Self-installing column stabilized offshore wind turbine system and method of installation

Abstract

A self-installing offshore column stabilized semi-submersible platform has at least one vertical buoyant ballastable column, a telescoping keel tank or stiffened damper plate movably connected with the vertical column that extends and retracts relative to a lower end thereof, and a non-collapsible turbine tower or a tilt and telescoping tower coupled to an upper end of the vertical column that telescopes and reciprocates relative thereto between a horizontal retracted position and an axially extended vertical position. A wind turbine with blades is coupled to a top portion of the tower assembly. The relative position and weight of the keel tank or damper plate is selectively adjustable to raise or lower the center of gravity of the entire mass of the semi-submersible platform including the wind turbine and tower assembly with respect to the center of buoyancy of the platform.

Claims

1. A self-installing offshore floating wind turbine system, comprising: a column stabilized semi-submersible platform having at least one vertically oriented buoyant ballastable column with one or more buoyant tanks or interior chambers enclosed by bulkheads including ballast control means for selectively adjusting the buoyancy thereof; a telescoping keel tank movably connected with said vertically oriented column by an elongate spindle slidably and telescopically mounted within said vertical column for extensible and retractable movement relative to a lower end thereof, said keel tank including ballast control means for selectively adjusting the ballast and weight thereof; a tilt and telescoping tower assembly including a first tower support frame mounted at a top end of said vertically oriented column, a lower tower section of said tower assembly hingedly connected at a lower end to said first tower support frame by laterally spaced pivot connections, a hydraulic cylinder on laterally opposed sides of said first tower support frame pinned at opposed ends between said first tower support frame and said lower tower section to pivot said tower assembly between a generally horizontal stored or transport position supported on said first tower support frame and a generally vertical operating position approximately 90 relative thereto, a second tower support frame mounted at a top end of said vertically oriented column spaced a distance from said first tower support frame for receiving and releasably engaging and supporting a bottom end of said lower section of said tower assembly when said tower assembly is pivoted to the generally vertical operating position; an upper tower section movably mounted in said lower tower section to telescope and reciprocate relative thereto between a retracted position and an axially extended position relative thereto, and extension and retraction means operably connected between said lower tower section and said upper tower section for moving said upper section between the retracted and extended positions; and a wind turbine coupled to a top portion of said upper tower section, and a plurality of blades coupled to said wind turbine, said wind turbine having a generally horizontal axis of rotation about which said blades rotate; wherein the relative position and weight of said keel tank is selectively adjustable to raise or lower the center of gravity of the entire mass of said semi-submersible platform including said wind turbine and said turbine tilt and telescoping tower assembly with respect to the center of buoyancy of said platform according to ballast and variable or fixed loads including loads imposed by said wind turbine and said tilt and telescoping tower assembly in the horizontal and the generally vertical operating positions; and said keel tank, in an extended position, providing water entrapment surfaces to increase hydrodynamic mass and flow damping to reduce heave, pitch and roll motions of said semi-submersible platform and said wind turbine in an operational mode.

2. The self-installing offshore floating wind turbine system according to claim 1, wherein a plurality of said column stabilized semi-submersible platforms are joined together by a plurality of open-frame truss structures formed of slender tubular members connected between adjacently spaced said vertically oriented columns to form a wind farm.

3. The self-installing offshore floating wind turbine system according to claim 1, wherein said at least one vertically oriented buoyant ballastable column comprises three of said vertically oriented buoyant ballastable columns joined together by a plurality of open-frame truss structures formed of slender tubular members connected between adjacently spaced said vertically oriented columns to form a generally triangular platform configuration; wherein respective said columns each have a telescoping keel tank movably connected therewith by an elongate spindle slidably and telescopically mounted within said respective column for extensible and retractable movement relative to a lower end thereof, each said keel tank including ballast control means for selectively adjusting the ballast and weight thereof; said tilt and telescoping wind turbine tower assembly is mounted at a top end of one of said vertically oriented columns; the relative position and weight of each said keel tank is selectively adjustable to raise or lower the center of gravity of the entire mass of said semi-submersible platform including said wind turbine and said tilt and telescoping turbine tower assembly with respect to the center of buoyancy of said platform according to ballast and variable or fixed loads including loads imposed by said wind turbine and said tilt and telescoping turbine tower assembly; and each said keel tank, in an extended position, providing water entrapment surfaces to increase hydrodynamic mass and flow damping to reduce heave, pitch and roll motions of said semi-submersible platform and said wind turbine in an operational mode.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIGS. 1 and 2 are schematic side elevation views of a mono-column embodiment of the self-installing wind turbine system in accordance with the present invention with a tilt and telescoping wind turbine tower assembly, shown in a retracted and horizontal position, and in a vertical extended position, respectively.

(2) FIG. 3 is a schematic side elevation showing a modification wherein the keel tank is provided with two removable nose cone attachments disposed in diametrically opposed relation to reduce drag during transportation.

(3) FIG. 4 is a schematic side elevation showing a modification wherein a plurality of pile guides are attached to the periphery of the keel tank which are received on, and connected to, vertical piles of a pile foundation on the seabed and structural brace members extending angularly between the bottom portion of the column and the upper portion of the keel tank.

(4) FIG. 5 is a schematic side elevation showing a plurality of the columns of the mono-column wind turbine systems joined together by a plurality of open-frame truss structures.

(5) FIG. 6 is a schematic perspective view of a tri-column embodiment of the self-installing wind turbine system in accordance with the present invention wherein three vertically oriented columns are joined together by open frame truss structures to form a generally triangular platform configuration. Also shown is a large single keel tank attached to the vertical spindles.

(6) FIG. 7 is a schematic side elevation showing the tri-column embodiment wherein the vertically oriented columns each have a telescoping keel tank.

(7) FIG. 8 is a schematic side elevation showing the tri-column embodiment of FIG. 7 with the extended keel tanks on the seabed and structural brace members extending angularly between the truss frame structure and the upper portion of the keel tanks.

(8) FIG. 9 is a perspective view of a stiffened motion damping plate which may be attached to the bottom of the telescoping spindle that may be utilized as an alternative to the keel tank.

(9) FIGS. 10 and 11 are schematic side elevation views of a mono-column embodiment of the self-installing wind turbine system with a stiffened damping plate attached to the spindle of the vertically oriented cylinder, shown in a retracted position and an extended position, respectively.

(10) FIG. 12 is a schematic side elevation view of the mono-column embodiment of FIGS. 10 and 11, showing the stiffened damping plate in an extended position and attached to and connected to vertical piles of a pile foundation on the seabed and structural brace members extending angularly between the bottom portion of the column and the upper portion of the keel tank.

(11) FIG. 13 is a schematic perspective view of a tri-column embodiment of the self-installing wind turbine system wherein each of the vertically oriented columns have a stiffened damping plate attached to the vertical spindles.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(12) The term column stabilized as used in the mobile offshore drilling industry refers to a class of mobile offshore drilling units (MODU) wherein the static stability is obtained from the water plane area and the overall center of buoyancy (CB) is allowed to be below the overall center of gravity (CG) of the floating unit with its static loads. When the center of gravity (CG) of the overall platform is situated below the overall center of buoyancy (CB), then positive natural stability is obtained. The term semi-submersible as used in the mobile offshore drilling industry refers to a particular type of floating vessel that is supported primarily on large pontoon-like structures submerged below the sea surface and operating decks are elevated perhaps 100 or more feet above the pontoons on large steel columns. The semi-submersible has the advantage of submerging most of the area of components in contact with the sea and minimizing loading from waves and wind. Semi-submersible platforms can operate in a wide range of water depths, including deep water.

(13) In the following detailed description, reference will be made to several embodiments of the invention that are illustrated in the accompanying drawings. The drawings are not to scale and the proportion of certain elements may be exaggerated for the purpose of illustration. Wherever possible, same or similar reference numerals are used in the drawings and the description to identify the same or similar components. The components that have been assigned numerals of reference and shown in earlier drawing figures and previously described in detail may be shown in subsequent drawing figures and assigned the same numerals of reference but will not be described again in detail in each figure to avoid repetition.

(14) Referring to the drawings by numerals of reference there is shown, somewhat schematically, FIGS. 1 and 2, a preferred mono-column embodiment of a self-installing wind turbine system 10 having a column stabilized semi-submersible platform 11 which includes a vertically oriented large diameter buoyant column 12 with a telescoping keel tank 13. The large diameter vertical buoyant column 12 has a base or bottom wall 12A enclosing its bottom end and defining a central chamber which contains one or more interior buoyant tanks or chambers enclosed by bulkheads, the, buoyancy of which can be selectively adjusted by means of conventional ballast control means. Buoyant columns and ballast control means are conventional in the art and therefore the structural details and components thereof are not shown in detail.

(15) A smaller diameter central cylindrical column may be mounted vertically in the large diameter column. The keel tank 13 has a central elongate vertical spindle 14 extending upwardly from the top end thereof and through the bottom wall 12A of the larger diameter column 12 and is slidably and telescopically mounted within the smaller diameter column within the column 12 and engaged with a raising and lowering mechanism on the base or bottom wall, such as a gear assembly or other conventional raising and lowering means for extensible and retractable movement relative to the larger diameter column 12 of the platform 11.

(16) One or more automatic control systems are provided to telescope the spindle 14 and to lock it at any desired length, and conventional pump control means is provided for selectively pumping water in and out of the keel tank 13 to partially or fully flood the keel tank and thereby adjust the weight and ballast. One or more internal or external locking mechanisms are provided to lock the telescopic spindle 14 and the keel tank 13 at its bottom end with respect to the larger diameter column 12.

(17) The structural details of such a telescoping keel tank arrangement are shown and described in detail in my U.S. Pat. Nos. 6,761,124 and 6,942,427, and which are incorporated herein by reference as if fully set forth in their entirety. By pumping water into or out of the keel tank 13, the collective water mass of the keel tank and thus the weight of the structure, is adjustably tuned to raise or lower the center of gravity (CG) of the entire mass of the floating platform structure according to ballast and other variable or fixed loads.

(18) A wind turbine 15 and turbine tower is mounted at the upper end of the of the large diameter column 12. The turbine tower may be either of a tilt and telescoping tower assembly 16, or a non-collapsible turbine tower 17. In a preferred embodiment, the tilt and telescoping tower assembly 16 has a base or lower section 16A and an upper section 16B. The wind turbine 15 is coupled to the top portion of the turbine tower 17 or end upper section 16B of the tilt and telescoping tower assembly 16 and a plurality of blades 15A are coupled to the turbine. The turbine 15 generally has a horizontal axis of rotation about which the blades rotate.

(19) In the example of the tilt and telescoping tower assembly 16, a first tower support frame 18 is mounted at the top end of the large diameter column 12 of the platform 11. The base or lower section 16A of the tower assembly 16 is hingedly connected to the support frame 18 at one end thereof by laterally spaced pivot connections 19. A hydraulic cylinder 20 on laterally opposite sides of the tower support frame 18 is pinned at opposed ends between the support frame 18 and the base or lower section 16A of the tower assembly 16 to pivot the tower assembly 16 between a generally horizontal stored or transport position supported on the support frame 18 (FIG. 1) and a generally vertical operating position approximately 90 relative thereto (FIG. 2). A second tower support frame 21 is mounted at the top end of the large diameter column 12 of the platform 11 forwardly of the first tower support frame 18 for receiving and releasably engaging the bottom end of the base or lower section 16A of the tower assembly 16 when the tower assembly is pivoted to the generally vertical operating position.

(20) The upper section 16B of the tower assembly 16 is movably mounted in the base or lower section 16A to telescope and reciprocate relative thereto between a retracted position and an axially extend position relative thereto. As shown in FIG. 2, the upper section 16B of the tower assembly 16 is moved between the retracted and extended positions by an extension and retraction mechanism 22 such as, for example but not limited thereto, a winch with sheaves and a wire line, a block and tackle assembly, a hydraulic cylinder, or a gear assembly, operably connected between the base or lower section 16A and the upper section 16B of the tower assembly. The tower assembly 16 may be pivoted and extended or retracted simultaneously.

(21) It should be understood from the foregoing that the present wind turbine 15 having a tilt and telescoping tower assembly 16 eliminates necessity of an external crane or derrick to install the wind turbine on site. The tower assembly 16 may be pivoted and telescoped to a compact horizontal position during transport of the platform and to avoid damage during severe weather and storm conditions, or to perform maintenance, or repair or replacement of parts.

(22) The wind turbine 15, including the tilt and telescoping tower assembly 16, may be assembled and mounted on the column 12 of the semi-submersible platform 11 in a sheltered area near the quayside. The whole structure is then towed to an offshore wind-farm or operational location by a tugboat that has anchor handling capability, rather than an expensive crane mounted on offshore construction vessels. The present platforms use less draft than a spar-type platform and can be fully assembled in quayside and towed with the keel tank 13 and the tilt and telescoping tower assembly 16 in a retracted compact position. The keel tank 13 is designed to have adequate buoyancy to support and float the superstructure with its own minimum draft for ease of wet-towing with a cost-effective tug boat. At the operational location, the telescoping keel tank 13 is ballasted to move it downward to the deepwater depth. The additional mass of the water column above the keel tank 13 resists the heave, pitch and roll oscillation of the supporting platform 11 due to wave excitation. During operation, the fully extended keel tank 13 provides the required stability to the horizontal and vertical loads of the wind turbine. The fully extended keel tank 13 is also distanced beneath the severe kinematics of wave particle motion, thereby significantly reducing wave excitation imparted to the supporting floating structure. In addition, the keel tank 13 provides water entrapment above and below the flat surfaces, thereby increasing the hydrodynamic mass and flow damping. These features reduce the heave, pitch and roll motion of the supporting floating structure in the operational mode. Conventional catenary mooring lines ML may be used for the purpose of station keeping of the floating platform.

(23) Although, for purposes of example, the keel tank 13 has been shown as having a generally cylindrical configuration, it should be understood that the keel tank could be oval-shaped to reduce drag during transportation. FIG. 3 shows a modification wherein the keel tank 13 is provided with two removable nose cone attachments 13A disposed in diametrically opposed relation to reduce drag during transportation.

(24) FIG. 4 shows, somewhat schematically, a modification wherein a plurality of pile guides 23 are attached to the periphery of an elliptical keel tank 13 in spaced apart relation and extend outwardly therefrom which are received on, and connected to, vertical piles 24 of a pile foundation on the seabed. Also shown are a plurality of structural brace members 25 that are attached at opposed ends to the bottom portion of the column 12 and the upper portion of the keel tank 13 to extend angularly therebetween for structural strength.

(25) As shown in FIG. 5, a plurality of the columns 12 of the mono-column wind turbine systems 10 may be joined together by a plurality of open-frame truss structures 26 formed of slender tubular members connected between adjacently spaced columns by welding, bolting, pinning, hinged connections, or other conventional assembly methods. This arrangement allows multiple mono-column wind turbine systems 10 to be joined together such as, for example, to form a wind farm. The components that are the same as previously described above are assigned the same numerals of reference but will not be described again in detail to avoid repetition.

(26) FIG. 6 shows, somewhat schematically, a tri-column embodiment of the stabilized semi-submersible platform 30 of the self-installing wind turbine system 10 wherein three of the vertically oriented large diameter columns 12 are joined together by a plurality of open frame truss structures 26 formed of slender tubular members connected between adjacently spaced columns to form a generally triangular platform configuration.

(27) FIG. 6 also shows a single telescoping keel tank 13B that has three elongate vertical spindles 14 each extending upwardly from the top end thereof and through the bottom wall of a respective larger diameter column 12 and slidably and telescopically mounted therein and engaged with a raising and lowering mechanism, such as a gear assembly or other conventional raising and lowering means for extensible and retractable movement relative to the larger diameter columns 12 of the platform 30. The bottom end of the vertical telescoping spindles 14 are connected to the top end of the single telescoping keel tank 13B by a swivel connection so as to allow the single telescoping keel tank to pivot relative to a horizontal plane when various ones of the spindles 14 are extended or retracted. The single telescoping keel tank 13B contains interior buoyant tanks or chambers enclosed by bulkheads, the buoyancy of which can be selectively adjusted by means of conventional ballast control means to selectively raise or lower opposite sides or ends of the keel tank and counteract offset loads with respect to the center of the floating platform. The single telescoping keel tank 13B may also be provided with a moon pool or central opening 13C through the center thereof through which items, such as equipment, tools, and/or supplies or modules comprising the same, can be lowered into or retrieved from the sea.

(28) However, it should be understood that each of the vertically oriented large diameter columns 12 of the tri-column embodiment of the stabilized semi-submersible platform 30 may have an individual telescoping keel tank 13, as shown and described previously with respect to the mono-column embodiments.

(29) FIG. 7 shows, somewhat schematically, a tri-column embodiment of the stabilized semi-submersible platform 30 of the self-installing wind turbine system 10 wherein three of the vertically oriented large diameter columns 12 each have a telescoping keel tank 13 and are joined together by a plurality of open frame truss structures 16 formed of slender tubular members connected between adjacently spaced columns to form a generally triangular platform configuration. FIG. 8 shows the tri-column embodiment of FIG. 7 with the extended keel tanks 13 on the seabed and structural brace members 27 extending angularly between the truss frame structure 26 and the upper portion of the keel tanks 13.

(30) In the examples of the tri-column embodiment of the stabilized semi-submersible platform 30 of the self-installing wind turbine system 10, the wind turbine 15, including either of the tilt and telescoping tower assembly 16 or the non-collapsible turbine tower 17 may be mounted on one of the three columns 12 of the semi-submersible platform. In the vertical extended position, the wind turbine 15 and tilt and telescoping tower assembly 16 or non-collapsible turbine tower 17 extend a distance above the platform, which may create a vertical offset in the static load.

(31) In both, the mono-column platform embodiments 11 and the tri-column platform embodiments 30, static stability is accomplished by the telescoping keel 13, which may be extended to bring the overall center of gravity (CG) down with respect to the free water surface, such that the center of buoyancy (CB) is located a distance below the still water level to provide increased stability to support the wind turbine 15 and the tilt and telescoping tower assembly 16 or non-collapsible turbine tower 17. Thus, the extended keel tank 13 is disposed in the inert water environment during the operational condition. The aerodynamic loads of the wind turbine during peak operations also are managed tactically by the telescoping keel-tank 13. The mooring system of the platform also offers some resistance to the aerodynamic loads in addition to the station keeping function.

(32) In the case of the tri-column embodiments with individual keel tanks, the large offset of the vertical load on one column 12, for example the front column, that supports the wind turbine 15 and tower assembly 16 or non-collapsible turbine tower 17 creates static list to the platform to a certain degree in the in-place condition. The offset load may be counteracted by extending the keel tanks 13 on the sides opposite to the column supporting the wind turbine 15 and tower assembly 16 or non-collapsible turbine tower 17, for example the rear columns 12. The keel tanks 13 on the on the rear side of the platform may be extended or retracted with respect to the keel tank on the front side of the platform to provide the platform with an even keel condition, and to counteract the moment created by the offset turbine offset loads with respect to the center of the floating platform.

(33) In the case of the tri-column embodiments with a single keel tank 13B, the large offset of the vertical load on one column 12, for example the front column, that supports the wind turbine 15 and tower assembly 16 or non-collapsible turbine tower 17 creates static list to the platform to a certain degree in the in-place condition. The offset load may be counteracted by extending the single keel tank 13B on the sides opposite to the column supporting the wind turbine 15 and tower assembly 16 or non-collapsible turbine tower 17, for example the rear columns. The rear portion of the single keel tank 13B on the on the rear side of the platform may be extended or retracted and ballasted with respect to the front portion on the front side of the platform to provide the platform with an even keel condition, and to counteract the moment created by the offset wind turbine loads with respect to the center of the floating platform.

(34) In both, the tri-column embodiments with a single keel tank 13B and tri-column embodiments with individual keel tanks 13, the keel tanks provide water entrapment above and below the flat surfaces, thereby increasing the hydrodynamic mass and flow damping that reduce the heave, pitch and roll motion of the supporting floating structure in the operational mode.

(35) FIG. 9 shows a stiffened motion damper plate 28 which may be attached to the bottom of the telescoping spindle 14 as an alternative to the keel tank to provide motion damping in both, the mono-column embodiments and the tri-column embodiments. The damper plate 28 has a generally flat surface with structural stiffeners. In the illustrated example, the damper plate 28 is shown as having a generally rectangular configuration, however, it should be understood that the damper plate may be of other configurations, such as for example, circular or polygonal.

(36) FIG. 10 shows a mono-column embodiment of the self-installing wind turbine system with a stiffened damper plate 28 attached to the spindle 14 of the vertically oriented cylinder 12 and in a retracted position. FIG. 11 shows the mono-column embodiment of FIG. 10 with the stiffened damper plate 28 in an extended position and attached to vertical piles 24 of a pile foundation on the seabed and structural brace members 25 extending angularly between the bottom portion of the column 12 and the upper portion of the damper plate 28. FIG. 12 shows a tri-column embodiment of the self-installing wind turbine system wherein each of the vertically oriented columns 12 have a stiffened damper plate 28 attached to the vertical spindle 14.

(37) The stiffened damper plate 28 provides water entrapment above and below the flat surfaces thereof, thereby increasing the hydrodynamic mass and flow damping that reduces the heave, pitch and roll motion of the supporting floating structure in the operational mode and also reduces resistance from water, waves, and current during wet transportation.

(38) While the present invention has been disclosed in various preferred forms, the specific embodiments thereof as disclosed and illustrated herein are considered as illustrative only of the principles of the invention and are not to be considered in a limiting sense in interpreting the claims. The claims are intended to include all novel and non-obvious combinations and sub-combinations of the various elements, features, functions, and/or properties disclosed herein. Variations in size, materials, shape, form, function and manner of operation, assembly and use, are deemed readily apparent and obvious to one skilled in the art from this disclosure, and all equivalent relationships to those illustrated in the drawings and described in the specification are intended to be encompassed in the following claims defining the present invention.