Abstract:
A pile based braced caisson structural support device includes a number of legs in is used to support a wind turbine. The wind turbine includes a base, a turbine generator and a blade mechanism. The legs are configured in a teepee type configuration such that the footprint of the base is larger than the footprint of the opposing end. This structural support can be used as a base for an offshore platform in that the support reduces the lateral forces on the support caused by wave action.

Description:
[0001]     This application claims priority to U.S. Provisional Application No. 60/626,912, filed on Nov. 12, 2004, which is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     This invention generally relates to structural supports. In particular, this invention relates to structural supports for, for example, wind turbines, or the like.  
         [0004]     2. Description of Related Art  
         [0005]     Conventional offshore platforms have deck legs that are vertical or are battered outward as they extend downwards. The conventional arrangement provides structurally efficient support for the deck but the associated dimensions of the platform at the water surface result in increased expense for the platform.  
         [0006]     Wind turbines have traditionally been supported on mono-piles when placed offshore. However, recently, efforts have taken place to position wind turbines in deeper water (approximately six to seven or more miles offshore) in part to increase the aesthetics of the view from the shoreline. However, with the movement of wind turbines further offshore, the employment of mono-piles as the base on which wind turbines are placed has become less cost effective.  
       SUMMARY OF THE INVENTION  
       [0007]     Accordingly, the present invention is directed to a wind turbine in combination with a structure support that provides a sturdy and cost effective support even in deep waters. This combination includes a wind turbine comprising a base and a blade mechanism. The structure support further includes at least three elements configured in a substantially teepee shaped configuration, where the at least three elements encompassing a substantially vertical member. A first end of the at least three elements is capable of being affixed to a structure and a second end of the at least three elements adapted to be in contact with a surface. The at least three elements intersect between the first end and the second end. The combination also includes a mounting flange connecting the structure support to the wind turbine.  
         [0008]     In accordance with a further embodiment of the present invention the at least three elements intersect above a waterline or at a waterline.  
         [0009]     In accordance with another exemplary aspect of the present invention, a method of constructing a wind turbine on a structure support is disclosed. At least three legs are provided in a teepee configuration. A first end of the first three legs are placed on a mounting surface and a deck is affixed to a second end of the at least three legs. A wind turbine mounting flange is affixed to the structure and a base is affixed to the mounting frame and turbine element is affixed to the base. A blade mechanism affixed to the turbine element.  
         [0010]     These and other features and advantages of this invention are described in or are apparent from the following detailed description of the embodiments. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     The embodiments of the invention will be described in detail, with reference to the following figures, wherein:  
         [0012]      FIG. 1  is a view in side elevation of an offshore platform according to the present invention;  
         [0013]      FIG. 2  is a view in front elevation of the offshore platform according to the present invention;  
         [0014]      FIG. 3  is a perspective view of the offshore platform with a wind turbine placed on a deck of the platform according to the present invention;  
         [0015]      FIG. 4  is a side perspective view of the offshore platform with a wind turbine placed on the deck of the platform according to the present invention;  
         [0016]      FIGS. 5-18  illustrate an exemplary method of assembling the offshore structure and wind turbine according to this invention;  
         [0017]      FIGS. 19-21  illustrate another exemplary method of assembling the offshore structure and wind turbine according to this invention;  
         [0018]      FIGS. 22 and 23  illustrate another exemplary offshore structure support foundation according to this invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]     The exemplary embodiments of this invention will be described in relation to a support structure, such as an oil and gas platform or a platform for the placement of additional structures, supported by three piles and a central vertical member, such as drill pipe. However, to avoid unnecessarily obscuring the present invention, the following description omits well-known structures and devices that may be shown in block diagram form or otherwise summarized. For the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It should be appreciated that the present invention may be practiced in a variety of ways beyond these specific details. For example, the systems and methods of this invention can be generally expanded and applied to support any type of structure. Furthermore, while exemplary distances and scales are shown in the figures, it is to be appreciated the systems and methods of this invention can be varied to fit any particular implementation.  
         [0020]      FIGS. 1 and 2  show an inward battered guide offshore platform indicated generally at  10  in which battered bracing piles  12   a ,  12   c  and  12   e  are arranged so as to minimize platform dimensions at the water surface  14  while maximizing the spacing of the piles as they extend upward from the water surface so that loads from a deck  16  at the top of the piles are transferred directly to the piling. For example, if three or more piles are employed to create the structure, they could be spaced apart 120 degrees. Piles  12   b  and  12   d  are conductor piles used in oil and gas platforms.  
         [0021]     The platform includes a pile guide structure  18  which fits over and is connected to a central vertical member  20  to receive the piles  12   a ,  12   c  and  12   e  at the water surface. The piles extend angularly through guides  22  of the pile guide structure in such a manner that the distance between piles is minimized at the water surface, but the distances between angled piles is maximized both at the ends supporting the deck  16  as well as at the opposed end buried below the mudline  24 . The pile guide connects the piles to act in unison to restrain lateral movement of the entire offshore platform  10  including the central vertical member  20 .  
         [0022]     The pile guide  18  also supports appurtenances such as ladders, boat landings, stairs, or the like, so that they can be installed in the field as a unit, thereby, for example, reducing installation expense for the platform. The legs  26  of the deck structure are connected to the tops of the piles. The increased pile spacing at the pile tops provides, for example, more structurally efficient support for the deck, reduced structural vibration periods for the platform and increased resistance to the rotation that results if the deck mass is eccentric to the central vertical member  20  than if the deck is supported by the central member. All field connections can be made above the water surface where structural integrity of the connections can be more easily verified than if the connections were made below the water surface.  
         [0023]     Once the piles  12   a ,  12   c  and  12   e  are in place, and the legs  26  and deck  16  are placed on the piles then, as shown in  FIGS. 3 and 4 , a wind turbine  100  can be installed.  FIGS. 3 and 4  show two different perspective views of the wind turbine  100  when installed on the deck  16  of platform  10 . The wind turbine  100  comprises: a base  125  including a lower section  110  and an upper section  120 ; a turbine element  130 ; and a blade mechanism  150  that comprises a rotor star  152  and individual blades  154 . While the wind turbine described herein comprises a base  125  and three individual blades  154 , other types of wind turbines can also be employed with the structure of  FIG. 1 , for example, in the manner described above. For example, a wind turbine with a single base part or having a multitude of parts that make up the base can be employed. Moreover, the wind turbine can also include more or a lesser number of blades as well as different types of blade mechanisms.  
         [0024]      FIGS. 5-19  illustrate an exemplary method for assembling a the platform  10  and wind turbine  100  in accordance with an exemplary embodiment of this invention with, for example, a barge boat, around a substantially vertical member  20  such as SSC  50  (Self Sustaining Caisson). In this exemplary embodiment, the SSC  50  has been installed by an oil and gas drilling rig, such as a rig drilling an exploration well. The vertical member  20  (SSC  50 ) can either be installed when the platform is assembled or alternately, the remaining parts of the platform can be assembled around a previously erected vertical member. This enables the platform to be advantageously built on existing already used oil drill caissons or mono-piles to support oil and gas wells.  
         [0025]     In  FIG. 5 , the position and orientation of the legs are determined and a lift boat  55  anchored and jacked-up relative to the installation point of the SSC  50 . Next, as illustrated in  FIG. 6 , the guide structure  18  is unloaded from the barge  60 . Then, as illustrated in  FIG. 7 , the piles  12   a ,  12   c  and  12   e , are unloaded, placed in the guide structure, and in  FIG. 8 , installed via the guide structure into, for example, the ocean floor with the aid of a pile driving hammer (e.g., a hydraulic hammer). As can be seen from this illustration, the piles  12   a ,  12   c  and  12   e  intersect at a point just above the water line. This allows, for example, the piles and all associated connections to be made above water. However, one would also understand that the intersection point could also reside at or below the waterline.  
         [0026]     In  FIG. 9 , the barge  60  is relocated and the deck  16  is unloaded. In  FIG. 10  the deck  16  including legs  26  are installed on the piles. In accordance with an exemplary embodiment of the invention, the deck can be modified to employ and support a wind turbine  100 . Specifically to support the turbine a mounted flange can be built on the deck  16 . The flange can be attached to the deck via bolting, grouting or welding. Although as illustrated in  FIG. 10 , the mounting flange  200  is shown being attached to the deck prior to placement on the legs  26 , the mounting flange  200  could be installed after the deck has been installed.  FIGS. 11 and 12  provide a side view and top view of the deck  16  and mounting flange  200  when installed.  
         [0027]     As illustrated in  FIG. 13 , once the mounting flange  200  is placed and set onto the deck  16 , the tower lower section  110  is unloaded from the lift boat  55  and installed onto the mounting frame  200 . Next, as illustrated in  FIG. 14 , the upper section  120  of the tower is unloaded and installed onto the tower lower section  110 . Once the upper section  120  of the base has been installed, as illustrated in  FIGS. 15 and 16 , the turbine  130  is removed from the lift boat and attached to the upper section  120  of the tower.  
         [0028]     As the tower lower section  110 , tower upper section  120  and turbine  130  are installed, the blade mechanism  150  is readied for installation. The installation of this part of the wind turbine  100  can be performed in a plurality of different ways, in accordance with the present invention, as discussed below.  
         [0029]     In accordance with one exemplary embodiment of the present invention, as illustrated in  FIGS. 17 and 18 , the complete, blade mechanism already fully assembled is unloaded from the lift boat  55  and attached to the turbine  130 .  
         [0030]     Alternatively, as illustrated in  FIGS. 19-21 , the blade mechanism does not need to be fully assembled prior to attachment to the turbine  130 . This is advantageous for several different reasons. The blade mechanism, if fully assembled would require extra stowage area for transport to the assembly area. If, for example, only two of the blades were assembled, then to the rotor star, then the required space needed to transport the blade mechanism is reduced. Furthermore, if the remaining blade is not attached to the rotor star until it is already attached to the turbine, additional monetary savings can be achieved since the crane employed to attach the blade can be smaller. In  FIG. 19 , the blade mechanism having the two blades attached to the rotor star is raised (via a crane) and attached to the turbine (as illustrated in FIG.  20 ). Finally, in  FIG. 21 , the remaining blade  158  is attached to the rotor star. Again,  FIGS. 3 and 4  provide a side views of the assembled wind turbine on the offshore structure support  10 .  
         [0031]     In accordance with another exemplary aspect of the present invention, a deck and associated mounting flange  300  is provided to receive a wind turbine, as illustrated in  FIGS. 22 and 23 . Specifically, the mounting flange  300  includes a body  310  and an elliptical (or spherical) head  320  extending below deck  16 . The body  310  is circular and includes a deck end  312  and a head end  314  portion. A wind turbine  100  is able to be attached to the foundation body  310  at the deck end  312  of the foundation body, via bolting, for example. The foundation body  310  is also able to receive legs  26  that are connected to the batter bracing piles  12   a ,  12   c  and  12   e . Note that four piles are illustrated in  FIG. 22 .  
         [0032]     The elliptical (or spherical) head  320  is attached to the foundation body  310  at its deck leg connection end and enables the turbine foundation  300  a more fatigue resistant connection at the deck leg. For this same reason, as illustrated in  FIG. 22 , the ends of the legs  26  also employ a curved surface. By making the intersection between the foundation body  310  and the elliptical (or spherical) head  320  as well as foundation body  310  and the elliptical shape of the legs  26 , a continuously curved intersection is provide and a sharp corner is avoided. As a result, hot spot stresses are reduced on the joints.  
         [0033]     Additionally in accordance with the present embodiment discussed with regard to  FIGS. 22 and 23 , the deck  16  includes structural support elements extending from the deck end of the turbine foundation to the edge of the deck  16 . While the deck  16  in the embodiment shown in  FIG. 23  is illustrated as octagonal, one could understand that the deck could be made to be other shapes also, (e.g., hexagonal, rectangular, circular, or the like).  
         [0034]     In accordance with another aspect of the present invention, the natural period of the offshore support structure can be adjusted to avoid the excessive vibration of the wind turbine while operating that would result if the natural period of the support structure was too close to matching the rotational period of the turbine. This tuning of the natural period can be accomplished by changing the size of the components of the support structure, by increasing or decreasing the batter of the piles, adjusting the spacing of the piles and/or by raising or lowering the elevations where the piles are laterally supported. The extent and combination of tuning measures required vary depending on the design and operational characteristics of the wind turbine and the water depth, meteorological and oceanographic conditions and soil characteristics at the location.  
         [0035]     For example, a typical three blade wind turbine is controlled by adjusting blade pitch to make one rotation about every 4.5 seconds in most wind conditions. Therefore, for a typical wind turbine one of the three blades would than pass the wind turbine support tower every 1.5 seconds. To avoid the wind turbine rotational periods and limit potential for destructive resonance, frequency forbidden zones are established for the natural frequency of the entire support structure. For a typical wind turbine the forbidden natural frequency zones could be 0.18 Hz to 0.28 Hz and 0.50 Hz to 0.80 Hz. Likewise, the target natural frequency would be 0.30 Hz to 0.33 Hz and higher order natural frequencies should be above 0.80 Hz. If computed eignfrequencies are in a forbidden zone tuning will be necessary. Tuning can then be accomplished in the manner discussed above.  
         [0036]     It is, therefore, apparent that there has been provided, in accordance with the present invention, a support and method for assembling a wind turbine for placement on an offshore support structure. While this invention has been described in conjunction with a number of illustrative embodiments, it is evident that many alternatives, modifications, and variations would be or are apparent to those of ordinary skill in the applicable arts. Accordingly, the disclosure is intended to embrace all such alternatives, modifications, equivalents and variations that are within in the spirit and scope of this invention.