Technical field

The present invention relates to a component for supporting a wind turbine, such as a foundation for supporting the wind turbine, or a wind power tower. The invention further relates to a method for manufacturing a component for supporting a wind turbine. The component can be used onshore as well as offshore.

Background

There are different types of foundations that are used for supporting a wind turbine depending on the location and size of the wind turbine and the properties of the ground. At present, most of the wind turbine foundations are made of concrete or steel. A disadvantage with conventional wind turbine foundation is that transport of the foundation is troublesome due to its weight and size.

WO2018/210864 discloses a foundation for supporting a wind turbine, where the foundation comprises a plurality of foundation segments made of concrete. The foundation segments are attached to each other and arranged so that they form an annular base element for supporting the wind turbine, wherein the periphery of the annular base element has a polygonal shape. Each of the foundation segments is L-shaped.

At present, most wind turbine towers are made of steel. Conventional steel drums are produced in a factory and then transported to the installation site. The drawback of this type of wind tower is heavy weight, resulting in difficulties in transport.

EP1624137A1 discloses a support column for a wind turbine consisting of an assembly of hollow-section column segments, which each comprise a composite formwork element having an inner tubular shell made of fibre reinforced polymer and an outer tubular shell made of fibre reinforced polymer and surrounding the inner tubular shell so as to define an annular chamber therebetween. The composite formwork element comprises spacing means designed to maintain the spacing between the inner and outer tubular shells. The spacing means may comprise a corrugated sheet in-between the inner and outer shells and bonded thereto. The bonding of the corrugated sheet to the shells is chemical, e.g. adhesive, or mechanical. This support column is made from lightweight composite formwork elements that are easy to transport.

CN106837705A discloses a composite wind turbine generator tower comprising an inner cylinder, an outer cylinder and a reinforcing layer between the inner cylinder and the outer cylinder. The reinforcing layer have may have a corrugated shape. The inner cylinder, the outer cylinder, and the reinforcing layer are prepared by using a composite material. A composite material is lighter than steel and concrete. However, a disadvantage with using a composite material in a foundation for a wind turbine is that the torsional rigidity of the foundation will not be sufficient to withstand the torsional forces acting on the foundation.

WO2020169393A1 discloses a wind energy installation component for a wind energy installation tower and a method for producing the wind energy installation component. The wind energy installation component comprises an outer wall element and an inner wall element arranged within the outer wall element so that a cavity is formed between them. A corrugated structural element is arranged in the cavity between the outer and inner wall elements. The first wall element is preferably designed as a ring segment or as a partial ring segment. The structural element may consist of steel, aluminium, titanium, or plastic material. The method for producing the wind turbine component comprises arranging a corrugated structural element on a first inner surface of a first wall element, and connecting the first wall element to the structural element, arranging a second wall element in a cavity formed by the first wall element, arranging the structural element between the first wall element and the second wall element, connecting the first wall element to the structural element and connecting the second wall element with the structural element preferably by means of an adhesive material. It is preferred that this connection is embodied without welding connections, since welding causes heating of the material, which often leads to embrittlement of the material.

There is a desire to have component for supporting a wind turbine that is light -weight and at the same has a good torsional rigidity.

Summary

It is an aim of the present invention to at least partly overcome the above problems, and to provide an improved component for supporting a wind turbine.

This aim is achieved by a component for supporting a wind turbine as defined in claim 1.

The component comprises a plurality of wall segments attached to each other so that the component in a cross section has a polygonal shape, wherein each of the wall segments comprises an outer wall element and an inner wall element arranged in parallel. The wall segments comprises a core element having a trapezoidal corrugated shape arranged between the outer and inner wall elements, wherein the outer wall element, the inner wall element, and the core element are made of steel suitable for laser welding, the core element comprises first and second straight sections arranged in parallel with the outer and inner wall elements, and the first and second straight sections are attached to the inner wall element and the outer wall elements respectively by laser welded joints. With the term "steel suitable for laser welding" is meant steel where the quality fulfils the requirement of SS-EN 10025-4:2019. This is a Swedish standard for steel. The standard states chemical composition and mechanical properties of the steel.

With a laser welded joint is meant a joint, weld, or seam achieved by laser welding.

This component is light -weight and at the same time has a good torsional rigidity and bending rigidity. The fact that the core elements have a trapezoidal corrugated shape, the inner and outer wall elements, and the core element are made of steel leads to high torsional rigidity and bending rigidity of the component. The laser welded joints are strong and has a high fatigue resistance. The heat affected zone of a laser welded joint is extremely small in comparison with conventional welding methods. Thus, the extension of the embrittlement of the material is small in comparison with conventional welding methods. Further, due to the narrow heat affected zones and high welding speed during the laser welding, the deformations in the component are negligibly small, which implies that residual stresses in the component are avoided. The laser welded joints are a necessity to get the individual items of the wall segments, such as the core element and inner and outer wall elements, to interact as a single component.

A further advantage with the component is that is possible to manufacture the component in an automated way, for instance using robots and digital twins. Due to the fact that each wall segments includes outer and inner wall elements arranged in parallel and a core element of a trapezoidal corrugated shape arranged between the wall elements so that the straight sections of the core element are arranged in parallel with the outer and inner wall elements, it is possible to attach the core element to the outer and inner wall elements by laser welding. Since the component comprises a plurality of wall segments attached to each other, it is possible to manufacture an essentially annular component with a core element having a trapezoidal corrugated shape.

With a trapezoidal corrugated shape is meant a wave shape where a wave has four straight sides, with one pair of parallel sides and one pair of non-parallel sides.

The core element comprises one or more first straight sections arranged in parallel with the outer wall element, and one or more second straight sections arranged in parallel with the inner wall element.

According to an embodiment of the invention, the first and second straight sections are elongated and extend with a length from a lower end to an upper end of the component.

According to an embodiment of the invention, the laser welded joint are stake welds. An advantage with stake welds is that the heat affected zone is small in comparison with conventional welding methods. According to an embodiment of the invention, the laser welded joints extend along the length of the first and second straight sections. Preferably, the laser welded joints extend continuously along the length of the first and second straight sections. The continuous joints make it possible to avoid stresses and exhaustion in the material of the straight sections. The continuous laser joints facilitate the load transfer between the core element and the outer and inner wall elements. In addition, the continuous laser joints contribute to decrease the source of stress concentrations and prolong the fatigue life of the straight sections.

According to an embodiment of the invention, at least one of the first straight sections and at least one of the second straight sections are attached to the inner and outer wall elements respectively by at least two parallel laser welded joints. Preferably, the two parallel laser welded joints extend continuously along the length of the first and second straight sections from a lower end to an upper end of the component. An advantage with this is that introduction of local bending moments in the welded joints is avoided Further, splits or gaps between the core element and the outer and inner wall elements are avoided.

According to an embodiment of the invention, first and second straight sections are elongated and extend between a lower end and upper end of the wall segment, and the width of at least some of the first and second straight sections is between 30 and 100 mm. This width makes it possible to house the welding head and a robot hand during the laser welding. Further, due to the small width of the straight sections, the shearing resistance of the component is improved.

According to an embodiment of the invention, the width of the laser welded joints is between 1 and 3 mm. Thus, the heat-affected zones caused by the laser welding are small.

According to an embodiment of the invention, the core element comprises a plurality of straight legs arranged between the first and second straight sections, and the angle between the straight legs and the first and second straight sections is between 40° and 55°, and preferably between 45° and 55°. An angle in those intervals improves the torsional rigidity of the component.

According to an embodiment of the invention, the distance between the outer and inner wall elements is between 0.1 m and 0.2 m.

According to an embodiment of the invention, the material thickness of the inner and outer wall elements is between 4 and 15 mm, and preferably between 5 and 10 mm. A small thickness of the wall elements reduces the weight of the component,

According to an embodiment of the invention, the material thickness of the core element is between 4 and 15 mm, and preferably between 5 and 10 mm. A small thickness of the core element reduces the weight of the component. According to an embodiment of the invention, the core element forms a plurality waves of a trapezoidal shape extending between the outer and inner wall elements, and each core element comprises between two and six waves, and preferably between two and four waves. Wall segments having core elements with less waves are easier to manufacture, and the material consumption is less leading to lower weight of the component.

According to an embodiment of the invention, the wavelength is between 0.15 m - 0.6 m. Having core element comprising between two and six waves, and preferably between two and four waves, with a wavelength between 0.15 m - 0.6 m leads to light weight wall elements.

According to an embodiment of the invention, wherein the component comprises more than 10 wall segments, and preferably more than 15 wall segments. The number of wall segments should be adapted to the desired size of the component. Many short wall segments facilitate logistics and material handling during manufacturing of the component.

According to an embodiment of the invention, the component comprises between 10 and 30 wall segments, and preferably between 15 - 25 wall segments.

According to an embodiment of the invention, the wall segments are tapered towards an upper end of the component. This makes it possible to form a component tapering towards its upper end.

Another aim of the present invention to provide a method for producing a component for supporting a wind turbine.

This aim is achieved by the method defined in claim 13.

The method includes manufacturing a plurality of wall segment and attaching the wall segments to each other to form a component having a polygonal shape. Manufacturing of the wall segments comprises:

- arranging one side of a trapezoidal corrugated sheet made of steel suitable for laser welding on an inner surface of a first wall element made of steel suitable for laser welding, so that elongated first straight sections of the corrugated sheet bears on the inner surface of the first wall element,

- attaching the corrugated sheet to the first wall element by performing laser welding along the first straight sections,

- arranging a second wall element made of steel suitable for laser welding on an opposite side of the corrugated sheet so that an inner surface of the second wall element bears on elongated second straight sections of the corrugated sheet, and

- attaching the second wall element to the corrugated sheet by performing laser welding along the second straight sections.

An advantage with this method is that the heat affected zones caused by the laser welding are narrow and deformations in the component are negligibly small, which implies that residual stresses in the component are avoided. The laser welded joints allows the core element and inner and outer wall elements interact as a single component. Another advantage with this method is that is possible to manufacture the component in an automated way, for instance using robots and digital twins.

Laser welding is a process used to join metals using a laser beam to form a welded joint.

The first and second straight sections are elongated and extend with a length from a lower end to an upper end of the wall segment. The welding is performed along the longitudinal axis of the straight sections so that laser welded joints are formed between the wall segment and the straight sections. The laser welding can be performed from the inside of the wall segment as well as from the outside of the wall segment. With the term performing laser welding along the straight sections is meant that the laser beam is moved in a direction parallel to the longitudinal axis of the straight section during the welding so that the result is a welded joint extending along the length of the straight section.

According to an embodiment of the invention, the laser welding is performed so that at least two parallel laser welded joints are formed between the first wall element and at least one of the first straight sections, and so that at least two parallel welded joints are formed between the second wall element and at least one of the second straight sections.

According to an embodiment of the invention, the wall segments are attached to each other by means of any of laser welding or laser hybrid welding.

According to an embodiment of the invention, the laser welding is performed by stake welding.

The component can be used on land as well as on water.

The invention also relates to use of the component for supporting offshore wind turbines. Since the component is light -weight and has a good torsional rigidity and bending rigidity, the component is suitable for offshore applications.

The invention also relates to a floating platform for supporting a wind tower plant in an offshore application comprising one or more of the components.

Brief description of the drawings

The invention will now be explained more closely by the description of different embodiments of the invention and with reference to the appended figures.

Fig. 1 shows an example of a component for supporting a wind turbine according to the invention in a perspective view. Fig. 2 shows the component in figure 1 in a side view.

Figs. 2a-b show cross sections A-A and B-B through the component in figure 1.

Fig. 3a shows an example of a wall segment in a front view.

Fig. 3b shows the wall segment in a perspective view.

Fig. 4 shows a cross-section C-C through the wall segment in figure3a.

Fig. 5. Shows an enlargement of a portion E of the wall segment in figure 4.

Fig. 6a illustrates two joined wall segments.

Fig. 6b shows a cross-section A-A through the two joined wall segments in figure 6a. Fig. 7 shows an example of a floating platform for supporting a wind turbine offshore.

Detailed description

Aspects of the present disclosure will be described more fully hereinafter with reference to the accompanying drawings. The photovoltaic device can, however, be realized in many different forms and should not be construed as being limited to the aspects set forth herein. Like numbers in the drawings refer to like elements throughout.

Figure 1 shows an example of a component 1 for supporting a wind turbine in a perspective view. Figure 2 shows the component 1 in a side view, figure 2a shows the component 1 in a cross-section A-A, and figure 2b shows the component 1 in a cross-section B-B. The component has an upper end la and a lower end lb. In the illustrated example, the component 1 tapers towards the upper end la. However, the component can have other shapes such as straight cylindrical. The component 1 comprises a plurality of elongated wall segments 2 attached to each other so that the component in a cross section has a polygonal shape, as shown in figures 2a-b. The shape of wall segments 2 can be rectangular, or a tetragon tapered towards the upper end la of the component 1. The wall segments 2 are elongated and extend with a length L from the lower end lb to the upper end la of the component. The number of wall elements of the component may vary. Preferably, the component comprises at least 6 wall segments 2 attached to each other to form a polygonal shape. For example, the component comprises between 10 and 30 wall segments, or between 15 and 25 wall segments to form an essentially annular cross section. However, in one aspect the component may have only 4 wall segments and the component has a square cross- section.

The component illustrated in figure 1 is a foundation for supporting a wind tower. The height of the component 1 depends on the application, and is, for example, between 5 m and 30 m. In this example, the component 1 comprises a connection member 3 for attaching the component 1 to a wind turbine tower. The wind turbine tower is then arranged on top of the component 1, and the component acts as an extension of the wind turbine tower. The connection member 3 is ring shaped and is attached to the upper ends 2a of the wall segments 2. The connection member 3 is provided means for attaching the connection member to the wind turbine tower, such as bolts and screws. Figure 3a shows an example of a wall segment 2 in a front view. Figure 3b shows the wall segment 2 in a perspective view. Each of the wall segments 2 comprises an outer wall element 4, and an inner wall element 6 arranged at a distance from the outer wall element 4 so that there is a space formed between the outer and inner wall elements 4, 6. The width of the outer wall element 4 is larger than the width of the inner wall element 6 so that two wall segments 2 form an angle relative each other when they are attached to each other, as shown in figure 6b. The outer and inner wall elements 4, 6 are plate shaped. For example, the outer and inner wall elements 4, 6 are made of sheets of steel suitable for laser welding. Preferably, the material thickness of the inner and outer wall elements 4, 6 is between 4 and 15 mm, and preferably between 5 and 10 mm. A small material thickness of the wall elements reduces the weight of the component. The outer and inner wall elements 4, 6 are arranged in parallel.

Each of the wall segments 2 comprises a core element 8 having a trapezoidal corrugated shape arranged in the space between the outer and inner wall elements 4, 6. The core element 8 is, for example, a trapezoidal corrugated sheet made of made of steel suitable for laser welding. The core element 8 keeps the outer and inner wall elements 4, 6 spaced apart. Preferably, the material thickness of the core element 8 is between 4 mm and 15 mm, and preferably between 5 mm and 10 mm. A small thickness of the core element reduces the weight of the component.

Figure 4 shows a cross-section C-C through the wall segment 2 in figure 3a. Figure 5 shows an enlargement of a portion E of the wall segment 2 in figure 4. Preferably, the distance D between the outer and inner wall elements 4, 6 is between 0.1 m and 0.2 m. The core element 8 has a thickness corresponding to the distance D between the inner and outer wall elements 4, 6. The wall segment 2 is elongated and has an upper end 2a and a lower end 2b, as shown in figure 3a. The core element 8 is elongated and extend between the upper and lower ends 2a-b of the wall segment 2, as shown in figure 3b. In one aspect, the core element 8 extend along the entire wall element 2 from the lower end lb to the upper end la of the component. The core element 8 is arranged in such a way as to define essentially axially extending channels 10 in the space between the wall elements 4, 6. The core element 8 form elongated channels 10 extending along the length of the wall segment 2. Preferably, there is no filling in the channels 10, in addition to air, to reduce the weight of the component.

The outer wall element 6, the inner wall element 4, and the core element 8 are made of steel suitable for laser welding. This means that the wall elements 4, 6 and the core element are made of steel where the quality meets or exceeds the requirement of EN 10025-4. The core element 8 is attached to the outer and inner wall elements 4, 6 by means of laser welded joints 20. For example, the laser welded joint are stake welds. Preferably, the width V of the first and second straight sections 12, 14 varies between 30 mm and 100 mm to make it possible to house a welding head and a robot hand during the laser welding. Further, a small width of the straight sections 12, 14 improves the shearing resistance of the component. Preferably, the width of the laser welded joints 20 is between 1 mm and 3 mm. Thus, the heat- affected zones caused by the laser welding are small.

The core element 8 comprises first and second straight sections 12, 14 arranged in parallel with the outer and inner wall elements 4, 6. The core element 8 may comprises one or more first straight sections 12 and at least two second straight sections 14. The one or more first straight section 12 bear on an inner surface 16 of the outer wall element 4. The second straight sections 14 bear on an inner surface 18 of the inner wall element 6. The first and second straight sections 12, 14 are attached to the inner and outer wall elements 4, 6 respectively by laser welded joints 20. The first and second straight sections 12, 14 are elongated and extend with the length L from the lower end lb to an upper end la of the component. The laser welded joints 20 extend along the length of the first and second straight sections 12, 14. Preferably, the laser welded joints 20 extend continuously along the length of the first and second straight sections 12, 14. The core element 8 further comprises a plurality of straight legs 22 arranged between the first and second straight sections 12, 14. Preferably, the angle a between the straight legs and the first and second straight sections 12, 14 is between 40° and 55°, and most preferably between 45° and 55°, as shown in figure 4, to improve the torsional rigidity of the component.

The core element 8 of the wall segment 2 ends and begins with straight end sections 12' having a shorter width than the first and second straight sections 12, 14. Preferably, the end sections 12' at the ends of the core element has a width slightly less than half the width of the first and second straight sections 12, 14. The end sections 12' end at distance from the endings of the outer wall element 4 to achieve a space for facilitating welding of the wall segments to each other, as shown in figure 4. For example, the distance between the end sections 12' and the ending of the outer wall element 4 is between 1 - 3 mm.

The core element 8 forms a plurality waves of a trapezoidal shape extending between the outer and inner wall elements 4, 6. Preferably, each core element 8 comprises between two and six waves, and preferably between two and four waves. Wall segments 2 having core elements 8 with less waves are easier to manufacture, and the material consumption is less leading to lower weight of the component. In the example illustrated in figure 4, the core element 8 has two waves. Each wave comprises one first straight section 12 or an end section 12', one second straight section 14 and two straight legs 22. Preferably, the wavelength W of the waves 24 is between 0.15 m - 0.6 m. The amplitude of the waves corresponds to the distance D between the outer and inner wall elements 4, 6 and is preferably between 0.1 m and 0.2 m. Having core elements 8 comprising between two and six waves, and preferably between two and four waves, with a wavelength between 0.15 m - 0.6 m and an amplitude between 0.1 m and 0.2 m leads to light weight wall elements, and accordingly light weight components.

Preferably, the first and second straight sections 12, 14, and the end sections are attached to the inner and outer wall elements 4, 6 respectively by at least two elongated and parallel laser welded joints 20, as shown in figures 3b, 4 and 5. In the illustrated example, the end section 12' is also attached to the outer wall element 14 with two laser welded joint. However, in another example, the straight end section 12' can be attached to the outer wall element 6 by one laser welded joint, and the first and second straight sections 12, 14, can be attached to the inner and outer wall elements 4, 6 respectively by two laser welded joints. In alternative embodiments, the first and second straight sections 12, 14, and the end sections 12' can be attached to the inner and outer wall elements 4, 6 respectively by one laser welded joint, or more than two elongated and parallel laser welded joints 20.

Figure 6a illustrates two joined wall segments 2. Figure 6b shows a cross-section A-A through the two joined wall segments in figure 6a.

In the following a method for producing the component is explained with reference to figure 4 and 6a-b.

In a first step, a plurality of wall segment 2 is manufactured. Core elements 8 can be manufactured by cutting a trapezoidal corrugated sheet made of steel suitable for laser welding into suitable pieces. The inner and outer wall elements 4, 6 can be manufactured by cutting a sheet made of steel suitable for laser welding into suitable pieces.

Manufacturing of a wall segment comprises placing the core element 8 on the inner surface 16, 18 of a first wall element, i.e. one of the inner and outer wall elements 4, 6, so that the straight sections 12, 12 , 14 of the core element 8 bear on the inner surface 16, 18 of the wall element 4, 6. The core element 8 is attached to the wall element 4, 6 by performing laser welding along the elongated straight sections 12, 12', 14 of the core element so that at least one elongated welded joint 20a is formed between the elongated straight sections 12, 12', 14 of the wall element 6 and the core element 8. Preferably, the elongated joints 20a extend continuously along the straight sections between the upper end 2a and the lower end 2b of the wall segment. In the illustrated example, the laser welding is performed so that two elongated joints 20a are formed along each of the straight sections. This can, for example, be done by using a laser welding apparatus with two welding heads. Preferably, the two elongated joints 20a are parallel. It is also possible to have only one welded joint 20a on each of the straight sections, or more than two welded joints 20a.

In a next step, an end plate can be attached to one of the ends 2a, 2b of the wall segment. The end plate is preferably made of steel and is attached to the core element 8 by welding, for example MAG welding.

Thereafter, a second wall element, i.e., the other of the inner and outer wall elements 4, 6 is positioned on an opposite side of the core element 8 so that an inner surface 16, 18 of the second wall element bears on straight sections 14 of the core element. The second wall element 4, 6 is attached to the core element 8 by performing laser welding along the straight sections 12, 12', 14 14 of the second wall element so that at least one elongated welded joint 20b is formed between the second wall element 6 and the core element 8. Preferably, the elongated joints 20b extend continuously along the straight sections between the upper end 2a and the lower end 2b of the wall element. The laser welding is now performed from the outside of the second wall element. The welded joints 20b penetrates through the second wall element 6 and into the straight sections 14 of the core element, as shown in figure 5. In the illustrated example in figure 9, the laser welding is performed so that two elongated joints 20b are formed along each of the second straight sections 14. Preferably, the two elongated joints 20b are parallel. It is also possible to have only one welded joint 20b on each of the second straight sections 14, or more than two welded joints 20a.

Suitably, the laser welding is performed by stake welding.

In an optional step, another end plate can be attached to other end of the wall segment. The other end plate is also preferably made of steel and is attached to the core element 8 by welding, for example MAG welding.

Thereafter, the wall segments 2 are attached to each other, as shown in figures 6a-b. For example, the wall segments 2 are attached to each other by means of laser welding or laser hybrid welding. In this step, the outer wall elements 4 of two wall segments 2 are attached to each other by welding, and the inner wall elements 6 of two wall segments 2 are attached to each other by welding, for example, by means of laser welding or laser hybrid welding. As seen in the figure, the core element 8 of the wall segments 2 ends and begins with straight end sections 12' having a shorter width than the first and second straight sections 12, 14 and the end sections 12' ends at distance from the endings of the outer wall element 4 so that a space 30 is formed between the core elements 8 of two neighboring wall segments. The end sections 12' of the core elements 8 of two neighboring wall segments 2 are preferably attached to each other by means of laser welding or laser hybrid welding.

The wall segments 2 are attached to each other to form the component 1. The wall segments 2 can be attached to each other to form a plurality wall sections. The wall sections can then be transported to site and attached to each other on site to form the component. This will facilities the transportation of the component.

The component 1 can be used onshore as well as offshore. The component according to the present invention is particularly suitable for use offshore due to its high strength and light weigh. Figure 7 schematically illustrates an example of a floating platform 32 for supporting a wind power plant offshore comprising a component 1. In this example, the floating platform 32 comprises three components 1 arranged in a triangular configuration. The components 1 are attached to each other by a plurality of beams. However, the platform 32 may comprises less than three or more than three components 1. The present invention is not limited to the embodiments disclosed but may be varied and modified within the scope of the following claims. For example, the number of wall segments and the size of the wall segments may vary. Further, the number of waves of the core element may vary.

Reference list

1. component la. upper end of the component lb. lower end of the component.

2. wall segment

2a. upper end of the wall segment 2b. lower upper end of the wall segment

3. Connection member

4. outer wall element 6. inner wall element,

8. core element

10. channels

12. first straight section

12' straight end section

14. second straight section

16. inner surface of the outer wall element

18. inner surface of the inner wall element

20, 20a-b Laser welded joints

22. Straight legs

30 Space

32 floating platform

V width of the first and second straight sections a. angle between straight legs and straight sections D. distance between outer and inner wall elements L. Length of wall segment W. wavelength