NL2021129B1

NL2021129B1 - Process to place a wind turbine

Info

Publication number: NL2021129B1
Application number: NL2021129A
Authority: NL
Inventors: Lanser Jan
Original assignee: Marine Innovators B V
Priority date: 2018-06-15
Filing date: 2018-06-15
Publication date: 2019-05-27
Also published as: NL2021129A

Abstract

The invention is directed to a process to place a wind turbine in a vertical position on the sea bed comprising the following steps; (a) providing a floating delivery vessel with the wind turbine positioned in a substantially horizontal position on the delivery vessel at sea level; (b) submerging at least the lower end of the delivery vessel to such a position that the upper end of the wind turbine is above the sea level and the lower end of the wind turbine points towards the sea bed; (c) providing a moveable support connected to the wind turbine; (d) erecting the combined moveable support and wind turbine to a substantially vertical position and (e) fixing the wind turbine to the sea bed.

Description

PROCESS TO PLACE A WIND TURBINE

The invention is directed to a process to place a wind turbine in a vertical position on the sea bed.

Such a process is described in Dutch patent application NL 2018377 of the same applicant.

This publication describes a process wherein a wind turbine connected to a submersible framework is submerged to the sea bed. The framework fixes itself to the sea bed and by means of buoyancy and a moveable arm of the framework the mast of the wind turbine is moved from a substantially horizontal position to a vertical position. The vertical wind turbine is subsequently fixed to the sea bed and the framework is returned to the water surface to receive a next wind turbine. An advantage of such a process is that a fully assembled wind turbine can be installed on the sea bed. This avoids having to assemble the generator, hub and blades at sea, which involves the use of stationary vessels provided with heavy duty cranes. A disadvantage however of this process is that the framework requires to submerge to the sea bed and return back to the water surface for every wind turbine to be installed. US2012/0308358 describes a partially submersible wind turbine transport vessel suited to transport and install floating wind turbines. Such a vessel can transport a wind turbine in a substantially horizontal position from shore to the off-shore location where the wind turbine is installed. At that off shore location the buoyancy of the transport vessel is altered such that the vessel rotates, the stern submerges and the combined vessel-wind turbine arrives in a vertical position. The floating wind turbine is disconnected from the vessel and anchored at its destined off shore location. The buoyancy of the vessel is increased by allowing pressurized air into the water-filled buoyancy tanks resulting in that the vessel returns to its horizontal floating position. The vessel may subsequently be used to fetch a next wind turbine. DE10332382 described a vessel suited to place the upper end of a wind turbine on a basis which is fixed to the sea bed. The vessel is provided with a substantially horizontal upper end of the wind turbine consisting of part of the upper end of the mast, generator, hub and blades. This upper end is erected using cables running over a beam extending away from the lower end of the mast. This creates a lever which results in that the mast moves from its horizontal position to a vertical position where it connects with the basis. A problem with this method is that the force required to erect the wind turbine is excessive. The size of off shore wind turbines are increasing and it is questionable if this method would be able to work with these new wind turbines. Further the method requires a very stable vessel when placing the top part on the basis. This is solved by providing a relatively large ship which can partly submerge using ballast tanks. A problem with the method of DE10332382 is that it requires that the positioning on the basis requires a stable and large vessel and that excessive forces on the cables are required for erecting the top part of the wind turbine onto such a basis.

The present invention provides an improved process which does not have this problem.

Process to place a wind turbine in a vertical position on the sea bed comprising the following steps, (a) providing a floating delivery vessel with the wind turbine positioned in a substantially horizontal position on the delivery vessel at sea level thereby defining a lower end of the vessel at which the lower end of the wind turbine is positioned and an upper end of the vessel at which the upper end of the wind turbine is positioned, (b) submerging at least the lower end of the delivery vessel to such a position that the upper end of the wind turbine is above the sea level and the lower end of the wind turbine points towards the sea bed, (c) providing a moveable support connected to the wind turbine, (d) erecting the combined moveable support and wind turbine to a substantially vertical position along a submerged and substantially horizontal axis of rotation, and (e) fixing the wind turbine to the sea bed.

An advantage of this process is that an entire and fully assembled wind turbine can be positioned vertically on the sea bed in a relatively simple manner. The forces required to erect the wind turbine are significantly less than in the referred to prior art process because the weight of the turbine is partly compensated by the fact that a large part of the wind turbine mast is submerged. The delivery vessel may have a simple design and does not have to be large to increase its stability. This is advantageous because it enables one to use more than one delivery vessel which can in turn quickly transport the fully assembled wind turbine from a shore location to the off-shore location where it is placed on the sea bed. At the shore location the wind turbines may be assembled in a horizontal position, may be horizontally stored and horizontally transported to the delivery vessel. This is advantageous because it avoids the use of large cranes and the like. The invention shall be described in more detail below wherein additional advantages will be explained. A wind turbine in the context of the present invention comprises a foundation, a mast, a generator, hub and blades. The term generator is in this context also meant to refer to a generator housing. Further, the blades will be connected to the rotation axis of the generator by means of a hub. This foundation may comprise anchoring means at its lower end which fix the wind turbine to the sea bed or connecting means to connect the foundation to a basis already present in the sea bed.

The substantially vertical positioned wind turbine as obtained in step (d) is suitably lowered onto the sea bed or onto a submerged pre-installed basis in the sea bed in step (e).

Fixing the wind turbine to the sea bed may be achieved with anchoring means which are part of the wind turbine. For example as described in the afore mentioned NL2018377, page 5, line 6-page 5, line 14 and Figures 13-15 and their description. Examples of suction anchors are described in W013152757. The anchoring means may also be piles or the mast itself, in case a mono-pile is used, which is drilled into the sea bed. In case the mast is a framework construction the anchors are suitably present at its three or four corners at their bottom end. Preferably the mast is a tubular mast and the foundation is a so-called mono-pile foundation or a tripod foundation. The tubular mast can have a constant diameter or can have a variable diameter that increases in the direction of the foundation.

When a pre-installed basis is used the wind turbine may be provided with a tubular mast. Such a wind turbine may be lowered onto a submerged pre-installed basis in the sea bed and connected to the pre-installed basis by means of, for example, a slip joint connection. The anchored base element may be a tubular element which has been anchored into the sea floor using a hydrohammer, preferably a submerged hydrohammer. Examples of such a pre-installed basis and connector is for example described in US2012137622 and in EP2910686. The connector of such a pre-installed basis will preferably be positioned as near to the sea bed as possible. By as near as possible is at least meant that the connection between foundation and pre-installed basis is less than 20% away from the sea bed relative to the local average sea depth. The wind turbine may also be provided with a support structure having multiple means to engage with multiple pre-installed anchors and wherein the wind turbine is lowered onto multiple anchors as the submerged preinstalled basis in the sea bed. Such a pre-installed anchor may be installed using a mould to accurately position the anchors relative to each other such that they can engage with the support structure of the wind turbine. The means to engage with multiple pre-installed anchors may also be the earlier referred to slip joint connections.

In the process of placing a wind turbine in a vertical position on the sea bed the delivery vessel suitably moves under and angle with the sea bed towards the sea bed by lowering the buoyancy at the lower end of the delivery vessel resulting in that the delivery vessel positions itself under and angle with the sea bed when it submerges. This movement suitably is such that the generator and blades of the wind turbine remain above sea level. The speed of submerging and the angle under which the delivery vessel submerges can be controlled by varying the buoyancy along the length of the delivery vessel. To more accurately position the delivery vessel on the sea bed use may be made of one or more directable thrusters which provide the lower end of the vessel with at least 3 to even 6 degrees of freedom.

While the lower end of the delivery vessel submerges to the sea bed the wind turbine itself may move towards the upper end of the delivery vessel along the length of the delivery vessel. This movement may be effected by the buoyancy of the lower end of the wind turbine itself. Such a movement is advantageous in a situation wherein the wind turbine is positioned towards the lower end of the vessel for balancing reasons when the vessel is used to transport the wind turbine at sea level. When such a positioning is too far towards the lower end of the vessel the lower end of the wind turbine may be end up too low when the vessel rests on the sea bed. By simultaneously moving the wind turbine along the length of the vessel as described while submerging the position of the wind turbine is improved.

In step (e) the erecting of the combined moveable support and wind turbine may be enhanced by increasing the buoyancy of the moveable support and/or wind turbine as will be further illustrated by the embodiments described below.

The moveable support may be any means which on the one hand support the wind turbine when erecting and enable a rotation along a submerged and substantially horizontal axis of rotation. This axis of rotation will suitably be as close to the sea bed as possible allowing an unobstructed movement of the lower end of the wind turbine relative to the sea bed. Higher elevated axis of rotation are of course possible but will result in that more power will be required to erect the wind turbine. The axis is preferably positioned in one position, meaning that in step (e) the axis of rotation itself does not move in any translational directions.

In one embodiment of this invention the moveable support is a moveable arm which moveable arm is rotatably fixed to a submerged vessel along the horizontal axis of rotation and wherein the moveable arm supports and erects the wind turbine to the substantially vertical position and wherein the submerged vessel is fixed to the sea bed in step (d).

The submerged vessel may be a framework as described in the afore mentioned NL2018377 and especially on page 7, line 17 to page 12, line 9, in Figures 2,6a, 6b, 6c, 7, 20a and 20b and in the description of these Figures. The framework is provided with a moveable arm which can rotate along a substantially horizontal axis. The arm is provided with supports for the wind turbine and is the moveable support as described before. In step (d) and (e) the framework may be fixed to the sea floor by means of anchors or by its own weight as described in the afore mentioned NL2018377 and especially on page 9, line 22 to page 11, line 3 and in Figures 20a and 20b and in the description of these Figures. Once the wind turbine is connected to the moveable arm of the framework the wind turbine may be erected and fixed to the sea floor in the manner described in the afore mentioned NL2018377 and especially in Figures 10 and the description of Figure 10 which shows how the wind turbine may be moved from position P2, i.e. a position at which the wind turbine may be connected to the moveable arm, to vertical position P4. The advantage of using a delivery vessel in combination with such a framework is that the submersible framework does not have to collect a new wind turbine at an on-shore location. For example, while performing step (d) and (e) the delivery vessel may collect a new wind turbine for a next placement at the on-shore location resulting in a more efficient logistic process.

The buoyancy of the moveable arm and/or wind turbine may be increased for achieving the erecting of the wind turbine in step (e). In addition the arm may be moved to erect the wind turbine using one or more actuators. The actuators may be for example hydraulic actuators, electromechanical actuators and spindle actuators. See also the afore mentioned NL2018377 and especially Figures 10 and 11 and their description illustrating such an actuator.

The delivery vessel and the framework may be connected by means of one or more cables when the delivery vessel submerges. These cables can direct and even pull the delivery vessel towards the framework. The one or more cables may be attached to the framework at one end and wherein its other free end is positioned in a retrievable manner at the water surface. Prior to submerging the delivery vessel the free end of the cable is connected to the lower end of the delivery vessel. The free end of the cable may be positioned in a retrievable manner at the water surface using a buoy. The cable may be a steel cable and preferably made of a high tensile strength polymer.

In a second embodiment the moveable support is the delivery vessel. In step (d) of such a process the lower end of the delivery vessel is directly or indirectly fixed to the sea bed such that when the wind turbine is erected a rotation results along a substantially horizontal axis.

When the lower end of the delivery vessel rests on the sea bed it is preferred that the vessel connects to the sea bed. Such a connection will prevent that the lower end of the vessel slips away when erecting, for example when the angle between the delivery vessel and the sea bed is small at the start of erecting. Such a connection may be achieved by means of anchor means present at the lower end of the delivery vessel. Alternatively the lower end of the vessel may connect to a preinstalled basis for a wind turbine as referred to above.

Once the delivery vessel rests on the sea bed and is suitably directly or indirectly connected to the sea bed the combined delivery vessel and wind turbine is erected. The forces required to erect this combination may be high and for that reason it is preferred to make use of buoyancy and pulling forces. The buoyancy forces may be achieved by increasing the buoyancy of the submerged parts of the delivery vessel and/or the wind turbine after the delivery vessel is connected to the sea bed. Increasing the buoyancy may be achieved by substituting a gas, suitably air, for water in the buoyancy compartments of the delivery vessel and optionally also in the lower compartments of the wind turbine.

The pulling forces used to erect the delivery vessel and wind turbine combination may be achieved by means of one or more cables connected to the upper half of the delivery vessel at one end and either directly or indirectly to the sea bed or to a floating vessel at the other end of the cable. By shortening these cables the delivery vessel may be further erected to a vertical position. These cables may be shortened by means of winches present on the delivery vessel itself or on the afore mentioned floating vessel. The cables may be directly fixed to the sea bed by means of anchors or via a vessel or jack-up vessel which itself is fixed to the sea bed. Jack-up vessels have legs which can be lowered to the sea bed such that the vessel itself can be positioned on said sea bed. Such vessels may be ships or platforms. Winches are then suitable present on such vessels or jack-up vessels. By shortening these cables, a force will be exercised on the upper end of the delivery vessel which results in that the vessel moves to a vertical position. The cables may be direct cables or be used in combination with two or more pulleys such to lower the tension on a single cable. The cable may be a steel cable and preferably made of a high tensile strength polymer, like for example Dyneema®. When a jack up vessel is used the one or more cables may be connected to a jack-up vessel via winches fixed to the jack-up vessel.

To avoid the delivery vessel to flip further than its vertical position it may be advantageous to have some means to stop or reduce the erecting motion. This may be one or more cables anchored to the sea bed or to a vessel in a substantially opposite direction as the earlier mentioned cables.

The length of these cables are preferably controlled by a winch on the delivery vessel.

Preferably the lower end of the delivery vessel is connected to two spaced apart jack-up vessels fixed to the sea bed such that the axle of rotation of step (d) runs from one jack-up vessel to the other jack-up vessel. Preferably the lower end of the vessel is connected to a leg of a first jack-up vessel and to a leg of the second jack-up vessel. By connecting the upper half of the vessel with both jack-up vessels by cables which can be shortened in use it is possible to erect the combination of delivery vessel and wind turbine to a vertical position.

The erecting of the delivery vessel and wind turbine is preferably performed in a direction in line with the direction of the waves, if present. More preferably in a counter direction of the waves. This is especially preferred if use is made of a large vessel or jack-up vessel. The erecting will then take place at the lee side of such a vessel where the waves may have a lower height. The height of the waves may even be further reduced by using a long ship positioned sideways with respect of the delivery vessel and/or by positioning wave reducing screens into the sea from the vessels.

Alternatively erecting may also be performed in the wind direction wherein the wind force is used to assist in the actual erecting. In such an embodiment it may be advantageous to position the stationary positioned blades of the wind turbine such that the wind has a maximum effect on the blades. Anchors directed in a windward direction may be used to position the floating delivery vessel from which position the submerging step is started.

In a third embodiment the moveable support is also the delivery vessel. In this process the moveable support is the delivery vessel, wherein the delivery vessel is comprised of a support for the wind turbine having an upper end and lower end corresponding to the upper and lower end of the wind turbine, a submersible part rotatably connected to the lower end of the support and a separate floating part which floating part is slidable connected to the upper end of the support. In step (d) the submersible part is fixed to the sea bed and the floating part floats at sea level and wherein in step (d) the distance between submerged part and the floating part is reduced resulting in a force which enhances the erecting of the wind turbine. This distance reducing may be achieved by means of cables connecting the submersible part with the floating part. When the submersible part is fixed to the sea bed the wind turbine will be positioned under an angle with the sea bed wherein the upper end of the wind turbine, as supported by the floating part, is above sea level. When this distance is shortened the floating part is pulled downwards. Because of the resulting buoyancy forces the floating part will move towards a point above the fixed submersible part and thereby erecting the wind turbine to a vertical position. The substantially horizontal axis is present on the submersible part. This process is advantageous compared to erecting an entire delivery vessel as described before in that the delivery vessel itself reduces in length in step (d) resulting in that less of the delivery vessel will have to be lifted to above the sea level.

The distance between submerged part and the floating part may also be reduced by means of a cable connected to an upwardly moving buoyancy compartment and wherein the cable runs over a fixed point at the lower end of the support. The upwardly moving buoyancy compartment will pull the floating part downwards via the cable running along this lower positioned point at the lower end of the support. This counter buoyancy effect may be an alternative or used in combination with winching in the earlier described cables. The buoyancy compartment is suitably positioned at the lower end of the support and filled with enough water when the submersible part is lowered to the sea bed. In step (d) this water is replaced by air, or any other gas, such that the buoyancy compartment will move upwardly. Preferably the buoyancy compartment is slidable connected to the support.

After erecting the combined delivery vessel and wind turbine in the above embodiments to a substantially vertical position the wind turbine is lowered onto the sea bed or onto a pre-installed basis. Preferably the buoyancy of the lower end of the wind turbine is such that it counters most of the weight of the wind turbine itself. This simplifies the lowering of the wind turbine onto the sea bed. This lowering may be performed by means present on the delivery vessel. Advantageously the lowering of the wind turbine is controlled by means present on the jack up vessel. In this way sensitive hydraulic means to fix the mast of the wind turbine and lower the wind turbine may be present on the jack-up vessel instead of on the submerged part of the delivery vessel.

The invention is also directed to the following delivery vessel which may be used in the above process according to the invention. Delivery vessel comprising one or more hulls, means to support an upper end of a wind turbine at an upper end of the vessel and means to support a lower end of a wind turbine foundation at a lower end of the vessel, one or more buoyancy compartments at the lower end of the vessel, which compartments can be independently from each other be filled with water or air, fixing means at the lower end of the vessel for allowing the lower end of the vessel to directly or indirectly fix to the sea bed.

The vessel may be a mono-hull or a multi hull vessel. A catamaran type vessel having two parallel hulls in the sailing direction is preferred because it provides a stable vessel in combination with a light structure. The catamaran type vessel is further advantageous because it may be simply adjusted for larger or smaller wind turbines by placing or cutting away an intermediate section in the hulls. This may seem like a drastic measure. This is not the case. A delivery vessel may be advantageously be used to place numerous wind turbines of the same size in one project. By adjusting the hulls as described the same vessel may be used for another project where a different size wind turbine is to be placed. Adjusting the length of the hulls may be simpler than building a new vessel for such a next project. Adjusting may also be achieved by connecting an upper end of the hull to a lower end of the hull at respective upper and lower ends of the vessel with a frame work which is variable in length. The hulls may be made of steel. To reduce weight the hulls may also be partly or in whole made of a fiber reinforced polymer composite, for example carbon fiber reinforced polymer composite.

The hull or hulls of the delivery vessel are provided with buoyancy compartments. In addition separate buoyancy compartments may be added. In case a catamaran type vessel is used such a separate buoyancy compartment may be positioned between the two hulls at the lower end of the vessel.

The means to support a wind turbine on the vessel are preferably such that they may fix the wind turbine in one position and guide the wind turbine in the longitudinal direction of the vessel in another position. This is advantageous when placing the wind turbine on the vessel in a substantially horizontal position. The movement of the wind turbine in this direction is also advantageous when the delivery vessel is submerged and the wind turbine needs to move towards the upper end of the vessel as explained above. A combination of hydraulically operated clamps and rollers supporting the wind turbine is an example of a suitable means to support the wind turbine.

When the delivery vessel is used to deliver the wind turbine to a submerged vessel as described above it may be preferred that the hulls have the shape of the letter U when seen from above, wherein the open end of the letter U is the lower end of the vessel. This opens end enables one to move the delivery vessel away from the submerged vessel once the wind turbine has been fixed to the submerged vessel. The invention is also directed to the use of this delivery vessel in the earlier described process wherein the moveable support is a moveable arm which moveable arm is rotatably fixed to a submerged vessel along the horizontal axis of rotation and wherein the moveable arm supports and erects the wind turbine to the substantially vertical position and wherein the submerged vessel is fixed to the sea bed in step (d).

When the delivery vessel is used as the moveable support as described above it may be advantageous to provide the hull with supporting means. The supporting means may be pivotally connected to the hull or hulls such that when the lower end of the vessel rests on the sea bed the delivery vessel can pivotally rotate from an angled position to a vertical position. The supporting means are preferably also provided with one or more buoyancy compartments which may be filled with water to balance the vessel when it is carrying the wind turbine and may be emptied when the vessel has placed the wind turbine and returns to shore to pick up a next wind turbine. When emptying this buoyancy compartment when the vessel rests on the sea bed it may be advantageous to direct the discharged water to the sea bed near the supporting means. This will facilitate an easy loosening of the vessel from the sea bed when bringing the delivery vessel to the water surface.

The support elements are suitably provided with anchoring means to connect the lower end of the delivery vessel to the sea bed or to a pre-installed basis for the wind turbine. Such anchoring means may be for example suction anchors

The delivery vessel may be provided with its own propulsion means or may be transported over sea by means of one or more tugs. The vessel may also be provided with one or more directable thrusters which can position the vessel when partly submerged. The thrusters are preferably arranged to provide the lower end of the delivery vessel with between 3 to 6 degrees of freedom when partly submerged.

The higher end of the delivery vessel may also be provided with means to connect one or more cables suited for erecting the vessel to a vertical position when the lower end of the vessel rests on the sea bed. The higher end of the vessel may also be provided with anchoring means, wherein the length of the anchoring cable can be controlled, suitably by winches as part of the vessel.

The delivery vessel having two parallel hulls suitably has at the lower end of the two hulls connecting means present which can in use connect the delivery vessel to two spaced apart jack-up vessels. Such connecting means enables that the delivery vessel can rotate along a substantially horizontal and submerged axis running from the one jack-up vessel to the other jack-up vessel. The connecting means suitably are present at either end of the axis and suitably are suited to connect with submerged means present on either jack-up vessel and more preferably to connect to a leg of a first jack-up vessel and to connect to a leg of the second jack-up vessel. The upper half of the vessel is suitably provided with means to connect a cable and preferably at least two cables. One cable can connect to the first jack-up vessel and the second cable can be connected to the second jack-up vessel. By shortening such cables the combination of delivery vessel and wind turbine can be erected to a vertical position. The invention is also directed to the use of this delivery vessel in the earlier described process wherein the lower end of the delivery vessel is connected to two spaced apart jack-up vessels fixed to the sea bed such that the axle of rotation of step (d) runs from one jack-up vessel to the other jack-up vessel.

The delivery vessel may also comprise of at least two hulls interconnected by means which are adjustable in length and by means to support a wind turbine, wherein one hull is a submersible part defining the lower end of the vessel one other hull is a separate floating part defining the upper part of the vessel. The submersible part may be fixed to the sea bed by its own weight. The submersible part may additionally be provided with means to fix this part to the sea bed, suitably suction anchors or screw anchors as the fixing means.

The means to support the wind turbine may be a framework having means to connect to the wind turbine and especially to the mast of the wind turbine. The support means will support the wind turbine during transport, the submerging step (b) and during the actual erection of the wind turbine in step (d). This support is slidable connected to the floating part enabling movement of the floating part relative to the support means in the direction running from floating part to submerged part. The support means are rotatably connected to the submersible part along a substantially horizontal axis. This delivery vessel is preferably used in a process as described earlier wherein in step (d) the submersible part is fixed to the sea bed and the floating part floats at sea level and wherein the erecting is enhanced by reducing the distance between submerged part and the floating part.

In some of the embodiments of the invention cables are mentioned which may be reduced in length thereby enhancing the erection in step (d). Such a cable which can be reduced in length is suitably a rope and pulley system having a fixed and moving axle. Preferably such a system comprises a block and tackle wherein several pulleys are mounted on the fixed and moving axles to reduce the tension in the cable while achieving the same pulling power.

The means which are adjustable in length are suitably cables which can be reduced in length by means of a winch resulting in that the distance between the floating part and the submerged part is reduced. Such a winch is suitably positioned on the floating part and by operation of the winch the floating part is pulled towards the submerged part. The energy required for this process will then substantially be provided by this winch or winches. The energy required to reduce this distance may also be obtained by buoyancy forces. In this embodiment the means which are adjustable in length are cables connected at one end to the floating part and at their other end at a counter buoyancy compartment. The cable runs from the floating part to the buoyancy compartment via a fixed point on the lower end of the means to support the wind turbine. This results in that the floating part can move in step (d) towards the submersible part while the buoyancy compartment moves upwardly. The buoyancy compartment may be increased in buoyancy in step (d) by for example replacing water with a gas, suitably air. The energy required for reducing the distance between the floating part and the submerged part will then be substantially be provided by the pumps which replace the water with air.

The process involving the floating part and the submerged part a described above is advantageous because the buoyancy forces enhancing the erection of the wind turbine are exercised on the wind turbine at the sea level. This results in the largest possible moment, i.e. the distance between the buoyancy compartment and the positioned horizontal axis of rotation at the sea bed. This in contrast with the earlier described embodiments where a possible buoyancy box is fixed at a relative short distance to the positioned horizontal axis of rotation. This results in that the dimensions of such a vessel may be smaller than for example the earlier described pre-installed framework of NL2018377. Smaller dimensions are results in that less subsea force, for example by currents, on the submerged parts of the vessel are exercised. This is advantageous because less counter measures will then be required. Counter measures are typically a dynamic positioning system and because of the reduced subsea forced a smaller dynamic positioning system may be used. A further advantage is that no large actuators are required which have to operate below sea level as in the earlier described pre-installed framework of NL2018377.

The invention is also directed to a combination of any one of the above describe delivery vessels according to the invention and a wind turbine.

The invention will be described by the following Figures.

Figure 1-6 illustrate how the process according to the invention may be performed. Figure 1 shows the starting situation which includes a floating U-shaped delivery vessel 1 with the wind turbine 2 positioned in a substantially horizontal position on the delivery vessel 1 thereby defining a lower end 3 of the vessel 1 at which the foundation 4 of the wind turbine 2 is positioned and an upper end 5 of the vessel 1 at which the upper end 6 of the wind turbine is positioned. Also shown is a cable 7 attached at one end to a buoy 8 and at its opposite end attached to a framework 9. For clarity reasons only one cable 7 is shown. This cable may be two cables 7 suited to be connected to the two legs of the U shaped delivery vessel 1. In this position the delivery vessel 1 floats on the water surface 9a and may be connected to a working vessel, like for example a tug boat. The buoyancy compartments 10 and 11 are for this reason filled with air. Framework 9 may be as described in Figure 2 of NL2018377. The framework 9 rests on the sea floor 12 and is provided with a moveable arm 13 which can rotate along a horizontal axis 14 by making use of a hydraulic actuator 15 as shown in Figure 6. Buoyancy means may be connected to moveable arm 13 as shown in figure 10 of IML2018377.

In Figure 2 at least the lower end 3 of the delivery vessel 1 is submerged by filling compartment 11 closest to the lower end 3 and optionally the lower compartment 4a of the wind turbine 2 with water while maintaining some buoyancy at the upper end 5 of vessel 1 and some buoyancy at the top of the wind turbine 2. The cable 7 is now connected to the lower end 3 of the vessel 1. By winching in cable 7 with winch 7a the vessel 1 moves under and angle with the sea floor 12 towards the sea floor 12 and towards framework 9.

Figure 3 shows the situation in which cable 7 is fully winched in and that the lower end 3 of vessel 1 is indirectly fixed to the sea floor 12 via framework 9. At framework 9 fixing means 99 as also shown in Figure 2 of NL2018377 are shown which connect with the foundation 4 of the wind turbine 2. In this manner the vessel 1 and the wind turbine 2 are firmly positioned with respect to the framework 9.

In Figure 4 the moveable arm 13 has been moved using actuator 15 (see Figure 6) and optionally by adding air to a buoyancy compartment connected to arm 13 towards the wind turbine 2 when connecting arm 13 to the wind turbine 2.

In Figure 5 it is shown that after the movable arm 13 is connected with the wind turbine 2 the vessel 1 can move away from the wind turbine 2 and the framework 9. For this movement the vessel 1 may be provided with thrusters or may be pulled in by a cable towards another vessel (not shown). For example the earlier referred to working vessel from which the process is controlled. Because delivery vessel 1 has the shape of a U it can easily free itself from the wind turbine 2 as connected to the moveable arm 13. The delivery vessel 1 may now be brought to the water surface 9a by increasing the buoyancy of the delivery vessel by filling compartment 11 with air. The delivery vessel 1 can now be re-used to position another wind turbine or basis of a wind turbine at another location. The wind turbine can now be erected to a substantially vertical position making use of hydraulic actuator 15 as shown in Figure 6. To further enable this movement it is preferred that buoyancy means are connected to moveable arm 13 and/or to the mast of the wind turbine 2 and/or by making use of the buoyancy of the mast of the wind turbine as illustrated in NL2018377. For example lower compartment 4a of wind turbine 2 can be cleared of the buoyancy water.

In Figure 6 the wind turbine 2 is fully erected to a vertical position. A hydraulic actuator 15 connects the moveable arm 13 with the framework 9 at a point between axis 14 and fixing means 99. The wind turbine 2 is provided with a tripod basis 16 as foundation 4 which can be fixed to the sea floor 12 by means of suction anchors 16a. Alternatively anchoring may be achieved with piles drilled into the sea floor by a hydrohammer as described in NL2018377. When fixing to the sea floor 12 water can be added to lower compartment 4a such to increase the underwater weight of the wind turbine 2 and enhance the anchoring process. Once the wind turbine 2 is fixed to the sea floor 12 the framework 9 can be disconnected from the wind turbine and move to a next position on sea floor 12 making use of means to transport the framework 9. Such means may be thrusters, caterpillar tracks and the like as further described in NL2018377. The framework may also be lifted from the sea bed by means of cables connected to one or more floating vessels. The framework may be lifted just above the sea bed and towed to the next wind turbine installation position. At this next position the process may be repeated to position a next wind turbine or its basis.

Figure 7 shows a storage vessel 17 for wind turbines 2 as seen from above. Storage vessel 17 has a harbor entry 18 preferably provided with a bottom 19 to decrease the influence of waves. In harbor entry 18 the U-shaped delivery vessel 1 can moor and to extract a wind turbine 2 from vessel 17. Vessel 17 shows three wind turbines 2. It may be envisaged that this number may be higher. Furthermore it may be envisaged that on board of vessel 17 the wind turbines are partly assembled.

Figure 8 shows storage vessel 17 of Figure 7 as seen from aside.

Figure 9 shows how more than one interconnected delivery vessel 1 - wind turbine 2 combination may be transported by a tug boat 20.

Figure 10 shows a front view of delivery vessel 21 which can be used as the moveable support. The delivery vessel 21 has two parallel hulls 22, means 23 to support a wind turbine 30. Support 23 is drawn schematically and may consist of a structure which supports the generator and mast of the wind turbine 30. Beam 23a connects the two hulls 22 and forms a structural triangle with supports 23. The wind turbine 24 has three blades 25, a hub 26 and a generator 27. Further shown are thrusters 28 for a displacement of the vessel 21 in a direction perpendicular to the hulls 22. The two moveable thrusters 29 can move the vessel in the direction of the hulls, optionally under an angle.

By controlling the thrusters independently the vessel may also rotate thereby being able to accurately position the vessel when it descends to the sea bed.

Figure 11 shows the vessel and wind turbine combination of Figure 10 from aside. A mast 30 and a foundation 31 are shown. Foundation 31 has a design which enables a connection to a basis already positioned on the sea bed. The vessel 1 has a lower end 32 at which the lower end 33 and foundation 31 of the wind turbine 24 is positioned and an upper end 34 of the vessel at which the upper end of the wind turbine is positioned. The hulls 22 are provided with buoyancy compartments 36, 37 at the upper and lower end of the vessel. A separate buoyancy compartment 3a is present between the two hulls 22. Buoyancy compartments 36, 37 and 3a can independently from each other be filled with water or air. Further support means 38 are shown at the lower end 32 of the vessel for allowing the lower end 32 of the vessel to rest on the sea bed. The supporting means 38 are pivotally connected to each hull 22 such that when the lower end 32 of the vessel rests on the sea bed the delivery vessel can pivotally rotate from an angled position to a vertical position as is shown in Figures 15 and 17. Supporting means 38 are each provided with three suction anchors 38a.

Figure 12 shows the vessel and wind turbine combination of Figure 10 from above. This figure further shows that thrusters 28 are not aligned. This enables one to separately operate these thrusters in opposite directions and thus create a lever which rotates the vessel. Further shown are means 39 to connect cables at the upper end 34 of the vessel and anchoring means 40 at the upper end of the vessel.

Figure 13 shows the vessel and wind turbine combination 44 of Figures 10-12 floating near a jack-up platform 42. A basis 43 for the wind turbine has been placed on sea bed 48 using for example a hydrohammer as described in EP2807307 or EP3022361 and operated from jack up platform 42. The basis 43 may alternatively be placed using another vessel than the jack up platform 42. Shown is that vessel and wind turbine combination 44 is loosely anchored by means of anchor cable 45 which is part of anchoring means 40. Two cables 46 (of which one is shown) are used to connect each hull 22 at its means 39 to connect cables to one or more winches 47 fixed to the jackup platform 42. The cable 46 is connected at one end to winch 47 and at its other end to an anchor 43a and runs via a fixed point at means 39 back and via an elevated point on the jack up platform 42.

Figures 14-16 show the consecutive phases of the erection process of the vessel 22 and the wind turbine combination 44. In Figure 14 the lower end of the vessel and wind turbine combination 44 is submerging by providing ballast water to the buoyancy tanks 37 (see figure 11). The lower end of the vessel 32 is moved to a position where it will rests on the sea bed 48. The positioning may be aided by shortening cable 46 and using thrusters 28 and 29 such that when the combination is in its vertical position the mast is substantially aligned with the basis 43. Support 38 rotates to a position where it can rest on the sea bed 48. Once the lower end of the vessel rests on the sea bed 48 the suction anchors 38a will connect the vessel to the sea bed. The combination 44 may then be erected to a vertical position by increasing the buoyancy of the vessel by adding air to buoyancy compartments 37 and 23a and by shortening cables 46 as shown in Figure 15. Suction anchors 38a avoid that the combination 44 will move upwards and sidewards during erection of the wind turbine. It may even be advantageous to increase the weight of the combination somewhat to improve the fixation to the sea bed. Cable(s) 45 may be put under a slight tension to avoid that the rotation to a full vertical position is executed too fast or that the combination 44 tilts over towards the jack up platform 42. When arrived at its vertical position the lower end of the mast is suitably above the basis 43. Subsequently an arm 49 fixed to the jack up platform 42 connects to the mast 30 of wind turbine 24. The connections 23 are disconnected and the mast is lowered onto the basis 43 where a slip joint connection as for example described in EP2910686 is made, resulting in a configuration as shown in Figure 16. After placing the wind turbine the vessel 22 is brought to the water surface by emptying the buoyancy compartments in the hulls 22. The thrusters may be used to keep the vessel free of the installed wind turbine and the anchor cables 45 are shortened to move the vessel away from the jack up platform 42.

Figure 17 shows an alternative configuration of the one shown in Figures 15-16 wherein three jack-up platforms 42,50, 50a (not shown) are used. Two jack-up platforms (50,50a), of which only jack-up platform 50 is shown, are positioned at either side of the partly submerging vessel 21. By means of shortening cable 51 connecting jack-up platform 50 with the upper end of vessel 21, the erection may be further enhanced.

Figures 19 and 18 shows an embodiment with only two jack-up platforms 52, 53 at either side of the lower end 32 of vessel 22. This lower end is connected to a substantially horizontal axis 54 which is rotatably connected to a leg 55 of jack-up platform 52 and rotatably connected to leg 56 of jack-up platform 53. Figure 19 also shows cable 56 which is used to erect the vessel 21 upwards to a vertical position.

Figure 20 shows the lower end 32 of one hull 22 of the vessel shown in Figure 18 provided with a rotatable axis 54.

Figure 21 shows another delivery vessel 59 according the invention having a floating hull 60 and a submersible hull 61 which are connected by a cable 62 and a support 63 for a wind turbine 64. The support 63 is a framework which supports the wind turbine from its upper end to its lower end 67 at a lower end 68 of the vessel 59. The hull 61 which is the lower end of the vessel 59 may be provided with one or more compartments provided with a mass with a greater density than water, for example grouting, and one or more buoyancy compartments such that it can float or can be lowered to the sea bed. The submergible hull 61 filled with water may act as a gravity based anchor and is provided with four screw anchors 69 to fix the lower end 68 of the vessel 59 directly to the sea bed. Cable 62 is adjustable in length using a winch 70 and a block and tackle mechanism which can pull floating hull 60 towards submersible hull 61. Winch 71 can pull the floating hull 60 back to the end of the support 63. The floating hull 60 is slidable connected to the support 63 by means of guide beams 63a.This enables movement of the floating hull 60 relative to the support 63 in the direction running from floating hull 60 to submerged hull 61. The support 63 is rotatably connected to the submersible hull 61 along a substantially horizontal axis 72. Furthermore, two actuators 73 connect the support 63 with the submersible hull 61. The wind turbine may be connected to the support 63 by means of clamps.

In figure 22 the submersible hull 61 is shown in more detail. Two cable blocks 74 are shown which are part of the block and tackle system. Four slides 75 are shown which rest on the sea bed.

Figure 23 shows the delivery vessel 59 with wind turbine 64 in a situation wherein the submersible hull 61 is fixed to sea bed 77 by means of screw anchors 69 and by means of its own weight as supported by slides 75. Cable 62 is shortened by pulling force S. Because of the buoyancy force B of floating hull 60 a resultant force R will result which enhances rotation of the support 63 and wind turbine 64 along axis 72.

Figure 24 shows the delivery vessel 59 with wind turbine 64 floating at sea level 76. In this situation the buoyancy compartments of submersible hull 61 are filled with air such to create buoyancy.

Figure 25 shows the situation where the submersible hull 61 is lowered to the sea bed and fixed to the sea bed. In this mode the floating hull 60 will ensure that the upper part of the wind turbine 64 remains above sea level 76. In a next mode cable 62 will be reduced in length resulting in a situation as shown in Figure 23.

Figure 26 shows the situation wherein the resulting force R will not be sufficient to further rotate the support and wind turbine. Now the actuators 73 are used to rotate the support and wind turbine to the final vertical position shown in Figure 27.

In the situation shown in Figure 27 the suction anchors 78 of the wind turbine 64 are used to fix the wind turbine 64 to sea bed 77.

In Figure 28 a delivery vessel 59 as in Figure 21 is shown. The difference is that cable 62 is now connected at one end to the floating part 60 and at their other end at a counter buoyancy compartment 80. The cable 62 runs from the floating part 60 to the counter buoyancy compartment 80 via a rotating disk 82 around the fixed shaft 72(see figure 30) underneath the lattice construction 63. The buoyancy of both the floating part 60 and the counter buoyancy compartment 80 will initiate the rotating moment on the lattice support construction 63 around the fixed axis 72, which is fixed on the submersible hull 61. In use the floating part 60 will move towards the fixed submersible part 61 guided by beams 63a while the counter buoyancy compartment 80 moves upwardly also guided by beams 63b. The counter buoyancy compartment 80 and the floating part 60 are connected by a second cable 82. This cable 82 runs from the floating part 60 to the buoyancy compartment 80 via a set of rotating disks 83 around the fixed shafts 83a as shown in Figure 30. Figure 30 shows the lattice construction 63 as the means to support the wind turbine combined with the floating part 60 and the buoyancy compartment 80 and their interconnected cables 62 and 82. The buoyancy compartment 80 is slidable connected and positioned within the framework of the lattice support construction 63.

Figure 29 shows a situation wherein floating part 60 is pulled towards submersible hull 61 and wherein the connected buoyancy compartment 80 has moved upwardly. Actuators may be present to further erect the wind turbine as shown in Figure 22.

Claims

A method for positioning a wind turbine in a vertical position on the seabed, comprising the steps of: a. Providing a floating delivery vessel, with the wind turbine positioned in a substantially horizontal position on the sea level delivery vessel, whereby a lower the end of the vessel is defined at the height of which the lower end of the wind turbine is positioned, and also an upper end of the vessel at the height of which the upper end of the wind turbine is positioned, b. the sinking of at least the lower end of the delivery vessel to such a position that the upper end of the wind turbine is above sea level and the lower end of the wind turbine points towards the seabed, c. providing a movable support connected to the wind turbine, d. erecting the combined movable support and the wind turbine in a substantially vertical position along a sunken and substantially horizontal axis of rotation, and e. attaching the wind turbine to the seabed.

The method of claim 1, wherein the delivery vessel moves at an angle with respect to the seabed and in the direction of the seabed by reducing the floating power at the lower end of the delivery vessel, with the result that the delivery vessel itself positions at an angle to the seabed when it is submerged.

A method according to any one of claims 1 to 2, wherein erecting the combined movable support and the wind turbine in step (d) is improved by increasing the driving power of the movable support and / or wind turbine.

A method according to any one of claims 1 to 3, wherein, after erecting the wind turbine in a substantially vertical position in step (d), the wind turbine in step (e) is lowered onto the seabed or to a submerged and pre-installed base on the seabed.

A method according to claim 4, wherein the wind turbine is provided with a tubular mast, wherein the wind turbine is lowered on a sunken and pre-installed base on the seabed, and wherein the connection between the tubular mast and the base is a sliding connection.

The method of claim 4, wherein the lower end of the wind turbine is provided with a support structure with multiple means cooperating with multiple and pre-installed anchors, and wherein the wind turbine is lowered onto multiple anchors as a sunken and pre-installed base on the seabed.

The method of claim 6, wherein the means for cooperating with multiple and pre-installed anchors are slide connections.

A method according to any of claims 1 to 7, wherein the movable support is the delivery vessel, wherein the delivery vessel consists of a support for the wind turbine with an upper end and with a lower end corresponding to the upper and lower end of the wind turbine, a sinkable part rotatably connected to the lower end of the support, and a separate floating part, this floating part being slidably connected to the upper end of the support, and in which in step (d) the part to be sunk is fixed on the seabed, and the floating part floats at sea level, and in which in step (d) the distance between the sunken part and the floating part is reduced, which gives rise to a force that erects the wind turbine facilitated.

The method of claim 8, wherein the distance between the sunken part and the floating part is reduced by shortening a cable.

The method of claim 8, wherein the distance between the sunken part and the floating part is reduced by means of a cable connected to an upwardly moving floating compartment, and wherein the cable runs over a fixed point at the lower end of the support.

The method of any one of claims 1 to 7, wherein the movable support is a movable arm, the movable arm is rotatably mounted on a sunken vessel along the horizontal axis of rotation, and wherein the movable arm supports and erects the wind turbine in the substantially vertical position, and in which the sunken vessel is attached to the seabed in step (d).

A method according to any of claims 1 to 7, wherein the movable support is the delivery vessel, and wherein in step (d) the lower end of the delivery vessel is directly or indirectly fixed on the seabed in such a way that, when the wind turbine is erected, a rotation takes place with a substantially horizontal axis.

A method according to claim 12, wherein erecting the combination of the delivery vessel and the wind turbine is realized with the aid of one or more cables connected at one end to the upper half of the delivery vessel and connected at the other end thereof with a jack vessel that has been moored on the seabed.

A method according to claim 12, wherein the lower end of the delivery vessel is connected to two spaced jack vessels that are fixed on the seabed in such a way that the rotation axis in step (d) of the one jack vessel sews. the other auger vessel is running.

A delivery vessel, comprising: one or more hulls, means for supporting an upper end of a wind turbine at an upper end of the vessel, and means for supporting a lower end of a wind turbine at a lower end of the vessel vessel, one or more air boxes at the lower end of the vessel, wherein these air boxes can be filled independently of each other with air or with water, fastening means at the lower end of the vessel, with which the lower end of the vessel directly or indirectly can be captured on the seabed.

The delivery vessel of claim 15, wherein the delivery vessel comprises at least two hulls interconnected by using means having an adjustable length, and connected by using means around the upper and lower supporting one end of a wind turbine, wherein one hull is a submersible part that defines the lower end of the vessel, while the other hull is a separate floating part that defines the upper part of the vessel.

17. Delivery vessel according to claim 16, wherein the sinkable part can anchor itself in the seabed using a gravity anchor, or is provided with suction anchors or with screw anchors as fastening means.

A delivery vessel according to any one of claims 16 to 17, wherein the means having an adjustable length are cables whose length can be reduced with the help of a winch.

The delivery vessel of any one of claims 16 to 17, wherein the means having an adjustable length are cables connected at one end to the floating member and connected at the other end to a counter-air chamber wherein the cable of the floating member passes through the air compartment through a fixed point at the lower end of the means to support the wind turbine such that, in use, the floating member can move toward the sinkable member while the air chamber moves upwards.

A delivery vessel according to claim 19, wherein the air chamber and the floating part are connected by using a second cable or cables, and wherein the cable runs from the floating part to the air chamber via a fixed point at the upper end of the means for supporting the upper end and the lower end of a wind turbine.

A delivery vessel according to any one of claims 19 to 20, wherein the air chamber is slidably connected to the means for supporting the upper and lower end of a wind turbine.

A delivery vessel according to any one of claims 16 to 21, wherein the floating part is slidably connected to means for supporting the upper and lower end of a wind turbine, thereby allowing movement of the floating part relative to the supporting means in the direction that goes from the floating part to the sunken part, and in which the means for supporting the upper and lower end of a wind turbine are rotatably connected to the sinkable part along a substantially horizontal axis.

A delivery vessel according to claim 15, wherein the vessel comprises two hulls parallel in the direction of travel.

The delivery vessel of claim 23, wherein the hulls are in the form of a letter U when viewed from above, wherein the open end of the letter U is the lower end (3) of the vessel (1).

A delivery vessel according to claim 23, wherein at the lower end of the two hulls there are connecting means which, during use, can connect the delivery vessel to two spaced jack vessels, and which allow the delivery vessel to rotate around a substantially horizontal and sunken shaft that runs from one jack vessel to the other jack vessel.

A combination of a delivery vessel according to any of claims 14 to 25, and of a wind turbine connected to the delivery vessel.

27. Use of a delivery vessel according to claim 24, in a method according to claim 13.

Use of a delivery vessel according to claim 25, in a method according to claim 14.

Use of a delivery vessel according to one of claims 16 to 22, in a method according to one of claims 8 to 10.