This is a National Phase Application filed under 35 U.S.C. 371 as a national stage of PCT/EP2017/081222, filed Dec. 1, 2017, an application claiming the benefit of European Application No. 16201924.4, filed Dec. 2, 2016, the content of each of which is hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to a method of manufacturing a plurality of wind turbine blades, to a manufacturing system for said method and to a wind turbine blade obtainable by said method.

BACKGROUND OF THE INVENTION

Wind power is becoming increasingly popular due to its clean and environmentally friendly production of energy. The rotor blades of modern wind turbines capture kinetic wind energy by using sophisticated blade design created to maximize efficiency. Turbine blades may today exceed 80 metres in length and 4 metres in width. The blades are typically made from a fibre-reinforced polymer material and comprise a pressure side shell half and a suction side shell half. The cross-sectional profile of a typical blade includes an airfoil for creating an air flow leading to a pressure difference between both sides. The resulting lift force generates torque for producing electricity.

The shell halves of wind turbine blades are usually manufactured using moulds. First, a blade gel coat or primer is typically applied to the mould. Subsequently, fibre reinforcement and/or fabrics are placed into the mould followed by resin infusion. A vacuum is typically used to draw epoxy resin material into a mould. Alternatively, prepreg technology can be used, in which a fibre or fabric pre-impregnated with resin forms a homogenous material which can be introduced into the mould. Several other moulding techniques are known for manufacturing wind turbine blades, including compression moulding and resin transfer moulding. The shell halves are assembled by being glued or bolted together substantially along a chord plane of the blade.

In vacuum assisted resin transfer moulding (VARTM), glass fibre plies are placed in a mould with the correct orientation and subsequently resin is forced to flow through the fibres using a vacuum pump. This is usually followed by a curing cycle at atmospheric pressure.

A typical moulding process includes bagging, resin infusion and subsequent curing.

Bagging involves placing a vacuum foil on the fibre plies that have been laid up on the tool. The vacuum foil is used to press this part to the tool and to allow a vacuum to be drawn into the void formed by the bag and the tool such that the fibres of the part are infused with resin. Typical vacuum foils may be formed by one or more plastic sheets which are placed to cover the blade. Infusion comprises feeding resin under a vacuum to wet the laid out fibres to form a solid shell part. In subsequent curing, heating and subsequently cooling may be applied to harden the resin.

International patent application WO 2013/113815 A1 relates to a manufacturing method for a wind turbine blade wherein a blade shell is initially moulded in a blade mould and subsequently transferred to a post-moulding station. Closing of a first and second blade half is performed at the post-moulding station which comprises an adjustable structure.

On the background of such prior art approaches it is a first object of the present invention to provide a method for moulding a shell part of a wind turbine blade which results in reduced cost and increased productivity of the manufacturing process.

It is another object of the present invention to provide a method for moulding a shell part of a wind turbine blade that is simple and applicable to a wide range of wind turbine blade types.

SUMMARY OF THE INVENTION

In a first aspect, the present invention relates to a method of manufacturing a plurality of wind turbine blades, the method comprising the steps of:a) providing a first stationary mould for moulding a lower shell half, providing a second stationary mould for moulding a lower shell half, and providing a third stationary mould for moulding an upper shell half,b) moulding a first lower shell half in the first stationary mould,c) moulding a first upper shell half in the third stationary mould,d) removing the first upper shell half from the third stationary mould,e) turning the first upper shell half relative to the first lower shell half and positioning the first upper shell half on the first lower shell half in the first stationary mould to form a closed wind turbine blade shell,f) bonding the first upper and lower shell halves to form a first wind turbine blade and subsequently removing the first wind turbine blade from the first stationary mould,g) moulding a second lower shell half in the second stationary mould before or during steps e) and/or f),h) moulding a second upper shell half in the third stationary mould during steps e) and/or f),i) removing the second upper shell half from the third stationary mould,j) turning the second upper shell half relative to the second lower shell half and positioning the second upper shell half on the second lower shell half in the second stationary mould to form a closed wind turbine blade shell, andk) bonding the second upper and lower shell halves to form a second wind turbine blade and subsequently removing the second wind turbine blade from the second stationary mould.

The present inventors have found that this method results in a considerable reduction of production costs as compared to prior art methods. Also, since the blade moulds do not have to be linked via a hinged turning mechanism, as in some prior art systems, space requirements are significantly lower, which makes the method flexible, simple and cost effective. Since the stationary moulds can be easily sourced and replaced, the present method is widely applicable to different blade types.

As used herein, the term “upper shell half” relates to the suction side shell half, whereas the term “lower shell half” relates to the pressure side shell half of a wind turbine blade. Preferably, the pressure side or suction side shell halves extend between a leading edge end and a trailing edge end to be located at respective leading and trailing edges of a finished wind turbine blade.

The stationary moulds of the present invention are substantially fixed moulds, such as moulds having substantially rigid foundations, such as concrete foundations. Providing the blade moulds as stationary moulds has the advantage of a relatively easily mould production, thus reducing expenses in this regard.

The moulding steps typically involve laying up a fibre-based material in the mould to form an uncured wind turbine blade shell half. The lay-up may be a manual or hand lay-up operation, or an automatic lay-up operation, e.g. spray lay-up, tape lay-up, fibre pultrusion, or automotive lay-up of plies. Typically, this is followed by a curing step which involves infusing said uncured shell half with a resin to cure the shell half. This infusion step may be an automatic or a manual process.

The moulded shell half has typically been substantially cured by the curing operation, preferably to a level where the blade shells can be handled without undergoing significant deformation of the shell structure. The duration of the curing operation performed will depend on the type of curing resin used in the manufacture of the blade shells, but may be on the order of 2-3 hours using standard resins. However, it will be understood that the blade shells may continue to undergo a curing process within the body of the blade shells for several hours after the denoted curing operation.

It will be understood that said curing steps comprises curing said shell half to a level wherein the shell half may be removed from a blade mould without deformation. It will further be understood that subsequent curing of the shell half may occur or the shell half may undergo a second curing operation after demoulding from the blade mould, e.g. in a dedicated curing oven.

The bonding step may involve applying an adhesive at a leading edge and a trailing edge of at least one of said shell halves, wherein said step of bonding may comprise arranging said shell halves to adhere the leading edge of the lower shell half to the leading edge of the upper shell half, and to adhere the trailing edge of the lower shell half to the trailing edge of the upper shell half. It will be understood that the invention is not limited to a direct connection between the respective leading and trailing edges of the shell halves, e.g. a tail piece or insert may be positioned between the leading edges and/or trailing edges of the shell halves.

The bonding step may further comprise the step of performing at least one intra-bonding operation on at least one of said shell halves. Preferably, said at least one intra-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.

Preferably, the method comprises repeating steps b) to k) for continuously manufacturing a plurality of wind turbine blades. Thus, during every positioning and/or bonding step in either of the first or second stationary moulds, the respective other mould for the lower shell half as well as the third stationary mould can be used for moulding the next lower and upper shell halves. It is thus preferred that in the second and each subsequent cycle, step b) is carried out before or during steps j) and/or k) of the previous cycle. Likewise, it is preferred that in the second and each subsequent cycle, step c) is carried out during steps j) and/or k) of the previous cycle.

In one embodiment, steps d) and/or i) comprise lifting the upper shell half from the third stationary mould to an elevated position. This may be done by a crane or similar lifting device.

In a preferred embodiment, a lifting beam is attached to the upper shell half prior to said lifting. The lifting beam may have an attachment point or lug arranged on its top side for connecting to a crane or other lifting device. Typically, the lifting beam is attached to the upper shell half on the underside of the beam.

Preferably, the lifting step is carried out by at least one crane device. In one embodiment, steps e) and/or j) comprise turning the upper shell half relative to the lower shell half in said elevated position, preferably using the crane device.

According to one embodiment of the present invention, the positioning operation of steps e) and/or j) comprises aligning the upper shell half with the lower shell half such that a leading edge and a trailing edge of the upper shell half are in register with a respective leading edge and a respective trailing edge of the lower shell half.

In a preferred embodiment, the third stationary mould comprises a flange portion comprising one or more through holes, wherein steps c) and/or h) involve arranging fibre material and/or resin over at least part of said flange portion, wherein steps c) and/or h) further involve drilling one or more bores into said fibre material and/or resin from underneath said flange portion using the through holes as drilling guide. Preferably, the third stationary mould comprises a flange portion on each side of the mould, each flange portion comprising one or more through holes, such as two or more, or three or more through holes.

Advantageously, the first and/or second stationary mould comprises a flange portion comprising one or more pins projecting upwardly from the flange portion, and wherein the positioning operation of steps e) and/or j) involves engaging said one or more pins within the respective bores. Preferably, the first and/or second stationary mould comprises a flange portion on each side of the mould, each flange portion comprising one or more pins, such as two or more, or three or more pins.

Typically, the method further comprises the step of performing at least one post-bonding operation on at least one of said blades subsequent to said bonding operations. Said post-bonding operation may be selected from one or more of the following: a leading edge grinding operation, wherein the leading edge surface of the bonded wind turbine blade is ground to a smooth surface; a trailing edge grinding operation, wherein the trailing edge surface of the bonded wind turbine blade is ground to a smooth surface; a blade repair operation, wherein a defect in the blade surface may be corrected, e.g. by applying a filler material; a coating operation, wherein at least one layer of gel coat or erosion resistant material or tape is applied to the external surface of the bonded wind turbine blade.

In another embodiment, the bonding operation of steps f) and/or k) involves clamping the upper shell half to the lower shell half. This could be done by using moveable vacuum clamps to secure the shell halves.

In another aspect, the present invention relates to a manufacturing system for the manufacture of wind turbine blades according to the method of the present invention, the system comprising:a first stationary mould for moulding a lower shell half,a second stationary mould for moulding a lower shell half,a third stationary mould for moulding an upper shell half,lifting means for removing an upper shell half from the third stationary mould,turning means for turning an upper shell half relative to a lower shell half,positioning means for positioning an upper shell half on a lower shell half in the first or second stationary mould to form a closed wind turbine blade shell.

Preferably, the lifting means, the turning means and/or the positioning means comprise at least one crane device. Preferably, said crane device constitutes each of said lifting means, turning means and positioning means. Said manufacturing system preferably also comprises one or more lifting beams that are attachable to the upper shell half prior to its lifting. The lifting beam may have an attachment point or lug arranged on its top side for connecting to a crane or other lifting device. Typically, the lifting beam is attached to the upper shell half on the underside of the beam.

In a preferred embodiment, the third stationary mould comprises a flange portion comprising one or more through holes. It is also preferred that the first and/or second stationary mould comprises a flange portion comprising one or more pins projecting upwardly from the flange portion for being able to carry out the above-described positioning step.

In another aspect, the present invention relates to a wind turbine blade manufactured according to the method of the present invention.

