Classifications

• • 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 
  • B63B21/00—Tying-up; Shifting, towing, or pushing equipment; Anchoring
  • B63B21/20—Adaptations of chains, ropes, hawsers, or the like, or of parts thereof
• • 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
  • B63B21/24—Anchors
  • B63B21/26—Anchors securing to bed
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
  • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
  • B63B77/00—Transporting or installing offshore structures on site using buoyancy forces, e.g. using semi-submersible barges, ballasting the structure or transporting of oil-and-gas platforms
  • B63B77/10—Transporting or installing offshore structures on site using buoyancy forces, e.g. using semi-submersible barges, ballasting the structure or transporting of oil-and-gas platforms specially adapted for electric power plants, e.g. wind turbines or tidal turbine generators
• • 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
  • F03D13/256—Arrangements for mounting or supporting wind motors; Masts or towers for wind motors specially adapted for offshore installation on a floating support, i.e. floating wind motors
• • 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
  • B63B21/20—Adaptations of chains, ropes, hawsers, or the like, or of parts thereof
  • B63B2021/203—Mooring cables or ropes, hawsers, or the like; Adaptations thereof
• • 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
  • B63B21/20—Adaptations of chains, ropes, hawsers, or the like, or of parts thereof
  • B63B2021/206—Weights attached to mooring lines or chains, or the like; Arrangements thereof
• • 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
  • B63B2021/505—Methods for installation or mooring of floating offshore platforms on site
• • 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
  • F05B2240/93—Mounting on supporting structures or systems on a structure floating on a liquid surface
• • 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
  • F05B2240/95—Mounting on supporting structures or systems offshore
• • 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
  • Y02E10/72—Wind turbines with rotation axis in wind direction
• • 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

Definitions

• the present invention relates to a floating structure for example for an offshore wind turbine. More precisely, the present invention relates to the subsea mooring of a floating structure on the seabed.
• support structures like jacket structures.
• Such a support structure rests on the seabed and is fixed to the ground with anchor devices.
• the support structure extends above the sea level to receive a wind turbine mast.
• this support structure is made of one piece and the greater the depth is, the higher the support structure must be.
• this solution is expensive.
• RNA rotor nacelle assembly
• the mooring lines are commonly made of steel chain and a length of synthetic material, for example polyester. This type of mooring line requires additional effort at installation when standard procedures are followed.
• the chains have been proved to be very fatigue sensitive in floating offshore wind farm domain due to the high repeatability of large tension cycles induced by the floating structure motions added to the external loads, for example as the wind turbine thrust force, that need to be restored by the mooring system.
• These external loads and constraints get bigger when the size of the floating structure and the wind turbine is getting bigger and its rate is increasing. Consequently, it is observed that mooring chain diameters are continuously increasing with increased wind turbine power, up to the limit of supply chain capacities. These large chain diameters induce a significant cost increase, limit the supply chain and complexify the mooring line installation.
• feedbacks from existing floating structure for example in the oil and gas domain, show that chains are the main contributor (approx. 50%) of mooring line failures.
• polyester have a visco-elasto-plastic behaviour that induces some changes of its stiffness and elongation properties over time depending on previous loadings. These changes can be more or less reversible depending on time where the rope is left with no tension (ie time left to let the recovering process to happen).
• this pre-stretching operation must be done ensuring that tension will be maintained in the rope. Else, the rope will contract and lose the benefits from the pre-stretch operation. Practically, maintaining the tension in the mooring line after pre-stretching operation will be not possible in the floating offshore wind turbine domain as the operation will be performed remotely from the floating structure before hooking up the mooring line to the floating structure.
• One aim of the present invention is to provide an enhanced and cheap mooring system for an offshore wind turbine comprising synthetic mooring lines.
• the invention relates to a mooring system for a floating structure, preferably a floating wind turbine platform, wherein the mooring system comprises at least one mooring line made of a synthetic material and without any chain section, and wherein the mooring line comprises an abrasion resistant section connected to an anchor, said abrasion resistant section being in contact with the seabed permanently or at least intermittently.
• the anchor could be buried under the seabed.
• the anchor could be protruded from the seabed.
• the present invention also concerns a mooring system for a floating structure, preferably a floating wind turbine platform, wherein the mooring system comprises at least one mooring line made of a synthetic material directly connected to an anchor, and wherein the mooring line comprises a protected section connected to an anchor, said protected section being in contact with the seabed permanently or at least intermittently.
• the anchor could be protruding from the seabed.
• the anchor could be buried under the seabed.
• the present invention also concerns an installation method of a floating structure, said method comprising a step of installation of at least one mooring line made of a synthetic material, the length of the synthetic material mooring line being 1 to 4% shorter, at equal tension, than a calculated design length of the synthetic material mooring line suitable for the floating structure at its implantation site.
• the length of the synthetic material mooring line stretches out to the calculated design length of the synthetic material mooring line suitable for the floating structure at its implantation site.
• the quasi-static stiffness of the synthetic material of the mooring line could increase between 10% to 100%.
• the installation step of at least one mooring line made of a synthetic material could comprise:
• the mooring line could comprise at least one buoyant segment or is linked to at least one submerged buoy at least between the first and third steps.
• Figure 1 is a side view of a schematic representation of an offshore wind farm of wind turbines with one mooring line according to a first embodiment in a first variant
• Figure 2 is a side view of a schematic representation of an offshore wind farm of wind turbines with one mooring line according to the first embodiment in a second variant
• Figure 3 is a side view of a schematic representation of the offshore wind farm of wind turbines of figure 2 in a first state
• Figure 4 is a side view of a schematic representation of the offshore wind farm of wind turbines of figure 2 in a second state
• Figure 5 is a side view of a schematic representation of the offshore wind farm of wind turbines with one mooring line according to a second embodiment in a first variant
• Figure 6 is a side view of a schematic representation of the offshore wind farm of wind turbines of figure 5 in a first state
• Figure 7 is a side view of a schematic representation of the offshore wind farm of wind turbines of figure 5 in a second state
• Figure 8 is a side view of a schematic representation of the offshore wind farm of wind turbines with one mooring line according to the second embodiment in a second variant.
• Figure 1 to 8 show a floating structure 3, for example a floating wind turbine platform designed to receive a wind turbine 4 and to float above the sea level SI.
• the floating structure 3 is moored to the seabed Sb by a mooring system 5.
• the mooring system 5 comprises at least one mooring line 51 made of a synthetic material and without any chain section.
• chain section shall be understood as a segment of two or more chains links made of steel.
• the mooring line 51 is made of a synthetic material and have an abrasion resistant section 52 connected to an anchor 53. Said abrasion resistant section 52 being in contact with the seabed permanently or at least intermittently. This abrasion resistant section 52 is connected to an anchor 53 mooring the floating structure 3 to the seabed Sb.
• This abrasion resistant section 52 can be, for example, the last 5% maximum of the length of the mooring line 51.
• the mooring line 51 comprises only a section made of a synthetic material and an abrasion resistant section 52.
• This abrasion resistant section 52 could be for example a metallic cable or a rope section made of High Modulus Polyethylene.
• the anchor 53 is for example buried under the seabed Sb.
• the abrasion resistant section 52 is then in contact with the seabed permanently.
• the abrasion resistant section 52 of the mooring line 51 allows the connection of the mooring line 51 to this buried anchor 53 without the synthetic material being buried into the seabed Sb.
• the synthetic material is sensitive to abrasion and can be deteriorate with the frictions with the sediments and the seabed Sb.
• the anchor 53 is for example protruding from the seabed Sb.
• the abrasion resistant section 52 is then in contact with the seabed intermittently.
• said mooring line 51 can comprise at least one buoyant segment 54 or can be linked to at least one submerged buoy.
• the floating structure 3 can be pushed by the wind or the water currents.
• the mooring line 51 are then tensed on one side and relaxed on the other side.
• the abrasion resistant section 52 can be intermittently in contact with the seabed Sb, as illustrated in figure 4.
• the mooring line 51 is made of a synthetic material directly connected to an anchor 53.
• directly connected to the anchor 53 we mean that, contrary to the first embodiment, the mooring line 51 does not have a n abrasion resistant section 52.
• the anchor 53 is protruding from the seabed Sb..
• the mooring line 51 can comprise at least one protected section 51a to protect the synthetic material from the friction with the sediments and the seabed Sb.
• This protected section 51a is in contact with the seabed permanently or at least intermittently
• This at least one protected 51a section can be any section of the mooring line 51 which is likely to be in contact with the sediments and the seabed Sb or buried in them.
• This at least one section of the mooring line 51 can be coated with a protective layer or be inserted into a sleeve.
• said mooring line 51 can comprise at least one buoyant segment 54 or can be linked to at least one submerged buoy.
• the floating structure 3 can be pushed by the wind or the water currents.
• the mooring line 51 are then tensed on one side and relaxed on the other side. In these conditions, the protected section 51a can be intermittently in contact with the seabed Sb, as illustrated in figure 7.
• the section of the mooring line 51 connected to the anchor 53, and at least partially buried can be a protected section.
• the protected section 51a is then partially buried and permanently in contact with the seabed.
• the synthetic material of the mooring line 51 could be chosen for example between polyester or a polyamide like the nylon.
• the end of the mooring line 51 hooked up to the floating structure 3 could comprise a short metallic section (not represented), made of a metallic cable or a rope section made of High Modulus Polyethylene.
• This mooring line 51 without any chain section is a cheaper mooring line than a mooring line comprising a chain section. Indeed, as the size of the floating structure 3 and the wind turbine 4 increases, the size of the chain links also increases and the costs also increase.
• the installation of the floating structure 3 and an entire offshore wind farm is made easier thanks to the synthetic mooring lines 51 that are lighter and easier to manipulate than chains, thus reducing the requirements in terms of installation vessels capacity. Ships and vessels needed for the installation are them smaller and cheaper.
• the present invention also concerns an installation method of a floating structure 3.
• This, method comprises a step of installation of at least one mooring line 51 made of a synthetic material.
• the length of the synthetic material mooring line 51 is 1 to 4% shorter, at equal tension, than a calculated design length of a synthetic material mooring line suitable for the floating structure 3 at its implantation site.
• the calculated design length corresponds to the mooring line length resulting from a standard mooring design.
• Standard mooring design consists in adjusting the mooring line length and strength to ensure that maximum floater offsets remain within allowable limits (typically inferior to 50% of the water depth in shallow waters, ie below 100m water depth), with maximum mooring line tension typically below 60% of the minimum breaking load under extreme event (typically 50-year return period storm).
• the mooring line 51 is made of a synthetic material and without any chain section.
• the mooring line 51 Due to this shorter length, at installation compared to the calculated design length, the mooring line 51 experiences higher tensions, when connected to the anchor 53 and the floating structure 3. This increase of the tension of the mooring line 51 during the installation allows avoiding an active pre-stretching of the mooring line 51. Then, it is no longer required to use dedicated vessels to perform the pre-stretching operation or to equip the floating structure 3 with high-capacity tensioning means. The installation of the floating structure 3, and consequently the installation of an entire offshore wind farm is cheaper and easier.
• the pre-stretching operation of the mooring line 51 is perform passively during the first weeks or months when the offshore wind turbine is in production and exposed to environmental loads.
• the wind, the swell and yearly storms generate large tensions in the mooring lines 51, stretching the mooring line similarly to an active pre-stretching operation.
• the passive prestretching relies on the environmental loadings (wave, wind, current) to perform this high tensioning of the synthetic line resulting in additional permanent elongation.
• the present invention consists in installing the line with on purpose shorter synthetic mooring line length (1% to 4% as mentioned previously) to anticipate the future elongation of the rope that will happen shortly after the installation due to environmental loading thus reaching the "nominal” or "calculated design” rope length.
• the tension during the installation can be between 12% and 20% of the minimum breaking limit of the mooring line 51.
• the tension of the mooring line 51 will reach the afore mentioned targeted nominal tension.
• the pre-stretching also affects the quasi-static stiffness of the synthetic material of the mooring line 51.
• quasi-static stiffness we mean the stiffness of the mooring line 51 when it is loaded slowly, leaving time for both the amorphous and crystalline parts of the synthetic material to react to the load.
• the resulting fiber stiffness is an average of the stiffness of both amorphous and crystalline parts.
• the length of the synthetic material mooring line 51 (initially 1% to 4% shorter than calculated design length) stretches out to the calculated design length of the synthetic material mooring line suitable for the floating structure 3 at its implantation site.
• the quasi-static stiffness of the synthetic material of the mooring line 51 could increase between 10% to 100%.
• the increase of the quasi-static stiffness could be between 10% and 50%.
• the increase of the quasi-static stiffness could be between 30% and 100%.
• the installation step of the at least one mooring line 51 made of a synthetic material may comprise:
• the mooring lines 51 are generally connected to an anchor 53.
• This anchor 53 could be pre-installed on the seabed Sb or installed during this first step with the mooring line 51 already connected.
• the length of the mooring line can be adjusted so that the synthetic material mooring line 51 is 1 to 4% shorter, at equal tension, than a calculated design length of a synthetic material mooring line suitable for the floating structure 3 at its implantation site.
• the floating structure 3 is towed on site by known means, for example on a barge or towed on site.
• the mooring lines 51 are generally lift and pulled in order to be hooked up to the floating structure 3.
• the mooring lines 51 will experience higher tensions, like described above.
• At least one buoyant segment 54 may be installed on the mooring line 51 in order to avoid any contact of the synthetic material with the sediments and the seabed.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Mechanical Engineering (AREA)
• Combustion & Propulsion (AREA)
• Ocean & Marine Engineering (AREA)
• Sustainable Energy (AREA)
• Sustainable Development (AREA)
• Life Sciences & Earth Sciences (AREA)
• General Engineering & Computer Science (AREA)
• Transportation (AREA)
• Ropes Or Cables (AREA)
• Other Liquid Machine Or Engine Such As Wave Power Use (AREA)
• Wind Motors (AREA)

Applications Claiming Priority (2)

Publications (1)

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ID=84982502

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Family Applications Before (1)

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• 2022
  • 2022-12-28 EP EP22315356.0A patent/EP4393808A1/de active Pending
• 2023
  • 2023-12-15 EP EP23833691.1A patent/EP4642684A1/de active Pending
  • 2023-12-15 JP JP2025533650A patent/JP2026500633A/ja active Pending
  • 2023-12-15 WO PCT/EP2023/086078 patent/WO2024141287A1/en not_active Ceased
  • 2023-12-15 KR KR1020257024765A patent/KR20250130340A/ko active Pending

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