Offshore Mooring Systems for Wind Turbines

Extreme sea conditions, particularly extreme operation gusts (EOGs), present a substantial threat to structures like floating offshore wind turbines (FOWTs) due the intense loads they exert. In this work, we simulate EOGs and analyze dynamic response of turbines. We conduct separate analyses operational state under rated speed, state, shutdown EOG, focusing on motion platform tension mooring lines FOWT. The results our study indicate that influence EOGs, FOWT changes significantly, especially in terms range variations. After passage an there are notable differences average each component turbine strategy. When compared normal during strategy enables reach value more rapidly. Subsequently, it also recovers stability quickly. However, operating conditions exhibits larger value. Regarding pitch motion, maximum can 10.52 deg, which may lead overall instability structure. Implementing stall effectively reduce swing amplitude 6.09 deg. Under action reaches 1376.60 kN, yet no failure or fracture occurs system.

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A scalable, low-cost, and environmentally friendly anchoring system for offshore floating wind turbines that uses multiple small helical anchors in close proximity connected by a template. This avoids massive anchoring solutions with high forces and weights. The helical anchors provide uplift, the template provides base stability, and an optional skirt adds lateral support. The modular system is easily manufactured, shippable, and installable compared to large anchors. It reduces costs, acoustic impacts, and transportation complexity for offshore wind farms.

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Moorings are a vital and often problematic component of any floating offshore renewable energy system, whether for wind or wave conversion, here we consider the M4 multi-float converter (WEC) system in 122 configuration. Previous experimental work has shown elastic cables to reduce extreme snap loads by factor about 6 when considering single between bow float mooring buoy (hawser), bed. Here, compare results two alternative configurations designed footprint as well loads. Both systems taut-slack with configuration 1 consisting 2 dual set-up one submerged an attempt further. The experimentally tested irregular (JONSWAP) conditions up limiting steepness, run times 35 minutes at 1:40 scale 3.5 hours full scale. Through statistical analysis it is concluded that both offer similar advantages terms reduction peak loads, display very load motion (hence power) statistics. Configuration displays slightly larger maximum forces yet these occur significantly lower frequencies (near surge natural frequency) reduced response frequencies. This demonstrates subtle changes line can be used affect fre... Read More

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Offshore mooring system that allows rotational motion of the vessel around a buoy while simultaneously transferring energy to or from the vessel. The system has a buoy with vertical and horizontal swivels connected to it. The vertical swivel connects to the vessel, allowing it to rotate around the buoy. The horizontal swivel has a spool that can pay out an electrical conduit to the vessel. This allows transferring power to or from the vessel as it rotates.

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Abstract Floating Offshore Wind (FOW) is the next frontier in clean and renewable wind energy exploitation of particular significance to European economy. To keep FOW competitive against other resources, Levelised Cost Energy (LCoE) should up with projections decade for commercial floating farms be economically viable. One contributors LCoE cost mooring system Turbine (FOWT). This paper presents a field investigation quarter scale Mechanical Compliance Device (MCD) added an inline heavy chain attached test platform. The MCD (i.e. Dublin Offshores Load Reduction aka LRD) aimed at peak load mitigation line FOWT, while allowing geometric compliance during operational conditions. campaign happened Q4 2020 Smart Bay Test Site (SBTS), Ireland. platform survived Hurricane Epsilon Storm Aiden period. tests validated Extension Curve selected MCD, demonstrating its effectiveness mitigating loads. These along prior scaled tank testing show that LRD prime candidate reducing demand high Minimum Breaking line. leads substantial reduction specification, thus, keeping capital as well operating co... Read More

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The objective of this paper is to carry out response analyses eight floating wind turbines and compare them together; something that not seen in previous research papers. From perspective, will the offset regarding motions six degrees freedom respective turbines. applied forces these consider come mainly from constant on turbines blades, as well waves currents. Different values are considered compared different speeds, velocities This also provides various innovative references related turbine software. Validation verification studies left for future work due complexity data provided paper. However, some comparisons made between obtained analysis results external references. mentioned unfortunately have with wave environmental conditions, power capacities, dimensional characteristics. dynamic studied shown maximum surge, sway, heave corresponds DTU Spar 1 turbine. roll yaw INO-WINDMOOR pitch WindFloat aero-hydro-servo-elastic method was used Sima software run analyses. It a time-domain analysis, it uses meters [m] [] describe offsets support structures

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A floating offshore wind power system that reduces yaw motion to improve power generation efficiency. The system uses a triangular floating body with three columns connected by pontoons. The wind turbine is mounted on one column. The mooring lines connecting the floating body to the seabed form a Y shape when viewed from above, reducing yaw motion compared to conventional X-shaped moorings.

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In recent years, the twin-barge float-over method has been widely used in offshore installations. This paper conducts numerical simulation and experimental research on installation of wind turbines (TBFOI-OWTs), focusing primarily seakeeping performance, also explores influence gap distance hydrodynamic behavior TBFOI-OWTs. Model tests are conducted ocean basin at Tsinghua Shenzhen International Graduate School. A physical model with a scale ratio 1:50 is designed fabricated, comprising two barges, truss carriage frame, small turbines, spread catenary mooring system. series tests, including free decay regular wave random carried out to investigate hydrodynamics The results good agreement, thereby validating accuracy method. motion RAOs TBFOI-OWTs small, demonstrating their performance. Compared situation, surge sway motions waves have greater ranges amplitudes. reveals that analysis cannot depend only, more importantly, nature realistic less favorable for responses controlled by motions natural frequencies incident frequency. It revealed between barges significant beam seas. Withi... Read More

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ABSTRACT This study presents an experimental investigation into the influence of anchorsoil interaction on dynamic behaviour tension leg platform (TLP)type floating wind turbines. A 1/100 scale model NREL 5MW reference turbine was fabricated using a 3D printer, with scaling parameters determined based Froude laws to ensure similarity between and prototype. comprehensive discussion applied principles is provided, along detailed description calibration procedures for customdeveloped sixaxis sensors used in experiments. Free vibration tests were performed scaled evaluate different anchoring systemssuction caissons, triplesuction caissons gravity anchorsunder varying seabed conditions. Throughout experiments, installed both nacelle within captured timedependent accelerations x , y z directions, as well rotational responses about same axes. To robustness repeatability results, each test conducted minimum three times, mitigating potential uncertainties. The findings demonstrated pronounced systems conditions dominant surge pitch frequencies model. Specifically, r... Read More

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Abstract. Floating offshore wind turbine (FOWT) systems are subject to complex environmental loads, with significant potential for damage in extreme storm conditions. Design simulations these conditions required assess the survivability of device some level confidence. Aero-hydro-servo-elastic engineering tools can be used a reasonable balance accuracy and computational efficiency. The models require many input parameters describe air water conditions, system properties, load calculations. Each has possible range, due either statistical uncertainty or variations time. Variation have important effects on resulting but it is not practical perform detailed assessments impact this every parameter. This work demonstrates method identify that most loads focus further inspection. process done specifically cases defined International Electrotechnical Commission design requirements floating turbines. analysis was performed using Energy Agency Wind 15 MW reference atop University Maine VolturnUS-S platform two US regions, Gulf Humboldt Bay. It found direction incident waves current, yaw misali... Read More

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Floating platform and installation method for reducing construction and installation costs of offshore platforms by using taut mooring and containing heavy materials in containers placed on the seafloor. The platform has a floating structure to support a tower, connected by tethers to an anchor structure with containers filled with materials like soil or gravel. The containers are fixed to the tethers and placed on the seabed. This allows the platform to be moored by tensioning the tethers to pull the floating structure into the water. The heavy contents of the containers provide the platform weight and stability without needing extensive concrete structures.

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The increasing demand for renewable energy sources has prompted significant interest in exploring offshore wind power. However, most of the studies literature are limited to onshore power generation with a lack long-term data from wide range operational turbines. This research explores design considerations and factors influencing Floating Offshore Wind Turbine (FOWT) by providing valuable insights into key areas that attention, thereby facilitating realization full performance FOWTs. While FOWTs present promising solution harnessing deep waters, challenges need be addressed. These include foundations can withstand harsh marine conditions, development effective strategies fabrication, installation, operation, maintenance decommissioning integration these comprehensive framework. specific guidelines standards further complicates issues. paper aims explore detail propose innovative solutions advance commercialization In this work, numerical simulations modelling techniques employed analyse dynamic response under various environmental conditions. FOWT transportation installation were br... Read More

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A novel towerless floating wind turbine (TFW) is proposed in this study and integrated with three wave energy converters (WECs) by the hinge joint to further increase stability of system. This aims reduce large pitch accelerations for nacelle excessive stresses at tower base when encountering amplitude waves. Based on numerical tests performed viscous corrected panel method, it revealed that in-phase excitation forces acting columns can result largest mooring tension short-period waves high-frequency oscillation appeared under specific conditions attributed triple-frequency components. The motion TFW platform be largely suppressed mitigating adverse effect induced superstructure. Hit abnormal wave, exhibits a significant hysteresis phenomenon maximum response due multi-system coupling effect. Compared traditional DeepCwind platform, survivability extreme sea states greatly improved, considering responses snap loads have been reduced transient stage, durations heave become much shortened decaying stage. enhanced integrating hinged WECs condition larger power-takeoff damping force but ... Read More

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A stability control system for large-scale offshore wind turbines mounted on semi-submersible floating foundations. The system uses sensors to monitor environmental factors like waves, wind, and currents, as well as the motion responses of the wind turbine and floating foundation. It integrates these data into a digital twin model to predict stability during storms. The system proactively adjusts mooring chain tension and ballast water levels before the storm to stabilize the floating foundation and prevent excessive motion. This improves stability compared to passive control methods that only respond during storms.

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Mooring system for shallow water floating wind turbines using tension leg platforms (TLPs) that provides stability and positioning without the need for large columns. The system has a central suction anchor on the seabed below the TLP, surrounded by distributed suction anchors. The TLP columns connect to tension moorings that converge at the central anchor and disperse anchors. This configuration provides stability through tension balance without requiring buoyancy from large columns.

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Shallow water mooring system for floating offshore wind turbines that improves stability in deep waters where fixed foundations are impractical. The mooring system uses tension legs, a balancing device, and a fixed block to prevent tilting and roll from ocean waves. The base has tension legs anchored to the seafloor, a fixed component for the wind turbine, and a balancing device inside. When the turbine tilts, a pressure chamber injects seawater into a receiver to counterbalance and stabilize the base. The fixed block has an indented section to prevent erosion from waves. This allows floating wind turbines to operate in deeper waters without being driven off course by wave action.

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Mooring system for floating offshore wind turbines that provides more even tension on the mooring lines to prevent loosening and damage. The system uses a rotating turret on the wind turbine foundation that transmits centrifugal force to the four mooring lines at the corners when the turbine rotates. This equalizes the tension on all four lines instead of just the one on the stressed side. This prevents loosening and breakage of the mooring lines when the turbine experiences lateral forces.

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A tensioned wind turbine foundation for offshore wind farms that can be anchored to rock seabeds in deep waters. The foundation has a rock anchoring system, a mooring cable, a semi-submersible module, a tower, and a wind turbine. The rock anchoring system attaches to the seabed rock formations. The mooring cable secures the foundation to the seabed. The semi-submersible module floats on the water and supports the tower and turbine. This allows deploying wind turbines in deep water areas without requiring expensive gravity foundations or complex pile driving. The tensioned foundation can be anchored to existing rock formations instead of requiring extensive seabed leveling or drilling. It reduces costs and simplifies construction compared to traditional foundations in challenging offshore environments.

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Group mooring of multiple floating offshore wind turbines together in a designated area at sea. The group mooring uses a mass mooring facility with concrete heavy structures arranged in a grid on the seabed. The turbines are moored to some of the concrete structures using lines. This allows multiple turbines to be moored in a grid pattern without collisions. It provides a centralized location for multiple turbines instead of individual moorings. This saves space compared to stacking turbines on land between productions.

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Tension devices for mooring lines of offshore wind turbines that provide constant tension in the mooring lines as the turbine moves in waves. The devices aim to prevent the turbine from being dragged by varying line tensions in different weather conditions. One device uses a float and weight that are neutrally buoyant when connected. Another device uses a parallelogram linkage with a weight and float that provides a force that increases slowly as the turbine moves. Both devices aim to maintain a constant force in the mooring lines even when the turbine isn't moving.

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