Tuned mass damper for floating structures

1. A tuned mass damper (TMD) system in combination with a floating offshore wind turbine (FOWT) platform comprising:

a barge FOWT platform having a hull configured to have a wind turbine tower mounted thereon; and

a TMD system mounted in the hull, the TMD system having:

a first TMD configured to operate at a first frequency; and

a second TMD configured to operate at a second frequency different than the first frequency;

wherein the first TMD includes a first water ballast chamber that defines a mass of the first TMD, and wherein the second TMD includes a second water ballast chamber that defines a mass of the second TMD.

2. The TMD system in combination with a FOWT platform according to claim 1 , wherein at least one of the first and second TMDs is configured to mitigate at least one of heave motion, heel motion, turbine harmonic loading, and wave environment loading of the barge FOWT platform.

3. The TMD system in combination with a FOWT platform according to claim 2 , wherein the TMD system further includes:

a controller attached to the FOWT platform; and

a sea state sensor mounted to the FOWT platform and operatively connected to the controller;

wherein the controller is configured to actively control an operating frequency of the first and second TMDs based on input from the sea state sensor.

4. The TMD system in combination with a FOWT platform according to claim 3 , wherein active control of the operating frequency of the first and second TMDs includes at least one of changing a stiffness of the first and second.

5. The TMD system in combination with a FOWT platform according to claim 3 , wherein the first TMD is configured to at least one of mitigate heeling and reduce rotational movement of the hull.

6. The TMD system in combination with a FOWT platform according to claim 5 , wherein the second TMD is configured to mitigate vertical motion of the hull.

7. The TMD system in combination with a FOWT platform according to claim 1 , wherein at least one of the first and second TMDs is configured to allow the FOWT platform to effectively operate with rigid body heave and heel natural frequencies within an intended wave energy range.

8. A tuned mass damper (TMD) system in combination with a floating offshore wind turbine (FOWT) platform comprising:

a FOWT platform having a center, at least three legs extending radially from the center, and configured to have a wind turbine tower mounted thereon; and

a TMD system, a portion of which is mounted in each of the legs, each leg having:

a first TMD at an outboard end of each leg and configured to operate at a first frequency; and

a second TMD at an inboard end of each leg configured to operate at a second frequency different than the first frequency;

wherein the first TMD includes a first water ballast chamber that defines a mass of the first TMD, and wherein the second TMD includes a second water ballast chamber that defines a mass of the second TMD.

9. The TMD system in combination with a FOWT platform according to claim 8 , wherein at least one of the first and second TMDs is configured to mitigate at least one of heave motion, heel motion, turbine harmonic loading, and wave environment loading of the FOWT platform.

10. The TMD system in combination with a FOWT platform according to claim 8 , wherein at least one of the first and second TMDs is configured to allow the FOWT platform to effectively operate with rigid body heave and heel natural frequencies within its intended wave energy range.

11. The TMD system in combination with a FOWT platform according to claim 8 , wherein the FOWT platform is a barge platform having a hull comprising a keystone and four legs attached thereto and defining a cross shape.

12. The TMD system in combination with a FOWT platform according to claim 9 , wherein at least one of the first and second TMDs is configured to mitigate at least one of heave motion, heel motion, turbine harmonic loading, and wave environment loading of the FOWT platform.

13. The TMD system in combination with a FOWT platform according to claim 12 , wherein at least one of the first and second TMDs is configured to allow the FOWT platform to effectively operate with rigid body heave and heel natural frequencies within an intended wave energy range.

14. The TMD system in combination with a FOWT platform according to claim 8 , wherein each first TMD further includes:

a first pressure chamber within each leg connected to a source of pressurized air and a having an air pressure greater than atmospheric pressure;

a first damper pipe having a closed first end and an open second end, the first end attached to an upper end of the first water ballast chamber, the first damper pipe extending toward a floor of the first water ballast chamber, such that the second end is spaced a distance apart from the floor of the first water ballast chamber; and

a first connecting pipe extending between the first pressure chamber and an upper portion of the first damper pipe, the first connecting pipe configured for the flow of pressurized air therethrough.

15. The TMD system in combination with a FOWT platform according to claim 14 , wherein each second TMD further includes:

a second pressure chamber within each leg connected to a source of pressurized air and a having an air pressure greater than an air pressure within the first pressure chamber;

a second damper pipe having a closed first end and on open second end, the first end attached to an upper end of the second water ballast chamber, the second damper pipe extending toward a floor of the second water ballast chamber, such that the second end is spaced a distance apart from the floor of the second water ballast chamber; and

a second connecting pipe extending between the second pressure chamber and an upper portion of the second damper pipe, the second connecting pipe configured for the flow of pressurized air therethrough.

16. The TMD system in combination with a FOWT platform according to claim 15 , wherein first connecting pipe and the second connecting pipe include an adjustable orifice, and wherein an inside diameter of the adjustable orifices are adjustable for active control of the flow of pressurized air from the first pressure chamber and the second pressure chamber, respectively.

17. A tuned mass damper (TMD) system in combination with a floating offshore wind turbine (FOWT) platform comprising:

a semi-submersible FOWT platform having a center, at least three legs extending radially from the center, a center column, an outer column at a distal end of each of the at least three legs, and configured to have a wind turbine tower mounted on the center column; and

a TMD system mounted in the FOWT platform and including a horizontally oriented first TMD mounted in each of the legs, and a vertically mounted second TMD mounted in each of the columns;

wherein the first TMDs in each leg include a first water ballast chamber that defines a mass of the first TMD, and wherein the second TMDs in each column include a second water ballast chamber that defines a mass of the second TMD; and

wherein each of the first and the second TMDs may be configured to operate at a different frequency.

18. The TMD system in combination with a FOWT platform according to claim 17 , wherein at least one of the first and second TMDs is configured to mitigate at least one of heave motion, heel motion, turbine harmonic loading, and wave environment loading of the FOWT platform; and wherein at least one of the first and second TMDs is configured to allow the FOWT platform to effectively operate with rigid body heave and heel natural frequencies within its an intended wave energy range.