WO2011079973A2

WO2011079973A2 - Method of construction of a tower of a wind turbine and tower

Info

Publication number: WO2011079973A2
Application number: PCT/EP2010/064319
Authority: WO
Inventors: Martin Johan Smith Jensen; Esben Vadstrup
Original assignee: Siemens Aktiengesellschaft
Priority date: 2009-12-18
Filing date: 2010-09-28
Publication date: 2011-07-07
Also published as: DE112010004883T5; WO2011079973A3

Abstract

The invention concerns a method of construction of a tower (1') of a wind turbine with an outside (O) and an inside (J) comprising a ground section (3) of concrete and a higher section (5') of a material different from concrete which ground section (3) and higher section (5') are joined together at an interface (10) in a region of which interface (10) a filling material (9) is injected, whereby the filling material (9) is completely injected from the inside (J) of the tower (1'). The invention also concerns a tower (1') of a woind turbine constructed by such method.

Description

Method of construction of a tower of a wind turbine and tower

The present invention concerns a method of construction of a tower of a wind turbine with an outside and an inside, the wind turbine comprising a ground section of concrete and a higher section of material different from concrete, which ground section and higher section are joined together at an interface. In the region of this interface a filling material is injected. The invention also concerns a tower of a wind turbine with an outside and an inside comprising a ground section of concrete and a higher section of material different from concrete which ground section and higher section are joined together at an interface in a region of which inter- face there is a filling material.

The technological evolution in wind power generation involves increasingly larger and more powerful machines which optimize the output power. However, this goes along with taller and heavier towers. Thus, the development of such towers has to be done according to different rules related to design crite^¬ ria such as load, material strength and dynamic behaviour as well as construction, transport and installation conditions. It is possible to produce towers for wind power applications using basically tubular sections made of steel. However, this is limited to a height of the tower of approximately 80 m. Higher towers involving higher loads require more resistant structures. On the other hand transport parameters for the transport of wind turbines to their location of operation al^¬ low only diameters of wind turbine towers segments of about 4.5 m. That in return means that the steel plate thickness of such towers segments needs to be increased when one wants to build higher towers than 80 m in order to increase the sta- bilty. However, that also has its narrow limits because of cost and material saving considerations. Therefore, towers of the kind mentioned in the introduction have been introduced. In particular, concrete is used for certain parts of a wind turbine towers, in particular at the bottom of the tower. Instead of producing a complete tower out of concrete, it is preferred due to the large heights of such towers, to produce only a ground section this way. That means that the effort and material and also the costs for producing wind turbine towers of large heights above 80 m can be kept within a reasonable limit.

EP 1 947 328 Al discloses a joining device for such hybrid wind turbine towers which is intended for fixing a metal sec^¬ tion of a wind turbine tower to a concrete section of this tower. The joining device comprises a metal body provided with a number of anchoring openings that are adapted such that the material of the concrete portion passes there^¬ through. However, the joining device is partly cast into the wind turbine tower and it is difficult to get the joining de^¬ vice in level as this component is large and heavy and diffi- cult to handle in such height.

WO 2005/015013 Al discloses a tower of a wind turbine com^¬ prising a concrete towers section and a steel towers section having an end portion embedded into the concrete tower sec- tion. The steel tower section at its embedded end portion comprises anchoring elements. Said anchoring elements project radially from both inner and outer surfaces of the wall of the steel tower section. However, a very large concrete wall thickness is needed in such a tower design in order to with- stand horizontal load components resulting from such protrud^¬ ing elements. Thus, this construction is not very advanta^¬ geous for hybrid wind turbine towers .

It is also known to provide the interface between the con- crete and the steel section or a section of another material, by using a filling material between the segments together with a number of pretension bolts. Such construction is shown in Fig . 1 : It shows a detail of a wind turbine tower 1 comprising a ground section 3 made of concrete and a higher section 5 made of steel. The ground section 3 and the higher section 5 are joined together at an interface 10. For that purpose, use is made of two bolts 7a, 7b which are directed through channels 11 in the ground section 3 and through holes in the foot of the higher section 5. A part of section 5 is directed to the outside 0 and another part of it is directed to the inside J of the tower 1. At either end of the bolts 7a, 7b nuts 13a,

13b, 13c, 13d are affixed so that by tightening the nuts 13a, 13b, 13c, 13d a strong connection between the ground section 3 and the higher section 5 is achieved. In order to provide for a connection between the ground section 3 and higher sec- tion 5 which does not let water through and thus clearly isolates the inside J from the outside 0, a filling material 9 is injected in the region of the interface 10, i.e. on top of the ground section 3 and underneath the foot of the higher section 5.

In order to assemble the sections 3, 5 of a wind turbine tower 1 in the way resulting in a configuration according to Fig. 1, the following process is necessary in principle: Firstly, the concrete ground section 3 is produced, for in^¬ stance by slip moulding or by using prefabricated tower mod^¬ ules or by the so-called jump form technique. Secondly, the higher section 5 is lifted up to the level of the ground sec^¬ tion 3 by a crane. Thirdly, the higher section 5 is levelled by shims in between the ground section 3 and the higher sec^¬ tion 5. In the fourth step, the higher section 5 is bolted to the ground section 3 and in a fifth step the filling material 9 is filled into the gap remaining in the interface 10 in be^¬ tween the ground section 3 and the higher section 5. After that, the bolts 7a, 7b and nuts 13a, 13b, 13c, 13d are op^¬ tionally post-tensioned . It must be noted, however, that this particular construction is rather difficult and dangerous to produce: firstly, it is necessary to have a ground section 3 with an increased width in that region where the channels 11 for the bolts 7a, 7b are realized. Secondly, both tightening the bolt 13b which is orientated towards the outside 0 and filling the filling ma^¬ terial 9 into the gap in between the ground section 3 and the higher section 5 is complicated and can only be done by means of a platform placed outside the tower 1. This is not only an extra equipment needed and an extra process step during the process of the construction of the tower 1, but also consti^¬ tutes a potential danger for workers employed on the plat^¬ form. In particular, one has to imagine that the height of the ground section 3 maybe about 20 m or even higher and also that the construction of the tower 1 is sometimes carried out under severe weather conditions in dangerous locations such as strong wind forces offshore. To sum up, connecting a ground section 3 and a higher section 5 in the way described in the state of the art according to Fig. 1 implies a number of safety concerns and is also rather tedious and time- consuming .

It is therefore an object of the invention to provide for an improved possibility of how to join a higher section to a concrete ground section of a wind turbine tower, in particu^¬ lar to improve safety and/or effectivity and/or speed of this process .

According to the invention, this object is met by a method according to claim 1 and by a tower of a wind turbine accord^¬ ing to claim 13.

Thus, according to the invention, the above-mentioned method is enhanced by the measure that the filling material is com- pletely injected from the inside of the tower.

In other words, no work for the connection of the ground sec^¬ tion with the higher section needs to be carried out from a platform outside. For instance, this can be realised by in^¬ troducing a filling material which cures very quickly so that while the filling material is injected from the inside of the tower it already hardens so fast, that once it reaches the outside it has become solid enough to stay in place. Another possibility is to limit the flow of the filling material from the inside to the outside by limiting means. Such limiting means will be specified later within the context of this de^¬ scription .

An advantage of this solution is that no work needs to be carried out on the outside. This also makes connection work easier and safer, in particular with reference to the filling of the filling material into the gap between the ground sec- tion and the higher section. And therefore, the shortcomings of the state of the art described above are virtually elimi^¬ nated .

According to the invention, the tower of the aforementioned kind is realised such that the extension of the filling mate^¬ rial is limited at the outside of the tower. Therefore, no work from outside of the tower is necessary to fill the gap in between the ground section and the higher section, which is made possible by the method according to the invention as described above. Limiting the extension of the filling mate^¬ rial may again be realised by choosing a particular filling material with properties such as described above or by using limiting means which will be specified below. Particularly advantageous embodiments and features of the in^¬ vention are given by the dependent claims, as revealed in the following description. Thereby, features revealed in the con^¬ text of the method may also be realized in the context of the tower and the other way round.

According to particular preferred embodiment grout is used as a filling material. This is due to the fact that grout pro^¬ vides a strong interface and at the same time does not shrink while it is being hardened. This is particularly important in the case described here as a control of the filling process is just carried out from one side, i.e. from the inside of the wind turbine tower. That means that the existance of spaces unfilled with filling material cannot be detected from the outside so that it must be made sure that such unfilled spaces do not occur. Therefore it is necessary to have a very reliable filling material, and grout is such material. As for the higher section, it is preferred that metal, pref^¬ erably steel, is used as its material. As steel is currently the material used for wind turbine towers consisting of one material only, the combination of a concrete ground section with a metal, preferably steel section as a higher section provides for reliable materials the reactions of which to en^¬ vironmental influences in the field of wind turbine towers are a well-known and examined.

As mentioned before, the method according to the invention can be realised for example by limiting means which limit the flow of the filling material. According to a particularly preferred embodiment, the flow of the filling material from the inside to the outside is limited by a cover at the out^¬ side which cover bridges the interface between the ground section and the higher section and which is positioned all around the circumference of the tower in the region of the interface. Such cover functions like a kind of adaptor and may comprise several parts aligned with each other along seg^¬ ments of the perimeter of the tower. This way it can be real- ized such that the cover parts combined will cover the com^¬ plete circumference along the segments of the tower. For that purpose the cover parts may also be interconnected, e.g. by fastening means. Such cover can be attached to either the ground section or the higher section before placing the higher section onto the ground section so that there is already provided the limiting means for the filling material on the outside of the tower. In other words, instead of providing for such limits in 20 metres or more height, the limits can already be assembled before the higher section is placed on top of the ground sec^¬ tion. For instance, the ground section can be completed and finished by attaching such cover to its perimeter on top.

It is further preferred that the cover used is part of a pro^¬ file which is attached, for instance bolted, to the ground section and/or to the higher section in the region of the interface. Such profile is characterised by the fact that it defines not just one circumferential plane as might be ex^¬ pected from a cover, but rather defines at least two planes one of which can be placed in a suitable way to bridge, i.e. to connect the ground section and the higher section. For instance, one plane may simply be an extension of the ground section, whilst the other plane may lead in the direction of the inside of the tower. This way it can be assured that filling material gets right up to the end of the ground sec^¬ tion but does not flow out on top once the filling material has been filled in sufficiently.

When using such profile, it is particularly preferred that it is made up of at least two parts, one first part which is at^¬ tached to the ground section or to the higher section and a second part which is attached to the first part. For example, the first part may be a lower part attached to the ground section and the second part may be an upper part directed to^¬ wards the higher section. However, the upper part would not necessarily need to be connected to the higher section, but is definitely connected to the first part. This means that the two parts mentioned may constitute different extensions or planes such as the ones described above. Using two differ^¬ ent parts of the profile also means that the first part may for example always be used as a standard construction element for all kinds of wind turbine towers, while the second part will be used out of a range of possible second parts and cho^¬ sen according to the size and general outlet and design of the wind turbine tower in the specific case. It has proven particularly advantageous if the cover is orientated at least partially under an angle, i.e. bigger than 0° and smaller than 90°, to the vertical extension of the tower. This means that the cover is neither orientated purely vertically nor purely horizontally. A purely vertical orien^¬ tation would increase the danger of filling material coming out at the upper end of the cover, i.e. in the region of the higher section, while a purely horizontal orientation would mean that the cover could not bridge the gap between the higher section and the ground section. Therefore, orientating the cover at least partially under an angle will circumvent these possible drawbacks effectively. It is furthermore preferred that the cover comprises a resil^¬ ient material. It can then be used more flexibly because the resilient material will adapt its shape so that it perfectly bridges the gap in between the ground section and the higher section. For instance, a metal cover can be used which has a sufficient resilience to be bent without breaking and/or without being deformed permanently. Such metal cover may be permanently fixed to either the ground section or the higher section and loosely connected with the other section. In addition, the shape of such resilient cover may be such that the cover functions like a spring. The loose connection to the second section may be realized such that this section is provided with a nose behind which in a direction facing into the inside of the tower there is orifice. An end part of the cover can then be inserted into the orifice and held in place by the nose. This has the effect that such assembly can be realized while the higher section is placed onto the ground section. The loose connection will nevertheless be a perma^¬ nent connection in effect due to the filling material being filled into the gap in between the two sections which pro- vides a kind of adhesive bonding of the cover to the higher section . It is thus also a preferred embodiment of the invention to bring the cover into permanent contact with a contact surface of the ground section and/or of the higher section in the region of the interface. This makes sure that a stable arrange- ment of the ground section, the higher section, the cover itself and the filling material is realized. Alternatively how^¬ ever, there may also be provided a possibility to remove the cover after the process of injection of the filling material. In such case the cover is only brought into a non-permanent contact with contact surfaces of the ground section and of the higher section and will be removed after the filling process, e.g. by tearing it off from the outside, in particu^¬ lar from below as this makes sure that noone needs to be situated up in the height of the interface of the higher sec- tion with the ground section. This can for instance be real^¬ ized by using a rope attached to the cover and pulling the rope from a position on the ground.

During the filling process it is important to make sure that the filling material fills out the complete gap in between the higher section and the ground section. While this can be made sure in the state of the art by visual control from both the inside and the outside of the tower, it is not possible or wished for in such way in the context of the present in- vention. Therefore, indicating means of a saturation of the gap in between the two sections need to be utilised. One par^¬ ticularly advantageous way how to reliably indicate such a saturation is reached by aligning an air hose from the outside to the inside, preferably along a bottom face side of the higher section in the region of the interface. This air hose defines an outlet for air during the injection of the filling material and shows as an indicator that the region of the interface is completely filled with filling material. This indication is given once the filling material comes out of the air hose at its end facing to the inside of the tower. This shows that the filling material has reached the upper end of the gap at that end of the air hose which is facing towards the cover. It is most advantageous if the air hose is situated at the highest point of the gap, in particular if it reaches up to a point very close to the cover. In this case a complete filling of the gap with filling material is indi^¬ cated when the filling material comes out at the end of the air hose facing to the inside of the tower. Such an air hose may be aligned at only one point along the circumference of the tower, however it is preferred to align several air hoses, preferably at certain constant intervals along the circumference of the tower.

A particularly advantageous way of aligning such an air hose is by including it into a shim which serves to level the higher section on the ground section at certain points along the circumference of the tower. For that purpose, the shim preferably has an orifice facing towards the higher section into which the air hose can be inserted and thus be fixed firmly enough and orientated in the correct way without any further effort of alignment. However, air hoses can also be attached to the higher section, e.g. by adhearing them to the higher section in the region of the interface or by other fixing means. It may be noted that the air hose may also serve as an outlet for gases, e.g. air, during the injection process, for instance in cases where gas bubbles rise up in the filling material during the injection process.

In order to increase stability and in order to have a larger interface between the higher section and the ground section, it is particularly preferred that the higher section is formed in an L-shape in a section in the region of the inter- face, a first part of the L-shape projecting upwards and a second part of the L-shape directed into the inside of the tower. Such L-shape is preferably such that the first part and the second part are essentially perpendicular. The effect of an L-shape of the higher section in this region is gener- ally that the higher section rests more stably on the ground section and can be easier brought into the correct orienta^¬ tion on the ground section, e.g. by shims. In addition, the increased interface region means that more filling material can be put into the gap between the ground section and the higher section which makes up for a more stable and a more water and gas proof connection between the two sections. Whereas in the state of the art the higher section and the lower section are connected by bolts both at the inside and at the outside of the tower, it is particularly advantageous in the context of the present invention if bolts connecting the ground section and the higher section are all positioned at the inside of the tower. This makes sure that not only the filling process can be carried out from the inside of the tower but also the bolting process, i.e. the firm connection process. This implies again a significant reduction of danger for staff in comparison with the state of the art where at least part of the bolting is carried out at the outside of the tower.

Other objects and features of the present invention will be^¬ come apparent from the following detailed description consid- ered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for the purposes of illustration and not as a definition of the limits of the invention. In the drawings, like reference numbers refer to like objects throughout. Objects in the diagrams are not necessarily drawn to scale.

Fig. 1 shows a section view of a detail of a wind turbine tower according to the state of the art,

Fig. 2 shows a section view of a detail of a wind turbine tower according to an embodiment of the present invention, Fig. 3 shows a more detailed section view of the interface between the ground section and the higher section of the wind turbine tower of Fig. 2, Fig. 4 shows a top view at the ground section of the wind turbine tower of Figs. 2 and 3.

Fig. 1 has already been discussed in the context of the de- scription of the state of the art.

Figure 2 shows a detail of a wind turbine tower 1 ' according to an embodiment of the invention in a section view. The tower 1 ' comprises a ground section 3 made of concrete and a higher section 5' made of steel which are interconnected by a bolt 7 which is led through a channel 11' in the ground sec^¬ tion 3. The bolt 7 projects into the inside J of the twoer at either end (only the top one of which is shown) . In the region of the interface 10 between the ground section 3 and the higher section 5' grout 9 is inserted as a filling material from the inside J of the tower 1 ' , whereas from the outside 0 the flow of the grout 9 is limited by a cover 17. The cover 17 is permanently fixed to the ground section 3 by a small bolt 19. The higher section 5' has an L-shape. It comprises a vertical part 5a' and a horizontal part 5b' which is orien^¬ tated in the direction of the inside J of the tower 1 ' . The vertical part 5a' and the horizontal part 5b' are perpedicu- lar to each other. An air hose 15 is aligned in the region of the interface 10 at a surface of the higher section 5', i.e. of the horizontal part 5b', which surface is orientated to^¬ wards the ground section 3.

This arrangement can be clearer seen in a detailed view of the interface 10 as shown in Fig. 3. In particular, it can be seen that the higher section 5' has a small nose 23 on the surface 22 facing towards the ground section 3 right by the outside 0 of the tower 1'. Behind the nose 23 in a direction towards the inside J a ring-shaped orifice 21 or groove is positioned. This orifice 21 serves as an abutment for the spring-like cover 17. Into the orifice 21 one end of the air hose 15 is led, whereas the other end of the air hose 15 is located at the inside J of the tower 1 ' . This way it can be made sure that the grout 9 which is filled from the inside J into the interface 10 will be filled into the complete gap of the interface 10 up to the highest level of the gap in the region close to the outside 0 of the tower 1 ' , this highest level being defined by the orifice 21. Only when this orifice 21 is filled with grout 9 the grout 9 will enter the air hose 15 and eventually come out at the other end of the air hose 15 to indicate that the filling has been completed.

The cover 17 comprises a first part 17a and a second part 17b. The second part 17b is connected to the ground section 3 by the bolt 19 as mentioned in the context of Fig. 2. The first part 17a is connected by another bolt 25 to the second part 17b. The second part 17b has a rectangular L-shape so that its one part projecting away from the ground section 3 is orientated in a purely vertical way. At the same time, the first part 17a also has an L-shape, however one which is not perpendicular in shape. Rather the angle of the first part 17a is bigger than 90°. Therefore, the overall shape of the cover 17 is partly angular with respect to the higher section 5' . The first part 17a ends up in the orifice 21 so that it is held by the nose 23 in the orifice 21. As the grout 9 fills up the complete interface 10 it also adheres the first part 17a to the higher section 5' of the tower 1'. The grout 9 also adheres the higher section 5' at its surface 22 to the ground section 3 at a surface 20 orientated towards the higher section 5 ' .

In Fig. 4 the interface 10 is shown in a top view with the higher section 5' not shown. Several features of the inven- tion according to this preferred embodiment can be seen clearer in this context. Firstly, it can be seen that all along the circumference of the tower 1' channels 11' have been inserted into the ground section 3. Secondly, shims 29 have been put onto the surface 20 of the ground section 3. They are used in order to level the higher section 5', i.e. to orientate it in a purely vertical way. In addition, air hoses 15 have been aligned all along the circumference of the tower 1 ' . This way one can make sure that the correct filling of the interface 10 can be controlled all along the circum^¬ ference of the tower 1' during the filling process. As men^¬ tioned above, the air hoses 15 may also be inserted into ori^¬ fices (not shown) in the shims 29 orientated towards the higher section 5'. This would make sure that the air hoses 15 are properly aligned close to the surface 22 of the higher section 5 ' .

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. The expression "distances" also includes a single distance .

Claims

1. Method of construction of a tower (1') of a wind turbine with an outside (0) and an inside (J) comprising a ground section (3) of concrete and a higher section (5') of a mate^¬ rial different from concrete which ground section (3) and higher section (5') are joined together at an interface (10) in a region of which interface (10) a filling material (9) is injected, whereby the filling material (9) is completely in- jected from the inside (J) of the tower (1') .

2. Method according to claim 1, whereby grout (9) is used as a filling material.

3. Method according to claim 1 or 2, whereby metal, prefera^¬ bly steel, is used as the material of the higher section (5' ) .

4. Method according to any one of the preceding claims, whereby the flow of the filling material (9) from the inside (J) to the outside (0) is limited by a cover (17) at the out^¬ side (0) which cover (17) bridges the interface (10) between the ground section (3) and the higher section (5') and which is positioned all around the circumference of the tower (1') in the region of the interface (10) .

5. Method according to claim 4, whereby the cover (17) used is part of a profile which is attached to the ground section (3) and/or to the higher section (5') in the region of the interface (10) .

6. Method according to claim 5, whereby the profile used is made up of at least two parts, one first part (17b) which is attached to the ground section (3) or to the higher section (5') and a second part (17a) which is attached to the first part (17b) .

7. Method according to any one claims 4 to 6, whereby the cover (17) is orientated at least partially under an angle to the vertical extension of the tower (1') .

8. Method according to any one of claims 4 to 7, whereby the cover (17) comprises a resilient material.

9. Method according to any one of claims 4 to 8, whereby the cover (17) is brought into permanent contact with a contact surface (20) of the ground section (3) and/or of the higher section (5') in the region of the interface (10) .

10. Method according to any one of the preceding claims, whereby an air hose (15) is aligned from the outside (0) to the inside (J), preferably along a bottom face side (22) of the higher section (5') in the region of the interface (10), which air hose (15) defines an outlet for air during the injection of the filling material (9) and which shows as an in^¬ dicator that the region of the interface (10) is completely filled with filling material (9) .

11. Method according to claim 10, whereby the air hose (15) is included it into a shim (29) which shim serves to level the higher section (5') on the ground section (3) at certain points along the circumference of the tower (1') .

12. Method according to any one of the preceding claims, whereby the higher section (5') is formed in an L-shape in a section in the region of the interface (10), a first part (5a') of the L-shape projecting upwards and a second part (5b') of the L-shape directed into the inside (J) of the tower ( 1 ' ) .

13. Method according to any one of the preceding claims, whereby bolts (7) connecting the ground section (3) and the higher section (5') are all positioned at the inside (J) of the tower ( 1 ' ) .

14. Tower (1') of a wind turbine with an outside (0) and an inside (J) comprising a ground section (3) of concrete and a higher section (5') of material different from concrete which ground section (3) and higher section (5') are joined to- gether at an interface (10) in a region of which interface (10) there is a filling material (9), whereby the extension of the filling material (9) is limited at the outside (0) of the tower ( 1 ' ) .