Patent Publication Number: US-2012023860-A1

Title: Adapter Configuration for a Wind Tower Lattice Structure

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to wind turbine tower structures, and more particularly to an adapter configuration that may utilized between the lattice tower and an upper tubular component of the wind turbine, or at the interface between a jacket foundation and tower for offshore wind turbines. 
     BACKGROUND OF THE INVENTION 
     Conventional wind turbine towers typically include a tubularpole construction to support a wind turbine at a considerable height to capture wind energy. The tubular tower configuration is relatively simple and easier to assemble, but utilizes a considerable amount of material, particularly steel. With the rising costs of these materials, the tubular towers become economically disadvantageous for certain hub heights and geographic regions. 
     The growing acceptance of wind energy as a significant alternative energy source depends on large part in maintaining the cost-per-kilowatt of power produced at an acceptable level. In this regard, lattice tower structures are gaining acceptance as a cost-effective alternative to the conventional tubular towers due, primarily, to significantly reduced amount of steel used in the lattice towers. 
     With certain conventional configurations, the wind tower structure includes a lower lattice tower section and an upper tubular section, with the machine head mounted atop the tubular section. A steel adapter is provided at the interface between the lattice tower section and the tubular section. In another known configurations, the machine head is supported directly atop of the lattice tower section, also with an adapter provided between the lattice tower section and the machine head. An example of this configuration is the “Space Frame Tower™” from Wind Tower Systems of Park City, Utah, USA, wherein a steel interface flange is welded to the top of the lattice tower. The yaw bearing ring in the machine head is bolted directly to this interface flange. 
     The interface between the lattice tower structure and the machine head or a tubular component that supports the machine head is crucial. The load transfer issues from the machine head to the vertical legs of the lattice tower can be quite complex. It is the conventional practice to use a welded steel adapter at this interface, as with the configurations discussed above. This steel adapter is, however, expensive to produce and requires skilled technicians (including welders) to configure the adapter to the tower, all of which adds to the overall cost of the wind turbine. 
     The concerns are similar with respect to offshore wind tower structures wherein the towers are connected to lattice or girder structures anchored to the sea bed with complex welded steel adapter structures. 
     Accordingly, an improved adapter configuration between the lattice tower structure and the machine head structure that is cost-effective and possesses superior load transfer capabilities is desirable. 
     BRIEF DESCRIPTION OF THE INVENTION 
     Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention. 
     In accordance with aspects of the invention, a wind turbine tower construction is provided having a lattice structure with a plurality of vertically oriented columns and cross-brace members. An adapter is molded onto a top of the lattice structure such that top portions of the columns are embedded into the adapter. The wind turbine tower structure may be land-based on an off-shore installation. 
     The adapter is configured for connection with structure that supports the machine head (“nacelle”) of the wind turbine, such as a tubular tower component on which the machine head is mounted or a component within the machine head. In this regard, the adapter may in one embodiment include a plurality of anchor bolts embedded therein for receipt of the tubular component. In another embodiment, a plurality of bolt holes may be defined through the adapter for receipt of respective bolts used to attach any manner of structure to the adapter. In still a further alternative embodiment, a plurality of threaded inserts may be provided in the adapter for receipt of a machine head component or other supporting structure. 
     The adapter is not limited to a particular moldable material, and may be formed of any suitable settable, hardened material formed onto and around the top portions of the columns. In a particular embodiment, the adapter is a concrete member poured and formed onto the top portions of the columns. In this concrete embodiment, any configuration of anchor members may be attached to the top portions of the columns and embedded in the concrete member. If anchor bolts are used in this embodiment, such bolts may be pre-tensioned in the concrete adapter. 
     The shape, dimensions, appearance, and the like, of the adapter are not limiting factors of the invention. In a particular embodiment, the adapter is formed as a cylindrical plate-like member. 
     In a unique embodiment, the lattice structure includes a plurality of vertically aligned and connected sections that may be erected at the wind turbine site. A top one of the sections may have the adapter pre-molded onto the columns. 
     It should be appreciated that the invention also encompasses a section of a wind turbine tower, wherein the section includes a plurality of vertically oriented columns and cross-brace members interconnected to define an open lattice structure, and with an adapter molded onto a top of the columns such that top portions of the columns are embedded into the adapter. The adapter may be configured in various different embodiments as discussed above. 
     The present invention also encompasses any manner of a wind turbine that incorporates a lattice structure with an adapter as set forth herein. 
     These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which: 
         FIG. 1  is a perspective view of a wind turbine with a lattice tower structure that may incorporate an adapter configuration in accordance with aspects of the invention; 
         FIG. 2  is a perspective view of an alternative embodiment of a wind turbine with a lattice tower structure and adapter configuration; 
         FIG. 3  is a side cut-away view of a top portion of a lattice tower structure with an adapter in accordance with aspects of the invention; 
         FIG. 4  is a perspective view of an embodiment of a lattice tower structure with an adapter; and, 
         FIG. 5  is a perspective view of an alternative embodiment of a lattice tower structure with an adapter. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents. 
       FIGS. 1 and 2  are perspective views of exemplary wind turbines  10  that may be configured in accordance with aspects of the invention. Although these wind turbines  10  are depicted as land-based structures, it should be appreciated that the invention is not limited in this regard and includes off-shore installations that utilize the adapter configuration and assembly in accordance with the invention. The wind turbines  10  include a plurality of blades  12  mounted to a rotor hub  14 , which in turn is rotationally supported by any manner of power generation components housed within a machine head  16  (which is also referred to as a “nacelle”), as is well known in the art. The machine head  16  is supported atop a tower structure  18 , which in the illustrated embodiments is an open lattice structure formed by columns or legs  20 , horizontal braces  22 , and diagonal braces  24 . The columns  20  are typically angle iron members or pipe members, and the braces  22 ,  24  are typically angle iron members. These lattice frame tower structures  48  are also referred to in the art as “space frame” towers. The lattice tower structure  48  may be fabricated in sections and erected at the wind turbine site. 
     In the embodiment of  FIG. 1 , the lattice tower structure  18  extends essentially to the nacelle  16  such that the machine head components are supported directly atop of the tower structure  18 . An adapter  30  in accordance with aspects of the invention is provided at the interface between the lattice tower structure  18  and nacelle  16 , as described in greater detail below. It may be desired to provide a cladding material  26  applied over the lattice tower structure  18 , which may be any type of suitable fabric, such as an architectural fabric designed for harsh weather conditions. The cladding  26  protects workers and equipment within the tower and provides an aesthetic appearance to the wind turbine  10 . 
     In the embodiment of  FIG. 2 , the nacelle  16  is supported atop a tubular component  38  that is, in turn, affixed to the lattice tower structure  18  via an adapter  30 . This adapter  30  may be in accordance with aspects of the present invention. 
     Referring to  FIGS. 3 through 5  in general, the adapter  30  that is affixed to the top of the lattice tower structure  18  is a molded component that is formed directly onto the top portions  32  of the lattice tower columns  20  such that the top portions  32  are embedded directly into the adapter  30 , as particularly illustrated in  FIG. 3 . The adapter  30  may be molded from any suitable type of settable, hardened material that may be formed directly onto the top portions  32  of the columns  20 , for example by being poured into a mold that is affixed to the top of the lattice tower structure  18  during the fabrication process. 
     In a particular embodiment, the adapter is a concrete member, with the top portions  32  of the columns  20  embedded directly into the concrete during the formation process. It should be appreciated that concrete is not a limiting material, and that other suitable types of settable, hardened materials may be used, for example, epoxies or other hardened adhesives, hardened plastics, and so forth. 
     In order to strengthen and ensure the integrity of the connection between the top portions  32  of the columns  20  and the adapter  30 , it may be desired to affix any manner of anchor members  34  onto the portions of the columns  20  that will be embedded in the adaptor  30 , as depicted in  FIG. 3 . End plates or head plates may also be provided atop the columns  20  for the same purpose. 
     It should be appreciated that the adapter  30  is not limited to any particular shape, size, dimensions, or aesthetic appearance, and that all of these characteristics may be varied to the moldable and shapeable characteristics of the adapter  30 . In the illustrated embodiment, the adapter  30  is a solid plate-like member, such as a concrete disc. In other embodiments, the adapter  30  may be a ring so that cables, ladders, and any other component may be routed through the adapter into the tubular section or machine head. 
     In the embodiment of  FIG. 2  wherein the adapter  30  is provided at the interface of the lattice tower structure  18  and a tubular component  38 , it may be desired to incorporate a plurality of anchor bolts  36  ( FIG. 3 ) with the adapter  30 . These anchor bolts  36  are configured for receipt of the bottom portion of the tubular component  38 , as depicted in  FIG. 3 . The bolts  36  may be embedded directly into the adapter  30  and include a threaded extension that extends from the upper surface of the adapter  30 , as depicted in  FIG. 4 . In other embodiments, the anchor bolts  36  may extend through holes that are drilled or formed into the adapter  30 , as depicted by the right-hand anchor bolt  36  in  FIG. 3 . The anchor bolts  36  may be pre-tensioned within the adapter  30 . It should be appreciated that the adapter  30  is not limited to any particular type of mechanical fastening between the adapter  30  and the tubular component  38 . 
     In the embodiment of  FIG. 1  wherein the adapter  30  constitutes the interface between the top of the lattice tower structure  18  and the nacelle  16 , the adapter  30  may be configured for direct attachment with one of the machine components within the nacelle  16 , such as the yaw bearing ring. In this regard, referring to  FIG. 5 , the adapter  30  may include a plurality of threaded inserts  44  for receipt of bolts used to attach the bearing ring to the adapter  30 . In an alternative embodiment, bolt holes may be defined completely through the adapter  30 , wherein bolts used to attach the bearing ring extend completely through the adapter  30  and are bolted at the underside of the adapter  30  similar to the configuration depicted in  FIG. 3 . 
     The adapter  30  may, in certain embodiments, constitute a component that is pre-formed onto a top section  40  ( FIG. 3 ) of a lattice tower structure  18 , wherein various sections of the tower structure are assembled at the wind turbine site. In this manner, the adapter  30  may be pre-formed onto a tower section  40  and transported intact with the tower section  40  to the wind turbine site. Alternatively, the adapter  30  may be formed atop the lattice tower structure  18  at the wind turbine site. 
     It should thus be appreciated that the present invention also encompasses any manner of a section  40  of a lattice tower structure that incorporates an adapter  30  in accordance with aspects of the present invention. 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.