JP7492283B1 - Method for constructing bottom-fixed offshore mounting system, bottom-fixed offshore mounting system, and offshore wind power generation device - Google Patents

Abstract

[Problem] To stably support a support part in an independent position even in an environment exposed to strong winds such as typhoons. [Solution] A bottom-mounted offshore platform 9 includes a steel base part 1 placed on the seabed and loaded with a granular weight 5, a support part 2 formed of a steel pipe whose lower end is connected to the base part 1 and placed in the sea in an up-down position with its upper end protruding above the sea, and a mooring mechanism 7 for suppressing the swinging of the support part 2. The base part 1 includes a bottom plate part 11, a socket cylinder part 12, a plurality of fixed wall parts 13, a peripheral wall part 14 forming an accommodation part 4 for the granular weight 5 on the inside, and a plurality of fixed wall parts 16, and is held in a fixed position by the granular weight 5 loaded on the accommodation part 4, and holds the support part 2 connected to the socket cylinder part 12 in a vertical position. The mooring mechanism 7 includes a plurality of ropes 70 that extend radially in a plan view and are connected to the outer periphery of the base 1, and a tension adjustment mechanism 71 that adjusts the tension of the ropes 70. The ropes 70 tensioned between the support 2 and the base 1 suppress the rocking of the support 2. [Selected Figure]

Description

The present invention relates to a bottom-fixed offshore mounting system that is installed on the ocean and a method for constructing the same, and an offshore wind power generation system, and in particular to a bottom-fixed offshore mounting system that is suitable for construction in sea areas with a water depth of 40 m to 120 m and can maintain a stable, self-supporting posture even in strong winds such as those caused by typhoons and a method for constructing the same, and an offshore wind power generation system equipped with a bottom-fixed offshore mounting system.

With the recent depletion of petroleum resources, renewable energy sources such as solar energy are attracting attention. However, solar power generation is subject to large fluctuations due to weather and cannot generate electricity at night, so wind power generation is attracting attention as an alternative renewable energy source. Wind power generation has been criticized for issues such as low-frequency noise near residential areas, so to avoid these issues, attention is being paid to installing wind power generation facilities offshore.

Offshore wind turbine power generation devices are broadly classified into floating types and fixed (bottom-mounted) types based on the method of installing an offshore mounting system for installing a wind turbine (see Patent Documents 1 to 3).
An offshore wind turbine equipped with a floating mounting system can be installed in waters with a depth of a given depth or more, for example, 100m or more, and since it is used floating on the sea surface, it is possible to mass-produce wind turbines with the same specifications. However, in the case of floating wind turbines, the mounting system itself needs to be large, which increases the manufacturing cost of each unit, resulting in poor profitability. In addition, it is difficult to install floating wind turbines in waters with a depth of 100m or less.

In contrast, offshore wind power generation equipment with fixed mounting systems has the advantage that the foundation is installed on the seabed, so the wind power generation equipment can be stably supported. However, various problems arise depending on the type of mounting system used and the water depth of the sea area where the equipment is installed. For example, wind power generation equipment with monopile-type mounting systems is preferably used in sea areas with a water depth of 35m or less. Monopile-type mounting systems have the lower end of a single metal pipe fixed to the seabed and support the wind power generator placed on the upper end that protrudes above the sea surface, reducing manufacturing costs. However, monopile-type mounting systems have the problem that they become unprofitable when the water depth is 35m or more, as manufacturing costs become high.

For this reason, wind power generation equipment equipped with a jacket-type mounting system consisting of a tower (steel tower) assembled with a steel frame is preferably used in sea areas with a water depth of 40 m or more. In this way, a jacket-type mounting system consisting of a steel tower has the characteristic of being less susceptible to the effects of waves. In addition, since the manufacturing technology for jacket-type mounting systems is established, like steel towers used for oil mining, it can be manufactured to accommodate a certain degree of water depth (for example, 40 m or more). However, wind power generation has a problem of low profitability compared to oil mining, making it less profitable. In particular, a jacket-type mounting system requires a thick and long anchor to be driven deep underground to fix the bottom end of the steel tower to the seabed, which makes the installation cost extremely high. In addition, since the jacket-type mounting system is manufactured with a steel frame, its useful life is short at about 25 years and it cannot be used for a long period of time, so in order to maintain the wind power generation system, it is necessary to replace the jacket, which further worsens the profitability.

JP 2016-113996 A JP 2005-180239 A JP 2003-206852 A JP 2017-203305 A

Furthermore, Patent Document 4 discloses a foundation for an offshore facility as a bottom-mounted foundation. The foundation for the offshore facility described in this publication includes a bottom plate installed on the seabed, a girder part having a steel girder member fixed integrally with the bottom plate part, a filler material arranged on the bottom plate part so as to be freely separated from the bottom plate part, a steel pipe support column rising from the bottom plate part, the lower end of the tower of the offshore facility being connected to the upper end of the steel pipe support column, one end of the steel girder member being joined to the lower side of the steel pipe support column, and a side wall part standing integrally on the outer periphery side from the bottom plate part. The foundation of this structure includes a side wall part standing around the bottom plate part fixed integrally to the steel pipe support column via the steel girder member, and the upper end of the steel pipe support column is placed on the seabed with the bottom plate part installed on the seabed and the filler material arranged freely separable on the bottom plate part being filled and placed on the seabed.

However, the above foundation has a drawback in that the bottom plate is made of reinforced concrete, and therefore takes time to manufacture. This is because it takes time for the concrete to harden after pouring the concrete with the formwork in place. For this reason, this foundation cannot be constructed in a short time, and there is a problem that the cost of construction cannot be reduced. This publication also states that the bottom plate may be made of steel. However, if the bottom plate is made of steel, the overall weight becomes lighter, and there is a problem that it cannot be sunk to the bottom of deep water. In particular, this bottom plate is integrally connected to the bottom plate by using the lower end of the steel pipe support as a weight, so that a hollow part is formed inside the steel pipe support. When attempting to sink the foundation of this structure to the bottom of the sea, it can be sunk in shallow water, but as the water becomes deeper, there is a problem that it cannot be sunk smoothly to the bottom of the sea because the buoyancy acting on the hollow support increases. In particular, if the bottom plate is made of steel, the weight becomes even lighter and it cannot be sunk to the bottom of deep water. For this reason, while the foundations described in this publication can be implemented in waters with a depth of 40m or less, they cannot be effectively used in waters with a depth of 40m or more.

In particular, in recent years, wind turbines with a generating capacity of 10 MW or more are becoming mainstream, and the foundations that support these large wind turbines require steel pipe supports with larger outer diameters. The problem is that steel pipe supports with larger outer diameters have even greater buoyancy, making them difficult to use in deeper waters.

As described above, the current situation is that no effective technology has yet been established for mounting wind turbines in waters 40 to 120 meters deep. In particular, in Japan, which has a long coastline and many steeply deep coastal areas, there are many mid-water areas that are suitable for wind conditions, and there is an urgent need to commercialize and popularize a highly economical method for use in these waters.

Furthermore, in recent years, offshore wind power generation equipment equipped with large wind power generators capable of generating 10 MW or more, which are becoming mainstream, requires the installation of large wind power generators with a height of 100 to 150 m on an offshore rack that protrudes above the water surface, and therefore the installation of such large wind power generators needs to be stably supported by the offshore rack. In particular, offshore racks installed in the sea are not only affected by ocean swells and tidal currents, but can also be exposed to strong winds with wind speeds of over 20 m/s and strong waves when a typhoon approaches. In particular, typhoons have tended to become stronger in recent years, sometimes with strong winds of over 40 m/s, which may have a negative impact on large wind power generators installed offshore. Therefore, it is important that offshore wind power generation equipment is designed so that large wind power generators installed on the sea surface can stably maintain a specified posture even when exposed to strong winds and waves caused by typhoons, etc.

The present invention was made in consideration of the above problems, and one of its objectives is to provide a bottom-mounted offshore platform that can be constructed in sea areas with a water depth of 40 to 120 meters, shortens the construction period and reduces manufacturing and installation costs, and can stably support the support column in an independent position even in environments exposed to strong winds such as typhoons, as well as a method for constructing the platform and an offshore power generation device.

Means for solving the problem and effects of the invention

A bottom-mounted offshore platform according to an embodiment of the present invention is a bottom-mounted offshore platform for installing a wind power generator on the ocean, and includes a steel base portion that is placed on the ocean floor in a fully submerged state and on which granular weights are loaded, a support portion formed of a cylindrical steel pipe whose lower end is connected to the base portion and that is placed in the ocean in a vertically extended position so that its upper end protrudes above the ocean, and a mooring mechanism that suppresses the swinging of the support portion. The base portion includes a bottom plate portion that is placed on the ocean floor, a socket cylinder portion that is fixed to the center of the bottom plate portion and into which the lower end of the support portion is inserted and connected, a plurality of fixed wall portions that are fixed to the side surface of the socket cylinder portion and the upper surface of the bottom plate portion to fix the socket cylinder portion to the bottom plate portion, a peripheral wall portion that is erected along the outer periphery of the bottom plate portion and forms an accommodation portion for the granular weights on the inside, and a plurality of fixed wall portions that are fixed to the inner side surface of the peripheral wall portion and the upper surface of the bottom plate portion to fix the peripheral wall portion to the bottom plate portion. The base is held in a fixed position by a granular weight loaded in the storage section, and is configured to hold the support section connected to the socket tube section in a vertical position. The mooring mechanism includes a plurality of ropes extending radially in a plan view from the upper end of the support section and having their tips connected to the outer periphery of the base section, and a tension adjustment mechanism for adjusting the tension of the ropes, and the plurality of ropes stretched between the support section and the base section suppress oscillation of the support section . The mooring mechanism includes a winder disposed at the upper end of the support section for winding up the ropes, and the winder serves as the tension adjustment mechanism.

The above-mentioned configuration has the advantage that the support column can be stably supported in an independent position even in an environment exposed to strong winds such as typhoons while the support column is placed in a vertical position relative to the base placed on the seabed. This is because the above-mentioned bottom-mounted offshore platform is equipped with a mooring mechanism for suppressing the swaying of the support column, which includes multiple ropes extending radially from the upper end of the support column in a plan view and connected to the outer periphery of the base, and a tension adjustment mechanism for adjusting the tension of the ropes, and the swaying of the support column is suppressed by the multiple ropes stretched between the support column and the base. In this way, in a structure in which multiple ropes are radially arranged in a plan view and stretched between the upper end of the support column and the outer periphery of the base, when the support column tilts in one direction, the tilting of the support column is suppressed by the tension acting on the ropes arranged in the opposite direction. Therefore, the support column can be stably supported in an independent position even in an environment exposed to strong winds such as typhoons.

Furthermore , with the above-described configuration, the tension of the rope can be easily adjusted by adjusting the winding state of the winder.

In another aspect of the present invention, the bottom-mounted offshore platform has a mooring mechanism that includes a fixing portion that is fixed to the peripheral wall of the base and to which the tip of the rope is connected, and this fixing portion can be a protruding piece that protrudes outward from the peripheral wall. According to the above configuration, the tip of the rope is connected to a protruding piece that protrudes outward from the peripheral wall of the base, so that the connection portion between the base and the rope can be located away from the support column, and the angle of inclination of the rope with respect to the vertical direction can be increased, allowing the tension of the rope to be effectively applied to the support column.

A bottom-mounted offshore platform according to another aspect of the present invention is a bottom-mounted offshore platform for installing a wind power generator on the ocean, and includes a steel base portion that is placed on the ocean floor in a fully submerged state and on which granular weights are loaded, a support portion formed of a cylindrical steel pipe whose lower end is connected to the base portion and that is placed in the ocean in a vertically extended position so that its upper end protrudes above the ocean, and a mooring mechanism that suppresses the swinging of the support portion. The base portion includes a bottom plate portion that is placed on the ocean floor, a socket tube portion that is fixed to the center of the bottom plate portion and into which the lower end of the support portion is inserted and connected, a plurality of fixed wall portions that are fixed to the side surface of the socket tube portion and the upper surface of the bottom plate portion to fix the socket tube portion to the bottom plate portion, a peripheral wall portion that is erected along the outer periphery of the bottom plate portion and forms a storage portion for the granular weights on the inside, and a plurality of fixed wall portions that are fixed to the inner side surface of the peripheral wall portion and the upper surface of the bottom plate portion to fix the peripheral wall portion to the bottom plate portion. The base is held in a fixed position by a granular weight loaded in the storage section, and is configured to hold the support section connected to the socket tube section in a vertical position. The mooring mechanism includes a plurality of ropes extending radially in a plan view from the upper end of the support section and having their tips connected to the outer periphery of the base section, and a tension adjustment mechanism for adjusting the tension of the ropes, and the plurality of ropes stretched between the support section and the base section suppresses rocking of the support section. The mooring mechanism includes intermediate rollers fixed to the side surfaces of the support section and along which intermediate portions of the ropes are guided, and the ropes located above the intermediate rollers are arranged in a position along the side surfaces of the support section, and the ropes located below the intermediate rollers are arranged in an inclined position away from the support section. According to the above configuration, the rope is tensioned in a state where the middle portion of the rope is guided by the middle roller provided on the side at the upper end of the support section. By positioning the rope close to the support section above the middle roller, safety around the support section near the sea surface is ensured, while by connecting the rope to the base section in an inclined position away from the support section below the middle roller, the inclination angle of the rope with respect to the vertical direction is increased and the tension of the rope can be effectively applied to the support section.

A bottom-mounted offshore platform according to another aspect of the present invention is a bottom-mounted offshore platform for installing a wind power generator on the ocean, and includes a steel base portion that is placed on the ocean floor in a fully submerged state and on which granular weights are loaded, a support portion formed of a cylindrical steel pipe whose lower end is connected to the base portion and that is placed in the ocean in a vertically extended position so that its upper end protrudes above the ocean, and a mooring mechanism that suppresses the swinging of the support portion. The base portion includes a bottom plate portion that is placed on the ocean floor, a socket tube portion that is fixed to the center of the bottom plate portion and into which the lower end of the support portion is inserted and connected, a plurality of fixed wall portions that are fixed to the side surface of the socket tube portion and the upper surface of the bottom plate portion to fix the socket tube portion to the bottom plate portion, a peripheral wall portion that is erected along the outer periphery of the bottom plate portion and forms a storage portion for the granular weights on the inside, and a plurality of fixed wall portions that are fixed to the inner side surface of the peripheral wall portion and the upper surface of the bottom plate portion to fix the peripheral wall portion to the bottom plate portion. The base is held in a fixed position by a granular weight loaded in the storage section, and is configured to hold the support section connected to the socket tube section in a vertical position. The mooring mechanism includes a plurality of ropes extending radially in a plan view from the upper end of the support section and having their tips connected to the outer periphery of the base section, and a tension adjustment mechanism for adjusting the tension of the ropes, and the plurality of ropes stretched between the support section and the base section suppresses rocking of the support section. The mooring mechanism includes a sub-tension adjustment mechanism for adjusting the tension of the ropes, and the sub-tension adjustment mechanism can include a tilting arm having one end connected to the outer periphery of the base section and arranged so as to be tiltable in a vertical plane, and a weight section fixed to the other end of the tilting arm. When the support column is in a vertical position, this sub-tension adjustment mechanism tensions the rope with a predetermined tension via the tilting arm, which is in a descending position due to the weight of the weight, and when the support column tilts in any direction from the vertical position, the rope arranged on the opposite side to the tilting direction of the support column pulls the tilting arm, causing the tilting arm to tilt to an ascending position against the weight of the weight. Furthermore, the tilting arm has a stopper that stops the tilting at a predetermined ascending position, and when the tilting arm tilts to the predetermined ascending position, the tilting arm is stopped via the stopper, thereby preventing the tilting of the support column.

A method for constructing a bottom-mounted offshore platform according to one embodiment of the present invention is a method for constructing a bottom-mounted offshore platform for installing a wind power generator on the ocean. This construction method includes a steel base part that is installed on the ocean bottom in a completely submerged state and on which granular weights are loaded, the base part including a bottom plate part installed on the ocean bottom, a cylindrical socket part fixed to the center part of the bottom plate part and into which a lower end of a support part is inserted and connected, a plurality of fixed wall parts fixed to the side surface of the cylindrical socket part and the upper surface of the bottom plate part to fix the cylindrical socket part to the bottom plate part, a peripheral wall part erected along the outer periphery of the bottom plate part to form a storage part for the granular weights on the inside, and a plurality of fixed wall parts fixed to the inner side surface of the peripheral wall part and the upper surface of the bottom plate part to fix the peripheral wall part to the bottom plate part, a support part formed of a cylindrical steel pipe and having a total length such that an upper end protrudes above the ocean when its lower end is connected to the base part installed on the ocean bottom, a predetermined amount of granular weights loaded on the storage part, and a base part including a support part that suppresses the swinging of the support part. The mooring mechanism includes a preparation step of preparing a mooring mechanism including a plurality of ropes extending radially from the upper end of the support column in a plan view and connected at their ends to the outer periphery of the base, and a tension adjustment mechanism for adjusting the tension of the ropes, the ropes being arranged at the upper end of the support column and winding up the ropes, a transport step of transporting the base, the support column, the granular weights, and the mooring mechanism to the ocean in a construction area of the bottom-mounted offshore platform, a foundation formation step of forming a foundation with a leveled upper surface on the seabed surface of the construction area, a foundation installation step of sinking the base into the seabed and installing it on the foundation, a support installation step of sinking the support column into the sea in a vertical position and inserting and connecting the lower end of the support column into the socket tube of the base installed on the seabed, and a loading step of loading the granular weights into the storage part of the base. Furthermore, in the base installation step, the ropes are let out while the base is suspended via the plurality of ropes, so that the base is lowered to the seabed.

According to the above method, in the foundation installation process in which the foundation is installed on the seabed, the foundation is suspended using multiple ropes of the mooring mechanism, and the ropes are let out to lower the foundation to the seabed, which has the advantage that the foundation can be safely and reliably lowered and installed in an accurate position on the foundation. In other words, by effectively utilizing the ropes of the mooring mechanism that suppress the rocking of the support column, the foundation can be reliably lowered to a fixed position on the seabed. In this way, the method of using ropes when lowering the foundation connects the ends of the ropes to the foundation in advance in the process prior to lowering the foundation, so that the ropes can be easily and reliably connected and fixed to the foundation placed on the seabed.

An offshore wind power generation device equipped with a bottom-mounted offshore mounting base according to one embodiment of the present invention includes any of the bottom-mounted offshore mounting bases described above and a wind power generator installed at the upper end of the support column.

1 is a schematic front view, partially in section, of an offshore wind turbine generator according to a first embodiment of the present invention. FIG. 2 is a schematic front view, partially in section, of the bottom-mounted offshore rack for the offshore wind power generation apparatus shown in FIG. 1 . FIG. 3 is an enlarged cross-sectional view of the bottom-fixed offshore rack shown in FIG. 2 . FIG. 4 is an enlarged sectional perspective view of the bottom-fixed offshore rack shown in FIG. 3 . FIG. 4 is a perspective view of a base portion of the bottom-fixed offshore platform shown in FIG. FIG. 11 is a perspective view showing another example of the base portion. FIG. 11 is a perspective view showing another example of the base portion. FIG. 4 is a perspective view showing an example of a fixing portion. FIG. 9 is a front view of the fixing portion shown in FIG. 8 . FIG. 2 is a front view showing an example of a winding machine. FIG. 4 is a side view illustrating an example of an intermediate roller. 12 is a partially sectional plan view of the intermediate roller shown in FIG. 11 . FIG. 13 is a partial cross-sectional front view showing another example of a mooring mechanism. FIG. 13 is a partial cross-sectional side view showing an example of a sub tension adjustment mechanism, illustrating a lowered position of a tilting arm. FIG. 13 is a partial cross-sectional side view showing an example of a sub tension adjustment mechanism, illustrating a raised position of a tilting arm. FIG. 2 is a process diagram showing a method for constructing a bottom-fixed offshore platform according to one embodiment of the present invention.

Prior to the present invention, the inventor developed a bottom-fixed offshore mounting system and a method for constructing the same that can be constructed in sea areas with a water depth of 40 to 120 m, shorten the construction period, and reduce manufacturing and installation costs. This bottom-fixed offshore mounting system is a bottom-fixed offshore mounting system for installing wind turbines offshore, and includes a steel base section that is placed entirely submerged on the seabed at a water depth of 40 to 120 m, a support column section with a total length of 50 m or more that is submerged in the sea with seawater flowing into it, its lower end connected to the base section on the seabed, and is placed in the sea in an extended position in the vertical direction with its upper end protruding above the sea, and a storage section for storing granular weights to be loaded on the base section. The base comprises a bottom plate that is installed on the seabed, a cylindrical socket that is fixed to the center of the bottom plate and into which the lower end of the support is inserted and connected, a number of fixed walls that are fixed to the side of the cylindrical socket and the top of the bottom plate to fix the cylindrical socket to the bottom plate, and a peripheral wall that stands along the outer periphery of the bottom plate and forms a storage section on the inside. The base is held in a fixed position by granular weights loaded on the storage section, and is configured to hold the support connected to the cylindrical socket in a vertical position.

The method for constructing a bottom-mounted offshore platform is a steel base on which granular weights are loaded when the platform is installed entirely submerged on the seabed at a depth of 40 to 120 meters, the base comprising a bottom plate installed on the seabed, a cylindrical socket part fixed to the center of the bottom plate and into which the lower end of the support part is inserted and connected, a plurality of fixed walls fixed to the side surface of the cylindrical socket part and the upper surface of the bottom plate to fix the cylindrical socket part to the bottom plate, and a peripheral wall erected along the outer periphery of the bottom plate to form a storage part for the granular weights on the inside, and a cylindrical steel pipe with its lower end connected to the base part installed on the seabed. The process includes a preparation step for preparing a support section having a full length with its upper end protruding above sea level, and a predetermined amount of granular weights to be loaded into the storage section; a transportation step for transporting the base section, support section, and granular weights to the sea level in the construction area of the bottom-mounted offshore platform; a foundation formation step for forming a foundation section with a leveled upper surface in a horizontal plane on the seabed surface of the construction area; a foundation installation step for sinking the base section into the seabed and installing it on the foundation section; a support installation step for sinking the support section into the sea in a vertical position and inserting and connecting the lower end of the support section into the socket tube of the base section installed on the seabed; and a loading step for loading the granular weights into the storage section of the base section.

In the above bottom-mounted offshore platform, the base placed on the seabed has a tube socket in the center of the bottom plate into which the lower end of the support column made of steel pipe is inserted, and the lower end of the support column is inserted into the tube socket to connect the base and base, so the base and support columns can be manufactured and transported separately, reducing manufacturing and transportation costs. In addition, during installation, the base and support columns can be submerged separately in the sea and connected while suppressing the adverse effects of the water depth of the construction area, making installation easier, shortening the construction period, and reducing construction costs. In addition, by making the base out of steel, the labor and time required for manufacturing the base can be reduced compared to conventional structures in which the foundation is constructed out of concrete, and the manufacturing costs of the base can be significantly reduced. Furthermore, the base is held in place by the weight of the granular weights when they are loaded into a storage section formed on the inside of a peripheral wall section that stands along the outer periphery of the bottom plate, and the support section is held in a vertical position. By transporting the base and the granular weights separately, transportation costs can be reduced, while the advantage of being able to easily transport and load even a large number of granular weights can be realized.

According to the above construction method, after the foundation part with a socket tube part in the center of the bottom plate part is installed on the seabed, the support part made of steel pipe is submerged in the sea and the lower end part of the support part is inserted into the socket tube part and connected to the foundation part. By submerging the foundation part and the support part in the sea in separate processes, the foundation part and the support part can be quickly submerged and installed in a fixed position while suppressing the adverse effects caused by the water depth of the construction area. In particular, by manufacturing the foundation part and the support part as separate members, the time and cost required for manufacturing and transportation can be reduced, and the construction period can be shortened and costs can be reduced. Furthermore, by making the foundation part out of steel, the labor and time required for manufacturing the foundation part can be reduced compared to the conventional structure in which the foundation is constructed from concrete, and the manufacturing cost of the foundation part can be significantly reduced. Furthermore, the base is held in place by the weight of the granular weights when they are loaded into the storage section formed inside the peripheral wall, and the support section is held in a vertical position. By transporting the base and the granular weights separately, transportation costs can be reduced, and even a large number of granular weights can be easily transported and loaded.

The fixed-bottom offshore rack and the construction method described above can be constructed in sea areas with a water depth of 40 to 120 m, and have the advantage of being able to shorten the construction period and reduce manufacturing and installation costs. However, in this type of fixed-bottom offshore rack, a large wind turbine with a generating power of 10 MW or more and a height of 100 to 150 m is installed, so it is important that the offshore rack stably supports such a large wind turbine. In particular, offshore racks installed in the sea are not only affected by ocean swells and tidal currents, but can also be exposed to strong winds with wind speeds of over 20 m/s when a typhoon approaches. Therefore, it is important that such large wind turbines installed on the sea surface are designed to be able to stably maintain a specified posture even when exposed to strong winds caused by typhoons, etc. The present invention was developed to solve these problems.

The following describes an embodiment of the present invention based on the drawings. However, the following embodiment is an example for embodying the technical idea of the present invention, and the present invention is not specified below. In addition, this specification does not specify the members shown in the claims to the members of the embodiment. In particular, the dimensions, materials, shapes, and relative positions of the components described in the embodiment are not intended to limit the scope of the present invention, and are merely explanatory examples, unless otherwise specified. Note that the size and positional relationship of the components shown in each drawing may be exaggerated to clarify the explanation. Furthermore, in the following explanation, the same name and symbol indicate the same or similar parts, and detailed explanation will be omitted as appropriate. Furthermore, each element constituting the present invention may be configured with the same member so that multiple elements are used by one member, or conversely, the function of one member may be shared by multiple members.

The bottom-fixed offshore rack of the present invention is a rack for installing a wind power generator on the ocean to generate wind power, and is primarily a rack for installing a wind power generator on the ocean with a water depth of 40m to 120m. However, the bottom-fixed offshore rack can also be used to install a wind condition observation device that measures wind condition data for wind power generation.

(Embodiment 1)
Fig. 1 is a schematic front view in partial section showing an installation state of an offshore wind power generation device 100 in which a wind power generator 6 is installed on a bottom-fixed offshore platform 9 according to embodiment 1. Figs. 2 to 5 are views showing the bottom-fixed offshore platform 9 of the offshore wind power generation device 100 shown in Fig. 1, in which Fig. 2 is a schematic front view in partial section, Figs. 3 and 4 are enlarged sectional views and enlarged sectional perspective views showing a connection structure between a base part 1 and a support part 2, and Fig. 5 is a perspective view of the base part 1. The bottom-fixed offshore platform 9 shown in these figures includes a base part 1 placed on the seabed and loaded with granular weights 5, a support part 2 whose lower end is connected to the base part 1 and whose upper end is extended in the vertical direction so as to protrude above the sea, and a mooring mechanism 7 that suppresses the swinging of the support part 2.

(Base part 1)
The base 1 includes a bottom plate 11 that is installed on the seabed, a socket cylinder 12 that is fixed to the center of the bottom plate 11 and into which the lower end 2B of the support 2 is inserted and connected, a plurality of fixed wall portions 13 that are fixed to the side surface of the socket cylinder 12 and the upper surface of the bottom plate 11 to fix the socket cylinder 12 to the bottom plate 11, a peripheral wall portion 14 that is erected along the outer periphery of the bottom plate 11 and forms a storage portion 4 for storing the granular weight 5 inside, and a plurality of fixed wall portions 16 that are fixed to the inner side surface of the peripheral wall portion 14 and the upper surface of the bottom plate 11 to fix the peripheral wall portion 14 to the bottom plate 11. The base 1 includes the bottom plate 11, the socket cylinder 12, the fixed wall portions 13, 16, and the peripheral wall portion 14 that are made of steel. Specifically, the base 1 is formed into a predetermined shape by cutting and joining a plurality of steel plates. In this way, a structure in which the base 1 is made of steel has the advantage that it can drastically reduce the time required for manufacturing and reduce manufacturing costs compared to conventional structures in which concrete is used to manufacture the base.

The bottom plate portion 11 is a flat steel plate having a predetermined area. The bottom plate portion 11 is, for example, formed of a plurality of steel plates connected together to have a predetermined area and shape. The bottom plate portion 11 is placed on the upper surface of the foundation portion 3 formed on the seabed and arranged in a fixed position. The bottom plate portion 11 is formed to have a sufficiently large area so that it can support the support portion 2 connected to the center portion in a vertical position in an upright position when placed on the seabed at a depth of 40 to 120 m. The bottom plate portion 11 can stably support the support portion 2 by, for example, having a maximum outer diameter of 25 m or more, preferably 30 m or more. However, if the bottom plate portion 11 is too large, the manufacturing cost and transportation cost will increase and the foundation portion 3 formed on the seabed will need to be widened, so the maximum outer diameter is set to 65 m or less, preferably 50 m or less. In addition, the thickness of the steel plate of the bottom plate portion 11 is set to 1 to 5 cm, for example 2 to 3 cm, so that it has sufficient strength.

The bottom plate portion 11 shown in Figure 5 is rectangular with sides measuring 30m to 45m, and has a square outer shape. However, the bottom plate portion 11 can also be rectangular, circular as shown in Figure 6, or polygonal as shown in Figure 7. The bottom plate portion 11 shown in Figure 7 is a regular octagon. Note that in a circular bottom plate portion 11, the diameter is the maximum outer diameter, and in a polygonal bottom plate portion 11, the maximum diagonal is the maximum outer diameter.

The socket cylinder 12 is formed of a steel peripheral wall 12A formed into a substantially cylindrical shape, and is fixed in the center of the upper surface of the bottom plate 11 in an upwardly opening position. The socket cylinder 12 has an inner shape that conforms to the outer peripheral surface of the lower end 2B of the support 2 so that the lower end 2B of the support 2 can be inserted inside. The socket cylinder 12 shown in the figure has a shape with a tapered section 12X whose inner shape gradually becomes larger toward the top, that is, the inner shape of the tapered section 12X conforms to the side of an inverted truncated cone, and the lower end 2B of the support 2 has a tapered shape whose outer shape gradually becomes smaller toward the bottom end, making it easier to insert the support 2 of this shape. In particular, the socket cylinder 12 shown in FIG. 3 is designed so that the outer peripheral surface of the lower end 2B of the support 2 is connected in a fitting structure in which the outer peripheral surface of the lower end 2B of the support 2 is in close contact with the inner peripheral surface of the socket cylinder 12 when the lower end 2B of the support 2 is inserted into the tapered section 12X and the lower end of the support 2 abuts against the bottom plate 11. In this way, the inner shape of the cylindrical socket portion 12 is shaped to match the outer shape of the lower end portion 2B of the support portion 2, and the two are connected in a fitted state, which has the advantage that the lower end portion 2B of the support portion 2 can be easily and reliably guided into the cylindrical socket portion 12 and connected without gaps. However, the lower end portions of the cylindrical socket portion and the support portion do not necessarily need to have a tapered shape to fit together, and can also be cylindrical to fit together.

The thickness of the peripheral wall 12A of the socket tube portion 12 is set to 3 cm to 10 cm, preferably 4 cm to 8 cm, so that the socket tube portion 12 can stably support the support portion 2 with the lower end portion 2B of the cylindrical support portion 2 inserted inside. The height of the peripheral wall 12A of the socket tube portion 12 is greater than the outer diameter of the support portion 2, for example, 1.2 to 2 times the outer diameter of the support portion 2. The socket tube portion 12 can stably support the support portion 2 by increasing the height and thickness of the peripheral wall 12A. However, since the manufacturing costs of the socket tube portion 12 increase when the peripheral wall 12A is made higher and thicker, the thickness is preferably set to the aforementioned range.

The socket cylinder 12 is fixed to the bottom plate 11 via a plurality of fixed walls 13. The fixed walls 13 shown in the figure are made by cutting a steel plate into a predetermined shape, a substantially trapezoidal rectangle in the figure, and the bottom edge is fixed to the upper surface of the bottom plate 11, and one side edge is fixed to the outer peripheral surface of the peripheral wall 12A, which is the side of the socket cylinder 12, to fix the socket cylinder 12 in a fixed position on the bottom plate 11. The side edge fixed to the side of the socket cylinder 12 is fixed by extending in the axial direction of the socket cylinder 12, and the fixed wall 13 is fixed so as to be in a vertical upright position relative to the bottom plate 11. The base 1 shown in the figure fixes the socket cylinder 12 to the bottom plate 11 via a plurality of fixed walls 13 extending radially from the outer peripheral surface of the socket cylinder 12 arranged in the center of the bottom plate 11. In this way, the structure in which the tubular socket portion 12 is fixed to the bottom plate portion 11 via multiple fixed walls 13 arranged radially from the tubular socket portion 12 can distribute the force acting from the support portion 2 to the tubular socket portion 12, achieving excellent strength.

The fixed wall portion 13 is preferably joined to the bottom plate portion 11 and the socket tube portion 12 by welding. By increasing the area of the fixed wall portion 13, lengthening the joint portion with the bottom plate portion 11, and lengthening the joint portion with the socket tube portion 12, the connection strength between the socket tube portion 12 and the bottom plate portion 11 can be increased, and by increasing the thickness of the fixed wall portion 13, strength against load and stress can be increased. For example, the thickness of the fixed wall portion 13 is 1 cm to 3 cm, the joint length with the bottom plate portion 11 is 1/5 or more, preferably 1/4 or more, of the maximum outer diameter of the bottom plate portion 11, and the joint length with the socket tube portion 12 is 1/3 or more, preferably 1/2 or more, of the height of the socket tube portion 12.

The peripheral wall 14 is erected along the outer periphery of the bottom plate 11, and forms a storage section 4 for loading the granular weight 5 inside. The base 1 shown in Figures 5 to 7 has a peripheral wall 14 along the outer periphery of the bottom plate 11, which has a planar shape equal to the outer shape of the bottom plate 11. The peripheral wall 14 shown in Figure 5 is a peripheral wall having a predetermined height and a square shape in plan view. The peripheral wall 14 having a square shape in plan view is formed into a predetermined shape by joining multiple steel plates having a predetermined length and width in the length direction and joining them at right angles at the corners. The peripheral wall 14 shown in Figure 6 is a peripheral wall having a predetermined height and a circular planar shape. The peripheral wall 14 having a circular shape in plan view is formed by bending multiple steel plates having a predetermined length and width with a predetermined radius of curvature and joining and connecting the multiple steel plates to each other to form a circular shape. The peripheral wall 14 shown in Figure 8 is a peripheral wall having a predetermined height and a regular octagonal shape in plan view. The peripheral wall 14, which has a regular octagonal shape in plan view, is formed into a predetermined shape by joining multiple steel plates of a predetermined length and width at the corners at a predetermined angle.

The height of the peripheral wall 14 determines the volume of the storage section 4 formed inside, so its height is determined taking into consideration the weight required for the base 1, in other words, so that the total weight of the granular weights 5 filled in the storage section 4 is optimal. The peripheral wall 14 is, for example, equal to or less than the height of the socket tube 12, and may be, for example, 4m to 10m, and preferably 5m to 8m. However, the total weight of the granular weights filled and loaded in the storage section varies not only with the volume of the storage section, but also with the density of the granular weights, so the height of the peripheral wall 14 is determined taking these factors into consideration.

The base 1 shown in Figures 5 to 7 has a peripheral wall 14 that is erected along the outer periphery of the bottom plate 11 and is fixed to the bottom plate 11 by welding. The base 1 shown in Figures 5 to 7 has an outer shape of the bottom plate 11 that is slightly larger than the outer shape of the peripheral wall 14, and has a flange 15 that protrudes outward. This allows the peripheral wall 14 to be firmly joined to the bottom plate 11, for example, by welding both the inner and outer boundary portions of the lower edge to the bottom plate 11. In this way, the structure in which the peripheral wall 14 is welded to the bottom plate 11 around the entire periphery can connect the peripheral wall 14 and the bottom plate 11 in a watertight manner, giving the entire base 1 a box-like appearance with an opening at the top. After being manufactured in a factory, the base 1 with this structure can be towed to a construction area while the entire base 1 is floating above the sea level. This has the advantage of reducing the effort, time, and transportation costs required for transportation.

Furthermore, the peripheral wall 14 shown in Figs. 5 to 7 is fixed to the bottom plate 11 via a plurality of fixed walls 16 arranged along the inside. This allows the peripheral wall 14 to be more firmly fixed to the bottom plate 11 in a vertical position. The fixed walls 16 are preferably joined to the peripheral wall 14 and the bottom plate 11 by welding. The fixed walls 16 can be increased in area, lengthened at their joints with the peripheral wall 14, and lengthened at their joints with the bottom plate 11 to increase the connection strength between the peripheral wall 14 and the bottom plate 11, and the thickened fixed walls 16 can increase the strength against loads and stresses due to the tension of the rope 70 of the mooring mechanism 7 described later. Therefore, the fixed walls 16 fixed to the peripheral wall 14 are provided at a plurality of locations, including a location facing a fixed portion 25 fixed to the outer circumferential surface of the peripheral wall 14 to connect the rope 70 described later. For example, the thickness of the fixed wall portion 16 is 1 cm to 3 cm, the joint length with the peripheral wall portion 14 is at least 1/2, preferably at least 2/3 of the height of the peripheral wall portion 14, and the joint length with the bottom plate portion 11 is at least 1/2, preferably at least 2/3 of the height of the peripheral wall portion 14.

As described above, the structure in which multiple fixed walls 13 are provided radially around the socket tube 12, or multiple fixed walls 16 are provided inside the peripheral wall 14 and protrude inward, has the feature that the fixed walls 13, 16 divide the storage section 4 into multiple partitioned areas 4A, and the granular weight 5 loaded in the storage section 4 is prevented from moving around the socket tube 12 or along the inner circumference of the peripheral wall 14, so that the granular weight 5 can be stably held in a fixed position. Here, the base 1 shown in FIG. 7 has a fixed wall 13 for fixing the socket tube 12 to the bottom plate 11 and a fixed wall 16 for fixing the peripheral wall 14 to the bottom plate 11 as an integral structure to form a single fixed plate 17. In this way, the base 1 in which the fixed wall 13 and the fixed wall 16 are integrally formed can fix the entire peripheral wall 14 to the bottom plate 11 more firmly. In addition, the storage section 4 can be reliably divided into multiple partitioned areas 4A by the multiple fixing plates 17 that connect the socket tube section 12 and the peripheral wall section 14. Furthermore, in FIG. 7, the tips of the eight fixing plates 17 that extend diagonally from the polygonal peripheral wall section 14 are extended to the inner peripheral surface of the corners of the peripheral wall section 14, so that the peripheral wall section 14 can be positioned and arranged in a fixed position via these fixing plates 17.

Furthermore, the base 1 shown in FIG. 7 has an intermediate wall 18 in the middle of the fixing plate 17 extending radially from the socket tube 12. The base 1 shown in the figure has an intermediate wall 18 in the shape of a ring in a plan view between the socket tube 12 and the peripheral wall 14, and further divides the partitioned area 4A surrounded by the socket tube 12, the peripheral wall 14, and the adjacent fixing plate 17 into two divided areas 4B, one inside and one outside. This structure has the feature that by further dividing the partitioned area 4A formed on the inside of the peripheral wall 14 into a plurality of divided areas 4B, the granular weight 5 can be prevented from moving in the radial direction of the support 2 within the partitioned area 4A, and the granular weight 5 stored in the storage section 4 can be stably held in a fixed position. Although not shown, the base 1 shown in FIG. 5 or FIG. 6 can also have an intermediate wall 18 between the socket tube 12 and the peripheral wall 14. This intermediate wall portion is fixed in a state in which it connects adjacent fixed wall portions 13 to each other, or connects adjacent fixed wall portions 16 to each other.

The base 1, which is placed on the seabed, is held in a fixed position by the granular weights 5 loaded in the storage section 4, but the granular weights 5 placed in the sea are subject to the effects of tidal currents and earthquake tremors. If the granular weights 5 move due to the effects of tidal currents or earthquakes, causing the balance of the entire granular weights 5 loaded in the storage section 4 to be lost, there is a risk that the base 1 will no longer be able to stably support the support section 2. In response to this, a structure that divides the storage section 4 into multiple areas with the fixed walls 13, 16 (fixed plate 17) and intermediate wall 19 can suppress the movement of the granular weights 5 inside the storage section 4, achieving the characteristic of being able to stably hold the base 1 for a long period of time.

(Support part 2)
As shown in Figs. 1 and 2, the support column 2 is a column extending in the vertical direction, and is arranged in the sea in a vertical position with its lower end connected to the base 1 installed on the seabed 50 and its upper end protruding above the sea. The support column 2 is formed of a cylindrical steel pipe, and has a total length with its upper end protruding above the sea while its lower end is connected to the base 1 installed on the seabed. The support column 2 shown in Figs. 1 and 2 connects the lower end 2B of the main body 2A arranged in the sea to the base 1, and fixes the wind power generator 6 to the upper end of the protruding part 2C protruding above the sea surface. The support column 2 is arranged in a position with its upper end protruding 10 m to 15 m above the sea surface. Therefore, the total length of the support column 2 is set to be 10 m to 15 m longer than the water depth at the installation site. For example, in a bottom-fixed offshore platform 9 to be installed in an ocean area with a water depth of 80 m, the overall length of the support section 2 is 90 to 95 m, with the upper end protruding 10 to 15 m above the sea surface.

The support column 2 is designed to have an optimal outer diameter, taking into consideration the strength required to stably support the wind power generator 6 installed at the upper end. The outer diameter of the support column 2 is also changed depending on the specifications of the buoyancy generator 6 to be installed on the support column 2 and the water depth of the sea area where the bottom-mounted offshore rack 9 is installed. For example, as shown in FIG. 1, the support column 2 that is installed in a sea area with a water depth of 40 m to 120 m and supports a wind power generator 6 with a power generation capacity of 10 MW to 15 MW can be stably supported by increasing the outer diameter. As an example, in a bottom-mounted offshore rack 9 installed in a sea area with a water depth of 50 m to 100 m, the outer diameter of the support column 2 can be 5 m to 15 m, preferably 6 m to 12 m. Furthermore, the thickness of the support column 2 is, for example, the thickness of the steel pipe that constitutes it, and is, for example, 3 cm to 10 cm, preferably 4 cm to 8 cm.

The support column 2 shown in Figs. 1 and 2 is formed of a cylindrical steel pipe having a predetermined outer diameter. Although not shown, the support column 2 formed of a cylindrical steel pipe is formed to a predetermined length by connecting multiple steel pipes. The support column 2 is formed by connecting multiple steel pipes, for example, with a length of 10 m to several tens of meters, to a predetermined total length. The opposing ends of each steel pipe are connected by welding, or flanges that protrude outward along the ends are provided, and the opposing flanges are connected via connectors, thereby connecting the multiple steel pipes in a straight line to a predetermined total length. However, the length of the steel pipes used and the number of pipes to be connected can be changed in various ways. In this way, the structure in which the support column 2 is formed of multiple steel pipes has the characteristic that it can be simply and easily manufactured while reducing manufacturing costs by using existing steel pipes. The support column 2 formed of multiple steel pipes is structured so that the entire interior of the steel pipe is a single cavity, and seawater is allowed to enter the interior when the support column 2 is submerged in the sea. This allows even long support columns 2 to be quickly lowered and installed in the sea, regardless of the water depth of the construction area.

The support section 2, which is lowered vertically into the sea, is connected by inserting its lower end into the socket tube section 12 of the base section 1 installed on the seabed. As described above, the socket tube section 12 shown in Figures 3 and 4 has a tapered section 12X whose inner shape gradually becomes larger toward the top, so that the lower end section 2B of the support section 2 has a tapered shape whose outer shape gradually becomes smaller toward the bottom end, and its outer circumferential surface is shaped to follow the side of an inverted truncated cone. In particular, the support section 2 shown in Figure 3 is connected by a fitting structure in which the outer circumferential surface of the lower end section 2B of the support section 2 is in close contact with the inner circumferential surface of the socket tube section 12 when the lower end section 2B is inserted into the socket tube section 12 and the lower end abuts against the bottom plate section 11. In this way, the outer shape of the lower end 2B of the support part 2 is shaped to fit the inner shape of the socket tube part 12, and the structure is such that they are connected in a fitted state, which has the advantage that the lower end 2B of the support part 2 can be easily and reliably guided into the socket tube part 12 and connected without gaps. However, the lower end of the support part can also be cylindrical without being tapered, and inserted into the cylindrical socket tube part.

As described above, when the base 1 is installed on the seabed, the support 2, whose lower end 2B is inserted into the socket tube 12, is stably connected by its outer peripheral surface being in close contact with the inner peripheral surface of the socket tube 12. Furthermore, the connection between the support 2 and the socket tube 12 can be fixed by filling it with underwater concrete 20 as shown in FIG. 3. Here, since the support 2 is connected to the socket tube 12 underwater, the inside of the support 2 is filled with seawater. Therefore, the concrete filled inside the connection between the socket tube 12 and the support 2 is underwater concrete 20. The underwater concrete 20 is, for example, pumped from offshore through a pipe and filled inside the lower end 2B of the support 2.

Figures 3 and 4 show the connection between the lower end 2B of the support 2 and the socket tube 12 of the base 1. Figure 3 shows a cross-sectional view of the state in which the inside of the lower end 2B of the support 2 is filled with underwater concrete 20, and Figure 4 shows an exploded cross-sectional perspective view of the internal structure of the support 2 and the socket tube 12 that are connected to each other. The base 1 and support 2 shown in these figures have a first anchor 21 and a second anchor 22 that are embedded in the underwater concrete 20, and the base 1 and support 2 are more firmly fixed via the first anchor 21 and the second anchor 22 that are embedded in the underwater concrete 20.

The base 1 has a first anchor 21 that is embedded in the underwater concrete 20 in the center of the socket tube 12. The first anchor 21 is provided in the center of the socket tube 12 in a position that protrudes upward from the bottom plate 11. The first anchor 21 in the figure is made by combining multiple steel beams in a well shape, and is fixed to the bottom plate 11 so that it protrudes a predetermined height from the upper surface of the bottom plate 11 via the steel beams that serve as supporting materials. This first anchor 21 is provided in a position that does not interfere with the lower end 2B of the support 2 that is inserted into the socket tube 12.

The support section 2 is provided with a second anchor section 22 buried in the underwater concrete 20 inside the lower end 2B. The second anchor section 21 is provided at the lower end 2B of the support section 2 in a position that protrudes inward from the inner surface. The second anchor section 21 in the figure is a combination of multiple steel frames formed by connecting the opposing inner surfaces of the lower end of the support section 2 to each other in a well shape, and is provided in multiple stages up and down. This second anchor section 22 is also provided in a position that does not interfere with the first anchor section 21 provided inside the socket tube section 12 when the lower end 2B of the support section 2 is inserted into the socket tube section 12. According to the above structure, the first anchor section 21 and the second anchor section 22 are buried in the underwater concrete 20 filled inside the socket tube section 12 with the lower end 2B of the support section 2 inserted. This allows the base section 1 and the lower end 2B of the support section 2 to be reliably fixed. Furthermore, the structure in which underwater concrete 20 is filled inside the lower end 2B of the support section 2 has the advantage that the underwater concrete 20 acts as a weight to position the center of gravity of the support section 2 downward, allowing the support section 2 to be more stably maintained in a vertical position.

The first anchor portion 21 and the second anchor portion 22 shown in the figure are only one example, and are not limited to the above structure. The first anchor portion 21 and the second anchor portion 22 can be any other structure that can be embedded in the underwater concrete 20 to fix the base portion 1 and the support portion 2 to the underwater concrete 20. Furthermore, the first anchor portion 21 and the second anchor portion 22 can have rebars arranged in both or either one of them to fix the base portion 1 and the support portion 2 more firmly as reinforced concrete.

Furthermore, the support section 2 can be partially hollow in order to stably hold it in a vertical position. The support section 2 made of a cylindrical steel pipe can have a hollow area in the main body section 2A placed in the sea to form a hollow section 23. The support section 2 can have a hollow section 23 in the upper part of the support section 2, for example, by draining the seawater inside the upper part of the main body section 2A placed in the sea. This structure can easily provide a hollow section 23 in the upper part of the support section 2 by sucking up and draining a part of the seawater filled in the support section 2 with a suction mechanism such as a pump. In this way, the support section 2 equipped with the hollow section 23 can reduce the weight relative to the buoyancy by making the inside hollow, and can effectively increase the buoyancy, so the load acting on the base section 1 can be reduced. For example, in the support section 2 made of a steel pipe with a thickness of 6 cm and an outer diameter of about 6 m, a load of more than 500 t can be reduced by draining 20 m of seawater from the sea surface. Furthermore, by providing a hollow section 23 at the top of the support section 2, the center of gravity of the support section 2 can be positioned at a lower position relative to the center of buoyancy, which is the center of the buoyancy acting on the support section 2, and this has the advantage that the support section 2, which is positioned to extend in the vertical direction, can be stably maintained in a vertical position.

(Granular weight 5)
As described above, the base 1 installed on the seabed has the lower end of the support 2 inserted into the socket tube 12 to be connected, and the granular weight 5 is loaded and held in a fixed position. The base 1 has a storage section 4 formed inside the peripheral wall 14 to store the granular weight 5. The granular weight 5 filled in the storage section 4 is a weight formed into granules of a predetermined size, and for example, gravel, crushed stone, ore, slag, etc. can be used. The granular weight 5 is preferably iron ore or slag. When the granular weight 5 is iron ore, the specific gravity is high at about 3.4, so that sufficient weight can be secured while reducing the volume. In addition, since the iron that flows out from the iron ore becomes a nutrient for seaweed, there is also an effect of improving the growth environment of surrounding organisms. In addition, when the granular weight is slag, the manufacturing cost can be reduced while effectively utilizing slag that is generated in large quantities as waste.

The granular weight 5 has an outer diameter of 100 mm or less, preferably 60 mm or less. The granular weight 5 is either gravel, crushed stone, ore, or slag. In particular, for crushed stone, ore, and slag, the above outer diameter has the advantage of making it easy to fill the storage section 4. In addition, when removing the granular weight 5, it can be efficiently sucked and removed using a suction device such as a suction or underwater sand pump. In particular, the suction device can easily suck and transport granular gravel, crushed stone, ore, slag, etc. with an outer diameter of several centimeters by transporting the slurry using a water transport method.

(Platform 24)
The platform 24 is an installation stand for placing the wind power generator 6 at a predetermined position on the ocean, and is fixed in a horizontal position to the upper end of the support column 2 that is disposed so that its upper end protrudes above the ocean. The platform 24 is disposed in a horizontal position, and the wind power generator 6 is mounted on the upper surface. Furthermore, in addition to the wind power generator 6, various monitoring devices and various observation devices can also be mounted on the platform 24. Examples of such devices include bird radars, surveillance cameras, weather radars for meteorological observation, and wind condition observation devices such as wind vanes, wind gauges, and anemometers.

(Mooring mechanism 7)
The mooring mechanism 7 comprises a plurality of ropes 70 extending radially in a planar view from the upper end of the support portion 2 and having their tips connected to the outer periphery 14 of the base portion 1, and a tension adjustment mechanism 71 for adjusting the tension of these ropes 70.

(Rope body 70)
The cord 70 is made of wire, rope, chain, or other wire material. The wire material used for the cord 70 has a strength that will not break even when the support part 1 is pulled when the support part 1 is subjected to strong winds or rough waves due to a typhoon or the like. As such a cord 70, a high-strength wire, a synthetic fiber rope, a metal chain, or the like can be used. In the mooring mechanism 7, a plurality of cords 70 are arranged radially in a plan view in order to suppress tilting of the support part 2 in all directions. Each cord 70 is stretched between the upper end of the support part 2 and the outer periphery of the base part 1, and the tension of the cords pulls the upper part of the support part 2 outward to hold the support part 2 in a vertical position. The plurality of cords 70 arranged radially are arranged at equal intervals and are stretched so that the tension is uniform, thereby suppressing tilting in any direction. In the mooring mechanism shown in the figure, four cords are arranged extending in all directions at equal intervals. However, the number of cords 70 can be 3 to 16, preferably 3 to 8.

(Fixed portion 25)
The mooring mechanism 7 includes a fixing portion 25 that is fixed to the peripheral wall portion 14 of the base portion 1 and to which the tip of the rope 70 is connected. The fixing portion 25 includes a protruding piece 25A that protrudes outward from the peripheral wall portion 14. The rope 70 that is connected to the outer periphery of the base portion 1 has its tip connected to the protruding piece 25A and is connected to the base portion 1. In this manner, the structure that connects the rope 70 to the protruding piece 25A that protrudes outward from the outer periphery of the base portion 1 has the characteristic that the connection position of the rope 70 is separated from the support portion 2, thereby effectively pulling the support portion 2, and effectively preventing interference between the granular weight 5 loaded in the storage portion 4 and the connection portion of the rope 70.

In the base 1 shown in FIG. 5, the protruding pieces 25A are fixed in a vertical position to the outer peripheral surface of the four corners of the peripheral wall 14, which is square in plan view, so as to extend in the diagonal direction, forming the fixing parts 25. In addition, in the base 1 shown in FIG. 7, the protruding pieces 25A are fixed in a vertical position to the outer peripheral surface of the eight corners of the peripheral wall 14, which is regular octagonal in plan view, so as to extend in the diagonal direction, forming the fixing parts 25. In this way, the structure in which the protruding pieces 25A are provided in the diagonal direction in the base 1, which is polygonal in plan view, has the feature that the fixing parts 25 can be arranged in the diagonal direction where the maximum outer diameter is the largest, so that the tip of the cord 70 can be connected to the position farthest from the support part 2, and the support part 2 can be effectively pulled. Here, in the base 1, which is circular in plan view, four or more protruding pieces 25A are fixed at equal intervals to the outer peripheral surface of the peripheral wall 14. In the base 1 shown in FIG. 6, six protruding pieces 25A are fixed at equal intervals in a vertical position. Furthermore, the fixing portion 25 fixed to the peripheral wall portion 14 is preferably fixed at a position facing the fixing wall portion 16 fixed to the inside of the peripheral wall portion 14. This is because the peripheral wall portion 14 can be stably held against the tension of the cord body 70 acting on the fixing portion 25.

The protruding piece 25A shown in the figure is a flat metal plate, and this metal plate is fixed in a vertical position to the outer peripheral surface of the peripheral wall portion 14. The fixing portion 25, which arranges the protruding piece 25A made of a metal plate in a vertical position in this way, has the characteristic that it can stably support the connected rope body 70 against the tension of the rope body 70 when pulled by the rope body 70. The protruding piece 25A shown in the figure has a through hole 25a and fixes the tip of the rope body 70 via a metal connector 26 fixed to this through hole 25a. As an example, the connector 26 shown in Figures 8 and 9 is composed of a U-shaped metal fitting 26A and a connector pin 26B that connects the opposing tips of the U-shaped metal fitting 26A. However, any other member that can connect the tip of the rope body to the protruding piece can be used as the connector.

The fixing portion 25 shown in Figures 5 to 9 has fixing pieces 25B on both sides of the vertically oriented protruding piece 25A, and these fixing pieces 25B are fixed to the outer circumferential surface of the peripheral wall portion 14 to place the protruding piece 25A in a fixed position. The fixing pieces 25B are fixed to the peripheral wall portion 14 by welding, or as shown in Figures 8 and 9, are fixed to the peripheral wall portion 14 via a number of fasteners 27. For example, bolts and nuts are used as such fasteners 27. The peripheral wall portion 14 and the fixing pieces 25B, which are connected via the fasteners 27, are fixed in a fixed position by inserting a bolt into a through hole opened in advance at a position facing each other, and screwing a nut onto the tip of the bolt.

(Tension adjustment mechanism 71)
The tension adjustment mechanism 71 applies tension to the rope 70 arranged across the upper end of the support 2 and the outer periphery of the base 1 to tension it with a predetermined tension. The tension adjustment mechanism 71 can be a winding machine 72 arranged at the upper end of the support 2 to wind the rope 70. The tension adjustment mechanism 71 shown in FIG. 10 is a winding machine 72 that winds up the rear end side of the rope 70 whose tip is fixed to the outer periphery of the base 1. The winding machine 72 shown in FIG. 10 uses a high-strength wire as the rope 70, and is structured to adjust the tension by winding this high-strength wire around a winding drum 73. The winding machine 72 shown in the figure includes a winding drum 73 that winds up the rope 70, a drive motor 74 that rotates the winding drum 73, and a transmission 75 that changes the speed of the rotation of the drive motor 74 to rotate the winding drum 73 with a large torque. The winding machine 72 is, for example, installed on the platform 24 and has a structure for unwinding the rope 70 downward. By fixing the winding machine 72 to the platform 24 in this manner, the tension acting on the rope 70 can be stably adjusted.

(Intermediate roller 76)
2, the mooring mechanism 7 is provided with an intermediate roller 76 that is fixed to the side surface of the support column 2 and guides the middle portion of the rope 70. In the mooring mechanism 7 shown in the figure, the rope 70 arranged above the intermediate roller 76 is arranged in a substantially vertical position along the side surface of the support column 2, and the rope 70 arranged below the intermediate roller 76 is arranged in an inclined position away from the support column 2. In this structure, the rope 70 is pulled and tensioned by the tension adjustment mechanism 71 while the middle portion of the rope 70 is guided by the intermediate roller 76 provided on the side surface at the upper end of the support column 2. At this time, the rope 70 is arranged close to the support column 2 above the intermediate roller 76, and safety around the support column 2 near the sea surface can be ensured. In addition, below the intermediate roller 76, by connecting the rope 70 to the base portion 1 in an inclined position that moves it away from the support portion 2, the inclination angle of the rope 70 with respect to the vertical direction can be increased, and the tension of the rope 70 can be effectively applied to the support portion 2.

11 and 12, the intermediate roller 76 is fixed to the fixed rib 28 fixed to the side of the support 2 and arranged in a fixed position. The intermediate roller 76 in the figure includes a roller member 77 arranged rotatably at a position away from the side of the support 2, a pair of connecting plates 78 that rotatably arrange the roller member 77, and a connector 79 for fixing the pair of connecting plates 78 to the fixed rib 28. The above intermediate roller 76 is arranged in a fixed position of the support 2 in a predetermined posture with the pair of connecting plates 78 fixed to the fixed rib 28 via the connector 79. The roller member 77 is arranged so that the rotation axis is in a horizontal posture and is tangent to the support 2, and rotates in a state where the rope body 70 can move up and down. The above intermediate roller 76 is connected to the support 2 in a detachable manner. Therefore, in the mooring process for tensioning the rope 70, the leading end is fixed to the outer periphery of the base 1, and the trailing end is wound around a winder 72 arranged on the platform 24 at the top end of the support 2. The middle part of the rope 70 is guided to the middle roller 76, and the middle roller 76 can be fixed to the support 2.

The above-mentioned mooring mechanism 7 suppresses the swinging of the support part 2 by tensioning the multiple cords 70 arranged radially in a plan view between the upper end of the support part 2 and the outer periphery of the base part 1 to a predetermined tension. Here, as shown in FIG. 1, the mooring mechanism 7 suppresses the swinging so that the tilt angle (θ) at which the support part 2 tilts with respect to the vertical direction does not become larger than a predetermined angle. The mooring mechanism 7 can set the limit value of the tilt angle (θ) of the support part 2 to, for example, 5 degrees. Therefore, when the support part 2 is tilted 5 degrees with respect to the vertical direction, the mooring mechanism 7 adjusts the tension by the tension adjustment mechanism 71 so that the cords 70 on the opposite side to the tilting direction are in a taut state and the support part 2 does not tilt any further.

Furthermore, the mooring mechanism 7 can change the tension of the rope 70 between normal times and emergency times when a typhoon is approaching. For example, during normal times, the tension of the rope 70 by the tension adjustment mechanism 71 can be set to be weak, i.e., the rope 70 is not taut but is stretched so that it is somewhat loose, allowing a certain degree of swaying, while during emergency times when a typhoon is approaching, the tension of the rope 70 by the tension adjustment mechanism 71 can be set to be strong to suppress the swaying of the support section 2. In this case, during an emergency, even if the support section 2 tilts due to strong winds or swells, the tension is increased so that it does not tilt to the limit value of the aforementioned inclination angle (θ). The tension adjustment mechanism 71 can adjust the tension of the rope 70, for example, by remote operation or wireless control. This allows the tension of the rope 70 to be safely adjusted without climbing onto the platform, even in situations where a typhoon is approaching.

(Sub tension adjustment mechanism 81)
13 to 15 further includes a sub-tension adjustment mechanism 81 that adjusts the tension of the rope 70. The sub-tension adjustment mechanism 81 shown in the figures includes a tilting arm 82 that is connected at one end to the outer periphery of the base 1 and is arranged to be tiltable within a vertical plane, and a weight part 83 fixed to the other end of the tilting arm 82. One end of the tilting arm 82 is fixed to the peripheral wall part 14 of the base 1 via the aforementioned fixing part 25, and the tip of the rope 70 is connected to the middle part of the other end side that extends in a direction away from the support 1.

In the sub-tension adjustment mechanism 81, when the support 2 is in a vertical position, the rope 70 is tensioned with a predetermined tension via the tilting arm 82 in a descending position (see FIG. 14) due to the weight of the weight 83, and when the support 2 tilts in any direction from the vertical position, the rope 70 arranged on the opposite side to the tilting direction of the support 1 pulls the tilting arm 82, tilting the tilting arm 82 to an ascending position (see FIG. 15) against the weight of the weight 83. Furthermore, the tilting arm 82 is provided with a stopper 84 that stops the tilting in a predetermined ascending position, and when the tilting arm 82 rises to the predetermined tilting position, the rise of the tilting arm 82 is stopped via the stopper 84 to prevent the tilting of the support 2. The stopper 84 shown in the figure is a cam member fixed to the rear end of the tilting arm 82, and the cam surface is abutted against the peripheral wall 14 of the base 1 to stop the tilting of the tilting arm 82. Furthermore, the tilting arm 82 shown in the figure is equipped with a second stopper 85 that stops the tilting even in a predetermined descent position, and when the tilting arm 82 descends to the predetermined tilt position, the descent of the tilting arm 82 is stopped via the stopper 85. The second stopper 85 shown in the figure is also a cam member fixed to the rear end of the tilting arm 82, and the cam surface abuts against the peripheral wall portion 14 of the base portion 1 to stop the tilting of the tilting arm 82.

The above-described mooring mechanism 7 allows the tension acting on the rope 70 to be adjusted not only by the winder 71 provided at the upper end of the support 2, but also by the sub-tension adjustment mechanism 81 provided at the base 1. The sub-tension adjustment mechanism 81 connects the weight 83 to a first connection 87 provided at the tip of the tilting arm 82, and connects the tip of the rope 70 to a second connection 88 provided in the middle of the tilting arm 82. The rope 70 can be connected to the second connection 88 via the aforementioned connector 26. The sub-tension adjustment mechanism 81 with this structure can adjust the tension (T) acting on the rope 70 by the weight (W) of the weight 83 connected to the tip of the tilting arm 82. Furthermore, the sub-tension adjustment mechanism 81 shown in the figure can adjust the tension acting on the rope 70 by using the principle of leverage by adjusting the ratio between the length (L1) from the tilt axis 86 of the tilt arm 82 to the first connection part 87 and the length (L2) from the tilt axis 86 of the tilt arm 82 to the second connection part 88.

This sub-tension adjustment mechanism 81 suppresses the tilting of the support part 2 by applying tension (T) determined by the pulling force of the winder 72, the leverage ratio of the tilting arm 82, and the weight (W) of the weight part 83 to the rope 70, and when a larger external force is applied to the support part 1 and the support part 2 attempts to tilt, the tilting arm 82 tilts from the descending position (Figure 14) to the ascending position (Figure 15), and when the tilting arm 82 rises to its limit position, the rise of the tilting arm 82 is stopped by the stopper 84, suppressing the tilting of the support part 2. The stopper 84 of the tilting arm 82 can effectively suppress the swinging of the support part 2 by specifying a stop position so that the support part 2 does not tilt until the tilt angle (θ) of the support part 2 reaches the limit value mentioned above.

For example, as shown by the solid line in FIG. 13, when the tilting arm 82 is in the lowered position, the sub-tension adjustment mechanism 81 allows a certain degree of swinging by tensioning the rope 70 so that it is not taut but is slightly loose, and when the support column 2 tilts in any direction, the rope 70 arranged on the opposite side to the tilting direction of the support column 1 becomes taut, thereby suppressing the tilting of the support column 2. Furthermore, when the support column 2 tilts from this state, the tilting arm 82 pulled by the rope 70 tilts from the lowered position to the raised position, and when the support column 2 tilts until the tilt angle (θ) of the support column 2 reaches the aforementioned limit value as shown by the dashed line in FIG. 13, the stopper 84 stops the rise of the tilting arm 82, and the tension of the taut rope 70 is maximized, effectively suppressing the tilting of the support column 2.

As described above, the mooring mechanism 7 can be structured to allow a certain degree of rocking of the support column 2 by adjusting the tension of the rope 70, but when the support column 2 tilts to an angle where the inclination angle (θ) of the support column 2 reaches its limit, the rope 70 is in a taut state, reliably preventing the support column 2 from tilting.

As shown in Figure 1, the bottom-mounted offshore mounting platform 9 having the above structure is used as an offshore wind power generation device 100 by installing a wind power generator 6 on the upper end of the support column 2. Although not shown, the bottom-mounted offshore mounting platform 9 can also be used as an offshore wind condition observation device by installing a wind condition observation device on the upper end of the support column 2.

(Wind turbine generator 6)
As shown in Fig. 1, the wind power generator 6 includes a windmill 60 that rotates by receiving wind power, a generator (not shown) that converts the kinetic energy of the rotating windmill 60 into electrical energy, a nacelle 63 that houses the generator, and a tower 64 for placing the nacelle 63 at a predetermined height. The windmill 60 includes a plurality of blades 61, which are fixed at equal intervals to a hub 62 provided in the center. The wind power generator 6 is installed in a predetermined position on a bottom-mounted offshore platform 9, with the base of the tower 64 fixed to the upper end of the support part 2. The offshore wind power generation device 100 shown in the figure includes a work platform 24 provided at the base of the tower 64 and along the outer periphery of the upper end of the support part 2.

The fixed-bottom offshore rack 9 described above is constructed in the following steps.
[Preparation process]
In this process, there are prepared a steel base 1 to be placed on the seabed, a support column 2 formed from a cylindrical steel pipe with a total length such that its upper end protrudes out onto the ocean while its lower end is connected to the base 1, a predetermined amount of granular weights 5 to be loaded into the storage section 4 of the base 1, a number of ropes 70 that constitute the mooring mechanism 7, and a tension adjustment mechanism 71 that adjusts the tension of the ropes 70. As shown in Figs. 3 to 5, the steel base 1 is manufactured to have a structure including a bottom plate 11 to be installed on the seabed, a cylindrical socket 12 fixed to the center of the bottom plate 11 and into which the lower end of the support 2 is inserted and connected, a plurality of fixed walls 13 fixed to the side of the cylindrical socket 12 and the upper surface of the bottom plate 11 to fix the cylindrical socket 12 to the bottom plate 11, a peripheral wall 14 erected along the outer periphery of the bottom plate 11 to form a storage section 4 on the inside, and a plurality of fixed walls 16 fixed to the inner side of the peripheral wall 14 and the upper surface of the bottom plate 11 to fix the peripheral wall 14 to the bottom plate 11. The granular weight 5 is prepared in a predetermined amount to be loaded into the storage section 4, and is a weight that can hold the base 1 and the support 2 in a fixed position when the storage section 4 is filled. For the granular weight 5, for example, iron ore crushed to a predetermined size is used. In the above preparation process, the base portion 1 and the support portion 2 are manufactured in a factory.

[Transportation process]
The base 1, support column 2, and granular weights 5 prepared in the preparation process are transported to the ocean in a construction area where the bottom-fixed offshore rack 9 will be constructed. At this time, the base 1 manufactured in the preparation process, in which the peripheral wall 14 erected along the outer periphery of the bottom plate 11 is connected to the bottom plate 11 in a watertight manner to form the entire base 1 into a box shape with an upward opening, can be towed in a state where the base 1 is floating on the sea surface in the transportation process to the ocean in the construction area. Furthermore, the granular weights 5, which are iron ore, are transported by a crushed stone carrier.

[Foundation formation process]
As shown in FIG. 16A, a foundation 3 for installing the foundation 1 is formed on the seabed in the area where the bottom-mounted offshore platform 9 is to be constructed. The foundation 3 is formed on the seabed surface 50 to improve the surface condition of the seabed on which the foundation 1 is to be installed and to stably place the foundation 1 on the upper surface. The foundation 3 is formed, for example, so that the outer shape of the foundation rubble layer 31 is 1 to 10 m, preferably 3 to 5 m, larger than the outer shape of the foundation 1. The upper surface of the foundation 3 is leveled to a horizontal plane so that the foundation 1 can be placed in a horizontal position. As shown in FIG. 2 and FIG. 3, the foundation 3 includes a foundation rubble layer 31 provided by excavating the entire area where the foundation 1 is to be installed to a predetermined depth from the seabed surface 50 and laying rubble 32 on the excavated part 30 formed one step lower, and a covering member 33 arranged on the upper surface of the foundation rubble layer 31. The foundation rubble layer 31 is formed by stacking a number of rubble stones 32 laid in the excavation section 30 to a predetermined thickness, and the upper surface is leveled to a flat surface. A covering member 33 is laid on the flat upper surface of the foundation rubble layer 31. The covering member 33 is a plate-like or sheet-like member having a weight that presses the foundation rubble layer 31 from above so that the rubble stones 32, sand, and soil that constitute the foundation rubble layer 31 do not flow out due to the upsurge and downsurge of the tsunami, and covers the entire upper surface of the foundation rubble layer 31. As such a covering member 33, an asphalt mat 33A can be used. The asphalt mat 33A is asphalt molded into a mat shape of a predetermined thickness, and has a specific gravity that does not flow away even in strong tidal currents, and flexibility that allows it to deform along the surface of the foundation rubble layer 31. The covering member 33 made of the asphalt mat 33A is laid in close contact with the upper surface of the foundation rubble layer 31, and presses the foundation rubble layer 31 from the upper surface with its own weight. This effectively prevents the large amount of rubble 32 constituting the rubble foundation layer 31 from being washed away by strong tides or tsunamis, which would cause deformation of the foundation 3. However, the covering member may also be a covering layer of slowly cooled blast furnace slag laid to a predetermined thickness. In the foundation formation step shown in Fig. 16(A), the entire top surface of the foundation 3 is leveled to a horizontal plane, but the foundation 3 may also be formed so that the central part, which is the area where the base 1 is to be installed, is one step lower than the outer periphery, although this is not shown. In the base installation step, the base 1 is installed in the central part, which is one step lower, of the foundation 3 leveled to this shape.

In addition, concrete panels can be used as covering members. This foundation can prevent the rubble that constitutes the rubble layer from flowing out by laying multiple concrete panels on the top surface of the rubble layer. Furthermore, the foundation 2 can also be made by placing concrete blocks or concrete panels on the asphalt mat 33A laid on the top surface of the rubble layer 31.

[Base installation process]
In this process, as shown in FIG. 16B, the base 1 transported to the construction area in the transportation process is sunk to the seabed and installed on the foundation 3. When sinking the base 1, the base 1 is suspended via a plurality of ropes 70, and the ropes 70 are let out to sink the base 1 to the seabed. The plurality of ropes 70 are wound around a drum or the like, and their ends are connected to the fixing parts 25 provided on the outer periphery of the base 1. The base 1 is sunk in the sea while suspended by the plurality of ropes 70, and the ropes 70 are let out from the drum to lower the base 1 under its own weight and sink to the seabed. At this time, the ropes 70 are let out while checking the installation position with an underwater camera or the like, so that the base 1 can be installed at an accurate position on the foundation 3.

[Support column installation process]
In this step, as shown in FIG. 16C, the support column 2 transported to the construction area in the transportation step is submerged in the sea in a vertical position, and the lower end is connected to the base 1 installed on the seabed. As shown in FIG. 16C, the support column 2 is submerged in seawater in a vertical position while allowing seawater to penetrate into the cylindrical steel pipe, so that the support column 2 can be smoothly submerged in seawater by its own weight regardless of the water depth of the construction area. The lower end 2B of the support column 2 that has been submerged to the seabed is inserted into the socket cylinder 12 provided on the base 1 and connected to a fixed position, as shown in FIG. 3 and FIG. 4. In this step, the support column 2 can be accurately inserted into the socket cylinder 12 while checking the position of the lower end 2B of the support column 2 with an underwater camera or the like.

[Concrete filling process]
In this step, as shown in Fig. 16D, the underwater concrete 20 is filled inside the lower end 2B of the support part 2 inserted into the socket tube part 12, and the base part 1 and the support part 2 are fixed together. The underwater concrete 20 is, for example, pumped from offshore through a pipe and filled inside the lower end 2B of the support part 2. The underwater concrete 20 filled into the lower end 2B of the support part 2 is filled in a state in which the first anchor part 21 provided in the base part 1 and the second anchor part 22 provided in the support part 2 are buried, as shown in Fig. 3. As a result, when the underwater concrete 20 is hardened, the base part 1 and the support part 2 are firmly fixed together via the buried first anchor part 21 and second anchor part 22.

[Loading process]
In this process, a predetermined amount of granular weights 5 are loaded and filled into the storage section 4 of the base 1. Figure 16(E) shows an example in which a predetermined amount of granular weights 5 is suspended to the seabed using a storage container 51 with an openable bottom, and the bottom of the storage container 51 is opened above the storage section 4 to allow the granular weights 5 to sink and fill the storage section 4. This method makes it possible to simply and reliably load the granular weights 5 at predetermined positions in the storage section 4. However, the granular weights 5 can also be scattered from the sea surface and allowed to sink.

Figure 16 (E) shows an example in which a predetermined amount of granular weights 5 are loaded into the storage section 4 after the lower end 2B of the support section 2 is connected to the base section 1. However, the present invention does not specify the timing for loading the granular weights 5 into the storage section 4 to the above timing, i.e., a process after the support section 2 is connected to the base section 1. The granular weights 5 can also be loaded into the storage section 4 at various times.

The loading process can be divided into a first loading process in which the granular weights 5 are loaded into the storage section 4 as a pre-process of the base installation process or in the base installation process, and a second loading process in which the granular weights 5 are loaded into the storage section 4 as a post-process of the base installation process, and the granular weights 5 can be filled into the storage section 4. In this method, a certain amount of granular weights 5 are loaded into the storage section 4 as the first loading process before the base 1 is sunk to the seabed or during the process of sinking the base 1 to the seabed. In particular, in the first loading process, the granular weights 5 can be loaded into the storage section 4 on the ocean or in water near the sea surface, so that a large amount of granular weights 5 can be loaded efficiently and accurately. In this way, by loading a certain amount of granular weights 5 into the storage section 4 to increase the overall weight and sinking the base 1 to the seabed, the base 1 can be lowered straight down while suppressing the influence of tides, etc., and quickly installed in an accurate position. After the base 1 is sunk to the seabed and set in place, the remaining granular weights 5 are loaded into the storage section 4 in the second loading process.

[Mooring process]
As shown in Fig. 16(F), the rear ends of the multiple ropes 70, the tips of which are connected to the outer periphery of the base 1, are wound by a winder 72 installed on the platform 24 at the upper end of the support 2, and the ropes 70 are tensioned between the tips of the support 2 and the outer periphery of the base 1. The winder 72, which is a tension adjustment mechanism 71, adjusts the tension by the rotation torque of winding the ropes 70 onto a winding drum 73. The multiple ropes 70 are wound by the winder 72 with their middle parts guided by an intermediate roller 76 arranged on the side of the upper end of the support 2, and are tensioned with a predetermined tension. The multiple ropes 70 are tensioned while the winding torque is adjusted so that they are tensioned in a balanced manner in a radially tensioned state.

As described above, in the loading process, a predetermined amount of granular weights 5 is filled into the storage section 4 of the base section 1, and the load of the large amount of granular weights 5 holds the base section 1 in a fixed position, while the support section 2 connected to the socket tube section 12 of the base section 1 is held in a vertical position. In this way, the support section 2 connected to the base section 1 is positioned with its upper end protruding above the sea surface.

Furthermore, the granular weights 5 can be allowed to settle in the form of an aggregate filled in a mesh material or a water-permeable bag. In this case, they can also be hung from a crane or similar device and filled accurately. Furthermore, as shown by the dotted line in the figure, weights 55 can also be installed around the peripheral wall 14 of the base 1. This structure ensures that the base 1 is prevented from shifting horizontally. Such weights 55 can be an aggregate of the aforementioned granular weights 5 filled in a bag, or they can be concrete blocks or similar.

At this time, the weights 55 arranged around the peripheral wall 14 of the base 1 are preferably arranged in an area where no fixed parts are provided. For example, as shown in Figures 13 to 15, when a sub-tension adjustment mechanism 81 that limits the tilting of the support column 2 is provided, the sub-tension adjustment mechanism 81 can operate normally by not placing the weights 55 at the position where the sub-tension adjustment mechanism 81 is provided. However, this weight can be omitted depending on the environment of the installation location.

The wind power generator 4 is installed on the upper end of the support column 2 of the bottom-mounted offshore rack 9 constructed as described above, as shown in FIG. 1, to construct the offshore wind power generation device 100.

[Generator installation process]
As shown in FIG. 1 , a wind power generator 4 is installed on the upper end of the support column 2 of the bottom-mounted offshore rack 9 constructed as described above, thereby constructing an offshore wind power generation device 100 .

The present invention can be suitably constructed as a bottom-mounted offshore rack for placing wind turbines offshore, even in waters 40 to 120 meters deep.

100... Offshore wind power generation device 1... Base section 2... Support section 2A... Main body section 2B... Lower end section 2C... Protruding section 3... Foundation section 4... Storage section 4A... Compartment area 4B... Divided area 5... Granular weight 6... Wind power generator 7... Mooring mechanism 9... Bottom-mounted offshore rack 11... Bottom plate section 12... Socket tube section 12X... Tapered section 12A... Peripheral wall 13... Fixed wall section 14... Peripheral wall section 15... Flange section 16... Fixed wall section 17... Fixed plate 18... Intermediate wall section 20... Underwater concrete 21... First anchor section 22... Second anchor section 23... Hollow section 24... Platform 25... Fixed section 25A... Protruding piece 25a... Through hole 25B... Fixed piece 26... Connector 26 A...U-shaped metal fitting 26B...connecting pin 27...fixing device 28...fixing rib 30...excavation section 31...foundation rubble layer 32...rubbish rock 33...covering member 33A...asphalt mat 50...seabed surface 51...storage container 55...weight body 60...wind turbine 61...blade 62...hub 63...nacelle 64...tower 70...rod body 71...tension adjustment mechanism 72...winding machine 73...winding drum 74...driving motor 75...gearbox 76...intermediate roller 77...roller member 78...connecting plate 79...connecting device 81...sub-tension adjustment mechanism 82...tilting arm 83...weight portion 84...stopper 85...second stopper 86...tilting shaft 87...first connecting portion 88...second connecting portion

Claims (6)

A bottom-mounted offshore rack for installing a wind turbine generator on the ocean,
A steel base part that is placed on the seabed in a fully submerged state and on which granular weights are loaded;
A support part formed of a cylindrical steel pipe, the lower end of which is connected to the base part and which is placed in the sea in a vertically extended position so that the upper end protrudes above the ocean;
A mooring mechanism for suppressing the swinging of the support portion;
Equipped with
The base portion is
A bottom plate portion to be installed on the seabed;
a cylindrical socket portion fixed to a central portion of the bottom plate portion and into which a lower end portion of the support portion is inserted and connected;
a plurality of fixing walls fixed to a side surface of the cylindrical socket portion and an upper surface of the bottom plate portion to fix the cylindrical socket portion to the bottom plate portion;
a peripheral wall portion that is erected along an outer periphery of the bottom plate portion and forms an accommodation portion for the granular weight on the inside;
a plurality of fixing walls fixed to an inner surface of the peripheral wall portion and an upper surface of the bottom plate portion to fix the peripheral wall portion to the bottom plate portion;
Equipped with
the base portion is held in a fixed position by the granular weight loaded in the storage portion, and is configured to hold the support portion connected to the socket tube portion in a vertical position;
The anchoring mechanism includes:
A plurality of cords extending radially from the upper end of the support portion in a plan view and having their tips connected to the outer periphery of the base portion;
A tension adjustment mechanism for adjusting the tension of the rope body,
The plurality of ropes stretched between the support column and the base suppress the swinging of the support column ,
The mooring mechanism includes a winding machine arranged at the upper end of the support column for winding up the rope, and the winding machine serves as the tension adjustment mechanism . The bottom-fixed offshore platform according to claim 1,
The mooring mechanism includes a fixing portion fixed to the peripheral wall portion of the base portion and to which a tip end of the rope body is connected,
The fixed portion is a protruding piece protruding outward from the peripheral wall portion. A bottom-mounted offshore rack for installing a wind turbine generator on the ocean,
A steel base part that is placed on the seabed in a fully submerged state and on which granular weights are loaded;
A support part formed of a cylindrical steel pipe, the lower end of which is connected to the base part and which is placed in the sea in a vertically extended position so that the upper end protrudes above the ocean;
A mooring mechanism for suppressing the swinging of the support portion;
Equipped with
The base portion is
A bottom plate portion to be installed on the seabed;
a cylindrical socket portion fixed to a central portion of the bottom plate portion and into which a lower end portion of the support portion is inserted and connected;
a plurality of fixing walls fixed to a side surface of the cylindrical socket portion and an upper surface of the bottom plate portion to fix the cylindrical socket portion to the bottom plate portion;
a peripheral wall portion that is erected along an outer periphery of the bottom plate portion and forms an accommodation portion for the granular weight on the inside;
a plurality of fixing walls fixed to an inner surface of the peripheral wall portion and an upper surface of the bottom plate portion to fix the peripheral wall portion to the bottom plate portion;
Equipped with
the base portion is configured to be held in a fixed position by the granular weight loaded in the storage portion and to hold the support portion connected to the socket tube portion in a vertical position;
The anchoring mechanism includes:
A plurality of cords extending radially from the upper end of the support portion in a plan view and having their tips connected to the outer periphery of the base portion;
A tension adjustment mechanism for adjusting the tension of the rope body,
The plurality of ropes stretched between the support column and the base suppress the swinging of the support column,
The mooring mechanism includes an intermediate roller that is fixed to a side surface of the support column and through which an intermediate portion of the rope body is guided,
The cord is disposed above the intermediate roller in a position along a side surface of the support column,
The rope body, which is disposed below the intermediate roller, is disposed in an inclined position away from the support column portion toward the base portion. A bottom-mounted offshore rack for installing a wind turbine generator on the ocean,
A steel base part that is placed on the seabed in a fully submerged state and on which granular weights are loaded;
A support part formed of a cylindrical steel pipe, the lower end of which is connected to the base part and which is placed in the sea in a vertically extended position so that the upper end protrudes above the ocean;
A mooring mechanism for suppressing the swinging of the support portion;
Equipped with
The base portion is
A bottom plate portion to be installed on the seabed;
a cylindrical socket portion fixed to a central portion of the bottom plate portion and into which a lower end portion of the support portion is inserted and connected;
a plurality of fixing walls fixed to a side surface of the cylindrical socket portion and an upper surface of the bottom plate portion to fix the cylindrical socket portion to the bottom plate portion;
a peripheral wall portion that is erected along an outer periphery of the bottom plate portion and forms an accommodation portion for the granular weight on the inside;
a plurality of fixing walls fixed to an inner surface of the peripheral wall portion and an upper surface of the bottom plate portion to fix the peripheral wall portion to the bottom plate portion;
Equipped with
the base portion is held in a fixed position by the granular weight loaded in the storage portion, and is configured to hold the support portion connected to the socket tube portion in a vertical position;
The anchoring mechanism includes:
A plurality of cords extending radially from the upper end of the support portion in a plan view and having their tips connected to the outer periphery of the base portion;
A tension adjustment mechanism for adjusting the tension of the rope body,
The plurality of ropes stretched between the support column and the base suppress the swinging of the support column,
The mooring mechanism includes a sub-tension adjustment mechanism for adjusting the tension of the rope body,
The sub tension adjustment mechanism is
a tilting arm having one end connected to an outer periphery of the base and arranged to be tiltable in a vertical plane, and having the other end extended in a direction away from the support column and connected to a tip of the cord;
a weight portion fixed to the other end side of the tilting arm,
When the support column is in a vertical position, the rope is tensioned with a predetermined tension via the tilting arm, which is in a lowered position due to the weight of the weight section.
When the support column is tilted in any direction from a vertical position, the rope arranged on the opposite side to the tilting direction of the support column pulls the tilting arm, tilting the tilting arm to an ascending position against the weight of the weight section,
Furthermore, the tilting arm is provided with a stopper that stops the tilting at a predetermined raised position, and when the tilting arm tilts to the predetermined raised position, the tilting of the tilting arm is stopped via the stopper, thereby suppressing the tilting of the support section. A method for constructing a bottom-mounted offshore rack for installing a wind turbine generator on the ocean, comprising the steps of:
A steel base that is placed on the seabed in a fully submerged state and loaded with granular weights;
A bottom plate portion to be installed on the seabed;
a cylindrical socket portion fixed to a central portion of the bottom plate portion and into which a lower end portion of the support column is inserted and connected;
a plurality of fixing walls fixed to a side surface of the cylindrical socket portion and an upper surface of the bottom plate portion to fix the cylindrical socket portion to the bottom plate portion;
a peripheral wall portion that is erected along an outer periphery of the bottom plate portion and forms an accommodation portion for the granular weight on the inside;
a plurality of fixing walls fixed to an inner surface of the peripheral wall portion and an upper surface of the bottom plate portion to fix the peripheral wall portion to the bottom plate portion;
A base portion comprising:
A support part formed of a cylindrical steel pipe, the support part having a total length such that the upper end of the support part protrudes above the ocean while the lower end of the support part is connected to the base part installed on the seabed;
A predetermined amount of the granular weights loaded in the storage section;
A mooring mechanism for suppressing the swinging of the support portion,
A plurality of cords extending radially from the upper end of the support portion in a plan view and having tips connected to the outer periphery of the base portion;
a tension adjusting mechanism for adjusting the tension of the rope; and a winding machine disposed at an upper end of the support column for winding up the rope .
A mooring mechanism comprising:
A preparation step of preparing
a transporting step of transporting the base portion, the support portion, the granular weights, and the mooring mechanism onto the ocean to a construction area of the bottom-fixed offshore platform;
a foundation forming step of forming a foundation having a leveled upper surface on the seabed surface of the construction area;
a base installation process of sinking the base into the seabed and installing it on the foundation;
a support part installation process for submerging the support part in the sea in a vertical position and inserting a lower end of the support part into the socket tube part of the base part installed on the seabed to connect the support part to the socket tube part of the base part installed on the seabed;
a loading step of loading the granular weight into the storage portion of the base portion;
a mooring step of stretching the plurality of ropes between an upper end of the support column and an outer periphery of the base;
Including,
A method for constructing a bottom-mounted offshore platform, in which, in the base installation process, the base is suspended via the multiple ropes and the ropes are let out to lower the base to the seabed. An offshore wind power generation device including a bottom-mounted offshore rack,
The bottom-fixed offshore platform according to any one of claims 1 to 4 ,
A wind power generator installed at an upper end of the support pole;
An offshore wind power generation device comprising:

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