FLOATING WINDMILL

Abstract

The invention provides a floating windmill, comprising a floating element and a wind turbine. The floating windmill is distinguished in that it further comprises: a tension leg, an anchoring, a buoyancy element, a swivel and a cross bar, wherein the swivel is arranged in the buoyancy element. In operation, the floating windmill in operation is configured with the wind turbine in an upper end of the floating element extending up above the sea level, with a lower end or part of the floating element submerged in the sea, with the cross bar in one end connected to the lower part or end of the floating element and in the opposite end connected to the buoyancy element, with the buoyancy element fully submerged, preferably at safe draught depth below surface for service vessels and/or marine transport ships, with the tension leg arranged between the buoyancy element and the anchoring on the seabed. The floating windmill configured with the wind turbine in the upper end can weathervane freely around the buoyancy element, wherein in a low force condition when the forces by ocean current, wind and waves are low the floating element, the buoyancy element and the tension leg is oriented in substance in vertical direction and the cross bar is oriented in substance in horizontal direction, wherein in a high force condition when the forces by ocean current, wind and waves are high the shape of the floating element, cross bar, buoyancy element and tension leg is stretched by the forces to provide a shape like a lazy-s configuration, which change in shape and dynamic behavior reduce extreme stress levels.

Claims

1. A floating windmill, comprising a floating element and a wind turbine, floating windmill comprising: a tension leg, an anchoring, a buoyancy element, a swivel and a cross bar, wherein the swivel is arranged in the buoyancy element; wherein the floating windmill in operation is configured with the wind turbine in an upper end of the floating element extending up above the sea level, with a lower end or part of the floating element submerged in the sea, with the cross bar in one end connected to the lower part or end of the floating element and in the opposite end connected to the buoyancy element, with the buoyancy element fully submerged, preferably at safe draught depth below surface for service vessels and/or marine transport ships, with the tension leg arranged between the buoyancy element and the anchoring on the seabed; and wherein the floating element with the wind turbine in the upper end can weathervane freely around the buoyancy element, wherein in a low force condition when the forces by ocean current, wind and waves are low the floating element, the buoyancy element and the tension leg is oriented in substance in vertical direction and the cross bar is oriented in substance in horizontal direction, wherein in a high force condition when the forces by ocean current, wind and waves are high the shape of the floating element, cross bar, buoyancy element and tension leg is stretched by the forces to provide a shape like a lazy-s configuration, which change in shape and dynamic behavior reduce extreme stress levels.

2. The floating windmill according to claim 1, comprising a releasable coupling between the cross bar and the buoyancy element.

3. The floating windmill according to claim 1, comprising a releasable coupling between the cross bar and the floating element.

4. The floating windmill according to claim 1, including no gear rim in the upper end of the floating element, in the nacelle and/or wind turbine.

5. A method of fabrication, transport, installation or maintenance of the floating windmill of claim 1, comprising fabricating, transporting, installing, or maintaining the windmill in components.

6. The method according to claim 5, wherein installation takes place by transporting the floating element and the wind turbine to the windmill site, where the components are coupled to the buoyancy element that has been preinstalled with an anchor on the seabed, preferably the buoyancy element includes a buoyancy system allowing to bring the buoyancy element up and down between a surface position and a submerged position, whereby the coupling can take place near or at the surface position.

7. The method according to claim 5, wherein maintenance takes place by replacing components on the windmill field, by installing a new component and transporting away the part that is damaged or need maintenance or repair, as one combined operation, preferably by a single trip with a single vessel.

8. The method according to claim 5, wherein the anchor, the tension leg and the buoyancy element are preinstalled, whilst the floating element with the cross bar is coupled to the buoyancy element on the windmill site, wherein the cables are preinstalled out from the swivel, arranged on the cross bar and is pulled into the inner part of the floating element, with or without a coupling in dry location inside the floating element.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0032] FIG. 1 illustrates an embodiment of a floating windmill of the invention.

[0033] FIG. 2 illustrates an embodiment of a floating windmill of the invention, as viewed from the side, and

[0034] FIG. 3 illustrates the embodiment of FIG. 2 as viewed from an angle.

DETAILED DESCRIPTION OF THE INVENTION

[0035] Reference is made to FIG. 1, illustrating an embodiment of a floating windmill 1 of the invention, comprising a floating element 2 and a wind turbine 3. The floating windmill further comprises: a tension leg 4, an anchoring 5, a buoyancy element 6, a swivel 7 and a cross bar 8, wherein the swivel is arranged in the buoyancy element.

[0036] The illustrated floating windmill comprises a spar buoy as the floating element 2, with the wind turbine 3 in the upper end above the sea level. The lower end of the floating element is submerged in the sea and is connected to one end of the cross bar 8 and the opposite end of the cross bar is connected to the buoyancy element 6. The buoyancy element 6 is fully submerged and in a lower end is connected to the upper end or part of tension leg 4, which lower end or part of the tension leg is connected to the anchoring 5.

[0037] The anchoring preferably is a weight anchor or a suction anchor or a combination of a weight anchor and a suction anchor. Other anchors, such as pile anchors, can be used.

[0038] The floating element 2 can weathervane freely around the buoyancy element 6, as indicated by a rotation symbol above the buoyancy element.

[0039] The operation state as illustrated is a low force condition, meaning that the forces by ocean current, wind and waves are low, not forcing the components/elements significantly out of an equilibrium condition or orientation taken when no current, wind or waves are present. Not significantly out of an equilibrium condition or orientation means less than 5° out of orientation for elements oriented vertical or horizontal, as defined.

[0040] As the skilled person will understand, the equilibrium condition is deviated from by more than 5° in a high force condition, drawing out the shape of the configuration of the elements towards a lazy s shape. This is illustrated by a turning angle of the tensioning leg and buoyancy element by dashed line, exceeding 5°. For clarity, such dashed line deviation is indicated only for the buoyancy element as being pulled out of vertical orientation by high forces. The skilled person will understand that also the angular orientation of the cross bar and for many embodiments also the angular orientation of the floating element will change when stretched towards a lazy s shape.

[0041] As mentioned, FIG. 2 illustrates an embodiment of a floating windmill of the invention, as viewed from the side in a low force condition, wherein the s-like shape of the structures is clear. FIG. 3 illustrates the embodiment of FIG. 2 as viewed from an angle. The numeric references are as for FIG. 1, however, FIG. 2 also refer to the waterline by numeric reference 9. FIGS. 2 and 3 are more to scale for a larger depth embodiment than the embodiment illustrated in FIG. 1. The figures are in general but not necessarily out of scale, in order to illustrate features clearly.

[0042] Preferably, the anchor, the tension leg and the buoyancy element are preinstalled, whilst the floating element with the cross bar is coupled to the buoyancy element on the windmill site, wherein the cables are preinstalled out from the swivel, arranged on the cross bar and is pulled into the inner part of the floating element, with or without a coupling in dry location inside the floating element. Preassembling can be in alternative configurations, preferably involving coupling at least two preassembled groups of components with the cross bar in one or both ends.

[0043] The tension leg can be a flexible wire or a number of flexible wires, preferably combined with a buoyancy system in the buoyancy element or connectable from a vessel, such as a pump and required piping and valves for adjusting a ballast water level in the buoyancy element, for moving the buoyancy element up to or near the surface when coupling to the cross bar and down to operation position. The tension leg can also be or comprise a rigid element, or several rigid elements, such as three elements in triangular configuration, providing torsional stiffness. Rigid elements can have a cone and a guideline in the upper end, for allowing controlled deployment when installing, retrieving, and ballasting the buoyancy element with combined ballasting and hoisting. The buoyancy element preferably comprises a retrievable transponder with electrical and/or hydraulic coupling for controlled ballasting and controlled winching, wherein the buoyancy element comprises an electric or hydraulic winch and/or an electric or hydraulic pump or a hydraulic coupling to a ballast pump on the ship.

[0044] Preferably, also the buoyancy element comprises a releasable coupling, towards the tension leg.

[0045] Preferably, also the floating element comprises a buoyancy system and/or facilities for connecting to a buoyancy system on a vessel. The buoyancy system can be a pump, in the floating element or in a vessel, and required piping and valves for adjusting a ballast water level in the floating element. Thereby, installation, replacement or maintenance of the wind turbine, nacelle or parts thereof can be simplified by submerging more of the floating element.

[0046] Preferably, the submerging can be down to a level where the nacelle is reachable by a ship crane on the ship used for installation.

[0047] As the skilled person will know, the anchor can be a single anchor vertically below the buoyancy element in equilibrium position. However, also several anchors, such as suction anchors are possible embodiments within the term one anchor, arranged in substance close together as one unit below the buoyancy element but positioned apart as the soil conditions dictate for sufficient strength. One big weight anchor that can be weighted on site to sufficient weight/strength is a preferable embodiment in many shallow areas with relatively rigid bottom.

[0048] The invention also provides energy islands or energy hubs with or without windmills but with one or more of the maximum stress level reducing structure; a tension leg, an anchoring, a buoyancy element, preferably a swivel, and a cross bar, wherein the swivel, if present, is arranged in the buoyancy element, and wherein said structure is arranged as a dynamic s-lazy s structure stretched out from s to lazy s shape in high force conditions as defined in claim 1.

[0049] The floating windmill or energy island of the invention can preferably comprise vertical axis windmills since such windmills can be arranged closer together than horizontal axis windmills. No wind shadow, resulting in no requirement for weathervaning and no requirement for gear rim are further advantages by vertical axis windmills.

[0050] The floating windmill or energy island of the invention can preferably comprise a frame with numerous windmills that are self-aligning against the eye of the wind, preferably on a non-weathervaning energy island, or the frame itself weathervanes as a single floating windmill, wherein the frame preferably is arranged on a triangular floater or semi-submerged floater anchored according to the invention.

[0051] The floating windmill or energy island of the invention can preferably comprise water current turbines, suspended from the floating windmill or/and anchored, preferably retrievable for facilitating installation and maintenance.

[0052] The floating windmill or energy island of the invention can preferably comprise solar panels. The floating windmill or energy island of the invention can preferably comprise batteries.

[0053] The floating windmill or energy island of the invention can preferably comprise any of the energy-producing structures herein described, in any combination, and/or coupling to standalone equipment in the surrounding area, thereby expanding the floating windmill of the invention into an energy island and/or an energy hub.