NO347390B1 - A floating unit assembly - Google Patents

A floating unit assembly Download PDF

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Publication number
NO347390B1
NO347390B1 NO20211519A NO20211519A NO347390B1 NO 347390 B1 NO347390 B1 NO 347390B1 NO 20211519 A NO20211519 A NO 20211519A NO 20211519 A NO20211519 A NO 20211519A NO 347390 B1 NO347390 B1 NO 347390B1
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Norway
Prior art keywords
primary
buoy
floating unit
connection point
unit assembly
Prior art date
Application number
NO20211519A
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Norwegian (no)
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NO20211519A1 (en
Inventor
Niklas Norman
Original Assignee
Semar As
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Filing date
Publication date
Application filed by Semar As filed Critical Semar As
Priority to NO20211519A priority Critical patent/NO347390B1/en
Publication of NO20211519A1 publication Critical patent/NO20211519A1/en
Publication of NO347390B1 publication Critical patent/NO347390B1/en

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03D—WIND MOTORS
    • F03D13/00—Assembly, mounting or commissioning of wind motors; Arrangements specially adapted for transporting wind motor components
    • F03D13/20—Arrangements for mounting or supporting wind motors; Masts or towers for wind motors
    • F03D13/25—Arrangements for mounting or supporting wind motors; Masts or towers for wind motors specially adapted for offshore installation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B21/00—Tying-up; Shifting, towing, or pushing equipment; Anchoring
    • B63B21/50—Anchoring arrangements or methods for special vessels, e.g. for floating drilling platforms or dredgers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B35/00—Vessels or similar floating structures specially adapted for specific purposes and not otherwise provided for
    • B63B35/44—Floating buildings, stores, drilling platforms, or workshops, e.g. carrying water-oil separating devices
    • B63B2035/4433—Floating structures carrying electric power plants
    • B63B2035/446—Floating structures carrying electric power plants for converting wind energy into electric energy
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2240/00—Components
    • F05B2240/90—Mounting on supporting structures or systems
    • F05B2240/96—Mounting on supporting structures or systems as part of a wind turbine farm
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/70—Wind energy
    • Y02E10/727—Offshore wind turbines

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Combustion & Propulsion (AREA)
  • Sustainable Energy (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Development (AREA)
  • General Engineering & Computer Science (AREA)
  • Ocean & Marine Engineering (AREA)
  • Steering Control In Accordance With Driving Conditions (AREA)
  • Adjustment Of The Magnetic Head Position Track Following On Tapes (AREA)
  • Paper (AREA)
  • Laying Of Electric Cables Or Lines Outside (AREA)

Description

A FLOATING UNIT ASSEMBLY
TECHNICAL FIELD
The present invention relates to a floating unit assembly.
BACKGROUND OF THE INVENTION
A floating unit assembly, e.g. a system that comprises a plurality of floating units, may be maintained in a desired position range by means of a mooring system.
For instance, CN111071400A discloses a system that contains a plurality of anchor bases, each one of which being connected to several floating units by means of mooring lines. For large water depths, CN111071400A also proposes the use of buoys in the system.
However, the mooring system disclosed in CN111071400A mainly offers an individual flexibility for each floating unit in the system which results in an expensive and complex mooring system.
Moreover, according to its abstract, EP 2604501 A1 relates to a system of floating and weight-stabilized wind turbine towers with separately floodable compartments and aerodynamic overwater encasement and the appertaining semisubmersible mooring structures including anchorage on the seabed, a horizontally floating underwater mooring meshwork and an actinomorphic buoy-cable-mooring to the wind turbine towers.
However, EP 2604501 A1 fails to disclose a floating unit assembly with secondary buoys positioned outside outer primary buoys which in turn are positioned outside a first area accommodating the floating units of the floating unit assembly.
In order to improve the mooring system disclosed in CN111071400A, each one of PCT/EP2020/082934, PCT/EP2021/069316 and PCT/EP2021/082302 discloses a floating unit assembly with floating units connected to buoys via connection lines. The buoys are in turn connected to a seafloor via one or more taut lines. It should be noted that PCT/EP2020/082934, PCT/EP2021/069316 and PCT/EP2021/082302 have not been published at the time of filing of the present application.
In the floating unit assembly according to each one of PCT/EP2020/082934, PCT/EP2021/069316 and PCT/EP2021/082302, the floating unit assembly disclosed therein implies that a large portion of the station keeping flexibility of the floating unit assembly may be attributed to the flexibility of the buoys and taut lines rather than to the connection lines.
The flexibility distribution in accordance with the above in turn implies an appropriate restoring load sharing capability in-between floating units connected to the same buoy, which in turn may result in appropriately low costs for the floating unit assembly.
For any floating unit assembly, for instance for a floating unit assembly according to any one of PCT/EP2020/082934, PCT/EP2021/069316 and PCT/EP2021/082302, there may be a need for further improving the station-keeping capabilities thereof.
SUMMARY OF THE INVENTION
In view of the above, an object of the present invention is to provide a floating unit system that can provide appropriate station-keeping characteristics in a cost-efficient manner.
The above object is obtained by a first aspect of the present invention in accordance with claim 1.
As such, the present invention relates to a floating unit assembly arranged in a body of water with a seafloor. The floating unit assembly comprises:
- at least one floating unit,
- at least one primary buoy,
- wherein each one of the at least one primary buoy is connected to at least one of the at least one floating unit by a respective primary connection line,
- wherein at least one of the at least one primary buoy is connected to at least one secondary buoy by a respective secondary connection line,
- wherein each primary buoy is connected to a respective primary seafloor connection point on the seafloor via one or more primary taut lines,
- wherein each secondary buoy is connected to a secondary seafloor connection point on the seafloor via one or more secondary taut lines, and
wherein, for a primary buoy being connected to at least one secondary buoy by a respective secondary connection line, a first horizonal distance between the first seafloor connection point of the primary buoy and the second seafloor connection point of the one secondary buoy is larger than a second horizontal distance between the primary buoy and the secondary buoy when no environmental loads are imparted on the floating unit assembly.
The larger horizontal distance at the sea floor as compared to the horizontal distance between the primary buoy and the secondary buoy implies that the secondary buoy is located with an offset towards the primary buoy as compared to the second seafloor connection point. In other words, as seen from the second seafloor connection point to the secondary buoy, the secondary taut line is inclined at least in a direction towards the primary buoy. This in turn implies that the secondary buoy and the one or more secondary taut lines enable pre-tensioning of the secondary connection line when no environmental loads are imparted on the floating unit assembly. Such a pre-tensioning may in turn result in that the position of the primary buoy may be controlled in an appropriate manner.
Moreover, the floating unit assembly according to the present invention may imply additional effects. Purely by way of example, in environmental conditions in which a wind load is coming from one direction and in which e.g. current loads are coming from approximately the opposite direction, the secondary buoy or buoys may improve the station-keeping possibilities of the floating unit assembly.
As another non-limiting example, the floating unit assembly according to the present invention implies that excessive slacking of primary connection lines can be avoided, in particular the floating unit assembly according to the present invention implies that excessive slacking of primary connection lines in the outer areas of the floating unit assembly can be avoided.
As used herein, the term “horizontal distance” refers to the Euclidean horizontal distance between two points. As such, for a first point p1 with coordinates (x1,y1,z1) and second point p2 with coordinates (x2,y2,z2), the horizontal distance d between the points p1 and p2 can be determined by the following equation:
Optionally, the secondary connection line(s) connected to a primary buoy is/are separated from any primary connection line connected to the primary buoy by a first angle of at least 90 degrees as seen in a horizontal plane when no environmental loads are imparted on the floating unit assembly.
Since the secondary buoy is arranged such that the first angle is larger than 90 degrees, the secondary buoy is able to exert a pulling force on the primary buoy counteracting at least a component of a pulling force from the floating unit acting on the primary buoy via the primary connection line.
Optionally, the secondary connection line is connected to the secondary buoy at a secondary buoy connection point, the secondary buoy connection point being associated with a secondary buoy offset ratio being the ratio between the horizontal distance from the secondary buoy connection point to the secondary seafloor connection point and the vertical distance from the secondary buoy connection point to the secondary seafloor connection point when no environmental loads are imparted on the floating unit assembly. Preferably, the secondary buoy offset ratio is at least 0.05, preferably at least 0.1.
Thus, the secondary buoy is not located completely above the secondary seafloor connection point and can thus exert a pulling force on the primary buoy counteracting at least a component of a pulling force from the floating unit acting on the primary buoy via the primary connection line.
Optionally, for a primary buoy being connected to at least one secondary buoy by a respective secondary connection line, the respective primary connection line is connected to the primary buoy at a primary buoy connection point, the primary buoy connection point being associated with a primary buoy offset ratio being the ratio between the horizontal distance from the primary buoy connection point to the primary seafloor connection point and the vertical distance from the primary buoy connection point to the primary seafloor connection point when no environmental loads are imparted on the floating unit assembly. The secondary buoy offset ratio is greater than the primary buoy offset ratio.
The above implies that the primary buoy may provide an appropriate flexibility to the floating unit assembly.
Optionally, for a primary buoy being connected to at least one secondary buoy by a respective secondary connection line, the vertical distance from the secondary buoy connection point to the secondary seafloor connection point is greater than the vertical distance from the primary buoy connection point to the primary seafloor connection point when no environmental loads are imparted on the floating unit assembly.
Purely by way of example, the ratio between the vertical distance from the secondary buoy connection point to the secondary seafloor connection point and the vertical distance from the primary buoy connection point to the primary seafloor connection point may be at least 1.1, preferably at least 1.3.
As the floating unit is forced away from its normal position by environmental loads, such as waves, water currents and/or wind, the primary and secondary buoys are pulled away from their normal positions. The sideways movement of the primary and secondary buoys is also associated with a pendulum motion of each buoy around its respective seafloor connection point. As the angle between each respective taut line and the respective primary or secondary vertical axis increases, so too does the horizontal force on the respective buoy. The force on the respective taut line is proportional to the buoyancy of each respective buoy. Since the secondary taut line is longer than the primary taut line, the relative increase in horizontal force on the primary buoy upon horizontal displacement of the buoy is larger than the relative increase in horizontal force on the secondary buoy, which results in the movement of the floating device primarily being restricted by the horizontal force component of the buoyancy of the primary buoy.
In other words, the primary buoy(s) may be the main contributors for controlling the positions of the floating units in rough weather, whilst the secondary buoys may provide a biasing force which is less dependent on weather conditions.
Optionally, for a primary buoy being connected to at least one secondary buoy by a respective secondary connection line, the buoyancy of the primary buoy is greater than the buoyancy of the secondary buoy. Preferably, a ratio between the buoyancy of the primary buoy and the buoyancy of the secondary buoy is greater than 2, more preferred greater than 4.
As the floating unit is forced away from its normal position by environmental loads, such as waves, water currents and/or wind, the primary and secondary buoys are pulled away from their normal positions. The sideways movement of the primary and secondary buoys is also associated with a pendulum motion of each buoy around its respective seafloor connection point. As the angle between each respective taut line and the respective primary or secondary vertical axis increases, so too does the horizontal force on the respective buoy.
The force on the respective taut line is proportional to the buoyancy of each respective buoy. Since the buoyancy of the primary buoy is greater than the buoyancy of the secondary buoy, the relative increase in horizontal force on the primary buoy upon horizontal displacement of the buoy is larger than the relative increase in horizontal force on the secondary buoy, which results in the movement of the floating device primarily being restricted by the horizontal force component of the primary taut line pulling the primary buoy. In other words, the primary buoy(s) will be able to control the positions of the floating units in rough weather, whilst the secondary buoys will provide a biasing force which is less dependent on weather conditions.
Optionally, at least one, preferably each, secondary buoy is adapted to intersect a still water surface of said body of water when no environmental loads are imparted on said floating unit assembly.
As such, one or more of the secondary buoys may be used for demarcation, i.e. marking the outer boundaries of the floating using assembly. As a non-limiting example, the secondary buoy is adapted to intersect a still water surface of said body of water and may be provided with signal emitting means, such as light signal emitting means, e.g. beacons or the like, in order to present information indicative of the presence, and possibly also the boundaries of the floating unit assembly.
The floating unit assembly comprises at least three floating units spaced-apart such that they together delimit a first area, wherein the floating unit assembly comprises a plurality of outer primary buoys positioned outside the first area such that they together delimit a second area, wherein each one of the outer primary buoys is connected to at least one floating unit. Moreover, the floating unit assembly comprises a plurality of secondary buoys positioned outside the second area, each such secondary buoy being connected to at least one of the outer primary buoys.
The outer primary buoys provide anchor points around the first area with primary connection lines preventing floating units at the circumference of the first area from collapsing inwards into the first area, thereby promoting improved integrity of distribution of the floating units. The secondary buoys are positioned around the second area, thereby enabling a horizontal biasing force to be applied to the outer primary buoys via the secondary connection lines connecting the outer primary buoys with the secondary buoys. The biasing force from the secondary buoys thereby promotes improved integrity of distribution of the outer primary buoys around the first area.
Each floating unit connected to a least one primary buoy by a respective primary connection line is located in the first area. In other words, the floating unit assembly is free from floating units outside the first area. Moreover, though purely by way of example, each one of the secondary buoys may be located outside the first area.
Optionally, at least one primary buoy of the floating unit assembly is connected to two – six, preferably three, floating units.
Optionally, the at least one primary buoy of the floating unit assembly being connected to two – six, preferably three, floating units is located in the first area.
Optionally, a primary buoy is connected to three floating units, whereby the primary buoy is positioned in a triangular area formed between the respective three floating units connected to the primary buoy.
Optionally, the position of the primary buoy within the triangular area is such that the three respective primary connection lines connecting the primary buoy to the respective three floating units are separated 110-130 degrees in a horizontal plane, even more preferably 120 degrees, when no environmental loads are imparted on the floating unit assembly.
Optionally, the primary buoy connected to two – six, preferably three, floating units, is connected to each floating unit by means of a respective primary connection line, whereby each respective primary connection line connects a floating unit connection point of the floating unit to a respective primary buoy connection point associated with the primary buoy, each one of the respective primary connection lines being associated with a nominal horizontal distance and a maximum horizontal distance, wherein:
- the nominal horizontal distance is the horizontal distance between the respective primary buoy connection point and the floating unit connection point in a condition when no environmental loads are imparted on the floating unit assembly, and - the maximum horizontal distance is the largest horizontal distance that can be obtained between the respective primary buoy connection point and the floating unit connection point whilst being connected by the respective primary connection lines.
Optionally, the primary buoy connected to two – six, preferably three, floating units, is connected to the respective primary seafloor connection point on the seafloor via one or more primary taut lines in such a manner that, for each respective primary connection lines connecting the primary buoy to a floating unit, the ratio between the maximum horizontal distance and the nominal horizontal distance is less than 110%, preferably less than 105%, more preferred less than 102%.
As such, the floating unit assembly according to the above comprises primary connection lines that only to a limited extent provide station-keeping flexibility to the floating unit assembly, thereby implying that a large portion of the station-keeping flexibility of the floating unit assembly may be attributed to the flexibility of the primary buoys and primary taut lines rather than to the primary connection lines. As has been in indicated hereinabove in the background of the invention, attributing the flexibility of the floating unit assembly to the primary buoys and to the primary taut lines implies an appropriate restoring load-sharing capability between floating units connected to the same primary buoy which in turn may result in appropriately low costs for the floating unit assembly.
Optionally, the primary buoy connected to two – six, preferably three, floating units, is connected to the respective primary seafloor connection point on the seafloor via one or more primary taut lines in such a manner that, for each floating unit and its each respective primary connection lines connected to the primary buoy:
- the primary buoy connection point assumes a nominal primary buoy position in a condition when no environmental loads are imparted on the floating unit assembly; - the primary buoy connection point assumes a maximum primary buoy position when the floating unit assembly is in a condition in which the maximum horizontal distance is reached between the primary buoy connection point and the floating unit connection point for the respective primary connection line, and
- a horizontal distance between the nominal primary buoy position and the maximum primary buoy position is greater than, preferably at least two times greater than, more preferred at least five times greater than, the difference between the maximum horizontal distance and the nominal horizontal distance.
Again, the floating unit assembly according to the second aspect of the present disclosure implies that a major part of the flexibility may be attributed to the movement of the primary buoys rather than to the characteristics of the primary connection lines.
Optionally, the primary buoy connected to two – six, preferably three, floating units, is connected to the respective primary seafloor connection point on the seafloor via one or more primary taut lines in such a manner that, for each floating unit and its each respective primary connection lines connected to the primary buoy:
- the primary buoy connection point assumes an intermediate primary buoy position when the floating unit assembly is in a condition in which an intermediate horizontal distance is reached between the primary buoy connection point and the floating unit connection point for the respective primary connection lines, the intermediate horizontal distance being the average of the nominal horizontal distance and the maximum horizontal distance, and
- a horizontal distance between the intermediate primary buoy position and the maximum primary buoy position is greater than, preferably at least two times greater than, more preferred at least five times greater than, the difference between the maximum horizontal distance and the intermediate horizontal distance.
Optionally, one respective primary connection line connecting one of the two to six, preferably three to six, more preferred three, floating units to the same primary buoy has a largest nominal horizontal distance of the respective primary connection lines connecting the floating units to the same primary buoy and wherein one respective primary connection line connecting one of the two to six, preferably three to six, more preferred three, floating units to the same primary buoy has a smallest nominal horizontal distance of the respective primary connection lines connecting the floating units to the same primary buoy, the ratio between the largest nominal horizontal distance and the smallest nominal horizontal distance being less than 1.1, preferably less than 1.05.
As such, the lines connecting floating units to the additional buoy may be of approximately the same length.
Optionally, the respective primary connection lines connected to at least one, preferably each one, of the plurality of primary buoys, as seen in a plan view of the floating unit assembly, extend equiangularly from the primary buoy when no environmental loads are imparted on the floating unit assembly.
Optionally, the floating unit assembly comprises at least a pattern portion being such that a plan view of the pattern portion forms a hexagonal pattern having straight lines and corners, wherein three floating units and three primary buoys are connected to each other by respective primary connection lines, forming the straight lines, and are located in the corners of the hexagonal pattern such that a floating unit and a primary buoy are always located in two adjacent corners of the hexagonal pattern.
Optionally, at least one of the floating units, preferably each one of the floating units, comprises a wind turbine.
BRIEF DESCRIPTION OF THE DRAWINGS
With reference to the appended drawings, below follows a more detailed description of embodiments of the invention cited as examples.
In the drawings:
Fig.1 is a schematic plan view of a portion of floating unit assembly according to an embodiment of the present invention;
Fig.2 is a schematic plan view of a portion of floating unit assembly according to another embodiment of the present invention;
Fig.3 is a schematic side view of a portion of an embodiment of a floating unit assembly;
Figs.4a – 4c illustrate schematic side views of a portion of an embodiment of a floating unit assembly, and
Fig. 5 illustrates a schematic perspective view of a portion of another embodiment of a floating unit assembly.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Fig.1 is a schematic plan view of a portion of floating unit assembly 1 according to an embodiment of the present invention. Furthermore, Fig.2 illustrates another embodiment of a floating unit assembly 1.
Generally, each one of the Fig.1 and Fig.2 embodiments of the floating unit assembly 1 comprises at least one floating unit 3, at least one primary buoy 4 and at least one secondary buoy 6. In general, and as exemplified in each one of Fig.1 and Fig.2, the floating unit assembly 1 generally comprises a plurality of floating units 3, a plurality of primary buoys 4 and a plurality of secondary buoy 6.
Moreover, as indicated in each one of Fig.1 and Fig.2, each one of the at least one primary buoy 4 is connected to at least one of the at least one floating unit 3 by a respective primary connection line 5. Additionally, at least one of the at least one primary buoy 4 is connected to at least one secondary buoy 6 by a respective secondary connection line 7.
In the drawings, a floating unit 3 is indicated by a square, a primary buoy 4 is indicated by a circle and a secondary buoy 6 is indicated by a hexagonal.
As may be gleaned from each one of the Fig.1 and Fig.2 embodiments, embodiments of the floating unit assembly 1 according to the present invention may assume a plurality of different types of shapes and configurations. Fig.3 illustrates a portion of an embodiment of a floating unit assembly 1 according to the present invention. Purely by way of example, the Fig.3 portion may form part of the Fig.1 embodiment, the Fig.2 embodiment, or any other embodiment of the floating unit assembly 1.
As may be gleaned from Fig.3, the floating unit assembly 1 is arranged in a body of water 19 with a seafloor 2 and the floating unit assembly 1 comprises:
- at least one floating unit 3,
- at least one primary buoy 4,
- wherein each one of the at least one primary buoy 4 is connected to at least one of the at least one floating unit 3 by a respective primary connection line 5,
- wherein at least one of the at least one primary buoy 4 is connected to at least one secondary buoy 6 by a respective secondary connection line 7,
- wherein each primary buoy 4 is connected to a respective primary seafloor connection point 8 on the seafloor 2 via one or more primary taut lines 9,
- wherein each secondary buoy 6 is connected to a secondary seafloor connection point 10 on the seafloor 2 via one or more secondary taut lines 11.
Fig, 3 illustrates that the floating unit assembly 1 may comprise a first anchor 20 and a second anchor 21. The first primary seafloor connection point 8 may be the connection point at which the one or more primary taut lines 9 is connected to the first anchor 20. In a similar vein, the second seafloor connection point 10 may be the connection point at which the one or more secondary taut lines 11 is connected to the second anchor 21.
Moreover, as indicated in Fig.3, for a primary buoy 4 being connected to at least one secondary buoy 6 by a respective secondary connection line 7, a first horizonal distance h1 between the first seafloor connection point 8 of the primary buoy 4 and the second seafloor connection point 10 of the one secondary buoy 6 is larger than a second horizontal distance h2 between the primary buoy 4 and the secondary buoy 6 when no environmental loads are imparted on the floating unit assembly.
Purely by way of example, the secondary connection line 7 may be connected to the secondary buoy 6 at a secondary buoy connection point 22 and the secondary connection line 7 may be connected to the primary buoy 4 at a primary buoy connection point 25’ for the secondary connection line 7. As used herein, the second horizontal distance h2 between the primary buoy 4 and the secondary buoy 6 may be defined as the horizontal distance between the secondary buoy connection point 22 and the primary buoy connection point 25’ for the secondary connection line 7.
As such, and as illustrated in Fig.3, the one secondary buoy 6 and its one or more secondary taut lines 11 is inclined towards the primary buoy 4 to which the secondary buoy 6 is connected by a respective secondary connection line 7.
Moreover, as indicated in Fig.3, the body of water 19 is associated with a water depth WD which is the vertical distance from the seafloor 2 to a still water surface 28 of the body of water 19. As a non-limiting example, applicable for each embodiment of the floating unit assembly 1, a ratio h1/WD between the first horizonal distance h1 and the water depth WD may be at least 1, preferably at least 2.
Turning back to Fig.1, though purely by way of example, it is illustrated therein that at least one secondary connection line 7 connected to a primary buoy 4 is separated from any primary connection line 5 connected to the primary buoy 4 by a first angle a1 of at least 90 degrees as seen in a horizontal plane p1 when no environmental loads are imparted on the floating unit assembly 1.
The above feature is illustrated in Fig.1 in an implementation in which each one of two secondary connection lines 7 connected to a primary buoy 4 is separated from any primary connection line 5 connected to the primary buoy 4 by a first angle a1. In the Fig.1 implementation of the above features, the first angle a1 is substantially the same for the two secondary connection lines 7. However, it is contemplated that the first angle a1 may be different for the two secondary lines 7. However, the first angle a1 is preferably at least 90 degrees as seen in a horizontal plane p1 when no environmental loads are imparted on the floating unit assembly 1.
Referring again to Fig.3, it is exemplified therein that the secondary connection line 7 is connected to the secondary buoy 6 at a secondary buoy connection point 22. The secondary buoy connection point 22 is associated with a secondary buoy offset ratio being the ratio between the horizontal distance 23 from the secondary buoy connection point 22 to the secondary seafloor connection point 10 and the vertical distance 24 from the secondary buoy connection point 22 to the secondary seafloor connection point 10 when no environmental loads are imparted on the floating unit assembly. As a non-limiting example, the secondary buoy offset ratio is at least 0.05, preferably at least 0.1.
In a similar vein as for the secondary buoy 6, Fig.3 also illustrates an embodiment in which, for a primary buoy 4 being connected to at least one secondary buoy 6 by a respective secondary connection line 7, the respective primary connection line 5 is connected to the primary buoy 4 at a primary buoy connection point 25. In the Fig.3 embodiment, the primary buoy connection point 25 for the primary connection line 5 is the same as the primary buoy connection point 25’ for the secondary connection line 7.
However, it is also envisaged that the primary buoy connection point 25 for the primary connection line 5 may be different from the primary buoy connection point 25’ for the secondary connection line 7.
The primary buoy connection point 25 is associated with a primary buoy offset ratio being the ratio between the horizontal distance 26 from the primary buoy connection point 25 to the primary seafloor connection point 8 and the vertical distance 27 from the primary buoy connection point to the primary seafloor connection point 8 when no environmental loads are imparted on the floating unit assembly. As a non-limiting example, the secondary buoy offset ratio may be greater than the primary buoy offset ratio. Although a non-zero horizontal distance 26 from the primary buoy connection point 25 to the primary seafloor connection point 8 is illustrated in Fig.3, it is contemplated that that the horizontal distance 26 from the primary buoy connection point 25 to the primary seafloor connection point 8 may be zero or at least close to zero for at least some primary buoys 4 forming part of a floating unit assembly 1 according to embodiments of the present invention.
Furthermore, Fig.3 also illustrates an embodiment in which, for a primary buoy 4 being connected to at least one secondary buoy 6 by a respective secondary connection line 7, the vertical distance 24 from the secondary buoy connection point 22 to the secondary seafloor connection point 10 is greater than the vertical distance 27 from the primary buoy connection point 25 to the primary seafloor connection point 8 when no environmental loads are imparted on the floating unit assembly 1.
Purely by way of example, the ratio between the vertical distance 24 from the secondary buoy connection point 22 to the secondary seafloor connection point 10 and the vertical distance 27 from the primary buoy connection point 25 to the primary seafloor connection point 8 may be at least 1.1, preferably at least 1.3.
Moreover, though purely by way of example, a total distance associated with the secondary buoy 6 may be defined as the total Euclidian distance from the secondary buoy connection point 22 to the secondary seafloor connection point 10 and can be determined using the above-mentioned horizontal distance 23 and the vertical distance 24 associated with the secondary buoy 6. Moreover, a reference distance associated with the secondary buoy 6 may be determined by subtracting the horizontal distance 23 associated with the secondary buoy 6 from the above-mentioned total distance associated with the secondary buoy 6.
Moreover, though purely by way of example, a total distance associated with the primary buoy 4 may be defined as the total Euclidian distance from the primary buoy connection point 25 to the primary seafloor connection point 8 and can be determined using the above-mentioned horizontal distance 26 and the vertical distance 27 associated with the primary buoy 4. Moreover, a reference distance associated with the primary buoy 4 may be determined by subtracting the horizontal distance 26 associated with the primary buoy 4 from the above-mentioned total distance associated with the primary buoy 4.
As a non-limiting example, the reference distance associated with the secondary buoy 6 may be greater than the reference distance associated with the primary buoy 4.
Additionally, for a primary buoy 4 being connected to at least one secondary buoy 6 by a respective secondary connection line 7, the buoyancy of the primary buoy 4 may be greater than the buoyancy of the secondary buoy 6. As a non-limiting example, a ratio between the buoyancy of the primary buoy 4 and the buoyancy of the secondary buoy 6 may be greater than 2, more preferred greater than 4.
Furthermore, as exemplified in Fig.3, at least one of, preferably each, secondary buoy 6 may be adapted to intersect the still water surface 28 of the body of water 19 when no environmental loads are imparted on the floating unit assembly.
Reference is again made to Fig.2, illustrating an embodiment of the floating unit assembly 1 in which the floating unit assembly 1 comprises at least three floating units 3 spaced-apart such that they together delimit a first area 14. In the Fig.2 embodiment, the first area 14 is enclosed by a first area demarcation line 29.
Moreover, Fig.2 illustrates that the floating unit assembly 1 comprises a plurality of outer primary buoys 4a positioned outside the first area 14 such that they together delimit a second area 15. In the Fig.2 embodiment, the second area 15 is enclosed by a second area demarcation line 30 such that the second area 15 extends between the first area demarcation line 29 and the second area demarcation line 30.
As may be gleaned from Fig.2, each one of the outer primary buoys 4a is connected to at least one floating unit 3. Moreover, the Fig.2 floating unit assembly 1 comprises a plurality of secondary buoys 6 positioned outside the second area 15 and each such secondary buoy 6 is connected to at least one of the outer primary buoys 4a.
Furthermore, Fig.2 illustrates an embodiment in which each floating unit 3 connected to a least one primary buoy 4 by a respective primary connection line 5 is located in the first area 14. Put differently, the second area 15 may be free from floating units forming part of the floating unit assembly 1. Moreover, though purely by way of example, the first area 14 may be free from secondary buoys 6.
Furthermore, as illustrated in Fig.2, at least one primary buoy 4b of the floating unit assembly 1 may be connected to two – six, preferably three, floating units 3. In particular, in the Fig.2 embodiment, the at least one primary buoy 4b of the floating unit assembly 1 being connected to two – six, preferably three, floating units 3 is located in the first area 14.
Additionally, as indicated in Fig.2, a primary buoy 4b is connected to three floating units 3, whereby the primary buoy 4b is positioned in a triangular area 18 formed between the respective three floating units 3 connected to the primary buoy 4b. Furthermore, as indicated in Fig.2, the position of the primary buoy 4b within the triangular area 18 may be such that the three respective primary connection lines 5 connecting the primary buoy 4b to the respective three floating units 3 are separated 110-130 degrees in a horizontal plane, even more preferably 120 degrees, when no environmental loads are imparted on the floating unit assembly.
Non-limiting examples of the interaction between a primary buoy 4b and a floating unit 3 will now be discussed with references to Fig.4a – 4c.
As such, with reference to Figs.4a – 4c, the floating unit assembly 1 illustrated therein is such that each primary connection line 5 connects a primary buoy connection point 25 of a primary buoy 4 to a floating unit connection point 31 of a floating unit 3 and each primary connection line 5 is associated with a nominal horizontal distance dnom and a maximum horizontal distance dmax. In the Fig.4a – 4c example, the primary buoy 4 is also connected to an additional primary connection line 5’ which may be connected to an additional floating unit (not shown in Fig.4a – Fig.4c). As such, the primary buoy 4 illustrated in Fig.4a – Fig.4c may be a primary buoy 4 located in the first area 14 as has been mentioned hereinabove with reference to Fig.2. However, it is also contemplated that the primary buoy 4 may be positioned outside the first area 14 and thus may be located in the second area 15, reference again being made to Fig.2. In such an implementation, the primary buoy 4 may be connected to a secondary connection line 7 instead of the additional primary connection line 5’ illustrated in Fig.4a for example.
Irrespective of the location of the primary buoy 4 and the connection lines connected thereto, with reference to Fig.4a, the nominal horizontal distance dnom is the horizontal distance between the primary buoy connection point 25 and the floating unit connection point 31 in a condition when no environmental loads are imparted on the floating unit assembly 1.
Purely by way of example, and as may be gleaned in Fig.4a, the primary connection line 5 may have a catenary shape when no environmental loads are imparted on the floating unit assembly 1. In Fig.4a, such a catenary shape has been exaggerated in order to elucidate the difference between the Fig.4a and Fig.4b conditions. As has been indicated above, the nominal horizontal distance dnom may for instance be determined using mooring system software such as as MIMOSA®, OrcaFlex® or Flexcom®.
Further, as indicated in Fig.4a, at least one, preferably each one, of the primary connection lines 5 imparts a restoring force R on the floating unit to which the primary connection line is connected when no environmental loads are imparted on the floating unit assembly 1. The restoring force R has a horizontal component Rhor being at least 75%, preferably at least 85%, more preferred at least 95 % of the restoring force. As such, the ratio between the horizontal component Rhor and the total restoring force R may be at least 75%, preferably at least 85%, more preferred at least 95 %.
Moreover, as illustrated in Fig.4b, the maximum horizontal distance dmax is the largest horizontal distance that can be obtained between the primary buoy connection point 25 and the floating unit connection point 31 whilst being connected by the primary connection line. In Fig.4b, the primary connection line 5 has been illustrated as a substantially straight line connecting the primary buoy connection point 25 and the floating unit connection point 31 when the maximum horizontal distance dmax therebetween is obtained. However, it is of course possible that the primary connection line 5 will assume a catenary shape – although less pronounced as compared to the Fig.4a condition - also when the maximum horizontal distance dmax is obtained.
Purely by way of example, the maximum horizontal distance dmax is the maximum distance that can be obtained between the primary buoy connection point 25 and the floating unit connection point 31 until a breaking load or breaking stress has been obtained in the primary connection line 5, assuming that the primary buoy 4 maintains being connected to the seafloor 2 via the one or more taut lines 9. As a non-limiting example, the maximum horizontal distance dmax may for instance be determined using mooring system software such as as MIMOSA®, OrcaFlex® or Flexcom®. To this end, with reference to Fig.4b, for instance using a mooring system software, the floating unit 3 may be imparted a movement away from the seafloor connection point 8 until the load or stress in the primary connection line 5 has reached a predetermined breaking load or stress. When such a predetermined braking load or stress is identified, the maximum horizontal distance dmax may be determined. Of course, the above procedure can also be carried out for each of the of the floating units 4, e.g. each one of the floating units of the Fig.1 or Fig.2 embodiments, at the same time.
According to the present invention, for at least a first primary connection line 5 of the primary connection lines, the ratio between the maximum horizontal distance dmax and the nominal horizontal distance dnom is less than 110%, preferably less than 105%, more preferred less than 102%.
The above ratio can be achieved in a plurality of different ways. Purely by way of example, and as indicated in Fig.4a and Fig.4b, the ratio can be achieved by implementing the primary connection line 5 so as to assume a catenary shape when no environmental loads are imparted on the floating unit assembly 1 (see Fig.4a) and so as to assume a shape with a less pronounced catenary shape when the maximum horizontal distance dmax is obtained between the primary buoy connection point 25 and the floating unit connection point 31.
As another non-limiting example, the above-mentioned ratio can be obtained by an elastic primary connection line 5 that may be substantially straight even when no environmental loads are imparted on the floating unit assembly 1 and which is allowed to be extended, e.g. elastically extended, in order to arrive at the maximum horizontal distance dmax.
Of course, it is also envisaged that a combination of the above-mentioned alternatives, viz the catenary shape and the extension, e.g. elastic extension, of the primary connection line 5 may be implemented in embodiments of the floating unit assembly 1.
According to embodiments of the floating unit assembly 1, as exemplified in Fig.4a and Fig.4b, the primary buoy 4, to which the first primary connection line 5 is connected, is connected to the seafloor 2 via one or more taut lines 9 in such a manner that the primary buoy connection point 25 assumes a nominal primary buoy position in a condition when no environmental loads are imparted on the floating unit assembly. Again, such a condition is illustrated in Fig.4a.
Moreover, the primary buoy 4, to which the first primary connection line 5 is connected, is connected to the seafloor 2 via one or more taut lines 9 in such a manner that the primary buoy connection point 25 assumes a maximum primary buoy position when the floating unit assembly 1 is in a condition in which the maximum horizontal distance dmax is reached between the primary buoy connection point 25 and the floating unit connection point 31 for the first primary connection line 5.
Moreover, a horizontal distance Lmax between the nominal primary buoy position and the maximum primary buoy position is greater than, preferably at least two times greater than, more preferred at least five times greater than, the difference Δmax between the maximum horizontal distance dmax and the nominal horizontal distance dnom.
Moreover, with reference to Fig.4c, in embodiments of the floating unit assembly 1, at least the first primary connection line 5 of the primary connection lines is associated with an intermediate horizontal distance dinter being the average of the nominal horizontal distance and the maximum horizontal distance. Furthermore, in the Fig.4c embodiment, the primary buoy 4, to which the first primary connection line 5 is connected, is connected to the seafloor 2 via one or more taut lines 9 in such a manner that the primary buoy connection point 25 assumes an intermediate primary buoy position when the floating unit assembly is in a condition in which the intermediate horizontal distance dinter is reached between the primary buoy connection point 25 and the floating unit connection point 31 for the first primary connection line 5.
Moreover, as indicated in Fig.4c, a horizontal distance Linter between the intermediate primary buoy position and the maximum primary buoy position is greater than, preferably at least two times greater than, more preferred at least five times greater than, the difference Δinter between the maximum horizontal distance dmax and the intermediate horizontal distance dinter.
The above features imply that when the floating unit 3 has been offset from its nominal position and thereafter is offset further, a major part of the flexibility may be attributed to the movement of the primary buoy 4 rather than to the characteristics of the first primary connection line 5. This in turns implies that in a storm condition for instance in which elements of the floating unit assembly will be positioned in static offset positions as compared to nominal positions, a major part of the dynamic flexibility may be attributed to the movement of the primary buoy 4 rather than to the characteristics of the first primary connection line 5.
It should be noted that in embodiments of the floating unit assembly 1 the first primary connection lines 5 need not necessarily have the above-mentioned ratio between the maximum horizontal distance dmax and the nominal horizontal distance dnom. Instead, the desired distribution of the station keeping flexibility of the floating unit assembly 1 may be achieved by the fact that the flexibility derivable from the primary taut lines 9 and the primary buoys 4 is greater than the flexibility derivable from the primary connection lines 5 even when a not negligible flexibility can be attributed to the primary connection lines 5.
As such, with reference to Figs.4a – 4b, in embodiments of the floating unit assembly 1, the nominal horizontal distance dnom is the horizontal distance between the primary buoy connection point 25 and the floating unit connection point 31 in a condition when no environmental loads are imparted on the floating unit assembly. Moreover, as has been presented hereinabove with reference to Fig.4b, the maximum horizontal distance dmax is the largest horizontal distance that can be obtained between the primary buoy connection point 25 and the floating unit connection point 31 whilst being connected by the primary connection line 5.
Moreover, with reference to Fig.4a and Fig.4b, the primary buoy 4, to which the first primary connection line 5 is connected, is connected to the seafloor 2 via one or more taut lines 9 in such a manner that the primary buoy connection point 25 assumes a nominal primary buoy position in a condition when no environmental loads are imparted on the floating unit assembly 1. Again, such a condition is illustrated in Fig.4a. Moreover, with reference to Fig.4b, the primary buoy 4 is connected to the seafloor 2 via one or more primary taut lines 9 in such a manner that the primary buoy connection point 25 assumes a maximum primary buoy position when the floating unit assembly 1 is in a condition in which the maximum horizontal distance dmax is reached between the primary buoy connection point 25 and the floating unit connection point 31 for the first primary connection line 5.
Embodiments of the floating unit assembly 1 may be such that a horizontal distance Lmax between the nominal primary buoy position and the maximum primary buoy position is greater than, preferably at least two times greater than, more preferred at least five times greater than, the difference Δmax between the maximum horizontal distance dmax and the nominal horizontal distance dnom.
Moreover, again with reference to Fig.4b and Fig.4c, the first primary connection line 5 may be associated with an intermediate horizontal distance dinter being the average of the nominal horizontal distance dnom and the maximum horizontal distance dmax. Moreover, the primary buoy 4, to which the first primary connection line 5 is connected, is connected to the seafloor 2 via one or more taut lines 9 in such a manner that the primary buoy connection point 25 assumes an intermediate primary buoy position (see Fig.4c) when the floating unit assembly 1 is in a condition in which the intermediate horizontal distance dinter is reached between the primary buoy connection point 25 and the floating unit connection point 31 for the first primary connection line 5. A horizontal distance Linter between the intermediate primary buoy position and the maximum primary buoy position is greater than, preferably at least two times greater than, more preferred at least five times greater than, the difference between the maximum horizontal distance dmax and the intermediate horizontal distance dnom.
Reference is now made to Fig.5 and the above presentation with reference to Fig.4a – Fig. 4c. As indicated in Fig.5, in embodiments of the floating unit assembly 1 according to the present invention, a primary buoy 4 connected to two – six, preferably three, floating units 3, may be connected to each floating unit 3 by means of a respective primary connection line 5. Moreover, though purely by way of example, each respective primary connection line 5 connects a floating unit connection point 31 (not shown in Fig.5) of the floating unit 3 to a respective primary buoy connection point 25 (not shown in Fig.5) associated with the primary buoy 4, each one of the respective primary connection lines 5 being associated with a nominal horizontal distance dnom and a maximum horizontal distance dmax, wherein:
- the nominal horizontal distance dnom is the horizontal distance between the respective primary buoy connection point 25 and the floating unit connection point 31 in a condition when no environmental loads are imparted on the floating unit assembly, and
- the maximum horizontal distance dmax is the largest horizontal distance that can be obtained between the respective primary buoy connection point 25 and the floating unit connection point 31 whilst being connected by the respective primary connection lines 5.
Furthermore, again with reference to the Fig.5 embodiment, the primary buoy 4 connected to two – six, preferably three, floating units 3, may be connected to the respective primary seafloor connection point 8 (not shown in Fig.5) on the seafloor 2 via one or more primary taut lines 9 in such a manner that for each respective primary connection line 5 connecting the primary buoy 4 to a floating unit 3, the ratio between the maximum horizontal distance and the nominal horizontal distance is less than 110%, preferably less than 105%, more preferred less than 102%.
Moreover, again with reference to Fig.5, though purely by way of example, the primary buoy 4 connected to two – six, preferably three, floating units 3, may connected to the respective primary seafloor connection point 8 on the seafloor 2 via one or more primary taut lines 9 in such a manner that, for each floating unit 3 and its each respective primary connection line 5 connected to the primary buoy 4:
- the primary buoy connection point 25 assumes a nominal primary buoy position in a condition when no environmental loads are imparted on the floating unit assembly 10;
- the primary buoy connection point 25 assumes a maximum primary buoy position when the floating unit assembly is in a condition in which the maximum horizontal distance is reached between the primary buoy connection point 25 and the floating unit connection point for the respective primary connection line 5, and
- a horizontal distance Lmax between the nominal primary buoy position and the maximum primary buoy position is greater than, preferably at least two times greater than, more preferred at least five times greater than, the difference Δmax between the maximum horizontal distance dmax and the nominal horizontal distance dnom.
Furthermore, as another non-limiting example, the primary buoy 4 connected to two – six, preferably three, floating units 3, is connected to the respective primary seafloor connection point 8 on the seafloor 2 via one or more primary taut lines 9 in such a manner that, for each floating unit 3 and its each respective primary connection lines 5 connected to the primary buoy 4:
- the primary buoy connection point 25 assumes an intermediate primary buoy position when the floating unit assembly is in a condition in which the intermediate horizontal distance dinter is reached between the primary buoy connection point 25 and the floating unit connection point 31 for the respective primary connection lines 5, and
- a horizontal distance Linter between the intermediate primary buoy position and the maximum primary buoy position is greater than, preferably at least two times greater than, more preferred at least five times greater than, the difference between the maximum horizontal distance dimax and the intermediate horizontal distance dinter.
Furthermore, again with reference to Fig.5, one respective primary connection line 5 connecting one of the two to six, preferably three to six, more preferred three, floating units 3 to the same primary buoy 4 has a largest nominal horizontal distance dnom,max of the respective primary connection lines 5 connecting the floating units 3 to the same primary buoy 4 and wherein one respective primary connection line 5 connecting one of the two to six, preferably three to six, more preferred three, floating units 3 to the same primary buoy 4 has a smallest nominal horizontal distance dnom,min of the respective primary connection lines 5 connecting the floating units 3 to the same primary buoy 4. The ratio between the largest nominal horizontal distance dnom,max and the smallest nominal horizontal distance dnom,in may be less than 1.1, preferably less than 1.05.
Moreover, Fig.5 illustrates an embodiment in which the respective primary connection lines 5 connected to at least one, preferably each one, of the plurality of primary buoys 4, as seen in a plan view of the floating unit assembly 1, extend equiangularly from the primary buoy 4 when no environmental loads are imparted on the floating unit assembly.
Reverting to Fig.2, it should be noted that embodiments of the floating unit assembly 1 may comprise at least a pattern portion being such that a plan view of the pattern portion forms a hexagonal pattern having straight lines and corners, wherein three floating units 3 and three primary buoys 4 are connected to each other by respective primary connection lines 5, forming the straight lines, and are located at the corners of the hexagonal pattern such that a floating unit 3 and a primary buoy 4 are always located at two adjacent corners of the hexagonal pattern.
It should be noted that that the floating unit 1 according to the present invention is preferably used for a wind farm. As such, at least one of the floating units 3, preferably each one of the floating units 3, comprises a wind turbine 32, see e.g. Fig.3.
It is to be understood that the present invention is not limited to the embodiments described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims.

Claims (19)

1. A floating unit assembly (1) arranged in a body of water (19) with a seafloor (2), said floating unit assembly (1) comprising:
- at least one floating unit (3),
- at least one primary buoy (4),
- wherein each one of said at least one primary buoy (4) is connected to at least one of said at least one floating unit (3) by a respective primary connection line (5),
- wherein at least one of said at least one primary buoy (4) is connected to at least one secondary buoy (6) by a respective secondary connection line (7),
- wherein each primary buoy (4) is connected to a respective primary seafloor connection point (8) on said seafloor (2) via one or more primary taut lines (9),
- wherein each secondary buoy (6) is connected to a secondary seafloor connection point (10) on said seafloor (2) via one or more secondary taut lines (11), and
wherein, for a primary buoy (4) being connected to at least one secondary buoy (6) by a respective secondary connection line (7), a first horizonal distance (h1) between the first seafloor connection point (8) of said primary buoy (4) and the second seafloor connection point (10) of said one secondary buoy (6) is larger than a second horizontal distance (h2) between the primary buoy (4) and the secondary buoy (6) when no environmental loads are imparted on said floating unit assembly (1),
wherein the floating unit assembly (1) comprises at least three floating units (3) spaced-apart such that they together delimit a first area (14),
wherein the floating unit assembly (1) comprises a plurality of outer primary buoys (4a) positioned outside the first area (14) such that they together delimit a second area (15), wherein each one of the outer primary buoys (4a) is connected to at least one floating unit (3), and
wherein the floating unit assembly (1) comprises a plurality of secondary buoys (6) positioned outside the second area (15) and each such secondary buoy (6) being connected to at least one of said outer primary buoys (4a),
c h a r a c t e r i z e d i n t h a t each floating unit (3) connected to a least one primary buoy (4) by a respective primary connection line (5) is located in said first area (14).
2. The floating unit assembly (1) according to claim 1, wherein the secondary connection line(s) (7) connected to a primary buoy (4) is/are separated from any primary connection line (5) connected to the primary buoy (4) by a first angle (a1) of at least 90 degrees as seen in a horizontal plane (p1) when no environmental loads are imparted on said floating unit assembly.
3. The floating unit assembly (1) according to claim 1 or claim 2, wherein said secondary connection line (7) is connected to said secondary buoy (6) at a secondary buoy connection point (22), said secondary buoy connection point (22) being associated with a secondary buoy offset ratio being the ratio between the horizontal distance (23) from said secondary buoy connection point (22) to said secondary seafloor connection point (10) and a vertical distance (24) from said secondary buoy connection point (22) to said secondary seafloor connection point (10) when no environmental loads are imparted on said floating unit assembly, preferably the secondary buoy offset ratio is at least 0.05, preferably at least 0.1.
4. The floating unit assembly (1) according to claim 3, wherein, for a primary buoy (4) being connected to at least one secondary buoy (6) by a respective secondary connection line (7), said respective primary connection line (5) is connected to said primary buoy (4) at a primary buoy connection point (25), said primary buoy connection point (25) being associated with a primary buoy offset ratio being the ratio between the horizontal distance (26) from said primary buoy connection point (25) to said primary seafloor connection point (8) and the vertical distance (27) from said primary buoy connection point (25) to said primary seafloor connection point (8) when no environmental loads are imparted on said floating unit assembly, said secondary buoy offset ratio being greater than said primary buoy offset ratio.
5. The floating unit assembly (1) according to claim 4, wherein, for a primary buoy (4) being connected to at least one secondary buoy (6) by a respective secondary connection line (7), the vertical distance (24) from said secondary buoy connection point (22) to said secondary seafloor connection point (10) is greater than the vertical distance (27) from said primary buoy connection point (25) to said primary seafloor connection point (8) when no environmental loads are imparted on said floating unit assembly.
6. The floating unit assembly (1) according to any one of claims 1-5, wherein, for a primary buoy (4) being connected to at least one secondary buoy (6) by a respective secondary connection line (7), the buoyancy of the primary buoy (4) is greater than the buoyancy of the secondary buoy (6), preferably a ratio between the buoyancy of the primary buoy (4) and the buoyancy of the secondary buoy (6) being greater than 2, more preferred greater than 4.
7. The floating unit assembly (1) according to any of the preceding claims, wherein at least one of, preferably each, secondary buoy (6) is adapted to intersect a still water surface (28) of said body of water when no environmental loads are imparted on said floating unit assembly (1).
8. The floating unit assembly (1) according to any one of claims 1-7, wherein at least one primary buoy of said floating unit assembly (1) is connected to two – six, preferably three, floating units (3).
9. The floating unit assembly (1) according to claim 8, wherein said at least one primary buoy of said floating unit assembly (1) being connected to two – six, preferably three, floating units (3) is located in said first area (14).
10. The floating unit assembly (1) according to claim 8 or claim 9, wherein a primary buoy (4) is connected to three floating units (3), whereby said primary buoy (4) is positioned in a triangular area (18) formed between the respective three floating units (3) connected to the primary buoy (4).
11. The floating unit assembly (1) according to claim 10, wherein the position of the primary buoy (4) within the triangular area (18) is such that the three respective primary connection lines (5) connecting the primary buoy (4) to the respective three floating units (3) are separated 110-130 degrees in a horizontal plane, even more preferably 120 degrees, when no environmental loads are imparted on said floating unit assembly.
12. The floating unit assembly (1) according to any one of claims 8 - 11, wherein said primary buoy (4) connected to two – six, preferably three, floating units (3), is connected to each floating unit (3) by means of a respective primary connection line (5), whereby each respective primary connection line (5) connects a floating unit connection point of said floating unit to a respective primary buoy connection point associated with said primary buoy (4), each one of said respective primary connection lines (5) being associated with a nominal horizontal distance (dnom) and a maximum horizontal distance (dmax), wherein:
- said nominal horizontal distance (dnom) is the horizontal distance between said respective primary buoy connection point and said floating unit connection point in a condition when no environmental loads are imparted on said floating unit assembly, and
- said maximum horizontal distance (dmax) is the largest horizontal distance that can be obtained between said respective primary buoy connection point and said floating unit connection point whilst being connected by said respective primary connection lines (5).
13. The floating unit assembly (1) according to claim 12, wherein said primary buoy (4) connected to two – six, preferably three, floating units (3), is connected to said respective primary seafloor connection point (8) on said seafloor (2) via one or more primary taut lines (9) such that for each respective primary connection line (5) connecting said primary buoy (4b) to a floating unit (3), the ratio between said maximum horizontal distance (dmax) and said nominal horizontal distance (dnom) is less than 110%, preferably less than 105%, more preferred less than 102%.
14. The floating unit assembly (1) according to claim 12 or claim 13, wherein said primary buoy (4) connected to two – six, preferably three, floating units (3), is connected to said respective primary seafloor connection point (8) on said seafloor (2) via one or more primary taut lines (9) such that, for each floating unit (3) and its each respective primary connection lines (5) connected to said primary buoy (4):
- said primary buoy connection point (25) assumes a nominal primary buoy position in a condition when no environmental loads are imparted on said floating unit assembly (10);
- said primary buoy connection point (25) assumes a maximum primary buoy position when said floating unit assembly (1) is in a condition in which said maximum horizontal distance (dmax) is reached between said primary buoy connection point (25) and said floating unit connection point (31) for said respective primary connection line (5), and
- a horizontal distance (Lmax) between said nominal primary buoy position and said maximum primary buoy position is greater than, preferably at least two times greater than, more preferred at least five times greater than, the difference (Δmax) between said maximum horizontal distance (dmax) and said nominal horizontal distance (dnom).
15. The floating unit assembly (1) according to claim 14, wherein said primary buoy (4) connected to two – six, preferably three, floating units (3), is connected to said respective primary seafloor connection point (8) on said seafloor (2) via one or more primary taut lines (9) in such a manner that, for each floating unit (3) and its each respective primary connection lines (5) connected to said primary buoy (4):
- said primary buoy connection point (25) assumes an intermediate primary buoy position when said floating unit assembly (1) is in a condition in which an intermediate horizontal distance (dinter) is reached between said primary buoy connection point (25) and said floating unit connection point (31) for said respective primary connection line (5), said intermediate horizontal distance being the average of said nominal horizontal distance (dnom) and said maximum horizontal distance (dmax), and
- a horizontal distance (Linter) between said intermediate primary buoy position and said maximum primary buoy position is greater than, preferably at least two times greater than, more preferred at least five times greater than, the difference (Δinter) between said maximum horizontal distance (dmax) and said intermediate horizontal distance (dinter).
16. The floating unit assembly (1) according to any one of claims 8 - 15, wherein one respective primary connection line (5) connecting one of said two to six, preferably three to six, more preferred three, floating units (3) to the same primary buoy (4) has a largest nominal horizontal distance (dnom,max) of the respective primary connection lines (5) connecting said floating units (3) to the same primary buoy (4) and wherein one respective primary connection line (5) connecting one of said two to six, preferably three to six, more preferred three, floating units (3) to the same primary buoy (4) has a smallest nominal horizontal distance (dnom,min) of the respective primary connection lines (5) connecting said floating units (3) to the same primary buoy (4), the ratio (dnom,max/ dnom,min) between the largest nominal horizontal distance (dnom,max) and the smallest nominal horizontal distance (dnom,min) being less than 1.1, preferably less than 1.05.
17. The floating unit assembly (1) according to any one of the claims 8 - 16, wherein the respective primary connection lines (5) connected to at least one, preferably each one, of said plurality of primary buoys (4), as seen in a plan view of said floating unit assembly, extend equiangularly from said primary buoy (4) when no environmental loads are imparted on said floating unit assembly (1).
18. The floating unit assembly (1) according to any one of the claims 8 - 17, wherein said floating unit assembly (1) comprises at least a pattern portion being such that a plan view of said pattern portion forms a hexagonal pattern having straight lines and corners, wherein three floating units (3) and three primary buoys (4) are connected to each other by respective primary connection lines (5), forming said straight lines, and are located at the corners of said hexagonal pattern such that a floating unit (3) and a primary buoy (4) are always located at two adjacent corners of said hexagonal pattern.
19. A floating unit assembly (1) according to any one of the preceding claims, wherein at least one of said floating units (3), preferably each one of said floating unit (3), comprises a wind turbine.
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WO2008047011A2 (en) * 2006-10-20 2008-04-24 Nenuphar Network of floaters, especially for anchoring wind turbines and/or underwater generators on deep marine sites
EP2604501A1 (en) * 2011-12-15 2013-06-19 Andreas Graf System of anchoring and mooring of floating wind turbine towers and corresponding methods for towing and erecting thereof
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