WO2012093136A2

WO2012093136A2 - Mould and method for manufacturing shell parts

Info

Publication number: WO2012093136A2
Application number: PCT/EP2012/050078
Authority: WO
Inventors: Peter Bæk
Original assignee: Lm Wind Power A/S
Priority date: 2011-01-05
Filing date: 2012-01-04
Publication date: 2012-07-12
Also published as: WO2012093136A3

Abstract

The mould (70) for manufacturing a shell part of a wind turbine blade comprises a moulding surface (76) with a shape that defines a surface of the shell part. The moulding surface has a longitudinal direction (114) and a total length. The moulding surface (76) comprises a flexible part (72, 96) extending in the longitudinal direction of the moulding surface (76) and having a length (l) corresponding to at least 1/10 of the total length (L) of the moulding surface (76).Furthermore, a method for manufacturing shell parts is disclosed.

Description

Mould and method for manufacturing shell parts

Field of the Invention

The present invention relates to a mould for manufacturing a shell part of a wind turbine blade structure, the structure comprising a fibre reinforced matrix material and having a longitudinal direction, the mould comprising a moulding surface with a shape that defines a surface of the shell part, and the moulding surface having a longitudinal direction and a total length. The invention further relates to a method of manufacture using such a mould.

Background of the Invention

Manufacturing of large wind turbine blade structures is by nature space consuming. Furthermore, this problem is enhanced as even a minor change in the structure, e.g. only relating to one end of the structure, commonly re- quires a complete, separate mould.

Wind turbine blades of fibre-reinforced polymer are usually manufactured as shell parts in moulds, where the top side and the bottom side of the blade profile (typically the pressure side and suction side, respectively) are manu- factured separately by arranging glass fibre mats in each of the two mould parts. Afterwards, the two halves are glued together, often by means of internal flange parts. Glue is applied to the inner face of the lower blade half before the upper blade half is lowered thereon. Additionally, one or two reinforcing profiles (beams or webs) are often attached to the inside of the lower blade half prior to gluing to the upper blade half.

The shell parts for the wind turbine blade are typically manufactured as fibre composite structures by means of VARTM (vacuum assisted resin transfer moulding), where liquid polymer, also called resin, is filled into a mould cav- ity, in which fibre material has been priorly inserted, and where a vacuum is generated in the mould cavity, hereby drawing in the polymer. The polymer can be thermoset plastic or thermoplastics.

Vacuum infusion or VARTM is a process used for moulding fibre composite mouldings, where uniformly distributed fibres are layered in one of the mould parts, the fibres being rovings, i.e. bundles of fibre bands, bands of rovings, or mats, which are either felt mats made of individual fibres or woven mats made of fibre rovings. The second mould part is often made of a resilient vacuum bag, and is subsequently placed on top of the fibre material. By gen- erating a vacuum, typically 80% to 95% of the total vacuum, in the mould cavity between the inner side of the mould part and the vacuum bag, the liquid polymer can be drawn in and fill the mould cavity with the fibre material contained herein. So-called distribution layers or distribution tubes, also called inlet channels, are used between the vacuum bag and the fibre mate- rial in order to obtain as sound and efficient a distribution of polymer as possible. In most cases, the polymer applied is polyester or epoxy, and most often the fibre reinforcement is based on glass fibres or carbon fibres.

From DE 198 33 869 C1 it is known to provide a mould for wind turbine blades in a number of sections. In an embodiment, separate mould sections are provided for the root region, the mainboard region and the tip region. However, in order to accommodate even a minor change in the structure of the wind turbine blade, a complete, separate mould section is required. In a further consideration, it is desired to provide an improved manufacturing process for wind turbine blades.

A wind farm in general comprises a plurality of individual wind turbines having at least two wind turbine blades, the individual wind turbines distributed across the wind farm. A wind farm is generally classified as having a particular wind class, e.g. IEC Wind Class I, II, or III, and wind turbine blades for the wind farm are manufactured according to the suitability of the blades for that wind class.

However, while the general wind conditions for the wind farm may be classi- fiable as a particular wind class, the individual wind turbines in the farm may encounter localised environmental conditions dependent on turbine location. For example, the airflow at a particular turbine may be disrupted by upwind positioning of other turbines in the farm, or local geography at the turbine, e.g. hills or chasms, may cause updrafts at the turbine location. In such a situation, as each of the wind turbines in the wind farm are designed to accommodate the ideal wind conditions at the wind farm, due to the localised conditions for each turbine the individual wind turbine efficiency may be reduced. The object of the present invention is to provide a mould that is more versatile than prior art moulds in terms of being applicable for the manufacture of shell parts having varying structure. There is a further object to provide an improved manufacturing process for wind turbine blades. Summary of the Invention

In view of this object, the moulding surface of an adaptive mould comprises a flexible part extending in the longitudinal direction of the moulding surface and having a length corresponding to at least 1/10 of the total length of the moulding surface.

In this way, the moulding surface of the mould may, along the flexible part of the moulding surface, be adapted to differing shapes of shell parts to be produced, whereby the need for a large number of different moulds or mould sections may be eliminated. Furthermore, by means of the mould according to the invention, even minor changes to the shape of the moulding surface may now be performed in order to fine tune performance, whereby such mi- nor changes previously may have been considered not profitable to perform, as a complete new mould or mould section would have been required.

Preferably, the adaptive mould comprises at least one moveable longitudinal section provided at a trailing edge and/or a leading edge of the moulding surface, and wherein the adaptive mould further comprises at least one substantially rigid longitudinal section adjacent said at least one moveable longitudinal section, said at least one moveable longitudinal section flexibly coupled to said at least one substantially rigid longitudinal section.

Preferably, said at least one moveable longitudinal section is actuatable to form an adjustable leading edge and/or trailing edge surface for a shell part of a wind turbine blade. Preferably, said at least one substantially rigid longitudinal section of said adaptive mould is used to form at least one load-bearing section of a shell part of a wind turbine blade

Preferably, said adaptive mould comprises a plurality of moveable longitudi- nal sections provided at a trailing edge and/or a leading edge of the moulding surface, wherein said plurality of moveable longitudinal sections are individually actuatable.

In an embodiment, the flexible part of the moulding surface extends from an area at the root region to an area at the tip region.

In an embodiment, the flexible part of the moulding surface has a length corresponding to at least 1/2, advantageously at least 2/3, more advantageously at least 3/4 and most advantageously at least 9/10, of the total length of the moulding surface. In an embodiment, the flexible part of the moulding surface is associated with at least one hinge connecting a first part and a second part of the moulding surface. Thereby, the shape of the moulding surface of the mould may flexibly be changed by mutual movement of the first part and the second part relatively to each other.

Said first part and said second part may be hinged together about a hinge axis extending substantially in the longitudinal direction of the mould. Thereby, for instance in the case of the shell parts produced being parts of wind turbine blades, the camber of the blades may be appropriately changed by mutual movement of the first part and the second part relatively to each other.

In an embodiment, the second part of the moulding surface is split up into at least a first and a second section that are individually hinged to the first part. Thereby, the position of different sections of the second part may be changed differently in relation to the first part, thereby enabling varying adaptation of the shape of the moulding surface of the mould over a distance. Thereby, a large number of shell parts having different shapes may be produced by means of one mould. For instance, in the case of the shell parts produced being parts of wind turbine blades, the camber of the blades may be changed differently at different longitudinal positions along the blade by different positioning of different sections of the second part in relation to the first part. In an embodiment, the at least first and second sections of the second part of the moulding surface are hinged together. Thereby, it may be ensured that different sections of the second part do not part from each other, so that they follow each other in succession forming a continuous course. This may contribute to forming a smooth shape of the moulding surface of the mould. In an embodiment, at least one of the hinges connecting parts or sections of the mould are formed by a flexible connection, such as a pivot joint allowing a certain degree of play, or even such as a kind of ball joint. This may contribute further to forming a smooth shape of the moulding surface of the mould. Hinges in the form of such flexible connections may further enable parts or sections of the mould connected by means of the hinges to have a rigid or rather rigid configuration without thereby locking these parts or sections mutually. In an embodiment, the flexible part of the moulding surface of the mould is formed at least partly by a flexible plate element preferably comprising a fibre reinforced matrix material. This may contribute even further to forming a smooth shape of the moulding surface of the mould. In an embodiment, hinges connecting parts or sections of the mould are formed by the flexible plate element. Thereby, flexible hinges may be obtained by the flexible plate element that may also form a part of the moulding surface of the mould. Thereby, a smooth shape of the moulding surface of the mould may be obtained.

In an embodiment, the moulding surface of the mould is shielded from hinges connecting parts or sections of the mould by means of the flexible plate element. Thereby, hinges supporting a structure of connected parts or sections of the mould and/or limiting relative movement between these elements, may be covered by a flexible plate element forming part of the moulding surface of the mould, thereby forming a smooth shape of the moulding surface of the mould.

In an embodiment, an edge of the moulding surface extending along the flexible part of the moulding surface is height adjustable, preferably next to an element adapted to form a sidewall of the mould. Thereby, for instance in the case of the shell parts produced being parts of wind turbine blades, the airfoil profile of the blades may be produced with a pointed trailing edge as well as with a truncated or flat-back trailing edge by appropriate height positioning of said edge of the moulding surface in relation to said element adapted to form a sidewall of the mould. In a top position of said edge in relation to said element adapted to form a sidewall, a pointed trailing edge may be obtained. On the other hand, in a position lower than said top position of said edge in relation to said element adapted to form a sidewall, a truncated or flat-back trailing edge may be produced. Furthermore, by controlling the height position of said edge in relation to said element adapted to form a sidewall, the width of the resulting truncated or flat-back trailing edge may be controlled.

In an embodiment, the flexible part of the moulding surface is supported by one or more individually adjustable actuators, such as electrically driven linear actuators or hydraulic or pneumatic cylinders. Thereby, the position of one or more areas of the moulding surface may be adjusted by means of the actuator or actuators, whereby the shape of the moulding surface may be adapted to the shape of the surface of the shell part to be moulded. The ac- tuators may be controlled by a computer programme.

In an embodiment, the flexible part of the moulding surface is adapted to be supported by a preferably substantially non-compressible fluid in one or more separate cavities of the mould that may be individually filled with said fluid. Thereby, the position of one or more areas of the moulding surface may be adjusted by pumping or leading fluid into or out from said cavities, whereby the shape of the moulding surface may be adapted to the shape of the surface of the shell part to be moulded. The fluid flow into or out from said cavities may be controlled by means of pumps and/or valves which in turn may be controlled by means of a computer programme. In an embodiment, the oblong composite structure is a wind turbine blade having a root region and a tip region. Advantageously, the wind turbine blade is assembled from at least a first and a second shell part. Thus, the mould assembly may be used to mould one of these shell parts, e.g. a shell part forming a pressure side of the wind turbine blade and/or a suction side of the wind turbine blade. However, the invention is also applicable to closed, hollow mouldings comprising e.g. a mould core and two outer mould part, where the wind turbine blade is infused in a one-shot process. Accordingly the invention provides a mould for manufacturing a shell part of a wind turbine blade, the shell part comprising a fibre reinforced matrix material and having a longitudinal direction, the mould comprising a moulding surface with a shape that defines a surface of the shell part, and the moulding surface having a longitudinal direction and a total length, wherein the moulding surface of the mould comprises a flexible part which is adapted to change a aerodynamic shape, such as a pressure side and/or a suction side, of a longitudinally extending moulding section of the mould. Thus, the mould is adapted to change the shape of the pressure side and/or suction side of a longitudinal section of the mould, thereby making it possible to mould wind turbine blade having different aerodynamic shapes using the same mould or moulds.

In one embodiment, the mould is adapted for changing a camber line of the longitudinally extending section.

Advantageously, the flexible part is extending in the longitudinal direction of the moulding surface and having a length corresponding to at least 1/10 of the total length of the moulding surface. In one embodiment, the mould is shaped for moulding a shell part for a wind turbine having a profiled contour, wherein the profiled contour is divided into: a root region having a substantially circular or elliptical profile closest to the hub, an airfoil region having a lift-generating profile furthest away from the hub, and a transition region between the root region and the airfoil region, the transition region having a profile gradually changing in the radial direction from the circular or elliptical profile of the root region to the lift-generating profile of the airfoil region.

In an embodiment, the flexible part of the moulding surface has a length corresponding to at least 1/10, or at least 1/4, or at least 1/2, advantageously at least 2/3, more advantageously at least 3/4 and most advantageously at least 9/10, of the total length of the airfoil region.

The present invention further relates to a modular mould system comprising at least one mould as described above. In an embodiment, the mould system comprises a plurality of separate mould sections for moulding root regions with different shapes. Hereby, an efficient mould system may be achieved, which may, for instance, be adapted for producing wind turbine blades for a number of different variations of hub connections. This may be achieved by exchanging only the mould section for moulding root regions. The shape of the mould section for moulding airfoil regions may be adapted by flexibly changing the shape of the moulding surface of the mould along a flexible part of the mould. Thus, the need for having a full mould for each variant of hub connections may be alleviated. Typically, different manufacturers of wind turbines have their own hub connection schemes, which are is generally mutu- ally incompatible.

In an embodiment, the mould system comprises a plurality of separate mould sections for moulding tip regions with different shapes. According to a specific embodiment, the mould system comprises a plurality of separate mould sections for moulding transition regions with different contours. According to another specific embodiment, the mould system comprises a plurality of separate mould sections for moulding airfoil regions with different contours.

According to another specific embodiment, the separate mould sections of the mould system are combinable in a plurality of ways, so that when the mould system is in different configurations, shell parts with varying dimensions and/or shapes may be manufactured.

The present invention further relates to a mould system comprising a mould as described above, wherein the system comprises a control system, such as a computer controlled system, adapted to control the position of individual parts or sections of the flexible part of the moulding surface according to predefined and/or user defined values and/or parameters. Thereby, the position of one or more areas of the moulding surface may be adjusted by means of an actuator or actuators, whereby the shape of the moulding surface may be adapted to the shape of the surface of the shell part to be moulded.

The present invention further relates to a method of successively manufacturing at least a first and a second shell part of a composite wind turbine struc- ture, the structure comprising a fibre reinforced matrix material and having a longitudinal direction, the second shell part having a surface shape that is different than the surface shape of the first shell part.

The method is characterized by, after having manufactured the first shell part, but before manufacturing the second shell part, flexibly changing the shape of a flexible part of the moulding surface of the mould along a length corresponding to at least 1/10 of the total length of the mould. Thereby, the above described features may be achieved. There is further provided a method for manufacturing a wind turbine blade for use in a wind farm, the method comprising the steps of: receiving data corresponding to characteristics of a wind farm: selecting a template wind turbine blade design for use within said wind farm based on the received characteristic data;

arranging an adaptive blade mould according to the selected template blade design;

receiving a design order for a particular wind turbine blade for use at a particular location within said wind farm;

adjusting at least a portion of said adaptive blade mould based on said received design order;

forming at least a portion of a wind turbine blade in said adaptive blade mould, wherein said portion of the wind turbine blade is adapted for use at the particular location within said wind farm.

By using a blade template for the wind farm to initially configure the adaptive mould, and then fine-tuning the mould with regard to individual wind turbine blades or blade sets for use in the wind farm, the efficiency of the individual wind turbines within the wind farm can be easily maximised, to account for localised variations in predicted turbine performance. Preferably, said step of receiving data comprises receiving information comprising at least one of the following: wind farm location; wind farm geography; wind class rating for the wind farm; location of wind turbines in the wind farm.

Additionally or alternatively, the method may further comprise the step of cal- culating a wind class rating suitable for the wind farm.

Preferably, said step of selecting a template wind turbine blade design for use with said wind farm comprises selecting a template wind turbine blade suitable for the wind class rating for said wind farm. Preferably, said step of receiving a design order comprises receiving information comprising at least one of the following: location co-ordinates of a particular wind turbine in the wind farm; local geography for a particular wind turbine in the wind farm; a localized wind profile for the location of a particular wind turbine in the wind farm.

Additionally or alternatively, the design order may comprise information comprising design limitations for a particular wind turbine blade in the wind farm. Preferably, said step of adjusting comprises varying at least one of a leading edge or a trailing edge of said adaptive mould, dependent on the received design order.

Detailed Description of the Invention

The invention will now be explained in more detail below by means of examples of embodiments with reference to the very schematic drawing, in which

Fig. 1 is a perspective view of a wind turbine, Fig. 2 is a perspective view of a wind turbine blade,

Fig. 3 is a cross-sectional view of an airfoil profile,

Fig. 4 is a top view and a side view, respectively, of a wind turbine blade,

Figs. 5 to 8 show transversal cross-sectional views of different embodiments of a mould according to the invention,

Figs. 9 shows a longitudinal cross-section of an embodiment of the mould according to the invention, Figs. 10 shows a top view of an embodiment of the mould according to the invention,

Fig. 1 1 shows a top view of an embodiment of a modular mould system ac- cording to the invention, and

Fig. 12 illustrates a method for manufacturing a wind turbine blade for use in a wind farm using an adaptive mould according to the invention. Fig. 1 illustrates a conventional modern upwind wind turbine according to the so-called "Danish concept" with a tower 4, a nacelle 6 and a rotor with a substantially horizontal rotor shaft. The rotor includes a hub 8 and three blades 10 extending radially from the hub 8, each having a blade root 16 nearest the hub and a blade tip 14 furthest from the hub 8. The rotor has a radius de- noted R.

Fig. 2 shows a view of a wind turbine blade 10. 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 an airfoil region 34 furthest away 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 the opposite direction of the leading edge 18. The airfoil region 34 (also called the profiled region) has an ideal or almost ideal blade shape with respect to generating lift, whereas the root region 30 due to structural considerations has a substantially circular or elliptical cross- section, which for instance makes it easier and safer to mount the blade 10 to the hub. The diameter (or the chord) of the root region 30 may be constant along the entire root area 30. The transition region 32 has a transitional profile gradually changing from the circular or elliptical shape of the root re- gion 30 to the airfoil profile of the airfoil region 34. The chord length of the transition region 32 typically 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 rfrom the hub.

A shoulder 40 of the blade 10 is defined as the position, where the blade 10 has its largest chord length. The shoulder 40 is typically provided at the boundary between the transition region 32 and the airfoil region 34.

It should be noted that the chords of different sections of the blade normally do not lie in a common plane, since the blade may be twisted and/or curved (i.e. pre-bent), thus providing the chord plane with a correspondingly twisted and/or curved course, this being most often the case in order to compensate for the local velocity of the blade being dependent on the radius from the hub.

Figs. 3 and 4 depict parameters, which in the following are used to explain the geometry of a wind turbine blade. Fig. 3 shows a view of an airfoil profile 50 of a typical blade of a wind turbine depicted with the various parameters, which are typically used to define the geometrical shape of an airfoil. The airfoil profile 50 has a pressure side 52 and a suction side 54, which during use - i.e. during rotation of the rotor - normally face towards the windward (or upwind) side and the leeward (or downwind) side, respectively. The airfoil 50 has a chord 60 with a chord length c extending between a leading edge 56 and a 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 a symmetrical profile is given by a camber line 62, which is a median line through the airfoil profile 50. The median line can be found by drawing inscribed circles from the lead- ing edge 56 to the trailing edge 58. The median line follows the centres of these inscribed circles and the deviation or distance from the chord 60 is called the camber f. The asymmetry can also be defined by use of parameters called the upper camber (or suction side camber) and lower camber (or pressure side camber), which are defined as the distances from the chord 60 and the suction side 54 and pressure side 52, respectively.

Airfoil profiles are often characterised by the following parameters: the chord length c, the maximum camber f, the position d_f of the maximum camber f, the maximum airfoil thickness t, which is the largest diameter of the inscribed circles along the median camber line 62, the position d_t of the maximum thickness t, and a nose radius (not shown). These parameters are typically defined as ratios to the chord length c. Thus, a local relative blade thickness t/c is given as the ratio between the local maximum thickness t and the local chord length c. Further, the position d_p of the maximum pressure side camber may be used as a design parameter, and of course also the position of the maximum suction side camber.

Fig. 4 shows other geometric parameters of the blade. The blade has a total blade length L. As shown in Fig. 3, the root end is located at position r = 0, and the tip end located at r = L. The shoulder 40 of the blade is located at a position r = L_w, and has a shoulder width W, which equals the chord length at the shoulder 40. The diameter of the root is defined as D. The curvature of the trailing edge of the blade in the transition region may be defined by two parameters, viz. a minimum outer curvature radius r₀ and a minimum inner curvature radius r,, which are defined as the minimum curvature radius of the trailing edge, seen from the outside (or behind the trailing edge), and the minimum curvature radius, seen from the inside (or in front of the trailing edge), respectively. Further, the blade is provided with a prebend, which is defined as Ay, which corresponds to the out of plane deflection from a pitch axis 22 of the blade. In the following description of a mould 70 according to the invention, indicated directions such as up and down, height adjustable and the like, refer to the normal operational position of the mould, that is, when the mould is placed on the ground. Positions such as left and right relate to the mould as depicted in the actual figures referred to.

Fig. 5 illustrates a transversal cross-section along the line V-V in Fig. 10 through a first embodiment of a mould 70 according to the invention. The mould 70 comprises a chassis or frame 74 carrying an upward open moulding surface 76 having a shape that defines a surface of the shell part to be manufactured as a fibre composite structure by means of VARTM as described above. Such a structure comprises a fibre reinforced matrix material and has a longitudinal direction, such as defined by the pitch axis 22 seen in Fig. 4. The moulding surface 76 has a longitudinal direction and a total length L. The mould 70 shown forms the first mould part in the VARTM process, whereby the second (not shown) opposite mould part is made of a resilient vacuum bag that is subsequently placed on top of the fibre material placed on the upward open moulding surface 76, as likewise described above.

In the figures, the mould according to the invention is exemplified by means of a mould suitable for the manufacture of one of two shell parts of a wind turbine blade having a root region and a tip region. However, the mould according to the invention may be a mould suitable for the manufacture of a shell part of any oblong composite structure. Furthermore, the mould according to the invention may be a mould suitable for the manufacture of a single shell part forming itself any oblong composite structure, such as a wind turbine blade formed by a single shell part. In the embodiment shown in Fig. 5, the moulding surface 76 comprises a first fixed part 78 and a second flexible part 72. The fixed part 78 of the moulding surface is illustrated as being supported by a solid section 80 of the frame 74 that is hatched in the figure; however, the fixed part 78 may be supported in other suitable ways. The shape of the fixed part of the moulding surface is fixed. The left edge of the second flexible part 72 of the moulding surface is connected flexibly to the first fixed part 78 by means of a hinge 82. The right edge of the flexible part 72 of the moulding surface is connected directly to the frame 74 of the mould 70. The shape of flexible part 72 of the moulding surface 76 is flexibly adaptable to a desired shape of the surface of the shell part to be manufactured by means of the mould 70. A first shape of the flexi- ble part 72 is indicated by a solid line 72', and a second possible shape of the flexible part 72 is indicated by a broken line 72". Many other shapes of the flexible part 72 are possible by appropriate positioning of the actuator 90. The flexible part 72 of the moulding surface 76 is formed by a flexible plate element comprising a fibre reinforced matrix material. However, the flexible part 72 may be formed by any flexible plate element suitable to adapt its shape as required.

The second flexible part 72 of the moulding surface 70 comprises a first part 84 and a second part 86 that are hinged together by means of a hinge 88. The moulding surface 76 of the mould 70 is shielded from the hinges 82, 88 by means of a flexible plate element forming the flexible part 72; however, the moulding surface 76 may be shielded from the hinges in other suitable ways or may not be shielded from the hinges. The hinge axes of the hinges 82, 88 extend in the longitudinal direction of the moulding surface 76; how- ever, each of the axes may also individually extend at an angle, such as for instance 10, 20, 30 or even 45 degrees, to the longitudinal direction of the moulding surface 76. The flexible part 72 of the moulding surface 70 may comprise any suitable number of parts hinged together by means of hinges. There is required some flexibility of at least the second part 86 of the flexible part 72. However, the right edge of the flexible part 72 of the moulding sur- face could be connected displaceably to the frame 74 of the mould 70, and in this case, the first part 84 and the second part 86 of the flexible part 72 may in fact by formed as rigid parts, as the required flexibility of the flexible part 72 could be provided by the hinges 82, 88 together with said displaceable con- nection. On the other hand, the hinges 82, 88 could be formed by a flexible plate element. Furthermore, the hinges 82, 88 may be completely left out and the flexible part 72 may be partly or entirely formed by a flexible plate element. Based on the above, it may be understood that the shape of flexible part 72 of the moulding surface 76 may be flexibly adaptable to a desired shape of the surface of the shell part to be manufactured to a certain extent, that is, the shape of flexible part 72 may not necessarily be able to adapt to each and every exact shape that could be imagined; however, the shape may be adaptable to a shape close to the desired shape.

The flexible part 72 has a length I extending in the longitudinal direction of the moulding surface 76 corresponding to at least 1/10 of the total length L of the moulding surface, see Fig 10. It may be preferred that the flexible part 72 extends from an area at the root region to an area at the tip region. Furthermore, the flexible part of the moulding surface may have a length corresponding to at least 1/2, preferably at least 2/3, more preferred at least 3/4 and most preferred at least 9/10, of the total length of the moulding surface or of the total length of the airfoil region.

In the embodiment shown in Fig. 5, the flexible part 72 of the moulding surface 70 is supported by means of an actuator 90, for instance in the form of a linear actuator, such as an electric, hydraulic or pneumatic cylinder, the upper end of which is flexibly connected to the first part 84 and the second part 86 of the flexible part 72 by means of the hinge 88 also connecting said parts, and the lower end of which is connected to a bottom of the frame 74 of the mould 70 by means of a hinge 92. By adjustment of the length between the ends of the actuator 90, the shape of the flexible part 72 of the moulding surface 76 may be flexibly adapted in a stepless way as illustrated in Fig. 5 and described above. The shapes of the flexible part 72 indicated by means of the solid line 72' and the broken line 72", respectively, are just two possible shapes of many possible.

Fig. 9 illustrates a longitudinal cross-section of a specific variation of the embodiment shown in Fig. 5. According to this specific variation, the second flexible part 72 of the moulding surface 76 is split up into four sections 73', 73", 73"', 73"" that are individually hinged to the first fixed part 78 of the moulding surface 76 by means of hinges 82. The four sections 73', 73", 73"', 73"" are furthermore mutually interconnected by means of hinges 94. The second flexible part 72 of the moulding surface 76 may be split up into any suitable number of sections. The hinges 94 may interconnect either the first parts 84 of the flexible part 72 of the moulding surface 70 or the second parts 86, or both the first parts 84 and the second parts 86 may be mutually interconnected. Hinges 82, 88, 94 connecting parts or sections of the mould may be any kind of suitable hinge, including slide connections, ball joints, etc. In order to provide sufficient flexibility of the flexible part 72 of the moulding surface, the hinges may be of a type allowing a certain degree of play. Fig. 6 illustrates an embodiment corresponding to that shown in Fig. 5, except for the fact that in the embodiment shown in Fig. 6, the entire or substantially the entire cross-section of the moulding surface 76 has the form of a flexible part 96. The flexible part 96 is formed by a single flexible plate element of which the left and right edges are connected to the frame 74. The central area of the flexible part 96 is supported by means of two actuators 98, 100 in the form of linear actuators positioned at a distance from each other. The solid line and the broken line indicate, respectively, two shapes out of many possible shapes of the moulding surface 76.

Fig. 7 illustrates an embodiment corresponding to that shown in Fig. 6, ex- cept for the fact that in the embodiment shown in Fig. 7, the right edge 102 of the flexible part 96 of the moulding surface is supported by means of a third linear actuator 104, so that it is height adjustable next to an element 106 adapted to form a sidewall of the mould 70. Thereby, for instance an airfoil profile of a wind turbine blade may be produced with a pointed trailing edge as well as with a truncated or flat-back trailing edge by appropriate height positioning of the right edge 102, whereby the element 106 forms the flat back of the trailing edge. When the moulding surface 76 has the shape indicated in the figure by a solid line, a wind turbine blade with a pointed trailing edge may be produced; however, when the moulding surface 76 has the shape indicated in the figure by a broken line, a wind turbine blade with a truncated or flat-back trailing edge may be produced. Of course, many other shapes of the moulding surface 76 than those indicated in the figure are possible by appropriate positioning of the actuators 98, 100, 104. By varying the shape of a wind turbine blade so that a truncated or flat-back trailing edge is obtained, a virtual chord or chord length of the wind turbine blade may be varied. In an embodiment where the blade shape is changed between a profile with a substantially pointed trailing edge to a truncated trailing edge shape, the virtual chord length is understood to be the distance be- tween the leading edge and the point, where the airstreams meet behind the trailing edge. In yet another embodiment, the moulding surface of a corresponding second mould part may be varied corresponding to the first mould part. Thus, the first mould and the second mould may for instance be used for moulding shell parts of a pressure side and a suction side of a wind tur- bine blade respectively. Accordingly, both the shape of the pressure side and the suction side may be varied. In one embodiment, the trailing edge of the two parts may be varied so that for instance the local twist of a blade section may be varied.

Fig. 8 illustrates an embodiment corresponding to that shown in Fig. 6, ex- cept for the fact that in the embodiment shown in Fig. 8, the two actuators 98, 100 shown in Fig. 6 in the form of linear actuators have been replaced by three separate cavities 108, 1 10, 1 12 formed in the mould 70 and adapted to be individually filled with a preferably substantially non-compressible fluid in order to support the flexible part 96 of the moulding surface 76 and to adjust the shape of the flexible part 96. The three separate cavities 108, 1 10, 1 12 are separated from each other by means of two flexible partition walls 1 16, 1 18, respectively. The two flexible partition walls 1 16, 1 18 are adapted to follow the shape of the flexible part 96 of the moulding surface 76, as indicated in the figure by means of broken lines. The flexible partition walls 1 16, 1 18 may, for instance, be made of an elastic rubber membrane or a bellows- like metal wall in order to be able to change their length according the shape of the flexible part 96.

A mould system may comprise a not shown control system, such as a com- puter controlled system, adapted to control the position of individual parts or sections of the flexible part 72, 96 of the moulding surface 76 according to predefined and/or user defined values and/or parameters.

Fig. 1 1 illustrates a modular mould system 1 100, which comprises a number of first mould sections 1 101 , a number of second 5 mould sections 1 102, and a number of third mould sections 1 193. Naturally, the system may further comprise any number of additional mould sections. It is illustrated that e.g. the first mould sections 1 101 are not required to have identical dimensions but rather may be made to fit the corresponding section of the object to be moulded. The mould system may in particular comprise a plurality of separate mould sections for moulding root regions with different shapes and/or a plurality of separate mould sections for moulding tip regions with different shapes.

In a further enhancement of the invention, and with reference to Fig. 12, there is provided a method of manufacture of wind turbine blades for use in a wind farm, the method operable to efficiently provide wind turbine blades fine-tuned for efficient performance at the wind farm, the method using an adaptive mould as described above. When a location for a wind farm is selected, at least one general characteristic of the wind farm is determined, step 200, for example the IEC Wind Class of the wind farm location. This provides an indication of the general wind strength at the wind farm location. There may also be determined the characteristic information such as the wind farm location, geography, locations of individual wind turbines within the wind farm, any other special considerations, etc.

It will be understood that different template designs of wind turbine blade may be available, with individual designs having different characteristics, e.g. dif- ferent rates of camber, lift, drag, strength, etc., suitable for usage in different environments, e.g. different wind class zones.

Based on the characteristic information, in particular the wind class at the wind farm, a particular wind turbine blade design template may be selected from a range of different blade designs, step 202. This information may be entered to an adaptive mould system as described above, such that the mould is adjusted to a shape suitable to produce the selected wind turbine blade design, step 204. With reference to step 206, there is further provided a design order for a wind turbine blade, preferably a set of wind turbine blades, for use at a particular wind turbine in the wind farm. The design order comprises at least one characteristic based on the wind turbine blade to be manufactured. Preferably, said characteristic comprises the exact location of the wind turbine in the wind farm, but said characteristic may additionally or alternatively comprise further information relating to that particular turbine or wind turbine blade, e.g. the local geography of the particular wind turbine, a localised profile of the wind conditions at the particular wind turbine, design limitations e.g. blade length or noise-reducing requirements for the particular wind turbine, or any other suitable detail regarding the wind turbine location and/or predicted per- formance.

Based on the details of the particular design order, in step 208 the adaptive mould is fine-tuned to provide a mould to manufacture a wind turbine blade tailored for the particular wind turbine, the blade based on the original tem- plate blade design for the wind farm. The fine-tuning involved may comprise an adjustment of the leading edge and/or the trailing edge of the mould surface, for example to provide an adjusted camber, trailing edge, lift-to-drag ratio, etc. of a manufactured wind turbine blade. The particular shell part of the blade (or blade set) can then be formed in the adjusted adaptive blade mould, step 210, and subsequently removed, step 212. It will be understood that any suitable forming method may be used, e.g. hand lay up or automatic lay up of fibre material for subsequent curing. Furthermore, it will be understood that the adaptive mould may be used to create single blade shell parts for later assembly into a complete wind turbine blade, or the adaptive mould may be coupled with a second adaptive mould via a turning device, such that an entire blade may be formed by joining a matched pair of shell parts at the mould. At step 214, the steps 210 and 212 may be repeated until all parts of the wind turbine blade (or blade set) determined by the design order are completed. This may comprise simply the moulding of individual shell parts for the blade (or blade set), or may comprise the complete manufacturing proc- ess for the blade (or blade set).

Once the design order has been fulfilled for a particular blade (or blade set) within the wind farm, the system checks if the production has been completed for all blades in the wind farm, step 216. If the wind farm is not yet complete, the process returns to step 206 with the receipt of a new design order for a new blade or blade set for use in the wind farm.

If the blades (or blade shell parts) have been produced for each of the individual turbines within the wind farn, then the process is complete, step 218.

Through use of such a design and manufacture method, it is possible to select a general template blade design nominated for a particular wind farm, and to then adapt the blades for use at individual wind turbines in said farm based on the individual wind turbine characteristics, to improve overall wind farm efficiency.

It will be understood that this method is preferably performed with any of the embodiments of adaptive mould as described above. The invention has been described with reference to different embodiments. However, the scope of the invention is not limited to the illustrated embodiments, and alterations and modifications may be carried out without deviating from the scope of the invention. List of reference numerals 2 wind turbine

4 tower

6 nacelle

8 hub

10 blade

14 blade tip

16 blade root

18 leading edge

20 trailing edge

22 pitch axis

30 root region

32 transition region

34 airfoil region

41 first airfoil profile

42 second airfoil profile

43 third airfoil profile

44 fourth airfoil profile

45 fifth airfoil profile

46 sixth airfoil profile

50 airfoil profile

52 pressure side

54 suction side

56 leading edge

58 trailing edge

60 chord

62 camber line / median line

c chord length

dt position of maximum thickness

d_f position of maximum camber

d_P position of maximum pressure side camber f camber L blade length

r local radius, radial distance from blade root t thickness

Ay prebend

70 mould

72 second flexible part

72' first shape of flexible part

72" second shape of flexible part

73', 73", 73'", 73 sections of flexible part

74 frame

76 moulding surface

78 first fixed part

80 solid section

82 hinge

84 first part of flexible part

86 second part of flexible part

88 hinge

90 actuator

92 hinge

94 hinge

96 flexible part

98, 100 actuators

102 right edge of the flexible part

104 linear actuator

108, 1 10, 1 12 cavities

1 14 longitudinal direction of moulding surface 1 16 flexible partition wall

1 18 flexible partition wall

Claims

1 . A method for manufacturing a wind turbine blade for use in a wind farm, the method comprising the steps of:

receiving data corresponding to characteristics of a wind farm: selecting a template wind turbine blade design for use within said wind farm based on the received characteristic data;

2. The method of claim 1 , wherein said step of receiving data comprises receiving information comprising at least one of the following: wind farm loca- tion; wind farm geography; wind class rating for wind farm; location of wind turbines in wind farm.

3. The method of claim 1 or claim 2, wherein said step of selecting a template wind turbine blade design for use with said wind farm comprises selecting a template wind turbine blade suitable for a wind class rating for said wind farm.

4. The method of any preceding claim, wherein said step of receiving a design order comprises receiving information comprising at least one of the fol- lowing: location co-ordinates of a particular wind turbine in the wind farm; local geography for a particular wind turbine in the wind farm; a localized wind profile for the location of a particular wind turbine in the wind farm.

5. The method of any preceding claim, wherein said step of adjusting com- prises varying at least one of a leading edge or a trailing edge of said adaptive mould, dependent on the received design order.

6. An adaptive mould (70) for manufacturing a shell part of a wind turbine blade, the structure comprising a fibre reinforced matrix material and having a longitudinal direction, the mould comprising a moulding surface (76) with a shape that defines a surface of the shell part, and the moulding surface having a longitudinal direction (1 14) and a total length, characterized in that the moulding surface (76) of the mould (70) comprises a flexible part (72, 96) extending in the longitudinal direction (1 14) of the moulding surface (76) and having a length (I) corresponding to at least 1 /10 of the total length (L) of the moulding surface (76).

7. The mould of claim 6, wherein the adaptive mould comprises at least one moveable longitudinal section provided at a trailing edge and/or a leading edge of the moulding surface, and wherein the adaptive mould further comprises at least one substantially rigid longitudinal section adjacent said at least one moveable longitudinal section, said at least one moveable longitudinal section flexibly coupled to said at least one substantially rigid longitudinal section.

8. The mould of claim 7, wherein said at least one moveable longitudinal section is actuatable to form an adjustable leading edge and/or trailing edge surface for a shell part of a wind turbine blade.

9. The mould of claim 7 or claim 8, wherein said at least one substantially rigid longitudinal section of said adaptive mould is used to form at least one load-bearing section of a shell part of a wind turbine blade

10. The mould of any one of claims 7-9, wherein said adaptive mould comprises a plurality of moveable longitudinal sections provided at a trailing edge and/or a leading edge of the moulding surface, wherein said plurality of moveable longitudinal sections are individually actuatable.

1 1 . A mould according to any one of claims 6-10, wherein the flexible part (72, 96) of the moulding surface (76) is associated with at least one hinge (82) connecting a first part (78) and a second part (72) of the moulding surface (76), preferably about a hinge axis extending substantially in the longitudinal direction (1 14) of the mould (70).

12. A mould according to claim 1 1 , wherein the second part (72) of the moulding surface (76) is split up into at least a first and a second section (73', 73", 73'", 73"") that are individually hinged to the first part (78).

13. A mould according to claim 12, wherein the at least first and a second sections (73', 73", 73'", 73"") of the second part (72) of the moulding surface (76) are hinged together.

14. A mould according to any one of the claims 1 1 to 13, wherein at least one of the hinges (82, 88, 94) connecting parts or sections of the mould (70) are formed by a flexible connection, such as a pivot joint allowing a certain degree of play, or even such as a kind of ball joint.

15. A mould according to any one of claims 6-14, wherein the flexible part (72, 96) of the moulding surface (76) is formed at least partly by a flexible plate element preferably comprising a fibre reinforced matrix material.

16. A mould according to claim 15, wherein hinges (82, 88, 94) connecting parts or sections of the mould are formed by the flexible plate element.

17. A mould according to claim 15, wherein the moulding surface (76) of the mould (70) is shielded from hinges (82, 88, 94) connecting parts or sections of the mould by means of the flexible plate element.

18. A mould according to any one of claims 6-17, wherein an edge (102) of the moulding surface (76) extending along the flexible part (96) of the moulding surface (76) is height adjustable, preferably next to an element (106) adapted to form a sidewall of the mould (70).

19. A mould according to any one of claims 6-18, wherein the flexible part (72, 96) of the moulding surface (76) is supported by one or more individually adjustable actuators (90, 98, 100, 104), such as electrically driven linear actuators or hydraulic or pneumatic cylinders.

20. A modular mould system comprising at least one mould (70) according to any one of claims 6-19, wherein the mould system comprises a plurality of separate mould sections (1 101 ) for moulding root regions with different shapes and/or a plurality of separate mould sections (1 193) for moulding tip regions with different shapes.

21 . A mould system comprising a mould (70) according to any one of the claims 6-19, wherein the system comprises a control system, such as a computer controlled system, adapted to control the position of individual parts (84, 86) or sections (73', 73", 73'", 73"") of the flexible part (72, 96) of the moulding surface (76) according to predefined and/or user defined values and/or parameters.

22. A method of successively manufacturing at least a first and a second shell part of a wind turbine blade structure, the structure comprising a fibre reinforced matrix material and having a longitudinal direction, the second shell part having a surface shape that is different than the surface shape of the first shell part, characterized by, after having manufactured the first shell part, but before manufacturing the second shell part, flexibly changing the shape of a flexible part (72, 96) of the moulding surface (76) of the mould (70) along a length (I) corresponding to at least 1 /10 of the total length (L) of the mould (70).