Patent Description:
Modern wind turbine rotor blades are built from fiberreinforced plastics. A rotor blade typically comprises an airfoil having a rounded leading edge and a sharp trailing edge. The rotor blade is connected with its blade root to a hub of the wind turbine. Further, the rotor blade is connected to the hub by means of a pitch bearing that allows a pitch movement of the rotor blade. Long rotor blades experience high wind forces and are, thus, subjected to heavy loads.

Rotor blades may be made of two half-shells connected to each other. As rotor blades become longer, it may be advantageous to manufacture a rotor blade divided into two or more segments along a longitudinal axis (i.e. longitudinal segments) of the blade. Such blade segments are also known as spanwise segments. Further, such spanwise segments may be casted individually and connected together after casting. <CIT> shows a method for assembling spanwise segments of a wind turbine blade.

Connecting such spanwise segments of a blade is a challenging task since the segments may come from different molds. It may be important that the blade tip is placed correctly with respect to the blade root and a twist of the blade is as designed and intended. If this is not the case, the loads throughout the blade may change, e.g. during energy generation. This may lead to malfunction. For example, the blade may strike the tower.

<CIT> discloses a method of assembling a wind turbine blade from wind turbine blade elements. The wind turbine elements are equipped with alignment means in form of lasers and optical sensors. The lasers are mounted on the first element, and the optical sensors are mounted on the second element. During the alignment, one blade element may be fixed while the other blade element is moved to achieve suitable alignment as required by the sensor system.

<CIT> discloses a system and apparatus for the manufacture of a wind turbine blade where portions of a blade, preferably blade half shells, are formed in suitable molds, before transferring them to a post-molding station where post-molding operations can be performed. The blade shells are formed in the mold to have integrated flanges which facilitate easy handling of the blade shells during subsequent manufacturing operations. There is also described a blade cradle of a post-molding station to receive a wind turbine blade shell, where a lifting jack apparatus can be located within the blade cradle structure for the application of a lifting force to a surface of a blade shell received in the cradle, to facilitate access to all sections of the surface of the blade shell.

It is one object of the present invention to provide an improved method for connecting two wind turbine blade portions.

Accordingly, a method for connecting two wind turbine blade portions is provided. The method comprises the steps of: a) providing a first wind turbine blade portion and a second wind turbine blade portion, b) providing a plurality of first markers on the first blade portion and providing a plurality of second markers on the second blade portion, c) determining of target positions of the first markers and the second markers, d) aligning the wind turbine blade portions to each other and comparing actual positions of the first markers and the second markers with the target positions, and e) connecting the wind turbine blade portions together.

Therefore, a shape accuracy of the wind turbine blade can be improved. For example, two, three or more blade portions can be connected together. In particular, each blade portion comprises two blade shells arranged opposite and connected to each other. Providing markers on the blade portion means that the markers are set. Setting the markers may mean that physical markers are connected to the blade portion, created on the blade portion or digital markers are allocated to the blade portion. Aligning means that one of the blade portions or both are moved until the blade portions match as intended.

In particular, the first blade portion comprises an outer surface at which the first markers are provided. Preferably, the second blade portion comprises an outer surface at which the second markers are provided. In particular, the first markers and the second markers are arranged along a longitudinal direction of the blade. For example, at least three, four, five, six, seven, eight, nine, ten or more first markers are provided in step b). In particular, at least three, four, five, six, seven, eight, nine, ten or more second markers are provided in step b). Preferably, the wind turbine blade portions are side by side in longitudinal direction of the blade when aligned to each other.

According to an embodiment, the first wind turbine blade portion is molded by means of a first mold and the second wind turbine blade portion is molded by means of a second mold.

In particular, the first and the second blade portions are casted. Molding the blade by means of at least two molds has the advantage that longer blades may by manufactured. Preferably, the first mold is a multi-part, in particular two-part, mold and/or the second mold is a multi-part, in particular two-part, mold. This has the advantage that the blade portions may be accessible after molding without removing the blade portion from the lower part of the mold which carries the mold. Preferably, the first mold comprises a hollow space having a negative form of the first blade portion and/or the second mold comprises a hollow space having a negative form of the second blade portion.

According to a further embodiment, step b) is executed when the first wind turbine blade portion is in the first mold and/or the second wind turbine blade portion is in the second mold.

This has the advantage that the first and/or second blade portions are substantially stressless and, thus, undeformed. Preferably, step b) is executed during molding or afterwards. For example, the first blade portion lies in the first mold and/or the second blade portion lies in the second mold when step b) is executed. Therefore, a large contact surface between the respective blade portion and the respective mold is provided.

According to a further embodiment, initial positions of the first and the second markers are determined during or immediately after step b).

Preferably, the initial positions are measured and recorded. Thus, an ideal shape of the blade portion may be reproduced even after handling or manipulating the same.

According to a further embodiment, the target positions of the markers are determined by means of the initial positions of the first and the second markers.

Preferably, the initial positions of the first markers relative to each other are set as target positions of the first markers. In particular, the initial positions of the second markers relative to each other are set as target positions of the second markers.

According to a further embodiment, the target positions of the first and the second markers are determined by setting a relation between the initial position of the first markers relative to the initial positions of the second markers.

Alternatively or additionally, the target positions are determined by means of computer generated positions. For example, the initial positions can be combined with computer generated positions of the markers for obtaining the target positions of the first and the second markers.

According to a further embodiment, the actual positions of the first and/or the second markers are detected by means of detecting means during step d).

This has the advantage that an exact alignment can be controlled. Preferably, the detecting means comprise a sensor, in particular sensors, and/or a camera, in particular cameras.

Step d) is executed by means of digital image correlation.

Digital image correlation and tracking is an optical method that employs tracking and image registration techniques for accurate 2D and 3D measurements of changes in images. This method can be used to measure full-field displacement and strains. Compared to strain gages and extensometers, the amount of information gathered about the fine details of deformation during mechanical tests is increased due to the ability to provide e.g. both local and average data using digital image correlation. This has the advantage that a real time measurement and alignment can be executed.

According to a further embodiment, step d) is executed by means of a carrying device which is configured to move the first wind turbine blade portion in at least <NUM>, <NUM>, <NUM> or <NUM> degrees of freedom relative to the second wind turbine blade portion.

The carrying device may comprise a first support structure, in particular a first trolley or yoke, configured to support the first blade portion at one contact surface and a second support structure, in particular a second trolley or yoke, configured to support the first blade portion at another contact surface. For example, the first and the second support structures are configured to move in longitudinal direction of the blade relative to each other when supporting the first blade portion. In particular, the second blade portion is fixed.

Preferably, the carrying device is configured to move the first blade portion in longitudinal direction of the blade and/or in height direction and/or in a side direction which is perpendicular to the longitudinal direction. Preferably, the carrying device is configured to rotate or tilt the first blade portion around the longitudinal direction and/or the height direction and/or the side direction.

In particular, the first and the second support structures comprise a lifting system for lifting the blade portion. For example, the first and the second support structures comprise a tilt system for tilting and/or twisting the blade portion. Preferably, three, four, five, six or more support structures, in particular a trolleys or yokes, are provided for supporting the first blade portion.

According to a further embodiment, the carrying device is configured to move the second wind turbine blade portion in at least <NUM>, <NUM>, <NUM> or <NUM> degrees of freedom relative to the first wind turbine blade portion.

The carrying device may comprise a third support structure, in particular a third trolley or yoke, configured to support the second blade portion at one contact surface and a fourth support structure, in particular a fourth trolley or yoke, configured to support the second blade portion at another contact surface. For example, the third and the fourth support structures are configured to move in longitudinal direction of the blade relative to each other when supporting the second blade portion.

In particular, the third and the fourth support structures comprise a lifting system for lifting the second blade portion. For example, the third and the fourth support structures comprise a tilt system for tilting and/or twisting the second blade portion. Preferably, three, four, five, six or more support structures, in particular trolleys or yokes, are provided for supporting the second blade portion.

According to a further embodiment, in step d) and/or e) leading edges of the first and the second wind turbine blade portions face downward or upward.

Thus, handling the blade portion during step d) and/or e) is improved.

According to a further embodiment, the first and the second markers are digitally generated points and/or concretely provided on the respective wind turbine blade portion.

Digitally generated points have the advantage that setting such points can be executed e.g. automatically. Concretely provided markers (i.e. physical markers) have the advantage that such points may be visible without equipment.

According to a further embodiment, the first wind turbine blade portion and the second wind turbine blade portion are longitudinal segments of the wind turbine blade.

This means, when the blade is completed, the segments are arranged one after another along the longitudinal axis of the blade. In particular, an angle between connecting surfaces of the wind turbine blade portions and a longitudinal axis of the wind turbine blade is at least <NUM>°, in particular <NUM>°.

Further, a method for producing a wind turbine is provided. The method comprises the steps of: a2) connecting two wind turbine blade portions according to such a method for connecting two wind turbine blade portions such that a wind turbine blade is provided, and b2) connecting the wind turbine blade to a hub of the wind turbine.

Therefore, a wind turbine having long wind turbine blades can be provided. Preferably, the method comprises further the steps of providing a tower, a nacelle and a hub of the wind turbine.

Wind turbine presently refers to an apparatus converting the wind's kinetic energy into rotational energy, which may again be converted to electrical energy by the apparatus.

Also, a method for connecting two molded portions is described. The method comprises the steps of: a3) molding a first portion by means of a first mold and a second portion by means of a second mold, b3) providing first markers on the first portion when the first portion is in the first mold and second markers on the second portion when the second portion is in the second mold, and c3) connecting the first and the second portions together by means of the first and the second markers.

This has the advantage that the first and the second portions are substantially stressless and, thus, undeformed when providing the markers. Therefore, a shape accuracy of two connected portions can be improved. The first and the second portion may be molded by means of casting.

Providing the markers on the first portion means that the markers are set. Preferably, the first portion lies in the first mold and/or the second portion lies in the second mold during step b3). Therefore, a large contact surface between the respective portion and the respective mold is provided. Preferably, the first and the second portions are connected to form a component. The component e.g. may be a wind turbine blade or any other component.

Preferably, the first mold is a multi-part, in particular two-part, mold and/or the second mold is a multi-part, in particular two-part, mold. Preferably, the first mold comprises a hollow space having a negative form of the first portion and/or the second mold comprises a hollow space having a negative form of the second portion.

The embodiments and features described with reference to the method for producing a wind turbine blade of the present invention apply mutatis mutandis to the method for connecting two molded portions of the present invention and vice versa.

The person skilled in the art may also add individual or isolated aspects and features to the most basic form of the invention which is defined by the appended claims.

<FIG> shows a wind turbine <NUM>. The wind turbine <NUM> comprises a rotor <NUM> connected to a generator (not shown) arranged inside a nacelle <NUM>. The nacelle <NUM> is arranged at an upper end of a tower <NUM> of the wind turbine <NUM>.

The rotor <NUM> comprises three blades <NUM> (i.e. wind turbine blades). The blades <NUM> are connected to a hub <NUM> of the wind turbine <NUM>. Rotors <NUM> of this kind may have diameters ranging from, for example, <NUM> to <NUM> meters or even more. The blades <NUM> are subjected to high wind loads. At the same time, the blades <NUM> need to be lightweight. For these reasons, blades <NUM> in modern wind turbines <NUM> are manufactured from fiberreinforced composite materials, e.g. by means of casting. Oftentimes, glass or carbon fibers in the form of unidirectional fiber mats are used. Such blades <NUM> may also include woods and other reinforcement materials.

<FIG> shows the blade <NUM>. The blade <NUM> comprises an aerodynamically designed portion <NUM> which is shaped for optimum exploitation of the wind energy and a blade root <NUM> for connecting the blade <NUM> to the hub <NUM>. Further, the blade <NUM> comprises a blade tip <NUM> which faces away from the blade root <NUM>. The blade <NUM> extends in a longitudinal direction L which points from the blade root <NUM> towards the blade tip <NUM>. The blade <NUM> has a length M which, for example, may be between <NUM> to <NUM> or even more. The wind turbine blade <NUM> comprises a leading edge <NUM> and a trailing edge <NUM>.

<FIG> shows a perspective view of a blade portion <NUM> (also referred as first blade portion) and a blade portion <NUM> (also referred as second blade portion). The blade portion <NUM> comprises the blade tip <NUM> and the blade portion <NUM> comprises the blade root <NUM>. Further, the blade portion <NUM> comprises a connecting surface <NUM> and the blade portion <NUM> comprises a connecting surface <NUM>. The blade portions <NUM>, <NUM> are configured to be connected at together the connecting surfaces <NUM>, <NUM>. For example, the connecting surfaces <NUM>, <NUM> run essentially perpendicular to the longitudinal direction L. The blade portions <NUM>, <NUM> are longitudinal segments of the blade <NUM> (see e.g. <FIG>).

The blade portion <NUM> is casted by means of a mold <NUM> (also referred as first mold) and the blade portion <NUM> is casted by means of a mold <NUM> (also referred as second mold). Preferably, the mold <NUM> is a multi-part mold comprising a lower mold part <NUM> and an upper mold part (not shown). For example, the upper mold part may be removed after molding the blade portion <NUM> as shown in <FIG>. Preferably, the mold <NUM> is a multi-part mold comprising a lower mold part <NUM> and an upper mold part (not shown).

This has the advantage that the blade portions <NUM>, <NUM> may be accessible after molding without removing the blade portion <NUM>, <NUM> from the lower mold part <NUM>, <NUM>. Preferably, the mold <NUM> comprises a hollow space <NUM> having a negative form of the blade portion <NUM>. In particular, the mold <NUM> comprises a hollow space (not shown) having a negative form of the blade portion <NUM>.

As shown in <FIG> an outer surface <NUM> of the blade portion <NUM> is exposed. Markers <NUM> (also referred as first markers) are provided on the surface <NUM>. Further, an outer surface <NUM> of the blade portion <NUM> is exposed. Markers <NUM> (also referred as second markers) are provided on the surface <NUM>. The markers <NUM>, <NUM> can be set when the blade portions <NUM>, <NUM> lie in the molds <NUM>, <NUM>. Therefore, a large contact surface between the blade portions <NUM>, <NUM> and the molds <NUM>, <NUM> is provided. This has the advantage that the blade portions <NUM>, <NUM> are substantially stressless and, thus, undeformed.

After providing the markers <NUM>, <NUM> initial positions of the markers <NUM>, <NUM> may be determined, e.g. by means of measuring and recording the same. Further, target positions of the markers <NUM>, <NUM> may be determined by setting a relation between the initial position of the markers <NUM> relative to the initial positions of the markers <NUM>.

Alternatively or additionally, the target positions are determined by means of computer generated positions. For example, the initial positions can be combined with computer generated positions of the markers <NUM>, <NUM> for obtaining the target positions of the markers <NUM>, <NUM>. The markers <NUM>, <NUM> may be digitally generated points and/or concretely provided or created on the surface <NUM>, <NUM>. In particular, <NUM> - <NUM>, <NUM> - <NUM>, <NUM> - <NUM>, or <NUM> to <NUM> markers <NUM> are provided. For example, <NUM> - <NUM>, <NUM> - <NUM>, <NUM> - <NUM>, or <NUM> to <NUM> markers <NUM> are provided. The markers <NUM> and/or the markers <NUM> may be arranged in at least two rows along the longitudinal direction L.

<FIG> shows a perspective view of the blade portions <NUM>, <NUM>. The blade portions <NUM>, <NUM> are carried by a carrying device <NUM>. The carrying device <NUM> is configured to move the blade portion <NUM> in at least <NUM>, <NUM>, <NUM> or <NUM> degrees of freedom relative to the blade portion <NUM>. In particular, the carrying device <NUM> is configured to move the blade portion <NUM> in longitudinal direction L and/or in height direction H and/or in side direction Y which is perpendicular to the height direction H and the longitudinal direction L. Preferably, the carrying device <NUM> is configured to rotate or tilt the blade portion <NUM> around the longitudinal direction L and/or the height direction H and/or the side direction Y.

The carrying device <NUM> may comprise a support structure <NUM>, in particular a trolley or yoke, configured to support the blade portion <NUM> at one contact surface <NUM> and a support structure <NUM>, in particular a trolley or yoke, configured to support the blade portion <NUM> at another contact surface <NUM>. Preferably, more support structures <NUM>, <NUM>, <NUM>, in particular trolleys or yokes, are provided for supporting the blade portion <NUM>.

The carrying device <NUM> may also be configured to move the blade portion <NUM> in at least <NUM>, <NUM>, <NUM> or <NUM> degrees of freedom relative to the blade portion <NUM>. In particular, the carrying device <NUM> is configured to move the blade portion <NUM> in longitudinal direction L and/or in height direction H and/or in side direction Y which is perpendicular to the height direction. Preferably, the carrying device <NUM> is configured to rotate or tilt the blade portion <NUM> around the longitudinal direction L and/or the height direction H and/or the side direction Y. The carrying device <NUM> may comprise a support structure <NUM>, in particular a trolley or yoke, configured to support the blade portion <NUM> at one contact surface <NUM> and a support structure <NUM>, in particular a trolley or yoke, configured to support the blade portion <NUM> at another contact surface <NUM>.

<FIG> shows a perspective view of the support structure <NUM> of the carrying device <NUM>. The support structure <NUM> comprises a frame <NUM> to which wheels <NUM> are connected. Further, a motor <NUM> may be provided for driving the support structure <NUM> by means of the motor <NUM>. The support structure <NUM> is, thus, configured to move in longitudinal direction L (see e.g. <FIG>).

Further, the support structure <NUM> comprises a receptacle <NUM> for receiving the blade portion <NUM>. The receptacle <NUM> interacts with the contact surface <NUM> of the blade portion <NUM> (see <FIG>) by means of arc shaped surfaces <NUM> which are provided at, in particular movable, holding shells <NUM>, <NUM>. Each shell <NUM>, <NUM> may be arc shaped. The holding shells <NUM>, <NUM> may be arranged side by side forming a V-shape or U-shape.

<FIG> shows a schematical side view of the carrying device <NUM>. The support structure <NUM> comprise a lifting system <NUM>, in particular a lifting platform, for lifting the receptacle <NUM> and the blade portion <NUM> (see e.g. <FIG>) in height direction H. The lifting system <NUM> may comprise a hydraulic or pneumatic mechanism (not shown) or an electric motor for lifting.

For example, actuators <NUM> for adjusting a tilt angle α of each shell <NUM>, <NUM> may be provided. The actuators <NUM> may be hydraulic, pneumatic or electric actuators. The actuators <NUM> and the shells <NUM>, <NUM> may be comprised by a tilt system <NUM> for tilting and/or twisting the blade portion <NUM>. All support structures <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> may be designed as described for support structure <NUM>.

<FIG> shows a perspective view of the blade portions <NUM>, <NUM> when aligning the same to each other. The carrying device <NUM> comprises a control unit <NUM> to which all support structures <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> are (e.g. electrically and/or by means of communication means) connected. Further, the control unit <NUM> may be connected to a computer <NUM>. Furthermore, detecting means <NUM> may be provide for detecting the actual positions of the markers <NUM>, <NUM>. This has the advantage that an exact alignment between the blade portions <NUM>, <NUM> can be controlled.

Preferably, the detecting means comprise sensors and/or a cameras <NUM>, in particular exactly two cameras <NUM>. The detecting means <NUM> may be connected to the computer <NUM> and/or the control unit <NUM>. Preferably, digital image correlation is applied for measuring the actual positions of the markers <NUM>, <NUM> and/or a movement of the markers <NUM>, <NUM>. As shown in <FIG> and <FIG> the leading edges <NUM> of the blade portions <NUM>, <NUM> face downward. However, the leading edges <NUM> of the blade portions <NUM>, <NUM> may face upward. When the support structures <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> are correctly piloted such that the blade portions <NUM>, <NUM> are aligned, the blade portions <NUM>, <NUM> can be connected together.

<FIG> shows a block diagram of a method for connecting two blade portions <NUM>, <NUM>. In a step S1 the blade portion <NUM> and the blade portion <NUM> are provided. The blade portions may be provided by means of casting. In a step S2 a plurality of markers <NUM> are provided on the blade portion <NUM> and a plurality of markers <NUM> are provided on the blade portion <NUM>. In an optional step S3 initial positions (e.g. when the blade portions lie in the molds <NUM>, <NUM>, see <FIG>) of the markers <NUM>, <NUM> are determined. Alternatively or additionally the markers <NUM>, <NUM> are provided at predetermined positions at the blade portions <NUM>, <NUM>.

In a step S4 target positions of the markers <NUM>, <NUM> are determined. This can be executed by means of calculating the target positions for a connected blade <NUM>, wherein the initial positions obtained in step S3 may be used as input values. In a step S5 detecting means <NUM> are provided for detecting actual positions of the markers <NUM>, <NUM>.

In a step S6 the blade portions <NUM>, <NUM> are aligned to each other and the actual positions of the markers <NUM>, <NUM> are compared with the target positions until an acceptable deviation is obtained. In a step S7 the blade portions <NUM>, <NUM> are connected together. In particular, the actual positions of the markers <NUM>, <NUM> are detected by the detecting means <NUM> during step S7.

<FIG> shows a block diagram of a method for producing a wind turbine. In a steps S11 the blade <NUM> which is ready to mount is provided, wherein the blade <NUM> is provided by the method for connecting two wind turbine blade portions <NUM>, <NUM> (see <FIG>). In a step S12 the tower <NUM> is provided and sited. In a step S13 a nacelle <NUM> and a hub <NUM> are connected to the tower <NUM>. In a step S14 a blade <NUM> is connected to the hub <NUM> of the wind turbine <NUM>.

<FIG> shows a block diagram of a method for connecting two molded portions <NUM>, <NUM>. In a step S21 a portion <NUM> is molded by means of a mold <NUM> and a portion <NUM> is molded by means of a mold <NUM>. In a step S22 markers <NUM> are provided (e.g. set) on the portion <NUM> when the portion <NUM> is (e.g. lies) in the mold <NUM> and markers <NUM> are provided (e.g. set) on the portion <NUM> when the portion <NUM> is (e.g. lies) in the mold <NUM>. In a step S23 portions <NUM>, <NUM> are connected together by means of the markers <NUM>, <NUM> to form a component, in particular a blade <NUM>. Therefore, a shape accuracy of two connected portions can be improved.

The features explained with reference to <FIG> apply mutatis mutandis to the methods of <FIG>.

Claim 1:
A method for connecting two wind turbine blade portions (<NUM>, <NUM>), the method comprising the steps of:
a) providing (S1) a first wind turbine blade portion (<NUM>) and a second wind turbine blade portion (<NUM>),
b) providing (S2) a plurality of first markers (<NUM>) on the first blade portion (<NUM>) and providing a plurality of second markers (<NUM>) on the second blade portion (<NUM>),
c) determining (S4) of target positions of the first markers (<NUM>) and the second markers (<NUM>),
d) aligning (S6) the wind turbine blade portions (<NUM>, <NUM>) to each other and comparing actual positions of the first markers (<NUM>) and the second markers (<NUM>) with the target positions, wherein step d) is executed by means of digital image correlation, and
e) connecting (S7) the wind turbine blade portions (<NUM>, <NUM>) together.