Abstract:
A wind turbine and method for assembling a wind turbine is provided. The wind turbine is configured to stand on a foundation, and the wind turbine assembly includes a tower and an elevated tower foundation. The elevated tower foundation has multiple support members having a plurality of main support members and a plurality of bracing members. The bracing members are connected to the main support members. The tower is mounted on the elevated tower foundation.

Description:
FIELD OF THE INVENTION 
       [0001]    The field of this disclosure relates generally to wind turbines, and more particularly to a tower for a wind turbine. 
       BACKGROUND OF THE INVENTION 
       [0002]    Wind turbines are increasingly used for the generation of electrical energy. A wind turbine typically comprises a rotor-driven turbine generator mounted atop a tower constructed of multiple tower sections that are stacked and secured together. These sections may be cylindrical, frusto-conical or other suitable shape, and may be generally solid, tubular, or lattice-type sections. For example, one conventional wind turbine assembly includes a tower in which multiple tower sections each comprise a single-piece cylindrical or frusto-conical steel section. These sections are joined together to reach above ground a height sufficient to provide clearance for the turbine blades and to support the generator at an altitude where there are sufficient wind velocities for adequate power generation. Many towers for utility grade wind turbines are about 80 meters in height. 
         [0003]    The lowermost tower section (often referred to as a base section) of the wind turbine assembly tower is secured to the foundation (e.g., a concrete slab or other suitable foundation). The diameter of each tower section, and in particular the base section must be large enough in cross-section (e.g., diameter) to withstand the aerodynamic loads produced by wind forces and gravitational loads that are imposed by the mass of the heavy turbine generator and the drive sections of the turbine. As wind turbine towers have become increasingly taller, the cross-sectional dimensions of the tower base section has created difficulties in the ground transportation (e.g., by truck or rail) of these base sections due to size limitations or roadways, bridges and tunnels through which these sections must pass in route to their assembly destination. For example, if the diameter of the tower is greater than 4.3 meters, difficulty may be encountered during ground transport. Manufacturing difficulties can also arise when the thickness of the tower wall is greater than about 40 mm (e.g., problems with steel plate rolling and accurately obtaining plate gap tolerance). 
         [0004]    Wind turbine tower manufacturers have had to use other means, such as increasing the shell thicknesses of the sections or using guy wires, to hold smaller cross-sectioned towers in place and support the tower against the aerodynamic and structural loads encountered by the tower. While these measures have been helpful, they have their limits and have not sufficiently met the need for a wind turbine tower of greater height that is also capable of ground transport. It has been heretofore un-economical to construct and transport towers greater than about 80 to about 100 meters in height. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0005]    In one aspect of the present invention, a wind turbine assembly is provided and configured to stand on a foundation. The wind turbine assembly includes a tower and an elevated tower foundation. The elevated tower foundation has multiple support members having a plurality of main support members and a plurality of bracing members. The bracing members are connected to the main support members. The tower is mounted on the elevated tower foundation. 
         [0006]    In another aspect of the present invention, a method of fabricating a wind turbine tower includes the steps of shipping tower components to a wind turbine location. At least some of the tower components are shipped in an un-assembled state. The next step includes assembling the tower components to form an upper tower portion and a lower tower portion. A placing step places the lower tower portion on one or more foundation elements. A subsequent step includes placing the upper tower portion on the lower tower portion. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a schematic elevation of one embodiment of a wind turbine assembly mounted on a foundation by a tower mount. 
           [0008]      FIG. 2  is a perspective view of one embodiment of the tower mount of the wind turbine assembly of  FIG. 1 ; 
           [0009]      FIG. 3  is a perspective view of one embodiment of an elevated tower foundation that can be used with a conventional wind turbine tower. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0010]    Referring now to the drawings and in particular to  FIG. 1 , one known wind turbine is indicated generally at  100 . In this embodiment, wind turbine assembly  100  comprises a horizontal axis  114  wind turbine. Alternatively, wind turbine assembly  100  may comprise a vertical axis wind turbine. Wind turbine assembly  100  generally comprises a tower  102  standing upright on a suitable foundation  104  (e.g., a concrete slab, ground surface or other suitable foundation), and a wind turbine generator, generally indicated at  105 . Wind turbine generator  105  generally comprises a nacelle  106  mounted on tower  102 , and a rotor  108  coupled to nacelle  106 . Rotor  108  has a rotatable hub  110  and a plurality of rotor blades  112  coupled to hub  110 . Illustrated rotor  108  comprises three rotor blades  112 . Alternatively, rotor  108  may have more or less than three rotor blades  112 . Blades  112  are positioned about rotor hub  110  to facilitate rotating rotor  108  to transfer kinetic energy from the wind into usable mechanical energy, and subsequently, electrical energy. Blades  112  are mated to hub  110  by coupling a blade root portion  120  to hub  110  at a plurality of load transfer regions  122 . Load transfer regions  122  have a hub load transfer region and a blade load transfer region (both not shown in  FIG. 1 ). Loads induced in blades  112  are transferred to hub  110  via load transfer regions  122 . 
         [0011]    Tower  102  is tubular, and in the illustrated embodiment it is annular and has an internal cavity (not shown) extending longitudinally within tower  102  from foundation  104  up to nacelle  106 . Tower  102  generally comprises a plurality of individual tower sections  124  that are connectable to each other in a stacked, end-to-end (e.g., one on top of the other) relationship to form tower  102 . Tower sections  124  may each be of generally constant transverse cross-sectional dimension (e.g., a constant diameter in the illustrated embodiment in which tower sections  124  are each generally annular), or one or more of tower sections  124  may be frusto-conical, and/or the transverse cross-sectional dimension of one or more of tower sections  124  may be constant but different from that of one or more of the other tower sections—such as in a stepped configuration in which the transverse cross-sectional dimension of each tower section  124  decreases as the sections are stacked toward to the top of tower  102 . In addition, the present invention can be used with towers of many shapes, including but not limited to, tubular, cylindrical, conical, frusto-conical, frustum, elliptical and rectangular shaped towers. The present invention can also be used with towers constructed as lattices, free standing lattices, cantilevered pipe, tubular and guyed lattice or poles, as well as other suitable towers. In known towers, a highest height obtainable has been about 80 to 100 meters. 
         [0012]    As illustrated in  FIG. 1 , a known tower mount  127  is seated on and suitably secured to foundation  104  for supporting tower  102 . The tower mount  127  can also be referred to as a foundation mounting piece (FMP). The tower can be bolted to the FMP directly. However, towers mounted on a FMP can add cost and result in more expensive wind turbines. Alternatively, a wind turbine tower can be attached directly to the base, and this type of mount can be referred to as an anchor type design. In the anchor type the tower base is bolted to the concrete base/foundation using anchor bolts. 
         [0013]    With particular reference to  FIG. 2 , tower mount  127  is generally tubular in the manner of tower sections  124 , and in the illustrated embodiment it is generally annular, and has an upper end  210 , a lower end  220  (shown in  FIG. 2 ) and a circumferential sidewall  230  (shown in  FIG. 2 ) extending therebetween. The terms upper and lower are used herein with reference to the orientation of tower  102  as illustrated in  FIG. 1 . Lower end  220  is suitably configured for use in securing tower mount  127  to foundation  104 . 
         [0014]    It would be advantageous if a higher tower could be designed to take advantage of higher mean wind speeds at higher elevations. An improved tower is herein described that can be used alone or in conjunction with known wind turbine towers to obtain wind turbine towers of about 120 to about 150 meters or more in height. In addition, the present invention can be used with towers that are fastened to foundation mounting pieces or towers incorporating the aforementioned anchor type design. 
         [0015]      FIG. 3  illustrates a perspective view of an improved wind turbine tower assembly according to aspects of the present invention. In this embodiment a conventional tower  102  having multiple sections  124  may be used, although not required, with elevated foundation  300 . The elevated foundation can be comprised of tower mount or tower flange  310 , pole supports  320 , foundation supports  330  and bracing members  340 . 
         [0016]    Elevated foundation may be configured to have a height of about 20 to about 60 meters or more. Heights below or above this range are also possible, and the specific height is guided by location specific requirements. A conventional 80 to 100 meter tower  102 , which is a tubular wind tower structure, can be mounted to the elevated foundation  300  via tower mount  310 . The elevated foundation  300  can be fabricated from seamless or fabricated pipes or tubes and/or I-beams (or other beams), and may incorporate intervening bracing members  340  (e.g., stiffeners and cross-members) for better rigidity. 
         [0017]    The tower mount  310  may comprise one or more elements and can be configured similar to the tower mount  127  shown in  FIG. 2 . The tower  102  can be bolted an/or welded to tower mount  310 . 
         [0018]    The pole supports  320  can be made from seamless pipes that can be directly shipped to wind turbine sites and can be welded and assembled on-site. In this manner, a large tower foundation  300  may be easily shipped to remote wind turbine sites, thereby avoiding logistical and transportation issues. Once the elevated foundation  300  is installed at the site then a conventional tower  102  can be fastened (e.g., bolted) to the tower mount  310 . 
         [0019]    Foundation supports  330  may comprise reinforced concrete or other suitable material. One foundation support is shown under each pole support  320 , however, it is to be understood that one or more foundation supports could be used. For example, a single foundation support or reinforced concrete could be configured to support all the pole supports  320 . 
         [0020]    The bracing members  340  provide rigidity and stiffness between pole supports  320 . The bracing members can be easily attached to the pole supports with fasteners and/or welding. For the sake of clarity, only a few bracing members  340  are shown, however, it is to be understood that one or more bracing members  340  may connect some or all of pole supports  320 . 
         [0021]    According to one aspect of the present invention, pole supports may be constructed from seamless pipes of about 30 meters in length and about 1 to 2 meters in diameter. The pipes can be welded gas metal arc welding (GMAW), pulsed GMAW, shielded metal arc welding (SMAW), flux cored arc welding, or any other suitable automatic or manual welding processes. The bracing members may be attached to the pole supports using any of the above welding techniques or via any suitable fastener. 
         [0022]    The present invention provides many advantages which include, but are not limited to, use of conventional wind turbine towers on elevated foundation, ease of transportation of tower components, reduced cost of materials and ease of assembly. 
         [0023]    When introducing elements of the present invention or preferred embodiments thereof, the articles “a”, “an”, “the”, and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including”, and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. 
         [0024]    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 languages of the claims. 
         [0025]    As various changes could be made in the above constructions and methods without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.