Asymmetric floating wind turbine equipment

Abstract

The floating wind turbine facility includes an asymmetric floating wind turbine structure connected to the bottom of a body of water by a mooring system. The floating wind turbine structure includes a wind turbine mounted on a semi-submersible floating platform, and the floating wind turbine structure is oriented such that when wind approaches the wind turbine structure in the dominant wind direction at the location of the floating wind turbine facility, the wind turbine is positioned on the upwind side of the center of mass of the floating wind turbine structure.

Description

Technical Field

[0001] The present invention relates to the field of floating wind turbines. In particular, the present invention relates to a mooring configuration for asymmetric floating wind turbine installations.

Background Art

[0002] FIG. 1 is a schematic plan view of a semi-submersible floating wind turbine installation 1 that is asymmetric with respect to rotation and moored to the seabed in a well-known configuration. The wind turbine installation 1 includes a semi-submersible floating platform having three columns, namely, two empty columns 2 and a third column 3 that supports the wind turbine itself. The three columns 2, 3 are connected in a triangular ring configuration by three connecting members 4 to form the platform. The wind turbine installation is moored to the seabed using three mooring cables 5, with one mooring cable 5 directly connected to each column 2, 3.

[0003] At the location of the wind turbine installation 1, the prevailing wind propagates in the positive direction along the x-axis shown in FIG. 1. This is the direction in which the wind most commonly propagates at the location of the wind turbine. The wind turbine installation 1 in FIG. 1 is oriented such that the column 3 (i.e., the column that supports the wind turbine) is positioned on the leeward side of the installation 1 in the direction of the prevailing wind, and the empty columns 2 are positioned on the windward side of the installation 1. The mooring cables 5 serve to hold the wind turbine installation 1 in this orientation by resisting the yaw (sway) motion of the wind turbine installation 1.

[0004] Compared with other orientations, the configuration shown in FIG. 1 provides favorable motion characteristics for the floating wind turbine installation 1. In the case of an asymmetric floating wind turbine installation as shown in FIG. 1, the force of the wind acting on the wind turbine installation creates a yaw moment that tends to orient the wind turbine installation in a direction where the column supporting the wind turbine installation is positioned on the leeward side of the wind turbine installation. This is known as "weathervaning". It will be understood that the installation 1 in FIG. 1 is oriented so as to be in its equilibrium position when the wind approaches the installation along the predominant wind direction (i.e., the positive x-direction). In this case, no yaw moment is generated. Since the wind most commonly propagates in the direction of the predominant wind, the installation 1 is in its equilibrium position or near its equilibrium position for most of the time. Any change in the wind direction away from the predominant wind direction is likely to be small, resulting in a relatively small yaw moment away from the position shown in FIG. 1. Therefore, the installation 1 in FIG. 1 is oriented towards a stable equilibrium position.

[0005] The arrangement of the mooring cables 5 shown in FIG. 1 is also favorable. The restoring yaw stiffness of this arrangement of mooring cables (i.e., the resistance provided by the mooring cables 5 against yaw) is maximum when the wind approaches the installation 1 directly between two adjacent mooring cables and minimum when the wind approaches directly over one mooring cable. Therefore, the arrangement of the mooring cables shown in FIG. 1 provides optimal restoring yaw stiffness with respect to the most common wind conditions observed at the location of the installation, i.e., when the wind approaches along or in the vicinity of the predominant wind direction.

[0006] Therefore, it will be understood that the installation 1 shown in FIG. 1 exhibits relatively stable yaw characteristics in the most common wind conditions observed at the location of the installation.

[0007] However, this orientation does not provide optimal conditions for power generation. The reasons are as follows: during operation, the thrust of the dominant wind acting on the wind turbine facility 1 causes the structure to sway vertically (i.e., rotated about the transverse axis), and at this time, the upwind side of the wind turbine facility 1 (i.e., the column 2) is forced to float at a higher position in the water, and the downwind side (i.e., the column 3) is forced to sink to a lower position in the water. As a result, the height of the wind turbine above the water surface decreases, the wind turbine interacts with the wind at a lower altitude, and the wind at a lower altitude usually has a lower average speed than the wind at a higher altitude. Consequently, the power output of the wind turbine decreases.

Summary of the Invention

Means for Solving the Problem

[0008] According to a first aspect of the present invention, there is provided a floating wind turbine facility including an asymmetric floating wind turbine structure connected to the bottom of a water area by a mooring system, the floating wind turbine structure including a wind turbine attached to a semi-submersible floating platform, the floating wind turbine structure being held in a predetermined position by the mooring system such that the wind turbine is positioned on the upwind side of the center of mass of the floating wind turbine structure in the direction of the dominant wind at the location of the wind turbine facility.

[0009] Viewed from another perspective, the present invention can be regarded as providing a floating wind turbine facility including an asymmetric floating wind turbine structure connected to the bottom of a water area by a mooring system, the floating wind turbine structure including a wind turbine attached to a semi-submersible floating platform, the floating wind turbine structure being oriented such that when the wind approaches the wind turbine structure in the direction of the dominant wind at the location of the wind turbine facility, the wind turbine is positioned on the upwind side of the center of mass of the floating wind turbine structure.

[0010] The predominant wind direction at the location of the wind turbine installation is the direction in which the wind mainly propagates at the location of the wind turbine installation. It is understood that the wind direction is likely to change over time, and thus the wind does not always blow in the same predominant direction. However, the predominant wind direction is the most common direction in which the wind blows at the location of the wind turbine installation. Although the wind tends to propagate in the predominant direction at the macroscale, it may locally deviate from the predominant direction, for example, due to obstacles and / or local topography.

[0011] The reference to the floating wind turbine structure being asymmetric means that the floating wind turbine structure is rotationally asymmetric about a vertical axis, for example, a vertical axis passing through the center point of the floating wind turbine structure (i.e., the center point of the floating wind turbine structure as seen in a horizontal plane, for example, from above). This can be achieved by positioning the wind turbine at a location away from the center point of the floating platform (i.e., a location that is not the center point of the floating platform) when viewed in the horizontal plane.

[0012] The mooring system is provided to maintain the floating wind turbine structure at its installation location, and in particular, acts to maintain the intended orientation of the floating wind turbine structure, for example, its orientation with respect to the predominant wind direction, by resisting the yaw of the floating wind turbine structure. However, the mooring system may allow some (relatively small) movements of the floating wind turbine structure, such as those that can be caused by wind, current, and / or waves, while maintaining the wind turbine on the windward side of the floating wind turbine structure in the direction of the predominant wind. For example, the floating wind turbine structure can pitch about its transverse axis due to, for example, the thrust acting on the floating wind turbine structure by the wind.

[0013] During operation, due to the wind force acting on the floating wind turbine facility, the floating wind turbine structure rotates longitudinally (i.e., pitches) about a lateral axis passing through its center of mass (i.e., an axis from side to side). When the floating wind turbine structure pitches, a part of the floating structure sinks deeper into the water, while another part rises above the water surface. When the wind blows in the dominant direction, the thrust exerted on the floating wind turbine structure by the wind causes the windward side of the floating wind turbine structure to rise further above the waterline, and the leeward side of the floating wind turbine structure to sink further below the waterline. Since the wind turbine is located windward of the center of mass of the floating wind turbine structure, this pitching motion of the floating wind turbine structure raises the wind turbine and effectively increases the height of the wind turbine above the water surface. As a result, the wind turbine will interact with the wind at a higher altitude above the water surface, and this wind usually has a higher average wind speed than the wind at a lower altitude. This can increase the power generation of the wind turbine. By positioning the wind turbine on the windward side of the floating wind turbine structure, it has been found that the annual power generation of the wind turbine can increase by up to 2% (e.g., 1% - 1.5%) compared to a conventional floating wind turbine structure with the wind turbine arranged on the leeward side (e.g., as shown in FIG. 1). This can, for example, improve the profit rate by up to 20%.

[0014] The pitch angle of the floating wind turbine structure tends to vary around an average value over time as a result of dynamic movements, for example, due to the influence of waves and / or tides on the floating structure. Generally, when wind force is acting on the floating wind turbine structure, the average pitch angle is larger compared to when no wind is acting on the wind turbine. In the case of the rated wind speed, the average pitch angle of the floating wind turbine structure can be between 6° and 14° (with respect to the vertical direction).

[0015] Preferably, the wind turbine can be positioned (substantially) exactly upwind of the center of mass of the floating wind turbine structure in the direction of the prevailing wind. That is, the angle formed between the prevailing wind direction and the straight line passing through the position of the wind turbine and the center of mass of the floating wind turbine installation can be 0°, or substantially (±5°) 0°. For a given thrust, this orientation maximizes the increase in the height of the wind turbine achieved at the average pitch angle. This typically results in a maximum increase in the power output of the wind turbine. However, an increase in power output can also be achieved when an angle of up to 60° is formed between the prevailing wind direction and the straight line passing through the position of the wind turbine and the center of mass of the floating wind turbine installation. Therefore, the angle formed between the prevailing wind direction and the straight line passing through the position of the wind turbine and the center of mass of the floating wind turbine installation can be up to 60°, preferably up to 45°, more preferably up to 30°.

[0016] The semi-submersible platform can include a plurality (e.g., three) of columns connected by connecting members (e.g., in a triangular ring configuration). The connecting members may all be of the same length. Thus, if the semi-submersible platform includes three columns, the columns can be connected in an equilateral triangle shape.

[0017] The wind turbine is preferably supported by one of the columns, e.g., attached to one of the columns. The other columns among the plurality of columns may be empty, i.e., only one of the columns can support the wind turbine.

[0018] The separation between adjacent columns can be between 50 m and 100 m, preferably between 70 and 80 m. Thus, the length of the connecting members can be between 50 m and 100 m, preferably between 70 m and 80 m.

[0019] Since pitching is a rotational movement about the lateral axis, it will be understood that the achievable increase in the height of the wind turbine (caused by pitching) is proportional to the distance between the lateral axis of the floating wind turbine structure and the position of the wind turbine. Thus, the greater this distance, the greater the achievable increase in height. The distance between the center of gravity of the floating wind turbine structure and the position of the wind turbine can be affected by the column spacing and thus the length of the connecting members. Therefore, increasing the length of the connecting members can result in a greater achievable increase in the height of the wind turbine and thus a greater increase in the power generation amount.

[0020] Each column may have a circular cross-section, i.e., may be formed as a circular column, or may have a polygonal cross-section. That is, each column may be formed as a polygonal (e.g., triangular, square, trapezoidal, pentagonal, etc.) column.

[0021] The columns can have a diameter between 10 m and 20 m, preferably between 14 m and 16 m.

[0022] One or more or each of the columns can include or define a ballast tank for storing air and / or ballast. Ballast, such as water, can be held within one or more of the ballast tanks. For example, the ballast can be distributed among the ballast tanks such that the floating wind turbine structure maintains a roll angle of 0° or substantially 0° (i.e., within ±5°) when there is no wind acting on the wind turbine (i.e., in a windless state). To achieve this, the mass of the ballast in the ballast tank supporting the wind turbine can be made less than the mass of the ballast in the ballast tanks of the other columns.

[0023] A semi-submersible platform may include one or more pontoons extending between two of a plurality of columns, for example, two adjacent columns. Each column may be connected to an adjacent column via a pontoon. The pontoon may be hollow and may define a ballast tank for holding air and / or ballast. During operation of the floating wind turbine installation, the pontoon may be located below the waterline. The pontoon can serve to dampen the movement of the floating wind turbine structure during use and can also be used to provide the buoyancy required during installation of the floating wind turbine structure.

[0024] The semi-submersible platform can employ passive ballast, that is, the ballast within each column and / or pontoon can be kept constant during operation. Alternatively, the semi-submersible platform can include an active ballast system for changing the amount and mass of the ballast held within one or more of the ballast tanks (e.g., of the columns and / or pontoons) during use. The active ballast system can include one or more pumps for pumping liquid ballast (e.g., water) into and / or out of the ballast tanks (e.g., of the columns and / or pontoons).

[0025] The ballast can be distributed between the ballast tanks of the columns and / or the ballast tanks of the pontoons such that when the wind turbine is operating at the rated wind speed, the average pitch angle of the floating wind turbine structure is between 6° and 14°.

[0026] When the wind turbine is attached to a semi-submersible platform (and optionally when the platform is loaded with ballast), the columns may extend up to 20 m from the waterline.

[0027] A wind turbine may include a tower and a rotor attached to the upper end of the tower, preferably rotating about a horizontal axis. The tower may have a length (i.e., height) of at least 75 m, preferably more than 100 m, more preferably more than 130 m. The tower can be attached to one of the columns of a semi-submersible floating platform.

[0028] The rotor may include a hub and a plurality of, preferably three, blades attached to the hub.

[0029] The wind turbine is preferably a horizontal axis wind turbine, i.e., the rotor is arranged to rotate about a substantially horizontal axis during use.

[0030] When the floating wind turbine structure heaves as a result of the restoring force imparted to the floating structure by the dominant wind, it will be appreciated that the rotor of the wind turbine is positioned at a higher position above the water surface and thus interacts with wind that typically has a higher average wind speed than the wind at lower altitudes. As a result, the power output of the wind turbine can increase.

[0031] The length of the blade can be at least 75 m, preferably 100 m or more, more preferably 130 m or more.

[0032] The turbine may include a nacelle attached to the upper end of the tower. The rotor can be attached to the nacelle, for example via a hub, and arranged to rotate relative to the nacelle.

[0033] The nacelle is preferably rotatably attached to the tower so as to enable rotation of the nacelle relative to the tower about the longitudinal axis of the tower. By doing so, the rotor can be yawed into the oncoming wind.

[0034] The turbine may include a generator coupled to the rotor to generate electricity by rotation of the rotor. The generator can be mounted within the nacelle.

[0035] The rated power output of the wind turbine can be more than 10 MW, preferably more than 15 MW, and most preferably more than 20 MW. The rated power output of the wind turbine can be between 15 MW and 23 MW.

[0036] The mooring system may include a plurality (e.g., three or more) of mooring cables directly or indirectly connected to the floating wind turbine structure. In order to connect the floating wind turbine facility to the bottom of the water area, each mooring cable can be fixed to the bottom of the water area at one end (i.e., the anchor end) and connected to the floating wind turbine structure at the other end (i.e., the connection end).

[0037] The length of the mooring cable depends on the location of the floating wind turbine facility and the water depth. However, typically, the mooring cable can have a length between 800 m and 900 m.

[0038] One or more or each of the mooring cables may be fixed to the bottom of the water area by an anchor chain. One end of the anchor chain may be connected to the anchor end of the mooring cable, and the other end of the anchor chain may be fixed to the bottom of the water area. The length of the anchor chain may be between 20 m and 40 m.

[0039] One or more or each of the mooring cables may be connected to the floating wind turbine structure via a pendant rope or using a pendant rope. The pendant rope may include two or more pendant ropes for connecting the end of the mooring cable to the floating wind turbine facility. Each pendant rope may be connected to one end (i.e., the connection end) of the mooring cable at its first end and connected to the floating wind turbine facility (e.g., to a semi-submersible platform) at its second end.

[0040] The two or more pendant ropes of the pendant rope can have a length between 75 m and 125 m.

[0041] Two or more attachment ropes of the attachment ropes may be connected to the floating wind turbine installation at two or more different (spaced apart) positions or connection points. For example, the attachment rope may connect a single mooring rope to more than one (e.g., two or more) columns of a semi-submersible platform. In some arrangements, two or more attachment ropes may be connected to different ones of the columns respectively.

[0042] Two or more attachment ropes of different attachment ropes may be connected to the floating wind turbine installation at the same common connection point.

[0043] The mooring rope may be connected to the floating wind turbine structure (e.g., a semi-submersible platform) above the waterline or below the waterline, e.g., at the lower end of the semi-submersible platform.

[0044] Using one or more attachment ropes to attach the mooring rope to the floating wind turbine structure may help to stabilize the roll and yaw of the floating structure. When an attachment rope is provided, the yaw restoring stiffness of the mooring system is significantly improved when the pretension is the same compared to a configuration where the mooring rope is directly connected to the floating platform (e.g., the configurations shown in FIGS. 1 and 2). This leads to a reduction in yaw motion, and since the coupling from pitch motion decreases when the yaw motion is reduced, it may also lead to a reduction in roll motion. Even in a mooring system where the mooring rope is directly connected to the floating structure, the restoring yaw stiffness can be similarly improved by increasing the pretension of the mooring rope. However, this may increase the load on the mooring rope, which may increase the fatigue of the mooring rope and shorten its lifespan.

[0045] In one arrangement, the semi-submersible platform includes three columns (arranged, for example, in a triangular ring configuration), and the mooring system includes three mooring lines. Each mooring line of the three mooring lines may be connected to the floating wind turbine structure by respective pendant lines each including two pendant ropes, where each pendant rope is connected to a different one of the columns of the semi-submersible platform. In this way, each mooring line can be connected to two columns via the pendant ropes. Each of the columns of the semi-submersible platform may be (indirectly) connected to two of the mooring lines via the (respective) pendant ropes.

[0046] In an alternative arrangement, the semi-submersible platform may include three columns (arranged, for example, in a triangular ring configuration), where the wind turbine is attached to one of the columns and the mooring system may include four mooring lines. Each mooring line can be directly connected to the floating wind turbine structure. Two of the four mooring lines can be connected to the column supporting the wind turbine, for example, at the same connection point. Each of these two mooring lines may be offset from the dominant wind direction by up to 30° and may be separated from each other by up to 60°. That is, this pair of mooring lines may straddle the dominant wind direction, where one of the mooring lines is arranged at up to 30° from the dominant wind direction in the clockwise direction and the other mooring line is arranged at up to 30° from the dominant wind direction in the counterclockwise direction. The other two mooring lines can be connected to different ones of the other two columns respectively. Thus, the column supporting the wind turbine can be connected to two mooring lines, and the other two of the three columns can be respectively connected to a single mooring line each. This arrangement may provide improved yaw restoring stiffness from the mooring system, similar to the case when using the above-described pendant ropes, compared to the arrangement shown in FIG. 1. However, compared to the case of using pendant ropes, this arrangement is more complex and is likely to be more costly.

[0047] In the above arrangement, the mooring system may include one or more additional mooring cables connected to the columns. One or more of the other two columns (i.e., the columns that do not support the wind turbine) may be connected (e.g., directly) to one or more of the additional mooring cables. Both of the other two columns may be connected to their respective additional mooring cable(s) (or multiple additional mooring cables). Thus, one or both of the other columns may be connected to two or more mooring cables.

[0048] In yet another arrangement, the semi-submersible platform may include three columns (e.g., arranged in a triangular ring configuration), where the wind turbine is attached to one of the columns and the mooring system may include three mooring cables. Two of the three mooring cables can be connected (e.g., directly) to the column supporting the wind turbine, for example, at the same connection point. These two mooring cables may each be offset by up to 30° from the dominant wind direction and may be separated from each other by up to 60°. That is, this pair of mooring cables may straddle the dominant wind direction, where one of the mooring cables is arranged at up to 30° from the dominant wind direction in the clockwise direction and the other mooring cable is arranged at up to 30° from the dominant wind direction in the counterclockwise direction. The other of the three mooring cables can be connected to both of the other two of the three columns via or using attachment ropes. The other of the three mooring cables can be connected to the floating wind turbine structure by an attachment rope including two attachment rope cables. Each attachment rope cable can be connected to a different one of the other two columns (i.e., the columns that do not support the wind turbine) of the semi-submersible platform. In this way, the other of the three mooring cables can be connected to the other two columns via the attachment ropes. This arrangement has been found to provide improved yaw restoring stiffness from the mooring system as compared to the arrangement shown in FIG. 1, similar to the arrangements described above.

[0049] The mooring cables can be arranged equidistantly around the floating wind turbine structure. For example, they can be arranged at an angle of 120° apart around the floating wind turbine structure.

[0050] The mooring system may be asymmetric. This means that the mooring system is rotationally asymmetric about a vertical axis (e.g., passing through the center point of the mooring system) when viewed in the horizontal plane. This can be achieved by having mooring cables connected to the floating wind turbine installation using attachment ropes of different lengths. For example, the mooring system may include two mooring cables connected to the floating wind turbine installation by an attachment rope having a first length, and a third mooring cable connected to the floating wind turbine installation by an attachment rope having a second length shorter than the first length. The two mooring cables may be connected to the columns of the semi-submersible platform on which the wind turbine is supported (by at least one attachment rope of each attachment rope). The third mooring cable may not be connected to the column to which the wind turbine is attached.

[0051] Compared with a symmetric mooring system, an asymmetric mooring system can provide a more stable system by improving the support of the floating wind turbine structure when the wind is blowing in the dominant direction. This can help prevent undesirable movement of the floating wind turbine installation and also prevent undesirable large loads from being applied to the floating wind turbine installation and the mooring system.

[0052] One or more or all of the mooring cables (and attachment ropes if there are any) may be arranged as catenaries. Thus, the mooring cable may be a catenary mooring cable.

[0053] The attachment ropes and mooring cables may be made of any suitable material such as a chain, wire (e.g., steel wire), or fiber rope (e.g., polyester rope) or a combination thereof. The attachment ropes and mooring cables may be made of the same material or different materials.

[0054] The attachment rope can be connected to the mooring cable by a joint such as a vacuum explosion welded transition joint.

[0055] The mooring cable and / or the pendant cable can be connected to the floating wind turbine installation using connectors such as fairleads.

[0056] One or more or all of the mooring cables may be connected to a clump weight and / or a buoy. The clump weight and / or the buoy can be connected to the mooring cable between its anchor end and its connection end. Thereby, additional tension is applied to the mooring cable.

[0057] The floating wind turbine installation is preferably located offshore, i.e., installed at sea. Therefore, the floating wind turbine installation may be connected to the seabed by a mooring system. However, the floating wind turbine installation may be installed in other suitable waters, such as lakes, rivers, etc.

[0058] According to another aspect of the present invention, there is provided a method of mooring an asymmetric floating wind turbine structure in a body of water, the floating wind turbine structure including a wind turbine mounted on a semi-submersible floating platform, the method including connecting the floating wind turbine structure to the bottom of the body of water using a mooring system such that the floating wind turbine structure is held in a predetermined position by the mooring system, wherein the wind turbine is positioned upwind of the center of mass of the floating wind turbine structure in the direction of the predominant wind at the location of the floating wind turbine structure.

[0059] Viewed another way, the present invention can be considered to provide a method of mooring an asymmetric floating wind turbine structure in a body of water, the floating wind turbine structure including a wind turbine mounted on a semi-submersible floating platform, the method including connecting the floating wind turbine structure to the bottom of the body of water using a mooring system such that the wind turbine is positioned upwind of the center of mass of the floating wind turbine structure when the wind approaches the floating wind turbine structure in the direction of the predominant wind at the location of the floating wind turbine structure.

[0060] In such a method, the floating wind turbine structure and / or the mooring system may be as described above and may include one or more or all of their preferred features or optional features. Thus, the floating wind turbine structure and the mooring system may form a floating wind turbine installation as described above with any of its optional features.

[0061] Next, specific preferred embodiments of the present invention will be described in more detail, merely by way of example, with reference to the accompanying drawings.

Brief Description of the Drawings

[0062]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10A

Figure 10B

Figure 10C

Figure 11A

Figure 11B

Figure 11C

Figure 12A

Figure 12B

Figure 12C

Figure 13A

Figure 13B

Figure 13C

Figure 14A

Figure 14B

Figure 14C

DETAILED DESCRIPTION OF THE INVENTION

[0063] The known wind turbine installation of FIG. 1 has been described above. FIG. 2 is a schematic plan view of a proposed floating wind turbine installation 10 including an asymmetric floating wind turbine structure 11 held in a fixed position by three mooring cables 12a, 12b, 12c fixed to the seabed. The floating wind turbine structure 11 includes a semi-submersible floating platform formed by three columns 13, 14 connected in a triangular ring configuration by three connecting members 15. Two of the columns 13 are empty (i.e., do not support the wind turbine), while the third column 14 supports the wind turbine 16. The wind turbine 16 is a conventional horizontal-axis wind turbine and includes a tower that supports a nacelle. The nacelle houses a generator and supports a rotor including a plurality of, for example, three rotor blades. The tower is supported in a substantially upright orientation by the semi-submersible platform.

[0064] Each mooring cable 12a, 12b, 12c is directly connected to the floating wind turbine structure 11 (specifically, the columns 13, 14 of the floating wind turbine structure 11).

[0065] The columns 13, 14 include ballast tanks for accommodating ballast such as air and water. The ballast can be added to and / or removed from the columns 13, 14 in order to achieve a heel angle of approximately 0° in a windless state. To achieve this, the column 14 supporting the wind turbine 16 may be mainly filled with air. The floating wind turbine structure 11 may include one or more pumps for adding liquid ballast (e.g., seawater) to the ballast tank and / or removing liquid ballast from the ballast tank.

[0066] Similar to FIG. 1, the prevailing wind at the location of the floating wind turbine facility 10 propagates along the positive x-axis as shown in FIG. 2. The floating wind turbine structure 11 is oriented such that the column 14 to which the wind turbine 16 is attached is on the upwind side of the floating wind turbine structure 11 in the direction of the prevailing wind. Specifically, the column 14 supporting the wind turbine 16 is located on the upwind side of the center of mass C m of the floating wind turbine structure 11 when the wind approaches the floating wind turbine facility 10 in the direction of the prevailing wind (i.e., the direction along the positive x-axis shown in FIG. 2). The mooring cables 12a, 12b, 12c provide resistance to the yawing of the floating wind turbine structure 11, thereby maintaining the wind turbine 16 on the upwind side of the wind turbine structure 11 in the direction of the prevailing wind. While the floating wind turbine structure 11 may experience a (relatively small) yaw motion (e.g., due to the influence of wind, tidal current, and / or waves on the wind turbine structure 11), the mooring cables 12a, 12b, 12c act to maintain the wind turbine structure 11 in the (substantially) desired orientation.

[0067] As described above, the wind thrust acting on the floating wind turbine structure 11 causes the floating wind turbine structure 11 to oscillate vertically about a lateral axis (i.e., an axis from side to side) passing through its center of mass C m In the orientation shown in FIG. 2, due to the pitch motion of the floating wind turbine structure 11 caused by the wind thrust acting in the direction of the prevailing wind, the column 13 located on the downwind side of the center of mass C m sinks low into the water, and the center of mass Cm The column 14 (which supports the wind turbine 16) located on the upwind side will float high in the water. As a result, the average height of the wind turbine 16 (and the rotor of the wind turbine 16) above the water surface increases, and the rotor of the wind turbine 16 interacts with the wind at a higher altitude. This increase in average height may lead to an increase in power output by the wind turbine 16. This is because the wind speed (and its kinetic energy) typically increases with altitude, meaning that more energy can be extracted from the wind by the wind turbine 16 and converted into electricity.

[0068] The floating wind turbine installation 10 shown in FIG. 2 has advantages in terms of increased power generation, but may be troubled by undesirable motion characteristics and an increase in load on the mooring cables 12a - c and other components of the floating wind turbine installation 10.

[0069] When the wind approaches the floating wind turbine structure 11 along the dominant wind direction (i.e., the positive x - axis in FIG. 2), no yaw motion is generated by the wind force acting on the structure 11. Therefore, the arrangement shown in FIG. 2 is oriented towards the equilibrium position when the wind approaches along the dominant wind direction. However, this is an unstable equilibrium position. Due to the above - mentioned wind - seeing effect, when the wind approaches the floating wind turbine structure 11 away from the direction of the dominant wind, a yaw moment is generated, and the structure 11 is forced to sway in a direction in which the column 14 supporting the wind turbine 16 is positioned on the downwind side of the installation. Since the moment arm between the wind thrust and the center of mass C m of the floating structure 11 is large, even a small change in the wind direction away from the dominant wind direction results in a relatively large yaw moment (compared to, for example, the typical yaw moments generated in the floating wind turbine installation shown in FIG. 1).

[0070] Furthermore, since the wind most commonly approaches the floating wind turbine structure 11 along or in close proximity to the dominant wind direction, the wind usually approaches the floating wind turbine structure 11 above a single mooring cable 12c. In this case, the restoring yaw stiffness of the mooring system is at its lowest, and the mooring system is less resistant to the wind - seeing yaw motion.

[0071] Also, when the wind approaches the wind turbine structure 11 through a single mooring cable (e.g., mooring cable 12c), a significant portion of the load is applied to that mooring cable. However, when the wind approaches between two adjacent mooring cables, the load is distributed between the two mooring cables. Therefore, when the wind approaches between two adjacent mooring cables, the load applied to each mooring cable is reduced. As a result, when the wind approaches through a single mooring cable, that mooring cable receives a greater load and fatigue increases. This can shorten the lifespan of the mooring cable.

[0072] An alternative wind turbine installation 20 designed to at least partially mitigate these problems is shown in FIG. 3.

[0073] The floating wind turbine installation 20 of FIG. 3 includes a floating wind turbine structure 11 that is mainly the same as that described above with respect to FIG. 2. This includes a semi-submersible floating platform formed by three columns 13, 14 connected in a triangular ring configuration by three connecting members 15, and the wind turbine 16 is supported by one of the columns 14. Similar to the floating wind turbine installation 10 of FIG. 2, when the wind approaches the floating wind turbine installation 20 in the direction of the predominant wind (i.e., the direction along the positive x-axis shown in FIG. 3), the column 14 that supports the wind turbine 16 is oriented to be positioned upwind of the center of mass C m of the floating wind turbine structure 11.

[0074] In FIG. 3, the floating wind turbine structure 11 is held in a predetermined position by a mooring system including three mooring cables 21a, 21b, 21c and three attachment ropes 22. Each of the mooring cables 21a, 21b, 21c is connected to the floating wind turbine structure 11 (specifically, the columns 13, 14 of the floating wind turbine structure 11) via its respective attachment rope 22. Therefore, the mooring system includes three mooring cables 21a - c each connected to the floating wind turbine structure via its respective attachment rope 22.

[0075] Similar to the above-described arrangement, the mooring cables 21a, 21b, and 21c provide resistance to the yawing of the floating wind turbine structure 11 so as to maintain the wind turbine 16 on the upwind side of the wind turbine structure 11 in the direction of the prevailing wind.

[0076] Each pendant rope 22 includes two pendant rope cables 22a. In each pendant rope 22, one pendant rope cable 22a is connected to one of the columns 13, 14, and the other pendant rope cable 22a is connected to another one of the columns 13, 14 (i.e., different columns 13, 14). Accordingly, each mooring cable 21a - c is connected to two different columns 13, 14 via the pendant rope 22.

[0077] The mooring cable 21a is connected to the column 14 that supports the wind turbine 16 via one pendant rope cable 22a and is connected to the empty column 13 via another pendant rope cable 22a. The mooring cable 21b is connected to the column 14 that supports the wind turbine 16 via one pendant rope cable 22a and is connected to a (different) empty column 13 via another pendant rope cable 22a. The mooring cable 21c is connected to an empty column 13 via one pendant rope cable 22a and is connected to a (different) empty column 13 via another pendant rope cable 22a. Accordingly, each column 13, 14 is connected to two mooring cables 21a - c via their respective pendant rope cables 22a.

[0078] The presence of the pendant rope imparts more favorable motion characteristics to the wind turbine facility 20 as compared to the mooring system shown in FIG. 2.

[0079] By connecting the mooring cables 21a - c to the floating - type wind turbine structure 11 via the attachment ropes 22, for a given pretension, the yaw - restoring rigidity of the mooring system is significantly improved compared to the mooring systems shown in FIGS. 1 and 2. Further, due to the orientation of the mooring cables 21a - c, the yaw - restoring rigidity of the mooring system is maximized when the wind approaches the floating - type wind turbine structure 11 along the dominant wind direction (i.e., along the positive x - axis). As described above, the restoring yaw rigidity of the mooring system is maximized when the wind approaches between two adjacent mooring cables, which occurs in the facility 20 shown in FIG. 3 when the wind approaches along the dominant wind direction.

[0080] In the floating - type wind turbine facility 20 shown in FIG. 3, since the column 14 supporting the wind turbine 16 is oriented with the windward side of the floating - type platform above the water, the floating - type wind turbine facility 20, like the wind turbine facility 10 shown in FIG. 2, benefits from an increase in power generation. The thrust exerted on the floating - type wind turbine structure 11 by the wind blowing in the dominant wind direction (i.e., along the positive x - axis shown in FIG. 3) subjects the floating - type wind turbine structure 11 to heave about a lateral axis passing through its center of mass C m As a result, the column 13 located on the leeward side of the facility 20 sinks deeper into the water, and the column 14 supporting the wind turbine 16 rises higher in the water. Consequently, the rotor of the wind turbine 16 comes to interact with the wind at a higher altitude, generally having a higher average speed, thereby increasing the power output by the wind turbine 16.

[0081] Another wind turbine facility 30 is shown in FIG. 4. The floating - type wind turbine facility 30 in FIG. 4 includes the floating - type wind turbine structure 11, which is mainly the same as that described above with respect to FIGS. 2 and 3, and thus will not be described in detail here to avoid repetition. The floating - type wind turbine facility 30 is oriented such that the column 14 supporting the wind turbine 16 is positioned on the windward side of the center of mass C m of the floating - type wind turbine structure 11 in the direction of the dominant wind (i.e., along the positive x - axis shown in FIG. 4).

[0082] In the facility 30 of FIG. 4, the floating wind turbine structure 11 is held in a predetermined position by a mooring system including four mooring cables 31a, 31b, 31c, and 31d. The mooring cables 31a, 31b, 31c, and 31d provide resistance to the sway of the floating wind turbine structure 11 so as to maintain the wind turbine 16 on the upwind side of the floating wind turbine structure 11 in the direction of the dominant wind.

[0083] Each of the mooring cables 31a, 31b, 31c, and 31d is directly connected to the floating wind turbine structure 11 (specifically, the columns 13 and 14 of the floating wind turbine structure 11), that is, without a pendant rope.

[0084] Two mooring cables 31a and 31b are directly connected to the column 14 that supports the wind turbine 16. Accordingly, the column 14 is directly connected to the two mooring cables 31a and 31b.

[0085] Since the other two mooring cables 31c and 31d are each directly connected to the empty column 13, each empty column 13 is directly connected to one of the mooring cables 31c and 31d. That is, one mooring cable 31c is connected to the empty column 13, and another mooring cable 31d is connected to a different empty column 13.

[0086] The arrangement shown in FIG. 4 can provide increased yaw restoring rigidity from the mooring system as compared with the arrangement shown in FIG. 1.

[0087] Yet another wind turbine facility 40 is shown in FIG. 5. The floating wind turbine facility 40 in FIG. 5 includes the floating wind turbine structure 11, which is mainly the same as that described above with respect to FIGS. 2 to 4, and thus will not be described in detail here to avoid repetition. In the floating wind turbine facility 40, the column 14 that supports the wind turbine 16 is oriented such that it is positioned on the upwind side of the center of mass C m of the floating wind turbine structure 11 in the direction of the dominant wind (that is, along the positive x-axis shown in FIG. 5).

[0088] In the facility 40 of FIG. 5, the floating wind turbine structure 11 is held in a predetermined position by a mooring system including three mooring cables 41a, 41b, 41c and one pendant rope 42 connected to the mooring cable 41a. The mooring cables 41a, 41b, 41c and the pendant rope 42 provide resistance to the sway of the floating wind turbine structure 11 so as to maintain the wind turbine 16 on the upwind side of the floating wind turbine structure 11 in the direction of the prevailing wind.

[0089] The mooring cable 41a is connected to the floating wind turbine structure 11 via the pendant rope 42. The pendant rope includes two pendant rope cables 42a. Each of the pendant rope cables 42a is connected to one of the two hollow columns 13 such that one pendant rope cable 42a is connected to each hollow column 13.

[0090] Two additional mooring cables 41b, 41c are directly connected to the column 14 that supports the wind turbine 16, and as a result, the column 14 is connected to the two mooring cables 41b, 41c.

[0091] The mooring system of FIG. 5 improves the yaw stiffness as compared to the arrangement shown in FIG. 1.

[0092] In the wind turbine facilities 10, 20 shown in FIGS. 2 to 5, the column 14 that supports the wind turbine 16 is oriented such that it is exactly upwind of the center of mass C of the floating wind turbine structure 11 in the direction of the prevailing wind (i.e., the positive x-axis shown in the figure). That is, there is an angle θ of 0° between the prevailing wind direction and the straight line passing through the center and the center of mass C of the wind turbine 16. However, when the wind turbine facility 20 is oriented at an angle θ of up to ±60° from the direction of the prevailing wind, that is, when there is an angle θ of up to ±60° between the prevailing wind direction and the straight line passing through the center and the center of mass C of the wind turbine 16, it has been found that the power output of the wind turbine 16 increases significantly, although it is smaller. FIG. 6 shows the wind turbine facility 20 of FIG. 3 oriented at an angle θ from the prevailing wind direction propagating along the positive x-axis shown in the figure. m That is, there is an angle θ of 0° between the prevailing wind direction and the straight line passing through the center and the center of mass C of the wind turbine 16. However, when the wind turbine facility 20 is oriented at an angle θ of up to ±60° from the direction of the prevailing wind, that is, when there is an angle θ of up to ±60° between the prevailing wind direction and the straight line passing through the center and the center of mass C of the wind turbine 16, it has been found that the power output of the wind turbine 16 increases significantly, although it is smaller. m However, when the wind turbine facility 20 is oriented at an angle θ of up to ±60° from the direction of the prevailing wind, that is, when there is an angle θ of up to ±60° between the prevailing wind direction and the straight line passing through the center and the center of mass C of the wind turbine 16, it has been found that the power output of the wind turbine 16 increases significantly, although it is smaller. m However, when the wind turbine facility 20 is oriented at an angle θ of up to ±60° from the direction of the prevailing wind, that is, when there is an angle θ of up to ±60° between the prevailing wind direction and the straight line passing through the center and the center of mass C of the wind turbine 16, it has been found that the power output of the wind turbine 16 increases significantly, although it is smaller. FIG. 6 shows the wind turbine facility 20 of FIG. 3 oriented at an angle θ from the prevailing wind direction propagating along the positive x-axis shown in the figure.

[0093] In the orientation shown in FIG. 6, the increase in power output by the wind turbine may be reduced compared to the case where the column 14 supporting the wind turbine 16 is exactly upwind of the center of mass C of the floating wind turbine structure 11 (for example, as shown in FIG. 3). However, the wind approaching the floating wind turbine installation 10 at an angle θ of up to ±60° may still provide sufficient thrust to raise the column 14 supporting the wind turbine 16 higher in the water as a result of the pitching motion. As described above, this may lead to an increase in the power output by the wind turbine. Typically, the height of the wind turbine 16 increases more significantly, and thus the power output increases more significantly, when the angle θ is smaller, for example, 45° or 30°. m The additional guy ropes 22a, 42a and the mooring ropes 12a - c, 21a - c, 31a - d, 41a - c described above can be made of various materials including mooring chains, wire ropes, polyester ropes, and others. The additional guy ropes 22a, 42a and the mooring ropes 12a - c, 21a - c, 31a - d, 41a - c may be made of the same material or different materials. In some floating wind turbine installations 10, 20, 30, 40, the mooring ropes 12a - c, 21a - c, 31a - d, 41a - c may be formed of multiple segments, which may include different materials.

[0094] The additional guy ropes 22a, 42a and the mooring ropes 12a - c, 21a - c, 31a - d, 41a - c may have the same or different thicknesses.

[0095] The additional guy ropes 22a, 42a can be connected to the mooring ropes 21a - c, 41a with a vacuum explosion welded transition joint, for example, a joint such as Triplate®.

[0096]

[0097] ​The pendant ropes 22a, 42a and / or the mooring ropes 12a to 12c, 21a to 21c, 31a to 31d, 41a to 41c may be connected to the floating wind turbine structure 11 (for example, the columns 13, 14 of the floating wind turbine structure 11) using connectors such as fairleads.

[0098] A simulation was performed to compare the response of the floating wind turbine installation 20 of FIG. 3 when the wind approaches at an angle θ of 0° with the response of the floating wind turbine installation 20 when the wind approaches at an angle θ of 180°. Thereby, it will be understood that the response of the floating wind turbine installation 20 when the column 14 supporting the wind turbine 16 is positioned on the upwind side of the floating wind turbine structure 11 (for example, as shown in FIG. 3) and the response of the floating wind turbine installation 20 when the column 14 supporting the wind turbine 16 is positioned on the downwind side of the floating wind turbine structure 11 (similar to the known orientation shown in FIG. 1) can be compared.

[0099] The simulation data was obtained by modeling the motion characteristics of a floating wind turbine installation 20 having three columns 13, 14 extending 18 m above the waterline, a tower 138 m high, and a 23 MW wind turbine 16 having a rotor with three blades 136 m long located at the top of the tower. In this example, the length of the connecting member 15 connecting the columns 13, 14 is 77.45 m each. The modeled system has pendant ropes 22a made of steel wire, each 100 m long, and mooring ropes 21a to 21c made of polyester rope, each 855 m long. Anchor chains 30 m long connect the ends of each mooring rope to the seabed.

[0100] In the simulation, it was assumed that the waves approach the floating wind turbine installation 20 from the same direction as the wind.

[0101] A base-case simulation study was conducted using a wind shear profile index α of 0.14 recommended by IEC standard 61400-1:2019. The study found that when the wind approaches the wind turbine installation 20 at an angle θ of 0°, the annual power generation of the wind turbine 16 increases by 1.5% compared to when the wind approaches the wind turbine installation 20 at an angle θ of 180°.

[0102] Another simulation study was carried out using a wind shear profile index α of 0.10. This study also showed that when the wind approaches the wind turbine installation 20 at an angle θ of 0°, the annual power generation of the wind turbine 16 increases compared to when the wind approaches the wind turbine installation 20 at an angle θ of 180°. In this case, the increase in annual power generation was 1.1%.

[0103] Next, with reference to FIGS. 7 to 14, selected results from the simulation study will be described.

[0104] FIG. 7 shows the simulated average height of the nacelle of the wind turbine 16 from the water surface compared to the wind speed at the height of the nacelle in a windless state. The graph shows how the average height of the nacelle changes with increasing wind speed for the cases of θ = 0° and θ = 180°. It can be seen that when the wind approaches the floating wind turbine installation 20 at an angle θ of 0°, the average height of the nacelle tends to increase as the wind speed increases. On the other hand, when the wind approaches the floating wind turbine at an angle θ of 180°, the height of the nacelle tends to decrease as the wind speed increases. FIG. 7 shows a difference in height of more than 16 m at a wind speed of about 11 m / s -1 (±1 m / s -1 ), which is a typical rated wind speed of wind turbines installed in the North Sea.

[0105] Wind tends to propagate at different speeds at different altitudes, generally becoming faster at higher altitudes. Thus, it will be understood that the nacelle and the rotor of the wind turbine 16 interact with winds of different speeds depending on the height above the water surface. FIG. 8 shows the simulated average wind speed at the (actual) height of the nacelle (i.e., the height at which the nacelle is located at the average pitch angle of the floating wind turbine structure 11 due to the thrust effect of the wind) compared to the average wind speed at the (nominal) height of the nacelle in a windless state. As can be seen, the average wind speed at the actual height of the nacelle when the wind approaches the floating wind turbine installation 20 at an angle θ of 0° is generally faster than the average wind speed at the actual height of the nacelle when the wind approaches the floating wind turbine installation 20 at an angle θ of 180°.

[0106] The amount of energy that can be extracted from the wind by a wind turbine is proportional to the cube of the wind speed. FIG. 9 shows how the cube of the simulated average wind speed at the actual nacelle height (which is proportional to the available wind energy) varies with respect to the average wind speed at the nominal nacelle height. As can be seen, the cube of the average wind speed at the actual nacelle height, and thus the available wind energy, is higher when the wind approaches the floating wind turbine installation 20 at an angle θ of 0° compared to when the wind approaches the floating wind turbine installation 20 at an angle θ of 180°. For example, when the average wind speed at the nominal nacelle height is 10.5 m / s -1 it was found that the available wind energy is approximately 6% higher when the wind approaches the floating wind turbine installation 20 at an angle θ of 0° than when the wind approaches the floating wind turbine installation 20 at an angle θ of 180°.

[0107] When the wind direction is the rated wind speed of 11 m / s -1The simulated effects on the power generation of the wind turbine are shown in FIGS. 10A to 10C. The simulated maximum power generation is shown in FIG. 10A, the simulated average power generation is shown in FIG. 10B, and the simulated minimum power generation is shown in FIG. 10C. From FIG. 10B, it can be seen that the average power generation when the wind approaches the floating wind turbine facility 20 at an angle θ of 0° is consistently greater near the rated wind speed compared to when it approaches at an angle θ of 180°.

[0108] The simulated roll motions of the floating wind turbine structure 11 having a mooring system as shown in FIG. 3 are shown in FIGS. 11A to 11C. FIG. 11A shows the simulated maximum roll motion, FIG. 11B shows the simulated average roll motion, and FIG. 11C shows the simulated minimum roll motion.

[0109] The simulated yaw motions of the same floating wind turbine structure 11 are shown in FIGS. 12A to 12C. FIG. 12A shows the simulated maximum yaw motion, FIG. 12B shows the simulated average yaw motion, and FIG. 12C shows the simulated minimum yaw motion.

[0110] The simulated pitch motions of the same floating wind turbine structure 11 are shown in FIGS. 13A to 13C. FIG. 13A shows the simulated maximum pitch motion, FIG. 13B shows the simulated average pitch motion, and FIG. 13C shows the simulated minimum pitch motion.

[0111] The simulated tower bottom bending moments of the floating wind turbine facility 20 are shown in FIGS. 14A to 12C. FIG. 14A shows the maximum bottom bending moment, FIG. 14B shows the average bottom bending moment, and FIG. 14C shows the minimum bottom bending moment.

[0112] FIGS. 11 to 14 show that the roll motion, yaw motion, and pitch motion of the floating wind turbine structure 11 and the loads applied to the floating wind turbine structure 11 are of the same order when the wind approaches the floating wind turbine facility 20 at an angle θ of 0° and when it approaches at an angle θ of 180°.

Claims

1. A floating wind turbine facility, including an asymmetric floating wind turbine structure connected to the seabed of a body of water by a mooring system, The floating wind turbine structure includes a wind turbine mounted on a semi-submersible floating platform. The floating wind turbine structure is held in a predetermined position by the mooring system such that the wind turbine is positioned upwind of the center of mass of the floating wind turbine structure in the direction of the prevailing wind at the location of the wind turbine facility. Floating wind turbine equipment.

2. The floating wind turbine equipment according to claim 1, wherein the angle between the prevailing wind direction and the line passing through the position of the wind turbine and the center of mass of the floating wind turbine equipment is 60° or less.

3. The floating wind turbine system according to claim 1 or 2, wherein the wind turbine is positioned substantially just upwind of the center of mass of the floating wind turbine structure in the direction of the prevailing wind.

4. The floating wind turbine facility according to claim 1, wherein the semi-submersible floating platform includes three columns connected by connecting members in a ring-shaped configuration.

5. The floating wind turbine facility according to claim 4, wherein the wind turbine is supported on one of the columns of the semi-submersible floating platform.

6. The mooring system includes four mooring lines connected to the floating wind turbine structure. Two of the four mooring cables are connected to the columns supporting the wind turbine. Two of the four mooring ropes are connected to two different of the other two of the three posts. The floating wind turbine equipment according to claim 5.

7. The floating wind turbine equipment according to claim 6, wherein the mooring cable is directly connected to the floating wind turbine structure.

8. The mooring system includes three mooring lines connected to the floating wind turbine structure. Each of the three mooring lines is connected to the floating wind turbine structure by its respective auxiliary ropes, which include two auxiliary ropes, and each of the two auxiliary ropes is connected to one of the two columns of the semi-submersible platform, such that each mooring line is connected to one of the two columns of the semi-submersible platform. The floating wind turbine equipment according to claim 4 or 5.

9. The floating wind turbine facility according to claim 8, wherein each of the three columns is connected to two of the three mooring cables.

10. The mooring system includes three mooring lines connected to the floating wind turbine structure. Two of the three mooring cables are connected to the pillars supporting the wind turbine. One of the three mooring ropes is connected to the other two of the three posts via a reinforcing rope. The floating wind turbine equipment according to claim 5.

11. The floating wind turbine equipment according to claim 10, wherein the two mooring cables connected to the column supporting the wind turbine are directly connected to the column.

12. The floating wind turbine structure according to claim 1, wherein the mooring system includes a plurality of mooring lines, preferably three, directly or indirectly connected to the floating wind turbine structure.

13. The floating wind turbine structure according to claim 12, wherein at least one mooring rope is connected to the floating wind turbine structure by an auxiliary rope.

14. The floating wind turbine equipment according to claim 6, wherein the mooring rope is a catenary mooring rope.

15. The floating wind turbine facility according to claim 1, wherein the mooring system is an asymmetric mooring system.

16. The floating wind turbine structure according to claim 15, wherein the mooring system includes two mooring ropes connected to the floating wind turbine structure by each of the first length auxiliary ropes, and a third mooring rope connected to the floating wind turbine structure by the second length auxiliary rope having a shorter length than the first length.

17. The floating wind turbine system according to claim 1, wherein the wind turbine includes a tower and a rotor attached to the upper end of the tower, and the rotor includes a rotor hub and a plurality, preferably three, blades attached to the hub.

18. A method for mooring an asymmetric floating wind turbine structure in a body of water, wherein the floating wind turbine structure includes a wind turbine mounted on a semi-submersible floating platform, the method comprising using a mooring system to tether the floating wind turbine structure to the bottom of the body of water such that the floating wind turbine structure is held in a predetermined position by the mooring system, wherein the wind turbine is positioned upwind of the center of mass of the floating wind turbine structure in the direction of the prevailing wind at the location of the floating wind turbine structure.

19. The method according to claim 18, wherein the floating wind turbine structure and the mooring system form the floating wind turbine equipment according to claim 1.

Images