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Title:
WIND TURBINE COMPRISING AN OFFSHORE SUPPORT
Document Type and Number:
WIPO Patent Application WO/2017/204640
Kind Code:
A1
Abstract:
The present invention relates to a wind turbine, comprising: - a mast with a peripheral wall; and - an offshore support configured to support the mast, the offshore support comprising: - a first part comprising a monopile which is driven into a seabed and has a peripheral wall; - a second part which defines a throughflow part and is provided with at least one passage along a longitudinal length thereof; and - wherein the throughflow part comprises one or more than one reinforcing element which: - when the monopile and the mast have the same cross-sectional dimension, extends substantially in line with the peripheral walls thereof; and - when the monopile and the mast have a differing cross-sectional dimension, extends substantially along a truncated cone defined by the differing dimensions.

Inventors:
WINKES, Jasper Stefan (Groot Hertoginnelaan 62, 2517 E Den Haag, 2517 E, NL)
Application Number:
NL2017/050336
Publication Date:
November 30, 2017
Filing Date:
May 26, 2017
Export Citation:
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Assignee:
FISTUCA B.V. (P.O. Box 1029, 2600 BA DELFT, 2600 BA, NL)
International Classes:
F03D13/20; E02D27/42; E02D27/52; F03D13/25
Attorney, Agent or Firm:
HAAN, Raimond Johannes Gerardus (Bezuidenhoutseweg 57, 2594 AC Den Haag, 2594 AC, NL)
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Claims:
Claims

1. A wind turbine, comprising:

- a mast with a peripheral wall; and

- an offshore support configured to support the mast, the offshore support comprising:

- a first part comprising a monopile which is driven into a seabed and has a peripheral wall;

- a second part which defines a throughflow part and is provided with at least one passage along a longitudinal length thereof;

characterized in that the throughflow part comprises one or more than one reinforcing element which:

- when the monopile and the mast have the same cross-sectional dimension, extends substantially in line with the peripheral walls thereof; and

- when the monopile and the mast have a differing cross-sectional dimension, extends substantially along a truncated cone defined by the differing dimensions.

2. Wind turbine as claimed in claim 1 , wherein the offshore support further comprises a third part configured to engage the mast of the wind turbine. 3. Wind turbine as claimed in claim 1 or 2, wherein the offshore support comprises a peripheral wall, and wherein the passage comprises at least two throughflow openings in the peripheral wall of the throughflow part of the offshore support.

4. Wind turbine as claimed in claim 3, wherein the throughflow openings extend in longitudinal direction of the throughflow part, and wherein the throughflow openings have an elongate slot shape.

5. Wind turbine as claimed in claim 3 or 4, wherein the reinforcing element is a reinforcing profile which extends in longitudinal direction of the throughflow part and which is formed by the peripheral wall situated between the throughflow openings.

6. Wind turbine as claimed in claim 5, wherein recessed wall parts of two adjacent throughflow openings are connected on the mutually facing sides to the peripheral wall, wherein the wall parts are bent toward each other and connected to each other, wherein the wall parts, together with the peripheral wall situated between the adjacent throughflow openings, enclose the reinforcing profile of a substantially triangular cross-section extending in longitudinal direction of the offshore support.

7. Wind turbine as claimed in at least one of the claims 4-6, wherein the reinforcing element extends within a volume enclosed by the throughflow part.

8. Wind turbine as claimed in at least one of the foregoing claims, wherein:

- the monopile has a first diameter;

- the mast has a second diameter;

- wherein the first diameter of the monopile is larger than the second diameter of the mast; and

- the throughflow part of the monopile narrows in the direction of the mast.

9. Wind turbine as claimed in at least one of the foregoing claims, wherein at least two adjacent reinforcing elements are arranged one of converging and diverging relative to each other in the longitudinal length of the throughflow part.

10. Wind turbine as claimed in at least one of the foregoing claims, wherein one or more than one reinforcing element extends between two attachment points on the peripheral wall of the offshore support, wherein these attachment points are offset relative to each other in a peripheral direction of the offshore support.

11. Wind turbine as claimed in at least one of the foregoing claims, wherein the first part of the offshore support is provided with a stop configured to engage a pile -driving attachment. 12. Wind turbine as claimed in claim 10, wherein the pile -driving attachment has a form which can close round the second part and has a length such that the pile-driving attachment can extend from the stop to at least a position beyond the throughflow part of the offshore support.

13. Wind turbine as claimed in claim 11 or 12, wherein the part of the pile-driving attachment closing round the throughflow part of the offshore support has a conical shape.

14. Wind turbine as claimed in at least one of the foregoing claims, wherein the least one passage is arranged close to an outer end of the offshore support. 15. Wind turbine as claimed in any of the claims 1-13, wherein the offshore support is integrated with the monopile.

16. Wind turbine as claimed in any of the claims 1-13, wherein the offshore support is arranged as an add-on on the monopile.

17. Wind turbine as claimed in at least one of the foregoing claims, wherein the throughflow part extends in a range between sea level and a maximum of 25 metres below sea level, preferably a maximum of 20 metres below sea level and more preferably a maximum of 15 metres below sea level.

18. Wind turbine as claimed in at least one of the foregoing claims, comprising eight reinforcing elements.

Description:
Wind turbine comprising an offshore support

The invention relates to a wind turbine which comprises an offshore support.

An example of such an offshore support is a so-called monopile which is arranged in the seabed and functions as support for a wind turbine. Another example of an offshore support is a so- called jacket.

Monopiles have been found particularly suitable for applications at a limited water depth, for instance of 25 metres.

Advantages of monopiles are the reliable and proven technology which is moreover relatively easy to calculate. Manufacture is relatively simple and quick and the monopiles can be transported in relatively compact manner on a vessel. Furthermore, monopiles are easy to handle and easy to install with a pile-driver.

Partly because of the above stated advantages there is a current trend to also develop monopiles for greater water depths, for instance 30-60 metre water depth, i.e. a range in which jackets are currently much utilized. Jackets are however latticework constructions and thereby much more complex, whereby they lack many of the above stated advantages of monopiles.

So-called XL monopiles are being developed for the use of monopiles in the range of 30- 60 metres water depth. As a result of their greater length these XL monopiles have a longer moment arm to the seabed in which they are arranged, and the larger diameter of up to as much as a top diameter of 7 metres in the zone loaded by wave action moreover provides them with a large frontal surface area against which the waves can strike. The dynamic load resulting from the wave action has a substantially quadratic relation to the diameter of the monopile.

The longer moment arm and the larger exposed surface both contribute toward the dynamic load on the XL monopile. This dynamic load is preferably kept as low as possible because this load greatly influences the fatigue lifespan of the monopile.

DE-B3-10 2010 012094 represents the closest prior art and relates to a gravity base for an offshore wind turbine, wherein between a foundation body lying on the seabed and the mast is provided a latticework construction which extends close to the water surface. This latticework construction has such large dimensions that it can if desired be arranged around a monopile that has become unstable.

US-A1-2014/086691 and DE-Al-10 2011 102546 are acknowledged as further prior art.

An object of the present invention is to provide a wind turbine with an offshore support wherein said drawbacks do not occur, or at least do so to lesser extent.

Said object is achieved according to the invention with the wind turbine according to the invention, comprising:

- a mast with a peripheral wall; and - an offshore support configured to support the mast, the offshore support comprising:

- a first part comprising a monopile which is driven into a seabed and has a peripheral wall;

- a second part which defines a throughflow part and is provided with at least one passage along a longitudinal length thereof; and

- wherein the throughflow part comprises one or more than one reinforcing element which:

- when the monopile and the mast have the same cross-sectional dimension, extends substantially in line with the peripheral walls thereof; and

- when the monopile and the mast have a differing cross-sectional dimension, extends substantially along a truncated cone defined by the differing dimensions.

The first part comprises a monopile driven into a seabed which is pile -driven into the seabed.

In order to reinforce the offshore support, for instance against torsional load, the throughflow part of the offshore support of the wind turbine comprises one, or more than one reinforcing element. The weakness caused by the passages can be at least partially compensated by the one, or more than one reinforcing element.

When the monopile and the mast have the same cross-sectional dimension, the reinforcing element extends substantially in line with the peripheral walls thereof and, when the monopile and the mast have a differing cross-sectional dimension, extends substantially along a truncated cone defined by the differing dimensions. This results in a slender and elegant construction which guarantees an optimal force transmission. Forces from the mast are transmitted optimally from the mast to the second part of the offshore support and transmitted optimally from the second part of the offshore support to the monopile.

By providing passages and reinforcing elements in the throughflow part the wind turbine will on the one hand be less susceptible to dynamic load resulting from the wave action. The reinforcing elements of the offshore support of the wind turbine can on the other hand impart a high strength for the transmission of longitudinal forces. Particularly the reduced susceptibility to the dynamic load of the wave action results in less fatigue, whereby the offshore support can be designed in lighter form.

The throughflow part is preferably provided with at least one passage along the longitudinal length thereof. Dynamic load on the offshore support resulting from the wave action will be considerably reduced by arranging this at least one passage at or slightly below sea level. The waves will after all flow partially through the passage instead of striking wholly against the offshore support.

Although a wind turbine with an offshore support according to the invention can reduce the dynamic load on different types of support and in different applications, such an offshore support is particularly advantageous in combination with XL monopiles at relatively great depth, for instance a water depth of 30-60 metres. As a result of their greater length these XL monopiles have a longer moment arm to the seabed in which they are arranged, and the larger diameter of up to as much as 7 metres at sea level moreover provides them with a large frontal surface area against which the waves can strike.

The offshore support can itself be integrated with a monopile, although it is also possible to envisage the offshore support being arranged as an add-on on a monopile - which is itself pile- driven some distance below the sea level. In both cases the passages are ideally placed where the dynamic load resulting from the wave action is highest, i.e. at or just below sea level.

Although the invention is not limited thereto, for material-saving and weight-reducing reasons the offshore support preferably takes a hollow form, and the offshore support comprises a peripheral wall, wherein the passage comprises at least two throughflow openings in the peripheral wall of the throughflow part of the offshore support. The offshore support can for instance be integrated into a monopile or can be an add-on arrangeable on a monopile.

According to a preferred embodiment, the throughflow openings extend in longitudinal direction of the throughflow part, wherein the throughflow openings have an elongate slot shape. Because of the elongate slot shape extending in longitudinal direction of the throughflow part the slot-like passage extends over a height range. The passage can hereby be placed such that the sea level is always at passage height in all tidal conditions (low and high tide). The passage can moreover allow through waves of differing height.

According to a further preferred embodiment, the reinforcing element is a reinforcing profile which extends in longitudinal direction of the throughflow part and which is formed by the peripheral wall situated between the throughflow openings.

According to yet another preferred embodiment, recessed wall parts of two adjacent throughflow openings are connected on the mutually facing sides to the peripheral wall, wherein the wall parts are bent toward each other and connected to each other, wherein the wall parts, together with the peripheral wall situated between the adjacent throughflow openings, enclose the reinforcing profile of a substantially triangular cross-section extending in longitudinal direction of the offshore support. The wall material of the recesses is thus utilized to reinforce the offshore support.

In order to influence the flow around the offshore support as little as possible it is preferred that the reinforcing element extends within a volume enclosed by the offshore support. A higher (torsional) stiffness is obtained by forming crosswise connections.

According to yet another preferred embodiment, the monopile has a first diameter and the mast has a second diameter, and wherein the first diameter of the monopile is larger than the second diameter of the mast, and the throughflow part of the monopile narrows in the direction of the mast. Because of the narrowing, the relatively large diameter of an XL monopile (of as much as 8-10 metres close to the seabed) can connect to a conventional mast of a wind turbine of a more limited diameter.

A further increase in the (torsional) stiffness can be obtained when, according to yet another preferred embodiment, at least two adjacent reinforcing elements are arranged one of converging and diverging relative to each other in the longitudinal length of the throughflow part.

A particularly advantageous embodiment results when the offshore support is provided with eight reinforcing elements.

A further increase in the (torsional) stiffness can likewise be obtained when, according to yet another preferred embodiment, one or more than one reinforcing element extends between two attachment points on the peripheral wall of the offshore support, wherein these attachment points are offset relative to each other in a peripheral direction of the offshore support. In a further preferred embodiment the attachment points are arranged on the peripheral wall of the throughflow part of the offshore support.

Because the offshore support, and more particularly the throughflow part thereof, is provided with at least one passage along the longitudinal length of the body, the strength and stiffness of the offshore support decreases. In order to enable pile-driving of the offshore support with a minimal load on the throughflow part provided with the at least one passage, according to yet another preferred embodiment the first part is provided with a stop configured to engage a pile- driving attachment. When the pile -driving attachment is arranged on the offshore support, they together form an assembly with which the monopile of the offshore support can be driven into the ground surface.

According to yet another preferred embodiment, the pile-driving attachment has a form which can close round the second part and has a length such that the pile-driving attachment can extend from the stop to at least a position beyond the throughflow part of the offshore support. A pile-driver can drive in the offshore support via the pile -driving attachment, wherein the load on the throughflow part provided with the at least one passage is minimal.

According to yet another preferred embodiment, the part of the pile -driving attachment closing round the throughflow part of the offshore support has a conical shape. The pile -driving attachment can hereby be arranged close-fittingly around and over a narrowing throughflow part, while the diameter on which the pile-driver has to engage can be brought closer to the dimension of a conventional monopile with a diameter on the upper side of about 6.5 m.

According to yet another preferred embodiment, the least one passage is arranged close to an outer end of the offshore support.

According to yet another preferred embodiment, the offshore support is integrated with the monopile, and then forms an offshore foundation. According to yet another, alternative preferred embodiment, the offshore support is placeable as an add-on on the monopile.

According to yet another preferred embodiment, the throughflow part extends in a range between sea level and a maximum of 25 metres below sea level, preferably a maximum of 20 metres below sea level and more preferably a maximum of 15 metres below sea level. The dynamic load resulting from wave action and current is greatest around sea level and just below sea level. The greatest moment arm on which the wave action can act is moreover located close to sea level. Because the throughflow part extends according to the invention to a maximum depth below sea level, the wind turbine with offshore support according to the invention is distinguished from for instance offshore jacket constructions.

Preferred embodiments of the present invention are further elucidated in the following description with reference to the drawing, in which:

Figure 1 is sectional view of a wind turbine arranged on an offshore support according to the invention;

Figures 2 and 3 show a side and perspective view of an offshore support according to a first preferred embodiment;

Figures 4 and 5 show a side and perspective view of an offshore support according to a second preferred embodiment;

Figures 6 and 7 show a side and perspective view of an offshore support according to a third preferred embodiment;

Figures 8 and 9 show a side and perspective view of an offshore support according to a fourth preferred embodiment;

Figure 10 is a perspective view of the offshore support according to figure 8;

Figures 11 and 12 show a perspective and top view of an offshore support according to a fifth preferred embodiment;

Figures 13 and 14 show a side and perspective view of an offshore support according to a sixth preferred embodiment; and

Figures 15 and 16 show a side and top view of an offshore support according to a seventh preferred embodiment.

Offshore support 1 shown in figure 1 comprises a monopile 2. This offshore support 1 comprises a longitudinal body 4 provided with the number of passages 6 along the longitudinal length of longitudinal body 4. Placed on offshore support 1 is a wind turbine 8 which is arranged with its mast 10 directly (or indirectly via a transition piece) on offshore support 1.

Passages 6 in longitudinal body 4 are arranged close to an outer end of body 4 of offshore support 1, more particularly at sea level 12. Because passages 6 have an elongate slot shape, they can also remain at the sea level position when there is a fluctuation in the water depth, i.e. the distance between sea level 12 and seabed 14. The desired operation can thus be guaranteed in the case of tidal changes (low water and high water) and in the case of waves of differing height.

Although offshore support 1 forms an integral part with monopile 2 in the shown embodiment, according to an alternative embodiment offshore support 1 can be placeable as an add-on (not shown) on a monopile 2.

Different embodiments are shown in the following figures 2-14. Although offshore support 1 is not necessarily limited thereto, in all shown embodiments body 4 of offshore support 1 is hollow and body 4 comprises a peripheral wall 16, wherein passage 6 comprises at least two throughflow openings 18 in peripheral wall 16. These throughflow openings 18 extend in longitudinal direction of the longitudinal hollow body 4, wherein throughflow openings 18 have an elongate slot shape.

Because passages 6 weaken the body 4 of offshore support 1 locally, one or more than one reinforcing element 20 is preferably provided.

Such a reinforcing element 20 can for instance be embodied as a reinforcing profile 22 which extends in longitudinal direction of body 4 and which is formed by the peripheral wall 16 located between throughflow openings 18 (figures 13 and 14), but can also comprise a separately arranged reinforcing profile 22. In figures 2-12 the reinforcing profiles 22 are embodied as tubular reinforcing elements 20 integrated into peripheral wall 16.

Shown in figures 13 and 14 is an alternative embodiment wherein recessed wall parts 22 of two adjacent throughflow openings 18 are connected on the mutually facing sides 24 to peripheral wall 16. These wall parts 22 are bent toward each other and connected to each other, wherein wall parts 22, together with the peripheral wall 16 located between the adjacent throughflow openings 18, define the reinforcing profile 22 extending in longitudinal direction of body 4. In the shown embodiment reinforcing profile 22 has a substantially triangular cross-section, wherein one side of the triangle is formed by an interrupted part of the somewhat curved peripheral wall 16.

In figures 12 and 13 reinforcing profiles 22 are formed by folding wall parts 22 toward the volume enclosed by hollow body 4 of offshore support 1 and connecting them to each other within the volume enclosed by offshore support 1. The reinforcing profile 22 which forms reinforcing element 20 consequently extends within a volume enclosed by offshore support 1 , where it has minimal influence on the flow. An embodiment of reinforcing profile 22 directed outwardly of body 4 would enlarge the contact area with which body 4 is exposed to current and wave action, this being disadvantageous.

In the shown embodiments body 4 of offshore support 1 comprises in each case a first part 26 which has a tubular form, a second part 28 which forms a throughflow part and a third part 30 which has a tubular or annular shape (figures 2-16). It is noted here that a ring is deemed a species of tube, wherein the length of the tube has in the case of a ring a limited size relative to the diameter.

In the embodiments of figures 4-12 the first part 26, i.e. the monopile, has a first diameter and third part 30 has a second diameter, wherein the first diameter of first part 26 is larger than the second diameter of third part 30, and throughflow part 28 of first part 26 narrows in the direction of third part 30. Third part 30 is configured for connection to the mast of the wind turbine, although it is also possible to envisage third part 30 forming part of mast 10 and throughflow part 28 engaging directly on mast 10.

The (torsional) stiffness of offshore support 1 can be further increased by arranging adjacent reinforcing elements 20 converging or diverging relative to each other in the longitudinal length of body 4, as shown in figures 6 and 7.

The (torsional) stiffness of offshore support 1 can be increased still further when, as shown in figures 11 and 12, one or more than one reinforcing element 20 extends between two attachment points on peripheral wall 16 of offshore support 1, wherein these attachment points are offset relative to each other in a peripheral direction of offshore support 1.

In the side view of figure 8 the first part 26 of offshore support 1 is provided with a stop 32 on which a pile-driving attachment 34 can be arranged. Pile -driving attachment 34 can be arranged during pile -driving in order to relieve the load on second part 28 of offshore support 1 in which throughflow openings 18 are arranged. After the pile-driving the wind turbine can be arranged with its mast 10 on offshore support 1.

The situation in which pile-driving attachment 34 is arranged on stop 32 is shown in figure

9. Because pile -driving attachment 34 has a shape which closes round second part 28 of offshore support 1 and has a length such that pile-driving attachment 34 extends from stop 32 to at least a position beyond throughflow part 28 (and preferably also beyond third part 30) of offshore support 1, a pile-driver can transmit its force via pile -driving attachment 34 to first part 26 of offshore support 1.

Pile -driving attachment 34 preferably fits substantially closely around the narrowing second part 28, i.e. the throughflow part with throughflow openings 18. For this reason the pile- driving attachment 34 which closes round second part 28 of offshore support 1 has a conical shape in figures 8 and 9.

Shown in figures 15 (side view) and 16 (top view) is an embodiment wherein two adjacent reinforcing elements are arranged in each case one of converging and diverging relative to each other in the longitudinal length of the throughflow part. An increase in the (torsional) stiffness is hereby obtained. The reinforcing elements extend in a W-configuration in the throughflow part and thus have a zigzag shape.

A highly advantageous embodiment is provided with a limited number of only eight reinforcing elements 20. The limited number of only eight reinforcing elements 20 results in relatively large throughflow openings. In addition, the disposition of reinforcing elements 20 is such that - irrespective of the direction of load transversely of offshore support 1 - four of the eight reinforcing elements 20 are always under strain of tension and the other four of the eight reinforcing elements 20 are under strain of pressure. An optimal distribution of load over reinforcing elements 20 is thus realized with a minimal number of reinforcing elements 20.

Although they show preferred embodiments of the invention, the above described embodiments are intended only to illustrate the present invention and not to limit the specification of the invention in any way. When measures in the claims are followed by reference numerals, such reference numerals serve only to contribute toward the understanding of the claims, but are in no way limitative of the scope of protection. It is particularly noted that the skilled person can combine technical measures of the different embodiments. The described rights are defined by the following claims, within the scope of which many modifications can be envisaged.