Patent Publication Number: US-2009232659-A1

Title: Concrete to fabricate the nacelle of a wind turbine

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to wind turbines. Particularly, it relates to a nacelle of a wind turbine or other structures provided on top of the tower of a wind turbine and methods of manufacturing nacelle and/or other structures of a wind turbine. 
     The increasing demand for power generation with wind turbines result in a desire for reducing costs and improving characteristics of components of a wind turbine. 
     For example, noise generated by a wind turbine can be partly mechanical. Mechanical noise is generated mainly from rotating machinery in the nacelle, particularly the gear box and the generator. However, there may also be contributions from cooling fans, auxiliary equipment (such as pumps and compressors), bearings and the yaw system. Mechanical noise is often at a plurality of frequencies or a tone which maybe caused by the meshing frequency of a stage of the gear box. Noise emission of the wind turbine should be minimized to an admissible sound pressure level depending on the allowed noise source in a certain location. 
     Further, the use of low-cost materials for a component of a wind turbine is desired. Thereby, the production costs of manufacturing a component with a certain material has to be considered. 
     SUMMARY OF THE INVENTION 
     In view of the above, according to one embodiment, a structure of a wind turbine according to independent claim  1 , a wind turbine according to independent claim  10 , and a method of manufacturing a structure of a wind turbine are provided. 
     According to one embodiment, a structure of a wind turbine selected from the group consisting of: a nacelle of a wind turbine, a hub of a wind turbine, and fairings of a wind turbine is provided. The structure includes a structure housing comprising a concrete material. 
     According to another embodiment, a wind turbine having a nacelle or another structure selected from the group consisting of a hub and fairings is provided. The wind turbine includes a structure wall comprising a concrete material. 
     According to an even further embodiment, a method of manufacturing a structure of a wind turbine is provided. The method includes providing reinforced concrete in a structure wall shape; and hardening the concrete. 
     Further embodiments, aspects, advantages and features are apparent from the dependent claims, the description and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A full and enabling disclosure of the present invention, including the best mode thereof, to one of ordinary skill in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures, wherein: 
         FIG. 1  shows a schematic view of a portion of a wind turbine having a nacelle with a housing comprising concrete material; 
         FIG. 2  shows an enlarged view of the nacelle including the housing of the nacelle according to embodiments described herein; 
         FIG. 3  shows an enlarged view of a further nacelle including the housing of the nacelle according to embodiments described herein; and 
         FIG. 4  shows a schematic view of a portion of a further wind turbine having a nacelle with a housing comprising concrete material; 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to the various embodiments, one or more examples of which are illustrated in the figures. Each example is provided by way of explanation of the invention and is not meant as a limitation of the invention. For example, features illustrated or described as part of one embodiment can be used on or in conjunction with other embodiments to yield yet a further embodiment. It is intended that the present invention includes such modifications and variations. 
     Modern wind turbines experience and increase in size and rated power. In particular, megawatt and multi-megawatt wind turbines are more commonly installed. Thereby, the increase in size and rated power of the wind turbines also result in an increasing amount of materials required. Accordingly, substituting expensive materials with low-cost materials gets increasingly important. 
     According to embodiments described herein, concrete and, in particular reinforced concrete, is used to manufacture the nacelle of wind turbine generator systems. 
       FIG. 1  illustrates embodiments of wind turbine  100 .  FIG. 1  shows a portion of a wind turbine, wherein an upper part of the tower  20  is shown. The nacelle  22  is mounted on the tower  20 . The nacelle  22  carries the hub  26  to which the rotor blades  28  are mounted. The rotation of the rotor is transferred to the gear box  34  by the drive train  32 . The gear box  34  is connected to the generator  36  by a shaft  33 . These and other components like the yaw drive, a breaking system, a cooling system and electronic devices are provided in the nacelle  22  of the wind turbine  100 . 
     The nacelle  22  has a housing portion  120  or a wall, which comprises a concrete material. Thereby, typically reinforced concrete can be used. 
     According to different embodiments, which can be combined with other embodiments described herein, the concrete nacelle can be reinforced by materials and/or woven materials of the group consisting of, for example, steel, plastic, cotton, glass, mono filament polypropylene, span basalt, synthetic materials, natural materials and combinations thereof. 
     According to yet other embodiments, alternatively or additionally steel cages, steel reinforcement bars (re-bar) or other cages and/or bars can be used for reinforcement. Thereby, it is possible to increase the amount of tension force that can be taken by the concrete. 
     According to embodiments described herein, concrete as a low-cost material that can easily be brought into nearly any shape can be used for manufacturing the nacelle. Thereby concrete also provides a material which can significantly reduce acoustic emission from the machine head compared to other materials. Additionally, concrete is less inflammable than fiber composite structures like fiber reinforced plastic. 
     Generally, according to embodiments described herein, which can be combined with other embodiments described herein, every type of concrete, which may typically be reinforced can be used for manufacturing the housing of a structure from the group consisting of: a nacelle of a wind turbine, a hub of a wind turbine, and fairings of a wind turbine. Thereby, as typical examples, lightweight concrete, air-entrained concrete and/or other types of concrete described herein. 
     According to embodiments described herein, concrete as a mixture of cement and water, wherein cementitious materials such us fly ash, slag cement and aggregates can be included is used as a material for the nacelle, in particular the wall of the nacelle housing. Concrete solidifies and hardens after mixing due to hydration. Before hydration, concrete can be brought into any shape and, thus, a nacelle can be easily manufactured. 
     According to specific embodiments, refractory cement might be used for providing better ability to withstand elevated temperatures. 
     According to yet further embodiments, which can be combined with other embodiments described herein, sand, natural gravel, crushed stones, air-cooled blast furnace slag, ash, remainders from recycling can be used as aggregates in the cement. Further optionally, chemical admixtures like accelerators, air-entrainers, plasticizers and corrosion inhibitors can be added. Additionally or optionally also mineral admixtures like fly ash, slag, silica fume can be adhered for providing the desired material characteristic of the concrete use to manufacture the nacelle. As a further alternative cork-cement may be also be used. 
     According to yet further embodiments, in particular, for off-shore applications wherein seawater might have corrosive effects on concrete, porcelain cement and cement using more than 50% or 60% of slag as an aggregate can be used to improve the resistance to seawater. 
     Further, according to some implementations, high-strength concrete can be used by lowering the water-cement ratio and, optionally at silica fume. Generally, other forms of high-performance concrete (HPC) can be used to improve the characteristics of concrete, for example with regard to long-term mechanically properties, long life in severe environments, permeability, volumes debility, and the like. 
     According to yet further embodiments, shotcrete can be used to shoot concrete on to a frame or structure, which might for example be provided by woven material. Thereby a concrete nacelle can be easily manufactured. 
     As shown in  FIG. 1 , the nacelle  22  and the base plate  40  which may according to different embodiments be a single base frame (or bedplate), or which may also have different individual or connected frames like a main frame and a generator frame, are connected to each other by connecting members  142 . 
     Other embodiments and details of a concrete material included in a nacelle are shown in  FIG. 2 .  FIG. 2  shows an enlarged view of a nacelle having a housing portion  120 . Within the nacelle the base frame  40  is included carrying the gear box  34  and the generator  36 . As described above, the gear box is connected to the rotor by a drive train  32  and the generator is connected to the gear box by shaft  33 . Within the housing  120  of the nacelle, which includes concrete material, reinforcement bars  122  are provided. Typically, the reinforcement bars can be made of steel, a plastic material and/or a natural material. Additionally or alternatively the reinforcement can be provided by a cage. According to further alternatives or additional options hooks, and connections between reinforcing bars can be provided as shown in the area  222 . 
     According to some embodiments, which can be combined with other embodiments described herein, the connection between the base frame  40  and the nacelle housing  120  can be provided by connecting members  242  which connect a reinforcement portion of the concrete material with the base frame. 
     Other embodiments of concrete materials that can be used for manufacturing the nacelle housing  120  are illustrated with regard to  FIG. 3 . The concrete material of the nacelle housing  120  includes fibers  322  which can be of a steel material, plastic material and/or glass material. Typically the fibers are homogenously but arbitrarily distributed within the concrete material. According to yet further embodiments, a fiber reinforcement can be combined with a re-bar reinforcement that has been described with respect to  FIG. 2 . 
     Generally, concrete has a relatively high compressive strength but lower tensile strength. Thus, as described above, reinforced concrete can be used. Thereby, for example, steel or fiber reinforcement in the form of bars (re-bar), meshes or fibers can be utilized. According to different embodiments, fibers can be made of steel, glass, synthetic or natural materials. Typical steel reinforced (ferroconcrete) structures may include anchorage like anchor plates or bending of the re-bar, for example into 90 degree bend or 100 degree hook. As a further example, fiber-reinforced plastic re-bar reinforcement can alternatively or additionally used. 
     According to different embodiments, the fiber reinforced concrete can have fiber length of 30 to 80 mm, for example 45 mm, wherein the fiber diameter can be about 1 mm. Typical embodiments have a volume fraction of fibers in the concrete from 0.1 to 3%. 
     According to yet further embodiments, it is possible to manufacture the concrete nacelle by providing a mesh of glass fibers, plastic fibers or steel fibers and shoot the concrete on the mesh on order to provide a shotcrete nacelle housing. 
     According to yet further embodiments, which can be combined with other embodiments described herein, the reinforced concrete structures can be pre-stressed in order to better withstand tensile forces. Generally concrete can withstand compressive forces. By pre-stressing the concrete such that a compressive force acts on the concrete without any outside forces, the ability to withstand tensile stress can be improved. By introducing compressive stress in the concrete material prior to super imposed loads being generated in operation the stress limits in the concrete for both compression attentions can be optimized. Thereby, according to specific examples, the pre-stressing can be achieved by using steel tendons or bars that are subjected to a tensile force prior to casting the concrete, in pre-tension concrete, or after concrete has cured, in posed-tension concrete. 
       FIG. 4  illustrates embodiments, which are similar to the embodiments described with respect to  FIG. 1  and which can be combined with embodiments described with respect to  FIGS. 2 and 3 . Additionally to the nacelle housing  120  being manufactured with concrete materials, a coating  420  can be provided on the outside of the concrete nacelle. Thereby, protection of the concrete nacelle can be achieved. Typically, the coating system can be of a highly flexible material like liquid synthetic materials, composites or plastics, which are provided on web and/or fabric. 
     Generally, the thickness of the housing of the wall of the nacelle including concrete material can be in arrange of 1 cm to 10 cm, for example 2 cm. By providing modern reinforcement materials, which also allow for a reduced thickness of the wall of the nacelle, the weight increase that might occur in light of the concrete material is limited. 
     According to yet further embodiments, which can be combined with other embodiments described herein, a method of manufacturing a structure of a wind turbine including providing reinforced concrete in a structure wall shape; and hardening the concrete, may include at least one option from the group of providing the reinforced concrete in conducted by pouring the concrete in a mold including reinforcement therein or shooting the concrete at a structure, frame or web. 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to make and use the invention. While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modifications within the spirit and scope of the claims. Especially, mutually non-exclusive features of the embodiments described above may be combined with each other. 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 have 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 language of the claims. 
     According to yet other embodiments, which can be combined with other embodiments described herein, the manufacturing comprising a concrete material can be similarly applied to the spinner/hub of a wind turbine or other kinds of fairings that are applied to the wind turbine. 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to make and use the invention. While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims. Especially, mutually non-exclusive features of the embodiments described above may be combined with each other. 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 have 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 language of the claims.