WO2010057187A2 - Tower construct suitable for wind turbines along with methods for fabricating and erecting the same - Google Patents

Abstract

A tower construction comprising at least one tower section including a plurality of panel segments attached to each other in a cruciform configuration. Each panel includes a surrounding frame that supports a fill material, which is preferably cast into the frame. Preferably the fill material is a reinforced concrete. A surrounding shell is disposed about each tower section. The shell includes a plurality of support rings that are attached to the tower section. A plurality of fencing panels are attached to the support rings to enclose the tower section, thereby protecting the panels from the elements.

Description

TOWER CONSTRUCT SUITABLE FOR WIND TURBINES ALONG WITH METHODS FOR FABRICATING AND ERECTING THE SAME

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of U.S. Provisional Application Serial No. 61/115,416, filed on November 17, 2008, the disclosure of which is hereby incorporated by reference in its entirety.

BACKGROUND

Renewable energy resources, such as wind and solar power continue to gain popularity around the World. For instance, the United States currently has an overall wind generating capacity of over 21,000 MW of electricity. The popularity of wind power appears to be a growing trend. According to the American Wind Energy Association's estimates, in 2007 alone, wind generating capacity increased in the U.S. by 45%. It is also estimated that American wind farms will generate an estimated 49 billion kilowatt-hours of wind energy in 2008, which is about 1.5 % of the U.S. electricity supply, powering the equivalent of over 5.7 million homes.

Wind power depends on the strength and consistency of the wind impinging upon a wind turbine's rotor blades. As wind travels close to the ground friction between the air and surface of the Earth, known as wind shear, slows the speed of the wind, robbing it of some of its power. As height increases, the effects of wind shear lessen. The height of a wind turbine's tower is thus an important factor in maximizing the power output of a particular wind turbine. The taller the turbine tower, the more powerful the wind impinging on the rotor blades. Accordingly, there has been a trend towards taller and taller turbine towers. Over the years tower heights have grown from 24 meters to over 100 meters. Tower height, however, must be tailored to the specific terrain and requirements of a particular site. As the heights of turbine towers increase so does the cost of their construction. As a consequence, the cost of taller towers must be justified by a corresponding increase in turbine output due to less wind shear at the greater heights.

There are at least three types of tower structures traditionally used for supporting a wind turbine: lattice, conical steel, and concrete towers. Each style has its own advantages and disadvantages. A lattice tower is generally less expensive and most often used for smaller turbines. Also, lattice towers are thought by some to be less aesthetically pleasing when compared to tubular towers. Steel conical towers, while more aesthetically pleasing, are also more expensive than lattice constructions. Furthermore, as tower heights grow ever higher the base diameter of a conical tower will typically increases as well. As such, prefabricated steel towers may already be reaching their height limits because the required corresponding base diameter is difficult, if not impossible, to transport and therefore expensive to transport to the installation site from the fabrication facility. Specifically, bridge height limits the diameter of a tower section that may be transported by roadway. Concrete towers have the advantage of being formed in place at the installation site so that transport is of less concern. Concrete also has the advantage of high weight capacity and being more effective at absorbing vibrations inherent with turbine rotor dynamics when compared to other structures. However, with current construction techniques concrete towers are typically more expensive overall because they are generally formed with curved or circular sections.

While it is believed that current tower structures adequately meet the intended scope of their design, there still exists a need for improved turbine towers, tower structures generally, and tower construction methods. There is a need for tower structures that have the aesthetics of tubular towers, the structural characteristics of concrete, and the ability to reach the heights necessary for modern wind turbine applications. Furthermore, there is a need for tower structures and methods of construction that provide a relatively inexpensive tower that can be constructed on-site.

SUMMARY

Provided herein is a tower construction comprising at least one tower section including a plurality of panel segments attached to each other in a cruciform configuration. Each panel includes a surrounding frame that supports a fill material, which is preferably cast into the frame. Preferably the fill material is a reinforced concrete. A surrounding shell is disposed about each tower section. The shell includes a plurality of support rings that are attached to the tower section. A plurality of fencing panels are attached to the support rings to enclose the tower section, thereby protecting the panels from the elements.

These and other objects of the present application will become more readily appreciated and understood from a consideration of the following detailed description of the exemplary embodiments when taken together with the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a wind turbine incorporating a support tower according to a first exemplary embodiment;

FIG. 2 is a side view in elevation of the tower shown in FIG. 1 with the outer shell removed;

FIG. 3 is a top plan view of the tower shown in FIG. 2;

FIG 4 is an exploded perspective view of one of the sections comprising the tower shown in FIG. 2;

FIG. 5 is an enlarged exploded perspective view of the tower section shown in FIG. 4 illustrating the interlocking of the panel segments; FIG. 6 A is an enlarged perspective view of an alternate construction of the panels shown in FIG. 5, illustrating panel post-tensioning members;

FIG. 6B is an enlarged partial perspective view of yet another alternate construction of the panels shown in FIG. 5 illustrating a tower post-tensioning member;

FIG. 7 A is an enlarged exploded perspective view of a tower section according to an exemplary embodiment;

FIG. 7B is an enlarged exploded perspective view of a tower section according to another exemplary embodiment;

FIG. 8 is a perspective view of a portion of female framing member;

FIG. 9 is a partial cross-section of a male panel segment;

FIG. 10 is a partial cross-section of a female panel segment;

FIG. 11 is a partial perspective view of a tower section with the shell panels removed, illustrating the attachment of the shell support structures;

FIG. 12 is a partial perspective view of a tower section with shell panels installed;

FIG. 13 is a partial exploded perspective view of an exemplary flange mount for a wind turbine nacelle;

FIG. 14 is a partial perspective view of the shell assembly;

FIG. 15 is an enlarged partial perspective view of the shell assembly, as viewed from inside the shell, and particularly illustrating the attachment of a shell panel;

FIG. 16 is an enlarged partial perspective view of the shell assembly, as viewed from outside the shell, and illustrating the attachment of a shell panel;

FIG. 17 is a cross-sectional view illustrating the profile of a shell panel;

FIG. 18 is an end view illustrating the profile of a male frame member; and FIG. 19 is an end view illustrating the profile of a female frame member.

DETAILED DESCRIPTION

In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which are shown, by way of illustration, specific embodiments for the contemplated tower construction. The embodiments illustrated by the figures are described in sufficient detail to enable those skilled in the art to practice the tower construction, and it is to be understood that other embodiments may be utilized and changes may be made without departing from the spirit and scope of the present disclosure. The following detailed description is, therefore, not to be taken in a limiting sense.

The tower construction described herein is particularly suited for use with wind turbines. FIG. 1 illustrates a wind turbine 10 incorporating an exemplary embodiment of a support tower. Tower 20 is supported by a concrete footing 16. Tower 20 in turn supports turbine nacelle 12, which includes rotor 14. It should be understood that while the tower construction disclosed herein is introduced with respect to use with wind turbines, the disclosed tower construction would also be suitable for other applications in which supporting a structure above a surface is required. Furthermore, an ordinarily skilled artisan will appreciate that while the tower shown includes three tower sections, different multiples and lengths of sections may be combined to produce towers of varying heights.

Tower 20 shown in FIG. 1 is shown in more detail in FIGS. 2 and 3. In these figures the outer shell of tower 20 has been removed in order to more clearly illustrate the construction of tower sections 22, 24, and 26. In this case each tower section is tapered upwardly from its bottom end towards its top-end. Alternatively, each subsequent section could be of a narrower width. Tapering or narrowing each section of the towers results in less mass at the top of the tower where it is narrower yet provides structural strength at the base of the tower. FIG. 3 is a top view of the tower illustrating the cruciform shape of the tower sections.

Referring now to FIG. 4, each tower section is comprised of two interlocking panel segments. Upper section 26 is preferably comprised of precast panels 30 and 32, which slidably engage one another in an interlocking fashion. As mentioned above, each panel is tapered. For instance, upper ends 33 and 37 of panels 30 and 32 respectively are the same width and narrower than lower ends 31 and 35.

With further reference to FIG. 5 the interlocking construction of section 26 may be better appreciated. Each panel includes a framework 40 comprised of frame members joined together. For instance, panel 30 includes frame 40 which is constructed from frame members, such as frame member 44 and 46. The frame members are joined together preferably by welding. The panel is cast with a fill material 50, such as concrete. It is contemplated that each panel, such as panels 30 and 32, are fabricated on-site thereby eliminating the need for transporting large tower sections. It is further contemplated that portable roll forming machines could produce frame members on-site. Alternatively, the frame members could be fabricated with the use of a press brake, for instance, which is well known in the art. The frame members could be formed in the various profiles and welded together into the desired frame configuration. Each panel could then be cast on-site using locally available concrete sources. Furthermore, each panel could be cast on top of the previously cast panel resulting in a stack of panels ready for assembly on site.

With continued reference to FIG. 5 it can be seen that panel 30, for instance, includes elongate channel 62 which extends from upper end 33 approximately midway to lower end 31. Similarly panel 32 includes elongate channel 64 extending from lower end 35 to approximately midway to upper end 37. When assembled, channels 64 and 62 engage bearing surfaces 63 and 65 respectively. Accordingly, an interlocking cruciform tower section is formed.

FIG. 6 A illustrates an alternative construction of a panel 130. Structural concrete is often post-stressed in order to isolate the concrete from any tensile load. As in the case of a tower, the concrete could potentially be exposed to tensile loads due to bending forces. In order to counteract potential tensile loads panel 130 includes panel tension members or tendons 152(1) and 152(2). Each tension member is either cast into the concrete or is inserted through a cavity formed into the concrete when cast. The tension members may be constructed of rod or cables with suitable fittings. Fasteners are applied on each end of the tensile member and tightened in order to compress the concrete between each end of the tension member. For instance, tension member 152(1) is fastened on each end by a threaded nut 151 and washer 153. Panel 130 may also include notches 160(1) - 160(4), which provide a relief area so that the ends of tension members 152 and the accompanying hardware 151 and 153 do not interfere with successive stacking of panels.

FIG. 6B illustrates another alternative construction of a panel 230. This figure shows a partial panel segment 230 of the lower tower section 222 supported by footing 216. While shown in the figure as a single cylindrical footing, footing 216 may be of any suitable foundation configuration as known in the art. For example, the footing maybe a cruciform shaped footing or a set of piers in a cruciform layout. In addition to panel tension member 252(1), this construction includes tower tension member 254(1), which when coupled to subsequent tower tension members, facilitates post-tensioning the entire tower as a single unit. Tower tension member 254(1) includes hook fitting 257(1) and loop fitting 259. Hook 257(1) engages loop 255 that is anchored to footing 216. It may be desirable to countersink loop 255 into footing 216 in order to facilitate assembly of the tower without damaging loop 255. Loop 259 receives hook 257(2) that is connected to the tension member 254(2), which is associated with the subsequent tower section. In this way each successive tower segment's tower tension member may be connected together. At the top of the highest tower section, for example, the tower tension members may be tightened using a suitable fastener (251, 253) such as shown with respect to panel tension member 252(1). Thus the entire tower may be tensioned as one unit. Furthermore, by utilizing loop 255 the tower is anchored to footing 216. While hook and loop fittings are provided here for illustrative purposes, other known cable and rod connecting devices may be employed, such as threaded sleeves, turnbuckles, and the like.

In an alternative embodiment as shown in FIG. 7 A, the cruciform tower construction may comprise a main panel 330 and two half size panels 332 and 334. Each panel includes a frame similar to that as described above with respect to FIGS. 1-6. For example, main panel 330 includes frame 340 cast with fill material 350. Similarly, panels 332 and 334 include frames 342 and 344, respectively. In this embodiment, the half size panels 332 and 334 are secured to the main panel 330. Preferably, the half size panels are welded to the main panel along edges of the frames. For instance, frame 344 includes frame member 345, which may be welded to frame member 341 of main panel 330. Half size panel 332 can be secured to main panel 330 in a similar manner. Alternatively, the main panel and half size panels may include attachment brackets that allow the tower to be assembled and disassembled with threaded fasteners, for example.

FIG. 7B illustrates another embodiment of the cruciform tower construction similar to that shown in FIG. 7 A. This embodiment comprises a main panel 430 and two half size panels 432 and 434. Half panels 432 and 434 may be attached to main panel 430, as explained above, by welding or bolting. In addition, this embodiment includes horizontal tension members 452(1) and 452(2) that extend through the half panels and main panel as shown. Tension members 452(1) and 452(2) are similar to those described above with respect to FIG. 6A, except that they run horizontally instead of vertically along the height of the tower. Notches or, recesses, 460(1)- 460(4) are formed on the outside edges of half panel frames 442 and 444 in order to provide clearance for tensioning hardware. Main panel 430 includes apertures 453(1) and 453(2) which allow tension members 452(1) and 452(2) to pass therethrough. It can be appreciated that, when tensioned, the half panels 432 and 434 are drawn tight against main panel 430 along frame member 441, thereby strengthening the assembly of the panels and post-stressing the concrete in halfpanels 432 and 434.

As described above with respect to FIG. 5 each panel includes a framework comprised of frame members. FIG. 8 shows a female frame member 46 having groove 60. FIG. 9 shows a cross-section of a panel having a male frame member 44. Tongue 61 of frame member 44 is sized and configured to engage groove 60. Referring briefly again to FIG. 5, it can be appreciated that not only do channels 62 and 64 interlock, the frame members of each panel also interlock via tongues and grooves on respective mating surfaces of the panels 30 and 32. Specifically, channels 62 and 64 are formed with male frame members 44 and bearing surfaces 65 and 63, on the other hand, are formed with female frame members 46.

FIG. 10 is a cross-section of a female frame member cast with fill material 50, in this case concrete. The fill material 50 may include reinforcements, such as wire mesh or rebar. In this case the material 50 is reinforced with rebar 53(1) and 53(2). Reinforcement 53 may also provide an anchor for tabs and angles (discussed below) that may be necessary for mounting tower sections together as well as mounting flanges for securing the tower to a footing or the turbine nacelle.

The tongue and groove configuration of the frame members provides for additional structural engagement and also acts as a guide for assembling mating panels together. Indeed, the tongue and groove arrangement allows for the panels to be assembled either in an upright orientation or a laying down orientation. Assembling the panels together in a laying down orientation may be advantageous in that a smaller, less expensive, crane may be used to handle the panels.

With reference to FIGS. 11 and 12, tower 20 may also include surrounding shell 71, which is comprised of a plurality of tapered fencing panels 70 attached to panel support rings 72. Each fencing panel 70 extends the entire height of the tower. Support rings 72 are in turn attached, to section 26 for instance, with standoffs or spacers 74. Here again, each ring 72 and each fencing panel 70 could be formed on-site with an appropriate roll forming machine. Alternatively, tapered panels 70 may be formed in sections utilizing a press brake. Also, a section curving machine could be employed to form the support rings from channel material. As an alternative to using spacers 74, the support rings may be attached directly to the panel segments with suitable fasteners, welding, or by engaging notches formed in the tongue of the male frame members. While shown here as circular, support rings 72 could be in the form of other rounded shapes, such as ovals, oblongs, and ellipses, to name a few. Providing tower 20 with a rounded outer shell provides an aesthetic and aerodynamic form. An elliptical support ring could be oriented with its minor axis transverse to the prevailing wind direction of a given turbine field, thus reducing the drag and stress on the tower. Also shown in FIG. 11 are various connectors contemplated for strengthening the joints between panels and successive tower sections. The frame members may be welded together where they interface, such as joint 38. Additional strength may be provided, however, with the addition of angle connectors 56, which may also be welded as mentioned above to the internal reinforcing structure 53. Similarly, tower sections may be joined together by welding along the seam formed by the panel frame members. Joint connectors 52 may also be used to strengthen such joints by attaching the inner structure 53 of each panel to the next panel. Also, angle connectors 54 may be used to provide mounting surfaces to attach a flange to the tower. Flanges may be used either to mount the turbine nacelle or to attach the tower to a concrete foundation or footing such as shown in FIG. 1.

FIG. 13 shows an exemplary flange mounting structure 90 that is attached to the upper tower section 26 as described above. In this case, mounting structure 90 comprises a concrete cylinder with interior 92. Alternatively, mounting structure 90 may be formed from steel pipe or rolled plating. Interior 92 advantageously provides access to the opening in the bottom of nacelle 12. Mounting structure 90 may also include an access port, or man-hole, 94 in order to facilitate convenient access to interior 92 and nacelle 12. In this example, nacelle 12 includes a flange 15 with a plurality of mounting holes disposed therearound. Mounting structure 90 may include a plurality of threaded studs that mate with the holes in flange 13. Accordingly, nacelle 12 may be bolted to mounting structure 90. With reference to FIG. 12, it can be appreciated that panels 70 could extend over mounting structure 90 up to the bottom of the turbine nacelle.

It can be appreciated that the dimensions of these towers result in a large exterior surface area. This surface area may optionally support photovoltaic solar collectors. For instance, as shown in FIG. 12, adhesive backed, thin film laminate photovoltaic collectors 79 could be adhered to panels 70 as they are formed in a roll forming machine. Because the wind turbine is already connected to the power grid, the addition of collectors 79 is relatively cost efficient. It may be desirable to only apply solar panels to areas on the tower that are exposed to direct sunlight. Which side would depend on the Sun's path through the sky for a particular part of the World. Suitable photovoltaic laminates are available from United Solar Ovonic, LLC of Auburn Hills, Michigan.

Referring to FIGS. 14 - 16 the attachment of panels 70 to support rings 72 may be better appreciated. Support rings 72 are generally in the form of a channel that is bent around a diameter that is sized to contain the cruciform interlocking sections. Bracket 73 is fastened to ring 72 and panel 70 with screws 55 and mating nuts 57. Screws 55 extend through slots 75 and 77 formed through panel 70 and support rings 72 respectively. Also, each panel may be joined to its adjacent panel by securing with fasteners through slots 75 or by clinching each panel to the next. Preferably, caulking is applied to each panel as it is assembled, in order to create a weather resistant barrier around the cruciform structure. Each support ring 72 may be formed as a continuous ring or may be formed in halves or sections. Furthermore, when erecting tower 20 each panel 70 may be installed individually after the tower is erected and support rings 72 are installed. Alternatively, shell halves or sections may be pre-assembled and hung from standoffs 74 or the panel segments directly. The shell sections could be pre-assembled in an assembly jig that receives each panel as it exits a roll forming machine, as mentioned above. A roll forming machine could roll each support ring, which would then be placed in the assembly jig. As each panel exits the roll forming machine, the jig could rotate the support rings so that each subsequent panel exits the roll forming machine onto the next available mounting position. FIG. 17 illustrates the profile of panel 70. In this case panel 70 is formed with an arcuate central portion 76 with legs 78 and 78' extending therefrom. Preferably, leg portions 78 and 78' extend along a line extending perpendicularly from the surface of arcuate central portion 76. Alternatively, central portion 76 could be straight. FIGS. 18 illustrates the profile of male frame member 44. Frame member 44 is generally symmetrical about center point 89. Tongue 61 extends into shoulder portion 81. Arm portion 83 extends from shoulder portion 81 laterally from tongue portion 61. Leg 87 extends from elbow 85 in a direction generally perpendicular to arm 83 and opposite tongue 61. Referring to FIG. 19 it can be seen that female frame member 46 is similar to male frame number 44 except that legs 88 extend in the opposite direction as compared to legs 87. Accordingly, tongue 61 and groove 60 are mateable with each other.

Accordingly, the tower construction has been described with some degree of particularity directed to the exemplary embodiments thereof. It should be appreciated that the contemplated tower construction is defined by the following claims construed in light of the prior art so that modifications or changes may be made to the exemplary embodiments of the tower construction without departing from the concepts contained herein.

Claims

I claim:

1. A tower construction, comprising: at least one tower section including a plurality of panel segments attached to each other in a cruciform configuration, each panel segment including a surrounding frame and a fill material cast therein; and a shell surrounding said tower section, said shell including a plurality of support rings attached to said tower section and a plurality of fencing panels attached to said plurality of support rings.