System and method for manufacturing a reinforced wind turbine blade

Abstract

The present invention relates to a method and system for manufacturing a wind turbine blade. The method comprises the steps of forming a cured blade element (102) of a first blade shell, forming a cured blade element (102) of a second blade shell, transferring the cured blade element (102) of the first blade shell to a first cradle (92), and transferring the cured blade element (102) of the second blade shell to a second cradle (94). Each cradle comprises a mold body (96, 98) having a molding surface for abutting against a surface of the cured blade element to advantageously form a seal therebetween.

Description

Technical Field

[0001] The present invention relates to a system and a method for manufacturing a reinforced wind turbine blade, and a wind turbine blade obtainable by said method. Background Art

[0002] Wind turbine blades are typically manufactured using a first blade shell and a second blade shell molded in a pair of adjacent blade molds. First, a blade gel coat or primer is typically applied to the blade mold. Subsequently, fiber reinforcements and / or fabrics are placed into the mold and then resin infusion is performed. A vacuum is typically used to draw the epoxy resin material into the mold. Alternatively, a prepreg technique may be used, in which fibers or fabrics pre-impregnated with resin form a homogenous material that can be introduced into the mold.

[0003] Once the blade shell has been sufficiently cured, the vacuum bag is removed and further operations may be performed on the hardened shell. For example, blade laminates and / or webs may be installed in the blade shell, various repair or patching operations may be performed on the shell, such as grinding the shell surface.

[0004] The shell halves are assembled by gluing or bolting together substantially along the chord plane of the blade. To this end, an adhesive glue is applied to the edges of the shells while the shells are in the mould. The blade moulds are connected via an articulated rotation mechanism and the first blade mould comprising the first blade shell is correspondingly rotated relative to the second mould and the shell so that the first shell is positioned above the second shell. This allows the blade shells to be closed together along the edges of the shells to form a complete wind turbine blade with an upwind side and a downwind side. In order to allow the shells to be firmly bonded together, the blade mould maintains a suitable pressure along the outer surface of the blade shells, typically for approximately 3-4 hours.

[0005] Once the complete wind turbine blade is fully adhered, the first blade mould is hinged back into the open state, allowing access to the contained wind turbine blade. The blade can then be demoulded from the second blade mould and supported using a blade cart to perform further production operations such as grinding the outer blade surface, coating, etc.

[0006] High quality blade moulds are one of the most expensive parts in the blade manufacturing process, requiring extensive tooling and manufacturing prior to use to ensure accurate replication of the desired blade profile, as well as to allow the mould to be turned to join the blade shell sections together. In addition, even minor differences in blade characteristics (such as length, camber, etc.) will generally require a completely new blade mould for the manufacturing process.

[0007] The manufacture of blade moulds used in current processes can cost approximately €1-3 million, depending on where the moulds are manufactured, and the long transport times before new moulds can be used at the manufacturing plant can be a factor. This introduces considerable expense and travel time into the implementation of manufacturing processes for new wind turbine blades. Therefore, one of the limitations to the efficient implementation of wind turbine technology is the time required for the initial setup of a blade manufacturing system. A further limitation is the time taken to manufacture a single blade within such a system.

[0008] International patent application WO 2013 / 113815 A1 discloses a blade manufacturing using a dedicated post-molding station in a manufacturing process. A blade shell forming part of a wind turbine blade is initially molded in a blade mold, and the blade shell is subsequently transferred to a post-molding station, which allows various post-molding operations to be performed on the blade shell away from the mold, thereby increasing the productivity of the blade mold in the manufacturing process. The post-molding station may be operable to perform closing of a first blade shell and a second blade shell, thereby forming a wind turbine blade.

[0009] The inventors have found that such prior art systems and methods present certain limitations, particularly when a two-step infusion process is used, where a different blade element, such as a reinforcement structure (e.g. a spar cap or a main laminate), is first molded and infused followed by another blade element being molded and infused. An example of such a two-step molding method can be found in WO 2015 / 114098 A1.

[0010] It is therefore a first object of the present invention to provide a system and method for manufacturing wind turbine blades that overcomes these limitations.

[0011] In particular, it is an object of the present invention to achieve a flexible and efficient moulding operation, which saves time and costs and leads to improved stability of the resulting wind turbine blade. Summary of the invention

[0012] Therefore, in a first aspect, the present invention relates to a method of manufacturing a wind turbine blade, the method comprising the following steps:

[0013] - a solidified blade element forming a first blade shell,

[0014] - a solidified blade element forming a second blade shell,

[0015] - transferring the cured blade element of the first blade shell to the first carrier,

[0016] - transferring the cured blade elements of the second blade shell to second cradles, wherein each cradle comprises a mould body having a moulding surface and wherein each cured blade element is arranged in its respective cradle such that the moulding surface or a part thereof abuts against a surface of the cured blade element,

[0017] - forming a reinforcement section on the solidified blade element of the first blade shell in the first bracket,

[0018] - forming a reinforcement section on the solidified blade element of the second blade shell in the second bracket,

[0019] - closing said first blade shell and said second blade shell to form a closed wind turbine blade shell, and

[0020] - combining said first blade shell and said second blade shell in said closed wind turbine blade shell to form a wind turbine blade.

[0021] The inventors have found that using a bracket to carry out the steps of forming the reinforcement section and preferably closing the blade shell provides a greater throughput of wind turbine blades manufactured according to the method of the invention. Additionally, this allows for improved geometric fit and support of the cured blade element.

[0022] According to a preferred embodiment, each cured blade element is arranged in its corresponding bracket so that a section of the molding surface is placed under a portion of the cured blade element, the portion comprising a recess for accommodating a reinforcement section. Typically, the cured blade element will include a top surface and an opposing bottom surface. The top surface will typically be located on the inner side of the completed wind turbine blade, while the bottom surface will typically be located on the outer side of the completed wind turbine blade. Preferably, the cured blade element is manufactured to include a recess, which is preferably located in its top surface, for later forming an integrated reinforcement section therein. Therefore, in some embodiments, each cured blade element is arranged in its corresponding bracket so that a section of the molding surface contacts a section of the bottom surface of the cured blade element, wherein the section of the bottom surface is opposite to a section of the top surface of the cured blade element, the section of the top surface comprising a recess for accommodating a reinforcement section.

[0023] In a preferred embodiment, each curing blade element is arranged in its respective carrier so that the moulding surface or a portion thereof abuts against the surface of the curing blade element to form a seal therebetween. By providing a carrier having a mould body including a moulding surface for providing a seal with the surface of the curing element, the formation of the reinforcement section is greatly facilitated, in particular when vacuum assisted techniques such as vacuum assisted resin transfer moulding (VARTM) are used for resin infusion when forming the reinforcement section. This is particularly applicable compared to systems in which the reinforcement section is formed on the curing blade element without any underlying moulding surface forming a seal, such as a merely open carrier structure. Unlike such prior art systems, when using the method and system of the present invention, the formation of the reinforcement section no longer depends on the vacuum tightness of the blade element, because the seal formed with the moulding surface prevents the applied vacuum from being broken during resin infusion.

[0024] Preferably, the cured blade elements of the first blade shell are formed in a first blade mould. Likewise, the cured blade elements of the second blade shell are preferably formed in a second blade mould. Each cured blade element may be a cured blade shell comprising a recess for later forming a reinforcement section therein. The recess is preferably located in an upper surface of the cured blade element.

[0025] The cured blade element according to the present invention will typically be a cured blade shell, which preferably includes a recess. The cured blade element is typically an element of a blade shell that has been substantially cured by a curing operation, preferably cured to an extent that the blade element can be handled without its structure undergoing significant deformation. The duration for performing the curing operation will depend on the type of curing resin used in the manufacture of the blade element, but can be of the order of 2-3 hours using standard resins. However, it should be understood that the blade element may continue to undergo a curing process for several hours after the indicated curing operation. The cured blade element of the first blade shell will typically have a different shape from the cured blade element of the second blade shell.

[0026] Advantageously, the cured blade element may substantially correspond to an aerodynamic blade shell, wherein a recess may be formed in the blade element for accommodating a reinforcement section in a later step. Thus, the secondary fiber material may be arranged in said recess. Thus, the less critical step of forming the aerodynamic shell and the more critical part of forming the load-bearing structure may be separated. By forming a recess in a cured blade element such as an aerodynamic shell, the secondary fiber material may be arranged more easily without wrinkling the fiber layer and forming mechanically weak areas. Performing the two steps at different locations means that the two steps may be carried out sequentially and the throughput may be increased since work may be done on two different blade shell parts simultaneously.

[0027] Preferably, the moulding surface of the mould body or a part thereof abuts against the bottom surface of the cured blade element to form a seal therebetween. The cured blade element will typically comprise an upwardly directed top surface and an opposite downwardly directed bottom surface, wherein the recess for forming the reinforcement section on the cured blade element will typically be located in the top surface.

[0028] Preferably, the moulding surface of the mould body for providing a seal with the surface of the curing element corresponds at least partially to the surface of the upwind blade shell or the downwind blade shell. In another embodiment, the moulding surface of the mould body corresponds completely to the surface of the upwind blade shell or the downwind blade shell. Preferably, the seal formed between the moulding surface and the surface of the curing blade element is an airtight seal. In other embodiments, the seal may be a vacuum seal or an airtight seal.

[0029] In some embodiments, each cured blade element is arranged in its respective cradle such that the molding surface contacts the lowest point of the outer surface of the cured blade element as seen in a cross section of the cured blade element. In other words, each cured blade element may be arranged in its respective cradle such that the molding surface contacts the vertex or lowest point of the outer surface of the cured blade element as seen in a cross section of the cured blade element. In other words, each cured blade element may be arranged in its respective cradle such that the molding surface contacts a point of the outer surface of the cured blade element that has a maximum distance from the chord line of the finished wind turbine blade as seen in a cross section of the cured blade element.

[0030] Preferably, each cured blade element is arranged in its respective bracket so that the moulding surface is in contact with at least 20% (such as at least 30% or at least 40%) of the outer surface of the cured blade element. It is particularly preferred that each cured blade element is arranged in its respective bracket so that the moulding surface is in contact with at least 50% (such as at least 60% or at least 70%) of the outer surface of the cured blade element.

[0031] In another embodiment, the carrier comprises a plurality of movable suction cups for engaging the surface of the curing blade element. The suction cups are preferably movable between an advanced position for engaging the surface of the curing blade element and a retracted position for forcing the surface of the curing blade element against the molding surface of the mold body of the carrier.

[0032] In a preferred embodiment, the mould body comprises a plurality of movable suction cups embedded in the moulding surface for engaging the surface of the curing blade element.Preferably, the suction cups are linearly displaceable.

[0033] In a preferred embodiment, each suction cup is movable via an airtight passage provided in the mold body. Such an airtight passage may be provided by an airtight sleeve or sheath arranged in the mold body, thereby allowing linear movement of a support member (such as a rod or bar) to which the suction cup is fixed. The support member may be connected to an actuator, such as a pneumatic or hydraulic actuator, for achieving movement of the support member and the suction cup.

[0034] In an embodiment, the mould body comprises at least two, such as at least three, at least four, at least five or at least six, movable suction cups embedded in the moulding surface for engaging the surface of the curing blade element.

[0035] According to another embodiment, the suction cup is movable between an advanced position for engaging the surface of the solidifying blade element and a retracted position for forcing the surface of the solidifying blade element against the molding surface of the mold body. Thus, the airtightness between the molding surface and the lower surface of the solidifying blade element can be increased, thereby allowing more efficient vacuum-assisted molding of the reinforcement section.

[0036] In a preferred embodiment, the molding surface of the mold body includes one or more sealing elements. The sealing elements may protrude beyond the surrounding molding surface. In other embodiments, the sealing elements may be flush with the surrounding molding surface. In one embodiment, the sealing elements are elastically deformable. For example, they may be made of rubber. Providing one or more sealing elements may help to form a seal between the molding surface and the surface of the cured blade element. The sealing element may take the form of a liner or a strip. According to another embodiment, the sealing element is a sealing strip. In a preferred embodiment, such a sealing strip may enclose a section of the molding surface.

[0037] In a preferred embodiment, each curing blade element is arranged in its corresponding bracket so that a section of the molding surface enclosed by the sealing element is placed below a portion of the curing blade element, the portion comprising a recess for accommodating the reinforcement section. Typically, the curing blade element will include a top surface and an opposing bottom surface. The top surface will typically be located on the inner side of the blade of the completed wind turbine, while the bottom surface will typically be located on the outer side of the completed wind turbine blade. Preferably, the curing blade element is manufactured to include a recess, which is preferably located in its top surface, for later forming an integrated reinforcement section therein. In a preferred embodiment, each curing blade element is arranged in its corresponding bracket so that a section of the molding surface enclosed by the sealing element contacts a section of the bottom surface of the curing blade element, wherein the section of the bottom surface is opposite to a section of the top surface of the curing blade element, the section of the top surface comprising a recess for accommodating the reinforcement section.

[0038] According to another embodiment, the mould body or a part thereof is deformable, preferably elastically deformable. This allows the position of the leading and trailing edges of the shell to be adjusted before the closing and joining operation.

[0039] According to another embodiment, each bracket comprises a support frame for supporting the mold body. In a preferred embodiment, such a support frame may be a substantially open frame structure. The support frame may include a plurality of support members to support the mold body according to the present invention. In one embodiment, the support frame comprises one or more stationary support members and one or more movable support members, each of the movable support members being hinged to the stationary support member. In particular in combination with a deformable mold body, the mechanism can be used to adjust the leading and trailing edges of the blade shell before closing and combining.

[0040] In a preferred embodiment, the first bracket is hingedly connected to the second bracket. This allows closing the blade shell after completion of the reinforcement section and other possible post-moulding operations without the need to move the blade shell. According to another embodiment, the reinforcement section is a main laminate, a spar cap or a spar cross beam. The reinforcement section is preferably an integrated reinforcement section.

[0041] According to another embodiment, forming a cured blade element comprises the steps of laying up a primary fiber material in a mold, infusing the primary fiber material with a primary resin, and substantially curing the primary resin in the primary fiber material to form a cured blade element.

[0042] In a preferred embodiment, the step of forming a reinforcement section comprises the steps of laying a secondary fiber material on top of at least a portion of the cured blade element, infusing the secondary fiber material with a secondary resin, and curing the secondary resin in the secondary fiber material to form a reinforcement section on the cured blade element.

[0043] According to another embodiment, the step of forming the reinforcement section comprises the step of applying a vacuum bag on said secondary fiber material after laying up said secondary fiber material, and wherein said step of infusing said secondary fiber material with a secondary resin comprises a vacuum infusion process. In a preferred embodiment, the vacuum bag is applied on the cured blade element, wherein the vacuum bag is secured by an adhesive tape which is applied on the edge of the mold body before resin infusion. The adhesive tape may be a vacuum bag sealant tape known in the art, such as Tacky Tape® manufactured by ITW Polymers Sealants North America.

[0044] In a preferred embodiment, the step of laying up the primary fiber material comprises arranging the primary fiber material in a mold to define a recess for accommodating the reinforcement section, wherein the step of laying up the secondary fiber material comprises arranging the secondary fiber material in the recess. Thus, the secondary material can be arranged in the recess, which will simplify the laying procedure and ensure that a proper transition from the cured blade element to the integrally formed reinforcement section is obtained.

[0045] According to another embodiment, the primary resin comprises a relatively low strength resin, such as polyester. According to another embodiment, the secondary resin comprises a relatively high strength resin, such as vinyl ester, epoxy, polyurethane or a hybrid resin.

[0046] In a preferred embodiment at least one of the first or second blade shells forms an upwind blade shell or a downwind blade shell.Preferably, the first bracket is arranged to accommodate a cured blade element of a pressure side shell of a wind turbine blade and the second bracket is arranged to accommodate a cured blade element of a suction side shell of a wind turbine blade.

[0047] According to a further embodiment, the method comprises the step of rotating the first blade shell relative to the second blade shell to form a closed blade shell, wherein a bonding step is performed on the closed blade shell to form the wind turbine blade.

[0048] According to another embodiment, the combining step comprises moving a first bracket comprising a first blade shell relative to a second bracket comprising a second blade shell to close said first blade shell and said second blade shell to form the wind turbine blade. Preferably, the first bracket is hingedly coupled to the second bracket, wherein the moving step comprises hingedly engaging said first bracket or said second bracket to close said first blade shell and said second blade shell.

[0049] The carriage may further serve as a turning device.As an alternative, there may be a separate station for the turning operation, wherein the blade shell is moved from the post-moulding station to the turning station after the post-moulding operation is completed.

[0050] In a preferred embodiment, the method further comprises the step of aligning the first blade shell with the second blade shell such that during said combining step, the leading edge and the trailing edge of the first blade shell are in register with the corresponding leading edge and the corresponding trailing edge of the second blade shell. Preferably, said step of aligning comprises translationally moving at least one of said first and second brackets relative to one of said first and second brackets to align the first and second blade shells contained within said first and second brackets. The brackets are preferably positioned such that initially the leading edge side of said first blade shell is disposed adjacent to the leading edge side of said second blade shell. The step of moving (preferably articulating) is performed such that the trailing edge side of said first blade shell is in contact with the trailing edge side of said second blade shell.

[0051] The method of the present invention may further comprise the step of performing at least one post-molding operation on at least one of the first blade shell and the second blade shell in the cradle. In one embodiment, the bonding step is performed after the at least one post-molding operation. The post-molding operation may comprise a blade shell repair operation, a blade shell grinding operation, a blade root flange connection operation, a blade web installation operation, a gluing operation, a coating operation, an assembly operation for assembling at least two separate sections of a wind turbine blade shell to form a single wind turbine blade shell, a coating operation, an installation of a blade sensor system, an installation of a blade lightning protection system, a geometry inspection operation, a geometry adjustment operation for pushing or pulling a portion of a blade shell into place, such as a secondary curing operation in an oven, adding external components (e.g., pneumatic devices, fans, spoilers, stall fences), or any other suitable manufacturing or assembly operation, or any suitable non-destructive testing activity (e.g., wrinkle measurement, ultrasonic thickness measurement, phased array testing of glue bonding, etc.).

[0052] The manufacturing method is used to manufacture blades for wind turbines in a fast and efficient manner at a manufacturing location. In one embodiment, the cradle is arranged in the vicinity of the blade mould, preferably adjacent to the blade mould, to provide a relatively short transfer distance between the blade mould and the cradle. More preferably, the bonding step is performed in the vicinity of the cradle, preferably using the cradle. In an alternative embodiment, the cured blade element may be transported from the moulding location to a remote cradle.

[0053] Preferably, said wind turbine blade shell is a load bearing wind turbine blade shell.It will be appreciated that the step of forming a cured blade element comprises curing said blade element to a level where the blade element can be handled and transferred from a blade mould to a cradle without deformation.

[0054] The first and second brackets may comprise a plurality of support members to provide support to the mould body. The method may comprise the step of removing at least one of the support members to provide access to the mould body and / or to a surface of at least one of the first and second blade shells to facilitate the step of performing a post moulding operation.

[0055] Preferably, the step of transferring comprises demoulding the respective cured blade element from the respective blade mould.Preferably, the step of transferring comprises applying a vacuum lifting force to the cured blade element to demould the first and second cured blade shells.

[0056] Preferably, the step of performing at least one post-moulding operation comprises applying an adhesive at a leading edge and a trailing edge of at least one of the first blade shell and the second blade shell, wherein the bonding step comprises arranging the first blade shell and the second blade shell to adhere the leading edge of the first blade shell to the leading edge of the second blade shell, and to adhere the trailing edge of the first blade shell to the trailing edge of the second blade shell.

[0057] It will be appreciated that the invention is not limited to a direct connection between respective leading and trailing edges of the shells, for example a tail piece or insert may be positioned between the leading and / or trailing edges of the shells.

[0058] Preferably, the first blade shell and the second blade shell have a profile that depends on the wind turbine blade to be manufactured. Preferably, the method comprises the step of providing at least one of the first blade mould and the second blade mould for forming the cured blade element as a substantially fixed blade mould. Preferably, the blade mould has a substantially rigid base, such as a concrete base. Providing the blade mould as a fixed device means that the mould can be relatively easy to produce and the mould costs can be kept relatively low.

[0059] Preferably, the method comprises the step of laying up the fiber-based material in the inner surface of the blade mould to form an uncured blade element of the blade shell. The laying operation may be used for both blade elements of the respective first blade shell and second blade shell to form uncured first and second blade elements. The laying may be a manual or manual laying operation, or an automated laying operation, such as spray laying, tape laying, fiber pultrusion, automotive lay-up of piles, etc.

[0060] Preferably, the step of forming a cured blade element of the blade shell comprises infusing said uncured blade element with resin to cure the blade element. This infusing step may be an automated or manual process. Preferably, the method further comprises, after said transferring step, iteratively repeating said steps of laying up and curing in said first blade mould and in said second blade mould to provide a subsequent cured blade element.

[0061] By using the mould released by the transfer step to perform the next lay-up and curing operation, the productivity of the mould is greatly improved, since a new moulding operation can be performed immediately after the curing of the previous blade shell is completed. Thus, the occupation time of the blade mould due to post-moulding operations is reduced, preferably eliminated, thereby providing a more efficient use of overall resources and equipment.

[0062] Preferably, the method further comprises iteratively repeating said transferring step to transfer said subsequent cured blade element to a respective cradle. Preferably, the method further comprises iteratively repeating the steps of forming a reinforcement section on a cured blade element of a first blade shell in a first cradle and forming a reinforcement section on a cured blade element of a second blade shell in a second cradle.

[0063] Regarding the bonding step, preferably, the method further comprises the step of performing at least one internal bonding operation on at least one of the blade shells in at least one of the first bracket and the second bracket during the step of bonding the first blade shell with the second blade shell to form the wind turbine blade. Preferably, the at least one internal bonding operation is selected from one or more of the following: a blade shell repair operation, a surface grinding operation, a coating operation, a blade root flange finishing operation.

[0064] Regarding the curing step, preferably, the method further comprises the step of performing at least one internal curing operation on at least one of said blade elements in at least one of said moulds during the step of curing said blade elements. Preferably, said at least one internal curing operation is selected from one or more of the following: a grinding operation, a blade shell repair operation.

[0065] Preferably, the first bracket is hingedly coupled to the second bracket, wherein the closing mechanism is operable to hinge the first bracket relative to the second bracket. Preferably, when the first and second brackets are closed, the first bracket is translationally movable relative to the second bracket to align the first blade shell with the second blade shell within the closed bracket to form a wind turbine blade.

[0066] Preferably, the cured blade elements are housed in respective brackets with the inner surface of the subsequently completed blade shell facing upwards. Preferably, the brackets are configured such that the first bracket and the second bracket are positioned adjacent to each other. Thus, an articulation operation of one bracket relative to the other bracket provides an effective closing method for the included blade shells. Since the closing operation can be performed using the brackets, the latter provides an optimal position for a gluing operation to apply adhesive to one or both of the included blade shells. Preferably, the first and second brackets are arranged to apply a bonding pressure to the first and second blade shells when the first and second brackets are closed.

[0067] As bonding of the shells may require application of bonding pressure to the shells to be bonded, the brackets may be arranged to force the shells together to produce effective bonding of the shells. Preferably, at least one of the brackets comprises a pressure member extending substantially along the length of the bracket. Preferably, the pressure member is operable to apply pressure along a portion of the length of a blade shell received in the bracket. Preferably, the pressure member is operable to apply bonding pressure along an edge of a blade shell received in the bracket.

[0068] Preferably, the wind turbine blade shell comprises a profiled shell body having a leading edge side and a trailing edge side. In a further embodiment, at least one bracket is rotatable about a central longitudinal axis of the bracket. By providing a rotatable bracket, access to different sections of the contained blade shell may be improved by rotating the bracket and the contained shell.

[0069] The single cradle may rotate about its own longitudinal axis. Additionally or alternatively, when the cradle is closed, the first and second cradles may rotate about the longitudinal axis to allow the wind turbine blade formed by the first and second blade shells to rotate when the shells are joined together in the closed cradle.

[0070] In another aspect, the invention relates to a manufacturing system for manufacturing a wind turbine blade formed from a pair of cured blade shells bonded together, the system comprising:

[0071] - a first blade mould for forming a cured blade element of a first blade shell;

[0072] - a second blade mould for forming a cured blade element of a second blade shell;

[0073] a reinforcement station comprising a first bracket for receiving a cured blade element of a first blade shell and for forming a reinforcement section on the cured blade element of the first blade shell, and a second bracket for receiving a cured blade element of a second blade shell and for forming a reinforcement section on the cured blade element of the second blade shell,

[0074] - a closing mechanism operable to close said first blade shell and said second blade shell to form a wind turbine blade,

[0075] Wherein each carrier comprises a mould body having a moulding surface, and wherein each cured blade element is arrangeable in its respective carrier such that the moulding surface or a part thereof abuts against a surface of the cured blade element.

[0076] According to a preferred embodiment, each curing blade element may be arranged in its respective bracket such that a section of the moulding surface is placed below a portion of the curing blade element, said portion comprising a recess for accommodating the reinforcement section. In some embodiments, each curing blade element is arranged in its respective bracket such that a section of the moulding surface is in contact with a section of the bottom surface of the curing blade element, wherein said section of the bottom surface is opposite to a section of the top surface of the curing blade element, said section of the top surface comprising a recess for accommodating the reinforcement section.

[0077] In a preferred embodiment, each curing blade element may be arranged in its respective carrier such that the moulding surface, or a portion thereof, abuts against a surface of the curing blade element to form a seal therebetween.

[0078] The use of such a manufacturing system enables relatively fast and efficient manufacturing of wind turbine blades, thereby allowing for maximum efficient use of blade moulds. A closing mechanism is operable to join the first blade shell and the second blade shell together to form a wind turbine blade having an upwind section and a downwind section. In one embodiment, the reinforcement station is located in the vicinity of the first blade mould and the second blade mould. Alternatively, the reinforcement station is remote from the first blade mould and the second blade mould. Preferably, the reinforcement station comprises the closing mechanism.

[0079] In a preferred embodiment, the mold body of the carriage comprises a plurality of movable suction cups embedded in the molding surface for engaging the surface of the solidifying blade element. The suction cups can advantageously be moved between an advanced position for engaging the surface of the solidifying blade element and a retracted position for forcing the surface of the solidifying blade element against the molding surface of the mold body.

[0080] In a preferred embodiment, each suction cup is movable via an airtight passage provided in the mold body. Such an airtight passage may be provided by an airtight sleeve or sheath arranged in the mold body, thereby allowing linear movement of a support member (such as a rod or bar) to which the suction cup is fixed. The support member may be connected to an actuator, such as a pneumatic or hydraulic actuator, for achieving movement of the support member and the suction cup.

[0081] In a preferred embodiment, the molding surface of the mold body comprises one or more sealing elements. The sealing element may protrude beyond the surrounding molding surface. According to another embodiment, the sealing element is a sealing strip. In a preferred embodiment, such a sealing strip may enclose a section of the molding surface. The sealing element (such as a sealing strip) may be arranged in a groove provided in the molding surface.

[0082] Preferably, the system further comprises a lifting device operable to demould or remove the first and second cured blade elements from the first and second blade moulds. Preferably, the lifting device is also operable to transfer the first and second cured blade elements to the consolidation station.

[0083] The first blade mould and the second blade mould may together form a blade moulding station. Preferably, the first blade mould and the second blade mould are used in a lay-up process of a fibre composite material to produce the first cured blade element and the second cured blade element. Preferably, the manufacturing system further comprises an infusion mechanism operable to infuse the fibre composite material with a resin to cure the fibre composite material to form the first cured blade element and the second cured blade element.

[0084] In a preferred embodiment, the closing mechanism is coupled to the reinforcement station, the closing mechanism being operable to move the first bracket relative to the second bracket to close the first and second blade shells accommodated in the bracket to form a closed wind turbine blade shell.

[0085] Features described above with reference to the method may also be applied to the manufacturing system of the present invention, and vice versa.

[0086] In another aspect, the present invention relates to a wind turbine blade manufactured according to the method described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0087] Certain embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0088] Figure 1 A wind turbine is shown;

[0089] Figure 2 A schematic diagram of a wind turbine blade is shown;

[0090] Figure 3 Shows Figure 2 A schematic diagram of the airfoil profile of a blade;

[0091] Figure 4 is a perspective view of a blade shell manufactured using the method of the present invention, the blade shell comprising a cured blade element and a reinforcement section;

[0092] Figure 5 is a perspective view of a manufacturing system according to the present invention,

[0093] Figure 6 is a perspective view of a mold body according to the present invention,

[0094] Figure 7 is a partial enlarged view of the mold body according to the present invention,

[0095] Figure 8 is a partial cross-sectional view of a mold body according to the present invention,

[0096] Fig. 9 is a perspective view of another embodiment of a mold body according to the present invention,

[0097] Fig.10 is a perspective view of another embodiment of a mold body according to the present invention,

[0098] Fig.11 shows different cross-sectional views of a mold body according to the invention, and

[0099] Fig.12 is a cross-sectional view of another embodiment of a mold body according to the present invention. DETAILED DESCRIPTION

[0100] Figure 1 A conventional modern upwind wind turbine according to the so-called "Danish concept" is illustrated, having a tower 4, a nacelle 6 and a rotor with a substantially horizontal rotor axis. The rotor comprises a hub 8 and three blades 10 extending radially from the hub 8, each blade having a blade root 16 closest to the hub and a blade tip 14 farthest from the hub 8. The rotor has a radius indicated as R. Although a three-bladed upwind wind turbine design is presented here, it should be understood that the present invention is equally applicable to blades of other wind turbine designs, such as two-bladed wind turbines, downwind wind turbines, etc.

[0101] Figure 2 A schematic diagram of a first embodiment of a wind turbine blade 10 according to the invention is shown. The wind turbine blade 10 has the shape of a conventional wind turbine blade and comprises a root region 30 closest to the hub, a profiled or airfoil region 34 farthest from the hub and a transition region 32 between the root region 30 and the airfoil region 34. The blade 10 comprises a leading edge 18 facing the direction of rotation of the blade 10 when the blade is mounted on the hub, and a trailing edge 20 facing in the opposite direction of the leading edge 18.

[0102] The airfoil region 34 (also referred to as the profiled region) has an ideal or almost ideal blade shape in terms of generating lift, while the root region 30 has a substantially circular or elliptical cross section due to structural considerations, which, for example, makes it easier and safer to mount the blade 10 to the hub. The diameter (or chord) of the root region 30 can be constant along the entire root region 30. The transition region 32 has a transition profile that gradually changes from the circular or elliptical shape of the root region 30 to the airfoil profile of the airfoil region 34. The chord length of the transition region 32 generally increases with increasing distance r from the hub. The airfoil region 34 has an airfoil profile with a chord extending between the leading edge 18 and the trailing edge 20 of the blade 10. The width of the chord decreases with increasing distance r from the hub.

[0103] The shoulder 40 of the blade 10 is defined as the location where the blade 10 has its maximum chord length. The shoulder 40 is generally disposed at the boundary between the transition region 32 and the airfoil region 34.

[0104] It should be noted that the chords of different sections of the blade do not typically lie in a common plane, as the blade may be twisted and / or bent (i.e. pre-bent) providing a corresponding twisted and / or curved course for the chord plane, which is most often the case, in order to compensate for the local velocity of the blade which depends on the radius from the hub.

[0105] Figure 3 A schematic diagram of an airfoil profile 50 of a typical blade for a wind turbine is shown, depicting various parameters that are typically used to define the geometry of the airfoil. The airfoil 50 has a pressure side 52 and a suction side 54, which during use - i.e. during rotation of the rotor - typically face the windward (or upwind) side and the leeward (or downwind) side, respectively. The airfoil 50 has a chord 60 of chord length c extending between the leading edge 56 and the trailing edge 58 of the blade. The airfoil 50 has a thickness t, which is defined as the distance between the pressure side 52 and the suction side 54. The thickness t of the airfoil varies along the chord 60. The deviation from the symmetrical profile is given by the camber 62, which is the center line through the airfoil profile 50. This center line can be found by drawing inscribed circles from the leading edge 56 to the trailing edge 58. This center line follows the centers of these inscribed circles, and the deviation or distance from the chord 60 is called the camber f. Asymmetry may also be defined using parameters referred to as camber and camber, which are defined as the distance of the chord 60 from the suction side 54 and the pressure side 52, respectively.

[0106] The airfoil profile is often characterized by the following parameters: chord length c, maximum camber f, location df of maximum camber f, maximum airfoil thickness t (which is the maximum diameter of the inscribed circle along the camber line 62), location dt of maximum thickness t, and nose radius (not shown). These parameters are usually defined as ratios of the chord length c.

[0107] The wind turbine blade may further comprise a pre-bent blade, wherein the body of the blade is designed to have a bend or curvature, preferably in the direction of the pressure side of the blade. The pre-bent blade is designed to flex during operation of the wind turbine, such that the blade straightens under the influence of an optimum wind speed for the wind turbine. Such a pre-bent blade will provide improved performance during operation of the wind turbine, resulting in a number of advantages, such as tower clearance, swept area, blade weight, etc.

[0108] One way to construct the wind turbine blade 10 includes forming the blade 10 into two separate shell pieces - a first piece substantially forming the pressure or upwind side 52 of the blade 10, and a second piece substantially forming the suction or downwind side 54 of the blade 10. Such shell pieces are typically formed in separate open blade molds conforming to the aerodynamic shape of the respective sides, and are subsequently joined together by closing the blade mold to form the wind turbine blade 10.

[0109] Figure 4 A perspective view of a blade shell 100 that can be manufactured using the method and system of the present invention is shown, the blade shell 100 consisting of a cured blade element 102, the blade element 102 comprising an aerodynamic shell portion and a root laminate, and an integrated reinforcement section 104 forming a spar cap or main laminate of the blade shell. The cured blade element 102 may also include a plurality of sandwich core materials arranged on the lateral sides of the reinforcement section 104 (not shown). It should be understood that the present invention can be applied to the manufacture of straight blades or pre-bent blades. Figure 4 The top surface of a blade shell or a cured blade element according to the invention is generally shown, while its bottom surface is Figure 4 facing downward in the view of the

[0110] Figure 5 An embodiment of a manufacturing system for manufacturing a wind turbine blade according to the present invention is illustrated. The manufacturing system comprises a blade molding station 70 and a reinforcement station 90. The blade molding station 70 comprises a set of first blade shell molds 72 and second blade shell molds 74. The blade molds 72, 74 comprise respective first inner surfaces 76 and second inner surfaces 78 arranged to produce first and second shaped blade shells having aerodynamic profiles substantially corresponding to respective upwind (or pressure side) and downwind (or suction side) halves of a wind turbine blade.

[0111] During the manufacture of a wind turbine blade, a layup operation is performed at a blade molding station 70, wherein multiple layers of a preferably fiber-based composite material are applied to the inner surfaces 76, 78 of blade molds 72, 74. The fiber layers are applied to conform to the mold shape and may be arranged in various thicknesses or densities depending on the structural requirements of the wind turbine blade to be manufactured.

[0112] exist Figure 5 In the illustrated embodiment, the blade moulding station 70 is provided with an automated fibre placement apparatus 80 which allows for machine-controlled placement of fibre-based material layers in the blade moulds 72, 74. The automated fibre placement apparatus comprises at least one fibre applicator device suspended on a movable stage arranged above the blade moulds 72, 74, the at least one fibre applicator device being operable to move along the length of the blade moulds 72, 74 so as to apply fibre layers (e.g. fibre tapes) to the inner surfaces 76, 78 of the blade moulds 72, 74.

[0113] However, it should be understood that the manufacturing system of the present invention can be implemented using any suitable placement mechanism, such as manual placement. In addition, the placement operation may include using pultruded elements or composite prepregs in the blade mold as an alternative or supplement to the fiber-based material layer.

[0114] Once sufficient layers of fiber-based material have been applied to the surfaces of the molds 72, 74, a curing operation is then performed to cure the fiber layers to a relatively hardened state. In one embodiment, this may include applying a cover or vacuum bag over the fiber layers to form a container, and then applying vacuum pressure to the interior of the container defined by the vacuum bag and the surfaces of the blade molds 72, 74.

[0115] The curing resin is then poured or injected into the interior of the container, the resin being spread throughout the fiber layers by the effect of the vacuum pressure. The resin is then allowed to cure and harden accordingly and connect the fiber-based material layers into a curing blade element, which preferably includes a cavity for later integration of a reinforcement section (not shown); the curing blade element has a structural profile corresponding to the surface shape of the blade mold 72, 74.

[0116] The term "cured blade element" is used herein to refer to a blade element that has been substantially cured (preferably to the extent that the blade element can be handled without undergoing significant deformation of the shell structure) by a curing operation. The duration for which the curing operation is performed will depend on the type of curing resin used in the manufacture of the blade shell, but may be of the order of 2-3 hours using standard resins. However, it will be appreciated that, after the indicated curing operation, the blade element itself may continue to undergo a curing process within the body of the blade element for several hours.

[0117] Thus, once the blade element has been substantially cured, the associated cover or vacuum bag may be removed and the cured blade element may be demoulded from the blade mould 72, 74. To demould the blade element, any manufacturing equipment that may be disposed above the blade mould 72, 74, such as the automated fibre applicator device 80, may be removed and a lifting device (not shown) may be positioned above the blade element contained in the blade mould 72, 74. The lifting device is operable to lift the cured blade element out of the blade mould 72, 74 and transfer the cured blade element to a consolidation station 90 where consolidation and optional post-moulding operations may be performed.

[0118] It will be appreciated that the transfer operation may be performed using any suitable lifting equipment for transferring wind turbine blade elements, such as a vacuum lift, a crane, a manual lift operation or the like.

[0119] The reinforcement station 90 comprises a first carriage 92 and a second carriage 94, each carriage comprising a mould body 96, 98 supported by a respective support frame. Each cured blade element may be arranged in its respective carriage for forming a reinforcement section on the cured blade element of each blade shell. The formation of the reinforcement section will typically comprise laying up additional fibre material on the cured blade element, preferably in a cavity prepared therein, followed by vacuum assisted resin infusion and curing.

[0120] The first bracket 92 and the second bracket 94 are arranged in a parallel longitudinal relationship, and the first bracket 92 is coupled to the second bracket 94 via a plurality of hinge mechanisms 95. The first bracket 92 is arranged to be hinged relative to the second bracket 94 so that the first bracket 92 is positioned above the second bracket 94 to form a closed arrangement. When in the closed position, the first bracket 92 can also be translationally movable relative to the second bracket 94 to correct the alignment between the first bracket 92 and the second bracket 94. The first bracket 92 can be movable relative to the second bracket 94 along a horizontal and / or vertical axis.

[0121] Examples of post-molding operations that may be performed on the blade shell at reinforcement station 90 may include, but are not limited to: a blade shell repair operation, including repairing any minor defects in the cured blade shell; a blade shell cutting or grinding operation, wherein a portion of the surface of the cured blade shell may be cut away or ground to present a relatively smooth profile; a blade root flange coupling operation, wherein a pair of blade root flanges provided on a first blade shell and a second blade shell are coupled together to form a single integral blade root flange; a gluing operation, wherein an adhesive is applied to the surface of the blade shell to bond the components or blade shells together; a coating operation, wherein the outer surface of the blade shell is coated with a coating (e.g., a gel coat or a suitable erosion-resistant material); a laminate installation operation, wherein a main laminate or other element of the interior of a wind turbine blade may be secured to the inner surface of one of the blade shells for positioning within the interior of the wind turbine blade; an overlamination operation; installation of internal blade components, such as load or deflection monitoring sensors, lightning protection systems, etc.; blade shell geometry survey; a secondary curing operation, such as in an oven; or any other suitable manufacturing or assembly operation.

[0122] Figure 6 One embodiment of a bracket 92 according to the present invention is illustrated. The bracket 92 includes a mold body 96 having a molding surface 97. The mold body 96 is supported by a support frame 99. The mold body 96 also includes a plurality of movable suction cups 100 embedded in the molding surface for engaging the surface of the cured blade element. This is done along the Figure 6 The section line in Figure 8 This can be best seen in the partial cross-sectional view of FIG.

[0123] and Figure 6 compared to, Figure 8 The mold body is shown in a state where a curing blade element 102 has been received therein. The suction cup 100 can be moved, for example, by means of a linearly displaceable rod 105 in an advanced position for engaging the bottom surface of the curing blade element 102 (see Figure 8 a) and a retracted position for forcing the bottom surface of the cured blade element 102 against the molding surface of the mold body 96 (see Figure 8 b). In the illustrated embodiment, the suction cup 100 is movable via an airtight sheath 103 disposed within the mold body, thereby allowing linear movement of the rod 105 to which the suction cup 100 is fixed. This arrangement allows improved resin infusion during the formation of the reinforcement section, since the tightness of the arrangement is no longer dependent on the tightness of the cured blade element. The molding surface abutting against the surface of the cured blade element 102 to form a seal therebetween provides the required tightness regardless of the thickness or material of the cured blade element. Figure 8b also illustrates a vacuum bag 120 held in place by adhesive tape 122, which is applied to the edge of the mold body prior to vacuum assisted resin infusion. During vacuum assisted resin infusion, the shell portion will be pressed against the mold surface to maintain the aerodynamic shape of the profile. In this embodiment, it is advantageous that the sheath of the suction cup is airtight.

[0124] Figure 7 Another embodiment of the present invention is illustrated in a partial enlarged view of FIG. Here, the support frame 99 includes a stationary support member 99a and a movable support member 99b hinged to the stationary support member 99a via a hinge 108. In particular, in combination with a deformable mold body 96, this mechanism can be used to adjust the leading and trailing edges of the blade shell before closing and bonding.

[0125] Fig. 9 Another embodiment of a bracket 92 according to the invention is illustrated. Again, the bracket 92 comprises a mould body 96 having a moulding surface 97. The mould body 96 is supported by a support frame 99. The moulding surface 97 of the mould body 96 comprises a sealing element 110 in the form of a sealing strip which encloses a section 112 of the moulding surface. Thus, the curing blade element can be arranged in the bracket 92 such that the section 112 of the moulding surface enclosed by the sealing element 110 is placed below a part of the curing blade element which comprises a recess for accommodating the reinforcement section. This is done along the Fig. 9 The section line in Fig.11 This is best seen in the cross-sectional view of FIG. Fig.10 The illustrated embodiment further comprises a plurality of movable suction cups 100 embedded in the moulding surface for engaging the surface of the curing blade element.

[0126] Fig.11 Shown along Fig. 9 FIG. 1 is a cross-sectional view of an embodiment of a mold body 96 according to the present invention, taken along the section line in FIG. 1 , but without showing the support frame. Fig.11 As shown in FIG. 1 , the mold body 96 includes a groove 116 enclosing a section 112 of the molding surface. Fig.11 b, the sealing strip 110 is arranged in the groove 116. Fig.11 c, a cured blade element 102 is placed in the mold body 96, the cured blade element 102 comprising a recess 114 for later forming an integrated reinforcement section therein. A section 112 of the molding surface enclosed by the sealing element 110 is located below the portion of the cured blade element 102 comprising the recess 114 for accommodating the reinforcement section 104 (see Fig.11 d). Thus, by providing a seal beneath the relevant portion of the curing blade element 102, an efficient vacuum assisted resin transfer can be achieved.

[0127] Fig.12 A cross-sectional view of another embodiment of a mold body for a bracket according to the present invention is shown. Here, the mold body 116 is arranged so that it contacts only a portion of the lower surface of the cured blade element 102. Similarly, the sealing strip 110 is arranged to enclose the portion of the molding surface that is arranged to form a reinforcement section 104 on the cured blade element 102. In this embodiment, the bracket may include a plurality of movable suction cups 100 placed outside the enclosed sealing section 104 to engage the surface of the cured blade element 102 and ensure the cross-sectional geometry. In this embodiment, the suction cups 100 can be arranged outside the mold body 116. An adhesive tape can be used to fasten a local vacuum bag to the cured blade element 102 around the reinforcement section (not shown). In this case, suction cups and their corresponding linearly displaceable rods 105 can be provided even without an airtight sheath.

[0128] The invention is not limited to the embodiments described herein and may be modified or adapted without departing from the scope of the invention.

Claims

1. A method for manufacturing a wind turbine blade, the method comprising the following steps: - a solidified blade element (102) forming a first blade shell, - a solidified blade element (102) forming a second blade shell, - transferring the cured blade element (102) of the first blade shell to a first bracket (92), - transferring the cured blade elements of the second blade shell to a second cradle (94), wherein each cradle comprises a mould body (96, 98) having a moulding surface (97) which corresponds completely to the surface of an upwind blade shell or a downwind blade shell, and wherein each cured blade element is arranged in its respective cradle such that the moulding surface (97) or a part thereof abuts against the surface of the cured blade element (102), - forming a reinforcement section (104) on the solidified blade element of the first blade shell in the first bracket, - forming a reinforcement section (104) on the solidified blade element of the second blade shell in the second bracket, - closing said first blade shell and said second blade shell to form a closed wind turbine blade shell, and - combining said first blade shell and said second blade shell in said closed wind turbine blade shell to form a wind turbine blade.

2. The method according to claim 1, wherein: Each curing blade element (102) is arranged in its respective carrier such that a section of the moulding surface is placed beneath a portion of the curing blade element (102) comprising a recess for receiving the reinforcement section.

3. The method according to claim 1 or 2, wherein: Each curing blade element is arranged in its respective carrier so that the moulding surface (97) or a portion thereof abuts against a surface of the curing blade element (102) to form a seal therebetween.

4. A method according to any one of the preceding claims, wherein: The mould body (96) comprises a plurality of movable suction cups (100) embedded in the moulding surface (97) for engaging the surface of the curing blade element.

5. The method according to claim 4, wherein: The suction cup (100) is movable between an advanced position for engaging a surface of the curing blade element (102) and a retracted position for forcing the surface of the curing blade element (102) against the molding surface of the mold body (96).

6. A method according to any one of the preceding claims, wherein: The molding surface of the mold body (96) includes one or more sealing elements (110).

7. The method according to claim 6, wherein: The sealing element (110) is a sealing strip enclosing a section (112) of the molding surface.

8. The method according to claim 6 or 7, wherein: Each curing blade element (102) is arranged in its respective carrier such that a section of the moulding surface enclosed by the sealing element is placed beneath a portion of the curing blade element (102) comprising a recess for accommodating a reinforcement section.

9. A method according to any one of the preceding claims, wherein: The mold bodies (96, 98) are elastically deformable.

10. A method according to any one of the preceding claims, wherein: The first bracket (92) is hingedly coupled to the second bracket (94).

11. A method according to any one of the preceding claims, wherein: The reinforcement section is a main laminate, a spar cap or a spar cross member.

12. A method according to any one of the preceding claims, wherein: The method comprises the step of rotating the first blade shell relative to the second blade shell to form a closed blade shell, and wherein a bonding step is performed on the closed blade shell to form a wind turbine blade.

13. A method according to any one of the preceding claims, wherein: The method further comprises the step of aligning the first blade shell with the second blade shell such that during the bonding step, a leading edge and a trailing edge of the first blade shell are in register with a corresponding leading edge and a corresponding trailing edge of the second blade shell.

14. A manufacturing system for manufacturing a wind turbine blade, the wind turbine blade being formed from a pair of bonded together cured blade shells, the system comprising: - a first blade mould (72) for forming a cured blade element (102) of a first blade shell; - a second blade mould (74) for forming a cured blade element (102) of a second blade shell; a reinforcement station (90) comprising a first bracket (92) for receiving the cured blade element of the first blade shell and for forming a reinforcement section (104) on the cured blade element of the first blade shell, and a second bracket (94) for receiving the cured blade element of the second blade shell and for forming a reinforcement section (104) on the cured blade element of the second blade shell, - a closing mechanism operable to close said first blade shell and said second blade shell to form a wind turbine blade, wherein each bracket (92, 94) comprises a mould body (96, 98) having a moulding surface (97) which corresponds exactly to the surface of an upwind blade shell or a downwind blade shell, and wherein each cured blade element (102) can be arranged in its respective bracket such that the moulding surface or a part thereof abuts against the surface of the cured blade element.

15. The manufacturing system according to claim 14, wherein: Each curing blade element (102) may be arranged in its respective carrier such that a section of the moulding surface is placed beneath a portion of the curing blade element (102) comprising a recess for receiving the reinforcement section.

16. The manufacturing system according to claim 14 or 15, wherein: Each curing blade element (102) may be arranged in its respective carrier such that the moulding surface or a portion thereof abuts against a surface of the curing blade element to form a seal therebetween.

17. A wind turbine blade manufactured according to the method of any one of claims 1-13.

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