Truss Cable Semi-submersible Floater for Offshore Wind Turbines and Construction Methods

Abstract

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.

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;