Cruciform floating offshore wind turbine platform

Abstract

A barge-type wind turbine platform that is capable of floating on a body of water and supporting a wind turbine includes a keystone. The keystone includes a steel tube concentrically mounted within the keystone, and a plurality of radially extending diaphragms that extend vertically between a lower wall of the keystone and an upper wall of the keystone, and extend radially between the steel tube and side walls of the keystone. A plurality of bottom beams are connected to the keystone and extend radially outwardly thereof, and the combined keystone and bottom beams define a foundation. A wind turbine tower is mounted to the keystone.

Description

[0001] TITLE

[0002] Cruciform Floating Offshore Wind Turbine Platform

[0003] BACKGROUND OF THE INVENTION

[0004]

[0001] This invention relates in general to floating platforms. In particular, this invention relates to embodiments of improved floating offshore wind turbine (FOWT) platforms that have a lower weight and are easier to manufacture and assemble than known FOWT platforms.

[0005]

[0002] Wind turbines for converting wind energy to electrical power are known and provide an alternative energy source for power companies. On land, large groups of wind turbines, often numbering in the hundreds of wind turbines, may be placed together in one geographic area. Siting these large groups of wind turbines may have limitations near dense population centers if they generate undesirably high levels of noise, or they may be viewed as aesthetically unpleasing. An optimum wind resource may not be available to these land-based wind turbines due to obstacles such as hills, woods, and buildings.

[0006]

[0003] Groups of wind turbines may also be located offshore, but near the coast at locations where water depths allow the wind turbines to be fixedly attached to a foundation on the seabed. Over the ocean, the flow of air to the wind turbines is not likely to be disturbed by the presence of various obstacles (i.e., as hills, woods, and buildings) resulting in higher mean wind speeds and more power. The foundations required to attach wind turbines to the seabed at these near-coast locations can be accomplished at relatively shallow depths, such as a depth of up to about 45 meters.

[0007]

[0004] The U.S. National Renewable Energy Laboratory has determined that winds off the U.S. Coastline over water having depths of 30 meters or greater have an energy capacity of about 3,200 TWh / yr. This is equivalent to about 90 percent of the total U.S. energy use of about 3,5OOTWh / yr. The majority of the offshore wind resource resides between 37 and 93 kilometers offshore where the water is over 60 meters deep. Fixed foundations for wind turbines in such deep water are not likely economically feasible. This limitation has led to the development of floating platforms for wind turbines. Known floating wind turbine platforms may be anchored to the seabed with mooring cables or lines and provide some stability to the tower and turbine against external loading from wind, waves, and current, as well as loading associated with the dynamics of the wind turbine mounted thereon.

[0005] Some known FOWT platforms may be formed from steel and are based on technology developed by the offshore oil and gas industry. Other known FOWT platforms may include components formed from pre-stressed or reinforced concrete, FRP, steel, or combinations of pre-stressed reinforced concrete, FRP, and steel. There remains however, a need to provide an improved FOWT platform particularly with the ever increasing size of potential wind turbines which have reached 15 to 30 MW.

[0008] SUMMARY OF THE INVENTION

[0009]

[0006] This application describes various embodiments of an improved FOWT platform. In particular, this invention relates to embodiments of improved FOWT platforms that have a lower weight and are easier to manufacture and assemble than known FOWT platforms.

[0010]

[0007] In one embodiment, a barge-type wind turbine platform that is capable of floating on a body of water and supporting a wind turbine includes a keystone. The keystone includes a steel tube concentrically mounted within the keystone, and a plurality of radially extending diaphragms that extend vertically between a lower wall of the keystone and an upper wall of the keystone, and extend radially between the steel tube and side walls of the keystone. A plurality of bottom beams are connected to the keystone and extend radially outwardly thereof, and the combined keystone and bottom beams define a foundation. A wind turbine tower is mounted to the keystone.

[0011]

[0008] In another embodiment, a barge-type wind turbine platform that is capable of floating on a body of water and supporting a wind turbine includes a keystone. The keystone includes a reinforced concrete bolt ring concentrically formed within the keystone, and a plurality of radially extending diaphragms that extend vertically between an intermediate horizontal wall of the keystone and an upper wall of the keystone, and extend radially between the reinforced concrete bolt ring and side walls of the keystone. A first pair bottom beams includes two bottom beams connected to opposite sides of the keystone. A second pair of bottom beams includes two bottom beams connected to opposite sides of the keystone, wherein the second pair of bottom beams has a longitudinal axis perpendicular to a longitudinal axis of the first pair of the bottom beams, the combined first and second pairs of bottom beams defining a foundation. A wind turbine tower has a circumferentially extending flange at a lower end thereof, and a transition member has a first circumferentially extending flange at an upper end thereof and a second circumferentially extending flange at a lower end thereof. The second circumferentially extending flange is connected to the reinforced concrete bolt ring, and the circumferentially extending flange of the wind turbine tower is connected to the first circumferentially extending flange of the transition member.

[0012]

[0009] In an additional embodiment, a method of assembling a barge-type wind turbine platform that is capable of floating on a body of water and supporting a wind turbine thereon includes: casting a base slab of a foundation, wherein the foundation includes a keystone and a plurality of bottom beams extending outwardly from the keystone; slip-forming vertical walls of the bottom beams and the keystone on the base slab; slip forming internal horizontal walls within the bottom beams and the keystone; casting a top slab of the foundation on the vertical walls of the bottom beams and the keystone over prepositioned precast panels; longitudinally and vertically post-tensioning the foundation; installing mechanical equipment in the foundation; and launching the foundation into a body of water.

[0010] In a further embodiment, a method of assembling a barge-type wind turbine platform that is capable of floating on a body of water and supporting a wind turbine thereon includes: forming a sub-assembly of a foundation, the subassembly comprising a first and a second bottom beam and a keystone; posttensioning the keystone and the first and second bottom beams; launching the subassembly into a body of water; adding ballast material to the sub-assembly; forming third and fourth bottom beams; launching the third and fourth bottom beams into the body of water; adding ballast material to the third and fourth bottom beams; attaching the third bottom beam to the sub-assembly; attaching the fourth bottom beam to the sub-assembly; and post-tensioning the third and fourth bottom beams to the keystone.

[0013] [Oil] In another embodiment, a wind turbine platform that is capable of floating on a body of water and supporting a wind turbine thereon includes a foundation. The foundation has three bottom beams extending radially from a keystone, three outer columns extending perpendicularly from the bottom beams at distal ends thereof, and a central column extending perpendicularly from the keystone. A circular heave plate is formed on a lower surface of each bottom beam at a distal end thereof, such that the heave plates extend outwardly therefrom.

[0012] Various advantages of the invention will become apparent to those skilled in the art from the following detailed description, when read in view of the accompanying drawings.

[0014] BRIEF DESCRIPTION OF THE DRAWINGS

[0015]

[0013] Fig. 1 is a perspective view of a first embodiment of an improved Floating Offshore Wind Turbine (FOWT) platform in accordance with this invention and shown with a wind turbine and wind turbine tower mounted thereon.

[0016]

[0014] Fig. 2 is a perspective view of the hull illustrated in Fig. 1 showing a first embodiment of the heave plates.

[0017]

[0015] Fig. 3 is a schematic perspective view of the hull illustrated in Figs. 1 and 2 showing a second embodiment of the heave plates.

[0018]

[0016] Fig. 4 is a side elevational view of the FOWT illustrated in Figs. 1 and 2.

[0019]

[0017] Fig. 5 is a front elevational view of the FOWT illustrated in Figs. 1, 2, and 4.

[0020]

[0018] Fig. 6 is a vertical cross-sectional view taken along the line 6 6 in

[0021] Fig. 2.

[0022]

[0019] Fig. 7 is a horizontal cross-sectional view taken along the line 7 - 7 in Fig. 6.

[0023]

[0020] Fig. 8 is a top plan view of the hull illustrated in Figs. 1 and 2.

[0024]

[0021] Fig. 9 is a vertical cross-sectional view taken along the line 9 - 9 in Fig.

[0025] 8 showing a first embodiment of a platform to tower connection.

[0026]

[0022] Fig. 10 is a cross-sectional elevational view of a portion of a second embodiment of the FOWT platform showing a second embodiment of a platform to tower connection.

[0023] Fig. 11 is a top plan view of the keystone and center column illustrated in Fig. 10.

[0027]

[0024] Fig. 12 is a horizontal cross sectional view take along the line 12 - 12 in Fig. 10.

[0028]

[0025] Fig. 13 is a cross sectional view take along the line 13 - 13 in Fig. 10.

[0029]

[0026] Fig. 14 is a perspective view of a first step of a first embodiment of a method of constructing a FOWT platform in accordance with this invention.

[0030]

[0027] Fig. 15 is a perspective view of a second step of the first embodiment of the method of constructing a FOWT platform in accordance with this invention.

[0031]

[0028] Fig. 16 is a perspective view of a third step of the first embodiment of the method of constructing a FOWT platform in accordance with this invention.

[0032]

[0029] Fig. 17 is a perspective view of a fourth step of the first embodiment of the method of constructing a FOWT platform in accordance with this invention.

[0033]

[0030] Fig. 18 is a perspective view of a first step of a second embodiment of a method of constructing a FOWT platform in accordance with this invention.

[0034]

[0031] Fig. 19 is perspective view of a second step of the second embodiment of the method of constructing a FOWT platform in accordance with this invention.

[0032] Fig. 20 is perspective view of a third step of the second embodiment of the method of constructing a FOWT platform in accordance with this invention.

[0035]

[0033] Fig. 21 is perspective view of a fourth step of the second embodiment of the method of constructing a FOWT platform in accordance with this invention.

[0036]

[0034] Fig. 22 is a top plan view of a third embodiment of a FOWT platform in accordance with this invention.

[0037]

[0035] Fig. 23 is an is a cross-sectional elevational view of a portion of a fourth embodiment of the FOWT platform. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0038]

[0036] The present invention will now be described with occasional reference to the illustrated embodiments of the invention. This invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein, nor in any order of preference. Rather, these embodiments are provided so that this disclosure will be more thorough, and will convey the scope of the invention to those skilled in the art.

[0039]

[0037] The embodiments of the invention disclosed below generally provide improvements to floating offshore wind turbine (FOWT) platforms that include, but are not limited to, reducing the complexity, overall weight, cost, simplifying the construction and assembly, and improving performance of the FOWT platform relative to known FOWT platforms.

[0040]

[0038] The embodiments of the improved FOWT platforms described and illustrated herein are suitable for a new generation of large wind turbines, such as commercial scale floating wind turbines with a power capacity within the range of about 15 MW to about 30 MW. The improved FOWT platforms described and illustrated herein may also be suitable for commercial scale floating wind turbines with a power capacity greater than about 30 MW and less than about 15 MW. Advantageously, the improved FOWT platforms described and illustrated herein may be manufactured at a lower cost relative to conventional, known FOWT platforms, and are easier to construct, assemble, and deploy than conventional, known FOWT platforms.

[0041]

[0039] Referring now to the drawings, particularly to Figs. 1, 2, 4, and 5, a first embodiment of an improved FOWT platform according to this invention is shown generally at 10.

[0040] The illustrated FOWT platform 10 includes a hull or foundation 12 that supports a wind turbine tower 14. The wind turbine tower 14 supports a wind turbine 16. The foundation 12 is a barge-type foundation, and is structured and configured to float in a body of water. Accordingly, a portion of the foundation 12 will be above water when the foundation 12 is floating in the water. Mooring lines (not shown) may be attached to the FOWT platform 10 and further attached to anchors (not shown) in the seabed to limit to movement of the FOWT platform 10 on the body of water.

[0042]

[0041] In the illustrated embodiment, the wind turbine tower 14 is tubular and may have any suitable outside diameter and height. In the illustrated embodiment, the outside diameter of the wind turbine tower 14 tapers from a first diameter at its base to a second, smaller diameter at its upper end. Alternatively, the outside diameter of the wind turbine tower 14 may have a uniform diameter. The wind turbine tower 14 may be formed from any desired material, including but not limited to steel, concrete, and fiber reinforced polymer (FRP) composite material. If desired, the wind turbine tower 14 may be formed in any number of sections 14 A, as shown in Figs. 4 and 5.

[0043]

[0042] The wind turbine 16 includes a hub 18. At least two rotor blades 20 are coupled to, and extends outward from, the hub 18. The hub 18 is rotatably coupled to an electric generator (not shown). The electric generator may be coupled via a transformer (not shown) and an underwater power cable (not shown) to a power grid (not shown). In the illustrated embodiment, the hub 18 has three rotor blades 20. In other embodiments, the hub 18 may have more or less than three rotor blades 20. The wind turbine 16 further includes a nacelle 21 opposite the hub 18.

[0043] Typically, a lower portion of the foundation 12 is submerged in a body of water. Accordingly, a portion of the foundation 12 will be above water when the foundation 12 is floating, semi- submerged, in the water, and a portion of the foundation 12 is also below the waterline. As used herein, the term waterline WL is defined as the approximate line where the surface of the water meets the FOWT platform 10.

[0044]

[0044] The illustrated foundation 12 may be formed from four bottom beams 22 that extend radially outwardly from a keystone 24 and provide buoyancy. When assembled together, the bottom beams 22 and the keystone 24 define the foundation 12 having a cruciform shape, i.e., having the shape of a cross. Additionally, the keystone 24 supports the tower 14. The tower 14 may be mounted to the keystone 24 via a transition member 26, configured, for example, as a steel tube, as shown in Fig. 10 and discussed below.

[0045]

[0045] If desired, a work platform 28 may be mounted near the base of the tower 14, and may include access-ways or catwalks 30 mounted around all or a portion of the base of the tower 14 and / or the work platform 28.

[0046]

[0046] In the embodiments illustrated herein, the wind turbine 16 is a horizontal-axis wind turbine. Alternatively, the wind turbine may be a vertical-axis wind turbine (not shown). The size of the wind turbine 16 will vary based on the wind conditions at the location where the FOWT platform 10 is anchored and the desired power output. For example, the wind turbine 16 may have an output of about 15 MW. Alternatively, the wind turbine 16 may have an output within the range of from about 15 MW to about 30 MW. Additionally, the wind turbine 16 may have an output of less than about 15 MW or more than about 30 MW.

[0047]

[0047] The illustrated keystone 24 is formed from both pre-stressed and / or conventionally reinforced concrete, and may include one or more internal cavities, described below. Any desired process may be used to manufacture the keystone 24, such as slip-forming or jump-forming, or with conventional concrete forms. Alternatively, other processes such as those used in the precast concrete industry may also be used. The concrete of the keystone 24 may be reinforced with any conventional reinforcement material, such as chopped fiber, steel reinforcing bar (rebar), and FRP rebar. Alternatively, the keystone 24 may be formed from high performance concrete, FRP, steel, or combinations of pre- stressed reinforced concrete, high performance concrete, FRP reinforcement, and steel.

[0048]

[0048] The illustrated bottom beams 22 are formed from pre-stressed and / or reinforced concrete as described above. Alternatively, the bottom beams 22 may be formed from high performance concrete, FRP, steel, or combinations of prestressed and reinforced concrete, high performance concrete, FRP, and steel. The bottom beams 22 may be formed to any desired length.

[0049]

[0049] The keystone 24 and each pair of opposing bottom beams 22 may then be assembled and post- tensioned longitudinally to define the foundation 12. The keystone 24 and the bottom beams 22 may be post-tensioned by any desired posttensioning method, thus applying a compressive force between the keystone 24 and the bottom beams 22.

[0050]

[0050] The foundation 12 may have any desired size. For example, in the illustrated embodiment, the length of a pair of bottom beams 22 when connected to the keystone 24 is about 75 m. The width of each bottom beam 22 is about 15.5 m, and the height of each bottom beam is about 16 m, wherein the foundation 12, when floating, has a draft within the rage of about 6 m to about 10 m.

[0051]

[0051] As best shown in Figs. 1 and 2, heave plates 32 may be formed on a lower surface of each bottom beam 22, such that the heave plates 32 extend outwardly from the side and end walls of each bottom beam 22 from a longitudinal mid-point thereof. The heave plates 32 may be formed from any of the materials used to form the bottom beams 22, as described above.

[0052] Alternatively, as shown in Fig. 3, the foundation 12A may include heave plates 34 formed on an entire perimeter of the lower surface of each bottom beam 22, such that the heave plates 34 extend outwardly from the side and end walls of each bottom beam 22. The illustrated heave plates 32 and 34 extend about 2 m outwardly from the side and end walls of each bottom beam 22. In other embodiments, the heave plates 32 and 34 may extend outwardly from the side and end walls of each bottom beam 22 a distance equal to about 10 percent to about 39 percent of the width of each bottom beam 22.

[0052]

[0053] Although each bottom beam 22 has the shape of a rectangular prism, it will be understood the distal ends of each bottom beam 22 may be rounded or arcuate, as shown in Fig. 22

[0053]

[0054] The pairs of bottom beams 22, including the keystone 24 connected therebetween, are generally hollow. The bottom beams 22 include a plurality of diaphragms or walls 36 that extend vertically between a lower base or slab 38 of the bottom beams 22 and an upper slab 40 of the bottom beams 22, and extend transversely between opposing side walls 42 of the bottom beams 22.

[0054]

[0055] As shown in Fig. 9, each bottom beam 22 may also have one or more longitudinally extending, horizontal diaphragms or walls 56 that may extend between any two or more of the keystone 24, the walls 36, the distal end of the bottom beam 22, or any portion of the bottom beam 22 between the keystone 24 and the distal end of the bottom beam 22. It will be understood that the longitudinally extending walls 56 are not required.

[0055]

[0056] As shown in Figs. 6 and 7, the walls 36 define hollow chambers 44 that may be filled or partially filled with fluid or ballast water, such as sea water. It will be understood that each such chamber 44 may include a valve and / or a pump (not shown) to selectively add and remove ballast water from each chamber 44.

[0057] The keystone 24 includes a steel tube 46 concentrically mounted within the keystone 24 and, depending on loading requirements, may include a plurality of radially extending diaphragms or walls 48 that extend vertically between a lower base or slab 50 of the keystone 24 and an upper slab 52 of the keystone 24, and extend radially between the steel tube 46 and the side walls of the keystone 24. Thus, it will be understood that the keystone 24 may also be formed without the walls 48. The steel tube 46 may be connected to a concrete- steel shear wall 62, 48 within the keystone 24.

[0056]

[0058] Like the bottom beams 22, the walls 48 within the keystone 24 define hollow chambers 54 that may be filled or partially filled with fluid or ballast water, such as sea water. It will be understood that each such chamber 54 may include a valve and / or a pump (not shown) to selectively add and remove ballast water from each chamber 54.

[0057]

[0059] As shown in Fig. 9, the steel tube 46 may include a circumferentially extending flange 58 and the wind turbine tower 14 may include a circumferentially extending flange 60 at a lower end thereof. The flange 60 of the wind turbine tower 14 may therefore be connected to the flange 58 of the steel tube 46 by bolts and nuts (not shown). Alternatively, the flanges 58 and 60 may be connected by any other desired fasteners or by welding.

[0058]

[0060] Referring now to Fig. 10, a cross-sectional elevational view of a portion of a second embodiment of the FOWT foundation 120 is illustrated and shows a second embodiment of a platform to tower connection. The foundation 120 includes the transition member 26 having a first circumferentially extending flange 64 at an upper end thereof and a second circumferentially extending flange 65 at a lower end thereof. The foundation 120 also includes a keystone 66 that is similar to the keystone 24. The keystone 66 includes a reinforced concrete bolt ring 68, a top plan view of which is shown in Fig. 11, concentrically formed within the keystone 66 and a plurality of radially extending diaphragms or walls 70 that extend vertically between an intermediate horizontal wall 72 of the keystone 66 and an upper wall 74 of the keystone 66, and extend radially between the concrete bolt ring 68 and the side walls of the keystone 66.

[0059]

[0061] Like the keystone 24, the walls 70 within the keystone 66 define hollow chambers 76 that may be filled or partially filled with fluid or ballast water, such as sea water. It will be understood that each such chamber 76 may include a valve and / or a pump (not shown) to selectively add and remove ballast water from each chamber 76.

[0060]

[0062] As shown in Fig. 10, the second circumferentially extending flange 65 may be connected to the reinforced concrete bolt ring 68 by bolts and nuts (not shown). The flange 60 of the wind turbine tower 14 may be connected to the flange 64 of the transition member 26 by bolts and nuts (not shown).

[0061] Alternatively, the flanges 60 and 64 may be connected by any other desired fasteners or by welding.

[0062]

[0063] Fig. 12 is a cross sectional view taken along the line 12 12 in Fig. 10, and Fig. 13 is a cross sectional view taken along the line 13 - 13 in Fig. 10.

[0063]

[0064] As described above, the keystones 24 and 66 and each pair of opposing bottom beams 22 may be assembled and post-tensioned longitudinally to define the foundations 12 and 120. As shown in Figs. 12 and 13, post-tensioning tendons 78 may extend longitudinally through the bases of the bottom beams 22 and the keystone 66 therebetween. Although not illustrated, post- tensioning tendons 78 may also extend longitudinally through the side walls and upper walls of the bottom beams 22 and the keystone 66 therebetween. Portions of the foundations 12 and 120 may be post- tensioned vertically. For example, post-tensioning tendons 80 extend vertically through the side walls of the keystone 66, as shown in Fig. 10.

[0064]

[0065] Figs. 14 through 17 illustrate a first embodiment of a method of constructing the FOWT platform 10 using conventional casting methods on land. In a first step of the method shown in Fig. 14, a base slab 152 of a foundation 150 is cast and includes heave plates 151. Like the heave plates 32, the heave plates 151 may be formed on a lower surface of each bottom beam 156, such that the heave plates 151 extend outwardly from the side and end walls of each bottom beam 156 from a longitudinal mid-point thereof. The heave plates 151 may be formed from any of the materials used to form the bottom beams 22, as described above. Alternatively, as shown in Fig. 3 in reference to the heave plates 32, the heave plates 151 may be formed on an entire perimeter of the lower surface of each bottom beam 156, such that the heave plates 151 extend outwardly from the side and end walls of each bottom beam 156.

[0065]

[0066] In a second step of the method, as shown in Fig. 15, the vertical walls 154 of the foundation 150 are cast on the base slab 152, thus all of the vertical walls of the bottom beams 156 and the keystone 158, and if desired, any internal horizontal walls within the bottom beams 156 and the keystone 158, may also be cast.

[0066]

[0067] In a third step of the method, as shown in Fig. 16, a top slab 160 of the foundation 150 is cast using stay-in-place pre-cast concrete formwork (not shown). In a fourth step of the method, shown in Fig. 17, longitudinal and vertical post-tensioning, such as shown in Figs. 10, 12, and 13, and mechanical outfitting, such as for example the work platform 28, of the foundation 150 occurs. Once completed, the foundation 150 may be launched into a body of water by any desired method, such as by using a ramp or a barge (not shown).

[0068] The method illustrated in Figs. 14 through 17 may be accomplished using multiple casting stations or may use an assembly line approach.

[0067]

[0069] Figs. 18 through 21 illustrate a second embodiment of a method of constructing the FOWT platform 10. In a first step of the method shown in Fig. 18, a sub-assembly 172 of a foundation 170 comprises two bottom beams 174 a keystone 176, and may be formed and assembled on shore or on a barge (not shown) or in a body of water, as shown in Fig. 18. Once the sub-assembly 172 is assembled, the keystone 176 and the bottom beams 174 may be post-tensioned by any desired post-tensioning method, thus applying a compressive force between the keystone 176 and the bottom beams 174. The sub-assembly 172 may then be launched into the body of water and be ballasted with the addition of ballast material, such as sea water. In a second step of the method, as shown in Fig. 19, third and fourth bottom beams 178 may be formed and assembled on shore or on a barge (not shown) or in a body of water, as shown in Fig. 19. Once the bottom beams 178 are assembled, they may be launched into the body of water and be ballasted with the addition of ballast material, such as sea water.

[0068]

[0070] In a third step of the method, as shown in Fig. 20, the third bottom beam 178 may be attached to the sub-assembly 172. Similarly, in a fourth step of the method, as shown in Fig. 21, the fourth bottom beam 178 may be attached to the sub-assembly 172, and the third and fourth bottom beams 178 post-tensioned to the keystone 176 by any desired post-tensioning method, thus defining the foundation 170.

[0069]

[0071] As shown in Figs. 18 through 21, each bottom beam 174 and 178 includes a heave plate 175. Like the heave plates 32 and 151, the heave plates 175 may be formed on a lower surface of each bottom beam 174 and 178, such that the heave plates 175 extend outwardly from the side and end walls of each bottom beam 174 and 178 from a longitudinal mid-point thereof. The heave plates 175 may be otherwise the same as the heave plates 32 and the heave plates 151.

[0070]

[0072] Alternatively, the method of constructing the foundation 170 shown Figs. 18 through 21 , may be accomplished by a casting and slip-forming process on a semi-submersible barge (not shown).

[0071]

[0073] In an additional alternative method of constructing the foundation 170, the bottom beams 174 and 178 may be formed in segments or sections (not shown). The sections of the bottom beams 174 and 178 may then be assembled together and to the keystone 176, and longitudinally post- tensioned together to form a watertight foundation 170. This alternative method of constructing the foundation 170 may be performed on shore or a dock and launched into a body of water with a barge. Additionally, sections of the foundation 170 may be assembled on shore or a dock and launched into a body of water via a drydock or with a barge. Final assembly of the sections of the foundation 170 may occur in the body of water using bridge pontoon assembly methods similar to the method illustrated in Figs. 18 through 21.

[0072]

[0074] In a further alternative method of constructing a foundation similar to the foundation 170, steel fabrication methods may be used, wherein the keystone and the bottom beams, although not illustrated, are formed primarily from steel. For example, such a keystone and four bottom beams may be separately formed for assembly on quayside or on a barge, wherein the keystone and the bottom beams are then bolted and / or welded together. Alternatively, portions of such a steel foundation may be assembled, on site or in a factory, for example one bottom beam may be bolted and / or welded to the keystone. The additional three bottom beams may then be bolted and / or welded to the pre-formed keystone and bottom beam.

[0075] It will be understood that in each of the embodiments of the foundation described herein above, attachments for the mooring cables may be comprised of post-tensioned anchor plates, such as steel anchor plates, and anchored to the seabed.

[0073]

[0076] It will be further understood that in each of the embodiments of the foundation described herein above, the thickness of the vertical walls of the bottom beams and the keystone may taper from a first thickness at a lower end of the vertical walls to a second thickness, smaller than the first thickness, at an upper end of the vertical walls, as hydrostatic and hydrodynamic loads decrease.

[0074]

[0077] Referring now to Fig. 22 a third embodiment of a FOWT platform is shown generally at 180. It will be understood that the methods of constructing and assembling a foundation described herein may be applied to a FOWT platform that includes a foundation 182 having three bottom beams 184 extending radially from a keystone 186. As shown in Fig. 22, the foundation 182 also includes three outer columns 188 extending perpendicularly from the bottom beams 184 at distal ends thereof, a central column 190 extending perpendicularly from the keystone 186, and upper beams 192 extending radially from the center column 190 to each of the outer columns 188. In the illustrated embodiment, each bottom beam 184 includes a circular heave plate 194. Like the heave plates 32, 151, and 175, the heave plates 194 may be formed on a lower surface at a distal end of each bottom beam 184, such that the heave plates 194 extend outwardly therefrom.

[0075]

[0078] Fig. 23 is an is a cross-sectional elevational view of a portion of a fourth embodiment of the FOWT platform 200 having a foundation 202. The foundation 202 is similar to the foundation 120 shown in Fig. 10 and includes four bottom beams 22 and the keystone 66. The keystone 66 includes the reinforced concrete bolt ring 68 concentrically formed within the keystone 66 and the plurality of radially extending diaphragms or walls 70 that extend vertically between an intermediate horizontal wall 72 of the keystone 66 and an upper wall 74 of the keystone 66, and extend radially between the concrete bolt ring 68 and the side walls of the keystone 66, as best shown in Fig. 11 .

[0076]

[0079] As shown in Fig. 23, the flange 60 of the wind turbine tower 14 may be directly connected to the reinforced concrete bolt ring 68 by bolts and nuts (not shown). Alternatively, the flange 60 may be connected to the bolt ring 68 by any other desired fasteners or by welding.

[0077]

[0080] In addition to the embodiments of the improved FOWT platforms, and the methods of manufacturing and assembling the embodiments of the improved FOWT platforms described and illustrated herein, it will be understood that the methods of manufacturing and assembling described herein may be applied to any desired FOWT platform, including but not limited to FOWT platforms having a heel tank damper system, a tuned mass damper system, and other motion mitigations systems incorporated therein.

[0078]

[0081] The principle and mode of operation of this invention have been explained and illustrated in its preferred embodiment. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.

Claims

CLAIMSWhat is claimed is:

1. A barge-type wind turbine platform capable of floating on a body of water and supporting a wind turbine thereon comprising: a keystone; wherein the keystone includes a steel tube concentrically mounted within the keystone, and a plurality of radially extending diaphragms that extend vertically between a lower wall of the keystone and an upper wall of the keystone, and extend radially between the steel tube and side walls of the keystone; a plurality of bottom beams connected to the keystone and extending radially outwardly thereof, the combined keystone and bottom beams defining a foundation; and a wind turbine tower mounted to the keystone.

2. The barge-type wind turbine platform according to claim 1, wherein the plurality of bottom beams are three bottom beams.

3. The barge-type wind turbine platform according to claim 1, wherein the plurality of bottom beams are configured as: a first pair bottom beams including two bottom beams connected to opposite sides of the keystone; and a second pair of bottom beams including two bottom beams connected to opposite sides of the keystone, wherein the second pair of bottom beams has a longitudinal axis perpendicular to a longitudinal axis of the first pair of the bottom beams, the combined first and second pairs of bottom beams defining the foundation.

4. The barge-type wind turbine platform according to claim 3, wherein the steel tube is connected to a concrete- steel shear wall within the keystone.

5. The barge-type wind turbine platform according to claim 4, wherein the diaphragms within the keystone define hollow chambers that are configured such that ballast water is selectively added and removed from the hollow chambers.

6. The barge-type wind turbine platform according to claim 5, further including at least one pump fluidly connected to the hollow chambers and operative to selectively add and remove the ballast water from each of the hollow chambers.

7. The barge- type wind turbine platform according to claim 4, wherein the steel tube includes a circumferentially extending flange at an upper end thereof, wherein the wind turbine tower includes a circumferentially extending flange at a lower end thereof, and wherein the flange of the wind turbine tower is connected to the flange of the steel.

8. The barge-type wind turbine platform according to claim 4, wherein the first and second pairs bottom beams and the keystone define a foundation having a cruciform shape.

9. The barge-type wind turbine platform according to claim 3, further including heave plates formed on a lower surface of each bottom beam, the heaveplates extending outwardly from side and end walls of each bottom beam from a longitudinal mid-point thereof.

10. The barge-type wind turbine platform according to claim 3, further including heave plates formed on a lower surface of each bottom beam, the heave plates extending outwardly from side and end walls of each bottom beam on an entire perimeter thereof.

11. The barge-type wind turbine platform according to claim 4, wherein each bottom beam in each of the first and second pairs of bottom beams, and the keystone connected therebetween, are generally hollow.

12. The barge-type wind turbine platform according to claim 11, wherein each of the bottom beams include a plurality of transverse diaphragms that extend vertically between a lower wall of the keystone and an upper wall of the keystone, and extend transversely between opposing side walls of the bottom beams.

13. The barge-type wind turbine platform according to claim 12, wherein each bottom beam further includes at least one longitudinally extending diaphragm that extends between any two or more of the keystone, the transverse diaphragms, a distal end of the bottom beam, and any portion of the bottom beam between the keystone and the distal end of the bottom beam.

14. The barge-type wind turbine platform according to claim 13, wherein the transverse diaphragms within each bottom beam define hollowchambers that are configured such that ballast water is selectively added and removed from the hollow chambers.

15. The barge-type wind turbine platform according to claim 14, further including at least one pump fluidly connected to the hollow chambers and operative to selectively add and remove the ballast water from each of the hollow chambers.

16. The barge-type wind turbine platform according to claim 13, wherein each bottom beam has the shape of a rectangular prism.

17. The barge-type wind turbine platform according to claim 16, wherein a distal end of each bottom beam is rounded.

18. The barge-type wind turbine platform according to claim 3, wherein the keystone and each pair of opposing bottom beams are assembled and posttensioned longitudinally, and wherein the keystone and each bottom beam are post-tensioned vertically.

19. The barge-type wind turbine platform according to claim 14, wherein the foundation is formed from one of pre-stressed reinforced concrete, high performance concrete, FRP, steel, and combinations of pre-stressed reinforced concrete, high performance concrete, FRP, and steel20. A barge-type wind turbine platform capable of floating on a body of water and supporting a wind turbine thereon comprising: 1a keystone; wherein the keystone includes a reinforced concrete bolt ring concentrically formed within the keystone, and a plurality of radially extending diaphragms that extend vertically between an intermediate horizontal wall of the keystone and an upper wall of the keystone, and extend radially between the reinforced concrete bolt ring and side walls of the keystone; a first pair bottom beams including two bottom beams connected to opposite sides of the keystone; a second pair of bottom beams including two bottom beams connected to opposite sides of the keystone, wherein the second pair of bottom beams has a longitudinal axis perpendicular to a longitudinal axis of the first pair of the bottom beams, the combined first and second pairs of bottom beams defining a foundation; a wind turbine tower having a circumferentially extending flange at a lower end thereof; and a transition member having a first circumferentially extending flange at an upper end thereof and a second circumferentially extending flange at a lower end thereof; wherein the second circumferentially extending flange is connected to the reinforced concrete bolt ring, and the circumferentially extending flange of the wind turbine tower is connected to the first circumferentially extending flange of the transition member.

21. The barge-type wind turbine platform according to claim 20, wherein the keystone and each pair of opposing bottom beams are assembled andpost-tensioned longitudinally, and wherein the keystone and each bottom beam are post-tensioned vertically.

22. A method of assembling a barge-type wind turbine platform capable of floating on a body of water and supporting a wind turbine thereon, the method comprising: slip-forming a base slab of a foundation, wherein the foundation includes a keystone and a plurality of bottom beams extending outwardly from the keystone; slip-forming vertical walls of the bottom beams and the keystone on the base slab; slip forming internal horizontal walls within the bottom beams and the keystone; slip forming a top slab of the foundation on the vertical walls of the bottom beams and the keystone; longitudinally and vertically post-tensioning the foundation; installing mechanical equipment in the foundation; and launching the foundation into a body of water.

23. The method according to claim 22, wherein the method is accomplished using one of multiple casting stations and an assembly line approach.

24. A method of assembling a barge-type wind turbine platform capable of floating on a body of water and supporting a wind turbine thereon, the method comprising:forming a sub-assembly of a foundation, the sub-assembly comprising a first and a second bottom beam and a keystone; post-tensioning the keystone and the first and second bottom beams; launching the sub-assembly into a body of water; adding ballast material to the sub-assembly; forming third and fourth bottom beams; launching the third and fourth bottom beams into the body of water; adding ballast material to the third and fourth bottom beams; attaching the third bottom beam to the sub-assembly; attaching the fourth bottom beam to the sub-assembly; and post-tensioning the third and fourth bottom beams to the keystone.

25. The method according to claim 24, wherein the sub-assembly, the third bottom beam, and the fourth bottom beam are formed and assembled on one of land, a barge, and in a body of water.

26. The method according to claim 24, wherein the ballast material is sea water.

27. The method according to claim 24, wherein the sub-assembly, the third bottom beam, and the fourth bottom beam are formed by a slip-forming process on a semi-submersible barge.

28. A wind turbine platform capable of floating on a body of water and supporting a wind turbine thereon comprising: a foundation having: three bottom beams extending radially from a keystone; three outer columns extending perpendicularly from the bottom beams at distal ends thereof; and a central column extending perpendicularly from the keystone; and a circular heave plate formed on a lower surface of each bottom beam at a distal end thereof, such that the heave plates extend outwardly therefrom.

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