Truss Cable Semi-submersible Floater for Offshore Wind Turbines and Construction Methods
Truss cable semi-submersible floater for offshore wind turbines and construction methods are provided. A floating system includes a hull, a tensioned cable system, and a tower. The hull includes vertical buoyant columns with one column at the center of the pattern, larger size column base tanks, and a truss system, all of which are coupled to each other for supporting the tower and wind turbines. The column can be made of hybrid materials, including steel and composite-concrete. The steel section and the composite-concrete section of the column can be connected by grouting. The tensioned cable system including upper, lower, and diagonal tensioned cables to connect the column, the column base, and the tower to reduce the bending moments and improve stability, strength and dynamic performance of the hull structure.
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This present application claims the benefits of priority from the United States of America provisional application No. 61/407,730, entitled “TRUSS CABLE SEMI-SUBMERSIBLE FLOATER FOR OFFSHORE WIND TURBINES AND CONSTRUCTION METHODS”, filed on Oct. 28, 2010.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENTNot applicable.
REFERENCES
- (1) U.S. Pat. No. : 4,702,321, Filing date: Sep. 20, 1985, Issue date: Oct. 27, 1987
- (2) U.S. Pat. No. : 6,263,824, Filing date: Dec. 23, 1997, Issue date: Jul. 24, 2001
- (3) U.S. Pat. No. : 7,819,073, Filing date: Jun. 2, 2006, Issue date: Oct. 26, 2010
- (4) U.S. Pat. No. : 7,612,462, Filing date: Apr. 24, 2008, Issue date: Nov. 3, 2009
Embodiments of present invention relate generally to the field of floating offshore wind turbines for offshore wind power generation. More particularly, embodiments of present invention relate to the field of a semi-submersible floater with a truss system for connecting the columns and a tensioned cable system for connecting the main structural components to improve structural strength and integrity, and associated methods for construction and installation. Furthermore, the invention also relates to the use of composite materials for the whole or part of the semi-submersible wind turbine floater construction.
BACKGROUND OF INVENTIONConventionally, semi-submersible floaters used in deepwater offshore oil and gas exploration and production are built with columns and pontoons which are enclosed buoyant structures using steel material as shown in
Truss cable semi-submersible floater for offshore wind turbines and construction methods are provided to provide more cost and weight efficient floater with better stability and structural strength and dynamic performance for offshore wind turbines. Parts of the structure can be made of composite materials.
With reference to
The tower 6 extends from the top of the center column 1a to the rotor for supporting the turbine and rotor blades. The tower 6 can be formed as a column structure. In some embodiment, as shown in
With reference to
In some embodiment, the floater can include a mooring line 5. The hull with three outer columns 1b can have 3 mooring lines 5, which can be pre-installed with drag anchor, suction anchor, or pile anchor for stabilizing the floater.
With reference to
With reference to
In some embodiments, a method of constructing a column with composite materials includes providing composite donut-shaped rings, placing multiple composite donut rings on each other vertically to form a composite section of a column, providing a steel section of the column and connecting it to the composite section of the column by grouting, attaching a watertight composite membrane to the inside or outside of the composite donut rings for connecting the composite donut rings and ensuring water tightness, placing a substantially vertical girder into the column, placing a deck into the column to divide the column into two watertight compartments. All or parts of the methods described above can be done on the land. Besides, a method of constructing a floater can further include installing a column base, a tensioned cable system, a tower, and a tower sleeve to the column, and coupling upper and lower trusses to the upper and lower ends of the columns. Then, the assembly of the columns can be loaded into water. The installation of turbine tower and assembly can be done in sequence in the water at quayside. Finally, the entire assembly of the floating system can be towed to the sea preferably at a draft within the depth of the column base, towered to in-service draft and fixed at the seabed with pre-set mooring lines.
Claims
1. A floating system comprising:
- a plurality of horizontal lower and upper truss system;
- a plurality of vertical buoyant columns, with one column at the center of the pattern, coupled with the truss system at the upper level;
- a plurality of large base tanks with diameters greater than the vertical buoyant columns, coupled with the truss system and the vertical columns, with one large base tank at the center of the pattern, at the lower level for ballast water or solid material;
- a wind turbine assembly supported by the column at the center of the pattern associated with the central large base tank at the lower level while horizontally constrained at the upper level by the truss system;
- a plurality of tensioned cable system of multiple tensioned cables to connect diagonally the wind turbine tower at the middle portion and the upper ends of the vertical buoyant columns together;
- a plurality of tensioned cable system of multiple tensioned cables to connect diagonally the upper and lower ends of the vertical buoyant columns;
- a plurality of mooring lines linking the floating system to the sea floor.
2. The floating system according to claim 1 wherein said entire assembly can be constructed using conventional steel and composite materials according to a method comprising;
- donut shape rings and tubes made of composite material first to form one column ring;
- the donut rings are placed on top of each other and filled with concrete to each tube;
- a watertight composite membrane is glued to the donut rings either from inside or outside or both to ensure the water tightness of the column and connecting each of the composite rings;
- the composite column section is coupled with the upper and lower sections of the column by grouting;
- the upper and lower sections of the column are made of conventional steel;
- the upper and lower trusses are welded to the column upper and lower sections;
- the assembly of the floating system is carried out on land;
- the completed floating system is loaded out into the water at quay;
- the wind turbine tower and assembly is installed on the floating system at quad side;
- the floating system is towed to sea at a installation tow draft within the depth of the large base tanks;
- the floating system is connected to the pre-set mooring lines at sea;
- the floating system is lowered to the in-service draft by water ballasting.
3. The floating system according to claim 1 wherein said entire assembly having a sleeve system for the wind turbine tower comprising,
- a tower sleeve associated with the center column at the upper level connected by the truss system to the outer columns;
- the tower sleeve is to allow the tower to penetrate it without rigid connection;
- the tower sleeve is to have contact pads to contact the tower at certain points;
4. The floating system according to claim 1 wherein said entire assembly having a truss system comprising horizontal truss space frame members at the lower and upper levels;
5. The truss system according to claim 4 wherein said truss space frame members can be made of light-weight composite material;
6. The floating system according to claim 1 wherein said entire assembly having a tensioned cable system comprising diagonal tensioned cables;
7. The floating system according to claim 1 wherein said entire assembly having a vertical buoyant column at the center of the pattern;
8. The floating system according to claim 1 wherein said entire assembly having a plurality of base tanks with diameter greater than the vertical buoyant columns;
International Classification: B63B 35/44 (20060101); B63B 21/50 (20060101);