Offshore wind turbine installation

Abstract

A method of at least partially installing at least one wind turbine at an offshore site (5) is described, the method comprising: loading at least one lower tower portion (3) of the wind turbine onto a vessel, the lower tower portion (3) having a span less than the entire wind turbine tower; transporting the lower tower part (3) to an offshore site (5); lifting and guiding the lower tower part (3) such that the lower end (7) approaches a tower connection part (7) provided at the offshore foundation; the lower end (7) of the lower tower part (3) is connected to a tower connection part (8).

Description

Technical Field

[0001] This invention relates to a method for at least partially installing at least one wind turbine at an offshore site. Furthermore, this invention relates to a lower tower section or tower transport vessel, particularly configured to perform the above-described method. Additionally, this invention relates to a system for installing at least one wind turbine at an offshore site, comprising a lower tower section transport vessel. Background Technology

[0002] Conventionally, setting up an offshore wind turbine requires completing the foundation and laying cables at the offshore site. After the foundation is completed, the offshore wind turbine is typically installed in a single step using a specific turbine installation vessel. However, the increasing size and weight of wind turbines today complicates the conventional installation process. In particular, the stability of the vessel used for securing the load at sea and for installation has become compromised. Furthermore, the increased size of wind turbine towers sometimes exceeds the typical capacity of cranes in pre-assembly ports.

[0003] Therefore, it has been observed that the installation of offshore wind turbines using conventional methods has become increasingly complex and / or significantly inefficient or problematic.

[0004] Therefore, a method for at least partially installing at least one wind turbine at an offshore site may be required, and a vessel for transporting the lower tower portion, particularly to achieve this installation method, may also be needed. Furthermore, an integrated system for installing at least one wind turbine at an offshore site may be required, which at least mitigates conventionally observed problems or disadvantages. Summary of the Invention

[0005] This need can be met by the subject matter according to the independent claims. Advantageous embodiments of the invention are described by the dependent claims.

[0006] According to an embodiment of the present invention, a method is provided for at least partially installing at least one wind turbine at an offshore site, the method comprising: loading at least one lower tower portion of the wind turbine onto a vessel (e.g., referred to as "lower tower portion and / or tower transport"), the span of the lower tower portion being less than the entire wind turbine tower; transporting the lower tower portion to the offshore site; lifting and guiding the lower tower portion such that its lower end approaches a tower connection portion provided at an offshore base; and connecting the lower tower portion to the tower connection portion at its lower end.

[0007] This method can be implemented essentially by a transport vessel carrying the lower tower section according to an embodiment of the invention, which will be described in detail below.

[0008] When a wind turbine is fully installed at an offshore site, it may include a wind turbine tower, which includes at least a lower tower section and at least one additional tower section, particularly an upper tower section, and / or one or more intermediate tower sections. Furthermore, the fully installed wind turbine may include a nacelle mounted on the upper portion of an erected tower, particularly on top of the upper tower section. The nacelle may include a generator mechanically connected to a hub. At the hub, multiple wind turbine blades are installed within the completed wind turbine.

[0009] This method may not necessarily involve installing the complete wind turbine, but it may at least involve installing the lower tower section at an offshore site. For installing the lower tower section, it may essentially only require a vessel for transporting the lower tower section. For the complete installation or erection of the offshore wind turbine, one or more additional vessels may be required, whose construction and / or configuration may differ from that of the vessel transporting the lower tower section. It should be noted that the term "lower tower section transport vessel" should not be construed as limiting the type of vessel unless the vessel is configured or suited to at least perform the methodological steps of transporting the lower tower section and lifting and guiding it.

[0010] For the loading and / or connecting steps, additional equipment may be required, which may be separate from the vessel. However, according to embodiments of the invention, the loading and connecting steps may also be performed by equipment and / or personnel included in the vessel transported in the lower tower section.

[0011] Loading can be carried out using a crane, which may be part of the vessel's lower tower section or, for example, a land-based crane. Loading may involve lifting and laterally moving the lower tower section, particularly when it is in an upright position. For example, on an inland site (e.g., a port), a storage area can be provided to supply pre-assembled lower tower sections (e.g., from one or more factories or assembly sites) to the storage area, and the lower tower sections can be stored there. In particular, the lower tower sections can be secured to the inland site by storage and securing equipment, especially to enable the reception of multiple lower tower sections and their securing at the lower end, for example, arranged in a regular or irregular two-dimensional array.

[0012] The lower tower sections can be loaded one by one, particularly using cranes installed or arranged on the vessel handling the lower tower sections, and can be placed on and secured to the vessel's loading area, which in particular includes connecting and securing devices for rigidly connecting and securing the lower ends of the respective lower tower sections to the vessel. Loading may involve vertically lifting the lower tower sections and / or laterally moving the lower tower sections and vertically lowering them onto the corresponding connecting and securing devices in the vessel's loading area.

[0013] Then, one or more lower tower sections loaded onto the lower tower section transport vessel can be transported in an upright manner, especially when the lower tower section(s) are covered to avoid contamination of the interior of the respective lower tower section.

[0014] An offshore site can be a site at sea. When a vessel arrives at the offshore site, the lower tower section can be lifted and guided, allowing the vessel's equipment and / or equipment from one or more other vessels to be transported using the lower tower section. An offshore foundation can be a foundation rigidly connected to the seabed or seafloor. Offshore foundations can include concrete and / or metals such as steel.

[0015] The tower connection portion can also be referred to as a base transition member. The tower connection portion may include one or more connecting members or connecting capabilities, such as, for example, flanges. Furthermore, the lower end of the lower tower portion may, for example, include a flange with multiple through holes. The flange at the lower end of the lower tower portion can be connected to the flange of the tower connection portion at the offshore base, and can be secured to each other, for example, by multiple bolts, to connect the lower tower portion and its lower end to the tower connection portion.

[0016] The lower tower section can have a substantially cylindrical symmetry or geometry. The cross-section of the lower tower section can be substantially circular. The lower tower section can consist of one or more metal ring sections that are fully pre-assembled when loaded onto the transport vessel. The lower tower section does not represent the entire length of the wind turbine tower, but may correspond to the lower portion, which is part of the overall wind turbine tower.

[0017] In other embodiments, the entire tower can be transported, stored, and installed.

[0018] By pre-assembling and installing the lower tower section in a single step, lifting and guiding requirements at the offshore site can be reduced. Installation can be carried out by a dedicated vessel, also known as a lower tower section transport vessel, to carry the lower portion of the wind turbine tower. The lower tower section can be, for example, the bottom tower section, which comprises approximately 1 / 4 to 1 / 2 of the total length of the wind turbine tower and / or approximately 1 / 3 to 2 / 3 of the total weight of the wind turbine tower. The lower tower section can be stored vertically on the dedicated vessel and can be installed, for example, prior to the installation of the remaining upper tower, nacelle, and blades.

[0019] Typically, wind turbine towers are installed at offshore sites in a complete configuration (i.e., as a single piece), whose substantial weight and height sometimes exceed the capacity of the corresponding handling and installation equipment. When a wind turbine tower is divided into two or more pieces, or is removed entirely in a manner different from the conventional approach, the second piece of the offshore secured tower carries additional weight and requires significantly more space to accommodate twice the number of tower sections. Transporting and installing these pieces by vessel can take longer and may incur higher costs.

[0020] Therefore, according to the present invention, a dedicated vessel is provided for transporting the tower and / or the lower tower section.

[0021] When the lower tower section is provided and installed according to the method of the invention, installation can be simplified because the length and weight of the corresponding lower tower section are less than those of a conventional complete tower. Consequently, specialized vessels can transport and install an increased number of wind turbine lower tower sections, and usability is improved because, for example, a crane on the vessel does not need to handle such a long length for tower installation. Furthermore, the self-weight of each wind turbine carried can be significantly less than that of conventionally used wind turbines. The stability of the specialized vessel can also be greatly improved because the center of gravity of the tower is significantly lowered, for example, during transport. Moreover, the weight reduction associated with the tower enables the transport and installation of a greater number of wind turbines.

[0022] According to an embodiment of the invention, during loading and / or transporting and / or lifting and / or guiding the lower tower section, the lower tower section is in a substantially upright position, in particular, the longitudinal direction of the lower tower section is oriented substantially vertically.

[0023] When in an upright position, the lower tower section can be loaded and / or transported from the vessel, as well as lifted and guided, in a simpler manner because its orientation does not need to be changed. Typically, wind turbine towers may have already been transported in a substantially horizontal orientation, thus requiring a change in orientation before installation at the offshore site. When in an upright position, the lower tower section can be oriented particularly vertically, i.e., essentially the same orientation adopted after installation at the offshore site.

[0024] According to an embodiment of the invention, the vessel includes a crane, wherein loading and / or lifting and / or guiding of the lower tower section is performed using the crane, particularly when the vessel is freely afloat at sea.

[0025] When the vessel (for transporting the lower tower section) includes a crane, additional lifting and / or guiding equipment may not be required at the offshore site, meaning no additional vessel may be needed for the installation. The crane can be configured to accommodate the height of the lower tower section, which can be significantly less than the overall height of the wind turbine tower. The crane may include at least one crane boom or crane beam, and the load of the lower tower section can be coupled to the top of the crane boom or crane beam, particularly to crane wire or rope with hooks or any connecting components. This simplifies the installation process.

[0026] According to an embodiment of the invention, the vessel includes a guiding device for guiding the lower tower portion toward the tower connection portion, the guiding device being particularly adapted to apply traction at at least one or two locations of the lower tower portion spaced apart in the longitudinal direction of the lower tower portion.

[0027] The crane may include a hook to which a lower tower section can be attached to bear the weight of the lower tower section. Therefore, the lower tower section can be attached to the crane at a single location, area, or point bearing substantially the entire weight of the lower tower section. This allows the lower tower section to have the freedom to rotate or oscillate slightly about its support position on the crane. To avoid or at least mitigate rotational movement of the lower tower section, a guiding device can be used, configured to ensure the safe movement of the lower section from the loading area on the vessel to a laterally spaced position at or above the offshore base. Thus, the guiding device allows the lower tower section to be held substantially vertically during lifting and / or guiding (e.g., lateral movement) by applying specific traction forces at at least two locations. The at least two locations of the lower tower section can be vertically spaced to easily maintain the intended orientation of the lower tower section. This allows for a safer, more accurate, and faster installation process.

[0028] According to an embodiment of the invention, the guiding equipment includes a pull rope connected at one end to a crane and / or a ship, and at the other end to a bottom position and / or a middle position and / or a top position of the lower tower section, wherein the tension of the pull rope is controlled and / or adjusted, particularly for guiding the lower tower section.

[0029] Therefore, a specific implementation scheme is provided using conventionally available guy ropes. Guy ropes may include, for example, metal steel ropes and / or steel wires. Guy ropes may be connected, for example, at one end to a midpoint of the crane beam and at the other end to the top portion of the lower tower section. Other guy ropes may be connected, for example, at one end to the vessel, particularly in a vertical position similar to the loading area, and at the other end to the lower end or middle section of the lower tower section. When several guy ropes are provided connected at vertically spaced locations on the lower tower section, guidance can be carried out safely, and in particular, the vertical orientation of the lower tower section can be substantially maintained throughout the lifting and / or guiding process.

[0030] According to an embodiment of the invention, during the lifting and / or guiding of the lower tower section, an active or passive heave compensator is connected between the lower tower section and the crane beam. Thus, the heave compensator can be a separate unit.

[0031] In another embodiment, heave compensation capability may be a function built into or within the crane (e.g., beam, boom, or cable).

[0032] Heave compensators can (at least partially) compensate for the heave (e.g., vertical) movement of a freely floating vessel at sea. Consequently, the connection between the lower end of the lower tower section and the tower connection provided at the offshore base can be implemented more safely, with little or no risk of collision between the lower end of the lower tower section and the tower connection provided at the offshore base. (Passive) heave compensators may include springs and damping devices. Active heave compensators may also include a compressor and hydraulic system for actively counteracting any vertical movement of the crane top caused by the corresponding movement of the vessel. This installation method can thus be implemented using conventionally available heave compensators.

[0033] According to an embodiment of the invention, the vessel includes storage installation and fixing equipment arranged in the vessel's loading area for vertically installing and fixing multiple (e.g., 5, 10, 20 or up to 60) lower tower sections, particularly having a substantially circular cross-section, in a regular 2D array, for each lower tower section having a loading capacity, particularly between 200 t and 1200 t or even higher.

[0034] The mounting and securing equipment may include, for example, multiple securing components, such as bolts and / or clamps for mounting and securing multiple lower tower sections. The mounting and securing equipment can be removed from the vessel and / or configured or supplied according to the geometry of the lower tower sections to be secured and transported. This allows for convenient and safe loading and transport of multiple lower tower sections.

[0035] According to embodiments of the invention, the mounting and securing equipment is suitable for mounting and securing lower tower sections with different diameters, particularly between 5 m and 15 m or 20 m, or even larger. This provides great flexibility, thereby supporting wind turbines of different sizes.

[0036] According to an embodiment of the invention, the lower tower portion spans between ¼ and ½ of the total height of the wind turbine tower and / or has a weight between 1 / 3 and 2 / 3 of the total weight of the wind turbine tower, wherein the lower tower portion has been previously pre-assembled, either entirely or partially, at an onshore site, particularly at a pre-assembly port and / or (one or more) manufacturers.

[0037] According to other embodiments of the invention, other values ​​may be possible. The lower tower section may be completed when loaded onto a dedicated vessel, in the sense that no additional installation or modification is required for proper operation later on a marine site.

[0038] According to embodiments of the invention, the method further includes transporting and / or lifting and / or guiding and / or connecting one or more intermediate tower sections to the top of a lower tower section or to the top of a corresponding uppermost tower section.

[0039] The middle (or upper, see below) tower section can, for example, span between 1 / 4 and 1 / 2 (or less) of the total wind turbine tower height and can have between 1 / 3 and 2 / 3 (or less) of the total wind turbine tower weight. Other values ​​may be possible. This can further improve and simplify the installation of the entire wind turbine.

[0040] According to embodiments of the invention, the method further includes transporting and / or lifting and / or guiding and / or connecting one or more upper tower sections to the top of a lower tower section or to the top of a corresponding uppermost tower section; transporting and / or lifting and / or guiding and / or connecting one or more nacelles, including a hub, to the top of an upper tower section or to the top of a corresponding uppermost tower section; and transporting and / or lifting and / or guiding and / or connecting one or more blades to the hub supported at the nacelle, particularly for transport using a transport vessel and for lifting and / or guiding and / or connecting using an installation vessel, the one or two vessels being different from the vessel used to transport the lower tower section.

[0041] Thus, the installation of at least one complete wind turbine can be achieved. This method can be implemented, for example, by a system for installing at least one wind turbine at an offshore site, according to an embodiment of the invention, which will be described in further detail below.

[0042] According to an embodiment of the invention, during transport and / or before lifting, the lower tower section is covered by a tower section cover. The method includes removing the tower section cover before lifting and / or guiding the lower tower section; and / or after connecting the lower tower section: covering the lower tower section with the tower section cover. This cover protects the interior of the corresponding tower section from contamination or damage.

[0043] According to an embodiment of the invention, the method further includes providing personnel with access from the ship to the platform (the wind turbine's entry / exit point / area).

[0044] This allows the lower tower section to be guided more accurately to the tower connection section at the base, for example, by visually inspecting or automatically checking (e.g., by personnel or a team) the position and / or movement of the lower tower section, particularly relative to or about the tower connection section. The installation personnel or team can, for example, visually monitor or follow the guidance process and can provide control signals for controlling the crane and / or guiding equipment to correct any deviations from the expected movement or positioning (laterally and / or vertically). Furthermore, the connection can then be performed, for example, by manually inserting bolts or clamps and / or nuts.

[0045] It should be understood that features disclosed, described, explained, or provided individually or in any combination for the method of at least partially installing at least one wind turbine at an offshore site may also be applied, provided, or adopted individually or in any combination by the lower tower portion of the transport vessel according to embodiments of the invention, and vice versa.

[0046] According to an embodiment of the present invention, a vessel is provided for transporting a lower tower portion of at least one wind turbine at an offshore site. The vessel includes: a loading area for loading at least one lower tower portion of the wind turbine, the span of which is less than the entire wind turbine tower; a motor for moving the vessel at sea to transport the lower tower portion to the offshore site; and lifting and guiding equipment adapted to lift and guide the lower tower portion such that its lower end approaches a tower connection portion provided at an offshore base, so that the lower tower portion is connected to the tower connection portion at its lower end.

[0047] The vessel can be configured to substantially implement the method of at least partially installing a wind turbine at an offshore site, as explained or described above. Thus, the method can be implemented and carried out in a simple manner.

[0048] According to embodiments of the present invention, a system for installing at least one wind turbine at an offshore site is provided, the system comprising: a transport vessel for the lower tower portion according to the preceding claims; a transport vessel adapted to: transport one or more upper tower portions and / or one or more nacelles including a hub and / or one or more blades; and an installation vessel adapted to: lift and / or guide and / or connect one or more upper tower portions to the top of the lower tower portion or to the top of a corresponding uppermost tower portion; and / or lift and / or guide and / or connect one or more nacelles including a hub to the top of the upper tower portion or to the top of a corresponding uppermost tower portion; and / or lift and / or guide and / or connect one or more blades to the hub supported at the nacelle.

[0049] This allows for the simple and cost-effective installation of multiple complete wind turbines at offshore sites.

[0050] The entire wind turbine tower can have a height between 80 m and 115 m, and a tower diameter between 5 m and 15 m. Other values ​​are possible.

[0051] The aspects and other aspects of the invention as defined above will become apparent from examples of embodiments described below and will be explained with reference to these examples. The invention will be described in more detail below with reference to examples of embodiments, but the invention is not limited thereto. Attached Figure Description

[0052] Embodiments of the invention will now be described with reference to the accompanying drawings. The invention is not limited to the illustrated or described embodiments.

[0053] Figure 1 The illustration schematically depicts the loading steps of a method for at least partially installing at least one wind turbine at an offshore site according to an embodiment of the present invention. Figure 2 The illustration shows the transport steps of a method for at least partially installing at least one wind turbine at an offshore site according to an embodiment of the present invention. Figure 3 and Figure 4 The illustration shows the lifting steps of a method for at least partially installing at least one wind turbine at an offshore site according to an embodiment of the present invention. Figure 5 and Figure 6 The illustration shows the guiding and lowering steps of a method for at least partially installing at least one wind turbine at an offshore site according to an embodiment of the present invention. Figure 7 The illustration shows the guiding step and the end of the connecting step in a method for at least partially installing at least one wind turbine at an offshore site according to an embodiment of the present invention; and Figure 8 The illustration shows a multi-part wind turbine, each part of which includes a lower tower section carried out by a vessel transported by a lower tower section according to an embodiment of the present invention. Detailed Implementation

[0054] The illustrations in the attached diagrams are schematic.

[0055] Figure 1 The loading step of the method for at least partially installing at least one wind turbine at an offshore site according to an embodiment of the present invention, as illustrated in the figure, is performed using a (lower tower portion transport) vessel 1 according to an embodiment of the present invention. The (lower tower portion transport) vessel 1 includes a loading area 2 for loading at least one lower tower portion 3a with a span less than the entire wind turbine tower. The vessel 1 also includes a motor (not shown) for moving the vessel 1 on the sea 4 to transport the lower tower portion 3a to the offshore site 5 (illustrated in the figure). Figure 2 (Middle). The vessel 1 also includes lifting and guiding equipment 6, which is adapted to lift and guide the lower tower section 3, such that the lower end 7 (illustrated in...) Figure 4 , Figure 5 , Figure 6 (China) is close to providing in Figure 4 The tower connection section 8 at the offshore base (not shown in the image, as it is below sea level) is illustrated in [the image]. Figure 4 , Figure 5 , Figure 6 (in the middle), used to connect the lower tower section 3 to the tower connection section 8 at the lower end 7.

[0056] like Figure 1 As illustrated, vessel 1 includes storage, installation, and securing equipment 15 arranged in the vessel's loading area 2 for mounting and securing multiple lower tower sections 3, specifically in a regular two-dimensional array. Individual mounting and securing areas 15a, b, c, ... can be adapted to support the mounting and securing of lower tower sections 3 with different diameters. Lower tower sections 3a can, for example, span between ¼ and ½ of the entire wind turbine tower height.

[0057] To load multiple lower pylon sections 3a, b, c, ... onto the loading area 2 of vessel 1, the multiple lower pylon sections (marked by reference numeral 3 in the attached drawings) are stored on land-based loading and storage equipment 9, thereby enabling the multiple lower pylon sections 3a, b, c, ... to be stored in an upright position. For example... Figure 1 As can be seen, during the loading of the lower tower section 3a, it is in a vertical orientation, that is, an upright position. Thus, the longitudinal direction is essentially vertically oriented.

[0058] In the embodiment illustrated in the figure, the lifting and guiding equipment 6 includes a crane 10. Figure 2 The diagram illustrates the transportation steps after multiple lower tower sections 3 have been loaded onto vessel 1. Vessel 1 then approaches the offshore site 5.

[0059] Figure 3 and Figure 4 The diagram illustrates the lifting steps of the installation method, for which crane 10 is used. As a result, vessel 1 is now freely floating on sea 4. Figure 3 In the steps illustrated, a crane 10 is used to remove the tower section cover 11 that covers the upper portion of the lower tower section 3a. The tower section cover 11 is removed before lifting and / or guiding the lower tower section 3a. After the lower tower section 3a is connected to the tower connection portion 8, the tower section cover 11 can cover the lower tower section 3a.

[0060] According to an embodiment of the invention, the method further includes providing personnel with a passage 25 from the ship to the platform 26 of the base.

[0061] like Figure 4 As illustrated, the lower tower section 3a is then lifted using a crane 10. During the lifting and / or guiding of the lower tower section 3a, an active or passive heave compensator 12 is connected between the lower tower section 3a and the crane beam 13, particularly the retaining rope or retaining wire 14.

[0062] exist Figure 5 As illustrated in the diagram, the lower tower section 3a is lowered after it has been guided vertically above the tower connection section 8 provided at the base. The vessel 1 includes a guiding device 15' for guiding the lower tower section 3a toward the tower connection section 3. The guiding device 15' includes a pull rope 16, which is connected at one end 17 to the crane 10 and at the other end to a top position of the lower tower section 3a, marked by reference numeral 18. The tension of the pull rope 16 can be controlled to achieve the desired positioning and orientation of the lower tower section 3a.

[0063] Figure 6 The diagram illustrates the lowering step of lowering the lower end 7 of the lower tower portion 3a towards the tower connection portion 8 at the base. The lower end 7 of the lower tower portion 3a includes an inwardly inclined protrusion 23 inside the circular flange 22, which facilitates its insertion into the circular opening 24 of the tower connection portion 8.

[0064] The ship or installation process may also use illustrations. Figure 7 The additional pull rope 19 (included in the guide equipment 15') is installed at one end 20 on the vessel 1 (e.g., near the loading area 2) and at the other end at the middle position 21 of the lower tower section 3a.

[0065] exist Figure 7 In this process, by properly operating the crane 10 and the ropes 16, 19, and especially by controlling their respective tensions, the lower tower section 3a has been lowered to the tower connection section 8 at the contact base. This control can be performed, for example, by installation personnel or team members operating the corresponding control devices based on a visual inspection of the installation or guidance procedure.

[0066] Ship 1 can install the lower tower section 3 onto the ship one by one, and Figure 8 The diagram shows multiple lower tower sections 3 installed at the respective installation sites. After that, vessel 1 can return to port for loading, and then install additional tower sections at other offshore sites.

[0067] That is, after installing all or at least some of the lower tower sections at the corresponding offshore site, the installation method may further include, for example, installing the corresponding upper tower section on top of the lower tower section, and then installing the nacelle on top of the upper tower section, and then installing the wind turbine blades to the corresponding hub to complete the installation of the entire wind turbine.

[0068] According to embodiments of the invention, a portion of the tower can be installed directly from the manufacturing point, eliminating the need for transport to a pre-assembly port. The vessel used for transporting the lower tower portion can also be referred to as a bottom tower installation vessel. The bottom tower installation vessel (BTIV) can pick up all the lower tower portions from the manufacturer and move them to the installation site. The lower tower portions can be installed to a transition piece (TP), also referred to as the tower connection portion at the base.

[0069] The feed vessel can carry all remaining tower sections, blade racks (including rotor blades), and nacelles, and can be moved to the installation site. The feed vessel can deliver all remaining wind turbine components to the installation vessel, which can be configured to install the remaining wind turbine components starting from the already installed lower tower section.

[0070] The installation vessel may then remain at sea and therefore may not return to any port. The installation vessel may then wait for the arrival of another feeder vessel in order to continue the installation of other wind turbines at the offshore site.

[0071] It should be noted that the term "comprising" does not exclude other elements or steps, and "a" or "an" does not exclude multiple. Furthermore, elements described in association with different embodiments may be combined. It should also be noted that reference numerals in the claims should not be construed as limiting the scope of the claims.

Claims

1. A method for at least partially installing at least one wind turbine at an offshore site (5), the method comprising: At least one lower tower section (3) of the wind turbine is loaded onto the vessel (1) at an onshore site, wherein the span of the lower tower section (3) is smaller than that of the entire wind turbine tower. The lower tower section (3) is transported to the offshore site (5) by the vessel (1); Lift and guide the lower tower section (3) so that the lower end (7) approaches the tower connection section (8) provided at the offshore base; The lower tower section (3) is connected to the tower connection section (8) at the lower end (7). The vessel (1) includes a crane (10). The loading and / or lifting and / or guiding of the lower tower section (3) are performed using the crane (10).

2. The method according to the preceding claim, wherein, During loading and / or transporting and / or lifting and / or guiding the lower tower section (3), the lower tower section (3) is in a substantially upright position, in particular, the longitudinal direction of the lower tower section is oriented substantially vertically.

3. The method according to any one of the preceding claims, in, While the vessel (1) is freely floating on the sea (4), the crane (10) is used to perform the loading and / or the lifting and / or guiding of the lower tower section (3).

4. The method according to any one of the preceding claims, wherein, The vessel (1) includes guiding equipment (10, 15') for guiding the lower tower portion (3) toward the tower connection portion (8), the guiding equipment (15') being particularly adapted to apply traction at at least two locations (18, 21) of the lower tower portion (3) spaced apart along the longitudinal direction of the lower tower portion (3).

5. The method according to the preceding claim, wherein, The guiding equipment (15') includes pull ropes (16, 19) connected at one end to the crane (10) and / or the vessel (1), and at the other end to the bottom and / or middle (21) and / or top (18) of the lower tower section (3). In particular, in order to guide the lower tower section (3), the tension of the pull rope is controlled and / or adjusted.

6. The method according to any one of the preceding claims, wherein, During the lifting and / or guiding of the lower tower section (3), an active or passive heave compensator (12) is connected between the lower tower section (3) and the crane beam (10) or crane wire (14).

7. The method according to any one of the preceding claims, wherein, The vessel (1) includes storage installation and fixing equipment (15a, b, c, ...) arranged in the vessel loading area (2) for vertically installing and fixing multiple, particularly 20 to 60, lower tower sections (3) having substantially circular cross-sections, in particular in a regular 2D array, for each lower tower section (3) having a loading capacity particularly between 700 t and 1200 t.

8. The method according to the preceding claim, wherein, The installation and fixing equipment (15a, b, c, ...) is suitable for installing and fixing lower tower sections (3) with different diameters, particularly between 5 m and 15 m.

9. The method according to any one of the preceding claims, wherein, The lower tower section (3) spans between 1 / 4 and 1 / 5 of the total height of the wind turbine tower, and / or has a weight between 1 / 3 and 1 / 5 of the total weight of the wind turbine tower. The lower tower section (3) had previously been fully pre-assembled on land, particularly at the pre-assembly port.

10. The method according to any one of the preceding claims, further comprising: Transport and / or lift and / or guide and / or connect one or more intermediate tower sections to the top of the lower tower section (3) or to the top of the corresponding uppermost tower section.

11. The method according to any one of the preceding claims, further comprising: Transport and / or lift and / or guide and / or connect one or more upper tower sections to the top of the lower tower section (3) or to the top of the corresponding uppermost tower section; Transport and / or lift and / or guide and / or connect one or more nacelles, including the hub, to the top of the upper tower section or to the top of the corresponding uppermost tower section; One or more blades are transported and / or lifted and / or guided and / or attached to a hub supported at the nacelle. In particular, for the transport using transport vessels and for the lifting and / or guiding and / or connecting using installation vessels, one or both vessels are different from the vessels used for handling the lower tower section.

12. The method according to any one of the preceding claims, wherein, During transport and / or before lifting, the lower tower section (3) is covered by a tower section cover (11), the method comprising: Before lifting and / or guiding the lower tower section (3), remove the tower section cover (11); and / or After connecting the lower tower section (3): The lower tower section (3) is covered with the tower section cover (11).

13. The method according to any one of the preceding claims, further comprising: Provide personnel with access (25) from the vessel (1) to the platform (26) of the base.

14. A lower tower section (3) and / or a tower transport vessel (1) for at least partially installing at least one wind turbine at an offshore site (5), said vessel comprising: Loading area (2), the loading area (2) is used to load at least one lower tower section (3) and / or tower of a wind turbine at an onshore site, the span of the lower tower section (3) being less than the entire wind turbine tower; A motor for moving the vessel (1) at sea (4) in order to transport the lower tower section (3) from the land site to the sea site (5); Lifting and guiding equipment (6) is adapted to lift and guide the lower tower portion (3) such that the lower end (5) approaches the tower connection portion (8) provided at the offshore base for connecting the lower tower portion (3) to the tower connection portion (8) at the lower end (7).

15. A system for installing at least one wind turbine at an offshore site, the system comprising: The lower tower section (3) and / or the tower transport vessel (1) as described in the preceding claim; Transport vessels, the transport vessels being suitable for: Transport one or more upper tower sections and / or one or more nacelles including hubs and / or one or more blades; The installation vessel is suitable for: Lift and / or guide and / or connect one or more upper tower sections to the top of the lower tower section (3) or to the top of the corresponding uppermost tower section; and / or One or more nacelles, including the hub, are lifted and / or guided and / or connected to the top of the upper tower section or the top of the corresponding uppermost tower section; and / or One or more blades are lifted and / or guided and / or connected to a hub supporting the nacelle.

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