Heel tank dampers for floating structures.

Abstract

The barge-type wind turbine platform combined with a heel tank damper includes a keystone and two pairs of bottom beams, each pair having two bottom beams connected to opposite sides of the keystone, the combined pair of bottom beams defining a foundation. A U-shaped ballast duct is attached or formed within each pair of bottom beams. Each ballast duct contains ballast water, and the ballast water extends from an outwardly extending portion of each bottom beam of each pair of bottom beams, such that an air volume is defined between the surface of the ballast water in each outwardly extending portion and the outwardly facing wall of each outwardly extending portion, and an internal damping element is provided within each ballast duct. The heel tank damper is defined by the ballast ducts and their respective internal damping elements.

Description

[Technical Field]

[0001]

[0001] The present invention relates generally to floating platforms, and more particularly to an improved floating offshore wind turbine (FOWT) platform having an improved mass damper system configured to mitigate undesirable dynamic response due to heeling during operation. [Background technology]

[0002]

[0002] Wind turbines for converting wind energy into electricity are known and provide an alternative energy source for power companies. On land, large clusters of wind turbines, often amounting to hundreds of wind turbines, may be installed together in one geographical area. These clusters may generate undesirably high levels of noise and may appear aesthetically unpleasing. These onshore wind turbines may not have optimal air flow due to obstacles such as hills, trees, and buildings.

[0003]

[0003] Clusters of wind turbines may also be located offshore, but near shore, at depths that allow the wind turbines to be fixedly attached to foundations on the seabed. At sea, the airflow to the wind turbines is less disrupted by the presence of various obstacles (i.e., hills, trees, and buildings), resulting in higher average wind speeds and more power. At these coastal locations, the foundations required to attach the wind turbines to the seabed are relatively expensive and can only be achieved at relatively shallow depths, such as a maximum depth of about 45 meters.

[0004]

[0004] The National Renewable Energy Laboratory has determined that winds along the U.S. coastline with water depths of 30 meters or more have an energy capacity of approximately 3,200 TWh / year. This represents approximately 90 percent of the U.S.'s total energy use of approximately 3,500 TWh / year. The majority of offshore wind resources are located between 37 and 93 kilometers offshore, in water depths of more than 60 meters. Fixed foundations for wind turbines in such deep waters are likely not economically feasible. This limitation has led to the development of floating platforms for wind turbines. Known floating wind turbine platforms are anchored to the seabed with mooring lines and can provide some stability to the tower and turbine against external loads from wind, waves, and currents, as well as loads associated with the dynamics of the wind turbine mounted thereon. However, floating wind turbine platforms and the tower and turbine mounted thereon can still experience undesirable instability due to external loads from wind, waves, and currents.

[0005]

[0005] It would therefore be desirable to provide a floating wind turbine platform with an improved mass damper system configured to mitigate undesirable dynamic response due to heel motion during operation. Summary of the Invention [Means for solving the problem]

[0006] This application describes various embodiments of a FOWT platform with an improved mass damper system configured to mitigate undesirable dynamic response due to heel motion during operation. In one embodiment, a barge-type wind turbine platform combined with a heel tank damper, capable of floating on water and supporting a wind turbine thereon, includes a keystone, a first pair of bottom beams having two bottom beams connected to opposite sides of the keystone, and a second pair of bottom beams including two bottom beams connected to opposite sides of the keystone, the second pair of bottom beams having longitudinal axes perpendicular to the longitudinal axis of the first pair of bottom beams, and the combined first and second pair of bottom beams defining a foundation. Each bottom beam in the first pair of bottom beams and the second pair of bottom beams has an outwardly extending portion at a distal end, and a U-shaped ballast duct is attached or formed within each of the bottom beam pairs and extends between the outwardly extending portions of each bottom beam of each bottom beam pair. Each ballast duct contains ballast water, and the ballast water extends from the outwardly extending portion of each bottom beam of each bottom beam pair, such that an air volume is defined between the surface of the ballast water in each outwardly extending portion and the outwardly facing wall of each outwardly extending portion, and an internal damping element is provided within each ballast duct. A heel tank damper is defined by the ballast ducts and their respective internal damping elements.

[0007]

[0007] In a second embodiment, a method of reducing dynamic response due to heeling in a barge-type wind turbine platform capable of floating on water and supporting a wind turbine thereon, the barge-type wind turbine platform having a keystone, a first pair of bottom beams having two bottom beams connected to opposite sides of the keystone, a second pair of bottom beams having two bottom beams connected to opposite sides of the keystone, the second pair of bottom beams having longitudinal axes perpendicular to the longitudinal axis of the first pair of bottom beams, the first pair of bottom beams and the second pair of bottom beams combined defining a footing, The barge-type wind turbine platform includes: a barge-type wind turbine platform, each bottom beam in the second pair of bottom beams having an outwardly extending portion at a distal end; the first pair of bottom beams and the second pair of bottom beams defining a foundation having a cruciform shape; a U-shaped ballast duct attached to and / or formed within each of the bottom beam pairs, extending between the outwardly extending portions of each bottom beam of each bottom beam pair; each ballast duct containing ballast water extending from the outwardly extending portion of each bottom beam of each bottom beam pair, such that an air volume is defined between a surface of the ballast water in each outwardly extending portion and an outwardly facing wall of each outwardly extending portion; and an internal damping element within each ballast duct. A heel tank damper is defined by the ballast ducts and their respective internal damping elements. The method includes reducing dynamic response due to heel motion by using ballast water within the ballast ducts as mass elements vibrating in a predetermined direction.

[0008] In another embodiment, a barge-type wind turbine platform combined with a heel tank damper, capable of floating on water and supporting a wind turbine thereon, includes four connected bottom beams extending radially outward from a center point and defining a foundation having a cross shape, each having an outwardly extending portion at a distal end, an outwardly facing wall of each outwardly extending portion having an opening extending between the interior of the outwardly extending portion and the atmosphere outside the outwardly extending portion, and a cross-shaped wall having four legs extending vertically between the lower wall of each beam and the upper wall of each beam, the distal end of each of the four legs being spaced from the distal end wall of the respective beam. The integral heel tank damper has multiple ballast conduits formed between the cross-shaped walls and the walls of each beam, the ballast conduits defining multiple fluid flow paths within the foundation.

[0009]

[0009] In an additional embodiment, a barge-type wind turbine platform combined with a heel tank damper, capable of floating on water and supporting a wind turbine thereon, includes a keystone, a first pair of bottom beams having two bottom beams connected to opposite sides of the keystone, and a second pair of bottom beams having two bottom beams connected to opposite sides of the keystone, the second pair of bottom beams having a longitudinal axis perpendicular to the longitudinal axis of the first pair of bottom beams, the combined first pair of bottom beams and the second pair of bottom beams defining a foundation having a cruciform shape, each bottom beam in the first pair of bottom beams and the second pair of bottom beams having an outwardly extending portion at a distal end, a U-shaped ballast conduit mounted in and / or formed within each of the bottom beam pairs, extending between the outwardly extending portions of each bottom beam of each pair of bottom beams, and each a ballast conduit having ballast water therein extending from the outwardly extending portion of each bottom beam of each pair of bottom beams, such that a volume of air is defined between a surface of the ballast water in each outwardly extending portion and an outwardly facing wall of each outwardly extending portion; an interior wall within each bottom beam extending vertically between a lower wall and an upper wall of each bottom beam, the interior wall extending longitudinally from a distal end wall of each bottom beam to a vertically extending exterior wall of a keystone; and a cross-shaped wall within the keystone extending vertically between the lower wall and the upper wall of the keystone, each leg of the cross-shaped wall being longitudinally aligned with one of the interior walls of the bottom beams, the exterior wall and each leg of the cross-shaped wall of the keystone having a vertically extending fluid flow opening formed therein, defining an internal damping element. The heel tank damper system is defined by a combination of a plurality of fluid flow paths defined by ballast conduits and fluid flow openings in the keystone wall.

[0010] In a further embodiment, a semi-submersible wind turbine platform combined with a heel tank damper, capable of floating on water and supporting a wind turbine thereon, includes a keystone, three bottom beams extending radially outward from the keystone, a central column attached to the keystone, and three outer columns attached to distal ends of the bottom beam, wherein the central column, each outer column, the keystone, and the space inside the bottom beam therebetween define three generally U-shaped ballast conduits, each ballast conduit having ballast water therein, the ballast water extending from an upper portion of the central column to an upper portion of an outer column, such that a volume of air is defined between the surface of the ballast water in each column and the outward-facing wall of each column, and the semi-submersible wind turbine foundation includes an internal damping element within each ballast conduit. The heel tank damper is defined by the combination of the three ballast conduits.

[0011] Various advantages of the present invention will become apparent to those skilled in the art from the following detailed description when read in light of the accompanying drawings. [Brief explanation of the drawings]

[0012] [Figure 1]

[0012] FIG. 1 is a perspective view of a first embodiment of an improved barge-style floating offshore wind turbine (FOWT) platform in accordance with the present invention, shown with a wind turbine and wind turbine tower mounted thereon. [Figure 2]

[0013] FIG. 2 is a cross-sectional view taken along line 2-2 of FIG. [Figure 3]

[0014] FIG. 3 is a cross-sectional view taken along line 3-3 of FIG. [Figure 4]

[0015] FIG. 10 is a perspective view of a second embodiment of a FOWT platform according to the present invention shown with a wind turbine and a wind turbine tower mounted thereon. [Figure 5]

[0016] FIG. 5 is a perspective view of a first portion of the FOWT platform shown in FIG. 4, showing a first fluid flow conduit. [Figure 6]

[0017] FIG. 5 is a perspective view of a second portion of the FOWT platform shown in FIG. 4, showing a second fluid flow conduit. [Figure 7]

[0018] FIG. 10 is a schematic perspective view of a ballast conduit in a third embodiment of a FOWT platform according to the present invention. [Figure 8]

[0019] FIG. 8 is a top view of the FOWT platform shown in FIG. 7. [Figure 9]

[0020] FIG. 10 is a cross-sectional top view of a fourth embodiment of a FOWT platform according to the present invention. [Figure 10]

[0021] FIG. 10 is a perspective view of one leg of a fifth embodiment of a FOWT platform according to the present invention. [Figure 11]

[0022] FIG. 10 is a side elevation view in cross section of a sixth embodiment of a FOWT platform in accordance with the present invention. [Figure 12]

[0023] FIG. 12 is a cross-sectional top view taken along line 12-12 of FIG.

[0024] FIG. 12A is an enlarged view of a portion of the FOWT platform shown in FIG. [Figure 13]

[0025] FIG. 13A is a side elevational view in cross section of a portion of a seventh embodiment of a FOWT platform according to the present invention.

[0026] FIG. 13B is a side elevational view in cross section of a portion of an alternative embodiment of the FOWT platform shown in FIG. 13A. [Figure 14]

[0027] FIG. 10 is a side elevational view in cross section of an eighth embodiment of a FOWT platform according to the present invention, shown in a first position. [Figure 15]

[0028] FIG. 15 is a side elevation view of a cross section of the FOWT platform shown in FIG. 14 shown in a second position. [Figure 16]

[0029] FIG. 13 is a perspective view of a ninth embodiment of a FOWT platform according to the present invention, shown with a wind turbine and wind turbine tower mounted thereon. [Figure 17]

[0030] 17 is a cross-sectional view taken along line 17-17 of FIG. 16. [Figure 18]

[0031] FIG. 18 is a cross-sectional view of an alternative embodiment of the FOWT platform shown in FIGS. 16 and 17. [Figure 19]

[0032] FIG. 19 is a cross-sectional view of an additional alternative embodiment of the FOWT platform shown in FIGS. 16, 17, and 18. DETAILED DESCRIPTION OF THE INVENTION

[0013]

[0033] The present invention will now be described with occasional reference to illustrated embodiments of the invention. However, the present invention may be embodied in different forms and should not be construed as limited to the embodiments set forth herein, nor should it be construed as limited to any particular order of preference. Rather, these embodiments are provided so that this disclosure will be thorough and will convey the scope of the invention to those skilled in the art.

[0014]

[0034] Embodiments of the present invention disclosed below generally provide improvements to floating offshore wind turbine (FOWT) platforms, including, but not limited to, providing an improved mass damper system configured to mitigate undesirable dynamic response due to heel motion during operation.

[0015]

[0035] As used herein, the term parallel is defined as lying in a plane substantially parallel to the horizon, and the term vertical is defined as lying substantially perpendicular to the plane of the horizon.

[0016]

[0036] As used herein, the term heel or heeling refers to a rotation resulting from the combined effects about the roll and pitch axes, which may be caused by wind pressure, waves, and / or ocean currents.

[0017]

[0037] The embodiments of the improved FOWT platform described and illustrated herein are suitable for commercial-scale floating turbines with power capacities in the range of about 15 MW to about 30 MW. The improved FOWT platform described and illustrated herein may also be suitable for commercial-scale floating turbines with power capacities greater than about 30 MW and less than about 15 MW. The improved FOWT platform described and illustrated herein advantageously has an improved mass damper system configured to mitigate undesirable dynamic responses of the FOWT platform, such as due to heeling during operation.

[0018]

[0038] Referring now to the drawings, and particularly to FIGS. 1 through 3, a first embodiment of an improved FOWT platform in accordance with the present invention is shown generally at 10.

[0039] The illustrated FOWT platform 10 includes a hull or foundation 12 that supports a wind turbine tower 14. The wind turbine tower 14 supports a wind turbine 16. The foundation 12 is a barge-type foundation, structured and configured to float on water. Accordingly, when the foundation 12 is floating on water, a portion of the foundation 12 is above water. To limit movement of the FOWT platform 10 above water, mooring lines (not shown) may be attached to the FOWT platform 10 and may also be attached to anchors (not shown) on the seabed.

[0019]

[0040] In the illustrated embodiment, the wind turbine tower 14 is tubular and may have any suitable outer diameter and height. In the illustrated embodiment, the outer diameter of the wind turbine tower 14 tapers from a first diameter at its base to a second, smaller diameter at its upper end. Alternatively, the outer diameter of the wind turbine tower 14 may have a uniform diameter. The wind turbine tower 14 may be formed from any desired material, including, but not limited to, steel, concrete, fiber-reinforced polymer (FRP) composites, and composite laminate materials. If desired, the wind turbine tower 14 may be formed from any number of sections 14A.

[0020]

[0041] The wind turbine 16 may be conventional and may include a rotatable hub 18. At least one rotor blade 20 is coupled to the hub 18 and extends outwardly from the hub 18. The hub 18 is rotatably coupled to a generator (not shown). The generator may be coupled to an electrical grid (not shown) via a transformer (not shown) and an underwater power cable (not shown). In the illustrated embodiment, the hub 18 has three rotor blades 20. In other embodiments, the hub 18 may have more than four or fewer than three rotor blades 20. Opposite the hub 18, a nacelle 21 is attached to the wind turbine 16.

[0021]

[0042] Typically, the lower portion of the foundation 12 may be submerged to a depth within a range of about 30 ft to about 100 ft (about 9.1 m to about 30.5 m). Accordingly, when the foundation 12 is floating semi-submersible in water, a portion of the foundation 12 is above the water and a portion of the foundation 12 is below the waterline. As used herein, the waterline is defined as the approximate line where the surface of the water meets the FOWT platform 10.

[0022]

[0043] The illustrated foundation 12 may be formed from four bottom beams 22 that extend radially outward from a keystone 24 and provide buoyancy. When assembled together, the bottom beams 22 and keystone 24 define a cruciform shape, i.e., a cross-shaped foundation 12. Additionally, the keystone 24 supports the tower 14. The tower 14 may be attached to the keystone 24 via a transition member 26, configured, for example, as a steel tube.

[0023]

[0044] If desired, a work platform 28 may be mounted to the base of the tower 14 and may include a gangway or elevated gangway 30 mounted around all or a portion of the base of the tower 14 and / or the work platform 28.

[0024]

[0045] In the embodiment illustrated herein, the wind turbine 16 is a horizontal axis wind turbine. Alternatively, the wind turbine may be a vertical axis wind turbine (not shown). The size of the wind turbine 16 varies based on the wind conditions at the location where the FOWT platform 10 is anchored and the desired power output. For example, the wind turbine 16 has an output of approximately 15 MW. Alternatively, the wind turbine 16 may have an output in the range of approximately 15 MW to approximately 30 MW. Additionally, the wind turbine 16 may have an output less than approximately 15 MW or greater than approximately 30 MW.

[0025]

[0046] The illustrated keystone 24 may be formed from prestressed reinforced concrete and may include one or more internal cavities, as described below. Any desired process may be used to manufacture the keystone 24, such as spun concrete processes or using conventional concrete forms. Alternatively, other processes, such as those used in the precast concrete industry, may also be used. The concrete of the keystone 24 may be reinforced with any conventional reinforcing material, such as high-tensile steel cables and high-tensile steel reinforcing bars, or REBARs. Alternatively, the keystone 24 may be formed from high-performance concrete, FRP, steel, or a combination of prestressed reinforced concrete, high-performance concrete, FRP, and steel.

[0026]

[0047] The illustrated bottom beam 22 is formed from prestressed reinforced concrete as described above. Alternatively, the bottom beam 22 may be formed from high performance concrete, FRP, steel, or a combination of prestressed reinforced concrete, high performance concrete, FRP, and steel. The bottom beam 22 may be formed having any desired length.

[0027]

[0048] The keystone 24 and bottom beam 22 may then be assembled and longitudinally post-tensioned to define the pair of bottom beams 22A and 22B and thus the foundation 12. The keystone 24 and bottom beam 22 may be post-tensioned by any desired post-tensioning method, thereby applying compression between the keystone 24 and the bottom beam 22.

[0028]

[0049] 1-3, each bottom beam 22 includes an outwardly extending portion 32 at its distal end (extending upwardly when viewed in FIGS. 1-3). The upwardly facing wall of each outwardly extending portion 32 includes an opening 34 that extends between the interior of the outwardly extending portion 32 and the atmosphere outside the outwardly extending portion 32.

[0029]

[0050] A first pair of bottom beams 22A is shown in cross section in Figure 2 and includes two bottom beams 22 connected to opposite sides of a keystone 24. A second pair of bottom beams 22B is shown in cross section in Figure 3 and includes two bottom beams 22 connected to opposite sides of a keystone 24 and having longitudinal axes perpendicular to the longitudinal axis of the first pair of bottom beams 22A. A generally U-shaped ballast conduit 36 ​​is attached or formed within each of the bottom beam pairs 22A, 22B and extends between the outwardly extending portions 32 of each bottom beam 22 of each bottom beam pair 22A, 22B. Each ballast conduit 36 ​​also includes an internal damping element 38 therein. The internal damping elements 38 may be any desired damping elements, including, but not limited to, a wall or partition having a fixed opening or orifice therethrough, a wall or partition having a movable or otherwise adjustable orifice therethrough, a gate valve, and / or any other valve or structure that reduces or controls the flow of ballast water between the bottom beams 22 of the bottom beam pair 22A, 22B. The ballast conduits 36 and their respective internal damping elements 38 define a heel tank damper 39.

[0030]

[0051] 2 and 3 , each ballast conduit 36 ​​is filled with a fluid or ballast water, such as seawater. It will be understood that each ballast conduit 36 ​​includes a valve and / or a pump (not shown) for selectively adding and removing ballast water from each ballast conduit 36. Because each of the outwardly extending portions 32 includes an opening 34 open to the atmosphere outside the foundation 12, when the FOWT platform 10 is moved, such as by heeling, turbine harmonic loads, or wave environmental loads, the ballast water in the bottom beam pair 22A, 22B can move up and down within the outwardly extending portions 32, as indicated by arrow A. It will be understood that the ballast conduit 36 ​​in the bottom beam pair 22A is fluidly connected to the ballast conduit 36 ​​in the bottom beam pair 22B. It will further be understood that the ballast conduit 36 ​​in the bottom beam pair 22A may, if desired, intersect above, below, or through (via one or more pipes or tubes) the ballast conduit 36 ​​in the bottom beam pair 22B, as described herein below.

[0031]

[0052] Advantageously, the FOWT platform 10 having the heel tank damper 39 is configured to mitigate undesirable dynamic responses of the FOWT platform 10, such as due to heeling during operation.

[0032]

[0053] The mitigation of undesirable dynamic response described above is achieved by: (1) Use of internal fluid ballast, i.e., ballast water, within ballast conduit 36 ​​of foundation 12 as the mass element of a damper system capable of vibrating in a defined or predetermined direction, as shown by arrow A in FIGS. 2 and 3. (2) the use of ballast water within the ballast conduit 36 ​​of the foundation 12, where the frequency response of the internal fluid ballast is determined by the total mass of fluid within the ballast conduit 36, the total submerged length of the ballast conduit 36, and the free surface area at each vertical end of the ballast conduit 36, i.e., within the outwardly extending portion 32; (3) the use of an internal damping element 38, such as an orifice, within a ballast conduit 36 ​​containing ballast water as a means of controlling the fluid mass response phase; This can be achieved, at least in part, by

[0033]

[0054] 4 through 6, a second embodiment of a FOWT platform according to the present invention is generally designated 40. The FOWT platform 40 is similar to the FOWT platform 10 and includes a foundation 42 that supports the wind turbine 16 mounted on the wind turbine tower 14, as described above. The foundation 42 is a barge-type platform that is structured and configured to float on water. Accordingly, when the foundation 42 is floating on water, a portion of the foundation 42 is above water. To limit movement of the FOWT platform 40 above water, mooring lines (not shown) may be attached to the FOWT platform 40 and may also be attached to anchors (not shown) on the seabed.

[0034]

[0055] The illustrated foundation 42 may be formed from four bottom beams 44 that extend radially outward from a keystone 46 and provide buoyancy. When assembled together, the bottom beams 44 and keystone 46 define a cruciform shape, i.e., a cross-shaped foundation 42. As described above, the keystone 46 supports the tower 14. The tower 14 may be attached to the keystone 46 via the transition piece 26.

[0035]

[0056] If desired, a work platform 28 may be mounted to the base of the tower 14 and may include a gangway or elevated passageway 30 mounted around all or a portion of the base of the tower 14 and / or the work platform 28. The keystone 46 and bottom beam 44 may be formed and assembled as described above.

[0036]

[0057] As shown in Figures 4-6, keystone 46 includes a first fluid flow conduit 46A formed in a lower portion thereof and a second fluid flow conduit 46B formed in an upper portion thereof.

[0058] Similar to the FOWT platform 10, each bottom beam 44 includes an outwardly extending portion 48 at its distal end (extending upwardly when viewed from FIGS. 4 to 6 ). The upwardly facing wall of each outwardly extending portion 48 includes an opening 50 that extends between the interior of the outwardly extending portion 48 and the atmosphere outside the outwardly extending portion 48.

[0037]

[0059] A first pair of bottom beams 44A is shown in FIG. 5 and includes two bottom beams 44 connected on opposite sides of a keystone 46. A second pair of bottom beams 44B is shown in FIG. 6 and includes two bottom beams 44 connected on opposite sides of the keystone 46 and having longitudinal axes perpendicular to the longitudinal axis of the first pair of bottom beams 44A. The bottom beam pairs 44A, 44B, including the connected keystone 46 therebetween, are generally hollow and define a generally U-shaped ballast conduit 52 extending between the outwardly extending portions 48 of each bottom beam 44 of each pair of bottom beams 44A, 44B. The ballast conduits 36, 52, and their respective fluid flow conduits 46A, 46B define heel tank dampers 55 and 57.

[0038]

[0060] 5 and 6 , each ballast conduit 52 is filled with ballast water, such as seawater. A line 54 indicates the ballast water level in each outward extension 48. Because each outward extension 48 includes an opening 50 that is open to the atmosphere outside the foundation 42, the ballast water in the bottom beam pair 44A, 44B can move up and down within the outward extension 48 when the FOWT platform 40 is moved by heeling, turbine harmonic loads, wave environmental loads, or the like.

[0039]

[0061] 5 and 6, the keystone 46 includes a first fluid flow conduit 46A and a second fluid flow conduit 46B formed therein. The first fluid flow conduit 46A is configured to allow ballast water to flow within the ballast conduit 52 of the second bottom beam pair 44B, as indicated by arrows 56. Similarly, the second fluid flow conduit 46B is configured to allow ballast water to flow within the ballast conduit 52 of the first bottom beam pair 44A, as indicated by arrows 58. As shown, the ballast conduit 52 of the bottom beam pair 44A is not fluidly connected to the ballast conduit 52 of the bottom beam pair 44B. Thus, ballast water is contained in separate / overlapping fore-aft and side-to-side conduits, specifically, the fluid flow conduits 46A and 46B, which are arranged in an advantageous cross-tank configuration.

[0040]

[0062] The FOWT platform 40 with heel tank dampers 55 and 57 is advantageously configured such that ballast water defines a mass element within the cruciform shape of the foundation 42, and the heel tank dampers 55 and 57 enable the foundation 42 to operate effectively at a rigid body heel natural frequency within its intended wave energy range. As used herein, a rigid body heel natural frequency is a frequency associated with any combination of pitch or roll motion of a rigid body.

[0041]

[0063] Additionally, heel tank dampers 55 and 57 use ballast water as mass elements arranged in a cross tank configuration that allows for effective response mitigation about both the pitch P axis and the roll R axis of foundation 42 shown in FIG. 4 .

[0042]

[0064] 7 and 8 , a third embodiment of a FOWT platform according to the present invention is shown generally at 60. Specifically, FIG. 7 is a schematic perspective view of a heel tank damper 79 within the FOWT platform 60. The FOWT platform 60 is similar to the FOWT platforms 10 and 40 and includes a foundation 62 that supports the wind turbine 16 mounted on the wind turbine tower 14, as described above. The foundation 62 is barge-shaped and structured and configured to float on water. Accordingly, when the foundation 62 is floating on water, a portion of the foundation 62 is above water. To limit movement of the FOWT platform 60 above water, mooring lines (not shown) may be attached to the FOWT platform 60 and may further be attached to anchors (not shown) on the seabed.

[0043]

[0065] The illustrated foundation 62 may be formed from four bottom beams 64 that extend radially outward from a keystone 66 and provide buoyancy. When assembled together, the bottom beams 64 and keystone 66 define a cruciform shape, i.e., a cross-shaped foundation 62. As described above, the keystone 66 supports the tower 14. The tower 14 may be attached to the keystone 66 via the transition piece 26.

[0044]

[0066] If desired, a work platform 28 may be mounted to the base of the tower 14 and may include a gangway or elevated passageway 30 mounted around all or a portion of the base of the tower 14 and / or the work platform 28. The keystone 66 and bottom beam 64 may be formed and assembled as described above.

[0045]

[0067] Similar to FOWT platforms 10 and 40, each bottom beam 64 includes an outwardly extending portion 68 at its distal end (extending upwardly as viewed in FIG. 7 ). The upwardly facing wall of each outwardly extending portion 68 includes an opening 70 that extends between the interior of the outwardly extending portion 68 and the atmosphere outside the outwardly extending portion 68.

[0046]

[0068] The first pair of bottom beams 64A includes two bottom beams 64 connected on opposite sides of a keystone 66. The second pair of bottom beams 64B includes two bottom beams 64 connected on opposite sides of the keystone 66 and having longitudinal axes perpendicular to the longitudinal axis of the first pair of bottom beams 64A. The bottom beam pairs 64A, 64B, including the connected keystone 66 therebetween, are generally hollow and define generally U-shaped ballast conduits 72A and 72B, respectively, extending between the outwardly extending portions 68 of each bottom beam 64 of each pair of bottom beams 64A, 64B.

[0047]

[0069] As shown in FIG. 7 , each ballast duct 72A, 72B is filled with ballast water, such as seawater. Line 74 indicates the ballast water level in each outward extension 68. Because each outward extension 68 includes an opening 70 that is open to the atmosphere outside the foundation 62, the ballast water in the bottom beam pair 64A, 64B can move up and down within the outward extension 68 when the FOWT platform 60 is moved by heeling, turbine harmonic loads, wave environmental loads, or the like. However, unlike the FOWT platform 40, the ballast ducts 72A, 72B intersect and are fluidly connected within the interior of the keystone 66A, defining a heel tank damper 79. Thus, ballast water is contained in the intersecting front-rear and left-right ballast ducts 72A and 72B arranged in an advantageous cross-tank configuration.

[0048]

[0070] Figure 8 is a top view of the FOWT platform 60 having the foundation 62 shown in Figure 7. Advantageously, in an embodiment such as the foundation 62 where the ballast conduits 72A, 72B intersect and connect within the interior of the keystone 66, the foundation 62 will experience an equivalent damper response for dynamic heeling about any orientation of the heel. Such an equivalent damper response occurs when the foundation 62 experiences a 0-degree rotation, i.e., a rotation about the longitudinal axis of either of the bottom beam pairs 64A, 64B (see line 76 in Figure 8), or when the foundation 62 experiences a 45-degree rotation, i.e., a rotation about line 78 in Figure 8.

[0049]

[0071] Referring now to FIG. 9 , a portion of a fourth embodiment of a FOWT platform according to the present invention is generally designated 80. FIG. 9 is a cross-sectional top view of the fourth embodiment of the FOWT platform 80 according to the present invention. The FOWT platform 80 has a similar external shape and size to the FOWT platform 60 and includes a foundation 82 that supports the wind turbine 16 mounted on the wind turbine tower 14, as described above. The foundation 82 is a barge-type foundation and is structured and configured to float on water. Accordingly, when the foundation 82 is floating on water, a portion of the foundation 82 is above water. To limit movement of the FOWT platform 80 above water, mooring lines (not shown) may be attached to the FOWT platform 80 and may also be attached to anchors (not shown) on the seabed.

[0050]

[0072] The illustrated foundation 82 may be formed from four bottom beams 84 that extend radially outward from a central point 86 and provide buoyancy. When assembled together, the bottom beams 84 have a cruciform shape, i.e., define the foundation 82 having a cross shape. Additionally, although not shown in FIG. 9 , each bottom beam 84 includes an outwardly extending portion 68 at a distal end (extending upwardly when looking at FIG. 7 ) and an opening 70 that extends between the interior of the outwardly extending portion 68 and the atmosphere outside the outwardly extending portion 68.

[0051]

[0073] As shown in FIG. 9 , the cross-shaped wall 88 has four legs 88L that extend vertically between the lower wall or base 90 of each beam 84 and the upper wall (not shown) of each beam 84. The distal end of each of the legs 88L is spaced from the distal end wall 84A of each beam 84. The wall 88 defines a unique, integral heel tank damper 93 that includes multiple ballast conduits 91, and thus extended fluid flow paths, within the foundation 82, i.e., between the wall 88 and the wall of each beam 84. Examples of extended fluid flow paths are indicated by arrows 92. As shown, the wall 88 increases the overall length of the ballast conduits 91 relative to the ballast conduits described herein above. The increased length of the ballast conduits 91 facilitates reducing the natural frequency of the heel tank damper 93. Advantageously, the natural frequency of the heel tank damper 93 in the foundation 82 can be increased or decreased by varying the overall length of the leg 88L of the wall 88 in each beam 84.

[0052]

[0074] Referring now to FIG. 10 , a portion of a fifth embodiment of a FOWT platform according to the present invention is generally designated 100. FIG. 10 is a perspective view of one leg 102 of the FOWT platform 100 according to the present invention. The FOWT platform 100 has a similar external shape and size to the FOWT platform 80 and includes a foundation (not shown) that supports the wind turbine 16 mounted on the wind turbine tower 14, as described above. The foundation is a barge-type foundation, structured and configured to float on water. Accordingly, when the foundation is floating on water, a portion of the foundation is above water. To limit movement of the FOWT platform 100 above water, mooring lines (not shown) may be attached to the FOWT platform 100 and may also be attached to anchors (not shown) on the seabed.

[0053]

[0075] Leg 102 represents one portion of a foundation that will include additional legs 102 having longitudinal axes perpendicular to the longitudinal axis of the leg 102 shown.

[0076] The illustrated legs 102 may be formed as one individual member or may be formed from two bottom beams (not shown) extending outward from a keystone (not shown, but similar to keystone 66). As explained above, the legs 102 provide buoyancy to the foundation. When assembled together, the legs 102 define a foundation having a cruciform shape, i.e., a cross-shaped foundation.

[0054]

[0077] Leg 102 is formed as two parallel tanks, including a first tank 104 and a second tank 106, each defining a heel tank damper. First tank 104 includes an outwardly extending portion 108 (extending upward as viewed in FIG. 10 ) at each distal end thereof. The upwardly facing wall of each outwardly extending portion 108 includes an opening 110 extending between the interior of outwardly extending portion 108 and the atmosphere outside outwardly extending portion 108. The interior of first tank 104 defines a generally U-shaped ballast conduit 112 extending between outwardly extending portions 108 at opposite ends of first tank 104, further defining the first heel tank damper. Optionally, ballast conduit 112 may include an internal damping element, such as damping element 38, at or near the center of ballast conduit 112.

[0055]

[0078] The second tank 106 is similar to the first tank 104, but is larger than the first tank 104, and includes an outwardly extending portion 114 (extending upwardly as viewed in FIG. 10 ) at each distal end thereof. The upwardly facing wall of each outwardly extending portion 114 includes an opening 116 extending between the interior of the outwardly extending portion 114 and the atmosphere outside the outwardly extending portion 114. The interior of the second tank 106 defines a generally U-shaped ballast conduit 118 extending between the outwardly extending portions 114 at opposite ends of the second tank 106, and further defines a second heel tank damper. Optionally, the ballast conduit 118 may include an internal damping element, such as damping element 38, at or near the center of the ballast conduit 112. As shown in FIG. 10, the first tank 104 is mounted adjacent to, but not fluidly connected to, the second tank 106 .

[0056]

[0079] The legs 102, which are mounted at right angles to one another to form a base (not shown), are fluidly connected to one another.

[0080] The parallel ballast conduits 112 and 118 combine to define a heel tank damper 119 configured to allow the ballast conduits 112 and 118 to attenuate different frequencies. In the embodiment shown in Figure 10, the first tank 104 is structured and configured for a relatively high frequency response, and the second tank 106 is structured and configured for a relatively low frequency response.

[0057]

[0081] 11, 12, and 12A, a portion of a sixth embodiment of a FOWT platform in accordance with the present invention is shown generally at 120. Figure 11 is a side elevation view of a cross section of FOWT platform 120 in accordance with the present invention, and Figure 12 is a top view of a cross section of FOWT platform 120. Figure 12A is an enlarged view of a portion of FOWT platform 120.

[0058]

[0082] The FOWT platform 120 has an external shape and size similar to the FOWT platform 60 and includes a foundation 122 that supports the wind turbine 16 mounted on the wind turbine tower 14, as described above. The foundation 122 is a barge-type foundation and is structured and configured to float on water. Accordingly, when the foundation 122 is floating on water, a portion of the foundation 122 is above water. To limit movement of the FOWT platform 120 above water, mooring lines (not shown) may be attached to the FOWT platform 120 and may further be attached to anchors (not shown) on the seabed.

[0059]

[0083] The illustrated foundation 122 may be formed from four bottom beams 124 that extend radially outward from a keystone 126 and provide buoyancy. When assembled together, the bottom beams 124 and keystone 126 define a cruciform shape, i.e., a cross-shaped foundation 122. As described above, the keystone 126 supports the tower 14. The tower 14 may be attached to the keystone 66 via a transition piece 26.

[0060]

[0084] Similar to FOWT platforms 10, 40, and 60, each bottom beam 124 includes an outwardly extending portion 128 at its distal end (extending upwardly as viewed in FIG. 11 ). The upwardly facing wall of each outwardly extending portion 128 includes an opening (not shown, but similar to opening 70 shown in FIG. 7 ) that extends between the interior of outwardly extending portion 128 and the atmosphere outside outwardly extending portion 128.

[0061]

[0085] The first pair of bottom beams 124A includes two bottom beams 124 connected on opposite sides of a keystone 126. The second pair of bottom beams 124B includes two bottom beams 124 connected on opposite sides of the keystone 126 and having longitudinal axes perpendicular to the longitudinal axis of the first pair of bottom beams 124A. The bottom beam pairs 124A, 124B, including the connected keystone 126 therebetween, define a plurality of generally U-shaped ballast conduits, described in detail below, extending between outwardly extending portions 128 of each bottom beam 124 of each pair of bottom beams 124A, 124B.

[0062]

[0086] Each bottom beam 124 includes an interior wall 132 that extends vertically between a lower wall or base 134 and an upper wall 136 of each bottom beam 124, and further extends longitudinally from a distal end wall 125 of each bottom beam 124 to a vertically extending outer wall 138 of the keystone 126 and upward into the outwardly extending portion 128 of each bottom beam 124.

[0063]

[0087] Keystone 126 includes a cross-shaped wall 140 extending vertically between a lower wall or base 142 and an upper wall 144 of keystone 126. Each leg of cross-shaped wall 140 is longitudinally aligned with one of the interior walls 132 of bottom beam 124. Wall 138 and each of the legs of cross-shaped wall 140 have a vertically extending fluid flow opening 145 formed therein to define an internal damping element.

[0064]

[0088] 12 and 12A, a plurality of generally U-shaped ballast conduits 146 and 148 extend between the outwardly extending portions 128 of each bottom beam 124 of each bottom beam pair 124A, 124B, respectively. The combination of the plurality of fluid flow paths defined by the ballast conduits 146 and 148 and the fluid flow openings in the walls 138 and 140 of the keystone 126 defines a heel tank damper system 149, which advantageously uses the structure of the ballast conduits 146 and 148 and the flow of ballast water through the fluid flow openings 145 to achieve a desired degree of damping.

[0065]

[0089] 13A, a portion of a seventh embodiment of a FOWT platform in accordance with the present invention is shown generally at 150. Figure 13A is a side elevational view in cross section of a portion of a FOWT platform 150 in accordance with the present invention.

[0066]

[0090] FOWT platform 150 is substantially similar to FOWT 10 and includes keystone 24 and bottom beam 22, which may be assembled and longitudinally post-tensioned to define bottom beam pair 154 as shown in FIG. 13A . Although not shown, FOWT platform 150 includes a second bottom beam pair substantially similar to bottom beam pair 154. Bottom beam pair 154 also includes external damping elements 152 mounted in the upward-facing wall of each outwardly extending portion 32 in place of the openings 34 of FOWT 10. External damping elements 152 may be any desired type of damping element, including, but not limited to, fixed openings through the upward-facing wall of each outwardly extending portion 32, movable or otherwise adjustable orifices therethrough, gate valves, and any other valves or structures that control the flow of air between the interior of outwardly extending portion 32 and the atmosphere outside outwardly extending portion 32.

[0067]

[0091] Thus, the combination of the ballast conduit 36, the internal damping element 38, and the external damping element 152 defines an integrated heel tank damper 156. The FOWT platform 150, and each of the embodiments of the FOWT platform described herein, may include any desired number of sensors, such as position sensors, motion sensors, and environmental condition sensors (not shown), and includes a controller, such as a computer, configured to operate and monitor the sensors and to adjust any of the valves, pumps, orifices, and the like within the FOWT platform.

[0068]

[0092] Advantageously, the response of the integrated heel tank dampers described herein, such as integrated heel tank damper 156, may be actively or passively set, tuned, and / or adjusted via adjustments to the mass or damping of heel tank damper 156. As used herein, stiffness may be defined as any restoring force acting on the heel tank damper with the effect of returning the heel tank damper to its equilibrium position.

[0069]

[0093] For example, the heel tank damper 156 may be actively or passively tuned by adjusting one or both of the outer damping element 152 and the inner damping element 38 .

[0094] Figure 13B is a side elevation view in cross section of a portion of an alternative embodiment of the FOWT platform 150 shown in Figure 13A. The FOWT platform 150A shown in Figure 13B is similar to the FOWT platform 150, but does not include the external damping element 152. Rather, the FOWT platform 150A includes an air duct, generally indicated at 157, extending between each outwardly extending portion 32 of the bottom beam pair 154. The combination of the ballast conduit 36, the internal damping element 38, and the air duct 157 thus defines an integrated heel tank damper 156A.

[0070]

[0095] Thus, the air volumes within each outwardly extending portion 32 of the bottom beam pair 154 are fluidly connected by air duct 157, thus providing a two-way heel-tank response by ventilation or cross-talk between the air volumes within each outwardly extending portion 32.

[0071]

[0096] 14 and 15, cross-sectional views of an eighth embodiment of a FOWT platform according to the present invention, similar to FOWT platforms 10 and 150, are shown generally at 160. Figure 14 is a cross-sectional side elevation view of FOWT platform 160 shown in a first position, and Figure 15 is a cross-sectional side elevation view of FOWT platform 160 shown in a second position.

[0072]

[0097] FOWT platform 160 includes a foundation 162 having two bottom beam pairs, one of which is shown at 164. Bottom beam pair 164 includes a keystone 166 and two bottom beams 168 and can be assembled and longitudinally post-tensioned as shown in FIGS. 14 and 15.

[0073]

[0098] The two bottom beam pairs 164 and the keystone 166, when assembled together, have a cruciform shape, i.e., define the cross-shaped foundation 162. As explained above, the keystone 166 supports the tower 14. The tower 14 may be attached to the keystone 166 via the transition piece 26.

[0074]

[0099] Similar to FOWT platforms 10, 40, and 60, each bottom beam 164 includes an outwardly extending portion 170 at its distal end (extending upwardly when viewed in FIGS. 14 and 15 ). The upwardly facing wall of each outwardly extending portion 170 includes an opening (not shown, but similar to opening 70 shown in FIG. 7 ) extending between the interior of the outwardly extending portion 170 and the atmosphere outside the outwardly extending portion 170. Additionally, the base 162 may include an external damping element 152 or an air conduit (not shown) between the two outwardly extending portions 170 to allow air movement therebetween.

[0075]

[0100] Generally U-shaped ballast conduits 172 are defined within the bottom beam pairs 164 and extend between the outwardly extending portions 170 of each bottom beam 164 of each bottom beam pair 164. The ballast conduits 172 include an internal damping element 174 at or near the center of the ballast conduits 172. The ballast conduits 172 are filled with ballast water, such as seawater. The internal damping element 174 may be any desired damping element, including, but not limited to, a gate valve and a wall or partition having a movable or otherwise closeable orifice therethrough. The ballast conduits 172 and their respective internal damping elements 174 define a heel tank damper 176.

[0076]

[0101] FIG. 14 shows the movement of water in the heel tank damper 176 when the gate valve 174 is in the open position, such as during wave movement of the FOWT platform 160. FIG. 15 shows the FOWT platform 160 with the gate valve 174 in the closed position, with a larger portion of the ballast water in one half (the left half as viewed in FIG. 15 ) of the heel tank damper 176, thereby righting the FOWT platform 160 and reducing the effects of external moments on the FOWT platform 160. It will be appreciated that the gate valve 174 can be opened or closed actively or passively. Advantageously, the FOWT platform 160 can be righted under external moments via opening and closing the gate valve 176. For example, when the ballast water in the ballast conduit 172 moves to a desired position and the FOWT platform 160 is righted, such as when a larger portion of the ballast water is in half of the heel tank damper 176 as shown in FIG. 15, the valve 174 can be closed to allow the FOWT platform 160 to balance while floating.

[0077]

[0102] The frequency response of the heel tank damper 176 can be actively or passively tuned by adjusting the total mass of the damper heel tank damper 176, for example by adding or removing ballast water.

[0078]

[0103] One or both of the inner damping element 38 and the outer damping element 152 may be (1) to respond to waves having a peak wave period ranging from 5 seconds to 19 seconds; and (2) To respond to a period range, i.e., a period range in which the pitch and roll natural period Tn is greater than about 20 seconds. It can be actively or passively tuned.

[0079]

[0104] The FOWT platform system response may be actively or passively monitored to identify and actively tune heel tank dampers, such as heel tank damper 176, to mitigate effects from wave excitation, heel response, tower bending, or any other undesirable system dynamics.

[0080]

[0105] It will be appreciated that any of the FOWT platform embodiments described herein may be used in combination with one or more external sensors, such as on a wave buoy (not shown). In this manner, the setpoint of a heel tank damper, such as heel tank damper 176, may be actively tuned based on external measurements received from the wave buoy. Additional external sensors may also be provided on a FOWT platform, such as FOWT platform 160.

[0081]

[0106] 16 and 17 , a ninth embodiment of a FOWT platform according to the present invention is shown generally at 180. The FOWT platform 180 includes a foundation 182 that supports the wind turbine 16 mounted on the wind turbine tower 14, as described above. The foundation 182 is semi-submersible and is structured and configured to float in the water in a semi-submersible state. Accordingly, when the foundation 182 is floating in the water, a portion of the foundation 182 is above the water. To limit movement of the FOWT platform 180 above the water, mooring lines (not shown) may be attached to the FOWT platform 180 and may also be attached to anchors (not shown) on the seabed.

[0082]

[0107] The illustrated foundation 182 may be formed from three bottom beams 184 that extend radially outward from a keystone 186 and provide buoyancy. When assembled together, the bottom beam 184 and keystone 186 define the foundation 182. An interior or central post 188 is attached to the keystone 186, and three outer posts 190 are attached to or near the distal end of the bottom beam 184. The center post 188 and outer posts 190 extend outward (upward, as viewed in FIGS. 16 and 17 ) and perpendicular to the bottom beam 184, also providing buoyancy. The axes of the center post 188 and outer posts 190 are also substantially parallel. Additionally, the center post 188 supports the tower 14. The bottom beam 184, keystone 186, and posts 188 and 190 may be formed as described above in this specification.

[0083]

[0108] A connecting walkway or elevated passageway 192 extends radially from and is connected to the central pillar 188 and also to each of the outer pillars 190. A connecting ladder 194 may be attached to one or more of the central pillar 188 and outer pillars 190.

[0084]

[0109] If desired, a support member or top beam (not shown) may extend radially from the center post 188 and may be connected to each of the center post 188 and outer posts 190. An elevated narrow passage 192 may be mounted on the top beam, if provided.

[0085]

[0110] The upwardly facing wall of each central post 188 and outer post 190 may include an opening 196 extending between the interior of the post 188,190 and the atmosphere outside the post 188,190.

[0111] The columns 188, 190, keystone 186, and then bottom beam 184 are generally hollow. The center column 188, each outer column 190, keystone 186, and the space inside the bottom beam 184 therebetween define a generally U-shaped ballast conduit 198. The combination of the three ballast conduits 198 defined by the three outer columns 190, the three bottom beams 184, keystone 186, and center column 188 defines a heel tank damper 199. It will be understood that one or more of the keystone 186 and bottom beam 184 may include any of the damper elements described hereinabove.

[0086]

[0112] 17, each ballast conduit 198 is filled with ballast water, such as seawater. Because each of the pillars 188, 190 includes an opening 196 that is open to the atmosphere outside the foundation 182, when the FOWT platform 182 is moved, such as by heeling, turbine harmonic loads, or wave environmental loads, the ballast water in the pillars 188, 190 can move up and down within the pillars 188, 190, as shown by arrow A.

[0087]

[0113] It will be understood that the heel tank damper embodiments described and illustrated herein may be integrally formed within any desired FOWT platform foundation, including but not limited to a tension leg platform (TLP), barge, spar, semi-submersible, or hybrid concepts such as where the mass consists of water ballast provided within a foundation or hull structure that is vibrable within a ballast conduit as shown by arrow A in FIG. 17 .

[0088]

[0114] A barge-type FOWT platform foundation, such as that shown in Figures 16 and 17, advantageously uses ballast water as a mass element in a tuned mass damper (TMD) to mitigate design drive response. Additionally, a TMD using ballast water as a mass element, such as a heel tank damper 199, can be provided on an existing barge-type FOWT platform foundation or hull design to mitigate undesirable dynamic response due to heel motion, turbine harmonic loads, and / or wave environmental loads. Furthermore, a TMD using ballast water as a mass element, such as a heel tank damper 199, can be provided on an existing barge-type FOWT platform foundation or hull design, where the TMD allows the barge-type FOWT platform foundation or hull to operate effectively at its rigid-body heel natural frequency within its intended wave energy range, with additional external damping in the form of viscous drag loads on the foundation or hull.

[0089]

[0115] FIG. 18 is a cross-sectional view of an alternative embodiment of the foundation 182 shown in FIG. 17. The foundation 182A shown in FIG. 18 is similar to the foundation 182 but does not include the openings 196. Rather, the foundation 182A includes external damping elements 197 mounted on the upwardly facing walls of the center column 188 and the outer columns 190. The external damping elements 197 may be any desired type of damping element, including, but not limited to, fixed openings through the upwardly facing walls of each of the center column 188 and the outer columns 190, movable or otherwise adjustable orifices therethrough, gate valves, and any other valves or structures that control the flow of air between the interior of the center column 188 and the outer columns 190 and the atmosphere outside the center column 188 and the outer columns 190. The combination of the three ballast conduits 198 defined by the three outer columns 190, the three bottom beams 184, the keystone 186, and the center column 188 defines a heel tank damper 199A. It will be appreciated that one or more of the keystone 186 and the bottom beam 184 may include any of the damper elements described hereinabove.

[0090]

[0116] Figure 19 is a cross-sectional view of an alternative embodiment of the foundation 182 shown in Figures 17 and 18. The foundation 182B shown in Figure 19 is similar to the foundation 182A, but does not include the external damping elements 197. Rather, the FOWT platform 182B includes air ducts, generally indicated at 195, extending between each outer column 190 and the center column 188. The combination of the three outer columns 190, the three bottom beams 184, the keystone 186, and the three ballast conduits 198 defined by the center column 188 defines a heel tank damper 199B. It will be understood that one or more of the keystone 186 and the bottom beams 184 may include any of the damper elements described hereinabove.

[0091]

[0117] The principles and modes of operation of this invention have been explained and illustrated in its preferred embodiments. It will be understood, however, that the invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit and scope.

Claims

1. 1. A barge-type wind turbine platform combined with a heel tank damper, capable of floating on water and supporting a wind turbine thereon, 1. A barge-type wind turbine platform, comprising: The cornerstone and a first bottom beam pair including two bottom beams connected to opposite sides of the keystone; a second pair of bottom beams including two bottom beams connected to opposite sides of the keystone, the second pair of bottom beams having longitudinal axes perpendicular to the longitudinal axis of the first pair of bottom beams, the first pair of bottom beams and the second pair of bottom beams combined defining a foundation; Including, each bottom beam in the first pair of bottom beams and the second pair of bottom beams includes an outwardly extending portion at a distal end thereof; a U-shaped ballast conduit mounted or formed within each of the bottom beam pairs and extending between the outwardly extending portions of each bottom beam of each bottom beam pair; each ballast conduit having ballast water therein, the ballast water extending from the outwardly extending portion of each bottom beam of each bottom beam pair, a volume of air being defined between a surface of the ballast water in each outwardly extending portion and an outwardly facing wall of each outwardly extending portion; Internal damping elements within each ballast conduit a barge-type wind turbine platform, a heel tank damper defined by said ballast conduits and their respective internal damping elements; and A barge-type wind turbine platform combined with a heel tank damper, comprising:

2. 2. The barge-type wind turbine platform in combination with heel tank damper of claim 1, wherein the first pair of bottom beams and the second pair of bottom beams define a foundation having a cruciform shape.

3. 10. The barge-type wind turbine platform in combination with heel tank damper of claim 1, wherein the outwardly facing wall of each outwardly extending portion includes an opening extending between an interior of the outwardly extending portion and the atmosphere outside the outwardly extending portion.

4. 10. The barge-type wind turbine platform in combination with a heel tank damper as described in claim 1, wherein the internal damping element is one of a wall having an orifice therethrough, a wall having a movable orifice therethrough, and a gate valve.

5. 2. The barge-type wind turbine platform in combination with heel tank damper of claim 1, wherein the internal damping element is configured to control the flow of ballast water between the bottom beams of each of the bottom beam pairs.

6. 10. The barge-type wind turbine platform in combination with heel tank damper of claim 1, wherein an outwardly facing wall of each outwardly extending portion includes an external damping element attached thereto.

7. 7. The barge-type wind turbine platform in combination with a heel tank damper of claim 6, wherein the external damping element is one of a wall having an orifice therethrough, a wall having a movable orifice therethrough, and a gate valve configured to control air flow between an interior of the outward extension and the atmosphere outside the outward extension.

8. 2. The barge-type wind turbine platform in combination with a heel tank damper of claim 1, further comprising an air duct extending between each outwardly extending portion of each bottom beam pair, said air duct fluidly connecting the volumes of air within each outwardly extending portion of each bottom beam pair, said air duct configured to provide a two-way heel tank response by ventilating between the volumes of air within each outwardly extending portion.

9. the first beam pair defining a first leg and the second beam pair defining a second leg; each leg including a first tank defining a first U-shaped ballast conduit and a second tank defining a second U-shaped ballast conduit, said second tank being larger than said first tank; 10. The barge-type wind turbine platform in combination with heel tank damper of claim 1, wherein the first tank is mounted adjacent to the second tank, and the first tank and the second tank are not fluidly connected.

10. 10. The barge-type wind turbine platform combined with heel tank damper of claim 9, wherein each pair of first and second tanks defines a heel tank damper configured such that the first U-shaped ballast conduit and the second U-shaped ballast conduit operate to mitigate different frequencies of heel motion.

11. 1. A method of mitigating dynamic response due to heeling in a barge-type wind turbine platform capable of floating on water and supporting a wind turbine thereon, comprising:

1. A barge-type wind turbine platform, comprising: The cornerstone and a first bottom beam pair including two bottom beams connected to opposite sides of the keystone; a second pair of bottom beams including two bottom beams connected to opposite sides of the keystone, the second pair of bottom beams having longitudinal axes perpendicular to the longitudinal axis of the first pair of bottom beams, the first pair of bottom beams and the second pair of bottom beams combined defining a foundation; Including, each bottom beam in the first pair of bottom beams and the second pair of bottom beams includes an outwardly extending portion at a distal end thereof; the first pair of bottom beams and the second pair of bottom beams define a foundation having a cruciform shape; a U-shaped ballast conduit mounted or formed within each of the bottom beam pairs and extending between the outwardly extending portions of each bottom beam of each bottom beam pair; each ballast conduit having ballast water therein, the ballast water extending from the outwardly extending portion of each bottom beam of each bottom beam pair, a volume of air being defined between a surface of the ballast water in each outwardly extending portion and an outwardly facing wall of each outwardly extending portion; Internal damping elements within each ballast conduit a barge-type wind turbine platform, a heel tank damper defined by said ballast conduits and their respective internal damping elements; and Equipped with mitigating dynamic response due to heeling by using the ballast water in the ballast conduit as a mass element that can vibrate in a predetermined direction. A method comprising:

12. using ballast water in the ballast conduit such that the frequency response of the ballast water is determined by a total mass of the ballast water in the ballast conduit, a total submerged length of the ballast conduit, and a free surface area of ​​the ballast water in the outwardly extending portion; and Controlling fluid mass response phase using the internal damping element within the ballast conduit. The method of mitigating heel dynamic response in a barge-type wind turbine platform of claim 11 , further comprising one of:

13. 12. The method for mitigating dynamic response due to heel motion in a barge-type wind turbine platform of claim 11, wherein the heel tank damper is configured to enable the foundation to operate at a rigid body heel natural frequency within a predetermined wave energy range with external damping in the form of viscous drag loads on the foundation.

14. 12. The method for mitigating dynamic response due to heel motion in a barge-type wind turbine platform according to claim 11, wherein the foundation is configured such that the ballast water defines a mass element within the heel tank damper that enables the foundation to operate at a rigid body heel natural frequency within a predetermined wave energy range.

15. 12. The method of mitigating dynamic response due to heel motion in a barge-type wind turbine platform of claim 11, wherein the heel tank damper uses the ballast water as mass elements arranged in a cross-tank configuration that enables response mitigation about both the pitch axis and the roll axis of the foundation.

16. 12. The method for mitigating dynamic response due to heeling in a barge-type wind turbine platform of claim 11, wherein the ballast conduits in the first pair of bottom beams are not fluidly connected to the ballast conduits in the second pair of bottom beams, and the ballast water in the first pair of bottom beams and the second pair of bottom beams is separated into front-to-rear and left-to-right conduits arranged in a cross-tank configuration.

17. 12. The method of mitigating dynamic response due to heel motion in a barge-type wind turbine platform of claim 11, wherein the ballast conduits in the first pair of bottom beams and the second pair of bottom beams intersect and connect within an interior of the keystone such that the foundation experiences an equivalent damper response for dynamic heeling about any direction of heel motion.

18. 1. A barge-type wind turbine platform combined with a heel tank damper, capable of floating on water and supporting a wind turbine thereon, 1. A barge-type wind turbine platform, comprising: four connected bottom beams extending radially outward from a center point and defining a base having a cross-shaped configuration, each having an outwardly extending portion at a distal end; Including, an outwardly facing wall of each outwardly extending portion including an opening extending between an interior of the outwardly extending portion and the atmosphere outside the outwardly extending portion; a cross-shaped wall having four legs extending vertically between the lower wall of each beam and the upper wall of each beam, the distal end of each of the four legs being spaced from the distal end wall of each beam; a barge-type wind turbine platform, an integrated heel tank damper having multiple ballast conduits formed between the cross-shaped wall and the wall of each beam, the ballast conduits defining multiple fluid flow paths within the foundation; A barge-type wind turbine platform combined with a heel tank damper, comprising:

19. 20. A barge-type wind turbine platform combined with a heel tank damper as described in claim 18, wherein the natural frequency of the integrated heel tank damper in the foundation can be increased or decreased by changing the overall length of the four legs of the cross-shaped wall in each beam.

20. the first beam pair defining a first leg and the second beam pair defining a second leg; each leg including a first tank defining a first U-shaped ballast conduit and a second tank defining a second U-shaped ballast conduit, said second tank being larger than said first tank; 10. The barge-type wind turbine platform in combination with heel tank damper of claim 1, wherein the first tank is mounted adjacent to the second tank, and the first tank and the second tank are not fluidly connected.

21. 21. The barge-type wind turbine platform combined with heel tank damper of claim 20, wherein each pair of first and second tanks defines a heel tank damper configured such that the first U-shaped ballast conduit and the second U-shaped ballast conduit operate to mitigate different frequencies of heel motion.

22. 1. A barge-type wind turbine platform combined with a heel tank damper, capable of floating on water and supporting a wind turbine thereon, 1. A barge-type wind turbine platform, comprising: The cornerstone and a first bottom beam pair including two bottom beams connected to opposite sides of the keystone; a second pair of bottom beams including two bottom beams connected to opposite sides of the keystone, the second pair of bottom beams having longitudinal axes perpendicular to the longitudinal axis of the first pair of bottom beams, the first pair of bottom beams and the second pair of bottom beams combined defining a foundation having a cruciform shape; Including, each bottom beam in the first pair of bottom beams and the second pair of bottom beams includes an outwardly extending portion at a distal end thereof; a U-shaped ballast conduit mounted or formed within each of the pair of bottom beams and extending between the outwardly extending portions of each bottom beam; each ballast conduit having ballast water therein, the ballast water extending from the outwardly extending portion of each bottom beam of each bottom beam pair, a volume of air being defined between a surface of the ballast water in each outwardly extending portion and an outwardly facing wall of each outwardly extending portion; an interior wall within each bottom beam extending vertically between the lower and upper walls of each bottom beam, and further extending longitudinally from the distal end wall of each bottom beam to the vertically extending exterior wall of the keystone; a cross-shaped wall within the keystone extending vertically between the lower and upper walls of the keystone, each leg of the cross-shaped wall being longitudinally aligned with one of the interior walls of the bottom beam, the exterior wall and each of the legs of the cross-shaped wall of the keystone having a vertically extending fluid flow opening formed therein to define an interior damping element; and a barge-type wind turbine platform, a heel tank damper system defined by a combination of a plurality of fluid flow paths defined by the ballast conduit and the fluid flow openings in the wall of the keystone; A barge-type wind turbine platform combined with a heel tank damper, comprising:

23. 23. A barge-type wind turbine platform in combination with a heel tank damper as described in claim 22, wherein the flow of ballast water through the ballast conduit and the fluid flow openings of the heel tank damper system provides a damping response for the wind turbine platform.

24. 12. The method of mitigating dynamic response due to heeling in a barge-type wind turbine platform according to claim 11, further comprising the step of moving the internal damping element between an open position and a closed position, the internal damping element being moved to the closed position when ballast water in one of the ballast conduits moves to a desired position to right the wind turbine platform and balance it while floating.

25. 12. The method for mitigating dynamic response due to heel movement in a barge-type wind turbine platform as described in claim 11, further comprising one of the steps of actively and passively tuning the frequency response of the heel tank damper by adjusting the total mass of the ballast water.

26. 12. The method of mitigating dynamic response due to heel motion in a barge-type wind turbine platform as described in claim 11, further comprising one of the steps of actively and passively tuning the internal damping element 152 to respond to waves having a peak wave period in a range of from about 10 seconds to about 19 seconds and to respond to a period range in which the natural pitch and heel periods of the wind turbine platform are greater than about 20 seconds.

27. 12. The method for mitigating dynamic response due to heel motion in a barge-type wind turbine platform as described in claim 11, further comprising the steps of receiving external measurements from an environmental sensor on a wave buoy, and actively tuning the heel tank damper based on the external measurements received from the wave buoy.

28. 1. A semi-submersible wind turbine platform combined with a heel tank damper capable of floating on water and supporting a wind turbine thereon, 1. A semi-submersible wind turbine foundation comprising: The cornerstone and three bottom beams extending radially outward from said keystone; a central pillar attached to the keystone; three outer posts attached to the distal end of the bottom beam; Including, the center post, each outer post, the keystone, and the space therebetween within the bottom beam define three generally U-shaped ballast conduits; each ballast conduit having ballast water therein, the ballast water extending from an upper portion of the central pillar to an upper portion of the outer pillars, a volume of air being defined between a surface of the ballast water in each pillar and an outwardly facing wall of each pillar; Internal damping elements within each ballast conduit a semi-submersible wind turbine foundation, including: a heel tank damper defined by the combination of three of said ballast conduits; and A semi-submersible wind turbine platform combined with a heel tank damper, comprising:

29. 30. The semi-submersible wind turbine platform in combination with a heel tank damper as described in claim 28, wherein an outwardly facing wall of each pillar includes an opening extending between an interior of the pillar and the atmosphere outside the pillar.

30. 30. The semi-submersible wind turbine platform in combination with a heel tank damper as described in claim 28, wherein the internal damping element is one of a wall having an orifice therethrough, a wall having a movable orifice therethrough, and a gate valve.

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