VERTICAL AXIS WIND TURBINE AND METHOD OF JOINING BLADE AND STRUT

Abstract

A vertical axis wind turbine, comprising: a wind turbine body; a blade; and a strut having a first end coupled to the wind turbine body and a second end coupled to the blade using a fastening arrangement, wherein the fastening arrangement comprises a pliable fastening member pulling the blade towards the second end of the strut.

Claims

1. A vertical axis wind turbine, comprising: a wind turbine body; a blade; and a strut having a first end coupled to the wind turbine body and a second end coupled to the blade using a fastening arrangement, wherein the fastening arrangement comprises a pliable fastening member pulling the blade towards the second end of the strut, wherein the pliable fastening member passes around at least a portion of the blade.

2. The vertical axis wind turbine according to claim 1, wherein the blade comprises an internal passage accommodating the pliable fastening member.

3. The vertical axis wind turbine according to claim 1, wherein the pliable fastening member is at least partly made of textile material.

4. The vertical axis wind turbine according to claim 1, wherein the pliable fastening member comprises at least one sling.

5. The vertical axis wind turbine according to claim 1, wherein the fastening arrangement comprises a tensioning arrangement tensioning the pliable fastening member.

6. The vertical axis wind turbine according to claim 5, wherein the tensioning arrangement is attached to the strut at a position spaced apart from the second end of the strut.

7. The vertical axis wind turbine according to claim 5, wherein the tensioning arrangement comprises a tensioning actuator.

8. The vertical axis wind turbine according to claim 1, further comprising a positioning structure configured to define a relative arrangement of the blade and the second end of the strut.

9. The vertical axis wind turbine according to claim 8, wherein the positioning structure comprises at least one recess in one of the blade and the second end of the strut, and at least one protrusion in the other one of the blade and the second end of the strut, the at least one protrusion being configured to interact with the at least one recess to restrict relative movement between the second end of the strut and the blade.

10. A method of joining a blade and a strut of a vertical axis wind turbine, comprising the steps of: passing a pliable fastening member around at least a portion of the blade; arranging the blade and the strut in such a way that a joining surface of the blade faces an end of the strut; and pulling the blade towards the end of the strut using the pliable fastening member until the joining surface of the blade is pressed against the end of the strut.

11. The method according to claim 10, wherein: the strut includes a tensioning arrangement; and the step of pulling comprises the steps of: coupling the pliable fastening member to the tensioning arrangement; and operating the tensioning arrangement until the pliable fastening member has been subjected to a predefined tensile force.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] These and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing an example embodiment of the invention, wherein:

[0016] FIG. 1 is an illustration of an example of floating vertical axis wind turbines according to embodiments of the present invention arranged in an offshore wind farm;

[0017] FIG. 2 is a schematic side view of one of the vertical axis wind turbines in the offshore wind farm in FIG. 1;

[0018] FIGS. 3A-B are enlarged illustrations of the connection between blade and strut in the vertical axis wind turbine in FIG. 2;

[0019] FIG. 4 is a flow-chart schematically illustrating an example embodiment of the method according to the present invention;

[0020] FIGS. 5A-B are schematic illustrations of different steps in the flow-chart in FIG. 4; and

[0021] FIGS. 6A-C schematically show additional example configurations of the connection between blade and strut.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0022] FIG. 1 schematically shows an offshore wind farm 1 including a plurality of wind turbines 3, here in the form of vertical axle wind turbines (VAWTs) according to an example embodiment of the present invention, floating in the sea 5. These floating VAWTs 3 are shown to each have three blades 7, where each blade 7 is coupled to the wind turbine body 9 using two struts 11a-b. It should be noted that the scope of the claims is not limited to this particular type of VAWTs, but additionally encompasses, for example, land-based VAWTs, VAWTs with a smaller or larger number of blades and/or a smaller or larger number of struts per blade.

[0023] In FIG. 2, one of the VAWTs 3 in FIG. 1 is shown in a schematic side view, revealing an example configuration of the full VAWT 3, including the portion that is submerged in FIG. 1. As can be seen in FIG. 2, each of the struts 11a-b has a first end 13a coupled to the wind turbine body 9 and a second end 13b coupled to the blade 7 using a fastening arrangement (in FIG. 2, the first and second ends are only indicated by reference numerals for one of the struts 11b to avoid cluttering the drawings).

[0024] The fastening arrangement, which is not visible in FIG. 2, will be described with reference to FIGS. 3A-B, which are enlarged views of a portion of the VAWT 3 in FIG. 2, as indicated in FIG. 2.

[0025] FIG. 3A is a partial side view, in which the strut 11b is partly opened to reveal an example configuration of the above-mentioned fastening arrangement 15 that is used to couple the second end 13b of the strut 11b to the blade 7. As can be seen in FIG. 3A, the fastening arrangement comprises a pliable fastening member 17 pulling the blade 7 towards the second end 13b of the strut 11b. In the example configuration of the fastening arrangement 15 in FIG. 3A, the pliable fastening member 17 is illustrated in the form of a textile sling passing around the entire circumference of the blade 7. In embodiments where the pliable fastening member 17 is made of a textile material, it will be straight-forward for the skilled person to find a suitable material that is commercially available. Known from the maritime field are, for example, various kinds of polyester, such as UHMwPE, and Kevlar, etc.

[0026] In FIG. 3A, it is indicated by arrow 19 that a pulling force is acting on the pliable fastening member 17, so that the pliable fastening member 17 in turn pulls the blade 7 towards the second end 13b of the strut 11b. The contact forces at the contact interface between the blade 7 and the second end 13b of the strut 11b will give rise to friction forces.

[0027] In embodiments, the fastening arrangement 15, including the configuration of the contact interface, may be configured to provide sufficient friction to prevent relative movement between the blade 7 and the second end 13b of the strut 11b, even when various forces may act together to reduce the contact forces at the contact interface. Such forces may include the centrifugal force, wind force, and a component of the gravitational force acting on the blade 7, especially when wind and/or waves cause the VAWT 3 to deviate from a vertical orientation of the wind turbine body 9.

[0028] Through the use of a pliable fastening member 17, the substantial force required to prevent relative movement between the blade 7 and the strut 11b can be made to act on a relatively large area, reducing the stress on the blade 7 and/or strut 11b as compared to conventional bolted connections. Furthermore, a pliable fastening member 17 can be made considerably more resilient to fatigue than rigid connections.

[0029] The pulling force represented by the arrow 19 in FIG. 3A may be provided by a tensioning arrangement. An example configuration of such a tensioning arrangement will be described below with reference to FIG. 3B.

[0030] As is indicated in FIG. 3B, a tensioning arrangement 21 is provided for tensioning the pliable fastening member 17. The tensioning arrangement 21 is shown in FIG. 3B as being attached to the strut 11b at a position 23 spaced apart from the second end 13b of the strut 11b, to allow the tensioning arrangement 21 to provide the above-mentioned pulling force to the pliable fastening member 17.

[0031] In the example configuration of FIG. 3B, the tensioning arrangement 21 for tensioning the pliable fastening member 17 comprises a tensioning actuator 22 in the form of a screw. Various suitable screws are, per se, known, including roller screws, ball screws, lead screws etc. It should, however, be noted that other kinds of tensioning actuators may be beneficial depending on the requirements of the particular installation. Examples of such other kinds of tensioning actuators include a hydraulic cylinder, a spring, a bolt, etc. It should also be noted that the tensioning arrangement 21 could alternatively be arranged in or on the blade 7.

[0032] FIG. 4 is a flow-chart schematically illustrating an example embodiment of the method according to the present invention of joining a blade and a strut of a VAWT. FIGS. 5A-B are schematic illustrations of different steps in the flow-chart in FIG. 4.

[0033] Referring to FIG. 4 and FIG. 5A, the blade 7 and the strut 11b are arranged, in step 100, in such a way that a joining surface 25 of the blade 7 faces an end 13b of the strut 11b. As is schematically indicated in FIG. 5A, the VAWT 3 may be provided with a positioning structure configured to define a relative positional arrangement of the blade 7 and the end 13b of the strut 11b. In the example configuration in FIG. 5A, the positioning structure is indicated as an area 25 with a number of recesses 27 (only one indicated by a reference numeral in FIG. 5A) comprised in the blade 7, and an area 29 with complementary protrusions 31 at the end 13b of the strut 11b. The provision of the positioning structure may facilitate relative positioning of the blade 7 and the strut 11b, and may also assist in maintaining the desired relative positioning while applying tension to the pliable fastening member 17, as will be described below with reference to FIG. 5B.

[0034] As will be immediately obvious to the skilled person, many different configurations of the positioning structure will be possible, and may be beneficial depending on various circumstances, such as the material of the blade 7 and/or strut 11b and the method used for manufacturing the blade 7 and/or strut 11b. One example of an alternative configuration could be a guiding pin attached to one of the blade 7 and the strut 11b and a corresponding hole arranged to accommodate the guiding pin formed in the other one of the blade 7 and the strut 11b.

[0035] In FIG. 5A, the pliable fastening member 17 is indicated as surrounding the blade 7. Depending on the assembly facilities, and the size of the VAWT 3, etc, the pliable fastening member 17 may be installed before or after the positioning of the blade 7 and the strut 11b in relation to each other. According to one approach, the blade 7 and the strut 11b may first be arranged adjacent to each other, as shown in FIG. 5A, and then the pliable fastening member 17 may be pulled around the blade 7 before coupling both ends of the pliable fastening member 17 to the tensioning arrangement 21. According to another approach, the pliable fastening member 17 may first be coupled to the tensioning arrangement 21, and then the blade 7 may be inserted in the loop formed by the pliable fastening member 17, or the loop may be moved along the length of the blade 7 to the correct relative position of blade 7 and strut 11b.

[0036] After having arranged the blade 7 and the strut 11b in relation to each other and having passed the pliable fastening member 17 around at least a portion of the blade 7, regardless of how this is done, the blade 7 is then pulled, in step 101 towards the end 13b of the strut 11b until the joining surface 25 of the blade 7 is pressed against the end 13b of the strut 11b, by operating the tensioning arrangement 21. The tensioning arrangement 21 may be operated until the pliable fastening member 17 has been subjected to a predefined tensile force. This predefined tensile force may, for example, be determined using simulation, and may be selected to ensure none or limited relative movement between the blade 7 and the strut 11b, at the contact interface, when the VAWT 3 is in operation.

[0037] So far, embodiments of the VAWT 3 according to the present invention have been shown and described where the pliable fastening member 17 passes around the periphery of the blade 7. There are, however, many other ways to arrange the pliable fastening member 17 so that it can pull the blade 7 towards the end 13b of the strut 11b. Some of these other ways will be described below with reference to FIGS. 6A-C.

[0038] Turning first to FIG. 6A, the blade 7 is shown to comprise internal passages 35a-b accommodating the pliable fastening member 17. In the example configuration of FIG. 6A, the internal passages 35a-b pass through the blade 7 from the proximal side 37 of the blade 7 facing the wind turbine body 9 (see FIG. 2) to the distal side 39 of the blade 7 facing away from the wind turbine body 9.

[0039] According to another example configuration, which is schematically shown in FIG. 6B, the blade 7 comprises an internal passage 35 with both openings towards the proximal side 37 of the blade 7.

[0040] According to yet another example configuration, an end portion of the strut 11b may be provided with side-facing openings 41a-b for the pliable fastening member 17.

[0041] The person skilled in the art realizes that the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims.

[0042] In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.