Patent Description:
Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modem wind turbine typically includes a tower, generator, gearbox, nacelle, and one or more rotor blades. The rotor blades capture kinetic energy from wind using known foil principles and transmit the kinetic energy through rotational energy to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.

Wind turbines, but also other devices or arrangements, which operate in an elevated position over a surface of a respective ground, are often arranged on top of a tower supporting said device or technical arrangement. A tower is therefore subject of wind dynamics which can lead to undesired loads and status of the tower. Chinese utility model <CIT> refers to a tower section of thick bamboo vortex induced vibration protection module, device and wind generating set. European patent application <CIT> relates to a strake for a wind turbine tower, a method to handle the strake and an arrangement to mount the strake to the wind turbine.

Accordingly, the present disclosure is directed to provide a system for a tower segment, an improved tower segment having said system, an improved tower including said tower segment, and a wind turbine having set tower, in order to mitigate the disadvantages related to the known art. In particular, the erection process of respective tower shall be also rendered more efficiently.

In one aspect, the present disclosure is directed to a system for a tower segment of a tower, wherein the tower segment is configured for forming at least partially a part of a tower for carrying a structure, in particular for supporting a nacelle of a horizontal-axis wind turbine or a machine house of a vertical-axis wind turbine.

The tower segment and/or the respective tower has a longitudinal direction defined by a longitudinal axis and a radial direction defined by a radius, wherein a respective radius is extending in a (horizontal) plane being perpendicular to the longitudinal axis. Consequently, a circumferential direction lying in the radial (horizontal) plane can be determined. If not said otherwise, all references, specifications, orientations and directions as provided in the current disclosure are associated to the longitudinal, radial or circumferential direction of the tower segment and/or of the respective tower.

It is to be noted, that all directional references as provided within the current disclosure are provided with respect to a tower segment or a tower being in an operational state, in particular are provided with respect to the erected tower. The term "operational state" does not require that the technical structure which is supported by the tower (e.g. a nacelle of the wind turbine) needs to be in operation or even being mounted.

The system is configured to be attached, arranged, and/or mounted to the tower segment and comprises at least an airflow manipulation arrangement and a support arrangement. The airflow manipulation arrangement includes an airflow manipulator which - when mounted to the tower segment - is configured for affecting an airflow around the tower segment. For example, the airflow manipulator can be a flexible sheet being mounted to the tower segment and extending in radial direction, wherein an airflow passing around the tower and/or tower segment is re-directed and/or partially blocked by the airflow manipulator.

The support arrangement is configured for supporting the airflow manipulation arrangement and for mounting the airflow manipulation arrangement to the tower segment.

According to one aspect of the current disclosure, the airflow manipulation arrangement and the support arrangement are configured such, when mounted to the tower segment, that the airflow manipulator projects a tower diameter in radial direction by at least <NUM>%, in particular at least <NUM>%, preferred at least <NUM>%, in particular not more than <NUM>%, further in particular not more than <NUM>%, of the tower diameter. Hence, the airflow manipulator is extending beyond a radial diameter of the tower and/or of the tower segment by at least the provided values such that vortex shedding effects caused by an airflow facing the tower segment and affecting the tower segment are reduced by the airflow manipulator.

Alternatively, or in addition to the preceding aspect, a further aspect is introduced: when the airflow manipulation arrangement including the airflow manipulator is mounted to the tower segment with the help of the support arrangement, the airflow manipulator is projecting the tower segment in radial direction and is extending along the tower segment essentially in longitudinal direction such, that a vortex shedding effect affecting the tower caused by an airflow facing the tower is reduced by the airflow manipulator. By arranging the airflow manipulator essentially parallel to the tower segment an effective measure against vortex shedding effects is put in place.

In fact, both aspects, individually and as well in (partial) combination, are capable for the first time of providing a beneficial effect for a tower segment and/or tower formed by at least one of those tower segments: the system can be mounted to a tower or tower segment which is in the process of being directed, or even before being directed, wherein negative effects of a Kármán vortex street can be drastically reduced or even prevented. The use of the airflow manipulation arrangement influences an airflow around the tower segment in that way that a formation of an asymmetrical flow pattern forms around the body and related changes of the pressure distribution is prevented. This means that an alternate shedding of vortices cannot create periodic lateral (sideways) forces on the tower segment. By this an unwanted excitation of the tower - possibly near any eigenfrequency - is avoided.

According to an embodiment, the system is configured such that the airflow manipulation arrangement and the support arrangement can be temporarily attached to the tower segment by mounting and by a subsequent dismounting.

The term "tower segment" refers to a component of a tower which is subject to vibrations which can be caused by vortex shedding effects. According to a preferred embodiment, the tower can be formed by a plurality of tower segments being mounted to each other at flanches in longitudinal direction. However, a tower may as well be formed by one sole tower segment, and/or by a tower portion being different from a tower segment and by a tower segment.

According to an embodiment, the airflow manipulator - when being mounted to the tower segment - is extending the tower segment in longitudinal direction about a relevant, effective length. Specifically, at least <NUM>% of the longitudinal length of the tower segment comprises the airflow manipulator, which is in longitudinal direction arranged essentially parallel to the longitudinal axis of the tower segment and which is projecting the tower segment in radial direction.

Preferably, the airflow manipulator is extending the tower segment in longitudinal direction more than <NUM>%, in particular more preferably more than <NUM>%, and more preferred more than <NUM>% of the longitudinal length of the tower segment.

However, according to another embodiment - partially an additional or alternative embodiment - the airflow manipulator is extending the longitudinal length of the tower not more than <NUM>%, in particular not more than <NUM>%, further in particular not more than <NUM>%.

According to an embodiment, the term "the airflow manipulator projects a tower diameter" or "the airflow manipulator is extending along the tower segment" reflects that the airflow manipulator causes the presence of a reference area/projecting surface being located on or neighboring the external surface of the tower segment extending in a radial direction and/or in the longitudinal direction of the tower segment. In particular, the airflow manipulator forms a projected surface or a reference area perpendicular to the radial plane and/or extending parallel with respect to a radial direction of the segment. For example, the airflow manipulator can be a three-dimensional object having a projected surface or reference area perpendicular to the wind direction; a specific example, a sphere has a circular form as projected surface or reference area, a cylindrical form extending in longitudinal direction of the tower segment has a projected surface having a rectangular form.

According to an embodiment, the airflow manipulator forms an effectively flat surface extending perpendicular to the radial plane and/or extending parallel with respect to a radial direction of that segment. The term "effectively flat" refers to the airflow manipulator when being mounted to the tower segment, wherein the form of the effectively flat surface enables the mitigation and/or reduction of vortex shedding effects affecting the tower segment. For instance, if the airflow manipulator is subject to wind pressure, and therefore is bulging into a convex form in airflow direction, by definition such bulged airflow manipulator still comprises an essentially flat surface.

The support arrangement is configured such that the effectively flat surface does not deviate from a plane formed by the longitudinal direction and the radial direction - which could be defined as a radial plane - by more than <NUM>°, in particular not more than <NUM>°, preferably by not more than <NUM>°.

Additionally, or in the alternative, the support arrangement and/or the airflow manipulation arrangement is embodied such, that the airflow manipulator is essentially extending in one of the radial planes, while still having the effectively flat surface.

According to a beneficial aspect of the current disclosure, the airflow manipulator is configured such that a drag coefficient of the airflow manipulator does not exceed <NUM>, in particular does not exceed <NUM>, preferably does not exceed <NUM>, or more preferably does not exceed <NUM>. According to the invention, the airflow manipulator has a relative permeability of at least <NUM> liter per minute per square meter [l/(min*m<NUM>)], in particular at least <NUM>, preferred at least <NUM> liter per minute per square meter [l/(min*m<NUM>)], furthermore, in particular not more than <NUM> liter per minute per square meter [l/(min*m<NUM>)], further in particular not more than <NUM>, preferred not more than <NUM> liter per minute per square meter [l/(min*m<NUM>)].

In particular, or in the alternative, the airflow manipulator is configured such, that a surface of the airflow manipulator is not airtight and/or is not fully anticipating forces caused by wind pressure. For example, measures against vortex shedding effects as currently used mainly comprise airflow manipulation devices, for example strakes, which are fully airtight and non-permeable with respect to the airflow. As an example, tall metal smokestacks or other tubular structures such as antenna masts or tethered cables can be fitted with an external airtight corkscrew fin to introduce turbulence, so the load is less variable and resonant load frequencies have negligible amplitudes. It is to be noted as being a beneficial effect of the present disclosure, that complex and costly solutions as currently used can be avoided.

By configuring the airflow manipulator such, that a certain amount of an airflow facing the airflow manipulator may stream through the airflow manipulator, the positive effect for mitigating vortex shedding effects is maximized, wherein a disadvantageous of applying airflow related forces onto the tower segment is minimized. By this, the airflow manipulation arrangement may extend in radial direction about a predetermined length for preventing the formation of a vibration-causing Kármán vortex street, wherein pressure caused (static) forces affecting the tower by forming a bending moment are still acceptable.

According to a further aspect of the present disclosure, the airflow manipulator comprises a fabric, in particular the airflow manipulator is essentially made of a fabric. The term "essentially made of the fabric" reflects that at least <NUM>%, preferably at least <NUM>% of the airflow manipulator is made of the fabric. Hence, the airflow manipulator may have a sail-like appearance, wherein such sail is perpendicularly arranged with respect to the tower segment. In particular, the fabric can be a coarse-mesh fabric.

The airflow manipulator may have a mesh size of at least <NUM> millimeters, preferably of at least <NUM>, in particular of at least <NUM>.

Alternatively, the airflow manipulator may comprise a plurality of effective openings, in particular wherein the airflow manipulator itself is made from a relatively airtight material. This embodiment differs from the embodiment having a mesh by the relatively large size of the openings respect to the overall airflow manipulator, for example, an opening according to the described embodiment may have a diameter of at least <NUM>% of the radial width of the airflow manipulator.

According to an embodiment, an effective opening can have a circular, oval shape, or it is formed by a longitudinal slit or similar, or by a combination thereof.

Aforementioned embodiments of the airflow manipulator include the embodiments of the airflow manipulator at least partially consisting of a mesh or of a fabric and as well the embodiment of the airflow manipulator having an airflow manipulator surface with openings.

According to a specific embodiment, support arrangement comprises a support beam configured for being mountable to the tower wall and a support fixation device configured for fixating the support beam to the tower wall, in particular wherein, when mounted, the support beam extends essentially in radial direction. The support beam is configured for carrying - directly or indirectly - the airflow manipulation arrangement such that airflow manipulator extends the tower segment in radial direction as described in the preceding embodiments.

In one specific embodiment, the support arrangement comprises an upper support portion configured for receiving an upper manipulator portion of the airflow manipulator and a lower support portion configured for receiving a lower manipulator portion of the airflow manipulator such that the airflow manipulator is extending in longitudinal direction between the upper support portion and the lower support portion.

By this, the effectivity of the airflow manipulation arrangement is increased, in particular because the upper manipulator portion and the lower manipulator portion ensure that the airflow manipulator maintains its efficiently flat surface and/or that the bulging of the airflow manipulator is kept within acceptable limits.

The upper manipulator portion and the lower manipulator portion may both comprise a respective support beam, which can be mounted to a tower wall of the tower segment with the help of a respective support fixation device. For example, support beam and support fixation device may both be configured for holding the support beam in a position being essentially perpendicular to the longitudinal direction of the tower segment.

The upper manipulator portion can be mounted at an upper portion of the tower segment and the lower manipulator portion can be mounted at a lower portion of the tower segment, wherein a distance between the respective manipulator portion and the related end (tower flange) of the tower segment in longitudinal direction is less than <NUM>%, preferred less than <NUM>%, of an overall length of the tower segment in longitudinal direction.

In a further embodiment, the system comprises a mounting arrangement having mounting means for mounting the airflow manipulation arrangement to the support arrangement. For this purpose, the mounting arrangement comprises longitudinal holding means to be arranged in longitudinal direction between the upper support portion and the lower support portion.

The holding means may comprise a radially inner cable and a radially outer cable, wherein the support arrangement is configured such that the inner cable can be arranged more closely to the tower wall than the outer cable. By this, the holding means form a frame like support configuration, wherein the upper and lower support beam limit the support frame in longitudinal direction, and the outer cable and the inner cable act as radial limitations.

The mounting arrangement and the mounting means may be configured and positioned such, that a gap between a tower wall and the airflow manipulator does not exceed <NUM>%, in particular does not exceed <NUM>%, preferred does not exceed <NUM>%, of the diameter of the tower segment. For example, the inner cable can be arranged in radial direction with respect to the tower wall having a distance of not more than <NUM>%, in particular not more than <NUM>%, preferred not more than <NUM>% of the diameter of the tower segment.

According to an embodiment, the system may comprise at least three in particular four, preferably five, support arrangements, respective airflow manipulation arrangements, and respective mounting arrangements. For example, the support arrangements can be distributed equally around the tower segment.

Optional, the system may comprise assembling means configured for enabling at least partially a lowering of the support arrangement from the erected tower segment or from the erected tower. In particular, the system may comprise an assembling cable for supporting at least a part of the support arrangement during a disassembling process.

In one embodiment, the support arrangement comprises protection means configured for preventing the tower to be damaged or negatively impacted by a portion of the support arrangement when being lowered from its mounting position.

It is apparent for the skilled person, that the system, or at least an embodiment of the system as precedingly described, is configured to be mounted to a tower segment, in particular to a tower segment of a wind turbine, in order to mitigate vortex shedding effects possibly affecting of the tower segment. Usually, a tower segment for a large technical structure like a nacelle of the wind turbine has a notable size. A tower segment, for example of a tower of a typical wind turbine, has a diameter of at least <NUM>, preferred of at least <NUM>, more preferred of at least <NUM>, and/or a length in the longitudinal direction of at least <NUM>, preferred of at least <NUM>, more preferred of at least <NUM>.

Henceforth, it is noticeable for example from the size, the length and the width, of the airflow manipulation arrangement and/or of the support arrangement, if the system is suitable for being used at a tower segment of a wind turbine.

For example, if the airflow manipulation arrangement comprises an airflow manipulator having an elevated length while having a relatively small width, and/or if the support arrangement and/or the airflow manipulation arrangement are configured (and equipped with related instructions) for being attachable/detachable to a tower wall of a tower segment, then the system comprising the airflow manipulation arrangement and the support arrangements are indeed configured and suitable for being attached to a tower segment according to the current disclosure.

For example, a system having an airflow manipulation arrangement comprising an airflow manipulator, wherein the manipulator has a length of for example more than <NUM>, preferably more than <NUM>, possibly more than <NUM>, while having a width of at least <NUM>, preferably more than <NUM>, or in particular more than <NUM>, and wherein the system further comprises a support arrangement apparently being configured for supporting an upper portion of the airflow manipulation arrangement - for example holding openings, rings or screws are provided for mounting the airflow manipulator to the support arrangement -, said system is configured for being used with a tower segment of a tower of a large technical device such as a wind turbine.

According to a further aspect, a tower segment, preferably a tower segment of a wind turbine, having a system according to one of the preceding embodiments being attached to the tower segment is presented. This aspect focuses on the system being mounted to the tower segment, and thereby including both objects. The tower segment is part of a tower, preferably of a tower of a wind turbine, and has exemplary dimensions as discussed supra.

In the context of a specific embodiment it is described that the tower having a tower segment according to one of the preceding embodiments is configured for supporting a heavy technical structure. Such heavy technical structure can be a nacelle of a wind turbine. The weight of such technical structure and the configuration of the tower segment causes the tower segment and/or the tower including the tower segment to have at least a specific eigenfrequency when the technical structure is mounted to the tower (full-system-eigenfrequency), while having at least another eigenfrequency (interims-system-eigenfrequency) when there is no technical structure mounted to the tower or if the tower is in the process of being mounted.

According to an embodiment, if the heavy technical structure is mounted to the tower or to the tower segment, the tower segment and/or the tower are configured such that the tower/the tower segment cannot be excited - or at least cannot be effectively excited - by vortex shedding effects. That configuration includes that the full-system-eigenfrequency of the tower including the heavy technical structure is different from any exciting frequency caused by vortex shedding effects.

In contrast, if the overall structure, for example the wind turbine, is in the process of being erected, there is a certain timely phase when only the tower is erected without supporting the heavy technical structure mounted to the top of the tower. Specifically, during this phase, the tower and/or the tower segment can be heavily and negatively affected by vortex shedding effects because excitation frequencies of vortex shedding effects are in an effective range of the interims-system-eigenfrequency.

Therefore, it is one aspect of the current disclosure that the tower segment and/or a tower comprising such a tower segment is/are configured to have a full-system-eigenfrequency when the heavy technical structure, e.g. a nacelle of a wind turbine, is mounted to the tower segment, and that the tower segment and/or a tower comprising such a tower segment has/have at least a interims-system-eigenfrequency when no heavy technical structure, is mounted to the top of the tower segment and/or of the tower. The tower segment is configured such, that the full-system-eigenfrequency is different from an excitation frequency caused by vortex shedding effects. Furthermore, the tower segment is configured such that the interims-system-eigenfrequency is in the range of an excitation frequency caused by vortex shedding effects. The term "is different from an exciting frequency" reflects that no essential exciting can be affected, wherein the term "is in the range of an exciting frequency" means that an essential and potentially damaging resonance event or even a resonance catastrophic due to an effective periodic excitation can possibly take place. The term "excitation frequency caused by vortex shedding effects" represents a variety of frequencies caused by wind of variable that typical speed confronting the tower and flowing around the tower. The skilled person is able to determine the excitation frequency caused by vortex shedding effects when knowing dimensions and purpose of the tower segment.

In yet another aspect, the present disclosure is directed to a wind turbine having a nacelle mounted atop a tower having a tower segment with a system as described supra. The nacelle assembly includes a nacelle defining, at least, a plurality of side walls and a top wall. The nacelle rotatably supports a rotor including rotor blades.

In another aspect, the present disclosure is directed to a method for mounting a tower, in particular a tower of a wind turbine. The method comprising the following steps:.

Mounting a support arrangement as described supra to a tower segment of a tower as described above;.

prior or after to the preceding step, mounting/erecting the tower segment in order to form a tower;.

mounting a further component, functional technical structure and/or a nacelle of a wind turbine to the top of the tower; and.

disassembling the system from the tower, for example by lowering the airflow manipulation arrangement from the support arrangement, and further for example by lowering the support arrangement from the tower segment. In the alternative, the system can as be dismounted as a whole.

The assembly process of this is can be embodied as follows: while the tower segments are still on the ground, the support arrangements can be mounted to the tower. For example, the respective support beam can protrude the tower, wherein (outer and) inner fixation device are provided for mounting the support beam in their perpendicular position with respect to the tower wall.

According to an embodiment, the tower may be erected by placing tower segments on each other by connecting respective tower flanges. Subsequently, the airflow manipulation arrangement can be lifted to the respective tower segment. Also, the airflow manipulation arrangement can be mounted to the tower segments prior to erecting these tower segments.

According to an embodiment, the system can be fully preassembled and mounted to a tower segment before erecting the tower or before erecting tower segment.

Alternatively, the system can be partially mounted to the tower segment, for example, only the support arrangement and/or the mounting arrangement is attached to a tower segment, wherein the airflow manipulation arrangement is mounted to the support arrangement and/or mounting arrangement after the tower segment is directed.

These and other features, aspects and advantages of the present invention will be further supported and described with reference to the following description and appended claims.

A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which refers to the appended figures, in which:.

Single features depicted in the figures are shown relatively with regards to each other and therefore are not necessarily to scale. Similar or same elements in the figures, even if displayed in different embodiments, are represented with the same reference numbers.

<FIG> is a perspective view of an exemplary wind turbine <NUM>. In the exemplary embodiment, the wind turbine <NUM> is a horizontal-axis wind turbine. In the exemplary embodiment, the wind turbine <NUM> includes a tower <NUM> that extends from a support system <NUM>, a nacelle <NUM> mounted on tower <NUM>, and a rotor <NUM> that is coupled to nacelle <NUM>. In the exemplary embodiment, the rotor <NUM> has three rotor blades <NUM>.

The tower <NUM> is formed by an upper tower segment <NUM> and a lower tower segment <NUM> both having a tower wall <NUM>, which are connected to each other with the help of adjacent tower flanges <NUM>. In the exemplary embodiment, the tower <NUM> is fabricated from tubular steel to define a cavity (not shown in <FIG>) between a support system <NUM> and the nacelle <NUM>.

In one embodiment, the rotor blades <NUM> have a length ranging from about <NUM> meters (m) to about <NUM>. Alternatively, rotor blades <NUM> may have any suitable length that enables the wind turbine <NUM> to function as described herein. For example, other non-limiting examples of blade lengths include <NUM> or less, <NUM>, <NUM>, <NUM>, <NUM> or a length that is greater than <NUM>. As wind strikes the rotor blades <NUM> from a wind direction <NUM>, the rotor <NUM> is rotated about an axis of rotation <NUM>. As the rotor blades <NUM> are rotated and subjected to centrifugal forces, the rotor blades <NUM> are also subjected to various forces and moments. As such, the rotor blades <NUM> may deflect and/or rotate from a neutral, or non-deflected, position to a deflected position.

Moreover, a pitch angle of the rotor blades <NUM>, i.e., an angle that determines a perspective of the rotor blades <NUM> with respect to the wind direction, may be changed by a pitch system <NUM> to control the load and power generated by the wind turbine <NUM> by adjusting an angular position of at least one rotor blade <NUM> relative to wind vectors. During operation of the wind turbine <NUM>, the pitch system <NUM> may change a pitch angle of the rotor blades <NUM> such that the rotor blades <NUM> are moved to a feathered position, such that the perspective of at least one rotor blade <NUM> relative to wind vectors provides a minimal surface area of the rotor blade <NUM> to be oriented towards the wind vectors, which facilitates reducing a rotational speed and/or facilitates a stall of the rotor <NUM>.

In the exemplary embodiment, a blade pitch of each rotor blade <NUM> is controlled individually by a wind turbine controller <NUM> or by a pitch control system <NUM>.

Further, in the exemplary embodiment, as the wind direction <NUM> changes, a yaw direction of the nacelle <NUM> may be rotated about a yaw axis <NUM> to position the rotor blades <NUM> with respect to wind direction <NUM>. For this purpose, the nacelle <NUM> is rotatably supported by the tower <NUM>, more specifically, by a top flange <NUM> of the upper tower segment <NUM>. According to certain embodiments, the yaw axis <NUM>. Together with the longitudinal axes <NUM> of the tower <NUM>.

In the exemplary embodiment, the wind turbine controller <NUM> is shown as being centralized within the nacelle <NUM>, however, the wind turbine controller <NUM> may be a distributed system throughout the wind turbine <NUM>, on the support system <NUM>, within a wind farm, and/or at a remote control center. The wind turbine controller <NUM> includes a processor <NUM> configured to perform the methods and/or steps described herein. Further, many of the other components described herein include a processor. As used herein, the term "processor" is not limited to integrated circuits referred to in the art as a computer, but broadly refers to a controller, a microcontroller, a microcomputer, a programmable logic controller (PLC), an application specific integrated circuit, and other programmable circuits, and these terms are used interchangeably herein. It should be understood that a processor and/or a control system can also include memory, input channels, and/or output channels.

<FIG> is an enlarged sectional view of a portion of the wind turbine <NUM>. In the exemplary embodiment, the wind turbine <NUM> includes the nacelle <NUM> and the rotor <NUM> that is rotatably coupled to the nacelle <NUM>. More specifically, the hub <NUM> of the rotor <NUM> is rotatably coupled to an electric generator <NUM> positioned within the nacelle <NUM> by the main shaft <NUM>, a gearbox <NUM>, a high speed shaft <NUM>, and a coupling <NUM>. In the exemplary embodiment, the main shaft <NUM> is disposed at least partially coaxial to a longitudinal axis (not shown) of the nacelle <NUM>. A rotation of the main shaft <NUM> drives the gearbox <NUM> that subsequently drives the high speed shaft <NUM> by translating the relatively slow rotational movement of the rotor <NUM> and of the main shaft <NUM> into a relatively fast rotational movement of the high speed shaft <NUM>. The latter is connected to the generator <NUM> for generating electrical energy with the help of a coupling <NUM>.

The gearbox <NUM> and generator <NUM> may be supported by a main support structure frame of the nacelle <NUM>, optionally embodied as a main frame <NUM>. The gearbox <NUM> may include a gearbox housing that is connected to the main frame <NUM> by one or more torque arms. In the exemplary embodiment, the nacelle <NUM> also includes a main forward support bearing <NUM> and a main aft support bearing <NUM>. Furthermore, the generator <NUM> can be mounted to the main frame <NUM> by decoupling support means <NUM>, in particular in order to prevent vibrations of the generator <NUM> to be introduced into the main frame <NUM> and thereby causing a noise emission source.

Preferably, the main frame <NUM> is configured to carry the entire load caused by the weight of the rotor <NUM> and components of the nacelle <NUM> and by the wind and rotational loads, and furthermore, to introduce these loads into the top flange <NUM> of the upper tower segment <NUM> of the tower <NUM> of the wind turbine <NUM>.

However, the present disclosure is not limited to a wind turbine comprising a gearbox, but also wind turbines without a gearbox, thus, heading a so-called direct drive may be concerned as well.

For positioning the nacelle appropriately with respect to the wind direction <NUM>, the nacelle <NUM> may also include at least one meteorological mast <NUM> that may include a wind vane and anemometer (neither shown in <FIG>). The mast <NUM> provides information to the wind turbine controller <NUM> that may include wind direction and/or wind speed.

In the exemplary embodiment, the pitch system <NUM> is at least partially arranged as a pitch assembly <NUM> in the hub <NUM>. The pitch assembly <NUM> includes one or more pitch drive systems <NUM> and at least one sensor <NUM>. Each pitch drive system <NUM> is coupled to a respective rotor blade <NUM> (shown in <FIG>) for modulating the pitch angel of a rotor blade <NUM> along the pitch axis <NUM>. Only one of three pitch drive systems <NUM> is shown in <FIG>.

In the exemplary embodiment, the pitch assembly <NUM> includes at least one pitch bearing <NUM> coupled to hub <NUM> and to a respective rotor blade <NUM> (shown in <FIG>) for rotating the respective rotor blade <NUM> about the pitch axis <NUM>. The pitch drive system <NUM> includes a pitch drive motor <NUM>, a pitch drive gearbox <NUM>, and a pitch drive pinion <NUM>. The pitch drive motor <NUM> is coupled to the pitch drive gearbox <NUM> such that the pitch drive motor <NUM> imparts mechanical force to the pitch drive gearbox <NUM>. The pitch drive gearbox <NUM> is coupled to the pitch drive pinion <NUM> such that the pitch drive pinion <NUM> is rotated by the pitch drive gearbox <NUM>. The pitch bearing <NUM> is coupled to pitch drive pinion <NUM> such that the rotation of the pitch drive pinion <NUM> causes a rotation of the pitch bearing <NUM>.

Pitch drive system <NUM> is coupled to the wind turbine controller <NUM> for adjusting the pitch angle of a rotor blade <NUM> upon receipt of one or more signals from the wind turbine controller <NUM>. In the exemplary embodiment, the pitch drive motor <NUM> is any suitable motor driven by electrical power and/or a hydraulic system that enables pitch assembly <NUM> to function as described herein. Alternatively, the pitch assembly <NUM> may include any suitable structure, configuration, arrangement, and/or components such as, but not limited to, hydraulic cylinders, springs, and/or servo-mechanisms. In certain embodiments, the pitch drive motor <NUM> is driven by energy extracted from a rotational inertia of hub <NUM> and/or a stored energy source (not shown) that supplies energy to components of the wind turbine <NUM>.

The pitch assembly <NUM> also includes one or more pitch control systems <NUM> for controlling the pitch drive system <NUM> according to control signals from the wind turbine controller <NUM>, in case of specific prioritized situations and/or during rotor <NUM> overspeed. In the exemplary embodiment, the pitch assembly <NUM> includes at least one pitch control system <NUM> communicatively coupled to a respective pitch drive system <NUM> for controlling pitch drive system <NUM> independently from the wind turbine controller <NUM>. In the exemplary embodiment, the pitch control system <NUM> is coupled to the pitch drive system <NUM> and to a sensor <NUM>. During normal operation of the wind turbine <NUM>, the wind turbine controller <NUM> controls the pitch drive system <NUM> to adjust a pitch angle of rotor blades <NUM>.

In one embodiment, in particular when the rotor <NUM> operates at rotor overspeed, the pitch control system <NUM> overrides the wind turbine controller <NUM>, such that the wind turbine controller <NUM> no longer controls the pitch control system <NUM> and the pitch drive system <NUM>. Thus, the pitch control system <NUM> is able to make the pitch drive system <NUM> to move the rotor blade <NUM> to a feathered position for reducing a rotational speed of the rotor <NUM>.

According to an embodiment, a power generator <NUM>, for example comprising a battery and/or electric capacitors, is arranged at or within the hub <NUM> and is coupled to the sensor <NUM>, the pitch control system <NUM>, and to the pitch drive system <NUM> to provide a source of power to these components. In the exemplary embodiment, the power generator <NUM> provides a continuing source of power to the pitch assembly <NUM> during operation of the wind turbine <NUM>. In an alternative embodiment, power generator <NUM> provides power to the pitch assembly <NUM> only during an electrical power loss event of the wind turbine <NUM>. The electrical power loss event may include power grid loss or dip, malfunctioning of an electrical system of the wind turbine <NUM>, and/or failure of the wind turbine controller <NUM>. During the electrical power loss event, the power generator <NUM> operates to provide electrical power to the pitch assembly <NUM> such that pitch assembly <NUM> can operate during the electrical power loss event.

In the exemplary embodiment, the pitch drive system <NUM>, the sensor <NUM>, the pitch control system <NUM>, cables, and the power generator <NUM> are each positioned in a cavity <NUM> defined by an inner surface <NUM> of hub <NUM>. In an alternative embodiment, said components are positioned with respect to an outer surface <NUM> of hub <NUM> and may be coupled, directly or indirectly, to outer surface <NUM>.

<FIG> is a sectional view in radial direction and <FIG> is a sectional view in longitudinal direction through the tower <NUM> according to <FIG>, wherein a system according to the present disclosure is assembled to the tower segments <NUM>, <NUM>. The system comprises an airflow manipulation arrangement <NUM>, a support arrangement <NUM> for supporting the airflow manipulation arrangement <NUM> and for mounting the airflow manipulation arrangement <NUM> to a tower wall of <NUM> of the tower segments <NUM>, <NUM>.

The tower segments <NUM>, <NUM> and/or the respective tower <NUM> have a longitudinal direction <NUM> defined by a longitudinal axis <NUM> and a radial direction <NUM> defined by a radius of the tower segment <NUM>, <NUM>, wherein a respective radius is extending in a (horizontal) plane being perpendicular to the longitudinal axis <NUM>, <NUM>. Consequently, a circumferential direction lying in the radial (horizontal) plane can be determined. If not said otherwise, all references, specifications, orientations and directions as provided in the current disclosure are associated to the longitudinal direction <NUM>, radial direction <NUM> or circumferential direction of the tower segment <NUM>, <NUM> and/or of the respective tower <NUM>.

According to this embodiment it is shown in <FIG> that the system comprises five airflow manipulation arrangements <NUM> being mounted to the tower <NUM> of the upper tower segment <NUM> with the help of five respective support arrangements <NUM>.

The tower <NUM> and/or the respective tower segment <NUM>, <NUM> have an inner tower diameter <NUM>, wherein the tower diameter <NUM> is varying in longitudinal direction <NUM>.

<FIG> elaborates in detail an embodiment of the system being mounted to the upper tower segment <NUM>. The support arrangement <NUM> may comprise an upper support portion <NUM> and a lower support portion <NUM>, both including a support beam <NUM> which are mounted to the tower wall <NUM> with the help of respective support fixation devices <NUM>. Specifically, the support fixation device <NUM> and the support beam <NUM> may be configured such, that a support beam extends over an outer surface of the tower <NUM> in radial direction <NUM>, in particular in a horizontal direction or perpendicular to the tower wall <NUM>.

The airflow manipulation arrangement <NUM> comprises an airflow manipulator <NUM> extending in longitudinal direction <NUM> between the upper support portion <NUM> and the lower support portion <NUM>. The upper support portion <NUM> supports an upper manipulator portion <NUM> of the airflow manipulator <NUM>, while the lower support portion <NUM> is holding a lower manipulator portion <NUM> of the airflow manipulator <NUM>. For this purpose, the system may include a mounting arrangement <NUM> which is effectively, at least partially, arranged between the upper manipulator portion <NUM> and the upper support portion <NUM>, and effectively, at least partially, arranged between the lower manipulator portion <NUM> and the lower support portion <NUM>.

The airflow manipulator <NUM> projects the tower diameter <NUM> in radial direction <NUM> by <NUM>% to <NUM>% of the tower diameter <NUM>. Hence, the airflow manipulator <NUM> is extending beyond a radial diameter <NUM> of the tower <NUM> and/or of the tower segment <NUM>, <NUM> such that vortex shedding effects caused by an airflow facing the tower segment <NUM>, <NUM> are reduced by the airflow manipulator <NUM>.

For example, the mounting arrangement <NUM> may include mounting means <NUM> such as ropes, cables <NUM> and <NUM>, and related fixing devices <NUM>, <NUM> like screws. Furthermore, the mounting arrangement <NUM> may include an inner cable <NUM>, an outer cable <NUM>, support devices <NUM> and tensioning devices <NUM>. The inner cable <NUM> and the outer cable <NUM> are attached to the respective support beams <NUM> of the upper support portion <NUM> and the lower support portion <NUM> such, that a frame like support configuration is provided, wherein the upper and lower support beam <NUM> limit the support frame in longitudinal direction <NUM>, and the outer cable <NUM> and the inner cable <NUM> act in radial direction <NUM>.

The airflow manipulator <NUM> is made at least partially from a fabric <NUM> and is extending in the frame formed by the support beams <NUM> and the outer and the inner cable to <NUM>, <NUM>.

As shown in <FIG>, a plurality of systems is provided in order to cover a large part of the length of the tower <NUM>. When wind is flowing around the tower <NUM> having the system including the airflow manipulation arrangement mounted to the tower walls <NUM>, an airflow cannot be established next to the surface of the tower wall <NUM> since the airflow is disturbed by the airflow manipulators <NUM>. As a consequence, a Kármán vortex street affecting the tower cannot develop, which effectively inhibits negative effects of vortex shedding.

As reflected by <FIG> and <FIG>, the fabric <NUM> of the airflow manipulator <NUM> is not airtight in its entirety, but has an increased permeability due to a predetermined mesh configuration. Therefore, wind pressure collected by the airflow manipulation arrangements <NUM> and conducted as wind loads via the support arrangement <NUM> into the tower segments <NUM>, <NUM> be reduced. A portion of the airflow of the wind may still flow through the airflow manipulator <NUM>.

<FIG> introduces an alternative configuration of the airflow manipulator <NUM>, wherein the material and or fabric <NUM> of the airflow manipulator <NUM> comprises openings <NUM> in order to reduce related wind loads. The size of openings <NUM> and amount of the openings <NUM> provided are chosen such, that a buildup of a Kármán vortex street is still prevented by the flat surface of the airflow manipulator <NUM>, wherein wind loads are reduced due to the presence of openings <NUM>.

Furthermore, details of the mounting arrangement <NUM> are shown in <FIG>, wherein the inner cable <NUM> in the outer cable <NUM> forms a guiding system for the airflow manipulator <NUM>. In fact, the airflow manipulator <NUM> comprises receptive means, embodied as support devices <NUM> (holes), through which the inner cable <NUM>, respectively the outer cable <NUM> are guided.

The inner cable <NUM> and the outer cable <NUM> are mounted to the support beams <NUM> of the upper support portion <NUM> with the help of support devices <NUM>. For tensioning the cables <NUM>, <NUM>, tensioning devices <NUM> are provided at the lower support portion <NUM>.

The assembly process of this is can be embodied as follows: while the tower segments <NUM>, <NUM> are still on the ground <NUM>, the support arrangements <NUM> are mounted to the tower <NUM>. For example, the respective support beam <NUM> can protrude the tower <NUM>, wherein (outer and) inner fixation device <NUM> are provided for mounting the support beam in their perpendicular position with respect to the tower wall <NUM>.

Subsequently, the tower <NUM> may be erected by placing the tower segments <NUM>, <NUM> on each other by connecting respective tower flanges <NUM>. Subsequently, the airflow manipulation arrangement <NUM> can be lifted to the respective tower segment <NUM>, <NUM>. Also, the airflow manipulation arrangement <NUM> can be mounted to the tower segments <NUM>, <NUM> prior to erecting these tower segments.

After the nacelle <NUM> is mounted to a top flange <NUM> of the upper tower segment <NUM>, the system including the airflow manipulation arrangement <NUM> is dismounted. For this purpose, assembling cables <NUM> can be connected to an inner portion of the support beams <NUM>. When removing the respective support fixation device <NUM>, the support beam <NUM> can be lowered from the tower <NUM> by releasing the assembling cable <NUM>.

In particular, the support arrangement <NUM> comprises protection means configured for preventing the tower <NUM> to be damaged or negatively impacted by support arrangement <NUM> when being lowered from its mounting position.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the appended claims.

Claim 1:
A system for a tower segment (<NUM>, <NUM>) of a tower (<NUM>) of a wind turbine (<NUM>), the tower segment (<NUM>, <NUM>) having a longitudinal direction (<NUM>) and a radial direction (<NUM>), the system comprising:
- an airflow manipulation arrangement (<NUM>) having an airflow manipulator (<NUM>), and
- a support arrangement (<NUM>) configured for supporting the airflow manipulation arrangement (<NUM>) and for mounting the airflow manipulation arrangement (<NUM>) to the tower segment (<NUM>, <NUM>),
- wherein the airflow manipulation arrangement (<NUM>) and the support arrangement (<NUM>) are configured such, when mounted to the tower segment (<NUM>, <NUM>), that the airflow manipulator (<NUM>) projects a tower diameter (<NUM>) in radial direction (<NUM>) by at least <NUM>%, in particular at least <NUM>%, preferred at least <NUM>%, in particular not more than <NUM>%, further in particular not more than <NUM>%, and that a vortex shedding effect affecting the tower segment (<NUM>, <NUM>) caused by an airflow facing the tower segment (<NUM>, <NUM>) is reduced by the airflow manipulator (<NUM>), and/or
- wherein the airflow manipulator (<NUM>), when mounted to the tower segment (<NUM>, <NUM>), is extending along the tower segment (<NUM>, <NUM>) essentially in longitudinal direction (<NUM>) such, that a vortex shedding effect affecting the tower (<NUM>) caused by an airflow facing the tower (<NUM>) is reduced by the airflow manipulator (<NUM>), characterized in that the airflow manipulator is having a relative permeability of at least <NUM> liter per minute per square meter [<NUM>/ (min*m2 )].