Heel tank damper for floating structures

1 . A wind turbine platform capable of floating on a body of water and supporting a wind turbine thereon in combination with a heel tank damper comprising:

a wind turbine platform including:

a keystone;

a first pair bottom beams including two bottom beams connected to opposite sides of the keystone;

a second pair of bottom beams including two bottom beams connected to opposite sides of the keystone, wherein the second pair of bottom beams has a longitudinal axis perpendicular to a longitudinal axis of the first pair of the bottom beams, wherein the keystone, the first pair of bottom beams, and the second pair of bottom beams define a foundation;

wherein each bottom beam in the first and second pairs of bottom beams includes an outwardly extending portion at a distal end thereof; and

wherein a U-shaped ballast conduit is one of mounted and formed within each of the first pair of bottom beams and the second pair of bottom beams, and extends between the outwardly extending portions of each bottom beam of each of the first and second pairs of bottom beams;

wherein the U-shaped ballast conduits have ballast water therein, the ballast water extending from the outwardly extending portions of each bottom beam of each of the first and second pairs 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; and

an internal damping element within the U-shaped ballast conduits; and

a heel tank damper defined by the U-shaped ballast conduits and the internal damping element therein.

2 . The wind turbine platform in combination with the heel tank damper according to claim 1 , wherein the first and second pairs bottom beams define a foundation having a cruciform shape.

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

4 . The wind turbine platform in combination with the heel tank damper according to 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 . The wind turbine platform in combination with the heel tank damper according to claim 1 , wherein the internal damping element is configured to control the flow of ballast water between the bottom beams of each of the first pair of bottom beams and the second pair of bottom beams.

6 . The wind turbine platform in combination with the heel tank damper according to claim 1 , wherein an outwardly facing wall of each outwardly extending portion includes an external damping element mounted thereto.

7 . The wind turbine platform in combination with the heel tank damper according to 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, and is configured to control the flow of air between an interior of the outwardly extending portion and the atmosphere outside of the outwardly extending portion.

8 . The wind turbine platform in combination with the heel tank damper according to claim 1 , further including an air duct that extends between each outwardly extending portion of each pair of bottom beams, the air duct fluidly connecting the volume of air within each outwardly extending portion of each pair of bottom beams, the air duct configured to provide a bi-modal heel tank response from venting between a volume of air within each outwardly extending portion.

9 . The wind turbine platform in combination with the heel tank damper according to claim 1 ;

wherein the first pair of beams defines a first leg and the second pair of beams defines a second leg;

wherein each leg includes a first tank defining a first U-shaped ballast conduit and a second tank defining a second U-shaped ballast conduit, the second tank being larger than the first tank; and

wherein the first tank is mounted adjacent the second tank, such that the first tank and the second tank are not fluidly connected.

10 . The wind turbine platform in combination with the heel tank damper according to claim 9 , wherein each pair of first and second tanks define 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 . A method of mitigating dynamic responses from heel motion in a wind turbine platform capable of floating on a body of water and supporting a wind turbine thereon comprising:

a wind turbine platform including:

a keystone;

a first pair bottom beams including two bottom beams connected to opposite sides of the keystone;

a second pair of bottom beams including two bottom beams connected to opposite sides of the keystone, wherein the second pair of bottom beams has a longitudinal axis perpendicular to a longitudinal axis of the first pair of the bottom beams, wherein the keystone, the first pair of bottom beams, and the second pair of bottom beams define a foundation;

wherein each bottom beam in the first and second pairs of bottom beams includes an outwardly extending portion at a distal end thereof;

wherein the first and second pairs bottom beams define a foundation having a cruciform shape;

wherein a U-shaped ballast conduit is one of mounted and formed within each of the first pair of bottom beams and the second pair of bottom beams, and extends between the outwardly extending portions of each bottom beam of each of the first and second pairs of bottom beams; and

wherein the U-shaped ballast conduits have ballast water therein, the ballast water extending from the outwardly extending portions of each bottom beam of each of the first and second pairs 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; and

an internal damping element within the U-shaped ballast conduits; and

a heel tank damper defined by the U-shaped ballast conduits and the internal damping element therein;

the method including mitigating dynamic responses from heel motion by using the ballast water within the U-shaped ballast conduits as a mass element that is allowed to oscillate in a predetermined direction.

12 . The method of mitigating dynamic responses from heel motion in a wind turbine platform according to claim 11 , further including one of:

using the ballast water within the U-shaped ballast conduits such that a frequency response of the ballast water is determined by a total mass of the ballast water within the U-shaped ballast conduits, a total submerged length of the U-shaped ballast conduits, and a free surface area of the ballast water within the outwardly extending portions, and

using the internal damping element within the U-shaped ballast conduits to control a fluid mass response phase.

13 . The method of mitigating dynamic responses from heel motion in a wind turbine platform according to claim 11 , wherein the heel tank damper is configured to allow the foundation to operate with rigid body heel natural frequencies within a predetermined wave energy range, and in the presence of external damping in the form of viscous drag loading on the foundation.

14 . The method of mitigating dynamic responses from heel motion in a 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 allows the foundation to operate with rigid body heel natural frequencies within a predetermined wave energy range.

15 . The method of mitigating dynamic responses from heel motion in a wind turbine platform according to claim 11 , wherein the heel tank damper uses the ballast water as a mass element that is arranged in a cross-tank configuration that allows for response mitigation about both pitch and roll axes of the foundation.

16 . The method of mitigating dynamic responses from heel motion in a wind turbine platform according to claim 11 , wherein the ballast conduit within the first pair of bottom beams is not fluidly connected to the ballast conduit within the second pair of bottom beams, and wherein the ballast water in the first and second pairs of bottom beams is separated in fore-aft and side to side conduits arranged in a cross-tank configuration.

17 . The method of mitigating dynamic responses from heel motion in a wind turbine platform according to claim 11 , wherein the U-shaped ballast conduits in the first and second pairs of bottom beams intersect and are connected within an interior of the keystone such that the foundation will experience equivalent damper responses for dynamic heeling about any direction of heel motion.

18 . A wind turbine platform capable of floating on a body of water and supporting a wind turbine thereon in combination with a heel tank damper comprising:

a wind turbine platform including:

four connected bottom beams that extend radially outwardly from central point and define a foundation having a cruciform shape, wherein each bottom beam includes an outwardly extending portion at a distal end thereof;

wherein an outwardly facing wall of each outwardly extending portion includes an opening that extends between an interior of the outwardly extending portion and the atmosphere outside of the outwardly extending portion; and

a cross shaped wall having four legs that extend vertically between a lower wall of each beam and an upper wall of each beam, the distal ends of each of the four legs are spaced apart from distal end walls of each beam; and

an integrated heel tank damper having multiple ballast conduits formed between the cross shaped wall and the walls of each beam, the multiple ballast conduits defining multiple fluid flow paths within the foundation.

19 . The wind turbine platform in combination with the heel tank damper according to claim 18 , wherein a natural frequency of the integrated heel tank damper within the foundation may be increased and decreased by changing the lengths of the four legs of the cross shaped wall within each beam.

20 . The wind turbine platform in combination with the heel tank damper according to claim 1 ;

wherein the first pair of beams defines a first leg and the second pair of beams defines a second leg;

wherein each leg includes a first tank defining a first U-shaped ballast conduit and a second tank defining a second U-shaped ballast conduit, the second tank being larger than the first tank; and

wherein the first tank is mounted adjacent the second tank, such that the first tank and the second tank are not fluidly connected.

21 . The wind turbine platform in combination with the heel tank damper according to claim 20 , wherein each pair of first and second tanks define 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 . A wind turbine platform capable of floating on a body of water and supporting a wind turbine thereon in combination with a heel tank damper comprising:

a wind turbine platform including:

a keystone;

a first pair bottom beams including two bottom beams connected to opposite sides of the keystone;

a second pair of bottom beams including two bottom beams connected to opposite sides of the keystone, wherein the second pair of bottom beams has a longitudinal axis perpendicular to a longitudinal axis of the first pair of the bottom beams,

wherein the keystone, the first pair of bottom beams, and the second pair of bottom beams define a foundation having a cruciform shape;

wherein each bottom beam in the first and second pairs of bottom beams includes an outwardly extending portion at a distal end thereof;

wherein a U-shaped ballast conduit is one of mounted and formed within each of the first pair of bottom beams and the second pair of bottom beams, and extends between the outwardly extending portions of each bottom beam of each of the first and second pairs of bottom beams; and

wherein the U-shaped ballast conduits have ballast water therein, the ballast water extending from the outwardly extending portions of each bottom beam of each of the first and second pairs 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 that extends vertically between a lower wall and an upper wall of each bottom beam, and further extends longitudinally from distal end walls of each bottom beam to a vertically extending exterior wall of the keystone; and

a cross-shaped wall within the keystone that extends vertically between a lower wall and an upper wall of the keystone, wherein each leg of the cross-shaped wall is longitudinally aligned with one of the interior walls of the bottom beams, and wherein the exterior walls and each of the legs of the cross-shaped wall of the keystone have vertically extending fluid flow openings formed therein, and define an internal damping element; and

a heel tank damper system defined by the combination of the U-shaped ballast conduits and a plurality of fluid flow paths defined by the fluid flow openings in the walls of the keystone.

23 . The wind turbine platform in combination with the heel tank damper according to claim 22 , wherein the flow of ballast water through the U-shaped ballast conduits and the fluid flow openings of the heel tank damper system provides a damping response for the wind turbine platform.

24 . The method of mitigating dynamic responses from heel motion in a wind turbine platform according to claim 11 , further including the step of moving the internal damping element between an open position and a closed position, such that when ballast water within one of the U-shaped ballast conduits has moved to a desired position wherein the wind turbine platform is righted and balanced while floating, the internal damping element is moved to the closed position.

25 . The method of mitigating dynamic responses from heel motion in a wind turbine platform according to claim 11 , further including the step of one of actively and passively tuning a frequency response of the heel tank damper by adjusting a total mass of the ballast water.

26 . The method of mitigating dynamic responses from heel motion in a wind turbine platform according to claim 11 , further including the step of one of actively and passively tuning the internal damping element to respond to waves having with the range of from about 10 to about 19 second peak wave periods, and to respond to period ranges wherein the natural period of a pitch and heel of the wind turbine platform is greater than about 20 seconds.

27 . The method of mitigating dynamic responses from heel motion in a wind turbine platform according to claim 11 , further including the step of receiving external measurements from environmental sensors on a wave buoy and actively tuning the heel tank damper based on the external measurements received from the wave buoy.

28 . A semi-submersible wind turbine platform capable of floating on a body of water and supporting a wind turbine thereon in combination with a heel tank damper comprising:

a semi-submersible wind turbine foundation including:

a keystone;

three bottom beams that extend radially outwardly from the keystone;

a center column mounted to the keystone;

three outer columns mounted at distal ends of the bottom beams;

wherein a space within the center column, each outer column, the keystone and the bottom beam therebetween define three generally U-shaped ballast conduits;

wherein the U-shaped ballast conduits have ballast water therein, the ballast water extending from the outwardly extending portions of each bottom beam of each of the first and second pairs 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; and

an internal damping element within the U-shaped ballast conduits; and

a heel tank damper defined by the combination of the three U-shaped ballast conduits.

29 . The semi-submersible wind turbine platform in combination with the heel tank damper according to claim 28 , wherein an outwardly facing wall of each column includes an opening that extends between an interior of the column and the atmosphere outside of the column.

30 . The semi-submersible wind turbine platform in combination with the heel tank damper according to 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.