A supporting pillar for a wind power plant, a method for establishing a supporting pillar for a wind power plant and use of a supporting pillar

Abstract

A supporting pillar (1) for a wind power plant. The supporting pillar comprises an elongated body (5) configured to hold a wind-power turbine at an elevated position or transferring rotational energy to a rotor of a wind-power turbine. The elongated body comprises a center structure (10) configured to provide structural stability to the supporting pillar, and a protective layer (20) on the center structure configured to protect the center structure from interaction with the surrounding environment. The center structure mainly comprises a biological derived fibrous composition, and the protective layer comprises at least one rigid sheet (22) that is arranged prestressed attached to at least an outer surface of the center structure.

Description

[0001] TITLE: A supporting pillar for a wind power plant, a method for establishing a supporting pillar for a wind power plant and use of a supporting pillar

[0002] Field of the invention

[0003] The present invention relates to a supporting pillar for a wind power plant, in particular a supporting pillar for an offshore wind power plant. The supporting pillar comprises an elongated body configured to hold a wind power turbine at an elevated position and / or alternatively the supporting pillar is connected to a turbine rotor axis and the elongated body transfers rotational energy to the generator. The elongated body comprises a center structure configured to provide structural stability to the supporting pillar for holding a wind-power turbine or for transferring rotational energy to a rotor of a wind power turbine. The supporting pillar further comprises a protective layer on the center structure configured to protect the center structure from interaction with the surrounding environment.

[0004] The present invention further relates to a method for establishing a supporting pillar for a wind power plant and use of such a supporting pillar for a wind power plant.

[0005] Background of the invention

[0006] Wind power plants use different types of supporting pillars for holding a wind-power turbine with wind power blades at an elevated position, for example a horizontal-axis wind turbine (HAWT), or for holding wind power blades and transferring rotational energy by means of the supporting pillar to a rotor of a wind-power turbine, for example so called vertical-axis wind turbine (VAWT).

[0007] The supporting pillars may be of significant height, such as several hundred meters. Even heights up to 400 meters are suggested. In order to provide sufficient structural stability, prior art supporting pillars generally use various exclusive materials, such as fiber reinforced polymer, carbon fiber, etc. While providing sufficient strength, a problem with such materials is that they are costly and contribute significantly to the overall cost of the wind power plant.

[0008] In order to reduce the cost of supporting pillars alternative materials, such as various biological derived fibrous composition may be used. In particular laminated timber has shown to provide excellent properties as a structural material and may have higher strength to weight ratio compared to both concrete and steel. A problem with such biological derived fibrous composition is to avoid degradation in structural strength due to interaction with the surrounding environment, such as due to intrusion of moisture into the material of the supporting pillar. This problem is in particular pronounced for use of supporting pillar in offshore environments.

[0009] A further problem with prior art supporting pillars is how to assemble the supporting pillars with significant heights from a plurality of segments.

[0010] W02008153489 (A1) discloses an example of a wooden supporting pillar for a windpower unit.

[0011] CN 206220559 II discloses a fibre cloth to carry out post of prestressed reinforcement, relate to wooden technical field. CN 205936983 II discloses an external prestress concrete tower section of thick bamboo, including tower section of thick bamboo body. WO 2008 / 153489 A1 discloses a wind-power unit wherein the material of the supporting pillar is in all essentials wood. CN 217421428 II discloses a prestressed concrete-wood combined type wind driven generator tower drum. CN 211201336 II relates to a multidirectional prestress cylindrical orthogonal laminated wood structure wind power generation tower.

[0012] Summary of the invention

[0013] An object of the present invention is to provide an improved supporting pillar for a wind-power plant. In particular, a first object of the invention is to provide an improved supporting pillar that reduces the degradation in structural strength of a biological derived fibrous composition used for supporting pillar. A second object of the invention is to provide an improved supporting pillar that facilitates its assembly. A third object of the invention is to provide an improved method for assembling a supporting pillar.

[0014] These objects are obtained by a supporting pillar for a wind power plant, where the supporting pillar comprises an elongated body configured to hold a wind-power turbine at an elevated position and / or transferring rotational energy to a rotor of a wind power turbine. The body comprises a center structure configured to provide structural stability to the supporting pillar, and a protective layer on the center structure configured to protect the center structure from interaction with the surrounding environment.

[0015] The center structure mainly comprises a biological derived fibrous composition, and wherein the protective layer comprises at least one rigid sheet that is arranged prestressed attached to at least an outer surface of the center structure.

[0016] By means of that the protective layer is prestressed attached to at least the outer surface of the center structure, the outer surface is protected from intrusion of moisture into the biological derived fibrous composition. Furthermore, the prestressed condition of the rigid sheet enables fibers in the biological derived fibrous composition to be held in place, which assures that the structural stability of the supporting pillar is maintained.

[0017] The term biological derived fibrous composition is to be understood as a material derived from materials of biological origin, excluding fossilized materials or materials embedded in geological formations. The composition further comprises fibers contributing to its structural strength.

[0018] The protective layer has the function of protecting the center structure from the surrounding environment. The protective layer is in particular a layer having water resistant properties. The protective layer comprises the at least one rigid sheet of a material having form stability that assure that the protective layer stays attached in its prestressed condition on the center structure during the duration of the use of the supporting pillar.

[0019] According to an embodiment of the invention, the rigid sheet of the protective layer mainly comprises one of an aluminum alloy, glass-fiber reinforced plastic, thermoplastic, stainless steel, or a combination thereof. While the protective layer may include exclusive materials that are costly, the quantity of the protective layer is small in relation to the extent of the center structure and only contribute to a small fraction of the overall cost of the supporting pillar.

[0020] According to an embodiment of the invention, the protective layer has a thickness in the interval of 1 - 50 mm, preferably 2 - 10 mm. According to an embodiment of the invention, the center structure has a circular outer surface. Preferably, the center structure has a circular outer surface with a diameter in the interwall of 1 - 30 m, preferably 2 - 21 m.

[0021] According to an embodiment of the invention, the at least one rigid sheet of the protective layer is attached to the center structure by means of one of glue joint and a bolted joint, or a combination thereof.

[0022] The glue is adapted to form a prestressed adhesion between rigid sheet and the center structure by providing the glue at an elevated temperature, such as at a temperature between 20 and 50 °C. The glue is for example Epoxy.

[0023] According to an embodiment of the invention, the biological derived fibrous composition mainly comprises one of a wooden material, bamboo, straw, cotton, reed, hemp, flax, or a combination thereof. These materials have the advantage of providing high strength to weight ratio while being cost effective.

[0024] According to an embodiment of the invention, the wooden material mainly comprising glued laminated timber, such as glued laminated timber mainly comprising spruce. Laminated timber provides the advantage of having high strength to weight ratio while being cost effective.

[0025] According to an embodiment of the invention, the protective layer comprises two or more rigid sheets that have been joint by friction stir welding. Friction stir welding is in particular suitable for connecting rigid sheets of an aluminum alloy.

[0026] According to an embodiment of the invention, the protective layer is prestressed attached to the center structure in the interval of 5 - 100 MPa, preferably 10 - 30 MPa at an operational temperature of the supporting pillar. The operational temperature is typical in an interval of -10 °C to 30 °C.

[0027] According to an embodiment of the invention, the elongated body comprises an opening that extends along a longitudinal axis of the body and defining an inner surface of the center structure, wherein the protective layer is arranged to the inner surface of the center structure. The opening defines a hollow inner space of the supporting pillar. The hollow inner space may be used for wiring, etcetera. According to an embodiment of the invention, the wall thickness of the center structure is in the interval of 5 - 200 cm2.

[0028] According to an embodiment of the invention, the rigid sheet of the protective layer is wrapped in a spiral onto the center structure. By means of wrapping the protective layer in a spiral, the protective layer may be provided from a coil holding the rigid sheet, which facilitates the process of applying the rigid sheet and prestress attaching it to the center structure.

[0029] According to an embodiment of the invention, the elongated body comprises between two and 12 body segments, preferably three body segments, each having two end sides and two long sides, wherein the body segments are attached together at their long sides such that they jointly form the circumference of the body.

[0030] According to an embodiment of the invention, the elongated body comprises three elongated body segments, each having two end sides and two long sides, wherein the body segments are attached together at their long sides such that they jointly form the circumference of the body. By means of attaching three elongated body segments together so that they jointly form the circumference of the elongated body, a rigid attachment between the segments is obtained.

[0031] According to an embodiment of the invention, the three elongated body segments are arranged as respective truss assemblies, each comprising a hollow inner between the outer surface and the inner surface, and one or more support beams extending between outer surface and the inner surface. The truss assemblies have the advantage of providing improved strength to weight ratio.

[0032] According to an embodiment of the invention, the truss assemblies are arranged with convex outer surfaces and alignment parts configured to abut with and be connected to corresponding truss assembly so that they jointly form the circumference of the center structure. By means of the alignment parts, positioning and joining of the body segments are facilitated.

[0033] According to an embodiment of the invention, the three elongated body segments are fully enclosed in the protective layer. By means of fully enclosing the body segments, the handling of the body segments is facilitated. For example, the body segments may be stored outside, thereby exposed to wind and rain, prior to being assembled into the supporting pillar.

[0034] According to an embodiment of the invention, the three body segments have a tapered outer surface such that they jointly form a conical outer surface in the direction of the elongated extension of the supporting pillar.

[0035] According to an embodiment of the invention, the body segments comprising attachment means that attaches the body segments together along their long sides, wherein the attachment means comprises a tongue and groove joint. The tongue and groove joint of the attachment means may preferably be reinforced with one of glue joint and a bolted joint, or a combination thereof.

[0036] According to an embodiment of the invention, the body segments comprising further attachment means that attaches the body segments together along their short sides, wherein the further attachment means comprises a tongue and groove joint. The tongue and groove joint of the further attachment means may preferably be reinforced with one of glue joint and a bolted joint, or a combination thereof.

[0037] According to an embodiment of the invention, the body segments comprising a first type segment, a second type segment and a third type segment, wherein the length of the third type segment is one third of the first type segment and the length of the second type segment is two third of the first type segment, wherein the body is compiled connecting end sides and long sides of the first, second and third type segments such that an end side connection between two body segments is located at long sides of the other two body segments forming the circumference.

[0038] By means of the configuration of the first type segment, the second type segment and the third type segment, the elongated body is compiled in such a manner that end side connections are located at long sides of the other two segments forming the circumference of the elongated body. Thereby, the strength of the connections between the segments are improved and the overall strength of the elongated body is improved.

[0039] The object of the invention is further obtained by means of a method for establishing a supporting pillar for a wind power plant, where the supporting pillar comprises an elongated body configured to hold a wind-power turbine at an elevated position or transferring rotational energy to a rotor of a wind-power turbine, wherein the method comprises the steps of:

[0040] - preparing at least one body segment of the elongated body by i) forming a center structure mainly comprising a biological derived fibrous composition, and ii) prestressed attaching a protective layer comprising at least one rigid sheet to at least an outer surface of the center structure.

[0041] According to an embodiment of the invention, the step of prestressed attaching the protective layer comprises forming one of glue joint and a bolted joint, or a combination thereof.

[0042] According to an embodiment of the invention, the step of prestressed attaching the protective layer comprises:

[0043] - attaching two or more rigid sheets to the center structure, and

[0044] - joining the two or more rigid sheets together, such as by friction stir welding.

[0045] According to an embodiment of the invention, the method comprises

[0046] - positioning the rigid sheet of the protective layer to the center structure by wrapping the protective layer in a spiral onto the center structure.

[0047] According to an embodiment of the invention, the method comprises

[0048] - preparing three elongated body segments having two end sides and two long sides, by: i) forming a center structure for the body segments mainly comprising a biological derived fibrous composition, and ii) prestressed attaching a protective layer comprising at least one rigid sheet to at least an outer surface of the center structure such that fibers of the fibrous composition are held in place, and

[0049] - connecting the three elongated body segments together at their long sides such that they jointly form the circumference of the body.

[0050] According to an embodiment of the invention, the method comprises:

[0051] - preparing a first type segment, a second type segment and a third type segment, wherein the length of the third type segment is one third of the first type segment and the length of the second type segment is two third of the first type segment, and - connecting end sides and long sides of the first, second and third type segments such that an end side connection between two body segments is located at long sides of the other two body segments forming the circumference.

[0052] The object of the invention is further obtained by means of use of a supporting pillar according to any of above embodiments of the invention.

[0053] According to an embodiment of the invention, the supporting pillar is used for holding structural members of a wind power plant at an elevated position.

[0054] According to an embodiment of the invention, the supporting pillar is used for transferring rotational energy to a turbine of a wind power plant.

[0055] Description of the figures

[0056] Embodiments of the present invention will now be described, by way of example only, with reference to the following figures, wherein:

[0057] Figure 1 shows a side view of a supporting pillar for a wind power plant according to an embodiment of the invention,

[0058] Figure 2a shows a cross section of a supporting pillar according to an embodiment of the invention,

[0059] Figure 2b shows a cross section of a supporting pillar according to a further embodiment of the invention,

[0060] Figure 3a shows a side view of a supporting pillar according to an embodiment of the invention, wherein the supporting pillar comprises connected segments, Figure 3b shows a cross section of a body segment in the form of a truss assembly according to an embodiment of the invention,

[0061] Figure 3c shows a cross section of three body segments from fig. 3b joined together according to an embodiment of the invention,

[0062] Figure 3d shows a perspective side view of fig. 3c,

[0063] Figure 3e shows a perspective side view of the body segment in fig. 3b,

[0064] Figure 3f shows a perspective side view of a further body segment,

[0065] Figure 4a shows a side view of a configuration of body segments for compiling the supporting pillar according to an embodiment of the invention,

[0066] Figure 4b shows three type body segments for compiling the supporting pillar in fig. 4a, Figure 5a shows a flow chart of a method for establishing a supporting pillar according to an embodiment of the invention,

[0067] Figure 5b shows a flow chart of a method for establishing a supporting pillar according to a further embodiment of the invention, and

[0068] Figure 5c shows a flow chart of a method for establishing a supporting pillar according to yet another embodiment of the invention.

[0069] Description of preferred embodiments of the invention

[0070] With reference to fig. 1, a side view of a supporting pillar 1 for a wind power plant according to an embodiment of the invention shown. The supporting pillar 1 comprises an elongated body 5 configured to be arranged in an upright position. The elongated body 5 is further configured to hold a wind-power turbine at an elevated position. The elongated body 5 is also configured to transfer rotational energy to a rotor of a wind-power turbine. The elongated body 5 is accordingly adapted with structural strength for such purpose.

[0071] The elongated body 5 comprises a center structure 10 configured to provide such structural stability to the supporting pillar 1. The center structure 10 mainly comprises a biological derived fibrous composition, preferably one of a wooden material, bamboo, straw, cotton, reed, hemp, flax, or a combination thereof. Such material has the advantage of having high strength to weight ratio, while being cost effective. Preferably, a wooden material mainly comprising glued laminated timber is used for the center structure 10.

[0072] The elongated body 5 further comprises a protective layer 20 on the center structure 10 configured to protect the center structure 10 from interaction with the surrounding environment. The protective layer 20 has in particular a water-resistant property. The protective layer 20 is at least arranged on an outer surface of the center structure 10. Preferably, the protective layer 20 is arranged fully enclosing the center structure 10.

[0073] The protective layer 20 further comprises at least one rigid sheet 22 that is arranged prestressed attached to the center structure 10 such that fibers of the fibrous composition are held in place. Thereby, the strength of the elongated body 5 is maintained during the duration of the use of the supporting pillar 1. The rigid sheet 22 is preferably prestressed attached to the center structure 10 in the interval of 5 - 100 MPa, preferably 10 - 30 MPa. The attachment is such that the prestressed interval is maintain at an operational temperature of the supporting pillar 1.

[0074] The rigid sheet 22 of the protective layer 20 preferably mainly comprises one of an aluminum alloy, glass-fiber reinforced plastic, thermoplastic, stainless steel, or a combination thereof. In particular, the aluminium alloy has advantages in that weight to strength ratio in view of its cost.

[0075] In the disclosed embodiment, the protective layer 20 comprises a plurality of rigid sheet 22 arranged next to each other and joint together at connections 24, for example by friction stir welding. In particular, the rigid sheet 22 in the form of an aluminium alloy has proven beneficial for joining by friction stir welding.

[0076] In an alternative embodiment, the rigid sheet 22 of the protective layer 20 is wrapped in a spiral onto the center structure 10. Thereby, the number of necessary joints are reduced. Furthermore, application of the protective layer 20 is facilitated in that the rigid sheet 22 may be stored and provided from a coil holding the rigid sheet 22.

[0077] In a preferred embodiment of the invention, the protective layer 20 has a thickness in the interval of 1 - 50 mm, preferably 2 - 10 mm. The thickness has proven sufficient for protecting the center structure 10 from intrusion of moisture. Furthermore, the thickness is sufficient for the suggested rigid sheets 22 to be maintain in the prestressed attachment to the center structure 10 during the duration of the use of the supporting pillar 1.

[0078] The rigid sheet 22 is preferably attached to the center structure 10 by means of one of glue joint and a bolted joint, or a combination thereof. Preferably, a glue is applied at an elevated temperature, such as above 20 °C. Thereby, the prestressed attachment is provided after the glue is curing. The glue is for example epoxy. The prestressed attachment may preferably be supported by a bolted joint.

[0079] With reference to fig. 2a, a cross section of a supporting pillar 1 according to an embodiment of the invention is shown. The protective layer 20 is attached to both an outer surface and an inner surface of the center structure 10. Furthermore, a plurality of the rigid sheets 22 are joint together connections 24 forming the protective layer 20. In fig. 2a, schematically four rigid sheets 22 on the outer surface are indicated prestressed attached.

[0080] With reference to fig. 2b, a cross section of a supporting pillar 1 according to a further embodiment of the invention is shown. The elongated body 5 is comprised by three body segments 50. The three body segments 50 are each having two end sides and two long sides. The three body segments 50 are attached together at their long sides so that they jointly form the circumference of the body 5.

[0081] The three body segments 50 comprising attachment means 52 that attaches the body segments 50 together along their long sides. Preferably, the attachment means 52 comprises a tongue and groove joint.

[0082] In the disclosed embodiment, the three body segments 50 are provided with the protective layer 20 at both the outer surface and the inner surface. The three body segments 50 however lacks protective layer 20 at their long sides, where the body segments 50 are attached by the attachments means 52. In an alternative embodiment, the three body segments 50 are provided with the protective layer 20 at all sides, thereby fully enclosing the center structure 10 of each body segment 50.

[0083] With reference to fig. 3a, a side view of a supporting pillar 1 according to an embodiment of the invention is shown. In fig. 3, schematically an embodiment the supporting pillar 1 is illustrated where the elongated body 5 comprises body segments 50 connected both at their long sides by means of the attachment means 52 and at their short sides by means of further attachment means 54.

[0084] With reference to fig. 3b-e, an embodiment of the invention is disclosed where the elongated body 5 is compiled of three elongated body segments 50 in the form of respective truss assemblies. In fig. 3b a cross section of one segment is shown. In fig. 3c is a cross section of three body segments 50 joined together shown. In fig. 3d is a perspective side view of the supporting pillar 1 in fig. 3c shown. In fig. 3e is a perspective side view of the body segment 50 in fig. 3b shown. In fig. 3f is a perspective side view of a further body segment 50 used in fig. 3a.

[0085] The truss assemblies comprising a hollow inner 60 between the outer surface and the inner surface of the elongated body 5. The truss assemblies further comprising beams 62 between the outer surface and the inner surface of the elongated body 5. In the disclosed embodiment, three beams 62 are shown. However, it shall be understood that other number of beams 62 may be applied. The beams 62 have the function of improving the structural stability to the body segments 50.

[0086] The truss assemblies further comprising alignment portions 64, see fig. 3b. The alignment portions 64 are configured to abut with and be connected to corresponding truss assembly so that they jointly form the circumference of the elongated body 5, as seen in fig. 3c.

[0087] In the disclosed embodiment of the invention, each of the body segments 50 are fully enclosed by the protective layer 20. However, it shall be understood that alternatively, only the outer surface of each body segment 50 is provided with the protective layer 20. In fig. 3b, 3c, the protective layer 20 is indicated by a dashed line.

[0088] In the disclosed embodiment of the invention, the outer surface is convex, and the inner surface is flat. The outer surface of the body segments 50 forms the circumference of the elongated body 5 when the body segments 50 have been joined together. In the disclosed embodiment, the outer surface of the elongated body has a circular circumference.

[0089] In a preferable embodiment of the invention, the three body segments 50 have a tapered outer surface along their longitudinal extension. Thereby, when joined together, they jointly form a conical outer surface in the direction of their extension.

[0090] With reference to fig. 4a, a side view of a configuration of body segments 50 for compiling the supporting pillar 1 according to an embodiment of the invention is shown. The body segments 50 comprising a first type segment 50a, a second type segment 50b and a third type segment 50c, see fig. 4b. The three body segments 50 is such that the length of the third type segment 50c is one third of the first type segment 50a and the length of the second type segment 50b is two third of the first type segment 50a.

[0091] The three body segments 50 are configured compiled such that they jointly form the circumference of the supporting pillar 1 and stacked on top of each other such that the jointly form the height of the supporting pillar 1 . Furthermore, the three body segments 50 are configured to be compiled such that an end side connection between two body segments 50 is located at long sides of the other two body segments 50 forming the circumference.

[0092] This is illustrated in fig. 4a where the column of segments to the left starting from the bottom comprises a third type segment 50c followed by two first type segments 50a. The middle column of the segments starting from the bottom comprises a second type segment 50b followed by a first type segment 50a and thereafter a second type segment 50b. The column of segments to the right starting from the bottom comprises two first type segments 50a followed by a third type segment 50c. Accordingly, end side connections are always located at long sides of the other two body segments 50 in adjacent columns. Thereby, the overall strength of the supporting pillar 1 is improved.

[0093] With reference to fig. 5a, a flow chart of a method for establishing a supporting pillar 1 according to an embodiment of the invention is disclosed.

[0094] The method comprises in a step 110, preparing at least one body segment 50 of the elongated body 5 by mean of in a step 120, forming a center structure 10 mainly comprising a biological derived fibrous composition, and in a step 130, prestressed attaching a protective layer 20 comprising at least one rigid sheet 22 to at least an outer surface of the center structure 10 such that fibers of the fibrous composition are held in place.

[0095] The at least one body segment 50 may be fully or partly attached with the protective layer 20. The step of prestressed attaching the protective layer 20 preferably comprises forming one of glue joint and a bolted joint, or a combination thereof. The step 130 may also comprise attaching two or more rigid sheets 22 to the center structure 10 and joining the sheets 22, such as by friction stir welding. The step 130 may also involve wrapping the rigid sheet 22 in a spiral on to the center structure 10.

[0096] With reference to fig. 5b, a flow chart of a method for establishing a supporting pillar 1 according to a further embodiment of the invention is disclosed. The method comprises, in a step 110 preparing three elongated body segments 50 having two end sides and two long sides, by in a step 120, forming a center structure 10 for the body segments 50 mainly comprising a biological derived fibrous composition, and in a step 130, prestressed attaching a protective layer 20 comprising at least one rigid sheet 22 to at least an outer surface of the center structure 10 such that fibers of the fibrous composition are held in place. The method further comprises, in a step 140, connecting the three elongated body segments 50 together at their long sides such that they jointly form the circumference of the elongated body 5.

[0097] With reference to fig. 5c, a flow chart of a method for establishing a supporting pillar 1 according to a further embodiment of the invention is disclosed. The method differs from the embodiment in fig. 5b in that step 110 of preparing the three elongated body segments 50 further comprises preparing a first type segment 50a, a second type segment 50b and a third type segment 50c, wherein the length of the third type segment 50c is one third of the first type segment 50a and the length of the second type segment 50b is two third of the first type segment 50a. The method further differs from the embodiment in fig. 5b in that step 140 comprises connecting end sides and long sides of first, second and third type segment 50a, 50b, 50c such that an end side connection between two body segments 50 is located at long sides of the adjacent body segments 50 forming the circumference.

[0098] In an embodiment of the invention, the supporting pillar 1 of the invention is used for holding structural members of a wind power plant at an elevated position, for example a wind turbine with wind blades. In an alternative embodiment of the invention, the supporting pillar 1 is used as a shaft for transferring rotational energy to a turbine of a wind power plant. In yet another embodiment of the invention, a first and second supporting pillar 1 is used in a counter rotating wind power plant.

[0099] It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims.

[0100] For example, it shall be understood that the embodiments in claim 11-17, and embodiments in method claim 23-25, may be applied independently of the features that the center structure being configured of the biological derived fibrous composition, and independent on the feature relating to the protective layer on the center structure.

Claims

Claims1. A supporting pillar (1) for a wind power plant, where the supporting pillar (1) comprises an elongated body (5) configured to hold a wind-power turbine at an elevated position and / or transferring rotational energy to a rotor of a wind-power turbine, wherein the elongated body (5) comprises:- a center structure (10) configured to provide structural stability to the supporting pillar (1), and- a protective layer (20) on the center structure (10) configured to protect the center structure (10) from interaction with the surrounding environment, characterized in that: the center structure (10) mainly comprises a biological derived fibrous composition, and wherein the protective layer (20) comprises at least one rigid sheet (22) that is arranged prestressed attached to at least an outer surface of the center structure (10).

2. The supporting pillar (1) according to claim 1 , wherein the rigid sheet (22) of the protective layer (20) mainly comprises one of an aluminum alloy, glass-fiber reinforced plastic, thermoplastic, stainless steel, or a combination thereof.

3. The supporting pillar (1) according to any of claim 1 and 2, wherein the protective layer (20) has a thickness in the interval of 1 - 50 mm, preferably 2 - 10 mm.

4. The supporting pillar (1) according to any of the previous claims, wherein the at least one rigid sheet (22) is attached to the center structure (10) by means of one of glue joint and a bolted joint, or a combination thereof.

5. The supporting pillar (1) according to any of the previous claims, wherein the biological derived fibrous composition mainly comprises one of a wooden material, bamboo, straw, cotton, reed, hemp, flax or a combination thereof.

6. The supporting pillar (1) according to claim 5, wherein the wooden material mainly comprising glued laminated timber, such as glued laminated timber mainly comprising spruce.

7. The supporting pillar (1) according to any of the previous claims, wherein the protective layer (20) comprises two or more rigid sheet (22)s that have been joint by friction stir welding.

8. The supporting pillar (1) according to any of the previous claims, wherein the protective layer (20) is prestressed attached to the center structure (10) in the interval of 5 - 100 MPa, preferably 10 - 30 MPa at an operational temperature of the supporting pillar (1).

9. The supporting pillar (1) according to any of the previous claims, wherein the elongated body (5) comprises an opening that extends along a longitudinal axis of the body (5) and defining an inner surface of the center structure (10), wherein the protective layer (20) is arranged to said inner surface of the center structure (10).

10. The supporting pillar (1) according to any of the previous claims, wherein the rigid sheet (22) of the protective layer (20) is wrapped in a spiral onto the center structure (10).

11. The supporting pillar (1) according to any of the previous claims, wherein the elongated body (5) comprises three elongated body segments (50), each having two end sides and two long sides, wherein the body segments (50) are attached together at their long sides such that they jointly form the circumference of the elongated body (5).

12. The supporting pillar (1) according to claim 11 , wherein the three elongated body segments (50) are arranged as respective truss assemblies, each comprising a hollow inner (60) between the outer surface and the inner surface, and one or more support beams (62) extending between the outer surface and the inner surface.

13. The supporting pillar (1) according to claim 11-12, wherein the truss assemblies are arranged with convex outer surfaces and alignment parts (64) configured to abut with and be connected to corresponding truss assembly so that they jointly form the circumference of the center structure (10).

14. The supporting pillar (1) according to claim 11-13, wherein the three elongated body segments (50) are fully enclosed in the protective layer (20).

15. The supporting pillar (1) according to claim 11-14, wherein the three body segments (50) have a tapered outer surface such that they jointly form a conical outer surface in the direction of the elongated extension of the supporting pillar (1).

16. The supporting pillar (1) according to claim 11-15, wherein the body segments (50) comprising attachment means (52) that attaches the body segments (50) together along their long sides, wherein the attachment means (52) comprises a tongue and groove joint.

17. The supporting pillar (1) according to any of claim 11-16, wherein the body segments (50) comprising further attachment means (54) that attaches the body segments (50) together along their short sides, wherein the further attachment means (54) comprises a tongue and groove joint.

18. The supporting pillar (1) according to any of claim 11-17, wherein the body segments (50) comprising a first type segment (50a), a second type segment (50b) and a third type segment (50c), wherein the length of the third type segment (50c) is one third of the first type segment (50a) and the length of the second type segment (50b) is two third of the first type segment (50a), wherein the elongated body (5) is compiled connecting end sides and long sides of the first, second and third type segments (50a, 50b, 50c) such that an end side connection between two body segments (50) is located at long sides of the other two body segments (50) forming the circumference.

19. A method for establishing a supporting pillar (1) for a wind power plant, which supporting pillar (1) comprises an elongated body (5) configured to hold a windpower turbine at an elevated position or transferring rotational energy to a rotor of a wind-power turbine, wherein the method comprises the steps of:- preparing at least one body segment (50) of the elongated body (5) by i) forming a center structure (10) mainly comprising a biological derived fibrous composition, and ii) prestressed attaching a protective layer (20) comprising at least one rigid sheet (22) to at least an outer surface of the center structure (10).

20. The method according to claim 19, wherein the step of prestressed attaching the protective layer (20) comprises forming one of glue joint and a bolted joint, or a combination thereof.

21. The method according to claim 19-20, wherein the step of prestressed attaching the protective layer (20) comprises:- attaching two or more rigid sheets (22) to the center structure (10), and- joining the two or more rigid sheets (22) together.

22. The method according to claim 19-21 , wherein the method comprises- positioning the at least one rigid sheet (22) of the protective layer (20) to the center structure (10) by wrapping the protective layer (20) in a spiral onto the center structure (10).

23. The method according to claim 19-22, wherein the method comprises- preparing three elongated body segments (50) having two end sides and two long sides, by: i) forming a center structure (10) for the body segments (50) mainly comprising a biological derived fibrous composition, ii) prestressed attaching a protective layer (20) comprising at least one rigid sheet (22) to at least an outer surface of the center structure (10), and- connecting the three elongated body segments (50) together at their long sides such that they jointly form the circumference of the body (5).

24. The method according to claim 19-23, wherein the method comprises:- preparing three elongated body segments (50) in form of truss assemblies having convex outer surfaces and alignment parts, and- connecting the three body segments (50) at their alignment parts such that they jointly form the circumference of the center structure (10).

25. The method according to claim 19-24, wherein the method comprises:- preparing a first type segment (50a), a second type segment (50b) and a third type segment (50c), wherein the length of the third type segment (50c) is one third of the first type segment (50a) and the length of the second type segment (50b) is two third of the first type segment (50a), and- connecting end sides and long sides of the first, second and third type segments (50a, 50b, 50c) such that an end side connection between two body segments (50) is located at long sides of the other two body segments (50) forming the circumference.

26. Use of a supporting pillar (1) according to any of claim 1-18.

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