Floating offshore structures

Patent metadata

Field	Value
Publication number	US-2016229494-A1
Application number	US-201414777727-A
Country	US
Kind code	A1
Filing date	Mar 26, 2014
Priority date	Mar 28, 2013
Publication date	Aug 11, 2016
Grant date	—

Abstract

Methods for controlling tension in mooring lines of a floating offshore structure having a buoyancy structure including one or more water tanks and the buoyancy structure providing excess buoyancy are provided. The methods comprise varying the mass and/or the centre of gravity of the floating offshore structure by varying the quantity of water in one or more of the water tanks. Also, floating offshore structures are disclosed, the structures comprising a buoyancy structure having one or more floater tanks providing excess buoyancy, and a plurality of tensioned mooring lines, and further comprising a control system for increasing and decreasing a quantity of water in one or more of the floater tanks. Also, possible uses of floating offshore structures are provided wherein under standard operating conditions, the floater tanks are at least partially filled with water.

First claim

1 . A method for controlling stability of a tension leg platform structure, the tension leg platform structure having a buoyancy structure providing excess buoyancy and a plurality of mooring lines, the buoyancy structure including one or more water tanks, the method comprising:
controlling tension in the mooring lines by changing a quantity of water in one or more of the water tanks, in order: to vary a mass of the tension leg platform structure; to vary a center of gravity of the tension leg platform structure; or to vary both the center of gravity and the mass of the tension leg platform structure.

2 . The method according to claim 1 , wherein the quantity of water in one or more of the water tanks is changed in response to one or more loads on the tension leg platform structure.

3 . The method according to claim 2 , wherein the mass of the tension leg platform structure is varied in response to a measured oscillation in order to reduce the measured oscillation.

4 . The method according to claim 2 , wherein the mass of the tension leg platform structure is varied in response to a tension measured in one or more of the mooring lines.

5 . The method according to claim 1 , wherein the tension leg platform structure comprises a wind turbine.

6 - 7 . (canceled)

8 . A floating offshore structure comprising:
a wind turbine, a tension leg platform including a plurality of radially outwardly extending braces, and a mooring line attached to each of the braces at one end and to a seabed at the other end wherein the floating offshore structure comprises a buoyancy structure having one or more water tanks for providing excess buoyancy, and a plurality of tensioned mooring lines, and further comprising a control system for increasing and decreasing a quantity of water in one or more of the water tanks to control the tension in the mooring lines.

9 . The floating offshore structure according to claim 8 , further comprising one or more sensors to measure the tension in one or more of the mooring lines.

10 . The floating offshore structure according to claim 9 , wherein the control system is adapted to adjust the quantity of water in one or more of the water tanks in response to a measured tension in one or more of the mooring lines.

11 . The floating offshore structure according to claim 8 , wherein one or more of the water tanks comprise
at least one one-way valve for increasing the quantity of water in the floater tank and at least one-way valve for decreasing the quantity of water in the floater tank.

12 . The floating offshore structure according to claim 8 , wherein one or more of the water tanks comprises two or more partitions.

13 - 14 . (canceled)

15 . The floating offshore structure according to claim 8 , wherein the braces are arranged to remain under a mean sea level.

16 . The floating offshore structure according to claim 15 , wherein each of the braces comprises one or more of the water tanks and the control system is adapted to increase and decrease the quantity of water in each of the water tanks.

17 . The floating offshore structure according to claim 8 , wherein the braces are arranged to remain above a mean sea level.

18 . The floating offshore structure according to claim 8 , comprising three braces.

19 . The floating offshore structure according to claim 8 , wherein the control system is configured to maintain the water tanks at least partially filled with water under standard operating conditions.

20 . The method according to claim 5 , wherein a quantity of water is changed in one or more of the water tanks while the wind turbine is operating.

21 . The method according to claim 4 , wherein the mass of the tension leg platform structure is increased in order to reduce the tension in the mooring lines.

22 . A method for controlling stability of a tension leg platform structure,
the tension leg platform structure having
a wind turbine,
a buoyancy structure providing excess buoyancy,.
a plurality of mooring lines, and
the buoyancy structure including one or more water tanks,
the method comprising:
operating the wind turbine; measuring a tension in the mooring lines; and reducing a quantity of water in one or more of the water tanks in order to maintain a tension in the mooring lines above a minimum tension.

23 . The method according to claim 22 , further comprising changing a centre of gravity of the tension leg platform structure.

Assignees

• Alstom Renewable Technologies

Inventors

• Bergua Roger

Classifications

• F03D13/22

  Foundations specially adapted for wind motors · CPC title

• F05B2240/93

  on a structure floating on a liquid surface · CPC title

• B63B21/502 Primary

  by means of tension legs · CPC title

• B63B22/20 Primary

  Ballast means · CPC title

• E02B2017/0091

  Offshore structures for wind turbines · CPC title