The present invention relates to a method for erecting a wind power plant and especially to method as defined in the preamble of independent claim 1. The present invention further relates to an arrangement for erecting a wind power plant and more particularly to an arrangement as defined in the preamble of independent claim 14.

Background of the invention

The height of the wind power plants keeps rising as the size of the rotors become bigger. The height of the wind power plants are also affected by better wind conditions, less turbulent winds and more homogenous wind distribution at higher altitudes from the ground level. Prior art towers of a wind power plant are either tubular towers, lattice towers or combinations thereof. Such towers of a wind power plant are generally too tall and heavy structures to enable elevation in one unit in full length at the place of erection location. Tubular towers may be erected in a conventional manner either by assembling them at the place of location from top to bottom or from bottom to top. Lattice towers or so-called hybrid towers, which consist of both tubular and lattice structures, are instead conventionally assembled from bottom to top. When the towers of the wind power plant have height 100 meters or less they may be erected using mobile cranes which may be easily and quickly transported to the place of erection location. However, when the height of the wind power plant exceeds 100 larger cranes are needed for erecting the wind power plants. According to the prior art, erecting towers consisting at least partly of lattice structures from bottom to top requires extremely large cranes that are capable of lifting parts of a tower to be assembled all the way to the top of the tower, which may be located at a height of even more than 150 m.

A problem with the above-described arrangement is that wind power plants are presently often situated in difficult terrain conditions, such as woods, whereto it is often very difficult and many times even impossible to transport such enormous cranes or mobile hoists since the road conditions in these places of location quite seldom suffice to enable huge cranes to be transported to the place of location of the wind power plant. Consequently, prior to starting a process for erecting a tower of a wind power plant, extensive road construction work has to be carried out at a place of location so as to enable hoisting devices and cranes to be transported thereto. This significantly slows down the wind power installation work and causes high costs. Furthermore, use of such extremely large cranes requires significant installation work as these cranes has to be of then transported in parts to the erection location.

Brief description of the invention

The object of the present invention is to provide a method and arrangement so as to overcome the prior art disadvantages. The objects of the present invention are achieved with a method according to the characterizing portion of claim 1. The objects of the present invention are further achieved with an arrangement according to the characterizing portion of claim 14.

The preferred embodiments of the invention are disclosed in the dependent claims.

The present invention relates to a method and arrangement for erecting the tower of the wind power plant from bottom to top. The present invention is based on the idea of using a fixed hoisting apparatus for erecting the tower of the wind power plant. The present invention relates to wind power plants having height over 100 meters and being at least partly constructed from lattice structure. In the present invention the tower of the wind power plant is erected in two steps. First the bottom part of the tower is erected and then the upper part of the tower is erected using a fixed hoisting apparatus. The bottom part of the tower is also used for supporting the upper part of the tower during erection of the upper part.

According to the present invention the wind power plant comprises a tower having a substantially conical lattice structured bottom part and an upper part extending from the bottom part. The wind power plant further comprising a nacelle installed to the top end of the upper part or in the vicinity thereof. The wind power plant is erected by providing a foundation for the wind power plant, erecting the bottom part and supporting the bottom part to the foundation and erecting the upper part and installing the upper part to the bottom part. The erection of the wind power plant is carried out with a fixed hoisting unit located within the bottom part of the tower. The upper part is erected by lifting the upper part telescopically upwards from inside the bottom part with a hoisting unit such that the vertical forces generated during the erection of the upper part are transferred to ground via the hoisting unit. During lifting of the upper part of the tower the upper part is horizontally supported with the bottom part of the tower such that horizontal forces generated during the erection are at least partly transported to bottom part of the tower and further to the foundation of the wind power plant.

The present invention has the advantage that the no extremely large cranes are needed for erecting the wind power plant having height more than 100 meters. This further means that the erection of the wind power plant may be carried out using the fixed hoisting apparatus and smaller mobile cranes. Thus extensive road constructions for extremely large cranes may be avoided. The fixed hoisting unit transferring the vertical forces to ground during the hoisting and the horizontal support provided with the lattice structured bottom part of the tower enable constructing very high wind power plants, higher than possible with any commonly known cranes. Furthermore, the mentioned support and force transferring arrangement lower wind risks during hoisting.

Brief description of the figures

In the following the invention will be described in greater detail, in connection with preferred embodiments, with reference to the attached drawings, in which

Figures 1 to 7 show erection steps of a wind power plant. Detailed description of the invention

The present invention relates to a method and arrangement for erecting a wind power plant. The present invention specifically relates to erecting a wind power plant having a height more than 100 meters, preferably more than 120 meters and comprising a tower having a substantially conical lattice structured bottom part and an upper part extending from the bottom part. The present invention therefore relates to wind power pant having tower with a substantially conical lattice structured bottom part having height under 100 meters and an upper part extending upwards from the bottom part 8. The height of the upper part is preferably at least half of the height of the bottom part such that the total height of the tower is at least 100 meters or more. The wind power plant further comprising a nacelle installed to the top end of the upper part or in the vicinity thereof. The tower of the wind power plant may be constructed fully from lattice structure such that the also the upper part of the tower is lattice structured. However, the upper part of the tower may also be tubular. The bottom part of the tower is conical and the upper part usually has substantially constant diameter or cross sectional area. It should be noted that the upper part of the tower may also be slightly conical or partly conical. The lattice structure of the tower is preferably made from metal, such a steel, beams or bars having open profile. It is also possible to use beams or bars having closed profile in at least some parts of the lattice structure. The bottom part and/or the upper part of the tower may be constructed from one or more prefabricated sections which are installed together before the erection of the wind power plant or during the erection of the wind power plant.

The figure 1 shows a first step of the erection of the wind power plant according to the present invention. A foundation 2 is provided on the erection location to ground 1 for the tower of wind power plant. The foundation 2 may comprise a uniform concrete slab or it may comprise separate foundation units for each leg of the lattice structured bottom part of the tower, as shown in figure 1.

After the foundation is made, a hoisting unit is installed and secured in the center of the erection location. The hoisting unit comprises hoisting tower 20 and hoisting device 24. In embodiment of figure 1 the hoisting device 24 is arranged to the upper end of the hoisting tower 20 or in the vicinity thereof. Alternatively the hoisting device may be provided to the lower end of the hoisting tower or in the vicinity thereof. In one embodiment the hoisting unit and hoisting device 24 is jacking device. The hoisting device 24 may be for example cable jack or screw jack or telescopical hydraulic cylinder. However, it should be understood that any other kind of hoisting device may be used in the present invention and the present invention is not restricted to any special kind of hoisting device. As shown in figure 1 the hoisting tower 20 is arranged on the ground 1 such that the vertical forces generated during hoisting may be transferred via the hoisting tower 20 to ground 1. In an alternative embodiment the hoisting tower 20 may be arranged on the foundation 2 such that the vertical forces generated during hoisting may be transferred via the hoisting tower 20 to foundation 2 and further to ground 1. The hoisting tower 20 may further be secured to the foundation 2 with guying ropes 22, as shown in figure 1. In one embodiment the guying ropes 22 are connected between the upper end of the hoisting tower 20 and the foundation for providing horizontal support for the hoisting tower 20. Guying ropes may also be replaced with some other support means. However, in an alternative embodiment the hoisting tower 20 may be horizontally supported to the bottom part of the tower with guying ropes or some other support means.

As shown in figure 1 the upper part 10 of the tower is then installed to the hoisting unit or in connection with the hoisting unit to be hoisted upwards with the hoisting device 24. The lower end of the upper part 10 of the tower is provided with a connection member 14 for installing the upper part 10 of the tower to the upper end of the bottom part of the tower. The connection member 14 may be separate part arranged to the upper part 10 or it may be an integral part of the upper part 10. The connection member 14 may be a connection ring or connection sleeve having means for securing the upper part 10 to the bottom part 8. Usually the bottom part of the tower is much higher the hoisting tower 20 and thus it is not possible to lift the upper part 10 of the tower directly height in which the lower end of the upper part 10 may be secured to the upper end of the bottom part of the tower. Therefore special hoisting supports are used for reaching the required height. In figure 1 a first hoisting support 27 is installed under the upper part 10 of the tower. Preferably the first hoisting support is arranged to the hoisting unit before the upper part 10 of the tower and the upper part 10 is placed on the first hoisting support 27. The hoisting support 27 may be tubular element, as sin figures 1 to 6, or it may be a lattice structured part. Alternative the hoisting support 27 may be any kind of element which may be used as a spacer or a hoisting aid for the upper part 10. It should however be understood that in this first step use of hoisting supports may also be neglected and the upper part 10 of the tower may be arranged to the hoisting unit without any hoisting supports. Furthermore, it should be mentioned that only a section of the upper part 10 of the may be arranged to the hoisting unit in this first step and one or more other sections of the upper part 10 may be connected to the preinstalled upper part 10 during the erection of the tower.

According to the above mentioned the first step of the method according to the present invention comprises providing the foundation 2, installing the hoisting unit to the erection location and placing or installing at least part of the upper part 10 of the tower to the hoisting unit ready to be hoisted upwards. The hoisting support 27 and the upper part 10 or the section thereof may be installed or lifted to the hoisting unit or inside the hoisting tower 20 using mobile crane or some other small or medium sized crane. It should understood that in some embodiment the upper part 10 of the tower and the possible hoisting support may be installed to the erection location before the hoisting unit, provided that the upper part 10 may be supported or kept in place until the hoisting unit is assembled. The upper part 10 may be kept in place with the mobile crane. Accordingly the upper part 10 or at least one upper section is arranged in connection with the hoisting unit before erecting the bottom part 8. In the second step of the present invention the bottom part of the tower is erected over the hoisting unit and the upper part 10 of the tower such that the bottom part of the tower surrounds the hoisting unit and the upper part 10 of the tower. The bottom part of the tower may be erected by connecting and assembling separate lattice parts together to form the lattice structured bottom part. Alternatively the bottom part of the tower may be constructed by connecting together two or more preassembled bottom sections

4, 5, 6, 7. The lower most bottom section 4 may also be part of the foundation 2 such that it is installed before installing the hoisting unit and/or the upper part 10 of the tower. As shown in figure 2, the preassembled bottom sections 5, 6, 7 are installed in place over the upper part 10 and the hoisting unit by lifting them from above the upper part 10 such that the upper part 10 extends through the bottom sections 5, 6, 7. This way the bottom sections may be installed in fully assembled form and connected to each other to form the bottom part of the tower. In an alternative embodiment the preassembled may be bottom sections 5, 6, 7 may also be installed sideways to their places. In this embodiment some diagonal lattice structures are unassembled to the bottom sections

5, 6, 7 such that the bottom sections 5, 6, 7 may be installed sideways over the upper part 10 and the hoisting unit.

Figure 3 shows the bottom part 8 of the tower in fully erected form and surrounding the upper part 10 and the hoisting unit. In other words the hoisting unit and the upper part 10 are surrounded by the bottom part 8. In figures 3 to 7 the foundation 2 and the diagonal of the lattice structured bottom part 8 are omitted for simplicity. Therefore, after the second step of the erection is completed the bottom part 8 of the tower of the wind power plant is completed and the upper part 10 is located within the bottom part 8 ready to be hoisted with the hoisting unit. In this position the upper end 12 of the upper part 10 extends a small distance out of the upper end 9 of the bottom part 8. The upper end 9 of the bottom part 8 forms a first support point for supporting the upper part 10 in substantially horizontal direction. The upper end 9 of the bottom part may be provided with a support ring enabling vertical movement of the upper part 10 and horizontal support for the upper part 10. Alternative the first support point is provided in the vicinity of the upper end 9 of the bottom part 8. The support ring may for example comprise bearings, rollers or the like facilitating the vertical movement of the upper part 10 through the support ring. Accordingly, the first support point provides substantially horizontal support for the upper part 10 when the upper part is in place as shown in figure 3 and during hoisting of the upper part 10. It should be noted that the support ring may also be replaced with some other support means. Therefore the first support point at the upper end 9 of the upper part is arranged to provide substantially horizontal support for the upper part and to transfer the horizontal forces generated by the upper part 10 via the bottom part 8 to the foundation 2 and there to ground 1. This means that the bottom part 8 may used as a horizontal support during erection of the upper part 10 for supporting the upper part 10 or at least one upper section such that at least part of the horizontal forces generated during the erection of the upper part 10 are transferred to the foundation 2 via the bottom part 8.

A second support point is provided to the upper end 26 of the hoisting tower 20 or in vicinity thereof for supporting the upper part 10 in substantially horizontal direction. The upper end 26 of the bottom part may also be provided with a support ring enabling vertical movement of the upper part 10 and horizontal support for the upper part 10. The support ring may for example comprise bearings, rollers or the like facilitating the vertical movement of the upper part 10 through the support ring. Accordingly, the second support point provides substantially horizontal support for the upper part when the upper part 10 is in place as shown in figure 3 and during hoisting of the upper part 10. Furthermore, the second support point also provides substantially horizontal support for the upper part before the bottom part 8 is erected over the upper part 10 and during the erection of the bottom part 8. Thus the second support point at the upper end 26 of the hoisting tower 20 is arranged to provide substantially horizontal support for the upper part 10 and/or the hoisting supports 27 and to transfer the horizontal forces generated by the upper part 10 and/or the hoisting support 27 via guying ropes 22 to the foundation 2 and there to ground 1 or to the bottom part 8. This means that the hoisting tower 20 may also used as a horizontal support during erection of the upper part 10 for supporting the upper part 10 or at least one upper section such that at least part of the horizontal forces generated during the erection of the upper part 10 may be transferred to the foundation 2 via guying ropes 22 or via the guying ropes 22 and the bottom part 8.

In the step three of the erection of the wind power plant nacelle 30 is installed to the upper end 12 of the upper part 10, as shown in figure 3. The nacelle 30 comprises at least wind turbine and the blades 32 of the wind turbine. The nacelle 30 may be lifted to the upper end 12 of the upper part 10 with a small or medium sized mobile crane. Accordingly the nacelle 30 is installed to the upper end 12 of the upper part before hoisting the upper part 10 to its final height enabling the use of small or medium sized crane. Furthermore, as the nacelle is installed after the erection of the bottom part 8 of the tower there is appropriate horizontal support for the upper part 10. The horizontal support is important as the nacelle provides a heavy mass to the upper end of the upper part 10 and may also generate substantially horizontal wind load. After the nacelle 30 is installed to its place to the upper end 12 of the upper part 10 the fourth step of the erection of the wind power plant may be started. In the fourth step the upper part 10 is hoisted and erected using the hoisting unit. The upper part 10 is hoisted by providing a substantially vertical hoisting force to the lower end of the upper part 10 or in the vicinity thereof or to lower end of the hoisting support 27 or in the vicinity thereof. The erection of the upper part 10 is carried out by lifting the upper part 10 telescopically upwards from inside the bottom part 8 with a hoisting unit such that the vertical forces generated during the erection of the upper part 10 are transferred to ground 1 via the hoisting unit. Accordingly the hoisting tower 20 receives the vertical forces generated by the upper part 10 and its mass and transfers them to ground 1 or via the foundation 2 to ground 1. This means the bottom part 8 does not receive vertical forces provided by the hoisting of the upper part 10 or the upper part itself during the hoisting of the upper part 10. Thus the bottom part 8 is not used for providing vertical support in hoisting the upper part 10.

When the upper part 10 is lifted a predetermined distance upwards in step four with the hoisting unit a second or new hoisting support 28 may be added under previous hoisting supports 27. The second hoisting support 28 is connected to the previous hoisting support 27 and then the lifting of the upper part may be continued. After the upper part 10 is lifted again a predetermined distance upwards with the hoisting unit a third or new hoisting support 29 may be added under previous hoisting supports 27, 28. This may be repeated a number of times until lower end or the connection member 14 at the lower end of the upper part 10 is close to the upper end 9 of the bottom part 8, as shown in figure 4. As disclosed above, during the telescopical erection of the upper part 10 the vertical forces generated during the erection of the upper part 10 are transferred to ground 1 via the hoisting unit and the bottom part 8 is used as a horizontal support during erection of the upper part 10 for supporting the upper part 10 such that the horizontal forces generated during the erection of the upper part 10 are transferred to the foundation 2 via the bottom part 8. In an alternative embodiment the connection member 14 is not installed before the start of the hoisting of the upper part 10. In this embodiment one or more of the hoisting supports may form a part of the upper part 10 of the tower. In other words the upper part 10 is assembled during hoisting by using the lower sections of the upper part 10 as hoisting supports. In this embodiment the connection member 14 may be installed after the lowermost upper section is added to the upper part 10 during hoisting. Finally in the fifth step of the erection the upper part 10 is lifted to its final height in which the lower end or the connection member 14 may be installed and/or secured to the top end 9 of the bottom part 8 or in the vicinity thereof after the lifting of the upper part 10 is finished, as shown in figure 5. When the upper part 10 is secured to the bottom part 8, the wind power plant is in fully erected state.

The fifth step the hoisting unit is disassembled in the sixth step. The disassembling of the hoisting unit is started by lowering the hoisting supports 27, 28, 29 and removing them, as shown in figure 6. After that the hoisting device 24 and the hoisting tower 20 are disassembled and removed. Then the erection of the wind power plant is finished. If the nacelle 30 needs service and maintenance work the hoisting unit may be reassembled and the upper part 10 of the tower may be lowered in reverse order to the position shown in figure 3. This enables service and maintenance work without extremely large cranes.

According to the above described the present invention also provides an arrangement for erecting a wind power plant. The wind power plant comprises a tower having a substantially conical lattice structured bottom part 8 and an upper part 10 extending upwards from the bottom part 8, a foundation 2 to which the bottom part 8 is supported and a nacelle 30 installed to the top end 12 of the upper part 10 or in the vicinity thereof. The arrangement comprising a hoisting apparatus for hoisting the upper part 10 telescopically upwards from inside the bottom part of the tower. The assembled and installed bottom part 8 forms part of the arrangement together with the foundation 2. Figure 3 shows the arrangement fully assembled and installed for erecting the tower and specifically for lifting the upper part 10 of the tower. According to the above mentioned the arrangement of the present invention comprises a hoisting tower 20 or the like hoisting frame. In figure 3 the hoisting tower 20 is lattice structured, but in an alternative embodiment it may also be some other kind. The hoisting tower 20 is installed and supported on the ground 1 or on the foundation 2. The arrangement further comprises a hoisting device 24. In the embodiment of figure 3 the hoisting device 24 is arranged to the upper end 26 of the hoisting tower 20 or in the vicinity thereof. Alternatively the hoisting device may be provided to the lower end of the hoisting tower or in the vicinity thereof or some other location. In one embodiment the hoisting unit and hoisting device 24 is jacking device. The hoisting device 24 may be for example cable jack or screw jack or hydraulic cylinder. However, it should be understood that any other kind of hoisting device may be used in the present invention and the present invention is not restricted to any special kind of hoisting device. As shown in figure 3 the hoisting tower 20 is arranged on the ground 1 such that the vertical forces generated during hoisting may be transferred via the hoisting tower 20 to ground 1. In an alternative embodiment the hoisting tower 20 may be arranged on the foundation 2 such that the vertical forces generated during hoisting may be transferred via the hoisting tower 20 to foundation 2 and further to ground 1. The hoisting tower 20 may further be secured to the foundation 2 with horizontal supports, such as guying ropes 22, as shown in figure 3. In one embodiment the guying ropes 22 are connected between the upper end of the hoisting tower 20 and the foundation 2 for providing horizontal support for the hoisting tower 20. Guying ropes may also be replaced with some other support means. However, in an alternative embodiment the hoisting tower 20 may be horizontally supported to the bottom part of the tower with guying ropes or some other support means.

The lattice structured bottom part 8 of the tower is assembled over the hoisting tower 20 such that the bottom part 8 surrounds the hoisting towers enabling telescopical erection of the upper part 10 of the tower through the bottom part 8. The bottom part 8 is secured to the foundation 2. The horizontal supports 22 of the hoisting tower may also alternatively be secured to the bottom part 8. The arrangement may also comprise one or more hoisting supports 27, 28, 29 arrangable under the upper part 10 for supporting the upper part 10 during hoisting such that the upper part 10 may be lifted high enough without extremely large hoisting tower or hoisting apparatus. Thus the hoisting supports work as spacers.

According to the above mentioned the hoisting apparatus comprising the hoisting tower 20 and the joisting device 24 is arranged to hoist the upper part 10 telescopically upwards from inside the bottom part 8 such that the vertical forces generated during the hoisting are transferred to ground 1 via the hoisting apparatus. Thus the vertical support needed during the hoisting or erection of the upper part 10 is provided with the hoisting apparatus and especially with the hoisting tower 20. Thus the vertical forces generated during the erection of the upper part 10 is transferred to the ground 1 via the hoisting tower 20. However, the upper part 10 needs also horizontal support during the erection and hoisting. Therefore, the arrangement is provided with at least one supporting point for supporting the upper part 10 or at least one upper section such that the horizontal forces generated during the hoisting of the upper part 10 are transferred to the foundation 2. The arrangement is provided with a first supporting point for supporting the upper part 10 or at least one upper section such that the horizontal forces generated during the hoisting of the upper part 10 are transferred to the foundation 2 via the bottom part 8. In one embodiment the first supporting point is provided to the upper end 9 of the bottom part 8 or in the vicinity thereof. The upper end 9 of the bottom part 8 may be provided with a support ring enabling vertical movement of the upper part 10 and horizontal support for the upper part 10. Alternative the first support point is provided in the vicinity of the upper end 9 of the bottom part 8. The support ring may for example comprise bearings, rollers or the like facilitating the vertical movement of the upper part 10 through the support ring. Accordingly, the first support point provides substantially horizontal support for the upper part 10 when the upper part is in place as shown in figure 3 and during telescopical hoisting of the upper part 10. It should be noted that the support ring may also be replaced with some other support means. In one embodiment the arrangement may be provided with a second supporting point in addition to the first supporting point for supporting the upper part 10 or at least one upper section or one or more hoisting support 27, 28, 29 such that the horizontal forces generated during the hoisting of the upper part 10 are transferred to the foundation 2. In the embodiment of figure 3, the second supporting point is provided to the upper end 26 of the hoisting tower 20 or in the vicinity thereof. The second supporting point is provided with bearings, rollers or the like for enabling vertical movement of the upper part 10 or a hoisting support 27, 28, 29 and for providing a substantially horizontal support during the hoisting of the upper part 10. The upper end 26 of the hoisting tower 20 may also be provided with a support ring or in the same way with the first support point.

According to the above mentioned the arrangement of the present invention uses the bottom part of the tower as horizontal support for hoisting or erecting the upper part. The vertical support is however provided with the hoisting apparatus. This enables telescopical erection of the tower without complicated structures and extremely large cranes. It is apparent to a person skilled in the art that as technology advanced, the basic idea of the invention can be implemented in various ways. The invention and its embodiments are therefore not restricted to the above examples, but they may vary within the scope of the claims.