Method of assembling and deploying a floating offshore wind turbine platform

Patent metadata

Field	Value
Publication number	US-12384500-B2
Application number	US-202017919363-A
Country	US
Kind code	B2
Filing date	Apr 16, 2020
Priority date	Apr 16, 2020
Publication date	Aug 12, 2025
Grant date	Aug 12, 2025

Abstract

A method of assembling and deploying a floating offshore wind turbine (FOWT) platform includes floating a buoyant floater and a hollow outer tank in a floating assembly, placing permanent ballast material in the hollow outer tank to define a mass, and sinking the mass to a seabed. The buoyant floater is moved to a position over the mass. Transit lines are attached between a lifting device in the buoyant floater and the mass to define a FOWT platform. The mass is lifted to a point directly under the buoyant floater and the FOWT platform is towed to an installation site. Mooring lines are attached between anchors in the seabed and the buoyant floater, and the mass is lowered to a depth wherein suspension lines attached thereto are taught, the mass with the suspension lines defining a suspended mass. The transit lines are then stored or removed from the mass.

First claim

What is claimed is:

1. A method of assembling and deploying a floating offshore wind turbine (FOWT) platform comprising:
floating a hollow outer tank in a floating assembly area of a body of water, the hollow outer tank having transit lines and suspension lines attached thereto;
floating a buoyant floater in the floating assembly area of the body of water;
placing permanent ballast material in the hollow outer tank to define a mass, and sinking the mass to a seabed of the body of water;
raising free ends of the transit lines and the suspension lines to a surface of the body of water with buoys;
moving the buoyant floater to a position over the mass;
attaching the transit lines to a lifting device in the buoyant floater and attaching the suspension lines to a portion of the buoyant floater, the combined buoyant floater and the mass defining a FOWT platform;
lifting the mass with the lifting device to a point directly under the buoyant floater;
towing the FOWT platform to an installation site in the body of water;
attaching mooring lines to anchors in the seabed and to the buoyant floater;
lowering the mass with the transit lines and the lifting device to a depth wherein the suspension lines are taught, thus suspending the mass with the suspension lines to define a suspended mass; and
one of storing and removing the transit lines from the mass.

2. The method of assembling and deploying a FOWT platform according to claim 1 , wherein the hollow outer tank and the buoyant floater are launched from one of a dock and shoreline into the body of water.

3. The method of assembling and deploying a FOWT platform according to claim 1 , wherein the permanent ballast material is iron ore.

4. The method of assembling and deploying a FOWT platform according to claim 1 , wherein the hollow outer tank defines a permanent ballast space and a variable ballast space, and wherein as the mass sinks, the variable ballast space fills with sea water.

5. The method of assembling and deploying a FOWT platform according to claim 1 , wherein the step of lifting the mass with the lifting device to a point directly under the buoyant floater includes attaching marker buoys to free ends of each of the transit lines and the suspension lines.

6. The method of assembling and deploying a FOWT platform according to claim 1 , further including installing a tower and a wind turbine on the buoyant floater prior to the step of lifting the mass with the lifting device to a point directly under the buoyant floater.

7. The method of assembling and deploying a FOWT platform according to claim 1 , wherein when the mass has been lifted and positioned directly under the buoyant floater, the FOWT platform is in a shallow draft configuration.

8. The method of assembling and deploying a FOWT platform according to claim 7 , wherein in the shallow draft configuration, the suspension lines are slack.

9. The method of assembling and deploying a FOWT platform according to claim 8 , wherein in the shallow draft configuration, the FOWT platform behaves as a rigid body having by a vertical center of gravity that is above its vertical center of buoyancy.

10. The method of assembling and deploying a FOWT platform according to claim 1 , wherein a first end wall of the hollow outer tank of the mass includes a fairlead for attaching at least one of the suspension lines.

11. The method of assembling and deploying a FOWT platform according to claim 1 , wherein a first end wall of the hollow outer tank of the mass includes a plurality of fairleads, each configured for attaching at least one of the suspension lines.

12. The method of assembling and deploying a FOWT platform according to claim 1 , wherein the buoyant floater includes:
a central hub;
three or more buoyant pontoons that extend radially outwardly from the central hub, and defining cross-shaped base;
a central column mounted to the central hub and extending outwardly and perpendicularly to the buoyant pontoons; and
braces connecting distal ends of the buoyant pontoons to an upper portion of the central column.

13. The method of assembling and deploying a FOWT platform according to claim 12 , further including a tower supporting a wind turbine on the central column.

14. The method of assembling and deploying a FOWT platform according to claim 12 , wherein at least one of the hollow outer tank, the central hub, the buoyant pontoons, and the central column are formed in sections.

15. The method of assembling and deploying a FOWT platform according to claim 13 , further including:
forming and assembling a plurality of the buoyant pontoons, the central hub, the mass, and the braces in an on-shore location;
assembling a first and a second pontoon to the central hub;
post-tensioning the assembled first and second pontoons and central hub from a distal end of the first pontoon to a distal end of the second pontoon to define a buoyant floater sub-assembly;
assembling a third and a fourth pontoon to the central hub of the buoyant floater sub-assembly; and
post-tensioning the assembled third and fourth pontoons and buoyant floater sub-assembly from a distal end of the third pontoon to a distal end of the fourth pontoon.

16. The method of assembling and deploying a FOWT platform according to claim 15 , further including:
forming sections of the central column;
assembling the sections of the central column on a first axial end wall of the central hub;
longitudinally post-tensioning the central column to the central hub;
attaching the braces between the buoyant pontoons and the central column;
installing the tower and the wind turbine, thus defining the buoyant floater; and
launching the buoyant floater into the body of water.

17. The method of assembling and deploying a FOWT platform according to claim 12 , further including:
forming and assembling a first and a second pontoon within a dry dock;
assembling the central hub within the dry dock;
assembling the first and second pontoons to the central hub;
post-tensioning the assembled first and second pontoons and central hub from a distal end of the first pontoon to a distal end of the second pontoon to define a buoyant floater sub-assembly;
launching the buoyant floater sub-assembly into a floating assembly area;
forming and assembling a third and a fourth pontoon within the dry dock;
temporarily post-tensioning each of the third and the fourth pontoons;
launching the third and the fourth pontoons into the floating assembly area;
assembling a third and a fourth pontoon to the central hub of the buoyant floater sub-assembly; and
post-tensioning the assembled third and fourth pontoons and buoyant floater sub-assembly from a distal end of the third pontoon to a distal end of the fourth pontoon, thus defining the buoyant floater.

18. The method of assembling and deploying a FOWT platform according to claim 17 , wherein the steps during the steps of post-tensioning the assembled first and second pontoons and central hub, and post-tensioning the assembled third and fourth pontoons and the buoyant floater sub-assembly occur in portions of the first, second, third, and fourth pontoons and the central hub that are above a water line when the buoyant floater sub-assembly and the third and fourth pontoons are floating in the body of water.

19. The method of assembling and deploying a FOWT platform according to claim 1 , wherein the suspended mass has a natural period of motion that is selected based on the mass and a geometric location of attachment points of the suspens

Assignees

• Univ Maine System

Inventors

• Viselli Anthony M
• Dagher Habib J
• Ward Jacob C
• Goupee Andrew J
• Allen Christopher K

Classifications

• B63B2035/446

  for converting wind energy into electric energy · CPC title

• B63B2001/044

  with a small waterline area compared to total displacement, e.g. of semi-submersible type · CPC title

• B63B21/50

  Anchoring arrangements {or methods} for special vessels, e.g. for floating drilling platforms or dredgers · CPC title

• B63B1/107

  Semi-submersibles; Small waterline area multiple hull vessels and the like, e.g. SWATH · CPC title

• F03D13/25

  specially adapted for offshore installation · CPC title