Vertical axis wind turbine and method of connecting the blades to the mast

Abstract

A vertical axis wind turbine includes a wind turbine body, a blade, and a mast having a first end coupled to the wind turbine body and a second end coupled to the blade using a fastening arrangement, the second end including a flexible fastener at the fastening arrangement that draws the blade toward the second end of the mast.

Description

[Technical field]

[0001] The present invention relates to a vertical axis wind turbine (VAWT) and a method for connecting the blades of a VAWT to a mast. [Background technology]

[0002] There are many variations of Vertical Axis Wind Turbines (VAWTs), with the "Darrieus" featuring curved blades connected to a central rotating shaft, while the "H" utilizes separate struts and blades. The struts support the blades spaced apart from the central shaft. Each type of VAWT has its advantages and disadvantages, one of the disadvantages of the "H" is the connection required between the blades and the struts. This connection is often nearly square, and to reduce aerodynamic drag, the volume or area available for the transfer of loads between the blades and the struts is highly limited. At the same time, the connection is subject to large centrifugal forces at the outermost portion of the rotating turbine.

[0003] To compete with horizontal axis wind turbines (HAWTs), which do not require any supports, further requirements for the blade-to-support connection are that it must be easy to install and remove when assembling the entire turbine, and that the connection must not be expensive.

[0004] Current solutions to this design challenge typically utilize some variation of metallic fasteners (bolts and nuts) to solve this mechanical problem. Because the blade-to-pillar connections are subject to large fatigue loads (loads that vary with the rotation of the VAWT), the resulting bolted designs often require a large number of bolts - a heavy and expensive solution.

[0005] It would therefore be desirable to provide an improved VAWT, particularly with improved blade-to-pillar connections. Summary of the Invention [Problem to be solved by the invention]

[0006] In view of the above and other shortcomings of the prior art, it is an object of the present invention to provide an improved VAWT having an improved blade-to-post connection. [Means for solving the problem]

[0007] According to a first aspect of the invention there is provided a vertical axis wind turbine comprising a wind turbine body, a blade and a mast having a first end for coupling to the wind turbine body and a second end comprising a fastening device comprising a flexible fastening member for drawing the blade towards the second end of the mast.

[0008] By the flexible fastener "pulling" the blade towards the second end of the post, it is understood to mean that the flexible fastener is positioned such that tension in the flexible fastener creates a contact force at the interface between the blade and the post.

[0009] The present invention is based on the recognition that a blade-to-pillar connection using flexible fasteners may be lighter and less prone to fatigue failure than a conventional bolted connection. Furthermore, the blade-to-pillar connection may be easier to disassemble, which may simplify the assembly procedure of the entire wind turbine. This is particularly important for offshore vertical axis wind turbines, which may be very large, such as over 50 meters in diameter.

[0010] Additionally, the use of flexible fasteners may allow for the design of fasteners that distribute the loads on the blade over a larger area than bolted connections, which may be particularly advantageous for vertical axis wind turbines whose blades are made of composite materials, as such blades offer a desirable combination of light weight and high strength, but may be relatively sensitive to point loads.

[0011] In various embodiments, the flexible fastening member may be made at least in part from a textile material, in which fibers, wires, strands, or bands are joined by a textile forming technique, such as weaving, braiding, or knitting. Thus, the flexible fastening member may have the desired properties by appropriate combination of fiber material and / or configuration, and textile forming technique(s). For example, from the use of textiles in mooring or sailing equipment, etc., it is known that mechanical bonds using fasteners made with textile materials may be made lighter and less susceptible to fatigue failure than traditional metallic bonds.

[0012] It is noted that while the use of flexible fasteners made with fibrous materials can be advantageous in many instances, in embodiments the flexible fasteners may instead be formed using other material configurations that do not use fibrous materials. For example, the flexible fasteners may be formed with one or more bands, such as metal bands, that may not be bonded by any fiber forming techniques.

[0013] According to a second aspect of the invention, a method of joining a blade and a pole of a vertical axis wind turbine includes positioning the blade and the pole so that a joining surface of the blade faces an end of the pole, and drawing the blade towards the end of the pole using a flexible fastener until the joining surface of the blade presses against the end of the pole.

[0014] Unless technically required, the steps of the methods according to various embodiments of the present invention need not be performed in any particular order.

[0015] These and other aspects of the present invention will now be described in detail with reference to the accompanying drawings, in which examples of the invention are shown. [Brief description of the drawings]

[0016] [Figure 1]FIG. 1 illustrates a floating vertical axis wind turbine according to an embodiment of the invention deployed at an offshore wind farm. [Diagram 2] FIG. 2 is a schematic side view of one of the vertical axis wind turbines in the offshore wind farm of FIG. [Figure 3A] FIG. 3A is a close-up view of the connection between the blade and the mast in the vertical axis wind turbine of FIG. [Figure 3B] 3B is another close-up view of the connection between the blade and the mast in the vertical axis wind turbine of FIG. 2. FIG. [Diagram 3] FIG. 4 is a flow chart that generally illustrates an embodiment of a method according to the present invention. [Figure 5A] FIG. 5A is a schematic diagram of a step in the flow chart of FIG. [Figure 5B] FIG. 5B is a schematic diagram of another step in the flow chart of FIG. [Figure 6A] FIG. 6A illustrates a further example of a blade-to-strut coupling configuration. [Figure 6B] FIG. 6B illustrates, in schematic form, yet another additional example of a coupling configuration between the blade and the strut. [Figure 6C] FIG. 6A illustrates, in schematic form, yet another additional example of a coupling configuration between the blade and the strut. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] 1 shows a schematic diagram of an offshore wind farm 1 comprising a number of wind turbines 3, which are vertical axis wind turbines (VAWTs) according to an example embodiment of the present invention, floating on the ocean 5. The floating VAWTs 3 are shown having three blades 7 each. The blades 7 are each connected to a wind turbine body 9 using two supports 11a and 11b. It should be noted that the scope of the claims is not limited to this particular type of VAWT 3, but additionally encompasses, for example, land-based VAWTs and VAWTs having fewer or more blades and / or fewer or more supports per blade.

[0018] In Figure 2, one of the VAWTs 3 in Figure 1 is shown in a schematic side view, which clearly shows an example embodiment of the entire VAWT 3, including the portion that is submerged in water in Figure 1. As can be seen in Figure 2, each of the struts 11a and 11b has a first end 13a that is connected to the wind turbine body 9 and a second end 13b that is connected to the blade 7 using a fastening device (in Figure 2, the first and second ends are only indicated by reference numbers to one of the struts 11b to avoid cluttering the drawing).

[0019] The fastening device is not visible in FIG. 2, but is described with reference to FIGS. 3A and 3B, which are enlarged views of VAWT3 in FIG. 2, as indicated therein.

[0020] FIG. 3A is a partial side view in which the strut 11b has been partially cut away to show an example of the configuration of the fastening device 15 described above that is used to connect the second end 13b of the strut to the blade 7. As can be seen in FIG. 3A, the fastening device comprises a flexible fastening member 17 that draws the blade 7 towards the second end 13b of the strut 11b. In the example of the configuration of the fastening device 15 in FIG. 3A, the flexible fastening member 17 is shown in the form of a textile sling that passes over the entire circumference of the blade 7. In the embodiment in which the flexible fastening member 17 is made of a textile material, the skilled person will have no difficulty in finding suitable commercially available materials. For example, various types of polyesters are known from the maritime sector, such as UHMWPE and Kevlar®.

[0021] 3A, an attractive force acts on the flexible fastener 17, which pulls the blade 7 towards the second end of the post 11b, as indicated by arrow 19. The contact force at the interface between the blade 7 and the second end 13b creates a frictional force.

[0022] In each embodiment, the fastening device 15 can be configured to include the configuration of the contact surface to provide sufficient friction to resist relative motion between the blade 7 and the mast second end 13b even when various forces may act together to reduce the contact force at the contact surface, including centrifugal forces acting on the blade 7, wind forces, and a component of gravity, especially when wind and / or waves cause the wind turbine body 9 of the VAWT 3 to tilt away from the vertical.

[0023] Through the use of flexible fasteners 17, the actual force required to restrain relative movement between the blade 7 and the strut 11b can be exerted over a relatively large area, reducing pressure on the blade 7 and / or the strut 11b, as compared to a conventional bolted connection. Additionally, flexible fasteners 17 can be made significantly stronger against fatigue than rigid connections.

[0024] The pulling force, represented by arrow 19 in Figure 3A, may be provided by a tensioning device, an example of the configuration of such a tensioning device is described below with respect to Figure 3B.

[0025] As shown in Figure 3B, a tensioning device 21 is provided for tensioning the flexible fastening member 17. In Figure 3B, the tensioning device 21 is shown connected to the post 11b at a location 23 spaced from the second end 13b of the post 11b, enabling the tensioning device 21 to apply the aforementioned pulling force to the flexible fastening member 17.

[0026] In the example of the configuration of Figure 3B, the tensioning device 21 for tensioning the flexible fastening member 17 comprises a tensioning actuator 22 in the form of a screw. Various suitable screws are known per se and include roller screws, ball screws, lead screws, etc. However, it is noted that other types of tensioning actuators may be useful depending on the requirements of the particular device. Such other types of tensioning actuators include hydraulic cylinders, springs, bolts, etc. It is also noted that the tensioning device 21 may alternatively be located inside or on the blade 7.

[0027] Figure 4 is a flow chart that illustrates, in schematic form, an embodiment of a method for coupling a blade to a strut of a VAWT according to the present invention, and Figures 5A and 5B are schematic diagrams of different steps in the flow chart of Figure 4.

[0028] 4 and 5A, the blade 7 and the post 11b are positioned in step 100 such that the bonding surface 25 of the blade 7 faces the end 13b of the post 11b. As shown diagrammatically in FIG. 5A, the VAWT 3 includes a positioning mechanism configured to determine the relative positioning of the blade 7 and the end 13b of the post 11b. In the example configuration in FIG. 5A, the positioning mechanism is shown as a region 25 including a plurality of recesses 27 (only one of which is shown by reference numeral in FIG. 5A) contained within the blade 7 and a region 29 including a set of complementary protrusions 31 at the end 13b of the post 11b. The provision of the positioning mechanism may facilitate the determination of the relative positioning of the blade 7 and the post 11b, and may also assist in maintaining the desired relative positioning when tensioning the flexible fastener 17, as shown with respect to FIG. 5B below.

[0029] As will be readily apparent to one of ordinary skill in the art, many different configurations of the positioning mechanism are possible and may be beneficial depending on various circumstances, such as the material of the blade 7 and / or post 11b and the method used to manufacture the blade 7 and / or post 11b. One example of an alternative configuration may be a guide pin attached to either the blade 7 or post 11b and a corresponding hole formed within the other of the blade 7 or post 11b and positioned to receive the guide pin.

[0030] In FIG. 5A, the flexible fastener 17 is shown to surround the blade 7. Depending on the assembly plant and the size of the VAWT 3, the flexible fastener 17 may be attached before or after the blade 7 and the post 11b are positioned relative to each other. In one approach, the blade 7 and the post 11b may first be positioned adjacent to each other as shown in FIG. 5A, and then the flexible fastener 17 may be drawn around the blade 7 and both ends of the flexible fastener 17 may be coupled to the tensioning device 21. In another approach, the flexible fastener 17 may first be coupled to the tensioning device 21, and then the blade 7 may be inserted into the loop formed by the flexible fastener 17 or the loop may be moved along the length of the blade 7 until the blade 7 and the post 11b are positioned relative to each other.

[0031] After the blade 7 and the post 11b have been positioned relative to one another and the flexible fastener 17 has been threaded around at least a portion of the blade 7, regardless of how this has been done, the tensioning device 21 may then be operated to pull the blade 7 towards the end of the post 11b and press the coupling surface 25 of the blade 7 against the end 13b of the post 11b, as in step 101. The tensioning device 21 may be operated until the flexible fastener 17 is under a predetermined tension. This predetermined tension may be determined, for example, using simulation, or may be selected to ensure that there is no or limited relative movement of the blade 7 and the post 11b at the contact surface when the VAWT 3 is in operation.

[0032] Thus far, there have been shown and described embodiments of a VAWT 3 according to the present invention that include flexible fasteners 17 passing around the periphery of the blade 7. However, there are many other ways in which the flexible fasteners 17 can be positioned so that they draw the blade 7 towards the end 13b of the post 11b. Some of these other ways are described below with respect to Figures 6A-6C.

[0033] Looking first at Figure 6A, the blade 7 is shown to include internal passages 35a and 35b that accommodate the flexible fastening members 17. In the example configuration in Figure 6A, the internal passages 35a and 35b run through the interior of the blade 7 from a proximal face 37 of the blade 7 that faces the wind turbine body 9 to a distal face that faces outwardly of the wind turbine body 9 (see Figure 2).

[0034] According to another example configuration, shown diagrammatically in FIG. 6B, the blade 7 may be provided with an internal passage 35 with both openings facing towards the proximal face 37 of the blade 7 .

[0035] According to yet another example configuration, the ends of the post 11b may be provided with laterally facing openings 41a and 41b for flexible fastening members 17 (see FIG. 6C).

[0036] Those skilled in the art will understand that the present invention is not limited to the preferred embodiments described above, but rather many modifications and variations are possible within the scope of the appended claims.

[0037] In the claims, the words "comprising" and "comprising" do not exclude other elements or steps, and the indefinite articles "a" and "an" do 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 measures cannot be used to advantage. Any reference signs in the claims should not be interpreted as limiting the scope.

Claims

1. 1. A vertical axis wind turbine, comprising: A wind turbine body; 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 device; Equipped with the fastening device includes a flexible fastening member that draws the blade toward the second end of the post; A vertical axis wind turbine, wherein the flexible fastening member passes around at least a portion of the blade.

2. The vertical axis wind turbine of claim 1 , wherein the blade includes an internal passageway that accommodates the flexible fastener.

3. 3. A vertical axis wind turbine as claimed in claim 1 or 2, wherein the flexible fastening member is at least partially formed of a textile material.

4. 4. The vertical axis wind turbine of claim 1, wherein the flexible fastening member comprises at least one sling.

5. 5. A vertical axis wind turbine as claimed in claim 1, wherein the fastening device comprises a tensioning device for tensioning the flexible fastening member.

6. 6. The vertical axis wind turbine of claim 5, wherein the tensioning device is connected to the strut at a location spaced from the second end of the strut.

7. 7. The vertical axis wind turbine of claim 5 or 6, wherein the tensioning device comprises a tensioning actuator.

8. 8. The vertical axis wind turbine of claim 1, further comprising a positioning mechanism configured to determine a relative positioning of the blade and the second end of the mast.

9. 9. The vertical axis wind turbine of claim 8, wherein the positioning mechanism comprises at least one recess on one of the blade and the second end of the pole and at least one protrusion on the other of the blade and the second end of the pole, the at least one protrusion configured to interact with the at least one recess to limit relative movement between the pole and the blade.

10. 1. A method of connecting a blade of a vertical axis wind turbine to a pole, comprising the steps of: passing a flexible fastener around at least a portion of the blade; positioning the blade and the strut such that a mating surface of the blade faces an end of the strut; drawing the blade toward the end of the post using the flexible fastener until the binding surface of the blade presses against the end of the post; A method comprising:

11. the strut is provided with a tensioning device; and The step of attracting comprises: coupling the flexible fastening member to the tensioning device; operating the tensioning device until the flexible fastening member is under a predetermined tension; Including, The method of claim 10.

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