Patent Application
20240318635
This invention relates generally to wind turbines, and more particularly to a hybrid wind turbine tower having a transition piece for connecting tower sections having different cross-sectional profiles, and to a method for assembling a wind turbine having such a transition piece.
Wind turbines are used to produce electrical energy using a renewable resource and without combusting a fossil fuel. Generally, a wind turbine converts kinetic energy from the wind into electrical power. A horizontal-axis wind turbine includes a tower, a nacelle located at the apex of the tower, and a rotor having a plurality of blades and supported in the nacelle by means of a shaft. The shaft couples the rotor either directly or indirectly with a generator, which is housed inside the nacelle. Consequently, as wind forces the blades to rotate, electrical energy is produced by the generator. Wind turbines may be located either on a land mass (on-shore) or within a body of water (off-shore).
The tower of a wind turbine is typically assembled from multiple tower sections positioned one on top of the other to form the tower. In one arrangement, a tower may include a lower tower section, one or more middle tower sections, and an upper tower section. During assembly, the lower tower section may be secured to a foundation of some sort (e.g., an anchor cage for on-shore wind turbines or a pile or platform for off-shore wind turbines), the one or more middle tower sections may be lifted onto the top of the lower tower section, then the upper tower section may be lifted onto the top of the uppermost middle tower section. Finally, the nacelle may be lifted onto the top of the upper tower section. A lifting device, such as a crane, may be used to lift the tower sections and nacelle into place.
The different tower sections are often made off-site and then transported to the installation site for the wind turbine where the tower sections are assembled (stacked) to form the tower. Each of these tower sections is generally tubular with a circular cross section and mounting interfaces, such as flanges, at opposing ends of the section. The mounting interfaces are configured to be connected (typically with bolts) to an adjacent tower section to assemble the tower. During operation of the wind turbine, the bending loads in the tower are largest at the bottom of the tower and decrease along the height of the tower with the bending loads being the smallest towards the top of the tower. To accommodate this bending load distribution, the tower may be conically shaped with the lowest tower section having the largest diameter and the highest tower section having the smallest diameter.
As the size of the wind turbines increase, the size of the lower tower sections has to increase to accommodate increased bending loads. There becomes a point where a tubular tower section made off-site is too large in diameter to be transported to the installation site. For example, the network of roads for on-shore wind turbines have limitations including the free height under bridges and tunnels, the turning radii of curves and bends, the weight limitations of certain roads, etc. that make the transport of large wind turbine tower sections impractical. Accordingly, to overcome such limitations, some manufacturers have turned to segmented wind turbine tower sections, wherein a tower section is formed by a plurality of tower segments which are coupled edge-to-edge to form the tower section. This allows large tower sections to be transported to the wind turbine installation site as separate segments, such as 4, 6, 8 or 10 segments, and then assembled at the installation site to form the tower sections.
Current segmented wind turbine towers typically have segmented tower sections along the full height of the tower, from the lowermost tower section to the uppermost tower section. While segmented wind turbine towers improve the transportability of the tower to the installation site, such segmented towers have a number of drawbacks as well. For example, the assembly of segmented tower sections is labour and time intensive compared to non-segmented tubular tower sections manufactured off-site. In this regard, the large number of bolted connections between adjacent tower segments (e.g., along vertical flanges or splice plates) and between adjacent tower sections (e.g., along horizontal flanges or splice plates) are generally performed manually with personnel both inside and outside the tower during assembly. Thus, a considerable amount of manual labour, and time, is required to construct the segmented wind turbine tower.
Accordingly, manufacturers continually seek improvements to the assembly of segmented wind turbine towers at a wind turbine installation site. More particularly, there is a need for a wind turbine tower that uses segmented tower sections adjacent a lower end of the tower, where the size of the tower sections may be large and difficult to transport; uses traditional tower sections adjacent an upper end of the tower, where the size of the tower sections are smaller and easier to transport; and provides for a transition between different types of tower sections at a location between the upper and lower ends of the tower.
To these and other ends, a hybrid wind turbine tower having a lower end mounted to a foundation and an upper end for connection to a nacelle of a wind turbine is disclosed. The hybrid tower includes at least one polygonal tower section connected to the foundation, wherein the at least one polygonal tower section includes a polygonal cross-sectional profile; at least one tubular tower section for connection to the nacelle, wherein the at least one tubular tower section includes a circular cross-sectional profile; and a transition piece disposed between the at least one polygonal tower section and the at least one tubular tower section, wherein the transition piece includes an upper portion having a circular cross-sectional profile connected to a lower end of the at least one tubular tower section, and a lower portion having a polygonal cross-sectional profile connected to an upper end of the at least one polygonal tower section. In an exemplary embodiment, the hybrid wind turbine tower may include a plurality of polygonal tower sections and a plurality of tubular tower section, and the transition piece may be disposed between the uppermost polygonal tower section and the lowermost tubular tower section.
In an exemplary embodiment, the transition piece may be integrated into the lower end of the at least one tubular tower section such that the transition piece and the at least one tubular tower section form a unitary structure, wherein the transition piece is intended to be permanently mounted to the lower end of the at least one tubular tower section (e.g., such as by welding and not by removable fasteners). In one embodiment, the transition piece may include a mounting interface at an upper end of the upper portion of the transition piece that is connected to a mounting interface at the lower end of the at least one tubular tower section. For example, in one embodiment, the mounting interface of the transition piece may be connected to the mounting interface of the at least one tubular tower section by a weld. In another embodiment, the mounting interfaces may include mounting flanges that are connected together by bolts or other removable fasteners. At the other end of the transition piece, a plurality of splice plates connects the lower portion of the transition piece to the upper end of the at least one polygonal tower section. In one embodiment, the at least one polygonal tower section is formed by a plurality of tower segments coupled edge-to-edge, and each tower segment includes one or more bends that collectively form the polygonal cross-sectional profile of the at least one polygonal tower section.
In one embodiment, the transition piece may have a one-piece construction. For example, the transition piece may be formed from a strip of stock material that is rolled and connected to itself at opposed ends of the strip (e.g., such as by welding) to form a ring. The one-piece ring may then be machined as needed to form the upper circular portion and lower polygonal portion of the transition piece. In another embodiment, the transition piece may be cast to form the upper and lower portions of the transition piece with the desired cross-sectional profile. The casting provides a transition piece having a continuous, monolithic construction. In yet another embodiment, the transition piece may have a two-piece construction. In this embodiment, a strip of stock material may be rolled, bent, and connected to itself at opposed ends of the strip to form the lower polygonal portion of the transition piece. In a similar manner, another strip of stock material may be rolled and connected to itself at opposed ends of the strip to form the upper circular portion of the transition piece and be machined if necessary to achieve a desired cross sectional profile. The separate pieces may then be connected together, such as through welding, at a connection joint to form the transition piece.
In one embodiment, the upper portion of the transition piece may include a first wall thickness, the lower portion of the transition piece may include a second wall thickness, and the second wall thickness may be less than the first wall thickness. Additionally, the upper portion of the transition piece may include a first height, the lower portion may include a second height, and the second height may be greater than the first height. In one embodiment, the transition piece has a height and a diameter, and the height-to-diameter ratio may be less than or equal to about 0.5. In an exemplary embodiment, at a connecting joint between upper and lower portions of the transition piece, the upper portion defines an inner radius and an outer radius (due to circular cross-sectional profile) and the lower portion defines an inner periphery and an outer periphery (due to polygonal cross-sectional profile), and the inner and outer periphery of the lower portion of the transition piece may be bounded by or remain within the confines of the inner and outer radius of the upper portion of the transition piece.
In another embodiment, a wind turbine includes the hybrid wind turbine tower described above, a nacelle mounted to the upper end of the tower; and a rotor having one or more wind turbine blades rotatably coupled to the nacelle.
In accordance with another aspect of the invention, a method of assembling a hybrid tower for a wind turbine is disclosed. The method includes connecting a lower end of at least one polygonal tower section to a foundation of a wind turbine, wherein the at least one polygonal tower section includes a polygonal cross-sectional profile; connecting a lower end of at least one tubular tower section to an upper end of the at least one polygonal tower section, wherein the at least one tubular tower section includes a circular cross-sectional profile; and disposing a transition piece between the at least one polygonal tower section and the at least one tubular tower section, wherein the transition piece includes an upper portion having a circular cross-sectional profile configured to connect to a lower end of the at least one tubular tower section, and a lower portion having a polygonal cross-sectional profile configured to connect to an upper end of the at least one polygonal tower section.
In one embodiment, disposing the transition piece between the at least one polygonal tower section and the at least one tubular tower section may include integrating the transition piece into the lower end of the at least one tubular tower section such that the transition piece and the at least one tubular tower section form a unitary structure. In an exemplary embodiment, the integrating occurs prior to connecting the at least one tubular tower section to the at least one polygonal tower section. In one embodiment, the assembly method may include hoisting the at least one tubular tower section, such as with a crane or other lifting apparatus, prior to connecting the at least one tubular tower section to the at least one polygonal tower section, and the transition piece is integrated into the lower end of the at least one tubular tower section prior to hoisting the at least one tubular tower section. In another embodiment, the assembly method may include transporting the at least one tubular tower section from a manufacturing facility to a wind turbine installation site, and the transition piece may be integrated into the lower end of the at least one tubular tower section prior to transporting the at least one tubular tower section.
In another embodiment, disposing the transition piece between the at least one polygonal tower section and the at least one tubular tower section includes connecting the transition piece to the lower end of the at least one tubular tower section prior to connecting the at least one tubular tower section to the at least one polygonal tower section. For example, the upper end of the transition piece may include a mounting flange and the lower end of the at least one tubular tower section may also include a mounting flange, and the mounting flanges may be connected together with bolts or other removable fasteners prior to connecting the at least one tubular tower section to the at least one polygonal tower section. In one embodiment, the assembly method may include hoisting the at least one tubular tower section prior to connecting the at least one tubular tower section to the at least one polygonal tower section, and the transition piece may be connected to the lower end of the at least one tubular tower section prior to hoisting the at least one tubular tower section.
In a further embodiment, disposing the transition piece between the at least one polygonal tower section and the at least one tubular tower section includes connecting the transition piece to the upper end of the at least one polygonal tower section prior to connecting the at least one polygonal tower section to the foundation. The connection between the transition piece and the at least one polygonal tower section may be via a plurality of splice plates, for example. In one embodiment, the assembly method may include hoisting the at least one polygonal tower section prior to connecting the at least one polygonal tower section to the foundation, and the transition piece may be connected to the upper end of the at least one polygonal tower section prior to hoisting the at least one tubular tower section. The at least one tubular tower section may then be coupled to the at least one polygonal tower section, such as via mounting flanges and removable fasteners.
In one embodiment, the at least one polygonal tower section may be formed by a plurality of tower segments having one or more bends formed therein, and wherein the method further includes connecting the plurality of tower segments edge-to-edge to form the at least one polygonal tower section.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above, and the detailed description given below, serve to explain the invention.
With reference to
The rotor 16 includes a hub 18 and one or more (e.g., three) blades 20 attached to the hub 18 at locations distributed about the circumference thereof. The blades 20 project radially outward from the hub 18 and are configured to interact with passing air currents to produce rotational forces that cause the hub 18 to spin about its longitudinal axis. This rotational energy is delivered to the generator housed within the nacelle 14 and converted into electrical power.
The tower 12 in
As depicted in
In an alternative embodiment, the transition piece 40a may be also be formed from a casting process such that the transition piece 40a may be considered to have a monolithic construction, i.e., one that does not have a welded seam such as that described above for the transition piece 40a made from flat plate stock. Casting the transition piece 40a allows it to be in its nearly final form right out of the casting so minimal additional reworking is required to achieve the final shape of the transition piece 40a.
The upper portion 50 has a wall thickness T1, and the lower portion 52 as a wall thickness T2. Generally, the wall thickness T2 may be less than the wall thickness T1. In an exemplary embodiment, the wall thickness T1 may be in the range of about 45-65 mm and is preferably about 55 mm, and the wall thickness T2 may be in the range of about 20-40 mm and is preferably about 30 mm. Other thickness values outside of these ranges may also be possible, depending on the particular application. Furthermore, in an exemplary embodiment, the upper portion 50 may have a height h1 in the range of about 150-250 mm and is preferably about 200 mm, and the lower portion 52 may have a height h2 in the range of about 250-350 mm and is preferably about 300 mm. The height h1 plus the height h2 generally defines the total height H of the transition piece 40b. The transition piece 40b also has a diameter D. In an exemplary embodiment, the transition piece 40b may have a height-to-diameter (H/D) ratio that is less or equal to about 0.5. For example, a transitional piece 40b with a diameter D of 4 m may have a height of about 2 m. Other height-to-diameter ratios may also be possible in alternative embodiments.
In an exemplary embodiment, each polygonal tower section 24, 24a may be made from a plurality of polygonal tower segments 80 coupled edge-to-edge using, for example, splice plates. Due to their generally large size, the plurality of polygonal tower segments 80 may be transported to the installation site unassembled and then assembled on site to form the individual polygonal tower sections 24, 24a. As shown in
In another embodiment, a transition piece 40c may be similar to transition piece 40b, but the mounting interface 78 may include a mounting flange 100 with a plurality of through holes 102 as depicted in
At the installation site, the transition piece 40c may be connected to the lower end of the tubular tower section 26a via fasteners 106 and then the two connected pieces hoisted up and connected to the uppermost polygonal tower section 24a via splice plates 90 and fasteners 92 as depicted in
The invention also contemplates a method of assembling the hybrid tower 12 for the wind turbine 10. In one embodiment, a lower end 110 (
In another embodiment of the method, the standalone transition piece 40c may be transported to the installation site without being connected to any other tower section 24, 26. Once at the installation site, the transition piece 40c may be connected to the lower end of the tubular tower section 26a via fasteners 106 and then those connected components hoisted up and connected to the upper end of the polygonal tower section 24a with splice plates 90 and fasteners 92 as depicted in
Aspects of the invention provide a hybrid tower with the lower, larger tower sections having a segmented design and with a polygonal cross-sectional profile, the upper, smaller tower sections having a traditional (non-segmented) tubular design and with a circular cross-sectional profile, and an intermediate transition piece that provides for a smooth transition between the different cross-sectional profiles. This hybrid tower arrangement provides the efficiencies of traditional tower sections for those sections having a size conducive to transport over the network of roads, while also providing the advantages of segmented tower sections for those sections that are problematic from a transport perspective. Moreover, aspects of the invention also provide assembly methods for a hybrid tower having an intermediate transition piece between the upper and lower ends of the tower that provide certain efficiencies in the assembly process. The assembly method may include integrating the transition piece into the lowermost tubular tower section, such as at the manufacturing facility or at least before the lowermost tubular tower section is hoisted for connection to an assembled polygonal tower section. The assembly method may alternatively include connecting the transition piece to the lower end of the lowermost tubular tower section prior to hoisting the lowermost tubular tower section for connection to an assembled polygonal tower section. The connection may be made using bolts or other removable fasteners and along mating mounting flanges. The assembly method may further alternatively include connecting the transition piece to the upper end of the uppermost polygonal tower section prior to hoisting the uppermost polygonal tower section for connection to the foundation or another polygonal tower section. This connection may be made using splice plates, for example.
While the present invention has been illustrated by a description of various preferred embodiments and while these embodiments have been described in some detail, it is not the intention of the Applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Thus, the various features of the invention may be used alone or in any combination depending on the needs and preferences of the user.
| Number | Date | Country | Kind |
|---|---|---|---|
| PA 2021 70335 | Jun 2021 | DK | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/DK2022/050141 | 6/24/2022 | WO |
