Semi-submersible floater, particularly for a floating wind turbine

1. A semi-submersible floater for a floating wind turbine, defining an operating state and a non-operating state, and comprising:

at least two outer columns,

a central column for receiving a payload, and

for each outer column, a pontoon-shaped branch connecting this outer column to the central column and defining a branch axis oriented from the central column towards this outer column,

each pontoon-shaped branch is formed by a first portion and a second portion positioned in this order along the corresponding branch axis with the first portion being closer to the central column and the second portion being further from the central column,

wherein the first portion has a length along this branch axis equal to or greater than 10% of a total length of said pontoon-shaped branch along this branch axis,

wherein the second portion has a length along this branch axis equal to or greater than 10% of the total length of said pontoon-shaped branch along this branch axis,

wherein each outer column comprises a ballast able to be filled with a ballast material, arranged in the extension of the pontoon-shaped branch connecting the central column to this outer column along the corresponding branch axis,

wherein in the operating state of the semi-submersible floater, the second portion of each branch is at least partially filled with a ballast material, and wherein the first portion of each branch does not contain any ballast material, and

wherein in the operating state of the semi-submersible floater, the volume of said ballast material of the ballast of each outer column is between 40% and 60% of the total volume of this ballast.

2. The semi-submersible floater according to claim 1 , wherein the volume of the ballast material of the second portion of each pontoon-shaped branch is between 80% and 100% of the total volume of this portion.

3. The semi-submersible floater according to claim 2 , wherein the length of the second portion of each pontoon-shaped branch is equal to or greater than 30% of the total length of this branch and equal to or less than 80% of the total length of this branch.

4. The semi-submersible floater according to claim 2 , wherein the first portion of each pontoon-shaped branch is tightly isolated from the second portion of this branch.

5. The semi-submersible floater according to claim 1 , wherein each second portion comprises a first compartment and a second compartment, the first compartment and the second compartment being positioned in this order along the branch axis, and

wherein in the operating state of the semi-submersible floater, the volume of the ballast material of each first compartment is between 40% and 60% of the total volume of this compartment and the volume of the ballast material of each second compartment is between 80% and 100% of the total volume of this compartment.

6. The semi-submersible floater according to claim 5 , wherein the ratio of a length of the second compartment of the second portion of each pontoon-shaped branch along the corresponding branch axis to a length of the first compartment of the second portion of this same branch along the corresponding branch axis, is between 2 and 4.

7. The semi-submersible floater according to claim 6 , wherein each second portion comprises at least one inner partition arranged in the second compartment of this portion, the inner partition dividing this compartment into at least two compartment parts.

8. The semi-submersible floater according to claim 6 , wherein the length of the second portion of each pontoon-shaped branch is equal to or greater than 30% of the total length of this branch and equal to or less than 80% of the total length of this branch.

9. The semi-submersible floater according to claim 5 , wherein each second portion comprises at least one inner partition arranged in the second compartment of this portion, the inner partition dividing this compartment into at least two compartment parts.

10. The semi-submersible floater according to claim 9 , wherein the length of the second portion of each pontoon-shaped branch is equal to or greater than 30% of the total length of this branch and equal to or less than 80% of the total length of this branch.

11. The semi-submersible floater according to claim 5 , wherein the length of the second portion of each pontoon-shaped branch is equal to or greater than 30% of the total length of this branch and equal to or less than 80% of the total length of this branch.

12. The semi-submersible floater according to claim 1 , wherein the length of the second portion of each pontoon-shaped branch is equal to or greater than 30% of the total length of this branch and equal to or less than 80% of the total length of this branch.

13. The semi-submersible floater according to claim 1 , wherein the first portion of each pontoon-shaped branch is tightly isolated from the second portion of this branch.

14. The semi-submersible floater according to claim 1 , wherein the central column does not contain any ballast material.

15. The semi-submersible floater according to claim 1 , wherein the ballast material comprises at least one of the materials from the following list:

seawater,

mud,

sand,

gravel.

16. The semi-submersible floater according to claim 1 , wherein the length of the second portion of each pontoon-shaped branch is equal to or greater than 30% of the total length of this branch and equal to or less than 80% of the total length of this branch.

17. The semi-submersible floater according to claim 1 , wherein the first portion of each pontoon-shaped branch is tightly isolated from the second portion of this branch.

18. A method for installing a semi-submersible floater for a floating wind turbine, the semi-submersible floater defining an operating state and a non-operating state, and comprising:

at least two outer columns,

a central column for receiving a payload, and

for each outer column, a pontoon-shaped branch connecting this outer column to the central column and defining a branch axis oriented from the central column towards this outer column,

each pontoon-shaped branch is formed by a first portion and a second portion positioned in this order along the corresponding branch axis with the first portion being closer to the central column and the second portion being further from the central column,

wherein the first portion has a length along this branch axis equal to or greater than 10% of a total length of said pontoon-shaped branch along this branch axis,

wherein the second portion has a length along this branch axis equal to or greater than 10% of the total length of said pontoon-shaped branch along this branch axis,

wherein each outer column comprises a ballast able to be filled with a ballast material, arranged in the extension of the pontoon-shaped branch connecting the central column to this outer column along the corresponding branch axis, and

wherein the method comprises the following steps for placing the semi-submersible floater in the operating state:

filling the second portion of each pontoon-shaped branch at least partially with a ballast material, and

leaving the first portion of each pontoon-shaped branch empty of ballast material, and

filling the ballast of each outer column with said ballast material, the volume of the ballast material of the ballast of each outer column being between 40% and 60% of the total volume of this ballast.