Vertical axis wind turbine and method of joining a blade to a 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 device, wherein the fastening device comprises a pliable fastening member that pulls the blade towards the second end of the strut.

Description

TECHNICAL FIELD

[0001] The present invention relates to vertical axis wind turbines (VAWTs) and to a method of joining a blade of a VAWT to a strut. BACKGROUND

[0002] There are various variants of vertical axis wind turbines (VAWTs), the 'Darrieus' type being characterised by its curved blades attached to a central rotational axis, and the 'H-type' utilising separate struts and blades. The struts hold the blades at a distance from the central axis. Each VAWT type has its advantages and disadvantages, one disadvantage of the H-type being the need for a connection between the blade and the strut. This connection is typically at a relatively flat angle to reduce aerodynamic drag, and the available volume or area to transfer loads between the blade and the strut is relatively limited. At the same time, this connection is in the outermost part of the rotating turbine, subject to high centrifugal forces.

[0003] A further requirement for the blade-strut connection is that it should be easy to install and remove when assembling the entire turbine, and that it should not be expensive in order for the VAWT to successfully compete with horizontal axis wind turbines (HAWTs) which do not require any struts.

[0004] Current solutions to this design problem typically utilise some variant of a metal fastener (bolt and nut) to solve the mechanical problem. Since the blade-strut connection is subject to high fatigue loads (loads vary with rotation of the VAWT), the resulting bolted connection design typically requires a large number of bolts, which is a bulky and expensive solution.

[0005] It would therefore be desirable to provide an improved VAWT, in particular a VAWT with an improved blade-strut connection. SUMMARY

[0006] In view of the above-mentioned and other drawbacks of the prior art, it is an object of the present invention to provide an improved VAWT with an improved blade-strut connection.

[0007] According to a first aspect of the present invention, there is thus provided 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 device, wherein the fastening device comprises a pliable fastening member which pulls the blade towards the second end of the strut.

[0008] The 'pulling' of the blade towards the second end of the strut by the pliable fastening member should be understood to mean that the pliable fastening member is arranged such that tension in the pliable fastening member generates a contact force at the interface between the blade and the strut.

[0009] The present invention is based on the recognition that a blade-stanchion connection using a pliable fastening member can be manufactured lighter and less susceptible to fatigue failure compared to a conventional bolted connection. Furthermore, it can be facilitated to disassemble the blade-stanchion connection, which can simplify the process of assembling the entire wind turbine. This can be particularly important for vertical axis wind turbines for offshore deployment, which can be very large, such as more than 50 meters in diameter.

[0010] In addition, the use of a pliable fastening member can enable a design of the fastening arrangement in which the load on the blade can be distributed over a relatively large area compared to a bolted connection. This can be particularly advantageous for vertical axis wind turbines in which the blades are made of composite material, as such blades can exhibit a desirable combination of low weight and high strength, but are relatively sensitive to point loads.

[0011] In various embodiments, the pliable fastening member can be at least partly made of a textile material. In a textile material, fibres, threads, strands or tapes are combined by a textile forming technique such as weaving, braiding or knitting. Thus, the desired properties of the pliable fastening member can be provided by a suitable combination of the fibrous material and / or configuration and the textile forming technique. For example, it is known from the use of textiles in mooring systems or sailing etc. that mechanical connections using textile-based fastening members can be manufactured lighter in weight and less susceptible to failure due to fatigue than conventional metallic connections.

[0012] Although the use of a pliable fastening member based on a textile can be advantageous in many cases, it should be noted that in embodiments the pliable fastening member can alternatively be made using other material configurations that are not based on fibres. For example, the pliable fastening member can be formed from one or more tapes such as metallic tapes, which can not be combined by any textile forming technique.

[0013] According to a second aspect of the invention, there is provided a method of joining a blade of a vertical axis wind turbine with a stanchion, the method comprising the steps of: arranging the blade and the stanchion such that a connection surface of the blade faces an end of the stanchion; and using a pliable fastening member to pull the blade towards the end of the stanchion until the connection surface of the blade is pressed against the end of the stanchion.

[0014] The steps of the method according to various embodiments of the invention do not necessarily need to be performed in any particular order, unless required by the technology. BRIEF DESCRIPTION OF DRAWINGS

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

[0016] Figure 1 is a diagrammatic illustration of an example of a floating vertical axis wind turbine according to an embodiment of the application arranged in an offshore wind farm;

[0017] Figure 2 is Figure 1 is a diagrammatic side view of one of the vertical axis wind turbines in the offshore wind farm in

[0018] Figures 3A-3B is Figure 2 is an enlarged view of the connection between a blade and a strut in the vertical axis wind turbine in

[0019] Figure 4 is a flow chart diagrammatically illustrating an example embodiment of a method according to the application;

[0020] Figures 5A-5B is Figure 4 is a diagrammatic illustration of the different steps in the flow chart in

[0021] Figures 6A-6C diagrammatically illustrates an additional example configuration of the connection between a blade and a strut. DETAILED DESCRIPTION

[0022] Figure 1 diagrammatically illustrates an offshore wind farm 1 comprising a plurality of wind turbines 3 floating in a sea 5, here in the form of vertical axis wind turbines (VAWTs) according to an example embodiment of the application. The floating VAWTs 3 are shown as each having three blades 7, wherein each blade 7 is coupled to a 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 VAWT, but additionally includes e.g. land-based VAWTs, VAWTs having a lower or higher number of blades and / or a lower or higher number of struts per blade.

[0023] in Figure 2 is shown in a diagrammatic side view in Figure 1 is one of the VAWTs 3 in Figure 1 is an example configuration of a complete VAWT 3, including Figure 2 as can be observed in Figure 2 in

[0024] Figure 2The invisible fastening means will be described with reference to Figures 3A-3B , Figures 3A-3B is Figure 2 an enlarged view of a part of the VAWT 3 indicated in Figure 2 .

[0025] Figure 3A is a partial side view in which the strut 11b is partly opened to show an example configuration of the fastening means 15 for coupling the second end 13b of the strut 11b to the blade 7. As can be observed in Figure 3A , the fastening means comprises a pliable fastening member 17 which pulls the blade 7 towards the second end 13b of the strut 11b. In the example configuration of the fastening means 15 in Figure 3A , the pliable fastening member 17 is shown in the form of a fabric sling which passes around the entire circumference of the blade 7. In embodiments in which the pliable fastening member 17 is made of a fabric material, the skilled person will readily find suitable materials which are commercially available. Examples of various types of polyester, such as UHMwPE and Kevlar, etc. are known from the maritime field.

[0026] In Figure 3A , the pulling force is indicated by arrow 19 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 force at the contact interface between the blade 7 and the second end 13b of the strut 11b will generate a friction force.

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

[0028] Compared to conventional bolted connections, by using the pliable fastening member 17, the considerable force required to prevent relative movement between the blade 7 and the strut 11b can act on a relatively large area, thereby reducing the stress on the blade 7 and / or the strut 11b. Furthermore, the pliable fastening member 17 can be made with a significantly greater fatigue resistance than a rigid connection.

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

[0030] AsFigure 3B A tensioning device 21 is provided for tensioning the pliable fastening member 17, as shown in Figure 3B The tensioning device 21 is shown in

[0031] In the example configuration of Figure 3B The tensioning device 21 for tensioning the pliable fastening member 17 comprises a tensioning actuator 22 in the form of a screw in the example configuration. Various suitable screws including roller screws, ball screws, lead screws, and the like are known per se. However, it should be noted that other types of tensioning actuators can also be beneficial depending on the requirements of the particular installation. Examples of such other types of tensioning actuators include hydraulic cylinders, springs, bolts, and the like. It should also be noted that the tensioning device 21 can alternatively be arranged in or on the blade 7.

[0032] Figure 4 is a flowchart schematically illustrating an example embodiment of a method of joining a blade of a VAWT with a strut according to the present application. Figures 5A-5B is a schematic illustration of the different steps in the flowchart in Figure 4

[0033] Referring to Figure 4 and Figure 5A In step 100, the blade 7 and the strut 1 lb are arranged such that the joining surface 25 of the blade 7 faces the end 13b of the strut 1 lb. As schematically shown in Figure 5A The VAWT 3 can be provided with a positioning structure configured to define the relative positional arrangement of the blade 7 and the end 13b of the strut 1 lb. In the example configuration of Figure 5A The positioning structure is represented as a region 25 having a plurality of recesses 27 (only one recess is represented in Figure 5A by reference numerals) included in the blade 7, and a region 29 having complementary protrusions 31 at the end 13b of the strut 1 lb. Providing the positioning structure can facilitate the relative positioning of the blade 7 and the strut 1 lb, and can also facilitate maintaining the desired relative positioning while tension is applied to the pliable fastening member 17, as will be described below with reference to Figure 5B

[0034] ​​It will be apparent to the skilled person that many different configurations of the positioning structure will be possible and can be beneficial, depending on various circumstances, such as the material of the blade 7 and / or the strut 1 lb and the method used to manufacture the blade 7 and / or the strut 1 lb. One example of an alternative configuration can be a guide pin attached to one of the blade 7 and the strut 1 lb, and a corresponding hole arranged to accommodate the guide pin in the other one of the blade 7 and the strut 1 lb.

[0035] In Figure 5A , the flexible fastening member 17 is shown as being wrapped around the blade 7. Depending on the size of the assembly facility and the VAWT 3, etc., the flexible fastening member 17 can be installed before or after the blade 7 and the strut 1 lb are positioned relative to each other. According to one method, the blade 7 and the strut 1 lb can first be arranged adjacent to each other as shown in Figure 5A , and then the flexible fastening member 17 can be pulled around the blade 7 before the two end portions of the flexible fastening member 17 are coupled to the tensioning device 21. According to another method, the flexible fastening member 17 can first be coupled to the tensioning device 21, and then the blade 7 can be inserted into the loop formed by the flexible fastening member 17, or the loop can be moved along the length of the blade 7 to the proper relative position of the blade 7 and the strut 1 lb.

[0036] After the blade 7 and the strut 1 lb have been arranged relative to each other and the flexible fastening member 17 has been passed around at least a portion of the blade 7, regardless of how this is accomplished, then in step 101, the blade 7 is pulled towards the end portion 13b of the strut 1 lb by operating the tensioning device 21 until the engagement surface 25 of the blade 7 is pressed against the end portion 13b of the strut 1 lb. The tensioning device 21 can be operated until the flexible fastening member 17 has been subjected to a predetermined tension. This predetermined tension can be determined, for example, using simulations, and can be chosen to ensure that there is no or limited relative motion between the blade 7 and the strut 1 lb at the contact interface when the VAWT 3 is in operation.

[0037] So far, embodiments of the VAWT 3 according to the present application have been shown and described in which the flexible fastening member 17 is passed around the periphery of the blade 7. However, there are many other ways to arrange the flexible fastening member 17 so that it can pull the blade 7 towards the end portion 13b of the strut 1 lb. Some of these other ways will be described below with reference to Figures 6A-6C .

[0038] Turning first to Figure 6A , the blade 7 is shown as including internal passages 35a-b that accommodate the flexible fastening member 17. In Figure 6AIn an example configuration of the internal channel 35a-b passes through the blade 7 from a proximal side 37 of the blade 7 facing the wind turbine body 9 (see Fig. 1) to a distal side 39 of the blade 7 facing away from the wind turbine body 9. Figure 2 ) to a distal side 39 of the blade 7 facing away from the wind turbine body 9.

[0039] According to another example configuration schematically shown in Figure 6B Fig. 4, the blade 7 comprises an internal channel 35 having two openings towards the proximal side 37 of the blade 7.

[0040] According to yet another example configuration, the end portion of the strut 1 1 b can be provided with side-facing openings 41 a-b for the pliable fastening member 17.

[0041] The person skilled in the art realizes that the present application is in no way limited to the preferred embodiments described above. Rather, numerous 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 can fulfil 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 can not be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. A vertical axis wind turbine, comprising: Wind turbine body; blade; as well as The support column has a first end and a second end, the first end being connected to the wind turbine body, and the second end being connected to the blade using a fastening device. The fastening device includes a flexible fastening member that pulls the blade toward the second end of the support column by a force that causes the blade to press against the second end of the support column. Wherein, the flexible fastening member bypasses at least a portion of the blade. The fastening device includes a tensioning device for tensioning the flexible fastening member, and The tensioning device is attached to the support at a location spaced apart from the second end of the support.

2. The vertical axis wind turbine according to claim 1, wherein, The blade includes an internal channel that accommodates the flexible fastening member.

3. The vertical axis wind turbine according to claim 1 or 2, wherein, The flexible fastening member is at least partially made of fabric material.

4. The vertical axis wind turbine according to claim 1 or 2, wherein, The flexible fastening component includes at least one sling.

5. The vertical axis wind turbine according to claim 1 or 2, wherein, The tensioning device includes a tensioning actuator.

6. The vertical axis wind turbine of claim 1 or 2, further comprising a positioning structure configured to define the relative arrangement of the blade and the second end of the support column.

7. The vertical axis wind turbine according to claim 6, wherein, The positioning structure includes at least one recess and at least one protrusion, the at least one recess being located in one of the second end of the blade and the strut, and the at least one protrusion being located in the other of the second end of the blade and the strut, the at least one protrusion being configured to interact with the at least one recess to limit relative movement between the second end of the strut and the blade.

8. A method for joining the blades of a vertical axis wind turbine to a strut, the method comprising the steps of: The flexible fastening member is wrapped around at least a portion of the blade; The blade and the support are arranged such that the mating surface of the blade faces the end of the support; as well as The blade is pulled toward the end of the support using the flexible fastening member until the mating surface of the blade presses against the end of the support, wherein: The support includes a tensioning device attached to the support at a location spaced apart from the ends of the support; and The pulling process includes the following steps: Connect the flexible fastening member to the tensioning device; and Operate the tensioning device until the flexible fastening member is subjected to a predetermined tension.

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