the surprisingly simple knowledge that a satisfactory amount of air can pass through the inventive design of the air intake assembly in a passive manner in the gondola interior. Thus, the complex active air intake can be reduced or even waived. In addition, the supplied air flow increases with increasing wind strength, ie just when there is also a higher cooling demand.

The air flow follows the indentation in the flow guide and flows toward the air inlet opening, through it and into the nacelle interior. Due to the design of the inlet in the direction of flow lying in front of the air inlet opening indentation is also achieved that the largest possible amount of air can flow into the interior of the gondola. This is because due to the indentation, air vortices are formed which at least in part prevent a boundary layer of the air flow from entering the air inlet opening due to the friction at the surface with respect to the outside air flow. The pressure loss during inflow is comparatively low.

By a recessed area is here to be understood a concave area of a part of the outer area with respect to a close vicinity of this area. In particular, it does not require a concave course of the surface in the inflow direction or extension direction of the indentation, even if the latter represents an advantageous realization. Thus, in particular, a region which is close to the direction of extent in the direction of extent the outer surface itself form a curvature to the outside with respect to a more distant environment, the concave area nevertheless forming an indentation with respect to the near surrounding area.

The realization of the air inlet arrangement according to the invention has features of a so-called NACA air inlet (National Advisory Committee for Aeronautics, ACR No. 5120), in particular the profile shown in FIGS. 3 to 5 corresponds to that of a NACA air inlet. This was developed to allow even at supersonic speed an aerodynamics of an aircraft as little as possible affecting air supply. Furthermore, NACA inlets are also used in automobiles (US 5,042,603), particularly where good aerodynamics of the vehicles is important, e.g. in racing and racing cars designed for racing purposes. Although the aerodynamic shape of the nacelle surface, in particular with respect to the air inlet assembly in wind turbines plays a completely minor role, it has surprisingly been found that can be achieved by the above-described effect of vortex formation that a larger amount of air flows into the nacelle interior and thus for a opposite conventional wind turbines provides improved airflow.

According to a particularly preferred embodiment, a surface normal defining a longitudinal direction of the indentation has a component in the direction of the inflow direction on the cross-sectional area of the air inlet opening and preferably extends approximately in anti-parallel thereto. Thus, the incoming air quantity can be increased again.

Suitably, the air inlet opening in this case extends in a depth direction directed from the flow guide surface to the interior of the gondola. Since the air flow in front of the air inlet opening is substantially tangential to the nacelle surface in this area, the inflowing air quantity can be further optimized by the air inlet opening arranged in the depth direction. Thus, the air inlet opening forms a step or discontinuity in the height profile of the outer surface between the boundary surface of the recess, eg the indentation floor, and the adjacent flow guide area, and the depth direction is approximately anti-parallel to the normal in this adjacent area. According to a particularly preferred embodiment, the boundary surface of the indentation has a first wall region whose wall height, which is determined with respect to the depth direction, decreases in the longitudinal direction. This promotes the above-mentioned vortex formation and ensures good inflow behavior along the wall area.

In a further preferred embodiment, the air inlet opening extends in a transverse, in particular perpendicular to the depth direction and transverse to the longitudinal direction extending width direction, and a distance in the width direction from the first wall portion to a longitudinal direction and with respect to the width direction through the center of the air inlet opening and in particular orthogonal to it extending axis x decreases in the longitudinal direction. In this way, a further improved air inflow behavior is achieved, since this profile of the wall region with respect to the width direction further promotes the advantageous vortex formation.

According to an expedient embodiment, the first wall region extends up to the air inlet opening, in particular while approximating the height profile of the flow guide at the upper end of the wall to the height profile of the adjacent flow guide. Thus, the inflowing air can be guided to the side of the air inlet opening and in particular a Lufückückstaubildung be prevented.

A further advantageous embodiment results when a ratio between width spacing and wall height in the range of 1 to 4, preferably 1, 3 to 3.3, in particular 1.7 to 2.7, and in particular if this ratio for up to 30 % of the longitudinal extent of the concave region, preferably up to 60%, in particular up to 80% is satisfied.

According to a further preferred embodiment, the first wall region extends to the end region of the recess facing away from the air inlet opening. An air backflow is avoided, and an air flow from the upstream of the indentation lying Strömungsleitflächenbereich to the indentation in a smooth manner.

According to a particularly preferred embodiment, the course of the first wall region is at least partially curved, and in particular the curvature in the longitudinal direction is first directed to the axis and then after passing through a point of inflection directed away from the axis. In this way, a further improved flow profile can be obtained since it is again better avoided that a boundary layer of the air flow reaches the air inlet opening due to the friction with the surface with respect to the outside air flow reduced flow velocity. The pressure loss is further reduced.

In this connection, the inflection point can be arranged in the range of 25 to 65% of the length, preferably 35 to 55%, in particular 40 to 50%. In this area, the specified effect is effectively amplified.

According to a particularly preferred embodiment, the decrease in the wall height with respect to the corresponding length of the wall region in the longitudinal direction defines an average gradient in the range of 3 ° to 20 °, preferably 5 ° to 10 °, in particular 6 ° to 8 °. This characteristic of the height profile of the indentation allows an optimized velocity profile of the incoming air and correspondingly low pressure losses can be achieved.

In this context, a bottom region of the indentation may extend in a straight line in a section through a plane determined by the longitudinal direction and the depth direction, and in particular the average gradient may define a ramp angle. An appropriately designed floor area can be easily realized structurally and ensures a suitable

Airflow profile.

According to a particularly preferred embodiment, the indentation, opposite the first wall region, has a second wall region, which in particular has the abovementioned properties of the first wall region. Thus, the advantages achieved on one side can be implemented on both sides, resulting in a over the full width of the air inlet opening satisfactory velocity profile and only a very small pressure drop of the incoming air.

According to an expedient embodiment, the axis extends perpendicular to the air inlet opening, and the air inlet arrangement is formed substantially symmetrical to the axis. In this way, a uniform flow profile of the incoming air be achieved. A limitation of the symmetry may be due to the fact that, for example, the wall portions fail due to the curvature of the flow guide area, in which the air inlet assembly is provided, of different lengths.

According to a particularly preferred embodiment, the bottom area dips into the outer surface of the nacelle as a slit-like cut. Thus, the air flow is already suitably guided towards the interior.

According to a particularly preferred embodiment, a width to height ratio of the air inlet opening is in the range of 2.5 to 5.5, preferably 3 to 5, in particular 3.5 to 4.5. This provides suitable inflow conditions in the opening area.

With regard to the arrangement of the air inlet assembly, the orientation is expediently expedient such that the longitudinal direction extends substantially to the windward side, so in accordance with the prior art designed as a so-called windward wind turbines, in which the rotor blades on the side facing the wind Gondola are facing the rotor.

In particular, it is preferred if a cutting angle between the rotor axis and the projection of the longitudinal direction of the indentation on the plane defined by the rotor axis and tower axis lies in a range of 0 to 30 °, preferably 0 to 20 °, in particular 0 to 10 °. Thus, the air intake arrangement can supply the largest possible amount of air.

According to an expedient embodiment, the air inlet arrangement is in the lower

Area of the nacelle, in particular arranged near the lowest area of the nacelle. In particular, with indirect cooling effect of the incoming air e.g. via a arranged in the lower half of the gondola heat exchanger, the supplied air reaches the cooling target faster.

In this regard, it is also advantageous if the recess is arranged with respect to the rotor axis in the region of the tower of the nacelle on the tower. This allows the air to flow into the rear area of the nacelle. With regard to the dimensioning of the air inlet arrangement, the invention provides no special restrictions. However, it is preferred that the length of the indentation in relation to the tower diameter at the nacelle level be in the range of 0.1 to 2, preferably from 0.25 to 1.5, more preferably from 0.5 to 1.25, especially from 0.8 to 1, 1. Preferred absolute dimensions are given in claims 22 to 25.

Although only one air intake arrangement has heretofore been mentioned, the number of provided air intake arrangements according to the invention is not further limited and two or more may be provided.

For discharging the inflowing air, at least one air outlet arrangement for the air supplied via the air inlet arrangement can expediently be provided, which can advantageously be arranged in particular in a region of the nacelle tapering in the direction of the rotor axis. The latter arrangement is particularly favorable with regard to the external flow, because the decrease in the speed of the outer flow in the tapered region of the nacelle facilitates the removal of the air and, on the other hand, the negative pressure in this region outside the nacelle favors the removal of air. Furthermore, the air can be efficiently guided out of the nacelle when the air outlet assembly has one or more features of the air intake assemblies described above.

As mentioned in the introductory part, the air supply serves primarily to cool the generator of the wind turbine. However, the air inlet arrangement downstream air duct can also be designed so that in addition an optionally coupled between the rotor and generator gearbox, a frequency converter and / or a transformer is cooled.

In procedural terms, the invention provides a method of operating a wind turbine essentially characterized in that the air supply to the nacelle interior is achieved at least in part in a passive manner by an air inflow through an air inlet arrangement having one or more of the above characteristics. Further features, details and advantages of the invention will become apparent from the following description with reference to the accompanying figures, of which

1 shows a nacelle of a wind turbine according to the invention in a side view,

FIG. 2 shows the gondola shown in FIG. 1 in a perspective view, FIG.

Fig. 3 shows a geometry of the indentation of

Fig. 4 shows the recess of the air inlet assembly in a sectional view taken along the axis X of Fig. 3, and Fig. 5 shows a sectional view of the first portion of the air inlet assembly taken along lines VV of Figs , Figs. 6a, b show a first realization of an air inlet arrangement according to the invention,

Figs. 7a, b show a second embodiment of an inventive air inlet arrangement.

In Fig. 1, a nacelle with nacelle housing 10 is shown in a side view, the lateral surface or outer surface 3 is formed convexly from the basic shape. Thus, the outer surface 3 of the housing 10 forms a flow guide for the wind flowing around the nacelle. Between the outer surface areas 3.1, 3.2 and 3.3, a recess 1 is formed. The indentation 1 represents a concave air inlet in the form of a gap continuously increasing and widening in the direction of flow a (hereinafter a) and against the drawn longitudinal direction I (hereinafter I). Outside air flowing along the lateral surface 3 with component in the direction of flow a , flows along the bottom surface 5 of the gap 1 and through the inlet opening 12 in the nacelle interior. The inlet opening 12 extends in a parallel to the plotted normal n (in the following n) extending height direction h (Fig. 2, hereinafter h) or the opposite direction of the depth of the gondola interior.

As can be seen from Fig. 1, the slit-shaped air inlet 1 spreads from a measured in the width direction w (hereinafter w) width W ₀ at the inlet opening 12 opposite end to the inlet opening 12, whose width is designated W. In this case, a wall surface 4, which compensates for a difference in height in the outer surface profile between the bottom surface 5 of the air inlet gap 1 and the transverse thereto adjacent area 3.3 of the outer surface 3, formed curved, but as better seen in the schematic representation of Fig. 3 and there will be explained in more detail. On the other hand, the wall surface 6 opposite the wall surface 4 compensates for a height difference of the bottom surface 5 from the region 3.2 of the outside surface 3 adjoining the outside, and is arranged substantially axially symmetrically with respect to the wall surface 4.

As can be seen from Fig. 1, but even better from Fig. 2, the gap 1 begins at its opposite end of the opening 12, to immerse under an imaginary shape-preserving continuation between the areas 3.1, 3.2 and 3.3 of the outer surface. It creates a kind of spoiler. The depth of the gap or the height h _{x of} the walls 4 and 6 rises to the opening 12 at its height H. In the illustrated embodiment, this increase is linear. The floor area 5 is formed like a ramp with a uniform inclination, wherein the inclination angle in the concrete embodiment is 7 °.

The air inlet assembly 1, 12 is formed in this embodiment at the level of the tower, not shown, near an insertion opening 7 for the upper end of the tower. The longitudinal direction I has substantially the same angle of inclination relative to the direction of gravity as the rotor axis, which is indicated in Figures 1 and 2 and designated R. Not shown in Figures 1 and 2 is an air outlet opening, e.g. may be formed at the rear tapered end of the nacelle.

Even though only one air inlet gap 1 and one air inlet opening 12 are shown in FIGS. 1 and 2, a symmetrically arranged further air inlet arrangement 1 ', 12' can be formed on the other side of the nacelle, for example. But it could also be provided several smaller sized air intake assemblies. Due to the profile of the air inlet gap 1, the air can pass through the inlet opening 12 at the speed of the outside air flow, thus providing improved ventilation of the nacelle interior. At extremely low pressure losses, an effective passive air supply is realized.

In Fig. 3, the profile of the air inlet gap 1 with respect to a spanned by the longitudinal direction I and width direction w plane can be seen again in more detail. The walls 4 and 6 are axisymmetric to the central axis X to each other. They extend substantially perpendicularly from the opening surface 12, curve in the direction of the axis X, reach a point of inflection at approximately 45% of the total length of the gap, after which they curve away from the central axis X, the curvature in Direction towards the wall end with width W ₀ increasingly reduced and the wall reaches the column end substantially in a linear form, namely at an angle of about 8 ° with respect to the central axis X. In the following Table 1, the relative width of the air inlet gap 1 is related to the width W of the air inlet opening with respect to the distance x in the direction of length I relative to the total length L indicated.

Table 1

In the present embodiment, the input width W _{0 of} the air inlet gap 1 is about 10% of the width of the gap at the air inlet opening 12. However, the input width W ₀ could also be larger or smaller, it being preferred that the ratio of input width W ₀ and end width W is in the range of 5 to 50%, preferably 10 to 30%, especially 10 to 25%.

Although the smooth curve shape of walls 4 and 6 shown in Fig. 3 is preferred, an approximate wall shape could also be realized by a polygon, or individual sections of low curvature could be replaced by straight courses. In Fig. 4 is a section is shown, which is taken through the central axis X of Fig. 3 in the height direction h, so that the course of the bottom 5 along the longitudinal direction I can be seen well. It can be seen that the bottom portion 5 is lowered against a dashed line indicating the height profile of the walls 4, 6, in the form of a ramp to the air inlet opening 12. By the height H of the air inlet opening 12 and the length L of the concave portion 1 results in an inclination angle α of the ramp as arctan (H / L). In the present embodiment, α is 7 °. Thus, the height h _x at the distance x from the air inlet port 12 is (1-x / L) H. A constant ramp slope is preferred, but the ramp slope need not be constant. In particular, it may be considered to also use a ramp with a variable pitch, eg as indicated by the wall curve 6 in FIG. 3, with an average pitch angle of eg 7 °.

FIG. 5 shows a cross-section along the lines V-V of FIGS. 3 and 4, respectively. It can be seen that the bottom surface 5 is evenly selected, the walls 4 and 6 enclosing a right angle with the bottom region 5 and with the outer surface regions 3.2 and 3.3 adjoining outwards. The latter, however, is an idealized representation that would be achievable while maintaining the symmetry of the air intake assembly only in a surface area with vanishing curvature. If the air inlet gap is embedded in a convex surface area, the two-sided right angle will not be realized and are e.g. the side walls in this illustration e.g. be inclined to a mid-perpendicular to the bottom surface 5. Alternatively, in an alternative embodiment, the bottom surface 5 could also be convex and in particular adapted to the convex outer surface regions 3.2 and 3.3. However, it could also be the entire recess in the cross-section, e.g. be formed parabolic, wherein the bottom portion then corresponds to the longitudinal course of the vertex line.

FIG. 6a shows an enlarged view, with respect to FIG. 1, of the air inlet opening arrangement in a first implementation. In this particular embodiment, the width W of the air inlet opening is 650 mm, the length L of the ramped inlet is 1523 mm, and the width W ₀ at the beginning of the gap is 100 mm. In Fig. 6b, the air inlet assembly of the first implementation is shown in a further enlarged view, but seen from the interior of the gondola. The height H of the air inlet port 12 is 236 mm in this example. A second embodiment of the air inlet assembly is shown in Figures 7a and 7b. These correspond, apart from different dimensions, to FIGS. 6a and 6b. However, in the second embodiment, the width W of the air intake port is 690 mm, and the height H is 200 mm. Length L and entrance width W _{0 of} the ramp-shaped inlet amount to 1350 mm and 180 mm in the second example.

With the air inlet arrangement according to the invention, the generator of the system, as well as a coupled between the rotor and generator gearbox can be cooled in an advantageous manner.

The above statements show that the details in the geometric realization of an improved air inlet arrangement for a nacelle of a wind turbine can be changed in manifold ways, the illustrated embodiments are therefore not to be interpreted as limiting the invention. Rather, the features of the invention disclosed in the above description and in the claims, both individually and in any combination for the realization of the invention in its various embodiments may be essential.

LIST OF REFERENCE NUMBERS

1 recess, air inlet (gap)

3 lateral surface (flow guide surface)

3.1, 3.2, 3.3 areas of the flow control surface

4 wall area

5 floor area

6 wall area

7 opening for tower

10 nacelle housing

12 air intake opening

H height of the inlet opening

L length of the indentation

R rotor axis

W width of the air inlet opening

W ₀ input width of the indentation

X axis a (a) direction of flow h (h) height direction

-h depth direction

I (I) Length direction n (n) Normal w (w) width direction h _x wall height

W _x distance wall axis

X distance from air inlet opening α ramp angle

Claims

1. Wind turbine with a tower, one arranged at the upper end of the tower, rotatably mounted with respect to the vertical tower axis and one of a housing (10) limited interior having nacelle, with respect to a transverse to the tower axis rotor axis (R) rotatably mounted with respect to the nacelle Rotor, which can be offset by an air flow in an approximately parallel to the rotor axis (R) extending Anström- direction (a) in a rotation about the rotor axis (R), wherein the nacelle housing (10) has a convex or planar flow guide surface (3) an airflow flowing in the direction of flow (a), and an air inlet arrangement (1, 12) arranged on the housing (10) and having an air inlet opening (12) for supplying air into the interior, characterized in that the air inlet arrangement (1, 12) in the direction of flow (a) in the direction of the air inlet opening (12) extending indentation (1) in the St 3) and the air inlet opening (12) between a boundary surface (5) of the recess (1) and the adjoining region (3.1) of the flow guide surface (3) is arranged.

2. Wind energy plant according to claim 1, wherein a longitudinal direction of the indentation (1) defining surface normal (I) on the cross-sectional area of the air inlet opening (12) has a component in the direction of flow (a), preferably approximately anti-parallel thereto.

3. Wind energy plant according to one of claims 1 or 2, wherein the air inlet opening (12) extends in one of the flow guide surface (3) to the gondola interior to be directed depth direction (-h).

4. Wind turbine according to claim 3, wherein the boundary surface of the recess (1) has a first wall portion (4), with respect to the depth direction (-h) certain wall height (h _x ) in the longitudinal direction (I) decreases.

5. Wind energy plant according to claim 3 or 4, wherein the air inlet opening (12) in a transverse, in particular perpendicular to the depth direction (-h) and transverse to the longitudinal direction (I) extending width direction (w) and wherein a distance (w _x ) in the widthwise direction (w) decreases longitudinally from the first wall portion (4) to an axis (X) extending in the longitudinal direction (I) and in the width direction (w) through the center of the air inlet port (12) and in particular orthogonal thereto.

6. Wind turbine according to one of claims 4 or 5, wherein the first wall portion (4) extends to the air inlet opening (12), in particular under alignment of the height profile of the flow guide (3.3) at the upper end of the wall to the height profile of the adjacent flow guide (3.1).

7. Wind turbine according to claim 5 or 6, wherein a ratio between width spacing (W _x ) and wall height (h _x ) in the range of 1 to 4, preferably 1, 3 to 3.3, in particular 1, 7 to 2, 7 lies.

8. Wind turbine according to claim 7, wherein said width / height ratio (w _x : h _x ) in the longitudinal direction (I) for up to 30% of the longitudinal extent (L) of the recess (1) is satisfied, preferably up to 60%, in particular up to 80%.

9. Wind turbine according to one of claims 4 to 8, wherein the first wall portion (4) to the air inlet opening (12) facing away from the end portion of the recess (1).

10. Wind turbine according to one of claims 4 to 9, wherein the course of the first wall portion (4) is at least partially curved and in particular the curvature in the longitudinal direction (I) first directed to the axis (X) and then after passing through a turning point of the axis (X) is directed away.

11. Wind turbine according to claim 10, wherein the inflection point in the range of 25 to 65% of the length (L) is arranged, preferably 35 to 55%, in particular 40 to 50%.

12. Wind turbine according to one of claims 4 to 11, wherein the decrease of the wall height (h _x ) with respect to the corresponding length (x) of the wall region (4) in the longitudinal direction (I) defines an average slope in the range of 3 ° to 20 ° , preferably 5 ° to 10 °, in particular 6 ° to 8 °.

13. Wind turbine according to one of claims 3 to 12, wherein a bottom region (5) of the recess (1) in a section through a longitudinal direction of (I) and depth direction (-h) certain plane is rectilinear and in particular the average slope of a ramp angle (α) defined.

14. Wind energy plant according to one of claims 4 to 13, wherein the indentation (1) opposite the first wall portion (4) has a second wall portion (6), in particular the mentioned in the preceding claims properties of the first wall portion (4).

15. Wind turbine according to claim 14, wherein the axis (X) extends perpendicular to the air inlet opening (12) and the air inlet assembly (1, 12) is formed substantially symmetrically to the axis (X).

16. Wind turbine according to one of claims 13 to 15, wherein the bottom portion (5) as a slit-like incision into the outer surface (3.2, 3.3) is immersed.

17. Wind turbine according to one of the preceding claims, wherein a ratio of width (B) to height (H) of the air inlet opening (12) in the range of 2.5 to 5.5, preferably 3 to 5, in particular 3.5 to 4.5 is located.

18. Wind turbine according to one of the preceding claims, in which a cutting angle between the rotor axis (R) and the projection of the longitudinal direction (I) of the recess (1) to the plane spanned by the rotor axis and tower axis in a range of 0 to 30 °, preferably 0 to 20 °, in particular 0 to 10 °.

Wind energy plant according to one of the preceding claims, wherein the air inlet arrangement (1, 12) is arranged in the lower region of the nacelle, in particular near the lowest region of the nacelle.

20. Wind turbine according to one of the preceding claims, wherein the indentation (1) with respect to the rotor axis (R) in the region of the attachment of the nacelle on the tower is arranged.

21. Wind turbine according to one of the preceding claims, wherein the length (L) of the recess (1) based on the tower diameter at the level of the nacelle in the

Range of 0.1 to 2, preferably from 0.25 to 1, 5, more preferably from 0.5 to 1, 25, in particular from 0.8 to 1, 1.

22. Wind turbine according to one of the preceding claims, wherein the width (W) of the air inlet opening (12) in the range of 0.4 m to 1, 2 m, preferably 0.5 m to 1, 0 m, in particular 0.6 m to 0.8 m.

23. Wind turbine according to one of the preceding claims, wherein the height (H) of the air inlet opening (12) in the range of 0.1 m to 0.4 m, preferably 0.15 to 0.3 m, in particular 0.2 m up to 0.25 m.

24. Wind energy plant according to one of the preceding claims, wherein the length (L) of the indentation (1) is in the range of 0.8 m to 2.2 m, preferably 1 m to 2 m, in particular 1, 2 m to 1, 8 m.

25. Wind energy plant according to one of the preceding claims, wherein the entrance width (W ₀ ) of the indentation (1) is in the range of 0.05 m to 0.4 m, preferably 0.08 m to 0.3 m, in particular 0, 1 m to 0.2 m.

26. Wind energy plant according to one of the preceding claims, characterized by two or more formed according to one of claims 1 to 17 and in particular according to one of claims 18 to 25 arranged air inlet arrangements.

27. Wind energy plant according to one of the preceding claims, characterized by at least one air outlet arrangement for the air inlet arrangement (1, 12) supplied air, which is arranged in particular in a tapering in the direction of the rotor axis portion of the nacelle, the air outlet assembly in particular a construction according to the construction of the air inlet arrangement specified in any one of claims 1 to 25.

28. Wind energy plant according to one of the preceding claims, in which with the air supplied through the air inlet arrangement (1, 12) cooled coupled to the rotor of the system pelter generator, coupled between the rotor and generator gear, a frequency converter and / or a transformer becomes.

29. A method for operating a wind turbine according to one of the preceding claims.