Journal articles: 'Offshore Floating Structures'

1

Konovessis, Dimitris, Kie Hian Chua, and Dracos Vassalos. "Stability of floating offshore structures." Ships and Offshore Structures 9, no. 2 (January 17, 2013): 125–33. http://dx.doi.org/10.1080/17445302.2012.747270.

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Ellinas, Charles P. "Floating Structures and Offshore Operations." Applied Ocean Research 11, no. 2 (April 1989): 112. http://dx.doi.org/10.1016/0141-1187(89)90014-x.

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Eatock Taylor, R. "Floating structures and offshore operations." Engineering Structures 11, no. 4 (October 1989): 290. http://dx.doi.org/10.1016/0141-0296(89)90048-5.

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Wang, Kun, Guo-Kang Er, and Vai Pan Iu. "Seismic analysis of nonlinear offshore moored floating structures." Advances in Structural Engineering 21, no. 9 (December 7, 2017): 1361–75. http://dx.doi.org/10.1177/1369433217744356.

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This article presents a numerical model for solving the nonlinear random vibrations of offshore moored floating structures under seismic excitation. The offshore moored floating structure consists of the floating platform and mooring cables. The floating platform is considered as a rigid body with 3 degrees of freedom. The nonlinear equations of motions of the mooring cables are established using the nonlinear cable elements that are formulated based on the extended Hamilton principle. The nonlinear hydrodynamic drag forces that act on both the floating platform and cables are considered. In order to carry out the random vibrational analysis, the connection conditions between the floating structure and mooring cables are given to formulate the equations of motions of the whole system. Finally, the moored floating structure under horizontal seismic ground accelerations with Kanai–Tajimi model are analyzed using Monte Carlo simulation method. The probability density functions of the displacements of the moored floating structure and the maximum tensile force in cables are presented. The influences of different sag-to-span ratios or inclined angles of the mooring cables on the mean value and standard deviation of the displacements of the floating structure and the maximum tensile force in cables are analyzed.

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Tomasicchio, Giuseppe Roberto, Elvira Armenio, Felice D'Alessandro, Nuno Fonseca, Spyros A. Mavrakos, Valery Penchev, Holger Schuttrumpf, Spyridon Voutsinas, Jens Kirkegaard, and Palle M. Jensen. "DESIGN OF A 3D PHYSICAL AND NUMERICAL EXPERIMENT ON FLOATING OFF-SHORE WIND TURBINES." Coastal Engineering Proceedings 1, no. 33 (December 14, 2012): 67. http://dx.doi.org/10.9753/icce.v33.structures.67.

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The knowledge of the behavior of floating offshore wind turbines (W/T) under wave and/or wind action remains one of the most difficult challenges in offshore engineering which is mostly due to the highly non-linear response of the structure. The present study describes the design process of a 3D physical experiment to investigate the behavior of the most promising structure technology of floating W/T: spar buoy (SB) and tension leg platform (TLP) under different meteo conditions. In order to properly design the two W/T models, the following topics have been analyzed: mooring lines, mass distribution, appropriate scaling factor and data relative to the geometrical characteristics, wave basin dimensions and wind and waves conditions. In addition, the Smoothed Particle Hydrodynamics method (SPH) (Monaghan 1994) has been considered to simulate the 3D behavior of a floating offshore W/T. In particular, the SPH, calibrated and verified on the basis of the experimental observations, may represent a reliable tool for preliminary test of changes in the floater geometry.

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Zhang, Ruo Yu, Chao He Chen, You Gang Tang, and Xiao Yan Huang. "Research Development and Key Technical on Floating Foundation for Offshore Wind Turbines." Advanced Materials Research 446-449 (January 2012): 1014–19. http://dx.doi.org/10.4028/www.scientific.net/amr.446-449.1014.

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The water area in which water depth is deeper than 50m has special advantage in wind turbine generation, because there are the stable wind speed and small Wind-shear. In such sea area, the offshore wind energy generating equipments should be set up on floating foundation structure. Therefore, it is of great significance to study the floating foundation structures that are available for offshore wind energy generation for the industrialization of the offshore wind power generation. In this paper, the basic type and working principles are reviewed for some novel floating structures developed in recent year. In addition, some key dynamical problems and risk factors of the floating structure are systemically analyzed for working load caused by turbine running and sea environment loads of floating structure. The results are valuable for designing the floating structures of wind turbine generation.

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Sclavounos, Paul. "Floating Offshore Wind Turbines." Marine Technology Society Journal 42, no. 2 (June 1, 2008): 39–43. http://dx.doi.org/10.4031/002533208786829151.

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Wind is a rapidly growing renewable energy source, increasing at an annual rate of 30%, with the vast majority of wind power generated from onshore wind farms. The growth of these facilities, however, is limited by the lack of inexpensive land near major population centers and the visual impact caused by large wind turbines.Wind energy generated from floating offshore wind farms is the next frontier. Vast sea areas with stronger and steadier winds are available for wind farm development and 5 MW wind turbine towers located 20 miles from the coastline are invisible. Current offshore wind turbines are supported by monopoles driven into the seafloor or other bottom mounted structures at coastal sites a few miles from shore and in water depths of 10-15 m. The primary impediment to their growth is their prohibitive cost as the water depth increases.This article discusses the technologies and the economics associated with the development of motion resistant floating offshore wind turbines drawing upon a seven-year research effort at MIT. Two families of floater concepts are discussed, inspired by developments in the oil and gas industry for the deep water exploration of hydrocarbon reservoirs. The interaction of the floater response dynamics in severe weather with that of the wind turbine system is addressed and the impact of this coupling on the design of the new generation of multi-megawatt wind turbines for offshore deployment is discussed. The primary economic drivers affecting the development of utility scale floating offshore wind farms are also addressed.

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Pham, Thanh-Dam, Minh-Chau Dinh, Hak-Man Kim, and Thai-Thanh Nguyen. "Simplified Floating Wind Turbine for Real-Time Simulation of Large-Scale Floating Offshore Wind Farms." Energies 14, no. 15 (July 28, 2021): 4571. http://dx.doi.org/10.3390/en14154571.

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Floating offshore wind has received more attention due to its advantage of access to incredible wind resources over deep waters. Modeling of floating offshore wind farms is essential to evaluate their impacts on the electric power system, in which the floating offshore wind turbine should be adequately modeled for real-time simulation studies. This study proposes a simplified floating offshore wind turbine model, which is applicable for the real-time simulation of large-scale floating offshore wind farms. Two types of floating wind turbines are evaluated in this paper: the semi-submersible and spar-buoy floating wind turbines. The effectiveness of the simplified turbine models is shown by a comparison study with the detailed FAST (Fatigue, Aerodynamics, Structures, and Turbulence) floating turbine model. A large-scale floating offshore wind farm including eighty units of simplified turbines is tested in parallel simulation and real-time software (OPAL-RT). The wake effects among turbines and the effect of wind speeds on ocean waves are also taken into account in the modeling of offshore wind farms. Validation results show sufficient accuracy of the simplified models compared to detailed FAST models. The real-time results of offshore wind farms show the feasibility of the proposed turbine models for the real-time model of large-scale offshore wind farms.

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Kim, Mun Sung, Kwang Hyo Jung, and Sung Boo Park. "WAVE INDUCED COUPLED MOTIONS AND STRUCTURAL LOADS BETWEEN TWO OFFSHORE FLOATING STRUCTURES IN WAVES." Brodogradnja 69, no. 3 (July 1, 2018): 149–73. http://dx.doi.org/10.21278/brod69309.

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As oil or gas field moves deeper offshore area, offshore offloading operations such as Tandem or Side-by-Side arrangement between two floating structures take place in many locations throughout the world and also have many hydrodynamic problems. Therefore, the researches on the motion response and hydrodynamic force including first and second order between two floating structures are needed to have the more safe offloading operability in waves. In this paper, prediction of wave induced motion responses and structural loads at mid-ship section with hydrodynamic interaction effect between two offshore floating structures in various heading waves are studied by using a linearized three-dimensional potential theory. Numerical calculations using three-dimensional pulsating source distribution techniques have been carried out for hydrodynamic pressure distribution, wave exciting force, twelve coupled linear motion responses, relative motions and wave loads of the barge and the ship in oblique waves. The computational results give a good correlation with the experimental results and also with other numerical results. As a result, the present computational tool can be used effectively to predict the wave induced motions and structural loads of multiple offshore floating structures in waves.

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Lai, Bin Bin, Cheng Bi Zhao, Xiao Ming Chen, You Hong Tang, and Wei Lin. "A Novel Structural Form of Semi-Submersible Platform for a Floating Offshore Wind Turbine with Hydrodynamic Performance Analysis." Applied Mechanics and Materials 477-478 (December 2013): 109–13. http://dx.doi.org/10.4028/www.scientific.net/amm.477-478.109.

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With the mature of floating offshore wind turbine technology, floating wind farm building in the deep sea becomes an inevitable trend. In the design of floating offshore wind turbine, the change of structural form is the main factor influencing hydrodynamic performance. This research, taking a typical sea condition in China's coastal areas as the object of study, designs a novel semi-submersible foundation for NREL 5 MW offshore wind turbine in 200 m deep water. In the design, deep-draft buoys structures are used to reduce the force of waves on the floating offshore, while damping structures are used to optimize the stability of wind turbine and reduce the heave amplitude. By means of numerical simulation method, the hydrodynamic performance of semi-submersible support is studied. Meanwhile, the response amplitude operators (RAOs) and the wave response motions of platform are calculated. The results in time domain indicate that the floating wind turbine system can keep safe and survive in the harsh sea condition, coupling wind, waves and currents. It is showed that the designed semi-submersible support of platform has excellent hydrodynamic performance. This change of structural form may serve as a reference on the development of offshore wind floating platform.

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Castro-Santos, Laura, Almudena Filgueira-Vizoso, Carlos Álvarez-Feal, and Luis Carral. "Influence of Size on the Economic Feasibility of Floating Offshore Wind Farms." Sustainability 10, no. 12 (November 28, 2018): 4484. http://dx.doi.org/10.3390/su10124484.

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This paper uses a method to analyze the economic influence of the size of floating offshore wind farms. The economic aspects analyzed, LCOE (Levelized Cost Of Energy) and costs, depend on the number of floating offshore wind turbines, which establishes the effect of the size of the farm. This influence has been carried out for a map in a specific location. Regarding the case study, 18 alternatives have been considered taking into account the total power of the farm and the types of floating platforms. These aspects have been studied for the location of Galicia (Spain). Results indicate how LCOE and costs vary when the size of the floating offshore wind farm is increased for the studied kinds of offshore structures. Results are useful for planning an offshore wind farm in deep waters in future investments.

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Maeda, Hisaaki, Celso Kazuyuki Morooka, Akio Kasahara, and Takeshi Kinoshita. "Motions of Floating Offshore Structures in Multi-Directional Waves." Journal of the Society of Naval Architects of Japan 1986, no. 160 (1986): 164–75. http://dx.doi.org/10.2534/jjasnaoe1968.1986.160_164.

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13

Wang, Kun, Guo-Kang Er, and Vai Pan Iu. "Nonlinear vibrations of offshore floating structures moored by cables." Ocean Engineering 156 (May 2018): 479–88. http://dx.doi.org/10.1016/j.oceaneng.2018.03.023.

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14

Kinoshita, T., and S. Takase. "Response Statistics of Moored Offshore Structures." Journal of Offshore Mechanics and Arctic Engineering 117, no. 3 (August 1, 1995): 159–65. http://dx.doi.org/10.1115/1.2827084.

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This paper discusses the prediction of extreme values for total first and second-order responses of a floating structure moored in random seas. It is hard to estimate the extreme values from time series simulation or experimental data of limited length. Several methods of theoretical estimation of the extreme values are examined. They are the SRSS formula introduced by Naess (1987, 1989), the modified SRSS with a correlation parameter, the SRSS with Naess (1987, 1989) corection factor, the approximate SRSS (Naess, 1989), and the formula proposed by authors previously. The results of those methods are compared, and it is confirmed that the last one is very promising.

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15

Bhattacharya, Subhamoy, Suryakanta Biswal, Muhammed Aleem, Sadra Amani, Athul Prabhakaran, Ganga Prakhya, Domenico Lombardi, and Harsh K. Mistry. "Seismic Design of Offshore Wind Turbines: Good, Bad and Unknowns." Energies 14, no. 12 (June 12, 2021): 3496. http://dx.doi.org/10.3390/en14123496.

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Large scale offshore wind farms are relatively new infrastructures and are being deployed in regions prone to earthquakes. Offshore wind farms comprise of both offshore wind turbines (OWTs) and balance of plants (BOP) facilities, such as inter-array and export cables, grid connection etc. An OWT structure can be either grounded systems (rigidly anchored to the seabed) or floating systems (with tension legs or catenary cables). OWTs are dynamically-sensitive structures made of a long slender tower with a top-heavy mass, known as Nacelle, to which a heavy rotating mass (hub and blades) is attached. These structures, apart from the variable environmental wind and wave loads, may also be subjected to earthquake related hazards in seismic zones. The earthquake hazards that can affect offshore wind farm are fault displacement, seismic shaking, subsurface liquefaction, submarine landslides, tsunami effects and a combination thereof. Procedures for seismic designing OWTs are not explicitly mentioned in current codes of practice. The aim of the paper is to discuss the seismic related challenges in the analysis and design of offshore wind farms and wind turbine structures. Different types of grounded and floating systems are considered to evaluate the seismic related effects. However, emphasis is provided on Tension Leg Platform (TLP) type floating wind turbine. Future research needs are also identified.

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Jiang, Changqing, Ould el Moctar, and Thomas E. Schellin. "Hydrodynamic Sensitivity of Moored and Articulated Multibody Offshore Structures in Waves." Journal of Marine Science and Engineering 9, no. 9 (September 18, 2021): 1028. http://dx.doi.org/10.3390/jmse9091028.

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Within the framework of Space@Sea project, an articulated modular floating structure was developed to serve as building blocks for artificial islands. The modularity was one of the key elements, intended to provide the desired flexibility of additional deck space at sea. Consequently, the layout of a modular floating concept may change, depending on its functionality and environmental condition. Employing a potential-flow-based numerical model (i.e., weakly nonlinear Green function solver AQWA), this paper studied the hydrodynamic sensitivity of such multibody structures to the number of modules, to the arrangement of these modules, and to the incident wave angle. Results showed that for most wave frequencies, their hydrodynamic characteristics were similar although the floating platforms consisted of a different number of modules. Only translational horizontal motions, i.e., surge and sway, were sensitive to the incident wave angle. The most critical phenomenon occurred at head seas, where waves traveled perpendicularly to the rotation axes of hinged joints, and the hinge forces were largest. Hydrodynamic characteristics of modules attached behind the forth module hardly changed. The highest mooring line tensions arose at low wave frequencies, and they were caused by second-order mean drift forces. First-order forces acting on the mooring lines were relatively small. Apart from the motion responses and mooring tensions, forces acting on the hinge joints governed the system’s design. The associated results contribute to design of optimal configurations of moored and articulated multibody floating islands.

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Zhang, Zhiyang, Weixing Liu, Xiongbo Zheng, Hengxu Liu, and Ningyu Li. "Numerical simulation of hydrodynamic oscillation of side-by-side double-floating-system with a narrow gap in waves." Open Physics 19, no. 1 (January 1, 2021): 188–207. http://dx.doi.org/10.1515/phys-2021-0021.

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Abstract In offshore oil and gas exploration and transportation, it is often encountered that the multi-floating structures work side by side. In some sea conditions, there is a strong coupling between the multi-floating structures that seriously affects the safety of offshore operations. Therefore, the prediction of the relative motion and force between the multi-floating structures and the wave elevation around the multi-floating-system has become a hot issue. At present, the problem of double-floating-system is mostly based on linear potential flow theory. However, when the gap width between two floating bodies is small, the viscous and nonlinear effects are not negligible, so the potential flow theory has great limitations. Based on the viscous flow theory, using the finite difference solution program of FLOW3D and using volume of fluid technology to capture the free surface, a three-dimensional numerical wave basin is established, and the numerical results of the wave are compared with the theoretical solution. On this basis, the hydrodynamic model of side-by-side double-floating-system with a narrow gap is established, and the flow field in the narrow gap of the fixed double-floating-system under the regular wave is analyzed in detail. The law of the gap-resonance is studied, which provides valuable reference for the future research on the multi-floating-system.

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Maeda, Hisaaki, Koichi Masuda, Shogo Miyajima, and Tomoki Ikoma. "Hydroelasitic Responses of Pontoon Type Very Large Floating Offshore Structures." Journal of the Society of Naval Architects of Japan 1996, no. 180 (1996): 365–71. http://dx.doi.org/10.2534/jjasnaoe1968.1996.180_365.

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19

Takaishi, Yoshifumi. "Recent Development of Regulation Rules Concerning to Floating Offshore Structures." PROCEEDINGS OF CIVIL ENGINEERING IN THE OCEAN 8 (1992): 5–10. http://dx.doi.org/10.2208/prooe.8.5.

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Moghaddam, Behrooz Tafazzoli, Ali Mahboob Hamedany, Jessica Taylor, Ali Mehmanparast, Feargal Brennan, Catrin Mair Davies, and Kamran Nikbin. "Structural integrity assessment of floating offshore wind turbine support structures." Ocean Engineering 208 (July 2020): 107487. http://dx.doi.org/10.1016/j.oceaneng.2020.107487.

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21

Ozguc, Ozgur. "A new risk-based inspection methodology for offshore floating structures." Journal of Marine Engineering & Technology 19, no. 1 (August 10, 2018): 40–55. http://dx.doi.org/10.1080/20464177.2018.1508804.

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HOMMA, Ryuichi. "Thick Steel Plates for Floating Offshore Wind Turbine Welded Structures." JOURNAL OF THE JAPAN WELDING SOCIETY 90, no. 6 (2021): 441–45. http://dx.doi.org/10.2207/jjws.90.441.

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23

Sun, L., G. H. Dong, Y. P. Zhao, and C. F. Liu. "Numerical analysis of the effects on a floating structure induced by ship waves." Journal of Ship Research 55, no. 02 (June 1, 2011): 124–34. http://dx.doi.org/10.5957/jsr.2011.55.2.124.

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Ship-generated waves can make bad effects on offshore structures. A numerical model is presented for evaluating the forces exerted on a nearby floating structure by ship generated waves. The ship waves were modeled using Michell thin-ship theory (Wigley waves), the forces were computed using a boundary element method in the time domain, and the motions of the offshore structures were evaluated using the equation of motion of the floating body, and predicted using the fourth-order Runge-Kutta method. The numerical method was validated by comparing its results to those of frequency-domain methods reported in the literature. It was then applied to calculate the force of ship waves on a floating box. The ship's speed, dimensions, and distance were varied. The numerical results indicate some useful rules for varying these factors.

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Nielsen, Morten E., Martin D. Ulriksen, and Lars Damkilde. "SOFIA - A simulation tool for bottom founded and floating offshore structures." Procedia Engineering 199 (2017): 1308–13. http://dx.doi.org/10.1016/j.proeng.2017.09.326.

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Liu, Haixiao, Zhou Li, and Yuming Zhang. "Offshore Geotechnical Problems in Deepwater Mooring Techniques for Large Floating Structures." American Journal of Engineering and Applied Sciences 11, no. 2 (February 1, 2018): 598–610. http://dx.doi.org/10.3844/ajeassp.2018.598.610.

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SASAKI, Daisuke, Takashi IKEDA, Yuji HARATA, and Yukio ISHIDA. "615 Passive Vibration Control of Offshore Floating Structures Using Multiple Pendula." Proceedings of Conference of Chugoku-Shikoku Branch 2015.53 (2015): _615–1_—_615–2_. http://dx.doi.org/10.1299/jsmecs.2015.53._615-1_.

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Abyn, Hadsan, M. Rafiqul Islam, Adi Maimun, Amin Mahmoudi, and Jaswar Kato. "EXPERIMENTAL STUDY OF MOTIONS OF TWO FLOATING OFFSHORE STRUCTURES IN WAVES." Brodogradnja 67, no. 2 (June 17, 2016): 1–13. http://dx.doi.org/10.21278/brod67201.

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28

Bergan, Pál G., Egil Mollestad, and Nils Sandsmark. "Non‐linear static and dynamic response analysis for floating offshore structures." Engineering Computations 2, no. 1 (January 1985): 13–20. http://dx.doi.org/10.1108/eb023596.

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Leimeister, M., A. Kolios, and M. Collu. "Critical review of floating support structures for offshore wind farm deployment." Journal of Physics: Conference Series 1104 (October 2018): 012007. http://dx.doi.org/10.1088/1742-6596/1104/1/012007.

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Bobillier, Bertrand, Subrata Chakrabarti, and Poul Christiansen. "Physical Modeling of Wind Load on a Floating Offshore Structure." Journal of Offshore Mechanics and Arctic Engineering 123, no. 4 (July 2, 2001): 170–76. http://dx.doi.org/10.1115/1.1410102.

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Wind is an important environmental parameter that influences the design of floating offshore structures, particularly in harsh environment. Because wind spectrum is broad-banded, computation of wind load on the floating structure is complicated. Moreover, the wind-induced slow-drift oscillation is an important design criterion. Simulated environment in a model test often includes wind effect. Accurate modeling of wind in a laboratory environment is, however, a difficult task. The wind tunnel provides a steady load on the superstructure quite accurately, but fails to show the effect of the changing free surface as well as dynamic effect. Therefore, simultaneous simulation of wind in the wave basin is desirable. A weight representing the steady wind load with a string and pulley arrangement at the center of the application of the superstructure is inadequate since it fails to simulate the variation of the wind spectrum. The generation and control of the design wind spectrum by an overhead bank of fans facing the model superstructure is an extremely difficult task due to large windage area. This paper presents an accurate and highly controllable method of the generation of variable wind simultaneously with waves and current in the wave basin that can be used with a variety of floating structure model. The concept was originally proposed by Kvaerner Oil & Gas International and implemented by the offshore model basin (OMB). In this method, a fan equipped with a constant-speed motor and blades with an adjustable pitch angle is directly mounted on the model deck above water. A digital signal generated from the specified wind spectrum is used to run the fan much like the wavemaker. A feedback system ensures the proper generation of the wind with the model motion. The method was successfully applied in several model tests of deepwater floating structures in which broad-banded wind spectra were generated. An example from an earlier such test is given here. The importance of the effect of the simulated wind spectrum on floating structures should be clear to a design engineer from this example.

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Magkouris, Alexandros, Kostas Belibassakis, and Eugen Rusu. "Hydrodynamic Analysis of Twin-Hull Structures Supporting Floating PV Systems in Offshore and Coastal Regions." Energies 14, no. 18 (September 20, 2021): 5979. http://dx.doi.org/10.3390/en14185979.

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In this paper, a novel model based on the boundary element method (BEM) is presented for the hydrodynamic analysis of floating twin-hull structures carrying photovoltaic panels, supporting the study of wave responses and their effects on power performance in variable bathymetry regions. The analysis is restricted to two spatial dimensions for simplicity. The method is free of any mild-slope assumptions. A boundary integral representation is applied for the near field in the vicinity of the floating body, which involved simple (Rankine) sources, while the far field is modeled using complete (normal-mode) series expansions that are derived using separation of variables in the constant depth half-strips on either side of the middle, non-uniform domain, where the depth exhibited a general variation, overcoming a mild bottom-slope assumption. The numerical solution is obtained by means of a low-order panel method. Numerical results are presented concerning twin-hull floating bodies of simple geometry lying over uniform and sloping seabeds. With the aid of systematic comparisons, the effects of the bottom slope and curvature on the hydrodynamic characteristics (hydrodynamic coefficients and responses) of the floating bodies are illustrated and discussed. Finally, the effects of waves on the floating PV performance are presented, indicating significant variations of the performance index ranging from 0 to 15% depending on the sea state.

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Manzano-Agugliaro, Francisco, Miguel Sánchez-Calero, Alfredo Alcayde, Carlos San-Antonio-Gómez, Alberto-Jesús Perea-Moreno, and Esther Salmeron-Manzano. "Wind Turbines Offshore Foundations and Connections to Grid." Inventions 5, no. 1 (January 28, 2020): 8. http://dx.doi.org/10.3390/inventions5010008.

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Most offshore wind farms built thus far are based on waters below 30 m deep, either using big diameter steel monopiles or a gravity base. Now, offshore windfarms are starting to be installed in deeper waters and the use of these structures—used for oil and gas like jackets and tripods—is becoming more competitive. Setting aside these calls for direct or fixed foundations, and thinking of water depths beyond 50 m, there is a completely new line of investigation focused on the usage of floating structures; TLP (tension leg platform), Spar (large deep craft cylindrical floating caisson), and semisubmersible are the most studied. We analyze these in detail at the end of this document. Nevertheless, it is foreseen that we must still wait sometime before these solutions, based on floating structures, can become truth from a commercial point of view, due to the higher cost, rather than direct or fixed foundations. In addition, it is more likely that some technical modifications in the wind turbines will have to be implemented to improve their function. Regarding wind farm connections to grid, it can be found from traditional designs such as radial, star or ring. On the other hand, for wind generator modeling, classifications can be established, modeling the wind turbine and modeling the wind farm. Finally, for the wind generator control, the main strategies are: passive stall, active stall, and pitch control; and when it is based on wind generation zone: fixed speed and variable speed. Lastly, the trend is to use strategies based on synchronous machines, as the permanent magnet synchronous generator (PMSG) and the wound rotor synchronous generator (WRSG).

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Keys, Matt. "Offshore structures – why all offshore facilities should have a demanning requirement." APPEA Journal 59, no. 2 (2019): 789. http://dx.doi.org/10.1071/aj18109.

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Most offshore structure design codes focus on setting appropriate safety factors to achieve an acceptable annual level of risk. Recent work by Atkins SNC-Lavalin, together with a large number of operators in Australian waters and the North Sea, has discovered that a large number of aging assets are implementing a demanning requirement to limit the risk of platform collapse to personnel, due to changes in loading or degradation of the structure. This work has shown there are two risk scenarios that should drive this requirement. The first scenario which is intended by the codes in limiting the overall annual risk. The second is to limit the collapse risk associated with a known forecast storm, as the level of risk from helicopter demanning is much lower. For all the older offshore fixed and permanently mooring floating structures assessed for a risk level considered acceptable for a forecast storm, this risk level would govern the sea-state demanning criteria. For recently installed facilities that are compliant with current standards, the findings were the same: that all facilities should have a demanning requirement. The level of this demanning sea-state limit has been shown to be lower than expected and is likely to occur only once in the asset’s life; therefore, the cost implications of implementing demanning procedures are minor. This paper presents the basis and range of findings for calculating the risks associated with an annual occurrence and an ‘in a forecast storm’ risk. Further, this paper proposes acceptable demanning limits for facilities designed to current and historical design codes.

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Zhang, Quan, Cheng Bi Zhao, Xiao Ming Chen, You Hong Tang, and Wei Lin. "Tendon Response of 10 MW Offshore Wind Turbine TLP Platform in Extreme Environment Condition." Applied Mechanics and Materials 477-478 (December 2013): 119–22. http://dx.doi.org/10.4028/www.scientific.net/amm.477-478.119.

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Deep-sea offshore wind resources are extremely abundant. Large offshore wind turbine is the future trend to utilize of deep-sea offshore wind resources. Because of excellent heaving, pitching and rolling performances, tension-leg platform ( TLP ) is one of best floating support structures for large wind turbine. However, under extreme environment condition, the large tendons which are required for large offshore wind turbine TLP platform will meet extreme response, even lead to damage. Extreme response of tendon of a 10 MW offshore wind turbine TLP platform ( an improved MOSES TLP ) in the extreme environment condition is studied here. It is showed that the global motions can meet the basic requirements for 10 MW floating wind turbine, where the maximum angle of TLP is less than 100. Meanwhile, the maximum tendon tension of the TLP in the simulation is less than the breaking force, which meets the requirements of API rules on tendon of TLP.

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Zhou, Xiao, Liu, Incecik, Peyrard, Li, and Pan. "Numerical Modelling of Dynamic Responses of a Floating Offshore Wind Turbine Subject to Focused Waves." Energies 12, no. 18 (September 9, 2019): 3482. http://dx.doi.org/10.3390/en12183482.

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In this paper, we present numerical modelling for the investigation of dynamic responses of a floating offshore wind turbine subject to focused waves. The modelling was carried out using a Computational Fluid Dynamics (CFD) tool. We started with the generation of a focused wave in a numerical wave tank based on a first-order irregular wave theory, then validated the developed numerical method for wave-structure interaction via a study of floating production storage and offloading (FPSO) to focused wave. Subsequently, we investigated the wave-/wind-structure interaction of a fixed semi-submersible platform, a floating semi-submersible platform and a parked National Renewable Energy Laboratory (NREL) 5 MW floating offshore wind turbine. To understand the nonlinear effect, which usually occurs under severe sea states, we carried out a systematic study of the motion responses, hydrodynamic and mooring tension loads of floating offshore wind turbine (FOWT) over a range of wave steepness, and compared the results obtained from two potential flow theory tools with each other, i.e., Électricité de France (EDF) in-house code and NREL Fatigue, Aerodynamics, Structures, and Turbulence (FAST). We found that the nonlinearity of the hydrodynamic loading and motion responses increase with wave steepness, revealed by higher-order frequency response, leading to the appearance of discrepancies among different tools.

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Baita-Saavedra, Eugenio, David Cordal-Iglesias, Almudena Filgueira-Vizoso, Àlex Morató, Isabel Lamas-Galdo, Carlos Álvarez-Feal, Luis Carral, and Laura Castro-Santos. "An Economic Analysis of An Innovative Floating Offshore Wind Platform Built with Concrete: The SATH® Platform." Applied Sciences 10, no. 11 (May 26, 2020): 3678. http://dx.doi.org/10.3390/app10113678.

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The goal of this work is to carry out an economic analysis of a novel floating offshore wind structure, of which the main material is concrete: the SATH® platform. It takes a step forward in floating marine wind energy research, in which traditional platforms are mainly composed of steel. The technique to calculate the costs of the platform and the economic parameters to decide if the farm is economically feasible are explained in the paper. This case study analyzes a possible farm of 500 MW located in Portugal and several scenarios considering different electric tariffs and capital costs (Scenario 1: electric tariff of 50 €/MWh and 6% of capital cost; Scenario 2: electric tariff of 50 €/MWh and 8% of capital cost; Scenario 3: electric tariff of 150 €/MWh and 6% of capital cost; Scenario 4: electric tariff of 150 €/MWh and 8% of capital cost). Results show the economic feasibility of a farm with the characteristics of Scenarios 3 and 4. This work is significant in order to provide a new approach to analyzing traditional floating offshore wind structures, which can represent a path towards the future of floating offshore renewable energy technologies.

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Garrison, C. J. "A Numerically Efficient Method for Analysis of Very Large Articulated Floating Structures." Journal of Ship Research 42, no. 03 (September 1, 1998): 174–86. http://dx.doi.org/10.5957/jsr.1998.42.3.174.

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A method is presented for evaluation of the motion of long structures composed of interconnected barges, or modules, of arbitrary shape. Such structures are being proposed in the construction of offshore airports or other large offshore floating structures. It is known that the evaluation of the motion of jointed or otherwise interconnected modules which make up a long floating structure may be evaluated by three dimensional radiation/diffraction analysis. However, the computing effort increases rapidly as the complexity of the geometric shape of the individual modules and the total number of modules increases. This paper describes an approximate method which drastically reduces the computational effort without major effects on accuracy. The method relies on accounting for hydrodynamic interaction effects between only adjacent modules within the structure rather than between all of the modules since the near-field interaction is by far the more important. This approximation reduces the computational effort to that of solving the two-module problem regardless of the total number of modules in the complete structure.

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Takezawa, Seiji, and Kentaro Kobayashi. "On the Motion Responses of Offshore Floating Structures in Directional Spectra Waves." Journal of the Society of Naval Architects of Japan 1989, no. 165 (1989): 141–52. http://dx.doi.org/10.2534/jjasnaoe1968.1989.141.

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Takezawa, Seiji, and Kentaro Kobayashi. "On the Motion Responses of Offshore Floating Structures in Directional Spectra Waves." Journal of the Society of Naval Architects of Japan 1989, no. 166 (1989): 139–50. http://dx.doi.org/10.2534/jjasnaoe1968.1989.166_139.

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Crudu, Liviu, Oana Marcu, and Diana Donose. "A comparative evaluation of the behaviour of some typical floating offshore structures." Analele Universităţii "Dunărea de Jos" din Galaţi. Fascicula XI, Construcţii navale/ Annals of "Dunărea de Jos" of Galati, Fascicle XI, Shipbuilding 42 (November 26, 2019): 97–102. http://dx.doi.org/10.35219/annugalshipbuilding.2019.42.13.

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Peccin Da Silva, Anderson, Andrea Diambra, and Dimitris Karamitros. "Macro-element modelling of suction-embedded plate anchors for floating offshore structures." E3S Web of Conferences 92 (2019): 16009. http://dx.doi.org/10.1051/e3sconf/20199216009.

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This work presents a new macro-element model to predict the behaviour of Suction Embedded Plate Anchors (SEPLAs) for floating offshore structures during keying and loading stages. Differently from previously published models for anchors, this new model is characterised by (i) a non-associated plastic potential with the aim of improving the prediction of anchor trajectory for the whole displacement domain and for a large range of padeye offsets; and (ii) by a strain-hardening rule enabling to predict the force and displacement mobilisation from the early stages of the keying process. The model was calibrated against LDFE analyses and compared with a broad set of LDFE and centrifuge tests results. The model proves capable of reproducing anchor rotation and displacement with good accuracy for a wide range of padeye offsets and distinct studies from the literature.

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Naess, A., O. Gaidai, and P. S. Teigen. "Extreme response prediction for nonlinear floating offshore structures by Monte Carlo simulation." Applied Ocean Research 29, no. 4 (November 2007): 221–30. http://dx.doi.org/10.1016/j.apor.2007.12.001.

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Salas, Marcos, Cristian Cifuentes, Richard Luco, Astrid Santander, Gonzalo Tampier, Claudio Troncoso, and Federico Zilic. "Naval and Oceanic Engineering: more than Ships and Offshore." Ciencia y tecnología de buques 11, no. 22 (March 20, 2018): 9. http://dx.doi.org/10.25043/19098642.159.

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Traditionally, Naval and Oceanic Engineering has been focused on research in surface and submarine ships; and fixed and floating offshore structures. More than 90% of world trade is transported by sea, so it is not surprising that most research efforts have been focused on making merchant ships more efficient and safer. Something similar is happening in the offshore industry driven by the demand for energy. Despite the evident need to perform research in the traditional fields of Naval and Oceanic Engineering, new challenges have caused universities and research centers to tackle new fields of research. This paper presents some of the research and innovations developed at the Institute of Naval and Maritime Sciences (ICNM) of the Austral University of Chile (UACH). These new frontiers for research address problems as diverse as the capturing of energy from waves and currents [1], the development of structures and systems for aquaculture [2], the design of autonomous underwater vehicles [3], the use of solar energy for the propulsion of small boats [4] and the design of floating ports for remote areas [5].

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Ibrahim, R. A., N. G. Chalhoub, and Jeffery Falzarano. "Interaction of Ships and Ocean Structures With Ice Loads and Stochastic Ocean Waves." Applied Mechanics Reviews 60, no. 5 (September 1, 2007): 246–89. http://dx.doi.org/10.1115/1.2777172.

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The influence of floating ice on the dynamic behavior of ships and offshore structures depends on many factors such as ice thickness and its relative speed with respect to the floating structure. The ice resistance to ship motion forms an essential problem in ship design and navigation. Furthermore, local or global ice loads acting on ocean systems are random and nonsmooth when impact interaction takes place. Impact loads on the bow of a ship navigating in solid ice may be modeled by a Poisson law. The measured stress amplitudes on the ship frame at the bow follow an exponential distribution. The nonhomogeneity and difference in ice microstructure, as well as the influence of salt and temperature, result in a great uncertainty in the ice strength. Therefore, the current review article aims at assessing the ice related problems encountered by offshore structures as well as by ships during their navigation. It also discusses the impacts of local and global ice loads on floating structures and reviews their existing probabilistic models. Moreover, this article covers the dynamic interaction of ice with flexible and rigid structures, and ships. In view of ice loads on marine systems, new design regulations have been introduced by international organizations that are involved in the design and building of ships as well as offshore structures. The ship stochastic stability and the first-passage roll stabilization problem associated with random ocean waves will also be described in an attempt to stimulate future research work dealing with ice impact loads. Moreover, due to the lack of research activities addressing the control problem of ships operating in icy waters, the current article will briefly discuss passive and active control schemes developed for controlling the ship roll motion. There are 529 references cited in this review article.

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Roddier, Dominique, and Joshua Weinstein. "Floating Wind Turbines." Mechanical Engineering 132, no. 04 (April 1, 2010): 28–32. http://dx.doi.org/10.1115/1.2010-apr-2.

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This article discusses the functioning of floating wind turbines. The engineering requirements for the design of floating offshore wind turbines are extensive. Wind turbine design tools usually consist of an aerodynamic model (for flow around the blades) coupled with a structural code. Aero-elastic models used in the design of fixed turbines calculate all the necessary loading parameters, from turbine thrust and power generation, to blade and tower deflections. The design of floating structures usually involves hydrodynamics tools such as WAMIT Inc.’s software for studying wave interactions with vessels and platforms, or Principia’s DIODORE, to predict the hydrodynamic quantities, such as added mass, damping and wave exciting forces, which are used as a kernel in the time domain simulations. In marine projects, design tools typically need to be validated against model tests in a wave tank or basin. Such work is performed frequently, and scaling laws are very well defined.

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Che, Xiling, Dayun Wang, Minglun Wang, and Yingfan Xu. "Two-Dimensional Hydroelastic Analysis of Very Large Floating Structures." Marine Technology and SNAME News 29, no. 01 (January 1, 1992): 13–24. http://dx.doi.org/10.5957/mt1.1992.29.1.13.

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We have reached a stage at which we are capable of building very large floating structures to meet the steadily increasing needs of ocean resource utilization or to fulfill some special industrial or civil purpose. When such a structure is large enough, its behavior in waves may be substantially different from that of ordinary offshore structures due to low resonant frequencies of the deformable body, and its analysis may require different techniques. In this paper, a two-dimensional hydroelastic theory is applied to a very large floating structure that may be multimodule and extend in the longitudinal direction. A revised strip theory is employed to analyze the hydrodynamic coefficients, but some modifications are introduced to allow for multibody cross sections. The structure is considered to be a flexible beam responding to waves in the vertical direction. Numerical examples are presented with reference to an integrated system of semisubmersibles. A simple model for engineering estimation is also presented.

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Yuen, M. M. F., and F. P. Chau. "A Hybrid Integral Equation Method for Wave Forces on Three-Dimensional Offshore Structures." Journal of Offshore Mechanics and Arctic Engineering 109, no. 3 (August 1, 1987): 229–36. http://dx.doi.org/10.1115/1.3257014.

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Wave forces on arbitrary-shaped three-dimensional offshore structures are analyzed by the proposed hybrid integral equation method. Eigenfunction expansion is used to represent velocity potential in the outer domain, while a set of integral equations is developed for the inner domain encompassing the structure. A floating dock and a step cylinder are used as test cases showing the validity of the method.

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Koike, T., T. Hiramoto, and H. Mori. "Seismic Risk Analysis of Mega-Floating Structure and Dolphin System." Journal of Offshore Mechanics and Arctic Engineering 121, no. 2 (May 1, 1999): 95–101. http://dx.doi.org/10.1115/1.2830084.

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The floating type structural system is applicable to large offshore structures including airports, power plants, and multi-purpose facilities. Such a large-scale floating structure should be in service at least 100 yr because of the large capital investments and social utilization, so it also should be designed to be safe and stable against several natural hazards and accidents during its service life. In this report, seismic response and risk analyses of a mega-floating structure supported with many dolphins (MFSD) are carried out to study the mutual interaction and its instability of the floating-dolphin system against earthquake attack. The final goal is to obtain the optimal allocation of dolphins to minimize the displacement of an MFSD.

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Salic, Tom, Jean Frédéric Charpentier, Mohamed Benbouzid, and Marc Le Boulluec. "Control Strategies for Floating Offshore Wind Turbine: Challenges and Trends." Electronics 8, no. 10 (October 18, 2019): 1185. http://dx.doi.org/10.3390/electronics8101185.

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The offshore wind resource has huge energy potential. However, wind turbine floating structures have to withstand harsh conditions. Strong wind and wave effects combine to generate vibrations, fatigue, and heavy loads on the structure and other elements of the wind turbine. These structural problems increase maintenance requirements and risk of failure, while reducing availability and energy production. Another challenge for wind energy is to reduce production costs in order to be competitive with other alternatives. From the control point of view, the objective of lowering costs can be achieved by operating the turbine close to its optimum point of operation under partial load, guaranteeing reliability by reducing structural loads and regulating the power generated in strong wind regimes. In this typical and challenging context, this paper proposes a critical state-of-the-art review, discussing challenges and trends on floating offshore wind turbines control.

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Kuzmin, Yu L., and O. A. Stavitsky. "Electrochemical protection against corrosion for steel bars in reinforced concrete structures exposed to seawater." Voprosy Materialovedeniya, no. 4(96) (January 8, 2019): 185–90. http://dx.doi.org/10.22349/1994-6716-2018-96-4-185-190.

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The paper analyzes ways to ensure long service life (up to 50 years) of reinforced concrete marine structures. It has been established that durability and maintenance-free operation of floating and coastal offshore structures for 50 and more years depend on corrosion of steel reinforcement which could be avoided by applying electrochemical protection. The parameters of electrochemical protection against corrosion of steel fittings are given.

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Journal articles on the topic 'Offshore Floating Structures'

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