Floating structures for offshore wind power generation

Abstract

A float structure (5) for offshore wind power generation comprises a float base (10) on which a wind turbine tower (1) is vertically installed and which is divided into a plurality of air chambers (11), and an air amount adjustment unit (20) which adjusts the amount of air in the air chambers (11) that are opposed to each other across the center of the float base (10). Each of the air chambers (11) comprises an open bottom portion and a soft film body (16) in slackened state that partitions the interior of the air chamber (11) into an air layer (17) and a water layer (18). Thus, the floating body structure (5) can be installed in any location, provides excellent stability, and may be suitably used for very large-scale wind power generation on the order of 20 MW or more.

Description

[Technical Field]

[0001] The present invention relates to a floating structure suitable for floating offshore wind power generation. [Background technology]

[0002] As a measure against global warming, one important initiative is to promote the use of renewable energy sources such as solar power and wind power, which do not emit carbon dioxide and do not depend on fossil fuels, in place of thermal power generation. Among wind power sources, offshore wind power generation is being promoted because it can obtain greater sustained wind power than onshore power generation and poses a lower risk of human casualties.

[0003] As shown in Figure 8, conventional offshore wind power generation can be broadly divided into two types of structures: bottom-fixed type (A) and floating types (B to E). Bottom-fixed types have a structure in which the support structure is embedded and fixed into the seabed 7. They are suitable for shallow waters where the seabed 7 has a gentle slope, and are widely used in the waters around Europe. However, bottom-fixed types have the disadvantage that installation locations are limited, as costs increase as the water depth increases and they depend on the strength of the ground, making installation difficult on soft seabed 7.

[0004] On the other hand, floating structures are tethered to the seabed7 by anchors or other mooring means. Compared to bottom-fixed structures, floating structures can be constructed in deeper waters, making them a suitable structure for offshore wind power generation in deep waters such as those around Japan. However, current floating structures have issues with their motion performance in waves and construction costs, and there is a need for further research and development.

[0005] Typical conventional floating offshore wind power generation facilities are classified into four types depending on the structure of the float: B. Barge type, C. Semi-submersible type, D. Tension leg platform (TLP) type, and E. Spar type.

[0006] The spar type E is a columnar structure with a center of gravity located lower than the center of the floating body, which gives it stability (see, for example, Patent Document 1). The construction process is simple, there are few moving parts, and the construction cost is lower than other types of structures. However, there are issues with assembly, transportation, and handling during installation, and the installation of large wind turbines is limited to deep waters. In addition, due to their deep draft, they cannot return to port for major repairs.

[0007] The semi-submersible type C is a semi-submersible structure consisting of multiple columns and horizontal members connecting them, with the float submerged to a specified draft (see, for example, Patent Document 2). Because the portion of the float near the sea surface 6 is small, it is relatively prone to tilting, but is less susceptible to the effects of waves and can be used in places with severe wave conditions. It is a float type suitable for installation offshore. Large-scale renovations are possible around ports. However, the structure requires mass to provide sufficient buoyancy and stability, and there are many members connected by welding, making processing difficult due to the complex structure, which increases construction costs.

[0008] The TLP type D is a structure that uses tension to moor a floating structure and a submerged structure on the seabed 7 (see, for example, Patent Document 3). Tension mooring places a large load on the mooring anchors, and the mooring force fluctuates greatly, making the installation process difficult and often requiring a custom-made installation vessel. It relies on the strength of the ground to be firmly supported by the foundation on the seabed 7. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] International Publication No. 2020 / 209728 [Patent Document 2] International Publication No. 2017 / 220878 [Patent Document 3] International Publication No. 2015 / 000909 Summary of the Invention [Problem to be solved by the invention]

[0010] As mentioned above, both fixed-bottom offshore wind turbines and floating offshore wind turbines have problems such as limited installation locations, stability in rough waves, and construction costs.

[0011] The present invention aims to solve the above problems and to provide a floating structure that is not limited by installation location, has excellent stability in rough waves, and is suitable for use in ultra-large wind turbines of 20 MW or more. [Means for solving the problem]

[0012] In order to solve the above-mentioned problems, the present invention provides a floating structure for offshore wind power generation that supports a wind turbine tower, wherein the floating structure has a structure in which the wind turbine tower is On the top It was erected, The bottom is released Multiple air chambers On the interior wall and air volume adjustment units that adjust the volume of air in the air chambers, the air volume adjustment units being opposed to each other across the center of the floating body base. Multiple The air chamber is Air chamber The inside is divided into an air layer and a water layer flexible membrane body of each The membrane is bonded to the inner wall of the air chamber in a relaxed state so as to follow the waveform between the air layer and the water layer. Adopt the configuration.

[0013] In an embodiment of the air volume adjustment unit for the floating structure for offshore wind power generation, the air volume adjustment unit is configured to have an air passage that connects the opposing air chambers and an on-off valve that opens and closes the communication of the air passage, and the air volume adjustment unit is configured to further have a blower provided in the air passage, and the on-off valve is configured to detect the pressure difference between the opposing air chambers and connect the air passages when the pressure difference exceeds a predetermined value.

[0014] Furthermore, as an embodiment of the floating foundation of the floating structure for offshore wind power generation, the floating foundation is configured to have a flat upper wall, a peripheral wall extending downward from the periphery of the upper wall, and partition walls hanging down from the upper wall and dividing the interior of the peripheral wall into a plurality of air chambers, the floating foundation is configured to have the wind turbine tower erected near the center, the floating foundation is configured to have a cavity formed near the center, the floating foundation is configured to have spare buoyancy units on the periphery or on the top surface, the floating foundation is configured to have a turret-type single-point mooring unit, and the air chamber is configured to have an extrusion prevention member that prevents the membrane body from protruding from the bottom. [Effects of the Invention]

[0015] By adopting the above-described configuration, the floating structure for offshore wind power generation of the present invention can reduce rocking caused by waves and tilting caused by strong winds, and a stable floating structure can be constructed at low cost.

[0016] Furthermore, the floating structure for offshore wind power generation of the present invention does not depend on the strength of the seabed ground and can be installed in relatively shallow waters, so it can be used in a wider range than conventional floating structures for offshore wind power generation. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic diagram showing an embodiment of a floating offshore wind power generation facility. FIG. [Figure 2] FIG. 2 is a schematic diagram showing the assembly structure of the floating structure of the embodiment. [Figure 3] 1A and 1B are diagrams showing the appearance of a floating structure according to an embodiment, in which (a) is a top view and (b) is a bottom view. [Figure 4] FIG. 2 is a schematic cross-sectional view taken along the line AA in FIGS. 3(a) and 3(b). [Figure 5] 1A and 1B are schematic diagrams showing the rocking state of a floating structure according to an embodiment of the present invention, in which (a) shows the case where the wavelength of the waves is equal to or less than the total length of the floating base, and (b) shows the case where the wavelength of the waves exceeds the total length of the floating base. [Figure 6]Schematic diagram showing an embodiment of single-point mooring, (a) when moored, and (b) when the floating structure is moving. [Figure 7] 1 is a schematic diagram showing the use state of an offshore wind power generation facility that employs the floating structure of the present invention. FIG. [Figure 8] FIG. 1 is a schematic diagram showing a type of conventional offshore wind power generation. DETAILED DESCRIPTION OF THE INVENTION

[0018] Next, a specific embodiment of the floating structure for offshore wind power generation of the present invention will be described with reference to the drawings.

[0019] In Figure 1, reference numeral 1 denotes a wind turbine tower for wind power generation, which is supported by an upright tower 2 and has blades 4 that rotate around a hub (rotor) 3; 5 denotes a floating structure that floats on the sea surface 6 and supports the wind turbine tower 1 from near the center using a support structure 9; and 30 denotes a turret-type single-point mooring unit that moored the floating structure 5 to the seabed 7 with a mooring line 8.

[0020] 2 to 4, the floating structure 5 includes a floating base 10 having the tower 2 erected on its upper surface and partitioned into a plurality of air chambers 11 with open bottoms, and air volume adjustment units 20 that adjust the volume of air in the air chambers 11 that face each other across the center of the floating base 10. In this embodiment, the wind turbine tower 1 is erected near the center of the floating base 10, but the wind turbine tower 1 may be erected at a position other than near the center of the floating base 10 as necessary.

[0021] The floating base 10 comprises a flat upper wall 12 on which the tower 2 is erected near the center, a peripheral wall 13 extending downward from the periphery of the upper wall 12 and surrounding the space below from the periphery of the upper wall 12, and a partition wall 14 hanging down the same length as the length from the underside of the upper wall 12 to the lower end of the peripheral wall 13 and dividing the interior of the peripheral wall 13 into multiple air chambers 11a to 11h.

[0022] Air chambers 11a to 11h are divided into multiple compartments with open bottoms, and membrane 16 made of a flexible material is attached in a relaxed state to the inside of peripheral wall 13 and partition wall 14, dividing them into air layer 17 and water layer 18. Here, the flexible material is a material such as polyester or polypropylene, and has the ability to follow the waveform between air layer 17 and water layer 18. Note that membrane 16 does not need to be attached to peripheral wall 13 and partition wall 14 in an airtight manner, and it is acceptable for a small amount of air or water to enter or exit due to breakage, etc.

[0023] In this embodiment, the floating base 10 has an upper wall 12 with a square planar shape, and the inside of the peripheral wall 13 is divided into eight air chambers 11a to 11h by partition walls 14, but the planar shape of the upper wall 12 may be a circle or a regular polygon, and the air chamber 11 may be divided into an appropriate number of chambers depending on the planar shape of the upper wall 12. Furthermore, the floating base 10 may be formed by creating a plurality of floating modules, each having an air chamber 11 with an open bottom, and joining and arranging a plurality of the floating modules around the tower 2.

[0024] Furthermore, in order to increase the floating base 10's stability when it is subject to significant rocking due to high waves or strong winds, spare buoyancy units 15 (four in this embodiment) are provided on the outer periphery of the peripheral wall 13, and spare watertight compartments (spare buoyancy units) 15a (four in this embodiment) are provided on the upper surface of the upper wall 12, but these spare buoyancy units 15 and 15a can be provided as needed.

[0025] Since the membrane body 16 follows the waveform, the joints of the peripheral edge are joined in a relaxed state to the peripheral wall 13 and the partition wall 14, which are the inner walls of the air chamber 11, so if the inclination angle of the floating base 10 is large, there is a risk that part of the membrane body 16 will protrude from the bottom of the air chamber 11. Therefore, to deal with the membrane body 16 protruding, a grid member 19 can be installed at the bottom of the air chamber 11 as a protrusion prevention member.

[0026] As shown in Figures 4 and 5, the floating structure 5 is equipped with an air volume adjustment unit 20 that adjusts the amount of air in the air chambers 11 facing each other across the center of the floating base 10, and includes an air passage 21 that connects the opposing air chambers 11a and 11e, an on-off valve 22 that opens and closes the communication of the air passage 21, a blower 23 provided in the air passage 21, and a pressure sensor 24 that detects the pressure in each of the opposing air chambers 11a and 11e.

[0027] As shown in Figures 2 and 3(a), in this embodiment, the air passage 21 that constitutes the air amount adjusting unit 20 is arranged to connect opposing air chambers 11a and 11e with air chambers 11c and 11g, but instead, the air passage 21 may be arranged to connect opposing air chambers 11b and 11f with air chambers 11d and 11h, or further, for air chambers 11a to 11h, the air passage 21 may be arranged to connect all opposing air chambers 11 together.

[0028] The air amount adjusting unit 20 is configured to detect the pressures in the air chambers 11a and 11e using the pressure sensor 24, and to close the on-off valve 22 when the detected pressure difference between the air chambers 11a and 11e is within a predetermined value, and to open the on-off valve 22 when the detected pressure difference between the air chambers 11a and 11e exceeds the predetermined value. Furthermore, the blower 23 assists in sending air from the air chamber 11 with the higher pressure to the air chamber 11 with the lower pressure through the air passage 21 when the on-off valve 22 is open. The air passage 21 is made of a material and has a shape that provides low airflow resistance.

[0029] As shown in Figures 3(b) and 4, the single-point mooring unit 30 is installed in the center of a cavity 31 surrounded by multiple air chambers 11a to 11h formed in the floating base 10, and adopts a turret type that prevents the floating structure 5 from drifting by single-point mooring. In this embodiment, the single-point mooring unit 30 is installed in the cavity 31 of the floating base 10, but this is not limited thereto, and the mooring unit 30 may be installed in any one of the multiple air chambers 11 of the floating base 10.

[0030] The single-point mooring unit 30 is connected to the inside of the bulkhead 14 that forms the inner circumferential surface of the cavity 31 and is composed of a ball bearing 32 that rotatably supports the floating foundation 10, and a cylindrical column 33 that is removably held on the inner periphery of the ball bearing 32 and connected to the mooring line 8. In addition, the upper part of the cavity 31 is provided with a support structure 9 on which the tower 2 is erected.

[0031] A locking mechanism 34 is installed on the upper surface of the upper wall 12 arranged around the single-point mooring unit 30. The locking mechanism 34 engages with a cylindrical column 33 to prevent the floating foundation 10 from rotating around the single-point mooring unit 30, preventing the floating foundation 10 from rotating around the single-point mooring unit 30 due to tidal currents or wind force. The single-point mooring unit 30 is rigidly connected to the bulkhead 14 arranged around the cavity 31 by beams or the like (not shown).

[0032] Next, the manner of use and the effects of this embodiment will be described. The floating structure 5 of this embodiment is constructed at a shipyard or the like, and the upper wall 12, peripheral wall 13 and bulkhead 14 of the floating base 10 can be manufactured using steel material, FRP (fiber reinforced plastic), reinforced concrete, etc.

[0033] Next, a single-point mooring unit 30 is installed in the cavity 31 via a beam or the like (not shown), and the tower 2 is erected on the top surface of the floating foundation 10. After that, blades 4 that rotate around the hub 3 are placed on top of it, completing the floating offshore wind power generation equipment, which is then towed by a work boat to the sea area where it is to be installed.

[0034] When the floating structure 5 arrives at the planned installation area, as shown in Figure 6(a), the floating structure 5 is single-point moored by a mooring line 8. At this time, the floating structure 5 is single-point moored to the seabed 7 by a single-point mooring unit 30, so there is no risk of the mooring line 8 becoming tangled.

[0035] Furthermore, in the event of an emergency such as a typhoon, the floating structure 5 can be evacuated by detaching the cylindrical column 33 from the single-point mooring unit 30 and towing the floating structure 5 to a safe location, as shown in Figure 6(b).

[0036] Next, measures to prevent the floating structure 5 from tilting due to waves will be described below with reference to FIG.

[0037] (1) When the wavelength is relatively short (normal) As shown in Figure 5(a), when the wavelength is sufficiently short compared to the overall length L of the floating foundation 10, the air amount adjustment unit 20 detects the pressure in the opposing air chambers 11a and 11e using the pressure sensor 24, and since the detected pressure difference between the air chambers 11a and 11e is within a predetermined value, it closes the on-off valve 22, preventing air from passing (moving) between the opposing air chambers 11a and 11e through the air passage 21. In this case, the effect of improving stability against steady wind pressure is achieved.

[0038] (2) When the wavelength approaches the total length L and reaches twice the total length L When the wavelength approaches the total length L of the floating base 10, the air volume control unit 20 detects the pressure in the opposing air chambers 11a and 11e using the pressure sensor 24, and the pressure difference between the detected air chambers 11a and 11e exceeds a predetermined value, so the opening / closing valve 22 opens, and air between the opposing air chambers 11a and 11e becomes easier to move through the air passage 21.

[0039] As shown in Figure 5(b), when a wave crests in the left air chamber 11a, the air in the air chamber 11a on the upper side of the wave (left side) is compressed by the wave, and the air in the air chamber 11a is pushed up by the wave pressure, facilitating the air movement to the air chamber 11e on the lower side of the wave (right side) as indicated by the arrow through the air passage 21. If the air movement speed is insufficient at this time, the blower 23 installed in the air passage 21 operates to assist the air flow and adjust the air flow speed. Conversely, when a wave trough reaches the left air chamber 11a, the air flow also moves in the opposite direction.

[0040] (3) When the wavelength is quite long When large waves with wavelengths sufficiently exceeding the total length L of the floating base 10 arrive, the air amount adjustment unit 20 opens the on-off valve 22 and also operates the blower 23, allowing the air between the opposing air chambers 11a and 11e to move quickly through the air passage 21. At this time, as in (2), when the crest of the wave reaches the left air chamber 11a, the air in the air chamber 11a on the upper side of the wave (left side) is compressed by the wave, and the air in that air chamber 11a moves through the air passage 21, operating the blower 23, to the air chamber 11e on the lower side of the wave (right side).

[0041] With this operation, the overturning moment caused by the upward wave force on the upper side of the wave (left side) is offset by the righting moment caused by the increased air on the lower side of the wave. Conversely, when the wave trough reaches the left air chamber 11a, the blower 23 operates in the opposite direction to quickly move the air flow in the opposite direction, and this time the overturning moment caused by the upward wave force on the lower side of the wave is suppressed by the increased air on the upper side of the wave, thereby reducing the inclination angle.

[0042] However, when waves with a fairly long wavelength are subjected to a steady load or force, if the opposing air chambers 11 are connected via the air passage 21, the floating body will be in the same state as a single inflatable floating body, and from the standpoint of stability, if strong winds continue to blow for a long period of time, the inclination angle of the floating base 10 will gradually increase, and there is a risk that the floating base 10 will capsize. Therefore, in such a case, the air amount adjustment unit 20 must close the on-off valve 22 and stop the blower 23, so that air cannot pass between the opposing air chambers 11 through the air passage 21.

[0043] As described above, the floating structure 5 of this embodiment has high static stability and can be equipped with ultra-large wind turbine towers of 20 MW or more, with turbine diameters of 250 to 300 m, as shown in Fig. 1. Furthermore, as shown in Fig. 7, the floating structure 5 of this embodiment does not depend on the strength of the seabed 7 and can be installed in relatively shallow waters, so it can be used in a wider range than conventional floating structures for offshore wind power generation. Furthermore, it can be used to generate power using marine energy such as wave power generation and tidal power generation, or can be used in combination with wind power generation, and is expected to be used for a variety of purposes. [Industrial Applicability]

[0044] Expanding the use of renewable energy sources such as wind power is one of the important measures to combat global warming. Offshore wind power generation, among other types of wind power generation, is being actively promoted because it can sustainably generate greater wind power than onshore wind power generation and poses a lower risk of human casualties. Experiments have shown that this invention has high stability even when equipped with next-generation ultra-large wind turbines (approximately 250-300m in height). In the future, we plan to conduct experiments on a scale close to full-scale and consider practical application. If the floating structure of this invention is put into practical use, it will be possible to install it not only in Japan but also in various ocean areas around the world. [Explanation of symbols]

[0045] A implantation type B Barge type C Semi-submersible type D Tension Leg Platform (TLP) type E-spar type L Total length of floating foundation 1. Windmill Tower 2. Tower 3 Hub (rotor) 4 blades 5 Floating structures 6 sea level 7 Undersea 8 Mooring lines 9 Support structure 10 Floating Foundation 11, 11a~11h air chamber 12 Upper wall 13 Peripheral wall 14 Bulkhead 15 Spare Buoyancy Unit 15a Spare watertight compartment (spare buoyancy unit) 16 Membrane body 17, 34 Air layer 18 Water layer 19 Grid member (anti-extension member) 20 Air volume control unit 21 Air passage 22 On-off valve 23 Blower 24 Pressure Sensor 30 Single Point Mooring Unit 31 Cavity 32 ball bearings 33 Cylindrical column 34 Locking mechanism

Claims

1. A floating structure for offshore wind power generation that supports a wind turbine tower, The floating structure comprises a floating base having the wind turbine tower erected on an upper surface and divided by inner walls into a plurality of air chambers with open bottoms, and air volume adjustment units that adjust the volume of air in the air chambers facing each other across the center of the floating base, Each of the plurality of air chambers has a flexible membrane that separates the air chamber into an air layer and a water layer, The membrane body is joined to the inner wall of the air chamber in a relaxed state so that it can follow the waveform between the air layer and the water layer.

2. 2. The floating structure for offshore wind power generation according to claim 1, wherein the air amount adjustment unit has an air passage that connects the opposing air chambers, and an on-off valve that opens and closes the communication of the air passage.

3. The floating structure for offshore wind power generation according to claim 2 , wherein the air amount adjustment unit further comprises a blower provided in the air passage.

4. 3. The floating structure for offshore wind power generation according to claim 2, wherein the on-off valve detects a pressure difference between the opposing air chambers, and opens the air passages when the pressure difference exceeds a predetermined value.

5. A floating structure for offshore wind power generation as described in Claim 3, wherein the opening / closing valve detects the pressure difference between the opposing air chambers and opens the air passages when the pressure difference exceeds a predetermined value.

6. 2. The floating structure for offshore wind power generation according to claim 1, wherein the floating foundation has a flat upper wall, a peripheral wall extending downward from a periphery of the upper wall, and partition walls hanging down from the upper wall and dividing the interior of the peripheral wall into a plurality of air chambers.

7. 3. The floating structure for offshore wind power generation according to claim 2, wherein the floating foundation has a flat upper wall, a peripheral wall extending downward from a periphery of the upper wall, and partition walls hanging down from the upper wall and dividing the interior of the peripheral wall into a plurality of air chambers.

8. 4. The floating structure for offshore wind power generation according to claim 3, wherein the floating foundation has a flat upper wall, a peripheral wall extending downward from a periphery of the upper wall, and partition walls hanging down from the upper wall and dividing the interior of the peripheral wall into a plurality of air chambers.

9. 5. The floating structure for offshore wind power generation according to claim 4, wherein the floating foundation has a flat upper wall, a peripheral wall extending downward from a periphery of the upper wall, and partition walls hanging down from the upper wall and dividing the interior of the peripheral wall into a plurality of air chambers.

10. A floating structure for offshore wind power generation as described in Claim 5, wherein the floating base has a flat upper wall, a peripheral wall extending downward from the periphery of the upper wall, and partition walls hanging down from the upper wall and dividing the interior of the peripheral wall into multiple air chambers.

11. The floating structure for offshore wind power generation described in Claim 1 has the wind turbine tower erected near the center of the floating base.

12. The floating structure for offshore wind power generation described in Claim 2 has the wind turbine tower erected near the center of the floating base.

13. The floating structure for offshore wind power generation described in Claim 3 has the wind turbine tower erected near the center of the floating base.

14. The floating structure for offshore wind power generation described in Claim 4 has the wind turbine tower erected near the center of the floating base.

15. The floating structure for offshore wind power generation described in Claim 5 has the wind turbine tower erected near the center of the floating base.

16. The floating structure for offshore wind power generation described in Claim 6 has the wind turbine tower erected near the center of the floating base.

17. The floating structure for offshore wind power generation described in Claim 7 has the wind turbine tower erected near the center of the floating base.

18. A floating structure for offshore wind power generation as described in Claim 8, in which the floating base has the wind turbine tower erected near the center.

19. A floating structure for offshore wind power generation as described in Claim 9, in which the floating base has the wind turbine tower erected near the center.

20. A floating structure for offshore wind power generation as described in Claim 10, in which the floating base has the wind turbine tower erected near the center.

21. A floating structure for offshore wind power generation described in any one of claims 1 to 20, wherein the floating base has a cavity formed near the center.

22. A floating structure for offshore wind power generation described in any one of claims 1 to 20, wherein the floating base has a spare buoyancy unit around or on its upper surface.

23. A floating structure for offshore wind power generation as described in Claim 21, wherein the floating base has spare buoyancy units around or on its top surface.

24. A floating structure for offshore wind power generation described in any one of claims 1 to 20, wherein the floating base has a turret-type single-point mooring unit.

25. A floating structure for offshore wind power generation as described in Claim 21, wherein the floating base has a turret-type single-point mooring unit.

26. A floating structure for offshore wind power generation as described in Claim 22, wherein the floating base has a turret-type single-point mooring unit.

27. ​​A floating structure for offshore wind power generation as described in Claim 23, wherein the floating base has a turret-type single-point mooring unit.

28. A floating structure for offshore wind power generation described in any one of claims 1 to 20, wherein the air chamber has an anti-extension member that prevents the membrane body from protruding from the bottom.

29. A floating structure for offshore wind power generation as described in Claim 21, wherein the air chamber has an anti-extension member that prevents the membrane body from protruding from the bottom.

30. A floating structure for offshore wind power generation as described in Claim 22, wherein the air chamber has an anti-extension member that prevents the membrane body from protruding from the bottom.

31. A floating structure for offshore wind power generation as described in Claim 23, wherein the air chamber has an anti-extension member that prevents the membrane body from protruding from the bottom.

32. A floating structure for offshore wind power generation as described in Claim 24, wherein the air chamber has an anti-extension member that prevents the membrane body from protruding from the bottom.

33. A floating structure for offshore wind power generation as described in Claim 25, wherein the air chamber has an anti-extension member that prevents the membrane body from protruding from the bottom.

34. A floating structure for offshore wind power generation as described in Claim 26, wherein the air chamber has an anti-extension member that prevents the membrane body from protruding from the bottom.

35. A floating structure for offshore wind power generation as described in Claim 27, wherein the air chamber has an anti-extension member that prevents the membrane body from protruding from the bottom.

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