Patent Application
20090191051
1. Technical Field
The subject matter described here generally relates to wind turbines, and, more particularly, to stackable nacelles for wind turbines.
2. Related Art
A wind turbine is a machine for converting the kinetic energy in wind into mechanical energy. If that mechanical energy is used directly by machinery, such as to pump water or to grind wheat, then the wind turbine may be referred to as a windmill. Similarly, if the mechanical energy is further transformed into electrical energy, then the turbine may be referred to as a wind generator or wind power plant.
Wind turbines use one or more airfoils in the form of a “blade” to generate lift and capture momentum from moving air that is them imparted to a rotor. Each blade is typically secured at its “root” end, and then “spans” radially “outboard” to a free, “tip” end. The front, or “leading edge,” of the blade connects the forward-most points of the blade that first contact the air. The rear, or “trailing edge,” of the blade is where airflow that has been separated by the leading edge rejoins after passing over the suction and pressure surfaces of the blade. A “chord line” connects the leading and trailing edges of the blade in the direction of the typical airflow across the blade. The length of the chord line is simply the “chord.”
Wind turbines are typically categorized according to the vertical or horizontal axis about which the blades rotate. One so-called horizontal-axis wind generator is schematically illustrated in
Modern nacelles 20 are typically assembled at a factory and then transported individually to each wind turbine 2 installation. As discussed in WIPO International Publication No. WO2007/132408, increasingly larger wind turbines require larger and larger nacelles with resulting transport difficulties. To address this problem, modern nacelles are sometimes assembled on-site from a kit including, among other things, smaller plate-shaped elements that are assembled by means of mountings at the place of use. However, such conventional techniques still require substantial logistical and assembly resources to implement at the factory and wind turbine 2 installation.
These and other aspects of such conventional approaches are addressed here by providing, in various embodiments, a stackable nacelle for a wind turbine, including a first piece having a top wall and integral first side walls extending at a first obtuse angle from each edge of the top wall; and a second piece, for mating with the first piece, having a bottom wall and integral second side walls extending at a second obtuse angle from each edge of the bottom wall.
Various aspects of this technology invention will now be described with reference to the following figures (“FIGS.”) which are not necessarily drawn to scale, but use the same reference numerals to designate corresponding parts throughout each of the several views.
The nacelle 30 can be made from any suitable material, including polyvinyl chloride and/or other plastics, such as polyester, vinylester, epoxy, and epoxy hybrid resins. Various reinforcing materials may also be used with these materials, including glass, metal, and/or carbon fibers. Furthermore, various manufacturing techniques may be used to configure these materials, including hand lay-up and/or spray lay-up. The nacelle 30 may also be formed from metal, such as sheet metal.
In the examples illustrated here, the stackable nacelle 30 for a wind turbine tower includes a first (or top) piece 32 having a top (or base) wall 34 and integral first side walls 36 extending at a first obtuse angle α from each edge of the top wall 34. Although the illustrated first angles α are substantially the same for each of the side walls 46, different angles may also be used. An optional nameplate contour 38 is also provided in the form of a blister or bump on top wall 34. Additional contours, opening, doors, hatches, vents and/or other surface features may also be provided near the nameplate contour 38 and/or in various other locations that will not significantly affecting the stackability of the nacelle 20.
A second (or bottom) piece 42 is provided for mating with the first piece 32 as best shown in
A first flange 50 extends from a free end of the first side walls 36, and a second flange 52 extends from a free end of the second side walls 46 for securing to the first flange 50. In addition to allowing the first and second pieces 32 and 42 to be easily secured, the flanges 50 help to enhance their structural rigidity. The illustrated examples show the flanges 50 and 52 extending around the nacelle 20 arranged in a single, substantially horizontal plane. That substantially horizontal plane will typically be arranged substantially parallel to the rotor 8, which is often inclined at an angle of about four degrees relative to ground. The substantially horizontal plane may also be angled upward or downward in a wide range from be from about negative ten to positive ten degrees, and a narrower range of about one to five degrees.
The flanges 50 and 52 may extend outward (as shown in these Figures) or inward into the nacelle 20. While such outwardly-extending flanges 50 and 52 generally enhance stackability, inwardly-extending flanges help to provide a smooth outer surface at the joint between the first and second pieces 32 and 42. The outwardly-extending flanges 50 and 52 are tapered or otherwise angled in order to deflect rain, and/or other precipitation, from the seal between the flanges. For example, the flanges 50 and 52 may be angled in the same generally downward direction when joined together. Alternatively, the exposed top surface of the (upper) flange 50 may be angled downward and/or both surfaces of the joined flanges 50 and 52 may be angled in opposite directions so as achieve a pointed taper configuration. An appropriate seal or sealant may be provided between the flanges 50 and 52. Alternatively, a flangeless and/or seal-less interface may also be used.
A fastener 54 may be provided for securing the first flange 50 to the second flange 52. For example, the fastener 54 may include a bolt and nut that fit through corresponding holes in the flanges 50 and 52 as illustrated in
In the examples illustrated here, each of the first and second pieces 32 and 42 is provided with a semicircular side opening 60 in the corresponding side walls 36 and 46 for accommodating the rotor 8 extending from the nacelle 30. In this configuration, the seam-line or joint between the two flanges 50 and 52 can be arranged to fall roughly midway between the top and bottom walls 24 and 44 and/or substantially parallel to the rotor 8, top wall 34, or ground, further aiding the ease of assembly the nacelle 30 around the rotor 8. However, a variety of configurations for the side opening 60 may also be provide for allowing the rotor 8 to extend from the nacelle 30. In addition, each of the first and second pieces 32 and 42 is provided with rounded corners where the top wall 34 and bottom wall 44 join respective side walls 36 and 46.
As illustrated in
The technology discussed above offer various advantages over conventional approaches. For example, the stackable nacelle 30 is a relatively simple assembly of two (or more) pieces with tapered walls which facilitate easy stacking for low-cost transportation and storage of multiple units and/or components thereof.
It should be emphasized that the embodiments described above, and particularly any “preferred” embodiments, are merely examples of various implementations that have been set forth here to provide a clear understanding of various aspects of this technology. It will be possible to alter many of these embodiments without substantially departing from scope of protection defined solely by the proper construction of the following claims.
