A vertical-axis wind turbine blade clamp and blade mounting system

Abstract

The invention pertains to wind energy generation equipment, specifically the mounting systems for vertical wind turbine blades. The proposed vertical-axis wind turbine blade clamp for releasably fixing a wind turbine blade; the clamp comprising: a first clamp part, a second clamp part and a fixing means for releasably connecting the first clamp part and the second clamp part; each clamp parts comprise stiffeners; the first clamp parts are configured to accommodate the wind turbine blade when the clamp is engaged; the clamp parts are configured with a conformal profile at the region interfacing with the blade, the conformal profile being equidistant to the profile of the wind turbine blade along the entire area of contact. The clamp is designed to exert a clamping force (Fƒ) within a range (F min <Fƒ<F max ), where F min and F max are determined according to formulas as set forth in claim 1.

Description

[0001] A^vertical-axis^wind^turbine^blade^clamp^and^blade^mounting^system Field^of^the^invention

[0001] The invention pertains to wind energy generation equipment, specifically themounting systems for vertical wind turbine blades predominantly made from non-metallic materials. Background^of^the^invention

[0002] Vertical-axis wind turbines offer advantages over traditional horizontal-axis turbines, particularly in their ability to capture wind from any direction and their suitability for various locations, including urban and low-wind environments. However, the efficiency of these turbines are heavily dependent on the design and implementation of their blade mounting systems. Traditional methods for attachingblades to the vertical rotor shaft have faced challenges, the most important of them isthe blades’ low local strength, causing their destruction, as well as the complexity ofthe fixing arrangement and limitations in the material and structural design. These issues are compounded in the context of blades made from advanced composite materials, such as fiberglass or carbon fiber, which require specialized mountingsolutions to accommodate their properties and to ensure optimal performance anddurability of the turbine.

[0003] There is known an H-type vertical shaft wind power plant [1], i.a. comprising a blade fixing device for fixing the blade to the wind power, where the blade and the blade holder are fixed by screws, i.e., the blade and the blade holder are fixed together by means of screws. Blade fixation mean is arc-shaped and adjacent on both sides of the blade. Moreover, each blade holder holds only one blade.

[0004] There is also known rotor-type windmill with vertical axis [2] with the sets ofaerodynamic blades, that have clamps corresponding to the arc-formed blades.

[0005] There is known a fan blade supporting system of wind driven generator utility model [3], that i.a. comprises the top support head, that includes an arc-shaped top plate, the arc-shaped bottom plate and the spring; the arc-shaped bottom plate is fixed with the arc-shaped top plate through the spring, the spring can rebound the forcereceived, and play a buffering effect, so as to achieve the purpose of shock absorption. A slot is formed in the middle of the upper surface of the arc-shaped top plate, and a plurality of arc-shaped shafts are evenly spaced and fixed in the slot, and a plurality of rubber rollers are hinged on each arc-shaped shaft at an evenly spaced interval. This solution, however, corresponds to means for blade transporting.

[0006] There is also known a clamping apparatus for securing a wind turbine blade [4], comprising a lower jaw and an upper jaw, convex pads and pressure surface. All of the adjustments occur essentially automatically (that is, with minimal manual intervention) as the wind blade is clamped. This is believed to be due to the shape of the wind blade at the given point it is clamped and the clamping forces and reaction forces balancing across the various pivot points. This solution, however, also corresponds to blade transporting arrangement.

[0007] There is known a vertical-axis wind turbine blade clamp [5], comprising a laser-cut steel clamp moulded to fit the exact geometric shape of the turbine blade airfoil, featuring an ultraviolet compression polymer gasket to prevent adverse reactions between the aluminium blade and steel clamp, attached to the wind rotor structure bya hinges, positioned at a distance from the longitudinal plane of the blade. The knownclamp cannot be used for securing fiberglass blades effectively, as it is designed for aluminum blades, which tolerate higher local loads at the connection point. Furthermore, the design of the hinges outside the longitudinal plane of the blade introduces structural complexity and unwanted tensile stress issues, particularly in multi-blade assemblies.

[0008] The known solutions for attaching blades to vertical-axis wind turbines are relatively ineffective in terms of material utilization and manufacturing efficiency. Clamps for metallic blades, such as aluminium, and non-metallic blades, such as fiberglass, require fundamentally different, non-obvious design approaches and load distribution strategies due to the differing mechanical properties and load tolerancesof these materials. Typically, vertical-axis wind turbine blades are made from materialslike fiberglass, carbon fiber, or their combinations, and are formed using contactmolding. In this manner, the blades are reinforced with additional layers of fiberglassat attachment points At this stage, threaded nuts are often embedded in the blade tofacilitate its connection to the wind turbine rotor by means of bolts. Advancedcomposite manufacturing methods such as pultrusion — a continuous, automatedprocess — reduce labor costs and allow for a higher fiberglass to resin ratio, enhancingmaterial strength and environmental sustainability. The limitation of this method isthe necessity for a uniform cross-section along the entire blade length. As a result, theminimum blade wall thickness with known fixturing methods is at least 4-5 mm, whichresults in blade weight and material loss, and the integration of rotor fixtures requires complex and time-consuming manual post-processing. Brief^summary^of^the^invention

[0009] The present invention aims to address these inefficiencies by proposing an innovative vertical-axis wind turbine blade clamp and blade mounting system that eliminates the need for extensive post-processing in blade attachment areas.

[0010] The set goal is reached by providing a vertical-axis wind turbine blade clamp for releasably fixing a wind turbine blade made of fiberglass or other non-metallic fiber- reinforced composite materials, the clamp is not supposed for aluminum or other metallic blades, the clamp comprising: a first clamp part, a second clamp part and afixing means for releasably connecting the first clamp part and the second clamp part;the first clamp part and the second clamp part each comprising stiffeners integrallyformed with the clamp parts. The clamp parts are configured to accommodate the windturbine blade when the clamp is engaged. The clamp parts are configured with a conformal profile at the region interfacing with the blade. The conformal profile being equidistant to the profile of the wind turbine blade along the entire area of contact.

[0011] According to an embodiment, the fixing means comprise a hinge connecting the first clamp part and the second clamp part at the leading edge of the blade and one or more bolted connections connecting the first clamp part and the second clamp part at the trailing edge of the blade.

[0012] According to the preferred embodiment, the clamp may further comprise a gasket made from an elastomeric material, positioned on the interior surfaces of the clamp parts, wherein the gasket is designed to conform to the profile of the wind turbine blade, providing secure engagement and uniform distribution of load between the clamp parts and the blade, as well as a moment-free connection between blade and clamp without unwanted tensile stresses.

[0013] The set goal is also reached by a vertical-axis wind turbine blade mounting system, comprising one or more clamps, wherein each clamp is rigidly connected to a blade holder through the stiffeners. The blade holder uniting multiple blades into an assembly. The blade assembly being connectable to a wind rotor by a fixing meansbetween the blade holders and the wind rotor. According to an embodiment, each windturbine blade can be secured by two clamps, with one clamp being positioned substantially at the lower third of the blade, and the other clamp positionedsubstantially at the upper third of the blade. However, depending on the length andconstruction of the blade and a wind rotor, three or even more clamps can be used.Brief^description^of^the^drawings

[0014] Fig. 1 – isometric right-side view of the vertical-axis wind turbine blade clampreleasably fixing a wind turbine blade;Fig. 2 – enlarged view of the clamp showing hinged connection of the clamp parts;Fig. 3 - isometric left-side view of the vertical-axis wind turbine blade clampreleasably fixing a wind turbine blade;Fig. 4 – general representation of the vertical-axis wind turbine blade (2) mountingsystem;Fig. 5 - connection of blade ends in a block with winglets attached to multiple blades.Detailed^description^of^the^invention

[0015] The claimed wind turbine blade clamp (1) is designed for releasably fixing a vertical-axis wind turbine blade (2). The clamp (1) comprising: a first clamp part (5), a second clamp part (6) and a fixing means (7, 8) for releasably connecting the first clamp part (5) and the second clamp part (6).

[0016] The fixing means (7, 8) can be bolts, screws, latches, hinges, and quick-releasemechanisms. According to one embodiment, the fixing means (7, 8) comprise a hinge(7) connecting the first clamp part (5) and the second clamp part (6) at the leadingedge of the blade (2) and one or more bolted connections (8) connecting the first clamppart (5) and the second clamp part (6) at the trailing edge of the blade (2).

[0017] The first clamp part (5) and the second clamp part (6) each further comprisestiffeners (9) integrally formed with the clamp parts (5, 6). The stiffeners (9) aredesigned to reinforce the structure of the clamp (1) and distribute load uniformly across the surface of the blade (2).

[0018] The first clamp part (5) and the second clamp part (6) are configured toaccommodate the wind turbine blade (2) when the clamp (1) is engaged. The clampparts (5, 6) are configured with a conformal profile at the region (11) interfacing withthe blade (2). The conformal profile being equidistant to the profile of the wind turbine blade (2) along the entire area of contact.

[0019] The clamp (1) is designed to enable or exert a clamping force Ff when engagedfor the secure attachment of the wind turbine blade (2) between the first clamp part(5) and the second clamp part (6), utilizing the gasket (10). The force Ff (N) should beselected in the range Fmin < Ff < Fmax,where Fmin is calculated by formula (I): ^^^^ =^^ ^^ (I), wherem (kg) is the weight of the wind turbine blade (2), K is the number of the clamps (1)on a blade (2), f is the coefficient of friction between the wind turbine blade (2)surface and the gasket (10) surface.Fmax is calculated using either formula (II) or formula (III):^^^^ =^^^^^ ^ (II), whereQr (N) is the force causing the appearance of maximum permissible stresses at theattachment points of the wind turbine blade (2) when loading the wind turbine blade (2) with a uniformly distributed load applied to its outer side perpendicular to the axis of rotation of the wind turbine in the vertical plane and in the direction to the axis ofrotation in the horizontal plane under the condition that Ff^= 0; Fr (N) is the maximalforce on the outside of the wind turbine blade (2) that occurs during operation of thewind turbine; K is the number of the clamps (1) on a blade (2);^^^ ^^ ^^^ ^.^^^^ ^ ^ ^(III), whereQc (N) is the the force causing the appearance of maximum permissible stresses at theattachment points of the wind turbine blade (2) when loading the wind turbine blade (2) with a uniformly distributed load applied to its inner side perpendicular to the axis of rotation of the wind turbine in the vertical plane and in the direction from the axisof rotation in the horizontal plane under the condition that Ff^= 0; m (kg) is the weightof the wind turbine blade (2); n (RPM) is the maximum rotation speed of the windturbine blade (2); L is width of the wind rotor (4); K is the number of the clamps (1) on a blade (2). The smallest value received according to formula (II) and formula (III) should be selected as calculated Fmax.

[0020] According to the preferred embodiment, the wind turbine blade clamp (1) may comprise a gasket (10) made from an elastomeric material, such as rubber orpolyurethane. The gasket (10) is configured to provide a thickness in the range of 2.5to 5 mm under compression. The gasket (10) is compressible to accommodatemanufacturing tolerances, thereby maintaining the clamping force within the rangeFmin <^Ff^<^Fmax. The gasket (10) positioned on the interior surfaces of the first clamppart (5) and the second clamp part (6). The gasket (10) is designed to conform to the profile of the wind turbine blade (2), providing secure engagement and uniformdistribution of load between the clamp parts (5, 6) and the blade (2). The gasket (10)is designed to secure the blade (2) in both transverse and longitudinal directions byproviding a non-slip surface. The gasket (10) is also designed to be compressed with apredetermined force. This ensures optimal performance in terms of sealing, vibration damping, and maintaining the integrity of the connection between the clamp and the wind turbine blade. The materials elasticity allows it to conform to the surfaces it contacts, providing a secure, non-slip grip, while the specified compression force ensures that the gasket maintains its shape and effectiveness over time, even undervarying environmental and operational conditions. The gasket (10) also ensurescushioning, allowing the blade (2) to flex under operational loads by absorbing anddistributing stress. The gasket (10) also helps to evenly distribute working loads acrossthe contact area, preventing stress concentrations and allows to compensate forpossible manufacturing inaccuracies in the clamp’s (1) profile.

[0021] According to the invention, a vertical-axis wind turbine blade (2) mountingsystem is also provided. The system comprising one or more clamps (1), which isrigidly connected to a blade holder (3) through the stiffeners (9). The blade holder (3) uniting multiple blades (2) into an assembly (12). The blade assembly (12) being connectable to a wind rotor (4) by a fixing means between the blade holders (3) and the wind rotor (4).

[0022] According to yet another embodiment, each wind turbine blade (2) is secured by two clamps (1), with one clamp (1) being positioned substantially at the lower third of the blade (2), and the other clamp (1) positioned substantially at the upper third of the blade (2).

[0023] Dependingon the length and construction of the blade (2) and the wind rotor (4),three or even more clamps can be used. The proposed clamp is suitable for blades madeof fiberglass, fiber-reinforced composites such as glass fiber-reinforced polymer or carbon fiber-reinforced polymer, and other non-metallic equivalents. It is not supposed for aluminum or other metallic blades due to their higher local stiffness andmore resistance to the non-uniformity clamping forces distributed.

[0024] According to the preferred embodiment the wind turbine blade mounting systemmay further comprise a winglet (25) positioned at each end of a blade assembly (12)to limit airflow along the blades (2). Each winglet (25) is attached to the ends ofmultiple blades (2) within the blade assembly (12) by: end caps (13) secured to theends of the blades (2) and having threaded bushings (14); bolts (15) passing throughthe winglet (25) and engaging the threaded bushings (14) to secure the winglet (25) tothe blades (2); elastic inserts (16) positioned within openings in the winglet (25) tocompensate for lateral displacements of the blades (2); outer shells (17, 18) made ofanti-friction material, enclosing the elastic inserts (16) and clamped together by screws (19); a spherical bearing with an inner spherical surface (20) and the outershells (17, 18) forming an outer bearing race to compensate for angular deflections ofthe blade ends; and a seal (21) made of anti-friction material surrounding the bladeprofile and pressed against the winglet (25) by an elastic element (22) to eliminate gaps between the blade ends and the winglet (25), ensuring continuous aerodynamic efficiency during operation.References Cited1. CN106762398A.2. LV13894B. 3. CN215566381U. 4. US2023184221A1. 5. US2014 / 099203A1.

Claims

Claims 1. A vertical-axis wind turbine blade clamp (1) for releasably fixing a wind turbineblade (2) made of fiberglass or a fiber-reinforced composite material, the clamp (1)comprising: a first clamp part (5), a second clamp part (6) and a fixing means (7, 8) forreleasably connecting the first clamp part (5) and the second clamp part (6); the firstclamp part (5) and the second clamp part (6) each comprise stiffeners (9) integrallyformed with the clamp parts (5, 6); wherein the first clamp part (5) and the secondclamp part (6) are configured to accommodate the wind turbine blade (2) when theclamp (1) is engaged; wherein the first clamp part (5) and the second clamp part (6)are configured with a conformal profile at a region (11) interfacing with the blade (2),the conformal profile being equidistant to the profile of the wind turbine blade (2)along the entire area of contact;wherein the fixing means (7, 8) comprise a hinge (7) connecting the first clamp part(5) and the second clamp part (6) at the leading edge of the blade (2) and one or morebolted connections (8) connecting the first clamp part (5) and the second clamp part(6) at the trailing edge of the blade (2);wherein the clamp (1) is designed to allow exertion of a clamping force Ff whenengaged for attachment of the wind turbine blade (2) between the first clamp part (5)and the second clamp part (6), utilizing the gasket (10); the force Ff to be selected inthe range of Fmin < Ff < Fmax, where Fmin is calculated by formula (I):^^^^ =^^ ^^ (I), wherem is the weight of the wind turbine blade (2), K is the number of the clamps (1) on ablade (2), f is the coefficient of friction between the wind turbine blade (2) surfaceand the gasket (10) surface; and Fmax is calculated using either formula (II) or formula(III), wherein the smallest value obtained according to formula (II) and formula (III) should be selected as calculated Fmax: ^^^^ =^^^^^ ^ (II), whereQr is the force causing the appearance of maximum permissible stresses at theattachment points of the wind turbine blade (2) when loading the wind turbine blade (2) with a uniformly distributed load applied to its outer side perpendicular to the axis of rotation of the wind turbine in the vertical plane and in the direction to the axis ofrotation in the horizontal plane under the condition that Ff^= 0; Fr is the maximal forceon the outside of the wind turbine blade (2) that occurs during operation of the windturbine; K is the number of the clamps (1) on a blade (2);^^^^ ^^^^.^^^^ ^ ^^ ^(III), whereQc is the the force causing the appearance of maximum permissible stresses at theattachment points of the wind turbine blade (2) when loading the wind turbine blade (2) with a uniformly distributed load applied to its inner side perpendicular to the axis of rotation of the wind turbine in the vertical plane and in the direction from the axisof rotation in the horizontal plane under the condition that Ff^= 0; m (kg) is the weightof the wind turbine blade (2); n is the maximum rotation speed of the wind turbineblade (2); L is width of the wind rotor (4); K is the number of the clamps (1) on a blade(2).

2. The wind turbine blade clamp (1) of claim 1, wherein the fixing means (7, 8) areselected from the group consisting of bolts, screws, latches, hinges, and quick-releasemechanisms.

3. The wind turbine blade clamp (1) of any preceding claims, further comprising agasket (10) made from an elastomeric material, positioned on the interior surfaces ofthe first clamp part (5) and the second clamp part (6), wherein the gasket (10) isdesigned to conform to the profile of the wind turbine blade (2), providing secureengagement and uniform distribution of load between the clamp parts (5, 6) and theblade (2), as well as a moment-free connection between blade and clamp withoutunwanted tensile stresses, wherein the gasket (10) is configured to provide a thickness in the range of 2.5 to 5 mm under compression.

4. A vertical-axis wind turbine blade (2) mounting system, comprising one or moreclamps (1) of any preceding claims, wherein each clamp (1) is rigidly connected to ablade holder (3) through the stiffeners (9), the blade holder (3) uniting multiple blades(2) into an assembly (12); the blade assembly (12) being connectable to a wind rotor(4) by a fixing means between the blade holders (3) and the wind rotor (4).

5. The wind turbine blade (2) mounting system of claim 4, wherein each clamp (1) isfixed with a clamping force Ff when engaged for attachment of the wind turbine blade(2) between the first clamp part (5) and the second clamp part (6), utilizing the gasket(10); the force Ff being in the range of Fmin < Ff < Fmax, where Fmin is calculated byformula (I):m is the weight of the wind turbine blade (2), K is the number of the clamps (1) on ablade (2), f is the coefficient of friction between the wind turbine blade (2) surface andthe gasket (10) surface; and Fmax is calculated using either formula (II) or formula (III),wherein the smallest value obtained according to formula (II) and formula (III) should be selected as calculated Fmax: ^^^^ =^^^^^ ^ (II), where Qr (N) is the force causing the appearance of maximum permissible stresses at the attachment points of the wind turbine blade (2) when loading the wind turbine blade (2) with a uniformly distributed load applied to its outer side perpendicular to the axis of rotation of the wind turbine in the vertical plane and in the direction to the axis ofrotation in the horizontal plane under the condition that Ff^= 0; Fr is the maximal forceon the outside of the wind turbine blade (2) that occurs during operation of the windturbine; K is the number of the clamps (1) on a blade (2);Qc (N) is the the force causing the appearance of maximum permissible stresses at theattachment points of the wind turbine blade (2) when loading the wind turbine blade (2) with a uniformly distributed load applied to its inner side perpendicular to the axis of rotation of the wind turbine in the vertical plane and in the direction from the axisof rotation in the horizontal plane under the condition that Ff^= 0; m is the weight ofthe wind turbine blade (2); n is the maximum rotation speed of the wind turbine blade(2); L is width of the wind rotor (4); K is the number of the clamps (1) on a blade (2).

6. The wind turbine blade (2) mounting system of claim 4 or 5, wherein each windturbine blade (2) is secured by two clamps (1), with one clamp (1) being positionedsubstantially at the lower third of the blade (2), and the other clamp (1) positionedsubstantially at the upper third of the blade (2).

7. The wind turbine blade (2) mounting system of claim 4 or 5, wherein each windturbine blade (2) is secured by three or more clamps (1), positioned substantiallyequidistant from each other on the blade (2).

8. The wind turbine blade (2) mounting system of claim 4 or 5, further comprising a winglet (25) positioned at each end of a blade assembly (12) to limit airflow along the blades (2), wherein each winglet (25) is attached to the ends of multiple blades (2)within the blade assembly (12) by: end caps (13) secured to the ends of the blades (2)and having threaded bushings (14); bolts (15) passing through the winglet (25) andengaging the threaded bushings (14) to secure the winglet (25) to the blades (2); elasticinserts (16) positioned within openings in the winglet (25) to compensate for lateraldisplacements of the blades (2); outer shells (17, 18) made of anti-friction material,enclosing the elastic inserts (16) and fixed together by screws (19); a spherical bearing with an inner spherical surface (20) and the outer shells (17, 18) forming an outerbearing race to compensate for angular deflections of the blade ends; and a seal (21)made of anti-friction material surrounding the blade (2) profile and pressed againstthe winglet (25) by an elastic element (22) to eliminate gaps between the blade ends and the winglet (25), ensuring continuous aerodynamic efficiency during operation.

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