Patent Application
20110138730
The subject matter described herein relates generally to methods and systems for wind energy systems, and more particularly, to methods and systems of off-shore wind turbines. Specifically, the subject matter described relates to a wind turbine tower segment, in particular for use in off-shore wind turbines, an off-shore wind turbine, an adaptor for use during off-shore wind turbine construction, and a method for erecting an off-shore wind turbine.
Due to limited availability of suitable areas for wind turbines on land, the concept of off-shore wind energy production has gained importance in recent years. In shallow coastal waters, one way of fixing wind turbines is to ram the lowest wind turbine tower segment into the sea bed. The segment is aligned vertically, and a hammer strikes its top repeatedly until the desired penetration depth of the segment into the sea bed is achieved.
The installation of off-shore wind turbines is critical. Off-shore wind turbine construction requires weather windows in which the weather conditions allow assembly of the wind turbines at sea. In particular, the wave height and the resulting motion of the boats and ships present is an important factor for the set-up and erection of off-shore wind turbines. It is generally aimed at reducing the set-up time to a minimum in order to fully utilize the weather windows by performing as many construction steps as possible in said weather windows.
Further, the segment which is rammed into the sea bed sometimes encounters heavy barriers such as large rocks or the like or other obstacles embedded in the sea bed. Subjecting the tower segment to repeated striking by the hammer in the presence of such obstacles induces large loads on the segment. Hence, damage to the lower segment occurs regularly. Further, due to obstacles in the ground, in many cases it is not possible to keep the segment perfectly aligned in the vertical direction. This situation can be compared to a nail in wood, the alignment of which can rarely be corrected once the nail is not perfectly aligned from the very beginning.
Constructional problems related to on-shore wind turbines may have similar effects. For instance, the foundation provided may not have a perfect horizontal alignment, e.g., because the foundation has unilaterally dropped after completion of the foundation.
In order to compensate for non-vertical segments in off-shore wind turbines, or to compensate for non-horizontal foundations in on-shore wind turbines, grouted joints are attached to the respective segment or the foundation with the surface being perfectly horizontal. These grouted joints can also be adapted to a surface that has been damaged by the hammerhead when submerging the segment into the sea bed. This is an additional step that needs to be performed and the grout needs time to cure. During curing time, the set-up has to be stopped which delays the set-up and increases the set-up costs significantly.
In light of the above, it is desirable to have a wind turbine segment, a wind turbine, and a wind turbine erection method that allow a fast and easy erection of the wind turbine.
In one aspect, a wind turbine tower segment for wind turbines is provided that includes a wind turbine tower segment body with a longitudinal axis; and a first and a second end. The surface of at least one of said first and said second end is non-perpendicular with respect to said longitudinal axis of said wind turbine tower segment.
In another aspect, a wind turbine is provided that includes at least one wind turbine tower segment as described herein.
In another aspect, a method for erecting a wind turbine is provided that includes providing a first wind turbine tower segment with a longitudinal axis, and providing a second wind turbine tower segment with a longitudinal axis. The second wind turbine tower segment has a first and a second end. The surface of at least one of the first and second end is non-perpendicular with respect to the longitudinal axis of the wind turbine tower segment. The method further includes mounting the second wind turbine tower segment to the first wind turbine tower segment.
According to a further aspect, an adaptor is provided which is configured to be placed on a wind turbine segment. The adaptor is capable of receiving strikes, such as from a hammerhead, and of transmitting the force of the strikes to the segment.
According to a further aspect, a method for fixation of a tower segment in the sea bed is provided. The method includes providing the segment, providing an adaptor on the upper end of the segment, and striking the adaptor with a hammerhead.
According to an aspect, the embodiments disclosed herein are particularly used in off-shore wind turbines.
Further aspects, advantages and features of the present invention are apparent from the dependent claims, the description and the accompanying drawings.
A full and enabling disclosure including the best mode thereof, to one of ordinary skill in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures wherein:
Reference will now be made in detail to the various embodiments, one or more examples of which are illustrated in each figure. Each example is provided by way of explanation and is not intended to be a limitation. For example, features illustrated or described as part of one embodiment can be used on or in conjunction with other embodiments to yield yet further embodiments. It is intended that the present disclosure includes such modifications and variations.
The embodiments described herein include a wind turbine system, particularly for off-shore use, that compensates for base segments that are not perfectly vertically oriented. More specifically, this compensation allows the erection of the wind turbine to continue without delay. In addition, according to embodiments, damage to the surface of the base segment are avoided.
As used herein, the term “wind turbine” is intended to be representative of any device that generates rotational energy from wind energy, and more specifically, converts kinetic energy of wind into mechanical energy. As used herein, the synonymously used terms “tower segment” and “segment” are intended to be representative of any constructive part of a wind turbine tower for supporting the nacelle. Typically, a plurality of segments is provided one atop of the other thereby forming the wind turbine tower. The plurality may include two, three, four, or even more tower segments. According to typical embodiments, the segments are cylindrical in shape. According to other embodiments, the exact shape of the segment might differ from a perfect cylinder. In both instances, a segment has a longitudinal axis (or also referred to as “axis” herein) along its larger extension. In a perfect turbine tower set-up, the longitudinal axis is typically aligned in the vertical direction. The segment has also a radial direction which is perpendicular to the longitudinal axis. As used herein, the term “off-shore wind turbine” is intended to be representative for any wind turbine that is positioned in salt or fresh water. Consequently, the term “sea bed” shall be understood as also embracing the ground of a lake, for instance, in those cases where the wind turbine is installed in a lake.
According to aspects described herein, at least one end of a segment is inclined. The inclined end may be the upper end, the lower end, or both the upper and lower end. As used herein, the “end” of a segment is intended to refer to the virtual plane that is formed by the end of the segment in the longitudinal direction. Typically, a segment end is shaped by the end of a circular tube. In many cases, a flange is positioned on the end. The indication of “upper” and “lower” is intended to refer to the segment's orientation once it forms part of the turbine tower.
As used herein, the indication of an “inclined end” of a segment is intended to be representative for any segment having an end where the surface of said end is non-perpendicular to the longitudinal axis of the segment. In particular, once the longitudinal axis of the segment is vertically aligned, the respective segment end is misaligned with the horizontal. In other words, the end is inclined (to the horizontal). The terms “horizontal” and “vertical”, respectively, as used herein are generally understood as “perpendicular to the gravitational force” and “parallel to the gravitational force”, respectively. The term “flange” as used herein is intended to be representative for any kind of rib or rim for strength, for guiding, or for attachment to another object, such as another segment. Typically, a flange is positioned at a segment's end.
Rotor blades 22 are spaced about hub 20 to facilitate rotating rotor 18 to enable kinetic energy to be transferred from the wind into usable mechanical energy, and subsequently, electrical energy. Rotor blades 22 are mated to hub 20 by coupling a blade root portion 24 to hub 20 at a plurality of load transfer regions 26. The load transfer regions 26 have a hub load transfer region and a blade load transfer region (both not shown in
In one embodiment, rotor blades 22 have a length ranging from approximately 15 meters (m) to approximately 91 m. Alternatively, rotor blades 22 may have any suitable length that enables wind turbine 10 to function as described herein. For example, other non-limiting examples of blade lengths include 10 m or less, 20 m, 37 m, or a length that is greater than 91 m. As wind strikes rotor blades 22 from a direction 28, rotor 18 is rotated about an axis of rotation 30. As rotor blades 22 are rotated and subjected to centrifugal forces, rotor blades 22 are also subjected to various forces and moments. As such, rotor blades 22 may deflect and/or rotate from a neutral, or non-deflected, position to a deflected position.
Moreover, a pitch angle or blade pitch of rotor blades 22, i.e., an angle that determines a perspective of rotor blades 22 with respect to wind direction 28, may be changed by a pitch adjustment system 32 to control the load and power generated by wind turbine 10 by adjusting the angular position of at least one rotor blade 22 relative to the wind vectors. Pitch axes 34 for rotor blades 22 are shown. During operation of wind turbine 10, pitch adjustment system 32 may change a blade pitch of rotor blades 22 such that rotor blades 22 are moved to a feathered position, such that the perspective of at least one rotor blade 22 relative to the wind vectors provides a minimal surface area of rotor blade 22 to be oriented towards the wind vectors, which facilitates reducing a rotational speed of rotor 18 and/or facilitates a stall of rotor 18.
In the exemplary embodiment, the blade pitch of each rotor blade 22 is controlled individually by a control system 36. Alternatively, the blade pitch for all rotor blades 22 may be controlled simultaneously by control system 36. Further, in the exemplary embodiment, as direction 28 changes, a yaw direction of nacelle 16 may be controlled about a yaw axis 38 to position rotor blades 22 with respect to direction 28.
Further aspects and details of the embodiments described herein are explained in the following with reference to the illustrating drawings. However, it shall be highlighted that the reference to specific figures is for illustrative purposes only. In particular, features explained with respect to one figure can also be combined with other embodiments that are explained with reference to another figure unless this combination is explicitly excluded.
Due to small misalignments that are occasionally unavoidable in practice, or due to heavy obstacles embedded in the sea bed, what may occur is that the first wind turbine segment has an angle to the vertical of some degrees. When referring to the segment in the context of orientation herein, this shall be interpreted as referring to the longitudinal axis of the segment. When referring to the alignment of the turbine segment herein, this shall be interpreted as referring to the segment's axis along the longitudinal extension of the segment. For instance,
As shown in
According to embodiments, both ends of the first tower segment 101 are non-inclined. Hence, if the fixation of the first tower segment in the sea bed functions as intended, the first segment is vertically aligned so that the upper segment 141 of the first segment 101 is horizontally aligned. However, in case the submerging of the tower segment into the sea bed results in a non-vertical alignment of the first tower segment, there is a resulting deviation angle of the segment (i.e. its longitudinal axis) to the vertical. Simultaneously, there is an identical deviation angle between the upper segment end 141 and the horizontal (only in the case of a non-inclined upper end).
The deviation angle between the longitudinal axis of the first segment and the vertical is shown in
After the fixation of the first segment 101 in the sea bed it may be realized that there is a resulting deviation angle 100 between the first segment and the vertical. In the case where the upper end is non-inclined, the deviation angle 100 between the first segment and the vertical is identical to the deviation angle 150 between the upper segment end 141 and the horizontal 150. In the case of an inclined upper segment end 141, the deviation angle 150 results from the addition or the difference of the inclination angle of the upper segment end 141 and the deviation angle 100.
In order to compensate for the deviation angle 150, it is possible that the responsible construction engineer measures the angle precisely and orders an inclined turbine segment from the segment's manufacturer. This shall be called “customized compensation” herein. Although the customized compensation requires an interruption to construction, according to some embodiments, it does not have a negative influence on the construction schedule. This is due to the fact that some off-shore wind turbines are erected according to a two-year cycle where the foundation and the cabling are installed in the first year, e.g. prior to the winter break, and the remaining components of the turbine are installed in the second year.
Hence, in the embodiments of a customized compensation, the first year construction plan may include the fixation of the first tower segment 101 in the sea bed. The resulting deviation angle 150 of the first segment end 141 is measured and transmitted to the segment manufacturer. The second year construction plan may include mounting the second tower segment 102 to the first tower segment 101 wherein the lower segment end 132 of the second tower segment is inclined at an angle that is identical to the deviation angle 150. Thus, in
Thus, the inclination angle of the lower end of the second wind turbine segment is adapted to compensate for the misalignment of the first tower segment. It is possible that only misalignments with a deviation angle larger than a deviation threshold value are compensated for. The deviation threshold value may be, for instance, in the range of up to 0.7°, such as 0.5°.
According to typical embodiments, the inclination angle of the lower end is at least 0.5°, specifically at least 1.0°, and even more specifically at least 1.5°. According to embodiments, the inclination angle of the lower end is a maximum of 2.5°, in particular a maximum of 2.0°, and even more specifically a maximum of 1.5°.
According to the exaggerated illustration, the upper end 141 of the first segment has an inclination angle 161. The inclination angle of a segment end as used herein shall be interpreted as the angle between the end's surface 141 with respect to a plane 151 that is perpendicular to the segment's longitudinal axis. Hence, standard tower segments as used in wind turbines have non-inclined segments, i.e. the inclination angles of their ends' surfaces are 0° with respect to planes perpendicular to their longitudinal axes.
In some cases, it might become apparent that the fixation of the first segment in the ground resulted in a deviation angle 100 between tower segment and vertical. In the shown embodiment, the deviation angle 100, which is identical to the deviation angle 150, is such that it adds to the inclination angle 161 of the upper end 141. Hence, in order to align the second segment 102 in a vertical direction, the lower end 132 of the second segment has to be provided with an inclination angle 172 that is the sum of the inclination angle 161 at the upper end of the first tower segment and the deviation angle 151 resulting from a non-perfect fixation of the first segment.
According to embodiments, two or more segments may be provided with one or more inclined ends. In the embodiments illustrated in
The provision of at least two segments each having one or more inclined ends allows for angular adjustment of the components relative to each other. It is a robust and flexible method of vertically orienting a wind turbine. By pivoting the segments with respect to each other, the resulting overall angle can be adjusted so that the upper segment, e.g. the third segment, is vertically aligned. A maximum deviation of the sum of the inclination angles can be corrected in this way. For instance, if the first segment has a deviation angle of up to 2°, and the combination of the upper end 141 of the first segment 101, the lower end 132 and upper end 142 of the second segment, and the lower end 133 of the third segment 103 have an inclination angle of 0.5°, it is possible to compensate for the deviation angle by pivoting the second and third segment with respect to each other and with respect to the first segment. As a result, the upper end of the third segment is horizontally aligned so that further segments (not shown) with non-inclined ends can be mounted thereon.
According to embodiments, one of the tower segments with at least one inclined end may have a length of less than 10 m, more specifically less than 5 m or even less than 3 m such as 1 m. In the case that the length is not smaller than 2 m, this segment may also comprise a door for entering and exiting the wind turbine. This segment would act as a transition segment.
According to embodiments, internal tower equipment such as cables, elevators, ladders etc. are azimuthally aligned therein. In particular, the length of the segment may be configured such that it is not necessary to fix the internal power equipment to this segment (e.g., the segment's walls). Rather, it is possible that the internal tower equipment can be routed from the tower segment on top thereof to the tower segment below it. This would further ease the construction of the wind turbine.
It is further possible that the segment with at least one inclined end provides one or more reception units for receiving and mounting a boat landing. For instance, the reception units may comprise holes for receiving bolts, pins, screws, or similar. The reception units may further be specifically shaped recesses or projections suitable for fixing and mounting the boat landing. Since the boat landing's position is normally dependent on the prevailing wave direction, which in turn has a time delayed correlation with the wind direction, and since the orientation of the segment with the at least one inclined end is determined by the deviation angle of the first segment, it is typical to provide the boat landing reception units distributed around the segment's circumference. This guarantees that the boat landing can be positioned on the lee side of the wind turbine (given the prevailing wave direction).
At the production of a segment with an inclined end, the following situation has to be taken into account: If the circular segment was simply cut so that the end would be inclined, the shape of the end's circumference would become elliptic as illustrated in
Hence, the inclined ends are typically not produced by simply cutting the segment's ends in an inclined way. The flanges of the segment such as the lower flange 112 and the upper flange 162 should fit to the corresponding flange of the segment that they are fixed to during construction of the wind turbine tower. In most cases, the number of holes for bolts, pins, screws or the like in the flanges of a non-inclined segment end is identical to the number of holes in the flange of an inclined segment end. The holes are typically positioned in an equidistant manner. The flanges of the inclined ends are normally circular in shape.
Thus, in order to produce the segments having at least one inclined end, one can choose from the following options.
First, in case of a segment having only one inclined end, the segment shape is amended from cylindrical to elliptic in the neighbouring region of the flange. The elliptical shaping of the segment is such that the segment end becomes circular in cross-section if it is cut with the desired inclination angle. In other words, if the segment was cut perpendicular to its longitudinal axis, the end would have an elliptical circumference. However, since it is cut slightly inclined, the elliptical shaping is thereby compensated so that the resulting circumference of the end is circular and fits to further segments. The neighbouring region is denoted with 222 in
Since only inclination angles of up to 2° or a maximum of 3° should be compensated for, the relationship between the minor axis and the major axis of the elliptic cross-sectional shaping of the segment is below 3%, e.g. 1%. The elliptical shaping may be accomplished by hammering, welding, or by exerting a drawing force onto the segment.
Second, in the case of a segment having two inclined ends with identical inclination angles at both ends, the segment is made elliptical in shape throughout the complete segment. The orientation of the inclinations is typically in the direction opposite to each other, i.e., displaced at 180°, as illustrated in
Third, in the case of a segment having two inclined ends with differing inclination angles, the segment is made elliptic at one flange and elliptic with a differing major semi-axis size at the other flange. The transition between circular and elliptic shape may, similar to what was described above, be accomplished in the neighbouring region of one of the flanges.
Although this explanation is given with respect to the second segment 102 and the upper end 142, the same applies to other segments, such as the first or the third segment, and other ends, such as the lower end 132.
In addition to what is shown in
According to wind direction measurements, it is apparent that, in most cases, the wind direction is not perfectly horizontal, but also consists of a vertical component. This is called “upflow wind” since the vertical component is generally pointing upwards. It has been found that the maximum energy yield from a wind turbine can be achieved with the rotor's plane being oriented somewhat inclined with respect to the vertical. It is generally possible to achieve this inclination of the rotor by providing a somewhat inclined tower. For instance, if an inclination of the rotor of 4° is desired, one could provide a wind turbine tower having an inclination of 4°. Although the illustration has referred to aiming at a vertically oriented turbine towers thus far, the embodiments described can also be used for providing a slightly inclined tower, such as at angles of up to 6°, e.g. between 3° and 5°. Embodiments described herein basically allow for the provision of any kind of inclination as long as the respective inclined ends at one or more segments are provided.
According to the embodiments illustrated thus far, the wind turbine is a mono-pile turbine wherein, at any given point along the tower height, only one tower segment is provided. For instance, the diameter of such a tower segment is in the range of between 4 and 8 m, specifically between 5 and 7 m.
The described wind turbine tower segments, wind turbines and methods can be applied similarly to the multi-pile tower technique. According to typical embodiments, the method for erection of the multi-pile tower includes fixation of at least two first tower segments in the sea bed, measuring the deviation angle at the upper end of at least one of the first tower segments, and providing respective second tower segments wherein at least one of the second segments has at least one inclined end. The inclination angle typically corresponds to the measured deviation angle.
In
According to a typical set-up, the flanges of the lower ends of the second segments are fixed to the flanges on the upper ends of the first segments. According to the shown illustration, the flange 1112 of the second segment 1102 is fixed to the flange 1111 of the first segment 1101, and the flange 2112 of the second segment 2102 is fixed to the flange 2111 of the first segment 2101. As shown, it is possible that the second segments meet at their upper end, for instance, at the third segment 103. The third segment may be a mono-pile.
In the case of a multi-pile tower, the described embodiments do not only help aligning the segments in the desired direction, the further effect being that it becomes possible for several segments to meet at a desired position. In other words, the alignment of segments by use of the described embodiments further allows the precise positioning of a segment's upper end so that, for instance, it can be fixed to other segments, or a mono-pile segment.
The described systems and methods allow the provision of perfectly aligned wind turbine towers. Grouted joints or similar are no longer necessary. The amount of work that is required to be done at sea is reduced and the overall stability and sustainability of the turbine tower is increased.
In addition, according to the embodiments described herein, off-shore wind turbine towers can, for instance, be made vertically aligned in an easier and faster way. In particular, in the case of at least two tower segments with inclined ends, the construction flexibility is increased, the overall production costs are reduced, and logistics are simplified.
Further, according to an aspect of the present disclosure, a method for fixation of a tower segment into the ground, and a method for erecting a wind turbine are provided. Further, an adaptor for use in the construction of a wind turbine is provided. The methods and the adaptor are particularly used for off-shore wind turbines.
According to an aspect, the method for fixation of a tower segment into the ground includes providing the segment; providing an adaptor on the upper end of the segment; and striking the adaptor with a hammerhead.
According to a further aspect, an adaptor is provided which is configured to be put onto a wind turbine segment. The adaptor is capable of receiving strikes, such as by a hammerhead, and of transmitting the force exerted through to the segment.
The adaptor has an upper end 430 configured to receive a hammerhead 500. The hammerhead 500 repeatedly strikes the upper end 430 of the adaptor in order to exert a force towards the sea bed. The adaptor transmits the force to the first segment 101. Thereby, the first segment is submerged into the sea bed 300.
According to typical embodiments, the upper surface 430 for receiving strikes from the hammer has a smaller diameter than the lower surface 410 of the adaptor 400. The shape of the surfaces is typical circular. Typical diameters of the lower end 410 range between 3 m and 10 m, more specifically between 5 m and 10 m. Typical diameters of the upper end 430 range between 0.5 m and 3 m, more specifically between 1 m and 2 m.
According to embodiments, the shape of the adaptor between the upper end and the lower end is tapered, in particular conical. According to embodiments, the adaptor is a reusable component. For instance, the adaptor may be shipped with the first segment to the construction site. After fixation of the first segment in the ground, the adaptor may be shipped back to shore. It is possible that it is reused for further wind turbine erections, possibly after a regular check and repair of the adaptor.
In some embodiments, the flange 420 of the adaptor 400 is highly stable so that it keeps the lower flange flat and undamaged. This can be achieved by providing stiffening elements to the flange 420 such as a reinforcing cone or an additional plate mounted to the lower end of the adaptor. For instance, in
Further, the adaptor may have an increased wall thickness as compared to the thickness of a wind turbine tower segment. For instance, the thickness may be at least 50 mm, more specifically at least 80 mm or even at least 100 mm. The flange of the adaptor may have a thickness of at least 1.5 times the thickness of the segment to be rammed into the sea bed. According to embodiments, the adaptor may be adapted to receive segments with an inclined end. In particular, the adaptor is reinforced such that it withstands transverse and shear forces originating from the vertical motion of the hammerhead, which are motion which are exerted, via the adaptor, to the inclined upper end of the wind turbine tower segment, in particular in case of an inclination angle of up to 2°.
Alternatively to what is shown in
Further, the lower end 410 may be provided with a stiffening plate for withstanding pressures and forces in the radial direction of the adaptor's lower end.
In contrast to construction methods known to the Inventor, the proposed method prevents severe damage to the upper end 141 of the first segment 101 caused by the hammer First, the adaptor allows a continuous and defined contact between the adaptor and the upper end of the first segment. Second, the hammerhead does not strike the segment directly. For instance, in those methods where the hammer directly strikes the upper end of the first segment 101, some misalignment of the hammerhead in respect to the upper end 141 may occur. This can result in increased forces at specific positions of the upper end and can thus result in damages to the surface of the upper end of the first segment, such as damage to the flange 111.
Exemplary embodiments of systems and methods for an off-shore wind turbine are described above in detail. The systems and methods are not limited to the specific embodiments described herein, but rather, components of the systems and/or steps of the methods may be utilized independently and separately from other components and/or steps described herein. Rather, the exemplary embodiment can also be implemented and utilized in connection with many other rotor blade applications.
Although specific features of various embodiments of the invention may be shown in some drawings and not in others, this is for convenience only. In accordance with the principles of the invention, any feature of a drawing may be referenced and/or claimed in combination with any feature of any other drawing.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. While various specific embodiments have been disclosed in the foregoing, those skilled in the art will recognize that the spirit and scope of the claims allows for equally effective modifications. Especially, mutually non-exclusive features of the embodiments described above may be combined with each other. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.
