Field of the Invention

In a first aspect, the present invention relates to a wind-power unit with vertical shaft comprising a wind turbine having a vertical turbine shaft, a tower supporting the wind turbine, a generator at the lower end of the tower and a unit shaft connecting the turbine shaft with the generator.

Further, the invention relates to a shaft component intended to constitute a section of the unit shaft of such a wind-power unit.

In a second aspect, the invention relates to a method for the construction of such a wind-power unit, and in a third aspect, to a use of the invented wind- power unit.

Background of the Invention

Wind-power units with vertical shaft have increasingly developed to become a competitive alternative to wind-power units with horizontal shaft and have several advantages in relation to the same. There are different types of wind- power units with vertical shaft, among others, units with a so-called H-rotor where the turbine blades are vertical. The present invention is primarily intended for H- rotor units but can also be applied to other kinds of wind-power units with vertical shaft.

Wind-power units of this type may be of relatively great dimensions with a length of the unit shaft in the order of 50-100 m and in certain cases even longer and a shaft diameter of up to some metres. Conventionally, the unit shaft is manufactured from steel. Thereby, the unit shaft becomes a very heavy body involving a high and expensive consumption of material.

Description of the Invention

The object of the present invention is to obviate the mentioned

disadvantages associated with such a unit shaft of conventional kind.

According to the first aspect of the invention, this object is attained by the fact that a wind-power unit of the kind specified by way of introduction has the special feature that the unit shaft, at least for the most part, is made of wood. Suitably, the unit shaft is practically entirely made from wood, possibly with the exception of certain fittings and connecting elements.

Thanks to this selection of material, the unit shaft can be made

considerably lighter and more inexpensive. Such a shaft of wood requires, per se, a greater amount of material than for a shaft of steel, in view of the difference in the properties of the materials. Accordingly, in case of a hollow unit shaft, the wall thickness of a wooden shaft becomes several times greater than the one of a steel shaft. However, since the density of steel is approx. 15 times greater than the one of wood, the total weight of a wooden shaft becomes approximately one third of a corresponding steel shaft. For a wind-power unit of the size of 3 MW, this represents a weight of approx. 15 1 and 40 t, respectively. In addition, there is a significant saving in costs to use the considerably more inexpensive construction material of wood. Moreover, the lower weight facilitates the construction of the wind-power unit, where great heights are concerned. From an LCA perspective, the usage of a wooden shaft also means a great advantage in view of the considerably lower energy that is consumed to produce wood compared with steel. In case of large wind-power units, for the corresponding reason, also the tower that supports the wind turbine is suitably made of wood. By then making the unit shaft of wood, the problems of different coefficient of thermal expansion that could occur if the unit shaft would be made of steel are eliminated.

According to a preferred embodiment of the wind-power unit, the unit shaft is hollow.

This further decreases its weight in comparison with a solid unit shaft or a unit shaft that has an exterior wood construction and an interior core structure.

According to an additional preferred embodiment, the unit shaft has a radial wall thickness in the interval of 20-100 mm.

Within this interval, for most sizes and diameters concerned, strength properties are achieved that are sufficient at the same time as the thickness is kept on a moderate level. Suitably, the thickness is within the narrower interval of 30-80 mm.

According to an additional preferred embodiment, the unit shaft is made of sheets of laminated wood or sheets of plywood.

This facilitates the manufacture of large tubular bodies that are concerned here. In addition, good strength is provided. According to an additional preferred embodiment, the sheets run in a helical shape around the centre axis of the unit shaft.

This entails a favourable absorption of the shearing forces in the shaft and allows also an efficient manufacturing method.

According to an additional preferred embodiment, the unit shaft comprises at least two layers of sheets, which run in mutually opposite helical directions.

Thereby, the force-transfer capacity becomes direction-independent and more uniform compared with only one layer. According to an additional preferred embodiment of the wind-power unit, the unit shaft has a circular cross-section contour having a diameter in the interval of 50-500 cm.

It is a significant advantage to use wood instead of steel above all in case of relatively large units. For large units, diameters in the mentioned interval are concerned, and therefore the invention is of particular interest here. For most sizes in question, a diameter in the interval of 120-250 cm should be suitable.

According to an additional preferred embodiment, the unit shaft has a cross-section contour that has at least three corners.

Thereby, the manufacture of the unit shaft is facilitated by the fact that the same can be joined together from sections that are combined of at least three portions in the circumferential direction.

According to an additional preferred embodiment, the corners of the contour are connected by straight lines forming a polygon.

This means that its sides are plane, which from certain aspects facilitates the manufacture of the sides and their joining. Suitably, the polygon is regular and has three, four, five, six, seven or eight corners.

According to an additional preferred embodiment, the corners of the contour are alternatively connected by arched sides.

Thereby, the torsional stiffness of the shaft is increased compared with the alternative with straight lines. The contour gets the shape of a deformed polygon. Preferably, it is shaped as a corresponding regular polygon, all the arc lines having the same shape and length. The arc-shape is suitably circular. The curvature of the arches is suitably such that convex outer surfaces are formed.

According to an additional preferred embodiment, the unit shaft is composed of a plurality of vertically distributed sections. Since a unit shaft of the type concerned has a considerable length and since it often is suitable to manufacture the unit shaft industrially on another site than where the wind-power unit is constructed, from a transportation point-of-view, it is advantageous to deliver the unit shaft in such sections in manageable lengths. In addition, this facilitates the construction on site.

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

Thereby, these have a length that is optimally adapted to transportation as well as the work of constructing the unit. Normally, lengths of 15-20 m should be most suitable.

According to an additional preferred embodiment, the sections are interconnected by connection means of steel.

This facilitates uniting the sections with each other in a simple way and with sufficient strength.

According to an additional preferred embodiment, the unit shaft is journaled in the tower in at least two places axially separated from each other, the unit shaft in these places having a circumferential lining of steel.

Thereby, wearing down of the wood is avoided at the journaling places. According to an additional preferred embodiment, the unit shaft is journaled in at least two axially separated supporting devices where each supporting device comprises at least three supporting components that abut against the unit shaft and that are connected with the inside of the tower.

The supporting devices replace the need of conventional bearings that are expensive and in addition entail complications because of the high height when bearing breakdown or other defects have to be taken care of. The supporting devices become considerably more inexpensive than conventional bearings and entail an improved operating economy thanks to service and attending to possible defects being facilitated. In addition, they can be made with relatively low weight. The supporting devices may in addition be made so that they give lower wear against the unit shaft than conventional bearings, which is an advantage if there is no steel lining of the shaft at the journaling places.

According to an additional preferred embodiment, each supporting component comprises two roller bodies arranged on a carrying element that is turnable around a vertical shaft between the two roller bodies. This entails low friction and low wear. By the boogie-like design, a good centring of the unit shaft between the supporting components is provided and contributes to the fact that the supporting device gets a desired flexibility that allows a certain movement laterally of the shaft without the journaling stability becoming impaired.

In accordance with the invention, the object set forth is further attained by a shaft component of the kind indicated by way of introduction having the special feature that the same, at least for the most part, is made of wood.

Suitably, the shaft component has a length in the interval of 5-30 m and a diameter, or the corresponding dimension, in the interval of 50-500 cm.

According to preferred embodiments of the invented shaft component, it is formed to constitute a section of a wind-power unit according to the present invention, particularly in accordance with any one of the preferred embodiments of the same.

In the second aspect of the invention, the object set forth is attained by a method of the kind indicated by way of introduction comprising the special measure that the unit shaft is manufactured essentially from wood.

According to a preferred embodiment of the invented method, the unit shaft is combined from a plurality of vertically distributed sections.

According to additional preferred embodiments of the method, the same is applied to provide a wind-power unit in accordance with the present invention, particularly in accordance with any one of the preferred embodiments of the same.

In the third aspect of the invention, the object set forth is attained by the use of a wind-power unit in accordance with the present invention, particularly in accordance with any one of the preferred embodiments of the same, in order to deliver energy to an electric mains.

The invented shaft component, the invented method and the invented use entail advantages of the corresponding kind as for the invented wind-power unit and the preferred embodiments of the same, and that have been accounted for above.

The preferred embodiments of the invention are defined in the dependent claims. It should be appreciated that additional preferred embodiments naturally may consist of all feasible combinations of the above-mentioned embodiments and of all feasible combinations of the same with individual or combined features that are seen in the subsequent description of embodiment examples.

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

Brief Description of the Drawings

Fig. 1 is a side view of a wind-power unit according to the invention.

Fig. 2 is a side view of the unit shaft of the wind-power unit according to Fig. 1.

Fig. 3 is a longitudinal section through a section of the unit shaft in Fig. 2. Fig. 4 is a side view of the section in Fig. 3.

Fig. 5 is a side view corresponding to the one in Fig. 4 according to an alternative embodiment example

Fig. 6 is a section through a detail of the section in Fig. 3.

Fig. 7 is a cross-section of a supporting device for the journaling of the unit shaft in a wind-power unit according to Fig. 1.

Fig. 8 is a section along the line VIII-VIII in Fig. 7.

Figs. 9 and 10 are sections corresponding to the one in Fig. 8 and illustrate two alternative embodiment examples of the supporting device.

Figs. 11-14 illustrate the contour of the unit shaft in some alternative embodiment examples.

Description of Embodiment Examples

Fig. 1 illustrates in a schematic side view a wind-power unit according to the invention. 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 rotationally 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 11a-11e, 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 slightly tapering 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 unit shaft 4 is essentially made of wood and is hollow.

The unit shaft 4 is shown separately in Fig. 2. It is composed of five sections 4a-4e that are attached end-to-end to each other by connecting elements adapted for the purpose. The upper end of the uppermost section 4a is provided with connecting elements for the connection to the turbine shaft and the lower end of the lowermost section 4e is provided with connecting elements for the

connection to the rotor shaft of the generator.

In Fig. 3, there is shown a section 4a of the unit shaft in cross-section. The length of such a section is suitably approx. 20 m. The diameter is approx. 2 m for a unit of 3 MW and the wall thickness of the wood material is approx. 25 mm.

Fig. 4 illustrates the structure of the section. The wood material consists of sheets of plywood. As is seen, the shaft is wound of strip-shaped plywood 10 helically wound around the centre axis.

In the example in Fig. 5, the wooden wall of the unit shaft has two layers of plywood 10, 12 helically wound in mutually opposite winding directions. According to an additional (non-illustrated) example, the wall has two plywood layers helically wound in the same direction, but with the joints between the winding turns axially displaced corresponding to half the strip width so that the winding becomes overlapping. The wall may alternatively consist of more layers than two.

For the connection of the shaft sections 4a-4e with each other, it is suitable to arrange connection means of steel. Fig. 6 shows an example of how such a one may be formed. Here, it consists of a bushing 24 arranged on the inside of the section and extends some decimetres inward. At the outer end, the bushing 24 has an outwardly directed radial flange 25 provided with holes 26 so that the same by a bolt joint can be connected to a similar bushing of an adjacent section.

Along the unit shaft 4, a number of supporting devices are arranged for the radial journaling thereof. These are placed mutually axially equidistantly at approx. 5-10 m. Each supporting device abuts against the unit shaft 4 and is mounted in the tower.

Fig. 7 is a section through the unit shaft 4 transverse to the shaft direction and illustrates an example of how the supporting device 13 may be formed. The shown supporting device consists of three supporting components 15 uniformly distributed in the circumferential direction around the unit shaft 4. Each supporting component 15 has two roller bodies 16 formed as wheels and that abut against the unit shaft 4. The wheels 16 are mounted on a carrying element 17. The carrying element 17 is turnable around a suspension shaft 18 in a holder 19 that via a cup spring 20 is attached to a supporting beam 21. The leaf spring 20 presses the supporting component 15 by a certain bias force against the unit shaft 4, suitably in the order of 1 kN. The supporting beam 20 is anchored in the tower 1. The supporting devices 13 may be axially situated right opposite the joints or anywhere along the sections.

Fig. 8 is a section along the line VIII-VIII in Fig. 3 and shows one of the wheels 16 abutting against the unit shaft 4 at a joint. In the example shown, the two sections 4a and 4b are united by a particular joint piece 22 between the bushings 24 at the end of the respective section. In this example, the bushings 24 are arranged on the outside of the respective section. The joint piece 22 is a steel ring that on the outside thereof has a groove 23 that forms a rolling path for the wheels 16 of the supporting device.

In Fig. 9, an alternative is illustrated wherein the supporting device is axially situated somewhere between the ends of a section 4a. The wheels 16 of the supporting device abut directly against the wood material of the shaft section 4a.

An additional alternative is illustrated in Fig. 10. In this example, the section 4a is provided with a short piece of steel lining 27 on the outside thereof. The steel lining 27 constitutes a rolling path for the wheels 16 of the supporting device.

Figs. 11—14 illustrate some alternative cross-sectional shapes to the circular shape of the unit shaft and the sections of which it is composed. In Fig.11 , the cross-section has the contour of a regular triangle and in Fig. 12 of a regular hexagon. Fig. 13 shows an example wherein the cross-section is a deformed regular triangle where the sides of the triangle are replaced by bulging circular lines. Fig. 14 shows an example wherein the cross-section is a deformed square where the sides of the square are replaced by curved-in circular lines.

For cross-section contours deviating from the ones of the circle, special arrangements are naturally needed for the radial journaling of the unit shaft, such as, e.g., to apply a circular tread to the journaling places.