NO20200232A1 - Foundation for an offshore wind turbine - Google Patents

Description

FOUNDATION FOR AN OFFSHORE WIND TURBINE

The description relates to an invention within the technical field of offshore wind energy. It describes a rotatable foundation for an offshore wind turbine, an apparatus for extracting energy from wind that includes the rotatable foundation, and more.

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 great 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. Wind forces are particularly critical. Calculations have shown that the tilting forces acting on a wind turbine at sea will typically be 15 times as strong in the primary direction of the wind relative to a direction 90 degrees to this. In order to prevent a wind turbine from tilting too much under harsh weather conditions at sea, it is important that the foundation is designed to counteract tilting caused by the aforementioned forces, and particularly tilting in the direction of the wind.

Stability against tilting is a challenge and cost driver for floating foundations, especially for floating foundations to be used in areas with the potential for violent wind and wave conditions. Existing solutions to ensure stability in such areas are often large, heavy and expensive. 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.

This document describes several solutions related to stability for an offshore wind turbine, where each of the solutions together or separately solves one or more challenges when extracting energy from offshore wind.

Another challenge when extracting offshore wind energy is related to the installation, dismantling and maintenance of equipment. A wind turbine has several heavy, large parts, located on or near the top of a wind turbine tower. For example, a nacelle can weigh several hundred tonnes, and it should preferably be installed over 100 meters above sea level. Lifting such equipment to or from the top of the tower is a complex and risky task, especially offshore and especially when the lifting is carried out from a vessel which in the waves at sea moves relative to a floating wind turbine foundation.

This document further describes several solutions related to production, installation, dismantling and/or maintenance of equipment.

In a first aspect of the disclosure, a ballast element is described for adding ballast to a floating foundation for a wind turbine and for adding righting force to the foundation upon tilting of the foundation, wherein the ballast element is formed with a hole to receive a righting leg associated with the foundation and wherein the ballast element comprises connection means to be movably suspended in an underside of the foundation.

The ballast element can, for example, be torus-shaped or cylindrical. The ballast element can typically be suspended via, for example, chain or some form of cable. The connection means can include, for example, one or more chains or cables or the like to hang the ballast element from the foundation. As the ballast element is freely suspended, and not rigidly fixed to the foundation, it can move relative to the foundation's structure, including the foundation's supporting legs. When tilted above a certain degree, the movement of the ballast element relative to the structure could be large enough for the ballast element to come into contact with the supporting leg, and at least part of the gravitational forces acting on the ballast element would then be able to act on the supporting leg as that it counteracts the tilt and thus has a righting and stabilizing effect on the foundation.

In another aspect of the description, a tower for a wind turbine for a floating foundation is described, where the tower has an internal cavity and an opening to the sea to receive water from a body of water in the internal cavity. The body of water can be part of an ocean, and the body of water can have waves. Such a design of the tower will be able to reduce buoyancy as a result of water displaced by the tower when the tower is in operational position and the lower part of the tower penetrates a sea surface, and will be able to reduce an effect of waves on the tower and its stability.

The lower part of the tower may be connected to a transition part belonging to the foundation, where the transition part is designed with an opening towards the sea leading to an opening to the opening of the tower, to allow the movement of water up through the transition part and to the tower. The lower part of the tower can act as a righting leg/a righting keel (herein, in this context, called keel) for the foundation, or stand in direct connection with a vertical, stabilizing part belonging to the foundation. The vertical stabilizing part may be designed with an opening to the sea throughout its length, an opening which may lead to the opening in the tower. The tower can be welded or bolted to the transition part.

Such an opening to the sea can allow waves to move freely into and into the cavity and assume approximately the same height as the waves on the outside of the cavity when the foundation with the tower is in an operational position, so that wave movements will have less impact on the foundation and reduce their impact on the tower.

The tower and/or the vertical stabilizing part may comprise a ventilation means to ensure that air can enter the cavity when the amount of water in the cavity decreases and to evacuate air when the amount of water in the cavity increases. Venting means may also be included as part of the floating apparatus to cool a generator.

In a third aspect of the description, a rotor for a wind turbine is described, where the rotor comprises a connection means for connecting the rotor and thereby an upper part of the wind turbine to one or more tie rods or one or more cables.

A non-rotating part of the rotor can be designed to take forces to relieve a bending moment on the tower.

In one embodiment, the rotor may have a central hole through the rotor to be penetrated by a coupling means which may be coupled to an internal structure in a nacelle or tower carrying the rotor. The connection means can be used to connect an upper part of a wind turbine to a first end of a tension rod which can be attached at a second end to an external attachment point, for example an attachment point on an outer part of a foundation for the wind turbine. With the help of this tie rod and the connection means, forces can be taken up to reduce the bending moment on, for example, the tower or a wind turbine foundation. By taking up bending moment when using tension rods, for example, transitions between a vertical part of the foundation and a horizontal part of the foundation can be protected against forces that could potentially be critical and that could lead to breakage. For example, a rigid connection between the horizontal, stabilizing part and a transitional part can be protected in this way. The solution can allow, for example, a higher wind turbine tower on the foundation.

In one embodiment, the rotor may comprise a swivel rotatably attached to an outer surface of the rotor, where the swivel comprises the connection means for connecting the rotor, and thereby an upper part of the wind turbine, to a tension rod.

In a fourth aspect of the disclosure, a nacelle for a wind turbine is described, wherein the nacelle comprises a front portion and a rear portion, wherein the front and rear portions are releasably lockable to each other to form the nacelle, wherein the front portion of the nacelle comprises a coupling means to connect the nacelle to a rotor.

The rear or front part may include a generator. The nacelle's front and rear parts can be mounted on an underlying surface which in turn can be a part of a tower pipe that can be penetrated by a tower for a wind turbine. Then the entire nacelle can be moved up and down along the tower on the tower tube. The tower pipe is attached to the tower.

The front and/or the rear part may be adapted to be attached to a hoisting means for hoisting the part or parts to or towards the top of the wind turbine.

The nacelle may comprise one or more further parts which can be releasably locked to the front and/or rear part of the nacelle. The front and rear parts of the nacelle can be releasably locked to each other via a tower for a wind turbine, in that the front and rear parts can both be locked to the tower and thereby locked to each other, and/or the front and rear parts of the nacelle can be releasably locked to each other.

The nacelle can be designed in such a way that it can be penetrated in its entirety by a wind turbine tower.

The nacelle may be designed with an opening to receive the wind turbine tower. The opening can be a substantially, for example, cylindrical or cone-shaped hole through the nacelle, from a lower surface of the nacelle to an upper surface of the nacelle.

A divisible nacelle can simplify operations for installation, dismantling, maintenance and the like.

In a fifth aspect of the description, an upper transition piece for a wind turbine is described, where the transition piece comprises an upper and a lower nacelle carrier, a hinge and a tilting mechanism, where the upper and the lower nacelle carrier are tiltably attached to each other at the hinge and where the tilting mechanism is connected to the upper and the lower nacelle carrier to tilt the two nacelle carriers relative to each other.

A nacelle can typically be attached to a wind turbine tower via the upper transition piece. The upper transition piece may further comprise a bearing to allow rotation of the nacelle relative to the wind turbine tower. The upper transition piece can further comprise a rotation means for rotating the nacelle relative to the tower.

One or both of the nacelle carriers can be vertically divisible into, for example, two parts, for example so that each part can be shaped like a crescent.

The tilting mechanism may comprise, for example, a hydraulic cylinder or an electric motor to supply a force to tilt the upper part relative to the tower.

The lower nacelle carrier can typically have a lower connection to the tower, as well as an upper connection to the upper nacelle carrier. The lower nacelle carrier may include the bearing and be connected to the tower via the bearing, to allow rotation of the nacelle carrier on the tower. Furthermore, the lower nacelle carrier can be connected to the upper nacelle carrier via the tilting mechanism. The upper nacelle carrier can, in addition to having a lower connection to the lower nacelle carrier, have an upper connection to a nacelle. The connection to the nacelle can be a connection via a bearing that allows rotation of the nacelle on the upper nacelle carrier. In a typical embodiment, the lower nacelle carrier or the upper nacelle carrier will comprise a bearing to allow rotation of the nacelle carrier on the tower or of the nacelle on the nacelle carrier, but it is also possible with a nacelle carrier without such a bearing and with a nacelle carrier with both a bearing on the lower nacelle carrier and a bearing on the upper nacelle carrier.

The rotation mechanism can be a mechanism for rotating the nacelle carrier relative to the tower or for rotating the nacelle relative to the nacelle carrier.

In a sixth aspect of the description, an angle stabilizer is described for stabilizing the direction of force of a force from an anchor line acting on a floating foundation for a wind turbine, wherein the angle stabilizer comprises a rigid angle stabilizer structure and a weight connected to the rigid angle stabilizer structure, and wherein the angle stabilizer is arranged to connect the anchor line to the foundation anchor point via the rigid angle stabilizer structure.

The angle stabilizer structure can comprise, for example, three rigid rods connected to each other so that they form a rigid triangular structure. The angle stabilizer may comprise an extender in the form of a rigid strut, a chain or a wire or the like which may be connected to the angle stabilizer structure. The solder can be connected to the angle stabilizer structure via the extension.

Several angle stabilizers can be connected to a foundation. For example, one angle stabilizer can be connected to a foundation for each of three anchor lines. A majority of the several angle stabilizers' weights can each be connected to at least one other of the several angle stabilizers' weights using, for example, stays, cables or chains or the like.

The foundation may be attached to a first corner of the angle stabilizer structure. The plumb line is typically connected, for example via a stay or a wire, to a lower part of the angle stabilizer structure, and the anchor line is typically connected to another corner of the angle stabilizer structure. The anchor line can have a typical cock's foot configuration, so that two parts, one of each anchor line can share a corner of the triangle. Other configurations of the angle stabilizer structure are of course possible, it need not be shaped like a triangle. Other variants of connecting, for example, the anchor line to the angle stabilizer or the angle stabilizer to the foundation or are also possible.

In a seventh aspect of the description and in a first aspect of the invention, a floating foundation for an offshore wind turbine is described, where the foundation comprises a transition part to support the wind turbine, and a stabilizing part to stabilize the transition part with or without the wind turbine,

where the stabilizing part comprises a horizontal part and a vertical part, both of which are rightly connected to the transition part,

wherein the vertical portion comprises a righting leg for projecting downward into a body of water in an operational position,

where the horizontal part comprises a righting arm and in connection with the righting arm, at a distance from the transition part, an anchor attachment,

so that the transition part in operational position, when the foundation is anchored, can rotate around the anchorage under the influence of natural forces, such as forces from wind, waves and/or current.

The foundation can be anchored to the seabed via an anchor line attached to the anchor.

The foundation can be free from direct anchoring of the transition part, which can be anchored only via the righting arm and the anchor attachment and an anchor line. The foundation may include an anchor and an anchor line. The foundation can be anchored via the anchor in such a way that the transition part can rotate around the anchor under the influence of natural forces such as waves, wind and/or current. The body of water is a body of water to support the foundation, a body of water the foundation can float on.

The foundation is designed to be anchored at the anchor, not at the transition part, so that the transition part in operational position, and thus also a wind turbine installed on the foundation, can rotate around the anchor under the influence of natural forces such as forces from waves, current and/or wind. In this way, the foundation can act self-orienting and turn and the wind turbine in an advantageous position in relation to stability and in relation to efficient production of energy. This advantageous position will typically be with the transition section mainly anchored downstream in terms of wind.

The anchor can be a device comprising several parts. For example, the anchor may comprise a vertical structure, which may be attached to the righting arm and in the operational position be directed some distance down into a body of water, and one or more connecting means for connecting an anchor line to the anchor.

The term "righting" refers to an effect in relation to the foundation's stability, typically an anti-tilt effect. The righting parts are usually rigidly attached to the transition part, directly or via other parts of the foundation, so that if a force acts on one of the parts, it will also act on and be counteracted by the others. The righting parts can, for example, be rigidly attached to the transition part, directly or via another righting structure, for example by being welded or bolted to the transition part, or one or more of the righting parts can be connected to the transition part via, for example, a hinge that allows movement in it smallest in one plane. The righting arm may in the further text be referred to as "the arm", "the righting arm" or, because it is part of the horizontal part of the foundation and/or because in some embodiments it is essentially horizontal when the foundation is in operational position in still water, like the "horizontal arm". The righting leg can be referred to in the further text as "the leg", "the righting leg" or, since it is part of the vertical part of the foundation and/or because in some embodiments it is essentially vertical when the foundation is in operational position in still water, like the "vertical leg". The stabilizing part of the foundation comprises a rigid structure comprising at least part of the transition part, the horizontal part and the vertical part.

The terms "leg" and "arm" should not be seen as limiting shape or design. The leg and the arm may both be of any shape that may be convenient or advantageous in some way. The leg can stand straight vertically down into the body of water in the operational position, or, for example, obliquely downwards. The leg can be split into, for example, two or three or more than three downward-pulling elements, each of which can be directed, for example, directly vertically downwards or obliquely downwards. They can, for example, project diagonally downwards from each other. So can the arm.

In a typical embodiment, the anchor attachment can be attached to a first end of the arm, while the transition part is attached to a second end of the arm, so that the arm extends in its longitudinal direction from the anchor attachment to the transition part. In an alternative embodiment, the arm can extend from the transition part, to the anchor attachment, and further through and past the anchor attachment. In a further embodiment, the arm can extend from the anchor attachment, to the transition part, and further through and past the transition part. In a further embodiment, the arm can extend through and past both the transition part and the anchor attachment. In all embodiments of the foundation according to the first aspect of the invention, the anchorage will be at a distance from the transition part, where the distance can be, for example, more than 10 meters, more than 20 meters, more than 30 meters, more than 50 meters, more than 70 meters, more than 100 meters, or over 150 meters.

The terms "vertical"/"mostly vertical" and "horizontal"/"mostly horizontal" typically refer to a position or shape of an object when the foundation is in an operational position under normal conditions in relation to wind and waves.

The vertical part of the foundation is a part of the foundation which in the operational position will essentially be an underwater part, in that in the operational position it will extend downwards into a body of water from the transition part or from the horizontal part of the foundation. The vertical part can act as a keel, and/or as ballast, to stabilize the foundation against tilt. The vertical part can typically extend over 20 metres, over 30 metres, over 50 metres, over 70 metres, over 100 meters or over 150 meters into the body of water from the surface of the body of water. The vertical part's primary purpose can typically be to act against lateral tilt, although it can also have a stabilizing effect against tilt in the longitudinal direction.

The longitudinal direction of the foundation can be said to be the direction from the anchorage to the transition part and vice versa. Sideways can then, for example, be tilted perpendicular to the longitudinal direction of the foundation.

The horizontal part of the foundation is a part of the foundation which, in the operational position, will mainly project horizontally from the transition part. It can face or be angled a few degrees upwards or downwards in relation to a horizontal plane, for example 5, 10 or 15 degrees upwards or downwards relative to the horizontal plane. The horizontal part can primarily act against tilting in the foundation's longitudinal direction.

The transition part is part of the foundation that a wind turbine can stand on and/or in connection with. In addition to the mentioned function, the term should not be read as limiting the form or design of the part. This transitional part is connected to the straightening arm and to the straightening leg. The leg can be directly connected to the transition part, or it can be connected to the transition part via, for example, the arm. The leg may be attached to the front part of the righting arm. The leg can, for example, be included as part of the anchorage, so that the foundation can freely rotate around the leg. This embodiment of the foundation has significant advantages in that there is less surface to be led through the water if the wind changes direction. This can be advantageous, for example, in relation to lateral stability. The leg can project directly downwards, straight downwards, or obliquely downwards, from a position where it is connected to another rigid structure belonging to the foundation, for example from a position on the righting arm, from a position on the transition part, or from the anchor attachment. The leg can, for example, project downwards from a position on the arm equal to or less than 25% of the length of the arm from the transition part, equal to or less than 50% of the length of the arm from the transition part, equal to or less than 75% of the length of the arm from the transition part, equal to or less than 90% of the arm's length from the transition part, or more than 90% of the arm's length from the transition part.

In order to stabilize the foundation in relation to lateral tilt, it can be advantageous to reduce friction that will arise between the structure of the foundation and a body of water when the foundation rotates. By placing the leg at, in connection with, or having the leg as part of the anchor rather than having the leg directly under the transition part, this friction will be reduced, as the distance the leg has to move through the body of water during rotation is less at the anchor will be less than at the transition section. This will also reduce friction and improve stability.

Such a placement of the leg will also be beneficial in relation to the influence of an ocean current on the position of the transition part in the water, and it will be able to provide a more even distribution of weight on the righting arm. Furthermore, it could be advantageous to avoid collisions with, for example, underwater structures.

A foundation according to the first aspect of the invention can offer better stability for a wind turbine, against forces from wind, waves and current in combination, relative to its vertical size and its mass, compared to known technology such as for example "Hywind", in that it is designed more appropriately.

The righting arm can be rigidly attached to the anchor attachment and to the transition part, and can form a rigid connection between the anchor attachment and the transition part.

The foundation will typically be designed so that in operational position it will follow the wind so that the transition part will normally remain mostly downstream anchored in a wind acting on the foundation. This means that if the wind blows directly from north to south, the foundation will typically rotate with the wind so that the transition part is south of the anchorage.

The wind forces will then primarily act on the wind turbine in the longitudinal direction of the righting arm.

Depending on the length, weight and design of the anchor and the arm, the arm will then be able to add very good stability properties to the foundation against tilting caused by wind forces. By aligning the foundation with forces affecting it, it will be able to prevent sideways tilt, which will have a major impact on its stability. Ocean currents and waves can also affect the position of the transition part relative to the anchorage, but under typical conditions the direction of the wind will typically have the greatest effect on the position.

Certain embodiments of the invention may have more than one righting arm. In embodiments with more than one righting arm, the righting arm connecting the anchorage to the transition part can be called the primary righting arm, and other righting arms can be called secondary righting arms. In embodiments with one or more other righting arms, it or they will typically not be parallel to the primary righting arm. Such a secondary righting arm will then be able to have a righting effect against tilt that deviates from the longitudinal direction of the primary righting arm. In most embodiments, the righting arm will be essentially horizontal, but in some embodiments, for example, can be angled somewhat downwards or upwards, relative to a horizontal plane, for example between the anchor attachment and the transition part.

The foundation and a wind turbine installed on the foundation are further exposed to tilting forces from the rotation of the wind turbine's blades and from waves, which will have a direction against which the righting arm has no particular effect. The correcting leg will have a stabilizing effect against these forces.

The righting arm which forms a connecting link between the anchor attachment and the transition part can be shaped like an elongated tube. The length of the arm will partly determine the tower's tilt in the direction of the wind when the transition part is pressed down as a result of the force of the wind against the turbine. The arm will typically be fully submersible during normal operation, or it may be semi-submersible. The anchor attachment can be attached to a first end of the righting arm, and the transition part to a second end.

The righting arm can have one or more chambers that can be selectively filled with or emptied of ballast. In embodiments where a righting arm has several chambers, the buoyancy point and/or center of gravity of the foundation can be adjusted by adjusting the contents of the chambers.

The buoyancy point and/or center of gravity of the foundation can in this way, by adjusting the contents of the chambers, be adjusted horizontally and/or vertically. This can be advantageous for stabilizing the foundation in relation to forces from the anchorage and after wind and/or wave conditions.

Note that when the foundation's stability is described, and its center of gravity and buoyancy point and the like, this may apply to the foundation with a wind turbine installed on the transition part of the wind turbine.

It can also be advantageous to have the foundation's buoyancy point as close to a surface of a body of water as possible. The foundation according to the first aspect of the invention allows the buoyancy point to be lifted by means of the horizontal part - in that the righting arm can have considerable buoyancy.

Typically, the weight in the arm, when the foundation is in operational position, will be balanced so that the arm is fully submersible to limit the impact of the waves' power, as well as having better control over the device's buoyancy. Depending on what is desired, one can for example change the amount of ballast and/or the placement of ballast in the righting arm so that it has, for example, positive buoyancy at the end attached to the transition part to carry at least part of the weight of the transition part, or in the end towards the leg if the leg is at the opposite end of the arm in relation to the transition part. It is normally desirable to have a distribution of ballast in the arm which means that bending of the arm is avoided in order to avoid strong bending forces on one or more parts of the arm or other structure rigidly attached to the arm.

The anchor may comprise a column further described as an anchor tower. The foundation can be configured so that at least part of the anchor tower projects above a water surface in the operational position and so that it can be pulled down into the water when the anchor is pulled downwards by downward forces applied to the anchor via an anchor line. In this way, the foundation's buoyancy at the anchorage can be increased to compensate for downward forces by the anchor tower displacing a larger volume of water when it is pulled downwards.

The mooring or the anchor tower can internally accommodate some or all parts belonging to one or more control systems and/or one or more transformers for power production and/or power transmission from a wind turbine, and/or a passage for a cable for power transmission to land.

The top of the anchor tower can be arranged as a landing platform for a helicopter.

The anchor tower can be rotatably attached to the anchor attachment, and thus not an integral part of the righting arm. The anchor tower can be an extension of the righting leg. In one embodiment, the anchor tower can be in the center in relation to the anchor lines, which will be advantageous in embodiments where the anchor tower has a passage for a cable to transmit power to shore.

The anchor may comprise an anchor ring. The anchor ring can be rotatably attached to a vertically oriented structure belonging to the anchor attachment. The vertically oriented structure can be the foundation's righting leg, the anchor tower, or another vertically oriented structure. The anchor ring can be shaped like a ring. The anchor ring can be penetrated by, for example, the vertically oriented structure or another part of the anchor attachment, or the anchor ring can penetrate the vertically oriented structure. The anchor ring may comprise one or more connecting means for connecting the anchor ring to one or more anchor lines. The anchor may comprise one or more angle stabilizers to stabilize the direction of the force acting on the anchor from the anchor line. These one or more angle stabilizers can be connected to the anchor ring. The anchor can be any type of anchor to anchor the foundation. The anchor line can be any type of anchor line. The foundation may comprise more than one anchor and at least one anchor line for each of the more than one anchors. In some embodiments, the foundation may include more than one anchorage. When anchoring at sea, it can in many cases be advantageous, and even necessary, with anchor lines made of material with a low specific weight. Such anchor lines are often expensive, compared to heavier alternatives. Embodiments of the foundation according to the invention can have anchor lines that have a higher specific weight, such as, for example, a steel anchor chain. A heavy anchor line can be beneficial for the foundation, as the weight of the anchor line can add weight to the anchor, which can be used to contribute to the stabilization of the foundation.

When strong wind forces act on a wind turbine standing on the foundation, they will blow the wind turbine and foundation backwards from the anchorage. The anchor will then pull on the anchor line, which will exert a counter force on the anchor. This counterforce will at least partially act vertically, exerting a force downwards in relation to the anchorage. This will have a further stabilizing, protecting effect on the foundation and the wind turbine.

As the anchor is pulled downwards, the angle from the anchor line to the anchor may change, and thus also the direction of the force exerted on the foundation by the anchor line. The anchor can therefore comprise an angle stabilizer to keep the direction of the force exerted on the anchor from the anchor line more stable. The angle stabilizer may comprise a rigid structure which includes a plumb bob, and which is arranged to be connected to the anchor and to the anchor line.

The righting leg is a structure primarily to stabilize the wind turbine foundation against tilting in directions other than the current prevailing wind direction. One purpose of the leg is to have a protective effect against lateral loads. The leg with its weight can further be used to equalize the loads in the longitudinal direction of the transition part. The position of the leg in relation to the tower and anchorage affects the distribution of the foundation's buoyancy and center of gravity and loads, for example from gravity, on the foundation's structure. The foundation can advantageously be designed so that the leg is placed in an advantageous position with regard to buoyancy point, center of gravity and/or structural loads.

To ensure lateral stability, it may be beneficial to add weight to a lower part of the leg and/or to extend the leg downwards. The leg can be shaped with a surface that provides great damping against lateral tilt. The leg can be designed, for example, as a column, a tube or a cone, but it can also advantageously have a flatter design in the vertical plane. The leg can function and/or be designed as a keel, or as a buoy.

The leg can be designed with one or more chambers that can be filled with ballast material. The leg may be without a chamber to receive ballast, and the body of the leg may itself constitute a ballast.

As the protecting leg is not the primary stabilizer against wind forces, but against smaller, lateral forces, its mass and/or length can be limited compared to, for example, the spar buoy used in the "Hywind" solution. This can be very advantageous, for example, in relation to the transport of foundations over sea areas with relatively shallow water and means that the floating foundation according to the first aspect of the invention can also be installed in sea areas with relatively shallow water.

In some embodiments, the leg will be located directly under a platform for a wind turbine tower on the transition section, preferably, but not necessarily, as a vertical extension of a tower. The leg can alternatively be placed at a horizontal distance from the platform, and at a horizontal distance from the transition part, for example in the direction from or towards the anchorage. The leg may be part of or directly connected to the tower of a wind turbine to be supported by the wind turbine foundation.

The leg can, for example, be designed as an open tube, allowing water to penetrate. An open bottom can minimize the water displacement of the leg in the operational position, thereby reducing buoyancy from the leg and/or the effect of the leg on the foundation. The leg can typically be rigidly attached to the transition part, directly or indirectly, for example via the arm.

The foundation can have more than one leg. In one embodiment, for example, one of several legs can be a lower part of the tower for a wind turbine, while another leg is independent of the tower and rigidly attached to an underside of the foundation at a distance from the tower. More legs can be advantageous because you can then achieve the same or better stability as you can achieve with one leg with more legs of smaller mass and/or length.

The righting leg can be rigidly attached to the transition part, either directly or via the arm. In embodiments of the foundation, the leg can be raised and lowered vertically. A leg that can be raised and lowered can, for example, be advantageous in cases where the foundation is to be towed out to sea over areas with a sea depth less than the depth of the leg in operational position.

The foundation can also include one or more water brakes. The one or more water brakes can be suspended from one or more lower parts of the foundation structure and can be advantageous in that they can slow down vertical movement of the foundation. They can be designed and suspended so that during vertical movement of the foundation they will push on a significant mass of water, which will ensure that they apply a force to the foundation against the direction of movement. They can be designed so that they primarily brake during vertical movement in one direction, for example upwards.

The foundation may comprise a motorized rotation means for controlled rotation of the foundation. In advantageous embodiments, the rotation means can be connected to a control system so that the foundation can be rotated back to an initial position. It can, for example, be set in such a way that if the device has rotated more than two revolutions around the anchor point, the rotation means will rotate the foundation two revolutions back. This can, for example, be advantageous in order to avoid unwanted entanglement of an electric cable between the facility and the seabed.

The means of rotation may, for example, include a truster. The rotation means will typically be placed in connection with the foundation at a distance from the anchorage, towards the transition part. In embodiments, the rotation means can be rigidly attached to the transition part of the foundation, or in an embodiment where it can rotate to control the force direction.

The foundation can further comprise a rudder. The rudder can, for example, be attached to the righting leg, but can also be attached to the transition part or to the righting arm independently of the leg. The rudder can be rotated 360 degrees. The rudder can be used to influence the rotation of the foundation, for example by turning it so that it influences the rotation towards an ocean current direction, for example to improve the stability of the foundation and/or to improve the orientation of a wind turbine mounted on the foundation in relation to a wind direction such that the wind turbine can more efficiently extract energy from the wind.

The righting leg of the foundation can be rotatable or comprise a rotatable part, and be shaped so that it can function as a rudder. In one embodiment, the foundation may have both a rotatable righting leg and a rudder. In such an embodiment, for example, the righting leg can be rotatable at a smaller angle than the rudder, and the rudder can be the primary means of adjusting the influence of an ocean current on the position of the transitional part of the foundation relative to the anchorage, and the righting leg can be a secondary means for that same.

Most known offshore wind turbines have a nacelle with attached blades, where the nacelle can be rotated to angle the blades in a way that makes them use a wind effectively to extract electrical energy – typically 90 degrees to the direction of the wind. With a foundation that is rotatable, it is not as important that the nacelle is rotatable 360 degrees. It is then conceivable that the nacelle could be rotationally fixed to the tower, or have less freedom of rotation, for example -10 degrees, -20 degrees, or -45 degrees.

The righting leg can be located at or near the anchorage. To stabilize a foundation in relation to lateral tilt, it can be advantageous to minimize friction between the structure of the foundation and a body of water that occurs when the foundation rotates. This friction can be reduced by limiting the distance the leg must move when rotating the foundation. It can thus be advantageous for the foundation's stability if the leg is placed at or near the center of rotation to limit said distance, to reduce friction.

In an eighth aspect of the description, a floating foundation for a wind turbine is described, where the foundation comprises:

- a transition part and a righting leg, where the righting leg projects downwards into a body of water when the foundation is in an operational position;

- a rigid structure, which comprises and connects at least part of the transition part and at least part of the righting leg; and

- a ballast element designed with a hole to receive the righting leg,

where the ballast element is movably suspended in the rigid structure, so that the righting leg penetrates the ballast element and so that the ballast element will come into contact with and have a righting effect on the righting leg and thus also have a righting effect on the foundation when the foundation is tilted above a certain degree.

The ballast element may be the ballast element according to the first aspect of the description.

The foundation according to the eighth aspect of the description may have any of the features mentioned in connection with the foundation according to the seventh aspect of the description.

In a ninth aspect of the description, a floating foundation for an offshore wind turbine is described, where the foundation includes:

- a transition part for carrying the wind turbine;

- a first and a second righting arm,

wherein the first arm and the second arm are attached to and extend from the transition member, and wherein the first arm comprises a hinge and via the hinge the link is connected to the transition member to allow movement of the first arm in the horizontal plane.

The floating foundation according to the ninth aspect of the disclosure may have the first and second arms attached to the transition portion at an angle between them of less than 120 degrees, of less than 110 degrees, of less than 100 degrees, or, typically, of about 90 degrees. The angle between the two arms can be less than 90 degrees or more than 120 degrees. The movement of the first arm that the hinge allows may be a movement that changes the angle between the two arms. The floating foundation may have more than two essentially horizontal, righting arms.

An outer part of the first and an outer part of the second arm of the latter foundation can be attached to each other with a fastening means such as a wire or a chain or the like.

An outer portion of the first arm and/or an outer portion of the second arm may each have an anchor attachment for connecting the arm to an anchor.

In a typical embodiment, the first arm can be attached to a first anchor located on a substantially opposite side of the first arm in relation to the second arm, via an anchor line that extends from the first arm's anchor attachment to the first anchor. The second arm can typically be attached to a second anchor located on a substantially opposite side of the second arm in relation to the first arm, via an anchor line that extends from the second arm's anchor attachment to the second anchor.

The first arm and the second arm may be floating arms, semi-submersible arms or fully submersible arms.

The first arm can have cavities that can selectively hold ballast or be empty of ballast. In this way, the buoyancy and center of gravity of the arm and thus also the buoyancy and center of gravity of the foundation can be adjusted. The arm can have several cavities along its longitudinal axis. The other arm may have such cavities.

As in connection with the previously described aspect of the description, descriptions such as "substantially horizontal" and "movement of the first arm in the horizontal plane" refer to the position and movement in the operational position of the foundation under normal, calm conditions at sea. This also applies to further description and further aspects of the description.

The foundation according to the ninth aspect of the description may be a foundation to be anchored in a manner that does not allow the foundation to rotate, or it may be a foundation to be anchored in a manner that allows rotation. The foundation can be anchored as mentioned above, where the first and the second arm are both anchored to their respective anchors. Alternatively, it can be anchored from one arm only, so that the foundation can rotate around the one arm's anchorage.

The foundation according to the ninth aspect may comprise any of the features mentioned in connection with the foundations according to the seventh and/or the eighth aspect of the description.

Any of the foundations according to the seventh, eighth or ninth aspect of the description may comprise one or more of the ballast element according to the first aspect of the description or the angle stabilizer according to the sixth aspect of the description, and/or a any of the features of one of the other foundations.

In a tenth aspect of the description, a wind turbine is described for an apparatus for extracting energy from wind, where the wind turbine has an upper part and a lower part, where the upper part is tiltably attached to the lower part by a hinge and where the wind turbine comprises a tilting mechanism to be able to tilt the upper part relative to the lower part, to be able to keep the upper part stable when the wind turbine is tilted.

The wind turbine's tower may further comprise a control unit linked to the tilting mechanism to automatically control the cylinder to keep the upper part correctly angled in relation to a horizontal plane. The upper part may comprise a nacelle with a rotor and blades. The upper part can further comprise a tower extension – a structure similar to the top part of a typical tower for a wind turbine – to which the nacelle is attached. The upper part of the wind turbine can be part of a tower for a wind turbine, and the lower part can be a tower or part of a tower for a wind turbine.

"Keeping the upper part stable" in this context can mean keeping an angle between the upper part and a horizontal plane stable. This can then happen by changing an angle between the upper part and the lower part, by tilting the wind turbine. The upper part can also be referred to as an "upper end".

As mentioned earlier, a floating wind turbine will be able to tilt under the influence of strong forces from wind and/or from waves. Such a tilt will be able to change the position of the wind turbine's blades in a way that impairs the wind turbine's ability to extract energy from the wind. By having a tiltable upper part, the wind turbine's blades can be held more stably in a position that allows efficient energy extraction. A wind turbine with a tiltable upper part can be advantageous for several types of floating foundations, but can be particularly advantageous for a foundation that can be rotated such as the foundation according to the first aspect of the invention or according to the eighth aspect of the description.

The wind turbine may comprise an upper transition piece. The nacelle can be connected to the tower via the upper transition piece. The upper transition piece can be rotatably attached to the tower, and/or the nacelle can be rotatably attached to the tower, so that the nacelle can be rotated relative to the tower about the tower's longitudinal axis.

The upper transition piece may comprise a tower tube; an upper and a lower nacelle carrier, the hinge, the tilting mechanism.

In an eleventh aspect of the description, a wind turbine is described for a floating device for extracting energy from wind, where the wind turbine comprises a lifting boom mounted on an upper part of the wind turbine's tower, above a position for a nacelle on the tower.

The lifting boom can comprise one or more pulleys and/or other lifting means, and can be used for raising and/or lowering a nacelle to or from an upper part of the tower. The lifting boom can, for example, be located at the top of the tower of the wind turbine.

The wind turbine may be part of a floating device for extracting energy from wind, where the device may further comprise any of the floating foundations according to the seventh, eighth or ninth aspect of the description. The wind turbine may comprise one or more of the tower according to the second aspect of the description, the rotor according to the third aspect of the description, the nacelle according to the fourth aspect of the description and/or the transition piece according to the fifth aspect of the description. In embodiments where the wind turbine includes the tower according to the second aspect of the description, the foundation of the wind turbine can be adapted to such a tower, in that the foundation has an opening for the tower towards the sea.

The wind turbine according to the tenth aspect of the description may comprise the transition piece according to the fifth aspect, the nacelle according to the fourth aspect, the rotor according to the third aspect or the tower according to the second aspect of the description and/or any preferably of the features mentioned in connection with the wind turbine according to the eleventh aspect of the description. The wind turbine according to the eleventh aspect of the description may comprise the transition piece according to the fifth aspect, the nacelle according to the fourth aspect, the rotor according to the third aspect or the tower according to the second aspect of the description and/or any preferably of the features mentioned in connection with the wind turbine according to the eleventh aspect of the description.

In a second aspect of the invention and a twelfth aspect of the description, a floating device for extracting energy from wind is described, where the device comprises a wind turbine and the foundation according to the seventh aspect of the description, where the foundation is anchored to a seabed via an anchor line connecting the foundation's anchorage with an anchor. A floating device for extracting energy from wind is also described, where the device comprises a wind turbine and the foundation according to the eighth or ninth aspect of the description, where the foundation is anchored to a seabed via an anchor line that connects the foundation's anchorage with an anchor.

The foundation can be anchored via several anchor lines, each leading to one or more anchors. The anchor lines can be connected to an anchor ring, which can be part of the anchor, and which can be rotatably attached to a vertically projecting structure belonging to the anchor. The anchor ring can typically be rotatable in relation to the vertical structure of the anchor attachment. The vertical structure can project upwards, downwards, or both upwards and downwards in a body of water in relation to the righting arm, preferably from an outer part of the righting arm. The vertical structure can penetrate the surface of the body of water. The anchor lines can be connected to the anchor anchor/anchor ring via angle stabilizers. A plurality of anchor lines and anchors may be beneficial in stabilizing the position of the foundation in a body of water in an operational position.

The wind turbine comprises a tower. The tower may have a cavity with an opening to receive water, and the foundation may have an opening to allow water to reach the opening of the tower, allowing water to penetrate the tower in situations where the tower penetrates a surface of a body of water. The opening may comprise an open lower end of the tower. An opening to allow water to flow into the tower can be beneficial to reduce buoyancy due to water pressure and to reduce the vertical impact of waves on the foundation and tower.

The tower, or a part of the tower, can be shaped like a tube, with an internal, axial cavity. Such a shape can reduce the mass of the tower relative to the tower's circumference and height compared to a tower that does not have such an internal cavity. Reduced mass can be beneficial in reducing the weight the wind turbine foundation must carry per meter of tower. A lower mass of the tower means that the need for mass in the keel to stabilize the foundation is reduced. The inner cavity can be of any shape. The inner cavity can extend from a lower end of the tower and in the longitudinal direction of the tower towards the upper end of the tower. The internal cavity may extend through the entire length of the tower, along a majority of the length of the tower or along a minority of the length of the tower. The cavity can extend 70% of the tower length, 30% of the tower length, 50% of the tower length, or any percentage of the tower length above 0% of the tower length and up to 100% of the tower length.

With a tower that is shaped like a tube with an opening at the bottom and an internal cavity, which allows water to flow into the cavity, the diameter of the tower can be increased without significant change in the amount of liquid displaced. A larger tower diameter can, for example, open up the use of a generator with a larger diameter, if the generator is in the tower.

The foundation can have an opening in the transition part through which a wind turbine's tower can be moved vertically. The method of stabilizing the foundation may include submerging the tower into a body of water. This could provide increased stability by allowing the tower to function as a keel, by moving the center of gravity of the tower, and the foundation with the tower, downwards, and/or by reducing the forces a wind turbine is exposed to on the foundation.

The apparatus may have a hoisting means for hoisting the tower up or down. The lifting means can, for example, comprise a winch which can, for example, stand on the transitional part of the foundation and one or more pulleys and cables which connect the winch to the tower.

The apparatus may have locking means to lock the tower in a position, to prevent unwanted vertical movement of the tower relative to the foundation. The locking means can be locking means for locking the tower in a small number of different positions, such as, for example, a top position, a middle position and a lowest position. In some embodiments, the locking means can lock the tower in additional positions, such as, for example, an upper middle position and a lower middle position.

The apparatus may have braking means to allow vertical movement of the tower and at the same time slow down the movement so that it does not become too fast. Such braking means can reduce the load on parts of the device, such as, for example, the transition part, nacelle and/or rotor.

The tower may have one or more internal chambers to receive ballast to change the mass of the tower. The tower may be attached to the foundation in a manner that allows vertical movement of the tower. The vertical position of the tower can then be adjusted by adjusting the mass of the tower, as it will be able to influence how far into a body of water the tower will sink. The tower may, for example, comprise one or more chambers which can be selectively filled with or emptied of water or air and means for filling or emptying the one or more chambers.

The apparatus may comprise a lifting means, for example a winch or a rack, to lift equipment or parts belonging to the wind turbine to or towards the top of the wind turbine's tower and/or to lift equipment down from the top of the tower. The lifting means can be a hoisting means for hoisting, for example, a nacelle or parts of a nacelle to the top of the tower. The lifting device can also be used to lift equipment down from the tower.

When lifting operations are carried out using lifting means belonging to vessels that move relative to a wind turbine on a floating foundation, the relative movement will complicate the lifting operation. Such a relative movement is avoided if lifting means are used which belong to the wind turbine itself. This simplifies the lifting operation.

The lifting means can be a lifting means for moving equipment, for example a nacelle, a rotor or blades, a distance to or from the top of a nacelle. For example, a vessel can be used to lift a nacelle 30 metres, or 50 metres, or 70 metres, or over 70 meters or under 30 metres, and the lifting means belonging to the wind turbine is used to lift the remaining meters to or from the top of a tower. The lifting means can otherwise be a lifting means for lifting equipment from a transition part belonging to the foundation for the wind turbine to the top of the tower.

The apparatus may comprise one or more additional lifting means for lifting equipment from a vessel to the transition part of the foundation.

The tower can be rotatably fixed to the foundation, typically to the transition part. The nacelle can be rotatably fixed to the tower. Rotationally fixed connections can be, for example, welded and/or bolted connections, and can be less complicated and more robust than more advanced connections that allow rotation. Such rotationally fixed connections can be used on a wind turbine standing on a rotatable foundation, as the foundation according to the first aspect of the invention, as a device according to the second aspect of the invention, as the foundation itself can then be oriented to set the wind turbine's blades correctly in relation to the wind direction .

With the nacelle rotatably attached to the tower, the wind turbine's generator can, among other things, be moved from the top of the tower down into the structure. The wind turbine may comprise a generator located in the transition part or in the tower near the transition part. "Near the transition part" can mean, for example, less than 10 meters from the transition part, vertically in the tower, less than 5 meters from the transition part, less than 3 meters from the transition part, or less than 1 meter from the transition part. That way, access to the generator for maintenance or repair can be easier, and the weight from the generator will be moved from the top of the tower, from the nacelle where the generator is normally located, to or towards a lower end of the tower. Moving weight downwards will have a significant effect on the stability of the apparatus, and it will be able to reduce the need for stabilizing weight and/or length of the foundation's vertical stabilizing part and/or horizontal stabilizing part. Moving the generator down to or towards the transition part can be advantageous in order to be able to use a type of generator that requires more space and/or is heavier. For example, a so-called "direct drive" generator can be used - a generator with a relatively large diameter compared to a conventional generator, but which does not require a gearbox.

The wind turbine can have a lower transition piece between the tower and the transition part. The tower can be connected to the transition part via the lower transition piece. In some embodiments, the tower can be releasably attached to the lower transition piece, and the lower transition piece can be releasably attached to the transition part. The generator can be located in the lower transition piece.

In embodiments of the floating apparatus, the floating apparatus may have a ballast element suspended at adjustable depth. In such embodiments, the apparatus may comprise lifting means for adjusting the depth of the ballast element. This can be particularly advantageous in embodiments of the apparatus that have a tower that can be moved vertically, to compensate for a changed center of gravity and/or buoyancy when the tower is moved vertically.

In a thirteenth aspect of the description, a floating device is described for extracting energy from wind, where the floating device comprises a plurality of wind turbines erected from one floating foundation.

The foundation can be any foundation for an offshore wind turbine, for example any of the foundations according to the seventh, eighth or ninth aspect of the description.

Each of the several wind turbines can comprise, for example, a plurality of blades, a nacelle, a rotor and a tower. The majority of wind turbines can be two wind turbines, three wind turbines, four wind turbines, five wind turbines, or more than five wind turbines. In alternative embodiments, for example, two or more wind turbines can have a common tower, but each have its own nacelle, rotor and blades. Several wind turbines can be linked together other than simply through the fact that they stand from the same foundation. They can also be connected to each other by means of a structure, such as a rod, a stay, a boom, a tower, or the like.

In one possible embodiment, two or more wind turbines can be attached to a horizontal tower brace which in turn is attached to a common vertical tower. The horizontal tower brace can be removably attached to the vertical tower, so that the horizontal tower brace can be detached from the tower and lifted down for, for example, maintenance or repair. Alternatively, the horizontal tower brace can be fixed, not removable, fixed to the tower, and the tower can be vertically movable fixed to the foundation so that the tower can be driven up or down vertically in relation to the foundation and thus can be lowered for maintenance or repairs of one or more of the wind turbines.

The foundations described above can be so advantageous in relation to known technology, that their bearing capacity relative to size, weight and horizontal and/or vertical extent can make it possible to support larger, more extensive structures than simple wind turbines.

A wind turbine's size is limited by the fact that the energy utilization can eventually, with increasing size of the wind turbine, become inefficient and present challenges related to a so-called "peripheral speed" of the blades. Then it can be more efficient to utilize the bearing capacity of the foundations by, instead of increasing the size of one wind turbine erected on the foundation, erecting several wind turbines from a foundation. In a typical wind farm, it will be possible to get better energy utilization of an area by placing several wind turbines on the same foundation.

One or more of a plurality of wind turbines on a common foundation may have any one or more of the features mentioned regarding wind turbines earlier in this document.

With several wind turbines on one foundation, they can be configured so that at least two of them do not rotate in the same direction, so that forces from the rotation of the wind turbines at least partially offset each other.

In a fourteenth aspect of the description, a floating device for extracting energy from wind is described, where the floating device comprises a wind turbine and a foundation, where the tower of the wind turbine comprises a hinge and is divided into an upper and a lower part, where the upper part of the tower and the lower portion of the tower is attached to each other by the hinge in a manner that allows the upper portion of the tower to be tilted between an upright position and a lowered position, and wherein the tower includes a locking means for releasably locking the tower in the upright position to prevent unwanted tilting from the upright position.

In a fifteenth aspect of the description, a floating apparatus for extracting energy from wind is described, wherein the floating apparatus comprises a wind turbine and a foundation and a hinge, wherein the tower of the wind turbine is hinged to the foundation at the hinge in a manner that allows the tower to be tilted between a lying position and an erect position, and wherein the turret comprises a locking means for releasably locking the turret in the upright position to prevent unwanted tilting from the upright position.

In a sixteenth aspect of the description, a floating device for extracting energy from wind is described, where the floating device comprises a foundation with a transition part, two wind turbine towers and a lifting tower,

where the lifting tower is centrally located on the transition part with one wind turbine tower on each side of it and comprises a lifting means for lifting the towers between a lying and a standing position, where the wind turbine towers each comprise a hinge which makes the towers movable about the hinge between said lying and standing position.

The hinge can connect the wind turbine towers to a transition part belonging to the foundation, or they can connect an upper part of the wind turbine towers to a lower part of the wind turbine towers. The hinge can arrange for all or part or parts of the wind turbine towers to be put down, for example so that they lie essentially horizontally. The wind turbine towers can also include locking means for locking the wind turbine towers in a position, for example in a lying position and/or in a standing position.

In an advantageous embodiment, the lifting means and the hinges can be adapted so that the towers, when lowered, are lowered to each side, symmetrically, so that an equilibrium is achieved. The towers can, for example, be laid down at an essentially 180 degree angle to each other and each at an essentially 90 degree angle to a horizontal part of the foundation. Alternatively, the towers can be laid down at an angle of less than 180 degrees to each other and less than 90 degrees to the horizontal part of the foundation.

Such a symmetrical solution could be advantageous for, for example, the assembly and disassembly of towers on floating structures, where maintaining stability can be crucial for a safe and feasible operation.

In a seventeenth aspect of the description, a floating device is described for extracting energy from wind, where the device comprises:

- a wind turbine and a foundation for supporting the wind turbine, where the wind turbine comprises a tower and the foundation comprises a substantially vertical, stabilizing part and a substantially horizontal, stabilizing part; and

- an upper and a lower tie rod and a connecting means, where

- the connecting means is firmly attached to an upper part of the tower;

- the upper tension rod extends from an outer part of the horizontal stabilizing part to the connecting means; and

- the lower tension rod extends from the outer part of the horizontal stabilizing part to a lower part of the vertical stabilizing part,

so that the tie rods can absorb bending moment to reduce potentially destructive forces acting on parts of the structure of the floating apparatus.

Any of the floating devices according to the twelfth, thirteenth, fourteenth, fifteenth, sixteenth or seventeenth aspects of the invention may comprise one or more of the ballast element according to the first aspect of the description, the tower according to the second aspect of the disclosure, the rotor according to the third aspect of the disclosure, the nacelle according to the fourth aspect of the disclosure, the transition piece according to the fifth aspect of the disclosure, the angle stabilizer according to the sixth aspect of the disclosure, any of the foundations according to the seventh, eighth or ninth aspect of the description, any of the wind turbines according to the tenth or eleventh aspect of the description, and/or any of the features mentioned in connection with one of the other floating devices.

In an eighteenth aspect of the description and a third aspect of the invention, a method is described for stabilizing a foundation for a wind turbine, where the method comprises the steps:

- to provide a foundation with a transition part, an anchor attachment and a righting arm, where the transition part and the anchor attachment are rigidly connected to each other via the righting arm;

- to anchor the foundation via the anchor in such a way that the transition part can rotate about the anchor to orient itself in an advantageous position; and

- allowing the foundation to orient itself, as a result of the influence of natural forces, until the transition part of the foundation is essentially anchored downstream in a wind acting on the foundation, so that the righting arm stabilizes the transition part against natural forces in the direction of the wind.

The foundation may for example be any of the foundations according to the seventh, eighth or ninth aspect of the description.

The method of stabilizing the foundation can further include at least partially controlling the orientation of the foundation in order to more accurately place the transition part in the desired position relative to the anchorage. The rotation can, for example, be controlled with the help of a rudder or with the help of a means of rotation such as a propeller. It can be very advantageous to at least partially control the orientation in order to precisely place the transition part in the desired position, as a more accurate placement of the transition part in relation to the anchorage will affect the stabilizing effect the arm will have against the forces applied to the foundation and turbine from wind and waves.

In a nineteenth aspect of the description, a method is described for stabilizing a floating foundation for a wind turbine, where the wind turbine comprises a rigid structure comprising a righting leg, where the method comprises the steps:

- providing a ballast element according to the first aspect of the description; and

- to hang the ballast element from an underside of the rigid structure belonging to the foundation, with the legs of the foundation through the holes of the ballast element, in a way that allows movement of the ballast element relative to the rigid structure and which means that the ballast element will come into contact with and exert a stabilizing force on the structure by tilting the foundation above a certain degree.

The legs of the foundation can be an extension of a tower for a wind turbine standing on the foundation. The foundation may for example be any of the foundations according to the seventh, eighth or ninth aspect of the description.

The method according to the third aspect of the invention may comprise the step:

- to hang the ballast element according to the first aspect of the description in an underside of the foundation, with the legs of the foundation through the holes of the ballast element, in a way that allows movement of the ballast element relative to the rigid structure and which means that the ballast element will come into contact with and exert a stabilizing force on the structure by tilting the foundation above a certain degree.

In a twentieth aspect of the description, a method is described for reducing bending forces on a connection between a vertical part and a horizontal part of a floating foundation for a wind turbine, where the method comprises the step:

- to stretch a tension member between an outer part of the foundation and a connection means that is in contact with an upper part of a tower for a wind turbine standing on the floating foundation and/or to stretch a tension member between an outer part of the foundation and a lower part of a vertical part of the foundation.

The outer part can be an essentially horizontal outer part, for example an outer part of the horizontal part of the foundation.

The connecting means can be, for example, a rod that extends from the tower, or from a rotationally fixed part of the rotor, or that projects through a central hole in the rotor, or a swivel on an outer, rotatable surface of the rotor.

The foundation can be, for example, any of the foundations according to the seventh, eighth or ninth aspect of the description.

In a twenty-first aspect of the disclosure, a method of installing a nacelle on a tower for a wind turbine is described, the method comprising the steps of:

- providing a nacelle according to the fourth aspect of the description;

- lifting the nacelle's front and rear parts to an installation position for the nacelle on the tower; - to releasably lock the front part of the nacelle to the rear part of the nacelle after lifting to the installation position, to combine the two parts.

In some embodiments of the nacelle, it can be completed by combining the front and rear parts. In other embodiments, the nacelle may have additional parts that need to be connected to the front and/or rear part to make it complete.

The method may include lifting one or more additional parts associated with the nacelle into installation position on the tower. The method may further comprise releasably locking one or more further parts to the nacelle's front and/or rear part, to combine the parts to form a complete nacelle.

In a twenty-second aspect of the description, a method is described for uninstalling a nacelle according to the fourth aspect of the description from a tower belonging to a wind turbine, the method comprising the steps:

- to release a releasable locking between a front and a rear part of the nacelle, and to release the parts of the nacelle from the tower;

- to lift the front and rear parts of the nacelle out of the tower.

The method may comprise releasing the additional parts of the nacelle and lifting the additional parts of the nacelle down from the tower.

The lifting can be carried out, for example, using lifting means belonging to the tower or belonging to a foundation on which the tower is erected or belonging to a vessel. The foundation can, for example, be any of the foundations according to the invention's seventh, eighth or ninth aspect. The nacelle can be, for example, the nacelle according to the fourth aspect of the description.

A wind turbine tower may comprise a guide means for guiding the nacelle parts when lifting the nacelle parts. For example, the tower may comprise a tower tube with an inner diameter greater than the outer diameter of the tower, to which the parts of the nacelle can be attached, which can guide the parts during lifting.

The steps comprising lifting the parts of the nacelle may comprise guiding the parts of the nacelle by means of the guide means during lifting of the parts of the nacelle.

The guide means may comprise a tower tube.

The procedure for installing the nacelle may include one or more of the following steps:

- to connect the front part of the nacelle to the tower tube;

- to connect the rear part of the nacelle to the tower tube;

- to hoist the tower tube to the nacelle position;

- disconnecting the front part of the nacelle from the tower tube and installing the front part of the nacelle to the tower; - disconnecting the rear part of the nacelle from the tower tube and installing the rear part of the nacelle to the tower; and or

- to remove the tower pipe from the tower.

The procedure for uninstalling the nacelle may include one or more of the following steps:

- to hoist a tower pipe up to or towards the nacelle of the tower;

- to uninstall the forward part of the nacelle from the tower;

- to uninstall the rear part of the nacelle from the tower;

- to connect the front part of the nacelle to the tower tube;

- to connect the rear part of the nacelle to the tower tube;

- to hoist down the tower pipe;

- disconnecting the front part of the nacelle from the tower tube and lifting the front part of the nacelle away from the tower; - disconnecting the rear part of the nacelle from the tower tube and lifting the rear part of the nacelle away from the tower; - to remove the tower pipe from the tower.

In one embodiment of the method, the front and rear parts of the nacelle can be screwed into one and the same tower tube. The front part of the nacelle can be attached to a front part of the tower tube, and the rear part of the nacelle can be attached to a rear part of the tower tube. The tower pipe can be fixed but movable attached to the tower, or it can be removably attached to the tower. The tower pipe can, for example, be disconnected and removed from the tower after installation of the nacelle to the top of the tower, or it can be disconnected from the tower after the nacelle has been lowered and removed from the tower by dismantling the nacelle from the tower. The tower may include the tower pipe.

The front part of the nacelle can be connected to the rear part of the nacelle through a part of the tower.

For example, a drive line can go from the rotor attached to the front part of the nacelle to a generator in the rear part of the nacelle. The tower can have a hole through which part of the driveline can connect the front part of the nacelle to the rear part of the nacelle

The hoisting device for hoisting the nacelle up and down can typically be a winch with cables or a toothed rack in the longitudinal direction of the tower, but is not limited to being one of the two examples mentioned.

In one embodiment, the tower can have several tower tubes, and each part of the nacelle can be connected to a separate tower tube. To avoid that the tower pipe can rotate unintentionally about the tower's axis during the lifting operation, the tower can have a guide rail along the length of the tower, to which, for example, the tower pipe can be connected.

In embodiments where the wind turbine has a rotatable nacelle, the tower can typically have two tower tubes outside of each other, arranged so that they can be mechanically rotated in relation to each other, where the innermost tower tube is attached to the tower and the outermost is attached to a nacelle or part of a nacelle.

A tower pipe can normally be placed, for example, above a position for a nacelle on the tower, below a position for a nacelle. A tower can have a tower tube above and a tower tube below a nacelle's position on the tower. The nacelle's position can be a position for installing a nacelle that is not installed on the tower, or a position where a nacelle is installed on the tower.

The tower can have a horizontal opening to connect a nacelle part to another nacelle part, for example a front part of the nacelle to a rear part of the nacelle.

In embodiments of the invention, the nacelle can be lifted up above the tower and lowered onto the tower, so that the tower penetrates the nacelle. The nacelle can then be attached to a tower pipe, and then the tower pipe can be lowered over the tower, so that the tower penetrates the tower pipe. The nacelle and/or tower tubes can have a funnel-like shape, which can be used to guide the nacelle and/or tower tube down over the tower. This can, for example, be a relevant solution in embodiments where the tower can be lowered, where the tower has a limited height, or where sufficiently dimensioned lifting equipment to hoist the nacelle and/or tower tube over a tall tower is available.

If a foundation for a floating device for extracting energy from wind includes the lifting means, this can further simplify the operations. Challenges associated with such operations when carried out on a typical nacelle are the nacelle's considerable weight and relative movements between a wind turbine's tower and vessels with lifting means.

In a twenty-third aspect, a floating apparatus for extracting energy from wind is described, wherein the apparatus comprises a foundation and two wind turbines, wherein the two wind turbines and their associated towers are raised from the foundation of the apparatus and connected to each other by at least one tension rod.

The two wind turbines may comprise a first wind turbine and a second wind turbine. The tension rod can connect an upper part of the first wind turbine's tower with a lower part of the second wind turbine's tower. Several tie rods can connect the two wind turbine towers. For example, a first tension rod can connect an upper part of the first wind turbine's tower to an upper part of the second wind turbine's tower, a second tension rod can connect an upper part of the first wind turbine's tower to a lower part of the second wind turbine's tower, and a third tension rod connecting a lower part of the first wind turbine's tower to an upper part of the second wind turbine's tower.

The two towers can each comprise a hinge by which hinges the towers can change between an upright and a lying position. The towers can be arranged so that they can be placed/erected symmetrically in relation to each other and a horizontal axis that runs parallel to a horizontal part of the device's foundation.

The foundation of the apparatus may be any foundation according to the seventh, eighth or ninth aspect of the description, or another type of foundation. The device's wind turbine can be connected to each other and/or to a section, typically an outer section, of a horizontal part of the foundation by a plurality of tension rods to take up bending moment.

The towers of the two wind turbines can be tilted upwards from the foundation in the raised position, so that the towers protrude from each other from the bottom of the towers towards the top of the towers. This will allow the towers to stand close to each other on the foundation, while there is plenty of room for the wind turbine blades to rotate without the risk of colliding at the top end of the towers.

The towers can be attached to each other and to the foundation via a solid support structure to absorb bending moment. The device can have both such a support structure and previously mentioned tension rods.

Any of the apparatus for extracting energy from wind may include a control system. The control system can, for example, be adapted to control the rotor brake, the angle of the rotor blades, the resistance in the generator, the rotation of the foundation, and/or the rotation of the nacelle and/or rotor. The control system may include one or more sensors, for example to retrieve information about wind speed, wind direction, wave height, ocean current strength and ocean current direction, the pitch of the rotor blades, the rotor's rotation speed, the position of the wind turbine and/or the position of the wind turbine. The information can be used in connection with the control system's management, and/or the information can be collected and sent to a recipient for other use, such as for example to collect metrological data and/or data for use, for example for further development of the design of devices for extracting energy from wind.

Such a control system can be particularly advantageous for devices with several wind turbines, among other things for reasons related to stability. The floating device, with a rotatable foundation, can rotate as a result of natural forces, which include wind, ocean currents and waves, in a direction that would normally place the transition part and the wind turbine downstream of the anchor in relation to the direction of the wind.

On a device that has a rotatable foundation and two or more wind turbines, the device's wind turbines can be affected by a wind so that the device rotates in the horizontal plane until there is equilibrium between the force the wind exerts on the wind turbines in relation to the anchor attachment. The force from the wind on the wind turbines can also lead to a downward force. Varying force on the wind turbines from the wind could lead to different downward forces applied to the device and its foundation from the two or more wind turbines. This inequality will in turn lead to sideways tilting of the appliance and its foundation.

The control system may include sensors to obtain information from several wind turbines.

The control system can further include a program to use information related to, for example, forces affecting the device, the position of the device, the position of the device, the pitch of the rotor blades and the rotor's rotation speed to calculate the stability of the device and whether control must be performed to improve stability. The control may include increased or decreased braking of a rotor, changed resistance in a generator, changed pitch of rotor blades, rotation of a nacelle, rotation of a rotor, rotation of a wind turbine tower, or rotation of the foundation, or other.

The control system can also be used to control the foundation to improve or optimize the device's energy production in relation to prevailing natural forces, including forces from wind, ocean currents and waves.

Such a control system can contribute to the stability of the device so that the dimensions of the foundation can be limited. For example, the length and/or weight of the foundation's vertical part can be reduced for a device with such a control system relative to a device without such a control system.

Any of the floating apparatus for extracting energy from wind according to the twelfth to seventeenth aspects of the specification and the twenty-third aspect of the specification may comprise any feature of a part for a floating apparatus for extracting energy from wind mentioned in connection with the procedures. Any of the wind turbines according to the tenth or eleventh aspects of the description may comprise any of the features mentioned in connection with parts for a wind turbine mentioned in connection with the methods. Any of the foundations according to the seventh to ninth aspects of the description may comprise any of the features of a foundation mentioned in connection with the methods.

The term "tilt" appears again in the document. This term refers to a change of position for an object relative to an axis or a plane or another object. For example, the tilt of the foundation is described. In this connection, "tilt" typically refers to a changed angle of a vertical part of the foundation relative to a horizontal plane, for example a horizontal plane given by a sea surface at calm seas.. A "tiltable" upper end of a wind turbine tower is an upper end whose position/angle can be changed relative to another part of the wind turbine tower.

When describing a tension rod between an upper part of a wind turbine and a part of a foundation, this tension rod can be attached to a connecting means on a face of the wind turbine rotor and the wind turbine blades, what can be referred to as the upstream blades in the wind when the wind is acting straight on the wind turbine blades. Other tie rods, for example tie rods connecting two towers, can be attached to the towers downstream of the blades.

A "tensioning rod" can be a cable, a chain, a fiber strap, or another type of line or a form of rod that is suitable for connecting and absorbing forces from, for example, a tower and a horizontal part of a foundation for a wind turbine or two wind turbine towers.

In the following, examples of preferred embodiments are described which are illustrated in the accompanying drawings, where:

Fig.1 illustrates a cross-section of a floating device for extracting wind energy, with the foundation according to the first aspect of the invention, and with a wind turbine standing on the foundation;

Fig.2 shows an alternative embodiment of the device with two wind turbines seen from the front;

Fig.3 shows an alternative embodiment of the device with two wind turbines seen from above;

Fig.4 shows an alternative embodiment of the device with one wind turbine seen from above;

Fig.5 shows an alternative embodiment of the device with a wind turbine seen from the front;

Fig.6 shows a cross-section of an alternative embodiment of the device with a natural division of foundation transition piece and tower;

Fig.7 shows a cross-section of a further alternative embodiment of the foundation and the wind turbine, where the wind turbine has a divisible nacelle and the apparatus comprises lifting means for lifting the parts of the nacelle towards or from the top of the tower;

Fig 8 shows a cross-section of an embodiment of an upper transition piece;

Fig 9 shows a separable nacelle which is mounted on an upper transition piece which is penetrated by the tower;

Fig 10 shows a divisible nacelle which is mounted on an upper transition piece, where the nacelle is attached to a lift boom located in the upper part of the tower;

Fig.11 shows the upper transition piece in a lower position, where the nacelle's front and rear parts are detached from the upper transition piece and shown lifted away from the tower;

Fig.12 shows a section of a further alternative embodiment of the device, where a raise/lower tower is shown in the upper position, with free-hanging ballast suspended in the foundation;

Fig.13 shows a section of a further alternative embodiment of the device, where a raise/lower tower is shown in the lower position, with free-hanging ballast suspended in the foundation;

Fig.14 shows a section of a further alternative embodiment of the device, where a raise/lower tower is shown in the upper position, where the nacelle is tilted upwards to compensate for the device's tilt;

Fig.15 shows an alternative foundation for a floating device for extracting wind energy seen from above, where the foundation has a plurality of righting arms, two of which are linked to the transition part and where the arms are each connected to an anchor;

Fig.16 shows an alternative foundation for a floating device for extracting wind energy seen from above, where the foundation has three arms connected to a transition part, of which one of the arms is non-articulately connected to the transition part, where the device is anchored via an anchor attachment on an outer part of the non-articulated arm;

Fig.17 shows an alternative foundation for a floating device for extracting wind energy seen from above, where the device has three wind turbines and three arms;

Fig.18 shows a section of an anchor fitting belonging to a foundation for a floating device for extracting wind energy, where the anchor fitting comprises angle stabilizers;

Fig.19 shows an alternative embodiment of an apparatus with two wind turbines seen from the front, where the apparatus has a lift tower in the middle and where the wind turbine towers each have their own hinge and where an upper part of the wind turbine towers is tilted to a lower position around the hinge;

Fig. 20 shows the embodiment shown in Fig. 19 seen from the front, here with each of the towers raised to an upper position about the hinge;

Fig.21 shows an alternative embodiment of the device with two wind turbines seen from the front, where the device has a lift tower in the middle which in an extension also includes a vertical leg, where the upper part of two wind turbine towers is hinged against the lift tower and is tilted to a lower position about the hinge;

Fig. 22 shows the embodiment of the apparatus shown in Fig. 21 seen from the front, here with erected lift tower and erected wind turbines;

Fig.23 shows the embodiment of the apparatus shown in figure 21 and figure 22 seen from the front, with a lift tower in the middle which in an extension also includes a vertical leg lowered to the operational position, where both wind turbine towers are raised to an upper position on a hinge;

Fig.24 shows an alternative embodiment of the device with two wind turbines seen from the front, with a lift tower in the middle which in an extension also includes a vertical leg, where the tower stands in the lower position mounted on horizontal tower stays on which the nacelles are attached;

Fig. 25 shows the embodiment shown in figure 24 seen from the front, where the lift tower is in the upper position mounted on horizontal tower struts to which the nacelles are attached;

Fig.26 shows an alternative embodiment of the device with two wind turbines seen from the front, with a lift tower in the middle which, in an extension, also includes a vertical leg, where the upper part of the tower is connected to a lift mechanism, which here is shown to have lowered horizontal tower stays that are the nacelles mounted on to a lower position; and

Fig.27 shows an alternative embodiment of the device with four wind turbines seen from the front, in an operational position.

Note that the figures are intended to illustrate the invention(s) described in the document, not necessarily to accurately reproduce the details of the illustrated items. The figures are not drawn to scale.

Figure 1 shows an embodiment of the foundation 1 according to the first aspect of the invention, in operational position in a sea 900 with a sea surface 901, where the foundation 1 has an anchor attachment 11, a transition part 12, a vertical, righting leg 13 and a horizontal, righting arm 14 which connects the anchor attachment 11 with the transition part 12.

The leg 13 and the arm 14 are in the embodiment cylindrical, and both have a plurality of chambers 16 which can be selectively filled with water 162 or other ballast heavier than water, or with air 161 or other substance lighter than water, to adjust the foundation's weight and /or buoyancy point. Normally, the contents of the chambers 16 will be of such a mass that the arm 14 is sufficiently heavy to lie below the sea surface, but in some cases it may be relevant to change the contents of the chambers 16 so that the arm 14 can be semi-submersible.

In the embodiment in Figure 1, the leg 13 is connected to the arm 14 at a first end of the arm 14, while the transition part 12 is connected to the arm 14 at a second, opposite end of the arm 14.

On the transition part 12 there is a wind turbine 2. The wind turbine has a tower 21, a nacelle 22, a rotor 23 and blades 24. Together with the foundation 1, the wind turbine 2 forms a floating device 100 for extracting energy from wind.

The horizontal righting arm 14 is shown here with air 161 in three chambers 16 closest to the transition part 12, and one chamber closest to the leg 13 to take up a significant part of the weight of the transition part 12 and the leg 13. Furthermore, the horizontal righting arm 14 has water 162 air in the remaining other chambers 16. The number of chambers 16 and the distribution of air 161 and water 162 in them is only shown to illustrate that it is possible to have a selective distribution of weight and buoyancy in the chambers 16, it is not necessarily representative of how the distribution will look in a stable operational embodiment.

In the embodiment shown, the vertical, straightening leg 13 has a lowest section 15 with a material of very high specific gravity.

The foundation 1 is anchored by means of anchor 3 which is connected to the foundation's 1 anchorage 11 via anchor lines 31. The anchorage 11 includes an anchor tower 70 which projects up from the arm 14 and above the sea surface 901. This anchor tower 70 will be able to counteract forces applied to the foundation 1 from a anchor line 31 in that the anchor tower 70, by being pulled down, will displace water and thus ensure increased buoyancy.

As the foundation 1 is anchored in the anchor 11 with a horizontal distance to and rigidly connected to the transition part 12, the transition part 12 can rotate around the anchor 11. The foundation 1 is built and anchored so that it will naturally rotate as a result of forces from wind, current and/or waves. The embodiment of the foundation 1 includes a motorized propeller 17, which can be used to control the rotation of the foundation 1. The propeller 17 can, for example, be used to rotate the foundation back to an initial position if the foundation has, for example, rotated more than 1 revolution from the initial position. This can be advantageous, for example, to avoid tangles of any cables and/or lines and/or the like connected to the device 100. In most cases, the foundation 1 will naturally rotate so that the main wind direction will be equal to the direction from the anchorage 11 to the transition part 12, as that the transitional part 12 remains essentially downstream of the anchorage 11 in a wind acting on the foundation. Therefore, the wind turbines 2 are mounted as shown in Figure 1, with the front of the wind turbine with rotor 23 and blades 24 facing the anchor 11, so that the blades 24 are essentially in an optimal position, 90 degrees to the wind direction.

To reduce a bending moment between the righting arm 14 and the tower 21, the apparatus 100 further includes a first tension rod 43 which extends from the first end of the arm, at the anchor tower 70, to a front portion of the nacelle 22 at the rotor 23. To reduce a bending moment between the the straightening arm 14 and the straightening leg 13, the apparatus 100 further includes a second tension rod 44 which extends from a lower part of the straightening leg 13 to the straightening arm 14 near the transition part 12.

In the embodiment, the transition part 12 to the foundation 1 has a vertical transition part section 121 and a horizontal transition part section 122. The wind turbine 2 stands on the vertical section 121 and the horizontal, righting arm 14 is rigidly attached to the horizontal section 122. In harsh conditions, for example with high waves and strong wind, the foundation 1 will be able to be subjected to strong bending moments and/or shear forces between the vertical part 121 and the horizontal part 122. Therefore, the foundation 1 is also equipped with a construction element 123 to absorb such forces.

In the embodiment, the transition part 12 further has an open lower end 125. The open solution allows water to move in the lower end 125, which reduces the buoyancy directly under the wind turbine 2, and will be stabilizing, especially vertically, as waves due to the design will have less effect on the vertical position of the wind turbine 2 as the waves can freely flow into the transition part 12 and tower 21.

Figure 2 shows an embodiment of a floating device 100 for extracting energy from wind seen from the front in operational position, with the foundation 1 with two wind turbines 2. Each wind turbine 2 has a tower 21 which is articulated in an upper tower part 211 and a lower tower part 212 The two upper tower parts 21 are connected by cables 73 and the two lower tower parts by a stay 74. The foundation has a vertical, straightening leg 13 and a horizontal, straightening arm 14, both of which are connected to a transition part 12.

Figure 3 shows an embodiment of a floating device 100 for extracting energy from wind 1 seen from above in operational position, where the device 100 has two wind turbines 2 raised from a foundation 1. The two wind turbines 2 each have their own tower 21. The towers 21 are connected via a wire 73. The foundation 1 has a straightening, horizontal arm 14, and an anchor point 11 connected to a first end of the arm 14 and a transition part 12 for carrying the wind turbines 2 connected to a second, opposite end of the arm 14. The apparatus 100 further has a tension rod 43 stretched from each wind turbine's 2 rotor 23 to the anchor point 11.

Figure 4 shows an embodiment of the floating device 100 seen from above in operational position, where the device comprises a wind turbine 2 and a foundation 1, where the wind turbine 2 is erected on a transition part 12 belonging to the foundation 1. This device 100 also has a tension rod 43 stretched between an anchor attachment 11 belonging to the foundation 1 and the rotor 23 of the wind turbine 2 to take up bending forces.

Figure 5 shows an embodiment of the apparatus 100 from the front in operational position, where the apparatus has a wind turbine 2 erected on a foundation 1 a wind turbine 2. The apparatus further comprises a ballast element 45 which is movably suspended in the foundation 1, in order to stabilize the foundation 1. The ballast element 45 has a center hole that is penetrated by a vertical, righting leg 13 belonging to the foundation 1. When the foundation 1 is tilted, the ballast element 45 will come into contact with the righting leg 13 and apply a force to the righting leg 13 that will have a righting effect on the foundation 1.

Figure 6 illustrates a lower transition piece 75 which houses a generator 25 to connect a tower 21 with a transition part 12. In the figure it is illustrated that the lower transition piece 75 is a separate part in relation to the tower 21 and the transition part 12. The generator 25 can be turned , so that it stands on its edge in the lower transition piece 76 to be taken out of the lower transition piece 75, for example for repair or to replace the generator 25. The lower transition piece 75 can be attached to the transition part 12 and to the tower 21, for example by welding or bolted on.

Figure 6 further shows an embodiment where the wind turbine's nacelle 22 is permanently rotatably attached to the tower 21, in that, in this embodiment, it is bolted firmly. In other embodiments, the nacelle 22 can, for example, be welded. In alternative embodiments, the nacelle 22 can be movably attached to the tower 21 but with limited mobility. A rotationally fixed connection potentially increases the structural strength of the connection between the tower 21 and the nacelle 22 compared to typical non-rotationally fixed connections.

The wind turbine 2 has a bevel gear 230, as well as a drive line 26 which runs from the rotor 23 to the generator 25 to transfer rotational forces to the generator 25 for the extraction of electrical energy. The nacelle 22 is further shown penetrated by the tower 21, with bevel gear 230 placed in a cavity in the tower 21 with a shaft into the rotor 23.

The rotationally fixed connection between the tower 21 and the nacelle 22 allows the generator 25 to be placed in the lower transition piece 75 at a distance from the nacelle 22. In this embodiment, the generator 25 is advantageously placed at the very bottom of the foundation 1 transition part 12. Such a placement means that the generator 25 is lighter available for maintenance and/or repair. Another very significant advantage of the generator 25 being moved down into the lower transition piece 75, below the tower 21 is that the diameter of the transition part 21 can be utilized. Furthermore, by moving the weight of the generator 25 closer to the sea surface, the potential tilting forces that must be taken into account with regard to the foundation's stability will be significantly reduced. Thus, the foundation 1 can have sufficient stability with a shorter and/or lighter horizontal, righting arm 14 and/or vertical, righting leg 13, seen in relation to a foundation for an apparatus 100 with the generator 25 located in the nacelle of the wind turbine 2.

The foundation 1 shown in Figure 6 also has a ballast tank 141 located on an opposite side of the transition part 12 in relation to the foundation 1 anchorage 11, which can be selectively filled or emptied of ballast, where the ballast can for example be seawater. This ballast tank 141 can typically be filled with water under normal conditions, but is emptied of water to provide buoyancy on the back of the wind turbine 2 in strong winds to counteract tilting.

Figure 7 further shows an alternative embodiment of the device 100, and of the foundation 1 and the wind turbine 2, where the nacelle 22 is lowered to a lower position. In this embodiment, the wind turbine has a divisible nacelle 22 which is penetrated by tower 21. The nacelle 22 has a front part 221 and a rear part 222 which is mounted on an upper nacelle carrier 92. The apparatus 100 comprises lifting means 27 which include a winch with pulleys and cables, which can be used to lift the nacelle's 22 parts 221, 222.

Figure 7 further shows that bevel gear 230 is in rear nacelle part 222 and disconnected from drive shaft 261. Front nacelle part 221 and rear nacelle part 222 can then be detached from upper nacelle carrier 92.

Figure 8a shows an upper transition piece 90. The transition piece comprises a tower pipe 91 which can be placed around part of a tower 21 to carry a nacelle 22 on the tower 21. The tower pipe 91 is shown here with an outward cone to simplify placement of the tower pipe 91 around the tower 21. The tower tube 91 can be attached to the tower 21 to carry a load of the nacelle 22. The tower tube comprises an upper nacelle carrier 92 and a lower nacelle carrier 93, as well as a tilting mechanism 80 which here includes a hydraulic cylinder 81 and a hinge 82 to allow tilting of the upper nacelle carrier 92 relative to the lower nacelle carrier 93, as well as an upper rotation means 96 and an upper bearing 94 to rotate the upper nacelle carrier 92 relative to the lower nacelle carrier 93, and a lower rotation means 97 and a lower bearing 95 to rotate the lower nacelle carrier 93 on the tower tube 91 and relative to the tower 21. By having both the upper rotation means 96 and the lower rotation means 97, the tower tube has a redundant rotation mechanism.

Figure 8b shows another embodiment of an upper transition piece 90, where the upper transition piece comprises a tower pipe 91 which can be placed around part of a tower 21. The tower pipe 91 can be attached to a tower for a wind turbine, and can carry the load of a nacelle 22 The tower tube 91 comprises an upper nacelle carrier 92, as well as an upper bearing 94 to rotate the upper nacelle carrier 92 about the tower tube 91 by means of an upper rotation means 96.

Figure 9 shows an embodiment of a divisible nacelle 22 in its upper position mounted on an upper transition piece 90, which is penetrated by a tower 21. The rear part 222 and front part 221 of the nacelle 22 are fixedly mounted on an upper nacelle carrier 92 belonging to the transition piece 90, and the tower tube 91 is fixedly mounted to tower 21. The tower 21 comprises a lifting means 27, mounted on an upper end of the tower 21. Figure 9 further shows a rotor 23 attached to the front part 221 of the nacelle 22, and a rigid attachment structure 231 mechanically attached to a stationary part of the rotor 23.

The attachment structure 231 connects a tension rod to the stationary part of the rotor and through it to the nacelle 22 and the upper part of the tower 21. Tension rod 43 is further attached to device 251 which is designed to absorb wind forces acting against the nacelle 22.

Figure 10 illustrates a nacelle 22 in a middle position mounted on an upper transition piece 90 which is penetrated by a tower 21. The transition piece 90 comprises a tower tube 91 and an upper nacelle carrier 92. The nacelle 22 is firmly mounted on the nacelle carrier 92. The tower tube 91 is detached from the tower 21 and can thus be moved up and down. The tower 21 comprises a lifting means 27 which comprises pulleys and a hoisting cable. The hoist line 27 is attached to the nacelle 22 and carries the weight of the nacelle 22. This alternative embodiment shows what is often called a "direct drive configuration" where the generator 25 constitutes the main weight. Figure 10 further shows an attachment structure 231 which is mechanically attached to the tower 21, and a tension rod 43 attached to the attachment structure 231. The tension rod 43 is shown here resting against a stationary part of a rotor 23 belonging to the nacelle 22. The attachment structure 231 is attached to tension rod 43 which is designed to take wind forces acting against the nacelle 22.

Figure 11 shows a tower pipe 91 with a nacelle 22 in a lower position, where the tower pipe 91 is penetrated by a tower 21. The tower pipe 91 rests against a lower part of the tower 21. The nacelle 22 has a front part 221 and a rear part 222 as in figure is detached from the upper nacelle carrier 92 and which hangs in each of its hoist lines 26. Figure 11 further shows a rotor 23 with a rotating part 232 and a swivel 233 attached to rotatably attached to the rotating part 232 of the rotor 23 so that the swivel 233 can rotate relative to the rotating part 232 of the rotor 23. The swivel 233 functions as an attachment structure 231 to connect a tension rod 43 to the tower 21 via the nacelle 22 via the rotor 23.

Figure 12 further shows an alternative embodiment of the foundation 1 and the wind turbine 2. In this embodiment, the transition part 12 has an opening to allow vertical movement of the wind turbine 2, which allows the tower 21 to be lowered into a body of water 900. The foundation 1 has a ballast element 45 which is movably suspended by cables from the transition part 12 of the foundation 1. The ballast element 45 is not rigidly attached to the foundation 1, but is penetrated by a righting leg 13 belonging to the foundation 1. The ballast element 45 will therefore have a righting effect on the foundation 1 in that it will exert a force of foundation 1's righting leg 13, which in this embodiment is an extension of the tower 21, when foundation 1 is tilted.

A lower part of the tower 21 can then, when submerged, function as a second, righting, vertical leg 13. The tower 21 also has a pressure-tight chamber 126 which can be selectively filled with, for example, air or water.

The foundation also has a lifting means 27 by a winch to move the wind turbine 2 vertically, and a locking ring 41 to lock the tower 21 in a vertical position.

In this embodiment, the wind turbine 2 has a nacelle 22 which can be divided into a front part 221 and a rear part 222, with a generator 25 in the rear part 222 of the nacelle 22. The wind turbine 2 also has a drive line 26 that extends from the rotor 23, through the nacelle 22 front part 221 and the tower 21 and to the generator 25. The front part 221 of the nacelle and the rear part 222 of the nacelle each have a connection 223 to connect the nacelle part 221, 222 to the tower 21.

The driveline has three parts: a front driveline part 261 in the forward nacelle part 221, a middle driveline part 262 in the tower 21, and a rear driveline part 263 in the rear nacelle part 222. These three driveline parts 261, 262, 263 are connected together when the front nacelle part 221 and the rear nacelle part 222 is connected to the tower 21.

If the nacelle 22 is to be lowered to a lower level, the middle driveline part 262 must be disconnected from the front driveline part 261 and the rear driveline part 263. Then the nacelle 22 can be lowered to the transition part 12.

The wind turbine 2 can be lowered, for example, for disassembly or assembly of equipment, or for maintenance of equipment, such as nacelle 22, rotor 23 or other, or it can be lowered to improve stability, by moving the tower 21 further down. As the lower part of the tower 21 functions as the foundation 1's righting leg 13, lowering the tower will lead to an extension, down into the body of water, of the righting leg 13.

Figure 13 shows the same embodiment of wind turbine 2 and foundation 1 as Figure 12, but with the wind turbine 2 lowered significantly so that it is in a lower position. The tower 21 in Figure 13, which is in a lower position than that shown in Figure 12, with a larger part of the tower 21 submerged in water, holds water in a larger proportion of the chamber 126 than the tower 21 shown in Figure 12. The wind turbine 2 can is lowered, for example, for dismantling or installing equipment, or for maintenance of equipment, such as nacelle 22, rotor 23 or other, or it can be lowered to improve stability.

Figure 14 shows an alternative embodiment of the device 100, with a foundation 1 and a wind turbine 2. The wind turbine has a penetrable nacelle 22, which is penetrated by the wind turbine's tower 21. The nacelle 22 is further tiltably mounted on the tower 21, so that the nacelle 22 and thus also blades mounted on the nacelle 22 can be held more stably vertically by tilting the foundation 1 and so that the nacelle 22 can, for example, be tilted to create a greater distance between the blades 24 and the tower 21 in strong winds.

Furthermore, the foundation 1 in this embodiment has an anchor attachment 11, a first tension member 43 that extends from the foundation 1 anchor attachment 11 to a front part of the nacelle 22 and a second tension member 44 that extends from the foundation 1 anchor attachment 11 to a ballast element 45 that hangs in cables from the transition part 12 of the foundation 1. The ballast element 45 is not rigidly attached to the foundation 1, but will have a righting effect on the foundation in that it will exert a force on the righting leg 13 of the foundation 1, which in this embodiment is an extension of the tower 21, by tilting the foundation 1.

Figure 15 shows an alternative embodiment of the apparatus 100, including an alternative embodiment of a foundation 1, where the foundation 1 does not have a righting leg, but instead has a first substantially horizontal righting arm 51, a second essentially horizontal righting arm 52 and a third essentially horizontal straightening arm 53. The second arm 52 and the third arm 53 are each connected to a transition part 12 via each hinge 54. The hinge 54 allows some movement of the aforementioned arms 52, 53 relative to the first the arm 51 and relative to the foundation 1 the transition part 12 in the horizontal plane. The transition part 12 carries a wind turbine 2.

Note that when "movement in the horizontal plane" is described, it applies when the foundation lies flat, in its normal position, on still water. When foundation 1 is tilted, the plane will be tilted accordingly.

Each of the essentially horizontal, righting arms 51, 52, 53 is mounted on an anchor tower 70 in connection with the anchor attachment 11, and is anchored via the anchor attachment 11 and an anchor line 31 connected to an anchor 3. The arms 51, 52, 53 are further connected to each other via ropes 55. The ropes 55 limit movement of the arms 51, 52, 53 relative to each other. In combination with the hinges, the ropes mean that the arms can move somewhat, but that the movement is limited. Alternative embodiments without ropes, with or without other movement-limiting means, such as spring-based movement-limiting means, are conceivable.

Figure 16 shows an alternative foundation 1 with a first horizontal straightening arm 51, a second horizontal straightening arm 52 and a third horizontal straightening arm 53. The second arm 52 and the third arm 53 are each connected to a transition part 12 with each its own hinge 54. The hinge 54 allows some movement of the aforementioned arms 52, 53 relative to the transition part 12 in the horizontal plane. The straightening arm 51 is rigidly attached to the transition part 12 which carries a wind turbine 2.

The first arm 51 has an anchor attachment 11 and is anchored via the anchor attachment 11 and an anchor line 31 connected to an anchor 3 so that the foundation 1 can rotate about the anchor attachment 11 on a straight arm 51. The arms 51, 52, 53 each have a first end and a other end. The arms are, at their other ends, connected to each other via cables 55, and are connected to the foundation 1 at their first ends. The chains 55 limit movement of the arms 51, 52, 53 relative to each other.

Figure 17 shows an alternative embodiment of the apparatus 100, which includes an alternative foundation 1 and three wind turbines 2. The foundation 1 does not have a righting leg, but has a first essentially horizontal righting arm 51, a second essentially horizontal righting arm 52 and a third, essentially horizontal righting arm 53. The second and third arms 52, 53 are each connected to the first righting arm 51 via their own hinge 54. The hinge 54 allows some movement of the second arm 52 and the third arm 53 relative to the first righting arm 51 in the horizontal plane. Each of the horizontally straightening arms 51,52,53 is connected to a transition part 12.

The first righting arm 51 has a first end and an opposite second end, where the first end has an anchor attachment 11 and the other end is connected to the transition part 12 of the foundation 1. The foundation 1 is anchored via the anchor attachment 11, connected to an anchor line 31 connected to anchor 3. In this way, the foundation 1 can rotate about the anchor attachment 11.

The second arm 52 and the third arm 53 are connected to the first arm 51 and to the transition part 12 using cables. The chains 55 limit movement of the arms 51, 52, 53 relative to each other.

One of the wind turbines 2 is erected on the transition part of the foundation 1, one is erected on an outer part of the second arm 52, and one is erected on an outer part of the third arm 53. Each of the second arm 52 and the third arm 53 has a transition part 12 to carry their respective wind turbines 2.

Figure 18 shows an embodiment of an anchor attachment 11 belonging to a foundation 1 for a floating device 100 to extract energy from wind. The anchor 11 includes an angle stabilizer 32 which is intended to stabilize an angle of attack B from the anchor line 31 towards the floating apparatus 100, an anchor ring 34 and an anchor post 35. Angle stabilizer 32 consists of an upper anchor point 36, a lower anchor point 37, a rigid, righting stabilizer arm 38 and a plumb bob 33. Upper anchor point 36 is connected to the anchor ring 34. The anchor ring 34 is rotatably attached to the anchor fixing column 35 which is in turn attached to a righting arm 14 belonging to the foundation 1. It can be advantageous to have a plurality of anchors 3 with associated anchor lines 31 connected angle stabilizer 32, to stabilize the direction of force from the anchor line 31 on the anchor attachment 11 and to keep the position of the foundation 1 stable. Figure 18 shows two anchors 3, but it may be advantageous to have more than two, for example three or four or five anchors 3. Angle of attack B can be designed from 0 to 180 degrees, and will typically be project-specific based on, among other things, the depth ratio. Typical angle B under normal conditions will be within the range of 20 to 45 degrees

The angle stabilizers 32 comprise a rigid structure 39. In the embodiment shown, the rigid structure 39 is shaped like a right-angled triangle. A first corner of the rigid structure 39 is connected to the anchor ring 34, a second corner of the rigid structure 39 is connected to a plumb line 33, and a third corner of the rigid structure 39 is connected to an anchor line 31. The plumb lines 33 are again connected to each other. The solders 33 are connected to each other and to the rigid structure 39 of the yaw stabilizer via rigid, stabilizing struts 38. Alternatively, the solders 33 can be connected to each other and/or to the rigid structure 39 via, for example, cables or chains.

Figure 19 shows an embodiment of a floating device 100 for extracting energy from wind where two wind turbines 2 are placed on one foundation 1. The wind turbines 2 each have a tower 21 with an upper part 211 and a lower part 212 which are hinged together by a hinge 72. The lower part of the lower tower 21 is attached to the transition part 12. The towers are attached to each other, at the top of their lower part 212, by a brace 78. The apparatus 100 also has a lifting tower 79 which is temporarily attached to the transition part 12 and to the two lower towers 21. Hoist tower 79 is advantageously in the embodiment in the center between the two towers and perpendicular to hinges 72. Hoist tower 79 has a hoist device 77, which can pull in two hoist lines 76. The hoist lines extend from hoist device 77, over each upper pulley and on to each tower 21, at their upper part 211, where they are fixed. In the division between the upper part 211 and the lower part 212 of the towers 21 there is a flange on each side (not shown). When the lift device 77 pulls the two lift lines 76, the two upper tower parts 211 will be tilted parallel about each hinge 72 towards an upper operational position. The hinges 72 will position the two flanges in a position where they are optimally arranged to be screwed or welded together when the towers 21 have reached their operational, erected position. The lift device 77 can pull individually on the two lift lines 76 to ensure stability.

Figure 20 shows the same as Figure 19 but now with the two towers 21 raised to an upper position where the upper tower part 211 and the lower tower part 212 can be assembled together, and one can fasten the two towers together with cables 73. Lift tower 79 will typically be removed when the towers 21 have been raised to the operational position.

Figures 21, 22 and 23 show an embodiment of a floating device 100 for extracting energy from wind where two wind turbines 2 are placed on a foundation 1 which includes, among other things, a ballast element 45 which can be raised and lowered. The ballast element 45 is shown in an upper position, suspended in the transition part 12 in Figures 21 and 22. The same apparatus 100 is also shown in Figure 23. The apparatus 100 has two wind turbine towers 21, and a central, supporting tower 215. The central tower 215 can be raised and lowered vertically. A lower part of the central tower 215 acts as a vertical, righting leg 13 for the foundation 1. The foundation 1 includes a transition part 12 for supporting the wind turbines. The transition part 12 has an opening through which the central tower 215 penetrates. The central tower 215 also penetrates the ballast element 45, which, like the transition part, has an opening for such penetration. In Figure 23, the central tower 215 is lowered to a low operational position similar to ballast 45.

The two wind turbine towers 21 of the apparatus 100 are hinged to the central tower 215, and can be lowered or raised at the hinges 72 using lifting means which include lifting cables 28 connected to an upper part of the central tower 215 and an upper part of each of the two wind turbine towers 21 .

Figure 23 shows the apparatus 100 in an operational position, where the central tower 212, like the ballast element 45, is lowered to a low position. Raising and lowering the central tower 215 is done by moving water out of or into one or more chambers in the central tower 215, primarily in a lower part of the central tower 215, using suitable means for the purpose. This can, for example, be means that include a pump (not shown). In the raised position, the wind turbine towers 21 can be connected to each other using one or a plurality of lifting cables 28 or, for example, using struts.

Figures 24 and 25 show two alternative embodiments of a floating device 100 for extracting energy from wind where two wind turbines 2 are placed on one foundation 1. The two wind turbines are connected to each other and to a common, central tower 215, via each horizontal tower strut 213 and a connection unit 214. Figure 25 shows the device 100 in operational position, while Figure 24 shows the device 100 with submerged wind turbines 2. Raising and lowering the central tower 215 can typically be done by respectively evacuating water from and filling water in legs 13, in order to thereby change the buoyancy in the central tower 215. The two tower struts 213 are in an outer part connected to an upper part of the central tower 215, and, in figure 25, to a transition part 12 belonging to the foundation 1.

Figure 26 shows an alternative embodiment of a floating device 100 for extracting energy from wind where two wind turbines 2 are placed on one foundation 1. The two wind turbines are connected to each other and to a common, central tower 215, each via its own horizontal tower strut 213 and a connection unit 214. The device has a hoist device/a lifting means 77 which is connected to two cables 76 which, via two pulleys at the top of the central tower 214, are attached to each wind turbine 2 at the nacelle of the wind turbines (not shown). The lifting device 77 will be able to raise and lower horizontal tower struts 213 from a lower service position to an upper operational position.

Figure 27 shows further embodiments of floating device 100 for extracting energy from wind in one of several possible configurations where more than two wind turbines 2 are placed on one foundation 1.

It should be noted that all of the above embodiments illustrate the invention, but do not limit it, and those skilled in the art will be able to devise many alternative embodiments without departing from the scope of the following claims. In the requirements, reference numbers in parentheses should not be seen as limiting.

The use of the verb "to comprise" and its various forms does not exclude the presence of elements or steps not mentioned in the claims. The indefinite articles "an", "ei" or "et" before an element do not exclude the presence of several such elements.

The fact that certain features are listed in different mutually dependent claims does not indicate that a combination of these features cannot be advantageously used.

Claims (80)

Patent claims 1. A floating foundation for an offshore wind turbine, where the foundation comprises a transition part to support the wind turbine, and a stabilizing part to stabilize the transition part with or without the wind turbine, where the stabilizing part comprises an equal or nearly horizontal part and an equal or nearly vertical part both of which are rightly connected to the transition part, where the vertical part comprises a righting leg to project downwards into a body of water when the foundation is in operational position, where the horizontal part comprises an anchor and a righting arm, where the foundation is designed with the anchor fixed to the righting arm at a distance from the transition part, so that the transition part in operational position, when the foundation is anchored, can rotate around the anchor under the influence of natural forces which forces from wind, waves and/or currents. 2. The floating foundation according to claim 1, where the vertical part and/or the horizontal part is rigidly and firmly attached to the transition part, directly or via another rigid structure. 3. The floating foundation according to claim 1, where the horizontal part is attached to the transition part via a hinge. 4. The floating foundation according to claim 1, claim 2 or claim 3, where the anchor attachment and the transition part are attached to each end of the arm. 5. The foundation according to any one of claims 1 to 4 where the anchorage includes parts of or all of the vertically stabilizing part. 6. The foundation according to any one of claims 1 to 5, where the anchorage includes the leg and where therefore the leg is at a horizontal distance from the transition part. 7. The foundation according to any one of claims 1 to 6, wherein the foundation has an opening in the transition portion to allow water from a body of water on which the foundation is intended to float to penetrate through the opening and/or to allow elevation and lowering of a wind turbine tower through the opening. 8. The foundation according to any one of claims 1 to 7, where the arm and/or leg of the foundation may comprise one or more chambers that can be selectively filled with or emptied of ballast, so that the foundation's buoyancy and center of gravity can be adjusted. 9. The foundation according to any one of claims 1 to 8, wherein the anchorage comprises an anchor tower, the anchor tower being fixedly attached to the righting arm such that an upper part of the anchor tower in the operational position is normally above a surface of a body of water and a lower part of the anchor tower in the operational position is normally below the surface of the water body. 10. The foundation according to claim 9, wherein the anchor tower has a cavity to accommodate control systems and transformers for power generation for a wind turbine. 11. The foundation according to claim 10, where the anchor tower cavity accommodates one or more control systems and/or one or more transformers for power production for a wind turbine and/or a wind farm's power production. 12. The foundation according to any one of claims 9 to 11, where the anchor tower comprises a landing pad for a flying device, such as a drone or a helicopter. 13. The foundation according to any one of claims 1 to 12, wherein the foundation comprises a rudder for manipulating the effect of a current on a rotation of the foundation. 14. The foundation according to any one of claims 1 to 13, wherein the foundation comprises one or more water brakes to slow vertical movement of the foundation. 15. A ballast member for supplying ballast to a foundation for a wind turbine and righting force on the foundation upon tilting of the foundation, wherein the ballast member is formed with a hole to receive a righting leg associated with the foundation and wherein the ballast member includes connection means for being movably suspended in an underside of the foundation. 16. An angle stabilizer for a foundation of a floating apparatus for extracting energy from wind, for stabilizing the direction of force of a force from an anchor line acting on the foundation, the angle stabilizer comprising a rigid angle stabilizer structure and a weight attached to the rigid angle stabilizer structure, the angle stabilizer is arranged to be movably connected to the foundation and where the angle stabilizer is arranged to be connected to the anchor line. 17. The foundation according to any one of claims 1 to 14, where the foundation comprises the ballast element according to claim 15, where the ballast element is movably connected to a rigid structure associated with the foundation, with the leg penetrating the hole of the ballast element in a way that means that the ballast element will come into contact with and have a straightening effect on the leg and thus also have a straightening effect on the foundation when the foundation is tilted above a certain degree. 18. The floating foundation according to any one of claims 1 to 14, 17 or 18, where the foundation further comprises a second righting arm, where at least one of the two righting arms comprises a hinge and via the hinge the joint is connected the transition part to allow movement of at least one of the two righting arms in the horizontal plane. 19. The floating foundation according to claim 18, where the foundation further comprises at least one additional righting arm. 20. The floating foundation according to claim 19, wherein at least one of the at least one further straightening arms comprises a hinge and via the hinge the link is connected to the transition part to allow movement of the at least one of the at least one further straightening the arms in the horizontal plane. 21. The floating foundation according to any one of claims 1 to 14, or 17 to 20, where the foundation comprises the angle stabilizer according to claim 16, where the angle stabilizer is movably suspended in or by the anchor attachment. 22. The floating foundation according to any one of claims 1 to 14 or 17 to 21, wherein the leg is connected to the righting arm at a horizontal distance from the transition member. 23. The floating foundation according to claim 22, where the leg is connected to an outer end of the righting arm, at or adjacent to the anchor. 24. A floating apparatus for extracting energy from wind, the apparatus comprising a foundation according to any one of claims 1 to 14 or 17 to 23 and a wind turbine. 25. The floating apparatus according to claim 24, wherein the apparatus further comprises a tension rod stretched between an upper part of the wind turbine and an outer part of the horizontal part of the foundation to take up a bending moment acting on the structure of the apparatus. 26. The floating apparatus according to claim 24 or 25, wherein the apparatus further comprises a tension rod stretched between a lower part of the vertical part of the foundation and an outer part of the horizontal part of the foundation to take up a bending moment acting on the structure of the apparatus. 27. A method for stabilizing a foundation for a wind turbine, the method comprising the steps: - providing a foundation according to any one of claims 1 to 14 or 17 to 23; - to anchor the foundation via the anchor in such a way that the transition part can rotate about the anchor as defining a center for the rotation to orient itself in an advantageous position; and - allowing the foundation to orientate itself, as a result of the influence of natural forces, until the transition part of the foundation is downwind of the anchorage, so that the righting arm stabilizes the transition part against natural forces in the direction of the wind. 28. A tower for a wind turbine for a floating foundation, the tower having an internal cavity and an opening to the sea to receive water from a body of water in the internal cavity. 29. A rotor for a wind turbine, where the rotor comprises a connection means for connecting the rotor and thereby an upper part of the wind turbine to one or more tension rods or one or more cables or the like. 30. The rotor according to claim 29, where the rotor comprises a swivel rotatably attached to an outer surface of the rotor, where the swivel comprises the connection means. 31. The rotor according to claim 30, where the rotor has a central hole through the rotor and a connection means for penetrating the rotor through the hole, where the connection means is suitable for attachment to a nacelle to connect a tension rod or a cable or the like via the connection means to the nacelle and through it to the upper part of the wind turbine. 32. A nacelle for a wind turbine, the nacelle comprising the rotor according to any one of claims 29 to 31. 33. A nacelle for a wind turbine, wherein the nacelle comprises a forward portion and a rear portion, wherein the forward and rear portions are releasably lockable to each other to form a complete nacelle, wherein the forward portion of the nacelle comprises coupling means for connecting the nacelle of a rotor. 34. The nacelle according to claim 33, wherein the nacelle comprises the rotor according to any one of claims 29 to 31. 35. A nacelle for a wind turbine, wherein the nacelle has a through opening vertically through the nacelle, such that the nacelle can be mounted on a wind turbine tower by receiving the tower through the opening. 36. The nacelle according to claim 32, 33 or 34, wherein the nacelle has a continuous opening vertically through the nacelle, so that the nacelle can be mounted on a wind turbine tower by receiving the tower through the opening. 37. An upper transition piece for a wind turbine, where the transition piece comprises an upper and a lower nacelle carrier for supporting a nacelle, a hinge and a tilting mechanism, where the upper and lower nacelle carriers are tiltably attached to each other at the hinge and where the tilting mechanism is connected to the upper and the lower nacelle carrier to tilt the two nacelle carriers relative to each other. 38. The upper transition piece according to claim 37, wherein the upper transition piece comprises a bearing and a rotation means to allow rotation of a nacelle carried by the nacelle carrier relative to a wind turbine tower. 39. The upper transition piece according to claim 37 or 38, wherein the upper transition piece has a vertical, through opening, so that the upper transition piece can be mounted on the wind turbine tower by receiving the tower through the opening. 40. A tower for a wind turbine, where the tower has an upper part and a lower part, where the upper part of the tower and the lower part of the tower are connected to each other via a hinge, so that an angle between the upper part and the lower part can be changed, so that the upper part of the tower can be lowered or raised. 41. The tower according to claim 40, wherein the tower further comprises a locking means for locking the tower in the raised, operational position. 42. The tower according to any one of claims 40 or 41, wherein the tower has an internal cavity and an opening to the sea to receive water from a body of water in the internal cavity. 43. A floating foundation for a wind turbine, where the foundation comprises: - a transition part and a righting leg, where the righting leg projects downwards into a body of water when the foundation is in an operational position; - a rigid structure, which comprises and connects at least part of the transition part and at least part of the righting leg; and - the ballast element according to claim 15, where the ballast element is movably suspended in the rigid structure, so that the righting leg penetrates the ballast element and so that the ballast element will come into contact with and have a righting effect on the righting leg and thus also have a righting effect on the foundation when the foundation is tilted above a certain degree. 44. A floating foundation for an offshore wind turbine, where the foundation includes: - a transition part for carrying the wind turbine; - an essentially horizontal, stabilizing part, which includes a first and a second righting arm, wherein the first arm and the second arm are attached to and extend from the transition member, and wherein the first arm comprises a hinge and via the hinge the link is connected to the transition member to allow movement of the first arm in the horizontal plane. 45. A wind turbine for an apparatus for extracting energy from wind, where the wind turbine has an upper part and a lower part, where the upper part is tiltably attached to the lower part by a hinge and where the wind turbine comprises a tilting mechanism for being able to tilt it the upper part relative to the lower part, in order to be able to keep the upper part stable when the wind turbine tilts. 46. The wind turbine according to claim 45, wherein the tilting mechanism comprises a hydraulic cylinder connected to the upper and lower parts to tilt the upper part relative to the lower part. 47. The wind turbine according to claim 45 or 46, where the tilting mechanism further comprises a control unit linked to the hydraulic cylinder to automatically control the cylinder to keep the upper part correctly angled in relation to optimizing the wind turbine's energy recovery. 48. A wind turbine for extracting energy from wind, where the wind turbine comprises: - the upper transition piece according to any one of claims 37 to 39; and or - the rotor according to any one of claims 29 to 31; and or - the nacelle according to any one of claims 32 to 36; and or - the tower according to any one of claims 28 or 40 to 42; and/or - a lifting boom mounted on an upper part of the wind turbine to lift equipment or parts of the wind turbine towards or from the upper part of the wind turbine. 49. The wind turbine according to any one of claims 45 to 47, wherein the wind turbine comprises: - the upper transition piece according to any one of claims 12 to 14; and or - the rotor according to any one of claims 3 to 5; and or - the nacelle according to any one of claims 6 to 10; and or - the tower according to any one of claims 2 or 15 to 17; and/or - a lifting boom mounted on an upper part of the wind turbine to lift equipment or parts of the wind turbine towards or from the upper part of the wind turbine. 50. A floating apparatus for extracting energy from wind, the apparatus comprising a foundation according to any of claims 1 to 14 or 17 to 23 and/or a wind turbine according to any of claims 45 to 49 . 51. A floating device for extracting energy from wind, where the device comprises: - a wind turbine and a foundation for supporting the wind turbine, where the wind turbine comprises a tower and the foundation comprises a substantially vertical, stabilizing part and a substantially horizontal, stabilizing part; and - an upper and a lower tie rod and a connecting means, where - the connecting means is firmly attached to an upper part of the tower; - the upper tension rod extends from an outer part of the horizontal stabilizing part to the connecting means; and - the lower tie rod extends from the outer portion of the horizontal stabilizing member to a lower portion of the vertical stabilizing member so that the tie rods can absorb bending moment to reduce potentially destructive forces acting on parts of the structure of the floating apparatus . 52. The floating apparatus according to claim 51, wherein the foundation of the apparatus is a foundation according to any one of claims 1 to 14 or 17 to 23. 53. The floating apparatus according to any one of claims 50 to 52, wherein the wind turbine of the apparatus is a wind turbine according to any one of claims 45 to 49. 54. The floating apparatus according to any one of claims 24 to 26 or 50 to 53, wherein the apparatus is anchored to a seabed via an anchor on the seabed and an anchor line connecting the anchor to the foundation anchorage. 55. The floating apparatus according to any one of claims 24 to 26 or 50 to 54, wherein the tower of the wind turbine has one or more internal chambers that can be selectively filled with or emptied of ballast, to adjust the mass of the tower. 56. The floating apparatus according to any one of claims 24 to 26 or 50 to 55, wherein the apparatus comprises a lifting means for lifting equipment or parts of the wind turbine to or towards the top of the wind turbine tower. 57. The floating apparatus according to any one of claims 24 to 26 or 50 to 56, wherein the tower of the wind turbine is rotatably attached to the foundation and wherein the nacelle of the wind turbine is rotatably attached to the tower. 58. The floating apparatus according to any one of claims 24 to 26 or 50 to 57, wherein the wind turbine comprises a generator, a drive line, a rotor and a lower transition piece, the lower transition piece serving as a link between the tower of the wind turbine and the transition part of the foundation and includes the wind turbine's generator, where the wind turbine's driveline connects the wind turbine's rotor to the generator. 59. The floating apparatus according to any one of claims 24 to 26 or 50 to 58, the wind turbine comprising a generator, a driveline and a rotor, wherein the wind turbine's generator is integrated into the transition portion of the apparatus, and wherein the wind turbine's driveline connects the wind turbine's rotor to the generator. 60. A floating apparatus according to any one of claims 24 to 26 or 50 to 59, wherein the apparatus comprises a hoisting tower comprising lifting means for raising a wind turbine tower. 61. The floating apparatus according to claim 60, where the apparatus further comprises at least two towers, each of which comprises a hinge, where each tower's hinge facilitates the tower being lowered or raised about the hinge. 62. The floating apparatus according to claim 61, where the lifting means are connectable to the towers so that the lifting means can raise or lower the towers about the hinge of the towers, and where the towers are arranged on the transition part of the apparatus in such a way that they can be raised or lowered symmetrically to maintain a weight balance to ensure stability. 63. A method for stabilizing a floating foundation for a wind turbine, where the wind turbine comprises a rigid structure and a righting leg, where the righting leg projects downwards into a body of water when the foundation is in an operational position, where the method comprises the steps: - providing a ballast element according to claim 15; and - to hang the ballast element from an underside of the rigid structure belonging to the foundation, with the legs of the foundation through the holes of the ballast element, in a way that allows movement of the ballast element relative to the rigid structure and which means that the ballast element will come into contact with and exert a stabilizing force on the leg and thereby the rigid structure when the foundation is tilted above a certain degree. 64. The method according to claim 27, where the method further comprises the steps: - providing a ballast element according to claim 15; and - to hang the ballast element from an underside of a rigid structure belonging to the foundation, with the legs of the foundation through holes in the ballast element, in a way that allows movement of the ballast element relative to the rigid structure and which means that the ballast element will come into contact with and exert a stabilizing force on the structure by tilting the foundation above a certain degree. 65. The method according to claim 27, 63 or 64, where the foundation comprises a rotation means and the method further comprises the step: - to control rotation of the foundation using the rotation means to place the transition part of the foundation in an advantageous position in relation to the foundation's anchorage. 66. The method according to claim 27, 63, 64 or 65, where the foundation comprises a rotation means and the method further comprises the step: - to control rotation of the foundation to drive the transition part back to an initial position to avoid entanglement of a cable or the like when using the rotation means. 67. A method for reducing bending forces on a connection between a vertical part and a horizontal part of a floating foundation for a wind turbine, where the method comprises the step: - to stretch a tension rod between an outer part of the horizontal part of the foundation and a connecting means that is in contact with an upper part of a tower for a wind turbine standing on the floating foundation and/or to stretch a tension rod between an outer part of the horizontal part of the foundation and a lower part of a vertical part of the foundation. 68. A method of installing a nacelle on a tower for a wind turbine, the method comprising the steps of: - providing a nacelle comprising a front part and a rear part, the front and rear parts being releasably lockable to each other to form a complete nacelle; - lifting the front part of the nacelle and the rear part of the nacelle to an installation position for the nacelle on the tower; - to releasably lock the front part of the nacelle to the rear part of the nacelle after lifting to the installation position, to combine the two parts to install the nacelle to the wind turbine tower. 69. A method of uninstalling a nacelle from a tower for a wind turbine, wherein the nacelle comprises a front portion and a rear portion, wherein the front and rear portions are releasably lockable to each other to form a complete nacelle, the method comprising the steps : - to release a releasable locking between a front and a rear part of the nacelle, and to release the parts of the nacelle from the tower; - to lift the nacelle's front and rear parts down away from the tower. 70. The method according to claim 68 or 69, where the wind turbine is part of an apparatus which further comprises a foundation for the wind turbine and a lifting means, where the lifting is carried out using the apparatus's lifting means. 71. The method according to any one of claims 68 to 70, wherein the apparatus further comprises a guide means for guiding the nacelle parts when lifting the nacelle parts, the method comprising one or more of the steps: - to connect the front part of the nacelle to the tower tube; - to connect the rear part of the nacelle to the tower tube; - hoisting the tower tube to an installation position for the nacelle; - disconnecting the front part of the nacelle from the tower tube and installing the front part of the nacelle to the tower; and - to disconnect the rear part of the nacelle from the tower tube and install the rear part of the nacelle to the tower. 72. A method for erecting a tower belonging to an apparatus for extracting energy from wind, where the apparatus comprises a foundation with a lift tower and at least two wind turbine towers connected to the foundation, where the lift tower comprises a lifting means connected to the two wind turbine towers, where the method comprises the step: - to use the lifting means to raise the wind turbine towers. 73. The method according to claim 72, wherein the step of "using the lifting means to erect the wind turbine towers" includes lifting the towers towards or from an erected position symmetrically such that a weight load on the foundation from the towers is equal on two sides of a horizontal axis to ensure the foundation's stability while the lift is carried out. 74. The floating apparatus according to any one of claims 24 to 26 or 50 to 62, wherein the foundation of the apparatus is a foundation for supporting a plurality of wind turbines and wherein the apparatus comprises a plurality of wind turbines. 75. The floating device according to claim 74, where the floating device has two wind turbines, where the two wind turbines stand on the transition part of the foundation, where the two wind turbines each have their own tower and the towers are connected by one or more structures, such as one or several tie rods, and where the two towers in the erected position stand at an equal but opposite angle in relation to a vertical axis from the transition part of the foundation so that they slope away from each other from the position of the towers on the transition part of the foundation to their upper end. 76. The floating device according to claim 75, where the two wind turbines at the rotor of the wind turbines are connected via tension rods to a section, for example an outer section, of the horizontal part of the foundation, and/or where the two wind turbines at an upper end are connected to each other via tie rods. 77. The floating apparatus according to any one of claims 24 to 26, 50 to 62 or 74 to 76, wherein the apparatus comprises a control system for controlling one or more parts of the apparatus to improve the stability of the apparatus or to improve the stability of the apparatus ability to extract energy from the wind. 78. The floating device according to claim 77, wherein the control system comprises one or more sensors for obtaining information that can be used to control the one or more parts of the device and a program for using the information to determine a beneficial adjustment of i at least one of the one or more parts of the apparatus that can be controlled to improve the stability of the apparatus or to improve the ability of the apparatus to extract energy from the wind. 79. The device according to claim 78, where the device comprises two wind turbines and where the control system comprises one or more sensors to retrieve information related to how forces from the wind turbines affect the stability of the device and where the control system is linked to one or more parts of the device that can be adjusted to affect the stability of the device. 80. A method for stabilizing a device for extracting energy from wind, where the device is a device according to claim 79, where the method comprises the steps: 1. using the one or more sensors to obtain information about how forces from the wind turbines affects the stability of the device; 2. using the control system program to determine a beneficial adjustment of at least one of the one or more parts of the apparatus that can be adjusted to affect stability of the apparatus; and 3. to allow the control system to automatically adjust one or more of the one or more parts of the apparatus that can be adjusted to affect the stability of the apparatus based on what was determined by the program in point 2.