VERTICALLY INSTALLED SPAR AND CONSTRUCTION METHODS

Abstract

A vertically installed Spar-type floater for offshore wind turbine and related construction method are provided. The floating system is a gravity stabilized deep-draft floater including a plurality of vertically extending columns, each column containing a ballast material; a ballast tank coupled to the lower end of each of the columns; a top deck having a plurality of through-bores approximate its periphery coupled to the upper end of each of the columns; a wind turbine assembly supported by the top deck at the center; a plurality of mooring lines linking the floating system to the sea floor. The floating system has a temporary vertically towing configuration which: allows the entire, floating wind turbine system to be assembled at a quayside and towed vertically to an offshore site, and self-installed into operating configuration.

Description

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR

Not 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) Top Plants: Hywind Floating Wind Turbine, North Sea, Norway, Power Magazine Article, Dec. 1, 2009

(4) U.S. Pat. No. 7,819,073, Filing date: Jun. 2, 2006, Issue date: Oct. 26, 2010

(5) U.S. Pat. No. 7,612,462, Filing date: Apr. 24, 2008, Issue date: Nov. 3, 2009

FIELD OF INVENTION

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 a vertically installed wind turbine Spar-type floater, which can be assembled at a quayside vertically and installed vertically together with the wind turbine tower and rotor blades mounted in upright operating position, and towed at sea together with a wind turbine assembly mounted on the top deck in upright operating position and installed vertically at an offshore wind farm site

BACKGROUND OF INVENTION

Conventionally, a category of deep-draft caisson floaters, most commonly referred to as the Spar [Ref. 1 and 2], has been used for deepwater oil and gas drilling and production as shown in FIG. 1. A key characteristic of a Spar-type floater is that it usually has along slender body and is stabilized by gravity by maintaining its vertical center of gravity lower than the center of buoyancy. More recently the Spar floater concept has also been used as a floating wind turbine for offshore wind power generation [Ref. 3] as shown in FIG. 2. Such a conventional Spar-type floater requires the buoyant hull be built onshore and towed offshore in horizontal position and upended in deepwater for topside installation. More particularly, a conventional Spar-type wind floater is built onshore and towed offshore in horizontal position as shown in FIG. 3, and upended in deepwater for installing the turbine tower and rotor blades assembly by a floating heavy lift crane vessel as shown in FIG. 4. Such conventional Spar-type floater and offshore installation method is costly. A conventional

Spar-type wind floater could be vertically assembled at a quayside with water depth in excess of 100 meter from the quay throughout to the offshore wind farm site as mentioned in [Ref. 4]. However, there are very few locations in the World, mostly in Norway, with such deep water depth for application. The present invention aims to provide an innovative Spar-type floater with unique configuration which enables a floating wind turbine to be constructed, towed vertically and installed offshore at significantly lower cost than a conventional Spar-type floater.

SUMMARY OF INVENTION

A vertically installed Spar-type floating wind turbine system for offshore Wind power generation and related construction methods are provided. The present invention can be assembled at a quayside vertically and towed at sea together with a wind turbine assembly mounted on the top deck in upright operating position and installed vertically at an offshore wind farm site to provide a more cost-effective floating wind turbine system for offshore wind power generation.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a prior art of a Spar-type floater used in oil and gas drilling production according to some embodiments of the present invention.

FIG. 2 illustrates a prior art of a Spar-type floater used in offshore wind power generation according to some embodiments of the present invention.

FIG. 3 illustrates a prior art of horizontal towing of a Spar-type wind turbine floater according to some embodiments of the present invention.

FIG. 4 illustrates a prior art of installing a wind turbine tower and rotor blades onto a Spar-type wind turbine floater by a heavy lift crane vessel according to some embodiments of the present invention.

FIG. 5 illustrates a perspective view of present invention of a vertically installed Spar-type floating wind turbine system in permanent operating configuration according to some embodiments of the present invention.

FIG. 6 illustrates a perspective view of present invention of a vertically installed Spar-type floating wind turbine system in temporary towing configuration according to some embodiments of the present invention.

FIG. 7 illustrates a front view of the vertically installed Spar-type floating wind turbine system in permanent operating configuration according to some embodiments of the present invention.

FIG. 8 illustrates a side view of the vertically installed Spar-type floating wind turbine system in temporary towing configuration according to some embodiments of the present invention.

FIG. 9 illustrates the quayside construction method and assembly sequence of the vertically installed Spar-type floating wind turbine system according to some embodiments of the present invention.

FIG. 10 illustrates the offshore installation method and sequence of the vertically installed Spar-type floating wind turbine system at an offshore wind farm site according to some embodiments of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Preferred embodiments of the present invention are shown in FIG. 5 through 10 above with detailed description as follows.

With reference to FIG. 5, a floating wind turbine system 2 in operating configuration includes a plurality of vertically extending columns 4; a ballast tank 6 coupled to the lower end of each of the columns 4; a top deck 8 coupled to the upper end of each of the columns; a wind turbine assembly, comprising a tower 10, a nacelle 12 and rotor blades 14, supported by the top deck; and a plurality of mooring lines 16 linking the said floating system to the sea floor. The floating wind turbine system 2 has a referred range of in-service operating draft of 80 to 120 meters. The columns 4 are empty and, the lower column segment contains a ballast material most commonly sea water. With respect to the columns 4, the preferred number of columns is three and the preferred cross-section is circular which may be of same diameter throughout Or of different diameters at different elevations. The ballast tank 6 located at the bottom of the floater contains a ballast material most commonly of high density solid material, such as iron ore or sand or concrete, and is flooded in the operating configuration in the preferred embodiment. The top deck 8 is above the sea level supporting the turbine tower 10 which has the lower end coupled to a structural support located at the center of the top deck 8. The ballast tank 6 and the top deck 8 can have various configurations which are, but not limited to, circular, triangular, rectangular, square, hexagon, octagon or star, or other non-regular shapes. The preferred top deck 8 configuration has a plurality of through-bores at which the upper end of each of the columns 4 is connected; Connections between the columns 4 and the top deck 8 can be of welded or grouted by means of concrete. Connections between the turbine tower 10 and the top deck 8 can be of bolted, or welded or grouted by means of concrete.

With reference to FIG. 6, a floating wind turbine system in temporary towing configuration 18 includes a plurality of vertically extending columns 4; a ballast tank 6 coupled to the lower end of each of the columns 4; a top deck 8 coupled to the upper end of the ballast tank 6; a wind turbine assembly, comprising a tower 10, a nacelle 12 and rotor blades 14, supported by the top deck 8; a plurality of stability tanks 20, and a locking and quick release system 22 linking each of the stability tanks 20 to the top deck 8. The top deck 8 is preferred to be above the sea level during the towing with offshore installation equipment mounted on the top surface. The stability tanks 20 provide stability during the vertical towing of the entire wind turbine assembly. While FIG. 6 shows three stability tanks 20 each having a set of lock and quick release system 22, the present invention also covers various other stability tank and towing configurations such as but not limited to a single stability tank configuration, two stability tank configuration, four stability tank configuration with corresponding locking and quick release systems. The stability tanks 20 can be purposely built or converted from existing marine cargo barges. The locking and quick release system 22 provides the connection between the top deck 8 and the stability tank 20 during the towing and allows quick separation during removal of the stability tank 20 after the floating wind turbine completes the configuration change from the towing configuration 18 to the operating configuration 2.

FIG. 7 shows a front view of the floating wind turbine 2 in operating configuration. FIG. 8 shows a side view of the floating wind turbine 18 in towing configuration.

With reference to FIG. 9, the construction and assembly sequence at a quayside of the floating wind turbine system 18 in towing configuration is described. Step I shows the ballast tank 6 is first put on the water and secured by temporary mooring to a quayside (not shown), and the top deck 8 is put on top of the ballast tank 6. Step II shows the stability tanks 20 are connected to the top deck 8 and the columns 4 coupled to the periphery through-bores and turbine tower 10 coupled to the center of the top deck 8 supporting structure. In Step II, the columns 4 and the turbine tower 10 can be lifted by a conventional crane on land and put on the top deck 8 one by one either in single piece or several segments. Temporary construction struts can be used to provide temporary stability for the extended columns 4. Step III shows the nacelle 12 and rotor blades 14 are lifted by a conventional crane (not shown) and mounted on the turbine tower 10. In Step III, the nacelle 12 and rotor blades 14 can also be lifted separately one by one in a more conventional way for wind turbine assembly. Step IV shows the floating wind turbine system in towing configuration 18 is completely assembled at quayside. Sea-fastenings are provided to form a rigidly-connected assembly. Solid ballast is put into the ballast tank 6. The floating wind turbine system in towing configuration 18 is ready to be towed offshore.

With reference to FIG. 10, the offshore towing and installation sequence converting the floating wind turbine system from the towing configuration 18 into the operating configuration 2 are described. Continuing from above Step IV Step V shows the floating wind, turbine system towing configuration 18 is towed vertically by a conventional tug boat (not shown) to the offshore wind farm site. Step VI shows the floating wind turbine system towing configuration 18 is being transformed into the operating configuration 2 by lowering the columns 4 vertically through the through-bores in the top deck 8. In this step, the stability tanks 20 are still connected to the top deck 8 to provide stability for the entire assembly. The sea-fastenings for coupling the columns 4 to the top deck 8, and the ballast tank 6 to the top deck 8 are removed. The ballast tank 6 coupled to the columns 4 moves downward vertically under gravity to a deeper draft. Ballast water is pumped into the columns 4 to further lower the ballast tank 6 to the final draft at which the upper end of the column 4 is just above the top deck 8 at a pre-determined elevation for final connection. Permanent connections are made between the top deck 8 and the columns 2. Step VII shows the stability tank 20 is being moved away from the top deck 8 by a tug boat (not shown). The locking and quick release system 22 is activated to create initial separation between the stability tank 20 and the top deck 8 allowing the tug boat (not shown) to pull the stability tank 20 away. Step VIII shows lines are hooked up to the floating wind turbine system 2 in operating configuration.

The above figures and description are preferred embodiments of the present invention and preferred main points of the construction methods and assembly sequences for quayside assembly and offshore towing and installation. All modifications, equivalents, and alternatives to the above preferred embodiments are to be covered in the character and scope of the present invention.

Claims

1. A floating system comprising: a plurality of vertically extending columns, each column containing a ballast material;a ballast tank coupled to the lower end of each of the columns;a top deck having a plurality of through-bores approximate its periphery coupled to the upper end of each of the columns at the through-bores;a wind turbine assembly supported by the top deck at the center support structure;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 temporarily arranged in a vertically towing configuration, comprising: the vertically extending columns according to claim 1;the ballast tank according to claim 1 coupled to the lower end of each of the columns;the top deck according to claim 1 coupled temporarily to the upper end of the ballast tank,the top deck comprising a plurality of through-bores approximate its periphery, a column extending through each of the through-bores;the wind turbine assembly according to claim 1 supported by the top deck;one stability tank or a plurality of stability tanks coupled to the floating system;a locking and quick release system linking each said stability tank to the top deck to form a vertical towing assembly.

3. The floating system according to claim 1 wherein said deck comprising a structural system having a plurality of through-bores approximate its periphery and a support structure for the turbine tower.

4. The top deck according to claim 3 wherein said throughbore having a deck guiding system.

5. The top deck according to claim 3 wherein said deck guiding system having a locking and release mechanism.

6. The floating system according to claim 1 wherein said column having a column guiding system allowing said column to move relative to the deck within the said deck throughbore.

7. The deck guiding system according to claim 5 wherein said deck locking and release mechanism controlling the position of said column during said floating system offshore installation process.

8. The floating system according to claim 2 wherein said stability tank having a locking and release system linking the said stability tank to the said top deck.

9. The stability tank according to claim 8 wherein said locking and release system having a quick release mechanism to allow quick separation of the said stability tank from the said deck during the said floating system offshore installation.

10. The floating system according to claim 1 wherein said ballast tank conventionally made of steel material having the option of being made of composite material with hybrid of steel, fiber and concrete.

11. A method of vertically assembling the said floating system according to claim 2 at a quayside as illustrated in F1G. 9, comprising: Step I: coupling a deck to a ballast tank at a quayside, the deck comprising a plurality of through-bores approximate its periphery;Step II: coupling one or more temporary towing stability tanks to the deck; extending a column through each of the through-bores; coupling the lower end of each column to the ballast tank;Step III: coupling a wind turbine assembly to the top of the deck;Step IV: coupling a locking and quick release system and sea-fastenings to the deck and each of the stability tanks, whereby the wind turbine, the deck, the columns, the ballast tank, the stability tanks and the locking and quick release system form an assembly, inputting a quantity of ballast material to the ballast tank;

12. A method of vertically towing and installing a floating system according to claim 1 over a sea floor as illustrated in FIG. 10, comprising: Step V: continuing the steps from claim 11 above, towing vertically the assembly to an offshore wind farm site;Step VI: removing the sea-fastenings between the deck and the ballast tank, thus allowing the ballast tank coupled with the lower end of each of the columns to freely lower to a deeper draft, further allowing the upper end of each of the columns to reach a pre-determined elevation approximate to the deck by inputting a ballast material mostly water to the columns; coupling the upper end of each of the columns to the deck by welding or grouting or bolting or other methods;Step VII: activating the quick release system and pulling away each of the stability tanks by using a tugboat,Step VIII: coupling the floating system with the mooring lines to the sea floor.