WO2011081599A1

WO2011081599A1 - A method for the construction of a wind-power unit and a device for carrying out the method

Info

Publication number: WO2011081599A1
Application number: PCT/SE2010/051486
Authority: WO
Inventors: Hans Bernhoff
Original assignee: Vertical Wind Ab
Priority date: 2009-12-29
Filing date: 2010-12-27
Publication date: 2011-07-07
Also published as: SE0951033A1; SE534402C2

Abstract

The invention concerns a method for the construction of a wind-power unit having a wind turbine (2) supported by a tower (1 ), the tower being composed from a plurality of vertically distributed sections (11 a-11 e). The method according to the invention comprises placing a first section (11a) on a construction site of the wind-power unit, lifting the first section (11a) a distance corresponding to at least the length of a second section (11b), placing the second section (11 b) on the construction site, attaching the first section {11a) to the second section for the formation of a composed tower part, and lifting the composed tower part a distance corresponding to the length of a next additional section (11 c). This is then carried out a number of times depending on how many sections that the tower is composed of, after which the last set out section (11 e) is anchored on the construction site. The invention also concerns a lifting device for carrying out the method and a use of the constructed wind-power unit.

Description

A METHOD FOR THE CONSTRUCTION OF A WIND-POWER UNIT AND A DEVICE FOR CARRYING OUT THE METHOD

Field of the Invention

In a first aspect, the present invention relates to a method for the construction of a wind-power unit having a wind turbine supported by a tower, the tower being composed of a plurality of vertically distributed sections, where each section essentially is made of wood, the wind-power unit comprising a unit shaft that connects the wind turbine with a generator arranged at a lower end of the tower.

in a second aspect, the invention relates to a lifting device for the use in the construction of a wind-power unit provided with a tower.

In a third aspect, the invention relates to a use of a wind-power unit constructed by means of the invented method.

Background of the Invention

Wind-power units are increasingly used for the generation of electrical energy. In order to keep pace with increased use of wind power, there is a trend toward larger and larger units for making the wind power a commercially competitive alternative to an even greater extent. Accordingly, wind-power units of up to 3 MW are of immediate interest. It can be assumed that even greater wind-power units may be realised in a reasonably near future, increase of the effect implies that the tower that normally supports the wind turbine becomes higher. For really large wind-power units, the tower height may become up to 150 m and in certain cases even greater heights can be foreseen.

For practical reasons, such towers are built section by section. Thanks to moderate section lengths, the sections can be industrially prefabricated, which entails an improved total economy for the construction of a wind-power unit. Accordingly, a wind-power unit with vertical shaft is disclosed in WO 2008/153489 wherein the supporting tower, among other things for transportation reasons, is composed of sections. A suitable section length is 5-20 m.

When the tower should be built up of such sections, the natural way is to build from bottom to top, i.e.. the lowermost section is first set out. then the next section on top of this, and so on. For high towers, high cranes are required in that connection. To mount a crane of hundred metres or more leads to high costs for its transportation and erection. Some tens of transport lorries are required only to transport the crane there and about a week of work to raise it. This entails great problems with costs.

In order to facilitate the construction of high wind-power units it is known to build the sections of the tower part from "top to bottom". i.e in reverse order to what seems natural. Such a method is described in US 2009087311, according to which thus a first section of the tower is placed on the construction site. This one is then raised whereafter a second section is put in place, and the composed section thereby created is men raised in order to allow a third section to be put in place, etc.

This method, however, does not fully solves the problem when

constructing a wind-power unit of the kind to which the present invention relates, where a unit shaft connects the wind turbine with a generator at the tower end of the tower.

Further, the present invention relates to a wind-power unit with the tower sections being of wood. Therefore the method known from US 2009087311 cannot be applied for constructing the tower without specific additional measures. This because wooden sections cannot be joined in such a simple manner as the steel sections that are used in US 2009087311

Description of the Invention

In these circumstances, the object of the present invention is to try reducing the costs of construction of a wind-power unit of the kind initially specified particularly as for the construction of the tower thereof, and its unit shaft.

In accordance with the first aspect of the invention, the object set forth is attained by a method of the kind indicated by way of introduction comprising the special measures A to H indicated below:

A. applying connecting elements at at least one end of each section, which connecting elements are made of another material than the one the section essentially is made of,

B. placing a first section on a construction site of the wind-power unit,

C. lifting the first section a distance corresponding to at least the length of a next section, D. placing the next section on the construction site,

E. attaching the first section to the next section for the formation of a composed tower part,

F. carrying out the measures B to D one or more times,

6. anchoring the lowermost, i.e., the last one set out of said sections on the construction site.

H. composing the unit shaft from a plurality of shaft sections, the composition of the unit shaft comprising the corresponding measures B to 6 that have been indicated for the composition of the tower.

Accordingly, the tower is built "from top to bottom", i.e., in reverse order to what seems to be natural. Thereby, the need is eliminated of a high crane and the disadvantages associated therewith. It is true that, in this method, a lifting device is required that manages considerably greater load than when a high crane is used to build the tower "from bottom to top", but this is well outweighed by the advantages mat follow from not needing to raise a high crane.

To construct a wind-power unit made of wood, has advantages, among other things decreased weight compared with steel. Advantages of low weight become particularly accentuated in the method according to the present invention since practically the entire tower is to be lifted.

Thanks to that each section is provided with connecting elements of another material than wood at least one end thereof, the attachment of the sections to each other, attachment of the wind turbine to the uppermost section and attachment of the lowermost section on the construction site, e.g., to a foundation, are facilitated. The connecting elements are suitably made of steel or fibre reinforced plastic. Preferably, they are formed as flanges having bolt holes.

The wind-power unit comprises a unit shaft that connects the wind turbine with a generator arranged at the tower end of the tower, the unit shaft being composed from a plurality of shaft sections by means of the corresponding measures by which the tower is composed.

In certain kinds of wind-power units, e.g., such having a vertical turbine shaft, placement of the generator at the lower end of the tower entails

considerable advantages, in doing so, it facilitates to form also the thus requisite unit shaft of sections, and by applying the same method principle for the building up of the unit shaft, the same lifting equipment as is used for the tower can be used also for the unit shaft. Each shaft section can be lifted simultaneously together with the respective corresponding tower section, particularly if the shaft sections and the tower sections are equally long. These may, per se, be of different lengths.

According to a preferred embodiment of the invented method, between the measures E and F, the following measures are taken.

E1. lifting the composed tower part a distance corresponding to at least the length of a next additional section,

E2. placing said next additional section on the construction site,

E3. attaching said next additional section to the composed tower part so that the composed tower part includes also said next additional section, E4. carrying out the measures E1 to E3 one or more times.

This means that the tower consists of three or more sections, and the more sections concerned, the higher the tower and the greater the advantages of the invented method.

According to an additional preferred embodiment, the number of times that is indicated in E4 is 3-10.

This means that the tower is built up of totally 5-12 sections, which is the number that is suitable for the great majority of larger sizes and applications.

According to an additional preferred embodiment, each section has a length in the interval of 5-30 m.

This constitutes a suitable weighing between, on one hand, limiting the number of sections to minimize the mounting work and, on the other hand, staying within a practically manageable length of the sections. If the sections are manufactured on another site, which often is efficient, for transportation technical reasons, it is suitable to limit the section length to max. 20 m. Normally, it is most efficient that the sections are equally long. However, it is within the scope of the invention to carry out the method with sections of different lengths. In case of upwardly tapering towers, it may be considered to make the sections with increasing lengths as seen from bottom to top. Thereby, the sections can be made with a uniform weight. According to an additional preferred embodiment, the method comprises applying a lifting means to the upper end of the first section of the tower, which lifting means is arranged for lifting up the wind turbine to the upper end of the tower.

In this way, the wind turbine can be lifted up to the top of the tower without a high crane being needed for it. There are other alternatives to getting the wind turbine in place without a high crane, but they become impractical and

complicated. By means of the lifting means, e.g., a crane or a winch drum, at the upper end of the tower, either the entire wind turbine can be lifted up or it can be lifted up in parts to be composed up there. The lifting means is suitably applied before the upper section is lifted.

According to an additional preferred embodiment, the method comprises applying guiding means along the outside of the tower.

By means of such guiding means, the wind turbine can be held and guided when it is lifted up by means of a crane arranged at the upper end of the tower. This makes the lifting up of the wind turbine safer and less sensitive to winds.

According to an additional preferred embodiment, the wind turbine has a vertical turbine shaft.

It is judged that for this kind of wind-power unit, it is more realistic that high or very high towers will be common than for turbines with horizontal shaft. Since the advantages of the invented method are more significant the higher the tower is. the application of the invention to this type of wind-power units is of particular interest.

According to additional preferred embodiments of the invented method, the same is carried out by means of a lifting device in accordance with the present invention, particularly according to any one of the preferred embodiments of the same.

In doing so, the invented method profits from the advantages that are provided by such a lifting device and that are accounted for below.

The tower sections can be delivered to the installation site as completed entire sections, which may be circular or polygonal in cross-section.

Alternatively, each tower section may be delivered in parts laterally. Each part is elongate and corresponds to the full length of the section and is in cross- section a circular arc or one or some sides of a polygon. The parts are joined, for instance by agglutination, along the longitudinal edges of the parts. In case of, e.g., a dodecahedral section, it may be delivered in three parts with four polygon sides in each part. Each part may naturally consist of only one side of the polygon.

In the second aspect of the invention, the object set forth is attained by the fact that a lifting device of the kind indicated by way of introduction has the special features that the lifting device is formed to be able to lift a tower part composed of a plurality of vertically distributed sections with the tower part essentially vertically orientated during the lift, and that the device comprises at least three columns, a lifting device vertically displaceable along the columns and driving means for vertical displacement of the lifting device.

A lifting device formed in such a way gives the possibility of carrying out the invented method in a relatively easy way and entails therefore the advantages that follow thereof. By means of three or more columns raised around the installation site of the wind-power unit, the stability required for the kind of unstable lift it means to push an elongate load upward is ensured.

The loading platform facilitates attachment of a tower section to the tower part situated above the same and eliminates the need of a separate sky lift or the like.

Thanks to that the lifting device is dimensioned for a lifting distance in the interval of 5-30 m, it is particular expedient for carrying out the invented method as the sections that are handled normally have lengths within this interval. The method neither requires higher lifts than it barely being possible to put a section in place under the tower part that has been lifted up.

Since the lifting device is dimensioned for a lifting force corresponding to at least 501, the lifting force is adapted to the total weight of the tower part that maximally has to be lifted, i.e., the weight of the entire tower minus the weight of the lowermost section. For small wind-power units, a lifting device of this type does normally not come into question. In practice, neither there should be requirements of a lifting force that exceeds what corresponds to 1 0001.

According to a preferred embodiment of the invented lifting device, it comprises guide means for vertical guiding of the tower part during lifting.

Thereby, the risk of the tower part tipping sideward during the construction is decreased. In the third aspect of the invention, a wind-power unit constructed by means of the invented method is used for delivering energy to an electric mains, particularly constructed in accordance with any one of the preferred embodiments of the same.

The above-mentioned preferred embodiments are defined in the dependent claims, it should be appreciated mat additional preferred embodiments naturally may consist of ail feasible combinations of the above-mentioned preferred embodiments and of all feasible combinations of the same with features that are seen in the subsequent detailed description of embodiment examples.

The invention is explained in more detail by the subsequent detailed description of embodiment examples, reference being made to the accompanying drawings.

Brief Description of the Drawings

Fig. 1 is a schematic side view of a wind-power unit of a kind in which the invention is applicable.

Figs. 2-9 illustrate symbolically the principle step by step of the method according to the invention.

Fig. 10 is a schematic perspective view of a lifting device according to the invention.

Fig. 11 is an explanatory sketch of a detail of the device in Fig. 10.

Fig. 12 is a view from above of a component of the detail in Fig.11.

Fig. 13 is an explanatory sketch of an alternative embodiment of the detail in Fig. 11.

Fig. 14 illustrates in a side view an aspect of an embodiment example of the method according to the invention.

Fig. 15 is a longitudinal section through a part of a wind-power unit in which the method according to an embodiment example of the invention is applicable.

Figs. 16-23 illustrate symbolically the principle step by step in an additional embodiment example of the method according to the invention.

Fig. 24 is a side view of a part of the tower of the wind-power unit adapted to an additional embodiment example of the invented method. Figs. 25-26 illustrate a step of the method according to an additional embodiment example of the invented method.

Fig. 27 is a perspective view of a detail of an alternative embodiment of a detail in Fig. 13.

Description of Embodiment Examples

Fig. 1 illustrates in a schematic side view a wind-power unit of a kind for which the invention is intended. The wind turbine 2 is of the so-called H-rotor type having a vertical turbine shaft 3 connected with vertical turbine blades 6 via stays 5. The turbine shaft 3 is rotationaliy fixedly connected with the unit shaft 4 that drives the generator 8 arranged on a foundation 7 arranged on the ground. Via an electric cable 9, the generator 8 delivers current to a mains.

The turbine is supported by a tower 1 in which the unit shaft 4 and turbine shaft 3 are axially and radially journaled. The tower 1 is composed of a plurality of tower sections 11 a-11 e, five ones in the example shown. The number of tower sections may be more or fewer depending on the size of the unit. At the upper end of the upper tower section 11a, a carrying structure 19 is arranged for the supporting of the wind turbine 2. The carrying structure 19 is attached to the tower section 11a. The tower in the example shown is tapering slightly upward and has accordingly a shape of a pyramid or a cone. However, it should be appreciated that the invention is suitable also when the tower has a constant width. The sections are essentially made of wood and are constructed of joined laminated beams. The unit shaft 4 is essentially made of wood and is hollow.

The tower is built up with one section at a time according to the principle illustrated in Figs. 2-9. These figures show in order how this is made. First, the section 11a that constitutes the uppermost section of the tower is set out on the installation site, which is illustrated in Fig. 2. The installation site may consist of a foundation of the type shown in Fig. 1.

In the next step, the section 11a set out first is lifted as shown in Fig. 3. It is lifted up so much that the lower end of the section 11 a is on a height above the installation site that is at least as great as the next section 11b. After that, the next section 11b is set out straight under the first section 11a as illustrated in Fig. 4.

When it is in place, the first section 11a is lowered so that the same will rest on top of the second section, after which the two sections are connected with each other. This step is illustrated in Fig. 5. The two first sections 11a, 11b now constitute a continuous unit, which in the next step, illustrated in Fig. 6, is lifted up high enough for allowing setting a third section 11c in place straight under the second section. In Fig. 7, the third section is in place, and in Fig. 8 the two first sections 1 a, 11 b have been towered down so that the second section 11b rests on the third one 11c. When the third the section 11c has been connected with the second section 11b, all three sections 11a, 11b, 11c are lifted, which now constitute a unit as shown in Fig. 9.

The corresponding procedure is then repeated some more times to construct the tower in Fig. 1 in its entirety, where also the two lowermost sections 11d, 11e are included. If the tower consists of more sections, the described steps are naturally repeated again the requisite a number of times.

By the invented method, no crane is needed that reaches up to the entire height of the tower. A lifting device for carrying out the method does not have to be much higher than the length of an individual section of the tower. However, it has to be dimensioned for considerable loads since it should be able to lift the weight of almost the entire tower. In addition, it has to be very robust and stable in view of the body that is to be lifted essentially being pushed up and being very elongate A tower of wood having a height of 60 m. a diameter of 3 m, and a wall thickness of 20 cm weighs approx. 1001. For a tower of 150 m, a diameter of 5 m and a wall thickness of 30 cm, the weight becomes approx. 4001.

A lifting device in accordance with the invention that is suited for managing this kind of heavy and complicated lift is illustrated schematically in Fig. 10. It consists of a number of columns 12, four ones in the example shown, which are symmetrically placed around the installation site of the tower. Each column has a length that is somewhat greater than the longest one of the sections 11a, 11e of the tower, i.e., in the order of 20-25 m. Each column is provided with driving means to jointly lift up a lifting device 13 that lifts the section 11b that most recently has been put in place together with the sections 11a that are attached on top of the section 11b that is lifted. The lifting device 13 is represented symbolically in Fig. 10 by a lift platform 13. At the top, the lifting device is provided with a work platform 14 as an aid in the assembling of two sections. The figure illustrates the beginning of a lift, and the lift is terminated when the lift platform has reached up side by side with the work platform 14 at the upper ends of the columns 12. In Fig. 10, there is also seen how the sections 11a, 11b can be fastened together. Each section has at each end a mounting flange 21. 26 having holes, the flanges 21, 26 being joined by a bolt joint. The sections in Fig.10 are illustrated with circular cross-section. For reasons of manufacturing technique, it is, however, often suitable that the tower has a polygonal cross-section, e.g., a dodecagonal shape. A mounting flange 21 , 26 is then arranged on each side of the polygon. The mounting flange is suitably made of steel or fibre reinforced plastic.

Fig. 11 illustrates an example of how the lifting device can be connected to the tower section 11b when it is to be lifted. The lift platform 13 is formed as a nrtg- shaped plate. Each column 12 is provided with one or more driving units 16 for the lifting motion. In the figure, this is symbolized as a hydraulic cylinder 16, but may of course be of any other expedient kind, e.g., mechanical with co-operating screw and ball nut. rack and pinion, or a rope that runs over a drum at the upper end of the lifting device.

On the lift platform 13, a number of carrying plates 15 are mounted. Each carrying plate is horizontally dispiaceabie by means of a driving device 17, which also this is symbolized by a hydraulic cylinder 17 in the figure.

Each tower section 11b has, in addition to the lower mounting flange 21 having bolt holes 22, a lifting flange 23 on each side of the polygon. The lifting flange is arranged some decimetres above the lower mounting flange 21 and has the purpose of enabling the lift.

When a section 11b is set out on the installation site, resting on the same by the lower flanges 21 thereof and is ready to be lifted, the lift platform is in its lower end position on a level with the space between the lower mounting flange 21 and the lifting flange 23. Each carrying plate 15 is then in the retracted position, from which it is pushed inward toward the tower section 11b by means of the driving unit 17, the carrying plate 15 being attached to the tower section 11b in a suitable way. After that, the lifting driving units 16 are activated so that the carrying platform is pushed upward and pushes the carrying plates 15 into abutment against the underside of the carrying flanges of the tower section 11 b, and lift the tower section 11b upon continued lifting motion via the same. In view of the great weight concerned, the lifting motion is naturally carried out utmost slowly.

When the lift is terminated, the lower mounting flange 21 of the section 11b is on a height above the installation site that allows that the next section 1 c can be put in place. After that, the flanges are brought to abutment against each other, either by lowering the lift platform 13 a short bit or by lifting, using a separate lifting device, the section 11c most recently put in place. When the bolt joint has been tightened, the lifting plates 15 are retracted from the position illustrated in the figure, the same clearing from the flanges of the sections. The lift platform 13 is then displaced down into its lower end position for a repetition of the procedure for the next section 11c.

In order to decrease the risk of tipping of the tower during the lifting, it may be suitable to apply lateral supports that counteract this. An example of such a one is shown in Fig. 11. where a bar 18 attached to each carrying plate 15 extends upward a number of metres and is provided with a support plate 20 at the upper end thereof. The bar 18 with the support plate 20 thereof is displaced together with the carrying plate 15 so that the support plate 20 is pushed against a side of the tower section 11b when the carrying plate 15 is pushed in between the mounting flange 21 and the carrying flange 23. Lateral supports may naturally be applied in many other ways and be manoeuvred separately.

Fig. 12 shows an example of the shape of a carrying plate 15 in case the tower Is dodecagonai and the number of supporting columns is four.

An alternative to the connection mechanism in Fig. 11 is illustrated in Fig. 13. Here, the lift platform 24 is attached to a connector ring 25 via bolt flanges 28. 29. The section 11a being lifted is placed with the lower mounting flange 21 thereof resting on the connector ring 25. and is accordingly lifted when the carrying platform 24 and the connector ring 25 fixedly connected with the same is lifted. The connector ring 25 is put on the installation site before the section in question is put in place there so that the section is placed on the connector ring 25. after which the connector ring 25 is bolted to the lift platform 24. The figure illustrates the position when the first section 11a is lifted to its upper end position. The next section 11b can then be put in place under the first one, after which the upper side of the upper mounting flange 26 thereof is brought into abutment against the underside of the connector ring 25, which suitably takes place by lifting the section 11b by means of a separate lifting device. After that, the sections 11a, 11b are bolted to each other with the connector ring 25 between the same. Therefore, also the connector ring is provided with through holes 27. The connector ring 25 is then detached from the carrying platform 24 by loosening the bolt flanges 28, 29 from each other. After that, the carrying platform 24 is lowered down to its lower end position to be attached to the next connector ring and for carrying out of the next lift.

The connector ring 25 may remain at the tower also when it has been erected.

Alternatively, the connector ring may be formed so that the same can be removed after the two sections have been Joined. Fig. 27 shows an example of such an embodiment. Here, the connector ring is divided in the circumferential direction into several segments. The figure schematically shows a part of such a segment 44. The segment has an outer peripheral part 45 that is situated radially outside the mounting flanges 21 , 26 of the sections that are to be joined, which mounting flanges are indicated by dashed lines in the figure. At the outer edge thereof, the outer part 45 has a bolt flange (not shown in the figure) for the connection to the lift platform 24 (see Fig. 13). From the outer part 45, a plurality of radially inwardly directed tongues 46 extend at intervals. Each tongue 46 has a portion 47 of uniform thickness in the axial direction of the tower and closest to the outer part 45, and transforms radially inward into a wedge-shaped portion 48.

In the joining, the portion 47 of uniform thickness is situated between the tower sections and the mounting flanges 21, 26 thereof, while the wedge-shaped portion is situated radially inside. Each bolt hole 22 of the mounting flanges 21 , 26 are situated halfway between two tongues 46. When the bolts are tightened through the bolt holes 22 and the corresponding holes of the subjacent mounting flange 26, the tower sections are joined. At each bolt, there is then an air gap between the upper mounting flange 21 and the lower one 26. After that, the entire segment 44 is slowly displaced radially outward in the direction of the arrow, so that the wedge-shaped portion 48 of the respective tongue is inserted between the mounting flanges 21, 26. In doing so, the distance between the mounting flanges 21, 26 will gradually decrease due to the weight of the upper section. When the tongues 46 of the segment have been entirely retracted from the space between the mounting flanges 21 , 26, the segment can be removed. The mounting flanges 21 , 26 are now in contact with each other and the bolts through the bolt holes 22 thereof can finally be tightened.

As a complement or alternative to the supporting device described above and having support plates 20, it is illustrated in Fig. 14 how the tower during the erection can be stabilized by means of support ropes. To the upper section 11a of the tower, three or more support ropes 30 are attached, each of which is connected with a wind-up drum 31 on the ground. As the tower is lifted, the ropes 30 are unrolled so that the tower all the time is steadied from tipping.

Also the unit shaft 4 (see Fig.1) that connects the turbine shaft 3 with the generator 8 is suitably made from sections in the similar way as the tower.

According to an embodiment alternative, illustrated in Fig. 15, the shaft sections 4a are equally long as the respective tower section 11a. In this example, a shaft section 4a is installed in a tower section 11a, among other things by means of an inwardly directed support flange 32 of the tower, on which an outwardly directed shaft support flange 33 of the shaft section 4a rests so that the shaft section 4a is supported by the tower section 11a. When the tower sections are lifted up as has been illustrated in Figs. 2-14, in this embodiment, this is carried out together with the respective shaft section as a unit. Also the shaft sections may be joined by flange joints. When the tower has been erected, the shaft 4 is somewhat lifted in relation to the tower 1 so that the flanges 32, 33 clear from abutment against each other.

Figs. 16-23 illustrate an alternative example of the method, wherein the shaft sections 4a, 4b. etc., and the tower sections 11a, 11b. etc., are lifted separately, but according to the same basic principle that is illustrated for only the tower in Figs. 2-9. In Fig. 16, a first shaft section is set out on the installation site and has. in Fig. 17, been lifted up, after which, in Fig. 18, a first tower section is set out and is, in Fig. 19, lifted up. After that, the next shaft section 4b is set out in Fig. 20, which together with the first shaft section 4a is lifted up in Fig. 21. In Fig. 22, the next tower section 11b is then set out, which in Fig. 23 is lifted up together with the first tower section 11a, after which the whole procedure is repeated until the entire tower is constructed.

An additional example is illustrated in Fig. 24. which shows the lower section 11e of a finished constructed tower. An opening 34 is recessed in this section 11e, which opening extends almost along the entire section. The opening 34 has a width that allows insertion of a shaft section 4a through the same. The shaft sections 4a, etc., are men lifted up inside the tower 1 by means of a lifting device at the upper end thereof. When the wind-power unit is constructed, the opening 34 can be sealed to secure the supporting capacity. The mounting of the wind turbine 2 of the wind-power unit (see Fig. 1) is naturally also a structurally intricate procedure when very high towers are concerned. One possibility is that the wind turbine 2 is mounted on the upper tower section when it is lifted in the way previously described. From considerations of space and for reasons of stability, it may, however, be suitable not to mount the wind turbine 2 until after the tower having been erected. Wind action may otherwise become problematic.

In Fig. 25, there is illustrated schematically an embodiment example of the method, wherein the wind turbine is lifted up for mounting on the raised tower, also at this stage of the construction, no building crane of a height of the same size as the tower being needed. The wind turbine is hoisted by means of a crane 42 that is mounted on the top of the tower. The crane 42 may be premounted on the upper end of the uppermost section when it is lifted up. By means of ropes 43 attached to the stays 5 of the wind turbine, the wind turbine is hoisted from the ground to the top of the tower. To stabilize the hoisting, a guide 41 is arranged on the tower 1 and along which the turbine shaft 3 is guided. Instead of a crane, a winch drum may alternatively be mounted at the top of the tower, wherein the hoisting may be effected from a winch at the ground level by means of ropes that run over the drum. In the guiding of the wind turbine 2 or a part thereof along the guide 41, it may be suitable to mount the wind turbine on a transportation unit, e.g., a wheeled trolley, which runs along the guide 41.

Fig. 26 illustrates the final phase of the hoisting of the wind turbine 2 When the turbine shaft 3 has reached the top of the tower, it is stopped from further movement upward. When the crane 42 continues the lifting motion, this entails that the wind turbine is tipped upward around a horizontal axis that extends through the point where the tower end of the turbine shaft abuts against the upper end of the guide 41. When the wind turbine has been turned up into the vertical position, it is mounted to the tower 1.

The Figs. 25 and 26 show how the entire wind turbine 2 is lifted up in this way. Due to the size of the wind turbine 2. it is, however, in most cases

advantageous to hoist it in parts, each blade 6 with the appurtenant stay 5 being hoisted separately.

Claims

1. Method for the construction of a wind-power unit having a wind turbine (2) supported by a tower (1), the tower (1) being composed from a plurality of vertically distributed sections (11a-11e), where each section (11a~11e) essentially is made of wood, the wind-power unit comprising a unit shaft (4) that connects the wind turbine (2) with a generator (8) arranged at the lower end of the tower (1), characterized by the following measures: A. applying connecting elements (21 , 26) at at least one end of each section (11a-11e), which connecting elements are made of another material than the one the section (11 a~11e) essentially is made of,

B. placing a first section (11 a) on a construction site of the wind-power unit,

C. lifting the first section (11 a) a distance corresponding to at least the length of a next section (11b),

D. placing the next section (11 b) on the construction site,

E. attaching the first section (11a) to the next section (11 b) for the formation of a composed tower part,

F. carrying out the measures B to D one or more times,

6. anchoring the lowermost, i.e., the last one set out of said sections (11b) on the construction site.

H. composing the unit shaft (4) from a plurality of shaft sections, the composition of the unit shaft (4) comprising the corresponding measures B to G that have been indicated for the composition of the tower.

2. Method according to claim 1 , characterized in that, between measure £ and measure F, the following measures are taken:

E1. lifting the composed tower part a distance corresponding to at least the length of a next additional section (11c),

E2. placing said next additional section (11c) on the construction site

E3. attaching said next additional section (11c) to the composed tower part so that the composed tower part includes also said next additional section (11c), E4. carrying out the measures E1 to E3 one or more times,

3. Method according to claim 2, characterized in that the number of times indicated in E4 is 3-10.

4. Method according to any one of claims 1-3, characterized in that each section (11a-11e) has a length in the interval of 5-30 m.

5. Method according to any one of claims 1-4, characterized by applying a lifting means (42) at the upper end of the first section (11a) of the tower (1), which lifting means is arranged for lifting up the wind turbine (2) or a part thereof to the upper end of the tower (1).

6. Method according to claim 5, characterized by applying guiding means (41) along the outside of the tower (1).

7. Method according to claim 6, characterized in that the wind turbine (2) or a part thereof during lifting is attached to a transportation unit that is lifted by the lifting means (42) and guided by the guiding means (41).

8. Method according to any one of claims 1-7, characterized in that the wind turbine (2) has a vertical turbine shaft (3).

9. Method according to any one of claims 1-8, characterized by carrying out the method by means of a lifting device (10) according to any one of claims 10-11.

10. Lifting device (10) for the use in the construction of a wind -power unit provided with a tower, characterized in that the lifting device is formed to be able to lift a tower part composed of a plurality of vertically distributed sections with the tower part essentially vertically orientated during the lifting, and which device comprises at least three columns (12), a lifting device (13) vertically displaceable along the columns (12) and driving means (16) for vertical displacement of the lifting device (13), and a work platform (14) at the upper ends of the columns (12), and that the lifting device (10) is dimensioned for a lifting distance in the interval of 5-30 m, and for a lifting force corresponding to at least 501.

11. Lifting device according to claim 12, characterized in that the lifting device (10) comprises guide means (20) for vertical guiding of the tower part during lifting.

12. Use of a wind-power unit constructed by means of the method according to any one of claims 1-9, characterized in that the wind-power unit is used to deliver energy to an electric mains.