A WIND TURBINE WITH A CABLE SUPPORTING STRUCTURE

Abstract

A wind turbine (1) comprising a tower structure comprising a main tower part (2) extending along a substantially vertical direction and at least two arms(3) is disclosed. Each arm (3) extends away from the main tower part (2) along a direction having a horizontal component, and the arms (3) are arranged to perform yawing movements. Two or more energy generating units (4) are mounted on the tower structure in such a manner that each arm (3) of the tower structure carries at least one energy generating unit(4), each energy generating unit (4) comprising a rotor (5) with a hub carrying a set of wind turbine blades(6). The main tower part (2) is provided with a cable supporting structure (7) allowing power cables (8) of a power grid to be mounted on the main tower part (2).

Claims

1. A wind turbine comprising: a tower structure comprising a main tower part being anchored, at a lower part, to a foundation structure, the main tower part extending along a substantially vertical direction, the tower structure further comprising at least two arms, each arm extending away from the main tower part along a direction having a horizontal component, the arms being arranged to perform yawing movements about an axis defined by the substantially vertical direction of the main tower part, and two or more energy generating units mounted on the tower structure in such a manner that each arm of the tower structure carries at least one energy generating unit, each energy generating unit comprising a rotor with a hub carrying a set of wind turbine blades, wherein the main tower part is provided with a cable supporting structure allowing power cables of a power grid to be mounted on the main tower part, the main tower part thereby being configured to function as a power mast.

2. The wind turbine according to claim 1, wherein the arms of the tower structure form part of a single transverse structure.

3. The wind turbine according to claim 1, wherein the cable supporting structure is mounted on the main tower part of the tower structure at a position which is lower than a connecting position between the main tower part and at least two of the arms.

4. The wind turbine according to claim 1, wherein the cable supporting structure is or comprises a cassette arranged to hold the power cables, the cassette being configured to be hoisted along the main tower part of the tower structure.

5. The wind turbine according to claim 1, wherein the cable supporting structure has an aerodynamic shape arranged for directing wind towards the energy generating units.

6. The wind turbine according to claim 1, wherein the cable supporting structure is mounted on the main tower part of the tower structure via a vibration dampening arrangement.

7. The wind turbine according to claim 1, wherein a service crane arranged in the tower structure or in one of the energy generating units is configured for use during service of the power cables and/or the cable supporting structure.

8. The wind turbine according to claim 7, wherein at least one of the arms of the tower structure is provided with a hatch allowing a part of the service crane to pass there through.

9. A method for performing service on an energy generating unit of a wind turbine according to claim 1, the method comprising the steps of: performing yawing movements of at least one of the arms of the tower structure, in order to move the arm to a position in which an energy generating unit carried by the arm is clear of the power cables mounted on the main tower part, and performing service on the energy generating unit while the arm is in this position.

10. The method according to claim 9, wherein the step of performing yawing movements comprises moving the arm to a position in which the arm extends away from the main tower part along a direction which defines an angle of approximately 90 with a direction defined by the power cables mounted on the main tower part.

11. The method according to claim 9, wherein the step of performing yawing movements comprises moving the arm to a position in which the arm extends away from the main tower part along a direction which defines an angle of approximately 70 with a direction defined by the power cables mounted on the main tower part.

12. The method for mounting power cables on a wind turbine according to claim 1, he method comprising the steps of: arranging a cassette on the ground at a position near the main tower part of the tower structure, attaching power cables to the cassette, attaching the power cables to cassettes of at least one neighbouring wind turbine, and hoisting the cassette along the main tower part, the hoisting being coordinated with hoisting the cassettes of the neighbouring wind turbines.

13. The method according to claim 12, wherein the step of hoisting the cassette is performed using a jacking mechanism.

14. The method according to claim 12, wherein the step of hoisting the cassette is performed using at least one service crane arranged in the tower structure or in one of the energy generating units of the wind turbine.

15. The method according to claim 12, further comprising the steps of mounting the power cables on the main tower part by means of a cable supporting structure, and subsequently lowering the cassette to the ground.

16. The method according to claim 12, further comprising the step of mounting the cassette on the main tower part, the cassette thereby forming a cable supporting structure.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0072] The invention will now be described in further detail with reference to the accompanying drawings in which

[0073] FIG. 1 is a front view of two wind turbines according to a first embodiment of the invention,

[0074] FIG. 2 is a perspective view of one of the wind turbines of FIG. 1,

[0075] FIG. 3 is a top view of one of the wind turbines of FIG. 1, in a first position,

[0076] FIG. 4 is a top view of one of the wind turbines of FIG. 1, in a second position,

[0077] FIG. 5 illustrates mounting of a rotor on a wind turbine according to an embodiment of the invention,

[0078] FIG. 6 illustrates service being performed on a cable supporting structure mounted on a wind turbine according to an embodiment of the invention,

[0079] FIG. 7 is a perspective view of a wind turbine according to a second embodiment of the invention,

[0080] FIG. 8 illustrates mounting of power cables on wind turbines in accordance with a method according to an embodiment of the invention,

[0081] FIG. 9 is a front view of two wind turbines according to a third embodiment of the invention, and

[0082] FIGS. 10-12 show various cable supporting structures for a wind turbine according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

[0083] FIG. 1 is a front view of two wind turbines 1 according to a first embodiment of the invention. Each wind turbine 1 comprises a tower structure with a main tower part 2 extending along a substantially vertical direction, and two arms 3, each arm extending away from the main tower part 2 along a substantially horizontal direction. It should be noted that the arms 3 could, alternatively, extend away from the main tower part 2 along a direction which forms an angle with the vertical direction defined by the main tower part 2, which differs from 90, as long as the direction has a horizontal component. For instance, the arms 3 may extend along a direction which is inclined, following an upwards direction from the main tower part 2 towards a free end of the arm 3.

[0084] Each arm 3 carries an energy generating unit 4 comprising a rotor 5 with a set of wind turbine blades 6.

[0085] The main tower part 2 of each wind turbine 1 is further provided with a cable supporting structure 7, and a number of power cables 8, two of which are shown, of a power grid are attached to the main tower parts 2 of the wind turbines 1, via the cable supporting structures 7. Accordingly, the main tower parts 2 serve the function of wind turbine towers as well as the function of power masts. This allows the total costs of establishing the wind turbines 1 as well as the power grid to be reduced.

[0086] The arms 3 are arranged to perform yawing movements, i.e. rotating movements about a substantially vertical axis which coincides with the vertical direction defined by the corresponding main tower part 2. This allows the arms 3 to be arranged in any suitable orientation with respect to the direction along which the power cables 8 extend. Accordingly, the energy generating units 4 can be arranged in a position which is well clear of the power cables 8, and this allows service to be performed on the energy generating units 4 in a safe manner. This will be described in further detail below.

[0087] In the embodiment of FIG. 1, the arms 3 of each wind turbine 1 form part of a single transversal structure, and thereby the arms 3 are moved together when yawing movements are performed.

[0088] FIG. 2 is a perspective view of one of the wind turbines 1 of FIG. 1. The arms 3 have been yawed to a position where they extend along a direction which is not parallel to the direction along which the power cables 8 extend.

[0089] FIG. 3 is a top view of one of the wind turbines 1 of FIG. 1. In FIG. 3, the arms 3 have been yawed to a position where they extend along a direction which is substantially perpendicular to the direction along which the power cables 8 extend. In this position, the energy generating units 4 are positioned as far away from the power cables 8 as possible. This allows service to be performed on the energy generating units 4 in a safe manner, i.e. without risking collisions with the power cables 8. In particular, components may be hoisted directly to and from the energy generating unit 4 without risking collisions between the components and the power cables 8. Furthermore, the service can be performed from a hardstand 9 formed at a distance from the main tower part of the wind turbine.

[0090] FIG. 4 is also a top view of one of the wind turbines 1 of FIG. 1. In FIG. 4, the arms 3 have been yawed to a position where they extend along a direction which forms an angle of approximately 70 with the direction along which the power cables 8 extend. In this position, the energy generating units 4 are also arranged at a distance from the power cables 8. Furthermore, the rotor 5 of one of the energy generating units 4 points in a direction away from the power cables 8. This allows the entire rotor 5 or one or more wind turbine blades 6 to be hoisted to or from the energy generating unit 4 from the hardstand 9, without risking collisions with the power cables 8, and while personnel and possibly an external crane can be position at a safe distance from the power cables 8.

[0091] FIG. 5 illustrates mounting of a rotor 5 on a wind turbine 1 according to an embodiment of the invention. The wind turbine 1 comprises a tower structure with a main tower part 2 and two arms 3, each being adapted to carry an energy generating unit. A cable supporting structure 7 having a number of power cables 8 attached thereto is mounted on the main tower part 2. The wind turbine 1 could, e.g., be of the kind illustrated in FIGS. 1-4.

[0092] An external crane 10 is in the process of hoisting a rotor 5 with three wind turbine blades 6 to an operating position on the wind turbine 1. The arms 3 of the wind turbine 1 have been yawed to a position in which they extend along a direction which is not parallel to the direction along which the power cables 8 extend. Thereby the ends of the arms 3 are arranged at positions which are well clear of the power cables 8, and can therefore be accessed in a safe manner without risking collisions with the power cables 8. The arms 3 could, e.g., be yawed to the position illustrated in FIG. 4.

[0093] FIG. 6 illustrates service being performed on a cable supporting structure 7 mounted on a wind turbine 1 according to an embodiment of the invention. The wind turbine 1 comprises a tower structure with a main tower part 2 and two arms 3, each being adapted to carry an energy generating unit. A hatch 11 is formed in one of the arms 3 of the wind turbine 1, allowing a wire 12 of a service crane (not shown) arranged in the arm 3, in the main tower part 2 or in an energy generating unit to pass there through, as shown in FIG. 6. Thereby the service crane can be used for performing service on the cable supporting structure 7. Furthermore, in the case that power cables are attached to the cable supporting structure 7, the service crane could also be used for performing service on the power cables. Finally, the service crane could be used for hoisting the cable supporting structure 7 and/or power cables to or from the mounting position on the main tower part 2.

[0094] FIG. 7 is a perspective view of a wind turbine 1 according to a second embodiment of the invention. The wind turbine 1 according to the second embodiment of the invention is similar to the wind turbine 1 according to the first embodiment of the invention in the sense that it comprises a tower structure with a main tower part 2 and two arms 3, each arm carrying an energy generating unit 4 with a rotor 5 carrying a set of wind turbine blades 6, and in the sense that a cable supporting structure 7 having a number of power cables 8 attached thereto is mounted on the main tower part 2.

[0095] The wind turbine 1 of FIG. 7 is further provided with two guy wires 13, each being attached to the main tower part 2 and anchored to the ground by means of an anchor block 14. The guy wires 13 are capable of handling part of the loads on the wind turbine 1, which can be expected during normal operation. However, the guy wires 13 will only be able to handle loads, in particular bending loads, along the direction indicated by arrow 15, but not loads along the direction indicated by arrow 16, due to the positions of the guy wires 13. However, loads along the direction indicated by arrow 16 can be partly handled by the power cables 8. Accordingly, a set of guy wires 13 and a set of anchoring points 14 can be omitted.

[0096] FIG. 8 illustrates mounting of power cables 8 on wind turbines 1 in accordance with a method according to an embodiment of the invention. FIG. 8 shows three wind turbines 1, each comprising a tower structure with a main tower part 2 and two arms 3. Cable supporting structures 7 having power cables 8 attached thereto are being mounted on the main tower parts 2 of the wind turbines 1 in the following manner.

[0097] Initially, a cable supporting structure 7, in the form of a cassette, is positioned on the ground near each of the wind turbines 1. Power cables 8 are then attached to the cable supporting structures 7 in such a manner that neighbouring cable supporting structures 7 are interconnected by the power cables 8.

[0098] Then the cable supporting structure 7 of a first wind turbine 1a is hoisted slightly along the main tower part 2 of the wind turbine 1a. When the cable supporting structure 7 has reached a certain level, hoisting of the cable supporting structure 7 of a second wind turbine 1b is initiated. The second wind turbine 1b is a neighbouring wind turbine with respect to the first wind turbine 1a, in the sense that the cable supporting structures 7 of the first wind turbine 1a and the second wind turbine 1b are directly interconnected by the power cables 8. The hoisting of the cable supporting structure 7 of the first wind turbine 1a may be continued while the cable supporting structure 7 of the second wind turbine 1b is hoisted. Alternatively, hoisting of the cable supporting structure 7 of the first wind turbine 1a may be interrupted until the cable supporting structure 7 of the second wind turbine 1b has reached the same level as the cable supporting structure 7 of the first wind turbine 1a. In this case, the hoisting of the cable supporting structure 7 of the first wind turbine 1a may be resumed when the cable supporting structure 7 of the second wind turbine 1b reaches the level, while the hoisting of the cable supporting structure 7 of the second wind turbine 1b is interrupted.

[0099] In any event, when the cable supporting structure 7 of the second wind turbine 1b reaches the level, hoisting of the cable supporting structure 7 of a third wind turbine 1c is initiated, similarly to the situation described above. The third wind turbine 1c is a neighbouring wind turbine with respect to the second wind turbine 1b.

[0100] Thus, the cable supporting structures 7 of the neighbouring wind turbines 1 are sequentially hoisted along the respective main tower parts 2, in a coordinated manner, until a mounting position for each of the cable supporting structures 7 has been reached. Thereby it is avoided that the distance between cable supporting structures 7 of two neighbouring wind turbines 1 exceeds the length of the power cables 8 interconnecting the two cable supporting structures 7. This allows the power cables 8 to be fixed on the cable supporting structures 7 while these are positioned on the ground, thereby minimising the number of operations which are required after the cable supporting structures 7 have been hoisted to the mounting position. This increases the safety and reduces the costs during installation.

[0101] FIG. 8 illustrates a point in time of the process described above, in which the cable supporting structure 7 of the first wind turbine 1a has almost reached the mounting position, the cable supporting structure 7 of the second wind turbine 1b has been hoisted approximately half the distance from the ground to the mounting position, and hoisting of the cable supporting structure 7 of the third wind turbine 1c has just been initiated.

[0102] FIG. 9 is a front view of two wind turbines 1 according to a third embodiment of the invention. The wind turbines 1 are similar to the wind turbines illustrated in FIG. 1, and they will therefore not be described in detail here. However, each of the wind turbines 1 illustrated in FIG. 9 comprises four arms 3, each carrying an energy generating unit 4 with a rotor 5 carrying a set of wind turbine blades 6.

[0103] FIGS. 10-12 show cable supporting structures 7 for a wind turbine according to an embodiment of the invention.

[0104] FIG. 10 is a cross sectional view of a cable supporting structure 7 mounted on a main tower part 2. The cable supporting structure 7 is provided with cable holders 17, onto which power cables (not shown) can be mounted. The cable supporting structure 7 has an upper surface 18 with a curved shape. The curved shape of the upper surface 18 has the effect that wind flowing towards the cable supporting structure 7 is deflected in an upwards direction. In the case that the cable supporting structure 7 is mounted on the main tower part 2 at a position below the arms carrying the energy generating units, this will cause the wind to be directed towards the rotors of the energy generating units. Thereby the power production of the wind turbine is increased.

[0105] FIG. 11 is a top view of a cable supporting structure 7 mounted on a main tower part 2. The cable supporting structure 7 of FIG. 11 could, e.g., be the cable supporting structure 7 illustrated in FIG. 10. Line 19 indicates the position of the cable holders illustrated in FIG. 10. In the cable supporting structure 7 of FIG. 11, the area of the curved upper surface 18, seen by the wind, is larger when the wind direction is perpendicular to the lines 19, i.e. when the wind direction is parallel to the direction defined by the power cables, than when the wind direction is parallel to the lines 19, i.e. when the wind direction is perpendicular to the direction defined by the power cables. Therefore, the ability of the curved upper surface 18 to deflect the incoming wind in an upwards direction is better when the wind direction is parallel to the direction defined by the power cables. When the wind direction is substantially parallel to the direction defined by the power cables, a higher wind wake, caused by neighbouring wind turbines, must be expected. It is therefore more relevant to direct the wind towards the rotors in this case.

[0106] FIG. 12 is a top view of an alternative cable supporting structure 7 mounted on a main tower part 2. The cable supporting structure 7 of FIG. 12 could also be the cable supporting structure 7 illustrated in FIG. 10. However, the cable supporting structure 7 of FIG. 12 is rotationally symmetric, and thereby the ability of the curved upper surface 18 to deflect the incoming wind in an upwards direction is the same, regardless of the direction of the incoming wind.