SPACEFRAME NACELLE FOR A WIND TURBINE GENERATOR AND METHOD OF MANUFACTURING THE SPACEFRAME NACELLE
A nacelle for a wind turbine generator includes a spaceframe having at least one exterior panel and at least one interior panel joined to the exterior panel. Each of the exterior and interior panels have a plurality of generally U-shaped channel portions with flanges extending outward from the channel portion. The flanges of the exterior panel are joined to the flanges of the interior panel to define a plurality of ribs, a plurality of joints, and a plurality of openings.
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This application is a continuation-in-part of co-pending U.S. application Ser. No. 12/169,766 filed Jul. 9, 2008 and entitled Spaceframe Wind Turbine Energy Converter Structure, which is hereby incorporated by reference in its entirety.
BACKGROUND OF THE INVENTIONThe field of the invention relates generally to nacelles for wind turbine generators, and more particularly to a nacelle having a spaceframe fabrication and a method of manufacturing the spaceframe nacelle.
Wind turbine generators use wind energy to generate electricity and typically include a tower, a nacelle mounted on a top of the tower, and a hub and blade assembly connected to the nacelle. Wind causes the hub and blade assembly to rotate with respect to the nacelle thereby creating mechanical energy that is converted by a generator, which is typically housed in the nacelle, into useable electrical energy. The nacelle encloses the inner workings of the machine head and includes a heavy bedplate that supports the main shaft, bearings and drivetrain components. The bedplate can be fabricated from thick metal plates or cast from molten metal, which adds substantial weight to the top of the tower.
However, much of the weight of the bedplate and nacelle is excessive in that the nacelle is primarily a non-load bearing enclosure used to keep the weather from directly impacting the various components (e.g., generator) of the wind turbine generator housed therein. The excessive weight of the bedplate and nacelle significantly increases manufacturing cost, transportation cost, assembly cost, and maintenance cost of the wind turbine generator. In addition, the weight of the machine head also impacts the tower structure needed to support it with its attendant costs.
BRIEF DESCRIPTION OF THE INVENTIONIn one aspect, a nacelle for a wind turbine generator generally includes a spaceframe including at least one exterior panel and at least one interior panel joined to the exterior panel. Each of the exterior and interior panels have a plurality of generally U-shaped channel portions with flanges extending outward from the channel portion. The flanges of the exterior panel are joined to the flanges of the interior panel to define a plurality of ribs, a plurality of joints, and a plurality of openings.
In another aspect, a nacelle for a wind turbine generator generally comprises a spaceframe including a plurality of ribs, a plurality of joints, and a plurality of openings. The spaceframe comprises at least a first region and a second region. The first region has a first load-bearing strength and the second region has a second load-bearing strength. The first load-bearing strength of the first region is greater than the second load-bearing strength of the second region.
In still another aspect, a wind turbine generator generally includes a tower, a nacelle rotatably coupled to a tower top for rotational movement with respect to the tower, and a blade and hub assembly operatively coupled to the nacelle. The nacelle includes a spaceframe including at least one exterior panel and at least one interior panel joined to the exterior panel. The exterior panel and interior panel collectively define a plurality of ribs, a plurality of joints, and a plurality of openings.
In yet another aspect, a method of constructing a spaceframe for a nacelle generally includes stamping a first sheet of metal to form a plurality of openings therein and forming a plurality of generally U-shaped channels with flanges extending outward from the channels in the first sheet of metal. A second sheet of metal is stamped to form a plurality of openings therein and formed to have a plurality of generally U-shaped channels with flanges extending outward from the channels in the second sheet of metal. The U-shaped channels and associated flanges of the first sheet of metal are aligned with the U-shaped channels and associated flanges of the second sheet of metal so that the aligned U-shaped channels cooperatively define a generally box-shaped cross-section and the flanges are in engagement. The flanges of the first sheet of metal and the flanges of the second sheet of metal are securely joined.
The blades 112 are spaced about the blade and hub assembly 108 to facilitate rotating the blade and hub assembly 108 to transfer kinetic energy from the wind into usable mechanical energy, and subsequently, electrical energy. More specifically, as the wind strikes the blades 112, the blade and hub assembly 108 is rotated about its rotational axis 124. Preferably, the blades 112 are positioned such that they face into the wind. Since the wind direction readily changes, the blades 112, and thereby the nacelle 106, need to be able to rotate with respect to the tower 102 so that the blades can remain substantially facing into the wind. That is, by rotating the nacelle 106, the blades can be rotated such that the wind direction is generally parallel to the rotational axis 124 to maximize the amount of wind striking the blades. As such, the nacelle 106 and the blades 112 can rotate with respect to the tower 102 about a rotational axis 126 that is generally transverse to the blade and hub assembly rotational axis 124 and that is substantially coaxial with a longitudinal axis of the tower 102.
A portion of the nacelle 106 is broken away in
With reference to
As illustrated in
With reference now to
In one embodiment, the various regions 170, 172, 174, 176 of the spaceframe 160 can have different predetermined load-bearing strength characteristics. In the exemplary embodiment illustrated in
The load-bearing strength of the various regions 170, 172, 174, 176 of the spaceframe 160 can be varied in different ways including using a different type of material in each of the different regions, changing the thickness of the material in the different regions, changing the cross-section shape of the material, or a combination thereof. In one embodiment, for example, the spaceframe 160 can be constructed of low to medium strength steel in regions of the spaceframe exposed to lower stress during use and high strength steel in regions exposed to higher stress during use.
Moreover, the overall mass of the spaceframe 160 is considerably less than the mass of nacelles constructed using conventional techniques. For example, a conventional cast or fabricated nacelle for a 7.5 MW wind turbine generator having a bedplate has an average mass of approximately 91.6 metric tons. On the other hand, a comparable spaceframe 160 has an average mass between 21.9 metric tons and about 45.5 metric tons. Accordingly, the average mass of the spaceframe 160 for a 7.5 MW wind turbine generator is approximately 50% to 76% less than the average mass of a conventional nacelle for the same sized wind turbine generator.
The spaceframe 160 can be optimized, non-optimized, or a continuation thereof. An optimized spaceframe 160 includes specifically tailoring the different regions 170, 172, 174, 176 of the spaceframe to exhibit one or more predetermined performance characteristic (e.g., load-bearing strength, stiffness, fatigue life). The spaceframe can be optimized by varying the size of the openings 168, the joining method (which are described in detail below), and the thickness and/or type of the material used to make the ribs 164 and joints 166. As a result, each of the specific regions 170, 172, 174, 176 of the spaceframe 160 can be tailored to have predetermined strength, stiffness, and fatigue life. The spaceframe 160 is considered to be non-optimized if it has only one size opening or repeating pattern and only one joining method used throughout the structure. Typically, the average mass of the optimized spaceframe 160 is less than half of that of a comparable non-optimized spaceframe.
The exterior panel 180 is joined to the interior panel 182. More specifically, the flanges 186 of the exterior panel 180 are aligned with and joined to the flanges 186′ of the interior panel 182 as explained in more detail below. As a result, the exterior panel 180 and interior panel 182 cooperatively define the plurality of ribs 164, joints 166, and openings 168 of the spaceframe 160. As seen in
In the exemplary embodiment, each of the exterior panel 180 and the interior panel 182 are sheet metal or plate metal members. First and second sheets of metal are stamped to form the openings 168 and pressed to form the U-shaped channel portions 184, 184′ and the flanges 186, 186′ for fabricating the respective exterior and interior panels 180, 182. In one embodiment, the exterior panels 180 and interior panels 182 are offset from each other such that their peripheries are not aligned with each other. In other words, the interior panels 182 are staggered with respect to the exterior panels 180. In the illustrated embodiment, the exterior panel 180 and interior panels 182 are constructed from the same material, with the same thickness, and with the same cross-sectional shape. It is contemplated, however, that the exterior and interior panels 180, 182 or portions thereof can be formed from different materials, materials having different thicknesses, and/or different cross-sectional shapes. It is also contemplated that each of the exterior panel 180 and the interior panel 182 of the spaceframe 160 may include a single panel member or a plurality of panel members.
The spaceframe 160, and more particularly the exterior and interior panels 180, 182 thereof, can be constructed of metal, metal alloys, composites, polymers, and/or combinations thereof. In one embodiment, the spaceframe 160 is constructed using metal alloys such as an aluminum alloy or a steel alloy. In another embodiment, the spaceframe 160 is constructed from steel materials that are similar to those used in the automobile and truck industries including mild steel/low carbon steel, dent resistant steel, high strength steel, and heat/treatable/martensitic steels. Mild steel/low carbon steel (MS) has excellent formability, manufacturability, and low cost. Dent resistant steel (DRS) is a low-carbon, higher strength steel. High strength steel (HSS) is used where durability is the primary concern. Complex shapes, however, may be more difficult to manufacture with high strength steel. Heat-treatable/martensitic steel offers high strength-to-weight ratio (used to reduce weight for light-weight designs) but it is expensive.
Other materials can also be used to form the spaceframe 160. For example, medium carbon steel, high carbon steel, alloy steels including Cr, Ni, Si, and Mn, may also be used for constructing the spaceframe 160. In another embodiment, combinations of different materials may be used to construct the spaceframe 160. For example, the spaceframe 160 may utilize high alloy, high strength steel in higher stress regions and low alloy, low strength, and less expensive steel in lower stress regions. In one embodiment, the exterior panel 180 and the interior panel 182 each have a thickness between about 6-9 millimeters (mm), which is two or three times greater then the sheet metal or panel metal members typically used in automotive applications (e.g., 2-3 mm) As mentioned above, it is contemplated that the thickness of the exterior panel 180 and/or the interior panel 182 of the spaceframe 160 can vary in different areas of the spaceframe.
The exterior panel 180 of the spaceframe 160 can be joined to the interior panel 182 in any suitable manner including welding, riveting, and crimping. In one suitable method, which is illustrated in
With reference to
Resistance seam welding can by done at high speeds as compared with many other welding techniques. Moreover, resistance seam welding can be used to weld low strength carbon steel plates to high strength carbon steel plates. Thus, when different metals are used to construct the exterior panel 180, the interior panel 182, or portions thereof, resistance seam welding can be suitably used to join the panels together.
Another suitable welding technique that can be used to join the exterior panel 180 and the interior panel 182 of the spaceframe 160 is a high-energy beam welding process such as electron beam welding or laser beam welding. Electron beam welding is a fusion welding process that produces coalescence of materials with heat obtained by impinging a beam composed of high energy electrons onto a joint to be welded. Laser beam welding is a fusion joining process that produces coalescence of materials with the heat obtained from concentrated beam of coherent, monochromatic light impinging on a joint to be welded. Laser beam welding is a low heat input process that produces low part distortion. Because laser beam welding does not use electrodes, the welded metal is free from contamination that may be present when electrodes are used in the welding process. Both electron beam welding and laser beam welding can be focused to a smaller area.
During the fillet welding process, external filler wire can be added. In one embodiment, the filler wire includes the same or similar material as the exterior panel 180 and/or the interior panel 182. It is contemplated that the filler wire can be made from materials different than those of the exterior panel 180 and/or the interior panel 182. Conventional welding processes, such as Gas Metal Arc welding (GMAW), Flux Cored Arc welding (FCAW), Shield Manual Welding (SMAW) and Gas Tungsten Arc Welding processes, can be used to form the fillet welds 602. Typically, the fillet welds 602 work well with shear stress type of loading.
The exterior and interior panels 180, 182 can also be mechanically joined together, e.g., by using mechanical fasteners (shown in
In use, the insert 900 is placed in one of the openings 168 formed in the spaceframe 160 so that each of the upper flanges 908 engage one of the flanges 186 of the exterior panel 180 as seen in
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 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.
Claims
1. A nacelle for a wind turbine generator, the nacelle comprising a spaceframe including at least one exterior panel and at least one interior panel joined to the exterior panel, each of the exterior and interior panels having a plurality of generally U-shaped channel portions with flanges extending outward from the channel portion, the flanges of the exterior panel being joined to the flanges of the interior panel to define a plurality of ribs, a plurality of joints, and a plurality of openings.
2. The nacelle of claim 1, wherein the exterior and interior panels are joined together by welds.
3. The nacelle of claim 1, wherein the exterior and interior panels are joined together using rivets.
4. The nacelle of claim 1, wherein the exterior and interior panels are joined together using crimping inserts.
5. The nacelle of claim 1, wherein each of the exterior panel and the interior panel is a stamped sheet metal member.
6. The nacelle of claim 1, wherein each of the ribs has a generally square cross-sectional shape.
7. The nacelle of claim 1, further comprising a shell covering the spaceframe.
8. A nacelle for a wind turbine generator, the nacelle comprising a spaceframe including a plurality of ribs, a plurality of joints, and a plurality of openings, the spaceframe comprising at least a first region and a second region, the first region having a first load-bearing strength and the second region having a second load-bearing strength, the first load-bearing strength of the first region being greater than the second load-bearing strength of the second region.
9. The nacelle of claim 8, wherein the openings of the spaceframe located in the second region are larger than the openings located in the first region.
10. The nacelle of claim 8, wherein the ribs and joints of the spaceframe located in the second region are formed from a material that is different than a material used to form the ribs and joints located in the first region.
11. The nacelle of claim 8, wherein an average mass of the spaceframe is approximately 50% to 76% less than an average mass of a conventional, bedplate nacelle adapted for use with the same sized wind turbine generator as the spaceframe.
12. The nacelle of claim 8, wherein the spaceframe comprises a front region, a back region, and a middle region extending between the front and back regions, and wherein the first region corresponds to the front region and the second region corresponds to the middle region.
13. The nacelle of claim 12, wherein the spaceframe is optimized so that each of the regions of the spaceframe has a predetermined strength, stiffness, and fatigue life.
14. A wind turbine generator comprising:
- a tower;
- a nacelle rotatably coupled to a top of the tower for rotational movement with respect to the tower, the nacelle comprising a spaceframe including at least one exterior panel and at least one interior panel joined to the exterior panel, the exterior panel and the interior panel collectively defining a plurality of ribs, a plurality of joints, and a plurality of openings; and
- a blade and hub assembly operatively coupled to the nacelle.
15. A method of constructing a spaceframe for a nacelle, said method comprising:
- stamping a first sheet of metal to form a plurality of openings therein;
- forming a plurality of generally U-shaped channels with flanges extending outward from the channels in the first sheet of metal;
- stamping a second sheet of metal to form a plurality of openings therein;
- forming a plurality of generally U-shaped channels with flanges extending outward from the channels in the second sheet of metal;
- aligning the U-shaped channels and associated flanges of the first sheet of metal with the U-shaped channels and associated flanges of the second sheet of metal so that the aligned U-shaped channels cooperatively define a generally box-shaped cross-section and the flanges are in engagement; and
- securely joining the flanges of the first sheet of metal and the flanges of the second sheet of metal.
16. The method of claim 15, wherein securely joining the flanges of the first sheet of metal and the flanges of the second sheet of metal comprises welding the flanges of the first sheet of metal and the flanges of the second sheet of metal together.
17. The method of claim 16, wherein welding the flanges of the first sheet of metal and the flanges of the second sheet of metal comprises welding the flanges together using a resistance seam welding process.
18. The method of claim 16, wherein welding the flanges of the first sheet of metal and the flanges of the second sheet of metal comprises welding the flanges together using a high-energy beam welding process.
19. The method of claim 15, wherein securely joining the flanges of the first sheet of metal and the flanges of the second sheet of metal comprises crimping the flanges of the first sheet of metal and the flanges of the second sheet of metal together using a crimpable insert, said insert being designed to provide sufficient clamping load in all primary load paths and direction.
20. The method of claim 15, wherein securely joining the flanges of the first sheet of metal and the flanges of the second sheet of metal comprises inserting mechanical fasteners through the flanges of the first sheet of metal and the flanges of the second sheet of metal.
Type: Application
Filed: Jun 30, 2009
Publication Date: Aug 5, 2010
Applicant: GENERAL ELECTRIC COMPANY (Schenectady, NY)
Inventors: Lawrence Willey (Simpsonville, SC), Shanmuga-Priyan Subramanian (Rheine), Sujith Sathian (Zachary, LA)
Application Number: 12/494,666
International Classification: E04H 12/00 (20060101);