OFF SHORE WIND ENERGY INSTALLATION FOUNDATION SYSTEM

Abstract

The invention relates to a marine structure comprising a foundation system with three or more suction buckets. The suction buckets are designed to be installed in the seafloor to operate as a foundation or part of it to support an offshore structure resting onto the seafloor. The suction buckets support a connector body and the connector body is designed to support a payload. The invention also relates to a method of installing a suction bucket. During the method, the suction bucket bottom penetrates the seafloor and fluid is removed from the suction space such that penetration proceeds by suction.

Claims

1-17. (canceled)

18. Offshore structure that is provided with a foundation system with three or more suction buckets to be installed in the seabed, which buckets are located at the corners of an imaginary polygon, viewed in top view, to act as a foundation system or part thereof for carrying an offshore structure supported on the seabed, the suction buckets carrying a connector body and the connector body adapted for carrying a payload.

19. Offshore structure according to claim 18 which is designed as an offshore wind energy installation of at least 9 MW extending upwards from the seabed at an offshore location where the seabed is at least 50 meters below the local water level, and from this installation runs a electricity cable to an electricity consumer on land to bring the offshore generated electricity to it.

20. Offshore structure according to claim 18, and with a star-shaped, seen in top view, connector body with the same number of external corners as there are suction buckets, which external corners are formed by the radial outwardly extending arms which provide the star shape; and with a single vertical tower placed, centrally, between the suction buckets, seen in top view, formed by a single tube and made of thin-walled steel, which carries the gondola of the windmill at its top, the gondola with the rotor blades at least 20 meters above the local water level.

21. Offshore structure according to claim 18, wherein the tower rests on top of the foundation system and the connector body rests on top of all suction buckets; configured so that the foundation system is as deep as possible below the water level and the tower has the largest possible length; the tower is located completely above the underside of the connector body, is hollow and thin-walled with a wall thickness between 20 and 200 millimetres and above the water level prismatic over its entire length and is rigidly mounted to the connector body.

22. Offshore structure according to claim 18, wherein each suction bucket is a vertical thin-walled steel cylinder with a wall thickness of at least 3 millimetres and with a diameter between 10 and 15 meters, which at its top end is closed in airtight manner by a top plate and at its lower end, which is in fluid communication with the suction space inside the suction bucket, is open and extends into the seabed with this lower end and is during installation in the seabed by hydraulic underpressure generated in the suction space inside the cylinder, generated by an external suction pump connected to an at the top plate provided suction port with suction valve in fluid communication with the suction space, penetrated deeper into the seabed to be almost completely in the seabed; the suction buckets have a mutual spacing of at least 5 meters and provide a statically balanced or overbalanced support for the connector body; each suction bucket contains a moulded filling body inside, with which after completion of the sucking, the gap between the top of the seabed inside the suction bucket and the top plate is completely filled up and which filling body has a height between 10 and 100 centimetres and prevents that the suction bucket is pushed deeper into the seabed by the structure resting on top of it.

23. Offshore structure according to claim 18 wherein the connector body has arms which are the elements extending from the central part of the connector body radially outwardly to each relevant suction bucket and attached thereto at their ends; the connector body has a flat underside and is a completely closed body and completely hollow and has a closed, thin-walled monocoque construction whose external walls carry the loads.

24. Offshore structure according to claim 18, wherein the cross-section of the arms of the connector body is box-shaped with an angular cross-section and wherein the arms of the connector body extend horizontal and are made from flat plates, and the four flat sides, i.e. the top, bottom, left side and right side, of each arm connect to each other via angular corners.

25. Offshore structure according to claim 18, wherein the tower, the connector body and the suction buckets are rigidly mounted so that all loads, including vertical and horizontal loads, bending moments and torsion, are transmitted from the tower to the suction buckets via the connector body; the attachment of the tower to the connector body is arranged as a beam of which a single longitudinal end is fixedly wedged so that the tower extends vertically upwards from the connector body as a cantilever beam, in other words the tower is above the connector body free from structures that transfer mechanical loads from the tower onto the seabed.

26. Offshore structure according to claim 18, wherein the foundation system extends a maximum of 15 meters above the local seabed and is located completely below the highest point of the connector body and only in the area downwards from the highest point of the connector body extend structures that are to the tower attached and transfer all loads, from the tower to the seabed.

27. Offshore structure according to claim 18, wherein the arms of the connector body have a height, measured at their location of maximum height, between 0.75 and 1.5 times the diameter of the tower at the level of the connector body and have a width, measured at their location of maximum width, between 0.5 and 1.0 times their height, measured at their place of maximum height.

28. Offshore structure according to claim 18, wherein the connector body and the tower are equipped with one or more quick couplings which keep, as the only means, the tower and the connector body together in a load bearing manner, wherein the quick couplings allow uncoupling without causing permanent damage to the parts involved in the coupling.

29. Offshore structure according to claim 28, wherein the complete force flow from the connector body to the tower, and vice versa, flows for a minimum of 95% via the quick couplings.

30. Offshore structure according to claim 28, wherein the one or more quick couplings provide a clamping of the tower in the connector body, or vice versa, by wedging action and driven by the gravity force acting on the tower, so that by moving of the longitudinal end of the tower clamped in the connector body due to wobbling of the tower, the tower is increasingly tightly clamped to the connector body.

31. Offshore structure according to claim 28, wherein the one or more quick couplings are each provided with one or two first wedging means, e.g. conical rings, provided to the tower, that are conically or wedge shaped at one side and one or two second wedging means, e.g. conical rings, provided to the connector body, that are wedge or conically shaped at one side, such that there are one or two pairs of each a first and a second wedging means such that when the quick coupling is engaged, by inserting the tower into the connector body or vice versa, the wedging means are co axial and parallel and the wedge or conical sides of the wedging means of a pair face and contact each other, the first wedging means at the inner side or within the second wedging means, or vice versa, in case there are two pairs, the distance between the two first wedging means rings equals the distance between the two second wedging means, viewed in longitudinal direction of the tower, wherein a pair provides a slip joint (see FIG. 15).

32. Method of installing the offshore structure according to claim 18, wherein a first sub-unit comprising the suction buckets and the connector body and a second sub-unit comprising the tower are provided, and the first and second sub-units are subsequently, separate from each other, at least 10 meters apart, floating in the water transported by sailing over a distance of at least 100 or 1000 meters to the offshore installation location, with the first subunit in upright position, and then the first and second sub-unit, floating in the water, are combined into the offshore construction.

33. Method according to claim 32, wherein during the float transport in the water to the offshore installation location, the first and the second subunit sail underneath one or more bridges, of a fixed type, for car traffic crossing the water way, without obstructing the car traffic across the bridge.

34. Method according to claim 32, wherein the first subunit and the second subunit are combined by activating quick couplings at the connector body and the tower.

35. Offshore structure that is provided with a foundation system with three or more suction buckets to be installed in the seabed, which buckets are located at the corners of an imaginary polygon, viewed in top view, to act as a foundation system or part thereof for carrying an offshore structure supported on the seabed, the suction buckets carrying a connector body and the connector body adapted for carrying a payload; wherein the offshore structure is designed as an offshore wind energy installation of at least 9 MW extending upwards from the seabed at an offshore location where the seabed is at least 50 meters below the local water level, and from this installation runs a electricity cable to an electricity consumer on land to bring the offshore generated electricity to the electricity consumer; the connector body is star-shaped, seen in top view, with the same number of external corners as there are suction buckets, which external corners are formed by the radial outwardly extending arms which provide the star shape; and the offshore structure is provided with a single vertical tower placed centrally between the suction buckets, seen in top view, formed by a single tube and made of thin-walled steel, which carries the gondola of the windmill at its top, the gondola with the rotor blades is provided at least 20 meters above the local water level; the single vertical tower rests on top of the foundation system and the connector body rests on top of all suction buckets; and the offshore structure is configured so that the foundation system is as deep as possible below the water level and the tower has the largest possible length; the tower is located completely above the underside of the connector body, is hollow and thin-walled with a wall thickness between 20 and 200 millimetres and is above the water level prismatic over its entire length and is rigidly mounted to the connector body; each suction bucket is a vertical thin-walled steel cylinder with a wall thickness of at least 3 millimetres and with a diameter between 10 and 15 meters, which at its top end is closed in airtight manner by a top plate and at its lower end, which is in fluid communication with the suction space inside the suction bucket, is open and extends into the seabed with this lower end and is during installation in the seabed by hydraulic underpressure generated in the suction space inside the cylinder, generated by an external suction pump connected to an at the top plate provided suction port with suction valve in fluid communication with the suction space, penetrated deeper into the seabed to be almost completely in the seabed; the suction buckets have a mutual spacing of at least 5 meters and provide a statically balanced or overbalanced support for the connector body; the connector body has arms which are the elements extending from the central part of the connector body radially outwardly to each relevant suction bucket and attached thereto at the ends of the arms are the suction buckets; the connector body has a flat underside and is a completely closed body and is completely hollow and has a closed, thin-walled monocoque construction whose external walls carry the loads; the cross-section of the arms of the connector body is box-shaped with an angular cross-section and wherein the arms of the connector body extend horizontal and are made from flat plates, and the four flat sides, i.e. the top, bottom, left side, right side, of each arm connect to each other via angular corners; the tower, the connector body and the suction buckets are rigidly mounted so that all loads, including vertical and horizontal loads, bending moments and torsion, are transmitted from the tower to the suction buckets via the connector body; the attachment of the tower to the connector body is arranged as a beam of which a single longitudinal end is fixedly wedged so that the tower extends vertically upwards from the connector body as a cantilever beam, in other words the tower is above the connector body free from structures that transfer mechanical loads from the tower onto the seabed; the foundation system extends a maximum of 15 meters above the local seabed and is located completely below the highest point of the connector body and only in the area downwards from the highest point of the connector body extend structures that are to the tower attached and transfer all loads, from the tower to the seabed.

Description

[0032] The invention is further illustrated by way of non-limiting, presently preferred embodiments providing the best way of carrying out the invention and shown in the drawings.

[0033] FIG. 1A-C show a first embodiment from three different angles; FIG. 2-4 show a perspective view of a second, third and fourth embodiment, respectively; FIG. 5A-C show a perspective view, of exploded type, of three alternative ways of mounting the monopole to the foundation system; FIG. 6-8 show in side view the three main phases during a possible manner of installing the off shore wind energy installation; FIG. 9-14 show prior art foundation systems; FIG. 15 shows a double slip joint in section from the side.

[0034] FIG. 1 shows three suction buckets, on top of it a star schaped connector body having three arms, each radially outward converging, and there above a single upright tube providing a mast and/or tower and/or monopole. The lower part of the mast has a conical shape.

[0035] FIG. 2 shows three suction buckets, there above a triangular shaped connector body and there above a prismatic mast. The water level 100 is also illustrated. FIG. 3 shows four suction buckets, a star shaped connector body having tour arms and above it a prismatic mast. FIG. 4 shows a scar shaped connector body having three arms and a prismatic mast.

[0036] In FIG. 5A the lower end of the mast penetrates the connector body. In FIG. 5B the lower end of the mast penetrates a from the connector body upwards projecting transition piece. In FIG. 5C the transition piece penetrates the lower end of the mast. In all three cases the slip joint can be applied.

[0037] According to FIG. 6, the suction buckets and connector body provide a sub assembly separate from the mast or tower or monopole. This subassembly was sailed to its final offshore location and there the suction buckets were penetrated into the sea bed. After that part of the mast was added (FIG. 7) and after that a further part of the mast was added (FIG. 8).

[0038] Different from FIG. 6-8, an alternative manner of installation is to sail the subassembly shown in FIG. 7 (buckets, connector body and monopole mutually assembled at a remote location) to the final offshore location and install it there, after which the payload is added.

[0039] FIG. 9 shows a jacket type, FIG. 10 a tripod type, FIG. 11 a tripod type, FIG. 12 a tri pile type, FIG. 13 a buried type and FIG. 14 a tension leg type offshore structure.

[0040] Typically, there are three stages during penetration of the suction bucket into the sea floor by suction within the suction space. In the initial stage the open bottom of the suction bucket has penetrated the seabed by gravity, such that the suction space is sealed. The second stage is obtained by removing water from the suction space by pumping, such that suction is created within the suction space such that the suction bucket penetrates deeper into the seabed, thus its top comes closer to the seabed. In the third stage the suction bucket is penetrated to its final depth, providing its design load bearing capacity for a weight resting on top of it. Typically, the top bulkhead is spaced from the sea floor. Within the suction space internal from the side wall of the bucket, the surface of the sea floor material rises due to penetration of the suction bucket. Such seabed part captive within the suction space is also called soil plug. Typically the void between the bulkhead and the soil plug is tilled by a slab or body. The suction space is bounded by the top bulkhead, the cylindrical side wall and the open end opposite the top bulkhead.

[0041] FIG. 15 shows an inner tube, e.g. the monopole, and an outer tube, e.g. the wall of the central hole of the connector body to receive the monopole. Each tube is provided with two axially spaced conical rings, providing two pairs of each an inner ring of the inner tube and an outer ring of the outer tube. Due to the downward directed force Fv, oriented according to the gravity force, the radially inward directed clamping forces are generated (only shown for the upper pair).

[0042] The invention is not limited to the above described and in the drawings illustrated embodiments. E.g. the marine structure can have a different number of suction buckets. The drawing, the specification and claims contain many features in combination. The skilled person will consider these also individually and combine them to further embodiments. Features of different in here disclosed embodiments can in different manners be combined and different aspects of some features are regarded mutually exchangeable. All described or in the drawing disclosed features provide as such or in arbitrary combination the subject matter of the invention, also independent from their arrangement in the claims or their referral.