The present invention concerns a wind turbine and a method to erect the tower of a wind turbine in accordance with the claims. Background of the Invention

The continuing transition toward renewable energy sources, caused by, among other things, the dwindling supply of oil and the global environmental crisis (climate change), has resulted in an accelerated pace of construction of wind turbines that has never been higher than it is today. The current costs incurred in erecting a wind turbine are considerable and constitute a limiting constraint on the rate of development of wind power. There is therefore a great need for a wind turbine that has a design that allows the wind turbine to be produced and erected in a more cost efficient manner than previously known designs of wind turbines.

That the costs of erecting wind turbines (current known types of designs) are high depend on a number of different reasons. First, wind turbines are especially expensive to construct because their components are manufactured at a production facility and then moved

(transported) over long distances to the place where the wind turbine is to be erected. A wind turbine tower usually consists of large sections, typically twenty meters long, which are moved by truck, boat or similar to the erection site of the wind turbine. Tower sections usually have a width that requires escort by service vehicles and police when they are transport on roads.

The bulky size of a wind turbine's prefabricated components also restricts the sites that are possible to exploit for erecting wind turbines without having to establish costly roads and the like. When erecting wind turbines in places such as mountain tops, hilly terrain or the like, it is difficult and costly to build the necessary roads and other infrastructure. The prefabrication of a wind turbine tower in sections at factory facilities is also limiting in other aspects. For example, a tower made up of prefabricated segments will limit the tower's maximum building height. This is caused by the fact that lower sections of a higher tower, are larger in diameter. The tower will be increasingly difficult to transport with respect to the tower's height.

l A further reason why tower sections are manufactured at one location and then moved to the erection site is that welding should preferably be carried out in weather-protected areas, so that the welding seams attain a high level of quality. Similar problems also apply to painting and other surface finishing of the tower. Another reason that existing wind turbines are expensive to construct is caused by the fact that during their erection it is costly to lift components such as the upper sections of the tower, the nacelle (housing), the propeller blades and other components to the upper part of the wind turbine. The tower's height is limited to a large extent by the cranes that lift the components to the top of the tower, which may exceed a height of 80 meters above ground. Mobile cranes with this height lifting capacity are expensive both to own and operate so there are only a small number of mobile cranes which have the ability to lift components to this height.

Because these cranes are few in number it usually takes considerable time to plan and transport a mobile crane with sufficient capacity to the location of the wind turbine erection site which results in considerable costs. There is therefore a need for a more cost effective method of lifting components to the top of the tower.

A further problem with towers of previously existing wind turbines being built in sections, is that each section is usually dependent on blank rings, flanges and the like which are held together with screws, bolts or other similar torque dependent fasteners often called bolt joining or bolt screwing. The problem here is that it is difficult to ensure that the tightening of the above mentioned fasteners is performed with adequate torque. Inadequate tightening can in the worst case cause a section to loosen which in turn may result in total tower failure with the possibly of disastrous consequences. This type of design is also expensive to manufacture and is not as structurally sound as for example towers with welded sections. From a stress and fatigue standpoint, welded tower sections are preferable to other types of designs. Yet another problem with so called bolt joining or bolt screwing of a wind turbine tower's sections is that this type of joining reduces considerably the towers life span compared with a tower with sections that are welded together. Bolt joining or bolt screwing is also much more costly compared with welding. It is obvious that there exits a need for better methods of wind tower erection. Prior Art

Structures designed to extract energy from the wind by means of blades or propellers are already known. For example, windmills and wind turbines that are arranged to turn in their lower parts are previously known. Patent GB2413367 describes for example a tower for a wind turbine that is arranged to rotate in its lower section. The design according to

GB2413367 does not include segments that consist of at least one first mantle part and at least one second mantle part in the same manner as the present invention. Further this design does not include a bearing such as a slewing bearing, slewing ring or similar as does the present invention. This design differs in substantial ways from the present invention. Patent US2009090069 describes the construction of a tower for a wind turbine. The tower is erected in several segments in the tower's axial direction. Each respective segment consists of panels which are connected with the aid of a fixture or similar not connected to the tower. The panels of each segment are mounted together in a fixture at a place to the side of the tower and the panels are not joined together in the tower's lower part during erection, as is done in the present invention. Furthermore, the different sections of the design's tower are bolted together which differs greatly from the present invention, which utilizes welding to join together its segments and sections. The design according to patent US2009090069 is much more costly to manufacture and erect than the present invention. It also has the disadvantage that it is difficult to ensure that the tightening of its bolts is performed with adequate torque. The design described in US2009090069 differs substantially in both its fabrication and method of erection compared with the present invention's design and erection method.

US20090087311 describes a method for constructing and operating a wind turbine. The method described uses an external lifting system to lift the tower sections and nacelle in the vertical direction. This design is dependent on several guide rails mounted externally along the entire length of the tower for the lifting mechanism to be able to lift the nacelle to the top of the tower, which differs substantially from the present invention. Furthermore the nacelle includes a tower penetrating hole which is penetrated by its tower according to the description in US20090087311, and this also differs substantially from the present invention. This design further includes entirely prefabricated tower sections that are joined together by bolts during their erection, unlike the present invention that utilizes welding to join its mantle plates together during its erection. Another significant difference in the design according to

US20090087311 compared with the present invention is that it does not include for example a slewing bearing in the lower part of its tower which allows the tower to turn. This design is significantly costlier to manufacture, transport and erect than the present invention.

Brief Description of the Invention Concept

The main purpose of the present invention is to achieve a new type of wind turbine which can in a more cost effective manner be manufactured and erected than previously known structures. A further purpose of the present invention is to provide a method for erecting (building) wind turbine towers that is more efficient than existing designs. A yet further purpose of the present invention is to provide a wind turbine which is pivotally arranged in its lower part in relation to the tower's vertical axis. Detailed Description of the Invention

The invention will be described in greater detail below with reference to the accompanying schematic drawings that in an exemplifying purpose show the current preferred embodiments of the invention.

Figurers 1 A and IB show a wind turbine in accordance with the present invention. Figurers 2 - 8 show the sequential erection of a wind turbine tower.

With reference to the figures is shown a wind turbine 1 in accordance with the present patent application. The wind turbine 1 includes at least one tower 2 and at least one base foundation 3. The tower is arranged to rotate around a rotational axis 4 in the tower's 2 axial direction. The tower has an upper end (top) 5 and a lower end 6. The tower 2 includes at least one internal space (not shown in the figures). The tower 2 is preferably erected on a base foundation 3 which is constructed in accordance with previously known or hereafter developed, design and construction techniques.

The tower 2 is preferably arranged to rotate via at least one bearing 7 or similar. In the exemplifying embodiment of the wind turbine 1 shown in Figure 1 A, the tower 2 is via a bearing 7 pivotally arranged relative the base foundation 3 in the tower's axial direction. In the alternative embodiment shown in Figure IB, the tower 2 includes an upper segment 8 and a bottom segment 9 which via at least one bearing 7 are pivotally arranged in relation to one another. The lower segment 9 of the tower 2 is preferably permanently arranged relative the base foundation and the upper segment 8 of the tower 2 is pivotally arranged in relation to the fixed lower segment 9 of the tower 2 or alternatively the base foundation 3 or both in the tower's axial direction.

The bearing 7 in the preferred embodiment consists of at least one slewing bearing, slewing ring or the like. The slewing bearing (slewing ring) is preferably permanently mounted in the base foundation or in the lower segment 9 of the tower. The tower is rotated relative the slewing bearing (slewing ring) using at least one slewing gear (not shown in the figures) or similar. The rotation of the tower or the tower's upper segment in alternative embodiments may be achieved with other technology suitable for this purpose.

The tower 2 is at its top 5, or the top's vicinity, equipped with at least one nacelle (housing) 10 or the like. The nacelle 10 has at least one rotor with an accompanying propeller (not shown in the figures) that is bearingly arranged. Preferably, the rotor is bearingly arranged around an essentially horizontal axis. In alternative embodiments, it is conceivable that the rotor is bearingly arranged around an axis that differs from an essentially horizontal direction.

The propeller propels via the rotor, or other power transferring body, at least one power generating unit which generates electrical energy. The power generating unit includes at least one generator. Preferably the rotor transfers torque directly to the generator. In alternative embodiments, the power generating unit may include at least one gearbox or the like. The electric energy generated by the generator is intended to be transferred to at least one consumer, at least one power grid or the like. The transfer of electrical energy is accomplished in accordance with known technology and this is why it is not described in more detail in this patent application.

Figures 2-8 show sequentially how the wind turbine's tower 2 is erected. In the preferred embodiment of the present invention the tower 2 is built in sections 11 on-site, the place where the tower is to be erected. The tower is erected by sections 11 of the tower 2 being assembled sequentially in the tower's 2 lower end 6 and then sequentially erected upwards in a vertical direction. Section 11 after section 11 are completed sequentially and united with the previously united sections 1 1 until the desired height of the tower is obtained. After the desired height of the tower 2 is achieved, the tower 2 or alternatively the tower's upper segment 8 or alternatively the intermediate segment or segments are connected (secured) to the bearing 7. The nacelle is lifted into place before the tower is erected in its entire axial length. Preferably the nacelle is lifted into place after a few sections have been completed. After the nacelle has been lifted into place it is joined (mounted) to the tower. The nacelle is lifted into place at a height on the tower where the nacelle does not hinder the process of joining the sections of the lower end of the tower.

Figures 2 and 3 show that each section 11 (segments) consist of at least one first mantle part 12 and at least one second mantle part 13. The first mantle part 12 and the second mantle part 13 are joined, alternatively connected, to each other during the formation of a section

(revolution). Each section preferably forms a cylinder. The cylinder's diameter may vary according to the cylinder's axial direction. The mantle parts consist preferably of plates which are formed by bending, roller bending, or with another suitable for the purpose known techniques. The mantel plates (mantle parts) have preferably a radial or similar form. In alternative embodiments the mantle plates (mantle parts) may be of a different form suitable for the purpose, such as elliptical or other form (shape) suitable for the purpose. The form (shape) of the sections may thus deviate from an essentially cylindrical shape (form).

The number and dimensions of mantle parts (mantle plates) may vary widely within the scope of the present invention. The number and dimensions of the mantle plates depend on the tower's height and diameter (at the circular cross section) or another form of the tower's cross section. The dimensions of the mantle plates are also accordingly adjusted in regards to transportation considerations involved in transporting these plates to the erection site.

Figures 4-6 show how the exemplary first mantle plate 12 and the second mantle plate 13 are joined to each other with at least one vertical weld seam 14. Figure 4 shows how one first vertical weld seam is welded. All vertical seams 14 between the mantle plates, included in a section, are welded together. Welding is carried out by at least one welding outfit (at least one welding tip or the like) 15 being moved in the vertical direction. The welding of vertical weld seams 14 may be carried out in the open air but is preferably accomplished in a sheltered enclosure that connects to the tower 2. A shelter from weather conditions may consist of at least one tent or other temporary structure or similar located adjacent to, or in close proximity to the tower. More specifically, one first vertical seam 15 is welded in accordance with Figure 4. Then the tower is rotated in accordance with arrow 16, or in the opposite direction, as shown in Figure 5. After the tower is rotated, at least one second vertical weld seam 14 is then welded as shown in Figure 6. It is conceivable that more than one vertical weld seam is welded simultaneously. Welding is carried out according to previously known art and techniques and this is why it is not described in more detail in this patent application. Figure 7 shows how two sections are joined with at least one horizontal weld seam 17. During the welding of the essentially horizontal weld seams 17, which joins the sections together, it is done preferably by the tower being rotated around the tower's axial direction in accordance with arrow 16 or in the opposite direction. The welding outfit can thus be connected in a stationary position. In alternative embodiments, it is conceivable that the welding of the weld seam 17 is accomplished with the tower 2 standing stationary and with welding equipment (outfit) that moves around the tower. It is also conceivable that both the welding outfit and the tower move around the tower's 2 axial direction in connection with welding. The welding of horizontal weld seams 17 can be done in the open but occurs preferably in a sheltered space (enclosure) that connects to the tower. A shelter from weather conditions may for example consist of at least one tent or at least one other temporary structure connected to the tower. Welding is carried out according to previously known art and techniques and this is why it is not described in more detail in this patent application.

Figure 8 shows that after a section is completed and joined (assembled) to previously completed sections (revolutions) the tower is erected in a vertical direction. This erection is carried out with the aid of at least one lifting body 18 and preferably several lifting bodies 18.

The lifting bodies 18 consist of lifting devices whose length may be adjusted. The lifting bodies 18 are in their one end 19 connected to the tower, or tower's upper part. The lifting bodies 18 are in their second end 20 connected to the base foundation or, alternatively, the tower's lower part. The lifting body 18 in the preferred embodiment consists of ball screws or the like. In alternative embodiments the lifting body 18 may consist of hydraulic jacks or other for the purpose suitable devices.

Surface treatment may also be carried out when the tower rotates in conjunction with its initial construction or during subsequent maintenance. Surface treatment of the tower may even be performed in the open, but treatment is preferably carried out in a weather shielding shelter or the like. A shelter from weather conditions may for example consist of at least one tent or at least one temporary structure adjacent the tower.

During the erection of the tower at least one support, at least one supporting device such as a strut or similar (not shown in the figures) is preferably used, which in its one end is placed against the ground or the like and which in its other end is placed against the tower

(preferably a distance up the tower). The strut (struts, braces) or the like is removed after the tower is completely erected. In the detailed description of the present invention, design details may have been omitted which are apparent to persons skilled in the art. Such obvious design details are included to the extent necessary so that the proper and full performance of the present invention is achieved. For example, cables (wires, lines) or similar are included to the extent necessary so that an adequate function of the wind turbine is obtained. Furthermore, it is assumed that adequate plate thicknesses are used to ensure that proper durability of the tower is obtained.

Even if certain preferred embodiments have been described in detail, variations and modifications within the scope of the invention may become apparent for specialists in the field and all such are regarded as falling within the scope of the following claims. For example, it is conceivable that the tower in alternative embodiments is united (joined) together with another for the purpose suitable unifying (joining) method. In alternative embodiments, it is also conceivable that the wind turbine's tower and nacelle are built so that the propeller is placed behind the tower in relation to wind direction. The wind passes through the tower first and then the propeller. Advantages of the Invention

Several advantages are achieved with a wind turbine and a method for erecting a wind turbine in accordance with the present invention. The most obvious advantages are that the wind turbine provides logistical advantages such as less bulky transports to the erection site. The tower's included parts are significantly smaller than the prefabricated tower sections that are currently used in wind turbine towers. The tower's included parts may be prefabricated closer to erection site without requiring a specific facility for the manufacture of tower sections. A further advantage is that the tower's shape can be optimized in relation to wind flow. Yet another important advantage of the present invention is that it reduces considerably the number of bolt joints necessary to erect the tower. The fact that the tower sections of the present invention are welded together means the elimination of bolt joints along the tower's elongated body, which allows for a longer life span and greater strength for the tower as well as facilitating its erection and the lifting of components to the top of the tower. The advantage of a longer life span for the tower of the present invention allows for components such as the generator, propeller and the like to be replaced when they are either worn out or no longer as effective as newer designs without having to construct a new tower, which reduces investment costs considerably.