An offshore wind turbine with a temporary platform and a tagline system

Abstract

An offshore wind turbine (1) comprising an up-tower crane, a temporary platform (8) mounted on the tower (2) at a down-tower position, and a tagline system is disclosed The tagline system comprises at least one tagline (13) and at least one winch. Each tagline (13) is configured to be connected, at one end, to a component (10) being hoisted to or lowered from the nacelle (3) by means of the up-tower crane, and, at an opposite end, to one of the at least one winch. Each tagline (13) is further connected to an outlier point (14) formed on the temporary platform (8), each outlier point (14) being arranged at a distance from the tower (2). Furthermore, a method for replacing a component (10) in a nacelle (3) of an offshore wind turbine (1) is disclosed.

Description

[0001] AN OFFSHORE WIND TURBINE WITH A TEMPORARY PLATFORM AND A TAGLINE

[0002] SYSTEM

[0003] FIELD OF THE IVENTION

[0004] The present invention relates to an offshore wind turbine comprising a foundation, a tower supported by the foundation and a nacelle mounted on the tower. The offshore wind turbine according to the invention is provided with an up-tower crane, a temporary platform and a tagline system allowing for replacement of components in the nacelle. The method further relates to a method for replacing a component in the nacelle of such an offshore wind turbine.

[0005] BACKGROUND OF THE INVENTION

[0006] For offshore wind turbines, it is often a challenge to install or replace components, in particular heavy components, in the nacelle. Such installing or replacement requires lifting and / or lowering of the component by means of a crane or similar hoisting equipment substantially along the tower of the wind turbine, between a position in the nacelle and a position on a seagoing vessel. The crane may, e.g., be positioned at an up-tower position of the wind turbine, on the seagoing vessel or on a separate floating or jacked-up vessel.

[0007] Wind and waves at the offshore location of the offshore wind turbine impacts the wind turbine as well as the seagoing vessel, and may therefore cause mutual movements therebetween. Furthermore, when a component to be installed or replaced is suspended from the crane, it may also be affected by the wind and / or the movements of the offshore wind turbine and / or the seagoing vessel, to an extent which introduces a risk of collisions between the component and the wind turbine, in particular the tower of the wind turbine. Therefore guidance of the component is required during the hoisting and / or lowering thereof. For onshore wind turbines, guidance for components being hoisted to and / or lowered from the nacelle may be provided by means of taglines connected, at one end, to the component, and held by personnel at an opposite end. However, for offshore wind turbines such an arrangement is not feasible, because it is not possible to position the personnel supposed to hold the taglines in the vicinity of the offshore wind turbine, since this would either position the personnel on water or on a vessel which is likely to move relative to the offshore wind turbine, thus introducing a risk to the personnel.

[0008] DESCRIPTION OF THE INVENTION

[0009] It is an object of embodiments of the invention to provide an offshore wind turbine which allows for safe and easy installing and / or replacement of components in a nacelle of the offshore wind turbine.

[0010] It is a further object of embodiments of the invention to provide a method for replacing a component in a nacelle of an offshore wind turbine in a safe and easy manner.

[0011] According to a first aspect the invention provides an offshore wind turbine comprising a foundation, a tower supported by the foundation and a nacelle mounted on the tower, wherein the offshore wind turbine further comprises:

[0012] - an up-tower crane mounted in, on or near the nacelle,

[0013] - a temporary platform mounted on the tower at a down-tower position, and

[0014] - a tagline system comprising at least one tagline and at least one winch, each tagline being configured to be connected, at one end, to a component being hoisted to or lowered from the nacelle by means of the up-tower crane, and, at an opposite end, to one of the at least one winch, each tagline further being connected to an outlier point formed on the temporary platform, each outlier point being arranged at a distance from the tower. Thus, according to the first aspect, the invention provides an offshore wind turbine. In the present context the term 'offshore wind turbine' should be interpreted to mean a wind turbine which is positioned at an offshore location, such as at sea or on a lake. The offshore wind turbine comprises a foundation, a tower supported by the foundation and a nacelle mounted on the tower. The nacelle may further carry a rotor with a number of wind turbine blades, and it may house a number of relevant wind turbine components, such as a gearbox, a generator, a main shaft, a main bearing, a transformer, various electrical components, etc.

[0015] The offshore wind turbine further comprises an up-tower crane. In the present context the term 'up-tower crane' should be interpreted to mean a crane being located at an up-tower position of the wind turbine, i.e. at a position at or near the top of the tower and / or the nacelle. Accordingly, the up-tower crane is mounted in, on or near the nacelle. Thus, the up-tower crane can be applied for hoisting and / or lowering components between a down-tower position and an up- tower position, e.g. an installing position in the nacelle.

[0016] Furthermore, the offshore wind turbine comprises a temporary platform mounted on the tower at a down-tower position, i.e. at a position being near the base of the tower and the surface of the water, and essentially opposite the up- tower position. In the present context the term 'temporary platform' should be interpreted to mean a platform which is not intended for being permanently mounted on the tower of the offshore wind turbine, for instance during normal operation of the offshore wind turbine. Instead, the temporary platform is only intended for being mounted on the tower of the offshore wind turbine for a limited period of time, such as while performing a specified task. Furthermore, the temporary platform should be mounted on the tower in such a manner that it can easily be dismantled from the tower without causing structural damage to the tower.

[0017] Finally, the offshore wind turbine comprises a tagline system comprising at least one tagline and at least one winch. Each tagline is configured to be connected, at one end, to a component being hoisted to or lowered from the nacelle by means of the up-tower crane. The end of the tagline may be directly attached to the component, or it may be indirectly connected to the component. For instance, the end of the tagline may be attached to a connecting or lifting device or interface, such as a yoke, eyelet, etc., which is in turn connected to the component. In any event, a connection is established between the end of the tagline and the component.

[0018] Each tagline is further configured to be, directly or indirectly, connected, at an opposite end, to one of the at least one winch. Thus, for each tagline, one end is connected to the component and another, opposite, end is connected to one of the at least one winch. Accordingly, when operating the at least one winch, this has an impact on the at least one tagline, and this impact is transferred to the component via the at least one tagline. Thus, the hoisting / lowering movement of the component can be controlled by means of the at least one tagline, and by appropriately operating the at least one winch. In particular, transversal or sideways movements of the component can be controlled in this manner, so as to reduce the risk of collisions between the component and the tower of the offshore wind turbine.

[0019] Furthermore, each tagline is connected to an outlier point formed on the temporary platform, each outlier point being arranged at a distance from the tower. Thus, each tagline preferably runs from the winch to the component being hoisted or lowered, via the outlier point. Thus, the position of the outlier point determines to which extent the path followed by the tagline deviates from a straight line interconnecting the winch and the connecting position at the component. Since the outlier point is arranged at a distance from the tower, the tagline is pulled away from the tower, thus significantly reducing the risk of collisions between the component and the tower.

[0020] Since the at least one outlier point is formed on the temporary platform, it is provided along with the temporary platform, and is therefore only available as long as the temporary platform remains mounted on the tower of the offshore wind turbine.

[0021] Accordingly, the tagline system, in cooperation with the temporary platform, ensures that the component can be safely and easily hoisted to or lowered from the nacelle, with minimal risk of collisions between the component and the offshore wind turbine, in particular between the component and the tower of the offshore wind turbine, and without the need for personnel holding the taglines.

[0022] Each of the at least one winch may be arranged at one of the outlier point(s). According to this embodiment, each winch is itself arranged at an outlier point, and thus at a distance from the tower of the offshore wind turbine. This ensures the appropriate distance between the component and the tower during lowering or hoisting of the component, in an easy manner, and without requiring additional components of the tagline system.

[0023] As an alternative, the tagline system may comprise at least one pulley, each pulley being arranged at one of the outlier point(s). According to this embodiment, the path followed by a given tagline runs from the winch, to the pulley at the outlier position, and further on to the contact point towards the component being hoisted or lowered. At the pulley, the direction of the path followed by the tagline will change.

[0024] The at least one winch may, in this case, be arranged at a position away from the respective outlier point, for instance on the temporary platform, e.g. close to the tower, or on or inside the tower. This will allow easy access to the at least one winch, while positioning the outlier point with the pulley at a significant distance from the tower, thus pulling the tagline far away from the tower and even further reducing the risk of collisions between the component and the tower.

[0025] The temporary platform may comprise at least one arm protruding from the temporary platform in a direction away from the tower, and each outlier point may be arranged at an extremity of one of the at least one arm. This positions the at least one outlier point at a significant distance from the tower, thus ensuring a large distance between the at least one tagline and the tower and minimising the risk of collisions between the component and the tower, without requiring a bulky temporary platform. Each arm may be movable between an extended position in which the extremity of the arm is arranged at a maximum distance to the tower, and a stow-away position. According to this embodiment, the at least one arm need only be in the extended position when a component is to be hoisted to or lowered from the nacelle, and the tagline system therefore needs to be in operation. The stowaway position may define a compact design of the temporary platform, which may, e.g., be suitable when mounting the temporary platform on the tower, when dismantling the temporary platform from the tower and / or when transporting the temporary platform. Furthermore, positioning the at least one arm in the stow-away position may allow more space for transferring a component from the temporary platform to a seagoing vessel, or vice versa.

[0026] Each arm may be movable between the extended position and the stow-away position by means of a swinging movement in a substantially horizontal plane. This is a simple and failsafe manner of moving the at least one arm. As an alternative, the at least one arm may be moved between the extended position and the stow-away position by means of a telescopic movement, by means of a swinging movement in a substantially vertical plane, or by means of any other suitable kind of movement. The temporary platform may be provided with suitable locking mechanisms for locking the at least one arm in the extended position, so as to avoid that the at least one arm accidentally moves to the stow-away position while the tagline system is operating.

[0027] The tagline system may comprise at least two taglines and at least two winches. This will allow transverse movements of the component being hoisted or lowered to be controlled in multiple directions.

[0028] The foundation may be a fixed foundation, i.e. a foundation being fixedly connected to the seabed, such as a jacket, a monopile or other suitable kinds of bottom fixed structures.

[0029] As an alternative, the foundation may be a floating foundation. According to this embodiment, the foundation of the offshore wind turbine is not fixedly connected to the seabed. Instead, the foundation is connected to one or more anchoring points on or in the seabed via wires, chains or similar connectors. Thus, the exact position of the offshore wind turbine is allowed to shift within a certain area defined by the position of the one or more anchoring points and the length of the connectors, subject to impact from wind and waves. Furthermore, offshore wind turbines with floating foundations follow vertical movements of passing waves, and they may tilt due to the impact of waves. Thus, offshore wind turbines with floating foundations are more exposed to impact from wind and waves than offshore wind turbines with fixed foundations. Accordingly, the present invention is particularly relevant in this case.

[0030] Each of the at least one winch may be provided with a damping mechanism. According to this embodiment, in addition to guiding the component and controlling transverse or sideways movement of the component during hoisting or lowering thereof, the at least one winch is also capable of dampening oscillating movements of the component, via the at least one tagline, and by means of the damping mechanism.

[0031] According to a second aspect the invention provides a method for replacing a component in a nacelle of an offshore wind turbine, the offshore wind turbine comprising a foundation, a tower supported by the foundation and a nacelle mounted on the tower, the method comprising the steps of:

[0032] - transporting a replacement component and a temporary platform to a site of the offshore wind turbine by means of a seagoing vessel,

[0033] - hoisting the temporary platform from the seagoing vessel towards the offshore wind turbine and mounting the temporary platform on the tower of the offshore wind turbine at a down-tower position,

[0034] - mounting at least one tagline by connecting one end of each tagline to a component to be replaced, and an opposite end of each tagline to one of at least one winch, and connecting each tagline to an outlier point formed on the temporary platform and arranged at a distance from the tower, lowering the component to be replaced from the nacelle towards the temporary platform by means of an up-tower crane mounted in, on or near the nacelle, and while controlling transverse movements of the component by means of the at least one tagline and the at least one winch, and

[0035] - disconnecting the component to be replaced from the at least one tagline and hoisting the component to be replaced from the temporary platform to the seagoing vessel.

[0036] Thus, according to the second aspect, the invention provides a method for replacing a component in a nacelle of an offshore wind turbine. The offshore wind turbine could, e.g., be a wind turbine according to the first aspect of the invention, and the remarks set forth above with reference to the first aspect of the invention are therefore equally applicable here. Thus, the offshore wind turbine comprises a foundation, a tower supported by the foundation and a nacelle mounted on the tower.

[0037] The component being replaced could, e.g., be a main component of the offshore wind turbine, such as a gearbox, part of a gearbox, a generator, a transformer, a main bearing, a main shaft, a hub, a wind turbine blade, etc. Alternatively, the component may be a temporary crane or a part of a temporary crane to be installed in or on the nacelle for hoisting or lowering heavy components to or from the nacelle.

[0038] In the method according to the second aspect of the invention, a replacement component and a temporary platform are initially transported to a site of the offshore wind turbine by means of a seagoing vessel.

[0039] Upon arrival by the seagoing vessel to the site of the offshore wind turbine, the temporary platform is hoisted from the seagoing vessel towards the offshore wind turbine, and the temporary platform is mounted on the tower of the offshore wind turbine at a down-tower position.

[0040] Next, at least one tagline is mounted by connecting one end of each tagline to a component to be replaced, and an opposite end of each tagline to one of at least one winch. Each tagline is further connected to an outlier point formed on the temporary platform and arranged at a distance from the tower. This has already been described in detail above with reference to the first aspect of the invention. Since the component is a component to be replaced, it is positioned in or near the nacelle, i.e. in an up-tower position.

[0041] The component to be replaced is then lowered from the nacelle towards the temporary platform by means of an up-tower crane mounted in, on or near the nacelle. While lowering the component, transverse movements of the component are controlled by means of the at least one tagline and the at least one winch. Thus, as described above with reference to the first aspect of the invention, appropriate operation of the at least one winch causes an impact to be transferred to the component, via the at least one tagline, thus controlling the transverse or sideways movements of the component during the lowering. Furthermore, the position of the at least one outlier point at a distance from the tower ensures that the component is pulled away from the tower, thus minimising the risk of collisions between the component and the tower during the lowering.

[0042] Finally, the component to be replaced is disconnected from the at least one tagline and hoisted from the temporary platform to the seagoing vessel. Thus, the component to be replaced is now ready for being transported away from the site of the offshore wind turbine and to an onshore location by means of the seagoing vessel.

[0043] The method may further comprise the steps of:

[0044] - hoisting the replacement component from the seagoing vessel to the temporary platform,

[0045] - connecting one end of each tagline to the replacement component,

[0046] - hoisting the replacement component from the temporary platform to the nacelle by means of the up-tower crane, and while controlling transverse movements of the component by means of the at least one tagline and the at least one winch, and disconnecting the replacement component from the at least one tagline and installing the replacement component in the nacelle.

[0047] According to this embodiment, once the component to be replaced has been lowered to the temporary platform, detached from the at least one tagline and possibly hoisted to the seagoing vessel, the replacement component can be transferred to the nacelle of the offshore wind turbine. To this end the replacement component is initially hoisted from the seagoing vessel to the temporary platform. This could be done before or after the component to be replaced is lowered to the temporary platform.

[0048] Each tagline is then connected to the replacement component, and the replacement component is hoisted from the temporary platform to the nacelle by means of the up-tower crane, and while controlling transverse or sideways movements of the replacement component by means of the at least one tagline and the at least one winch, essentially in the manner described above.

[0049] Finally, the replacement component is disconnected from the at least one tagline and installed in the nacelle, so as to replace the component which was previously lowered from the nacelle.

[0050] The method may further comprise the step of dismantling the temporary platform from the tower of the offshore wind turbine and hoisting the temporary platform to the seagoing vessel. According to this embodiment, the temporary platform is removed when the process of replacing the component in the nacelle of the offshore wind turbine has been completed.

[0051] The temporary platform may comprise at least one arm protruding from the temporary platform, the at least one outlier point being arranged at an extremity of one of the at least one arm, and the at least one arm may be movable between an extended position and a stow-away position. In this case the at least one arm may be in the stow-away position during the step of mounting the temporary platform on the tower of the offshore wind turbine. The at least one arm may then be moved to the extended position prior to the step of lowering the component to be replaced, and it may remain in this position while the component is being lowered, i.e. while the tagline system is operating.

[0052] When the component to be replaced has reached the temporary platform, the at least one arm may be moved to the stow-away position, either before or after the component to be replaced is disconnected from the at least one tagline, but in any event before the component to be replaced is hoisted from the temporary platform to the seagoing vessel. This allows more space for the hoisting of the component towards the seagoing vessel, in particular avoiding that the at least one arm fully or partly blocks the preferred hoisting path.

[0053] BRIEF DESCRIPTION OF THE DRAWINGS

[0054] The invention will now be described in further detail with reference to the accompanying drawings in which

[0055] Figs. 1-10 illustrate an offshore wind turbine according to an embodiment of the invention and various steps of a method for replacing a component in the nacelle of the offshore wind turbine in accordance with an embodiment of the invention.

[0056] DETAILED DESCRIPTION OF THE DRAWINGS

[0057] Fig. 1 is a perspective view of an offshore wind turbine 1 according to an embodiment of the invention. The offshore wind turbine 1 comprises a foundation (not shown) being fixedly connected to the seabed, a tower 2 supported by the foundation and a nacelle 3 mounted on the tower 2. The nacelle 3 carries a rotor 4 with three wind turbine blades 5. A landing platform 6 is permanently mounted on the tower 2 at a down-tower position.

[0058] A seagoing vessel 7 carrying a temporary platform (not shown) and a replacement component (not shown) is approaching the offshore wind turbine 1.

[0059] In Fig. 2, the seagoing vessel 7 has reached the offshore wind turbine 1, and is in the process of hoisting a temporary platform 8 from the seagoing vessel 7 towards the offshore wind turbine 1, by means of a crane 9 arranged on the seagoing vessel 7.

[0060] In Fig. 3, the temporary platform 8 has been mounted on the tower 2 at a down-tower position, and it is now ready for receiving components, equipment, personnel, etc. Thus, in Fig. 4, a replacement component 10 is being hoisted from the seagoing vessel 7 to the temporary platform 8, by means of the crane 9.

[0061] Fig. 5 shows the replacement component 10 on the temporary platform 8. It can also be seen that the temporary platform 8 comprises two arms 11, each being capable of performing a swinging movement about a pivot joint 12, thus moving the arm 11 between an extended position and a stow-away position. In Fig. 5 the arms 11 are in the stow-away position, arranging the arms 11 in abutment with sides of the temporary platform 8. When arranged in this position, the arms 11 will not interfere with the transfer of the replacement component 10 from the seagoing vessel 7 to the temporary platform 8. Furthermore, the stow-away position of the arms 11 is suitable during the transfer of the temporary platform 8 from the seagoing vessel 7 towards the tower 2, and during the mounting of the temporary platform 8 on the tower 2, since it provides a compact design of the temporary platform 8.

[0062] In Fig. 6, the arms 11 of the temporary platform 8 have been moved to the extended position, so that they now protrude from the temporary platform 8 in a direction away from the tower 2. Furthermore, two taglines 13 have been mounted in such a manner that one end of each tagline 13 is connected to the component 10, and another, opposite, end of each tagline 13 is connected to a winch (not shown). Each tagline 13 is further connected to an outlier point 14 formed at the extremities of the respective arms 11. This positions the part of each tagline 13 which is connected to the outlier point 14 at a distance from the tower 2.

[0063] Fig. 7 is a close-up of Fig. 6, showing the temporary platform 8 with the component 10 and the mounted taglines 13 in further detail. Fig. 8 is a sideview of the offshore wind turbine 1, where the component 10 is in the process of being hoisted from the temporary platform 8 towards the nacelle 3 by means of an up-tower crane (not shown) mounted in, on or near the nacelle 3. The component 10 is connected to the up-tower crane by means of a hoisting line 15. During the hoisting of the component 10, transverse movements of the component 10 are controlled by means of the taglines 13. The connections between the taglines 13 and the outlier points 14 ensure that the component 10 is pulled away from the tower 2, thus minimising the risk of collisions between the component 10 and the tower 2. Furthermore, this is achieved without requiring that personnel holds the taglines 13, and thus in a safe manner.

[0064] Fig. 9 shows the lower part of the tower 2 and the temporary platform 8 during the hoisting of the component.

[0065] Fig. 10 shows an alternative design of the arms 11 of the temporary platform 8, in which the arms 11 are movable between the extended position and the stowaway position by means of a telescopic movement. Fig. 10 shows the arms 11 in the extended position.

Claims

CLAIMS1. An offshore wind turbine (1) comprising a foundation, a tower (2) supported by the foundation and a nacelle (3) mounted on the tower (2), wherein the offshore wind turbine (1) further comprises:- an up-tower crane mounted in, on or near the nacelle (3),- a temporary platform (8) mounted on the tower (2) at a down-tower position, and- a tagline system comprising at least one tagline (13) and at least one winch, each tagline (13) being configured to be connected, at one end, to a component (10) being hoisted to or lowered from the nacelle (3) by means of the up-tower crane, and, at an opposite end, to one of the at least one winch, each tagline (13) further being connected to an outlier point (14) formed on the temporary platform (8), each outlier point (14) being arranged at a distance from the tower (2).

2. An offshore wind turbine (1) according to claim 1, wherein each of the at least one winch is arranged at one of the outlier point(s) (14).

3. An offshore wind turbine (1) according to claim 1, wherein the tagline system comprises at least one pulley, each pulley being arranged at one of the outlier point(s) (14).

4. An offshore wind turbine (1) according to any of the preceding claims, wherein the temporary platform (8) comprises at least one arm (11) protruding from the temporary platform (8) in a direction away from the tower (2), and wherein each outlier point (14) is arranged at an extremity of one of the at least one arm (11).

5. An offshore wind turbine (1) according to claim 4, wherein each arm (11) is movable between an extended position in which the extremity of the arm (11) is arranged at a maximum distance to the tower (2), and a stow-away position.

6. An offshore wind turbine (1) according to claim 5, wherein each arm (11) is movable between the extended position and the stow-away position by means of a swinging movement in a substantially horizontal plane.

7. An offshore wind turbine (1) according to any of the preceding claims, wherein the tagline system comprises at least two taglines (13) and at least two winches.

8. An offshore wind turbine (1) according to any of the preceding claims, wherein the foundation is a fixed foundation.

9. An offshore wind turbine (1) according to any of claims 1-7, wherein the foundation is a floating foundation.

10. An offshore wind turbine (1) according to any of the preceding claims, wherein each of the at least one winch is provided with a damping mechanism.

11. A method for replacing a component (10) in a nacelle (3) of an offshore wind turbine (1), the offshore wind turbine (1) comprising a foundation, a tower (2) supported by the foundation and a nacelle (3) mounted on the tower (2), the method comprising the steps of:- transporting a replacement component (10) and a temporary platform (8) to a site of the offshore wind turbine (1) by means of a seagoing vessel (7),- hoisting the temporary platform (8) from the seagoing vessel (7) towards the offshore wind turbine (1) and mounting the temporary platform (8) on the tower (2) of the offshore wind turbine (1) at a down-tower position,- mounting at least one tagline (13) by connecting one end of each tagline (13) to a component (10) to be replaced, and an opposite end of each tagline (13) to one of at least one winch, and connecting each tagline (13) to an outlier point (14) formed on the temporary platform (8) and arranged at a distance from the tower (2),- lowering the component (10) to be replaced from the nacelle (3) towards the temporary platform (8) by means of an up-tower crane mounted in, on or near the nacelle (3), and while controlling transverse movements of the component (10) by means of the at least one tagline (13) and the at least one winch, and- disconnecting the component (10) to be replaced from the at least one tagline (13) and hoisting the component (10) to be replaced from the temporary platform (8) to the seagoing vessel (7).

12. A method according to claim 11, further comprising the steps of:- hoisting the replacement component (10) from the seagoing vessel (7) to the temporary platform (8),- connecting one end of each tagline (13) to the replacement component (10),- hoisting the replacement component (10) from the temporary platform (8) to the nacelle (3) by means of the up-tower crane, and while controlling transverse movements of the component (10) by means of the at least one tagline (13) and the at least one winch, and- disconnecting the replacement component (10) from the at least one tagline (13) and installing the replacement component (10) in the nacelle (3).

13. A method according to claim 11 or 12, further comprising the step of dismantling the temporary platform (8) from the tower (2) of the offshore wind turbine (1) and hoisting the temporary platform (8) to the seagoing vessel (7).

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