Blade assemblies for masts connected to wind turbines, masts for wind power plants, and use of blade assemblies

Abstract

A blade assembly (1) for a mast (5) connected to a wind turbine. The blade assembly includes a main blade (10) including a main mounting portion (12) configured to be attached to the mast (5) and a main airfoil (16) protruding from the main mounting portion (12), and a biplane blade (20) connected to the main blade. The biplane blade extends between a first connection portion (22) and a second connection portion (24) to the main blade. The biplane blade includes a biplane airfoil (26) between the first connection portion and the second connection portion. The blade assembly further includes a main strut (30) configured to be connected between the main blade and the mast.

Description

Technical Field

[0001] The present invention relates to a blade assembly for a mast connected to a wind turbine. The blade assembly is configured to be attached to a mast that transmits energy to the wind turbine. The blade assembly includes a main blade having a main attachment portion configured to be attached to the mast and a main airfoil protruding from the main attachment portion. The blade assembly further includes a biplane blade connected to the main blade. The biplane blade extends between a first connection portion and a second connection portion to the main blade. The biplane blade includes a biplane airfoil between the first connection portion and the second connection portion.

[0002] The present invention further relates to a mast of a wind power plant including the blade assembly, and the use of the blade assembly.

Background Art

[0003] A wind power plant uses a blade assembly connected to a mast to transmit rotational energy to a turbine. The rotational energy can be transmitted directly to the turbine, such as a horizontal axis wind turbine (HAWT), or transmitted to the turbine by a mast, such as a vertical axis wind turbine (VAWT).

[0004] During the use of the blade assembly in a wind power plant, the blade assembly is subjected to large forces and moments. In order to increase the efficiency of the wind power plant, it is desirable to arrange the blade assembly with a long length. However, this will result in high forces and moments being applied to the blade assembly. The blade assembly is often constructed using various special materials such as fiber-reinforced polymers and carbon fibers in order to withstand these forces and moments. While providing high strength, such materials are expensive and pose a problem of having a great impact on the overall cost of the wind power plant.

[0005] To provide structural strength for the blade assembly, it is desirable to use less expensive materials such as aluminum alloy or wood.

[0006] U.S. Patent Application Publication No. 2014363303(A1) discloses a wind turbine blade having a biplane section. [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The object of the present invention is to provide an improved blade assembly for wind power plants. In particular, the first object of the present invention is to provide an improved blade assembly that allows the use of less expensive constituent materials such as aluminum alloy, wood, or a combination thereof. The second object of the present invention is to provide an improved blade assembly that allows for longer lengths compared to conventional blade assemblies. The third object of the present invention is to provide an improved blade assembly suitable for use in connection with horizontal-axis wind turbines (HAWTs). [Means for solving the problem]

[0008] These objectives are achieved by a blade assembly for a mast connected to a wind turbine, configured to be mounted on the mast. The blade assembly is A main blade including a main mounting portion configured to be attached to a mast and a main airfoil protruding from the main mounting portion, A biplane blade connected to a main blade, extending between a first connection portion and a second connection portion to the main blade, and including a biplane airfoil between the first connection portion and the second connection portion, Main struts configured to connect between the main blade and the mast Includes.

[0009] The main blade, using the main airfoil, functions as the primary energy absorber from the wind. The main blade defines the overall length of the blade assembly. The biplane blade is connected to the main blade by a first and a second connector. The biplane blade, using the biplane airfoil, functions as a secondary energy absorber from the wind. Together, the main blade and the biplane airfoil absorb energy from the wind.

[0010] Biplane blades have the added function of providing structural stability to the main blade. The structural stability of the main blade is further improved by the main struts extending between the main blade and the mast. The main function of the main struts is to absorb the thrust forces acting on the main blade. Together with the main struts, biplane blades improve the structural stability of the main blade.

[0011] The configuration of the blade assembly improves the overall structural stability of the blade assembly, which makes it possible to use less expensive materials such as aluminum alloy, wood, or a combination thereof. Alternatively, specialized materials such as fiber-reinforced polymers or carbon fibers may be used to further increase the length of the blade assembly compared to conventional blade assemblies.

[0012] According to one embodiment of the present invention, the main mounting portion is configured to be attached to a first portion of the mast, and the main strut is configured to be connected to a second portion of the mast, with the first and second portions of the mast spaced apart from each other by a certain distance. By arranging the mounting portion of the main blade to the mast and the mounting portion of the main strut to the mast separately from each other, the stability of the blade assembly is improved.

[0013] According to one embodiment of the present invention, the main blade includes a tip, and the first and second connection points of the biplane blade to the main blade are located between the main mounting portion and the tip of the main blade. The main blade extends from the main mounting portion to the tip. Connecting the biplane blade between the main mounting portion and the tip improves the structural stability of the blade assembly.

[0014] According to one embodiment of the present invention, the first connection portion of the biplane blade to the main blade is located adjacent to the main mounting portion.

[0015] According to one embodiment of the present invention, the second connection portion of the biplane blade to the main blade is located adjacent to the tip portion of the main blade.

[0016] According to one embodiment of the present invention, the biplane blade is shorter than the main blade, and the length of the biplane blade between the first and second connection points corresponds to 30% to 70% of the length of the main blade, preferably 40% to 60% of the length of the main blade. The main function of the biplane blade is to support the main blade, and for this purpose, it is sufficient that the biplane blade is shorter than the main blade.

[0017] According to one embodiment of the present invention, the biplane blade is positioned with respect to the central part of the blade relative to the main blade.

[0018] According to one embodiment of the present invention, the second connection portion of the biplane blade to the main blade is located at a distance from the main mounting portion that includes 1 / 3 to 2 / 3 of the length of the main blade, preferably half the length of the main blade. The main function of the biplane blade is to support the main blade, and for this purpose, the second connection portion is preferably located in the central part of the blade, away from the tip.

[0019] According to one embodiment of the present invention, the biplane blade includes a first portion that extends from a first connection and extends away from the main blade, thereby forming a first space between the first portion and the main blade, and the first portion of the biplane airfoil is positioned on the first portion.

[0020] According to one embodiment of the present invention, the biplane blade includes a second portion that extends from a second connection and extends away from the main blade, thereby forming a second space between the second portion and the main blade, and the second portion of the biplane airfoil is positioned on the second portion.

[0021] According to one embodiment of the present invention, the chord line of the first portion of the biplane airfoil is longer than the chord line of the second portion of the biplane airfoil.

[0022] According to one embodiment of the present invention, the chord line of the second portion of the biplane airfoil is longer than the chord line of the first portion of the biplane airfoil.

[0023] According to one embodiment of the present invention, the blade assembly further includes a sub-strut connected between the main blade and the biplane blade. The structural stability of the connection between the main blade and the biplane blade is improved by the sub-strut extending between the main blade and the biplane blade. The main function of the sub-strut is to absorb the thrust force between the main blade and the biplane blade.

[0024] According to one embodiment of the present invention, a biplane blade includes a connecting portion to which a first portion and a second portion of the biplane blade are connected, and a sub-strut is connected to this connecting portion. By connecting the sub-strut to the connecting portion between the first portion and the second portion of the biplane blade, the structural stability of the biplane blade is improved.

[0025] According to one embodiment of the present invention, the connection portion between the first part and the second part of the biplane blade is located farther away from the main blade than the first part and the second part of the biplane blade.

[0026] According to one embodiment of the present invention, the main strut is connected to the main blade at an angle within a range of ±25°, preferably within a range of ±10°, perpendicular to the extending direction of the main blade.

[0027] According to one embodiment of the present invention, the secondary strut is connected to the biplane blade at an angle within a range of ±25°, preferably within a range of ±10°, perpendicular to the extending direction of the biplane blade. [[ID=X]]

[0028] According to one embodiment of the present invention, the chord line of the airfoil of the biplane blade is shorter than the chord line of the airfoil of the main blade. The main function of the biplane blade is to support the main blade. For this purpose, it is preferable that the chord line of the airfoil of the biplane blade is shorter than the chord line of the airfoil of the main blade. As a result, the main blade functions as the main absorber of energy from the wind.

[0029] According to one embodiment of the present invention, the chord line of the airfoil of the biplane blade is within the range of 10% to 50% of the chord line of the airfoil of the main blade, preferably within the range of 20% to 30% of the chord line of the airfoil of the main blade.

[0030] According to one embodiment of the present invention, the secondary strut includes at least one beam arranged in a streamlined shape with respect to the displacement direction of the blade assembly. The streamlined arrangement of the at least one beam reduces the resistance force from the secondary strut against the rotation of the blade assembly.

[0031] According to one embodiment of the present invention, the sub-strut includes two or more beams connected to extend between different positions of the main blade and the biplane blade. By arranging a sub-strut having two or more beams, the structural stability of the connection between the main blade and the biplane blade is improved.

[0032] According to one embodiment of the present invention, the main mounting portion of the main blade includes two mounting portions that are separated from each other, and the two mounting portions are configured to form a mounting portion to the mast.

[0033] According to one embodiment of the present invention, the connection portion of the main strut includes two mounting portions that are separated from each other, and the two mounting portions are configured to form a mounting portion to the mast.

[0034] According to one embodiment of the present invention, the main blade and the biplane blade mainly consist of one of aluminum and wood, or a combination thereof.

[0035] According to one embodiment of the present invention, the tip of the main blade includes a leading edge comprising a layer of steel, titanium, and aluminum, or a combination thereof.

[0036] According to one embodiment of the present invention, at least one of a main blade and a biplane blade includes a beam assembly, preferably a box-shaped beam assembly, and an aerodynamic shell fixed to the beam assembly. The beam assembly has the function of providing primary structural stability to the main blade and / or biplane blade. The aerodynamic shell has the function of forming the main airfoil and / or biplane airfoil.

[0037] According to one embodiment of the present invention, the aerodynamic shell comprises a core and an inner layer and an outer layer attached to the core, the core mainly comprising one of a bio-derived composition, preferably wood, a para-aramid synthetic fiber composition or an aluminum honeycomb structure, a metal foam and a polymer foam, preferably mainly comprising Divinycell, and the inner layer and outer layer mainly comprising an aluminum alloy sheet.

[0038] According to one embodiment of the present invention, the core, inner layer, and outer layer are bonded to each other with an adhesive, preferably epoxy.

[0039] According to one embodiment of the present invention, the inner and outer layers of aluminum alloy sheets are joined by friction stir welding. Friction stir welding is particularly suitable for joining rigid sheets of aluminum alloy.

[0040] According to one embodiment of the present invention, the beam assembly includes a beam primarily composed of an aluminum alloy.

[0041] According to one embodiment of the present invention, the main blade, biplane blade, main strut, and sub-strut are made from separate elements.

[0042] According to one embodiment of the present invention, the beam assemblies of the main blade and the biplane blade are joined to each other by friction stir welding.

[0043] According to one embodiment of the present invention, at least one of the main blade and the biplane blade includes a leading edge along its extending direction, and the leading edge includes a reinforcing layer of one of steel, titanium, and aluminum, or a combination thereof. By providing a reinforcing outer layer at the leading edge, the problem of erosion at the leading edge is reduced. According to one embodiment, the outer layer may be partially or entirely replaced by a reinforcing outer layer on the core at the leading edge (e.g., in the form of a layer of aluminum alloy).

[0044] According to one embodiment of the present invention, the blade assembly includes a pin joint configured to hold the main blade, biplane blade, main strut, and secondary strut in a rotatably mounted position at their respective mounting points during the assembly of the blade assembly. The pin joint facilitates the assembly of the blade assembly.

[0045] According to one embodiment of the present invention, the blade assembly includes a locking means configured to lock a pin joint so that it does not rotate after the assembly of the blade assembly is complete. The locking means establishes permanent mounting of the main blade, biplane blade, main strut, and secondary strut.

[0046] The object of the present invention is further achieved by a wind power plant mast including a blade assembly according to any of the above embodiments.

[0047] The object of the present invention can be further achieved by using a blade assembly according to any of the embodiments described above.

[0048] Next, embodiments of the present invention will be described as merely examples with reference to the following drawings. [Brief explanation of the drawing]

[0049] [Figure 1a] This is a schematic diagram of a blade assembly according to one embodiment of the present invention. [Figure 1b] This is a schematic diagram of a blade assembly according to a further embodiment of the present invention. [Figure 1c] This is a schematic diagram of a blade assembly according to yet another embodiment of the present invention. [Figure 2] This diagram shows embodiments of the main blade, biplane blade, and main strut as separate elements. [Figure 3] This is a cross-sectional view of the main blade according to one embodiment of the present invention. [Figure 4]This is a schematic diagram of a blade assembly according to a further embodiment of the present invention. [Modes for carrying out the invention]

[0050] Figure 1 is a schematic diagram of a blade assembly 1 according to one embodiment of the present invention. The blade assembly 1 is shown connected to the mast 5 of a wind power plant.

[0051] The blade assembly 1 includes a main blade 10, which includes a main mounting portion 12 for attachment to the mast 5. The main blade 10 extends from the main mounting portion 12 to the tip portion 14. The main blade 10 includes a main airfoil 16 between the main mounting portion 12 and the tip portion 14. The main airfoil 16 may be positioned entirely or partially between the main mounting portion 12 and the tip portion 14.

[0052] The blade assembly 1 further includes a biplane blade 20 connected to the main blade 10. The biplane blade 20 includes a first connection portion 22 and a second connection portion 24 to the main blade 10. The biplane blade 20 further includes a biplane airfoil 26 between the first connection portion 22 and the second connection portion 24.

[0053] Preferably, the chord line of the biplane airfoil 26 of the biplane blade 20 is shorter than the chord line of the main airfoil 16 of the main blade 10. Preferably, the chord line of the biplane airfoil 26 of the biplane blade 20 is within the range of 10% to 50% of the chord line of the main airfoil 16 of the main blade 10, and preferably within the range of 20% to 30% of the chord line of the main airfoil 16 of the main blade 10.

[0054] The blade assembly 1 further includes a main strut 30 extending from the mast 5 to the main blade 10. The main strut 30 includes a first main strut connection portion 32 connecting the main strut 30 to the mast 5 and a second main strut connection portion 34 connecting the main strut 30 to the main blade 10. The main blade 10 is connected to the first portion 12a of the mast 5 by a main mounting portion 12. The main strut 30 is connected to the second portion 32a of the mast 5 by the main strut connection portion 32. In the disclosed embodiment, the first portion 12a of the mast 5 and the second portion 32a of the mast 5 are located apart from each other. However, it should be understood that the first portion 12a of the mast 5 and the second portion 32a of the mast 5 may be located adjacent to each other.

[0055] The blade assembly 1 further includes a sub-strut 40 connected between the main blade 10 and the biplane blade 20. The sub-strut 40 includes a first sub-strut connector 42 connecting the sub-strut 40 to the main blade 10 and a second sub-strut connector 44 connecting the sub-strut 40 to the biplane blade 20. In the embodiment disclosed in Figure 1, the main strut 30 and the sub-strut 40 are separate elements. However, it should be understood that the main strut 30 and the sub-strut 40 may be composed of a combined element.

[0056] In the disclosed embodiments, the biplane blade 20 is shorter than the main blade 10. The length of the biplane blade 20 between the first connector 22 and the second connector 24 corresponds to 30% to 70% of the length of the main blade 10, preferably 40% to 60% of the length of the main blade 10.

[0057] The biplane blade 20 includes a first portion 20a that extends from the first connection portion 22 and extends away from the main blade 10, thereby forming a first space 28a between the first portion 20a and the main blade 10. The first portion 26a of the biplane airfoil 26 is positioned on the first portion 20a.

[0058] Accordingly, the biplane blade 20 includes a second portion 20b that extends from the second connection portion 24 and extends away from the main blade 10, thereby forming a second space 28b between the second portion 20b and the main blade 10. The second portion 26b of the biplane airfoil 26 is positioned on the second portion 20b.

[0059] The biplane blade 20 includes a connecting portion 29 that connects a first portion 20a and a second portion 20b of the biplane blade 20. In the disclosed embodiment, a sub-strut 40 is connected to the connecting portion 29. In the disclosed embodiment, the first portion 20a and the second portion 20b of the biplane blade 20 have similar lengths. However, it should be understood that the first portion 20a and the second portion 20b of the biplane blade 20 may have different lengths.

[0060] In the disclosed embodiment, the connecting portion 29 between the first portion 20a and the second portion 20b of the biplane blade 20 is located further from the main blade 10 than the first portion 20a and the second portion 20b of the biplane blade 20. Thus, the connecting portion 29 forms the tip of the biplane blade 20.

[0061] In the disclosed embodiment, the main strut 30 is connected to the blade center of the main blade 10 by a second main strut connection 34. The biplane blade 20 is preferably positioned to extend symmetrically with respect to the blade center position. It should be understood that the biplane blade 20 may be positioned in an alternative manner. For example, the first connection 22 of the biplane blade 20 to the main blade 10 may be located adjacent to the main mounting portion 12 of the main blade 10. Correspondingly, the second connection 24 of the biplane blade 20 to the main blade 10 may be located adjacent to the tip portion 14 of the main blade 10.

[0062] In the disclosed embodiments, the main strut 30 is connected to the main blade 10 essentially perpendicular to the extending direction by a second main strut connector 34. However, it should be understood that the main strut 30 may be connected to the main blade 10 at an angle within ±25° perpendicular to the extending direction of the main blade 10, preferably at an angle within ±10° perpendicular to the extending direction of the main blade 10.

[0063] In the disclosed embodiment, the sub-strut 40 is connected to the biplane blade 20 at the connection portion 29 by a second sub-strut connection portion 44, essentially perpendicular to the biplane blade 20. However, it should be understood that the sub-strut 40 may be connected to the biplane blade 20 at an angle within ±25° perpendicular to the extending direction of the biplane blade 20, preferably at an angle within ±10° perpendicular to the extending direction of the biplane blade 20.

[0064] According to one embodiment of the present invention, the sub-strut 40 includes at least one beam that is streamlined with respect to the displacement direction of the blade assembly 1. In the disclosed embodiment, a single beam of the sub-strut 40 is shown. However, it should be understood that the sub-strut 40 may include two or more beams connected to extend between different positions of the main blade 10 and the biplane blade 20.

[0065] Referring to Figure 1b, further embodiments of the present invention are disclosed. In the embodiment of Figure 1b, the main strut 30 and the sub-strut 40 are in the form of a single unit. Therefore, the connection to the main blade 10 and the biplane blade 20 relates to the connection to the main strut 30 and the sub-strut 40 as a single unit.

[0066] Referring to Figure 1c, yet another embodiment of the present invention is disclosed. The present invention differs from the embodiments of Figure 1a and Figure 1b in that the blade assembly 1 does not include the sub-strut 40. The main blade 10 extends in a curved manner, whereas the biplane blade 20 extends in a straight manner.

[0067] Referring to Figure 2, embodiments of the main blade 10, biplane blade 20, and main strut 30 as separate elements are disclosed. It should be understood that the element shown as the main strut 30 in Figure 2 may have the function of both a main strut 30 and a secondary strut 40.

[0068] In the disclosed embodiment, the main mounting portion 12 of the main blade 10 includes two mounting portions 13a and 13b that are separated from each other. The two mounting portions 13a and 13b are configured to form a mounting portion to the mast 5.

[0069] Accordingly, the main strut connection portion 32 of the main strut 30 includes two mounting portions 33a and 33b that are separated from each other. The two mounting portions 33a and 33b are configured to form a mounting portion to the mast 5.

[0070] According to one embodiment of the present invention, the main blade 10 and the biplane blade 20 mainly comprise one of aluminum and wood, or a combination thereof. The combination of wood and aluminum provides structural strength to the blade assembly 1.

[0071] According to one embodiment of the present invention, the tip portion 14 of the main blade 10 includes a leading edge comprising a layer of steel, titanium, and aluminum, or a combination thereof.

[0072] Referring to Figure 3, a cross-section of a main blade 10 according to one embodiment of the present invention is shown. The corresponding embodiment is applicable to a biplane blade 20. The main blade 10 includes a beam assembly 50 and an aerodynamic shell 52 fixed to the beam assembly 40. The beam assembly 50 is preferably a box beam assembly.

[0073] The aerodynamic shell 52 includes a layered structure comprising a core 60 and an inner layer 62 and an outer layer 64 attached to the core 60. The core 60, the inner layer 62 and the outer layer 64 are bonded to each other with an adhesive, preferably epoxy. The inner layer 62 and the outer layer 64 are preferably aluminum alloy sheets joined by friction stir welding.

[0074] According to one embodiment of the present invention, the core 60 mainly comprises one of the following: a bio-derived composition, preferably wood, a para-aramid synthetic fiber composition, or an aluminum honeycomb structure, a metal foam, and a polymer foam, and preferably mainly comprises Divinycell. The inner layer 62 and the outer layer 64 mainly comprise aluminum alloy sheets.

[0075] Referring to Figure 4, a schematic diagram of a blade assembly 1 according to a further embodiment of the present invention is shown. The blade assembly 1 includes a pin joint 70 configured to hold the main blade 10, the biplane blade 20, the main strut 30, and the sub-strut 40 in a rotatably mounted state at their respective mounting points while the blade assembly 1 is being assembled.

[0076] According to one embodiment of the present invention, the blade assembly 1 includes a locking means configured to lock the pin joint 70 so that it does not rotate after the assembly of the blade assembly 1 is complete. The locking means is not shown.

[0077] It should be noted that the embodiments described above are illustrative rather than limiting, and that those skilled in the art can design many alternative forms without departing from the scope of the appended claims.

[0078] For example, it should be understood that the structural features and embodiments of the beam assembly 50 and the aerodynamic shell 52 can be applied independently of the structural features of the blade assembly 1.

Claims

1. A blade assembly (1) for a mast (5) connected to a wind turbine, configured to be attached to the mast (5), A main blade (10) including a main mounting portion (12) configured to be attached to the mast (5) and a main airfoil (16) protruding from the main mounting portion (12), A biplane blade (20) connected to the main blade (10), the biplane blade (20) extending between a first connection portion (22) and a second connection portion (24) to the main blade (10), and including a biplane airfoil (26) between the first connection portion (22) and the second connection portion (24). A blade assembly (1) including, The blade assembly (1) further comprises a main strut (30) configured to be connected between the main blade (10) and the mast (5).

2. The blade assembly (1) according to claim 1, wherein the main mounting portion (12) is configured to be attached to a first portion (12a) of the mast (5), the main strut (30) is configured to be connected to a second portion (32a) of the mast (5), and the first portion and the second portion of the mast (5) are spaced apart from each other by a certain distance.

3. The blade assembly (1) according to claim 1 or claim 2, wherein the main blade (10) includes a tip portion (14), and the first connection portion (22) and the second connection portion (24) of the biplane blade (20) to the main blade (10) are located between the main mounting portion (12) and the tip portion (14) of the main blade (10).

4. The blade assembly (1) according to any one of claims 1 to 3, wherein the first connection portion (22) of the biplane blade (20) to the main blade (10) is located adjacent to the main mounting portion (12).

5. The blade assembly (1) according to claim 3 or 4, wherein the second connection portion (24) of the biplane blade (20) to the main blade (10) is located adjacent to the tip portion (14) of the main blade (10).

6. The blade assembly (1) according to any one of claims 1 to 5, wherein the biplane blade (20) is shorter than the main blade (10), and the length of the biplane blade (20) between the first connecting portion (22) and the second connecting portion (24) corresponds to 30% to 70% of the length of the main blade (10), preferably 40% to 60% of the length of the main blade (10).

7. The blade assembly (1) according to any one of claims 1 to 6, wherein the biplane blade (20) is positioned with respect to the main blade (10) with respect to the center of the blade.

8. The blade assembly (1) according to any one of claims 1 to 7, wherein the biplane blade (20) includes a first portion (20a) that extends from the first connecting portion (22) and away from the main blade (10), thereby forming a first space (28a) between the first portion (20a) and the main blade (10), and the first portion (26a) of the biplane airfoil (26) is positioned on the first portion (20a).

9. The blade assembly (1) according to any one of claims 1 to 8, wherein the biplane blade (20) includes a second portion (20b) that extends from the second connecting portion (24) and away from the main blade (10), thereby forming a second space (28b) between the second portion (20b) and the main blade (10), and the second portion (26a) of the biplane airfoil (26) is positioned on the second portion (20b).

10. The blade assembly (1) according to claim 9, wherein the chord line of the first portion (26a) of the biplane airfoil (26) is longer than the chord line of the second portion (26b) of the biplane airfoil (26).

11. The blade assembly (1) according to claim 9, wherein the chord line of the second portion (26b) of the biplane airfoil (26) is longer than the chord line of the first portion (26a) of the biplane airfoil (26).

12. The blade assembly (1) according to any one of claims 9 to 11, further comprising a sub-strut (40) connected between the main blade (10) and the biplane blade (20).

13. The blade assembly (1) according to claim 12, wherein the biplane blade (20) includes a connecting portion (29) to which the first portion (20a) and the second portion (20b) of the biplane blade (20) are connected, and the sub-strut (40) is connected to the connecting portion (29).

14. The blade assembly (1) according to claim 13, wherein the connecting portion (29) between the first portion (20a) and the second portion (20b) of the biplane blade (20) is located further from the main blade (10) than the first portion (20a) and the second portion (20b) of the biplane blade (20).

15. The blade assembly (1) according to any one of claims 1 to 14, wherein the main strut (30) is connected to the main blade (10) at an angle within ±25° perpendicular to the extending direction of the main blade (10), preferably at an angle within ±10° perpendicular to the extending direction of the main blade (10).

16. The blade assembly (1) according to any one of claims 12 to 15, wherein the sub-strut (40) is connected to the biplane blade (20) at an angle within ±25° perpendicular to the extending direction of the biplane blade (20), preferably at an angle within ±10° perpendicular to the extending direction of the biplane blade (20).

17. The blade assembly (1) according to any one of claims 1 to 16, wherein the chord line of the biplane airfoil (26) of the biplane blade (20) is shorter than the chord line of the main airfoil (16) of the main blade (10).

18. The blade assembly (1) according to claim 17, wherein the chord line of the biplane airfoil (26) of the biplane blade (20) is within the range of 10% to 50% of the chord line of the main airfoil (16) of the main blade (10), preferably within the range of 20% to 30% of the chord line of the main airfoil (16) of the main blade (10).

19. The blade assembly (1) according to any one of claims 12 to 18, wherein the sub-strut (40) includes at least one beam that is streamlined with respect to the displacement direction of the blade assembly (1).

20. The blade assembly (1) according to any one of claims 12 to 19, wherein the sub-strut (40) includes two or more beams connected to extend between different positions of the main blade (10) and the biplane blade (20).

21. The blade assembly (1) according to any one of claims 1 to 20, wherein the main mounting portion (12) of the main blade (10) includes two mounting portions (13a, 13b) that are separated from each other, and the two mounting portions (13a, 13b) are configured to form a mounting portion to the mast (5).

22. The blade assembly (1) according to any one of claims 1 to 21, wherein the connecting portion of the main strut (30) includes two mounting portions (23a, 23b) that are separated from each other, and the two mounting portions (23a, 23b) are configured to form a mounting portion to the mast (5).

23. The blade assembly (1) according to any one of claims 1 to 22, wherein the main blade (10) and the biplane blade (20) mainly comprise one of aluminum and wood, or a combination thereof.

24. The blade assembly (1) according to any one of claims 1 to 23, wherein the tip portion (14) of the main blade (10) includes a leading edge comprising a layer of steel, titanium, and aluminum, or a combination thereof.

25. The blade assembly (1) according to any one of claims 1 to 24, wherein at least one of the main blade (10) and the biplane blade (20) includes the beam assembly (50), preferably a box-shaped beam assembly, and an aerodynamic shell (52) fixed to the beam assembly (50).

26. The aerodynamic shell comprises a core (60) and an inner layer (62) and an outer layer (64) attached to the core (60), wherein the core (60) mainly comprises one of a bio-derived composition, preferably wood, a para-aramid synthetic fiber composition, or an aluminum honeycomb structure, a metal foam, and a polymer foam, preferably mainly comprising Divinycell, and the inner layer (62) and the outer layer (64) mainly comprise an aluminum alloy sheet, according to claim 24, the blade assembly (1).

27. The blade assembly (1) according to any one of claims 24 to 26, wherein the core (60), the inner layer (62), and the outer layer (64) are bonded to each other with an adhesive, preferably epoxy.

28. The inner layer (62) and the outer layer (64) aluminum alloy sheets are joined by friction stir welding, as described in any one of claims 25 to 27, for the blade assembly (1).

29. The blade assembly (1) according to any one of claims 25 to 28, wherein the beam assembly (50) comprises a beam mainly comprising an aluminum alloy.

30. The blade assembly (1) according to any one of claims 12 to 29, wherein the main blade (10), the biplane blade (20), the main strut (30), and the sub-strut (40) are made from separate elements.

31. The blade assembly (1) according to any one of claims 24 to 30, wherein the beam assembly (50) of the main blade (10) and the biplane blade (20) is joined to each other by friction stir welding.

32. The blade assembly (1) according to any one of claims 1 to 31, wherein at least one of the main blade (10) and the biplane blade (20) includes a leading edge along its extending direction, and the leading edge includes a layer of steel, titanium, and aluminum, or a combination thereof.

33. The blade assembly (1) according to any one of claims 1 to 32, comprising a pin joint (70) configured to hold the main blade (10), the biplane blade (20), the main strut (30), and the sub-strut (40) in a rotatably mounted state at their respective mounting points while the blade assembly (1) is being assembled.

34. The blade assembly (1) according to claim 33, comprising a locking means configured to lock the pin joint (70) so that it does not rotate after the assembly of the blade assembly (1) is complete.

35. A mast (5) of a wind power plant, comprising the blade assembly (1) according to claims 1 to 34.

36. Use of the blade assembly (1) according to claims 1 to 34.

Images