Wall portion for a wind turbine tower Field of invention

The present invention relates to a wall portion for a wind turbine tower, and to a tower wall for a wind turbine. In particular, the present invention relates to a wall portion for a wind turbine tower comprising wall segments connected to each other using a connection member, and to a tower wall for a wind turbine comprising the wall portion.

Art Background

US 2008/0256892 Al discloses a wind energy plant tower, wherein a tower wall consists of a plurality of wall sections which comprise connection bores to connect to adjacent border sections in the longitudinal direction.

WO 2009/097858 discloses a tower element for a tower for a wind power plant, wherein the tower element is provided with inwardly facing flanges at the longitudinal sides, the flanges being connected to corresponding flanges on laterally arranged segments.

EP 2 136 017 Al discloses an upper tower ring and a lower tower ring arranged such that a bottom section of the upper ring overlaps the top section of the lower ring in a horizon- tal overlap region.

WO 2004/083633 discloses a tower section for a wind turbine, wherein vertical flanges are tightened together by bolts and wherein upper and lower horizontal flanges are provided to allow interconnection of tower sections one on top of each other . EP 2 006 471 Bl discloses a wind turbine tower having a po ^¬ lygonal cross-section, wherein the wind turbine tower comprises a number of segments which are connected with each other using a splice plate.

WO 2009/024356 discloses a pole construction for framework towers of wind power plants comprising corner posts composed of partial profiles. The corner posts are formed each of at least two partial profiles, wherein the partial profiles to- gether form a closed whole profile.

Summary of the Invention

There may be a need for a wall portion for a wind turbine tower which can easily be assembled into a wind turbine tower and which provides enhanced stability compared to a conven ^¬ tional wall portion for a wind turbine tower. Further, there may be a need for a tower wall for a wind turbine which may be easily assembled and which may have higher stability and stiffness compared to a conventional tower wall for a wind turbine. Further, there may be a need for a tower wall for a wind turbine having increased size (for example height and/or diameter of the tower) compared to a conventional wind tur ^¬ bine tower wall.

This need may be met by the subject matter according to the independent claims. Advantageous embodiments of the present invention are described by the dependent claims. According to an embodiment a wall portion for a wind turbine tower is provided, wherein the wall portion comprises: a first wall segment; a second wall segment; a connection mem ^¬ ber comprising a first surface portion mounted at the first wall segment and extending in a first direction, a second surface portion mounted at the second wall segment and ex ^¬ tending in a second direction, and an intermediate portion comprising an intermediate surface portion extending trans- verse to the first direction and transverse to the second di ^¬ rection .

The first wall segment as well as the second wall segment may both extend primarily in two lateral directions and may ex ^¬ tend in a thickness direction orthogonal to the two lateral directions. Thereby, an extent in the lateral directions may be 10 times, in particular 100 times, in particular 1000 times greater than an extent in the thickness direction. In particular, the first wall segment as well as the second wall segment may exhibit a planar shape, a shape of a cylinder segment, a shape of a cone segment, or a combination of the aforementioned shapes. In particular, the first wall segment and the second wall segment may be manufactured using a metal, such as steel, in particular stainless steel. In par ^¬ ticular, the first wall segment and/or the second wall seg ^¬ ment may be manufactured by rolling or casting a metal, such as steel or iron. In particular, the first wall segment and/or the second wall segment may have an extent in at least one of the lateral directions between 1 m and 20 m, in par ^¬ ticular 2 m and 10 m, in particular 3 m and 5 m. In particular, the first wall segment and/or the second wall segment may be integrally formed from a metal, such as steel. Accord ^¬ ing to an embodiment the first wall segment and/or the second wall segment may be formed by casting a metal.

The first wall segment may comprise a first main surface ex ^¬ tending in the two lateral directions of the first wall seg ^¬ ment and the second wall segment may comprise a second main surface extending in the two lateral direction of the second wall segment. The first main surface may be parallel to the second main surface, in particular the first main surface may be in a substantially same plane as the second main surface. In case that the first wall segment and/or the second wall segment comprises a cylindrical shape or a cone-like shape the first main surface and/or the second main surface may be curved surfaces. In this case a tangential plane may be de ^¬ fined at every point on the curved surface representing the first main surface and/or the second main surface. Thereby, an orientation of tangential planes of the first wall segment and the second wall segment at adjacent points may be con ^¬ structed in order to derive their relative orientation. Ac- cording to another embodiment the first main surface and the second main surface (or plane lying within these main surfaces) may include an angle with each other between 10° and 70°, in particular 20° and 60°, in particular 30° and 50°. Thereby, it may in particular be possible to assemble a po- lygonal wind turbine tower wall by connecting plural wall portions .

The first surface portion of the connection member may be oriented parallel or transverse, in particular orthogonal, to the first main surface. The second surface portion of the connection member may be oriented parallel or transverse, in particular orthogonal to the second main surface. In particu ^¬ lar, the first surface portion of the connection member may be in direct or indirect contact with a surface portion

(which may or may not be a surface portion of the first edge) of the first wall segment and the second surface portion may be in direct or indirect contact with a surface portion

(which may or may not be a surface portion of the second edge) of the second wall segment. In particular, this portion of the first wall segment may or may not include the first main surface and/or the portion of the second wall segment may or may not include the second main surface. The first surface portion of the connection member and/or the second surface portion of the connection member may or may not (di ^¬ rectly or indirectly) contact or be opposite to the first edge and the second edge, respectively.

In particular, when assembled into a wind turbine tower, the intermediate portion may protrude an inner main surface of the first wall segment and/or an inner main surface of the second wall segment towards an inside (or an outside) of the turbine tower. In particular, the intermediate portion may extend in a radial (alternatively azimuthal) direction in- wards (or outwards) , when the turbine tower is described in cylinder coordinates, having a vertical z-direction having the z-axis arranged along a longitudinal axis of the tower at the center of the tower, wherein the radial coordinate r de- fines an orthogonal distance from the z-axis. In particular, the amount to which the intermediate portion extends trans ^¬ verse to the first surface portion and/or the second surface portion may lie between 0.2 and 50, in particular 1.0 and 30, further in particular 2.0 and 20, times an extent of the first surface portion of the connection member and/or the extent of the second surface portion of the connection member. Thereby, a wall portion for a wind turbine having an in ^¬ creased stability and/or stiffness may be provided. Further, a wind turbine tower is provided which may be assem ^¬ bled from plural wall portions which may easily be trans ^¬ ported via a truck or a train without impeding constraints on the size of the assembled wind turbine tower. In particular, the assembled wind turbine tower wall may have a diameter be- tween 4 m and 20 m, in particular 7 m and 15 m and may have a height between 15 m and 300 m, in particular between 100 m and 200 m.

According to an embodiment the connection member is an inte- grally formed single part. Thereby the manufacturing of the connection member may be simplified.

According to an embodiment the first wall segment comprises a first edge, wherein the second wall segment comprises a sec- ond edge, and wherein the first wall segment and the second wall segment are arranged side by side such that the interme ^¬ diate portion is arranged between the first edge and the sec ^¬ ond edge . The first edge may comprise a surface portion of the first wall segment extending in the thickness direction of the first wall segment. The second edge may comprise a surface portion extending in the thickness direction of the second wall segment. In particular, the surface portion of the first edge may be arranged opposite to the surface portion of the second edge. The first edge may be spaced apart from the sec ^¬ ond edge by a distance between 10 mm and 100 mm, 15 mm and 85 mm, in particular 20 and 50 mm. In particular, the distance between the first edge and the second edge may be provided in order to allow arranging the intermediate portion of the connection member between the first edge and the second edge. In any case the intermediate portion is arranged between the first edge (of the first wall segment) and the second edge (of the second wall segment) . The intermediate portion may in particular extend orthogonally to the first surface portion of the connection member and orthogonally to the second sur- face portion of the connection member. In particular, the intermediate portion may extend transverse to the first surface portion of the connection member and transverse to the second surface portion of the connection member such that a stability and/or stiffness of the wall portion of a wind turbine tower is increased. An amount to which the intermediate por ^¬ tion extends transverse to the first surface portion and transverse to the second surface portion may depend on the application and may range between in particular 10 mm and 200 m, further in particular 20 mm and 150 mm, further in par- ticular 30 mm and 100 mm.

According to an embodiment the first surface portion of the connection member and the second surface portion of the connection member are (at least when considering tangential planes established at adjacent points on the first surface portion of the connection member and the second surface portion of the connection member) parallel to each other and in particular lie in (at least approximately) a same plane. In particular, the first surface portion of the connection mem- ber and the second surface portion of the connection member may lie in a same plane when the first surface portion of the connection member and the second surface portion of the connection member are parallel to the first main surface and/or the second main surface. In particular the first surface por ^¬ tion of the connection member and the second surface portion of the connection member may comprise curved surface por ^¬ tions .

According to an embodiment the first surface portion of the connection member and the second surface portion of the connection member (or tangential planes established at adjacent points on the first surface portion of the connection member and the second surface portion of the connection member) lie in two different planes including an angle between 10° and 70°, in particular between 40° and 50°, further in particular around 45°. Thereby, a wind turbine tower wall having a po ^¬ lygonal shape may be assembled from the wall portion or from several wall portions. Thereby, it is enabled to utilize a first wall segment and a second wall segment having essen ^¬ tially a planar shape, the first main surface and the second main surface being planes. Thereby, manufacturing of the first wall segment and/or the second wall segment may be fa- cilitated. In particular, the first wall segment and/or the second wall segment may be manufactured by rolling steel to achieve a flat (planar) shape.

According to an embodiment the wall portion further comprises at least one bolt arranged to mount the connection member to the first wall portion and/or to the second wall portion. Thereby welding the connection member to the wall portions may be avoided, thus simplifying the assembly of the wall portion. In particular, the first wall portion and/or the second wall portion may comprise one or more bores or holes into which the one or more bolts may be inserted.

According to an embodiment the connection member further comprises a further intermediate portion protruding from a sur- face portion of the connection member opposite to the first surface portion of the connection member and also opposite to the second surface portion of the connection member. The further intermediate portion may in particular provide addi- tional stability to the wall portion. In particular, when as ^¬ sembled into a wind turbine tower wall the intermediate por ^¬ tion as well as the further intermediate portion may extend along a radial direction or along a circumferential direc- tion. In particular, the intermediate portion and the further intermediate portion may extend radially inwards or radially outwards. Again, an amount to which the intermediate portion and/or the further intermediate portion extends (in particu ^¬ lar transverse to the surface portion of the connection mem- ber opposite to the first surface portion and the second sur ^¬ face portion) may depend on the specific application, as de ^¬ scribed above and may be selected appropriately.

In particular, the connection member may be manufactured from a metal, such as iron or steel, in particular stainless steel. Thereby, the connection member may provide by having the further intermediate portion additional stability and/or stiffness to the wall portion, in particular to a wind tur ^¬ bine tower wall assembled from plural wall portions.

According to an embodiment the first surface portion of the connection member (or a tangential plane thereof) is parallel to and in contact with a front side surface portion (or a tangential plane thereof) of the first wall segment and the second surface portion (or a tangential plane thereof) of the connection member is parallel to and in contact with a front side surface portion (or a tangential plane thereof) of the second wall segment. By providing a contact between the first surface portion of the connection member and the front side surface portion of the wall segment and pressing the two sur ^¬ face portions together (for example by tightening a bolt) a friction may be established between the connection member and the first wall segment. The same may hold for the second sur ^¬ face portion of the connection member and the front side sur- face portion of the second wall segment. The contact between the corresponding surface portions may be a direct or an in ^¬ direct contact. Direct contact may mean that no macroscopic structure is placed between the two surface portions but not excluding that contaminating atoms, compounds or layers may be in between the surface portions being in contact with each other (such as having thickness less than 2 mm) . When the surface portions are in indirect contact with each other, a macroscopic amount of material, such as a friction enhancing layer, may be arranged between the corresponding surface portions being in indirect contact with each other. By the contact between the first surface portion of the connection member and the front side surface portion of the first wall seg- ment a friction results which may enhance the stability of the connection between the connection member and the first wall segment. The same may hold for the stability between the connection member and the second wall segment. According to an embodiment the connection member further comprises a third surface portion opposite to and spaced apart from the first surface portion of the connection member, and a fourth surface portion opposite to and spaced apart from the second surface portion of the connection member, wherein a portion of the first wall segment is mounted between the first surface portion of the connection member and the third surface portion of the connection member and wherein a portion of the second wall segment is mounted between the second surface portion of the connection member and the fourth sur- face portion of the connection member.

The third surface portion may be in contact with a backside surface portion of the first wall segment and the fourth sur ^¬ face portion may be in contact with a backside surface por- tion of the second wall segment. Thereby, additional friction may be established between the connection member and the first wall segment as well as between the connection member and the second wall segment, thus even further increasing the stability of the wall portion.

According to an embodiment the first wall segment (and/or the second wall segment) comprises a hole in a front side surface of the first wall segment (and/or the second wall segment) spaced apart from the first edge (second edge) for inserting a bolt for mounting the first surface portion (second surface portion) of the connection member to the first wall segment (second wall segment) . Thereby, a longitudinal axis of the bolt may be oriented transverse, in particular orthogonal, to the main surface of the first wall segment. Further, a longi ^¬ tudinal axis of the bolt inserted into the second wall seg ^¬ ment may be oriented transverse, in particular orthogonal, to the main surface of the second wall segment. Thereby, a tight and strong connection between the first surface portion of the connection member and the first wall segment may be pro ^¬ vided .

According to an embodiment a wall portion is provided, wherein the first edge comprises a first flange extending transversely, in particular orthogonally, to a front side surface of the first wall portion, wherein the second edge comprises a second flange extending transversely, in particu ^¬ lar orthogonally, to a front side surface of the second wall portion, wherein the first flange is mounted at the first surface portion of the connection member and the second flange is mounted at the second surface portion of the con ^¬ nection member. In particular, the first flange may comprise a contact sur ^¬ face being oriented transversely, in particular orthogonally, to the front side surface of the first wall portion. In par ^¬ ticular, the second flange may comprise a contact surface be ^¬ ing oriented transversely, in particular orthogonally, to the front side surface of the second wall portion. In particular, the contact surface of the first flange may be in direct or indirect contact with the first surface portion of the con ^¬ nection member and the contact surface of the second flange may be in direct or indirect contact with the second surface portion of the connection member. Thereby, the connection member may entirely be arranged between the first flange and the second flange. In particular, the connection member may not protrude the first edge towards a lateral extent of the first wall portion and the connection member may not protrude the second edge towards a lateral extent of the second wall portion. In particular, the intermediate portion of the connection member may be arranged connecting or joining the first surface portion of the connection member and the second surface portion of the connection member such that the first surface portion and the second surface portion of the connec ^¬ tion member are spaced apart, in particular oriented parallel to each other, or oriented inclined to each other.

According to an embodiment the first flange (second flange) comprises a hole for inserting a bolt for mounting the first flange (second flange) to the first surface portion (second surface portion) of the connection member. Thereby, a longi- tudinal axis of the bolt inserted into the hole of the first flange may extend in a lateral direction of the main surface of the first wall segment. Further, a longitudinal axis of the bolt inserted into the hole of the second flange may ex ^¬ tend in a lateral direction of the main surface of the second wall segment. Thereby, resistance or stability against forces in different directions may be achieved by a combination of friction and strength of the bolt or bolts. Thereby, stabil ^¬ ity or stiffness requirements in different directions (such as in a vertical direction, circumferential direction, radial direction) may be appropriately adjusted by either adapting contacting surfaces and/or adapting dimensions or materials of bolts connecting the surfaces. Thereby, a higher flexibil ^¬ ity in building a wind turbine tower wall may be provided. According to an embodiment the intermediate portion joins the first surface portion of the connection member with the second surface portion of the connection member.

According to an embodiment a wall portion for a wind turbine tower is provided, wherein the wall portion comprises a first wall segment; a second wall segment, wherein the first wall segment and the second wall segment are arranged side by side; a connection member comprising a first surface portion mounted at the first wall segment, a second surface portion mounted at the second wall segment, and comprising an inter ^¬ mediate portion (also referred to as reinforcement section) joining the first surface portion with the second surface portion.

Thereby, an alternative solution for the object of providing a wall portion for a wind turbine tower having an enhanced stability and/or stiffness may be provided. The single inven- tive concept may be seen to provide the connection member with an additional reinforcement section which is adapted as an intermediate portion in the aforementioned embodiments and may alternatively be adapted as a section joining the first surface portion with the second surface portion. In particu- lar, the reinforcement section may be a structure in a plane different from a plane in which the first surface portion or the second surface portion of the connection member lie. The reinforcement section may provide increased stability or stiffness to the connection member and thus also to the wall portion for the wind turbine tower.

According to an embodiment the reinforcement section com ^¬ prises a portion extending parallel to the first surface por ^¬ tion of the connection member and to the second surface por- tion of the connection member and also comprises two portions extending transverse to the first surface portion of the con ^¬ nection member and transverse to the second surface portion of the connection member. The two portions extending transverse to the first surface portion and the second surface portion of the connection member may be provided to arrange the portion extending parallel to the first surface portion and the second surface portion of the connection member spaced apart by a distance from the first surface portion and the second surface portion of the connection member, wherein the distance may amount to between 10 mm and 200 mm, in par ^¬ ticular 20 mm to 150 mm, further in particular 50 mm to 120 mm. Thereby, the reinforcement section may effectively pro ^¬ vide increased stability to the wall portion. According to an embodiment a tower wall for a wind turbine is provided, wherein the tower wall comprises plural wall por ^¬ tions for a wind turbine tower as described above according to an embodiment, wherein the plural wall portions are mounted in a pairwise manner to form an annular wall section. In cross-section the annular wall section may have a polygonal shape, a circular shape, an oval shape or the like. In particular, the cross-section may comprise six, eight, ten, twelve or even more corners. Thereby, a tower wall having in ^¬ creased stability compared to a conventional tower wall may be provided.

According to an embodiment the first edge of the first wall segment and the second edge of the second wall segment extend in a longitudinal direction of the tower, in particular perpendicular to the annular cross-section of the tower wall. Due to the connection between the wall segments using the connection member, the wall sections being arranged side by side and having their edges oriented vertically (in the lon ^¬ gitudinal direction) may withstand higher bending forces re ^¬ sulting from impacting wind directed in a horizontal direc ^¬ tion perpendicular to the vertical direction (longitudinal direction of the tower) .

Thereby, it is enabled to assemble or build a wind turbine tower having increased size (height and/or diameter) compared to a conventional wind turbine tower. Since wind speed may increase with increasing heights from the ground, a wind tur- bine having a higher capacity or power may be provided.

Although embodiments have been described with respect to a wall portion for a wind turbine tower or a tower wall for a wind turbine, the features (disclosed individually or in com- bination) of these embodiments may also be applied to a method of manufacturing a wall portion for a wind turbine tower or a method of manufacturing a tower wall for a wind turbine . According to an embodiment a method of manufacturing a wall portion for a wind turbine tower is provided, wherein the method comprises arranging a first wall segment comprising a first edge side by side with a second wall segment comprising a second edge such that the first edge and the second edge are spaced apart; arranging an intermediate portion of a con ^¬ nection member between the first edge and the second edge such that the intermediate portion extends transverse to the first surface portion of the connection member and the second surface portion of the connection member; mounting a first surface portion of the connection member at the first wall segment; and mounting a second surface portion of the connec ^¬ tion member at the second wall segment.

It has to be noted that embodiments of the invention have been described with reference to different subject matters. In particular, some embodiments have been described with ref ^¬ erence to method type claims whereas other embodiments have been described with reference to apparatus type claims. How ^¬ ever, a person skilled in the art will gather from the above and the following description that, unless other notified, in addition to any combination of features belonging to one type of subject matter also any combination between features re- lating to different subject matters, in particular between features of the method type claims and features of the appa ^¬ ratus type claims is considered as to be disclosed with this document . The aspects defined above and further aspects of the present invention are apparent from the examples of embodiment to be described hereinafter and are explained with reference to the examples of embodiment. The invention will be described in more detail hereinafter with reference to examples of embodi- ment but to which the invention is not limited. Brief Description of the Drawings

Figure 1 schematically shows a side view of a portion of a wind turbine tower including a wall portion for a wind tur- bine tower according to an embodiment;

Figure 2 schematically shows a cross-sectional view of a wall portion according to an embodiment; Figure 3 schematically shows a cross-sectional view of a wall portion for a wind turbine tower according to another embodiment ;

Figure 4 schematically shows a cross-sectional view of still another embodiment of a wall portion for a wind turbine tower;

Figure 5 schematically shows a cross-sectional view of still another embodiment of a wall portion for a wind turbine tower;

Figure 6 schematically shows a cross-sectional view of still another embodiment of a wall portion for a wind turbine tower;

Figure 7 schematically shows a cross-sectional view of still another embodiment of a wall portion for a wind turbine tower;

Figure 8 schematically shows a cross-sectional view of still another embodiment of a wall portion for a wind turbine tower;

Figure 9 schematically shows a cross-sectional view of still another embodiment of a wall portion for a wind turbine tower . Detailed Description

The illustration in the drawing is schematically. It is noted that in different figures, similar or identical elements are provided with the same reference signs or with reference signs, which are different from the corresponding reference signs only within the first digit.

Thereby, elements, components and/or method steps similar in structure and/or function are denoted by reference signs dif ^¬ fering only in the first position. As far as an element, a component, or a method step is not described in detail with respect to a particular embodiment the description of the corresponding element, component, or method step with respect to another embodiment may serve as an auxiliary description for this element, component, or method step in the particular embodiment.

Figure 1 schematically shows a side view of a wall portion 100 for a wind turbine tower 101. The wind turbine tower 101 extends in a longitudinal direction or axis 103 (along the z- axis) which may be a symmetry axis of the wind turbine tower 101. The wind turbine tower 101 comprises a plurality of wall portions for a wind turbine tower from which only one wall portion 100 is illustrated in Figure 1.

The wall portion 100 comprises a first wall segment 105 com ^¬ prising a first edge 106 and the wall portion 100 further comprises a second wall segment 107 comprising a second edge 108. As will be described below in more detail below a con ^¬ nection between the first wall segment 105 and the second wall segment 107 is established using a connection member 109 which is at least partially arranged between the first edge 106 of the first wall segment 105 and the second edge 108 of the second wall segment 107. Thus, the connection member 109 provides a vertical connection between adjacent wall segments 105, 107. In general different embodiments of a wall portion for a wind turbine tower illustrated in Figures 2, 3, 4, 5, 6, 7, 8 and 9 may be used for assembling a wind turbine tower, such as the wind turbine tower 101 illustrated in Figure 1. In all illustrated embodiment the first wall segment and/or the sec ^¬ ond wall segment may have a planar shape, a cylindrical shape, a conical shape or the like. Figure 2 schematically illustrates a cross-sectional view

(perpendicular to the axis 103 in Fig. 1) of a wall portion 200 according to an embodiment. The wall portion 200 illus ^¬ trated in Figure 2 comprises a first wall segment 205 and a second wall segment 207 which are arranged side by side such that a first edge 206 of the first wall segment 205 is oppo ^¬ site and adjacent to a second edge 208 of the second wall segment 207. The first edge 206 extends perpendicular to a main surface 211 of the first wall segment 205 and the second edge 208 extends perpendicular to a main surface 212 of the second wall segment. In particular, the main surface 211 of the first wall segment 205 and the main surface 212 of the second wall segment 207 lie in a common plane. In other em ^¬ bodiments the main surface 211 of the first wall segment 205 and the main surface 212 of the second wall segment 207 may lie in different planes including an angle between 0 and 50°, in particular between 20 and 50°.

The first wall segment 205 and the second wall segment 207 are connected to each other using the connection member 209. The connection member 209 comprises a first surface portion 213 mounted at the first wall segment 205 and a second sur ^¬ face portion 215 mounted at the second wall segment 207. In particular, the first surface portion 213 and the second sur ^¬ face portion 215 of the connection member 209 lie in a common plane being parallel to the main surface 211 of the first wall segment and parallel to the main surface 212 of the sec ^¬ ond wall segment. The first surface portion 213 may be in di ^¬ rect or indirect contact with a front side surface portion 217 of the first wall segment and the second surface portion 215 of the connection member 209 may be in direct or indirect contact with a front side surface portion 219 of the second wall segment 207. By tightening bolts 221 the surface por- tions 213, 217 as well as the surface portions 215, 219 may be pressed together such that a friction is established be ^¬ tween the first surface portion 213 of the connection member 209 and the surface portion 217 of the first wall segment 205. Further, friction may be established between the second surface portion 215 of the connection member 209 and the surface portion 219 of the second wall segment 207. Thereby, a connection strength between the first wall segment 205 and the connection member 209 as well as between the second wall segment 207 and the connection member 209 may be established.

To further increase the connection strength and also to increase the stability or stiffness of the wall portion 200 the connection member 209 further comprises a reinforcement sec ^¬ tion comprising a portion 223 substantially extending paral- lei to the first surface portion 213 and the second surface portion 215 of the connection member 209 and wherein the connection member 209 further comprises two portions 225 joining the first surface portion 213 and the second surface portion 215 to the portion 223 of the connection member 209. A length of the portions 225 may depend on the application. The greater the length of the portions 225 of the connection member 209 the higher the stability provided by the connection member 209 may be. Figure 3 schematically illustrates a cross-sectional view of another embodiment of a wall portion 300 according to an embodiment. A first wall segment 305 comprises an edge 306 which is arranged opposed to a second edge 308 of a second wall segment 307. Thereby, the first wall segment 305 and the second wall segment 307 are arranged side by side such that the first edge 306 and the second edge 308 are spaced apart by a distance dl . dl may amount to between 10 mm to 100 mm, in particular between 20 mm and 70 mm, in particular around 50 mm. The clearance or distance between the first edge 306 and the second edge 308 may allow for arranging an intermedi ^¬ ate portion 327 of the connection member 309 in between the edges 306 and 308. Thereby, a stability of the connection be- tween the first wall segment 305 and the second wall segment 307 using the connection member 309 may be enhanced.

The connection member 309 further comprises a first surface portion 313 mounted at the first wall segment 305 and the connection member 309 comprises a second surface portion 315 mounted at the second wall segment 307. In particular, the first surface portion 313 may be in direct or indirect con ^¬ tact with a front surface portion 317 of the first wall seg ^¬ ment 305 and the second surface portion 315 of the connection member 309 may be in direct or indirect contact with a first surface portion 319 of the second wall segment 307.

In particular, the intermediate portion 327 of the connection member 309 protrudes (extends transversely, in particular or- thogonally) from the first surface portion 313 and from the second surface portion 315 of the connection member 309. Further, the first surface portion 313 is parallel to the second surface portion 315 of the connection member 309. When assembled to a wind turbine tower wall the first surface portion 313 and the second surface portion 315 of the connection mem ^¬ ber may be either arranged in an inside of the tower or at an outer surface of the wind turbine tower wall 101, as illus ^¬ trated in Figure 1. A surface portion of the intermediate portion of the connec ^¬ tion member 309 parallel to the main surface 311 of the first wall segment 305 and also parallel to the main surface 312 of the second wall segment is flush with these main surfaces, thus not protruding over these main surfaces. In other em- bodiments the intermediate portion 327 (or a distal surface thereof) may protrude over the main surface 311 and/or 312 for still increasing the stability of the wall portion 300. Figure 4 schematically illustrates a cross-sectional view of another embodiment of a wall portion 400. Differently from the embodiment illustrated in Figure 3 the wall portion 400 illustrated in Figure 4 comprises a first wall segment 405 and a second wall segment 407 whose main surfaces 411 and 412 do not lie in a common plane but include an angle a of about 45°. In other embodiments the angle a may amount to other values, in particular between 30° and 60°. Thereby, a wind turbine tower wall having a polygonal cross-section may be assembled using the wall portion 400. Depending on the angle a also the connection member 409 has an angled shape in that the first surface portion 413 being in contact with a front side surface portion 417 of the first wall segment includes an angle a with the second surface portion 415 of the con- nection member 409 being in contact with a front side surface portion 419 of the second wall segment 407. As in the embodi ^¬ ment illustrated in Figure 3 the intermediate portion 427 of the connection member 409 is arranged between the first edge 406 of the first wall segment 405 and the second edge 408 of the second wall segment 407. In the embodiment illustrated in Figure 4 the intermediate portion 427 protrudes over the main surfaces 411 of the first wall segment 405 and the main sur ^¬ face 412 of the second wall segment. Thereby, the stability of the wall portion 400 may be increased.

Figure 5 schematically illustrates another embodiment of a wall portion 500 according to an embodiment. The wall portion 500 illustrated in Figure 5 shows similarities to the wall portion 300 illustrated in Figure 3 but differs from this wall portion 300 in that the wall portion 500 illustrated in Figure 5 further comprises a third surface portion 529 oppo ^¬ site to and spaced apart by a distance d2 from the first sur ^¬ face portion 513 of the connection member 509 and in that it comprises a fourth surface portion 531 opposite to and spaced apart by the distance d2 from the second surface portion 515 of the connection member 509. Thereby, a portion of the first wall segment is arranged between and mounted between the first surface portion 513 and the third surface portion 529 of the connection member 509 and a portion of the second wall segment 507 is arranged between and mounted between the sec ^¬ ond surface portion 515 and the fourth surface portion 531 of the connection member 509, in particular using bolts 521. In other embodiments the first wall segment 505 and the second wall segment 507 (and thus main surfaces thereof) may not lie in a common plane but may include an angle similar as de ^¬ scribed with reference to Figure 4. Figure 6 schematically shows a cross-sectional view of an ^¬ other embodiment of a wall portion 600 according to an embodiment. The wall portion 600 illustrated in Figure 6 shows similarities to the wall portion 300 illustrated in Figure 3 but differs from this embodiment in that the wall portion 600 illustrated in Figure 6 further comprises a further interme ^¬ diate portion 633 comprised in the connection member 609. Thereby, the further intermediate portion 633 protrudes from a surface portion 634 of the connection member 609, wherein the surface portion 634 is opposite to the first surface por- tion 613 of the connection member 609 and also opposite to the second surface portion 615 of the connection member 609. In particular, the further intermediate portion 633 protrudes in a direction opposite to a protrusion direction of the intermediate portion 627, wherein the intermediate portion 627 is, as in the embodiments illustrated in Figures 3-5 arranged between the first edge 606 of the first wall segment 605 and the second edge 608 of the second wall segment 607. The fur ^¬ ther intermediate portion 633 (or/and the intermediate por ^¬ tion 627) may extend a distance d3 from the surface portion 634. Thereby, the distance d3 may amount to between 10 mm and 200 mm, in particular 30 mm and 100 mm. In other embodiments the first wall segment 605 and the second wall segment 607 may not lie in a common plane but may include an angle simi ^¬ lar as illustrated in Figure 4.

Figure 7 schematically illustrates a cross-sectional view of another embodiment of a wall portion 700 according to an embodiment. The embodiments illustrated in Figures 7, 8 and 9 differ from the embodiments illustrated in Figures 3, 4, 5, 6 in that the first wall segment 705 as well as the second wall segment 707 each comprise a flange forming the edges 706 and 708, respectively. In particular, the first wall segment 705 comprises a flange 735 extending transversely, in particular orthogonally, to the front side surface portion 717 of the first wall segment 705. Further, the second wall segment 707 comprises a flange 737 extending transversely, in particular orthogonally, to the front side surface portion 719 of the second wall segment 707. Thereby, the edge 706 of the first wall segment 705 is essentially formed by a connection sur ^¬ face of the flange 735.

The connection surface 706 of the flange 735 is in direct or indirect contact with the first surface portion 713 of the connection member 709. The second edge 708 is essentially formed by a connection surface of the flange 737 of the sec ^¬ ond wall segment 707. The connection surface 708 of the flange 737 is in direct or indirect contact with the second surface portion 715 of the connection member 709. Thereby, the first surface portion 713 as well as the second surface portion 715 of the connection member 709 are oriented trans ^¬ versely, in particular orthogonally, to the front side sur ^¬ face 717 of the first wall segment 705 and the second surface portion 715 of the connection member 709 is transverse, in particular orthogonal, to the front side surface 719 of the second wall segment 707.

The intermediate portion 727 joins the first surface portion 713 and the second surface portion 715 of the connection mem ^¬ ber 709. Herein, the intermediate portion 727 extends trans ^¬ verse, in particular orthogonal, to the first surface portion 713 and the second surface portion 715 of the connection mem ^¬ ber 709. In the embodiment illustrated in Figure 7 the con- nection member 709 comprises a further intermediate portion

733 also joining the first surface portion 713 and the second surface portion 715, wherein the intermediate portion 727 ex ^¬ tends parallel to and is opposite to the further intermediate portion 733 of the connection member 709. Due to the interme ^¬ diate portion 727 (and the further intermediate portion 733) of the connection member 709 the connection surfaces 706 of the first flange 735 and the connection surface 708 of the second flange 737 are spaced apart by a distance dl .

Figure 8 schematically illustrates a cross-sectional view of another embodiment of a wall portion 800 according to an embodiment. The embodiment illustrated in Figure 8 is similar to the embodiment of the wall portion 700 illustrated in Fig ^¬ ure 7 except that the further intermediate portion is missing in the wall portion 800 illustrated in Figure 8.

Figure 9 schematically illustrates a cross-sectional view of another embodiment of a wall portion 900 according to an embodiment. The wall portion 900 illustrated in Figure 9 has similarities with the wall portion 800 illustrated in Figure 8 except that the first wall segment 905 and the second wall segment 907 do not lie in a common plane, but include an an- gle a similar as in the case of embodiment 400 illustrated in Figure 4. The first wall segment 905 comprises a first flange 935 having a connection surface 906 being in direct or indirect contact with a first surface portion 913 of the con ^¬ nection member 909. The connection member 909 is mounted at the first wall segment 905 using a bolt 921 and mounted at the second wall segment 907 using another bolt 921. Depending on an inclination angle a (being the angle included by main surfaces of the first wall segment 905 and the second wall segment 907) the orientation of the first surface portion 913 and the second surface portion 915 of the connection member 909 relative to the intermediate portion 927 (or a surface thereof) may be adapted. Thus, connection members 909 having different shapes such that an angle between the first surface portion (or/and the second surface portion 915) and the in- termediate portion 927 (or a surface thereof) varies are pro ^¬ vided. Thereby, wind turbine tower walls having different ge ^¬ ometries, such as polygonal with 4, 6, 8, 10, 12 corners may be assembled using wall portions according to embodiments. It should be noted that the term "comprising" does not ex ^¬ clude other elements or steps and "a" or "an" does not ex ^¬ clude a plurality. Also elements described in association with different embodiments may be combined. It should also noted that reference signs in the claims should not be con strued as limiting the scope of the claims.