NO346706B1 - Floating wind turbine construction - Google Patents

Description

Field of the invention

The present invention relates to a floating wind turbine construction, comprising a foundation that floats in a body of water, where the floating foundation supports at least one tower equipped with a turbine. The floating foundation comprises a submerged, elongated and stabilizing buoyancy part attached to the lower part of the tower, and the floating foundation comprises one or more projecting stabilizer arm(s) which protrude in a direction transverse to the longitudinal direction of the elongated and stabilizing buoyancy part, said stabilizer arm penetrates a water surface to the body of water.

The description relates to an invention within the technical field of offshore wind energy. A technical solution is described to achieve sufficient stability of a floating foundation for one or more wind turbines, also referred to as a platform or floating wind turbine construction.

The background of the invention

In order to reduce pollution and limit global warming, it is desirable to develop technology that can make renewable energy more competitive.

Offshore wind is a particularly interesting resource related to renewable energy extraction. There is great potential in utilizing ocean areas and the wind over such areas to extract electrical energy. A challenge related to the extraction of energy from offshore wind is the cost. In order for offshore wind to be a competitive energy source, it is crucial that costs related to the production, installation and operation and maintenance of offshore wind turbines are reduced. In order to achieve this goal, it is important to develop new, cost-effective technology.

A large number of technical solutions have been developed for the production of wind energy offshore. Some of these are related to fixed foundations, while others are related to floating foundations. The floating foundations are advantageous in many cases, especially for use at sea depths, typically over 50 metres.

At sea, an offshore wind turbine and its foundation are exposed to strong forces from wind, waves and currents.

Discussion of prior art

A large number of technical solutions have been developed for the production of wind energy offshore. Some of these are related to fixed foundations, where the lower structure is rigidly and rotatably attached to the seabed. Typical but not limited names for such devices are Monopile, Tri-pod, Jacket, suction caisson, gravity base. While the upper part consists of a transition piece mounted windmill tower with associated windmill.

Another main type is floating foundations, which are anchored to the seabed. Here there are also a number of variants such as, typically, but not limited to, Barge, Semi-Submersible, multi-spar, spar, tension-leg platform. The majority of said devices are anchored in such a way that they cannot rotate, but use a nacelle that can rotate in relation to the tower.

Another type of floating platforms is designed in a way that allows it to rotate about the anchor point, further referred to as (rotating platforms). This type of device will be able to allow more of a wind turbine as it adjusts itself to the wind, which means that the turbines do not come in the shadow of each other, referred to as wake effect.

Stability to be able to support a turbine is a challenge and cost driver for floating foundations, especially for floating foundations that are to be used in areas with the potential for violent wind and wave conditions. In addition to the design of the floating foundation, how it is anchored is an important part of how it will behave under demanding conditions and thus be part of the total cost picture for a wind farm. As a general rule, "tight" moorings will give less movement on the platform, while loose moorings often referred to as "catenary anchorage" will allow the platform significantly more movement. The movements of a platform are mainly controlled by the influence of wind, as the wind will push the platform in the direction of the wind. Waves will also be able to contribute to significant movements on a floating platform, the waves will give a typical back and forth movement, in combination with up and down. Waves and wind will not always have the same direction, which makes the picture of movement for a platform somewhat complicated.

The platform's movement in the horizontal plane is often referred to as the "watch circle", which describes how much one can assume that the platform moves in relation to an imaginary center point.

The advantage of keeping the watch circle as small as possible is to limit dynamic stresses on, for example, electrical cables that are connected to a platform.

Furthermore, it is easier to plan the optimization of a wind farm if the platform is as stationary as possible under changing weather conditions. Normally, you will see that the stiffer the anchorages, the greater loads you can expect in connection with anchoring the systems, which can be cost-driving and thus negative.

Existing platform solutions are largely based on designs known from the oil industry. Of the main categories, there is the Tension Leg Platform (TLP), as an example the TetraSpar floater can be shown. The main principle for a TLP platform is that it is tensioned tightly against a seabed. Preferably with 3-6 chains or equivalent mooring lines or stays. The rigid suspension is achieved by using the platform's buoyancy, where the suspensions are a result of the platform pulling upwards in a body of water. While the anchor holds it at a preset depth, set by the length of the ankle line. This tight suspension helps limit the platform's movement horizontally and vertically under the influence of, for example, waves and wind.

Another main type is Semi-Submersible which typically floats on a water surface, where solutions for stabilization normally include at least three buoyancy towers that penetrate the water surface, where the buoyancy towers are mounted on a rigid platform where the main stability is a result of the buoyancy towers' area in the water surface and distance between the towers.

Wind Float can be cited as an example of a Semi-Submersible. It consists of three towers that penetrate a surface where the tower is mounted on top of one buoyancy tower. Furthermore, it is anchored with a set of mooring lines which are normally loosely attached between the floating foundation and anchoring on the seabed. The Star Wind Floater is another type of Semi-Submersible type platform, this consists of three buoyancy towers in a star formation. On which there is a tower in the center of the floating foundation on which a windmill tower is mounted.

Spar-Bouy is another type of floating foundation, an example of such a solution is known as "Hywind".

The offshore wind solution "Hywind" includes an example of a foundation for an offshore wind turbine, where the foundation is a floating vertical spar buoy. To counteract tilting forces, the spar buoy reaches deep into the sea in operational position, and it is usually very heavy. The weight is largely due to the spar buoy solution's need for correcting ballast. Its size makes it expensive to manufacture and to transport to its destination at sea, and it means that "Hywind" cannot be used in sea areas with limited depth.

The different types of platform design and anchoring systems have their clear advantages and disadvantages. Then in terms of costs, but also how the platform moves under varying weather conditions.

A Semi-Submersible platform with catenary anchoring will typically have, among others, the following advantages compared to a TLP platform:

• The platform maintains stability in the event of a break in one or more of the anchor lines, while a TLP here would be able to suffocate.

• The platform will be able to be towed as is to the final installation site, while a TLP will probably require special vessels.

in some cases the mooring systems will be cheaper.

• The tower and nacelle will normally be able to be assembled while the platform is lying and floating, for a TLP there will normally be a need for special vessels, or the entire assembly must be done on land.

A TLP platform will typically have, among others, the following advantages compared to a Semi-Submersible platform with catenary anchoring:

• Less structural mass

• Easier to industrialise

• No need for expensive dynamic cables, due to the rigid suspension

• No need for active ballasting to ensure stability.

US2009/091136 A1 relates to a floating wind turbine construction, comprising a foundation that floats in a body of water, where the floating foundation supports a tower equipped with a turbine, and that said floating foundation comprises a submerged, elongated and stabilizing buoyancy part arranged mainly vertically floating in the body of water and which is anchored to a solid foundation.

KR 101956032 B1 shows a floating foundation comprising stabilizing buoyancy parts arranged vertically floating in a body of water. The buoyant part is anchored to the seabed using anchor lines.

Purpose of the present invention

It is a purpose of the invention to produce a floating wind turbine construction that solves many of the challenges seen in today's constructions in relation to costs related to production, installation and operation and maintenance throughout the construction's lifetime.

This document describes a technical solution that has advantages over known technology by combining the known techniques Tension Leg Platform design with Semi-Submersible platform design. This with the intention of combining all the advantages of the two designs into one design. Furthermore, the invention has solved many of the disadvantages of the two previously described designs, in that one design solves the disadvantages of the other design and vice versa.

Summary of the invention

The above-mentioned purpose is achieved with a floating wind turbine structure, comprising a foundation floating in a body of water, where the floating foundation supports at least one tower equipped with a turbine, where said floating foundation comprises a submerged, elongated and stabilizing buoyancy part attached to the lower part of the tower, and that the floating foundation comprises one or more protruding stabilizer arm(s) which protrude in a direction transverse to the longitudinal direction of the elongated and stabilizing buoyancy part, said stabilizer arm penetrating a water surface to the water mass, characterized in that the submerged, elongated and stabilizing buoyancy part is arranged mainly horizontally floating in the body of water and is rigidly anchored to one or more fixed foundations that protrude from the seabed.

Alternative designs are specified in respective independent requirements.

A buoyant body can be mounted on the free end of the protruding stabilizer arm and project up or down into the body of water.

In a first embodiment, the projecting stabilizer arm can project from the lower part of the tower in a horizontal direction, and in an area above the body of water.

In a second embodiment, the protruding stabilizer arm can be immersed in the water mass and protrude from the elongated and stabilizing buoyancy part in a horizontal direction.

The stabilizer arm's buoyancy body may be equipped with a suspended weight.

Furthermore, the floating foundation can be rigidly anchored to the fixed foundation by a first rigid anchoring that runs from a first anchoring point on the elongated and stabilizing buoyancy part down to the fixed foundation, and by a second rigid anchoring that runs from a second anchoring point on the elongate and stabilizing buoyancy part and down to the fixed foundation.

Said first and second anchoring points are preferably on respective distal ends of the elongated and stabilizing buoyancy part.

Furthermore, said first and second anchoring can be tightenable anchoring lines or tension rods in the form of rigid pipes.

The first and second anchoring can be tightened to form a rigid connection between the elongated and stabilizing buoyancy part's first anchoring point, the fixed foundation and the elongated and stabilizing buoyancy part's second anchoring point.

The stabilizer arm can be anchored to the seabed. Alternatively, the stabilizer arm's buoyancy body can be anchored to the seabed.

The buoyancy body's suspended weight can also be anchored to the seabed.

The buoyancy part can include internal tanks that can be emptied and filled with ballast. The ballast can be transportable between tanks.

In one embodiment, the bottom-fixed foundation can be equipped with a rotatable anchoring mechanism. The rotatable anchoring mechanism may be a turntable anchor with connections for the first and second anchors. Alternatively, the rotatable anchoring mechanism may be an electric swivel with connections for the first and second anchors.

By using a rotatable anchoring mechanism, the tower can be placed on an off-center part of the buoyancy section. Likewise, the tower can be placed on the stabilizer arm.

Furthermore, the stabilizer arm can be equipped with a heave compensating device that slows movement in the water mass.

Description of figures

Preferred embodiments of the invention will be described in more detail below with reference to the accompanying figures, in which:

Figure 1 shows a floating wind turbine construction according to the invention.

Figure 2 shows a further variant of the wind turbine construction according to the invention.

Figure 3 shows a further variant of the wind turbine construction according to the invention.

Figure 4 shows a further variant of the wind turbine construction according to the invention.

Figures 5 and 6 are intended to illustrate the assembly and anchoring of a wind turbine construction according to the invention.

Description of preferred embodiments of the invention

Wind turbine construction according to the invention comprises a floating foundation 12 which floats partially submerged in a body of water 20, where the floating foundation 12 supports at least one tower 14 equipped with a wind turbine or a windmill 16. The lower part of the tower 14 will naturally form part of the floating foundation 12 , and consequently the floating foundation 12 is understood to include the lower part of the tower 14.

In alternative designs, the foundation 12 can comprise several towers 14, for example twin towers which are side-by-side and tilted in relation to each other.

The tower 14 projects up through the water surface to the body of water 20 and the tower's lower part 4 is located down in the body of water 20 when the floating wind turbine structure is installed. The tower's lower part 4 is further attached to an elongated and stabilizing buoyancy part 3 which is tightly tensioned and attached to a fixed foundation 25 on a seabed 30. The tensioning provides a rigid anchorage which partially prevents vertical, horizontal and rotational movement of the foundation 12 in the water mass 20. The tower's lower part 4 can in some configurations be part of the tower 14, so that the tower 14 is mounted directly on the buoyancy part 3.

The buoyancy part 3 can advantageously have a design where it is elongated to achieve greater stability. It can preferably have a length of 50, 80 or over 100 m. Elongated means that the buoyancy part 3 is essentially longer in one direction than in another direction. When using several stabilizer arms 6, the buoyancy part 3 can have a less elongated shape where the "diameter" becomes the length of the buoyancy part 3. The stability is then ensured by several stabilizer arms 6 which project from the buoyancy part 3 at different mutual angles in relation to each other in the horizontal plane, and there is less need for an elongated buoyancy part.

The buoyancy part's length or diameter will be able to increase foundation 12's stability. Then both in a floating position and in a submerged tense position. The buoyancy part 3 can have a varying volume that displaces the water mass 20 in its longitudinal direction, so that the stability of the foundation 12 can be optimized from a surfaced position, through an immersion sequence, until it is rigidly anchored submerged in the water mass 20.

The buoyancy part 3 can advantageously have a smaller area at its ends 3a, this to reduce the structure's hydrostatic load in a submerged position.

The rigidly tensioned buoyancy part 3 and the lower part 4 of the tower can be said to constitute or produce the rear buoyancy of the foundation 12. To this extent, the tower 14 can be positioned arbitrarily in the longitudinal direction of the elongated buoyancy part 3, but is preferably positioned in an area which provides equilibrium, freely floating in the water mass 20, or firmly suspended against the anchorages.

By using a rotatable anchoring mechanism 26, the tower 14 can be placed at or near one end of the elongated buoyancy part 3, i.e. the tower 14 is placed on a non-centred part of the buoyancy part 3. The tower with turbine will rotate the elongated buoyancy part under the influence of wind forces 3's longitudinal direction, in a direction approximately equal to the wind direction. In such a configuration, it will naturally be possible to mount several wind turbines on the floating foundation 12.

Furthermore, as mentioned, the floating foundation 12 comprises at least one protruding stabilizer arm 6 which projects in a direction mainly transverse to the longitudinal direction of the elongated and stabilizing buoyancy part 3. The stabilizer arm 6 thus forms part of the floating foundation 12. The length of the stabilizer arm 6 will have an impact on the floating foundation 12. Essentially, a longer stabilizer arm 6 will add more stability, and one will also be able to reduce the buoyancy of the buoyancy body 8, where typical length on the stabilizer arm 6 can be 50, 80, or over 100 m. The stabilizer arm 6 comprises a buoyancy body 8 which penetrates the water surface of the body of water 20. In one embodiment, the buoyancy body 8 is mounted on the free end of the protruding stabilizer arm 6 and projects up or down into the body of water 20.

The buoyancy body 8 and/or the stabilizer arm 6 are further described here as constituting or producing the foundation 12's forward buoyancy. Depending on the installation location and configuration, the stabilizer arm(s) 6 can be placed on either side of the buoyancy part 3, or in front and behind.

The tower 14 can be imagined in some project-specific configurations to be placed entirely on the stabilizer arm 6, instead of on the tower's lower part 4. The tower 14 can also be imagined to be partially placed above the stabilizer arm 6 and the tower's lower part 4. Alternatively, the tower 14 can also be an integral part of the buoyancy body 8. The tower 14 can therefore be located at both ends of the stabilizer arm 6.

The figures show a stabilizer arm 6 which protrudes mainly perpendicularly and transversely in relation to the buoyancy part 3. However, the stabilizer arm 6 can also protrude at an angle which is not perpendicular. In a variant not shown, two stabilizer arms 6 can protrude transversely in relation to the buoyancy part 3, where the angle of each stabilizer arm 6 can for example be approx. 45º in relation to the buoyancy part 3. The invention will also cover two stabilizer arms 6 which protrude in opposite directions in relation to the buoyancy part 3.

The buoyancy body 8 can be a pipe part which is mounted approximately perpendicular to the stabilizer arm 6, i.e. perpendicular to the stabilizer arm 6's longitudinal axis. Perpendicular does not mean an angle which is necessarily 90 degrees, but an angle which means that the buoyant body 8 projects up and down in the body of water in an approximately vertical direction.

The projecting stabilizer arm 6 preferably projects from the upper part of the lower part 4 of the tower 14, in a mainly horizontal direction. Depending on the operational conditions, it is conceivable that the stabilizer arm 6 is angled in such a way that it penetrates the water mass in its front part without the need for the buoyancy body 8. Or the stabilizer arm 6 and the buoyancy body 8 are considered an integral part.

The rear part of the stabilizer arm 6 is attached to the lower part 4 of the tower in an area above the body of water 20, and preferably at a height that places it above the wave zone.

In an alternative embodiment, at least the protruding stabilizer arm 6 can be placed submerged in the water mass 20 and project from the elongated and stabilizing buoyancy part 3 in a mainly horizontal direction. Or in the tower's lower part 4 its lower part or a combination of the buoyancy part 3 and the tower's lower part 4. In the version where the stabilizer arm 6 is submerged, it will be able to contribute to the foundation 12's buoyancy. The variant with submerged stabilizer arm 6 is shown in figure 2, while the remaining figures show the first variant.

The stabilizer arm 6 can be equipped with a heave compensating device that slows movement in the water mass. As an example, reference is made to figures 3 and 4, where it appears that the buoyancy body 8 or front part of the stabilizer arm 6 may comprise one or more suspended weights 10 which further contribute to the stabilizing effect on the floating foundation 12, as the weight 10 hangs further down in the body of water 20 The plumb line 10 can have a design such as, for example, a cone, plate, or other shape which causes it to slow down movement in the water mass 20. The plumb line 10 can in some designs be advantageously attached to the seabed 30. Then either as a rigid anchoring, or as a loose anchoring.

Connecting the floating wind turbine structure, and in particular the tower 14 and associated lower part 4, as well as stabilizer arm(s) 6 can be done by means of a flange connection, where the screwed flange connections have an inner and an outer ring for bolts in relation to the supporting structure .

As mentioned, the floating foundation 12 is rigidly anchored to the fixed foundation 25. In one embodiment of the invention, this can be carried out by a first rigid anchoring 22 running from a first anchoring point 28a on the elongated and stabilizing buoyancy part 3 down to the fixed foundation 25 , and in that a second rigid anchorage 24 runs from a second anchorage point 28b on the elongated and stabilizing buoyancy part 3 and down to the fixed foundation 25.

The first and second anchoring points 28a, 28b can be produced at respective distal ends of the elongated and stabilizing buoyancy part 3, or at other suitable places on the buoyancy part 3.

The anchorages 22, 24 can for example be chains, tension rods or the like which extend tightly down towards and to the fixed foundation 25 on the seabed 30 with the intention of keeping the buoyancy part 3 below the sea surface. The buoyancy part 3 is designed to have sufficient buoyancy to keep the anchors 22, 24 against the fixed foundation 25 rigid. In order to increase the stability of the floating wind turbine structure in one direction, it would be advantageous to have one or more braces placed apart in the direction in which increased stability is desired.

The first and second anchors 22,24 can thus be tightened to form a rigid connection between the elongated and stabilizing buoyancy part 3's first anchoring point 28a, the fixed foundation 25 and the elongated and stabilizing buoyancy part's 3 second anchoring point 28b.

Furthermore, the bottom-fixed foundation 25 can in one embodiment be equipped with a rotatable anchoring mechanism 26, for example the rotatable anchoring mechanism 26 can be a turntable anchoring with connections for the first and second anchorings 22,24. Another example is an electric swivel.

The fixed foundation 25 can, for example, be one or more suction anchors, anchors, or a combination of different anchoring types, which are suitable for Tension Leg solutions. The bottom-fixed foundation 25 protrudes from the seabed 30 and a little way up into the body of water 20, but so that the foundation does not stick out of the body of water 20. In an advantageous embodiment, said anchorages 22, 24 slope inwards from each side of the buoyancy part 3 towards the common anchoring in the fixed foundation 25. This type of inclined anchoring will reduce the movement of the wind turbine structure in certain directions, as well as probably reduce cost, but it can also use several anchorings that can either project vertically down or in an angular configuration, as shown in figure 4.

Several examples of fixed foundations 25 for use in conjunction with the invention can be gravity-based foundations, monopile foundations, sunken box foundations, multipile foundations, and foundations with several sunken boxes. Common is a first part that is inserted into the seabed and a second part that protrudes from the seabed 30.

The monopile construction is the most widely used variant today, and comprises a pipe that is piled (driven) into the seabed until it is fixed. In the upper part, the pipe includes a transition piece for receiving a tower for a windmill. The wind turbine construction according to the invention can be attached to said transition piece.

The buoyancy body 8 which is mounted on the front part of the stabilizer arm 6 is designed to carry some of the weight of the windmill structure. The buoyancy body can further in one embodiment, as shown in Figure 4, be arranged to be tightly attached to a fixed foundation 25 on the seabed 30 using chain 32 or equivalent, so that the buoyancy body 8 is not allowed to move in a vertical direction. The buoyancy body 8 can be designed as a cylinder, cone, cube, or have any other shape suitable for the purpose of the buoyancy body 8. Correspondingly, the plumb line 10 suspended in the buoyancy body 8 in one embodiment, as shown in Figure 4, can be arranged to be tightly attached to the buoyancy part 3, or the fixed foundation 25 on the seabed 30, using chain 34 or equivalent, so that the movement of the plumb bob 10 is limited.

The buoyancy body 8 with the associated stabilizer arm 6 has the task of adding stability to the floating windmill structure. The second or inner end part of the stabilizer arm 6 is attached to the rigidly tensioned buoyancy part 3 so that sufficient stability is achieved in all directions.

The buoyancy body 8 can further share an anchorage with the rigidly tensioned buoyancy part 3, in the sense that an anchorage 32 can run down into the body of water to one or more fixed foundations 25. Alternatively, the buoyancy body 8 can be loosely attached using at least one traditional anchorage where one uses longer anchor lines attached to an anchor on the seabed 30.

The connection between the rear part of the stabilizer arm 6 and the rear buoyancy of the structure in the form of the elongated and stabilizing buoyancy part 3 is designed to be bolted and or welded together, as shown in Figure 6. The described connection can be carried out while the parts are floating in a water mass . Between the tower's lower part 4 and the elongated buoyancy part 3, inclined braces 11, designed as struts, tubes or chain, wire configurations, can also be mounted.

The invention further facilitates the connection of the wind turbine structure to the anchoring device by means of anchors 22,24 (or anchoring lines as shown in Figure 4) before it reaches the final installation location. This in that the stabilizer arm 6 is arranged in such a way that the anchoring device, i.e. the anchoring mechanism 26 which is attached to the fixed foundation 25, can be attached and/or lifted up under the stabilizer arm 6, as shown in Figure 5. This can be done, for example, before transport to the installation site. The wind turbine structure is designed for the attachment of fixed or temporary lifting devices for raising and lowering said anchoring devices.

The wind turbine structure with mounted tower 14 and turbine 16 will in its normal position float in a way where the elongated buoyancy part 3 will partially penetrate the surface and thus retain stability at the quay and during towing. During installation, anchoring devices can be lowered to the seabed 30 in the desired position. When using, for example, a suction anchor as an anchoring device, it will be possible to use the anchoring to pull the wind turbine structure down into the body of water 20 to a depth where the upper part of the elongated buoyancy part 3 is located below and in the body of water 20, so that its buoyancy will lead to a rigid anchoring of the wind turbine structure .

Another way to achieve a rigid anchorage is by filling sufficient ballast water into the wind turbine construction so that it will settle at a depth and so that the wind turbine construction can be attached to the anchorage in the form of the fixed foundation 25, where ballast water can then be evacuated so that the anchors 22,24 (or the lines shown in figure 4) are tightened until they have achieved the desired pretension.

In order to increase stability when anchoring the wind turbine structure during installation and or operational operation, permanent or removable stabilizer legs 7 can be mounted on the elongated buoyancy part 3.

In order to increase stability and better control the angle of the foundation 12 during operation and installation of, for example, a tower and nacelle, as well as installation in a wind farm, tanks can be used inside the elongated buoyancy part 3 and the stabilizer arm 6 with its attached buoyancy body 8. The tanks (not shown) are connected with a pipe system, so that the water can be actively and controlled transported from one tank to another tank in the pipe system. Active and controlled means a closed loop that pumps water automatically, based on parameters and or sensors.

If necessary, for example if there are large waves, the stabilizer arm 6 or its buoyancy body 8 can be anchored in the form of rigid anchoring or traditional anchoring with slack lines against the anchor, which can for example be the same bottom-fixed foundation 25 as mentioned.

Claims (20)

Patent claims 1. A floating wind turbine structure, comprising a foundation (12) floating in a body of water (20), where the floating foundation (12) supports at least one tower (14) equipped with a turbine (16), and said floating foundation (12) comprises a submerged, elongated and stabilizing buoyant part (3) attached to the lower part of the tower (4), and the floating foundation (12) comprises one or more projecting stabilizer arm(s) (6) projecting in a direction transverse to the the longitudinal direction of the elongated and stabilizing buoyancy part (3), with said stabilizer arm (6) penetrating a water surface to the body of water (20), characterized in that the submerged, elongated and stabilizing buoyancy part (3) is arranged horizontally floating in the water mass (20) and is rigidly anchored to one or more fixed foundations (25) which protrude from a seabed (30), 2. The floating wind turbine structure in accordance with claim 1, characterized in that a buoyancy body (8) is mounted on the free end of the protruding stabilizer arm (6) and projects up or down into the body of water (20). 3. The floating wind turbine construction in accordance with claim 1, characterized in that the protruding stabilizer arm (6) projects from the lower part (4) of the tower (14) in a horizontal direction, and in an area above the body of water (20). 4. The floating wind turbine construction in accordance with claim 1, characterized in that the protruding stabilizer arm (6) is submerged in the body of water (20) and protrudes from the elongated and stabilizing buoyancy part (3) in a horizontal direction. 5. The floating windmill construction in accordance with claim 2, characterized in that the stabilizer arm (6) buoyancy body (8) is equipped with a suspended weight (10). 6. The floating wind turbine construction in accordance with claim 1, characterized in that the floating foundation (12) is rigidly anchored to the fixed foundation (25) by a first rigid anchoring (22) which runs from a first anchoring point (28a) on the elongated and stabilizing buoyancy part (3) and down to the fixed foundation (25), and by a second rigid anchorage (24) which runs from a second anchoring point (28b) on the elongated and stabilizing buoyancy part (3) and down to the fixed foundation ( 25). 7. The floating wind turbine construction in accordance with claim 6, characterized in that said first and second anchoring points (28a, 28b) are on respective distal ends of the elongated and stabilizing buoyancy part (3). 8. The floating wind turbine construction in accordance with claim 6, characterized in that said first and second anchoring (22,24) are tightenable anchoring lines or tension rods in the form of rigid pipes. 9. The floating wind turbine construction in accordance with claim 6, characterized in that said first and second anchorages (22,24) are tightenable to form a rigid connection between the elongated and stabilizing buoyancy part (3)'s first anchoring point (28a), the bottom-fixed foundation (25) and the elongated and stabilizing buoyancy part (3)'s second anchoring point (28b). 10. The floating wind turbine construction in accordance with claim 2, characterized in that the buoyancy body (8) of the stabilizer arm (6) is anchored to the seabed (30). 11. The floating wind turbine construction in accordance with claim 5, characterized in that the buoyancy body (8) suspended weight (10) is anchored to the seabed (30). 12. The floating wind turbine construction in accordance with claim 1, characterized in that the stabilizer arm (6) is anchored to the seabed (30). 13. The floating wind turbine construction in accordance with claim 1, characterized in that the buoyancy part (3) comprises internal tanks designed to be emptied and filled with ballast. 14. The floating wind turbine construction in accordance with claim 13, characterized in that the ballast is transportable between the tanks. 15. The floating wind turbine construction in accordance with claim 6, characterized in that the fixed foundation (25) is equipped with a rotatable anchoring mechanism (26). 16. The floating wind turbine construction in accordance with claim 15, characterized in that the rotatable anchoring mechanism (26) is a turntable anchoring with connections for the first and second anchoring (22,24). 17. The floating wind turbine construction in accordance with claim 16, characterized in that the rotatable anchoring mechanism is an electric swivel with connections for the first and second anchoring (22,24). 18. The floating wind turbine construction in accordance with claim 15, characterized in that the tower (14) is placed on a non-centered part of the buoyancy part (3). 19. The floating wind turbine construction in accordance with claim 15, characterized in that the tower 14 is placed on the stabilizer arm (6). 20. The floating wind turbine construction in accordance with claim 1, characterized in that the stabilizer arm (6) is equipped with a heave compensating device which slows movement in the water mass (20).