Patent Description:
Wind power is a clean and environmentally friendly source of energy. Wind turbines usually comprise a tower, generator, gearbox, nacelle, and one or more rotor blades. The wind turbine blades capture kinetic energy of wind using known airfoil principles. Modern wind turbines may have rotor blades that exceed <NUM> meters in length.

Wind turbine blades are usually manufactured by forming two shell parts or shell halves from layers of woven fabric or fibre and resin. Spar caps or main laminates are placed or integrated in the shell halves and may be combined with shear webs or spar beams to form structural support. Spar caps or main laminates may be joined to, or integrated within, the inside of the halves of the shell.

A number of manufacturing steps become more complicated as the blades increase in size. Any mistake made somewhere in the process is increasingly more time consuming to correct. One such process step is precise laying of fibres layers and precured elements on fibre layers already laid up in a blade part mould. Additionally, it is a problem to provide the spar cap with the desired dimensions and tolerances especially of the width and thickness. The width thickness and length of the spar cap usually increase with the size of the blade.

When manufacturing a wind turbine blade shell part, layers of dry fibre, such as fibre mats, are typically laid up first in a blade shell part mould. These layers will constitute the outer skin of the shell part. After adding the fibre layers, additional layers forming part of the spar cap, one or more precured elements can be added, forming a further part of the spar cap blade shell part. Spar caps are advantageously provided using this method. Adding the additional layers and the precured elements onto the outer skin fibre layers is tedious, and often the fibre layers get displaced or wrinkled or misplaced, thereby reducing the dimensional tolerances and the quality of the spar and the wind turbine blade shell and thereby probably also the complete blade shell.

<CIT> discloses a method and system for manufacture of a wind turbine blade by providing a plurality of precured elongate elements of a fibre reinforced resin composite material, stacking the plurality of precured elements with an interlayers of an elongate non-cured fibre material, thereby forming a stack of precured elements and interlayers and infusing resin into the stack of precured elements and interlayers in the mould.

It is therefore desirable to provide a method of manufacturing eliminating or reducing the drawbacks of known methods and provide an effective and reliable method of manufacturing spar caps of the desired dimensions and tolerances.

The present invention provides a method of manufacturing as defined in claim <NUM> as well as a system for manufacturing as defined in claim <NUM>, eliminating or reducing the drawbacks of known methods.

The present invention provides a method of manufacturing a spar cap for a wind turbine blade part, comprising the steps of:.

The present invention provides for a spar cap having dimensions with close tolerances as the spar cap is moulded in a spar cap mould maintaining the cured elements and the interlayer(s) in the desired position and preventing displacement thereof.

The plurality of precured elements can be stacked in a single row or in two or more rows of precured elements arranged laterally adjacent each other.

According to an embodiment the precured elements comprise carbon fibres and/or glass fibres.

According to a further embodiment the resin of resin composite material of the precured elements is epoxy resin, vinyl ester resin or polyester resin.

According to an additional embodiment the resin infused into the stack of precured elements and interlayer(s) is of the same type as the resin of the precured elements.

The resin infused into the stack of precured elements and interlayer(s) can also be of a type different from the resin of the precured elements.

According to an at present preferred embodiment the precured elements are plank-shaped or strip-shaped.

According to an additional at present preferred embodiment the plurality of precured elements are pultruded elements.

The fibres of the fibres material of the interlayer(s) can comprise glass fibres and/or carbon fibres.

In an embodiment the step of stacking of the precured elements to form a stack of precured elements and interlayer(s) comprises:.

Thereby it is advantageously obtained that the cured elements and the interlayer(s) are arranged precisely aligned when arranged in the mould and the dimensional tolerances improved.

According to an embodiment the step of moving the stack of precured elements and interlayer(s) to a spar cap mould comprises:.

According to a further embodiment the step of arranging the stack of precured elements and Interlayer(s) in the cavity of the spar cap mould comprises:.

According to an additional embodiment the step of arranging the stack of precured elements and interlayer(s) in the cavity of the spar cap mould comprises:.

Thereby the stack can be gently and precisely lowered down onto the surface of the bottom.

All the clamping devices can be removed from the stack after the stack has been arranged on the support members. Alternatively, the clamping devices can be removed gradually from the stack simultaneously with the removal of the support members or gradually prior to the gradual removal of the support members.

According to an embodiment the support members extend transversely of the elongate spar cap mould and are supported by upper faces of side walls of the mould.

The support members can be cylindrical members.

According to an advantageous embodiment of the method of the present invention comprises coating the surfaces of the mould bottom and the side walls of the mould cavity by a slip coating, such as a peel ply, prior to arranging the stack of precured elements and interlayer(s) in the cavity of the spar cap mould.

According to a further advantageous embodiment the step of infusing resin into the stack of precured elements and interlayer(s) in the mould comprises: coating the upper surface of the stack of precured elements and interlayers with a peel coating, such as peel ply, and cover the cavity of the spar cap mould with a vacuum bag and infuse the resin by vacuum assisted resin transfer moulding (VARTM).

An embodiment of the present invention of the can comprise carrying out an inspection of the cured stack of precured elements and interlayer(s) after the cured stack has been removed from the spar cap mould, conduct any required repairs of the cured stack and send the stack to shell part mould or a storage.

The cured stack of elements and interlayer(s), i.e. the cap, can have a width in the range <NUM>-<NUM>, a thickness or height in the range of <NUM>-<NUM> and a length in the range <NUM>-<NUM>.

At the shell part mould the cured stack of cured elements and interlayer(s), i. e the spar cap, is placed on the desired place of one or more fibres layers arranged in the shell part mould and additional shell materials and consumables are added, where after the shell part is infused, such as by VARTM.

A second aspect of the present invention relates to a wind turbine blade being provided with a spar cap manufactured by the method according to the present invention.

A third aspect of the present invention related to a wind turbine rotor being provided with at least one blade being provided with a spar cap manufactured by a method according to the present invention.

A fourth aspect of the present invention relates to a wind turbine comprising a wind turbine rotor being provided with at least one blade being provided with a spar cap manufactured by a method according to the present invention.

Embodiments of the invention will be described in more detail in the following with regard to the accompanying figures. The figures show one way of implementing the present invention and are not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.

<FIG> illustrates a conventional modern upwind wind turbine <NUM> according to the so-called "Danish concept" with a tower <NUM>, a nacelle <NUM> and a rotor with a substantially horizontal rotor shaft. The rotor includes a hub <NUM> and three blades <NUM> extending radially from the hub <NUM>, each blade having a blade root <NUM> nearest the hub and a blade tip <NUM> furthest from the hub <NUM>. The invention is not limited to use in wind turbines of this type.

The wind turbine blade <NUM> has the shape of a conventional wind turbine blade with a root end <NUM> and a tip end <NUM> and comprises a root region <NUM> closest to the hub, a profiled or airfoil region <NUM>, and a transition region <NUM> between the root region <NUM> and the airfoil region <NUM>.

The airfoil region <NUM> (also called the profiled region) preferably has an ideal shape with respect to generating hub rotation, whereas the root region <NUM> due to structural considerations has a substantially circular or elliptical cross-section, which for instance makes it easier and safer to mount the blade <NUM> to the hub. The diameter of the root region <NUM> may be constant along the entire root area <NUM>. The transition region <NUM> present in the wind turbine blade <NUM> in this example has a transitional profile gradually changing from the circular shape of the root region <NUM> to the airfoil profile of the airfoil region <NUM>. The chord length of the transition region <NUM> typically increases in an outward direction from the hub.

It should be noted that different sections of the blade normally do not have a common plane, since the blade may be twisted and/or curved (i.e. pre-bent) along a direction from the root region to the tip, this being most often the case, for instance to more or less compensate for the local velocity of the blade being dependent on the distance from the hub.

The wind turbine blade <NUM> comprises a blade shell which may for instance comprise two blade shell parts, a first blade shell part <NUM> and a second blade shell part <NUM>, for instance made at least partly of fibre-reinforced polymer. The first blade shell part <NUM> may for instance be part of a pressure side or upwind blade part. The second blade shell part <NUM> may for instance be part of a suction side or downwind blade part. The first blade shell part <NUM> and the second blade shell part <NUM> are typically joined together, such as glued together, along bond lines or glue joints <NUM> extending along the trailing edge <NUM> and the leading edge <NUM> of the blade <NUM>. Typically, the root ends of the blade shell parts <NUM>, <NUM> have a semi-circular or semi-oval outer cross-sectional shape that, when the first and second shell parts are joined, forms the root region, such as a circular or oval root region.

<FIG> is a schematic diagram illustrating a cross-sectional view of the exemplary wind turbine blade <NUM>, corresponding to line A-A in <FIG>. The wind turbine blade <NUM> comprises shear webs <NUM>, a first spar cap <NUM> that is part of the pressure side <NUM> of the blade <NUM>, and a second spar cap <NUM> that is part of the suction side <NUM> of the blade <NUM>. The spar caps provide structural strength to the blade and typically extend along the blade in a spanwise direction. Typically, spar caps will extend over <NUM>-<NUM>% of the blade length. The trailing edge <NUM> and leading edge <NUM> are also indicated in <FIG>.

<FIG> illustrates a first step of the method according to the present invention for manufacturing a spar cap , such as the spar caps <NUM> and <NUM> in <FIG> and where a plurality of precured elongate elements <NUM> of a fibre reinforced resin composite material are provided, preferably pultruded elements comprising carbon fibre. The precured elements <NUM> comprise a first main surface <NUM> and an opposite second main surface <NUM> and a first lateral face <NUM> and an opposite second lateral face <NUM> and a first end <NUM> and an opposite second end <NUM>, not shown in <FIG>. The precured elements <NUM> are stacked with an interlayer <NUM> of a non-cured fibre material between the first and second main surface <NUM>,<NUM> of successive precured elements <NUM>, thereby forming a loose stack <NUM> of precured elements <NUM> and interlayers <NUM>. The interlayers comprise carbon and/or glass fibres. In the embodiment shown the loose stack <NUM> comprises an array of two lateral adjacent rows, each comprising four elongate precured elements <NUM> separated by three interlayers <NUM>. The loose stack <NUM> has an upper stack surface <NUM>, an opposite lower stack surface <NUM>, a first lateral stack face <NUM> and an opposite second lateral stack face <NUM> and a first stack end <NUM> and an opposite second stack end <NUM>. The first and second stack end are not shown in <FIG>.

During stacking the precured elements <NUM> and interlayers <NUM> or after said stacking at least the lateral side walls <NUM>,<NUM> of the precured elements <NUM> are aligned and they are kept aligned by means of longitudinally spaced loose stack clamping devices <NUM>. A loose stack clamping device <NUM> surrounding a loose stack <NUM> is illustrated in <FIG>.

In the next step of the method of the present invention the loose stack <NUM> surrounded by the mutually spaced loose stack clamping devices <NUM> is moved to a spar cap mould <NUM> by connecting a lifting device, in the embodiment shown a lifting beam <NUM> with lifting ropes, to the loose stack clamping devices <NUM>, as shown in <FIG>. The loose stack <NUM> is moved to the spar cap mould and arranged above the mould essentially vertically in line with the mould <NUM>, as shown in <FIG> is a cross sectional view in reduced scale along the line C-C in <FIG> is a view in enlarged scale along the line D-D in <FIG>.

The loose stack of precured elements <NUM> and interlayers <NUM> can now be brought into the cavity <NUM> of the mould. However, before that is done a peel ply <NUM> is applied on the bottom surface <NUM> and the side wall surfaces <NUM> of cavity <NUM> of the mould <NUM>, as shown in <FIG>.

The loose stack <NUM> can be arranged in the cavity <NUM> of the mould by gradually bringing the lower stack surface <NUM> into contact with the bottom surface <NUM> of the mould <NUM> by gradually lowering the loose stack clamping devices <NUM> starting at the first stack end <NUM> and ending at the opposite second stack end <NUM> and simultaneously gradually removing the loose stack clamping devices starting at the clamping device closest to the first end <NUM> of the loose stack <NUM> and ending at the clamping device closest to the second end <NUM> of the loose stack <NUM>.

Alternatively, the loose stack can be arranged in the cavity <NUM> of the mould <NUM> by arranging a plurality of transversely extending and longitudinally mutually spaced support members in the form of cylindrical rollers <NUM> on the upper surfaces <NUM>,<NUM> of the side walls <NUM>,<NUM> of the mould <NUM>. Thereafter the loose stack <NUM> can be lowered downwards to be supported by the plurality of longitudinally spaced rollers <NUM>, as shown in <FIG>. Each roller <NUM> supports a portion of the loose stack <NUM>. The loose stack clamping devices <NUM> can now be removed from the loose stack. The lower surface <NUM> of the loose stack <NUM> is gradually brougt into contact with the surface <NUM> of the mould bottom of the mould cavity <NUM>, starting at the first stack end <NUM> and ending at the opposite second stack end <NUM>, by simultaneously gradually removing or displacing the rollers <NUM> starting from the roller closest to the first stack end <NUM> and ending at the support member closest to the opposite second stack end <NUM>, as shown in <FIG> disclose the situation where rollers <NUM> at the forward end of the loose stack <NUM> has been removed and the forward end of the loose stack has contacted the surface <NUM> of the bottom of the cavity <NUM> of the spar cap mould <NUM>.

All the clamping devices <NUM> can be removed from the stack <NUM> after the stack has been arranged on the rollers <NUM>. Alternatively, the clamping devices <NUM> can be removed gradually from the stack <NUM> simultaneously with the removal of the rollers <NUM> or gradually prior to the gradual removal of the rollers <NUM>.

As shown in <FIG> a peel ply <NUM> is arranged on the upper stack surface <NUM> when the entire length of the lose stack <NUM> has been arranged in the cavity <NUM> of the mould <NUM>. Thereafter, the cavity is covered with a vacuum bag <NUM>, vacuum is provided in the mould cavity and resin supplied to the mould cavity, i.e. resin is infused by vacuum assisted resin transfer moulding (VARTM). Subsequently the resin is allowed to cure, thereby forming the spar cap <NUM>, and the cured stack of precured elements and interlayers is removed from the mould as a spar cap <NUM> surrounded by peel ply <NUM>, as shown in <FIG>.

Claim 1:
Method of manufacturing a spar cap (<NUM>) for a wind turbine blade part (<NUM>), comprising the steps of:
- providing a plurality of precured elongate elements (<NUM>) of a fibre reinforced resin composite material comprising a first main surface (<NUM>) and a second opposite main surface (<NUM>) and a first lateral face (<NUM>) and a second opposite lateral face (<NUM>) and a first end and an opposite second end (<NUM>),
- stacking the plurality of precured elements, an interlayer (<NUM>) of an elongate non-cured fibre material being arranged between the first and second main surface of successive precured elements, thereby forming a stack (<NUM>) of precured elements (<NUM>) and interlayer(s), the stack having a lower stack surface (<NUM>, <NUM>) and an opposite upper stack surface (<NUM>), a first lateral stack face (<NUM>, <NUM>) and an opposite second lateral stack face (<NUM>), and a first stack end (<NUM>) and an opposite second stack end (<NUM>),
- moving the stack of precured elements and interlayer(s) to a spar cap mould comprising a mould bottom and mould side walls,
- arranging the stack of precured elements and interlayer(s) in the cavity of the spar cap mould I. (<NUM>)
- infusing resin into the stack of precured elements and interlayers in the mould,
- allow the resin to cure to form a cured stack of precured elements and interlayer(s) forming a spar cap,
- remove the cured stack of precured elements and interlayer(s) in from the mould, i.e. demould the stack.