US20150298772A1 - Floatable support structure for an offshore wind turbine or other device - Google Patents
Floatable support structure for an offshore wind turbine or other device Download PDFInfo
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- US20150298772A1 US20150298772A1 US14/692,715 US201514692715A US2015298772A1 US 20150298772 A1 US20150298772 A1 US 20150298772A1 US 201514692715 A US201514692715 A US 201514692715A US 2015298772 A1 US2015298772 A1 US 2015298772A1
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Images
Classifications
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02B—HYDRAULIC ENGINEERING
- E02B17/00—Artificial islands mounted on piles or like supports, e.g. platforms on raisable legs or offshore constructions; Construction methods therefor
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B22/00—Buoys
- B63B22/18—Buoys having means to control attitude or position, e.g. reaction surfaces or tether
- B63B22/20—Ballast means
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B1/00—Hydrodynamic or hydrostatic features of hulls or of hydrofoils
- B63B1/02—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving lift mainly from water displacement
- B63B1/10—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving lift mainly from water displacement with multiple hulls
- B63B1/107—Semi-submersibles; Small waterline area multiple hull vessels and the like, e.g. SWATH
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B21/00—Tying-up; Shifting, towing, or pushing equipment; Anchoring
- B63B21/50—Anchoring arrangements or methods for special vessels, e.g. for floating drilling platforms or dredgers
- B63B21/502—Anchoring arrangements or methods for special vessels, e.g. for floating drilling platforms or dredgers by means of tension legs
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B22/00—Buoys
- B63B22/04—Fixations or other anchoring arrangements
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B35/00—Vessels or similar floating structures specially adapted for specific purposes and not otherwise provided for
- B63B35/003—Vessels or similar floating structures specially adapted for specific purposes and not otherwise provided for for transporting very large loads, e.g. offshore structure modules
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B35/00—Vessels or similar floating structures specially adapted for specific purposes and not otherwise provided for
- B63B35/44—Floating buildings, stores, drilling platforms, or workshops, e.g. carrying water-oil separating devices
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B39/00—Equipment to decrease pitch, roll, or like unwanted vessel movements; Apparatus for indicating vessel attitude
- B63B39/02—Equipment to decrease pitch, roll, or like unwanted vessel movements; Apparatus for indicating vessel attitude to decrease vessel movements by displacement of masses
- B63B39/03—Equipment to decrease pitch, roll, or like unwanted vessel movements; Apparatus for indicating vessel attitude to decrease vessel movements by displacement of masses by transferring liquids
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D27/00—Foundations as substructures
- E02D27/32—Foundations for special purposes
- E02D27/42—Foundations for poles, masts or chimneys
- E02D27/425—Foundations for poles, masts or chimneys specially adapted for wind motors masts
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D27/00—Foundations as substructures
- E02D27/32—Foundations for special purposes
- E02D27/50—Anchored foundations
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D27/00—Foundations as substructures
- E02D27/32—Foundations for special purposes
- E02D27/52—Submerged foundations, i.e. submerged in open water
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- E—FIXED CONSTRUCTIONS
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- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D27/00—Foundations as substructures
- E02D27/32—Foundations for special purposes
- E02D27/52—Submerged foundations, i.e. submerged in open water
- E02D27/525—Submerged foundations, i.e. submerged in open water using elements penetrating the underwater ground
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
- F03D—WIND MOTORS
- F03D13/00—Assembly, mounting or commissioning of wind motors; Arrangements specially adapted for transporting wind motor components
- F03D13/20—Arrangements for mounting or supporting wind motors; Masts or towers for wind motors
- F03D13/22—Foundations specially adapted for wind motors
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
- F03D—WIND MOTORS
- F03D13/00—Assembly, mounting or commissioning of wind motors; Arrangements specially adapted for transporting wind motor components
- F03D13/20—Arrangements for mounting or supporting wind motors; Masts or towers for wind motors
- F03D13/25—Arrangements for mounting or supporting wind motors; Masts or towers for wind motors specially adapted for offshore installation
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B63B1/10—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving lift mainly from water displacement with multiple hulls
- B63B1/12—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving lift mainly from water displacement with multiple hulls the hulls being interconnected rigidly
- B63B2001/128—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving lift mainly from water displacement with multiple hulls the hulls being interconnected rigidly comprising underwater connectors between the hulls
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- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B21/00—Tying-up; Shifting, towing, or pushing equipment; Anchoring
- B63B21/50—Anchoring arrangements or methods for special vessels, e.g. for floating drilling platforms or dredgers
- B63B2021/505—Methods for installation or mooring of floating offshore platforms on site
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B35/00—Vessels or similar floating structures specially adapted for specific purposes and not otherwise provided for
- B63B35/44—Floating buildings, stores, drilling platforms, or workshops, e.g. carrying water-oil separating devices
- B63B2035/4433—Floating structures carrying electric power plants
- B63B2035/446—Floating structures carrying electric power plants for converting wind energy into electric energy
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02B—HYDRAULIC ENGINEERING
- E02B17/00—Artificial islands mounted on piles or like supports, e.g. platforms on raisable legs or offshore constructions; Construction methods therefor
- E02B2017/0039—Methods for placing the offshore structure
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02B—HYDRAULIC ENGINEERING
- E02B17/00—Artificial islands mounted on piles or like supports, e.g. platforms on raisable legs or offshore constructions; Construction methods therefor
- E02B2017/0091—Offshore structures for wind turbines
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
- F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
- F05B2240/00—Components
- F05B2240/90—Mounting on supporting structures or systems
- F05B2240/93—Mounting on supporting structures or systems on a structure floating on a liquid surface
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
- F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
- F05B2240/00—Components
- F05B2240/90—Mounting on supporting structures or systems
- F05B2240/95—Mounting on supporting structures or systems offshore
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/70—Wind energy
- Y02E10/727—Offshore wind turbines
Definitions
- the present invention relates to a floatable support structure configured to be anchored to the sea floor and to support an additional device such as an offshore wind turbine.
- a support structure for an offshore wind turbine must be stable and safe. Wind turbines can operate satisfactorily when motions due to wind current and waves are relatively small. However large motions of surge, sway, pitch, roll, yaw, and heave will result in inefficient operation or shutdown. Therefore, the support structure must have relatively small motions.
- the support structure motions are affected by the force of wind on the turbine blades, nacelle, and tower, by the wave and current forces on the submerged structure, by the period of the waves, by the period of the rotating turbine blades, and by the natural period of the entire structure, i.e. the time it takes to complete one cycle of motion when subjected to an excitation force. This period depends on the mass of the structure including the added mass of surrounding water, the stiffness of the structure itself (e.g. tower flexing and blade flexing), and the stiffness of the anchoring system of the structure.
- the period of the support structure is synchronous with the period of the waves, the wave forces will be amplified, leading to disruption of operations and/or structural failure. Therefore it is desirable to ensure that the natural period of the support structure differs substantially from the wave periods for all reasonably expected waves.
- VIMs Vortex Induced Motions
- the disclosure relates to an apparatus for supporting an additional structure near a surface of a body of water.
- a system which includes the apparatus and further includes the structure attached to the apparatus.
- the apparatus and the system are each configured to assume a rest position and orientation when the apparatus or system is floating at the surface and when the body of water is substantially still, where the rest orientation defines a vertical direction extending from the surface to a keel at a lowermost position of the apparatus.
- the apparatus includes a support member, which, in use, is attached to the additional structure; and buoyant units. Each buoyant unit is attached to the support member at or near the keel and extends from the keel in a longitudinal direction of the buoyant unit, which longitudinal direction defines an angle of approximately 35°-65° with respect to the vertical direction.
- Each of the buoyant units may have a certain cross-sectional area at a first position along the longitudinal direction, and a different cross-sectional area at a second position along the longitudinal direction.
- each of the buoyant units may have a certain cross-sectional area at a first portion of the buoyant unit that is distal from the keel, and a smaller cross-sectional area at a second portion of the buoyant unit that is proximal to the keel.
- each of the buoyant units may have a cross-sectional area that is substantially constant along the longitudinal direction.
- the buoyant units may be symmetrically disposed around the vertical direction.
- the buoyant units may be three buoyant units, four buoyant units, or more than four buoyant units.
- each buoyant unit that is distal from the keel may include a buoyant material, whose density is lower than the density of the body of water.
- At least a portion of each buoyant unit that is proximal to the keel may include a ballast material, whose density is equal to or higher than the density of the body of water.
- the apparatus or system may further include at least one anchor line or tether, configured to attach the apparatus to a substantially stationary position within the body of water.
- the anchor line or tether may include one or more catenary anchor lines, each attached to one of the buoyant units.
- the anchor line or tether may include one or more tendons, each attached to one of the buoyant units, and configured to assume a substantially vertical orientation to anchor the apparatus or system to the floor of the body of water.
- the apparatus or system may further include a heave plate at the keel.
- the floatable structure may include a wind turbine and associated tower.
- the support member may be attached to the tower.
- FIG. 1 is an elevation view of an exemplary floatable support structure with a tower and turbine attached, and anchored to the sea floor with a vertical tendon at the keel and taut catenary anchors.
- FIG. 2A is an enlarged elevation view of the support structure of FIG. 1 without the tower and turbine attached, and with additional vertical tendons.
- FIG. 2B is a view similar to FIG. 2A , showing an alternative embodiment of the shape of buoyant units.
- FIG. 3 is a plan view of the support structure of FIGS. 1 , 2 A, and 2 B without the tower and turbine attached.
- FIGS. 4A-4D are schematic illustrations showing the water plane area of an exemplary buoyant unit and its distance from the centroid of the structure, where:
- FIG. 4A is a side view of a buoyant unit when the support structure is in its upright position
- FIG. 4C is a side view of the buoyant unit when the support structure is tilted significantly.
- FIG. 5 is an elevation view, similar to that of FIG. 2 , showing a further embodiment of the support structure.
- FIG. 6 is a plan view of the support structure of FIG. 5 .
- Exemplary embodiments described herein provide a floatable support structure configured to be anchored to the sea floor and to support an offshore wind turbine or other device. Some embodiments are considered particularly useful for deep waters, such as in water depths greater than about 40 meters, and some embodiments can be used in depths of over one thousand meters.
- a floatable support structure 100 is shown supporting a wind turbine 200 and floating the wind turbine 200 on a water surface 302 .
- the floatable structure 100 is attached to the sea floor 304 by catenary anchor lines 402 or vertical tendons 404 or, as illustrated, by both catenary anchor lines 402 and a vertical tendon 404 .
- the structure 100 includes buoyant units 102 which meet at the keel 104 of the structure and extend slopingly upward from the keel 104 .
- the keel 104 should be understood to be the bottommost point or area of the structure 100 when the structure 100 is in its upright position, which position is seen in FIGS. 1 , 2 A, and 2 B. In other words, the horizontal line at the bottom of the structure 100 near where the tendon 404 attaches to the structure 100 in FIGS.
- the structure 100 also includes a generally central support member 106 which attaches to the buoyant units 102 at the keel 104 and extends generally vertically therefrom.
- the support member 106 is configured to attach to and to support a tower 202 of the turbine 200 .
- the buoyant units 102 and the support member 106 are connected to one another by various braces 108 , 110 and connecting members 112 .
- the buoyant units 102 are partly submerged in use, i.e. partly below the water surface 302 , as shown.
- the illustrated embodiments include three such buoyant units 102 , which slope outward from at or near the keel 104 to above the water surface 302 .
- three or more buoyant units 102 are provided.
- Each buoyant unit 102 is a generally tubular member whose diameter may vary along its length, as will be discussed in detail later.
- Each buoyant unit 102 intersects the support member 106 at an angle ⁇ of approximately 35-65°. In other words, the longitudinal direction of each buoyant unit 102 is about 35-65° from the longitudinal direction of the support member 106 , which is vertical when the structure is in its upright position, i.e. not being rocked by waves or wind.
- each buoyant unit 102 is a generally tubular member whose diameter varies along its length to provide a larger cross-sectional area at the top portion of the buoyant unit 102 than at the bottom. In the alternative embodiment illustrated in FIG. 2B , the diameter is substantially constant along the length.
- Each buoyant unit 102 includes several compartments 102 a , 102 b , 102 c , separated by water-tight bulkheads 114 , along its length. There may also be smaller sub-compartments (not illustrated) within these compartments 102 a , 102 b , 102 c .
- the upper compartments 102 a may contain buoyant material
- the lower compartments 102 c may contain ballast material.
- each buoyant unit can be selected to achieve the required buoyant force and water plane area and resulting moment of inertia of the structure 100 's cross section at the waterline 302 .
- An intermediate, or “transition” section 102 b connects the upper part 102 a of each buoyant unit 102 to the lower part 102 c of the buoyant unit 102 .
- the lower part 102 c has a smaller cross-sectional area than the upper part 102 a .
- ballast requirements as well as buoyancy requirements will dictate the length and cross-sectional area of each part 102 a , 102 b , 102 c of each buoyant unit 102 .
- both the buoyant units 102 and the support member 106 are steel tubular members, which may include ring stiffeners and/or longitudinal stiffeners on the interior to hold the round shape and to resist hydrostatic pressure.
- the units 102 and member 106 include ring stiffeners, and may additionally include longitudinal stiffeners.
- the tower 202 is supported by the support member 106 .
- the tower 202 extends from the support member 106 to high above the water surface 302 to support the wind turbine 200 .
- the tower 202 supports the nacelle 204 which supports the turbine rotor blades 206 , and which contains the controls, the generator, and other required components.
- the buoyant units 102 are connected to the support member 106 by braces 108 .
- the buoyant units 102 are connected to one another by braces 110 .
- the buoyant units 102 are further connected to the support member 106 by connecting members 112 .
- the support structure 100 is mounted to the sea floor 304 by catenary anchor lines 402 , which may include, for example, chain and/or wire rope, and/or polyester.
- the support structure 100 may additionally or alternatively be attached to the sea floor 304 by a vertical tether such as a tendon or tendons 404 .
- the tether or tethers may be wire ropes, chains, polyester ropes, or steel or metal tubes.
- the tendon or tendons 404 can be attached to the structure 100 at or near the keel 104 and/or at one or more of the buoyant units 102 . In a presently preferred embodiment, one tendon 404 is attached at each of the buoyant units 102 . In practice, it is unlikely that three anchor lines 402 would be used in conjunction with three tendons 404 at the buoyant units 102 and an additional tendon 404 at the keel 104 , as is illustrated. These illustrations are provided for the sake of completeness, to illustrate many possible attachment locations of anchor lines and tendons.
- the tendon or tendons 404 may be attached to the sea floor 304 via an anchor or anchors 406 .
- each anchor may be a suction pile, a driven pile, a drilled and grouted pile, a gravity anchor, or any anchor with the capacity to transmit the tendon forces to the sea floor.
- the support structure 100 can be fabricated, assembled, and launched at a quay, uprighted, then outfitted with the tower 202 and wind turbine 200 all at quay site.
- the assembled wind turbine 200 and support structure 100 can then be towed in upright position to its installation site and then be attached to previously installed anchors 406 or catenary anchor lines 402 .
- the support structure 100 is shown supporting an offshore wind turbine 200 and associated tower 202 .
- the structure 100 can also be used to support any other device, such as an electrical substation, or for oil and gas exploration and production.
- the support structure 100 is used to support a platform for a support station rather than a turbine 200 . Since these platforms are generally rectangular in plan view, the structure will typically have four buoyant units 102 rather than the three buoyant units 102 illustrated, each of which will attach to the platform at or near a corner thereof. In a presently preferred embodiment, the support member 106 extends through a blind hole or a through hole at the center of the platform to provide further support.
- FIGS. 4A-4D the stability of the exemplary structure 100 will now be discussed. It will be appreciated that the stability of the structure 100 is proportional to I/V, where I is the moment of inertia of the water plane area (for the hydrodynamic definition of moment of inertia, as opposed to the mass moment of inertia), and V is the volume of water displaced by the structure 100 .
- I is the moment of inertia of the water plane area (for the hydrodynamic definition of moment of inertia, as opposed to the mass moment of inertia)
- V the volume of water displaced by the structure 100 .
- FIGS. 4A-4D illustrate the stability of a single one of the buoyant units 102 .
- the moment of inertia I is proportional to A 2 , where A is the water plane area of the buoyant unit 102 , in other words, the cross-sectional area of the buoyant unit 102 that is presented to the surface of the water (i.e. the cross-section taken vertically, as opposed to along the longitudinal axis of the buoyant unit 102 ), and is the horizontal distance from the centroid of the water plane area of the buoyant unit 102 to the centroid of the water plane area of the entire structure 100 .
- FIG. 4A one of the buoyant units 102 is shown along with the support member 106 , when the structure 100 is upright, i.e. not being rocked by waves or wind.
- the additional buoyant units 102 are omitted from these FIGS. for simplicity.
- the orientation of the buoyant unit 102 in FIG. 4A is the same as that illustrated in FIGS. 1 , 2 A, and 2 B.
- the water plane area i.e. the cross-section presented to the water surface 302 , is elliptical, as seen in FIG. 4B .
- the major diameter d major,1 is the distance between where the left and right edges of the unit 102 intersect the waterline 302 in FIG. 4A .
- the horizontal distance 1 from the center of the ellipse to the centroid of the structure 100 which in this case is the center of the water plane area of the support unit 106 , is also shown in FIG. 4B .
- FIG. 4C the structure 100 is shown tilted dramatically to the left. Again, the water plane area of the buoyant unit 102 is elliptical, as seen in FIG. 4D .
- the minor diameter d minor is again equal to d unit .
- d major,2 d unit /sin ⁇ , where ⁇ is the new angle at which the unit 102 intersects the water line 302 .
- the horizontal distance 2 from the centroid of the water plane area of the buoyant unit 102 to the centroid of the structure 100 is also larger than that of FIG. 4B , since the center of the water plane area of the buoyant unit 102 is farther to the left due to the larger major diameter d major,2 .
- centroid of the water plane area of the entire structure 100 is no longer coincident with the centroid of the water plane area of the support member 106 , but is shifted slightly to the left.
- 2> 1 the contribution of each buoyant unit 102 to the moment of inertia I of the structure 100 , which is proportional to A 2 , increases when the respective unit 102 tips, providing increased stability when the structure 100 is impacted by waves or wind.
- a floating support structure should be subjected to relatively small motions when affected by wind, waves, and current in the directions of surge, sway, pitch, roll, yaw, and heave.
- the natural period depends on, among other parameters, the mass of the structure.
- the sloping buoyant units 102 of the above-described exemplary embodiments have a plan view that presents a large area exposed to water above and below the units. This results in a large added mass when considering heave, i.e. vertical motions, of the floatable structure.
- the structure 100 further includes a heave plate 150 .
- heave may not be much of a concern once the structure 100 is anchored to the sea floor 304 with the tendon or tendons 404 , but heave can be a problem when the structure 100 is being towed from the quay to the installation site.
- the structure 100 further includes the heave plate 150 , which minimizes heave while the structure 100 is being towed to the installation site and/or after installation.
- a heave plate is typically generally plate-shaped; i.e. has two roughly parallel planar surfaces and is relatively thin in the direction perpendicular to these planes.
- the planar surfaces are typically disposed perpendicular to the direction of heave (i.e. roughly horizontal, parallel to the surface of the water 302 and to the sea floor 304 ) for increasing the effective mass of the structure to which they are attached (in this case the structure 100 ).
- a plate so attached affects the dynamic behavior of the structure 100 by increasing the effective mass and the viscous drag in the heave (vertical) direction.
- the heave plate 150 can be any relatively thin square, circular, rectangular, or any other shape of plate, and can either be solid or have holes punched in it.
- the heave plate 150 is circular, and is strengthened by hexagonal ridges 152 .
- the shape of the plate 150 and ridges 152 are exemplary only and are in no way intended to be limiting.
- the heave plate 150 may have any shape in plan view and may have any number and configuration of ridges and/or holes on or in it.
- the stiffness of the lines 402 , 404 can be selected accordingly, for example, by selecting an appropriate material. Additionally or alternatively, the mass of the structure can be selected, for example, by adding or subtracting ballast.
- buoyant units are sloped. The result is that the formation of vortexes are disrupted and VIMs are diminished.
- Another feature of some of the above-described exemplary embodiments is that the very large cost of offshore construction can mostly be avoided. Except for the preset anchors and their attachment to the floatable structure, the fabrication, assembly, launching and outfitting of the complete wind turbine structure can be accomplished at or near the quay. This will, however, require reasonably deep water at the quay and no overhead obstructions that would interfere with towing to the installation site. This feature is aided by the sloping buoyant units and the fact that they intersect the water surface with a large elliptical waterplane area at a large distance from the centerline of the structure. A requirement for stability for a floating body is that the body's metacenter be above the center of gravity of the body. The metacentric height (i.e.
- the distance between the center of gravity and the metacenter is equal to the moment of inertia of the waterplane area divided by the volume of displaced water plus or minus the distance between the centers of buoyancy and gravity when the body is in equilibrium.
Abstract
An apparatus for supporting an additional structure near a surface of a body of water, and a system which includes the apparatus and further includes the structure attached to the apparatus. The apparatus and the system are each configured to assume a rest position and orientation when the apparatus or system is floating at the surface and when the body of water is substantially still, where the rest orientation defines a vertical direction extending from the surface to a keel at a lowermost position of the apparatus. The apparatus includes a support member, which, in use, is attached to the additional structure; and buoyant units. Each buoyant unit is attached to the support member at or near the keel and extends from the keel in a longitudinal direction of the buoyant unit, which longitudinal direction defines an angle of approximately 35°-65° with respect to the vertical direction.
Description
- This application claims priority to U.S. Provisional Application Ser. No. 61/982,258, filed Apr. 21, 2014, the disclosure of which is hereby incorporated by reference.
- The present invention relates to a floatable support structure configured to be anchored to the sea floor and to support an additional device such as an offshore wind turbine.
- A support structure for an offshore wind turbine must be stable and safe. Wind turbines can operate satisfactorily when motions due to wind current and waves are relatively small. However large motions of surge, sway, pitch, roll, yaw, and heave will result in inefficient operation or shutdown. Therefore, the support structure must have relatively small motions. The support structure motions are affected by the force of wind on the turbine blades, nacelle, and tower, by the wave and current forces on the submerged structure, by the period of the waves, by the period of the rotating turbine blades, and by the natural period of the entire structure, i.e. the time it takes to complete one cycle of motion when subjected to an excitation force. This period depends on the mass of the structure including the added mass of surrounding water, the stiffness of the structure itself (e.g. tower flexing and blade flexing), and the stiffness of the anchoring system of the structure.
- If the period of the support structure is synchronous with the period of the waves, the wave forces will be amplified, leading to disruption of operations and/or structural failure. Therefore it is desirable to ensure that the natural period of the support structure differs substantially from the wave periods for all reasonably expected waves.
- Vortex Induced Motions (VIMs) are another factor affecting the motions of a floating wind turbine support structure. VIMs are defined as motions caused by vortexes that form from current moving past a structure.
- The disclosure relates to an apparatus for supporting an additional structure near a surface of a body of water. Also disclosed is a system which includes the apparatus and further includes the structure attached to the apparatus. The apparatus and the system are each configured to assume a rest position and orientation when the apparatus or system is floating at the surface and when the body of water is substantially still, where the rest orientation defines a vertical direction extending from the surface to a keel at a lowermost position of the apparatus. The apparatus includes a support member, which, in use, is attached to the additional structure; and buoyant units. Each buoyant unit is attached to the support member at or near the keel and extends from the keel in a longitudinal direction of the buoyant unit, which longitudinal direction defines an angle of approximately 35°-65° with respect to the vertical direction.
- Each of the buoyant units may have a certain cross-sectional area at a first position along the longitudinal direction, and a different cross-sectional area at a second position along the longitudinal direction. For example, each of the buoyant units may have a certain cross-sectional area at a first portion of the buoyant unit that is distal from the keel, and a smaller cross-sectional area at a second portion of the buoyant unit that is proximal to the keel. There may be a transitional portion of the buoyant unit between the first portion and the second portion, such as a tapered transitional portion.
- Alternatively, each of the buoyant units may have a cross-sectional area that is substantially constant along the longitudinal direction.
- The buoyant units may be symmetrically disposed around the vertical direction.
- The buoyant units may be three buoyant units, four buoyant units, or more than four buoyant units.
- At least a portion of each buoyant unit that is distal from the keel may include a buoyant material, whose density is lower than the density of the body of water. At least a portion of each buoyant unit that is proximal to the keel may include a ballast material, whose density is equal to or higher than the density of the body of water.
- The apparatus or system may further include at least one anchor line or tether, configured to attach the apparatus to a substantially stationary position within the body of water. The anchor line or tether may include one or more catenary anchor lines, each attached to one of the buoyant units. The anchor line or tether may include one or more tendons, each attached to one of the buoyant units, and configured to assume a substantially vertical orientation to anchor the apparatus or system to the floor of the body of water.
- The apparatus or system may further include a heave plate at the keel.
- The floatable structure may include a wind turbine and associated tower. The support member may be attached to the tower.
- Exemplary embodiments will be described in more detail with reference to the accompanying drawings, in which:
-
FIG. 1 is an elevation view of an exemplary floatable support structure with a tower and turbine attached, and anchored to the sea floor with a vertical tendon at the keel and taut catenary anchors. -
FIG. 2A is an enlarged elevation view of the support structure ofFIG. 1 without the tower and turbine attached, and with additional vertical tendons. -
FIG. 2B is a view similar toFIG. 2A , showing an alternative embodiment of the shape of buoyant units. -
FIG. 3 is a plan view of the support structure ofFIGS. 1 , 2A, and 2B without the tower and turbine attached. -
FIGS. 4A-4D are schematic illustrations showing the water plane area of an exemplary buoyant unit and its distance from the centroid of the structure, where: -
FIG. 4A is a side view of a buoyant unit when the support structure is in its upright position; -
FIG. 4B is a cross-sectional view showing the water plane area of the buoyant unit ofFIG. 4A and the distance of the water plane area from the centroid of the structure; -
FIG. 4C is a side view of the buoyant unit when the support structure is tilted significantly; and -
FIG. 4D is a cross-sectional view showing the water plane area of the buoyant unit in the configuration ofFIG. 4C and the distance of the water plane area from the centroid of the structure. -
FIG. 5 is an elevation view, similar to that ofFIG. 2 , showing a further embodiment of the support structure. -
FIG. 6 is a plan view of the support structure ofFIG. 5 . - Exemplary embodiments described herein provide a floatable support structure configured to be anchored to the sea floor and to support an offshore wind turbine or other device. Some embodiments are considered particularly useful for deep waters, such as in water depths greater than about 40 meters, and some embodiments can be used in depths of over one thousand meters.
- Turning to
FIG. 1 , afloatable support structure 100 is shown supporting awind turbine 200 and floating thewind turbine 200 on awater surface 302. Thefloatable structure 100 is attached to thesea floor 304 bycatenary anchor lines 402 orvertical tendons 404 or, as illustrated, by bothcatenary anchor lines 402 and avertical tendon 404. - With further reference to
FIGS. 2A , 2B, and 3, thestructure 100 includesbuoyant units 102 which meet at thekeel 104 of the structure and extend slopingly upward from thekeel 104. (As used herein, thekeel 104 should be understood to be the bottommost point or area of thestructure 100 when thestructure 100 is in its upright position, which position is seen inFIGS. 1 , 2A, and 2B. In other words, the horizontal line at the bottom of thestructure 100 near where thetendon 404 attaches to thestructure 100 inFIGS. 1 , 2A, and 2B is the keel.) Thestructure 100 also includes a generallycentral support member 106 which attaches to thebuoyant units 102 at thekeel 104 and extends generally vertically therefrom. Thesupport member 106 is configured to attach to and to support atower 202 of theturbine 200. Thebuoyant units 102 and thesupport member 106 are connected to one another byvarious braces members 112. - The
buoyant units 102 are partly submerged in use, i.e. partly below thewater surface 302, as shown. The illustrated embodiments include three suchbuoyant units 102, which slope outward from at or near thekeel 104 to above thewater surface 302. In some presently preferred embodiments, three or morebuoyant units 102 are provided. Eachbuoyant unit 102 is a generally tubular member whose diameter may vary along its length, as will be discussed in detail later. Eachbuoyant unit 102 intersects thesupport member 106 at an angle θ of approximately 35-65°. In other words, the longitudinal direction of eachbuoyant unit 102 is about 35-65° from the longitudinal direction of thesupport member 106, which is vertical when the structure is in its upright position, i.e. not being rocked by waves or wind. - In the embodiment illustrated in
FIG. 2A , eachbuoyant unit 102 is a generally tubular member whose diameter varies along its length to provide a larger cross-sectional area at the top portion of thebuoyant unit 102 than at the bottom. In the alternative embodiment illustrated inFIG. 2B , the diameter is substantially constant along the length. Eachbuoyant unit 102 includesseveral compartments tight bulkheads 114, along its length. There may also be smaller sub-compartments (not illustrated) within thesecompartments upper compartments 102 a may contain buoyant material, and thelower compartments 102 c may contain ballast material. The diameter and length of theupper compartment 102 a of each buoyant unit can be selected to achieve the required buoyant force and water plane area and resulting moment of inertia of thestructure 100's cross section at thewaterline 302. An intermediate, or “transition”section 102 b connects theupper part 102 a of eachbuoyant unit 102 to thelower part 102 c of thebuoyant unit 102. In the embodiment illustrated inFIG. 2A , thelower part 102 c has a smaller cross-sectional area than theupper part 102 a. Depending on requirements for stability, a large portion of eachbuoyant unit 102 will be filled with ballast. Therefore ballast requirements as well as buoyancy requirements will dictate the length and cross-sectional area of eachpart buoyant unit 102. - In a presently preferred embodiment, both the
buoyant units 102 and thesupport member 106 are steel tubular members, which may include ring stiffeners and/or longitudinal stiffeners on the interior to hold the round shape and to resist hydrostatic pressure. In a presently particularly preferred embodiment, theunits 102 andmember 106 include ring stiffeners, and may additionally include longitudinal stiffeners. - The
tower 202 is supported by thesupport member 106. Thetower 202 extends from thesupport member 106 to high above thewater surface 302 to support thewind turbine 200. In more detail, thetower 202 supports thenacelle 204 which supports the turbine rotor blades 206, and which contains the controls, the generator, and other required components. - The
buoyant units 102 are connected to thesupport member 106 bybraces 108. Thebuoyant units 102 are connected to one another by braces 110. Near thekeel 104, thebuoyant units 102 are further connected to thesupport member 106 by connectingmembers 112. - The
support structure 100 is mounted to thesea floor 304 bycatenary anchor lines 402, which may include, for example, chain and/or wire rope, and/or polyester. - The
support structure 100 may additionally or alternatively be attached to thesea floor 304 by a vertical tether such as a tendon ortendons 404. In some embodiments, the tether or tethers may be wire ropes, chains, polyester ropes, or steel or metal tubes. By selecting an appropriate length, modulus of elasticity, and/or cross-sectional area of the tendon or tendons (in addition to further design considerations which will be discussed later with reference toFIGS. 4A-4D ), the natural period of thestructure 100 in heave, surge, sway, pitch, roll, and yaw can be made not to coincide with the wave period of any waves that can be expected in the particular area at which thesupport structure 100 is installed. As is further seen inFIGS. 2A and 2B , the tendon ortendons 404 can be attached to thestructure 100 at or near thekeel 104 and/or at one or more of thebuoyant units 102. In a presently preferred embodiment, onetendon 404 is attached at each of thebuoyant units 102. In practice, it is unlikely that threeanchor lines 402 would be used in conjunction with threetendons 404 at thebuoyant units 102 and anadditional tendon 404 at thekeel 104, as is illustrated. These illustrations are provided for the sake of completeness, to illustrate many possible attachment locations of anchor lines and tendons. - The tendon or
tendons 404 may be attached to thesea floor 304 via an anchor or anchors 406. Depending on the applied force from thetendon 404 and the sea floor conditions, each anchor may be a suction pile, a driven pile, a drilled and grouted pile, a gravity anchor, or any anchor with the capacity to transmit the tendon forces to the sea floor. - It will be appreciated that the
support structure 100 can be fabricated, assembled, and launched at a quay, uprighted, then outfitted with thetower 202 andwind turbine 200 all at quay site. The assembledwind turbine 200 andsupport structure 100 can then be towed in upright position to its installation site and then be attached to previously installed anchors 406 or catenary anchor lines 402. - In the illustrated embodiments, the
support structure 100 is shown supporting anoffshore wind turbine 200 and associatedtower 202. Thestructure 100 can also be used to support any other device, such as an electrical substation, or for oil and gas exploration and production. - In some unillustrated embodiments, the
support structure 100 is used to support a platform for a support station rather than aturbine 200. Since these platforms are generally rectangular in plan view, the structure will typically have fourbuoyant units 102 rather than the threebuoyant units 102 illustrated, each of which will attach to the platform at or near a corner thereof. In a presently preferred embodiment, thesupport member 106 extends through a blind hole or a through hole at the center of the platform to provide further support. - Turning now to
FIGS. 4A-4D , the stability of theexemplary structure 100 will now be discussed. It will be appreciated that the stability of thestructure 100 is proportional to I/V, where I is the moment of inertia of the water plane area (for the hydrodynamic definition of moment of inertia, as opposed to the mass moment of inertia), and V is the volume of water displaced by thestructure 100. For the sake of simplicity,FIGS. 4A-4D illustrate the stability of a single one of thebuoyant units 102. It will further be appreciated that the moment of inertia I is proportional to A 2, where A is the water plane area of thebuoyant unit 102, in other words, the cross-sectional area of thebuoyant unit 102 that is presented to the surface of the water (i.e. the cross-section taken vertically, as opposed to along the longitudinal axis of the buoyant unit 102), and is the horizontal distance from the centroid of the water plane area of thebuoyant unit 102 to the centroid of the water plane area of theentire structure 100. - Turning to
FIG. 4A , one of thebuoyant units 102 is shown along with thesupport member 106, when thestructure 100 is upright, i.e. not being rocked by waves or wind. The additionalbuoyant units 102 are omitted from these FIGS. for simplicity. The orientation of thebuoyant unit 102 inFIG. 4A is the same as that illustrated inFIGS. 1 , 2A, and 2B. Assuming a circular cross-section for theupper part 102 a of the buoyant unit 102 (taken along the longitudinal direction of the buoyant unit 102), the water plane area, i.e. the cross-section presented to thewater surface 302, is elliptical, as seen inFIG. 4B . The minor diameter dminor of the ellipse is equal to the cross-sectional (along the longitudinal axis) diameter of theunit 102, dminor=dunit. The major diameter dmajor,1 is the distance between where the left and right edges of theunit 102 intersect thewaterline 302 inFIG. 4A . Elementary trigonometry tells us that this distance dmajor,1=dunit/sin α, where α is the angle at which theunit 102 intersects thewater line 302, i.e. α=90°−θ. The horizontal distance 1 from the center of the ellipse to the centroid of thestructure 100, which in this case is the center of the water plane area of thesupport unit 106, is also shown inFIG. 4B . - Turning now to
FIG. 4C , thestructure 100 is shown tilted dramatically to the left. Again, the water plane area of thebuoyant unit 102 is elliptical, as seen inFIG. 4D . The minor diameter dminor is again equal to dunit. However, dmajor,2 now much larger. dmajor,2=dunit/sin β, where β is the new angle at which theunit 102 intersects thewater line 302. The horizontal distance 2 from the centroid of the water plane area of the buoyant unit 102 to the centroid of the structure 100 is also larger than that ofFIG. 4B , since the center of the water plane area of the buoyant unit 102 is farther to the left due to the larger major diameter dmajor,2. Note that in this case, the centroid of the water plane area of the entire structure 100 is no longer coincident with the centroid of the water plane area of the support member 106, but is shifted slightly to the left. However, in practice, 2> 1. Thus, the contribution of eachbuoyant unit 102 to the moment of inertia I of thestructure 100, which is proportional to A 2, increases when therespective unit 102 tips, providing increased stability when thestructure 100 is impacted by waves or wind. - As was mentioned in the background section, a floating support structure should be subjected to relatively small motions when affected by wind, waves, and current in the directions of surge, sway, pitch, roll, yaw, and heave. The natural period depends on, among other parameters, the mass of the structure. The sloping
buoyant units 102 of the above-described exemplary embodiments have a plan view that presents a large area exposed to water above and below the units. This results in a large added mass when considering heave, i.e. vertical motions, of the floatable structure. - Turning now to
FIGS. 5 and 6 , in a further alternative embodiment, thestructure 100 further includes aheave plate 150. It will be appreciated that, in embodiments with a vertical tendon ortendons 404, heave may not be much of a concern once thestructure 100 is anchored to thesea floor 304 with the tendon ortendons 404, but heave can be a problem when thestructure 100 is being towed from the quay to the installation site. Furthermore, in embodiments without a vertical tendon ortendons 404, such as embodiments in which thestructure 100 is secured withcatenary anchor lines 402 and nottendons 404, heave may be a concern even once thestructure 100 is installed. Therefore, in some embodiments, thestructure 100 further includes theheave plate 150, which minimizes heave while thestructure 100 is being towed to the installation site and/or after installation. - A heave plate is typically generally plate-shaped; i.e. has two roughly parallel planar surfaces and is relatively thin in the direction perpendicular to these planes. The planar surfaces are typically disposed perpendicular to the direction of heave (i.e. roughly horizontal, parallel to the surface of the
water 302 and to the sea floor 304) for increasing the effective mass of the structure to which they are attached (in this case the structure 100). A plate so attached affects the dynamic behavior of thestructure 100 by increasing the effective mass and the viscous drag in the heave (vertical) direction. Theheave plate 150 can be any relatively thin square, circular, rectangular, or any other shape of plate, and can either be solid or have holes punched in it. - In the illustrated embodiment, the
heave plate 150 is circular, and is strengthened by hexagonal ridges 152. The shape of theplate 150 and ridges 152 are exemplary only and are in no way intended to be limiting. Theheave plate 150 may have any shape in plan view and may have any number and configuration of ridges and/or holes on or in it. - To ensure that the period of the support structure differs substantially from all expected wave periods, the stiffness of the
lines - Since VIMs are particularly pronounced on current moving past vertical, column-like elements, in presently preferred embodiments, the buoyant units are sloped. The result is that the formation of vortexes are disrupted and VIMs are diminished.
- Another feature of some of the above-described exemplary embodiments is that the very large cost of offshore construction can mostly be avoided. Except for the preset anchors and their attachment to the floatable structure, the fabrication, assembly, launching and outfitting of the complete wind turbine structure can be accomplished at or near the quay. This will, however, require reasonably deep water at the quay and no overhead obstructions that would interfere with towing to the installation site. This feature is aided by the sloping buoyant units and the fact that they intersect the water surface with a large elliptical waterplane area at a large distance from the centerline of the structure. A requirement for stability for a floating body is that the body's metacenter be above the center of gravity of the body. The metacentric height (i.e. the distance between the center of gravity and the metacenter) is equal to the moment of inertia of the waterplane area divided by the volume of displaced water plus or minus the distance between the centers of buoyancy and gravity when the body is in equilibrium. The configuration of the embodiments described herein, with a large separation between each buoyant unit's waterplane area, results in a high metacenter and good stability both when free floating while being towed and also when anchored.
- The combination of small motions (due to the structure having a natural period that is not synchronous with wave periods), reduced vortex induced motions, and good stability due to a high metacenter, results in a safe and stable floating structure. The fact that most offshore construction can be avoided results in an economical installation.
- As will be understood by those skilled in the art, the present invention may be embodied in other specific forms without departing from the essential characteristics thereof. Many other embodiments are possible without departing from the essential characteristics thereof. Many other embodiments are possible without deviating from the spirit and scope of the invention. These other embodiments are intended to be included within the scope of the present invention, which is set forth in the following claims.
Claims (34)
1. An apparatus for supporting an additional structure near a surface of a body of water,
wherein the apparatus is configured to assume a rest position and orientation when the apparatus is floating at the surface and when the body of water is substantially still, wherein the rest orientation defines a vertical direction extending from the surface to a keel at a lowermost position of the apparatus,
the apparatus comprising:
a support member configured to be attached to the additional structure; and
a plurality of buoyant units, wherein each buoyant unit is attached to the support member at or near the keel and extends from the keel in a generally longitudinal direction of the buoyant unit, wherein the longitudinal direction of each buoyant unit defines an angle of approximately 35°-65° with respect to the vertical direction.
2. The apparatus of claim 1 , wherein each of the buoyant units comprises a first cross-sectional area at a first position along the longitudinal direction, and a second, different cross-sectional area at a second position along the longitudinal direction.
3. The apparatus of claim 1 , wherein each of the buoyant units comprises a first cross-sectional area at a first portion of the buoyant unit disposed distal from the keel, and a second, smaller cross-sectional area at a second portion of the buoyant unit disposed proximal to the keel.
4. The apparatus of claim 3 , wherein each of the buoyant units further comprises a transitional portion of the buoyant unit disposed between the first portion and the second portion.
5. The apparatus of claim 4 , wherein a cross-section at the transitional portion is tapered.
6. The apparatus of claim 1 , wherein each of the buoyant units comprises a cross-sectional area that is substantially constant along the longitudinal direction.
7. The apparatus of claim 1 , wherein the buoyant units are symmetrically disposed around the vertical direction.
8. The apparatus of claim 1 , wherein the plurality of buoyant units comprises three buoyant units.
9. The apparatus of claim 1 , wherein the plurality of buoyant units comprises at least four buoyant units.
10. The apparatus of claim 1 , wherein at least a portion of each buoyant unit that is distal from the keel comprises a buoyant material, wherein a density of the buoyant material is lower than a density of the body of water.
11. The apparatus of claim 1 , wherein at least a portion of each buoyant unit that is proximal to the keel comprises a ballast material, wherein a density of the ballast material is equal to or higher than a density of the body of water.
12. The apparatus of claim 1 , further comprising at least one anchor line or tether, configured to attach the apparatus to a substantially stationary position within the body of water.
13. The apparatus of claim 12 , wherein the anchor line or tether comprises one or more catenary anchor lines, wherein each of the catenary anchor lines is attached to one of the buoyant units.
14. The apparatus of claim 12 , wherein the anchor line or tether comprises one or more tendons, wherein each of the tendons is attached to one of the buoyant units, wherein each of the tendons is configured to assume a substantially vertical orientation to anchor the apparatus to a floor of the body of water.
15. The apparatus of claim 1 , further comprising a heave plate disposed at the keel.
16. A floatable system, comprising:
a floatable structure; and
an apparatus for supporting the floatable structure near a surface of a body of water,
wherein the system is configured to assume a rest position and orientation when the system is floating at the surface and when the body of water is substantially still, wherein the rest orientation defines a vertical direction extending from the surface to a keel at a lowermost position of the apparatus,
the apparatus comprising:
a support member, wherein the support member is attached to the additional structure; and
a plurality of buoyant units, wherein each buoyant unit is attached to the support member at or near the keel and extends from the keel in a generally longitudinal direction of the buoyant unit, wherein the longitudinal direction of each buoyant unit defines an angle of approximately 35°-65° with respect to the vertical direction.
17. The system of claim 16 , wherein each of the buoyant units comprises a first cross-sectional area at a first position along the longitudinal direction, and a second, different cross-sectional area at a second position along the longitudinal direction.
18. The system of claim 16 , wherein each of the buoyant units comprises a first cross-sectional area at a first portion of the buoyant unit disposed distal from the keel, and a second, smaller cross-sectional area at a second portion of the buoyant unit disposed proximal to the keel.
19. The system of claim 18 , wherein each of the buoyant units further comprises a transitional portion of the buoyant unit disposed between the first portion and the second portion.
20. The system of claim 19 , wherein a cross-section at the transitional portion is tapered.
21. The system of claim 16 , wherein each of the buoyant units comprises a cross-sectional area that is substantially constant along the longitudinal direction.
22. The system of claim 16 , wherein the buoyant units are symmetrically disposed around the vertical direction.
23. The system of claim 16 , wherein the plurality of buoyant units comprises three buoyant units.
24. The system of claim 16 , wherein the plurality of buoyant units comprises at least four buoyant units.
25. The system of claim 16 , wherein at least a portion of each buoyant unit that is distal from the keel comprises a buoyant material, wherein a density of the buoyant material is lower than a density of the body of water.
26. The system of claim 16 , wherein at least a portion of each buoyant unit that is proximal to the keel comprises a ballast material, wherein a density of the ballast material is equal to or higher than a density of the body of water.
27. The system of claim 16 , further comprising at least one anchor line or tether, configured to attach the apparatus to a substantially stationary position within the body of water.
28. The system of claim 27 , wherein the anchor line or tether comprises one or more catenary anchor lines, wherein each of the catenary anchor lines is attached to one of the buoyant units.
29. The system of claim 27 , wherein the anchor line or tether comprises one or more tendons, wherein each of the tendons is attached to one of the buoyant units, wherein each of the tendons is configured to assume a substantially vertical orientation to anchor the system to a floor of the body of water.
30. The system of claim 16 , wherein the floatable structure comprises a wind turbine and associated tower.
31. The system of claim 30 , wherein the support member is attached to the tower.
32. The system of claim 16 , further comprising a heave plate disposed at the keel.
33. A support system for supporting a structure adjacent to a surface of a body of water, comprising:
a support member defining a resting axis;
a plurality of buoyant units attached to the support member at or near a keel of the support system for enhancing buoyancy thereof and for reducing vortex induced vibration, wherein each of the buoyant units is at least partially filled with buoyant material such that each of the buoyant units has a net buoyancy which helps support the structure, and wherein each of the buoyant units defines a longitudinal direction, and wherein the longitudinal direction of each buoyant unit defines an angle of approximately 35°-65° with respect to the resting axis of the support member.
34. The support system of claim 33 , wherein the longitudinal direction of each buoyant unit is not parallel to the longitudinal direction of any of the other buoyant units.
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US20160318628A1 (en) * | 2013-12-30 | 2016-11-03 | Google Inc. | Spar Buoy Platform |
JP2019521043A (en) * | 2016-06-20 | 2019-07-25 | ナス アンド ウインド アンデュストリー | Floating body device supporting an offshore wind turbine and corresponding floating wind turbine unit |
CN112086893A (en) * | 2020-08-25 | 2020-12-15 | 中国能源建设集团广东省电力设计研究院有限公司 | Boarding structure of offshore booster station |
SE2100014A1 (en) * | 2021-01-28 | 2022-07-29 | Josok Ab | Wind Power Plant |
SE2100015A1 (en) * | 2021-01-28 | 2022-07-29 | Josok Ab | Mooring System |
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WO2015164386A1 (en) | 2014-04-21 | 2015-10-29 | Copple Robert W | Floatable support structure for an offshore wind turbine or other device |
KR20180108195A (en) * | 2017-03-24 | 2018-10-04 | 마스텍중공업 주식회사 | Floating offshore wind power generation plant |
SE542925C2 (en) | 2018-01-19 | 2020-09-15 | Freia Offshore Ab | Floating wind power platform |
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EP4323644A1 (en) | 2021-04-12 | 2024-02-21 | Stiesdal Offshore A/S | Offshore wind turbine system and offshore platform |
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FR2970695B1 (en) | 2011-01-25 | 2013-01-04 | Dcns | FLOATING SUPPORT FOR OFFSHORE STRUCTURE OF WIND TYPE |
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FR2977857B1 (en) * | 2011-07-15 | 2013-08-23 | Dcns | FLOATING SUPPORT FOR AN OFFSHORE STRUCTURE SUCH AS IN PARTICULAR A WINDMILL |
KR20140029666A (en) * | 2012-08-29 | 2014-03-11 | 한국건설기술연구원 | Floating structure for wind turbine tower |
WO2015164386A1 (en) | 2014-04-21 | 2015-10-29 | Copple Robert W | Floatable support structure for an offshore wind turbine or other device |
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2015
- 2015-04-21 WO PCT/US2015/026893 patent/WO2015164386A1/en active Application Filing
- 2015-04-21 US US14/692,715 patent/US20150298772A1/en not_active Abandoned
- 2015-04-21 JP JP2016563408A patent/JP6607867B2/en active Active
- 2015-04-21 EP EP15783470.6A patent/EP3131808B1/en active Active
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2016
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US8893638B2 (en) * | 2010-01-29 | 2014-11-25 | Dcns | Floating support for offshore structure such as a wind generator in particular |
Cited By (9)
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US20160318628A1 (en) * | 2013-12-30 | 2016-11-03 | Google Inc. | Spar Buoy Platform |
JP2019521043A (en) * | 2016-06-20 | 2019-07-25 | ナス アンド ウインド アンデュストリー | Floating body device supporting an offshore wind turbine and corresponding floating wind turbine unit |
CN112086893A (en) * | 2020-08-25 | 2020-12-15 | 中国能源建设集团广东省电力设计研究院有限公司 | Boarding structure of offshore booster station |
SE2100014A1 (en) * | 2021-01-28 | 2022-07-29 | Josok Ab | Wind Power Plant |
SE2100015A1 (en) * | 2021-01-28 | 2022-07-29 | Josok Ab | Mooring System |
WO2022164371A1 (en) * | 2021-01-28 | 2022-08-04 | Josok Ab | Mooring system |
WO2022164368A1 (en) * | 2021-01-28 | 2022-08-04 | Josok Ab | Wind power plant |
SE545543C2 (en) * | 2021-01-28 | 2023-10-17 | Tjololo Ab | Semi-submersible Wind Power Platform |
SE545666C2 (en) * | 2021-01-28 | 2023-11-28 | Tjololo Ab | Mooring System |
Also Published As
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US9663915B2 (en) | 2017-05-30 |
US20160362861A1 (en) | 2016-12-15 |
US9803328B2 (en) | 2017-10-31 |
US20170241094A1 (en) | 2017-08-24 |
JP6607867B2 (en) | 2019-11-20 |
EP3131808B1 (en) | 2022-08-03 |
EP3131808A4 (en) | 2017-11-15 |
JP2017513763A (en) | 2017-06-01 |
WO2015164386A1 (en) | 2015-10-29 |
EP3131808A1 (en) | 2017-02-22 |
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