Transport of a tower of a wind turbine

Abstract

The disclosed concerns a method of transporting a tower of a wind turbine in an upright position to an assembly site of the wind turbine, whereby the tower is equipped with a strake set comprising a number of strakes positioned to lead from a top of the tower in the upright position down towards a bottom of the tower, at least one of the strakes being realized as a detachable strake. The invention also concerns a strake set and transport assembly.

Claims

1. A strake set for the external surface of a tower of a wind turbine for transport in an upright position to an assembly site of the wind turbine, comprising: a number of independently adjustable strakes, wherein at least one of the strakes has a helicity which is adjustable when the strake is attached to the tower of a wind turbine at at least one point; wherein at least one of the independently adjustable strakes includes a rope, wherein the rope is covered along at least a substantial part of its longitudinal extension with a covering structure which substantially increases the wind resistance of the strake, and the covering structure is not directly attached to the tower and is not directly attached to the rope.

2. The strake set according to claim 1, wherein the covering structure may move with respect to the rope.

3. The strake set according to claim 1, wherein the covering structure is comprised of individual sections.

4. The strake set according to claim 1, wherein the portion of the rope covered with the covering structure is a distance sufficient to cover a quarter of a height of the tower.

5. The strake set according to claim 1, wherein the covering structure has a cross-sectional shape with reference to the longitudinal extension of the strake, the cross-sectional shape comprising a geometrical figure with at least three angles.

6. The strake set according to claim 5, wherein the geometrical figure comprises a number of planes interconnecting the angles, each of the number of planes having essentially a same extension in the cross-section.

7. The strake set according to claim 5, wherein the covering structure is assembled about the rope over a mechanical reinforcement structure, the mechanical reinforcement structure configured to support the covering structure in the geometrical figure.

8. The strake set according to claim 1, wherein the covering structure leaves at least one terminating portion of the rope uncovered.

9. The strake set according to claim 1, wherein the covering structure comprises a flexible film material.

10. The strake set according to claim 2 wherein the rope comprises a fibre material.

11. A turbine tower equipped with a strake set according to claim 1.

Description

BRIEF DESCRIPTION

(1) Some of the embodiments will be described in detail, with reference to the following figures, wherein like designations denote like members, wherein:

(2) FIG. 1 shows a perspective view of a strake set according to an embodiment;

(3) FIG. 2 shows a perspective view of a wind turbine tower according to an embodiment;

(4) FIG. 3 shows a side view of the same wind turbine tower as in FIG. 2;

(5) FIG. 4 shows a diagram of calculated lift forces on a tower according to the state of the art under different wind speed conditions;

(6) FIG. 5 shows a simulation result of vortex shedding behaviour of the same tower as referred to in FIG. 4;

(7) FIG. 6 shows a diagram of calculated lift forces on a tower according to an embodiment of the invention under the same wind speed conditions as referred to in FIG. 4;

(8) FIG. 7 shows a simulation result of vortex shedding behaviour of the same tower as referred to in FIG. 6;

(9) FIG. 8 shows a perspective view of a raising device according to a preferred embodiment;

(10) FIG. 9 shows a first side view of the same raising device placed on top of a tower in a locked position;

(11) FIG. 10 shows a second side of the same raising device without the tower;

(12) FIG. 11 shows a detailed view of a detail from FIG. 9;

(13) FIG. 12 shows perspective sectional view of a further detail of the same raising device;

(14) FIG. 13 shows a top view of the same raising device equipped with a cover; and

(15) FIG. 14 shows a perspective view of the same raising device with the cover placed on top of a tower.

DETAILED DESCRIPTION

(16) FIG. 1 shows an embodiment of a strake set 103 according to the invention. It comprises three detachable strakes 101, two of which are shown here. All detachable strakes 101 are of the same make, i.e. identical. Each of the detachable strakes comprises a rope 105 of an ultra-high molecular weight polyethylene fibre material. The ropes 105 are both encompassed along parts of their longitudinal extensions L.sub.1 by a covering structure 109. The ropes 105 project from the covering structure 109 at either side of the longitudinal extensions L.sub.1 reaching from an upper end US to a lower end LS. In a designated position (cf. FIGS. 2 and 3) the strakes 101 are connected to the tower of a wind turbine such that the upper end US faces essentially vertically upwards and the lower end LS faces essentially vertically downwards when to wind turbine tower is positioned in an upright position.

(17) At either longitudinal ends US, LS the covering structures 109 are equipped with an end piece 106 through which the ropes 105 are led via openings in the end piece 106. At the lower ends LS there is also attached a (circular) end stop 108, here a metal end stop, with a diameter of 100 mm and a thickness of 10 mm, which end stop 108 prevents the covering structures 109 from uncontrolledly slipping down along the ropes 105 when the detachable strake 101 is suspended.

(18) The shape of the end pieces 106 represents the cross-sectional shapes S of the covering structures 109 all along the longitudinal extensions L.sub.1. They are triangular shapes S defined by three planes P.sub.1, P.sub.2, P.sub.3 (represented here by lines P.sub.1, P.sub.2, P.sub.3) which are interconnected via three angles a.sub.1, a.sub.2, a.sub.3. Thereby the planes P.sub.1, P.sub.2, P.sub.3 have the same extension, namely 300 mms, and the three angles a.sub.1, a.sub.2, a.sub.3 all have the same value, namely 60. The triangular shape S thus constitutes an equal-sided triangle.

(19) Each of the covering structures 109 comprises five structure sections 109a, 109b, 109c, 109d, 109e having a longitudinal extension each of 1020 mm. More structure sections may be added if necessary to increase the length of coverage of the ropes 105, for instance if the strakes 101 are to be attached to higher towers.

(20) The structure sections 109a, 109b, 109c, 109d, 109e are assembled adjacent to each other but may also be separated from each other, for instance to extend the overall extension of the covering structure over a wider area of the rope 105. The division of the covering structure 109 into structure sections 109a, 109b, 109c, 109d, 109e makes it easier to transport and store the strakes 101 when they are detached from a wind turbine tower. The structure sections 109a, 109b, 109c, 109d, 109e and thus the covering structure 109 are comprised of flexible film material comprising polystyrene.

(21) At the upper ends US of the ropes 105 there are connected detachable connection interfaces 107 realized as thimbles 107 of the ropes 105. By these connection interfaces 107 the strakes 101 can be connected to a top of a tower of a wind turbine

(22) Such tower 111 of a wind turbine 100 is shown in FIGS. 2 and 3. The three strakes 101 (all of which are shown in these two depictions) of the strake set 103 are detachably connected to the top T of the tower 111, from where the go along the outer surface of the tower 111 towards the bottom B of the tower 111. FIG. 3 shows the overall longitudinal extension L.sub.2 of the tower 111 from the top T to the bottom B. At the top T a nacelle (not shown) of the wind turbine 100 can be attached when the tower 111 is installed at its bottom B on a designated foundation (not shown). The covering structures 109 of the strakes 101 only reach downwards at a length L.sub.3 of the tower 111, namely along about a third of its total longitudinal extension L.sub.2. The ropes 105 (not depicted in FIGS. 2 and 3) extend further down to the bottom B of the tower 111 where they are affixed to the tower 111 at its outside surface.

(23) The strakes are assembled around the circumference of the tower 111 equidistantly, i.e. at the same angles of 120 from each other with reference to the tubular cross-section of the tower 111. They wind around the outer surface of the tower 111 in a helical shape so as to catch the wind, in particular in the upper region of the tower 111 where the covering structures 109 of the strakes 101 catch the wind to lead it further away from the tower 111 and thus to avoid vortex induced vibrations.

(24) In this exemplary embodiment, the tower 111 has a diameter of 3000 mm at its top T. The pitch of the helical shape (i.e. the helicity) of the strakes 101 is five times that diameter. The strakes 101 project from the outer surface of the tower 111 about 260 mm, i.e. essentially about 10% of the diameter of the tower 111.

(25) FIGS. 4 to 7 can serve to explain the effect of such strakes 101. FIGS. 4 and 5 show representative simulation results of the forces and airflow on a prior art tower 111 of a wind turbine. FIGS. 6 and 7 in contrast show representative simulation results of the forces and airflow on a tower 111 of a wind turbine equipped with a strake set 103 according to an embodiment of the invention.

(26) FIGS. 4 and 6 show diagrams of calculated (i.e. simulated) lift forces F on the towers 111, 111 over a time t under different wind speed conditions Vw, namely winds coming from a defined side at speeds of 24 m/s, 27.2 m/s and 30 m/s. It can be observed that these lift forces F vary enormously in FIG. 4, i.e. show strong oscillations, whereas the lift forces F are all nearly constant in FIG. 6. Oscillations in lift forces F induce vibrations, namely vortex induced vibrations.

(27) This can be explained when referring to FIGS. 5 and 7 depicting the vortex shedding 113, 113 of a prior art tower 111 (FIG. 5) in comparison with that of a tower 111 according to an embodiment of the invention (FIG. 7). The first vortex shedding (FIG. 5) is firstly substantially longer than the second one (FIG. 7) and also much narrower, situated right at the back of the tower 111 (seen from the wind direction) so that the lift forces F have a much stronger impact on the tower 111 than on the tower 111 where they are wider due to the strakes 101 of the strake set 103. The strakes 101 have the effect of leading a substantial part of the wind to the side of the tower 111 (seen from the wind direction) rather than directly behind it. This is irrespective of where the wind comes from as the strakes 101 are aligned around the tower 111 to essentially form the same surface of the tower 111 combined with the strakes 101.

(28) FIGS. 8 to 14 show explanatory depictions of a raising device which can be used together with a strake set according to the invention to form a transport assembly according to an embodiment of the invention.

(29) FIG. 8 shows a raising device 1 for raising a tower section (not shown) of a wind turbine. The raising device 1 comprises a connection member 3 realized as an eye 3 which is attached via a first hinge 5 to four connection shapes 28. To these connection shapes 28 there is each hingedly attached via a second hinge 9 a connection beam 27. The connection beams 27 are thus connected essentially at their first end via the second hinges 9 to the connection shapes 28 and at their second ends to third hinges 11 to holding members 19a, 19b, 19c, 19d (the two latter being obscured in the figure due to the perspective view) realized as claws 19a, 19b, 19c, 19d. The holding members 19a, 19b, 19c, 19d are realized as two pairs of corresponding holding members 19a, 19b, 19c, 19d, namely a first pair of corresponding holding members 19c, 19d is aligned along a first holding beam 21a and a second pair of corresponding holding members 19a, 19b is aligned along a second holding beam 21b.

(30) The raising device 1 thus further comprises a first holding beam 21a and a second holding beam 21b which is a perpendicularly positioned cross-beam to the first holding beam 21a. These two holding beams 21a, 21b are directly interconnected at the centre C of the raising device 1 and indirectly by diagonal connections 23 at about the middle of the distance of each holding beam 21a, 21b from the centre C of the raising device 1 to the end of the respective holding beam 21a, 21b. At these ends of the holding beams 21a, 21b fourth hinges 13 are positioned which connect each of the holding beams with one of the claws 19a, 19b, 19c, 19d.

(31) From the centre C of the raising device 1 at which the two holding beams 21a, 21b are interconnected directly, an upward-facing beam 30 is also connected to the two holding beams 21a, 21b (directly or indirectly). That beam 30 is hollow and essentially extends up to the connection shapes 28, but is not directly connected to these. Inside the hollow beam 30 there is positioned another guiding beam 7 which is connected to the connection shapes 28 and thus indirectly to the connection member 3.

(32) At either end of each of the holding beams 21a, 21b there are positioned legs 15 extending downwards (i.e. away from the connection member 3) on which the raising device 1 can rest stably if stored on ground. In addition, at all of these mentioned ends of the holding beams 21a, 21b there is also an eye 17. The eyes 17 can be used to move and steer the raising device (and a tower connected to it) in a circle, i.e. to orientate the tower during a raising and transport processes and in particular during assembly of the tower at a designated operating site. Further, the raising device 1 comprises a blocking mechanism 25 the function and details of which will be explained with reference to FIGS. 11 and 12.

(33) When the raising device 1 is raised by a raising machine such as a crane, it is connected to that raising machine via the connection member 3 which is thus raised in an upward direction U. Reversely, when the raising device 1 is lowered to the ground, it is lowered in a downward direction D until the connection member 3 goes downwards into the position shown in FIG. 8. At the same time, due to the movement mechanism of the raising device 1, the raising force while raising the raising device 1 in the upward direction is transferred via the four hinges 5, 9, 11, 13 into a moving force which tilts each of the holding members 19a, 19b, 19c, 19d in a locking direction L, i.e. out of the open position depicted in FIG. 8 into a locking position. Reversely, when no raising force is applied to the raising device 1 anymore, i.e. when the connection to the raising machine via the connection member 3 is released or lose, the weight of the upper parts of the raising device 1 is enough to move the holding members 19a, 19b, 19c, 19d from the locking position in an counter direction A to the locking direction L into the open position again. Additionally, this movement in the counter direction A may be supported by actors such as springs (not shown).

(34) In essence, this construction permits an automatic tilting movement of the holding members 19a, 19b, 19c, and 19d in both the locking direction L and the counter direction A based on the force exerted on the connection member 3. No manual or motor support of that movement is necessary.

(35) In this context, it can be stated that the term movement mechanism refers to all those movable parts of the raising device 1 which interconnect the connection member 3 with the holding members 19a, 19b, 19c, 19d serving to transfer the raising (and lowering) forces inflicted on the connection member 3 into forces for moving the holding members 19a, 19b, 19c, 19d into or out of the locking position, i.e. in the locking direction L or the counter direction A.

(36) Referring now to FIG. 9, which is a first side view of the same raising device 1 installed on top of a tower 31 of a wind turbine 100. The raising device 1 is thereby in a locked position, i.e. the holding members 19a, 19b, 19c, 19d have been moved completely in the locking direction L. Therefore they engage with an inwards protruding part (not shown) of an inner flange 29 of the tower 31 which inner flange 29 is comprised of the top element of the tower 31 which can be seen in FIG. 9 and of the inwards protruding part which cannot be seen. As the holding members 19a, 19b, 19c, 19d are all orientated with their locking directions towards the inner surface of the tower 31, their lower part has been tilted below the inner flange 29 so that the holding members 19a, 19b, 19c, 19d facing into four directions and all orientated in a 90 angle to the next holding member hold the inwards protruding part of the inner flange 29 firmly from underneath. In this arrangement, the feet 15 are positioned outside of the tower 31.

(37) FIG. 10 shows the same raising device 1 in a second side view which is perpendicular to the side view of FIG. 9. It can be seen here that along the first holding beam 21a (and the same applies with respect to the second holding beam 21b and all the elements connected with it) the holding members 19a, 19b, 19c, 19d are positioned fixedly via their fourth hinges 13 to the first holding beam 21a along a predefined distance d. The locking direction L.sub.1 of the holding member 19d at the right hand side is orientated away from the centre C of the raising device 1 further to the right whereas the locking direction L.sub.2 of the holding member 19c at the left hand side faces exactly in the opposite direction.

(38) Further, it can be seen in FIG. 10 that to each of the holding members 19a, 19b, 19c, 19d there is connected a connection eye 33 projecting towards the centre C of the raising device 1. These connection eyes 33 can be used to connect to a cover which will be explained with reference to FIGS. 13 and 14.

(39) FIGS. 11 and 12 serve to explain the blocking mechanism 25 in more detail. The blocking mechanism 25 comprises an inlet shell 35 for a pin 37 through which the pin 37 can be led inside the beam 30 (obscured in this figure due to the perspective). A handle 39 is connected to the pin 37 in order to facilitate manual (or motor-driven) movement of the pin 37 into the beam 30 and out again. At the lower end of the handle 39 two catch bolts 41a, 41b are positioned which are realized to firmly hold the handle 39 in a desired first, open, position (corresponding to the left catch bolt 41a) and in a desired second, blocked, position (corresponding to the right catch bolt 41b). Thus, the catch bolts 41a, 41b serve to fix the handle 39 in one of these two positions to prevent it from moving undesiredly.

(40) FIG. 12 shows a section view of the beam 30 with its inner guiding beam 7. In order for the pin 37 to block the movement of the movement mechanism, the guiding beam 7 comprises two recesses 26 along its longitudinal extension (i.e. the upward direction U and the downward direction D) one of which is depicted in FIG. 12. At two given predefined positions of the guiding beam 7 corresponding with the locking position and the open position of the holding members 19a, 19b, 19c, 19d the pin 37 can thus be inserted into the recesses 26 of the guiding beam 7 thus blocking the guiding beam 7 in its position and further blocking any movement of the movement mechanism.

(41) Turning to FIGS. 13 and 14, this shows the same raising device 1 which is further equipped with a cover 43. The cover 43 is connected to the raising device via 1 the connection eyes 33 (cf. FIG. 10) and serves to shield the inner side of the tower 31 from the ambient environment, in particular from rain or snow. The cover 43 comprises a first opening 47 realized as a service hatch 47 through which staff can climb in order to get from the inside of the tower 31 to the upper side of the cover 43 or reverse. Moreover, the cover 43 comprises four through-openings 45 through which the holding members 19a, 19b, 19c, 19d are inserted.

(42) Although the present invention has been disclosed in the form of preferred embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention.

(43) For the sake of clarity, it is to be understood that the use of a or an throughout this application does not exclude a plurality, and comprising does not exclude other steps or elements.