WO2010032075A1

WO2010032075A1 - Post-tensioned concrete and steel tower for wind generators

Info

Publication number: WO2010032075A1
Application number: PCT/IB2008/002439
Authority: WO
Inventors: Alejandro Cortina-Cordero; Jose Pablo Cortina-Ortega; Jose Pablo Cortina-Cordero
Original assignee: Alejandro Cortina-Cordero; Jose Pablo Cortina-Ortega; Jose Pablo Cortina-Cordero
Priority date: 2008-09-19
Filing date: 2008-09-19
Publication date: 2010-03-25

Abstract

A concrete tower for wind generators is described, said tower being characterized in that it comprises a foundation and a mixed concrete and steel structure composed of: (a) a concrete structure (20), which consists of concrete leg portions extending along the tower and comprising a plurality of circular segments (25) made of reinforced concrete, vertically stacked and joined together so as to be fastened to each other and to the foundation by means of pre-stressing elements, and, (b) a metal framework (30), which comprises framework portions which extend along the tower and comprise a plurality of structured metal beams (35), said framework portions being arranged between the concrete leg portions and joined thereto.

Description

POST-CONCRETE AND STEEL CONCRETE TOWER FOR WIND GENERATORS

BACKGROUND.

1. Field of the invention.

This description refers to pre-tensioned concrete towers. In particular, it refers to the construction of segmented towers of prestressed concrete to support wind generators. More particularly, the invention relates to a mixed structure of reinforced and pre-tensioned concrete in combination with a steel structure.

2. General background of the invention.

Different towers for wind generators have been proposed. For example, various towers have been constructed with reinforced metal structures consisting of a plurality of crossbars and metal posts. In addition, tubular steel structures have been built for the same purposes.

Said structures have various disadvantages, the main one of said inconveniences being the permissible height limitation and the cost of steel. Because wind generators offer resistance to wind currents, significant vertical and horizontal loads are generated that produce torsion of the structures. In some cases, said metal structures collapse due to the action of the wind and the weight of the generators.

Concrete towers (or concrete) are known for wind generators and other applications made of formwork or sliding formwork, and towers of pre-tensioned concrete are also known. Prestressed concrete is called a concrete which, prior to commissioning, reinforcements are introduced by means of cables or steel wires. The pre-tensioning effort can be transmitted to the concrete in two ways: by means of pre-tensioned reinforcements (usually wires), a method used mostly in prefabricated elements; or by post-tensioned reinforcements (generally strands, cable groups), a method used mostly in castings in situ. For example, the German utility model DE 29809541 U (& EP 0 960 986) describes a sectioned tower of prestressed concrete for wind generators. According to said publication, sections of ring concrete, tapered or frustoconic, are manufactured, which are subsequently mounted one on top of the other and joined by prestressing elements. According to this publication, they are able to mount towers of more than one hundred meters high and even more than two hundred meters.

For its part, the publication of the international patent application No. WO-2004007955 in the name of Aloys Wobben, of the ENERCON company, also describes a construction system for sectioned towers. Said publication describes the use of molds to manufacture each concrete section of the tower in a workshop. Before casting the concrete, tubular ducts that are immersed in the concrete are introduced into the mold through which the prestressing cables are subsequently introduced-covered, so that the formed ring sections have high quality and precision. The ENERCON company, to assemble the towers, forms the first - (and larger) 4 or 5 sections of the err halves tower, or in complete sections that are then divided to transport them to the destination. Then, these halves are assembled and the sections are mounted on each other, see THE WINDBLAT, THE ENERCON MAGAZINE, Hugue Building Blocks, copy 03/2001, September 22, 2001, pages 8 and 9.

Patent application WO-2003069099 (& US-7, 160,085 & EP 1 474 579) MECAL describes a tower for hybrid wind generators which comprises (a) a lower portion of pre-tensioned concrete, sectioned -in ring sections-, and also segmented -the ring sections are formed of several segments-; and (b) a tubular upper portion of steel. This tower has many drawbacks, among which the following are listed:

a) By virtue of the fact that the tower is tapered, to make the tower a mold is required for each segment. b) Because the segments have staggered side edges that must subsequently be cemented. The lateral junction of the concrete segments must be very precise. This union can be done without problems at floor level but more than ten meters it is a real problem to make such joints. Particularly more than sixty meters high and with a wind of more than 40 km per hour from the place selected for the construction and optimal operation of wind turbines, the task of precision assembly is very complicated.

c) Because the concrete segments are manufactured independently, it is even more difficult to match them.

d) The vibration of the turbine is intended to be absorbed by a metallic element that connects the concrete sections with the metal sections, the metal towers are generally weak. They often do not support the weight of the nacellus (or wind generator) and collapse. In addition, due to the vibration they can enter resonance and collapse. In this way, the tower of patent WO-2003069099 (& US-7, 160,085 & EP 1 474 579) incorporates all the disadvantages of metal towers in a concrete tower. This tower is particularly unsuitable for areas of high seismicity, such as the Mexican territory, the western United States and in general the countries of the Pacific Basin, where telluric movements are frequent.

On page 6 lines 22 to 29 of publication WO-2003069099, the applicant indicates that for the assembly of the tower a crane is used that climbs inside or outside the body of the tower. Such a construction process is impractical. The applicant loses sight of the fact that the concrete segments are more than ten meters long with a weight of several tons, so that

The crane necessarily requires a foothold on the ground, otherwise the tower would collapse when lifting the first pieces. Moreover, the fact that

The tower is tapered, it implies the use of a special crane that is capable of varying its diameter with the height. -TO-

The inventor also fails to indicate the characteristics of the scaffolding and safety facilities indispensable for the builders to be able to perform the precision bonding of the concrete segments that is required according to the description of WO-2003069099.

Therefore, the tower of the patent WO-2003069099 (& US-7, 160,085 '& EP 1 474 579), has many drawbacks that make it unworkable.

For its part, the Spanish company INNEO21 has filed patent applications for some concepts regarding the construction of prestressed, sectioned and segmented concrete towers. Thus, the patent application US-2006156681 A1 (& ES-1058539U) describes a sectioned and segmented concrete tower; Application US-2008040983A1 (& ES 1061396) describes a mold for manufacturing the concrete segments; and patent ES-1060629 describes a union between segments by means of horizontal prestressing.

Patent application WO-2006111597A1 (& EP-067434514 & ES 2246734A1) of CONCRETE & STEEL also describes a pre-tensioned, sectioned and segmented concrete tower for wind generators.

The ENERCON ₁ MECAL, INNEO21 and CONCRETE & STEEL towers mentioned above share the following drawbacks:

a) In accordance with this construction technique, the segments or sections that form the towers are manufactured in a suitable installation for this purpose, and subsequently said segments are transported to the site where the tower is erected. Subsequently each of the tower segments is mounted by means of a crane. Such transportation of the tower segments increases the manufacturing costs of the towers.

b) The towers of the state of the art mentioned above are generally you taper That is, they have a progressive narrowing, so that the base generally has a diameter greater than the upper end of the tower where the nacelle or electric generator is mounted. Such characteristic results in the need to build a particular mold to manufacture each frustoconic concrete segment. The need to produce a mold to manufacture each concrete segment results in an additional disadvantage of said construction systems. On the other hand, the adjustment of the cast pipes within said system also results in a problem. ENERCON WO2002004766 patent addresses this problem.

In addition, the segments with which the concrete towers are manufactured are very heavy, consequently, the towers must be manufactured with large amounts of concrete so that they are capable of supporting their own weight. Due to the weight of these concrete segments, their assembly requires large cranes, which results in high construction costs.

SUMMARY OF THE INVENTION

A first object of the invention is to provide a mixed tower of prestressed concrete and steel.

Another object of the invention is to provide a tower with better use of the characteristics of the materials, which give the tower adequate resistance to winds and earthquakes.

Another object of the invention is to provide a tower that uses only one type of mold for all the concrete segments used in the tower.

A further object of the invention is to provide an improved method for constructing and assembling a segmented prestressed concrete tower in the same place where the tower is erected. Still another object of the invention is to provide a method of building a tower that does not require the use of heavy construction equipment.

Still another object of the invention is to provide an improved system for manufacturing and assembling a pre-tensioned concrete tower.

The previous objectives of the invention are achieved by providing a pre-tensioned concrete tower for wind generators, characterized in that it comprises a foundation and a mixed, elongated structure comprising: (a) a concrete structure (20) consisting of leg portions of concrete (21, 22, 23) and consisting of a plurality of circular segments (25) made of reinforced concrete, vertically stacked and joined together, and linked to the foundation by means of prestressing elements; and (b) a metal reinforcement (30), comprising spaced portions of reinforcement (31, 32, 33), on the flat faces of the mixed polygonal cross-sectional structure, which extend along the length of the tower, the reinforcement metallic consists of a plurality of structured metal beams (35), arranged between said concrete leg portions;

BRIEF DESCRIPTION OF THE DRAWINGS

As an example, reference is now made to the accompanying drawings.

FIG. 1 illustrates the pre-tensioned concrete tower in accordance with the invention.

FIG. 2 illustrates a top plan view of the tower of the present invention.

FIG. 3 illustrates a side elevation view of the tower in accordance with the invention. FIG. 4 illustrates an embodiment of the concrete tower with extension.

DETAILED DESCRIPTION OF THE INVENTION

The design and construction of a support tower for a wind power generation system, its original construction development, designed to perform in a fast, fast, economical and reliable way, a mixed annular structure of reinforced and pre-tensioned concrete is described. in combination with structural steel. The tower has aesthetics and the slenderness necessary to support the loads to which it will be subjected, such as its own weight, the weight of the generator, the weight and movement of the blades, wind thrust and seismic forces.

The height of the structure above the ground level can be preferably variable between 80 and 150 meters, depending on the capacity and type of generator to be used. The geometry of the tower is sized and modulated to meet all the service limit states and final limit states of the various current building regulations.

In accordance with the present invention, a tower is described which comprises a body formed by a mixed structure of reinforced, elongated and prestressed concrete, preferably post-tensioned, in combination with structural steel. The section of the tower is variable and decreases depending on its height.

In an embodiment of the invention, a tower is also described which, in elevation, has two sections distinguishable by its geometry: a body having a variable cross section from its base to approximately two thirds of its height; and an extension that has a constant cylindrical section in its upper part that is approximately one third of the total height of the tower.

As illustrated in the embodiment of FIGS. 1 and 2, the body (12) of Ia tower (10) has an axisymmetric cross section whose perimeter can be assimilated to a polygon - illustrated as a triangle - with straight parts (16) and rounded corners (14), hereinafter referred to as the polygonal cross section. The polygonal cross-section of the body (12) of the tower (10) decreases as a function of the height of the tower, to form a tapered structure in elevation, that is, it becomes thinner as it gains height.

The metal armor (30) of the body (12) consists of an open soul metal structure. The metal reinforcement (30) comprises three spaced portions of reinforcement (31, 32, 33), which extend along the tower in the straight part of the polygonal cross section, between the vertices and form the flat faces of the tower. Each of the portions (31, 32, 33) consists of a plurality of structured beams (35), preferably made of steel.

The mixed structure of the tower (10) includes a concrete structure (20) comprising portions of concrete leg (21, 22, 23), spaced apart, which extend along the tower at the vertices of The polygonal cross-section between the reinforcement portions (31, 32, 33) of the metal reinforcement (30) and attached thereto. Each of the concrete leg portions (21, 22, 23) comprises a plurality of circular segments (25) made of reinforced concrete, stacked vertically and pre-tensioned.

In this way, in the corners (14) of the polygonal cross-section of the tower the concrete structure (20) is defined, while in the straight parts (16) of the polygonal cross-section the metal reinforcement (30) is defined. , which extend along the body (12) of the tower (10).

As will be apparent to a person skilled in the art, the metal reinforcement may include curved beams. In this way the "straight" parts of the polygonal sections would then be rounded. With this configuration it is possible to build a tower for wind generators of circular or elliptical, tapered or toroidal cross-section. The decrease of the polygonal cross section of the tower (10) is achieved by reducing the dimensions of the beams (35) that form the corresponding reinforcement portions (31, 32, 33) of the metal reinforcement (30) until the circular segments (25) converge to become a circular ring. According to FIGS. 1, 2 and 3, the tower also includes a ring (27) that has the function of flange for the union with the wind generator.

The circular segments (25) that form the concrete leg portions of the mixed structure, are prefabricated and mounted on the site. The continuity of the concrete segments (25) is achieved through prestressing elements, such as prestressing cables or strands that are anchored in the foundation of the tower and subsequently placed and tensioned (post-tensioned) inside the segments

Laterally, the circular segments (25) are joined to the metal reinforcement (30) by means of a joint that allows them to work structurally as a single section.

According to the present invention, it is provided that the circular segments (25) that make up the concrete structure (20) have the same dimensions and shape. In the embodiment illustrated in the figures, which have a triangular cross section, segments of 120 ° are used. Obviously if the tower will be manufactured with a square, rectangular, pentagonal, hexagonal or any other polygonal configuration, then segments with the necessary angle are used so that said segments converge in a circular ring in the upper portion of the tower, for example , (a) rectangular section, requires four leg portions made from 90 ° segments; (b) pentagonal section, requires five leg portions made from 72 ° segments; etc. In the case of a tower of circular or elliptical cross-section, depending on the number of leg portions to be used, the segments must have the necessary angle to converge on the upper circular ring. In the embodiment illustrated in FIG. 1, 17 short segments are illustrated.

However, it will be evident to a person skilled in the art that said short segments can be replaced by longer segments, so that the tower includes, for example, 7 long segments. As is evident to a technician in the field, the dimensions of each segment depend on the design of the tower.

Thus, unlike the towers of the prior art, a special mold is not required to manufacture each segment of the tower (25). According to the preferred embodiment of the present invention, only a single type of mold is used to manufacture all the circular segments (25). As will be apparent to a person skilled in the art, not only a physical mold is used, but a plurality of molds having the same characteristics, that is, the same type of mold.

The metal reinforcement is assembled by welding and / or screws or bolts, with or without reinforcement elements. So that each and every one of the segments (25) are attached to the metal reinforcement. The beams can be structured to form a particular arrangement, for example a honeycomb structure or an inclined beam structure as shown in FIGS. 1, 3 and 4, where the beams are inclined and join alternating circular segments (25). In addition, each circular segment (25) is connected to the adjacent upper and / or lower segment.

The preferred polygonal cross section is the triangular section, which exhibits a better performance with respect to the circular, elliptical, square and polygonal cross sections. In the case of towers with circular, elliptical, square and polygonal cross sections (of more than three sides) it is necessary to include reinforcement beams joining the segments (25) that are opposite. For example, in a tower with 1, 2, 3 and 4 leg portions, in addition to providing beams (metal armor) between adjacent concrete leg portions 1-2, 2-3, 3-4 and 4-1, it is it is necessary to join with beams the segments (25) of the leg portions 1 and 3, as well as 2 and 4. In towers with more portions of concrete legs, it is required to include more beams for the union of the leg portions. So that a leg portion is preferably joined with each and every one of the remaining portions.

During the construction of the tower the metal armor is first assembled at the site of the tower. The metal reinforcement then serves to support the prefabricated concrete segments, for the assembly of the tower it is sufficient to use a light crane, it should be mentioned that the weight of the circular segments 25 is approximately 1/6 of the weight of a full-frustoconic ring section of a tower of the prior art. So its handling is facilitated.

In another embodiment, the molds or formwork can be attached to the metal reinforcement so that the circular segments (25) are successively cast in their final position.

In another embodiment of the invention, a system of formwork or sliding formwork can be used to form integral portions of concrete leg.

Once the tower is built and in use, it functions as a tripie (in the case of the realization with three portions of concrete leg). The weight of the tower and the nacelle is distributed between the portions of concrete leg (21, 22, 23) that transmit the loads (weight and vertical loads due to wind) to the foundation, while the metal structure (30 ) holds the leg portions together.

Thus, the metal reinforcement provides resistance to vertical and horizontal loads, mainly the loads derived from the movement of the blades, the thrust of winds and the seismic forces. In this way, the metal reinforcement serves a double purpose: to form a support for the placement of the molds and the casting of the circular segments (25) and to provide structural support for the tower during its operation. The hollow core metal armor (30) allows the passage of air through it and therefore offers less resistance to wind currents and therefore becomes more resistant to wind force. Optionally, closing covers can be included to close the open spaces of the reinforcement portions (31, 32, 33) of the metal reinforcement. These covers can consist of sheets of steel, aluminum, plastic, Gypsum plaster, concrete or brick and mortar walls.

On the other hand, the concrete legs of the concrete structure provide the tower with the necessary resistance to support the weight of the generator, the same weight of the tower and the horizontal loads due to wind and / or seismic action.

According to an embodiment of the invention, illustrated in FIG. 4, the tower includes an extension (19). Preferably, the extension (19) of the tower consists of a cylindrical portion of prestressed concrete. Optionally, the cylindrical portion may consist of a metal tube. Said extension can be manufactured in one piece, or in segments. Generally a steel cylinder is manufactured from steel sheets, which are in turn rolled and welded.

In addition, according to the invention, the upper end of the cylindrical extension section includes a ring (28) that serves as a flange for the placement of the wind generator.

Said extension (19) consists of a cylindrical member that has a constant diameter up to the maximum height of the tower. The materials used in the design are reinforced and pre-tensioned concrete and / or structural steel. According to a preferred embodiment of the invention, illustrated in FIG. 4, the extension (19) consists of a plurality of cylindrical modules (29) of post-tensioned concrete joined together by means of pre-stress elements, such as cables or strands that are placed (hardened) and pre-tensioned (post-tensioned) inside the walls of the modules (not illustrated). In accordance with the embodiment of the invention described above, it is provided that the cylindrical modules (29) that make up the extension (19) have the same dimensions. In this way, only one type of mold is required, cylindrical. As will be apparent to one skilled in the art, it is not used only one ^{^} physical mold, but a plurality of molds having the same characteristics. In accordance with the present invention, while the tower is being assembled, the cylindrical segments may be manufactured and, in turn, hoisted by means of a crane, placed and attached to the tower by means of pre-stress elements, such as cables or strands that are placed (hardened) and pre-tensioned (post-tensioned) inside the walls of the segments in a manner well known to a person skilled in the art.

In another embodiment of the invention, the extension can be a tube or duct of square or polygonal section.

The molds are conditioned by incorporating the tubes for post-tensioning as well as the necessary accessories, and then a vertical casting is carried out and can be demoulded the next day, so that the molds are used every third day. The number of molds is unlimited and the number of units to be used depends on the magnitude of the work and its construction program.

According to the present invention, a considerably lower number of moides of molds is used compared to those used in the construction procedures of the chimney-type towers of the prior art.

The molding and casting of the concrete circular segments (25) and the assembly and assembly of the tower (10) is carried out at the site according to the following process:

to. Manufacture of the mold for the manufacture of the segments: Given the precision required for the prefabricated parts, the mold for manufacturing The circular concrete sector is carried out in a workshop following the established design and tolerances, the mold is preferably manufactured based on profiles, plates and sheets of steel and responds to a pre-established modular design according to the height of the tower, in general, the Tower height is designed in circular segments whose height varies between 3 and 15 m.

b. Manufacture of metal parts: All metal structure is enabled in the workshop and transported in parts ready to be assembled on site. That is, the segments of beams are cut in the necessary measures, they are drilled for the introduction of screws or bolts, as well as other accessories, such as electrical accessories, reinforcement elements are incorporated, etc.

C. Construction of the substructure of the tower: The substructure or foundation of the tower is built on the site. This element is made of reinforced concrete and is sized according to the mechanical characteristics of the soil. In general, this element functions as a "pedestal" of the tower and transmits to the ground the reactions of the same one that occur before seismic and wind solicitations. In this element all the necessary inserts and steps are disposed to subsequently include the pre-strain cables to achieve the continuity of the structure.

d. Installation of the metal structure: The metal structure is assembled with the appropriate equipment by moving it in the foundation and joining its parts to complete the pyramid formed by its parts.

and. Construction of the tower segments: Once the foundation is constructed, the molding, assembly and casting of the circular segments (25) that make up the tower is carried out. The inserts and connection elements necessary to achieve their union and continuity are included within the circular segments (25). F. Assembly and post-tensioning of the concrete structure of the tower: Once the setting and unmolding of the concrete segments is verified, they are assembled with the help of cranes of adequate capacity for this work. The assembly is carried out by lifting and superimposing the segments and simultaneously supporting them in the metal structure and joining them by welding the post-tensioning of the concrete segments (20) is carried out. A part of the post-tensioning is continuous from the foundation and across the entire height of the tower. The joints between segments are based on welded metal connections. The metal reinforcement (30) is mounted on the site by successively linking a plurality of beams with the circular concrete segments.

g. Assembly of the extension (19) of the tower: Since this section of the upper part of the tower is of constant cross section, it can be prefabricated on site if the decision is to make it in post-tensioned concrete and in plan, to later be transported and assembled on site, in case it was steel.

h. Injected and protection of post-tensioning anchors: Finally and after the total post-tensioning of the tower, the prestressing ducts are injected using an epoxy cement-based grout with a volume stabilizer. This slurry is also continuous throughout the length of the tower and is part of the system of union between segments.

The towers for wind generators of the present invention, are built more quickly and with simpler means compared to the towers of the prior art. The above advantages result in a tower with quality characteristics similar to the towers of

The prior technique, but built with lower production costs. A feature of the invention is that the quantity of the materials is used more efficiently. Thanks to the metal parts that are mounted in the first instance with light equipment, it is possible to achieve the geometry and the resistance necessary to mount the concrete segments

Having thus described the invention, it will be obvious that it can be varied in many ways. Such variations should not be considered as departing from the spirit and scope of the invention, and all modifications that are evident to a person skilled in the art, are considered to be included within the scope of the following claims.

Claims

1.- A tower for wind generators, characterized in that it comprises: (a) a concrete structure (20) consisting of concrete leg portions (21, 22, 23), formed from a plurality of circular segments (25) manufactured in reinforced concrete, vertically stacked and joined together, and linked to the foundation by means of prestressing elements; Y

(b) a metal reinforcement (30), comprising portions of reinforcement (31, 32, 33) disposed between said concrete leg portions (21, 22, 23) of the concrete structure (20) and attached thereto, which extend along the tower, formed of a plurality of structured metal beams (35).

2. The tower for wind generators according to claim 1, characterized in that the circular segments (25) of the concrete leg portions (21, 22, 23) have the same shape and dimensions.

3.- The tower for wind generators in accordance with claim 1, characterized in that it has a cross section that is progressively reduced in the direction of the upper end of the tower until the circular segments (25) converge to join with a ring circular (27).

4.- The tower for wind generators in accordance with claim 1, characterized in that the beams of the metal reinforcement are made of steel.

5. The tower for wind generators according to claim 1, characterized in that the tower has a polygonal cross section or has a circular or elliptical cross section.

6. The tower for wind generators according to claim 5, characterized in that the tower has a triangular cross section, square, rectangular, pentagonal or hexagonal.

7. The tower for wind generators according to claim 1, characterized in that it also comprises an extension, on the body of the tower, which consists of a cylindrical portion.

8. The tower for wind generators according to claim 7, characterized in that the cylindrical portion is selected from: (a) a plurality of cylindrical modules (29) of concrete joined together by means of prestressing elements, or (b ) a steel cylinder.

9. A wind power generation installation comprising a wind generator mounted on a tower for wind generators as defined in any of claims 1 to 8.

10. A method for manufacturing a tower for wind generators of claims 1 to 8, or the wind power generation installation of claim 9, comprising: a) providing a metal mold for manufacturing a plurality of circular segments (25 ); b) molding, assembling and casting a plurality of circular segments (25) of concrete, including the inserts and connection elements necessary to achieve the union and continuity of the adjacent upper and / or lower segments, supported in the metal reinforcement; c) build a substructure of the tower on the site, including pipelines for the introduction of prestressing elements; d) erect a metal reinforcement (30) on the substructure; e) assembling a plurality of circular segments (25) to form concrete leg portions (21, 22, 23), joined to the reinforcement portions (31, 32, 33) of the metal reinforcement (30); and f) post-tension the concrete leg portions (21, 22, 23) of the concrete structure (20).

11. The method for manufacturing a tower for wind generators according to claim 9, characterized in that it further comprises: h) mounting a tower extension (19) selected from: (a) a plurality of cylindrical modules (29) of concrete prestressed joined together by means of prestressing elements, or (b) a steel cylinder.