Stabilization system of a tower of a wind turbine, tower of a wind turbine and method of post-tensioning a tower of a wind turbine

Abstract

The present invention relates to a stabilization system of a tower of a wind turbine that stabilizes the tower under extreme loads to avoid the collapse of the tower. The invention also relates to a tower of a wind turbine comprising the stabilization system, and to a method of post-tensioning a tower of a wind turbine.

Description

[0001] STABILIZATION SYSTEM OF A TOWER OF A WIND TURBINE, TOWER OF A WIND TURBINE AND METHOD OF POST-TENSIONING A TOWER OF A WIND TURBINE

[0002] DESCRIPTION

[0003] OBJECT OF THE INVENTION

[0004] The present invention relates to a stabilization system of a tower of a wind turbine that stabilizes the tower under extreme loads to avoid the collapse of the tower.

[0005] The invention also relates to a tower of a wind turbine comprising the stabilization system of a post-tensioning element.

[0006] Also, the invention relates to a method of post-tensioning a tower of a wind turbine.

[0007] BACKGROUND OF THE INVENTION

[0008] Concrete towers of wind turbines, and concrete parts of hybrid towers, preferably made of steel and concrete, are commonly provided with a posttension system (e.g., cables, tendons, wires, strands... ) in order to ensure that the concrete is under compression stresses during the most of the wind turbine lifetime. That is, in order to avoid undesirable tension stresses in the structure that would lead to excessive cracks in concrete and fatigue in reinforcements.

[0009] Commonly, the post-tensioning elements (e.g., tendons) are uniformly distributed along the tower perimeter, so that the resultant post-tension force falls approximately in the central axis of the tower, avoiding in this way eccentric forces due to the post-tension system.

[0010] Wind industry standards and guidelines usually require a minimum amount of post-tension so that no decompression occurs in concrete under Quasipermanent load level. This load level (also known as D3 or S3 load level, depending on the guideline) is the one that is only exceeded during 1 % of the wind turbine lifetime. That is, by applying the minimum post-tension force required by guidelines, it is ensured that the structure will be subjected only to compressive stresses during the 99% of the wind turbine lifetime.

[0011] The post-tensioning elements (e.g., tendons) are usually located in the interior space of the tower, spanning from the foundation to an adapter disposed below the steel sections in case of a hybrid tower or below the nacelle in case of a full-concrete tower. Both ends of the post-tensioning elements are fixed in the foundation and adapter respectively. The post-tensioning elements never contact the tower due to their stiffness.

[0012] However, due to the fact that the wind does not actually blow with the same intensity in every direction, the load level related to a probability of exceedance of 1 % is not the same in every direction, resulting in asymmetrical loads on the full concrete tower or a concrete part of a hybrid tower. This can lead to collapse of the tower in case of extreme winds.

[0013] With the current wind turbine towers, the tower suffers a bending moment due to lateral loads. This bending moment is counterbalanced in the state of the art concrete towers with a concrete deviator located in contact with the posttensioning element that requires more manufacturing and installation efforts. The stabilization system of a tower of a wind turbine of the present invention solves all the above-mentioned drawbacks.

[0014] DESCRIPTION OF THE INVENTION

[0015] The present invention relates to a stabilization system of a tower of a wind turbine, wherein the tower comprises:

[0016] - a central vertical axis;

[0017] - an inner wall which defines an internal space inside the tower;

[0018] - a lower end which comprises a lower surface and partially the inner wall;

[0019] - an upper end which comprises an upper surface and partially the inner wall;

[0020] - at least one post-tensioning element located, at least partially, in the internal space inside the tower; the at least one post-tensioning element comprising a length measured from the lower end to the upper end;

[0021] - a tower height measured along the central vertical axis of the tower, from the lower surface to the upper surface when the tower is in an upright position; wherein the stabilization system comprises the at least one post-tensioning element which is configured to be disposed in at least:

[0022] - a first position wherein the at least one post-tensioning element is disposed at a first distance from the inner wall of the tower or from an attachment fixed to the inner wall of the tower or in contact with the inner wall of the tower or the attachment fixed to the inner wall of the tower, the first position corresponding to a first length of the at least one post-tensioning element measured from the lower end; and

[0023] - a second position wherein the at least one post-tensioning element is disposed in contact, at least partially, along the tower height, with the inner wall of the tower or with the attachment fixed to the inner wall of the tower such that a force against the inner wall of the tower is exerted, the second position corresponding to the first length of the at least one post-tensioning element measured from the lower end.

[0024] The stabilization system so constituted allows to generate, as well as the moment generated by the at least one post-tensioning element due to its displacement and eccentricity, an additional stabilizing moment generated by the contact of the at least one post-tensioning element with the inner wall of the tower in its second position that tends to return the tower to its undeformed position. Therefore, in case of extreme winds, the collapse of the tower is avoided.

[0025] Even if the at least one post-tensioning element is disposed in contact with the inner wall of the tower in the first position, the at least one post-tensioning element is not exerting a force against the inner wall of the tower.

[0026] In the first position, the at least one post-tensioning element does not contact in any point with the inner wall of the tower or with the attachment fixed to the inner wall of the tower, whereas in the second position, the at least one post-tensioning element is abutted in the inner wall of the tower or in the attachment fixed to the inner wall of the tower due to the displacement of the tower under extreme loads.

[0027] Due to the contact of the at least one post-tensioning element with the inner wall of the tower or with the attachment fixed to the inner wall of the tower, at least partially, the deformation and elongation of the post-tensioning element in the second position is increased and thus, a force is generated in the contact point or points, and in consequence, an associated moment. This associated moment counteracts at least partially the moment generated by the at least one post-tensioning element due to its displacement and eccentricity, making possible to achieve a greater deformation of the tower, and in consequence making possible to manufacture a more flexible tower capable of supporting greater displacements due to, e.g., wind forces.

[0028] In case the tower comprises a tower section comprising at least one concrete segment which in turn comprises at least one through hole configured to allocate the at least one post-tensioning element, the at least one through hole cannot be considered as the inner wall of the tower or the attachment in the sense of the first and second positions of the at least one post-tensioning element since it does not extend from the inner wall towards the central vertical axis of the tower.

[0029] Optionally, the first distance between the at least one post-tensioning element and the inner wall of the tower in the first position is between 0,01 m and 0,7m, preferably between 0,04m and 0,45m, and more preferably between 0,07m and 0,2m, in a radial direction of the tower.

[0030] Optionally, the tower comprises at least one concrete section which in turn comprises at least two concrete segments.

[0031] Optionally, the at least one concrete section comprises at least one protrusion extending from the inner wall towards the central vertical axis of the tower.

[0032] Optionally, the at least one protrusion of the at least one concrete section is disposed at the same height for each one of the at least two concrete segments.

[0033] Optionally, the at least one post-tensioning element contacts the at least one protrusion in the second position.

[0034] Optionally, the at least one protrusion extends circumferentially, at least partially, along the inner wall of the tower.

[0035] Optionally, the at least one protrusion is located in a top part of the at least two concrete segments of the at least one concrete section.

[0036] Optionally, the at least one protrusion is located adjacent to a horizontal joint between sections or between an upper section of the tower and a component of the wind turbine.

[0037] Optionally, the at least one protrusion is located in a part of the at least two concrete segments or the at least one concrete section different from the top part.

[0038] Optionally, the at least a protrusion comprises a gap, preferably a gap formed in a vertical joint between adjacent concrete segments when the concrete section comprises at least two concrete segments.

[0039] In this way, the at least one protrusion is the point of contact of the posttensioning element with the inner wall of the tower.

[0040] Optionally, the tower comprises at least two concrete sections, a lower section and an upper section, wherein at least one of the lower concrete section and the upper concrete section comprises the at least one protrusion, wherein the at least one post-tensioning element contacts the at least one protrusion of the upper concrete section, or the at least one protrusion of the lower concrete section or both of them. Optionally, the tower may comprise a plurality of concrete sections.

[0041] Optionally, the tower is a concrete tower or a hybrid tower comprising at least one steel section and at least one concrete section, wherein the concrete tower or the at least one concrete section of the hybrid tower comprises the stabilization system described above.

[0042] Optionally, the displacement of the at least one post-tensioning element from the first position to the second position or vice versa in a horizontal direction from the vertical axis to the inner wall is between 0,01 m and 0,7m, preferably between 0,04m and 0,45m, more preferably between 0,07m and 0,2m, in a radial direction of the tower.

[0043] Optionally, the stabilization system comprises a protective element configured to avoid the at least one post-tensioning element damage.

[0044] Optionally, the protective element is attached to the at least one posttensioning element.

[0045] Optionally, the protective element is attached to the inner wall of the tower. Optionally, the protective element is attached to the at least one protrusion. Optionally, the protective element comprises a chamfer disposed in the at least one protrusion. Preferably, the protective element is a plastic protective element.

[0046] Optionally, the system further comprises a resting plate configured to be disposed covering the gap of the protrusion. So configured, if the at least one post-tensioning element falls in the gap of the protrusion between the at least two concrete segments along the tower height, damages in the at least one posttensioning element are avoided.

[0047] The invention also relates to a tower of a wind turbine comprising:

[0048] - a central vertical axis;

[0049] - an inner wall which defines an internal space inside the tower;

[0050] - a lower end which comprises a lower surface and partially the inner wall;

[0051] - an upper end which comprises an upper surface and partially the inner wall;

[0052] - at least one post-tensioning element located in the internal space inside the tower;

[0053] - a tower height measured along the central vertical axis of the tower, from the lower surface to the upper surface when the tower is in an upright position; and

[0054] - at least one stabilization system as described above.

[0055] The invention also relates to a wind turbine comprising the tower described above.

[0056] Optionally, the wind turbine comprises at least two wind turbine excitation frequencies, preferably the 1 P and the 3P excitation frequencies, wherein the wind turbine is designed to be out of the at least two wind turbine excitation frequencies, more preferably in an interval between the 1 P and the 3P excitation frequencies. This interval between the 1 P and the 3P excitation frequencies is known as soft-stiff side of the excitation frequencies. Optionally, the wind turbine is designed taking into account the relative natural frequencies of the rotor and the blades of the wind turbine.

[0057] So, the tower of the wind turbine so constituted is more flexible as it is taller and has smaller diameter which is between 1 P and the 3P excitation frequencies needing this retention system to return them to their natural shape and this tower generates more Annual Energy Production (AEP), as well as lower amount of concrete which redounds in lower costs and an easier transportation.

[0058] Optionally, the tower further comprises at least a first concrete section which in turn comprises at least one concrete segment and a second concrete section which in turn comprises at least one concrete segment, wherein the at least one post-tensioning element is configured to be disposed in at least:

[0059] - the first position wherein the at least one post-tensioning element is disposed at a first distance from the inner wall of the tower comprising at least the first concrete section and the second concrete section, from the lower end to the upper end;

[0060] - the second position wherein the at least one post-tensioning element is disposed in contact, at least partially along the tower height with the inner wall of first concrete section and / or the second concrete section of the tower.

[0061] The invention also relates to a method of post-tensioning a tower of a wind turbine as described above, wherein method comprises:

[0062] - a first step wherein the at least one post-tensioning element is disposed at a first distance from the inner wall of the tower or from an attachment fixed to the inner wall of the tower, from the lower end to the upper end, such that the first distance is calculated in such a way that the at least one post-tensioning element is disposed in contact, at least partially along the tower height with the inner wall of the tower or the attachment fixed to the inner wall of the tower, in a second position.

[0063] Thus, in the second position, when the at least one post-tensioning element contacts the inner wall of the tower or the attachment fixed to the inner wall of the tower it elongates and exerts a force on the tower to return the tower to its natural state. This can be expressed in terms of Hooke’s Law:

[0064] F=AEb / L, being:

[0065] F: force exerted by the at least one post-tensioning element on the inner wall of the tower;

[0066] A: section of the at least one post-tensioning element; 5: elongation of the at least one post-tensioning element;

[0067] L: length of the at least one post-tensioning element in the first position.

[0068] BRIEF DESCRIPTION OF THE DRAWINGS

[0069] To complement the description being made and for the sake of a better understanding of the characteristics of the invention according to a preferred practical embodiment thereof, attached as an integral part of said description are a set of drawings wherein, for the purpose of illustration and not limiting the scope of the invention, the following is shown:

[0070] Figure 1 shows an elevation view of a tower of a wind turbine comprising the stabilization system of the present invention.

[0071] Figure 2 shows a top view of Figure 1 .

[0072] Figure 3 shows a section AA of Figure 2 with the stabilization system disposed in the first position, including a detail A.

[0073] Figure 4 shows a vertical section of the tower of Figure 1 with the stabilization system disposed in the second position, including a detail B and a detail C.

[0074] PREFERRED EMBODIMENT OF THE INVENTION

[0075] The invention is described in detail as follows. It relates to a stabilization system of a tower of a wind turbine, wherein the tower (100), as can be seen in Figure 1 , comprises:

[0076] - a central vertical axis (70);

[0077] - an inner wall (71 ) which defines an internal space inside the tower (100);

[0078] - a lower end (72) which comprises a lower surface (73) and partially the inner wall (71 );

[0079] - an upper end (74) which comprises an upper surface (75) and partially the inner wall (71 );

[0080] - at least one post-tensioning element (30) located, at least partially, in the internal space inside the tower (100), the at least one post-tensioning element (30) comprising a length measured from the lower end (72) to the upper end (74);

[0081] - a tower height (TH) measured along the central vertical axis (70) of the tower (100), from the lower surface (73) to the upper surface (75) when the tower is in an upright position; and wherein the stabilization system comprises the at least one post-tensioning element (30) which is configured to be disposed in at least:

[0082] - a first position (P1 ), shown in Figure 3, wherein the at least one posttensioning element (30) is disposed at a first distance (d1 ) from the inner wall (71 ) of the tower or from an attachment (80) fixed to the inner wall (71 ) of the tower, and corresponding to a first length (11 ) of the at least one post-tensioning element (30) measured from the lower end (72);

[0083] - a second position (P2), shown in Figure 4, wherein the at least one posttensioning element (30) is disposed in contact, at least partially, along the tower height (TH), with the inner wall (71 ) of the tower (100), as shown in detail B or with the attachment (80) fixed to the inner wall (71 ) of the tower, as shown in detail C, and also corresponding to the first length (11 ) of the at least one posttensioning element (30) measured from the lower end (72).

[0084] In the preferred embodiment shown in figures 3 and 4, the tower (100) comprises several concrete sections (50) which in turn comprises at least two concrete segments (10), wherein each one of the concrete sections comprises at least one protrusion (9) extending from the inner wall (71 ) towards the central vertical axis (70) of the tower (100), as can be seen in detail B. The tower further comprises an upper concrete section (50’) comprising at least two concrete segments (10) which in turn comprises at least one through hole (31 ) configured to allocate the at least one post-tensioning element (30), wherein the at least one through hole (31 ) cannot be considered as the at least one protrusion (9) since it does not extend from the inner wall (71 ) towards the central vertical axis (70) of the tower (100).

[0085] Preferably, the at least one protrusion (9) of the at least one concrete section (50) is disposed at the same height for each one of the at least two concrete segments (10).

[0086] In this preferred embodiment, the at least one protrusion (9) is the part of the inner wall (71 ) of the tower (100) that is contacted by the at least one posttensioning element (30) in the second position (P2), as can be seen in figure 4, detail B.

[0087] In the embodiment shown in figures 3 and 4, the at least one protrusion (9) is located in a top part of the at least two concrete segments (10) of the at least one concrete section (50), preferably located adjacent to a horizontal joint (90) between sections (50).

[0088] Optionally, the at least a protrusion (9) comprises a gap (11 ) formed in a vertical joint between adjacent concrete segments (10).

[0089] In this embodiment, the tower (100) is a full concrete tower comprising the stabilization system described above.

[0090] In the embodiment described above, the displacement of the at least one post-tensioning element (30) from the first position (P1 ) to the second position (P2) or vice versa in a horizontal direction from the vertical axis (70) to the inner wall (71 ) is between 0,01 m and 0,7m, preferably between 0,04m and 0,45m, more preferably between 0,07m and 0,2m, in a radial direction of the tower.

[0091] The stabilization system so constituted allows to generate, as well as the moment (M) generated by the at least one post-tensioning element (30) due to its displacement and eccentricity, an additional stabilizing moment (AM) generated by the contact of the at least one post-tensioning element (30) with the inner wall (71 ) of the tower (100) in its second position (P2) that tends to return the tower (100) to its undeformed position, as can be seen in Figure 4.

[0092] In the embodiment shown in Figure 4, the at least one post-tensioning element (30) is in contact with all the protrusions (9) along the inner wall (71 ) of the tower (100), In other embodiments, the at least one post-tensioning element (30) is in contact with some of the protrusions or in some points of the inner wall (71 ) of the tower (100) or only with one protrusion (1 ) or one point of the inner wall (71 ) of the tower.

[0093] Preferably, the stabilization system comprises a protective element (12) configured to avoid the at least one post-tensioning element damage. The protective element (12) is attached to the at least one post-tensioning element, to the inner wall of the tower or both of them. In case that the inner wall (71 ) of the tower comprises at least one protrusion (9) extending from the inner wall (71 ) towards the central vertical axis (70) of the tower (100), the protective element can be attached to the at least one protrusion (9).

[0094] Preferably, the protective element (12) comprises a chamfer (13) disposed in the at least one protrusion (9).

[0095] The invention also relates to a tower (100) of a wind turbine comprising:

[0096] - a central vertical axis (70);

[0097] - an inner wall (71 ) which defines an internal space inside the tower (100);

[0098] - a lower end (72) which comprises a lower surface (73) and partially the inner wall (71 );

[0099] - an upper end (74) which comprises an upper surface (75) and partially the inner wall (71 );

[0100] - at least one post-tensioning element (30) located in the internal space inside the tower (100);

[0101] - a tower height (TH) measured along the central vertical axis (70) of the tower (100), from the lower surface (73) to the upper surface (75) when the tower is in an upright position; and

[0102] - at least one stabilization system as described above.

[0103] Preferably, the tower (100) further comprises at least a first concrete section (50) which in turn comprises at least one concrete segment (10) and a second concrete section (50’) which in turn comprises at least one concrete segment (10), wherein the at least one post-tensioning element (30) is configured to be disposed in at least:

[0104] - the first position (P1 ), shown in Figure 3, wherein the at least one posttensioning element (30) is disposed at a first distance (d1 ) from the inner wall (71 ) of the tower or from an attachment (80) fixed to the inner wall (71 ) of the tower, from the lower end (72) to the upper end (74);

[0105] - second position (P2), shown in Figure 4, wherein the at least one posttensioning element (30) is disposed in contact, at least partially, along the tower height (TH), with the inner wall (71 ) of the tower (100) or with the attachment (80) fixed to the inner wall (71 ) of the tower.

Claims

CLAIMS1 . Stabilization system of a tower of a wind turbine, wherein the tower (100) comprises:- a central vertical axis (70);- an inner wall (71 ) which defines an internal space inside the tower (100);- a lower end (72) which comprises a lower surface (73) and partially the inner wall (71 );- an upper end (74) which comprises an upper surface (75) and partially the inner wall (71 );- at least one post-tensioning element (30) located, at least partially, in the internal space inside the tower (100), the at least one post-tensioning element (30) comprising a length measured from the lower end (72) to the upper end (74);- a tower height (TH) measured along the central vertical axis (70) of the tower (100), from the lower surface (73) to the upper surface (75) when the tower is in an upright position; wherein the stabilization system comprises the at least one post-tensioning element (30) which is configured to be disposed in at least:- a first position (P1 ) wherein the at least one post-tensioning element (30) is disposed at a first distance (d1 ) from the inner wall (71 ) of the tower or from an attachment (80) fixed to the inner wall (71 ) of the tower (100) or in contact with the inner wall (71 ) of the tower (100) or the attachment (80) fixed to the inner wall(71 ) of the tower (100), the first position (P1 ) corresponding to a first length (11 ) of the at least one post-tensioning element (30) measured from the lower end(72); and- a second position (P2) wherein the at least one post-tensioning element (30) is disposed in contact, at least partially, along the tower height (TH), with the inner wall (71 ) of the tower (100) or with the attachment (80) fixed to the inner wall (71 ) of the tower such that a force against the inner wall (71 ) of the tower (100) is exerted, the second position (P2) also corresponding to the first length (11 ) of the at least one post-tensioning element (30) measured from the lower end (72).

2. The stabilization system of claim 1 , wherein the first distance (d1 ) between the at least one post-tensioning element (30) and the inner wall (71 ) of the tower in the first position is between 0,01 m and 0,7m, preferably between 0,04m and 0,45m, and more preferably between 0,07m and 0,2m, in a radial direction of the tower.

3. The stabilization system of any one of previous claims, wherein the tower (100) comprises at least one concrete section (50) which in turn comprises at least one concrete segment (10), and wherein the inner wall (71 ) of the at least one concrete section (50) comprises at least one protrusion (9) extending from the inner wall (71 ) towards the central vertical axis (70) of the tower (100).

4. The stabilization system of claim 3, wherein the at least one post-tensioning element (30) contacts the at least one protrusion (9) in the second position (P2).

5. The stabilization system of any one of claims 3 or 4, wherein the at least one protrusion (9) extends circumferentially, at least partially, along the inner wall (71 ) of the tower.

6. The stabilization system of any one of claims 3 to 5, wherein the at least one concrete section (50) comprises at least two concrete segments (10), and wherein the at least one protrusion (9) of the at least one concrete section (50) is disposed at the same height for each one of the at least two concrete segments (10).

7. The stabilization system of any one of claims 3 to 6, wherein the at least one concrete section (50) comprises at least two concrete segments (10), and wherein the at least one protrusion (9) is located in a top part of the at least two concrete segments (10) of the at least one concrete section (50).

8. The stabilization system of claim 7, wherein the at least one protrusion (9) islocated adjacent to a horizontal joint (90) between sections or between an upper section of the tower and a component of the wind turbine.

9. The stabilization system of any one of claims 3 to 6, wherein the at least one concrete section (50) comprises at least two concrete segments (10), and wherein the at least one protrusion (9) is located in a part of the at least two concrete segments (10) or the at least one concrete section (50) different from a top part.

10. The stabilization system of any one of claims 3 to 8, wherein the at least a protrusion (9) comprises a gap (11 ), preferably a gap formed in a vertical joint between adjacent concrete segments when the concrete section comprises at least two concrete segments (10).

11. The stabilization system of claim 10 further comprising a resting plate configured to be disposed covering the gap (11 ) of the protrusion (9).

12. The stabilization system of any one of previous claims, wherein the tower comprises at least two concrete sections (50), a lower section and an upper section, wherein at least one of the lower concrete section and the upper concrete section comprises the at least one protrusion (9), wherein the at least one posttensioning element (30) contacts the at least one protrusion (9) of the upper concrete section, or the at least one protrusion (9) of the lower concrete section or both of them.

13. The stabilization system of any one of previous claims, further comprising a protective element (12) configured to avoid the at least one post-tensioning element (30) damage and attached to the at least one post-tensioning element (30) or to the at least one protrusion (9) extending from the inner wall (71 ) of the tower (100).

14. Tower (100) of a wind turbine comprising:- a central vertical axis (70);- an inner wall (71 ) which defines an internal space inside the tower (100);- a lower end (72) which comprises a lower surface (73) and partially the inner wall (71 );- an upper end (74) which comprises an upper surface (75) and partially the inner wall (71 );- at least one post-tensioning element (30) located in the internal space inside the tower (100);- a tower height (TH) measured along the central vertical axis (70) of the tower (100), from the lower surface (73) to the upper surface (75) when the tower is in an upright position; and- at least one stabilization system of any one of the previous claims.

15. Wind turbine comprising the tower (100) of claim 14.

16. A method of post-tensioning a tower of a wind turbine of any of claims 13 or 14 with the system of any of claims 1 to 12, wherein the method comprises:- a first step wherein the at least one post-tensioning element (30) is disposed at a first distance (d1 ) from the inner wall (71 ) of the tower or from an attachment fixed to the inner wall of the tower, from the lower end (72) to the upper end (74), such that the first distance (d1 ) is calculated in such a way that the at least one post-tensioning element (30) is disposed in contact, at least partially along the tower height (TH) with the inner wall (71 ) of the tower or the attachment fixed to the inner wall (71 ) of the tower, in a second position (P2).

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