Construction of floating wind turbine foundations

Abstract

A method of constructing a floatable foundation (100) for a wind turbine generator, the method comprising: providing three column sections (10a-d) at a foundation construction site (S); providing three pontoon sections (11a-c) at the foundation construction site (S); resting the three columns sections (10a-d) on a plurality of first supports (1) at the construction site (S); resting the three pontoon sections (11a-c) on a plurality of second supports (2) at the construction site (S); providing three brace sections (12a-c) at the foundation construction site (S); and fixing each of the three pontoon sections (11a-c) between different pairs of column sections (10a-d) and fixing each of the three brace sections (12a-c) between different pairs of column sections (10a-d).

Description

[0001] CONSTRUCTION OF FLOATING WIND TURBINE FOUNDATIONS

[0002] The present disclosure relates to construction of floating wind turbine foundations.

[0003] BACKGROUND

[0004] Floating wind turbine systems are being studied and developed by various research and development (R&D) groups, both within academia and industry, and provide a promising option for offshore electric power generation. Floating wind turbine systems rely on a moored, buoyant substructure base, onto which a wind turbine is mounted. Publications which may be useful to understand the field of technology include: EP 2 318 701 B1 ; WO 2009 / 131826 A2; WO 2013 / 110276 A1; WO 2010 / 021655 A2; WO 2020 / 167137 A1; EP 4 155 538 A1; WO 2023 / 014230 A1; and WO 2023 / 009010 A1.

[0005] Such systems are in many cases not presently cost-competitive compared to bottom-fixed systems, and not yet in widespread commercial use. However it is expected that further development of floating offshore wind technology can make such systems more competitive and a viable alternative at many locations in the near future. This applies particularly to offshore sites with large water depths (typically more than 50-70 m), which may be unsuitable for bottom-fixed installations.

[0006] With a projected continued increase in the need for renewable electric power generation in the future, there is a need for further improved technology in this area. The present disclosure has the objective to provide such improvements, or at least useful alternatives, to the current state of the art.

[0007] SUMMARY

[0008] In an example, there is provided a method of constructing a floatable foundation for a wind turbine generator, the method comprising: providing three column sections at a foundation construction site; providing three pontoon sections at the foundation construction site; resting the three columns sections on a plurality of first supports at the construction site; resting the three pontoon sections on a plurality of second supports at the construction site; providing three brace sections at the foundation construction site; and fixing each of the three pontoon sections between different pairs of column sections and fixing each of the three brace sections between different pairs of column sections.

[0009] The detailed description below and appended claims outline further inventive aspects and embodiments.

[0010] BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The above and other characteristics will become clear from the following description of illustrative, non-restrictive examples, with reference to the attached drawings, in which:

[0012] Fig. 1 is a perspective view of a foundation construction site.

[0013] Fig. 2 is an illustrative view of the foundation construction site showing self-propelled modular transporters and supports for column and pontoon sections.

[0014] Fig. 3 illustrates a floatable foundation being constructed.

[0015] Figs 4 and 5 illustrate steps in a method of constructing a floatable foundation.

[0016] Fig 6 illustrates steps in a method of constructing a floatable foundation.

[0017] Figs 7 and 8 illustrate steps in a method of constructing a floatable foundation.

[0018] Fig. 9 illustrates moving a floatable foundation onto a vessel.

[0019] Figs 10 and 11 illustrate types of floatable foundations.

[0020] Fig. 12 illustrates construction of a floatable foundation using a support frame.

[0021] Fig. 13 illustrates construction of a plurality of foundations at a construction site.

[0022] DETAILED DESCRIPTION

[0023] Fig. 1 illustrates a construction site S for constructing a floatable foundation 100 (see e.g. Figs 3 and 9). The floatable foundation 100 is constructed from three column sections 10a-c and three pontoon sections 11a-c which are interconnected to form a substantially triangular floater 100. The column sections 10a-c and the pontoon sections 11a-c are transported to the construction site S by means of self- propelled modular transporters 25. One of the column sections 10a-c may comprise an interface 19 for holding a wind turbine tower.

[0024] Fig. 2 illustrates the construction site S without the column sections 10a-c and pontoon sections 11a-c, but (for illustration purposes) with the self-propelled modular transporters 25 positioned between a plurality of first supports 1 arranged to support each of the column sections 10a-c. There may be a plurality of first supports 1 , in the illustrated example four first supports 1 , arranged to support each column section 10a-c. The first supports 1 are arranged such as to allow the self- propelled modular transporters 25 to move between at least two first supports 1 at each column position. The self-propelled modular transporters 25 will thus move from the positions as illustrated in Fig. 1 to the position illustrated in Fig. 2 while holding the column sections 10a-c, and subsequently lowering each respective column sections 10a-c onto the plurality of first supports 1.

[0025] Similarly, three pontoon sections 11a-c are brought to the construction site S and positioned onto a plurality of second supports 2. In this example, there are two second supports 2 for each pontoon section 11a-c. Each such pair of second supports 2 may be arranged so as to allow a self-propelled modular transporters 25 to move in between the second supports 2 with a pontoon section 11a-c and to subsequently lower the pontoon section 11a-c onto the pair of second supports 2.

[0026] The column sections 10a-c and the pontoon sections 11a-c may be transported to the construction site S by the self-propelled modular transporters 25 simultaneously, or sequentially.

[0027] With at least one pontoon section 11a-c and at least one column section 10a-c in place on the supports 1 ,2, they can be connected and rigidly fixed to each other, i.e. fixing each of the three pontoon sections 11a-c between different pairs of column sections 10a-c, for example by welding. Each of the pontoon sections 11a-c and each of the column sections 10a-c may be positioned in place at the construction site S and on the supports 1 ,2 before connecting the respective pontoon sections 11a and column sections 10a-c.

[0028] Advantageously, the three pontoon sections 11a-c can be brought to the construction site S and rested on the second supports 2 prior to bringing the three column sections 10a-c to the construction site S. This can provide advantages for the positioning of the sections 10a-c and 11 a-c on the supports 1 ,2, in that each column section 10a-c can be brought in and positioned adjacent the respective ends of the pontoon sections 11 a-c.

[0029] Alternatively, the column sections 10a-c and pontoon sections 11 a-c may be brought in place and / or connected in a different order, such as sequentially. For example, with reference to Fig. 1 , the first and second column sections 10a, b and the first pontoon section 11a may be brought to the construction site S and rested on the supports 1 ,2 before bringing in the second and third pontoon sections 11 b,c. This may ease the positioning of the sections. The third column section 10c may subsequently be brought in and positioned on the supports 1 adjacent the second and third pontoon sections 11b,c.

[0030] Optionally, the second column section 10b may be brought to the construction site S and rested on the supports 1 subsequent to bringing the first column section 10a and the first pontoon section 11a to the construction site S.

[0031] In one example, the first column section 10a and the first pontoon section 11a can be fixed together at the construction site S and subsequently the second column section 10b is brought to the construction site S, rested on the first supports 1, and fixed to the first pontoon section 11a.

[0032] After fixing the second column section 10b to the first pontoon section 11a, the second pontoon section 11b can be brought to the construction site S and rested on the second supports 2, and connected to the second column section 10b.

[0033] Subsequent to fixing the second pontoon section 11b to the second column section 10b, the third column section 10c can be brought to the construction site S and rested on the first supports 1. The third pontoon section 11c can be brought to the construction site S at any suitable time prior to bringing the third column section 10c. The second and third pontoon sections 11 b,c can then be fixed to the third column section 10c.

[0034] As the fixing of the pontoon sections 11a-c between different pairs of column sections 10a-c is carried out with the column sections 10a-c and the pontoon sections 11 a-c resting on the supports 1,2, the self-propelled modular transporters 25 can be removed and employed for other purposes while the floatable foundation 100 is being constructed at the construction site S. Adjustments in the position for one or more of the sections 10a-c and / or 11a-c during construction may, if necessary, be carried out by skidding or otherwise moving these at the construction site S, for example via jacks, in order to align the sections (or parts thereof) vertically and / or horizontally for connection.

[0035] The method may also include installing three brace sections 12a-c between different pairs of column sections 10a-c, as illustrated in Fig. 3 and described in further detail below.

[0036] The manufacturing of the three column sections 10a-c, the three pontoon sections 11a-c and / or the three brace sections 12a-c may advantageously be carried out spaced from the foundation construction site S, for example at a related location nearby the construction site S. (But manufacturing even farther away and transport of sections to the construction site S may also be relevant, for example where required special manufacturing equipment or facilities are not available near the construction site.) This can for example allow the sections to be manufactured indoors and / or at individual work stations having suitable, dedicated equipment therefor or being suitably arranged for manufacturing a specific section. This may, for example, include lifting equipment, welding stations (such as platforms for welding at different elevations), etc. In this manner, manufacturing of the sections may be carried out more efficiently compared to for example raising scaffolding and bringing manufacturing equipment to the construction site S. Advantageously, the column sections 10a-c, pontoon sections 11a-c and / or the brace sections 12a-c can be provided to the foundation construction site S with pre-installed equipment, such as outfitting and secondary structure features inside and / or outside. For example, fluid pipework, electric cabling, junction boxes, gangways, ladders, or other items may be laid and installed in the relevant sections during manufacturing, such as to avoid the need to lay and install such items at the construction site S. The section(s) may thus be pre-fabricated prior to being provided to the construction site S. This may include laying pipework, cables and / or junction boxes with ends or connection points at or adjacent the connection points between sections (such as near the interfaces 28c or 29c, described in further detail below). In this manner, electrical or fluid connections can be made up between sections in a simplified and efficient manner after fixing the sections together. Alternatively, or additionally, surface treatment of the sections 10a-c, 11a-c and / or 12a-c may be carried out during manufacturing of the section(s) and before providing the section(s) to the construction site S.

[0037] Alternatively, or additionally, one or more pumps may be pre-installed in the section(s) during manufacturing and before providing the section(s) to the construction site S. This can, for example, be ballast water pumps installed in one or more column section 10a-c or pontoon section 11a-c. By pre-installing pumps at the manufacturing stage, a need to have construction features (such as installation openings in the structure) for installation of such equipment at a later stage may be eliminated, providing for a more efficient overall construction process.

[0038] Alternatively, or additionally, external gangways and / or handrails may be installed on one or more of the sections, such as on the brace sections 12a-c, during manufacturing of the section(s) and before providing the section(s) to the construction site S. For example, by pre-installing gangways and / or handrails on the brace sections 12a-c, these items can be installed in a safer and more efficient manner, for example installing these at or near ground level during manufacturing, and not after fixing the brace sections 12a-c at the foundation 100.

[0039] As described above, the manufacturing of the section(s) 10a-c, 11a-c and / or 12a-c may be carried out at a location which is spaced from the foundation construction site S, for example a location which is dedicated for certain manufacturing steps. Advantageously, the manufacturing location may be an indoor location. In any of the examples and embodiments described or claimed herein, the construction site S may be an outdoor location.

[0040] The three column sections 10a-c can be manufactured with a pair of lower stubs 28a, b (see Fig. 1), where each of the lower stubs 28a, b have an interface, indicated as 28c in relation to lower stub 28b, configured for connection with a respective pontoon section 11a-c. Alternatively, or additionally, each of the three column sections 10a-c may be manufactured with a pair of upper stubs 29a, b, each of the upper stubs 29a, b having an interface 29c configured for connection with a respective brace section 12a-c.

[0041] If manufacturing the column sections 10a-c with such upper and / or lower stubs 28a- b,29a-b, manufacturing of the column sections 10a-c at a dedicated manufacturing location spaced from the construction site S, for example an indoor location, may be particularly advantageous in that more accuracy can be provided in the construction of the stubs 28a-b,29a-b and their interface to the other parts of the respective column section 10a-c. In this manner, more accurate construction of these regions of the floater foundation 100, which may include particularly stress / fatigue-sensitive areas, can be achieved. This can allow use of a more purpose-equipped manufacturing location for the column sections 10a-c without tying up the construction site S. The interfaces between the stubs 28a-b,29a-b and the pontoon sections 11a-c and / or brace sections 12a-c may be provided at locations which are less stress- / fatigue-critical, and thus will have more relaxed requirements in relation to tolerances and construction accuracy.

[0042] Illustrated most clearly in relation to Fig. 2, the plurality of first and second supports 1 ,2 may be arranged to define a transport path at a floor F of the construction site S such as to allow a self-propelled modular transporter 25 to move between at least two of the plurality of first supports 1 and / or between at least two of the plurality of second supports 2. The transport path may allow the self-propelled modular transporters 25 to move the constructed floatable foundation 100 out of the construction site S in one direction, whereby the supports 1 ,2 are so positioned as to provide a free transport path at the floor F for each of the self-propelled modular transporters 25, for example one or two self-propelled modular transporters 25 arranged under each column section 10a-c for the purpose of moving the completed floatable foundation 100.

[0043] The floatable foundation 100 may be moved away from the construction site S after the column sections 10a-c and the pontoon sections 11a-c have been connected, for example in a case where no brace sections 12a-c are used (see e.g. the abovementioned EP 4 155 538 A1) or in a case where brace sections 12a-c are mounted at the floatable foundation 100 at a different location.

[0044] In order to move the floatable foundation 100 self-propelled modular transporters 25 can be positioned below each of the column sections 10a-c and between at least two of the plurality of first supports 1. The self-propelled modular transporters 25 may be positioned in the same positions as when they were used to move the column sections 10a-c to the construction site S. The column sections 10a-c and pontoon sections 11 a-c may then be lifted off the supports 1,2, and moved away from the foundation construction site S by the self-propelled modular transporters 25. Optionally, the foundation 100 may be moved away from the construction site S via self-propelled modular transporters 25 positioned below one or more column sections 10a-c and below one or more pontoon section 11a-c, as illustrated in Fig. 9.

[0045] In alternative implementations, the foundation 100 may be moved by other means, such as skidding. The construction site S may, for example, comprise pre- established skidding tracks for this purpose.

[0046] In another aspect, there is provided a method of constructing a floatable foundation 100 for a wind turbine generator. In examples according to this aspect, the foundation 100 comprises brace sections 12a-c. The method is illustrated in relation to Figs 3-5.

[0047] In this method, a partially assembled floatable foundation 100 for a wind turbine generator is provided, where the partially assembled foundation 100 comprises three column sections 10a-c and three pontoon sections 11a-c fixed between different pairs of column sections 10a-c. The partially assembled foundation 100 may be constructed as described above, or it may be provided a different way.

[0048] Three brace sections 12a-c are fixed between different pairs of column sections 10a-c, as illustrated in Fig. 3. Advantageously, this may be carried out at the construction site S and in conjunction with (such as subsequently to or in parallel with) steps for constructing the partially assembled foundation 100 as described above.

[0049] As illustrated in Fig. 3 in relation to brace section 12a, the three brace sections 12a- c may be lifted into engagement with the respective pair of column sections 10a-c by means of at least one crane, in this example two cranes 20a, b. The brace section 12a-c may be temporarily fixed to the column sections 10a-c while being supported by the crane(s) 20a, b, and the connection may be made up (for example by welding) after the brace section 12a-c has been released by the crane(s) 20a, b. Optionally, the crane(s) 20a, b may hold the brace section 12a-c during the full connection process.

[0050] Illustrated in closer detail in Figs 4 and 5, the fixing of the brace sections 12a-c between column sections 10a-c may optionally comprise supporting the respective brace section 12a-c at the column sections 10a-c by hang-off support members 21, and, while supporting the brace section 12a-c by the hang-off support members 21 , permanently connecting (such as by welding) the brace section 12a-c to the column sections 10a-c.

[0051] The hang-off support members 21 may, for example, be steel protrusions welded or otherwise fixed to the brace sections 12a-c. The hang-off support members 21 may, as can be seen in Figs. 4 and 5, extend outwardly at end sections 30 of the brace section 12a-c. The brace section 12a-c may then be hung off via the hang-off support members 21 by landing the hang-off support members 21 at upward-facing surfaces 31 of the column sections 10a-c. Optionally, the column sections 10a-c may be manufactured with a prepared receiver profile, guide members and / or an engagement surface for this purpose, which receives or otherwise comes into engagement with the hang-off support members 21 when these are landed. Such guide members for alignment arranged at the column sections 10a-c can be seen in Figs 4 and 5. In this manner, the brace sections 12a-c are correctly positioned in relation to the column sections 10a-c for connection.

[0052] Advantageously, by use of hang-off support members, one may operate the crane(s) 20a, b to hang off the respective brace section 12a-c via the hang-off support members 21, and then release the crane(s) 20a, b from the brace section 12a-c. The final connection can be carried out with the brace section 12a-c supported via the hang-off support members 21, without the need to tie up the crane(s) 20a, b for support.

[0053] Advantageously, the three brace sections 12a-c can be fixed between pairs of upper stubs 29a, b at each respective column sections 10a-c, as illustrated. The upper stubs 29a, b may be configured to engage with the hang-off support members 21 for temporary support of the brace section 12a-c during connection.

[0054] Optionally, the pontoon sections 11a-c may also be installed in the same way as described above for the brace sections 12a-c, i.e. by lifting. The pontoon sections 11a-c may, for example, comprise similar hang-off support members as described above for the brace sections 12a-c, which may interact with the column sections 10a-c, advantageously with the lower stubs 28a, b.

[0055] Although the examples above describe providing the column sections 10a-c, pontoon sections 11a-c and brace sections 12a-c to the construction site S as manufactured units, it is also possible to do the manufacturing of the sections 10a-c, 11a-c and / or 12a-c fully or partly at the construction site S. An example of this is illustrated in Fig. 6, wherein the pontoon section 11b is provided as three parts 11b’, 11b” and 11b’”, which are connected (such as welded together) at the construction site S to form the pontoon section 11b. Similarly, the column section 10c is provided to the construction site S in two parts 10c’ and 10c”, which are connected at the construction site S to form the column section 10c.

[0056] The steps of fixing each of the pontoon sections 11a-c and / or the brace sections 12a-c to the column sections 10a-c may include arranging a work platform at the interfaces between the sections to be connected. This is illustrated in Figs 7 and 8.

[0057] A work platform 61 is arranged adjacent and / or about the interfaces 63 between the respective pontoon section 11a-c and column sections 11a-c. Similarly, a work platform 60 is arranged adjacent and / or about the interfaces 62 between the respective brace section 12a-c and column sections 11a-c.

[0058] The respective pontoon section 11a-c and / or brace sections 12a-c may then be fixed to the column sections 11a-c at the interfaces 63, from the work platform(s) 60,61.

[0059] The work platforms 60,61 may comprise scaffolding, and / or have suitable work floors for operators, such as welders, to work from. The work platforms 60,61 may advantageously comprise welding tents.

[0060] In one example, the work platform(s) 60,61 are provided on, or supported by, a movable support rig 64. The movable support rig 64 can, for example be movable on the floor F of the construction site S.

[0061] Work platform(s) 60,61 may comprise re-usable parts and / or equipment, such as welding tents, which can be dismounted and moved to a new position on the floater 100 according to the progress of the construction work. These may be standardised in size, attachment interfaces, etc., in order to allow such re-use.

[0062] As indicated in Figs 7 and 8, operations on the foundation 100 may be carried out in sequential steps, where for example lifting in of one brace section is carried out at the same time as another brace section is being fixed (such as welded) between the column sections. Different operations on the foundation 100 may be carried out concurrently. In this manner, efficient use of equipment and personnel can be achieved. As also illustrated in Fig. 9, the method may also include moving the floatable foundation 100 from the construction site S onto a vessel 55 by means of self- propelled modular transporters 25. The vessel 55 may, for example, be a barge operable to partially submerge such that the foundation 100 can be floated off the vessel 55. Optionally, or additionally, the vessel 55 may be a transport barge or vessel for transporting the foundation 100 to a different location, for example for installation of a wind turbine onto the foundation 100 or other operations to be carried out on the foundation 100, and thereafter to a final wind farm operating site. Alternatively, the foundation 100 may be wet-towed after having been floated.

[0063] Advantageously, for moving the foundation 100 onto the vessel 55, at least one self- propelled modular transporter 25 is positioned below a column section 10c and at least one self-propelled modular transporter 25 is positioned below a pontoon section 11a which is arranged oppositely the one column sections 10c. This may be suitable for moving the foundation 100 onto vessels having a limited deck width.

[0064] The examples above have been described in relation to a substantially triangular floatable foundation 100. The methods described herein may, however, be equally suitable for other foundation types. Figs 10 and 11 illustrate one such alternative foundation type, in the form of a “star-shaped” foundation 100. The foundation 100 comprises a central column section 10d configured to hold a wind turbine tower, and three outer column sections 10a-c. Each outer column section 10a-c is connected to the central column section 10d via a pontoon section 11a-c and, optionally, a brace section 12a-c. Similar manufacturing methods as described above may be utilised to manufacture and construct the foundation 100 according to these examples.

[0065] The methods described herein may also be applicable for the construction of other types of foundations, for example having a different number of column sections, pontoon sections and / or brace sections, and / or having a different arrangement of the respective sections.

[0066] Fig. 12 illustrates another example, in which a support frame 66 is used to support pairs of one pontoon section 11a and one brace section 12a at the construction site S. The frame 66 may be provided as a movable unit, for example to be movable with self-propelled modular transporters 25.

[0067] The frame 66 may be used to hold the pontoon section 11a and brace section 12a in place between column sections 10a-d while fixing these between a pair of column sections 10a-d. For this purpose, the frame 66 may, for example, comprise upper and lower horizontal beams on which the sections 11 a, 12a can rest, as illustrated in Fig. 12. This allows the sections 11a, 12a to be held in place at a correct height and orientation while constructing the foundation 100.

[0068] The sections 11a, 12a may be moved to the construction site S on the support frame 66, and thereby transported together with the support frame 66. The transport may be carried out using self-propelled modular transporters 25. Optionally, the frame 66 may have wheels or other means for transportation at or around the construction site S.

[0069] The sections 11a, 12a may be placed on the frame 66 at a different location from the construction site S, i.e. spaced from the construction site S.

[0070] With the arrangement and methods as illustrated in relation to Fig. 12, the crane(s) 20a, b may be used to place the sections 11a, 12a onto the frame 66. The crane(s) 20a, b may in such a case be placed spaced from the construction site S. Several frames 66 may be used, which may allow for a more efficient use of the crane(s) 20a, b and / or the construction site S.

[0071] Fig. 13 illustrates another example, wherein a plurality of foundations 100 are constructed concurrently at the construction site S. The different foundations 100 may be constructed in a sequential or staggered manner, so that they may be at different stages in the construction process. In this manner, facilities, equipment and personnel (such as welders) may be utilised in an efficient way, for example by moving between different foundations 100.

[0072] The foundations 100 may be arranged about a crane 67 at the construction site S, such that the foundations 100 are arranged at least partly within operational reach of the crane 67. The crane 67 is advantageously rotatable about a vertical axis. The crane 67 may be used, for example, for moving equipment (such as work platforms 60,61) or other items to the foundations 100. Such equipment or other items may, for example, be provided by self-propelled modular transporters 25 or other means to a position adjacent the crane 67 (such as between two foundations 100). Optionally, the crane 67 may be used to lift equipment or other items off a foundation 100, for example after completion of a construction step. The column sections 10a-d which comprises the interface 19 for holding a wind turbine tower may advantageously be arranged adjacent, i.e. closest to, the crane 67.

[0073] In any of the examples or embodiments described or claimed herein, the brace sections 12a-c may be flat panel beams, such as beams with rectangular or square cross-section profile. The brace sections 12a-c may be so-called box beams. In the illustrated examples, the brace sections 12a-c are flat panel beams having a substantially square cross-section transverse to its longitudinal direction. Optionally, the brace sections 12a-c may be tubular or another shape.

[0074] In any of the examples or embodiments described or claimed herein, the pontoon sections 11a-c may be flat panel sections, such as sections with rectangular or square cross-section profile. In the illustrated examples, the pontoon sections 11a-c are flat panel sections having a substantially rectangular cross-section transverse to its longitudinal direction. Optionally, the pontoon sections 11a-c may be tubular or another shape.

[0075] In any of the examples or embodiments described or claimed herein, the at least three column sections 10a-d may have a circular or a polygonal horizontal crosssection profile. In the illustrated examples, the column sections 10a-d are flat panel sections having a substantially hexagonal cross-section in the horizontal plane. In some examples, the cross-section may have a form of an irregular polygon. Optionally, the columns sections 10a-c may be circular or another shape.

[0076] Further inventive aspects and embodiments are outlined in the following numbered clauses.

[0077] A1. A method of constructing a floatable foundation (100) for a wind turbine generator, the method comprising: providing at least three column sections (10a-d) at a foundation construction site (S); providing three pontoon sections (11a-c) at the foundation construction site (S); resting the at least three columns sections (10a-d) on a plurality of first supports (1) at the construction site (S); fixing each of the three pontoon sections (11a-c) between different pairs of column sections (10a-d). A2. The method of any preceding clause, comprising: resting the three pontoon sections (11a-c) on a plurality of second supports (2) at the construction site (S).

[0078] A3. The method of any preceding clause, comprising: providing four column sections (10a-d) at the foundation construction site (S); and wherein the step of fixing each of the three pontoon sections (11a-c) between different pairs of column sections (10a-d) comprises fixing each of the three pontoon sections (11a-c) between a central column section (10d) and a respective outer column section (10a-c).

[0079] A4. The method of any preceding clause, comprising providing exactly three column sections (10a-c) at the foundation construction site (S).

[0080] A5. The method of any preceding clause, wherein the step of fixing each of the three pontoon sections (11a-c) between different pairs of column sections (10a-d) is carried out with the column sections (10a-d) and the pontoon sections (11a-c) resting on the first and second supports (1,2).

[0081] A6. The method of any preceding clause, comprising manufacturing each of the at least three column sections (10a-d), the three pontoon sections (11a-c) and / or the three brace sections (12a-c) at a manufacturing location which is spaced from the foundation construction site (S), and the method comprises transporting the respective sections (10a-d,11a-c and / or 12a-c) from the manufacturing location to the construction site (S).

[0082] A7. The method of any preceding clause, comprising manufacturing each of the at least three column sections (10a-d) with a pair of lower stubs (28a, b), the lower stubs (28a, b) having an interface (28c) configured for connection with a respective pontoon section (11a-c).

[0083] A8. The method of any preceding clause, wherein the step of fixing each of the three pontoon sections (11a-c) between different pairs of column sections (10a-d) comprises fixing each of the three pontoon sections (11a-c) between lower stubs (28a, b) at the respective column sections (10a-d).

[0084] A9. The method of any preceding clause, comprising manufacturing each of the at least three column sections (10a-d) with a pair of upper stubs (29a, b), the upper stubs (29a, b) having an interface (29c) configured for connection with a respective brace section (12a-c). A10. The method of any preceding clause, comprising manufacturing each of the at least three column sections (10a-d) with a circular or a polygonal horizontal cross-section profile.

[0085] A11. The method of any preceding clause, comprising: bringing the three pontoon sections (11a-c) to the construction site (S) and resting the three pontoon sections (11a-c) on the second supports (2) prior to bringing the at least three column sections (10a-d) to the construction site (S).

[0086] A12. The method of any preceding clause, comprising: bringing a first (10a) and a second (10b) of the at least three column sections (10a-d) and a first (11a) of the three pontoon sections (11a-c) to the construction site (S) and resting the first and second (10a, b) column sections and the first pontoon section (11a) on the supports (1,2); subsequently, bringing a second (11b) and a third (11c) of the three pontoon sections (11a-c) to the construction site (S) and resting the second and third pontoon sections (11 b,c) on the supports (1,2); subsequently, bringing a third (10c) of the at least three column sections (10a-d) to the construction site (S) and resting the third column section (10c) on the supports (1,2).

[0087] A13. The method of any preceding clause, comprising bringing the second column section (10b) to the construction site (S) and resting the second column section (10b) on the supports (1,2) subsequent to bringing the first column section (10a) and the first pontoon section (11a) to the construction site (S) and resting the first column section (10a) and the first pontoon section (11a) on the supports (1,2).

[0088] A14. The method of any preceding clause, comprising: with a first (10a) of the at least three column sections (10a-d) and a first (11a) of the three pontoon sections (11a-c) resting on the supports (1 ,2), fixing, such as welding, the first column section (10a) to the first pontoon section (11a); subsequent to fixing the first column section (10a) to the first pontoon section (11a), bringing a second (10b) of the at least three column sections (10a-d) to the construction site (S) and resting the second column section (10b) on the first supports (1); fixing, such as welding, the second column section (10b) to the first pontoon section (11a).

[0089] A15. The method of any preceding clause, comprising: bringing a third (11c) of the three pontoon sections (11a-c) to the construction site (S) and resting the third pontoon section (11c) on the second supports (2); subsequent to fixing the second column section (10b) to the first pontoon section (11a), bringing a second (11b) of the three pontoon sections (11a-c) to the construction site (S) and resting the second pontoon section (11b) on the second supports (2); fixing, such as welding, the second pontoon section (11b) to the second column section (10b); subsequent to fixing the second pontoon section (11 b) to the second column section (10b), bringing a third (10c) of the at least three column sections (10a-d) to the construction site (S) and resting the third column section (10c) on the first supports (1); fixing, such as welding, the second pontoon section (11b) to the third column section (10c) and the third pontoon section (11c) to the third column section (10c).

[0090] A16. The method of any preceding clause, wherein the plurality of first and second supports (1,2) are arranged to define a transport path at a floor (F) of the construction site (S) such as to allow a self-propelled modular transporter (25) to move between at least two of the plurality of first supports (1) and / or between at least two of the plurality of second supports (2).

[0091] A17. The method of any preceding clause, wherein the step of providing the at least three column sections (10a-d) at the foundation construction site (S) comprises moving each of the at least three column sections (10a-d) to the foundation construction site (S) by means of at least one self-propelled modular transporter (25).

[0092] A18. The method of any preceding clause, comprising positioning the at least one self-propelled modular transporter (25) between at least two of the plurality of first supports (1), and lowering the respective column sections (10a-d) onto the plurality of first supports (1). A19. The method of any preceding clause, comprising, subsequent to fixing each of the three pontoon sections (11a-c) between different pairs of column sections (10a-d), positioning at least one self-propelled modular transporter (25) below each of the column sections (10a-d) and between at least two of the plurality of first supports (1), lifting the column sections (10a-d) and pontoon sections (11a-c) off the plurality of first and second supports (1,2), and while supporting the column sections (10a-d) and pontoon sections (11a-c) on the self-propelled modular transporters (25), moving the column sections (10a-d) and pontoon sections (11a-c) away from the foundation construction site (S).

[0093] A20. A method, comprising: providing a partially assembled floatable foundation (100) for a wind turbine generator, the partially assembled foundation (100) comprising at least three column sections (10a-d) and three pontoon sections (11a-c) fixed between different pairs of column sections (10a-d), for example providing a partially assembled floatable foundation (100) by means of a method according to any preceding clause; providing three brace sections (12a-c); and fixing each of the three brace sections (12a-c) between different pairs of column sections (10a-d).

[0094] A21. The method of any preceding clause, wherein the steps of providing the three brace sections (12a-c) and fixing each of the three brace sections (12a-c) between different pairs of column sections (10a-d) are carried out at the foundation construction site (S).

[0095] A22. The method of any preceding clause, wherein the step of fixing each of the three brace sections (12a-c) between different pairs of column sections (10a-d) comprises lifting each of the three brace sections (12a-c) into engagement with the respective pair of column sections (10a-d) by means of at least one crane (20a, b).

[0096] A23. The method of any preceding clause, wherein the step of fixing each of the three brace sections (12a-c) between different pairs of column sections (10a-d) comprises: supporting the respective brace section (12a-c) at the respective pair of column sections (10a-d) by hang-off support members (21), and permanently connecting, such as welding, the brace section (12a-c) to the pair of column sections (10a-d).

[0097] A24. The method of any preceding clause, comprising: operating the at least one crane (20a, b) to hang off the respective brace section (12a-c) via the hang-off support members (21), and prior to permanently connecting the brace section (12a-c) to the pair of column sections (10a-d), releasing the at least one crane (20a, b) from the brace section (12a-c).

[0098] A25. The method of any preceding clause, wherein the hang-off support members (21) extend outwardly at end sections (30) of the brace section (12a-c), and wherein the step of hanging off the respective brace section (12a-c) via the hang-off support members (21) comprises landing the hang- off support members (21) at upward-facing surfaces (31) of the column sections (10a-d).

[0099] A26. The method of any preceding clause, wherein the step of fixing each of the three brace sections (12a-c) between different pairs of column sections (10a-d) comprises fixing each of the three brace sections (12a-c) between upper stubs (29a, b) at the respective column sections (10a-d).

[0100] A27. The method of any preceding clause, wherein the step of supporting the respective brace section (12a-c) at the respective pair of column sections (10a-d) by hang-off support members (21) comprises supporting the respective brace section (12a-c) on the upper stubs (29a, b).

[0101] A28. The method of any preceding clause, wherein the upward-facing surfaces (31) is arranged on the upper stubs (29a, b).

[0102] A29. The method of any preceding clause, wherein the column sections (10a-d) and / or the upper stubs (29a, b) comprises at least one of: a receiver profile, guide members or an engagement surface for interaction with the hang-off support members (21).

[0103] A30. The method of any preceding clause, wherein the step of fixing each of the three pontoon sections (11a-c) between different pairs of column sections (10a-d) comprises lifting each of the three pontoon sections (11a-c) into engagement with the respective pair of column sections (10a-d) by means of at least one crane (20a, b). A31. The method of any preceding clause, wherein the step of fixing each of the three pontoon sections (11a-c) between different pairs of column sections (10a-d) comprises: supporting the respective pontoon section (11a-c) at the respective pair of column sections (10a-d) by pontoon hang-off support members, and permanently connecting, such as welding, the pontoon section (11a- c) to the pair of column sections (10a-d).

[0104] A32. The method of any preceding clause, comprising: operating the at least one crane (20a, b) to hang off the respective pontoon section (11a-c) via the pontoon hang-off support members, and prior to permanently connecting the pontoon section (11a-c) to the pair of column sections (10a-d), releasing the at least one crane (20a, b) from the pontoon section (11a-c).

[0105] A33. The method of any preceding clause, wherein the pontoon hang-off support members extend outwardly at end sections of the pontoon section (11a-c), and wherein the step of hanging off the respective pontoon section (11a-c) via the pontoon hang-off support members comprises landing the pontoon hang-off support members at upward-facing surfaces of the column sections (10a-d).

[0106] A34. The method of any preceding clause, wherein the step of fixing each of the three pontoon sections (11a-c) between different pairs of column sections (10a-d) comprises fixing each of the three pontoon sections (11a-c) between lower stubs (28a, b) at the respective column sections (10a-d).

[0107] A35. The method of any preceding clause, wherein the step of supporting the respective pontoon section (11a-c) at the respective pair of column sections (10a-d) by pontoon hang-off support members comprises supporting the respective pontoon section (11a-c) on the lower stubs (28a, b).

[0108] A36. The method of any preceding clause, wherein the upward-facing surfaces is arranged on the lower stubs (28a, b).

[0109] A37. The method of any preceding clause, wherein the column sections (10a-d) and / or the lower stubs (28a, b) comprises at least one of: a receiver profile, guide members or an engagement surface for interaction with the pontoon hang-off support members.

[0110] A38. The method of any preceding clause, comprising: providing the column sections (10a-d) at the foundation construction site (S) with at least one of: internally installed pipework, internally installed cabling and / or electric junction boxes, internally and / or externally applied surface treatment, one or more installed pumps, or externally installed gangways and / or handrails, providing the pontoon sections (11a-c) at the foundation construction site (S) with at least one of: internally installed pipework, internally installed cabling and / or electric junction boxes, internally and / or externally applied surface treatment, one or more installed pumps, or externally installed gangways and / or handrails, and / or providing the brace sections (12a-c) at the foundation construction site (S) with at least one of: internally installed pipework, internally installed cabling and / or electric junction boxes, internally and / or externally applied surface treatment, one or more installed pumps, or externally installed gangways and / or handrails.

[0111] A39. The method of any preceding clause, comprising: manufacturing the one or more of the column sections (10a-d), pontoon sections (11a-c) and / or brace sections (12a-c) with the internally installed pipework, internally installed cabling and / or electric junction boxes, internally and / or externally applied surface treatment, one or more installed pumps, or externally installed gangways and / or handrails at a location spaced from the foundation construction site (S) prior to the step(s) of providing the column sections (10a-d), pontoon sections (11a-c) and / or brace sections (12a-c) at the foundation construction site (S).

[0112] A40. The method of any preceding clause, wherein the location spaced from the foundation construction site (S) is an indoor location and / or the construction site (S) is an outdoor location.

[0113] A41. The method of any preceding clause, comprising moving the floatable foundation (100) from the construction site (S) onto a vessel (55) by means of a plurality of self-propelled modular transporters (25).

[0114] A42. The method of any preceding clause, wherein the step of moving the floatable foundation (100) from the construction site (S) onto a vessel (55) comprising moving the floatable foundation (100) with at least one of the plurality of self-propelled modular transporters (25) positioned below one of the at least three column sections (10a-d), and at least one of the plurality of self-propelled modular transporters (25) positioned below one of the three pontoon sections (11a-c), the one pontoon section (11a) being arranged oppositely the one column sections (10c).

[0115] A43. The method of any preceding clause, wherein the step of fixing each of the three pontoon sections (11a-c) between different pairs of column sections (10a-d) comprises: arranging a work platform (61) adjacent and / or about interfaces (63) between the respective pontoon section (11a-c) and column sections (10a- c), and fixing, such as welding, the respective pontoon section (11a-c) to the column sections (10a-c) at the interfaces (63).

[0116] A44. The method of any preceding clause, wherein the step of fixing each of the three brace sections (12a-c) between different pairs of column sections (10a-d) comprises: arranging a work platform (60) adjacent and / or about interfaces (62) between the respective brace section (12a-c) and column sections (10a-c), and fixing, such as welding, the respective brace section (12a-c) to the column sections (10a-c) at the interfaces (62).

[0117] A45. The method of any preceding clause, comprising supporting the work platform(s) (60,61) by a movable support rig (64).

[0118] A46. The method of any preceding clause, comprising: supporting pairs of sections (11 a, 12a), each pair of sections (11 a, 12a) comprising one pontoon section (11a-d) and one brace section (12a-c), on a support frame (66) at the construction site (S).

[0119] A47. The method of any preceding clause, comprising supporting the pair of sections (11a, 12a) on the support frame (66) at the construction site (S) while fixing the respective pontoon section (11 a-d) and the respective brace section (12a-c) between different pairs of column sections (10a-d).

[0120] A48. The method of any preceding clause, comprising moving the pairs of sections (11a, 12a) to the construction site (S) on the support frame (66).

[0121] A49. The method of any preceding clause comprising moving the pairs of sections (11a, 12a) to the construction site (S) on the support frame (66) via at least one self-propelled modular transporter (25). A50. The method of any preceding clause, comprising: concurrently constructing a plurality of foundations (100), such as two or three foundations (100), at the construction site (S).

[0122] A51 . The method of any preceding clause, wherein the plurality of foundations (100) are arranged about a crane (67) and at least partly within operational reach of the crane (67).

[0123] A52. The method of any preceding clause, wherein the crane (67) is rotatable about a vertical axis.

[0124] A53. The method of any preceding clause, wherein one (10c) of the column sections (10a-d) comprises an interface (19) for holding a wind turbine tower, and wherein each of the plurality of foundations (100) are arranged with the one (10c) column section (10a-d) comprising the interface (19) positioned adjacent the crane (67).

[0125] Improved technology as described herein may be employed to reduce cost and for more effective use of existing facilities, equipment and supply chains. According to examples and embodiments described herein, more efficient use of equipment (such as cranes, work stations, scaffolding towers or other equipment) and / or workspace facilities can be achieved. Alternatively, or additionally, examples and embodiments described herein may be suitable to reduce the amount of work carried out at high elevations, improving safety and efficiency. Alternatively, or additionally, examples and embodiments described herein may provide increased operational flexibility, in that requirements for the construction site (for example relating to availability of special equipment) may be relaxed. In some implementations, “serial production” can be achieved, with efficient repeated use of the same equipment, facilities and personnel to produce a series of foundations 100.

[0126] The invention is not limited by the embodiments described above; reference should be had to the appended claims.

Claims

CLAIMS1. A method of constructing a floatable foundation (100) for a wind turbine generator, the method comprising: providing three column sections (10a-d) at a foundation construction site (S); providing three pontoon sections (11a-c) at the foundation construction site (S); resting the three columns sections (10a-d) on a plurality of first supports (1) at the construction site (S); resting the three pontoon sections (11a-c) on a plurality of second supports (2) at the construction site (S); providing three brace sections (12a-c) at the foundation construction site (S); and fixing each of the three pontoon sections (11a-c) between different pairs of column sections (10a-d) and fixing each of the three brace sections (12a-c) between different pairs of column sections (10a-d).

2. The method of claim 1, comprising manufacturing each of the three column sections (10a-d), the three pontoon sections (11a-c) and the three brace sections (12a-c) at a manufacturing location which is spaced from the foundation construction site (S), and the method comprises transporting the respective sections (10a-d,11a-c,12a-c) from the manufacturing location to the construction site (S).

3. The method of claim 2, comprising manufacturing at least one of the column sections (10a-d), pontoon sections (11a-c) or brace sections (12a-c) with internally installed pipework, internally installed cabling and / or electric junction boxes, one or more installed pumps, or externally installed gangways and / or handrails at the location spaced from the foundation construction site (S) prior to the step(s) of providing the column sections (10a-d), pontoon sections (11a-c) and brace sections (12a-c) at the foundation construction site (S).

4. The method of claim 3, wherein the location spaced from the foundation construction site (S) is an indoor location and the construction site (S) is an outdoor location.

5. The method of any preceding claim, comprising manufacturing each of the three column sections (10a-d) with a pair of lower stubs (28a, b), the lower stubs (28a, b) having an interface (28c) configured for connection with a respective pontoon section (11a-c), and the step of fixing each of the three pontoon sections (11a-c) between different pairs of column sections (10a-d) comprises fixing each of the three pontoon sections (11a-c) between lower stubs (28a, b) at the respective column sections (10a-d).

6. The method of any preceding claim, comprising manufacturing each of the three column sections (10a-d) with a pair of upper stubs (29a, b), the upper stubs (29a, b) having an interface (29c) configured for connection with a respective brace section (12a-c), and the step of fixing each of the three brace sections (12a-c) between different pairs of column sections (10a-d) comprises fixing each of the three brace sections (12a-c) between upper stubs (29a, b) at the respective column sections (10a-d).

7. The method of any preceding claim, wherein: the plurality of first and second supports (1,2) are arranged to define a transport path at a floor (F) of the construction site (S) such as to allow a self-propelled modular transporter (25) to move between at least two of the plurality of first supports (1), and the step of providing the three column sections (10a-d) at the foundation construction site (S) comprises moving each of the three column sections (10a-d) to the foundation construction site (S) by means of at least one self-propelled modular transporter (25).

8. The method of claim 7, comprising positioning the at least one self-propelled modular transporter (25) between at least two of the plurality of first supports(1), and lowering the respective column sections (10a-d) onto the plurality of first supports (1).

9. The method of any preceding claim, wherein the step of fixing each of the three brace sections (12a-c) between different pairs of column sections (10a- d) comprises: supporting the respective brace section (12a-c) at the respective pair of column sections (10a-d) by hang-off support members (21), and permanently connecting, by welding, the brace section (12a-c) to the pair of column sections (10a-d).

10. The method of claim 9 in conjunction with claim 6, wherein the step of supporting the respective brace section (12a-c) at the respective pair of column sections (10a-d) by hang-off support members (21) comprises supporting the respective brace section (12a-c) on the upper stubs (29a, b).

11. The method of claim 10, wherein the upper stubs (29a, b) comprises at least one of: a receiver profile, guide members or an engagement surface for interaction with the hang-off support members (21).

12. The method of any preceding claim, wherein the step of fixing each of the three pontoon sections (11a-c) between different pairs of column sections (10a-d) comprises: arranging a work platform (61) adjacent interfaces (63) between the respective pontoon section (11a-c) and column sections (10a-c), and fixing, by welding, the respective pontoon section (11a-c) to the column sections (10a-c) at the interfaces (63).

13. The method of any preceding claim, wherein the step of fixing each of the three brace sections (12a-c) between different pairs of column sections (10a- d) comprises: arranging a work platform (60) adjacent interfaces (62) between the respective brace section (12a-c) and column sections (10a-c), and fixing, by welding, the respective brace section (12a-c) to the column sections (10a-c) at the interfaces (62).

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