Construction of floating wind turbine foundations

Abstract

A method of constructing a floatable foundation 100 for a wind turbine generator, the method comprising constructing a base 101 having a tower interface 2 at a land-based construction site 102; receiving a first part 1a of a wind turbine tower 1 at the land based site, the first part having a first bolted flange 3a or weld interface and a base interface 4; with the base located at the land-based construction site, connecting the base interface and tower interfaces to fix the first part to the base; moving the base into a floating state; and mounting a second part 1b of the wind turbine tower, the second part having a second bolted flange 3b or weld interface configured to interface with the first bolted flange 3a or weld interface, to the first part by connecting the first and second bolted flanges or weld interfaces.

Description

The present disclosure relates to construction of floating wind turbine foundations. BACKGROUND 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 / 009010A1. 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. 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. SUMMARY In an example, there is provided a method of constructing a floatable foundation for a wind turbine generator, the method comprising: constructing a base of the floatable foundation at a land-based construction site, the base comprising a tower interface; receiving a first part of a wind turbine tower at the land-based construction site, the first part having a first bolted flange or weld connection interface and a base interface, the base interface configured for connection to the tower interface; with the base located at the land-based construction site, fixing the first part to the base by connecting the base interface to the tower interface; moving the base from the land-based construction site into a floating state; and with the base in the floating state, mounting a second part of the wind turbine tower, the second part having a second bolted flange or weld connection interface configured to interface with the first bolted flange or weld connection interface, to the first part by connecting the first and second bolted flanges or weld connection interfaces. The detailed description below and appended claims outline further inventive aspects and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS 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: Fig. 1 illustrates a base for a floatable foundation for a wind turbine generator located at a land-based construction site. Fig. 2 illustrates details of a wind turbine tower. Fig. 3 illustrates the floatable foundation at the land-based construction site during construction. Fig. 4 illustrates the floatable foundation in a floating state during construction. Fig. 5 illustrates the floatable foundation in a floating state during construction. Fig. 6 illustrates an example of a base for a floatable foundation having a substantially triangular configuration. DETAILED DESCRIPTION Fig. 1 illustrates a base 101 for a floatable (i.e. capable of floating or buoyant) foundation 100 for a wind turbine generator. The base 101 is constructed at a land-based construction site 102, for example a shoreside yard or industrial site. In the examples shown in Figs 1 and 3-5, the base 101 is in the form of a semisubmersible hull having a centrally arranged wind turbine tower 1. The base 101 may, alternatively, be of a different configuration. Fig. 6 illustrates an example of a different configuration, where the base 101 has a substantially triangular configuration. Methods described here may be used with any suitable base configuration. The base 101 is constructed with a tower interface 2 for connection of a wind turbine tower 1 to the base 101. The tower interface 2 may be a profile or flange for connection of the wind turbine tower 1 to the base 101 by welding. Alternatively, the tower interface 2 may be a bolted flange which is bolted to a corresponding flange of the turbine tower 1 at the base interface 4 (see below). The wind turbine tower 1 is received at the land-based construction site 102 from a remote tower manufacturing location. The wind turbine tower 1 may be manufactured at a remote manufacturing location and transported to the construction site land-based construction site 102. Fig. 2 illustrates the wind turbine tower 1. The wind turbine tower 1 has a first part 1a with a base interface 4 at one end section 1a’ of the first part 1a. The base interface 4 is configured for connection to the tower interface 2, thus it may have a corresponding profile as the tower interface 2 such that these can be connected by welding or bolting. Both the tower interface 2 and the base interface 4 may, for example, be tubular profiles of the same or closely similar dimensions and suitable for connection by welding, or may have corresponding bolted flange ends. The first part 1a of the wind turbine 1 further has a bolted flange 3a, i.e. a flange which is configured for connection to an adjacent flange via a plurality of bolts. The bolted flange 3a is arranged at an end section 1a” of the first part 1a opposite the base interface 4. The first part 1a may advantageously be a tubular section having a constant diameter between the base interface 4 and the bolted flange 3a. A second part 1b of the wind turbine tower 1 has a second bolted flange 3b configured to interface with, and be connected to, the first bolted flange 3a. The second part 1b, shown only in part in Fig. 2 but visible in full length in Fig. 5, may be a tapering tubular section, i.e. an elongate tubular section of non-constant diameter, which is tapering towards a nacelle interface 1b’ located at the upper end of the second part 1b (see Fig. 5). The second part 1b may be an intermediate part of the tower 1, if the tower 1 is provided in three or more parts. Construction of the floatable foundation 100 may be carried out in steps, where some steps are performed with the base 101 at the land-based construction site 102, and some steps are carried out while the base 102 is floating, for example in sea water 103 (see Fig. 4). Illustrated in Fig. 3, the construction of the floatable foundation 100 may include fixing the first part 1a to the base 102 by welding the base interface 4 to the tower interface 2 while the base 101 is located at the land-based construction site 102. If the interfaces 2,4 have bolted flanges, the fixing may be carried out by making up a bolted flange connection between these. Thereafter, the base 101 is moved from the land-based construction site 102 into a floating state, as illustrated in Fig. 4. This may, for example, be done by flooding a dry dock in which the base 101 is located such as to bring the base 101 into a floating state by means of its buoyancy, skidding the base 101 into water via a ramp or the like, moving the base 101 onto a submergible barge for example by means of self-propelled modular transporters 25 (see Fig. 6), lifting the base 101 and placing it into the water, etc. With the base 101 in the floating state, the construction method further comprises mounting the second part 1b to the first part 1a by connecting the bolted flanges 3a and 3b. The second part 1b may be lifted in place using specialized lifting equipment, such as a land-based or floating crane. This step may be carried out adjacent the land-based construction site 102, for example at a quayside of the land-based construction site 102. Alternatively, this step may be carried out away from the land-based construction site 102, such as farther offshore or at a different construction location. If the second part 1b is mounted at a different location than the land-based construction site 102, only the first part 1a may need to be transported to the land-based construction site 102. The second part 1b can be transported from the manufacturing location of the wind turbine tower 1 to the site where the second part 1b is to be mounted. After mounting the second part 1b, the construction of the floatable foundation 100 may continue by mounting further tower parts (if any). Then a nacelle may be mounted at the nacelle interface 1b’ at the top of the tower 1, as well as blades and other relevant parts of the wind turbine generator (not shown here), as would be readily appreciated by the skilled reader. Advantageously, the manufacturing location for the wind turbine tower 1 is an indoor location. The land-based construction site 102 may be an outdoor location. The manufacturing of the wind turbine tower 1 may include testing the interface between the bolted flanges 3a and 3b at the manufacturing location, prior to transporting the parts 1a,b of the wind turbine tower 1 to the relevant location(s). The testing may, for example, include high-accuracy measurements of each bolted flange 3a,3b, positioning the bolted flanges 3a,3b adjacent each other to verify a fit between these, and / or making up a temporary bolted connection between the first and second bolted flanges 3a, 3b to verify a fit between these. Optionally, in any of the examples and embodiments described or claimed herein, the flanges 3a and 3b may instead be interfaces for a welded connection between the tower parts 1a and 1b, and not bolted flanges. The construction steps, testing the interface between these, etc. may otherwise be the same as described above. Improved technology as described herein may be employed to reduce cost and for more efficient manufacturing and construction of floatable foundations for wind turbine generators, or components thereof. For example, by manufacturing the wind turbine tower 1 at a dedicated manufacturing location, a more efficient manufacturing and / or higher quality may be obtained. The manufacturing location may, for example, have specialized facilities, equipment and / or personnel for this purpose. By fixing the first part 1a to the base 101 with the base 101 on land, advantages in the construction workflow can be obtained. Disturbances due to the base 101 moving in the sea 103 is avoided for this construction step. Further, arrangement of supporting equipment, such as scaffolding and construction tools, is made easier. This may be a particular advantage for connecting components which are not manufactured at the same site, and / or by different entities, in that manufacturing inaccuracy can be easier dealt with, any adjustments which may be required can more easily be implemented. Furthermore, the interface between the wind turbine tower 1 and the base 101 is a region which will experience high loads and demanding conditions during use. Completing this interface on land can allow higher accuracies and higher construction quality. Optionally, the method may include doing an installation, completion and / or commissioning operation on electrical equipment arranged in the first part 1a, while the base 101 at the construction site 102. The electrical equipment may include cabling, cabinets and / or junction boxes for control of the wind turbine generator, for distribution of electric power produced, or for other purposes. The mounting of the first part 1a to the base 102 may advantageously be carried out with electrical equipment pre-installed in the first part 1a. The electrical equipment may, fully or partly, have been pre-installed in the first part 1a at the tower manufacturing location. Similarly as above, this may for example allow for a more efficient installation and / or improved quality, as the manufacturing location may have specialized facilities, equipment and / or personnel for this purpose. As such, the first part 1a may be transported from the tower manufacturing location to the construction site 102 with the electrical equipment at least partly pre-installed. Alternatively, or additionally, some or all of the electrical equipment can also be installed in the first part 1a after the first part 1a is mounted on the base 101 and prior to the base being moved into the floating state. Carrying out operations, for example operations relating to the connection of the first part 1a to the base 101 or operations related to electrical equipment, while the base 101 is land-based at the construction site 102 can reduces costs, as working hours are generally more expensive when carried out quayside or farther offshore. Health-and-safety risk for the construction operations can also be reduced. Mounting the second part 1b to the first part 1a can be done with bolted flanges which may be manufactured at the wind turbine tower manufacturing location, i.e. at the same site and / or by the same entity. Connecting tower parts by bolted flanges reduces the sensitivity during the mounting operation, for example sensitivity to movement in the sea 103 of the base 101, compared to for example a welding operation. Advantageously, the bolted flanges may also have been tested at the wind turbine tower manufacturing location, which can reduce the risk of operational problems during mounting. As such, the second part 1b can be lifted in place and connected to the first part 1a with reduced risk of operational problems. Examples of the present disclosure can thus allow efficient manufacturing and construction of floatable foundations for wind turbine generators, reduced risk of operational problems during construction and thus reduced project risk, and reliable interfaces particularly in fatigue-sensitive regions of the floatable foundation. The invention is not limited by the embodiments described above; reference should be had to the appended claims.

Claims

1. A method of constructing a floatable foundation (100) for a wind turbine generator, the method comprising:constructing a base (101) of the floatable foundation (100) at a land-based construction site (102), the base (101) comprising a tower interface (2);receiving a first part (1a) of a wind turbine tower (1) at the land-based construction site (102), the first part (1a) having a first bolted flange (3a) and a base interface (4), the base interface (4) configured for connection to the tower interface (2);with the base (101) located at the land-based construction site (102), fixing the first part (1a) to the base (102) by connecting the base interface (4) to the tower interface (2);moving the base (101) from the land-based construction site (102) into a floating state; andwith the base (101) in the floating state, mounting a second part (1b) of the wind turbine tower (1), the second part (1b) having a second bolted flange (3b) configured to interface with the first bolted flange (3a), to the first part (1a) by connecting the first and second bolted flanges (3a,b).

2. The method according to claim 1, wherein the step of fixing the first part (1a) to the base (102) comprises welding the base interface (4) to the tower interface (2).

3. The method according to any preceding claim, comprising:manufacturing the first and second parts (1 a, 1 b) of the wind turbine tower (1) at a manufacturing location which is spaced from the land-based construction site (102), andtransporting at least the first part (1a) from the manufacturing location to the land-based construction site (102).

4. The method according to claim 3, wherein the manufacturing location is an indoor location and / or the land-based construction site (102) is an outdoor location.

5. The method according to claim 3 or 4, comprising testing an interface between the first and second bolted flanges (3a,b) at the manufacturing location.

6. The method according to claim 5, wherein the step of testing the interface between the first and second bolted flanges (3a,b) comprises:positioning the first and second bolted flanges (3a,b) adjacent each other, such as in contact with each other, and / ormaking up a temporary bolted connection between the first and second bolted flanges (3a,b).

7. The method according to any preceding claim, wherein the first part (1a) is a tubular section having constant diameter between the base interface (4) and the first bolted flange (3a), and the second part (1b) is a tapering tubular section.

8. The method according to any preceding claim, the method comprising: with the base (101) located at the land-based construction site (102), and subsequent to the step of fixing the first part (1a) to the base (102), performing at least one of an installation, completion or commissioning operation on electrical equipment arranged in the first part (1a).

9. The method according to any preceding claim, wherein the step of fixing the first part (1a) to the base (102) is carried out with electrical equipment preinstalled in the first part (1a).

10. The method according to claim 8 or 9, comprising:pre-installing the electrical equipment in the first part (1a) at the manufacturing location, andtransporting the first part (1a) from the manufacturing location to the land-based construction site (102) with the electrical equipment pre-installed in the first part (1a).

11. A method of constructing a floatable foundation (100) for a wind turbine generator, the method comprising:constructing a base (101) of the floatable foundation (100) at a land-based construction site (102), the base (101) comprising a tower interface (2);receiving a first part (1a) of a wind turbine tower (1) at the land-based construction site (102), the first part (1a) having a first weld connection interface and a base interface (4), the base interface (4) configured for connection to the tower interface (2);with the base (101) located at the land-based construction site (102), fixing the first part (1a) to the base (102) by connecting the base interface (4) to the tower interface (2);moving the base (101) from the land-based construction site (102) into a floating state; andwith the base (101) in the floating state, mounting a second part (1b) of the wind turbine tower (1), the second part (1b) having a second weld connection interface configured to interface with the first weld connection interface, to the first part (1a) by welding the first weld connection interface to the second weld connection interface.

12. The method according to claim 11, wherein the step of fixing the first part (1a) to the base (102) comprises welding the base interface (4) to the tower interface (2).

13. The method according to claim 11 or 12, comprising:manufacturing the first and second parts (1a, 1b) of the wind turbine tower (1) at a manufacturing location which is spaced from the land-based construction site (102), andtransporting at least the first part (1a) from the manufacturing location to the land-based construction site (102).

14. The method according to claim 13, wherein the manufacturing location is an indoor location and / or the land-based construction site (102) is an outdoor location.

15. The method according to claim 13 or 14, comprising testing an interface between the first and second weld connection interfaces at the manufacturing location.

16. The method according to claim 15, wherein the step of testing the interface between the first and second weld connection interfaces comprises: positioning the first and second weld connection interfaces adjacent each other, such as in contact with each other.

17. The method according to any of claims 11-16, wherein the first part (1a) is a tubular section having constant diameter between the base interface (4) and the first bolted flange (3a), and the second part (1b) is a tapering tubular section.

18. The method according to any of claims 11-17, the method comprising: with the base (101) located at the land-based construction site (102), and subsequent to the step of fixing the first part (1a) to the base (102), performing at least one of an installation, completion or commissioning operation on electrical equipment arranged in the first part (1a).

19. The method according to any of claims 11-18, wherein the step of fixing the first part (1a) to the base (102) is carried out with electrical equipment preinstalled in the first part (1a).

20. The method according to claim 18 or 19, comprising:pre-installing the electrical equipment in the first part (1a) at the manufacturing location, andtransporting the first part (1a) from the manufacturing location to the land-based construction site (102) with the electrical equipment pre-installed in the first part (1a).Application No: GB2402785.6Examiner:Mr Robert ArnoldClaims searched: 1-10Date of search: 2 August 2024Patents Act 1977: Search Report under Section 17Documents considered to be relevant:Category Relevant to claims Identity of document and passage or figure of particular relevance X 1-10 WO 2023 / 244607 Al (TRENDSETTER VULCAN OFFSHORE INC) - See whole document, especially page 6 lines 10-14 and the figures. X 1-10 WO 2021 / 214362 Al (BLUENEWABLES S L) - See whole document, especially paragraphs 50-63 and the figures. X 1-10 JP 2018115636 A (PENTA OCEAN CONSTRUCTION CO LTD) - See whole document, especially paragraphs 44 &45 and the figures. X 1-10 CN 107575337 A (UNIV DALIAN TECH) - See whole document, especially the abstract and figures. X 1-10 US 2023 / 0392583 Al (WIJNING) - See whole document, especially paragraph 123 and the figures.Categories:X Document indicating lack of novelty or inventive step A Document indicating technological background and / or state of the art. Y Document indicating lack of inventive step if P Document published on or after the declared priority date but combined with one or more other documents of same category. before the filing date of this invention. & Member of the same patent family E Patent document published on or after, but with priority date earlier than, the filing date of this application.Field of Search:International Classification:Subclass Subgroup Valid From F03D 0013 / 25 01 / 01 / 2016Application No: GB2402785.6Examiner:Mr Robert ArnoldClaims searched: 11-20Date of search: 10 January 2025Patents Act 1977Further Search Report under Section 17Documents considered to be relevant:Category Relevant to claims Identity of document and passage or figure of particular relevance v A X v A X X 1-20 1-20 1-20 1-20 1-20 WO 2023 / 244607 Al (TRENDSETTER VULCAN OFFSHORE INC) - See whole document, especially page 6 lines 10-14 and the figures. WO 2021 / 214362 Al (BLUENEWABLES S L) - See whole document, especially paragraphs 50-63 and the figures. JP 2018115636 A (PENTA OCEAN CONSTRUCTION CO LTD) - See whole document, especially paragraphs 44 &45 and the figures. CN 107575337 A (UNIV DALIAN TECH) - See whole document, especially the abstract and figures. US 2023 / 0392583 Al (WIJNING) - See whole document, especially paragraph 123 and the figures.Categories: X Document indicating lack of novelty or inventive step A Document indicating technological background and / or state of the art. Y Document indicating lack of inventive step if combined with one or more other documents of same category. P Document published on or after the declared priority date but before the filing date of this invention. & Member of the same patent family E Patent document published on or after, but with priority date earlier than, the filing date of this application.Field of Search:Search of GB, EP, WO &US patent documents classified in the following areas of the UKCX :Worldwide search of patent documents classified in the following areas of the IPC____________F03D_____________________________________________________The following online and other databases have been used in the preparation of this search report SEARCH - PATENTInternational Classification:________________________________________________Subclass Subgroup Valid FromSubclass Subgroup Valid From F03D 0013 / 25 01 / 01 / 2016

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