WorldWideScience

Sample records for floating offshore structure

  1. Some aspects of arctic offshore floating structures

    Energy Technology Data Exchange (ETDEWEB)

    Lubbad, Raed Khalil

    2011-01-15

    The present work highlights some aspects related to the analyses of Arctic offshore floating structures. This thesis consists of five papers, which can be divided into two main categories. One category deals with the dynamics of slender structures with an emphasis on the prediction and suppression of vortex induced vibrations (VIV), and the other category examines the process of interaction between sloping structures and sea ice with focus on developing a numerical model to simulate this process in real time. Slender structures, such as mooring lines and marine risers, are very important for the offshore petroleum industry, which is currently approaching deeper waters. Increasingly, attention has been focused on predicting the susceptibility of these structures to VIV. In this thesis, two asymptotic techniques namely, the local analysis and the WKB methods, were used to derive closed-form solutions for the natural frequencies and mode shapes of slender line-like structures. Both the top-tensioned nearly-vertical configuration and the catenary configuration were considered. The accuracy of the solutions derived was established through comparison with other analytic solution techniques and with results of numerical finite element solutions. The effects of the bending stiffness and the effects of approximating the tension variation as a linear function were discussed. Experimental data on the multi-modal in-line and cross-flow response behaviour of a towed catenary model were analysed to examine the usefulness of the solutions for predicting the response frequencies and envelopes due to VIV. Helical strakes are often used as a mitigating measure to suppress the VIV of slender structures. This thesis presented an innovative method to fit ropes helically to a riser in the installation phase. Such a procedure will help to overcome the handling problem associated with the use of conventional sharp-edged strakes. Experimental investigations were then performed to verify

  2. Experimental study on moonpool resonance of offshore floating structure

    Directory of Open Access Journals (Sweden)

    Seung-Ho Yang

    2013-06-01

    Full Text Available Offshore floating structures have so-called moonpool in the centre area for the purpose of drilling, installation of subsea structures, recovery of Remotely-Operated Vehicle (ROV and divers. However, this vertical opening has an effect on the operating performance of floating offshore structure in the vicinity of moonpool resonance frequency; piston mode and sloshing mode. Experimental study based on model test was carried out. Moonpool resonance of floating offshore structure on fixed condition and motion free condition were investigated. And, the effect of cofferdam which is representative inner structure inside moonpool was examined. Model test results showed that Molin's theoretical formula can predict moonpool resonance on fixed condition quite accurately. However, motion free condition has higher resonance frequency when it is compared with that of motion fixed. The installation of cofferdam moves resonance frequency to higher region and also generates secondary resonance at lower frequency. Furthermore, it was found that cofferdam was the cause of generating waves in the longitudinal direction when the vessel was in beam sea.

  3. Applicability of WaveWatch-III wave model to fatigue assessment of offshore floating structures

    NARCIS (Netherlands)

    Zou, T.; Kaminski, M.L.

    2016-01-01

    In design and operation of floating offshore structures, one has to avoid fatigue failures caused by action of ocean waves. The aim of this paper is to investigate the applicability of WaveWatch-III wave model to fatigue assessment of offshore floating structures. The applicability was investigated

  4. Floating offshore turbines

    DEFF Research Database (Denmark)

    Tande, John Olav Giæver; Merz, Karl; Schmidt Paulsen, Uwe

    2014-01-01

    metric of energy production per unit steel mass. Floating offshore wind turbines represent a promising technology. The successful operation of HyWind and WindFloat in full scale demonstrates a well advanced technology readiness level, where further development will go into refining the concepts, cost...

  5. Offshore floating windmills

    International Nuclear Information System (INIS)

    1993-10-01

    The aim was to produce a general survey of the profitability of establishing floating offshore wind turbine arrays and to compare this with the cost and profitability of constructing offshore arrays with fixed foundations and arrays located on land sites. Aspects of design in all cases are described, also into relation to the special demands placed on dimensioning in relation to the types of location and foundation. The costs of the offshore arrays are evaluated in relation to capacity under conditions in Danish waters. The advantage of floating arrays is that they can be placed far out to sea where they can not be seen from the coast and thus not be considered to spoil the marine view. But as the water gets deeper the cost of floating foundations rises. It was found that it would not be technologically profitable to establish floating arrays at a depth of less than 30 - 40 meters which means that only the outer Danish waters can be taken into consideration. For depths of up to 70 meters, individual floating bases are more expensive than fixed ones but would be cheaper if a number of windmills could share the same anchor. For depths of more than 70 meters floating foundations would be the cheapest. The cost is dependent on the depth and distance from the coast and also on wind conditions. The main conclusion is that currently the cost of establishing wind turbine arrays in deeper outer waters on floating foundations is comparable to that of arrays sited at inner waters on solid foundations placed on the sea bed. (AB) (20 refs.)

  6. Fluid-structure interaction simulation of floating structures interacting with complex, large-scale ocean waves and atmospheric turbulence with application to floating offshore wind turbines

    Science.gov (United States)

    Calderer, Antoni; Guo, Xin; Shen, Lian; Sotiropoulos, Fotis

    2018-02-01

    We develop a numerical method for simulating coupled interactions of complex floating structures with large-scale ocean waves and atmospheric turbulence. We employ an efficient large-scale model to develop offshore wind and wave environmental conditions, which are then incorporated into a high resolution two-phase flow solver with fluid-structure interaction (FSI). The large-scale wind-wave interaction model is based on a two-fluid dynamically-coupled approach that employs a high-order spectral method for simulating the water motion and a viscous solver with undulatory boundaries for the air motion. The two-phase flow FSI solver is based on the level set method and is capable of simulating the coupled dynamic interaction of arbitrarily complex bodies with airflow and waves. The large-scale wave field solver is coupled with the near-field FSI solver with a one-way coupling approach by feeding into the latter waves via a pressure-forcing method combined with the level set method. We validate the model for both simple wave trains and three-dimensional directional waves and compare the results with experimental and theoretical solutions. Finally, we demonstrate the capabilities of the new computational framework by carrying out large-eddy simulation of a floating offshore wind turbine interacting with realistic ocean wind and waves.

  7. Floating wind generators offshore wind farm: Implications for structural loads and control actions

    International Nuclear Information System (INIS)

    Garcia, E.; Morant F, Quiles E.; Correcher, A.

    2009-01-01

    This paper describes the work currently carried out in the design of floating wind generators and their involvement in the future development of power generation in marine farms in depths exceeding 20 m. We discuss the main issues to be taken into account in the design of floating platforms, including the involvement of structural loads they bear. Also from a standpoint of control engineering are discussed strategies to reduce structural loads such a system to ensure adequate durability and therefore ensuring their economic viability. Finally, the abstract modeling tools for floating wind turbines that can be used in both structural design and the design of appropriate control algorithms

  8. SOFIA - A simulation tool for bottom founded and floating offshore structures

    DEFF Research Database (Denmark)

    Nielsen, Morten Eggert; Ulriksen, Martin Dalgaard; Damkilde, Lars

    2017-01-01

    This paper presents a recently developed simulation tool, SOFIA (Simulation Of Floaters In Action), suitable for modeling slender bottom founded and moored/freely floating space frame structures exposed to environmental loads. In contrast to traditional rigid body formulations of floating...... and structure domains, which are coupled through the structural equation of motion. The structural domain is handled by means of the finite element method, while large displacements and stress stiffening effects, exhibited by moored floating structures, are inherently included due to a co-rotational element...... formulation. The fluid domain is modeled by an appropriate water wave theory, and the hydrodynamic loads are evaluated at the instantaneous fluid-structure interface by means of a relative Morison equation. The equation of motion is solved in time domain, which makes SOFIA capable of handling bottom founded...

  9. Sensitivity analysis of floating offshore wind farms

    International Nuclear Information System (INIS)

    Castro-Santos, Laura; Diaz-Casas, Vicente

    2015-01-01

    Highlights: • Develop a sensitivity analysis of a floating offshore wind farm. • Influence on the life-cycle costs involved in a floating offshore wind farm. • Influence on IRR, NPV, pay-back period, LCOE and cost of power. • Important variables: distance, wind resource, electric tariff, etc. • It helps to investors to take decisions in the future. - Abstract: The future of offshore wind energy will be in deep waters. In this context, the main objective of the present paper is to develop a sensitivity analysis of a floating offshore wind farm. It will show how much the output variables can vary when the input variables are changing. For this purpose two different scenarios will be taken into account: the life-cycle costs involved in a floating offshore wind farm (cost of conception and definition, cost of design and development, cost of manufacturing, cost of installation, cost of exploitation and cost of dismantling) and the most important economic indexes in terms of economic feasibility of a floating offshore wind farm (internal rate of return, net present value, discounted pay-back period, levelized cost of energy and cost of power). Results indicate that the most important variables in economic terms are the number of wind turbines and the distance from farm to shore in the costs’ scenario, and the wind scale parameter and the electric tariff for the economic indexes. This study will help investors to take into account these variables in the development of floating offshore wind farms in the future

  10. A novel floating offshore wind turbine concept

    DEFF Research Database (Denmark)

    Vita, Luca; Schmidt Paulsen, Uwe; Friis Pedersen, Troels

    2009-01-01

    This paper will present a novel concept of a floating offshore wind turbine. The new concept is intended for vertical-axis wind turbine technology. The main purpose is to increase simplicity and to reduce total costs of an installed offshore wind farm. The concept is intended for deep water...... and large size turbines....

  11. Large floating structures technological advances

    CERN Document Server

    Wang, BT

    2015-01-01

    This book surveys key projects that have seen the construction of large floating structures or have attained detailed conceptual designs. This compilation of key floating structures in a single volume captures the innovative features that mark the technological advances made in this field of engineering, and will provide a useful reference for ideas, analysis, design, and construction of these unique and emerging urban projects to offshore and marine engineers, urban planners, architects and students.

  12. Floating Foundations for Offshore Wind Turbines

    DEFF Research Database (Denmark)

    Andersen, Morten Thøtt

    The concept of harnessing the power of the wind dates all the way back to the first ships traversing the seas. Later, windmills enabled the use of wind power for industrial purposes. Since then, technology has allowed the production of clean renewable energy through the use of wind turbines....... These turbines have traditionally been placed on land, but several factors have urged a move to offshore locations. Now the boundaries are being pushed into deeper and deeper waters, where the idea of floating offshore wind turbines has emerged. In less than a decade, these have gone from scattered small...

  13. Aeroelastic impact of above-rated wave-induced structural motions on the near-wake stability of a floating offshore wind turbine rotor

    Science.gov (United States)

    Rodriguez, Steven; Jaworski, Justin

    2017-11-01

    The impact of above-rated wave-induced motions on the stability of floating offshore wind turbine near-wakes is studied numerically. The rotor near-wake is generated using a lifting-line free vortex wake method, which is strongly coupled to a finite element solver for kinematically nonlinear blade deformations. A synthetic time series of relatively high-amplitude/high-frequency representative of above-rated conditions of the NREL 5MW referece wind turbine is imposed on the rotor structure. To evaluate the impact of these above-rated conditions, a linear stability analysis is first performed on the near wake generated by a fixed-tower wind turbine configuration at above-rated inflow conditions. The platform motion is then introduced via synthetic time series, and a stability analysis is performed on the wake generated by the floating offshore wind turbine at the same above-rated inflow conditions. The stability trends (disturbance modes versus the divergence rate of vortex structures) of the two analyses are compared to identify the impact that above-rated wave-induced structural motions have on the stability of the floating offshore wind turbine wake.

  14. Offshore concrete structures

    International Nuclear Information System (INIS)

    Lamas Pardo, M.; Carral Couce, L. M.

    2011-01-01

    In the offshore industry there are two possible materials for the construction of the hull of a structure; the steel and concrete, with the first one widely used until now, as in the rest of the shiphuidling industry of merchant ships, warships, etc. Materials such as aluminum, GRP or timber areused in small units with lengths lower than 100 m, and in less adverse conditions than in the offshore industry. Nevertheless, some ships/barges have been built of concrete in the past, but have been rather isolated cases which have not changed the practice in the industry. In the First and Second World War were built by the scarcity of materials, while the series of barges by Alfred A. Yee was a rare exception. Other units were also made in concrete, but almost anecdotal. Still, the behaviour of these concrete structures, especially in terms of maintenance, has been excellent. Therefore, the fact that the concrete has not had an adequate reception so far in shipbuilding, does not mean that in will not be the material best suited for the offshore industry in the future. The extra displacement and associated fuel costs in concrete ships have been found prohibitive in the past. But the loss of mobility of a concrete hull in relation to a steel hull can be perfectly offset by the advantages offered by the concrete, as the shipping and offshore industry have very different priorities. One of the main differences in these priorities is in terms of maintenance and resistance to fatigue, precisely where the concrete performs better. ships can easily be dry docked for maintenance and repair, while in the offshore platforms these works have to be done in situ so maintenance and fatigue are crucial to them. Besides these, the concrete has other advantages according to findings of several studies. And although they are interested in the conclusions that the makes as they came from people in the concrete industry, the fact that in recent years concrete offshore unit shave been built

  15. A Floating Offshore Wind Turbine in Extreme Wave Conditions

    DEFF Research Database (Denmark)

    Wehmeyer, Christof

    is an expected maximum wave in accordance with a Rayleigh distribution. The maximum waves are numerically represented by embedded Stream-function waves. The author compares the resulting bow tendon loading of the hybrid model to the measured responses, as a key performance indicator. 90% to 95% of the loads show...... a satisfying match, though the hybrid model over predicts the remaining 5% to 10% maximum loads by 32%, 34% and 29% for a linear irregular sea state, a nonlinear irregular sea state and a nonlinear irregular sea state with an embedded Stream-function wave, respectively. The limited number of sea states during...... important aspects, which make them non-conservative in use for FOWT: (A) The offshore wind industry intends to install floating structures at much lower water depth (from 50m onwards), than the offshore oil & gas industry (from 300m onwards). In such cases a linear wave theory approach might...

  16. Frequency-domain characteristics of aerodynamic loads of offshore floating vertical axis wind turbines

    DEFF Research Database (Denmark)

    Borg, Michael; Collu, M.

    2015-01-01

    The re-emerging interest in vertical axis wind turbines for floating offshore applications has led to a need to investigate the relatively complex dynamics of such floating offshore structures. Through the use of a coupled model of dynamics this article investigates the frequency......-domain characteristics of floating vertical axis wind turbine aerodynamic loads. The impact of platform induced motion on aerodynamic loads is discussed in detail, with results indicating an increase in aerodynamic loads of several orders of magnitude over the range of frequencies usually containing significant wave...

  17. Assessing Fatigue and Ultimate Load Uncertainty in Floating Offshore Wind Turbines Due to Varying Simulation Length

    Energy Technology Data Exchange (ETDEWEB)

    Stewart, G.; Lackner, M.; Haid, L.; Matha, D.; Jonkman, J.; Robertson, A.

    2013-07-01

    With the push towards siting wind turbines farther offshore due to higher wind quality and less visibility, floating offshore wind turbines, which can be located in deep water, are becoming an economically attractive option. The International Electrotechnical Commission's (IEC) 61400-3 design standard covers fixed-bottom offshore wind turbines, but there are a number of new research questions that need to be answered to modify these standards so that they are applicable to floating wind turbines. One issue is the appropriate simulation length needed for floating turbines. This paper will discuss the results from a study assessing the impact of simulation length on the ultimate and fatigue loads of the structure, and will address uncertainties associated with changing the simulation length for the analyzed floating platform. Recommendations of required simulation length based on load uncertainty will be made and compared to current simulation length requirements.

  18. Floating Offshore Wind in Hawaii: Potential for Jobs and Economic Impacts from Three Future Scenarios

    Energy Technology Data Exchange (ETDEWEB)

    Jimenez, Tony; Keyser, David; Tegen, Suzanne

    2016-04-18

    Construction of the first offshore wind power plant in the United States began in 2015, off the coast of Rhode Island, using fixed platform structures that are appropriate for shallow seafloors, like those located off the East Coast and mid-Atlantic. However, floating platforms, which have yet to be deployed commercially, will likely need to be anchored to the deeper seafloor if deployed in Hawaiian waters. To analyze the employment and economic potential for floating offshore wind off Hawaii's coasts, the Bureau of Ocean Energy Management commissioned the National Renewable Energy Laboratory (NREL) to analyze two hypothetical deployment scenarios for Hawaii: 400 MW of offshore wind by 2050 and 800 MW of offshore wind by 2050. The results of this analysis can be used to better understand the general scale of economic opportunities that could result from offshore wind development.

  19. Experimental study on the estimation method of hydrodynamic force acting on floating offshore structures; Futaishiki kaiyo kozobutsu ni kuwawaru ryutairyoku no suiteiho ni kansuru jikkenteki kenkyu

    Energy Technology Data Exchange (ETDEWEB)

    Hoshino, K; Kato, S [Ship Research Inst., Tokyo (Japan); Koterayama, W [Kyushu Univ., Fukuoka (Japan). Research Inst. for Applied Mechanics

    1996-04-10

    In the design of various floating offshore structures (FOS), the functionality, safety and amenity of FOSs were examined by estimating responses of FOSs to environmental external forces such as wave, wind and flow. In this paper, the estimation method of drag acting on the whole FOS was established by combining previous study results on hydrodynamic force acting on various bodies such as Reynolds number effect (RNE), 3-D effect (TDE) and interference effect (IE). This hydrodynamic force was also compared with that obtained from the experiment result on a FOS model for TLP to confirm the applicability of this estimation method. The estimation result on the drag coefficient in steady flow by considering RNE, TDE and IE well agreed with experimental one. The drag coefficient acting on FOSs in heaving could be estimated in practically sufficient accuracy by considering drag acting on not columns but only square columns. The estimation result on the drag coefficient acting on FOSs in surging by considering RNE, TDE and IE well agreed with experimental one. 12 refs., 10 figs., 1 tab.

  20. Unique ecological impacts associated with offshore floating nuclear power plants

    International Nuclear Information System (INIS)

    Adams, S.M.; McLean, R.B.

    1979-01-01

    The ecological impacts that could occur as a result of site construction and operation of an offshore floating nuclear power plant are identified by comparing the principal ecological features associated with offshore siting with those associated with the siting of onshore estuarine plants. In general, the ecological impacts of offshore nuclear plants should be relatively smaller than those of estuarine plants. Possible factors that could increase the relative impacts of offshore plants are high frequency of contact with schools of fish, siting near inlets to estuaries or other ecologically important areas, and the persistence of halogen residuals. Identifying the potential ecological impacts associated with the siting of offshore plants permits the development of various monitoring programs and measures to minimize these impacts

  1. Floating offshore wind turbines for shallow waters

    NARCIS (Netherlands)

    Bulder, B.H.; Henderson, A.; Huijsmans, R.H.M.; Peeringa, J.M.; Pierik, J.T.G.; Snijders, E.J.B.; Hees, M.Th. van; Wijnants, G.H.; Wolf, M.J.

    2003-01-01

    Bottom mounted Offshore wind turbines seem to have a promising future but they are restricted to shallow waters of Northern Europe. Many projects are planned or are in the phase of construction on the North Sea and the Baltic Sea. All projects that are planned have a water depth up to approximately

  2. Life cycle assessment of a floating offshore wind turbine

    Energy Technology Data Exchange (ETDEWEB)

    Weinzettel, Jan [Department of Electrotechnology, Faculty of Electrical Engineering, Czech Technical University in Prague, Technicka 2, Praha 166 27 (Czech Republic); Charles University in Prague Environment Center, U Krize 8, Prague 158 00 (Czech Republic); Reenaas, Marte; Solli, Christian [Industrial Ecology Programme, Norwegian University of Science and Technology (NTNU), 7491 Trondheim (Norway); Hertwich, Edgar G. [Industrial Ecology Programme, Norwegian University of Science and Technology (NTNU), 7491 Trondheim (Norway); Department of Energy and Process Engineering, Norwegian University of Science and Technology (NTNU), 7491 Trondheim (Norway)

    2009-03-15

    A development in wind energy technology towards higher nominal power of the wind turbines is related to the shift of the turbines to better wind conditions. After the shift from onshore to offshore areas, there has been an effort to move further from the sea coast to the deep water areas, which requires floating windmills. Such a concept brings additional environmental impact through higher material demand. To evaluate additional environmental burdens and to find out whether they can be rebalanced or even offset by better wind conditions, a prospective life cycle assessment (LCA) study of one floating concept has been performed and the results are presented in this paper. A comparison with existing LCA studies of conventional offshore wind power and electricity from a natural gas combined cycle is presented. The results indicate similar environmental impacts of electricity production using floating wind power plants as using non-floating offshore wind power plants. The most important stage in the life cycle of the wind power plants is the production of materials. Credits that are connected to recycling these materials at the end-of-life of the power plant are substantial. (author)

  3. Floating Offshore Wind in Oregon: Potential for Jobs and Economic Impacts from Two Future Scenarios

    Energy Technology Data Exchange (ETDEWEB)

    Jimenez, Tony [National Renewable Energy Lab. (NREL), Golden, CO (United States); Keyser, David [National Renewable Energy Lab. (NREL), Golden, CO (United States); Tegen, Suzanne [National Renewable Energy Lab. (NREL), Golden, CO (United States); Speer, Bethany [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2016-05-01

    Construction of the first offshore wind power plant in the United States began in 2015, off the coast of Rhode Island, using fixed platform structures that are appropriate for shallow seafloors, like those located off of the East Coast and mid-Atlantic. However, floating platforms, which have yet to be deployed commercially, will likely need to anchor to the deeper seafloor if deployed off of the West Coast. To analyze the employment and economic potential for floating offshore wind along the West Coast, the Bureau of Ocean Energy Management (BOEM) commissioned the National Renewable Energy Laboratory (NREL) to analyze two hypothetical, large-scale deployment scenarios for Oregon: 5,500 megawatts (MW) of offshore wind deployment in Oregon by 2050 (Scenario A), and 2,900 MW of offshore wind by 2050 (Scenario B). These levels of deployment could power approximately 1,600,000 homes (Scenario A) or 870,000 homes (Scenario B). Offshore wind would contribute to economic development in Oregon in the near future, and more substantially in the long term, especially if equipment and labor are sourced from within the state. According to the analysis, over the 2020-2050 period, Oregon floating offshore wind facilities could support 65,000-97,000 job-years and add $6.8 billion-$9.9 billion to the state GDP (Scenario A).

  4. Motion performance and mooring system of a floating offshore wind turbine

    Science.gov (United States)

    Zhao, Jing; Zhang, Liang; Wu, Haitao

    2012-09-01

    The development of offshore wind farms was originally carried out in shallow water areas with fixed (seabed mounted) structures. However, countries with limited shallow water areas require innovative floating platforms to deploy wind turbines offshore in order to harness wind energy to generate electricity in deep seas. The performances of motion and mooring system dynamics are vital to designing a cost effective and durable floating platform. This paper describes a numerical model to simulate dynamic behavior of a new semi-submersible type floating offshore wind turbine (FOWT) system. The wind turbine was modeled as a wind block with a certain thrust coefficient, and the hydrodynamics and mooring system dynamics of the platform were calculated by SESAM software. The effect of change in environmental conditions on the dynamic response of the system under wave and wind loading was examined. The results indicate that the semi-submersible concept has excellent performance and SESAM could be an effective tool for floating wind turbine design and analysis.

  5. Motion Performance and Mooring System of a Floating Offshore Wind Turbine

    Institute of Scientific and Technical Information of China (English)

    Jing Zhao; Liang Zhang; Haitao Wu

    2012-01-01

    The development of offshore wind farms was originally carried out in shallow water areas with fixed (seabed mounted) structures.However,countries with limited shallow water areas require innovative floating platforms to deploy wind turbines offshore in order to harness wind energy to generate electricity in deep seas.The performances of motion and mooring system dynamics are vital to designing a cost effective and durable floating platform.This paper describes a numerical model to simulate dynamic behavior of a new semi-submersible type floating offshore wind turbine (FOWT) system.The wind turbine was modeled as a wind block with a certain thrust coefficient,and the hydrodynamics and mooring system dynamics of the platform were calculated by SESAM software.The effect of change in environmental conditions on the dynamic response of the system under wave and wind loading was examined.The results indicate that the semi-submersible concept has excellent performance and SESAM could be an effective tool for floating wind turbine design and analysis.

  6. Floating Offshore Wind in California: Gross Potential for Jobs and Economic Impacts from Two Future Scenarios

    Energy Technology Data Exchange (ETDEWEB)

    Speer, Bethany [National Renewable Energy Lab. (NREL), Golden, CO (United States); Keyser, David [National Renewable Energy Lab. (NREL), Golden, CO (United States); Tegen, Suzanne [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2016-04-18

    Construction of the first offshore wind farm in the United States began in 2015, using fixed platform structures that are appropriate for shallow seafloors, like those located off of the East Coast and mid-Atlantic. However, floating platforms, which have yet to be deployed commercially, will likely need to anchor to the deeper seafloor if deployed off of the West Coast. To analyze the employment and economic potential for floating offshore wind along the West Coast, the Bureau of Ocean Energy Management (BOEM) has commissioned the National Renewable Energy Laboratory (NREL) to analyze two hypothetical, large-scale deployment scenarios for California: 16 GW of offshore wind by 2050 (Scenario A) and 10 GW of offshore wind by 2050 (Scenario B). The results of this analysis can be used to better understand the general scales of economic opportunities that could result from offshore wind development. Results show total state gross domestic product (GDP) impacts of $16.2 billion in Scenario B or $39.7 billion in Scenario A for construction; and $3.5 billion in Scenario B or $7.9 billion in Scenario A for the operations phases.

  7. The effects of second-order hydrodynamics on a semisubmersible floating offshore wind turbine

    International Nuclear Information System (INIS)

    Bayati, I; Jonkman, J; Robertson, A; Platt, A

    2014-01-01

    The objective of this paper is to assess the second-order hydrodynamic effects on a semisubmersible floating offshore wind turbine. Second-order hydrodynamics induce loads and motions at the sum- and difference-frequencies of the incident waves. These effects have often been ignored in offshore wind analysis, under the assumption that they are significantly smaller than first-order effects. The sum- and difference-frequency loads can, however, excite eigenfrequencies of a floating system, leading to large oscillations that strain the mooring system or vibrations that cause fatigue damage to the structure. Observations of supposed second-order responses in wave-tank tests performed by the DeepCwind consortium at the Maritime Research Institute Netherlands (MARIN) offshore basin suggest that these effects might be more important than originally expected. These observations inspired interest in investigating how second-order excitation affects floating offshore wind turbines and whether second-order hydrodynamics should be included in offshore wind simulation tools like FAST. In this work, the effects of second-order hydrodynamics on a floating semisubmersible offshore wind turbine are investigated. Because FAST is currently unable to account for second-order effects, a method to assess these effects was applied in which linearized properties of the floating wind system derived from FAST (including the 6x6 mass and stiffness matrices) are used by WAMIT to solve the first- and second-order hydrodynamics problems in the frequency domain. The method was applied to the Offshore Code Comparison Collaboration Continuation OC4-DeepCwind semisubmersible platform, supporting the National Renewable Energy Laboratory's 5-MW baseline wind turbine. In this paper, the loads and response of the system caused by the second-order hydrodynamics are analysed and compared to the first-order hydrodynamic loads and induced motions in the frequency domain. Further, the second

  8. Wake Influence on Dynamic Load Characteristics of Offshore Floating Wind Turbines

    DEFF Research Database (Denmark)

    Jeon, Minu; Lee, Soogab; Kim, Taeseong

    2016-01-01

    Because the flow conditions of an offshore floating wind turbine and onshore fixed wind turbine differ, it is debatable whether the aerodynamic load predictions of an offshore floating wind turbine using the conventional blade-element momentum theory, which does not consider the dynamic wake effe...

  9. Offshore concrete structures; Estructuras Offshore (mar adentro) de Hormigon

    Energy Technology Data Exchange (ETDEWEB)

    Lamas Pardo, M.; Carral Couce, L. M.

    2011-07-01

    In the offshore industry there are two possible materials for the construction of the hull of a structure; the steel and concrete, with the first one widely used until now, as in the rest of the shipbuilding industry of merchant ships, warships, etc. Materials such as aluminum, GRP or timber areused in small units with lengths lower than 100 m, and in less adverse conditions than in the offshore industry. Nevertheless, some ships/barges have been built of concrete in the past, but have been rather isolated cases which have not changed the practice in the industry. In the First and Second World War were built by the scarcity of materials, while the series of barges by Alfred A. Yee was a rare exception. Other units were also made in concrete, but almost anecdotal. Still, the behaviour of these concrete structures, especially in terms of maintenance, has been excellent. Therefore, the fact that the concrete has not had an adequate reception so far in shipbuilding, does not mean that in will not be the material best suited for the offshore industry in the future. The extra displacement and associated fuel costs in concrete ships have been found prohibitive in the past. But the loss of mobility of a concrete hull in relation to a steel hull can be perfectly offset by the advantages offered by the concrete, as the shipping and offshore industry have very different priorities. One of the main differences in these priorities is in terms of maintenance and resistance to fatigue, precisely where the concrete performs better. ships can easily be dry docked for maintenance and repair, while in the offshore platforms these works have to be done in situ so maintenance and fatigue are crucial to them. Besides these, the concrete has other advantages according to findings of several studies. And although they are interested in the conclusions that the makes as they came from people in the concrete industry, the fact that in recent years concrete offshore unit shave been built

  10. Dynamic Analysis of Mooring Cables with Application to Floating Offshore Wind Turbines

    OpenAIRE

    Petrone, C.; Oliveto, N. D.; Sivaselvan, M. V.

    2015-01-01

    Floating offshore wind turbines are recently being considered widely for adoption in the wind power industry, attracting interest of several researchers and calling for the development of appropriate computational models and techniques. In the present work, a nonlinear finite-element formulation is proposed and applied to the static and dynamic analysis of mooring cables. Numerical examples are presented, and in particular, a mooring cable typically used for floating offshore wind turbines is...

  11. The International Standards Organisation offshore structures standard

    International Nuclear Information System (INIS)

    Snell, R.O.

    1994-01-01

    The International Standards Organisation has initiated a program to develop a suite of ISO Codes and Standards for the Oil Industry. The Offshore Structures Standard is one of seven topics being addressed. The scope of the standard will encompass fixed steel and concrete structures, floating structures, Arctic structures and the site specific assessment of mobile drilling and accommodation units. The standard will use as base documents the existing recommended practices and standards most frequently used for each type of structure, and will develop them to incorporate best published and recognized practice and knowledge where it provides a significant improvement on the base document. Work on the Code has commenced under the direction of an internationally constituted sub-committee comprising representatives from most of the countries with a substantial offshore oil and gas industry. This paper outlines the background to the code and the format, content and work program

  12. Influence of Model Simplifications Excitation Force in Surge for a Floating Foundation for Offshore Wind Turbines

    DEFF Research Database (Denmark)

    Andersen, Morten Thøtt; Hindhede, Dennis; Lauridsen, Jimmy

    2015-01-01

    As offshore wind turbines move towards deeper and more distant sites, the concept of floating foundations is a potential technically and economically attractive alternative to the traditional fixed foundations. Unlike the well-studied monopile, the geometry of a floating foundation is complex and...

  13. Wake losses optimization of offshore wind farms with moveable floating wind turbines

    NARCIS (Netherlands)

    S.F. Rodrigues; R. Teixeira Pinto (Rodrigo); M. Soleimanzadeh (Maryam); P.A.N. Bosman (Peter); P. Bauer (Pavol)

    2015-01-01

    htmlabstractIn the future, floating wind turbines could be used to harvest energy in deep offshore areas where higher wind mean speeds are observed. Currently, several floating turbine concepts are being designed and tested in small scale projects; in particular, one concept allows the turbine to

  14. Methodology to Calculate the Costs of a Floating Offshore Renewable Energy Farm

    Directory of Open Access Journals (Sweden)

    Laura Castro-Santos

    2016-04-01

    Full Text Available This paper establishes a general methodology to calculate the life-cycle cost of floating offshore renewable energy devices, applying it to wave energy and wind energy devices. It is accounts for the contributions of the six main phases of their life-cycle: concept definition, design and development, manufacturing, installation, exploitation and dismantling, the costs of which have been defined. Moreover, the energy produced is also taken into account to calculate the Levelized Cost of Energy of a floating offshore renewable energy farm. The methodology proposed has been applied to two renewable energy devices: a floating offshore wave energy device and a floating offshore wind energy device. Two locations have been considered: Aguçadoura and São Pedro de Moel, both in Portugal. Results indicate that the most important cost in terms of the life-cycle of a floating offshore renewable energy farm is the exploitation cost, followed by the manufacturing and the installation cost. In addition, the best area in terms of costs is the same independently of the type of floating offshore renewable energy considered: Aguçadoura. However, the results in terms of Levelized Cost of Energy are different: Aguçadoura is better when considering wave energy technology and the São Pedro de Moel region is the best option when considering floating wind energy technology. The method proposed aims to give a direct approach to calculate the main life-cycle cost of a floating offshore renewable energy farm. It helps to assess its feasibility and evaluating the relevant characteristics that influence it the most.

  15. Efficient preliminary floating offshore wind turbine design and testing methodologies and application to a concrete spar design

    OpenAIRE

    Matha, Denis; Sandner, Frank; Molins i Borrell, Climent; Campos Hortigüela, Alexis; Cheng, Po Wen

    2015-01-01

    The current key challenge in the floating offshore wind turbine industry and research is on designing economic floating systems that can compete with fixed-bottom offshore turbines in terms of levelized cost of energy. The preliminary platform design, as well as early experimental design assessments, are critical elements in the overall design process. In this contribution, a brief review of current floating offshore wind turbine platform pre-design and scaled testing methodologies is provide...

  16. A comparison between the dynamics of horizontal and vertical axis offshore floating wind turbines.

    Science.gov (United States)

    Borg, M; Collu, M

    2015-02-28

    The need to further exploit offshore wind resources in deeper waters has led to a re-emerging interest in vertical axis wind turbines (VAWTs) for floating foundation applications. However, there has been little effort to systematically compare VAWTs to the more conventional horizontal axis wind turbine (HAWT). This article initiates this comparison based on prime principles, focusing on the turbine aerodynamic forces and their impact on the floating wind turbine static and dynamic responses. VAWTs generate substantially different aerodynamic forces on the support structure, in particular, a potentially lower inclining moment and a substantially higher torque than HAWTs. Considering the static stability requirements, the advantages of a lower inclining moment, a lower wind turbine mass and a lower centre of gravity are illustrated, all of which are exploitable to have a less costly support structure. Floating VAWTs experience increased motion in the frequency range surrounding the turbine [number of blades]×[rotational speed] frequency. For very large VAWTs with slower rotational speeds, this frequency range may significantly overlap with the range of wave excitation forces. Quantitative considerations are undertaken comparing the reference NREL 5 MW HAWT with the NOVA 5 MW VAWT. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  17. Fundamental study on aerodynamic force of floating offshore wind turbine with cyclic pitch mechanism

    International Nuclear Information System (INIS)

    Li, Qing'an; Kamada, Yasunari; Maeda, Takao; Murata, Junsuke; Iida, Kohei; Okumura, Yuta

    2016-01-01

    Wind turbines mounted on floating platforms are subjected to completely different and soft foundation properties, rather than onshore wind turbines. Due to the flexibility of their mooring systems, floating offshore wind turbines are susceptible to large oscillations such as aerodynamic force of the wind and hydrodynamic force of the wave, which may compromise their performance and structural stability. This paper focuses on the evaluation of aerodynamic forces depending on suppressing undesired turbine's motion by a rotor thrust control which is controlled by pitch changes with wind tunnel experiments. In this research, the aerodynamic forces of wind turbine are tested at two kinds of pitch control system: steady pitch control and cyclic pitch control. The rotational speed of rotor is controlled by a variable speed generator, which can be measured by the power coefficient. Moment and force acts on model wind turbine are examined by a six-component balance. From cyclic pitch testing, the direction and magnitude of moment can be arbitrarily controlled by cyclic pitch control. Moreover, the fluctuations of thrust coefficient can be controlled by collective pitch control. The results of this analysis will help resolve the fundamental design of suppressing undesired turbine's motion by cyclic pitch control. - Highlights: • Offshore wind offers additional options in regions with low onshore potential. • Two kinds of pitch control system: Steady pitch control and Cyclic pitch control. • Performance curves and unsteady aerodynamics are investigated in wind tunnel. • Fluctuations of thrust coefficient can be controlled by collective pitch control.

  18. A Comparison on the Dynamics of a Floating Vertical Axis Wind Turbine on Three Different Floating Support Structures

    OpenAIRE

    Borg, Michael; Collu, Maurizio

    2014-01-01

    To increase the competitiveness of offshore wind energy in the global energy market, it is necessary to identify optimal offshore wind turbine configurations to deliver the lowest cost of energy. For deep waters where floating wind turbines are the feasible support structure option, the vertical axis wind turbine concept might prove to be one of these optimal configurations. This paper carries out a preliminary investigation into the dynamics of a vertical axis wind turbine coupled with three...

  19. Existing methodologies in the design and analysis of offshore floating nuclear power plants

    International Nuclear Information System (INIS)

    Thangam Babu, P.V.; Reddy, D.V.

    1977-01-01

    The paper presents a comprehensive state-of-the-art on the design and analysis of Floating Nuclear Power Plants (FNPs). The recent accelerated growth of the offshore oil industry has considerably increased the confidence in the offshore FNP concept, in view of the vast potential for the transposition of available technology. The main advantages of FNPs are: (1) unlimited supply of the cooling water, (2) isolation of thermal, noise and radioactive pollution, (3) elimination of the need for large areas of unoccupied lands usually required for safety precaution, and (4) financial savings by using standardised design and production line approach. The topics covered in this paper are: Offshore Concept Evaluations; Siting Considerations; Design Considerations; Analysis; and Miscellaneous Considerations. (Fatigue and crack propagation, Model Studies and experimental investigation, Seismic instrumentation, Noise and vibration level considerations, Safety). A detailed bibliography is presented to indicate the immediate need for further research in the areas of dynamic analysis using improved mathematical modelling techniques incorporating water-structure interaction, and nonlinear effects of the supporting medium and the mooring system; safety analysis of FNPs to accident

  20. Effect of Second-Order Hydrodynamics on a Floating Offshore Wind Turbine

    Energy Technology Data Exchange (ETDEWEB)

    Roald, L.; Jonkman, J.; Robertson, A.

    2014-05-01

    The design of offshore floating wind turbines uses design codes that can simulate the entire coupled system behavior. At the present, most codes include only first-order hydrodynamics, which induce forces and motions varying with the same frequency as the incident waves. Effects due to second- and higher-order hydrodynamics are often ignored in the offshore industry, because the forces induced typically are smaller than the first-order forces. In this report, first- and second-order hydrodynamic analysis used in the offshore oil and gas industry is applied to two different wind turbine concepts--a spar and a tension leg platform.

  1. Grid Simulator for Testing a Wind Turbine on Offshore Floating Platform

    Energy Technology Data Exchange (ETDEWEB)

    Gevorgian, V.

    2012-02-01

    An important aspect of such offshore testing of a wind turbine floating platform is electrical loading of the wind turbine generator. An option of interconnecting the floating wind turbine with the onshore grid via submarine power cable is limited by many factors such as costs and associated environmental aspects (i.e., an expensive and lengthy sea floor study is needed for cable routing, burial, etc). It appears to be a more cost effective solution to implement a standalone grid simulator on a floating platform itself for electrical loading of the test wind turbine. Such a grid simulator must create a stable fault-resilient voltage and frequency bus (a micro grid) for continuous operation of the test wind turbine. In this report, several electrical topologies for an offshore grid simulator were analyzed and modeled.

  2. Investigation of the effects of platform motion on the aerodynamics of a floating offshore wind turbine

    Institute of Scientific and Technical Information of China (English)

    万德成

    2016-01-01

    Along with the flourishing of the wind energy industry, floating offshore wind turbines have aroused much interest among the academia as well as enterprises. In this paper, the effects of the supporting platform motion on the aerodynamics of a floating wind turbine are studied using the open source CFD framework OpenFOAM. The platform motion responses, including surge, heave and pitch, are superimposed onto the rotation of the wind turbine. Thrust and torque on the wind turbine are compared and analysed for the cases of different platform motion patterns together with the flow field. It is shown that the movement of the supporting platform can have large influences on a floating offshore wind turbine and thus needs to be considered carefully during the design process.

  3. Offshore Code Comparison Collaboration within IEA Wind Task 23: Phase IV Results Regarding Floating Wind Turbine Modeling; Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Jonkman, J.; Larsen, T.; Hansen, A.; Nygaard, T.; Maus, K.; Karimirad, M.; Gao, Z.; Moan, T.; Fylling, I.

    2010-04-01

    Offshore wind turbines are designed and analyzed using comprehensive simulation codes that account for the coupled dynamics of the wind inflow, aerodynamics, elasticity, and controls of the turbine, along with the incident waves, sea current, hydrodynamics, and foundation dynamics of the support structure. This paper describes the latest findings of the code-to-code verification activities of the Offshore Code Comparison Collaboration, which operates under Subtask 2 of the International Energy Agency Wind Task 23. In the latest phase of the project, participants used an assortment of codes to model the coupled dynamic response of a 5-MW wind turbine installed on a floating spar buoy in 320 m of water. Code predictions were compared from load-case simulations selected to test different model features. The comparisons have resulted in a greater understanding of offshore floating wind turbine dynamics and modeling techniques, and better knowledge of the validity of various approximations. The lessons learned from this exercise have improved the participants' codes, thus improving the standard of offshore wind turbine modeling.

  4. Experimental investigations on the aerodynamics and aeromechanics of wind turbines for floating offshore applications

    Science.gov (United States)

    Khosravi, Morteza

    -locked'' PIV measurements were also performed to elucidate further details about evolution of the unsteady vortex structures in the wake flow in relation to the position of the rotating turbine blades. The effects of the surge, heave, and pitch motions of the wind turbine base on the wake flow characteristics were examined in great details based on the PIV measurements. The findings derived from the present study can be used to improve the understanding of the underlying physics for optimal mechanical design of floating offshore wind turbines, as well as the layout optimization of floating offshore wind farms. Although, the mean power measurement results show little difference between the oscillating turbine and the bottom fixed turbine, but the excessive fluctuations in the power output of the oscillating turbine is anticipated to greatly reduce the power quality of such floating turbines. The load measurements also show substantial amount of difference both in terms of mean and the fluctuating components. The results of the wake study reveal that the wake of a wind turbine subjected to base motions, is highly dependent on which direction the turbine is oscillating. In the case of the moving turbine, the wake accelerates as the turbine is moving with the flow, hence, reducing the power extraction by the turbine. A decrease in Reynolds shear stress and the turbulent kinetic energy production was noted as the turbine was oscillating with the flow. However, as the turbine was moving into the flow, these effects reverse, and causes a deceleration in the wake of the moving turbine, hence increases the power production by the turbine, and increase the Reynolds shear stress and the turbulent kinetic energy. Finally, The wake flow field (x/D Darrieus type VAWT were also carried out by using a high-resolution PIV system, and the results obtained at two different horizontal (x-y) planes, at the equator height (H/2) and above the equator height (3H/4), for four different tip speed

  5. Recovery of uranium from seawater using wave power and floating offshore units

    International Nuclear Information System (INIS)

    Bjoerk, B.; Vallander, P.

    1981-06-01

    This report is a final contribution to a study of the technical and economic feasibility of floating units for the recovery of uranium from seawater. The seawater is supplied by wave energy and received by a sloping plane. An optimization was carried out which involved study of the number of storeys of adsorbent beds in a floating unit, the number and tonnage of service vessels and the number of moorings. Different adsorbent bed areas, thickness of layers of adsorbent material, length of floating units and length of extraction cycles were considered. The costs of a plant for each combination of optimization parameters were calculated and are presented. The most feasible offshore plant will recover uranium at a cost of about 1900 SEK/kg. It will comprise 22 floating units, each with an adsorbent bed area of 300 m 2 per metre of the unit and an adsorbent thickness of 0.10 metres. (Authors)

  6. Spar-type platform design for the offshore floating nuclear power plant

    International Nuclear Information System (INIS)

    Jurewicz, Jacob; Buongiorno, Jacopo; Todreas, Neil; Golay, Michael

    2014-01-01

    There exists the potential for substantial gains in safety, physical security, and economics for nuclear electricity supply through the development of an Offshore Floating Nuclear Plant (OFNP). Utilizing the most reliable and efficient construction techniques, this plant can be built from modular components in a shipyard as a partially submerged floating spar platform. The plant can then be floated to a site between 5 and 10 miles off the coast, moored in approximately 100-meter deep water, and connected to the grid via an underwater transmission line. The OFNP is designed to take full advantage of its environment to include passive cooling systems that eliminate the loss of ultimate heat sink accident, thereby decreasing the likelihood of severe accidents. The platform’s structural design, mooring system, and siting protect it against severe weather systems and render it immune to tsunamis and seismic activity. Furthermore, the OFNP containment design and venting procedures effectively eliminate the threat of serious land contamination, should a severe accident actually occur. The OFNP overall design builds on decades of offshore oil drilling experience and is derived from a shortened cylindrical spar platform. The platform has a skirt diameter of 75 m, a waterline diameter of 45 m, an operational draft of 48.5 m, and a total weight of about 38,200 tons when the skirt is empty. The spar design maximizes hydrodynamic stability, has been tested in various locations around the world in oil extraction, and offers significant protection to critical systems from external threats. The reactor containment is located below sea level and centered in a hull surrounded by seawater. This positioning offers both considerable physical security as well as unique opportunities in passive cooling. Watertight levels house safety critical systems (e.g. reactor, spent fuel pool, control room, battery room), the steam cycle, the condensate storage tank, and the desalination plant

  7. Wake losses optimization of offshore wind farms with moveable floating wind turbines

    International Nuclear Information System (INIS)

    Rodrigues, S.F.; Teixeira Pinto, R.; Soleimanzadeh, M.; Bosman, Peter A.N.; Bauer, P.

    2015-01-01

    Highlights: • We present a layout optimization framework for wind farms with moveable turbines. • Using moveable wind turbines in optimized layouts maximizes energy production. • Turbine and wind farm designers should cooperate to optimize offshore wind projects. - Abstract: In the future, floating wind turbines could be used to harvest energy in deep offshore areas where higher wind mean speeds are observed. Currently, several floating turbine concepts are being designed and tested in small scale projects; in particular, one concept allows the turbine to move after installation. This article presents a novel layout optimization framework for wind farms composed of moveable floating turbines. The proposed framework uses an evolutionary optimization strategy in a nested configuration which simultaneously optimizes the anchoring locations and the wind turbine position within the mooring lines for each individual wind direction. The results show that maximum energy production is obtained when moveable wind turbines are deployed in an optimized layout. In conclusion, the framework represents a new design optimization tool for future offshore wind farms composed of moveable floating turbines

  8. Recovery of uranium from seawater using wave power and floating offshore units

    International Nuclear Information System (INIS)

    Bjoerk, B.; Vallander, P.

    1981-03-01

    This report is the final contribution to a study of the technical and economic feasibility of floating units for the recovery of uranium from seawater. The seawater is supplied by wave energy and received by a sloping plane. An optimization was carried out which involved study of the number of storeys of adsorbent beds in a floating unit, the number and tonnage of service vessels and the number of moorings. Different absorbent bed areas, thicknesses of layers of adsorbent material, length of floating units and length of extraction cycles were considered. The annual uranium uptake was calculated for an offshore location 20 nautical miles to the south-east of South Africa. The costs of the total plant for each combination of optimization parameters were calculated and are presented. The cost of the recovered uranium for each combination of optimization parameters is shown. The most feasible offshore plant will recover uranium at a cost of about 1 900 SEK/kg. It will comprise 22 floating units, each with an adsorbent bed area of 300 m 2 per metre of the unit and an adsorbent thickness of 0.10 metres. A conceptual layout of the selected floating unit is shown in drawings. (author)

  9. Computational Fluid Dynamic Analysis of a Floating Offshore Wind Turbine Experiencing Platform Pitching Motion

    Directory of Open Access Journals (Sweden)

    Thanhtoan Tran

    2014-08-01

    Full Text Available The objective of this study is to illustrate the unsteady aerodynamic effects of a floating offshore wind turbine experiencing the prescribed pitching motion of a supporting floating platform as a sine function. The three-dimensional, unsteady Reynolds Averaged Navier-Stokes equations with the shear-stress transport (SST k-ω turbulence model were applied. Moreover, an overset grid approach was used to model the rigid body motion of a wind turbine blade. The current simulation results are compared to various approaches from previous studies. The unsteady aerodynamic loads of the blade were demonstrated to change drastically with respect to the frequency and amplitude of platform motion.

  10. Dynamic Response of a Floating Bridge Structure

    OpenAIRE

    Viuff, Thomas; Leira, Bernt Johan; Øiseth, Ole; Xiang, Xu

    2016-01-01

    A theoretical overview of the stochastic dynamic analysis of a floating bridge structure is presented. Emphasis is on the wave-induced response and the waves on the sea surface are idealized as a zero mean stationary Gaussian process. The first-order wave load processes are derived using linear potential theory and the structural idealization is based on the Finite Element Method. A frequency response calculation is presented for a simplified floating bridge structure example emphasising the ...

  11. Fuel flexibility in power generation onboard offshore floating units

    Energy Technology Data Exchange (ETDEWEB)

    Keep, Jeroen van [Waertsilae Corporation, Helsinki (Finland)

    2012-07-01

    Power Plants for offshore oil and gas installations utilizing dual fuel (DF) reciprocating engines are by many owners seen as an interesting alternative to conventional solutions due to the apparent advantages in fuel flexibility, fuel efficiency and lower emission. The paper summarizes the dual fuel technology, typical solutions for FPSO's and operational. Items that are discussed: DF operation and how it works; fuel flexibility, including transfer between fuel modes; fuel efficiency, also in production an important cost saver; emissions of the different fuel modes; size and weights, constraints; experiences of the P-63 project. With the above it is safe to conclude that the DF-technology is mature with important benefits for the offshore production market in certain specific applications, most notably the FPSO's for fields in low gas to oil ratios, bringing important fuel cost savings and also for new-built F-LNG/FSO/FPSO's where the power plant can be accommodated below decks, freeing up valuable deck space for the process plant. (author)

  12. Smart Novel Semi-Active Tuned Mass Damper for Fixed-Bottom and Floating Offshore Wind (Presentation)

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez Tsouroukdissian, Arturo [Alstom Renewable US LLC

    2016-05-02

    The intention of this paper is to present the results of a novel smart semi-active tuned mass damper (SA-TMD), which mitigates unwanted loads for both fixed-bottom and floating offshore wind systems. (Presentation Format).

  13. A Floating Offshore Wind Turbine in Extreme Wave Conditions

    DEFF Research Database (Denmark)

    Wehmeyer, Christof

    in order to include non-linear irregular incident waves as well as non-linear irregular incident waves with an embedded Stream-function wave. A linear background sea state into which a Stream-function wave was embedded was assumed no longer appropriate. Therefore a 2nd order sea state model was developed...... and served as well as the background sea state in which the Stream-function wave was embedded. The combined sea state was then applied in the numerical model in order to investigate the bow tendon responses of the FOWT TLP. A comparison of measured bow mooring responses and the numerically predicted bow......The PhD work evaluated the performance of engineering procedures, used in the design of bottom fixed offshore wind turbines, for the hydrodynamic ULS analysis of a FOWT tension leg platform (TLP). Dynamically sensitive topsides have been included and water depths were considered, where wave shapes...

  14. Application of a Monte Carlo procedure for probabilistic fatigue design of floating offshore wind turbines

    Directory of Open Access Journals (Sweden)

    K. Müller

    2018-03-01

    Full Text Available Fatigue load assessment of floating offshore wind turbines poses new challenges on the feasibility of numerical procedures. Due to the increased sensitivity of the considered system with respect to the environmental conditions from wind and ocean, the application of common procedures used for fixed-bottom structures results in either inaccurate simulation results or hard-to-quantify conservatism in the system design. Monte Carlo-based sampling procedures provide a more realistic approach to deal with the large variation in the environmental conditions, although basic randomization has shown slow convergence. Specialized sampling methods allow efficient coverage of the complete design space, resulting in faster convergence and hence a reduced number of required simulations. In this study, a quasi-random sampling approach based on Sobol sequences is applied to select representative events for the determination of the lifetime damage. This is calculated applying Monte Carlo integration, using subsets of a resulting total of 16 200 coupled time–domain simulations performed with the simulation code FAST. The considered system is the Danmarks Tekniske Universitet (DTU 10 MW reference turbine installed on the LIFES50+ OO-Star Wind Floater Semi 10 MW floating platform. Statistical properties of the considered environmental parameters (i.e., wind speed, wave height and wave period are determined based on the measurement data from the Gulf of Maine, USA. Convergence analyses show that it is sufficient to perform around 200 simulations in order to reach less than 10 % uncertainty of lifetime fatigue damage-equivalent loading. Complementary in-depth investigation is performed, focusing on the load sensitivity and the impact of outliers (i.e., values far away from the mean. Recommendations for the implementation of the proposed methodology in the design process are also provided.

  15. Hydroelastic responses of pontoon type very large floating offshore structures. 2nd Report. Effect of the water depth and the drift forces; Pontoon gata choogata futaishiki kaiyo kozobutsu no harochu chosei oto ni kansuru kenkyu. 2. Senkai eikyo to hyoryuryoku

    Energy Technology Data Exchange (ETDEWEB)

    Maeda, H; Miyajima, S [The University of Tokyo, Tokyo (Japan). Institute of Industrial Science; Masuda, K; Ikoma, T [Nihon University, Tokyo (Japan). College of Science and Technology

    1997-12-31

    Steady-state drift force in regular waves is theoretically analyzed. It is also studied under combined external force experimentally using a two-dimensional water tank. The fluid forces are analyzed by the pressure distribution method based on the potential theory, in which the effects of water depth are taken into account to discuss the effects of elastic deformation of the floating structure on the drift characteristics of steady-state waves. The tests were carried out using a wave-making circulating water tank equipped with a wind duct to create wind, waves and tidal flow. Drift force under a combined external force by wind, wave and/or tidal flow cannot be accurately predicted by arithmetically adding these components. For predicting drift force by tidal flow, it is necessary to take into account drag force in current at the floating structure bottom as well as that in wind at the front face. Drift force by tidal flow is affected by shallowness of water, which should be taken into account for drag forces. The floating structure will be deformed along the wave face as its stiffness decreases, basically decreasing steady-state drift force. 9 refs., 14 figs.

  16. Hydroelastic responses of pontoon type very large floating offshore structures. 2nd Report. Effect of the water depth and the drift forces; Pontoon gata choogata futaishiki kaiyo kozobutsu no harochu chosei oto ni kansuru kenkyu. 2. Senkai eikyo to hyoryuryoku

    Energy Technology Data Exchange (ETDEWEB)

    Maeda, H.; Miyajima, S. [The University of Tokyo, Tokyo (Japan). Institute of Industrial Science; Masuda, K.; Ikoma, T. [Nihon University, Tokyo (Japan). College of Science and Technology

    1996-12-31

    Steady-state drift force in regular waves is theoretically analyzed. It is also studied under combined external force experimentally using a two-dimensional water tank. The fluid forces are analyzed by the pressure distribution method based on the potential theory, in which the effects of water depth are taken into account to discuss the effects of elastic deformation of the floating structure on the drift characteristics of steady-state waves. The tests were carried out using a wave-making circulating water tank equipped with a wind duct to create wind, waves and tidal flow. Drift force under a combined external force by wind, wave and/or tidal flow cannot be accurately predicted by arithmetically adding these components. For predicting drift force by tidal flow, it is necessary to take into account drag force in current at the floating structure bottom as well as that in wind at the front face. Drift force by tidal flow is affected by shallowness of water, which should be taken into account for drag forces. The floating structure will be deformed along the wave face as its stiffness decreases, basically decreasing steady-state drift force. 9 refs., 14 figs.

  17. Unsteady aerodynamic analysis for offshore floating wind turbines under different wind conditions.

    Science.gov (United States)

    Xu, B F; Wang, T G; Yuan, Y; Cao, J F

    2015-02-28

    A free-vortex wake (FVW) model is developed in this paper to analyse the unsteady aerodynamic performance of offshore floating wind turbines. A time-marching algorithm of third-order accuracy is applied in the FVW model. Owing to the complex floating platform motions, the blade inflow conditions and the positions of initial points of vortex filaments, which are different from the fixed wind turbine, are modified in the implemented model. A three-dimensional rotational effect model and a dynamic stall model are coupled into the FVW model to improve the aerodynamic performance prediction in the unsteady conditions. The effects of floating platform motions in the simulation model are validated by comparison between calculation and experiment for a small-scale rigid test wind turbine coupled with a floating tension leg platform (TLP). The dynamic inflow effect carried by the FVW method itself is confirmed and the results agree well with the experimental data of a pitching transient on another test turbine. Also, the flapping moment at the blade root in yaw on the same test turbine is calculated and compares well with the experimental data. Then, the aerodynamic performance is simulated in a yawed condition of steady wind and in an unyawed condition of turbulent wind, respectively, for a large-scale wind turbine coupled with the floating TLP motions, demonstrating obvious differences in rotor performance and blade loading from the fixed wind turbine. The non-dimensional magnitudes of loading changes due to the floating platform motions decrease from the blade root to the blade tip. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  18. Efficient preliminary floating offshore wind turbine design and testing methodologies and application to a concrete spar design.

    Science.gov (United States)

    Matha, Denis; Sandner, Frank; Molins, Climent; Campos, Alexis; Cheng, Po Wen

    2015-02-28

    The current key challenge in the floating offshore wind turbine industry and research is on designing economic floating systems that can compete with fixed-bottom offshore turbines in terms of levelized cost of energy. The preliminary platform design, as well as early experimental design assessments, are critical elements in the overall design process. In this contribution, a brief review of current floating offshore wind turbine platform pre-design and scaled testing methodologies is provided, with a focus on their ability to accommodate the coupled dynamic behaviour of floating offshore wind systems. The exemplary design and testing methodology for a monolithic concrete spar platform as performed within the European KIC AFOSP project is presented. Results from the experimental tests compared to numerical simulations are presented and analysed and show very good agreement for relevant basic dynamic platform properties. Extreme and fatigue loads and cost analysis of the AFOSP system confirm the viability of the presented design process. In summary, the exemplary application of the reduced design and testing methodology for AFOSP confirms that it represents a viable procedure during pre-design of floating offshore wind turbine platforms. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  19. Conceptual Design of a Floating Support Structure and Mooring System for a Vertical Axis Wind Turbine

    DEFF Research Database (Denmark)

    Berthelsen, Petter Andreas; Fylling, Ivar; Vita, Luca

    2012-01-01

    This paper deals with the conceptual design of a floating support structure and mooring system for a 5MW vertical axis offshore wind turbine. The work is carried out as part of the DeepWind project, where the main objective is to investigate the feasibility of a floating vertical axis offshore wind...... turbine. The DeepWind concept consists of a Darrieus rotor mounted on a spar buoy support structure. The conceptual design is carried out in an iterative process, involving the different subcomponents. The present work is part of the first design iteration and the objective is to find a feasible floating...... support structure and mooring system for the DeepWind concept. The conceptual design is formulated as an optimization problem: Starting with an initial configuration, the optimization procedure tries to find a cheaper solution while satisfying a set of design requirements. This approach utilizes available...

  20. Analysis of the Induction and Wake Evolution of an Offshore Floating Wind Turbine

    Directory of Open Access Journals (Sweden)

    Matthew Lackner

    2012-04-01

    Full Text Available The degrees-of-freedom associated with offshore floating wind turbines (OFWTs result in a more dynamic flow field. The resulting aerodynamic loads may be significantly influenced by these motions via perturbations in the evolving wake. This is of great interest in terms of OFWT design, placement and simulation. This study presents free vortex wake method (FVM simulations of the NREL 5-MW wind turbine of a variety of platforms, operating in a range of wind speeds synthesized platform motion time series. Motion-induced wake perturbations are observed to affect induction. Transitions between windmill and propeller states are also observed.

  1. Smart Novel Semi-Active Tuned Mass Damper for Fixed-Bottom and Floating Offshore Wind (Paper)

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez Tsouroukdissian, Arturo [Alstom Renewable US LLC (GE Subsidiary); Lackner, Mathew [University of Massachusetts; Cross-Whiter, John [Glosten Associates; Park, Se Myung [University of Massachusetts; Pourazarm, Pariya [University of Massachusetts; La Cava, William [University of Massachusetts; Lee, Sungho [Glosten Associates

    2016-05-02

    The intention of this paper is to present the results of a novel smart semi-active tuned mass damper (SA-TMD), which mitigates unwanted loads for both fixed-bottom and floating offshore wind systems. The paper will focus on the most challenging water depths for both fixed-bottom and floating systems. A close to 38m Monopile and 55m Tension Leg Platform (TLP) will be considered. A technical development and trade-off analysis will be presented comparing the new system with existing passive non-linear TMD (N-TMD) technology and semi-active. TheSATMD works passively and activates itself with low power source under unwanted dynamic loading in less than 60msec. It is composed of both variable stiffness and damping elements coupled to a central pendulum mass. The analysis has been done numerically in both FAST(NREL) and Orcaflex (Orcina), and integrated in the Wind Turbine system employing CAD/CAE. The results of this work will pave the way for experimental testing to complete the technology qualification process. The load reductions under extreme and fatigue cases reach up significant levels at tower base, consequently reducing LCOE for fixed-bottom to floating wind solutions. The nacelle acceleration is reduced substantially under severe random wind and sea states, reducing the risks of failure of electromechanical components and blades at the rotor nacelle assembly. The SA-TMD system isa new technology that has not been applied previously in wind solutions. Structural damping devices aim to increase offshore wind turbine system robustness and reliability, which eases multiple substructures installations and global stability.

  2. Offshore code comparison collaboration continuation within IEA Wind Task 30: Phase II results regarding a floating semisubmersible wind system

    DEFF Research Database (Denmark)

    Robertson, Amy; Jonkman, Jason M.; Vorpahl, Fabian

    2014-01-01

    Offshore wind turbines are designed and analyzed using comprehensive simulation tools (or codes) that account for the coupled dynamics of the wind inflow, aerodynamics, elasticity, and controls of the turbine, along with the incident waves, sea current, hydrodynamics, mooring dynamics, and founda......Offshore wind turbines are designed and analyzed using comprehensive simulation tools (or codes) that account for the coupled dynamics of the wind inflow, aerodynamics, elasticity, and controls of the turbine, along with the incident waves, sea current, hydrodynamics, mooring dynamics......, and foundation dynamics of the support structure. This paper describes the latest findings of the code-to-code verification activities of the Offshore Code Comparison Collaboration Continuation project, which operates under the International Energy Agency Wind Task 30. In the latest phase of the project......, participants used an assortment of simulation codes to model the coupled dynamic response of a 5-MW wind turbine installed on a floating semisubmersible in 200 m of water. Code predictions were compared from load case simulations selected to test different model features. The comparisons have resulted...

  3. Uncertainty Analysis of OC5-DeepCwind Floating Semisubmersible Offshore Wind Test Campaign: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Robertson, Amy N [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

    2017-07-26

    This paper examines how to assess the uncertainty levels for test measurements of the Offshore Code Comparison, Continued, with Correlation (OC5)-DeepCwind floating offshore wind system, examined within the OC5 project. The goal of the OC5 project was to validate the accuracy of ultimate and fatigue load estimates from a numerical model of the floating semisubmersible using data measured during scaled tank testing of the system under wind and wave loading. The examination of uncertainty was done after the test, and it was found that the limited amount of data available did not allow for an acceptable uncertainty assessment. Therefore, this paper instead qualitatively examines the sources of uncertainty associated with this test to start a discussion of how to assess uncertainty for these types of experiments and to summarize what should be done during future testing to acquire the information needed for a proper uncertainty assessment. Foremost, future validation campaigns should initiate numerical modeling before testing to guide the test campaign, which should include a rigorous assessment of uncertainty, and perform validation during testing to ensure that the tests address all of the validation needs.

  4. Towards Interactive Steering of a Very Large Floating Structure Code by Using HPC Parallelisation Strategies

    KAUST Repository

    Frisch, Jerome; Gao, Ruiping; Mundani, Ralf-Peter; Wang, Chien Ming; Rank, Ernst

    2012-01-01

    Very large floating structures (VLFSs) have been used for broad applications such as floating storage facilities, floating piers, floating bridges, floating airports, entertainment facilities, even habitation, and other purposes. Owing to its small

  5. Recursive thoughts on the simulation of the flexible multibody dynamics of slender offshore structures

    NARCIS (Netherlands)

    Schilder, Jurnan Paul; Ellenbroek, Marcellinus Hermannus Maria; de Boer, A.

    2017-01-01

    In this work, the floating frame of reference formulation is used to create a flexible multibody model of slender offshore structures such as pipelines and risers. It is shown that due to the chain-like topology of the considered structures, the equation of motion can be expressed in terms of

  6. Design methods to assess the resistance of Offshore wind Turbine Structures impacted by a ship

    OpenAIRE

    Echeverry Jaramillo, Sara; Le Sourne, Hervé; Bela, Andreea; Pire, Timothée; Rigo, Philippe

    2017-01-01

    The dynamic modes of jacket, monopile and Floating offshore wind turbines (FOWT) after a collision event are presented. The authors have developed simplified analytical formulations based on plastic limit analysis to assess the resistance of an offshore wind turbine jacket impacted by a ship. For the case of collisions with monopile foundations and FOWT, the crushing behavior and structure dynamics are studied by means of finite element simulations. Numerical results for both monopile and flo...

  7. Dynamic analysis and design of offshore structures

    CERN Document Server

    Chandrasekaran, Srinivasan

    2015-01-01

    This book  attempts to provide readers with an overall idea of various types of offshore platform geometries. It covers the various environmental loads encountered by these structures, a detailed description of the fundamentals of structural dynamics in a class-room style, estimate of damping in offshore structures and their applications in the preliminary analysis and design. Basic concepts of structural dynamics are emphasized through simple illustrative examples and exercises. Design methodologies and guidelines, which are FORM based concepts are explained through a few applied example structures. Each chapter also has tutorials and exercises for self-learning. A dedicated chapter on stochastic dynamics will help the students to extend the basic concepts of structural dynamics to this advanced domain of research. Hydrodynamic response of offshore structures with perforated members is one of the recent research applications, which is found to be one of the effective manner of retrofitting offshore structur...

  8. Moored offshore structures - evaluation of forces in elastic mooring lines

    Science.gov (United States)

    Crudu, L.; Obreja, D. C.; Marcu, O.

    2016-08-01

    In most situations, the high frequency motions of the floating structure induce important effects in the mooring lines which affect also the motions of the structure. The experience accumulated during systematic experimental tests and calculations, carried out for different moored floating structures, showed a complex influence of various parameters on the dynamic effects. Therefore, it was considered that a systematic investigation is necessary. Due to the complexity of hydrodynamics aspects of offshore structures behaviour, experimental tests are practically compulsory in order to be able to properly evaluate and then to validate their behaviour in real sea. Moreover the necessity to carry out hydrodynamic tests is often required by customers, classification societies and other regulatory bodies. Consequently, the correct simulation of physical properties of the complex scaled models becomes a very important issue. The paper is investigating such kind of problems identifying the possible simplification, generating different approaches. One of the bases of the evaluation has been found consideringtheresults of systematic experimental tests on the dynamic behaviour of a mooring chain reproduced at five different scales. Dynamic effects as well as the influences of the elasticity simulation for 5 different scales are evaluated together. The paper presents systematic diagrams and practical results for a typical moored floating structure operating as pipe layer based on motion evaluations and accelerations in waves.

  9. On the fundamental performance of the floating offshore wave power device (FOWAD)

    International Nuclear Information System (INIS)

    Hotta, H.; Washio, Y.; Miyazaki, T.

    1990-01-01

    This paper reports on the wave power absorption, wave dissipation, mooring line tension and oscillation in regular and irregular (long created and short created) waves of the floating offshore wave power device (FOWAD) that were measured and analyzed by a scale model test in a wave tank. FOWAD is an oscillating water column type device equipped with air turbine generators, and air chambers facing the waves. Therefore, it belongs in the close of terminator type wave power devices. It has several projecting walls in front of each air chamber, several buoyancy compartments behind each chamber and stabilizer at the keel. The measured data indicates that, the performance and stability were improved in comparison with former terminator type devices, FOWAD absorbed about 30% of wave power and mooring line tension was within the limits of safety even in rough seas. Nevertheless the performance for dissipation of waves can be improved. This paper describes on the results of the model test and subsequent analysis

  10. An Aeroelastic Perspective of Floating Offshore Wind Turbine Wake Formation and Instability

    Science.gov (United States)

    Rodriguez, Steven N.; Jaworski, Justin W.

    2015-11-01

    The wake formation and wake stability of floating offshore wind turbines are investigated from an aeroelastic perspective. The aeroelastic model is composed of the Sebastian-Lackner free-vortex wake aerodynamic model coupled to the nonlinear Hodges-Dowell beam equations, which are extended to include the effects of blade profile asymmetry, higher-order torsional effects, and kinetic energy components associated with periodic rigid-body motions of floating platforms. Rigid-body platform motions are also assigned to the aerodynamic model as varying inflow conditions to emulate operational rotor-wake interactions. Careful attention is given to the wake formation within operational states where the ratio of inflow velocity to induced velocity is over 50%. These states are most susceptible to aerodynamic instabilities, and provide a range of states about which a wake stability analysis can be performed. In addition, the stability analysis used for the numerical framework is implemented into a standalone free-vortex wake aerodynamic model. Both aeroelastic and standalone aerodynamic results are compared to evaluate the level of impact that flexible blades have on the wake formation and wake stability.

  11. The typhoon effect on the aerodynamic performance of a floating offshore wind turbine

    Directory of Open Access Journals (Sweden)

    Zhe Ma

    2017-12-01

    Full Text Available The wind energy resource is considerably rich in the deep water of China South Sea, where wind farms have to face the challenge of extreme typhoon events. In this work, the typhoon effect on the aerodynamic performance of the 5MW OC3-Hywind floating offshore wind turbine (FOWT system has been investigated, based on the Aero-Hydro-Servo-Elastic FAST code. First, considering the full field observation data of typhoon “Damrey” is a long duration process with significant turbulence and high wind speed, so one 3-h representative truncated typhoon wind speed time history has been selected. Second, the effects of both the (variable-speed and collective-pitch control system of NREL 5 MW wind turbine and the motion of the floating platform on the blade aerodynamic performance of the FOWT system during the representative typhoon time history has been investigated, based on blade element momentum (BEM theory (coupled with potential theory for the calculation of the hydrodynamic loads of the Spar platform. Finally, the effects of different wind turbine control strategies, control parameter (KP–KI combinations, wave heights and parked modes on the rotor aerodynamic responses of the FOWT system have been clarified. The extreme typhoon event can result in considerably large extreme responses of the rotor thrust and the generated power due to the possible blade pitch angle error phenomenon. One active-parked strategy has been proposed for reducing the maximum aerodynamic responses of the FOWT system during extreme typhoon events.

  12. An Advanced Control Technique for Floating Offshore Wind Turbines Based on More Compact Barge Platforms

    Directory of Open Access Journals (Sweden)

    Joannes Olondriz

    2018-05-01

    Full Text Available Hydrodynamic Floating Offshore Wind Turbine (FOWT platform specifications are typically dominated by seaworthiness and maximum operating platform-pitch angle-related requirements. However, such specifications directly impact the challenge posed by an FOWT in terms of control design. The conventional FOWT systems are typically based on large, heavy floating platforms, which are less likely to suffer from the negative damping effect caused by the excessive coupling between blade-pitch control and platform-pitch motion. An advanced control technique is presented here to increase system stability for barge type platforms. Such a technique mitigates platform-pitch motions and improves the generator speed regulation, while maintaining blade-pitch activity and reducing blade and tower loads. The NREL’s 5MW + ITI Energy barge reference model is taken as a basis for this work. Furthermore, the capabilities of the proposed controller for performing with a more compact and less hydrodynamically stable barge platform is analysed, with encouraging results.

  13. Floating substructure flexibility of large-volume 10MW offshore wind turbine platforms in dynamic calculations

    International Nuclear Information System (INIS)

    Borg, Michael; Hansen, Anders Melchior; Bredmose, Henrik

    2016-01-01

    Designing floating substructures for the next generation of 10MW and larger wind turbines has introduced new challenges in capturing relevant physical effects in dynamic simulation tools. In achieving technically and economically optimal floating substructures, structural flexibility may increase to the extent that it becomes relevant to include in addition to the standard rigid body substructure modes which are typically described through linear radiation-diffraction theory. This paper describes a method for the inclusion of substructural flexibility in aero-hydro-servo-elastic dynamic simulations for large-volume substructures, including wave-structure interactions, to form the basis of deriving sectional loads and stresses within the substructure. The method is applied to a case study to illustrate the implementation and relevance. It is found that the flexible mode is significantly excited in an extreme event, indicating an increase in predicted substructure internal loads. (paper)

  14. Reliability analysis of an offshore structure

    DEFF Research Database (Denmark)

    Sorensen, J. D.; Faber, M. H.; Thoft-Christensen, P.

    1992-01-01

    A jacket type offshore structure from the North Sea is considered. The time variant reliability is estimated for failure defined as brittle fracture and crack through the tubular member walls. The stochastic modelling is described. The hot spot stress spectral moments as function of the stochasti...

  15. Damage Detection in an Offshore Structure

    DEFF Research Database (Denmark)

    Brincker, Rune; Kirkegaard, Poul Henning; Andersen, P.

    The structural integrity of a multi-pile offshore platform is investigated by using a vibration based damage detection scheme. Changes in structural integrity are assumed to be reflected in the modal parameters estimated from only output data using an Auto-Regressive Moving Average (ARMA) model....... By use of the estimates of the modal parameters and their corresponding variances a probability based damage indicator is formulated. This approach indicates, that since the construction of the platform, minor structural changes have taken place....

  16. Damage Detection in an Offshore Structure

    DEFF Research Database (Denmark)

    Brincker, Rune; Kirkegaard, Poul Henning; Andersen, Palle

    1995-01-01

    The structural integrity of a multi-pile offshore platform is investigated by using a vibration based damage detection scheme. Changes in structural integrity are assumed to be reflected in the modal parameters estimated from only output data using an Auto-Regressive Moving Average (ARMA) model....... By use of the estimates of the modal parameters and their corresponding variances a probability based damage indicator is formulated. This approach indicates, that since the construction of the platform, minor structural changes have taken place....

  17. Loads for use in the design of ships and offshore structures

    DEFF Research Database (Denmark)

    Hirdaris, S.E.; Bai, W.; Dessi, Daniele

    2014-01-01

    The evaluation of structural responses is key element in the design of ships and offshore structures. Fundamental to this is the determination of the design loads to support the Rule requirements and for application in direct calculations. To date, the current design philosophy for the prediction...... of motions and wave-induced loads has been driven by empirical or first-principles calculation procedures based on well-proven applications such as ship motion prediction programs. In recent years, the software, engineering and computer technology available to predict the design loads imposed on ships...... and offshore structures has improved dramatically. Notwithstanding, with the stepwise increase in the size and structural complexity of ships and floating offshore installations and the advances in the framework of Rules and Standards it has become necessary to utilise the latest technologies to assess...

  18. Comparison of simulations and offshore measurement data of a prototype of a floating combined wind and wave energy conversion system

    DEFF Research Database (Denmark)

    Yde, Anders; Larsen, Torben J.; Hansen, Anders Melchior

    2015-01-01

    In this paper, results from comparisons of simulations and measured offshore data from a floating combined wind and wave energy conversion system are presented. The device is a downscaled prototype that consists of a floating platform equipped with ten wave energy absorbers and three wind turbines....... The numerical model of the platform is based on the aeroelastic code, HAWC2, developed by DTU Wind Energy, which is coupled with a special external system that reads the output generated directly by the wave analysis software, WAMIT. The model also includes models for the dynamic mooring lines as well...... as the turbines non-linear yaw and teeter motion behavior. The main focus on the comparison will be on the statistical trends of the platform motion, mooring loads and turbine loads in measurements and simulations during different operational conditions such as increasing wind speed, wave height and wind...

  19. Active structural control of a floating wind turbine with a stroke-limited hybrid mass damper

    Science.gov (United States)

    Hu, Yaqi; He, Erming

    2017-12-01

    Floating wind turbines are subjected to more severe structural loads than fixed-bottom wind turbines due to additional degrees of freedom (DOFs) of their floating foundations. It's a promising way of using active structural control method to improve the structural responses of floating wind turbines. This paper investigates an active vibration control strategy for a barge-type floating wind turbine by setting a stroke-limited hybrid mass damper (HMD) in the turbine's nacelle. Firstly, a contact nonlinear modeling method for the floating wind turbine with clearance between the HMD and the stroke limiters is presented based on Euler-Lagrange's equations and an active control model of the whole system is established. The structural parameters are validated for the active control model and an equivalent load coefficient method is presented for identifying the wind and wave disturbances. Then, a state-feedback linear quadratic regulator (LQR) controller is designed to reduce vibration and loads of the wind turbine, and two optimization methods are combined to optimize the weighting coefficients when considering the stroke of the HMD and the active control power consumption as constraints. Finally, the designed controllers are implemented in high fidelity simulations under five typical wind and wave conditions. The results show that active HMD control strategy is shown to be achievable and the designed controllers could further reduce more vibration and loads of the wind turbine under the constraints of stroke limitation and power consumption. "V"-shaped distribution of the TMD suppression effect is inconsistent with the Weibull distribution in practical offshore floating wind farms, and the active HMD control could overcome this shortcoming of the passive TMD.

  20. Optimal Structural Reliability of Offshore Wind Turbines

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Tarp-Johansen, N.J.

    2005-01-01

    The main failure modes of modern large wind turbines are fatigue failure of wings, hub, shaft and main tower, local buckling of main tower, and failure of the foundation. This paper considers reliability-based optimal design of wind turbines. Compared to onshore wind turbines and building...... structures, humans spent little time in the vicinity of offshore wind turbines and the probability of human injury during storm conditions is small. Further environmental pollution will also in general be small in case of failure. One could therefore argue that the reliability level of offshore wind turbines...... can be lower than for onshore wind turbines and other civil engineering structures and can be assessed by reliability-based cost-optimization. Specifically this paper considers the main tower and foundation. Both fatigue and ultimate strength failure modes are included. Different formulations...

  1. Comparison of Simulations and Offshore Measurement Data of a Combined Floating Wind and Wave Energy Demonstration Platform

    DEFF Research Database (Denmark)

    Yde, Anders; Larsen, Torben J.; Hansen, Anders Melchior

    2015-01-01

    In this paper, results from comparisons of simulations and measured offshore data from a floating combined wind and wave energy conversion system are presented. The numerical model of the platform is based on the aeroelastic code, HAWC2, developed by DTU Wind Energy, which is coupled with a special...... external system that reads the output generated directly by the wave analysis software WAMIT. The main focus of the comparison is on the statistical trends of the platform motion, mooring loads, and turbine loads in measurements and simulations during different operational conditions. Finally, challenges...

  2. Extreme Value Predictions for Wave- and Wind-induced Loads on Floating Offshore Wind Turbines using FORM

    DEFF Research Database (Denmark)

    Joensen, Sunvard; Jensen, Jørgen Juncher; Mansour, Alaa E.

    2007-01-01

    duration of the time domain simulations needed (typically 60-300s to cover the hy-drodynamic memory effects in the response) the calcu-lation of the mean out-crossing rates of a given response are very fast. Thus complicated non-linear effects can be included. The FORM analysis also identifies the most...... probable wave episodes leading to given re-sponses. As an example the motions of floating foundations for offshore wind turbines are analysed taking into consid-eration both the wave and wind induced loads and con-sidering different mooring systems. The possible large horizontal motions make it important...

  3. Response Analysis and Comparison of a Spar-Type Floating Offshore Wind Turbine and an Onshore Wind Turbine under Blade Pitch Controller Faults

    DEFF Research Database (Denmark)

    Etemaddar, M.; Blanke, Mogens; Gao, Z.

    2016-01-01

    in the controller dynamic link library and a short-term extreme response analysis is performed using the HAWC2 simulation tool.The main objectives of this paper are to investigate how different faults affect the performance of wind turbines for condition monitoring purposes and which differences exist...... in the structural responses between onshore and offshore floating wind turbines. Statistical analysis of the selected response parameters are conducted using the six1-hour stochastic samples for each load case.For condition monitoring purpose,the effects of faults on the responses at different wind speeds and fault...... amplitudes are investigated by comparing the same response under normal operation.The severities of the individual faults are categorized by the extreme values of structural loads and the structural components are sorted based on the magnitude of the fault effects on the extreme values.The pitch sensor fixed...

  4. Dynamic modeling of a spar-type floating offshore wind turbine

    NARCIS (Netherlands)

    Savenije, L.B.; Ashuri, T.; Van Bussel, G.J.W.; Staerdahl, J.W.

    2010-01-01

    The installation of floating wind farms in deeper water is encouraged by the stronger and steadier wind, the lower visibility and noise impact, the absence of road restrictions, but also the absence or shortage of shallow water. In the summer of 2009, the first large-scale floating wind turbine

  5. Probabilistic Design of Offshore Structural Systems

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard

    1988-01-01

    Probabilistic design of structural systems is considered in this paper. The reliability is estimated using first-order reliability methods (FORM). The design problem is formulated as the optimization problem to minimize a given cost function such that the reliability of the single elements...... satisfies given requirements or such that the systems reliability satisfies a given requirement. Based on a sensitivity analysis optimization procedures to solve the optimization problems are presented. Two of these procedures solve the system reliability-based optimization problem sequentially using quasi......-analytical derivatives. Finally an example of probabilistic design of an offshore structure is considered....

  6. Probabilistic Design of Offshore Structural Systems

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard

    Probabilistic design of structural systems is considered in this paper. The reliability is estimated using first-order reliability methods (FORM). The design problem is formulated as the optimization problem to minimize a given cost function such that the reliability of the single elements...... satisfies given requirements or such that the systems reliability satisfies a given requirement. Based on a sensitivity analysis optimization procedures to solve the optimization problems are presented. Two of these procedures solve the system reliability-based optimization problem sequentially using quasi......-analytical derivatives. Finally an example of probabilistic design of an offshore structure is considered....

  7. Flexi-structure will cut offshore costs

    Energy Technology Data Exchange (ETDEWEB)

    Laird, R.

    1978-03-23

    A new support-tower design called Triflex, from Sea Energy Associates, could be used as a single-point mooring for tanker loading for small oilfields as well as for many other offshore production purposes. Triflex is a rigid tower designed to yield and move in sympathy with imposed wave and current forces when they exceed a predetermined limit. The tower can carry up to 4000 tons in water depths up to 300 m, and is lighter, is less expensive, and probably has greater safety advantages for rough conditions than existing North Sea structures. Extensive model testing has been carried out at Lanchester Polytechnic. Four different methods of construction are described.

  8. Offshore Floating Wind Turbine-driven Deep Sea Water Pumping for Combined Electrical Power and District Cooling

    International Nuclear Information System (INIS)

    Sant, T; Buhagiar, D; Farrugia, R N

    2014-01-01

    A new concept utilising floating wind turbines to exploit the low temperatures of deep sea water for space cooling in buildings is presented. The approach is based on offshore hydraulic wind turbines pumping pressurised deep sea water to a centralised plant consisting of a hydro-electric power system coupled to a large-scale sea water-cooled air conditioning (AC) unit of an urban district cooling network. In order to investigate the potential advantages of this new concept over conventional technologies, a simplified model for performance simulation of a vapour compression AC unit was applied independently to three different systems, with the AC unit operating with (1) a constant flow of sea surface water, (2) a constant flow of sea water consisting of a mixture of surface sea water and deep sea water delivered by a single offshore hydraulic wind turbine and (3) an intermittent flow of deep sea water pumped by a single offshore hydraulic wind turbine. The analysis was based on one year of wind and ambient temperature data for the Central Mediterranean that is known for its deep waters, warm climate and relatively low wind speeds. The study confirmed that while the present concept is less efficient than conventional turbines utilising grid-connected electrical generators, a significant portion of the losses associated with the hydraulic transmission through the pipeline are offset by the extraction of cool deep sea water which reduces the electricity consumption of urban air-conditioning units

  9. Offshore Floating Wind Turbine-driven Deep Sea Water Pumping for Combined Electrical Power and District Cooling

    Science.gov (United States)

    Sant, T.; Buhagiar, D.; Farrugia, R. N.

    2014-06-01

    A new concept utilising floating wind turbines to exploit the low temperatures of deep sea water for space cooling in buildings is presented. The approach is based on offshore hydraulic wind turbines pumping pressurised deep sea water to a centralised plant consisting of a hydro-electric power system coupled to a large-scale sea water-cooled air conditioning (AC) unit of an urban district cooling network. In order to investigate the potential advantages of this new concept over conventional technologies, a simplified model for performance simulation of a vapour compression AC unit was applied independently to three different systems, with the AC unit operating with (1) a constant flow of sea surface water, (2) a constant flow of sea water consisting of a mixture of surface sea water and deep sea water delivered by a single offshore hydraulic wind turbine and (3) an intermittent flow of deep sea water pumped by a single offshore hydraulic wind turbine. The analysis was based on one year of wind and ambient temperature data for the Central Mediterranean that is known for its deep waters, warm climate and relatively low wind speeds. The study confirmed that while the present concept is less efficient than conventional turbines utilising grid-connected electrical generators, a significant portion of the losses associated with the hydraulic transmission through the pipeline are offset by the extraction of cool deep sea water which reduces the electricity consumption of urban air-conditioning units.

  10. Safety evaluation report in the matter of Offshore Power Systems Floating Nuclear Plants (1-8). Docket No. STN 50-437

    International Nuclear Information System (INIS)

    1980-02-01

    The staff has performed an evaluation of a refractory sacrificial bed, called a core ladle, proposed by Offshore Power Systems (OPS) to be installed in Floating Nuclear Plants (FNPs) to delay the melt-through penetration of molten core debris in the unlikely event of a core meltdown accident. The core ladle design as proposed by OPS is in response to the staff's manufacturing license Condition 4 given in the Final Environmental Statement, Part III, NUREG-0502, dated December 1978 (FES-III). This condition requires that a pad constructed of magnesium oxide, or other equivalent refractory material, be installed in the FNP structure within the lower reactor cavity. The material must provide increased resistance to melt-through by the molten reactor core, must not react with core debris to form a large volume of gases, and must not have any deleterious effects on safety

  11. Floating axis wind turbines for offshore power generation—a conceptual study

    International Nuclear Information System (INIS)

    Akimoto, Hiromichi; Tanaka, Kenji; Uzawa, Kiyoshi

    2011-01-01

    The cost of energy produced by offshore wind turbines is considered to be higher than land based ones because of the difficulties in construction, operation and maintenance on offshore sites. To solve the problem, we propose a concept of a wind turbine that is specially designed for an offshore environment. In the proposed concept, a floater of revolutionary shape supports the load of the wind turbine axis. The floater rotates with the turbine and the turbine axis tilts to balance the turbine thrust, buoyancy and gravity. The tilt angle is passively adjustable to wind force. The angle is 30° at rated power. The simplicity of the system leads to further cost reduction of offshore power generation.

  12. RBI - Risk Based Inspection: new concept applied to management of FPSOs (Floating, Production and Storage Offshore) structural integrity; IBR-Inspecao baseada em risco: um novo conceito aplicado a gestao da integridade estrutural de FPSOs

    Energy Technology Data Exchange (ETDEWEB)

    Farias, Bruno de; Figueiredo, Eduardo; Luiz, Marcio [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil); Meurer, Gustavo; Duarte, Romulo; Belligotti, Rufo; Krzonkalla, Viviane [ABS Consulting, Rio de Janeiro, RJ (Brazil)

    2008-07-01

    Due to the difficulties of adapting the plan of inspection, typical of oil tankers, the units of the FPSO, began to occur large periods of unavailability of the cargo tanks. Also, with the expansion of the fleet, began to notice a difficulty in meeting the plan of inspection of the FPSO's hull. To improve the management of structural integrity of its FPSO's, PETROBRAS aims to ABS Consulting with the development and implementation of Risk-Based Inspection, known as RBI. This concept is applicable to various branches of industry. The companies began their implementation of oil by refineries. The development application for a ship's hull is recent and PETROBRAS is one of the first companies to implement the IBR for monitoring of the FPSO hull. (author)

  13. Strength Analysis of a Large-Size Supporting Structure for an Offshore Wind Turbine

    Directory of Open Access Journals (Sweden)

    Niklas Karol

    2017-04-01

    Full Text Available The offshore wind power industry is the branch of electric energy production from renewable sources which is most intensively developed in EU countries. At present, there is a tendency to install larger-power wind turbines at larger distances from the seashore, on relatively deep waters. Consequently, technological solutions for new supporting structures intended for deeper water regions are undergoing rapid development now. Various design types are proposed and analysed, starting from gravitational supports (GBS, through monopiles and 3D frame structures (jackets, tripods, and ending with floating and submerged supports anchored to the seabed by flexible connectors, including TLP type solutions.

  14. Recent Developments in the Construction of Floating Structures ...

    African Journals Online (AJOL)

    This paper presents the applications of floating structures in (a) creating land from the ocean for airports, container ports, cruise terminals, oil storage, power plants, fish farms, recreation facilities, aquatic observatories, residential facilities, marinas and even relay bases for receiving micro waves from outer space, etc, ...

  15. On Hydroelastic Body-Boundary Condition of Floating Structures

    DEFF Research Database (Denmark)

    Xia, Jinzhu

    1996-01-01

    A general linear body boundary condition of hydroelastic analysis of arbitrary shaped floating structures generalizes the classic kinematic rigid-body (Timman-Newman) boundary condition for seakeeping problems. The new boundary condition is consistent with the existing theories under certain...

  16. Adaptive Backstepping Control Based on Floating Offshore High Temperature Superconductor Generator for Wind Turbines

    Directory of Open Access Journals (Sweden)

    Feng Yang

    2014-01-01

    Full Text Available With the rapid development of offshore wind power, the doubly fed induction generator and permanent magnet synchronous generator cannot meet the increasing request of power capacity. Therefore, superconducting generator should be used instead of the traditional motor, which can improve generator efficiency, reduce the weight of wind turbines, and increase system reliability. This paper mainly focuses on nonlinear control in the offshore wind power system which is consisted of a wind turbine and a high temperature superconductor generator. The proposed control approach is based on the adaptive backstepping method. Its main purpose is to regulate the rotor speed and generator voltage, therefore, achieving the maximum power point tracking (MPPT, improving the efficiency of a wind turbine, and then enhancing the system’s stability and robustness under large disturbances. The control approach can ensure high precision of generator speed tracking, which is confirmed in both the theoretical analysis and numerical simulation.

  17. Dynamic characteristics between waves and a floating cylindrical body connected to a tension-leg mooring cable placed in a simulated offshore environment

    Directory of Open Access Journals (Sweden)

    Juhun Song

    2016-07-01

    Full Text Available Given the rapid progress made in understanding the dynamics of an offshore floating body in an ocean environment, the present study aimed to simulate ocean waves in a small-sized wave flume and to observe the motion of a cylindrical floating body placed in an offshore environment. To generate regular ocean waves in a wave flume, we combined a wave generator and a wave absorber. In addition, to precisely visualise the oscillation of the body, a set of light-emitting diode illuminators and a high-speed charge-coupled device camera were installed in the flume. This study also focuses on the spectral analysis of the movement of the floating body. The wave generator and absorbers worked well to simulate stable regular waves. In addition, the simulated waves agreed well with the plane waves predicted by shallow-water theory. As the period of the oncoming waves changed, the movement of the floating body was substantially different when tethered to a tension-leg mooring cable. In particular, when connected to the tension-leg mooring cable, the natural frequency of the floating body appeared suddenly at 0.391 Hz as the wave period increased.

  18. Submerged Fixed Floating Structure under the Action of Surface Current

    Directory of Open Access Journals (Sweden)

    Zhen Cui

    2018-01-01

    Full Text Available The implementation of floating structures has increased with the construction of new sluices for flood control. The overturning moment of floating structure and its influencing factors are the important parameters that determine the structural safety. It is essential to understand the overturning characteristics of these structures in currents. Based on hydrodynamic theory and equilibrium analysis, the hydraulic characteristics of a floating structure are discussed by means of theoretical analysis and experiments. A formula for the overturning moment is developed in terms of the time-averaged pressure on the structure. The corresponding parametric study aims to assess the effects of flow velocities, vertical positions, shape ratios and water levels on the overturning moment. The experimental results show that hydrodynamic factors have a significant influence on the overturning of the structure. Furthermore, a relationship is obtained between the overturning moment and the contributing parameters according to dimensional analysis and the linear fitting method of multidimensional ordinary least squares (OLS. The results predicted by the formula agree with the experimental results, demonstrating the potential for general applicability.

  19. Freely floating structures trapping time-harmonic water waves (revisited)

    OpenAIRE

    Kuznetsov, Nikolay; Motygin, Oleg

    2014-01-01

    We study the coupled small-amplitude motion of the mechanical system consisting of infinitely deep water and a structure immersed in it. The former is bounded above by a free surface, whereas the latter is formed by an arbitrary finite number of surface-piercing bodies floating freely. The mathematical model of time-harmonic motion is a spectral problem in which the frequency of oscillations serves as the spectral parameter. It is proved that there exist axisymmetric structures consisting of ...

  20. Human and organization factors: engineering operating safety into offshore structures

    International Nuclear Information System (INIS)

    Bea, Robert G.

    1998-01-01

    History indicates clearly that the safety of offshore structures is determined primarily by the humans and organizations responsible for these structures during their design, construction, operation, maintenance, and decommissioning. If the safety of offshore structures is to be preserved and improved, then attention of engineers should focus on to how to improve the reliability of the offshore structure 'system,' including the people that come into contact with the structure during its life-cycle. This article reviews and discusss concepts and engineering approaches that can be used in such efforts. Two specific human factor issues are addressed: (1) real-time management of safety during operations, and (2) development of a Safety Management Assessment System to help improve the safety of offshore structures

  1. The VolturnUS 1:8 Floating Wind Turbine: Design, Construction, Deployment, Testing, Retrieval, and Inspection of the First Grid-Connected Offshore Wind Turbine in US

    Energy Technology Data Exchange (ETDEWEB)

    Dagher, Habib [Univ. of Maine, Orono, ME (United States); Viselli, Anthony [Univ. of Maine, Orono, ME (United States); Goupee, Andrew [Univ. of Maine, Orono, ME (United States); Kimball, Richard [Maine Maritime Academy, Castine, ME (United States); Allen, Christopher [Univ. of Maine, Orono, ME (United States)

    2017-08-15

    Volume II of the Final Report for the DeepCwind Consortium National Research Program funded by US Department of Energy Award Number: DE-EE0003278.001 summarizes the design, construction, deployment, testing, numerical model validation, retrieval, and post-deployment inspection of the VolturnUS 1:8-scale floating wind turbine prototype deployed off Castine, Maine on June 2nd, 2013. The 1:8 scale VolturnUS design served as a de-risking exercise for a commercial multi-MW VolturnUS design. The American Bureau of Shipping Guide for Building and Classing Floating Offshore Wind Turbine Installations was used to design the prototype. The same analysis methods, design methods, construction techniques, deployment methods, mooring, and anchoring planned for full-scale were used. A commercial 20kW grid-connected turbine was used and was the first offshore wind turbine in the US.

  2. An experimental study of the effect of mooring systems on the dynamics of a SPAR buoy-type floating offshore wind turbine

    Directory of Open Access Journals (Sweden)

    Sinpyo Hong

    2015-05-01

    Full Text Available An experimental study of the effect of mooring systems on the dynamics of a SPAR buoy-type floating offshore wind turbine is presented. The effects of the Center of Gravity (COG, mooring line spring constant, and fair-lead location on the turbine’s motion in response to regular waves are investigated. Experimental results show that for a typical mooring system of a SPAR buoy-type Floating Offshore Wind Turbine (FOWT, the effect of mooring systems on the dynamics of the turbine can be considered negligible. However, the pitch decreases notably as the COG increases. The COG and spring constant of the mooring line have a negligible effect on the fairlead displacement. Numerical simulation and sensitivity analysis show that the wind turbine motion and its sensitivity to changes in the mooring system and COG are very large near resonant frequencies. The test results can be used to validate numerical simulation tools for FOWTs.

  3. Risk assessment for ship collisions against offshore structures

    DEFF Research Database (Denmark)

    Pedersen, Preben Terndrup

    2014-01-01

    to changes in ship traffic in the vicinity of the offshore structures and new developments within navigational equipment and pro¬cedures. The paper highlights some of the available analytical elements in collision frequency estimation and response calculations for different types of offshore installations......Offshore installations served by in-field vessels and/or situated in the vicinity of ship traf¬fic lanes are exposed to collision hazards such as risk of loss of life, economic loss, and environmental damage. Therefore, one of the many performance goals in the design phase of such structures...... and indicates how these tools can be applied to evaluate relevant risk control options....

  4. Modern earthquake engineering offshore and land-based structures

    CERN Document Server

    Jia, Junbo

    2017-01-01

    This book addresses applications of earthquake engineering for both offshore and land-based structures. It is self-contained as a reference work and covers a wide range of topics, including topics related to engineering seismology, geotechnical earthquake engineering, structural engineering, as well as special contents dedicated to design philosophy, determination of ground motions, shock waves, tsunamis, earthquake damage, seismic response of offshore and arctic structures, spatial varied ground motions, simplified and advanced seismic analysis methods, sudden subsidence of offshore platforms, tank liquid impacts during earthquakes, seismic resistance of non-structural elements, and various types of mitigation measures, etc. The target readership includes professionals in offshore and civil engineering, officials and regulators, as well as researchers and students in this field.

  5. Concept design and coupled dynamic response analysis on 6-MW spar-type floating offshore wind turbine

    Science.gov (United States)

    Meng, Long; Zhou, Tao; He, Yan-ping; Zhao, Yong-sheng; Liu, Ya-dong

    2017-10-01

    Tower, Spar platform and mooring system are designed in the project based on a given 6-MW wind turbine. Under wind-induced only, wave-induced only and combined wind and wave induced loads, dynamic response is analyzed for a 6-MW Spar-type floating offshore wind turbine (FOWT) under operating conditions and parked conditions respectively. Comparison with a platform-fixed system (land-based system) of a 6-MW wind turbine is carried out as well. Results demonstrate that the maximal out-of-plane deflection of the blade of a Spar-type system is 3.1% larger than that of a land-based system; the maximum response value of the nacelle acceleration is 215% larger for all the designed load cases being considered; the ultimate tower base fore-aft bending moment of the Spar-type system is 92% larger than that of the land-based system in all of the Design Load Cases (DLCs) being considered; the fluctuations of the mooring tension is mainly wave-induced, and the safety factor of the mooring tension is adequate for the 6-MW FOWT. The results can provide relevant modifications to the initial design for the Spar-type system, the detailed design and model basin test of the 6-MW Spar-type system.

  6. The offshore trend: Structural changes in the wind power sector

    International Nuclear Information System (INIS)

    Markard, Jochen; Petersen, Regula

    2009-01-01

    In recent years, the wind power sector has begun to move offshore, i.e. to use space and good wind speeds on the open sea for large scale electricity generation. Offshore wind power, however, is not just technologically challenging but also a capital intensive and risky business that requires particular financial and organizational resources not all potential investors might have. We therefore address the question, what impact offshore wind power may have on ownership and organizational structures in the wind power sector. We compare on- and offshore wind park ownership in Denmark, the UK and Germany. The analysis shows that offshore wind power in all three countries is dominated by large firms, many of which are from the electricity sector. In Denmark and the UK, also investors from the gas and oil industry play an important role in the offshore wind business. This development represents a major shift for countries such as Germany and Denmark, in which the wind power sector has grown and matured on the basis of investments by individuals, farmers, cooperatives and independent project developers. The structural changes by which offshore wind power is accompanied have consequences for turbine manufacturers, project developers, investors, associations and policy makers in the field.

  7. Concept Testing of a Simple Floating Offshore Vertical Axis Wind Turbine

    DEFF Research Database (Denmark)

    Friis Pedersen, Troels; Schmidt Paulsen, Uwe; Aagaard Madsen, Helge

    2013-01-01

    The wind energy community is researching new concepts for deeper sea offshore wind turbines. One such concept is the DeepWind concept. The concept is being assessed in a EU-FP7 project, called DeepWind. Objectives of this project are to assess large size wind turbines (5-20MW) based on the concept...... varying wind and wave conditions, and to compare such behaviour with computer code calculations. The concept turbine was designed and constructed by the project task partners, and all parts were assembled and installed at sea in the Roskilde fjord right next to DTU Risø campus. The turbine is under....... One task in the project is to test a 1kW concept rotor (not a scaled down MW size rotor) partly under field conditions in a fjord in Denmark, partly in a water tank under controlled conditions in Netherlands. The objective of testing the 1kW concept turbine is to verify the dynamical behaviour under...

  8. A GLANCE AT OFFSHORE WIND TURBINE FOUNDATION STRUCTURES

    Directory of Open Access Journals (Sweden)

    Jianhua Zhang

    2016-06-01

    Full Text Available Energy poverty and climate change are crucial issues we face in our societies. Offshore wind energy has been a reliable solution to both of these problems - solving our growing energy problems while reducing CO2 emission. Innovative foundation design is one of the setbacks faced by this industry. Designing and constructing a cost effective offshore wind farm is greatly hampered by technical and infrastructural challenges, especially in foundation structures. This paper provides a detailed overview of issues related to this problem, with the aim of eliminating the frequent misunderstandings which can arise among engineers and investors working in the offshore wind energy sector. It begins by investigating the latest data and recommendations regarding the design and deployment of various kinds of offshore wind turbine (OWT foundations. It provides a framework which enables us to study the different OWT foundations, including prototypes and their limitations. Various structural failure modes are highlighted and corrosion measures are presented. Moreover, various removal methods of support structures are put forward. Finally, this paper presents the setbacks preventing the spread of offshore wind energy and the future works for offshore wind energy applications.

  9. FIVE REGIONAL PERSPECTIVES OF CONSTRUCTING AN OFFSHORE CORPORATE STRUCTURE

    Directory of Open Access Journals (Sweden)

    Ana-Maria GEAMÃNU

    2015-04-01

    Full Text Available The offshore company, the emblem of the tax haven jurisdictions, is owned by non-residents and it conducts activities outside the island of incorporation in order to benefit from tax advantages. The purpose of this paper is to conduct a comparative analysis on the trends of constructing the offshore corporate structures at the level of five regions where tax havens have been identified: The Caribbean Sea and Central America; Europe; Asia; The Indian Ocean and The Pacific Ocean. Based on the tax and corporate legislations the analysis is focused on the main tax advantages offered by these entities, the incorporation and administration procedures as well as the costs involved. The results have shown that pure offshore corporate legislation is to be found at the level of only three geographic areas: The Caribbean Sea and Central America; The Indian Ocean and The Pacific Ocean and the offshore law is predominantly international, with only fine regional differences.

  10. Stochastic Fatigue Analysis of Jacket Type Offshore Structures

    DEFF Research Database (Denmark)

    Sigurdsson, Gudfinnur

    In this paper, a stochastic reliability assessment for jacket type offshore structures subjected to wave loads in deep water environments is outlined. In the reliability assessment, structural and loading uncertainties are taken into account by means of some stochastic variables. To estimate stat...... statistical measures of structural stress variations the modal spectral analysis method is applied....

  11. Recursive thoughts on the simulation of the flexible multibody dynamics of slender offshore structures

    Science.gov (United States)

    Schilder, J.; Ellenbroek, M.; de Boer, A.

    2017-12-01

    In this work, the floating frame of reference formulation is used to create a flexible multibody model of slender offshore structures such as pipelines and risers. It is shown that due to the chain-like topology of the considered structures, the equation of motion can be expressed in terms of absolute interface coordinates. In the presented form, kinematic constraint equations are satisfied explicitly and the Lagrange multipliers are eliminated from the equations. Hence, the structures can be conveniently coupled to finite element or multibody models of for example seabed and vessel. The chain-like topology enables the efficient use of recursive solution procedures for both transient dynamic analysis and equilibrium analysis. For this, the transfer matrix method is used. In order to improve the convergence of the equilibrium analysis, the analytical solution of an ideal catenary is used as an initial configuration, reducing the number of required iterations.

  12. Model for economical analysis of oil and gas deepwater production concepts : Comparisons of life cycle cost of subsea production systems vs. floating structures with dry wellheads.

    OpenAIRE

    Romero Mata, Omar

    2010-01-01

    Master's thesis in Offshore technology The scope of the work was to create a model that will allow the comparison of Life Cycle Costs (LCC) for subsea production systems and floating structures with dry wellheads for the Mexican territorial waters of the Gulf of Mexico. To give validity to the model, an empirical comparison on the resulting recovery factor based on data of the US Gulf of Mexico was included. This comparison is intended to answer ¿Is there a significant diffe...

  13. Plasma structures in front of a floated emissive electrode

    International Nuclear Information System (INIS)

    Ishiguro, S.; Sato, N.

    1993-01-01

    A particle simulation with plasma source is carried out on plasma structures generated by an electron emissive electrode floated in a collisionless plasma. When low-temperature, high-density thermal electrons are emitted, there appears a negative potential dip in front of the electrode, which is always accompanied by a low-frequency oscillation. On the other hand, three regimes of plasma structures appear for an electron beam injection. When a high-flux electron beam is injected, an electron sheath is generated in front of the electrode. The sheath reflects ions flowing to the electrode, providing an increase in the plasma density. When a low-flux electron beam is injected, no electron sheath is generated. When an intermediate-flux beam is injected, the electron sheath structure appears periodically in time. The lifetime of the sheath is proportional to the system length. These results of beam injection are almost consistent with those of a Q-machine experiment

  14. Benefits of Risk Based Inspection Planning for Offshore Structures

    DEFF Research Database (Denmark)

    Straub, D.M.; Goyet, J.; Sørensen, John Dalsgaard

    2006-01-01

    The economical benefits of applying risk-based inspection planning (RBI) for offshore structures subject to fatigue are evaluated based on experiences from past industrial projects. To this end, the factors influencing the cost of inspection, repair and failure of structures are discussed......, the financial benefit of RBI is assessed....

  15. The 5 MW DeepWind floating offshore vertical wind turbine concept design - status and perspective

    DEFF Research Database (Denmark)

    Schmidt Paulsen, Uwe; Aagaard Madsen, Helge; Kragh, Knud Abildgaard

    2014-01-01

    , and a generator design tool “NESSI”. HAWC2 has been adopted for VAWT rotors by DTU Wind Energy in the project and is explained on its technical capability to embrace integrated modeling of the different physical aspects. NESSI, developed at AAU (Aalborg University) is presented with focus on key elements...... in generator design. The paper presents new developments in the current design of a novel rotor shape with overspeed control. Rotor performance, design structural key figures and upscaling potential are reported. New results implemented on permanent magnets generator and - bearing technology show...

  16. CARIBBEAN OFFSHORE CORPORATE STRUCTURES UNDER A SWOT ANALYSIS

    Directory of Open Access Journals (Sweden)

    Ana-Maria GEAMÃNU

    2015-04-01

    Full Text Available Tax havens have long been under the attention of numerous Governments and International Organizations which triggered the concern of an uneven playing field in the taxation area. As a result numerous amendments have been made to both their commercial and tax legislations in order to be in line with the internationally agreed tax standards. The aim of this article is to conduct a SWOT analysis on the offshore corporate structures found in the Caribbean landscape. Based on a selection process of the most commonly recognized tax havens in the Caribbean region and an analysis of their offshore companies at the level of incorporation, administration, activities conducted and costs, a set of frequently met characteristics have been identified which stand at the basis of the SWOT analysis. The results stand to present a comprehensive four dimension framework of the offshore corporate structures in regards to their strengths, weaknesses, opportunities and threats.

  17. Model Development and Loads Analysis of an Offshore Wind Turbine on a Tension Leg Platform with a Comparison to Other Floating Turbine Concepts: April 2009

    Energy Technology Data Exchange (ETDEWEB)

    Matha, D.

    2010-02-01

    This report presents results of the analysis of a 5-MW wind turbine located on a floating offshore tension leg platform (TLP) that was conducted using the fully coupled time-domain aero-hydro-servo-elastic design code FAST with AeroDyn and HydroDyn. The report also provides a description of the development process of the TLP model. The model has been verified via comparisons to frequency-domain calculations. Important differences have been identified between the frequency-domain and time-domain simulations, and have generated implications for the conceptual design process. An extensive loads and stability analysis for ultimate and fatigue loads according to the procedure of the IEC 61400-3 offshore wind turbine design standard was performed with the verified TLP model. This report compares the loads for the wind turbine on the TLP to those of an equivalent land-based turbine. Major instabilities for the TLP are identified and described.

  18. Reliability-Based Optimal Design for Very Large Floating Structure

    Institute of Scientific and Technical Information of China (English)

    ZHANG Shu-hua(张淑华); FUJIKUBO Masahiko

    2003-01-01

    Costs and losses induced by possible future extreme environmental conditions and difficulties in repairing post-yielding damage strongly suggest the need for proper consideration in design rather than just life loss prevention. This can be addressed through the development of design methodology that balances the initial cost of the very large floating structure (VLFS) against the expected potential losses resulting from future extreme wave-induced structural damage. Here, the development of a methodology for determining optimal, cost-effective design will be presented and applied to a VLFS located in the Tokyo bay. Optimal design criteria are determined based on the total expected life-cycle cost and acceptable damage probability and curvature of the structure, and a set of sizes of the structure are obtained. The methodology and applications require expressions of the initial cost and the expected life-cycle damage cost as functions of the optimal design variables. This study includes the methodology, total life-cycle cost function, structural damage modeling, and reliability analysis.

  19. Physical Modelling of Geotechnical Structures in Ports and Offshore

    Directory of Open Access Journals (Sweden)

    Bałachowski Lech

    2017-04-01

    Full Text Available The physical modelling of subsoil behaviour and soil-structure interaction is essential for the proper design of offshore structures and port infrastructure. A brief introduction to such modelling of geoengineering problems is presented and some methods and experimental devices are described. The relationships between modelling scales are given. Some examples of penetration testing results in centrifuge and calibration chamber are presented. Prospects for physical modelling in geotechnics are also described.

  20. Value of information-based inspection planning for offshore structures

    DEFF Research Database (Denmark)

    Irman, Arifian Agusta; Thöns, Sebastian; Leira, Bernt J.

    2017-01-01

    with each inspection strategy. A simplified and generic risk-based inspection planning utilizing pre- posterior Bayesian decision analysis had been proposed by Faber et al. [1] and Straub [2]. This paper provides considerations on the theoretical background and a Value of Information analysis......-based inspection planning. The paper will start out with a review of the state-of-art RBI planning procedure based on Bayesian decision theory and its application in offshore structure integrity management. An example of the Value of Information approach is illustrated and it is pointed to further research......Asset integrity and management is an important part of the oil and gas industry especially for existing offshore structures. With declining oil price, the production rate is an important factor to be maintained that makes integrity of the structures one of the main concerns. Reliability based...

  1. Stochastic Analysis of Offshore Steel Structures An Analytical Appraisal

    CERN Document Server

    Karadeniz, Halil

    2013-01-01

    Stochastic Analysis of Offshore Steel Structures provides a clear and detailed guide to advanced analysis methods of fixed offshore steel structures using 3D beam finite elements under random wave and earthquake loadings. Advanced and up-to-date research results are coupled with modern analysis methods and essential theoretical information to consider optimal solutions to structural issues. As these methods require and use knowledge of different subject matters, a general introduction to the key areas is provided. This is followed by in-depth explanations supported by design examples, relevant calculations and supplementary material containing related computer programmers. By combining this theoretical and practical approach Stochastic Analysis of Offshore Steel Structures cover a range of key concepts in detail including: ·         The basic principles of standard 3D beam finite elements and special connections, ·         Wave loading - from hydrodynamics to the calculation of wave load...

  2. Structural Robustness Evaluation of Offshore Wind Turbines

    DEFF Research Database (Denmark)

    Giuliani, Luisa; Bontempi, Franco

    2010-01-01

    in the framework of a safe design: it depends on different factors, like exposure, vulnerability and robustness. Particularly, the requirement of structural vulnerability and robustness are discussed in this paper and a numerical application is presented, in order to evaluate the effects of a ship collision...

  3. Structural Integrity Management for Fixed Offshore Platforms in Malaysia

    OpenAIRE

    Narayanan Sambu Potty; Mohammad Kabir B. Mohd Akram

    2009-01-01

    Structural Integrity Management (SIM) is important for the protection of offshore crew, environment, business assets and company and industry reputation. API RP 2A contained guidelines for assessment of existing platforms mostly for the Gulf of Mexico (GOM). ISO 19902 SIM framework also does not specifically cater for Malaysia. There are about 200 platforms in Malaysia with 90 exceeding their design life. The Petronas Carigali Sdn Bhd (PCSB) uses the Asset Integrity Management ...

  4. Final environmental statement related to the proposed manufacture of floating nuclear power plants by Offshore Power Systems: (Docket No. STN 50-437): Part 2, A generic environmental statement considering the siting and operation of floating nuclear power plants

    International Nuclear Information System (INIS)

    1976-09-01

    The proposed action is the issuance of a manufacturing license to Offshore Power Systems for the startup and operation of a proposed manufacturing facility located at Blount Island, Jacksonville, Florida (Docket No. STN 50-437). No nuclear fuel will be handled or stored at the manufacturing site. The plants will be fueled after they have been towed to and moored within protected basins at specific locations designated by the purchaser and after an operating license has been issued by the Nuclear Regulatory Commission. Each nuclear generating plant, mounted on a floating platform, has a net capacity of 1150 MWe. This energy is provided by a pressurized water reactor steam supply system consisting of a Westinghouse four-loop 3425-MWt unit with an ice-condenser containment system. When one or more of these units is located within a single breakwater, the installation is designated an offshore power station. Volume 2 contains the siting criteria, regulations, effects of construction, effects of operation, and a safety analysis. 2 figs., 2 tabs

  5. Wind Loads on Ships and Offshore Structures Estimated by CFD

    DEFF Research Database (Denmark)

    Aage, Christian; Hvid, S.L.; Hughes, P.H.

    1997-01-01

    Wind loads on ships and offshore structures could until recently be determined only by model tests, or by statistical methods based on model tests. By the development of Computational Fluid Dynamics or CFD there is now a realistic computational alternative available. In this paper, wind loads...... on a seagoing ferry and on a semisubmersible offshore platform have been estimated by CFD. The results have been compared with wind tunnel model tests and, for the ferry, a few full-scale measurements, and good agreement is obtained. The CFD method offers the possibility of a computational estimate of scale...... effects related to wind tunnel model testing. An example of such an estimate on the ferry is discussed. Due to the time involved in generating the computational mesh and in computing the solution, the CFD method is not at the moment economically competitive to routine wind tunnel model testing....

  6. Final environmental statement. Final addendum to Part II: Manufacture of floating nuclear power plants by Offshore Power Systems. DOCKET-STN--50-437

    International Nuclear Information System (INIS)

    1978-06-01

    This Addendum to Part II of the Final Environmental Statement related to manufacture of floating nuclear power plants by Offshore Power Systems (OPS), NUREG-0056, issued September 1976, was prepared by the U.S. Nuclear Regulatory Commission (NRC), Office of Nuclear Reactor Regulation. The staff's basic evaluation is presented in NUREG-0056. The current Addendum provides further consideration of a number of topics discussed in NUREG-0056, particularly additional consideration of shore zone siting at estuarine and ocean regions. This Summary and Conclusions recapitulates and is cumulative for Part II of the FES and the current Addendum. Augmentations to the Summary and Conclusions presented in Part II of the FES and arising from the evaluations contained in this Addendum are italicized

  7. An Integrated Structural Strength Analysis Method for Spar Type Floating Wind Turbine

    Institute of Scientific and Technical Information of China (English)

    胡志强; 刘毅; 王晋

    2016-01-01

    An integrated structural strength analysis method for a Spar type floating wind turbine is proposed in this paper, and technical issues related to turbine structure modeling and stress combination are also addressed. The NREL-5MW “Hywind” Spar type wind turbine is adopted as study object. Time-domain dynamic coupled simulations are performed by a fully-coupled aero-hydro-servo-elastic tool, FAST, on the purpose of obtaining the dynamic characteristics of the floating wind turbine, and determining parameters for design load cases of finite element calculation. Then design load cases are identified, and finite element analyses are performed for these design load cases. The structural stresses due to wave-induced loads and wind-induced loads are calculated, and then combined to assess the structural strength of the floating wind turbine. The feasibility of the proposed structural strength analysis method for floating wind turbines is then validated.

  8. Towards Interactive Steering of a Very Large Floating Structure Code by Using HPC Parallelisation Strategies

    KAUST Repository

    Frisch, Jerome

    2012-09-01

    Very large floating structures (VLFSs) have been used for broad applications such as floating storage facilities, floating piers, floating bridges, floating airports, entertainment facilities, even habitation, and other purposes. Owing to its small bending rigidity, VLFS deforms elastically when subjected to wave action. This elastic deformation due to wave is called hydro elastic response and it can be obtained by solving the interaction between the surface wave and the floating structure in the frequency domain. In solving the fluid-structure interaction, the floating structure can be modelled by applying the finite element method, whereas the fluid part may be analyzed by using the Green\\'s function method. When using the Green\\'s function which satisfies the boundary condition on the free-surface, the sea bottom and that at infinite distance from the floating structure, the unknown parameters to be determined for the fluid part can be minimized to be only those associated with the wetted surface of the floating structure. However, in the evaluation of the Green\\'s function, extensive computation time O(N2) is needed (N is the number of unknowns). Therefore, acceleration techniques are necessary to tackle the computational complexity. Nowadays, standard multi-core office PCs are already quite powerful if all the cores can be used efficiently. This paper will show different parallelisation strategies for speeding up the Green\\'s function computation. A shared memory based implementation as well as a distributed memory concept will be analysed regarding speed-up and efficiency. For large computations, batch jobs can be used to compute detailed results in high resolution on a large computational cluster or supercomputer. Different speed-up computations on clusters will be included for showing strong speed-up results. © 2012 IEEE.

  9. Integrated Multidisciplinary Constrained Optimization of Offshore Support Structures

    International Nuclear Information System (INIS)

    Haghi, Rad; Molenaar, David P; Ashuri, Turaj; Van der Valk, Paul L C

    2014-01-01

    In the current offshore wind turbine support structure design method, the tower and foundation, which form the support structure are designed separately by the turbine and foundation designer. This method yields a suboptimal design and it results in a heavy, overdesigned and expensive support structure. This paper presents an integrated multidisciplinary approach to design the tower and foundation simultaneously. Aerodynamics, hydrodynamics, structure and soil mechanics are the modeled disciplines to capture the full dynamic behavior of the foundation and tower under different environmental conditions. The objective function to be minimized is the mass of the support structure. The model includes various design constraints: local and global buckling, modal frequencies, and fatigue damage along different stations of the structure. To show the usefulness of the method, an existing SWT-3.6-107 offshore wind turbine where its tower and foundation are designed separately is used as a case study. The result of the integrated multidisciplinary design optimization shows 12.1% reduction in the mass of the support structure, while satisfying all the design constraints

  10. Wind-wave induced dynamic response analysis for motions and mooring loads of a spar-type offshore floating wind turbine

    Institute of Scientific and Technical Information of China (English)

    马钰; 肖龙飞; 胡志强

    2014-01-01

    Due to the energy crisis and the environmental issues like pollution and global warming, the exploration for renewable and clean energies becomes crucial. The offshore floating wind turbines (OFWTs) draw a great deal of attention recently as a means to exploit the steadier and stronger wind resources available in deep water seas. This paper studies the hydrodynamic characteristics of a spar-type wind turbine known as the OC3-Hywind concept and the dynamic responses of the turbine. Response characteristics of motions and mooring loads of the system under different sea states are evaluated and the effects of the loads induced by the wind and the wave on the system are discussed. The calculations are carried out with the numerical simulation code FAST in the time domain and the frequency analysis is made by using the FFT method. The results and the conclusions from this paper might help better understand the behavior characteristics of the floating wind turbine system under actual ocean environments and provide valuable data in design and engineering practice.

  11. Structural Dynamic Analysis of Semi-Submersible Floating Vertical Axis Wind Turbines

    Directory of Open Access Journals (Sweden)

    Jeremiah Ishie

    2016-12-01

    Full Text Available The strong and stable wind at offshore locations and the increasing demand for energy have made the application of wind turbines in deeper water surge. A novel concept of a 5 MW baseline Floating Vertical Axis Wind Turbine (FVAWT and a 5 MW optimised FVAWT with the DeepWind Darrieus rotor and the optimised DeepWind Darrieus rotor, respectively, were studied extensively. The structural responses, fatigue damages, platform global motions and mooring line dynamics of the FVAWTs were investigated comprehensively during normal operating conditions under steady wind and turbulent wind conditions, using a coupled non-linear aero-hydro-servo-elastic code (the Simo-Riflex-DMS code which was developed by Wang et al. for modeling FVAWTs. This coupled code incorporates the models for the turbulent wind field, aerodynamics, hydrodynamics, structural dynamics, and generator controller. The simulation is performed in a fully coupled manner in time domain. The comparison of responses under different wind conditions were used to demonstrate the effect of turbulence on both FVAWTs dynamic responses. The turbulent wind condition has the advantage of reducing the 2P effects. Furthermore, comparative studies of the FVAWTs responses were undertaken to explore the advantages of adopting the optimised 5 MW DeepWind Darrieus rotor over the baseline model. The results identified the 5 MW optimised FVAWT to having: lower Fore-Aft (FA but higher lower Side-Side (SS bending moments of structural components; lower motions amplitude; lower short-term fatigue equivalent loads and a further reduced 2P effects.

  12. Asset Decommissioning Risk Metrics for Floating Structures in the Gulf of Mexico.

    Science.gov (United States)

    Kaiser, Mark J

    2015-08-01

    Public companies in the United States are required to report standardized values of their proved reserves and asset retirement obligations on an annual basis. When compared, these two measures provide an aggregate indicator of corporate decommissioning risk but, because of their consolidated nature, cannot readily be decomposed at a more granular level. The purpose of this article is to introduce a decommissioning risk metric defined in terms of the ratio of the expected value of an asset's reserves to its expected cost of decommissioning. Asset decommissioning risk (ADR) is more difficult to compute than a consolidated corporate risk measure, but can be used to quantify the decommissioning risk of structures and to perform regional comparisons, and also provides market signals of future decommissioning activity. We formalize two risk metrics for decommissioning and apply the ADR metric to the deepwater Gulf of Mexico (GOM) floater inventory. Deepwater oil and gas structures are expensive to construct, and at the end of their useful life, will be expensive to decommission. The value of proved reserves for the 42 floating structures in the GOM circa January 2013 is estimated to range between $37 and $80 billion for future oil prices between 60 and 120 $/bbl, which is about 10 to 20 times greater than the estimated $4.3 billion to decommission the inventory. Eni's Allegheny and MC Offshore's Jolliet tension leg platforms have ADR metrics less than one and are approaching the end of their useful life. Application of the proposed metrics in the regulatory review of supplemental bonding requirements in the U.S. Outer Continental Shelf is suggested to complement the current suite of financial metrics employed. © 2015 Society for Risk Analysis.

  13. Vertical Dynamic Stiffness of Offshore Foundations

    DEFF Research Database (Denmark)

    Latini, Chiara; Cisternino, Michele; Zania, Varvara

    2016-01-01

    Nowadays, pile and suction caisson foundations are widely used to support offshore structures which are subjected to vertical dynamic loads. The dynamic soil-structure interaction of floating foundations (foundations embedded in a soil layer whose height is greater than the foundation length) is ...

  14. Surface and Internal Waves due to a Moving Load on a Very Large Floating Structure

    Directory of Open Access Journals (Sweden)

    Taro Kakinuma

    2012-01-01

    Full Text Available Interaction of surface/internal water waves with a floating platform is discussed with nonlinearity of fluid motion and flexibility of oscillating structure. The set of governing equations based on a variational principle is applied to a one- or two-layer fluid interacting with a horizontally very large and elastic thin plate floating on the water surface. Calculation results of surface displacements are compared with the existing experimental data, where a tsunami, in terms of a solitary wave, propagates across one-layer water with a floating thin plate. We also simulate surface and internal waves due to a point load, such as an airplane, moving on a very large floating structure in shallow water. The wave height of the surface or internal mode is amplified when the velocity of moving point load is equal to the surface- or internal-mode celerity, respectively.

  15. Floating Offshore Wind in Oregon: Potential for Jobs and Economic Impacts in Oregon Coastal Counties from Two Future Scenarios

    Energy Technology Data Exchange (ETDEWEB)

    Jimenez, Tony [National Renewable Energy Lab. (NREL), Golden, CO (United States); Keyser, David [National Renewable Energy Lab. (NREL), Golden, CO (United States); Tegen, Suzanne [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2016-07-01

    This analysis examines the employment and potential economic impacts of large-scale deployment of offshore wind technology off the coast of Oregon. This analysis examines impacts within the seven Oregon coastal counties: Clatsop, Tillamook, Lincoln, Lane, Douglas, Coos, and Curry. The impacts highlighted here can be used in county, state, and regional planning discussions and can be scaled to get a general sense of the economic development opportunities associated with other deployment scenarios.

  16. Strengthening, modification and repair techniques’ prioritization for structural integrity control of ageing offshore structures

    International Nuclear Information System (INIS)

    Samarakoon, Samindi M.K.; Ratnayake, R.M. Chandima

    2015-01-01

    Structural integrity control is vital for existing ageing as well as newly built offshore and onshore structures. Structural integrity control becomes highly sensitive to interventions under a potential loss of structural integrity when it comes to offshore oil and gas production and process facilities. This is mainly due to the inherent constraints present in carrying out engineering work in the offshore atmosphere. It has been further exacerbated by the ageing offshore structures and the necessity of carrying out life extension toward the end of their design service lives. Local and international regulations demand the implementation of appropriate strengthening, modification and repair plans when significant changes in the structural integrity are revealed. In this context, strengthening, modification and repair techniques such as welding, member removal/reduction of loading, mechanical clamping and grouted repairs play a vital role. This manuscript presents an approach for prioritizing the strengthening, modification and repair techniques using a multi-criteria analysis approach. An analytic hierarchy process has been selected for the analysis via an illustrative case. It also provides a comprehensive overview of currently existing; strengthening, modification and repair techniques and their comparative pros and cons. - Highlights: • Structural integrity control (SIC) of ageing and intact offshore structures. • Strengthening, modification and/or repair (SMR) techniques have been explained. • Application of multi-criteria analysis conserving SI has been illustrated. • SMR techniques prioritization and sensitivity analysis has been performed

  17. Structural health and prognostics management for offshore wind turbines :

    Energy Technology Data Exchange (ETDEWEB)

    Myrent, Noah J.; Kusnick, Joshua F.; Barrett, Natalie C.; Adams, Douglas E.; Griffith, Daniel

    2013-04-01

    Operations and maintenance costs for offshore wind plants are significantly higher than the current costs for land-based (onshore) wind plants. One way to reduce these costs would be to implement a structural health and prognostic management (SHPM) system as part of a condition based maintenance paradigm with smart load management and utilize a state-based cost model to assess the economics associated with use of the SHPM system. To facilitate the development of such a system a multi-scale modeling approach developed in prior work is used to identify how the underlying physics of the system are affected by the presence of damage and faults, and how these changes manifest themselves in the operational response of a full turbine. This methodology was used to investigate two case studies: (1) the effects of rotor imbalance due to pitch error (aerodynamic imbalance) and mass imbalance and (2) disbond of the shear web; both on a 5-MW offshore wind turbine in the present report. Based on simulations of damage in the turbine model, the operational measurements that demonstrated the highest sensitivity to the damage/faults were the blade tip accelerations and local pitching moments for both imbalance and shear web disbond. The initial cost model provided a great deal of insight into the estimated savings in operations and maintenance costs due to the implementation of an effective SHPM system. The integration of the health monitoring information and O&M cost versus damage/fault severity information provides the initial steps to identify processes to reduce operations and maintenance costs for an offshore wind farm while increasing turbine availability, revenue, and overall profit.

  18. Structural health and prognostics management for offshore wind turbines :

    Energy Technology Data Exchange (ETDEWEB)

    Griffith, Daniel; Resor, Brian Ray; White, Jonathan Randall; Paquette, Joshua A.; Yoder, Nathanael C.

    2012-12-01

    Operations and maintenance costs for offshore wind plants are expected to be significantly higher than the current costs for onshore plants. One way in which these costs may be able to be reduced is through the use of a structural health and prognostic management system as part of a condition based maintenance paradigm with smart load management. To facilitate the creation of such a system a multiscale modeling approach has been developed to identify how the underlying physics of the system are affected by the presence of damage and how these changes manifest themselves in the operational response of a full turbine. The developed methodology was used to investigate the effects of a candidate blade damage feature, a trailing edge disbond, on a 5-MW offshore wind turbine and the measurements that demonstrated the highest sensitivity to the damage were the local pitching moments around the disbond. The multiscale method demonstrated that these changes were caused by a local decrease in the blades torsional stiffness due to the disbond, which also resulted in changes in the blades local strain field. Full turbine simulations were also used to demonstrate that derating the turbine power by as little as 5% could extend the fatigue life of a blade by as much as a factor of 3. The integration of the health monitoring information, conceptual repair cost versus damage size information, and this load management methodology provides an initial roadmap for reducing operations and maintenance costs for offshore wind farms while increasing turbine availability and overall profit.

  19. Wave response analyses of floating crane structure; Crane sen no jobu kozobutsu no haro oto

    Energy Technology Data Exchange (ETDEWEB)

    Nobukawa, H.; Takaki, M.; Kitamura, M.; Ahou, G. [Hiroshima University, Hiroshima (Japan). Faculty of Engineering; Higashimura, M. [Fukada Salvage and Marine Works Co. Ltd., Osaka (Japan)

    1996-12-31

    Identifying a dynamic load acting on a lifted load in a floating crane moving in waves is important for preparing an operation manual for the floating crane. Analyses were made on motions in waves of a floating crane with a lifting load of 3,600 tons, with considerations given to deformation of the crane structure. Discussions were given on a dynamic load acting on a lifted load. If a case that considers elastic deformation in the crane structure is compared with a case that does not consider same in calculating hull motions of the floating crane, the difference between them is small if wave length {lambda} to the ship length L is about 0.5. However, if {lambda}/L is 1.0 and 1.5, the difference grows very large. Therefore, the effect of deformation in the crane structure on hull motions of the floating crane cannot be ignored in these cases. A dynamic load acting on a lifted load that considers deformation in the crane structure is about 5% of lifted weight in a headsea condition in which the wave height is 2 m and {lambda}/L is 1.5. As opposed, an estimated value of a dynamic load when the crane structure is regarded as a rigid body is 13%, which is 2.6 times as great as the case that considers deformation of the crane structure. 3 refs., 17 figs., 1 tab.

  20. Wave response analyses of floating crane structure; Crane sen no jobu kozobutsu no haro oto

    Energy Technology Data Exchange (ETDEWEB)

    Nobukawa, H; Takaki, M; Kitamura, M; Ahou, G [Hiroshima University, Hiroshima (Japan). Faculty of Engineering; Higashimura, M [Fukada Salvage and Marine Works Co. Ltd., Osaka (Japan)

    1997-12-31

    Identifying a dynamic load acting on a lifted load in a floating crane moving in waves is important for preparing an operation manual for the floating crane. Analyses were made on motions in waves of a floating crane with a lifting load of 3,600 tons, with considerations given to deformation of the crane structure. Discussions were given on a dynamic load acting on a lifted load. If a case that considers elastic deformation in the crane structure is compared with a case that does not consider same in calculating hull motions of the floating crane, the difference between them is small if wave length {lambda} to the ship length L is about 0.5. However, if {lambda}/L is 1.0 and 1.5, the difference grows very large. Therefore, the effect of deformation in the crane structure on hull motions of the floating crane cannot be ignored in these cases. A dynamic load acting on a lifted load that considers deformation in the crane structure is about 5% of lifted weight in a headsea condition in which the wave height is 2 m and {lambda}/L is 1.5. As opposed, an estimated value of a dynamic load when the crane structure is regarded as a rigid body is 13%, which is 2.6 times as great as the case that considers deformation of the crane structure. 3 refs., 17 figs., 1 tab.

  1. Numerical hydrodynamic analysis of an offshore stationary–floating oscillating water column–wave energy converter using CFD

    Directory of Open Access Journals (Sweden)

    Ahmed Elhanafi

    2017-01-01

    Full Text Available Offshore oscillating water columns (OWC represent one of the most promising forms of wave energy converters. The hydrodynamic performance of such converters heavily depends on their interactions with ocean waves; therefore, understanding these interactions is essential. In this paper, a fully nonlinear 2D computational fluid dynamics (CFD model based on RANS equations and VOF surface capturing scheme is implemented to carry out wave energy balance analyses for an offshore OWC. The numerical model is well validated against published physical measurements including; chamber differential air pressure, chamber water level oscillation and vertical velocity, overall wave energy extraction efficiency, reflected and transmitted waves, velocity and vorticity fields (PIV measurements. Following the successful validation work, an extensive campaign of numerical tests is performed to quantify the relevance of three design parameters, namely incoming wavelength, wave height and turbine damping to the device hydrodynamic performance and wave energy conversion process. All of the three investigated parameters show important effects on the wave–pneumatic energy conversion chain. In addition, the flow field around the chamber's front wall indicates areas of energy losses by stronger vortices generation than the rear wall.

  2. Soil structure interaction in offshore wind turbine collisions

    DEFF Research Database (Denmark)

    Samsonovs, Artjoms; Giuliani, Luisa; Zania, Varvara

    2014-01-01

    Vessel impact is one of the load cases which should be accounted for in the design of an offshore wind turbine (OWT) according to design codes, but little guidance or information is given on the employed methodology. This study focuses on the evaluation of the distress induced in a wind turbine...... after a ship collision, thus providing an insight on the consequences of a collision event and on the main aspects to be considered when designing for this load case. In particular, the role of the foundation soil properties (site conditions) on the response of the structural system is investigated....... Dynamic finite element analyses have been performed taking into account the geometric and material nonlinearity of the tower, and the effects of soil structure interaction (SSI) have been studied in two representative collision scenarios of a service vessel with the turbine: a moderate energy impact...

  3. Cost-efficient foundation structures for large offshore wind farms

    International Nuclear Information System (INIS)

    Birch, C.; Gormsen, C.; Lyngesen, S.; Rasmussen, J. L.; Juhl, H.

    1997-01-01

    This paper presents the results of the development of a cost-efficient foundation for large (1.5 MW) offshore wind farms at water depth of 5 to 11 m. Previously, medium sized wind turbines (500 kW) in Denmark have been installed offshore at water depths of approximately 5 m on concrete gravity foundations. The installation of larger turbines at greater depth does, however, hold great promise in terms of wind environment and environmental considerations. The costs of a traditional gravity foundation at these increased water depths is expected to be prohibitive, and the aim of the project has been to reduce the foundations costs in general. This paper describes the theoretical basis for the geotechnical and structural design of three alternative concepts and presents an optimised layout of each based on a research and development project. The basis has been a wind farm consisting of 100 turbines. The R and D project has been undertaken by the consulting engineers Nellemann, Nielsen and Rauschenberger A/S (Gravity foundation), LICengineering A/S (Mono pile) and Ramboell (Tripod) in co-operation with the Danish utility engineering companies Elkraft and Elsamprojekt A/S. The project was partly financed by the participants and by the Danish Energy Agency through their 1996 Energy Research Programme (EFP-96). (au) 18 refs

  4. Application of the Aero-Hydro-Elastic Model, HAWC2-WAMIT, to Offshore Data from Floating Power Plants Hybrid Wind- and Wave-Energy Test Platform, P37

    DEFF Research Database (Denmark)

    Bellew, Sarah; Yde, Anders; Verelst, David Robert

    2014-01-01

    numerical models, which can combine the aerodynamic, hydrodynamic, structural exibility and mooring components. Very little oshore data exists, however, in order to validate these numerical models. Floating Power Plant are the developers of a oating, hybrid wind- and wave-energy device. The device uses...... the pitching wave energy devices, not only to increase and smooth the power output from the platform, but also to take the energy from the waves in a controlled manner, resulting in a stable platform for the wind turbine and a safe harbour for O&M. They are currently developing the nal design for their rst...... full-scale prototype, the P80, which has a width of 80 m. As part of the development, Floating Power Plant have completed 4 oshore test-phases (totalling over 2 years oshore operation) on a 37 m wide scaled test device, the P37. This paper focuses on the comparison of one of the leading numerical...

  5. Probabilistic Calibration of Fatigue Design Factors for Offshore Wind Turbine Support Structures

    DEFF Research Database (Denmark)

    Ramirez, José Rangel; Sørensen, John Dalsgaard

    2010-01-01

    for the considered offshore wind turbines in such a way that the specific uncertainties for the fatigue life are accounted in a rational manner. Similar approaches have been used for offshore oil & gas sub-structures, but the required reliability level for offshore wind turbines is generally lower and the fatigue......This paper describes a reliability-based approach to determine fatigue design factors (FDF) for offshore wind turbine support structures made of steel. The FDF values are calibrated to a specific reliability level and linked to a specific inspection and maintenance (I&M) strategy used...

  6. Study on design method and vibration reduction characteristic of floating raft with periodic structure

    Science.gov (United States)

    Fang, Yuanyuan; Zuo, Yanyan; Xia, Zhaowang

    2018-03-01

    The noise level is getting higher with the development of high-power marine power plant. Mechanical noise is one of the most obvious noise sources which not only affect equipment reliability, riding comfort and working environment, but also enlarge underwater noise. The periodic truss type device which is commonly applied in fields of aerospace and architectural is introduced to floating raft construction in ship. Four different raft frame structure are designed in the paper. The vibration transmissibility is taken as an evaluation index to measure vibration isolation effect. A design scheme with the best vibration isolation effect is found by numerical method. Plate type and the optimized periodic truss type raft frame structure are processed to experimental verify vibration isolation effect of the structure of the periodic raft. The experimental results demonstrate that the same quality of the periodic truss floating raft has better isolation effect than that of the plate type floating raft.

  7. Panorama 2013 - Offshore wind power

    International Nuclear Information System (INIS)

    Vinot, Simon

    2012-10-01

    While onshore wind power is already a well-developed global industry, offshore wind power is still in the consolidation and globalization phase. The most mature of marine renewable energies is beginning to venture off the European coast and even to other continents, driven by public policies and the ever increasing number of players joining this promising market, which should evolve into deeper waters thanks to floating structures. (author)

  8. Upwind design basis (WP4 : Offshore foundations and support structures)

    NARCIS (Netherlands)

    Fischer, T.; De Vries, W.E.; Schmidt, B.

    2010-01-01

    The presented design basis gives a summarized overview of relevant design properties for a later offshore wind turbine design procedures within work package 4. The described offshore site is located in the Dutch North Sea and has a water depth of 21m. Therefore it will be chosen as shallow site

  9. Estimation of Structure-Borne Noise Reduction Effect of Steel Railway Bridge Equipped with Floating Ladder Track and Floating Reinforced-Concrete Deck

    Science.gov (United States)

    Watanabe, Tsutomu; Sogabe, Masamichi; Asanuma, Kiyoshi; Wakui, Hajime

    A number of steel railway bridges have been constructed in Japan. Thin steel members used for the bridges easily tend to vibrate and generate structure-borne noise. Accordingly, the number of constructions of steel railway bridges tends to decrease in the urban areas from a viewpoint of environmental preservation. Then, as a countermeasure against structure-borne noise generated from steel railway bridges, we have developed a new type of the steel railway bridge equipped with a floating-ladder track and a floating reinforced-concrete (RC) deck. As a result of train-running experiment, it became apparent that the new steel railway bridge installed by double floating system has reduced a vibration velocity level by 10.5 dB(A) at main girder web as compared with a steel railway bridge installed by directly fastened track. This reduction effect was achieved by the ladder track and RC deck supported by resilient materials.

  10. Gradient based structural optimization with fatigue constraints of jacket structures for offshore wind turbines

    DEFF Research Database (Denmark)

    Oest, Jacob; Overgaard, Lars Christian; Lund, Erik

    2015-01-01

    design phase. The key challenge is to efficiently deal with the very large number of non-linear fatigue constraints and the very large time-history loads that are used in the design of offshore support structures. In this paper main emphasis will be on the analytical design sensitivity analysis used...

  11. Performance of Ships and Offshore Structures in Waves

    Directory of Open Access Journals (Sweden)

    Shukui Liu

    2012-01-01

    for predicting large amplitude motions of ships and floating structures in response to incoming waves in the frame of potential theory. The developed alternative set of time domain methods simulate the hydrodynamic forces acting on ships advancing in waves with constant speed. For motions’ simulation, the diffraction forces and radiation forces are calculated up to the mean wetted surface, while the Froude-Krylov forces and hydrostatic restoring forces are calculated up to the undisturbed incident wave surface in case of large incident wave amplitude. This enables the study of the above waterline hull form effect. Characteristic case studies on simulating the hydrodynamic forces and motions of standard type of ships have been conducted for validation purpose. Good agreement with other numerical codes and experimental data has been observed. Furthermore, the added resistance of ships in waves can be calculated by the presented methods. This capability supports the increased demand of this type of tools for the proper selection of engine/propulsion systems accounting for ship’s performance in realistic sea conditions, or when optimizing ship’s sailing route for minimum fuel consumption and toxic gas emissions.

  12. Les ouvrages pétroliers en mer Offshore Petroleum Structures

    Directory of Open Access Journals (Sweden)

    Susbielles G.

    2006-11-01

    the Cognac, Hondo, Ninian and Maureen fields are distinguished from the others by eithertheir architecture or their dimensions. Most of the concrete platforms are installed in the North Sea. The one on the Ninian field is largerthan all the others. An exceptionisBrazilwheretherearethreeplatforms in shallow water. For marginal fields or ta determine the exact characteristics of a discovered field, Mirr production is started up from subsea wellheads via a manifold and links ta a floating structure (semisubmersible platform, tanker. Few chang es have been made in semisubmersible platforms. Solely the Sedco709 platform is different from the others because it is dynamically positioned. The mort important offshore hoisting operations are done by very large capacity cranes. The designing of loading stations is done exclusively by a few companies. As for the laying of pipelines and pipes, it has evolved with the appearance of structures such as the Castoro VI barge of Saipem and the Apache barge of Santa Fe and the ship Flexservice I. Engineers still have the task of creating deep offshore development systems (water depth. greater than 500 m.

  13. Wave Simulation in Truncated Domains for Offshore Applications

    NARCIS (Netherlands)

    Wellens, P.R.

    2012-01-01

    There is a desire to assess extreme wave loads on offshore structures like Floating Production, Storage and Offloading (FPSO) vessels, either for design, or for evaluation when circumstances near the structure change. Design formulae for extreme wave loads are scarce and

  14. The effect of floating deck structures on underwater radiated noise

    NARCIS (Netherlands)

    Bosschaart, C.; Jansen, H.W.; Jong, C.A.F. de; Basten, T.

    2017-01-01

    A concept for underwater machinery noise mitigation of future civil and military ships is the application of a common deck structure, supporting multiple machines, which is installed on resilient mounts on the ship's foundation structure. TNO is addressing the availability and testing of tools to be

  15. Fresh water generators onboard a floating platform

    International Nuclear Information System (INIS)

    Tewari, P.K.; Verma, R.K.; Misra, B.M.; Sadhulkan, H.K.

    1997-01-01

    A dependable supply of fresh water is essential for any ocean going vessel. The operating and maintenance personnel on offshore platforms and marine structures also require a constant and regular supply of fresh water to meet their essential daily needs. A seawater thermal desalination unit onboard delivers good quality fresh water from seawater. The desalination units developed by Bhabha Atomic Research Centre (BARC) suitable for ocean going vessels and offshore platforms have been discussed. Design considerations of such units with reference to floating platforms and corrosive environments have been presented. The feasibility of coupling a low temperature vacuum evaporation (LTVE) desalination plant suitable for an onboard floating platform to a PHWR nuclear power plant has also been discussed. (author). 1 ref., 3 figs, 2 tabs

  16. Hydrodynamic Excitation Forces on Floating Structures with Finite Displacements

    DEFF Research Database (Denmark)

    Andersen, Morten Thøtt; Nielsen, Søren R. K.

    2015-01-01

    excitation force is solely a function of time, hence the body is fixed in reference to the wave field. In this paper, the instantaneous position of the body is included in the calculation of the excitation force. Even though the displacement of the structure relative to a characteristic wavelength...

  17. Reliability Analysis of Tubular Joints in Offshore Structures

    DEFF Research Database (Denmark)

    Thoft-Christensen, Palle; Sørensen, John Dalsgaard

    1987-01-01

    Reliability analysis of single tubular joints and offshore platforms with tubular joints is" presented. The failure modes considered are yielding, punching, buckling and fatigue failure. Element reliability as well as systems reliability approaches are used and illustrated by several examples....... Finally, optimal design of tubular.joints with reliability constraints is discussed and illustrated by an example....

  18. Probabilistic Fatigue Analysis of Jacket Support Structures for Offshore Wind Turbines Exemplified on Tubular Joints

    OpenAIRE

    Kelma, Sebastian; Schaumann, Peter

    2015-01-01

    The design of offshore wind turbines is usually based on the semi-probabilistic safety concept. Using probabilistic methods, the aim is to find an advanced structural design of OWTs in order to improve safety and reduce costs. The probabilistic design is exemplified on tubular joints of a jacket substructure. Loads and resistance are considered by their respective probability distributions. Time series of loads are generated by fully-coupled numerical simulation of the offshore wind turbine. ...

  19. On the modelling of the dynamics of elastically deformable floating structures

    DEFF Research Database (Denmark)

    Seng, Sopheak; Malenica, Sime; Jensen, Jørgen Juncher

    2015-01-01

    In this paper we are reexamining the dynamic equations of an elastically deformable floating structure to identify and evaluate the contribution from the inertia cross coupling terms which commonly have been neglected due to the assumption of small structural deformation. Numerical experiments...... on two vessels, a flexible barge, and a full scale ultra large container vessel, are designed for revealing the magnitude of errors introduced into the numerical solutions when these inertia cross coupling terms have been ignored. The results shows that in realistic conditions with strong structural...

  20. Offshore code comparison collaboration continuation (OC4), phase I - Results of coupled simulations of an offshore wind turbine with jacket support structure

    DEFF Research Database (Denmark)

    Popko, Wojciech; Vorpahl, Fabian; Zuga, Adam

    2012-01-01

    In this paper, the exemplary results of the IEA Wind Task 30 "Offshore Code Comparison Collaboration Continuation" (OC4) Project - Phase I, focused on the coupled simulation of an offshore wind turbine (OWT) with a jacket support structure, are presented. The focus of this task has been the verif......In this paper, the exemplary results of the IEA Wind Task 30 "Offshore Code Comparison Collaboration Continuation" (OC4) Project - Phase I, focused on the coupled simulation of an offshore wind turbine (OWT) with a jacket support structure, are presented. The focus of this task has been...... the verification of OWT modeling codes through code-to-code comparisons. The discrepancies between the results are shown and the sources of the differences are discussed. The importance of the local dynamics of the structure is depicted in the simulation results. Furthermore, attention is given to aspects...

  1. Historical Population Estimates For Several Fish Species At Offshore Oil and Gas Structures in the US Gulf of Mexico

    Science.gov (United States)

    Gitschlag, G.

    2016-02-01

    Population estimates were calculated for four fish species occurring at offshore oil and gas structures in water depths of 14-32 m off the Louisiana and upper Texas coasts in the US Gulf of Mexico. From 1993-1999 sampling was conducted at eight offshore platforms in conjunction with explosive salvage of the structures. To estimate fish population size prior to detonation of explosives, a fish mark-recapture study was conducted. Fish were captured on rod and reel using assorted hook sizes. Traps were occasionally used to supplement catches. Fish were tagged below the dorsal fin with plastic t-bar tags using tagging guns. Only fish that were alive and in good condition were released. Recapture sampling was conducted after explosives were detonated during salvage operations. Personnel operating from inflatable boats used dip nets to collect all dead fish that floated to the surface. Divers collected representative samples of dead fish that sank to the sea floor. Data provided estimates for red snapper (Lutjanus campechanus), Atlantic spadefish (Chaetodipterus faber), gray triggerfish (Balistes capriscus), and blue runner (Caranx crysos) at one or more of the eight platforms studied. At seven platforms, population size for red snapper was calculated at 503-1,943 with a 95% CI of 478. Abundance estimates for Atlantic spadefish at three platforms ranged from 1,432-1,782 with a 95% CI of 473. At three platforms, population size of gray triggerfish was 63-129 with a 95% CI of 82. Blue runner abundance at one platform was 558. Unlike the other three species which occur close to the platforms, blue runner range widely and recapture of this species was dependent on fish schools being in close proximity to the platform at the time explosives were detonated. Tag recapture was as high as 73% for red snapper at one structure studied.

  2. Experimental study on the response of very large floating structures (VLFS) in wave; Choogata futaishiki kaiyo kozobutsu no harochu oto ni kansuru jikkenteki kenkyu

    Energy Technology Data Exchange (ETDEWEB)

    Ota, M; Ikegami, H; Yamaguchi, Y [Mitsubishi Heavy Industries, Ltd., Tokyo (Japan)

    1997-10-01

    The elastic response of VLFS of 1200m long in wave was studied experimentally using a water tank and integral elastic model of 1/80 scale. As offshore airport, a ultra- thin box type floating structure of 5km long, 1km wide and several meter thick is used, and the effect of elasticity is not negligible for such a structure. The experiment used a water tank of 160m long, 30m wide and 3.1m deep. Supposing a water depth of 20m for real VLFSs, the experiment was carried out mainly in a local shallow water area prepared with a temporary bottom together with that in a deep water area. A simple mooring equipment with a linear spring equivalent to real VLFSs was used. The integral floating model was prepared by not mechanical but welded junction to obtain uniform elasticity. The response in wave showed a complicated 3-D behavior, offering useful data for verification of a behavior estimation method. The response was nearly equal between shallow and deep water areas at the same wave length, and the response amplitude in regular waves was equivalent to the significant amplitude in long and short crested irregular waves. 7 refs., 8 figs., 3 tabs.

  3. Going for the play: Structural interpretation in offshore Congo

    Energy Technology Data Exchange (ETDEWEB)

    Platt, N.; Philip, P. (GECO-PRAKLA Exploration Services, Woking (United Kingdom)); Walter, S. (ARK Geophysics Ltd., Milton Keynes, (United Kingdom))

    1993-01-01

    Looking for new hydrocarbons in frontier areas, geologists and geophysicists use very trick in the book: plate tectonics, magnetic and gravity data, plain old geological horse sense and lots of seismic data. An interpretation team is followed, as they pick their way through a seismic survey shot in offshore Congo, Africa, searching for those areas (the plays) that show the greatest promise. 17 figs., 9 refs.

  4. Second wind in the offshore wind industry

    International Nuclear Information System (INIS)

    Philippe, Edouard; Neyme, Eric; Deboos, Christophe; Villageois, Jean-Remy; Gouverneur, Philippe; Gerard, Bernard; Fournier, Eric; Petrus, Raymond; Lemarquis, David; Dener, Marc; Bivaud, Jean-Pierre; Lemaire, Etienne; Nielsen, Steffen; Lafon, Xavier; Lagandre, Pierre; Nadai, Alain; Pinot de Villechenon, Edouard; Westhues, Markus; Herpers, Frederick; Bisiaux, Christophe; Sperlich, Miriam; Bales, Vincent; Vandenbroeck, Jan; His, Stephane; Derrey, Thierry; Barakat, Georges; Dakyo, Brayima; Carme, Laurent; Petit, Frederic; Ytournel, Sophie; Westhues, Markus; Diller, Armin; Premont, Antoine de; Ruer, Jacques; Lanoe, Frederic; Declercq, Jan; Holmager, Morten; Fidelin, Daniel; Guillet, Jerome; Dudziak, Gregory; Lapierre, Anne; Couturier, Ludovic; Audineau, Jean-Pierre; Rouaix, Eric; De Roeck, Yann-Herve; Quesnel, Louis; Duguet, Benjamin

    2011-06-01

    After several keynote addresses, this publication contains contributions and Power Point presentations proposed during this conference on the development of offshore wind energy. The successive sessions addressed the following issues: the offshore mass production of electricity (examples of Denmark and Belgium, laying and protecting offshore cables), the space, economic and environmental planning (the Danish experience, the role of the Coastal area integrated management, importance of the public debate, so on), the logistics of port infrastructures (simulation tools, example of Bremerhaven, issues related to project management), innovation at the core of industrial strategies (high power wind turbines, the 6 MW Alstom turbine, chain value and innovation in offshore wind energy, the Vertiwing innovating project of a floating wind turbine, a bench test in Charleston, foundations, gravity base structures, the British experience, the Danish experience), the economic and organisational conditions for development, the validation and certification of technologies

  5. Reliability-based assessment of deteriorating ship-shaped offshore structures

    Energy Technology Data Exchange (ETDEWEB)

    Ayala-Uraga, Efren

    2009-11-15

    Floating production, storage and off loading ships, referred to as FPSOs, are hybrid structures in the sense that these vessels are ships being operated as offshore facilities. Production ships or FPSOs constitute an efficient solution for remote oil field locations due to their storage capacity of crude oil. Production ships are either tanker conversions or purpose-built vessels. Most of the applications of production ships are converted ocean-going oil tankers, of different ages, to operate in relatively benign environmental areas. Keeping in mind that merchant ships are usually dry-docked every fifth year for inspection, maintenance and repair (IMR) tasks, they are designed according to a more relaxed safety criteria compared to those normally applied for permanent offshore structures, in which the required IMR activities need to be carried out in-situ as they cannot be easily dry-docked. Moreover, ocean on-going ships may in principle avoid heavy weather conditions, whereas FPSOs are moored to a fixed location and could be exposed to harsher extreme conditions. Additionally, FPSOs are exposed to continuously varying still-water load effects, due to the permanent loading-off loading operations. These fundamental differences are even more important to recognize as most of the existing FPSOs around the globe are built based on converted hulls of oil tankers that have already operated during some years. This issue is particularly relevant for vessels whose service life need to be extended, as the deteriorating agents such as fatigue cracking and corrosion become more important. During the initial design of ship structures, the effects of fatigue and corrosion are accounted for separately. However, as the structure ages, the interaction between these two degrading agents increases, and thus such an interaction needs to be accounted for. Moreover, as the number of cracks in a hull structure increases with time, the likelihood of fracture occurrence in main structural

  6. The effect of corrosion on the structural reliability of steel offshore structures

    International Nuclear Information System (INIS)

    Melchers, Robert E.

    2005-01-01

    This paper considers essential theoretical concepts and data requirements for engineering structural reliability assessment suitable for the estimation of the safety and reliability of corroding ships, offshore structures and pipelines. Such infrastructure operates in a harsh environment. Allowance must be made for structural deterioration since protective measures such as paint coatings, galvanizing or cathodic protection may be ineffective. Reliability analysis requires accurate engineering models for the description and prediction of material corrosion loss and for the maximum depth of pitting. New probability-based models for both these forms of corrosion have been proposed recently and calibrated against a wide range of data. The effects of water velocity and of water pollution are reviewed and compared with recently reported field data for a corrosion at an offshore oil platform. The data interpreted according to the model show good correlation when allowance is made for the season of first immersion and the adverse effects of seawater velocity and of water pollution. An example is given to illustrate the application of reliability analysis to a pipeline subject to pitting corrosion. An important outcome is that good quality estimation of the longer-term probability of loss of structural integrity requires good modelling of the longer-term corrosion behaviour. This is usually associated with anaerobic corrosion. As a result, it cannot be extrapolated from data for short-term corrosion as this is associated with aerobic corrosion conditions

  7. The effect of corrosion on the structural reliability of steel offshore structures

    Energy Technology Data Exchange (ETDEWEB)

    Melchers, Robert E. [Centre for Infrastructure Performance and Reliability, Department of Civil, Surveying and Environmental Engineering, School of Engineering, University of Newcastle, University Drive, Callaghan NSW 2300 (Australia)]. E-mail: rob.melchers@newcastle.edu.au

    2005-10-01

    This paper considers essential theoretical concepts and data requirements for engineering structural reliability assessment suitable for the estimation of the safety and reliability of corroding ships, offshore structures and pipelines. Such infrastructure operates in a harsh environment. Allowance must be made for structural deterioration since protective measures such as paint coatings, galvanizing or cathodic protection may be ineffective. Reliability analysis requires accurate engineering models for the description and prediction of material corrosion loss and for the maximum depth of pitting. New probability-based models for both these forms of corrosion have been proposed recently and calibrated against a wide range of data. The effects of water velocity and of water pollution are reviewed and compared with recently reported field data for a corrosion at an offshore oil platform. The data interpreted according to the model show good correlation when allowance is made for the season of first immersion and the adverse effects of seawater velocity and of water pollution. An example is given to illustrate the application of reliability analysis to a pipeline subject to pitting corrosion. An important outcome is that good quality estimation of the longer-term probability of loss of structural integrity requires good modelling of the longer-term corrosion behaviour. This is usually associated with anaerobic corrosion. As a result, it cannot be extrapolated from data for short-term corrosion as this is associated with aerobic corrosion conditions.

  8. Preliminary design of offshore wind turbine support structures : The importance of proper mode shape estimation

    NARCIS (Netherlands)

    Van der Male, P.

    2013-01-01

    Offshore wind turbines are highly exposed to timevarying loads. For support structures, estimation of the fatigue damage during the lifetime of the structure is an essential design aspect. This already applies for the preliminary design stage. In determining the dynamic amplification in the

  9. Structure of the floating water bridge and water in an electric field.

    Science.gov (United States)

    Skinner, Lawrie B; Benmore, Chris J; Shyam, Badri; Weber, J K R; Parise, John B

    2012-10-09

    The floating water bridge phenomenon is a freestanding rope-shaped connection of pure liquid water, formed under the influence of a high potential difference (approximately 15 kV). Several recent spectroscopic, optical, and neutron scattering studies have suggested that the origin of the bridge is associated with the formation of anisotropic chains of water molecules in the liquid. In this work, high energy X-ray diffraction experiments have been performed on a series of floating water bridges as a function of applied voltage, bridge length, and position within the bridge. The two-dimensional X-ray scattering data showed no direction-dependence, indicating that the bulk water molecules do not exhibit any significant preferred orientation along the electric field. The only structural changes observed were those due to heating, and these effects were found to be the same as for bulk water. These X-ray scattering measurements are supported by molecular dynamics (MD) simulations which were performed under electric fields of 10(6) V/m and 10(9) V/m. Directional structure factor calculations were made from these simulations parallel and perpendicular to the E-field. The 10(6) V/m model showed no significant directional-dependence (anisotropy) in the structure factors. The 10(9) V/m model however, contained molecules aligned by the E-field, and had significant structural anisotropy.

  10. Systematic analysis on mooring systems of floating structures; Futai keiryuho ni kansuru keitoteki kenkyu

    Energy Technology Data Exchange (ETDEWEB)

    Yoshida, K; Suzuki, H; Ide, T [The University of Tokyo, Tokyo (Japan)

    1997-12-31

    Discussed herein are mooring performance requirements of the new types of marine structures now proposed, and characteristic ranges and future expansion potential of the existing mooring systems. The mooring systems studied for floating structures are catenary, single point (multi-leg and single-leg types), fixed structure with fender and tension leg mooring systems. The studied items include extraction of the elements that constitute rigidity of the spring for horizontal mooring, survey on and data collection for each element, determination of element ranges, programs for mooring analysis, assessment of mooring characteristic ranges, and potential development of the characteristic ranges. It is concluded that the existing systems with their current characteristic ranges and future possibility are insufficient for the future marine structures. It is therefore necessary to develop new mooring concepts, instead of expanding the current concepts, in order to meet the mooring performance requirements for the new marine structures. 14 refs., 9 figs., 11 tabs.

  11. Systematic analysis on mooring systems of floating structures; Futai keiryuho ni kansuru keitoteki kenkyu

    Energy Technology Data Exchange (ETDEWEB)

    Yoshida, K.; Suzuki, H.; Ide, T. [The University of Tokyo, Tokyo (Japan)

    1996-12-31

    Discussed herein are mooring performance requirements of the new types of marine structures now proposed, and characteristic ranges and future expansion potential of the existing mooring systems. The mooring systems studied for floating structures are catenary, single point (multi-leg and single-leg types), fixed structure with fender and tension leg mooring systems. The studied items include extraction of the elements that constitute rigidity of the spring for horizontal mooring, survey on and data collection for each element, determination of element ranges, programs for mooring analysis, assessment of mooring characteristic ranges, and potential development of the characteristic ranges. It is concluded that the existing systems with their current characteristic ranges and future possibility are insufficient for the future marine structures. It is therefore necessary to develop new mooring concepts, instead of expanding the current concepts, in order to meet the mooring performance requirements for the new marine structures. 14 refs., 9 figs., 11 tabs.

  12. Structural health monitoring tools for late and end of life management of offshore wind turbines

    DEFF Research Database (Denmark)

    McGugan, Malcolm; McKirdy, Scott

    2016-01-01

    The late and end of life stages in an offshore wind turbines (OWT) life cycle have unique features that must be considered. The initial focus on risks associated with start-up issues due to design, manufacturing or process elements gives way to a stable period of operation and maintenance...... margins and the predominance of low redundancy structures, accurate structural health monitoring can play a strong role in safe management and enable increased operating time at end of life and decommissioning. Late life operations of offshore wind farms can pose significant challenges, balancing...

  13. Natural Frequency and Damping Estimation of an Offshore Wind Turbine Structure

    DEFF Research Database (Denmark)

    Damgaard, Mads; Andersen, Jacob K. F.; Ibsen, Lars Bo

    2012-01-01

    During the last years, offshore wind turbines have increased significantly in size with larger rotors and more powerful generators. The costs are kept as low as possible by reducing the overall weight, which leads to very slender and flexible structures. An improper design may cause resonance due...... of an offshore wind turbine located in the North Sea. Simple Fourier Transformation and least square fitting to the vibration decay of ten “rotor stop” tests make it possible to evaluate the dynamic properties of the wind turbine structure. Based on the traditionally p-y curve method (Winkler type approach...

  14. FAST Model Calibration and Validation of the OC5-DeepCwind Floating Offshore Wind System Against Wave Tank Test Data

    Energy Technology Data Exchange (ETDEWEB)

    Wendt, Fabian F [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Robertson, Amy N [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Jonkman, Jason [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

    2017-06-03

    During the course of the Offshore Code Comparison Collaboration, Continued, with Correlation (OC5) project, which focused on the validation of numerical methods through comparison against tank test data, the authors created a numerical FAST model of the 1:50-scale DeepCwind semisubmersible system that was tested at the Maritime Research Institute Netherlands ocean basin in 2013. This paper discusses several model calibration studies that were conducted to identify model adjustments that improve the agreement between the numerical simulations and the experimental test data. These calibration studies cover wind-field-specific parameters (coherence, turbulence), hydrodynamic and aerodynamic modeling approaches, as well as rotor model (blade-pitch and blade-mass imbalances) and tower model (structural tower damping coefficient) adjustments. These calibration studies were conducted based on relatively simple calibration load cases (wave only/wind only). The agreement between the final FAST model and experimental measurements is then assessed based on more-complex combined wind and wave validation cases.

  15. FAST Model Calibration and Validation of the OC5- DeepCwind Floating Offshore Wind System Against Wave Tank Test Data: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Wendt, Fabian F [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Robertson, Amy N [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Jonkman, Jason [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

    2017-08-09

    During the course of the Offshore Code Comparison Collaboration, Continued, with Correlation (OC5) project, which focused on the validation of numerical methods through comparison against tank test data, the authors created a numerical FAST model of the 1:50-scale DeepCwind semisubmersible system that was tested at the Maritime Research Institute Netherlands ocean basin in 2013. This paper discusses several model calibration studies that were conducted to identify model adjustments that improve the agreement between the numerical simulations and the experimental test data. These calibration studies cover wind-field-specific parameters (coherence, turbulence), hydrodynamic and aerodynamic modeling approaches, as well as rotor model (blade-pitch and blade-mass imbalances) and tower model (structural tower damping coefficient) adjustments. These calibration studies were conducted based on relatively simple calibration load cases (wave only/wind only). The agreement between the final FAST model and experimental measurements is then assessed based on more-complex combined wind and wave validation cases.

  16. Integrity management of offshore structures and its implication on computation of structural action effects and resistance

    Science.gov (United States)

    Moan, T.

    2017-12-01

    An overview of integrity management of offshore structures, with emphasis on the oil and gas energy sector, is given. Based on relevant accident experiences and means to control the associated risks, accidents are categorized from a technical-physical as well as human and organizational point of view. Structural risk relates to extreme actions as well as structural degradation. Risk mitigation measures, including adequate design criteria, inspection, repair and maintenance as well as quality assurance and control of engineering processes, are briefly outlined. The current status of risk and reliability methodology to aid decisions in the integrity management is briefly reviewed. Finally, the need to balance the uncertainties in data, methods and computational efforts and the cautious use and quality assurance and control in applying high fidelity methods to avoid human errors, is emphasized, and with a plea to develop both high fidelity as well as efficient, simplified methods for design.

  17. Petrological and geochemical Highlights in the floating fragments of the October 2011 submarine eruption offshore El Hierro (Canary Islands): Relevance of submarine hydrothermal processes

    Science.gov (United States)

    Rodriguez-Losada, Jose A.; Eff-Darwich, Antonio; Hernandez, Luis E.; Viñas, Ronaldo; Pérez, Nemesio; Hernandez, Pedro; Melián, Gladys; Martinez-Frías, Jesús; Romero-Ruiz, M. Carmen; Coello-Bravo, Juan Jesús

    2015-02-01

    This paper describes the main physical, petrological and geochemical features of the floating fragments that were emitted in the initial stages of the 2011-2012 submarine eruption off the coast of the Canarian island of El Hierro, located 380 km from the Northwest African Coast. It attempts to assess the potential of radiometric analyses to discern the intriguing origin of the floating fragments and the differences between their constituent parts. In this regard, the material that conforms the core of the fragments contains the largest concentration of uranium (U) ever found in volcanic rocks of the Canary Islands. This enrichment in U is not found in the content of thorium (Th), hence the floating fragments have an unusual U/Th ratio, namely equal to or larger than 3. Although the origin of this material is under discussion, it is proposed that the enrichment in U is the result of hydrothermal processes.

  18. Hywind floating wind turbine project

    Energy Technology Data Exchange (ETDEWEB)

    Crome, Tim

    2010-07-01

    The Hywind floating wind turbine concept was developed by StatoilHydro. Technip was awarded the contract for engineering, fabrication and installation of a demonstration unit in May 2008 and the completed wind turbine was installed mid June 2009 at the west coast of Norway on 220 m water depth. The demonstration unit will generate 2,3 MW and is equipped with instrumentation for monitoring mooring forces, strains and motions. The fabrication of the SPAR type steel substructure was performed at Technip Offshore Finland facilities in Pori and was towed horizontally from Finland to Norway, where it was upended to a vertical position by water filling. The completed floating wind turbine was towed vertically to the final location west of Karmoey and connected to the pre-installed three legged anchor system using an Anchor Handling Tug type vessel. The wind turbine test period is scheduled to start in September 2009. Statoil will monitor the performance of the system for two years before decision will be taken for further development. The paper will present the main challenges and lessons learned through design, fabrication and installation of this first of its kind structure. Main emphasis will be on the special challenges experienced for this floating, catenary moored, slender unit which is highly exposed for wind induced forces in addition to current and waves in hostile North Sea environments. (Author)

  19. Dynamic analysis of a 5-MW tripod offshore wind turbine by considering fluid-structure interaction

    Science.gov (United States)

    Zhang, Li-wei; Li, Xin

    2017-10-01

    Fixed offshore wind turbines usually have large underwater supporting structures. The fluid influences the dynamic characteristics of the structure system. The dynamic model of a 5-MW tripod offshore wind turbine considering the pile-soil system and fluid structure interaction (FSI) is established, and the structural modes in air and in water are obtained by use of ANSYS. By comparing low-order natural frequencies and mode shapes, the influence of sea water on the free vibration characteristics of offshore wind turbine is analyzed. On basis of the above work, seismic responses under excitation by El-Centro waves are calculated by the time-history analysis method. The results reveal that the dynamic responses such as the lateral displacement of the foundation and the section bending moment of the tubular piles increase substantially under the influence of the added-mass and hydrodynamic pressure of sea water. The method and conclusions presented in this paper can provide a theoretical reference for structure design and analysis of offshore wind turbines fixed in deep seawater.

  20. Design of Offshore Wind Turbine Support Structures: Selected topics in the field of geotechnical engineering

    DEFF Research Database (Denmark)

    Bakmar, Christian LeBlanc

    .D. thesis was to enable low-cost and low-risk support structures to be designed in order to improve the economic feasibility of future offshore wind farms. The research work was divided in the following four selected research topics in the field of geotechnical engineering, relating to the monopile......Breaking the dependence on fossil fuels offers many opportunities for strengthened competitiveness, technological development and progress. Offshore wind power is a domestic, sustainable and largely untapped energy resource that provides an alternative to fossil fuels, reduces carbon emissions......, and decreases the economic and supply risks associated with reliance on imported fuels. Today, the modern offshore wind turbine offers competitive production prices for renewable energy and is therefore a key technology in achieving the energy and climate goals of the future. The overall aim of this Ph...

  1. Offshoring medium‐skill tasks, low‐skill unemployment and the skill‐wage structure

    NARCIS (Netherlands)

    Vallizadeh, Ehssan; Muysken, Joan; Ziesemer, Thomas

    2016-01-01

    This paper studies the direct and indirect channels through which offshoring affects the domestic skillwage structure and employment opportunities. To identify these channels, we develop a task-based model with unemployment that accounts for skill heterogeneity and endogenous allocation of domestic

  2. Reliability-Based Optimal Design of Experiment Plans for Offshore Structures

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Faber, Michael Havbro; Kroon, I. B.

    1993-01-01

    Design of cost optimal experiment plans on the basis of a preposterior analysis is discussed. In particular the planning of on-site response measurements on offshore structures in order to update probabilistic models for fatigue life estimation is addressed. Special emphasis is given to modelling...

  3. A Coupled VOF-Eulerian Multiphase CFD Model to Simulate Breaking Wave Impacts on Offshore Structures

    DEFF Research Database (Denmark)

    Tomaselli, Pietro; Christensen, Erik Damgaard

    2016-01-01

    Breaking wave-induced loads on offshore structures can be extremely severe. The air entrainment mechanism during the breaking process plays a not well-known role in the exerted forces. This paper present a CFD solver, developed in the Open-FOAM environment, capable of simulating the wave breaking...

  4. Stress analysis of partial sphere used for bottom shell of off-shore structure

    International Nuclear Information System (INIS)

    Nishimaki, Ko; Matsumoto, Kohei; Hori, Tohru; Takeshita, Haruyuki; Iwata, Setsuo

    1976-01-01

    In the near future, various huge off-shore structures will be constructed. Concrete shall become a leading material in the structures, owing to its versatile properties. One of the limitations of concrete is its low tensile strength. The problem of low tensile strength of concrete is dealt with in main by two different methods: by applying prestressing and by designing the structural configuration so that no tensile stresses appear. In the paper, the authors discuss the application of partially spherical shell to huge off-shore structures. Structural analysis by using the finite element method were done in order to investigate the feasibility of the structure. The results were arranged as to certain parameters to derive design charts by which the stresses of check points can be presumed. Optimum shape is also discussed. (auth.)

  5. Floating wind turbine system

    Science.gov (United States)

    Viterna, Larry A. (Inventor)

    2009-01-01

    A floating wind turbine system with a tower structure that includes at least one stability arm extending therefrom and that is anchored to the sea floor with a rotatable position retention device that facilitates deep water installations. Variable buoyancy for the wind turbine system is provided by buoyancy chambers that are integral to the tower itself as well as the stability arm. Pumps are included for adjusting the buoyancy as an aid in system transport, installation, repair and removal. The wind turbine rotor is located downwind of the tower structure to allow the wind turbine to follow the wind direction without an active yaw drive system. The support tower and stability arm structure is designed to balance tension in the tether with buoyancy, gravity and wind forces in such a way that the top of the support tower leans downwind, providing a large clearance between the support tower and the rotor blade tips. This large clearance facilitates the use of articulated rotor hubs to reduced damaging structural dynamic loads. Major components of the turbine can be assembled at the shore and transported to an offshore installation site.

  6. Moving loads on flexible structures presented in the floating frame of reference formulation

    Energy Technology Data Exchange (ETDEWEB)

    Hartweg, Stefan, E-mail: stefan.hartweg@web.de; Heckmann, Andreas, E-mail: andreas.heckmann@dlr.de [German Aerospace Center (DLR), Institute of System Dynamics and Control (Germany)

    2016-06-15

    The introduction of moving loads in the Floating Frame of Reference Formulation is presented. We derive the kinematics and governing equations of motion of a general flexible multibody system and their extension to moving loads. The equivalence of convective effects with Coriolis and centripetal forces is shown. These effects are measured numerically and their significance in moving loads traveling at high speed is confirmed. A method is presented to handle discontinuities when moving loads separate from the flexible structure. The method is extended from beam models to general flexible structures obtained by means of the Finite Element Method. An interpolation method for the deformation field of the modal representation of these bodies is introduced.The work is concluded by application of the method to modern mechanical problems in numerical simulations.

  7. 近海风电机结构动力响应极值预报%Prediction of Structural Dynamic Response Extreme Values of Offshore Wind Turbine

    Institute of Scientific and Technical Information of China (English)

    王立夫

    2017-01-01

    鉴于国内外在预报风浪共同作用下近海风电机的极限结构动力响应方面仍然面临挑战的现状,提出用最小二乘法高效精确地求解广义柏拉图分布中的待定参数,预报某5 MW漂浮式风电机塔筒平台接合处的前后向弯矩极值,并用蒙特卡罗仿真和诊断图证明了最小二乘法与传统的矩方法相比的优越性.可为浮式海上风电机的结构设计提供参考.%Due to the fact that it is still a challenge at both home and abroad on how to predict the extreme structural dynamic responses of an offshore wind turbine under the con current action of wind and waves,the method of least squares is used to more efficiently and accurately estimate the unknown parameters in the Generalized Pareto distribution so that the extreme values of the fore-aft bending moments at the tower-Spar interface of a 5 MW floating wind turbine are predicted.Monte Carlo simulation and diagnostic plots are used to test the advantages of the method of least squares over the traditional method of moments.The new method proposed will become a powerful tool for the people in their structural design of a floating offshore wind turbine.

  8. Statistical Evaluation of the Identified Structural Parameters of an idling Offshore Wind Turbine

    International Nuclear Information System (INIS)

    Kramers, Hendrik C.; Van der Valk, Paul L.C.; Van Wingerden, Jan-Willem

    2016-01-01

    With the increased need for renewable energy, new offshore wind farms are being developed at an unprecedented scale. However, as the costs of offshore wind energy are still too high, design optimization and new innovations are required for lowering its cost. The design of modern day offshore wind turbines relies on numerical models for estimating ultimate and fatigue loads of the turbines. The dynamic behavior and the resulting structural loading of the turbines is determined for a large part by its structural properties, such as the natural frequencies and damping ratios. Hence, it is important to obtain accurate estimates of these modal properties. For this purpose stochastic subspace identification (SSI), in combination with clustering and statistical evaluation methods, is used to obtain the variance of the identified modal properties of an installed 3.6MW offshore wind turbine in idling conditions. It is found that one is able to obtain confidence intervals for the means of eigenfrequencies and damping ratios of the fore-aft and side-side modes of the wind turbine. (paper)

  9. Evaluation on the effect of tsunami and seaquake on the floating structure; Tsunami kaishin no futai ni taisuru eikyo hyoka

    Energy Technology Data Exchange (ETDEWEB)

    Yoshida, K; Suzuki, H; Hosomi, I [The University of Tokyo, Tokyo (Japan); Nahata, H [The Long-Term Credit Bank of Japan, Ltd., Tokyo (Japan)

    1997-12-31

    The effects of tsunami and seaquake on large floating structures are theoretically studied, where these effects are followed in terms of local strength using the equation proposed by Sells to predict surface shapes changed by seaquake-caused uplift of the seabottom. The equation is combined with the one for tsunami propagation, to better predict the tsunami motion. The simulation results indicate the necessity of considering the effects of tsunami for the design of a large floating structure. The authors discuss that the effect of tsunami is minimized when a floating structure is set at a depth of at least 40 to 50m, chain length should be determined by equalizing the breaking weight with the load at which the structure starts to move, and a structure should be set at a position where it is not attacked by transverse waves. They also discuss that seaquake intensity should be predicted by the equation of motion of compressible fluid, and, noting local strength of a floating structure, it will not be damaged when it is at least 16mm thick under the conditions of 2m as seabottom uplift and 0.5m as draft depth. 15 refs., 9 figs., 2 tabs.

  10. Evaluation on the effect of tsunami and seaquake on the floating structure; Tsunami kaishin no futai ni taisuru eikyo hyoka

    Energy Technology Data Exchange (ETDEWEB)

    Yoshida, K.; Suzuki, H.; Hosomi, I. [The University of Tokyo, Tokyo (Japan); Nahata, H. [The Long-Term Credit Bank of Japan, Ltd., Tokyo (Japan)

    1996-12-31

    The effects of tsunami and seaquake on large floating structures are theoretically studied, where these effects are followed in terms of local strength using the equation proposed by Sells to predict surface shapes changed by seaquake-caused uplift of the seabottom. The equation is combined with the one for tsunami propagation, to better predict the tsunami motion. The simulation results indicate the necessity of considering the effects of tsunami for the design of a large floating structure. The authors discuss that the effect of tsunami is minimized when a floating structure is set at a depth of at least 40 to 50m, chain length should be determined by equalizing the breaking weight with the load at which the structure starts to move, and a structure should be set at a position where it is not attacked by transverse waves. They also discuss that seaquake intensity should be predicted by the equation of motion of compressible fluid, and, noting local strength of a floating structure, it will not be damaged when it is at least 16mm thick under the conditions of 2m as seabottom uplift and 0.5m as draft depth. 15 refs., 9 figs., 2 tabs.

  11. Optimization of offshore wind turbine support structures using analytical gradient-based method

    OpenAIRE

    Chew, Kok Hon; Tai, Kang; Ng, E.Y.K.; Muskulus, Michael

    2015-01-01

    Design optimization of the offshore wind turbine support structure is an expensive task; due to the highly-constrained, non-convex and non-linear nature of the design problem. This report presents an analytical gradient-based method to solve this problem in an efficient and effective way. The design sensitivities of the objective and constraint functions are evaluated analytically while the optimization of the structure is performed, subject to sizing, eigenfrequency, extreme load an...

  12. A comparison of extreme structural responses and fatigue damage of semi-submersible type floating horizontal and vertical axis wind turbines

    DEFF Research Database (Denmark)

    Cheng, Zhengshun; Aagaard Madsen, Helge; Chai, Wei

    2017-01-01

    •A comprehensive comparison of floating HAWTs and VAWTs with different blade number.•Extreme structural responses and fatigue damage are studied.•Both operational and parked conditions are considered.•The merits and disadvantages of floating HAWTs and VAWTs are revealed and highlighted.......•A comprehensive comparison of floating HAWTs and VAWTs with different blade number.•Extreme structural responses and fatigue damage are studied.•Both operational and parked conditions are considered.•The merits and disadvantages of floating HAWTs and VAWTs are revealed and highlighted....

  13. Stress state reassessment of Romanian offshore structures taking into account corrosion influence

    Science.gov (United States)

    Joavină, R.; Zăgan, S.; Zăgan, R.; Popa, M.

    2017-08-01

    Progressive degradation analysis for extraction or exploration offshore structure, with appraisal of failure potential and the causes that can be correlated with the service age, depends on the various sources of uncertainty that require particular attention in design, construction and exploitation phases. Romanian self erecting platforms are spatial lattice structures consist of tubular steel joints, forming a continuous system with an infinite number of dynamic degrees of freedom. Reassessment of a structure at fixed intervals of time, recorrelation of initial design elements with the actual situation encountered in location and with structural behaviour represents a major asset in lowering vulnerabilities of offshore structure. This paper proposes a comparative reassessment of the stress state for an offshore structure Gloria type, when leaving the shipyard and at the end of that interval corresponding to capital revision, taking into account sectional changes due to marine environment corrosion. The calculation was done using Newmark integration method on a 3D model, asses of the dynamic loads was made through probabilistic spectral method.

  14. Numerical Analysis of a Large Floating Wave Energy Converter with Adjustable Structural Geometry

    DEFF Research Database (Denmark)

    Ferri, Francesco; Pecher, Arthur Francois Serge; Kofoed, Jens Peter

    2015-01-01

    by the structural loads in extreme conditions. TheWeptos is a large floating WEC, with multiple absorbers, which has proven to be a serious candidate for the renewable energy market, due to both relevant power performance and reduced cost if compared with other WECs. The scope of this article is to compare two......The current cost of energy (CoE) from wave energy converters (WECs) is still significantly higher than other renewable energy resources, thus the sector has not yet reached a competitive level. WECs have a relative small turnover compared to the high capital cost, which to a large extent is driven...... different configurations of the Weptos machine, using the cost of energy (CoE) as a base of comparison. The numerical results are obtained via a multi-body analysis carried out in frequency domain....

  15. Ultra-Low Power Consuming Direct Radiation Sensors Based on Floating Gate Structures

    Directory of Open Access Journals (Sweden)

    Evgeny Pikhay

    2017-07-01

    Full Text Available In this paper, we report on ultra-low power consuming single poly floating gate direct radiation sensors. The developed devices are intended for total ionizing dose (TID measurements and fabricated in a standard CMOS process flow. Sensor design and operation is discussed in detail. Original array sensors were suggested and fabricated that allowed high statistical significance of the radiation measurements and radiation imaging functions. Single sensors and array sensors were analyzed in combination with the specially developed test structures. This allowed insight into the physics of sensor operations and exclusion of the phenomena related to material degradation under irradiation in the interpretation of the measurement results. Response of the developed sensors to various sources of ionizing radiation (Gamma, X-ray, UV, energetic ions was investigated. The optimal design of sensor for implementation in dosimetry systems was suggested. The roadmap for future improvement of sensor performance is suggested.

  16. Optimal Control of a Ballast-Stabilized Floating Wind Turbine

    DEFF Research Database (Denmark)

    Christiansen, Søren; Knudsen, Torben; Bak, Thomas

    2011-01-01

    Offshore wind energy capitalizes on the higher and less turbulent wind speeds at sea. The use of floating structures for deeper waters is being explored. The control objective is a tradeoff between power capture and fatigue, especially that produced by the oscillations caused by the reduced...... structural stiffness of a floating installation in combination with a coupling between the fore–aft motion of the tower and the blade pitch. To address this problem, the present paper models a ballast-stabilized floating wind turbine, and suggests a linear quadratic regulator (LQR) in combination with a wind...... estimator and a state observer. The results are simulated using aero elastic code and analysed in terms of damage equivalent loads. When compared to a baseline controller, this controller clearly demonstrates better generator speed and power tracking while reducing fatigue loads....

  17. Determination of current loads of floating platform for special purposes

    Science.gov (United States)

    Ma, Guang-ying; Yao, Yun-long; Zhao, Chen-yao

    2017-08-01

    This article studied a new floating offshore platform for special purposes, which was assembled by standard floating modules. The environmental load calculation of the platform is an important part of the research of the ocean platform, which has always been paid attention to by engineers. In addition to wave loads, the wind loads and current loads are also important environmental factors that affect the dynamic response of the offshore platform. The current loads on the bottom structure should not be ignored. By Fluent software, the hydrostatic conditions and external current loads of the platform were calculated in this paper. The coefficient which is independent of the current velocity, namely, current force coefficient, can be fitted through current loads, which can be used for the consequent hydrodynamic and mooring analyses.

  18. Reliability analysis of offshore structures using OMA based fatigue stresses

    DEFF Research Database (Denmark)

    Silva Nabuco, Bruna; Aissani, Amina; Glindtvad Tarpø, Marius

    2017-01-01

    focus is on the uncertainty observed on the different stresses used to predict the damage. This uncertainty can be reduced by Modal Based Fatigue Monitoring which is a technique based on continuously measuring of the accelerations in few points of the structure with the use of accelerometers known...... points of the structure, the stress history can be calculated in any arbitrary point of the structure. The accuracy of the estimated actual stress is analyzed by experimental tests on a scale model where the obtained stresses are compared to strain gauges measurements. After evaluating the fatigue...... stresses directly from the operational response of the structure, a reliability analysis is performed in order to estimate the reliability of using Modal Based Fatigue Monitoring for long term fatigue studies....

  19. Calculation for Hull Strength Construction in Offshore Structures

    African Journals Online (AJOL)

    PROF. O. E. OSUAGWU

    2013-09-01

    Sep 1, 2013 ... of hull plating, reinforcing stiffeners, girders, and other structures. This paper therefore used the .... From these equations we derive that. Safety of. Factor. Stress ..... machineries, systems etc. of the ships or barge under design.

  20. Evaluating stress analysis and failure criteria for offshore structures for Pechora Sea conditions

    Science.gov (United States)

    Nesic, S.; Donskoy, Y.; Zolotukhin, A.

    2017-12-01

    Development of Arctic hydrocarbon resources has faced many challenges due to sensitive environmental conditions including low temperatures, ice cover and terrestrial permafrost and extreme seasonal variation in sunlight. Russian offshore field development in Arctic region is usually associated with annual ice cover, which can cause serious damage on the offshore platforms. The Pechora Sea has claimed as one of the most perspective oil and gas region of the Russian Arctic with seven discovered oil and gas fields and several dozens of structures. Our rough assessment, based on in-place hydrocarbon volumes and recovery factor evaluation concept, indicates that Pechora Sea alone has in-place volumes amounting to ca. 20 billion barrel oil equivalent (BOE). This quantity is enough to secure produced volumes by 2040 exceeding 3 billion BOE [1] that indicates huge resource potential of the region. The environmental conditions are primarily function of water dynamics and ice cover. The sea is covered by the ice for greatest part of the year. In this article, the ice load simulations were performed using explicit dynamic analysis system in ANSYS software to determine best shape and size of an offshore platform for the Pechora Sea ice conditions. Different gravity based structures (GBS) were analyzed: artificial island, hollow cylindrical and conical concrete structures and four-leg GBS. Relationships between the stress, deformations and time were analyzed and important observations from the simulation results were a basis for selecting the most preferable structures.

  1. An investigation on fatigue in high-strength steel offshore structures

    DEFF Research Database (Denmark)

    Agerskov, Henning; Petersen, R.I.; Martinez, L. Lopez

    1998-01-01

    of the investigation, fatigue test series were carried out on both full scale tubular joints and smaller welded plate test specimens in high-strength steel as well as in conventional offshore structural steel. This paper gives a summary of the main results presented in two recent research reports [15, 16], from...... these investigations. A comparison between constant amplitude and variable amplitude fatigue test results shows shorter fatigue lives in variable amplitude loading than should be expected from the linear fatigue damage accumulation formula.Furthermore, in general longer fatigue lives were obtained for the test...... specimens in high-strength steel than those obtained in corresponding tests on joints in conventional offshore structural steel....

  2. An Investigation on Fatigue in High-Strength Steel Offshore Structures

    DEFF Research Database (Denmark)

    Agerskov, Henning; Petersen, R.I.; Lopez Martinez, L.

    1997-01-01

    . In the experimental part of the investigation, fatigue test series have been carried through on both full-scale tubular joints and smaller welded plate test specimens, in high-strength steel as well as in conventional offshore structural steel. The present document gives a summary of the main results presented in two...... recent research reports, Refs. 15 and 16, from these investigations.A comparison between constant amplitude and variable amplitude fatigue test results shows shorter fatigue lives in variable amplitude loading than should be expected from the linear fatigue damage accumulation formula. Furthermore......, in general longer fatigue lives were obtained for the test specimens in high-strength steel than those obtained in corresponding tests on joints in conventional offshore structural steel....

  3. A CAD model for energy efficient offshore structures for desalination and energy generation

    Directory of Open Access Journals (Sweden)

    R. Rahul Dev,

    2016-09-01

    Full Text Available This paper presents a ‘Computer Aided Design (CAD’ model for energy efficient design of offshore structures. In the CAD model preliminary dimensions and geometric details of an offshore structure (i.e. semi-submersible are optimized to achieve a favorable range of motion to reduce the energy consumed by the ‘Dynamic Position System (DPS’. The presented model allows the designer to select the configuration satisfying the user requirements and integration of Computer Aided Design (CAD and Computational Fluid Dynamics (CFD. The integration of CAD with CFD computes a hydrodynamically and energy efficient hull form. Our results show that the implementation of the present model results into an design that can serve the user specified requirements with less cost and energy consumption.

  4. Vertical structure of turbulence in offshore flow during RASEX

    DEFF Research Database (Denmark)

    Mahrt, L.; Vickers, D.; Edson, J.

    2001-01-01

    and dissipation. However, weakly stable and weakly unstable cases exhibit completely different vertical structure. With flow of warm air from land over cooler water, modest buoyancy destruction of turbulence and reduced shear generation of turbulence over the less rough sea surface cause the turbulence to rapidly...... with height and downward transport of turbulence energy toward the surface. With flow of cool air over a warmer sea surface, a convective internal boundary layer develops downstream from the coast. An overlying relatively thick layer of downward buoyancy flux (virtual temperature flux) is sometimes maintained...

  5. Position control of a floating nuclear power plant

    International Nuclear Information System (INIS)

    Motohashi, K.; Hamamoto, T.; Sasaki, R.; Kojima, M.

    1993-01-01

    In spite of the increasing demand of electricity in Japan, the sites of nuclear power plants suitable for conventional seismic regulations become severely limited. Under these circumstances, several types of advanced siting technology have been developed. Among them, floating power plants have a great advantage of seismic isolation that leads to the seismic design standardization and factory fabrication. The feasibility studies or preliminary designs of floating power plants enclosed by breakwaters in the shallow sea have been carried out last two decades in U.S. and Japan. On the other hand, there are few investigations on the dynamic behavior of floating power plants in the deep sea. The offshore floating nuclear power plants have an additional advantage in that large breakwaters are not required, although the safety checking is inevitable against wind-induced waves. The tension-leg platforms which have been constructed for oil drilling in the deep sea seem to be a promising offshore siting technology of nuclear power plants. The tension-leg mooring system can considerably restrain the heave and pitch of a floating power plant because of significant stiffness in the vertical direction. Different from seismic effects, wind-induced waves may be predicted in advance by making use of ocean weather forecasts using artificial satellites. According to the wave prediction, the position of the floating plant may be controlled by adjusting the water content in ballast tanks and the length of tension-legs before the expected load arrives. The position control system can reduce the wave force acting on the plant and to avoid the unfavorable response behavior of the plant. In this study a semi-submerged circular cylinder with tension-legs is considered as a mathematical model. The configuration of circular cylinder is effective because the dynamic behavior does not depend on incident wave directions. It is also unique in that it can obtain the closed-form solution of

  6. Offshore atomic power plants

    International Nuclear Information System (INIS)

    Anon.

    1975-01-01

    Various merits of offshore atomic power plants are illustrated, and their systems are assessed. The planning of the offshore atomic power plants in USA is reviewed, and the construction costs of the offshore plant in Japan were estimated. Air pollution problem may be solved by the offshore atomic power plants remarkably. Deep water at low temperature may be advantageously used as cooling water for condensers. Marine resources may be bred by building artificial habitats and by providing spring-up equipments. In the case of floating plants, the plant design can be standardized so that the construction costs may be reduced. The offshore plants can be classified into three systems, namely artificial island system, floating system and sea bottom-based system. The island system may be realized with the present level of civil engineering, but requires the development of technology for the resistance of base against earthquake and its calculation means. The floating system may be constructed with conventional power plant engineering and shipbuilding engineering, but the aseismatic stability of breakwater may be a problem to be solved. Deep water floating system and deep water submerging system are conceivable, but its realization may be difficult. The sea bottom-based system with large caissons can be realized by the present civil engineering, but the construction of the caissons, stability against earthquake and resistance to waves may be problems to be solved. The technical prediction and assessment of new plant sites for nuclear power plants have been reported by Science and Technology Agency in 1974. The construction costs of an offshore plant has been estimated by the Ministry of International Trade and Industry to be yen71,026/kW as of 1985. (Iwakiri, K.)

  7. Sizing of a spar-type floating support structure for DeepWind

    DEFF Research Database (Denmark)

    Schmidt Paulsen, Uwe

    The work describes is a revised work based on the Report RISOE-2614(EN)[1], which originally was carried out for Statoil. The company showed large interest in the VAWT technology for offshore application and expressed the concept of the creation of ideas within offshore (VAWT). Statoil provided...

  8. Structural Optimization of an Offshore Wind Turbines Transition Pieces for Bucket Foundations

    DEFF Research Database (Denmark)

    Nezhentseva, Anastasia; Andersen, Lars Vabbersgaard; Ibsen, Lars Bo

    Traditionally, offshore constructions are made of steel. The focus of this paper is optimization of a transition piece (TP) connecting the offshore wind turbine column with a suction bucket foundation. Suction caissons, typically used for shallow water depths, have been proved to be adequate...... in residual soil conditions for depths up to approximately 40 m. The existing design practice is limited to the use of steel-flange-reinforced shear panels. Desirable outcome is proposal of an alternative material which does not require extensive welding work. Compact reinforced composite (CRC) is suggested...... curved segments have been introduced between the conical part and the tubular parts of the structure. While the minimum amount of steel and concrete was required for the composite CRC–steel shell model, the pure CRC model appeared to be the least sensitive to geometrical imperfections, corresponding...

  9. Experimental Research on the Dynamic Response of Floating Structures with Coatings Subjected to Underwater Explosion

    Directory of Open Access Journals (Sweden)

    Feng Xiao

    2014-01-01

    Full Text Available This paper presents an experimental investigation into the dynamic response of three free floating stiffened metal boxes with protective coatings subjected to underwater explosion (UNDEX. One box was kept intact while the other two were, respectively, covered with monolithic coatings and chiral honeycomb coatings. Three groups of live fire tests with different attack angles and stand-off distances were conducted. The acceleration on the stiffener and strain peak on the bottom hull were selected as the major comparative criterions. Test results show that the impulse transmitted to the structure at the initial stage can be reduced, owing to the coating flexibility and fluid-structure interaction mechanism. Consequently, the acceleration peaks induced by both shock wave and bubble pulse were reduced. The shock environment can be more effectively improved by honeycomb coating when compared with monolithic coating. Most of the strain peaks decreased to a certain extent, but some of them were notably manifested, especially for honeycomb coating. The test affirms the fact that soft coating can cause stress concentration on the shell that is in direct contact with the coating due to the impedance mismatch between the interfaces of materials. A softer rubber coating induces a greater magnitude of strain.

  10. Resolving plate structure across the seismogenic zone in Cascadia from onshore-offshore receiver function imaging

    Science.gov (United States)

    Audet, P.; Schaeffer, A. J.

    2017-12-01

    Studies of the forearc structure in the Cascadia subduction zone using teleseismic P-wave receiver function have resolved structures associated with deep fluid cycling, such as the basalt-to-eclogite reaction and fluid overpressure within the subducting oceanic crust, as well as the serpentinization of the forearc mantle wedge. Unfortunately, the updip extent of the over-pressured zone, and therefore the possible control on the transition from episodic slow slip to seismic slip, occurs offshore and is not resolved in those studies. The Cascadia Initiative (CI) has provided an opportunity to extend this work to the locked zone using teleseismic receiver functions from the deployment of a dense line of ocean-bottom seismograph stations offshore of Washington State, from the trench to the coastline. Here we calculate P-wave receiver functions using data from offshore (CI) and onshore (CAFE) broadband seismic stations. These data clearly show the various scattered phases associated with a dipping low-velocity layer that was identified in previous studies as the downgoing oceanic crust. These signals are difficult to untangle offshore because they arrive at similar times. We process receiver functions using a modified common-conversion point (CCP) stacking technique that uses a coherency filter to optimally stack images obtained from the three main scattered phases. The resulting image shows along-dip variations in the character of the seismic discontinuities associated with the top and bottom of the low-velocity layer. Combined with focal depth information of regular and low-frequency earthquakes, these variations may reflect changes in the material properties of the megathrust across the seismogenic zone in Cascadia.

  11. Lake Michigan Offshore Wind Feasibility Assessment

    Energy Technology Data Exchange (ETDEWEB)

    Boezaart, Arnold [GVSU; Edmonson, James [GVSU; Standridge, Charles [GVSU; Pervez, Nahid [GVSU; Desai, Neel [University of Michigan; Williams, Bruce [University of Delaware; Clark, Aaron [GVSU; Zeitler, David [GVSU; Kendall, Scott [GVSU; Biddanda, Bopi [GVSU; Steinman, Alan [GVSU; Klatt, Brian [Michigan State University; Gehring, J. L. [Michigan State University; Walter, K. [Michigan State University; Nordman, Erik E. [GVSU

    2014-06-30

    project including to: 1) test and validate floating LIDAR technology; 2) collect and access offshore wind data; 3) detect and measure bird and bat activity over Lake Michigan; 4) conduct an over water sound propagation study; 5) prepare and offer a college course on offshore energy, and; 6) collect other environmental, bathometric, and atmospheric data. Desk-top research was performed to select anchorage sites and to secure permits to deploy the buoy. The project also collected and analyzed data essential to wind industry investment decision-making including: deploying highly mobile floating equipment to gather offshore wind data; correlating offshore wind data with conventional on-shore MET tower data; and performing studies that can contribute to the advancement and deployment of offshore wind technologies. Related activities included: • Siting, permitting, and deploying an offshore floating MET facility; • Validating the accuracy of floating LWS using near shoreline cup anemometer MET instruments; • Assessment of laser pulse technology (LIDAR) capability to establish hub height measurement of wind conditions at multiple locations on Lake Michigan; • Utilizing an extended-season (9-10 month) strategy to collect hub height wind data and weather conditions on Lake Michigan; • Investigation of technology best suited for wireless data transmission from distant offshore structures; • Conducting field-validated sound propagation study for a hypothetical offshore wind farm from shoreline locations; • Identifying the presence or absence of bird and bat species near wind assessment facilities; • Identifying the presence or absence of benthic and pelagic species near wind assessment facilities; All proposed project activities were completed with the following major findings: • Floating Laser Wind Sensors are capable of high quality measurement and recordings of wind resources. The WindSentinel presented no significant operational or statistical limitations in

  12. The Seismic Reliability of Offshore Structures Based on Nonlinear Time History Analyses

    International Nuclear Information System (INIS)

    Hosseini, Mahmood; Karimiyani, Somayyeh; Ghafooripour, Amin; Jabbarzadeh, Mohammad Javad

    2008-01-01

    Regarding the past earthquakes damages to offshore structures, as vital structures in the oil and gas industries, it is important that their seismic design is performed by very high reliability. Accepting the Nonlinear Time History Analyses (NLTHA) as the most reliable seismic analysis method, in this paper an offshore platform of jacket type with the height of 304 feet, having a deck of 96 feet by 94 feet, and weighing 290 million pounds has been studied. At first, some Push-Over Analyses (POA) have been preformed to recognize the more critical members of the jacket, based on the range of their plastic deformations. Then NLTHA have been performed by using the 3-components accelerograms of 100 earthquakes, covering a wide range of frequency content, and normalized to three Peak Ground Acceleration (PGA) levels of 0.3 g, 0.65 g, and 1.0 g. By using the results of NLTHA the damage and rupture probabilities of critical member have been studied to assess the reliability of the jacket structure. Regarding that different structural members of the jacket have different effects on the stability of the platform, an ''importance factor'' has been considered for each critical member based on its location and orientation in the structure, and then the reliability of the whole structure has been obtained by combining the reliability of the critical members, each having its specific importance factor

  13. Time domain calculation of connector loads of a very large floating structure

    Science.gov (United States)

    Gu, Jiayang; Wu, Jie; Qi, Enrong; Guan, Yifeng; Yuan, Yubo

    2015-06-01

    Loads generated after an air crash, ship collision, and other accidents may destroy very large floating structures (VLFSs) and create additional connector loads. In this study, the combined effects of ship collision and wave loads are considered to establish motion differential equations for a multi-body VLFS. A time domain calculation method is proposed to calculate the connector load of the VLFS in waves. The Longuet-Higgins model is employed to simulate the stochastic wave load. Fluid force and hydrodynamic coefficient are obtained with DNV Sesam software. The motion differential equation is calculated by applying the time domain method when the frequency domain hydrodynamic coefficient is converted into the memory function of the motion differential equation of the time domain. As a result of the combined action of wave and impact loads, high-frequency oscillation is observed in the time history curve of the connector load. At wave directions of 0° and 75°, the regularities of the time history curves of the connector loads in different directions are similar and the connector loads of C1 and C2 in the X direction are the largest. The oscillation load is observed in the connector in the Y direction at a wave direction of 75° and not at 0°. This paper presents a time domain calculation method of connector load to provide a certain reference function for the future development of Chinese VLFS

  14. Offshore wind energy developments

    DEFF Research Database (Denmark)

    Stolpe, Mathias; Buhl, Thomas; Sumer, B. Mutlu

    2014-01-01

    This chapter will give a brief overview of a few of the activities within offshore wind energy research, specifically 1) Support structure optimization, 2) Blade coatings for wind turbines; 3) Scour protection of foundations, 4) Offshore HVDC and 5) Offshore wind services....

  15. Micromechanisms with floating pivot

    Science.gov (United States)

    Garcia, Ernest J.

    2001-03-06

    A new class of tilting micromechanical mechanisms have been developed. These new mechanisms use floating pivot structures to relieve some of the problems encountered in the use of solid flexible pivots.

  16. Corrosion Protection Systems and Fatigue Corrosion in Offshore Wind Structures: Current Status and Future Perspectives

    Directory of Open Access Journals (Sweden)

    Seth J. Price

    2017-02-01

    Full Text Available Concerns over reducing CO2 emissions associated with the burning of fossil fuels in combination with an increase in worldwide energy demands is leading to increased development of renewable energies such as wind. The installation of offshore wind power structures (OWS is one of the most promising approaches for the production of renewable energy. However, corrosion and fatigue damage in marine and offshore environments are major causes of primary steel strength degradation in OWS. Corrosion can reduce the thickness of structural components which may lead towards fatigue crack initiation and buckling. These failure mechanisms affect tower service life and may result in catastrophic structural failure. Additionally, environmental pollution stemming from corrosion’s by-products is possible. As a result, large financial investments are made yearly for both the prevention and recovery of these drawbacks. The corrosion rate of an OWS is dependent on different characteristics of attack which are influenced by access to oxygen and humidity. Structural degradation can occur due to chemical attack, abrasive action of waves, and microorganism attacks. Inspired by technological and scientific advances in recent years, the purpose of this paper is to discuss the current protective coating system technologies used to protect OWS as well as future perspectives.

  17. Optimised and balanced structural and system reliability of offshore wind turbines. An account

    Energy Technology Data Exchange (ETDEWEB)

    Tarp-Johansen, N.J.; Kozine, I. (Risoe National Lab., DTU, Roskilde, (DK)); Rademarkers, L. (Netherlands Energy Research Foundation (NL)); Dalsgaard Soerensen, J. (Aalborg Univ. (DK)) Ronold, K. (Det Norske Veritas (DK))

    2005-04-15

    This report gives the results of the research project 'Optimised and Uniform Safety and Reliability of Offshore Wind Turbines (an account)'. The main subject of the project has been the account of the state-of-the art of knowledge about, and/or attempts to, harmonisation of the structural reliability of wind turbines, on the one hand, and the reliability of the wind turbine's control/safety system, on the other hand. Within the project some research pointing ahead has also been conducted. (au)

  18. Critical Factors Analysis for Offshore Software Development Success by Structural Equation Modeling

    Science.gov (United States)

    Wada, Yoshihisa; Tsuji, Hiroshi

    In order to analyze the success/failure factors in offshore software development service by the structural equation modeling, this paper proposes to follow two approaches together; domain knowledge based heuristic analysis and factor analysis based rational analysis. The former works for generating and verifying of hypothesis to find factors and causalities. The latter works for verifying factors introduced by theory to build the model without heuristics. Following the proposed combined approaches for the responses from skilled project managers of the questionnaire, this paper found that the vendor property has high causality for the success compared to software property and project property.

  19. An Introduction to Operational Modal Identification of Offshore Wind Turbine Structures

    DEFF Research Database (Denmark)

    Damgaard, Mads

    excitation originating from the rotating rotor and broadband excitation from air turbulence is present, which sets limitations on the applicability of operational modal analysis to wind turbine structures. The technical memorandum contains an introduction to the theory within experimental modal analysis and......The present technical memorandum “An Introduction to Operational Modal Identification of Offshore Wind Turbine Structures” is prepared in connection with an ongoing Ph.D study at Aalborg University. The memorandum is intended for use in the civil engineering field and may serve as an inspiration...

  20. Wind turbine structural dynamics - a review of the principles for modern power generation, onshore and offshore

    Energy Technology Data Exchange (ETDEWEB)

    Tempel, J. van der; Molenaar, D.-P.

    2002-07-01

    Wind turbines for electricity production have two seemingly opposing constraints; they need to be structural secure yet of low cost. To meet the first constraint, it would be an obvious choice to design a stiff structure of consequently large mass but this would drive up the cost. By reducing the mass a more cost effective turbine can be realized. However, such lightweight structures are by definition more flexible. To design a cost effective flexible system, thorough understanding of the dynamics is essential. This paper reviews the theoretical basics of the dynamic design options and applies these to realistic situations, including offshore machines under wave action. The wind energy converter and the support structure form an integrated dynamic system that must be developed in mutual interdependency and close co-operation. This paper provides a contribution to this integration process by extending the design approach initiated in the Opti-OW ECS study and the work of Kuhn. (author)

  1. Visual analysis of uncertainties in ocean forecasts for planning and operation of off-shore structures

    KAUST Repository

    Hollt, Thomas; Magdy, Ahmed; Chen, Guoning; Gopalakrishnan, Ganesh; Hoteit, Ibrahim; Hansen, Charles D.; Hadwiger, Markus

    2013-01-01

    We present a novel integrated visualization system that enables interactive visual analysis of ensemble simulations used in ocean forecasting, i.e, simulations of sea surface elevation. Our system enables the interactive planning of both the placement and operation of off-shore structures. We illustrate this using a real-world simulation of the Gulf of Mexico. Off-shore structures, such as those used for oil exploration, are vulnerable to hazards caused by strong loop currents. The oil and gas industry therefore relies on accurate ocean forecasting systems for planning their operations. Nowadays, these forecasts are based on multiple spatio-temporal simulations resulting in multidimensional, multivariate and multivalued data, so-called ensemble data. Changes in sea surface elevation are a good indicator for the movement of loop current eddies, and our visualization approach enables their interactive exploration and analysis. We enable analysis of the spatial domain, for planning the placement of structures, as well as detailed exploration of the temporal evolution at any chosen position, for the prediction of critical ocean states that require the shutdown of rig operations. © 2013 IEEE.

  2. Visual analysis of uncertainties in ocean forecasts for planning and operation of off-shore structures

    KAUST Repository

    Hollt, Thomas

    2013-02-01

    We present a novel integrated visualization system that enables interactive visual analysis of ensemble simulations used in ocean forecasting, i.e, simulations of sea surface elevation. Our system enables the interactive planning of both the placement and operation of off-shore structures. We illustrate this using a real-world simulation of the Gulf of Mexico. Off-shore structures, such as those used for oil exploration, are vulnerable to hazards caused by strong loop currents. The oil and gas industry therefore relies on accurate ocean forecasting systems for planning their operations. Nowadays, these forecasts are based on multiple spatio-temporal simulations resulting in multidimensional, multivariate and multivalued data, so-called ensemble data. Changes in sea surface elevation are a good indicator for the movement of loop current eddies, and our visualization approach enables their interactive exploration and analysis. We enable analysis of the spatial domain, for planning the placement of structures, as well as detailed exploration of the temporal evolution at any chosen position, for the prediction of critical ocean states that require the shutdown of rig operations. © 2013 IEEE.

  3. Risk Assessment Method for Offshore Structure Based on Global Sensitivity Analysis

    Directory of Open Access Journals (Sweden)

    Zou Tao

    2012-01-01

    Full Text Available Based on global sensitivity analysis (GSA, this paper proposes a new risk assessment method for an offshore structure design. This method quantifies all the significances among random variables and their parameters at first. And by comparing the degree of importance, all minor factors would be negligible. Then, the global uncertainty analysis work would be simplified. Global uncertainty analysis (GUA is an effective way to study the complexity and randomness of natural events. Since field measured data and statistical results often have inevitable errors and uncertainties which lead to inaccurate prediction and analysis, the risk in the design stage of offshore structures caused by uncertainties in environmental loads, sea level, and marine corrosion must be taken into account. In this paper, the multivariate compound extreme value distribution model (MCEVD is applied to predict the extreme sea state of wave, current, and wind. The maximum structural stress and deformation of a Jacket platform are analyzed and compared with different design standards. The calculation result sufficiently demonstrates the new risk assessment method’s rationality and security.

  4. Response characteristics of a long life type floating offshore airport in waves. 3rd Report. Response due to short waves and an attempt of active inclination control; Chojumyogata futaishiki kaijo kuko no harochu oto tokusei. Tanhachoiki no oto oyobi shisei seigyo no kokoromi

    Energy Technology Data Exchange (ETDEWEB)

    Hirayama, T.; Ma, N.; Nishio, O.; Sato, N. [Yokohama National University, Yokohama (Japan). Faculty of Engineering

    1996-12-31

    Notice was given on response characteristics in a short wavelength range of a large floating structure for an offshore airport consisting of semi-submersible replaceable type units, and influence of unit lacking. An attempt was also made on performing restoration of inclination change during unit lacking and suppression of long-cycle variation in waves by using air pressure control. The result of a numerical calculation based on a three-dimensional singular point method may be summarized as follows: mass force added vertically on columns in short wavelength range differs in the outer edges and the central part; relatively uniform values are shown in the central part; and interactive interference is recognized in wave forces in the vertical direction, but the influence therefrom decreases as the wave length decreases. Calculations on vertical movements and bending moments in waves were performed by using a mode synthesizing method. The calculations used fluid force which was calculated based on the three-dimensional singular point method utilizing symmetry with respect to each condition for a complete model plus unit lacking and unit lacking plus inclination control. As a result of verifying the calculations by using an experiment, relatively good agreement was achieved in either case. A high-frequency vibration experiment made clear the characteristics of elastic response in the short-wave length range. 14 refs., 14 figs.

  5. FLOAT Project

    DEFF Research Database (Denmark)

    Sørensen, Eigil V.; Aarup, Bendt

    The objective of the FLOAT project is to study the reliability of high-performance fibre-reinforced concrete, also known as Compact Reinforced Composite (CRC), for the floats of wave energy converters. In order to reach a commercial breakthrough, wave energy converters need to achieve a lower price...

  6. Analysis of the Nonlinear Static and Dynamic Behavior of Offshore Structures

    KAUST Repository

    Alfosail, Feras

    2015-01-01

    Understanding static and dynamic nonlinear behavior of pipes and risers is crucial for the design aspects in offshore engineering fields. In this work, we examine two nonlinear problems in offshore engineering field: vortex Induced vibration

  7. Impulse Based Substructuring for Coupling Offshore Structures and Wind Turbines in Aero-Elastic Simulations

    NARCIS (Netherlands)

    Van der Valk, P.L.C.; Rixen, D.J.

    2012-01-01

    In order to achieve the goal of 20% renewable energy in 2020, as set by the European Union, large offshore wind farms are either under construction or in development through-out Europe. As many of the "easy" locations are already under development, offshore wind farms are moving further offshore

  8. Offshore windfarms and their impact on fish abundance and community structure

    DEFF Research Database (Denmark)

    Stenberg, Claus; Dinesen, Grete E.; Deurs, Mikael van

    2012-01-01

    Deployment of offshore windfarms (OWF) is rapidly expanding. A before–after control impact (BACI) approach was used to study the impact of one of the world’s largest offshore windfarms (Horns Rev Offshore Windfarm) on fish assemblages and species diversity. Fish were generally more abundant in th...

  9. Aspects of structural health and condition monitoring of offshore wind turbines.

    Science.gov (United States)

    Antoniadou, I; Dervilis, N; Papatheou, E; Maguire, A E; Worden, K

    2015-02-28

    Wind power has expanded significantly over the past years, although reliability of wind turbine systems, especially of offshore wind turbines, has been many times unsatisfactory in the past. Wind turbine failures are equivalent to crucial financial losses. Therefore, creating and applying strategies that improve the reliability of their components is important for a successful implementation of such systems. Structural health monitoring (SHM) addresses these problems through the monitoring of parameters indicative of the state of the structure examined. Condition monitoring (CM), on the other hand, can be seen as a specialized area of the SHM community that aims at damage detection of, particularly, rotating machinery. The paper is divided into two parts: in the first part, advanced signal processing and machine learning methods are discussed for SHM and CM on wind turbine gearbox and blade damage detection examples. In the second part, an initial exploration of supervisor control and data acquisition systems data of an offshore wind farm is presented, and data-driven approaches are proposed for detecting abnormal behaviour of wind turbines. It is shown that the advanced signal processing methods discussed are effective and that it is important to adopt these SHM strategies in the wind energy sector.

  10. Aspects of structural health and condition monitoring of offshore wind turbines

    Science.gov (United States)

    Antoniadou, I.; Dervilis, N.; Papatheou, E.; Maguire, A. E.; Worden, K.

    2015-01-01

    Wind power has expanded significantly over the past years, although reliability of wind turbine systems, especially of offshore wind turbines, has been many times unsatisfactory in the past. Wind turbine failures are equivalent to crucial financial losses. Therefore, creating and applying strategies that improve the reliability of their components is important for a successful implementation of such systems. Structural health monitoring (SHM) addresses these problems through the monitoring of parameters indicative of the state of the structure examined. Condition monitoring (CM), on the other hand, can be seen as a specialized area of the SHM community that aims at damage detection of, particularly, rotating machinery. The paper is divided into two parts: in the first part, advanced signal processing and machine learning methods are discussed for SHM and CM on wind turbine gearbox and blade damage detection examples. In the second part, an initial exploration of supervisor control and data acquisition systems data of an offshore wind farm is presented, and data-driven approaches are proposed for detecting abnormal behaviour of wind turbines. It is shown that the advanced signal processing methods discussed are effective and that it is important to adopt these SHM strategies in the wind energy sector. PMID:25583864

  11. Domain structures of LiNbO3 crystals grown by a floating zone technique

    International Nuclear Information System (INIS)

    Kawakami, Shoji; Ishii, Eiichi; Tsuzuki, Akihiro; Sekiya, Tadashi; Torii, Yasuyoshi; Takahashi, Akio.

    1986-01-01

    LiNbO 3 single crystals were grown from the congruently melting composition by a floating zone technique. It was confirmed by etching that the single domain crystals were produced without applying any external electric field. When annealed above the Curie temperature, antiparallel domain appeared in the form of annual rings. (author)

  12. Turbomachinery systems for floating production applications

    Energy Technology Data Exchange (ETDEWEB)

    Windt, Jonathan P.; Kurz, Rainer [Solar Turbines Incorporated, San Diego, CA (United States)

    2008-07-01

    Since 1995 there has been a dramatic increase in oil and gas exploration and production using floating platforms in deeper waters located further offshore. This exploration started with tension leg platforms, progressed through SPARs and Semi-Submersibles, and later evolved into Floating Production Storage and Offloading (FPSO) vessels. Turbomachinery equipment installed on a floating platform or vessel will be expected to operate in the same manner as a land based machine, but in a variety of climate and environmental conditions that now includes motion. To operate successfully, specific design considerations for the turbo-machinery packages are required. It is critical to take into account the type of vessel, the expected list, trim and dynamic motion angles, the dynamic forces applied, the expected deck deflection as a result of those forces, understand the applicable class requirement, and where the equipment will be located on the vessel. This information is then translated into the design conditions to determine the type of mounting method to be used to attach the turbo-machinery package to the deck, the expected accelerations for structural analysis, and oil tank and system designs for fluid management. Furthermore, compressor designs need to allow utmost flexibility to adapt to changing operating conditions. (author)

  13. On the prediction of hydroelastic behaviors of a huge floating structure in waves. 2nd Report; Choogata futai no harochu dansei kyodo no suiteiho ni tsuite

    Energy Technology Data Exchange (ETDEWEB)

    Murai, M.; Kagemoto, H.; Fujino, M. [The University of Tokyo, Tokyo (Japan)

    1997-08-01

    On the hydroelastic behaviors of a huge floating structure, a mutual interaction theory based on the area division method is used for the analysis of a fluid problem and a mode analysis method is used for the analysis of deformation. On the continuous deformation of a floating structure, the structure is considered as a set of partial structures obtained when the plane shape was divided into squares and discretely handled as a series of rigid motions in the small partial structures obtained by dividing the partial structures more finely. The experimental result in a water tank and the distribution method at a singular point were compared on the deformation of the elastic floating structure estimated by calculation based on this formulation. The result showed that the estimation method on the hydroelastic problem proposed in this paper is valid. On the prediction of hydroelastic behaviors of a huge floating structure, various calculation examples indicate that the hydroelastic behavior is not only the relation between the structure length and wavelength, but also that the bending rigidity of a structure is a very important factor. For a huge floating structure in the 5,000 m class, up to shorter wavelength of about {lambda}/L = 1/100 must be investigated. 6 refs., 14 figs., 5 tabs.

  14. Soil-Structure Interaction for Non-Slender, Large-Diameter Offshore Monopiles

    DEFF Research Database (Denmark)

    Sørensen, Søren Peder Hyldal

    Offshore wind power is a domestic, sustainable and largely untapped energy resource. Today, the modern offshore wind turbine offers competitive production prices compared to other sources of renewable energy. Therefore, it is a key technology in breaking the dependence on fossil fuels...... and in achieving the energy and climate goals of the future. For offshore wind turbines, the costs of foundation typically constitute 20-30% of the total costs. Hence, improved methods for the design of foundations for offshore wind turbines can increase the competitiveness of offshore wind energy significantly....... The monopile foundation concept has been employed as the foundation for the majority of the currently installed offshore wind turbines. Therefore, this PhD thesis concerns the soil-pile interaction for non-slender, large-diameter offshore piles. A combination of numerical and physical modelling has been...

  15. Damping Wind and Wave Loads on a Floating Wind Turbine

    DEFF Research Database (Denmark)

    Christiansen, Søren; Bak, Thomas; Knudsen, Torben

    2013-01-01

    Offshore wind energy capitalizes on the higher and less turbulent wind speeds at sea. To enable deployment of wind turbines in deep-water locations, structures are being explored, where wind turbines are placed on a floating platform. This combined structure presents a new control problem, due......, and we show the influence that both wind speed, wave frequencies and misalignment between wind and waves have on the system dynamics. A new control model is derived that extends standard turbine models to include the hydrodynamics, additional platform degrees of freedom, the platform mooring system...

  16. Review of potential impacts to sea turtles from underwater explosive removal of offshore structures

    International Nuclear Information System (INIS)

    Viada, Stephen T.; Hammer, Richard M.; Racca, Roberto; Hannay, David; Thompson, M. John; Balcom, Brian J.; Phillips, Neal W.

    2008-01-01

    The purpose of this study was to collect and synthesize existing information relevant to the explosive removal of offshore structures (EROS) in aquatic environments. Data sources were organized and summarized by topic - explosive removal methods, physics of underwater explosions, sea turtle resources, documented impacts to sea turtles, and mitigation of effects. Information was gathered via electronic database searches and literature source review. Bulk explosive charges are the most commonly used technique in EROS. While the physical principles of underwater detonations and the propagation of pressure and acoustic waves are well understood, there are significant gaps in the application of this knowledge. Impacts to sea turtles from explosive removal operations may range from non-injurious effects (e.g. acoustic annoyance; mild tactile detection or physical discomfort) to varying levels of injury (i.e. non-lethal and lethal injuries). Very little information exists regarding the impacts of underwater explosions on sea turtles. Effects of explosions on turtles often must be inferred from documented effects to other vertebrates with lungs or other gas-containing organs, such as mammals and most fishes. However, a cautious approach should be used when determining impacts to sea turtles based on extrapolations from other vertebrates. The discovery of beached sea turtles and bottlenose dolphins following an explosive platform removal event in 1986 prompted the initiation of formal consultation between the U.S. Department of the Interior, Minerals Management Service (MMS) and the National Marine Fisheries Service (NMFS), authorized through the Endangered Species Act Section 7, to determine a mechanism to minimize potential impacts to listed species. The initial consultation resulted in a requirement for oil and gas companies to obtain a permit (through separate consultations on a case-by-case basis) prior to using explosives in Federal waters. Because many offshore

  17. Risk assessment by integrating interpretive structural modeling and Bayesian network, case of offshore pipeline project

    International Nuclear Information System (INIS)

    Wu, Wei-Shing; Yang, Chen-Feng; Chang, Jung-Chuan; Château, Pierre-Alexandre; Chang, Yang-Chi

    2015-01-01

    The sound development of marine resource usage relies on a strong maritime engineering industry. The perilous marine environment poses the highest risk to all maritime work. It is therefore imperative to reduce the risk associated with maritime work by using some analytical methods other than engineering techniques. This study addresses this issue by using an integrated interpretive structure modeling (ISM) and Bayesian network (BN) approach in a risk assessment context. Mitigating or managing maritime risk relies primarily on domain expert experience and knowledge. ISM can be used to incorporate expert knowledge in a systematic manner and helps to impose order and direction on complex relationships that exist among system elements. Working with experts, this research used ISM to clearly specify an engineering risk factor relationship represented by a cause–effect diagram, which forms the structure of the BN. The expert subjective judgments were further transformed into a prior and conditional probability set to be embedded in the BN. We used the BN to evaluate the risks of two offshore pipeline projects in Taiwan. The results indicated that the BN can provide explicit risk information to support better project management. - Highlights: • We adopt an integrated method for risk assessment of offshore pipeline projects. • We conduct semi-structural interview with the experts for risk factor identification. • Interpretive structural modeling helps to form the digraph of Bayesian network (BN) • We perform the risk analysis with the experts by building a BN. • Risk evaluations of two case studies using the BN show effectiveness of the methods

  18. Differences in plankton community structure and carbon cycling along a climate gradient from the Greenland Ice Sheet to offshore waters

    DEFF Research Database (Denmark)

    Arendt, K.E.; Nielsen, Torkel Gissel; Rysgaard, S.

    Huge differences in plankton community structures and biomasses are observed along a climate gradient from the Greenland Ice Sheet to offshore waters at the West Greenland coast. The offshore region has a high biomass of copepods dominated by Calanus spp., which are capable of consuming 55....... Protozooplankton accounts for 20-38% of the carbon turnover in the offshore and inland areas. However, protozooplankton like copepods has low ability to turn over the primary production close to the Ice Sheet. Increased run of from the Greenland Ice Sheet due to global warming could displace the existing climate...... gradient. This would have a profound influence on the future plankton community structure as well as the energy transfer to higher trophic levels in Arctic coastal ecosystems....

  19. Time-Domain Three Dimensional BE-FE Method for Transient Response of Floating Structures Under Unsteady Loads

    Directory of Open Access Journals (Sweden)

    R. E. S. Ismail

    Full Text Available Abstract This paper presents a direct time-domain three dimensional (3D numerical procedure to simulate the transient response of very large floating structures (VLFS subjected to unsteady external loads as well as moving mass. The proposed procedure employs the Boundary Element and Finite Element methods (FEM-BEM. The floating structure and the surrounding fluid are discretized by 4-node isoparametric finite elements (FE and by 4-node constant boundary elements (BE, respectively. Structural analysis is based on Mindlin's plate theory. The equation of motion is constructed taking into account the effect of inertia loading due to the moving mass. In order to obtain the hydrodynamic forces (added mass and radiation damping, the coupled natural frequencies are first obtained by an iterative method, since hydrodynamic forces become frequency-dependent. Then the Newark integration method is employed to solve the equation of motion for structural system. In order to prove the validity of the present method, a FORTRAN program is developed and numerical examples are carried out to compare its results with those of published experimental results of a scale model of VLFS under a weight drop and airplane landing and takeoff in still water condition. The comparisons show very good agreement.

  20. Managing Information Uncertainty in Wave Height Modeling for the Offshore Structural Analysis through Random Set

    Directory of Open Access Journals (Sweden)

    Keqin Yan

    2017-01-01

    Full Text Available This chapter presents a reliability study for an offshore jacket structure with emphasis on the features of nonconventional modeling. Firstly, a random set model is formulated for modeling the random waves in an ocean site. Then, a jacket structure is investigated in a pushover analysis to identify the critical wave direction and key structural elements. This is based on the ultimate base shear strength. The selected probabilistic models are adopted for the important structural members and the wave direction is specified in the weakest direction of the structure for a conservative safety analysis. The wave height model is processed in a P-box format when it is used in the numerical analysis. The models are applied to find the bounds of the failure probabilities for the jacket structure. The propagation of this wave model to the uncertainty in results is investigated in both an interval analysis and Monte Carlo simulation. The results are compared in context of information content and numerical accuracy. Further, the failure probability bounds are compared with the conventional probabilistic approach.

  1. Effective Method for Determining Environmental Loads on Supporting Structures for Offshore Wind Turbines

    Directory of Open Access Journals (Sweden)

    Dymarski Paweł

    2016-01-01

    Full Text Available This paper presents a description of an effective method for determining loads due to waves and current acting on the supporting structures of the offshore wind turbines. This method is dedicated to the structures consisting of the cylindrical or conical elements as well as (truncates pyramids of polygon with a large number of sides (8 or more. The presented computational method is based on the Morison equation, which was originally developed only for cylindrically shaped structures. The new algorithm shown here uses the coefficients of inertia and drag forces that were calculated for non-cylindrical shapes. The analysed structure consists of segments which are truncated pyramids on the basis of a hex decagon. The inertia coefficients, CM, and drag coefficients, CD, were determined using RANSE-CFD calculations. The CFD simulations were performed for a specific range of variation of the period, and for a certain range of amplitudes of the velocity. In addition, the analysis of influence of the surface roughness on the inertia and drag coefficients was performed. In the next step, the computations of sea wave, current and wind load on supporting structure for the fifty-year storm were carried out. The simulations were performed in the time domain and as a result the function of forces distribution along the construction elements was obtained. The most unfavourable distribution of forces will be used, to analyse the strength of the structure, as the design load.

  2. Identification of support structure damping of a full scale offshore wind turbine in normal operation

    DEFF Research Database (Denmark)

    Koukoura, Christina; Natarajan, Anand; Vesth, Allan

    2015-01-01

    damping from the decaying time series. The Enhanced Frequency Domain Decomposition (EFDD) method was applied to the wind turbine response under ambient excitation, for estimation of the damping in normal operation. The aero-servo-hydro-elastic tool HAWC2 is validated with offshore foundation load...... maxima of an impulse response caused by a boat impact. The result is used in the verification of the non aerodynamic damping in normal operation for low wind speeds. The auto-correlation function technique for damping estimation of a structure under ambient excitation was validated against the identified...... measurements. The model was tuned to the damping values obtained from the boat impact to match the measured loads. Wind turbulence intensity and wave characteristics used in the simulations are based on site measurements. A flexible soil model is included in the analysis. The importance of the correctly...

  3. One-Way Fluid-Structure Interaction Simulation of an Offshore Wind Turbine

    Directory of Open Access Journals (Sweden)

    Zhi-Kui Wang

    2014-07-01

    Full Text Available The Fluid-Structure Interaction (FSI has gained great interest of scholars recently, meanwhile, extensive studies have been conducted by the virtue of numerical methods which have been implemented on wind turbine models. The blades of a wind turbine have been gained a deep insight into the FSI analyses, however, few studies have been conducted on the tower and nacelle, which are key components of the wind turbine, using this method. We performed the one-way FSI analysis on a 2-MW offshore wind turbine, using the Finite Volume Method (FVM with ANSYS CFX solver and the RNG k-ε turbulence model, to achieve a comprehensive cognition of it. The grid convergence was studied and verified in this study, and the torque value is chosen to determine the optimal case. The superior case, which was chosen to conduct the FSI analysis, with a relative error is only 2.15%, thus, the accuracy of results is credible.

  4. Analysis of offshore platforms lifting with fixed pile structure type (fixed platform) based on ASD89

    Science.gov (United States)

    Sugianto, Agus; Indriani, Andi Marini

    2017-11-01

    Platform construction GTS (Gathering Testing Sattelite) is offshore construction platform with fix pile structure type/fixed platform functioning to support the mining of petroleum exploitation. After construction fabrication process platform was moved to barges, then shipped to the installation site. Moving process is generally done by pull or push based on construction design determined when planning. But at the time of lifting equipment/cranes available in the work area then the moving process can be done by lifting so that moving activity can be implemented more quickly of work. This analysis moving process of GTS platform in a different way that is generally done to GTS platform types by lifting using problem is construction reinforcement required, so the construction can be moved by lifting with analyzing and checking structure working stress that occurs due to construction moving process by lifting AISC code standard and analysis using the SAP2000 structure analysis program. The analysis result showed that existing condition cannot be moved by lifting because stress ratio is above maximum allowable value that is 0.950 (AISC-ASD89). Overstress occurs on the member 295 and 324 with stress ratio value 0.97 and 0.95 so that it is required structural reinforcement. Box plate aplication at both members so that it produces stress ratio values 0.78 at the member 295 and stress ratio of 0.77 at the member 324. These results indicate that the construction have qualified structural reinforcement for being moved by lifting.

  5. Multiple tuned mass damper based vibration mitigation of offshore wind turbine considering soil-structure interaction

    Science.gov (United States)

    Hussan, Mosaruf; Sharmin, Faria; Kim, Dookie

    2017-08-01

    The dynamics of jacket supported offshore wind turbine (OWT) in earthquake environment is one of the progressing focuses in the renewable energy field. Soil-structure interaction (SSI) is a fundamental principle to analyze stability and safety of the structure. This study focuses on the performance of the multiple tuned mass damper (MTMD) in minimizing the dynamic responses of the structures objected to seismic loads combined with static wind and wave loads. Response surface methodology (RSM) has been applied to design the MTMD parameters. The analyses have been performed under two different boundary conditions: fixed base (without SSI) and flexible base (with SSI). Two vibration modes of the structure have been suppressed by multi-mode vibration control principle in both cases. The effectiveness of the MTMD in reducing the dynamic response of the structure is presented. The dynamic SSI plays an important role in the seismic behavior of the jacket supported OWT, especially resting on the soft soil deposit. Finally, it shows that excluding the SSI effect could be the reason of overestimating the MTMD performance.

  6. WindFloat Pacific Project, Final Scientific and Technical Report

    Energy Technology Data Exchange (ETDEWEB)

    Banister, Kevin [Principle Power, Inc., Emeryville, CA (United States)

    2017-01-17

    PPI’s WindFloat Pacific project (WFP) was an up to 30 MW floating offshore wind demonstration project proposed off the Coast of Oregon. The project was to be sited approximately 18 miles due west of Coos Bay, in over 1000 ft. of water, and is the first floating offshore wind array proposed in the United States, and the first offshore wind project of any kind proposed off the West Coast. PPI’s WindFloat, a semi-submersible foundation designed for high-capacity (6MW+) offshore wind turbines, is at the heart of the proposed project, and enables access to the world class wind resource at the project site and, equally, to other deep water, high wind resource areas around the country.

  7. 1:50 Scale Testing of Three Floating Wind Turbines at MARIN and Numerical Model Validation Against Test Data

    Energy Technology Data Exchange (ETDEWEB)

    Dagher, Habib [Univ. of Maine, Orno, ME (United States); Viselli, Anthony [Univ. of Maine, Orno, ME (United States); Goupee, Andrew [Univ. of Maine, Orno, ME (United States); Allen, Christopher [Univ. of Maine, Orno, ME (United States)

    2017-08-15

    The primary goal of the basin model test program discussed herein is to properly scale and accurately capture physical data of the rigid body motions, accelerations and loads for different floating wind turbine platform technologies. The intended use for this data is for performing comparisons with predictions from various aero-hydro-servo-elastic floating wind turbine simulators for calibration and validation. Of particular interest is validating the floating offshore wind turbine simulation capabilities of NREL’s FAST open-source simulation tool. Once the validation process is complete, coupled simulators such as FAST can be used with a much greater degree of confidence in design processes for commercial development of floating offshore wind turbines. The test program subsequently described in this report was performed at MARIN (Maritime Research Institute Netherlands) in Wageningen, the Netherlands. The models considered consisted of the horizontal axis, NREL 5 MW Reference Wind Turbine (Jonkman et al., 2009) with a flexible tower affixed atop three distinct platforms: a tension leg platform (TLP), a spar-buoy modeled after the OC3 Hywind (Jonkman, 2010) and a semi-submersible. The three generic platform designs were intended to cover the spectrum of currently investigated concepts, each based on proven floating offshore structure technology. The models were tested under Froude scale wind and wave loads. The high-quality wind environments, unique to these tests, were realized in the offshore basin via a novel wind machine which exhibits negligible swirl and low turbulence intensity in the flow field. Recorded data from the floating wind turbine models included rotor torque and position, tower top and base forces and moments, mooring line tensions, six-axis platform motions and accelerations at key locations on the nacelle, tower, and platform. A large number of tests were performed ranging from simple free-decay tests to complex operating conditions with

  8. Large Eddy Simulation of Flows Associated with Offshore Oil and Gas Pipeline

    Directory of Open Access Journals (Sweden)

    Nizamani Z.

    2017-01-01

    Full Text Available Fluid structure interaction (FSI applications are of wide range from offshore fixed and floating structures to offshore pipelines. Reynolds Averaged Navier Stoke (RANS solution has limitation for unsteady and turbulent flow modelling. A possible approach is Large Eddy Simulation (LES and it is applied to flows past a circular cylinder located far above, near and on a flat seabed. The Reynolds number considered is based on the real situation off Malaysia Coast and is sub-critical around 105. Hydrodynamic quantities in terms of mean pressure are predicted and vortex shedding mechanism is evaluated. The results are validated by comparing the simulation and experimental previous studies.

  9. Reliability-Based Planning of Inspection, Operation and Maintenance for Offshore Oil & Gas Structures and Wind Turbines

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard

    2011-01-01

    Reliability-based cost-optimal planning of inspection, maintenance and operation has many applications. In this paper applications for planning of inspections for oil & gas jacket structures and of operation and maintenance of offshore wind turbines are described and illustrated by examples....

  10. Neuro System Structure for Vehicle Recognition and Count in Floating Bridge Specific Conditions

    Directory of Open Access Journals (Sweden)

    Slobodan Beroš

    2012-10-01

    Full Text Available The paper presents the research of the sophisticated vehiclerecognition and count system based on the application of theneural network. The basic elements of neural network andadaptive logic network for object recognition are discussed. Theadaptive logic network solution ability based on simple digitalcircuits as crucial in real-time applications is pointed out. Thesimulation based on the use of reduced high level noise pictureand a tree 2. 7. software have shown excellent results. The consideredand simulated adaptive neural network based systemwith its good recognition and convergence is a useful real-timesolution for vehicle recognition and count in the floating bridgesevere conditions.

  11. Second Order Nonlinear Hydroelastic Analyses of Floating Bodies - the Primary Consideration of Nonlinear Structure

    DEFF Research Database (Denmark)

    Chen, X.; Cui, W.; Jensen, Jørgen Juncher

    2003-01-01

    are introduced in this paper. With the examples of the motion and displacement reponses of a floating plate undergoing large vertical deflections in multidirectional waves, the analysis method of the couple action between the vertical deflections in multidirectional waves, the analysis method of the couple...... action between the vertical displacement and the fluid are presented in the frequency domain. The influence of the membrane forces to the vertical displacements, bending moments and the stress are discussed. The numerical results indicate that the membrane forces have influence on the vertical...

  12. HAWCStab2 with super element foundations: A new tool for frequency analysis of offshore wind turbines

    DEFF Research Database (Denmark)

    Henriksen, Lars Christian; Hansen, Anders Melchior; Kragh, Knud Abildgaard

    2013-01-01

    HAWCStab2 is a linear frequency domain aero-elastic tool, developed by DTU Wind Energy, suitable for frequency and stability analysis of horizontal axis 3 bladed wind turbines [1]. This tool has now been extended to also handle complex offshore foundation types, such as jacket structures...... and floating structures with mooring lines, using super elements calculated by the nonlinear time domain aero-elastic code HAWC2 [2,3]....

  13. Structural response analysis of very large floating structures in waves using one-dimensional finite element model; Ichijigen yugen yoso model ni yoru choogata futai no harochu kozo oto kaiseki

    Energy Technology Data Exchange (ETDEWEB)

    Fujikubo, M.; Yao, T.; Oida, H. [Hiroshima University, Hiroshima (Japan). Faculty of Engineering

    1996-12-31

    Formulation was made on a one-dimensional beam finite element which is effective in analyzing structural response of very large floating structures by modeling them on beams on an elastic foundation. This element allows strict solution of vibration response in the beams on the elastic foundation to be calculated efficiently for a case where mass and rigidity change in the longitudinal direction. This analysis method was used to analyze structural response of a large pontoon-type floating structure to investigate mass in the end part for the structural response and the effect of decay while passing the structure. With a pontoon-type floating structure, reduction in bends and bending stress in the end part of the floating structure is important in designing the structure. Reducing the mass in the end part is effective as a means to avoid resonance in these responses and reduce the responses. Increase in rigidity of a floating structure shifts the peak in quasi-static response to lower frequency side, and reduces response in resonance, hence it is advantageous for improving the response. Since incident waves decay while passing through the floating structure, response in the lower wave side decreases. The peak frequency in the quasi-static response also decreases at the end part of the structure in the upper wave side due to decay in wave force. 7 refs., 11 figs., 1 tab.

  14. Structural response analysis of very large floating structures in waves using one-dimensional finite element model; Ichijigen yugen yoso model ni yoru choogata futai no harochu kozo oto kaiseki

    Energy Technology Data Exchange (ETDEWEB)

    Fujikubo, M; Yao, T; Oida, H [Hiroshima University, Hiroshima (Japan). Faculty of Engineering

    1997-12-31

    Formulation was made on a one-dimensional beam finite element which is effective in analyzing structural response of very large floating structures by modeling them on beams on an elastic foundation. This element allows strict solution of vibration response in the beams on the elastic foundation to be calculated efficiently for a case where mass and rigidity change in the longitudinal direction. This analysis method was used to analyze structural response of a large pontoon-type floating structure to investigate mass in the end part for the structural response and the effect of decay while passing the structure. With a pontoon-type floating structure, reduction in bends and bending stress in the end part of the floating structure is important in designing the structure. Reducing the mass in the end part is effective as a means to avoid resonance in these responses and reduce the responses. Increase in rigidity of a floating structure shifts the peak in quasi-static response to lower frequency side, and reduces response in resonance, hence it is advantageous for improving the response. Since incident waves decay while passing through the floating structure, response in the lower wave side decreases. The peak frequency in the quasi-static response also decreases at the end part of the structure in the upper wave side due to decay in wave force. 7 refs., 11 figs., 1 tab.

  15. Soil-Structure Interaction For Nonslender, Large-Diameter Offshore Monopiles

    DEFF Research Database (Denmark)

    Sørensen, Søren Peder Hyldal

    Strong political and industrial forces, especially in Northern Europe, support the development of new technologies as well as improvements of existing technologies within the field of renewable energy. Offshore wind power is a domestic, sustainable and largely untapped energy resource. Today......, the modern offshore wind turbine offers competitive production prices compared to other sources of renewable energy. Therefore, it is a key technology in breaking the dependence on fossil fuels and in achieving the energy and climate goals of the future. For offshore wind turbines, the costs of foundation...... typically constitutes 20-30 % of the total costs. Hence, improved methods for the design of foundations for offshore wind turbines can increase the competitiveness of offshore wind energy significantly. The monopile foundation concept has been employed as the foundation for the majority of the currently...

  16. Structural inheritance and coastal geomorphology in SW Brittany, France: An onshore/offshore integrated approach

    Science.gov (United States)

    Raimbault, Céline; Duperret, Anne; Le Gall, Bernard; Authemayou, Christine

    2018-04-01

    The Variscan crystalline basement exposed along the SW Brittany coast recorded extensive long-term planation processes during Mesozoic times. Detailed onshore-offshore mapping (600 km2) in the Penmarc'h-Concarneau granitic coastal area reveals a km-scale, deeply fractured submarine rocky shelf. High-resolution offshore imagery (bathymetry and seismic reflection dataset), combined to structural field investigations, on these surfaces allow us to identify a preserved network of both ductile and brittle structures. The inherited fault pattern is dominated by the N160°E-trending and long-lived Concarneau-Toulven fault zone (CTFS) that separates two distinct morphostructural blocks, and strongly influences the seaward limit of the Concarneau submarine rocky shelf, as well as the linear coastline of the Concarneau embayment. The structural imprint of the CTFS decreases progressively westwards with respect to a composite network of large-scale N50°E- and N140°E-oriented faults bounding the seaward edge of the Penmarc'h rocky shelf. The latter in turn splits into three large-scale blocks along N50°E- (La Torche Fault - LTF), N140°E- (Saint Guénolé Fault - SGF) and N160°E-trending normal faults. The morphostructural evolutionary model applied here to the Penmarc'h-Concarneau granitic coastal area resulted from the combined effects of structural Variscan inheritance and post-Variscan tectonics. Paleo-stress analysis of striated fault planes indicates three main Cenozoic tectonic events, inferred to have operated from Eocene to post-Oligocene times. The 3D-architecture of the Concarneau embayment, as a rocky shelf partially sealed with quaternary sediments, chiefly resulted from the reactivation of the CTFS during Eocene and Oligocene times. Further west, the surface of the Penmarc'h rocky shelf was tilted southeastward by the brittle reactivation of the LTF, and dissected by a horst-graben network post-Oligocene in age. The present-day morphology of the Penmarc'h and

  17. Enhanced Structural Interpretation Using Multitrace Seismic Attribute For Oligo-Miocene Target at Madura Strait Offshore

    Science.gov (United States)

    Pratama Wahyu Hidayat, Putra; Hary Murti, Antonius; Sudarmaji; Shirly, Agung; Tiofan, Bani; Damayanti, Shinta

    2018-03-01

    Geometry is an important parameter for the field of hydrocarbon exploration and exploitation, it has significant effect to the amount of resources or reserves, rock spreading, and risk analysis. The existence of geological structure or fault becomes one factor affecting geometry. This study is conducted as an effort to enhance seismic image quality in faults dominated area namely offshore Madura Strait. For the past 10 years, Oligo-Miocene carbonate rock has been slightly explored on Madura Strait area, the main reason because migration and trap geometry still became risks to be concern. This study tries to determine the boundary of each fault zone as subsurface image generated by converting seismic data into variance attribute. Variance attribute is a multitrace seismic attribute as the derivative result from amplitude seismic data. The result of this study shows variance section of Madura Strait area having zero (0) value for seismic continuity and one (1) value for discontinuity of seismic data. Variance section shows the boundary of RMKS fault zone with Kendeng zone distinctly. Geological structure and subsurface geometry for Oligo-Miocene carbonate rock could be identified perfectly using this method. Generally structure interpretation to identify the boundary of fault zones could be good determined by variance attribute.

  18. Spatial-temporal analysis of coherent offshore wind field structures measured by scanning Doppler-lidar

    Science.gov (United States)

    Valldecabres, L.; Friedrichs, W.; von Bremen, L.; Kühn, M.

    2016-09-01

    An analysis of the spatial and temporal power fluctuations of a simplified wind farm model is conducted on four offshore wind fields data sets, two from lidar measurements and two from LES under unstable and neutral atmospheric conditions. The integral length scales of the horizontal wind speed computed in the streamwise and the cross-stream direction revealed the elongation of the structures in the direction of the mean flow. To analyse the effect of the structures on the power output of a wind turbine, the aggregated equivalent power of two wind turbines with different turbine spacing in the streamwise and cross-stream direction is analysed at different time scales under 10 minutes. The fact of considering the summation of the power of two wind turbines smooths out the fluctuations of the power output of a single wind turbine. This effect, which is stronger with increasing spacing between turbines, can be seen in the aggregation of the power of two wind turbines in the streamwise direction. Due to the anti-correlation of the coherent structures in the cross-stream direction, this smoothing effect is stronger when the aggregated power is computed with two wind turbines aligned orthogonally to the mean flow direction.

  19. Optimization of Support Structures for Offshore Wind Turbines Using Genetic Algorithm with Domain-Trimming

    Directory of Open Access Journals (Sweden)

    Mohammad AlHamaydeh

    2017-01-01

    Full Text Available The powerful genetic algorithm optimization technique is augmented with an innovative “domain-trimming” modification. The resulting adaptive, high-performance technique is called Genetic Algorithm with Domain-Trimming (GADT. As a proof of concept, the GADT is applied to a widely used benchmark problem. The 10-dimensional truss optimization benchmark problem has well documented global and local minima. The GADT is shown to outperform several published solutions. Subsequently, the GADT is deployed onto three-dimensional structural design optimization for offshore wind turbine supporting structures. The design problem involves complex least-weight topology as well as member size optimizations. The GADT is applied to two popular design alternatives: tripod and quadropod jackets. The two versions of the optimization problem are nonlinearly constrained where the objective function is the material weight of the supporting truss. The considered design variables are the truss members end node coordinates, as well as the cross-sectional areas of the truss members, whereas the constraints are the maximum stresses in members and the maximum displacements of the nodes. These constraints are managed via dynamically modified, nonstationary penalty functions. The structures are subject to gravity, wind, wave, and earthquake loading conditions. The results show that the GADT method is superior in finding best discovered optimal solutions.

  20. Analysis of Tide and Offshore Storm-Induced Water Table Fluctuations for Structural Characterization of a Coastal Island Aquifer

    Science.gov (United States)

    Trglavcnik, Victoria; Morrow, Dean; Weber, Kela P.; Li, Ling; Robinson, Clare E.

    2018-04-01

    Analysis of water table fluctuations can provide important insight into the hydraulic properties and structure of a coastal aquifer system including the connectivity between the aquifer and ocean. This study presents an improved approach for characterizing a permeable heterogeneous coastal aquifer system through analysis of the propagation of the tidal signal, as well as offshore storm pulse signals through a coastal aquifer. Offshore storms produce high wave activity, but are not necessarily linked to significant onshore precipitation. In this study, we focused on offshore storm events during which no onshore precipitation occurred. Extensive groundwater level data collected on a sand barrier island (Sable Island, NS, Canada) show nonuniform discontinuous propagation of the tide and offshore storm pulse signals through the aquifer with isolated inland areas showing enhanced response to both oceanic forcing signals. Propagation analysis suggests that isolated inland water table fluctuations may be caused by localized leakage from a confined aquifer that is connected to the ocean offshore but within the wave setup zone. Two-dimensional groundwater flow simulations were conducted to test the leaky confined-unconfined aquifer conceptualization and to identify the effect of key parameters on tidal signal propagation in leaky confined-unconfined coastal aquifers. This study illustrates that analysis of offshore storm signal propagation, in addition to tidal signal propagation, provides a valuable and low resource approach for large-scale characterization of permeable heterogeneous coastal aquifers. Such an approach is needed for the effective management of coastal environments where water resources are threatened by human activities and the changing climate.

  1. Preliminary Design of a Multi-Column TLP Foundation for a 5-MW Offshore Wind Turbine

    OpenAIRE

    Yongsheng Zhao; Jianmin Yang; Yanping He

    2012-01-01

    Currently, floating wind turbines (FWTs) may be the more economical and suitable systems with which to exploit offshore wind energy in deep waters. Among the various types of floating foundations for offshore wind farms, a tension leg platform (TLP) foundation can provide a relatively stable platform for currently available offshore wind turbines without requiring major modifications. In this study, a new multi-column TLP foundation (WindStar TLP) was developed for the NREL 5-MW offshore wind...

  2. Design and Aero-elastic Simulation of a 5MW Floating Vertical Axis Wind Turbine

    DEFF Research Database (Denmark)

    Vita, Luca; Schmidt Paulsen, Uwe; Aagaard Madsen, Helge

    2013-01-01

    This paper deals with the design of a 5MW floating offshore Vertical Axis Wind Turbine (VAWT). The design is based on a new offshore wind turbine concept (DeepWind concept), consisting of a Darrieus rotor mounted on a spar buoy support structure, which is anchored to the sea bed with mooring lines......-DTU. The numerical simulations take into account the fully coupled aerodynamic and hydrodynamic loads on the structure, due to wind, waves and currents. The turbine is tested in operative conditions, at different sea states, selected according to the international offshore standards. The research is part...... of the European project DeepWind (2010-2014), which has been financed by the European Union (FP7-Future Emerging Technologies)....

  3. Feasibility study on floating nuclear power station

    International Nuclear Information System (INIS)

    Kajima, Ryoichi

    1987-01-01

    It is stipulated that nuclear power plants are to be built on solid rock bases on land in Japan. However, there are a limited number of appropriate siting grounds. The Central Research Institute of Electric Power Industry has engaged since 1981 in the studies on the construction technology of power plants, aiming at establishing new siting technology to expand the possible siting areas for nuclear power plants. Underground siting is regarded as a proven technology due to the experience in underground hydroelectric power plants. The technology of siting on quaternary ground is now at the stage of verification. In this report, the outline of floating type offshore/inshore siting technology is introduced, which is considered to be feasible in view of the technical and economical aspects. Three fixed structure types were selected, of which the foundations are fixed to seabed, plant superstructures are above sea surface, and which are floating type. Aiming at ensuring the aseismatic stability of the plant foundations, the construction technology is studied, and the structural concept omitting buoyancy is possible. The most practical water depth is not more than 20 m. The overall plant design, earthquake isolation effect and breakwater are described. (Kako, I.)

  4. Final report WP 4.2 : Support Structure Concepts for Deep Water Sites: Deliverable D4.2.8 (WP4: offshore foundations and support structures)

    NARCIS (Netherlands)

    De Vries, W.E.; Vemula, N.K.; Passon, P.; Fischer, T.; Kaufer, D.; Matha, D.; Schmidt, B.; Vorpahl, F.

    2011-01-01

    With the number of offshore wind farms rapidly increasing, in a wide variety of site conditions and using different turbine sizes, the need for alternative support structures other than the conventional monopile structure is apparent and several projects have been realised using other support

  5. Topographical effects on wave exciting forces on huge floating structure. 2; Ogata futaishiki kaiyo kozobutsu ni sayosuru haryoku ni kansuru kenkyu. 2

    Energy Technology Data Exchange (ETDEWEB)

    Imai, Y [Hiroshima University, Hiroshima (Japan); Okusu, M [Kyushu Univ., Fukuoka (Japan). Research Inst. for Applied Mechanics

    1997-12-31

    A method to predict drift force acting on a floating structure has been developed for a marine structure consisting of a number of floating elements, positioned in a region having a slope at the sea bottom. When a huge marine structure, such as floating air port, is located in a coastal area, scale of the overall structure is very large, of the order of scale of water depth change. The new method assumes that a marine structure consisting of an infinite number of cylindrical floating elements is installed in parallel to the seashore, where symmetrical nature of the configuration allows to predict behavior of the whole system by analyzing one element. Integration of pressures acting on structure surfaces determines the horizontal component of the drift force acting on the structure. Being influenced by topography, drift force predicted peaks at a frequency different from that for the level predicted on the assumption of constant water depth. This indicates the necessity for consideration of seabottom slope and effects of broken waves at the seashore. 6 refs., 12 figs.

  6. Topographical effects on wave exciting forces on huge floating structure. 2; Ogata futaishiki kaiyo kozobutsu ni sayosuru haryoku ni kansuru kenkyu. 2

    Energy Technology Data Exchange (ETDEWEB)

    Imai, Y. [Hiroshima University, Hiroshima (Japan); Okusu, M. [Kyushu Univ., Fukuoka (Japan). Research Inst. for Applied Mechanics

    1996-12-31

    A method to predict drift force acting on a floating structure has been developed for a marine structure consisting of a number of floating elements, positioned in a region having a slope at the sea bottom. When a huge marine structure, such as floating air port, is located in a coastal area, scale of the overall structure is very large, of the order of scale of water depth change. The new method assumes that a marine structure consisting of an infinite number of cylindrical floating elements is installed in parallel to the seashore, where symmetrical nature of the configuration allows to predict behavior of the whole system by analyzing one element. Integration of pressures acting on structure surfaces determines the horizontal component of the drift force acting on the structure. Being influenced by topography, drift force predicted peaks at a frequency different from that for the level predicted on the assumption of constant water depth. This indicates the necessity for consideration of seabottom slope and effects of broken waves at the seashore. 6 refs., 12 figs.

  7. Seismogenic structures of the 2006 ML4.0 Dangan Island earthquake offshore Hong Kong

    Science.gov (United States)

    Xia, Shaohong; Cao, Jinghe; Sun, Jinlong; Lv, Jinshui; Xu, Huilong; Zhang, Xiang; Wan, Kuiyuan; Fan, Chaoyan; Zhou, Pengxiang

    2018-02-01

    The northern margin of the South China Sea, as a typical extensional continental margin, has relatively strong intraplate seismicity. Compared with the active zones of Nanao Island, Yangjiang, and Heyuan, seismicity in the Pearl River Estuary is relatively low. However, a ML4.0 earthquake in 2006 occurred near Dangan Island (DI) offshore Hong Kong, and this site was adjacent to the source of the historical M5.8 earthquake in 1874. To reveal the seismogenic mechanism of intraplate earthquakes in DI, we systematically analyzed the structural characteristics in the source area of the 2006 DI earthquake using integrated 24-channel seismic profiles, onshore-offshore wide-angle seismic tomography, and natural earthquake parameters. We ascertained the locations of NW- and NE-trending faults in the DI sea and found that the NE-trending DI fault mainly dipped southeast at a high angle and cut through the crust with an obvious low-velocity anomaly. The NW-trending fault dipped southwest with a similar high angle. The 2006 DI earthquake was adjacent to the intersection of the NE- and NW-trending faults, which suggested that the intersection of the two faults with different strikes could provide a favorable condition for the generation and triggering of intraplate earthquakes. Crustal velocity model showed that the high-velocity anomaly was imaged in the west of DI, but a distinct entity with low-velocity anomaly in the upper crust and high-velocity anomaly in the lower crust was found in the south of DI. Both the 1874 and 2006 DI earthquakes occurred along the edge of the distinct entity. Two vertical cross-sections nearly perpendicular to the strikes of the intersecting faults revealed good spatial correlations between the 2006 DI earthquake and the low to high speed transition in the distinct entity. This result indicated that the transitional zone might be a weakly structural body that can store strain energy and release it as a brittle failure, resulting in an earthquake

  8. Compound floating pivot micromechanisms

    Science.gov (United States)

    Garcia, Ernest J.

    2001-04-24

    A new class of tilting micromechanical mechanisms have been developed. These new mechanisms use compound floating pivot structures to attain far greater tilt angles than are practical using other micromechanical techniques. The new mechanisms are also capable of bi-directional tilt about multiple axes.

  9. The floating water bridge

    International Nuclear Information System (INIS)

    Fuchs, Elmar C; Woisetschlaeger, Jakob; Gatterer, Karl; Maier, Eugen; Pecnik, Rene; Holler, Gert; Eisenkoelbl, Helmut

    2007-01-01

    When high voltage is applied to distilled water filled in two glass beakers which are in contact, a stable water connection forms spontaneously, giving the impression of a floating water bridge. A detailed experimental analysis reveals static and dynamic structures as well as heat and mass transfer through this bridge

  10. Rigid finite element method in analysis of dynamics of offshore structures

    Energy Technology Data Exchange (ETDEWEB)

    Wittbrodt, Edmund [Gdansk Univ. of Technology (Poland); Szczotka, Marek; Maczynski, Andrzej; Wojciech, Stanislaw [Bielsko-Biala Univ. (Poland)

    2013-07-01

    This book describes new methods developed for modelling dynamics of machines commonly used in the offshore industry. These methods are based both on the rigid finite element method, used for the description of link deformations, and on homogeneous transformations and joint coordinates, which is applied to the modelling of multibody system dynamics. In this monograph, the bases of the rigid finite element method and homogeneous transformations are introduced. Selected models for modelling dynamics of offshore devices are then verified both by using commercial software, based on the finite element method, as well as by using additional methods. Examples of mathematical models of offshore machines, such as a gantry crane for Blowout-Preventer (BOP) valve block transportation, a pedestal crane with shock absorber, and pipe laying machinery are presented. Selected problems of control in offshore machinery as well as dynamic optimization in device control are also discussed. Additionally, numerical simulations of pipe-laying operations taking active reel drive into account are shown.

  11. Offshore structural trends from magnetic data over Cauvery Basin, east coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Subrahmanyam, A.S.; Lakshminarayana, S.; Chandrasekhar, D.V.; Murthy, K.S.R.; Rao, T.C.S.

    been interpreted as due to dyke intrusions. NE-SW lineament reflects the offshore extension of a major basement depression, viz, the Pondicherry depression. E-W lineation, south of Proto Novo reveals a basement high suggesting the seaward extension...

  12. Rigid Finite Element Method in Analysis of Dynamics of Offshore Structures

    CERN Document Server

    Wittbrodt, Edmund; Maczyński, Andrzej; Wojciech, Stanisław

    2013-01-01

    This book describes new methods developed for modelling dynamics of machines commonly used in the offshore industry. These methods are based both on the rigid finite element method, used for the description of link deformations, and on homogeneous transformations and joint coordinates, which is applied to the modelling of multibody system dynamics. In this monograph, the bases of the rigid finite element method  and homogeneous transformations are introduced. Selected models for modelling dynamics of offshore devices are then verified both by using commercial software, based on the finite element method, as well as by using additional methods. Examples of mathematical models of offshore machines, such as a gantry crane for Blowout-Preventer (BOP) valve block transportation, a pedestal crane with shock absorber, and pipe laying machinery are presented. Selected problems of control in offshore machinery as well as dynamic optimization in device control are also discussed. Additionally, numerical simulations of...

  13. Lake Michigan offshore ecosystem structure and food web changes from 1987 to 2008

    Science.gov (United States)

    Rogers, Mark W.; Bunnell, David B.; Madenjian, Charles P.; Warner, David M.

    2014-01-01

    Ecosystems undergo dynamic changes owing to species invasions, fisheries management decisions, landscape modifications, and nutrient inputs. At Lake Michigan, new invaders (e.g., dreissenid mussels (Dreissena spp.), spiny water flea (Bythotrephes longimanus), round goby (Neogobius melanostomus)) have proliferated and altered energy transfer pathways, while nutrient concentrations and stocking rates to support fisheries have changed. We developed an ecosystem model to describe food web structure in 1987 and ran simulations through 2008 to evaluate changes in biomass of functional groups, predator consumption, and effects of recently invading species. Keystone functional groups from 1987 were identified as Mysis, burbot (Lota lota), phytoplankton, alewife (Alosa pseudoharengus), nonpredatory cladocerans, and Chinook salmon (Oncorhynchus tshawytscha). Simulations predicted biomass reductions across all trophic levels and predicted biomasses fit observed trends for most functional groups. The effects of invasive species (e.g., dreissenid grazing) increased across simulation years, but were difficult to disentangle from other changes (e.g., declining offshore nutrient concentrations). In total, our model effectively represented recent changes to the Lake Michigan ecosystem and provides an ecosystem-based tool for exploring future resource management scenarios.

  14. On the sea-covering effect of a huge floating structure on the surrounding water; Choogata futai shuhen no kaisui ni taisuru kaimen shahei no eikyo ni tsuite

    Energy Technology Data Exchange (ETDEWEB)

    Fujino, M; Kagemoto, H; Hamada, T [The University of Tokyo, Tokyo (Japan)

    1997-12-31

    The numerical analysis program based on the difference method for dynamics of sea water with sea-surface displacement, flow rate, salt content and temperature as the parameters is modified to more accurately assess the effects of a huge marine structure on surrounding environment by adding the effects of insolation and boundary conditions of the sea-covering effects of the floating structure. The numerical simulation was done for summer and winter seasons, not in a sea area but using a rectangular bay with the floating structure at the center. A new flow evolves around the floating structure, due to the sea-covering effect. The flow patterns in summer and winter are clearly different, due to difference in insolation. The predicted flow is also sensitive whether stratification is considered or not, by which is meant that it is important what stratification effect is taken into account. Daily insolation changes are accompanied by vertical distribution of water temperature and its temporal change. These effects are also observed under the floating structure which shields insolation. 10 refs., 17 figs., 4 tabs.

  15. On the sea-covering effect of a huge floating structure on the surrounding water; Choogata futai shuhen no kaisui ni taisuru kaimen shahei no eikyo ni tsuite

    Energy Technology Data Exchange (ETDEWEB)

    Fujino, M.; Kagemoto, H.; Hamada, T. [The University of Tokyo, Tokyo (Japan)

    1996-12-31

    The numerical analysis program based on the difference method for dynamics of sea water with sea-surface displacement, flow rate, salt content and temperature as the parameters is modified to more accurately assess the effects of a huge marine structure on surrounding environment by adding the effects of insolation and boundary conditions of the sea-covering effects of the floating structure. The numerical simulation was done for summer and winter seasons, not in a sea area but using a rectangular bay with the floating structure at the center. A new flow evolves around the floating structure, due to the sea-covering effect. The flow patterns in summer and winter are clearly different, due to difference in insolation. The predicted flow is also sensitive whether stratification is considered or not, by which is meant that it is important what stratification effect is taken into account. Daily insolation changes are accompanied by vertical distribution of water temperature and its temporal change. These effects are also observed under the floating structure which shields insolation. 10 refs., 17 figs., 4 tabs.

  16. On the estimation method of hydrodynamic forces acting on a huge floating structure; Choogata futai ni hataraku haryoku ryutairyoku no suiteiho ni kansuru kenkyu

    Energy Technology Data Exchange (ETDEWEB)

    Kagemoto, H.; Fujino, M.; Zhu, T. [The University of Tokyo, Tokyo (Japan)

    1996-12-31

    A floating structure such as an international airport is anticipated to have a length of about 5,000 m and a width of about 1,000 m. A singular point method may be used as a method to estimate force that such a floating body is subjected to from waves. In order to derive a solution with practically sufficient accuracy, 1250 elements are required in the length direction and 250 elements in the width direction, or a total of 312,500 elements. Calculating this number of elements should use finally a linear equation system handling complex coefficients comprising 312,500 elements, which would require a huge amount of calculation time. This paper proposes a method to derive solution on wave forces acting on a super-large floating structure or fluid force coefficients such as added mass coefficients and decay coefficients at a practically workable calculation amount and still without degrading the accuracy. The structure was assumed to be a box-shaped structure. Strengths of the singular points to be distributed on each element were assumed to be almost constant except for edges in lateral, oblique and longitudinal waves. Under this assumption, the interior of the floating structure excepting its edges was represented by several large elements to have reduced the number of elements. A calculation method proposed based on this conception was verified of its effectiveness. 2 refs., 25 figs., 3 tabs.

  17. Offshore risk assessment

    CERN Document Server

    Vinnem, Jan-Erik

    2014-01-01

      Offshore Risk Assessment was the first book to deal with quantified risk assessment (QRA) as applied specifically to offshore installations and operations. Risk assessment techniques have been used for more than three decades in the offshore oil and gas industry, and their use is set to expand increasingly as the industry moves into new areas and faces new challenges in older regions.   This updated and expanded third edition has been informed by a major R&D program on offshore risk assessment in Norway and summarizes research from 2006 to the present day. Rooted with a thorough discussion of risk metrics and risk analysis methodology,  subsequent chapters are devoted to analytical approaches to escalation, escape, evacuation and rescue analysis of safety and emergency systems.   Separate chapters analyze the main hazards of offshore structures: fire, explosion, collision, and falling objects as well as structural and marine hazards. Risk mitigation and control are discussed, as well as an illustrat...

  18. The influence of plate thickness on the welding residual stresses from submerged arc welding in offshore steel structures

    DEFF Research Database (Denmark)

    Andreassen, Michael Joachim; Yu, Zhenzhen; Liu, Stephen

    2017-01-01

    Welding-induced residual tensile stresses and distortion have become a major concern in relation to the structural integrity of welded structures within the offshore wind industry. The stresses have a negative impact on the integrity of the welded joint, as they promote distortion, reduce fatigue...... leading to a better understanding of the distribution and development of the welding residual stresses. This can later be used to optimize the fatigue design, providing a more efficient and improved design. In this context, the current research is expected to benefit the offshore industry by leading...... to an improved design, which consequently may be included in future norms and standards. Submerged Arc Welding (SAW) was used to make a fully penetrated butt weld in 10 mm and 40 mm thick steel plates with the same welding parameters as used in the production procedures. The base material is thermomechanical hot...

  19. Floating barrier

    Energy Technology Data Exchange (ETDEWEB)

    1968-05-06

    This floating barrier consists of relatively long elements which can be connected to form a practically continuous assembly. Each element consists of an inflatable tube with an apron of certain height, made of impregnated fabric which is resistant to ocean water and also to hydrocarbons. Means for connecting one element to the following one, and means for attaching ballast to the apron are also provided.

  20. Breaking wave impact forces on truss support structures for offshore wind turbines

    Science.gov (United States)

    Cieślikiewicz, Witold; Gudmestad, Ove T.; Podrażka, Olga

    2014-05-01

    Due to depletion of the conventional energy sources, wind energy is becoming more popular these days. Wind energy is being produced mostly from onshore farms, but there is a clear tendency to transfer wind farms to the sea. The foundations of offshore wind turbines may be truss structures and might be located in shallow water, where are subjected to highly varying hydrodynamic loads, particularly from plunging breaking waves. There are models for impact forces prediction on monopiles. Typically the total wave force on slender pile from breaking waves is a superposition of slowly varying quasi-static force, calculated from the Morison equation and additional dynamical, short duration force due to the impact of the breaker front or breaker tongue. There is not much research done on the truss structures of wind turbines and there are still uncertainties on slamming wave forces, due to plunging breaking waves on those structures. Within the WaveSlam (Wave slamming forces on truss structures in shallow water) project the large scale tests were carried out in 2013 at the Large Wave Flume in Forschungszentrum Küste (FZK) in Hannover, Germany. The following institutions participated in this initiative: the University of Stavanger and the Norwegian University of Science and Technology (project management), University of Gdańsk, Poland, Hamburg University of Technology and the University of Rostock, Germany and Reinertsen AS, Norway. This work was supported by the EU 7th Framework Programme through the grant to the budget of the Integrating Activity HYDRALAB IV. The main aim of the experiment was to investigate the wave slamming forces on truss structures, development of new and improvement of existing methods to calculate forces from the plunging breakers. The majority of the measurements were carried out for regular waves with specified frequencies and wave heights as well as for the irregular waves based on JONSWAP spectrum. The truss structure was equipped with both

  1. Long-term Bat Monitoring on Islands, Offshore Structures, and Coastal Sites in the Gulf of Maine, mid-Atlantic, and Great Lakes—Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Peterson, Trevor [Stantec Consulting Services Inc., Topsham, ME (United States); Pelletier, Steve [Stantec Consulting Services Inc., Topsham, ME (United States); Giovanni, Matt [Stantec Consulting Services Inc., Topsham, ME (United States)

    2016-01-15

    This report summarizes results of a long-term regional acoustic survey of bat activity at remote islands, offshore structures, and coastal sites in the Gulf of Maine, Great Lakes, and mid-Atlantic coast.

  2. Risks to offshore installations in Europe due to natural hazards

    Science.gov (United States)

    Necci, Amos; Krausmann, Elisabeth

    2017-04-01

    Natural hazards, such as storms, earthquakes, or lightning are a major threat to industry. In particular, chemical plants, storage facilities, pipelines, and offshore oil and gas facilities are vulnerable to natural events which can cause hazardous materials releases and thereby endanger workers, the population and the environment. These technological accidents are commonly referred to as Natech accidents. Recent events have increased concerns about safety in the offshore oil and gas sector, and the need for improving knowledge on the matter has become evident. With those premises, we analyzed accidents, near misses and accident precursors at offshore facilities in Europe caused by natural events using both a statistical and a qualitative approach. For this purpose, we screened the World Offshore Accident Database (WOAD) to identify all incidents that featured natural events as causes or aggravating factors. A dataset of 1,085 global Natech events was built for the statistical analysis. Among those, a subset composed of 303 European records was selected. The results of the analysis showed that offshore Natech events in Europe are frequent; they resulted, however, in low consequences. The main threat to offshore facilities resulted from bad weather, such as strong winds and heavy seas. Storms can put intense loads on the structural parts of offshore installations, eventually exceeding design resistance specifications. Several incidents triggered by lightning strikes and earthquakes were also recorded. Substantial differences in terms of vulnerability, damage modality and consequences emerged between fixed and floating offshore structures. The main damage mode for floating structures was the failure of station keeping systems due to the rupture of mooring or anchors, mainly caused by adverse meteorological conditions. Most of the incidents at fixed offshore structures in Europe involved falling loads for both metal jacket and concrete base platforms due to storms. In

  3. Non-Parametric Bayesian Updating within the Assessment of Reliability for Offshore Wind Turbine Support Structures

    DEFF Research Database (Denmark)

    Ramirez, José Rangel; Sørensen, John Dalsgaard

    2011-01-01

    This work illustrates the updating and incorporation of information in the assessment of fatigue reliability for offshore wind turbine. The new information, coming from external and condition monitoring can be used to direct updating of the stochastic variables through a non-parametric Bayesian u...

  4. Coupled Simulations of Wind Turbines and Offshore Support Structures : Strategies based on the Dynamic Substructuring Paradigm

    NARCIS (Netherlands)

    Van der Valk, P.L.C.

    2014-01-01

    Large scale offshore wind power has been recognized as a key technology to increase the share of renewable energy. However, as this energy source is currently still relatively expensive, efforts are made to significantly reduce its costs. Cost reductions are to be achieved, for instance, by

  5. Computationally Efficient Modelling of Dynamic Soil-Structure Interaction of Offshore Wind Turbines on Gravity Footings

    DEFF Research Database (Denmark)

    Damgaard, Mads; Andersen, Lars Vabbersgaard; Ibsen, Lars Bo

    2014-01-01

    of a 5.0 MW offshore wind turbine is evaluated for different stratifications, environmental conditions and foundation geometries by the aeroelastic nonlinear multi-body code HAWC2. Analyses show that a consistent lumped-parameter model with three to five internal degrees of freedom per displacement...

  6. Wave loads on offshore wind turbines: Accurate tools and structural response

    DEFF Research Database (Denmark)

    Bredmose, Henrik

    2014-01-01

    Can the design models for offshore wind turbine wave loads be improved? And how will that change the overall load picture? Core questions of the Wave Loads project which was finalised in 2013 with two PhD theses, response calculations for jackets and monopiles, a detailed set of experiments and a3D...... coupled CFD wave solver...

  7. Gravitational and submersible offshore platform, and construction method. Nedsenkbar fralandsplattform av gravitasjonstypen og fremgangsmaate for fremstilling av samme

    Energy Technology Data Exchange (ETDEWEB)

    Berge, T.; Olsen, O.

    1985-06-17

    The invention concerns a submersible offshore platform of the gravitational type designed for great depths. The platform is made of concrete or the like comprising a sea-bed foundation, and a number of at least 3 cantilevered pillars connected to the prop section carrying the load-bearing structure and the platform deck. In addition, the platform consists of a cellular floating section, and the central part of it is lengthened upwards. The central column supports the prop section. There is a considerable space between the floating section and the bed foundation. The various steps of the construction methods are presented. 11 drawings.

  8. IEA Wind Task 23 Offshore Wind Technology and Deployment. Subtask 1 Experience with Critical Deployment Issues. Final Technical Report

    DEFF Research Database (Denmark)

    Lemming, Jørgen Kjærgaard

    The final report for IEA Wind Task 23, Offshore Wind Energy Technology and Deployment, is made up of two separate reports: Subtask 1: Experience with Critical Deployment Issues and Subtask 2: Offshore Code Comparison Collaborative (OC3). The Subtask 1 report included here provides background...... information and objectives of Task 23. It specifically discusses ecological issues and regulation, electrical system integration and offshore wind, external conditions, and key conclusions for Subtask 1. The Subtask 2 report covers OC3 background information and objectives of the task, OC3 benchmark exercises...... of aero-elastic offshore wind turbine codes, monopile foundation modeling, tripod support structure modeling, and Phase IV results regarding floating wind turbine modeling....

  9. Estimation of the vibration decrement of an offshore wind turbine support structure caused by its interaction with soil

    Energy Technology Data Exchange (ETDEWEB)

    Versteijlen, W.G; Metrikine, A.; Hoving, J.S.; Smidt, E.H.; De Vries, W.E. [Department Hydraulic Engineering, Faculty of Civil Engineering and Geosciences, Delft University of Technology TUD, Delft (Netherlands)

    2012-01-15

    In today's cutting costs environment in the offshore wind industry, significant achievements can be made with a better assessment of dynamic soil-pile interaction. Of the main damping mechanisms active at an OWT (offshore wind turbine), least is known about soil damping. The values for this contribution used in the industry today - mostly calculated analogously to a study performed in 1980 - are expected to be on the low side. More research on the topic is recommended. Presence of more damping than currently assumed, would signify that the (often) design driving fatigue damage accumulation is lower than assumed. This would justify designing more light-weight structures using less construction steel, or allowing for longer (insured) OWT lifetimes then the now applied 20 years. Both these measures significantly decrease costs of offshore wind. This paper evaluates measured signals of twelve 'rotorstop' - test on an OWT at Dong Energy owned - Burbo Banks windfarm. The vibration decay was measured with an accelerometer and strain gauges along the tower. A simplistic analytical model has been developed enabling analyses of the measured signals. Two main modal shapes were identified with similar shape, but deviating amplitudes in the soil profile. The large difference in damping that exists between the vibrations of these modes is attributed to the difference in influence that the soil can have on these vibrations. The found effect of soil on the damping of this particular OWT is significantly larger than the order of magnitude used in the industry today.

  10. Review of the reef effects of offshore wind farm structures and potential for enhancement and mitigation.

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2008-01-09

    The purpose of this report is to review the likely reef effects of offshore wind farm (OWF) structures focussing on two aspects of their physical presence: firstly, the likely reef effects on fish, shellfish and other marine biota and secondly, the potential to enhance the reef effect for commercially significant species.Turbine towers and their associated scour protection constitute surfaces readily colonised by a typical and broadly predictable assemblage of organisms, reflecting zonation patterns observed in adjacent intertidal and sub-tidal rocky shore communities. The physical impact and biological impact of OWFs will be proportional to the level (area/extent) of scour protection utilised and this will need to be assessed on a site specific basis. At sites where it is unnecessary or unworkable to exclude all fishing gears, some commercial species will probably benefit from the presence of turbine structures and their associated reefs as a result of the provision of enhanced habitat opportunities. Exploration of the potential for mussel culture appears to be one of the most straightforward economic opportunities which could be progressed within existing OWFs - although, development of appropriate technology for culture in water depths at OWFs will require some further investigation. The opportunities presented by seaweed culture in the UK have yet to be recognised and an appropriate strategic direction provided for the sector. At the present time there appears to be very little potential for fin fish culture within OWFs, as shallow water depths and current conditions are not ideal for cage culture of salmon or cod, and current market conditions and labour costs mean that culture of sea bass in UK waters could not compete favourably with Mediterranean mariculture. Evidence from a variety of sources indicates that one enhancement effect which requires further investigation, as it is potentially a valuable opportunity for restoration and management of commercially

  11. Basic investigation on deflection wave propagation and strength of very large floating structures; Choogata futai kozo no tawami hado denpa kyodo to kyodo ni kansuru kisoteki kosatsu

    Energy Technology Data Exchange (ETDEWEB)

    Tsubogo, T.; Okada, H. [University of Osaka Prefecture, Osaka (Japan). Faculty of Engineering

    1997-08-01

    The response strength in which deflection waves propagating in the elastic body of a large floating structure with an order of km in length and width was investigated. Attention was paid to the waves propagating the place fully away from the boundary of a very large floating body so as to obtain the dispersion relation of waves and the relation between incident waves and deflection waves. Next, the frequency response was checked from the aspect of the displacement amplitude and strength for beams and plates. The dispersion relation of waves propagating the place fully away from the boundary of a very large floating body and the relation between the waves and infinite-point incident waves were represented by an expression. Similarly, the waves propagates more than the infinite-point incident waves in frequency, wavelength, and speed. A lower-limit value exists in the propagation speed. The displacement and stress amplitudes are represented by a relational expression. For plates, the displacement amplitude increases when the wave direction coincides with the small-rigidity direction. The stress amplitude is maximized when the waves corresponding to the ``wave below a floating body = size of a characteristic wave number`` reach the large-rigidity direction. 10 refs., 10 figs., 2 tabs.

  12. A quick seismic assessment method for jacket type offshore structures by combining push-over and nonlinear time history analyses

    Energy Technology Data Exchange (ETDEWEB)

    Karimiyan, S.; Hosseini, M. [International Inst. of Earthquake Engineering and Seismology, Tehran (Iran, Islamic Republic of); Karimiyan, M. [Islamic Azad Univ., Tehran (Iran, Islamic Republic of). Earthquake Eng. Dept., School of Engineering

    2010-07-01

    Several offshore structures are located in seismic regions. In order to upgrade their seismic behaviour, their seismic vulnerability must be evaluated. It is thought that the most reliable type of analysis for seismic evaluation is nonlinear time history analysis (NLTHA), however, it is known to be a very time consuming method. This paper presented a quick procedure by combining the push over analysis (POA) and the NLTHA. The paper discussed both methods in detail. In order to identify the more critical members of the structure, based on the range of their plastic deformations, some POA were first performed. The NLTHA was then performed, focusing on the critical members, to obtain their vulnerability with higher reliability. An offshore structure of jacket type, installed in the Lavan oil field in the Persian Gulf in 1970, was also considered in order to demonstrate the efficiency of the proposed method. It was concluded from the numerical results that combining POA and NLTHA was a quick and reliable seismic evaluation method. The results demonstrated that although the vulnerability of the jacket structure was not very high, the level of damage was not the same for different members, and was dependent on their location in the structure and also its geometric orientation and load bearing situation. 6 refs., 1 tab., 8 figs.

  13. Some new offshore technologic trends and their possible influence on the world gas supply structure; Quelques nouvelles tendances technologiques en offshore et leur influence possible sur la structure de la disponibilite mondiale de gaz

    Energy Technology Data Exchange (ETDEWEB)

    Yakushev, V.S. [VNIIGAZ, OAO Gazprom (Russian Federation)

    2000-07-01

    According to Global Energy Scenarios (GES) role of natural gas as primary energy source in 21. century will grow considerably. In the same time gas industry has to response 3 challenges: environmental, technological and political to make these scenarios real. Development of new technological systems uniting offshore gas production, shuttle transport by tankers and CO{sub 2} sequestration looks like the most optimum way of these problems solution. Some new current technological trends are shown and the most probable technologic concept on gas production from deep and ultra-deep waters is suggested. Probable changes in the world gas supply structure caused by these systems application are discussed. (author)

  14. Preliminary Design of a Multi-Column TLP Foundation for a 5-MW Offshore Wind Turbine

    Directory of Open Access Journals (Sweden)

    Yanping He

    2012-10-01

    Full Text Available Currently, floating wind turbines (FWTs may be the more economical and suitable systems with which to exploit offshore wind energy in deep waters. Among the various types of floating foundations for offshore wind farms, a tension leg platform (TLP foundation can provide a relatively stable platform for currently available offshore wind turbines without requiring major modifications. In this study, a new multi-column TLP foundation (WindStar TLP was developed for the NREL 5-MW offshore wind turbine according to site-specific environmental conditions, which are the same as the OC3-Hywind (NREL conditions. The general arrangement, main structure and mooring system were also designed and investigated through hydrodynamic and natural frequency analyses. The complete system avoids resonance through the rotor excitations. An aero-hydro-servo-elastic coupled analysis was carried out in the time domain with the numerical tool FAST. Statistics of the key parameters were obtained and analysed and comparisons to MIT/NREL TLP are made. As a result, the design requirements were shown to be satisfied, and the proposed WindStar TLP was shown to have favourable motion characteristics under extreme wind and wave conditions with a lighter and smaller structure. The new concept holds great potential for further development.

  15. On the relative importance of loads acting on a floating vertical axis wind turbine system when evaluating the global system response

    DEFF Research Database (Denmark)

    Collu, Maurizio; Borg, Michael; Manuel, Lance

    2016-01-01

    Interest in offshore floating wind turbines has been growing over the last decade. While a number of studies have been conducted to model the dynamics of offshore floating HAWT systems (e.g. OC3-Phase IV, OC4-Phase II), relatively few studies have been conducted on floating VAWT systems, despite...... offshore floating VAWT, considering a turbulent wind field and stochastically generated waves, to assess the more critical loads and distinguish them from those with negligible effect, when estimating the global system response. The floating VAWT system considered is comprised of a 5MW rotor supported...

  16. Protonic charge defect structures in floating water bridges observed as Zundel and Eigen solvation arrangements

    Science.gov (United States)

    Teschke, Omar; de Castro, Jose Roberto; Valente Filho, Juracyr Ferraz; Soares, David Mendez

    2017-10-01

    Protonic arrangements were detected in water bridge structures using confocal Raman microscopy, and the spectra show two formed structures. The measured Raman spectra were modified using the voltage applied to the bridge structure, which changed the proportion of these two species. Initially, for a 6.3 kV applied voltage, there was a measurable increase in the bridge current above the Ohmic contribution and the observed Raman spectrum of this new injected specie corresponded to the computed spectrum for the Zundel protonic arrangement. As the voltage further increases a contribution from the Eigen proton solvation specie is added to the measured spectrum.

  17. A structural homologue of colipase in black mamba venom revealed by NMR floating disulphide bridge analysis.

    Science.gov (United States)

    Boisbouvier, J; Albrand, J P; Blackledge, M; Jaquinod, M; Schweitz, H; Lazdunski, M; Marion, D

    1998-01-01

    The solution structure of mamba intestinal toxin 1 (MIT1), isolated from Dendroaspis polylepis polylepis venom, has been determined. This molecule is a cysteine-rich polypeptide exhibiting no recognised family membership. Resistance to MIT1 to classical specific endoproteases produced contradictory NMR and biochemical information concerning disulphide-bridge topology. We have used distance restraints allowing ambiguous partners between S atoms in combination with NMR-derived structural information, to correctly determine the disulphide-bridge topology. The resultant solution structure of MIT1, determined to a resolution of 0.5 A, reveals an unexpectedly similar global fold with respect to colipase, a protein involved in fatty acid digestion. Colipase exhibits an analogous resistance to endoprotease activity, indicating for the first time the possible topological origins of this biochemical property. The biochemical and structural homology permitted us to propose a mechanically related digestive function for MIT1 and provides novel information concerning snake venom protein evolution. Copyright 1998 Academic Press.

  18. Corrosion protection of Arctic offshore structures: Final report. [Effects of temperature and salinity on required cathodic protection current

    Energy Technology Data Exchange (ETDEWEB)

    Sackinger, W.M.; Rogers, J.C.; Feyk, C.; Theuveny, B.

    1985-10-01

    Results are presented for a research program on corrosion prevention for Arctic offshore structures which are in contact with sea ice for a significant portion of the year. The electrical method most adaptable for structure protection involves the injection of impressed current from several remote anodes buried just beneath the sea floor. The electrical resistivity of annual sea ice as a function of temperature and salinity is presented. Details of the interface layers formed between sea ice and steel in the presence of current injection are shown. A computer program was developed to enable the calculation of protective current density into the structure, in the presence of ice rubble and ridges around the structure. The program and the results of an example calculation are given for a caisson- retained island structure. 81 refs., 103 figs., 3 tabs.

  19. Soil-Structure Interaction for Non-Slender, Large-Diameter Offshore Monopiles

    DEFF Research Database (Denmark)

    Sørensen, Søren Peder Hyldal

    conducted. The initial part of p-y curves for non-slender piles has been investigated by means of numerical modelling. The general behaviour of eccentrically loaded non-slender piles has been investigated by physical modelling. These tests have been conducted in the pressure tank at Aalborg University....... The monopile foundation concept has been employed as the foundation for the majority of the currently installed offshore wind turbines. Therefore, this PhD thesis concerns the soil-pile interaction for non-slender, large-diameter offshore piles. A combination of numerical and physical modelling has been....... Hence, the application of an overburden pressure is possible. The timescale of the backfill process and the compaction of soil material backfilled around piles in storm conditions have been investigated by means of large-scale physical modelling....

  20. Brief communication: Structural monitoring for lifetime extension of offshore wind monopiles: can strain measurements at one level tell us everything?

    Directory of Open Access Journals (Sweden)

    L. Ziegler

    2017-09-01

    Full Text Available Operators need accurate knowledge on structural reserves to decide about lifetime extension of offshore wind turbines. Load monitoring enables us to directly compare design loads with real loading histories of the support structure in order to calculate its remaining useful lifetime. Monitoring of every hot spot is technically and financially not feasible. This paper presents a novel idea for load monitoring of monopiles. It requires strain measurements at only one level convenient for sensor installation, such as tower bottom. Measurements are converted into damage equivalent loads for 10 min time intervals. Damage equivalent loads are extrapolated to other locations of the structure with a simulation model and statistical algorithm. For this, structural loads at all locations of the monopile are calculated with aero-hydro-elastic software and updated finite element models. Damage equivalent loads at unmeasured locations are predicted from the simulation results with a k-nearest neighbor regression algorithm. The extrapolation was tested with numerical simulations of an 8 MW offshore wind turbine. Results show that damage can be predicted with an error of 1–3 % if this is done conditional on mean wind speed, which is very promising. The load monitoring concept is simple, cheap and easy to implement. This makes it ideal for making decisions on lifetime extension of monopiles.

  1. Corrosion and corrosion protection of support structures for offshore wind energy devices (OWEA)

    Energy Technology Data Exchange (ETDEWEB)

    Momber, A. [Muehlhan AG, Schlinckstrasse 3, D-21107 Hamburg (Germany)

    2011-05-15

    The paper provides a review about the corrosion and corrosion protection of offshore wind energy devices (OWEA). Firstly, special features resulting from location and operation of OWEA are being discussed. Secondly, types of corrosion and corrosion phenomena are summarized in a systematic way. Finally, practical solutions to the corrosion protection of OWEA, including steel allowances, cathodic protection and coatings and linings, are discussed. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  2. Consideration on the dynamic behavior and the structural design of large scale floating structure. 2nd Report. Stability of elastic structure and design of elastic response; Choogata futai no kozo kyodo oyobi kozo sekkei ni kansuru kosatsu. 2. Dansei henkei wo koryoshita fukugensei oyobi kozo oto no sekkei

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, H.; Yoshida, K. [The University of Tokyo, Tokyo (Japan)

    1996-12-31

    A policy of improving a very large floating body was planned based on its dynamic characteristics, and a proposal was made thereon. Furthermore, discussions were given on stability that considers effect of elastic deformation required when a structure is mounted on a floating body. With respect to a structural design of a very large floating body in which elastic response is governing, and upon modeling the very large floating body into an aeolotropic plate on an elastic supporting floor, it was shown that the existing range of natural vibration speed in the elastic response is in higher range than the natural vibration speed of heave. It was also indicated that the peak height of response to waves in resonance is inversely proportional to wave frequency, and furthermore, degree of flowing in of vibration energy during the resonance is determined by an inner product of spatial vibration patterns of wave force and the excited mode shape. A proposal was made on a floating body improved of excessive response in the floating body edges by changing the characteristics of the floating body edges. In addition, discussions were given on stability that considers elastic deformation of a floating body that becomes necessary when a structure, such as a building, is built on a very large floating body. 9 refs., 9 figs., 3 tabs.

  3. Consideration on the dynamic behavior and the structural design of large scale floating structure. 2nd Report. Stability of elastic structure and design of elastic response; Choogata futai no kozo kyodo oyobi kozo sekkei ni kansuru kosatsu. 2. Dansei henkei wo koryoshita fukugensei oyobi kozo oto no sekkei

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, H; Yoshida, K [The University of Tokyo, Tokyo (Japan)

    1997-12-31

    A policy of improving a very large floating body was planned based on its dynamic characteristics, and a proposal was made thereon. Furthermore, discussions were given on stability that considers effect of elastic deformation required when a structure is mounted on a floating body. With respect to a structural design of a very large floating body in which elastic response is governing, and upon modeling the very large floating body into an aeolotropic plate on an elastic supporting floor, it was shown that the existing range of natural vibration speed in the elastic response is in higher range than the natural vibration speed of heave. It was also indicated that the peak height of response to waves in resonance is inversely proportional to wave frequency, and furthermore, degree of flowing in of vibration energy during the resonance is determined by an inner product of spatial vibration patterns of wave force and the excited mode shape. A proposal was made on a floating body improved of excessive response in the floating body edges by changing the characteristics of the floating body edges. In addition, discussions were given on stability that considers elastic deformation of a floating body that becomes necessary when a structure, such as a building, is built on a very large floating body. 9 refs., 9 figs., 3 tabs.

  4. Issues in offshore platform research - Part 1: Semi-submersibles

    Science.gov (United States)

    Sharma, R.; Kim, Tae-Wan; Sha, O. P.; Misra, S. C.

    2010-09-01

    Availability of economic and efficient energy resources is crucial to a nation's development. Because of their low cost and advancement in drilling and exploration technologies, oil and gas based energy systems are the most widely used energy source throughout the world. The inexpensive oil and gas based energy systems are used for everything, i.e., from transportation of goods and people to the harvesting of crops for food. As the energy demand continues to rise, there is strong need for inexpensive energy solutions. An offshore platform is a large structure that is used to house workers and machinery needed to drill wells in the ocean bed, extract oil and/or natural gas, process the produced fluids, and ship or pipe them to shore. Depending on the circumstances, the offshore platform can be fixed (to the ocean floor) or can consist of an artificial island or can float. Semi-submersibles are used for various purposes in offshore and marine engineering, e.g. crane vessels, drilling vessels, tourist vessels, production platforms and accommodation facilities, etc. The challenges of deepwater drilling have further motivated the researchers to design optimum choices for semi-submersibles for a chosen operating depth. In our series of eight papers, we discuss the design and production aspects of all the types of offshore platforms. In the present part I, we present an introduction and critical analysis of semi-submersibles.

  5. Issues in offshore platform research - Part 1: Semi-submersibles

    Directory of Open Access Journals (Sweden)

    R. Sharma

    2010-09-01

    Full Text Available Availability of economic and efficient energy resources is crucial to a nation's development. Because of their low cost and advancement in drilling and exploration technologies, oil and gas based energy systems are the most widely used energy source throughout the world. The inexpensive oil and gas based energy systems are used for everything, i.e., from transportation of goods and people to the harvesting of crops for food. As the energy demand continues to rise, there is strong need for inexpensive energy solutions. An offshore platform is a large structure that is used to house workers and machinery needed to drill wells in the ocean bed, extract oil and/or natural gas, process the produced fluids, and ship or pipe them to shore. Depending on the circumstances, the offshore platform can be fixed (to the ocean floor or can consist of an artificial island or can float. Semi-submersibles are used for various purposes in offshore and marine engineering, e.g. crane vessels, drilling vessels, tourist vessels, production platforms and accommodation facilities, etc. The challenges of deepwater drilling have further motivated the researchers to design optimum choices for semi-submersibles for a chosen operating depth. In our series of eight papers, we discuss the design and production aspects of all the types of offshore platforms. In the present part I, we present an introduction and critical analysis of semi-submersibles.

  6. Comparison of Welding Residual Stresses of Hybrid Laser-Arc Welding and Submerged Arc Welding in Offshore Steel Structures

    DEFF Research Database (Denmark)

    Andreassen, Michael Joachim; Yu, Zhenzhen; Liu, Stephen

    2016-01-01

    In the offshore industry, welding-induced distortion and tensile residual stresses have become a major concern in relation to the structural integrity of a welded structure. Particularly, the continuous increase in size of welded plates and joints needs special attention concerning welding induced...... residual stresses. These stresses have a negative impact on the integrity of the welded joint as they promote distortion, reduce fatigue life, and contribute to corrosion cracking and premature failure in the weld components. This paper deals with the influence and impact of welding method on the welding...... induced residual stresses. It is also investigated whether the assumption of residual stresses up to yield strength magnitude are present in welded structures as stated in the design guidelines. The fatigue strength for welded joints is based on this assumption. The two welding methods investigated...

  7. Numerical tools to predict the environmental loads for offshore structures under extreme weather conditions

    Science.gov (United States)

    Wu, Yanling

    2018-05-01

    In this paper, the extreme waves were generated using the open source computational fluid dynamic (CFD) tools — OpenFOAM and Waves2FOAM — using linear and nonlinear NewWave input. They were used to conduct the numerical simulation of the wave impact process. Numerical tools based on first-order (with and without stretching) and second-order NewWave are investigated. The simulation to predict force loading for the offshore platform under the extreme weather condition is implemented and compared.

  8. Wire Mesh Dampers for Semi-Floating Ring Bearings in Automotive Turbochargers: Measurements of Structural Stiffness and Damping Parameters

    Directory of Open Access Journals (Sweden)

    Keun Ryu

    2018-04-01

    Full Text Available The current work introduces a new semi-floating ring bearing (SFRB system developed for improving the rotordynamic and vibration performance of automotive turbochargers (TCs at extreme operation conditions, such as high temperature, severe external force excitation, and large rotor imbalance. The new bearing design replaces outer oil films, i.e., squeeze film dampers (SFDs, in TC SFRBs with wire mesh dampers (WMDs. This SFRB configuration integrating WMDs aims to implement reliable mechanical components, as an inexpensive and simple alternative to SFDs, with consistent and superior damping capability, as well as predictable forced performance. Since WMDs are in series with the inner oil films of SFRBs, experimentally determined force coefficients of WMDs are of great importance in the design process of TC rotor-bearing systems (RBSs. Presently, the measurements of applied static load and ensuing deflection determine the structural stiffnesses of the WMDs. The WMD damping parameters, including dissipated energy, loss factor, and dry friction coefficient, are estimated from the area of the distinctive local hysteresis loop of the load versus WMD displacement data recorded during consecutive loading-unloading cycles as a function of applied preload with a constant amplitude of motion. The changes in WMD loss factor and dry friction coefficient due to increases in preload are more significant for the WMDs with lower density. The present work shows, to date, the most comprehensive measurements of static load characteristics on the WMDs for application into small automotive TCs. More importantly, the extensive test measurements of WMD deflection versus increasing static loads will aid to anchor predictions of future computation model.

  9. Coupled Dynamic Modeling of Floating Wind Turbine Systems: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Wayman, E. N.; Sclavounos, P. D.; Butterfield, S.; Jonkman, J.; Musial, W.

    2006-03-01

    This article presents a collaborative research program that the Massachusetts Institute of Technology (MIT) and the National Renewable Energy Laboratory (NREL) have undertaken to develop innovative and cost-effective floating and mooring systems for offshore wind turbines in water depths of 10-200 m. Methods for the coupled structural, hydrodynamic, and aerodynamic analysis of floating wind turbine systems are presented in the frequency domain. This analysis was conducted by coupling the aerodynamics and structural dynamics code FAST [4] developed at NREL with the wave load and response simulation code WAMIT (Wave Analysis at MIT) [15] developed at MIT. Analysis tools were developed to consider coupled interactions between the wind turbine and the floating system. These include the gyroscopic loads of the wind turbine rotor on the tower and floater, the aerodynamic damping introduced by the wind turbine rotor, the hydrodynamic damping introduced by wave-body interactions, and the hydrodynamic forces caused by wave excitation. Analyses were conducted for two floater concepts coupled with the NREL 5-MW Offshore Baseline wind turbine in water depths of 10-200 m: the MIT/NREL Shallow Drafted Barge (SDB) and the MIT/NREL Tension Leg Platform (TLP). These concepts were chosen to represent two different methods of achieving stability to identify differences in performance and cost of the different stability methods. The static and dynamic analyses of these structures evaluate the systems' responses to wave excitation at a range of frequencies, the systems' natural frequencies, and the standard deviations of the systems' motions in each degree of freedom in various wind and wave environments. This article in various wind and wave environments. This article explores the effects of coupling the wind turbine with the floating platform, the effects of water depth, and the effects of wind speed on the systems' performance. An economic feasibility analysis of

  10. Analysis of the Nonlinear Static and Dynamic Behavior of Offshore Structures

    KAUST Repository

    Alfosail, Feras

    2015-07-01

    Understanding static and dynamic nonlinear behavior of pipes and risers is crucial for the design aspects in offshore engineering fields. In this work, we examine two nonlinear problems in offshore engineering field: vortex Induced vibration of straight horizontal pipes, and boundary layer static solution of inclined risers. In the first study, we analyze the effect of the internal velocity of straight horizontal pipe and obtain the vortex induced vibration forces via coupling the pipe equation of motion with the recently modified Van Der Pol oscillator governing the lift coefficient. Our numerical results are obtained for two different pipe configurations: hinged-hinged, and clamped- clamped. The results show that the internal velocity reduces the vibration and the oscillation amplitudes. Also, it is shown that the clamped-clamped pipe configuration offers a wider range of internal velocities before buckling instability occurs. The results also demonstrate the effect of the end condition on the amplitudes of vibration. In the second study, we develop a boundary layer perturbation static solution to govern and simulate the static behavior of inclined risers. In the boundary layer analysis, we take in consideration the effects of the axial stretch, applied tension, and internal velocity. Our numerical simulation results show good agreement with the exact solutions for special cases. In addition, our developed method overcomes the mathematical and numerical limitations of the previous methods used before.

  11. Offshoring Process

    DEFF Research Database (Denmark)

    Slepniov, Dmitrij; Sørensen, Brian Vejrum; Katayama, Hiroshi

    2011-01-01

    The purpose of this chapter is to contribute to the knowledge on how production offshoring and international operations management vary across cultural contexts. The chapter attempts to shed light on how companies approach the process of offshoring in different cultural contexts. In order...... of globalisation. Yet there are clear differences in how offshoring is conducted in Denmark and Japan. The main differences are outlined in a framework and explained employing cultural variables. The findings lead to a number of propositions suggesting that the process of offshoring is not simply a uniform...... technical-rational calculation of the most efficient organisation of activities across national borders, but it is rather specific to the parent companies’ national contexts....

  12. Basic studies on design supporting system of offshore structure. Part 2. Implementation of structural design supporting system of offshore structures; Kaiyo kozobutsu wo taisho to shita sekkei shien system ni kansuru kisoteki kenkyu. 2. Kaiyo kozobutsu no kozo sekkei shien system no kochiku

    Energy Technology Data Exchange (ETDEWEB)

    Nomoto, T.; Hamada, K.; Aoyama, K. [The University of Tokyo, Tokyo (Japan)

    1996-12-31

    In order to improve the existing design-supporting system for offshore structures, new functions are added to evaluate information of the products, especially those for structural designs. The structural analysis system should be provided with a function of design modification, to efficiently support the structural analysis of these structures. The new system adds hierarchy of various offshore structure models and three-dimensional dimensions to clarify structural and geometrical constraints and design-modification function. The design-modification function is included by use of the hierarchy. The other new functions are finite element analysis systems for the main structure and components, and rigidity calculation for the main structure. The main structure and functional element models are confirmed to be useful also for utilization of information, and provide necessary information of the product models. 11 refs., 11 figs.

  13. Basic studies on design supporting system of offshore structure. Part 2. Implementation of structural design supporting system of offshore structures; Kaiyo kozobutsu wo taisho to shita sekkei shien system ni kansuru kisoteki kenkyu. 2. Kaiyo kozobutsu no kozo sekkei shien system no kochiku

    Energy Technology Data Exchange (ETDEWEB)

    Nomoto, T; Hamada, K; Aoyama, K [The University of Tokyo, Tokyo (Japan)

    1997-12-31

    In order to improve the existing design-supporting system for offshore structures, new functions are added to evaluate information of the products, especially those for structural designs. The structural analysis system should be provided with a function of design modification, to efficiently support the structural analysis of these structures. The new system adds hierarchy of various offshore structure models and three-dimensional dimensions to clarify structural and geometrical constraints and design-modification function. The design-modification function is included by use of the hierarchy. The other new functions are finite element analysis systems for the main structure and components, and rigidity calculation for the main structure. The main structure and functional element models are confirmed to be useful also for utilization of information, and provide necessary information of the product models. 11 refs., 11 figs.

  14. Condensation of long-term wave climates for the fatigue design of hydrodynamically sensitive offshore wind turbine support structures

    DEFF Research Database (Denmark)

    Passon, Patrik; Branner, Kim

    2016-01-01

    important for hydrodynamically sensitive structures since the applied met-ocean parameters have a non-linear influence on calculated fatigue design loads. The present article introduces a new wave lumping method for condensation of the wave climate. The novelty is predominantly based on refined equivalence......Cost-efficient and reliable fatigue designs of offshore wind turbine support structures require an adequate representation of the site-specific wind–wave joint distribution. Establishment of this wind–wave joint distribution for design load calculation purposes requires typically a correlation...... of the marginal wind and wave distribution. This is achieved by condensation of the site-specific wave climate in terms of wave period or wave height lumping, subsequently used as input for a correlation with the corresponding wind climate. The quality of this resulting wind–wave correlation is especially...

  15. Offshoring R&D

    DEFF Research Database (Denmark)

    Hansen, Zaza Nadja Lee; Rasmussen, Lauge Baungaard

    2010-01-01

    Companies are increasingly offshoring R&D activities. Many firms, however, experience difficulties related to virtual teamwork across cultures and time zones. The research question is: How does increasing R&D offshoring impact transparency of communication structures and knowledge sharing? Using...... case studies from Danish multinational corporations with R&D activities in China, India or Eastern Europe this paper analyses the impact observed in these companies in regard to communication structures and knowledge sharing in management of offshored R&D activities. The findings show that companies...... attempt to increase transparency through formalisation of knowledge and clear communication structures. However, the influence of tacit knowledge, horizontal communication and culture seem largely overlooked. Therefore the authors suggest a context based approach to transparency accustomed...

  16. The Hidden Costs of Offshoring

    DEFF Research Database (Denmark)

    Møller Larsen, Marcus; Manning, Stephan; Pedersen, Torben

    2011-01-01

    of offshoring. Specifically, we propose that hidden costs can be explained by the combination of increasing structural, operational and social complexity of offshoring activities. In addition, we suggest that firm orientation towards organizational design as part of an offshoring strategy and offshoring......This study seeks to explain hidden costs of offshoring, i.e. unexpected costs resulting from the relocation of business tasks and activities outside the home country. We develop a model that highlights the role of complexity, design orientation and experience in explaining hidden costs...... experience moderate the relationship between complexity and hidden costs negatively i.e. reduces the cost generating impact of complexity. We develop three hypotheses and test them on comprehensive data from the Offshoring Research Network (ORN). In general, we find support for our hypotheses. A key result...

  17. Breaking wave impact on offshore tripod structures. Comparison of large scale experiments, CFD simulations, and DIN recommended practice; Wellenbrechen an Offshore Tripod-Gruendungen. Versuche und Simulationen im Vergleich zu Richtlinien

    Energy Technology Data Exchange (ETDEWEB)

    Hildebrandt, Arndt; Schlurmann, Torsten [Hannover Univ. (Germany). Franzius-Institut fuer Wasserbau und Kuesteningenieurwesen

    2012-05-15

    Coastal and near shore areas offer a large potential for offshore wind energy production due to strong and steady wind conditions. Thousands of offshore wind energy converters are projected for mass production within the next years. Detailed understanding of the extreme, dynamic wave loads on offshore structures is essential for an efficient design. The impact on structures is a complex process and further studies are required for more detailed load assessments, which is why breaking wave loads were investigated by the research project ''GIGAWIND alpha ventus - Subproject 1'' within the network ''Research at Alpha VEntus'' (RAVE). Large scale laboratory tests (1:12) with breaking waves have been carried out at the Large Wave Flume of the ''Forschungszentrum Kueste'' (FZK, Hanover) to reveal more detailed insights on the impact area, duration and development of the wave induced momentum, and intensity of pressures. In addition, local pressures calculated by a three-dimensional numerical impact simulation are compared to the Large Wave Flume experiments. Slamming coefficients have been derived from the physical model tests and CFD simulations for the comparison to load calculations based on guidelines. (orig.)

  18. Numerical response analysis of a large mat-type floating structure in regular waves; Matogata choogata futai kozobutsu no haro oto kaiseki

    Energy Technology Data Exchange (ETDEWEB)

    Yasuzawa, Y.; Kagawa, K.; Kitabayashi, K. [Kyushu University, Fukuoka (Japan); Kawano, D. [Mitsubishi Heavy Industries, Ltd., Tokyo (Japan)

    1997-08-01

    The theory and formulation for the numerical response analysis of a large floating structure in regular waves were given. This paper also reports the comparison between the experiment in the Shipping Research Institute in the Minitry of Transport and the result calculated using numerical analytic codes in this study. The effect of the bending rigidity of a floating structure and the wave direction on the dynamic response of a structure was examined by numerical calculation. When the ratio of structure length and incident wavelength (L/{lambda}) is lower, the response amplitude on the transmission side becomes higher in a wave-based response. The hydrodynamic elasticity exerts a dominant influence when L/{lambda} becomes higher. For incident oblique waves, the maximum response does not necessarily appear on the incidence side. Moreover, the response distribution is also complicated. For example, the portion where any flexible amplitude hardly appears exists. A long structure response can be predicted from a short structure response to some degree. They differ in response properties when the ridigity based on the similarity rule largely differs, irrespective of the same L/{lambda}. For higher L/{lambda}, the wave response can be easily predicted when the diffrection force is replaced by the concentrated exciting force on the incidence side. 13 refs., 14 figs., 3 tabs.

  19. Characteristics of Offshore Hawai';i Island Seismicity and Velocity Structure, including Lo';ihi Submarine Volcano

    Science.gov (United States)

    Merz, D. K.; Caplan-Auerbach, J.; Thurber, C. H.

    2013-12-01

    The Island of Hawai';i is home to the most active volcanoes in the Hawaiian Islands. The island's isolated nature, combined with the lack of permanent offshore seismometers, creates difficulties in recording small magnitude earthquakes with accuracy. This background offshore seismicity is crucial in understanding the structure of the lithosphere around the island chain, the stresses on the lithosphere generated by the weight of the islands, and how the volcanoes interact with each other offshore. This study uses the data collected from a 9-month deployment of a temporary ocean bottom seismometer (OBS) network fully surrounding Lo';ihi volcano. This allowed us to widen the aperture of earthquake detection around the Big Island, lower the magnitude detection threshold, and better constrain the hypocentral depths of offshore seismicity that occurs between the OBS network and the Hawaii Volcano Observatory's land based network. Although this study occurred during a time of volcanic quiescence for Lo';ihi, it establishes a basis for background seismicity of the volcano. More than 480 earthquakes were located using the OBS network, incorporating data from the HVO network where possible. Here we present relocated hypocenters using the double-difference earthquake location algorithm HypoDD (Waldhauser & Ellsworth, 2000), as well as tomographic images for a 30 km square area around the summit of Lo';ihi. Illuminated by using the double-difference earthquake location algorithm HypoDD (Waldhauser & Ellsworth, 2000), offshore seismicity during this study is punctuated by events locating in the mantle fault zone 30-50km deep. These events reflect rupture on preexisting faults in the lower lithosphere caused by stresses induced by volcano loading and flexure of the Pacific Plate (Wolfe et al., 2004; Pritchard et al., 2007). Tomography was performed using the double-difference seismic tomography method TomoDD (Zhang & Thurber, 2003) and showed overall velocities to be slower than

  20. Structure of the Lithosphere-Asthenosphere Boundary Onshore and Offshore the California Continental Margin from Three-Dimensional Seismic Anisotropy

    Science.gov (United States)

    Gomez, C. D.; Escobar, L., Sr.; Rathnayaka, S.; Weeraratne, D. S.; Kohler, M. D.

    2016-12-01

    The California continental margin, a major transform plate boundary in continental North America, is the locus of complex tectonic stress fields that are important in interpreting both remnant and ongoing deformational strain. Ancient subduction of the East Pacific Rise spreading center, the rotation and translation of tectonic blocks and inception of the San Andreas fault all contribute to the dynamic stress fields located both onshore and offshore southern California. Data obtained by the ALBACORE (Asthenospheric and Lithospheric Broadband Architecture from the California Offshore Region Experiment) and the CISN (California Integrated Seismic Network) seismic array are analyzed for azimuthal anisotropy of Rayleigh waves from 80 teleseismic events at periods 16 - 78 s. Here we invert Rayleigh wave data for shear wave velocity structure and three-dimensional seismic anisotropy in the thee regions designated within the continental margin including the continent, seafloor and California Borderlands. Preliminary results show that seismic anisotropy is resolved in multiple layers and can be used to determine the lithosphere-asthenosphere boundary (LAB) in offshore and continental regions. The oldest seafloor in our study at age 25-35 Ma indicates that the anisotropic transition across the LAB occurs at 73 km +/- 25 km with the lithospheric fast direction oriented WNW-ESE, consistent with current Pacific plate motion direction. The continent region west of the San Andreas indicates similar WNW-ESE anisotropy and LAB depth. Regions east of the San Andreas fault indicate NW-SE anisotropy transitioning to a N-S alignment at 80 km depth north of the Garlock fault. The youngest seafloor (15 - 25 Ma) and outer Borderlands indicate a more complex three layer fabric where shallow lithospheric NE-SW fast directions are perpendicular with ancient Farallon subduction arc, a mid-layer with E-W fast directions are perpendicular to remnant fossil fabric, and the deepest layer

  1. The Effects of Anthropogenic Structures on Habitat Connectivity and the Potential Spread of Non-Native Invertebrate Species in the Offshore Environment.

    Science.gov (United States)

    Simons, Rachel D; Page, Henry M; Zaleski, Susan; Miller, Robert; Dugan, Jenifer E; Schroeder, Donna M; Doheny, Brandon

    2016-01-01

    Offshore structures provide habitat that could facilitate species range expansions and the introduction of non-native species into new geographic areas. Surveys of assemblages of seven offshore oil and gas platforms in the Santa Barbara Channel revealed a change in distribution of the non-native sessile invertebrate Watersipora subtorquata, a bryozoan with a planktonic larval duration (PLD) of 24 hours or less, from one platform in 2001 to four platforms in 2013. We use a three-dimensional biophysical model to assess whether larval dispersal via currents from harbors to platforms and among platforms is a plausible mechanism to explain the change in distribution of Watersipora and to predict potential spread to other platforms in the future. Hull fouling is another possible mechanism to explain the change in distribution of Watersipora. We find that larval dispersal via currents could account for the increase in distribution of Watersipora from one to four platforms and that Watersipora is unlikely to spread from these four platforms to additional platforms through larval dispersal. Our results also suggest that larvae with PLDs of 24 hours or less released from offshore platforms can attain much greater dispersal distances than larvae with PLDs of 24 hours or less released from nearshore habitat. We hypothesize that the enhanced dispersal distance of larvae released from offshore platforms is driven by a combination of the offshore hydrodynamic environment, larval behavior, and larval release above the seafloor.

  2. Offshore Outsourcing

    DEFF Research Database (Denmark)

    Petersen, Bent; Benito, Gabriel R. G.; Dovgan, Olesya

    While the extant literature on offshore outsourcing deals with this operation mode in isolation, and typically with a focus on cost effects, we address the broader question of how companies choose and use outsourcing as part of foreign operation mode development and as a contributor to internatio...... that outsourcing can be used proactively to promote expanded international operations.......While the extant literature on offshore outsourcing deals with this operation mode in isolation, and typically with a focus on cost effects, we address the broader question of how companies choose and use outsourcing as part of foreign operation mode development and as a contributor...

  3. RAMSI management model and evaluation criteria for Nordic offshore wind asset

    Energy Technology Data Exchange (ETDEWEB)

    Tiusanen, R.; Jaennes, J. [VTT Technical Research Centre of Finland, Espoo (Finland); Liyanage, J. P. [Univ. of Stavanger, Center for Industrial Asset Management (Norway)

    2012-07-01

    The offshore wind energy sector is in the early stages of development, but it is growing fast. Due to the European Union's renewable-energy and climate goals along with national legislation, the offshore wind sector will develop strongly over the coming years in Europe. In the offshore wind energy sector, there are many different wind-turbine designs ranging from traditional mono pile structures to floating platforms, depending on the water depth. Today, most offshore turbines are based on onshore turbine designs, and turbine technology continues to develop incrementally. At the same time, there is strong demand in the market for new, innovative designs for offshore wind turbines whose main focus is reliability and cost efficiency. For floating offshore wind turbine designs, there may be new types of uncertainty and system risks compared with onshore wind turbines. Wind turbines in cold climates, such as those experienced in the Nordic countries, may be exposed to extreme conditions, such as formation of ice or very low temperatures that are outside the design limits of standard wind turbines. In the offshore wind energy sector, specification, implementation and verification of the so-called R&M's (Reliability, Availability, Maintainability, Safety and Inspect ability) requirements during development work are important for companies delivering wind turbines, from the perspective of system integrity. Decisions made before the formal design phase strongly determine the costs and benefits gained during the whole life cycle of a wind turbine. The benefits of implementing the R&M's program include support with investment decisions, cost management, improved management of resource requirements, systematic support with development and implementation of products, and integration of dependability and safety requirements. This publication outlines a model for managing R&M's factors during the conceptual design phase of an offshore wind turbine. The model

  4. A study of rotor and platform design trade-offs for large-scale floating vertical axis wind turbines

    Science.gov (United States)

    Griffith, D. Todd; Paquette, Joshua; Barone, Matthew; Goupee, Andrew J.; Fowler, Matthew J.; Bull, Diana; Owens, Brian

    2016-09-01

    Vertical axis wind turbines are receiving significant attention for offshore siting. In general, offshore wind offers proximity to large populations centers, a vast & more consistent wind resource, and a scale-up opportunity, to name a few beneficial characteristics. On the other hand, offshore wind suffers from high levelized cost of energy (LCOE) and in particular high balance of system (BoS) costs owing to accessibility challenges and limited project experience. To address these challenges associated with offshore wind, Sandia National Laboratories is researching large-scale (MW class) offshore floating vertical axis wind turbines (VAWTs). The motivation for this work is that floating VAWTs are a potential transformative technology solution to reduce offshore wind LCOE in deep-water locations. This paper explores performance and cost trade-offs within the design space for floating VAWTs between the configurations for the rotor and platform.

  5. Offshore Wind Turbine Design

    DEFF Research Database (Denmark)

    Frandsen, Sten; Hansen, Erik Asp; Ibsen, Lars Bo

    2006-01-01

    Current offshore wind turbine design methods have matured to a 1st generation state, manifested in the draft of a possible standard, IEC 61400-3 (2005). It is now time to investigate the possibilities of improving existing methods. To do so in an efficient manner a clear identification of the most...... important uncertainty drivers specific for offshore wind turbine design loads is required. Describing the initial efforts in a Danish research project, the paper points to focal points for research and development. These are mainly: soil-structure interaction, improved modelling of wave loads from deep...

  6. Offshore rectenna feasbility

    Science.gov (United States)

    Freeman, J. W.; Hervey, D.; Glaser, P.

    1980-01-01

    A preliminary study of the feasibility and cost of an offshore rectenna to serve the upper metropolitan east coast was performed. A candidate site at which to build a 5 GW rectenna was selected on the basis of proximity to load centers, avoidance of shipping lanes, sea floor terrain, and relocated conditions. Several types of support structures were selected for study based initially on the reference system rectenna concept of a wire mesh ground screen and dipoles each with its own rectifier and filter circuits. Possible secondary uses of an offshore rectenna were examined and are evaluated.

  7. Model-based control of a ballast-stabilized floating wind turbine exposed to wind and waves

    Energy Technology Data Exchange (ETDEWEB)

    Christiansen, Soeren

    2013-01-15

    The wind turbine is a commercial product which is competing against other sources of energy, such as coal and gas. This competition drives a constant development to reduce costs and improve efficiency in order to reduce the total cost of the energy. The latest offshore development is the floating wind turbine, for water depths beyond 50 meters where winds are stronger and less turbulent. A floating wind turbine is subject to not only aerodynamics and wind induced loads, but also to hydrodynamics and wave induced loads. In contrast to a bottom fixed wind turbine, the floating structure, the hydrodynamics and the loads change the dynamic behavior of a floating wind turbine. Consequently, conventional wind turbine control cause instabilities on floating wind turbines. This work addresses the control of a floating spar buoy wind turbine, and focuses on the impact of the additional platform dynamics. A time varying control model is presented based on the wind speed and wave frequency. Estimates of the wind speed and wave frequency are used as scheduling variables in a gain scheduled linear quadratic controller to improve the electrical power production while reducing fatigue. To address the problem of negative damped fore-aft tower motion, additional control loops are suggested which stabilize the response of the onshore controller and reduce the impact of the wave induced loads. This research is then extended to model predictive control, to further address wave disturbances. In the context of control engineering, the dynamics and disturbances of a floating wind turbine have been identified and modeled. The objectives of maximizing the production of electrical power and minimizing fatigue have been reached by using advanced methods of estimation and control. (Author)

  8. Structural steels for fixed offshore platforms: technical challenges at the Brazilian national supply chain; Acos estruturais para plataformas fixas offshore: desafios tecnicos junto a cadeia de suprimentos nacional brasileira

    Energy Technology Data Exchange (ETDEWEB)

    Castro, Fabio Modesti Orsini de [Promon Engenharia Ltda., Rio de Janeiro, RJ (Brazil)

    2012-07-01

    This paper presents the main technical requirements for structural steel applied to the construction of bottom fixed offshore platforms, based on the most widely adopted and recognized actual standards. The mechanical properties and lab tests necessary to fulfill the Risk Management and E and P companies requirements are presented aiming to build the theoretical bases necessary for the engineering design of projects of this kind. The main types of steel available in the national market are presented at the end, giving an overall look at the Brazilian steel supply chain. (author)

  9. New Insight Into the Crustal Structure of the Continental Margin offshore NW Sabah/Borneo

    Science.gov (United States)

    Barckhausen, U.; Franke, D.; Behain, D.; Meyer, H.

    2002-12-01

    The continental margin offshore NW Sabah/Borneo (Malaysia) has been investigated with reflection and refraction seismics, magnetics, and gravity during the recent cruise BGR01-POPSCOMS. A total of 4000 km of geophysical profiles has been acquired, thereof 2900 km with reflection seismics. The focus of investigations was on the deep water areas. The margin looks like a typical accretionary margin and was presumably formed during the subduction of a proto South China Sea. Presently, no horizontal movements between the two plates are being observed. Like in major parts of the South China Sea, the area seaward of the Sabah Trough consists of extended continental lithosphere which is characterised by a pattern of rotated fault blocks and half grabens and a carbonate platform of Early Oligocene to Early Miocene age. We found evidence that the continental crust also underlies the Sabah Trough and the adjacent continental slope, a fact that raises many questions about the tectonic history and development of this margin. The tectonic pattern of the Dangerous Grounds' extended continental crust can be traced a long way landward of the Sabah Trough beneath the sedimentary succession of the upper plate. The magnetic anomalies which are dominated by the magnetic signatures of relatively young volcanic features also continue under the continental slope. The sedimentary rocks of the upper plate, in contrast, seem to generate hardly any magnetic anomalies. Based on the new data we propose the following scenario for the development of the NW Sabah continental margin: Seafloor spreading in the present South China Sea started at about 30 Ma in the Late Oligocene. The spreading process separated the Dangerous Grounds area from the SE Asian continent and ceased in late Early Miocene when the oceanic crust of the proto South China Sea was fully subducted in eastward direction along the Borneo-Palawan Trough. During Lower and/or Middle Miocene, Borneo rotated counterclockwise and was

  10. 78 FR 26341 - Aguirre Offshore GasPort, LLC; Notice of Application

    Science.gov (United States)

    2013-05-06

    ... LNG terminal, the Aguirre Offshore GasPort Project will include a non-jurisdictional Energy Bridge Regasification Vessel functioning as the floating storage and regasification unit for the Project. The project...

  11. Use of knowledge based systems for rational reliability analysis based inspection and maintenance planning for offshore structures

    International Nuclear Information System (INIS)

    Tang, M.X.; Dharmavasan, S.; Peers, S.M.C.

    1994-01-01

    The structural integrity of fixed offshore platforms is ensured by periodic inspections. In the past, decisions made as to when, where and how to inspect have been made by engineers using rules-of-thumb and general planning heuristics. It is now hoped that more rational inspection and maintenance scheduling may be carried out by applying recently developed techniques based on structural reliability methods. However, one of the problems associated with a theoretical approach is that it is not always possible to incorporate all the constraints that are present in a practical situation. These constraints modify the decisions made for analysis data input and the interpretation of the analysis results. Knowledge based systems provide a mean of encapsulating several different forms of information and knowledge within a computer system and hence can overcome this problem. In this paper, a prototype system being developed for integrating reliability based analysis with other constraints for inspection scheduling will be described. In addition, the scheduling model and the algorithms to carry out the scheduling will be explained. Furthermore, implementation details are also given

  12. Pricing offshore wind power

    International Nuclear Information System (INIS)

    Levitt, Andrew C.; Kempton, Willett; Smith, Aaron P.; Musial, Walt; Firestone, Jeremy

    2011-01-01

    Offshore wind offers a very large clean power resource, but electricity from the first US offshore wind contracts is costlier than current regional wholesale electricity prices. To better understand the factors that drive these costs, we develop a pro-forma cash flow model to calculate two results: the levelized cost of energy, and the breakeven price required for financial viability. We then determine input values based on our analysis of capital markets and of 35 operating and planned projects in Europe, China, and the United States. The model is run for a range of inputs appropriate to US policies, electricity markets, and capital markets to assess how changes in policy incentives, project inputs, and financial structure affect the breakeven price of offshore wind power. The model and documentation are made publicly available. - Highlights: → We calculate the Breakeven Price (BP) required to deploy offshore wind plants. → We determine values for cost drivers and review incentives structures in the US. → We develop 3 scenarios using today's technology but varying in industry experience. → BP differs widely by Cost Scenario; relative policy effectiveness varies by stage. → The low-range BP is below regional market values in the Northeast United States.

  13. Secretory vesicles in live cells are not free-floating but tethered to filamentous structures: A study using photonic force microscopy

    International Nuclear Information System (INIS)

    Abu-Hamdah, Rania; Cho, Won Jin; Hoerber, J.K.H.; Jena, Bhanu P.

    2006-01-01

    It is well established that actin and microtubule cytoskeletal systems are involved in organelle transport and membrane trafficking in cells. This is also true for the transport of secretory vesicles in neuroendocrine cells and neurons. It was however unclear whether secretory vesicles remain free-floating, only to associate with such cytoskeletal systems when needing transport. This hypothesis was tested using live pancreatic acinar cells in physiological buffer solutions, using the photonic force microscope (PFM). When membrane-bound secretory vesicles (0.2-1.2 μm in diameter) in live pancreatic acinar cells were trapped at the laser focus of the PFM and pulled, they were all found tethered to filamentous structures. Mild exposure of cells to nocodazole and cytochalasin B, disrupts the tether. Immunoblot analysis of isolated secretory vesicles, further demonstrated the association of actin, myosin V, and kinesin. These studies demonstrate for the first time that secretory vesicles in live pancreatic acinar cells are tethered and not free-floating, suggesting that following vesicle biogenesis, they are placed on their own railroad track, ready to be transported to their final destination within the cell when required. This makes sense, since precision and regulation are the hallmarks of all cellular process, and therefore would hold true for the transport and localization of subcellular organelles such as secretory vesicles

  14. Secretory vesicles in live cells are not free-floating but tethered to filamentous structures: A study using photonic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Abu-Hamdah, Rania [Department of Physiology, Wayne State University School of Medicine, 5245 Scott Hall, 540 E. Canfield, Detroit, MI 48201 (United States); Cho, Won Jin [Department of Physiology, Wayne State University School of Medicine, 5245 Scott Hall, 540 E. Canfield, Detroit, MI 48201 (United States); Hoerber, J.K.H. [Department of Physics, University of Bristol, Bristol BS8 1TD (United Kingdom); Jena, Bhanu P. [Department of Physiology, Wayne State University School of Medicine, 5245 Scott Hall, 540 E. Canfield, Detroit, MI 48201 (United States)]. E-mail: bjena@med.wayne.edu

    2006-06-15

    It is well established that actin and microtubule cytoskeletal systems are involved in organelle transport and membrane trafficking in cells. This is also true for the transport of secretory vesicles in neuroendocrine cells and neurons. It was however unclear whether secretory vesicles remain free-floating, only to associate with such cytoskeletal systems when needing transport. This hypothesis was tested using live pancreatic acinar cells in physiological buffer solutions, using the photonic force microscope (PFM). When membrane-bound secretory vesicles (0.2-1.2 {mu}m in diameter) in live pancreatic acinar cells were trapped at the laser focus of the PFM and pulled, they were all found tethered to filamentous structures. Mild exposure of cells to nocodazole and cytochalasin B, disrupts the tether. Immunoblot analysis of isolated secretory vesicles, further demonstrated the association of actin, myosin V, and kinesin. These studies demonstrate for the first time that secretory vesicles in live pancreatic acinar cells are tethered and not free-floating, suggesting that following vesicle biogenesis, they are placed on their own railroad track, ready to be transported to their final destination within the cell when required. This makes sense, since precision and regulation are the hallmarks of all cellular process, and therefore would hold true for the transport and localization of subcellular organelles such as secretory vesicles.

  15. System evaluation of offshore platforms with gas liquefaction processes

    DEFF Research Database (Denmark)

    Nguyen, Tuong-Van; de Oliveira Júnior, Silvio

    2018-01-01

    Abstract Floating, production, storage and offloading plants are facilities used for offshore processing of hydrocarbons in remote locations. At present, the produced gas is injected back into the reservoir instead of being exported. The implementation of refrigeration processes offshore for liqu......Abstract Floating, production, storage and offloading plants are facilities used for offshore processing of hydrocarbons in remote locations. At present, the produced gas is injected back into the reservoir instead of being exported. The implementation of refrigeration processes offshore...... improvements are discussed based on an energy and exergy analysis. Compared to a standard platform where gas is directly injected into the reservoir, the total power consumption increases by up to 50%, and the exergy destruction within the processing plant doubles when a liquefaction system is installed....... It is therefore essential to conduct a careful analysis of the trade-off between the capital costs and operating revenues for such options....

  16. Electrical Structure of Future Off-shore Wind Power Plant with a High Voltage Direct Current Power Transmission

    DEFF Research Database (Denmark)

    Sharma, Ranjan

    The increasing demand of electric power and the growing consciousness towards the changing climate has led to a rapid development of renewable energy in the recent years. Among all, wind energy has been the fastest growing energy source in the last decade. But the growing size of wind power plants......, better wind conditions at off-shore and the general demand to put them out of sight have all contributed to the installation of large wind power plants in off-shore condition. However, moving wind power plants far out in the off-shore comes with many associated problems. One of the main challenges...... is the transmission of power over long distance. Historically, the power transmission from off-shore wind power plants has been done via HVAC submarine cables. This provides a simple solution, but AC cables cannot be arbitrarily long. It is shown in the report that major issues with HVAC cable transmission system...

  17. Design and Strength Calculations of the Tripod Support Structure for Offshore Power Plant

    Directory of Open Access Journals (Sweden)

    Dymarski C.

    2015-01-01

    Full Text Available The support structure being the object of the analysis presented in the article is Tripod. According to the adopted assumptions, it is a foundation gravitationally set in the water region of 60 m in depth, not fixed to the seabed, which can be used for installing a 7MW wind turbine. Due to the lack of substantial information on designing and strength calculations of such types of structures in the world literature, authors have made an attempt to solve this problem within the framework of the abovementioned project. In the performed calculations all basic loads acting on the structure were taken into account, including: the self mass of the structure, the masses of the ballast, the tower and the turbine, as well as hydrostatic forces, and aero- and hydrodynamic forces acting on the entire object in extreme operating conditions.

  18. Accessing offshoring advantages

    DEFF Research Database (Denmark)

    Mykhaylenko, Alona; Motika, Agnes; Wæhrens, Brian Vejrum

    2015-01-01

    . Assuming that different levels of synergy may exist between particular offshoring strategic decisions (choosing offshore outsourcing or captive offshoring and the type of function) and different offshoring advantages, this work advocates that the actual fact of realization of certain offshoring advantages...

  19. Structure, Kinematics and Origin of Radial Faults: 3D Seismic Observations from the Santos Basin, offshore Brazil

    Science.gov (United States)

    Coleman, Alexander; Jackson, Christopher A.-L.

    2017-04-01

    Salt stock growth is typically accompanied by the development of geometrically and kinematically complex fault networks in the surrounding country rock. The most common networks comprise radial faults; these are characterised by low displacement (stock into flanking strata. Radial faults are commonly observed in an arched, unpierced roof developed above a rising salt stock; in these cases, the faults are typically well-imaged seismically and likely form due to outer-arc extension during overburden stretching. Radial faults are also found at deeper structural levels, in strata flanking the diapir stem; in these cases, they are typically less well-imaged, thus their structure, kinematics and origin are less well understood. Furthermore, understanding the growth of radial faults may provide insights into hydrocarbon reservoir compartmentalisation and the evolution of neighbouring salt stocks. Here, we use high-quality 3D seismic reflection data from the Santos Basin, offshore Brazil to determine the structure and kinematics, and infer the likely origin of exceptionally well-imaged radial faults overlying and flanking a mature salt stock. Furthermore, we compare the geometric (e.g. throw, geometry, spacing, distribution etc.) and kinematic (e.g. timing of formation and duration of activity) characteristics of radial faults at both structural levels, allowing us to infer their temporal relationship and likely origins. We show that radial faults regardless of their structural level typically have aspect ratios of c. 1.8 - 2, are laterally-restricted in the vicinity of the salt, and have lengths of indices of c. 1, with low throw gradients of 0.05 - 0.1 at the upper tip indicate that radial faults were likely blind. Throws range from 5 - 80 ms, with throw-maxima within 1 - 2 radii of the salt diapir. However, we note that the position of the throw maxima is not at the same level for all radial faults. We propose that radial faults nucleate and initially grow as blind

  20. A Comparison Study of Offshore Wind Support Structures with Monopiles and Jackets for U.S. Waters: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Damiani, Rick; Dykes, Katherine; Scott, George

    2016-08-01

    U.S. experience in offshore wind is limited, and high costs are expected unless innovations are introduced in one or multiple aspects of the project, from the installed technology to the balance of system (BOS). The substructure is the main single component responsible for the BOS capital expenditure (CapEx) and thus one that, if improved, could yield significant levelized cost of energy (LCOE) savings. For projects in U.S. waters, multimember, lattice structures (also known as jackets) can render required stiffness for transitional water depths at potentially lower costs than monopiles (MPs). In this study, we used a systems engineering approach to evaluate the LCOE of prototypical wind power plants at six locations along the eastern seaboard and the Gulf of Mexico for both types of support structures. Using a reference wind turbine and actual metocean conditions for the selected sites, we calculated loads for a parked and an operational situation, and we optimized the MP- and jacket-based support structures to minimize their overall mass. Using a suite of cost models, we then computed their associated LCOE. For all water depths, the MP-based configurations were heavier than their jacket counterparts, but the overall costs for the MPs were less than they were for jackets up to depths of slightly less than 30 m. When the associated manufacturing and installation costs were included, jackets resulted in lower LCOE for depths greater than 40 m. These results can be used by U.S. stakeholders to understand the potential for different technologies at different sites, but the methodology illustrated in this study can be further employed to analyze the effects of innovations and design choices throughout wind power plant systems.

  1. A comparison study of offshore wind support structures with monopiles and jackets for U.S. waters

    Science.gov (United States)

    Damiani, R.; Dykes, K.; Scott, G.

    2016-09-01

    U.S. experience in offshore wind is limited, and high costs are expected unless innovations are introduced in one or multiple aspects of the project, from the installed technology to the balance of system (BOS). The substructure is the main single component responsible for the BOS capital expenditure (CapEx) and thus one that, if improved, could yield significant levelized cost of energy (LCOE) savings. For projects in U.S. waters, multimember lattice structures (also known as jackets) can render required stiffness for transitional water depths at potentially lower costs than monopiles (MPs). In this study, we used a systems engineering approach to evaluate the LCOE of prototypical wind power plants at six locations along the eastern seaboard and the Gulf of Mexico for both types of support structures. Using a reference wind turbine and actual metocean conditions for the selected sites, we calculated loads for a parked and an operational situation, and we optimized the MP- and jacket-based support structures to minimize their overall mass. Using a suite of cost models, we then computed their associated LCOE. For all water depths, the MP-based configurations were heavier than their jacket counterparts, but the overall costs for the MPs were less than they were for jackets up to depths of slightly less than 30m. When the associated manufacturing and installation costs were included, jackets resulted in lower LCOE for depths greater than 40m. These results can be used by U.S. stakeholders to understand the potential for different technologies at different sites, but the methodology illustrated in this study can be further employed to analyze the effects of innovations and design choices throughout wind power plant systems.

  2. Optimal design of galvanic corrosion protection systems for offshore wind turbine support structures

    DEFF Research Database (Denmark)

    Sarhadi, Ali; Abrahamsen, Asger Bech; Stolpe, Mathias

    2018-01-01

    the optimized anodes on the support structure, and finally evaluating the protective potential on the structure during the lifetime by calling the finite element (FE) software COMSOL. An algorithm based on Sequential Quadratic Programming (SQP) is used for optimizing the number and dimensions of the anodes...... the electrical isolation degradation of the structure coating as well as the mass reduction of the anodes during the CP lifetime. The performance of the proposed optimization process is examined on a mono bucket inspired (with some simplifications) by the Dogger Bank metrological mast in England. The optimized......The current work addresses a mass/cost optimization procedure for galvanic anode cathodic protection (GACP) systems based on both cathodic protection (CP) standards and numerical simulation. An approach is developed for optimizing the number and dimensions of the galvanic anodes, distributing...

  3. Stochastic dynamic response analysis of a floating vertical-axis wind turbine with a semi-submersible floater

    DEFF Research Database (Denmark)

    Wang, Kai; Moan, Torgeir; Hansen, Martin Otto Laver

    2016-01-01

    Floating vertical-axis wind turbines (FVAWTs) provide the potential for utilizing offshore wind resources in moderate and deep water because of their economical installation and maintenance. Therefore, it is important to assess the performance of the FVAWT concept. This paper presents a stochastic...... on the response is demonstrated by comparing the floating wind turbine with the equivalent land-based wind turbine. Additionally, by comparing the behaviour of FVAWTs with flexible and rigid rotors, the effect of rotor flexibility is evaluated. Furthermore, the FVAWT is also investigated in the parked condition...... dynamic response analysis of a 5MW FVAWT based on fully coupled nonlinear time domain simulations. The studied FVAWT, which is composed of a Darrieus rotor and a semi-submersible floater, is subjected to various wind and wave conditions. The global motion, structural response and mooring line tension...

  4. Wave kinematics and response of slender offshore structures. Vol 2: Recommendation for design

    Energy Technology Data Exchange (ETDEWEB)

    Ottesen Hansen, N.E.

    1999-08-01

    This memorandum comprises a design recommendation for slender structures exposed to wave and current loading in the sea. It is considered as an addendum to DS 499 or the DnV Classification Notes No. 30.5. Slender structures are structures as risers, well conductors, or structures with small diameter members which are dynamically amplified or liable to hydro-elastic vibrations such as vortex induced vibrations, self-excited vibrations and other dynamic phenomena. The newer type of steel platforms have a large number of these members attached to them. The present guideline is motivated by a number of failures of conductors. Some failures took place during drilling are were caused by fatigue which developed due to hydroelastic vibrations. Other failures have been caused by clamped conductors due to strong wave forces. The recommendations are based on full scale field measurements of waves and currents and of instrumented pipes in the North Sea both for high and for low Keulegan-Carpenter numbers. The measurements have been made under realistic storm conditions, which means that the recommendations are fully verified. (au)

  5. Offshore extension of the structural element of Udipi, confirmation from marine magneties

    Digital Repository Service at National Institute of Oceanography (India)

    Subrahmanyam, V.

    wavelength anomalies off Mangalore and relatively smooth zone further south Kasaragod. A prominent WNW-ESE structural element (fault) south off Coondapoor is observed in the three eastern profiles (A-A', B-B' and C-C') which was not reflected in the western...

  6. Pareto-Optimal Evaluation of Ultimate Limit States in Offshore Wind Turbine Structural Analysis

    Directory of Open Access Journals (Sweden)

    Michael Muskulus

    2015-12-01

    Full Text Available The ultimate capacity of support structures is checked with extreme loads. This is straightforward when the limit state equations depend on a single load component, and it has become common to report maxima for each load component. However, if more than one load component is influential, e.g., both axial force and bending moments, it is not straightforward how to define an extreme load. The combination of univariate maxima can be too conservative, and many different combinations of load components can result in the worst value of the limit state equations. The use of contemporaneous load vectors is typically non-conservative. Therefore, in practice, limit state checks are done for each possible load vector, from each time step of a simulation. This is not feasible when performing reliability assessments and structural optimization, where additional, time-consuming computations are involved for each load vector. We therefore propose to use Pareto-optimal loads, which are a small set of loads that together represent all possible worst case scenarios. Simulations with two reference wind turbines show that this approach can be very useful for jacket structures, whereas the design of monopiles is often governed by the bending moment only. Even in this case, the approach might be useful when approaching the structural limits during optimization.

  7. Probing Earth’s conductivity structure beneath oceans by scalar geomagnetic data: autonomous surface vehicle solution

    DEFF Research Database (Denmark)

    Kuvshinov, Alexey; Matzka, Jürgen; Poedjono, Benny

    2016-01-01

    to the conductivity structure beneath the ocean. We conclude that the sensitivity, depending on the bathymetry gradient, is typically largest near the coast offshore. We show that such sea-surface marine induction surveys can be performed with the Wave Glider, an easy-to-deploy, autonomous, energy-harvesting floating...

  8. Time-domain representation of frequency dependent inertial forces on offshore structures

    DEFF Research Database (Denmark)

    Krenk, Steen

    2013-01-01

    dependence is then approximated by a rational function, corresponding to a set of ordinary differential equations in the time domain. The MacCamy-Fuchs solution leads to a representation of the inertial force coefficient as a complex function with argument mainly corresponding to a 'phase lead', in contrast...... history of the inertial force is determined by processing the stable part of the transformation by a forward time integration, followed by an integration in the negative time-direction to obtain the final inertial force time history. The differential equations of the local inertial force at a cross......The inertial wave force on a vertical cylinder decreases with decreasing wave length, when the wave length is less than about six times the diameter of the diameter of the cylinder. In structures with a largediameter component like mono-towers the resonance frequency of the structure is typically...

  9. Offshore wind power: does France remain ashore?

    International Nuclear Information System (INIS)

    Bongrain, T.

    2015-01-01

    France benefits from favorable geographical conditions for offshore wind power but the development of a dedicated industrial sector is slow. 6 projects of wind power farms where turbines are rooted in the seabed are expected to operate progressively from 2018, they represent a cumulated power capacity of 2920 MW. A call for projects has been launched by French authorities for floating offshore wind farms off Brittany and in the mediterranean sea but it will not be sufficient to help to fulfill the declared goal of 40% of the electricity produced in France should be of renewable origin. The main weakness is the cost and countries like Germany benefit from the shallow waters of the North sea to install wind farms at lower costs. The solution could be the development in France of an industrial sector dedicated to floating wind turbines that are easier to install in deep water and can be settled farther off the coast to meet the demand of environmentalists for seascape preservation. More sites could become available for floating wind turbines than for seabed-rooted ones and as the consequence the market for floating systems may become more important. (A.C.)

  10. Wave kinematics and response of slender offshore structures. Vol 4: Wave kinematics

    Energy Technology Data Exchange (ETDEWEB)

    Riber, H.J.

    1999-08-01

    The kinematics of large surface waves has been measured by means of sonar's placed on the sea floor at the Tyra field. Measurements from the most severe storm are analysed and extreme wave velocity profiles are compared to Stoke wave velocity profiles. Statistical distributions of crest velocity and wave celerity are presented. The analysis shows how the deviation from the Stokes prediction varies with wave heights and steepness. Analyses of the directional wave field leads to the conclusion that the extreme waves are three-dimensional. It is shown that the peculiar kinematics of extreme waves is of great relevance to the design of jacket type structures. (au)

  11. Stochastic model for joint wave and wind loads on offshore structures

    DEFF Research Database (Denmark)

    Ditlevsen, Ove Dalager

    2002-01-01

    _s,T_z)$ from the North Sea a well fitting joint distribution of $(H_s,T_z)$ is obtained as a so-called Nataf model. Since the wave field is wind driven, there is a correlation between the time averaged wind velocity pressure $Q$ and the characteristic wave height in the stationary situation. Using the Poisson...... process model to concentrate on those load events that are of importance for the evaluation of the safety of the structure, that is, events with $Q$ larger than some threshold $q_0$, available information about the wind velocity pressure distributionin high wind situations can be used to formulate a Nataf...

  12. The structure of the stably stratified internal boundary layer in offshore flow over the sea

    Science.gov (United States)

    Garratt, J. R.; Ryan, B. F.

    1989-04-01

    Observations obtained mainly from a research aircraft are presented of the mean and turbulent structure of the stably stratified internal boundary layer (IBL) over the sea formed by warm air advection from land to sea. The potential temperature and humidity fields reveal the vertical extent of the IBL, for fetches out to several hundred of kilometres, geostrophic winds of 20 25 m s-1, and potential temperature differences between undisturbed continental air and the sea surface of 7 to 17 K. The dependence of IBL depth on these external parameters is discussed in the context of the numerical results of Garratt (1987), and some discrepancies are noted. Wind observations show the development of a low-level wind maximum (wind component normal to the coast) and rotation of the wind to smaller cross-isobar flow angles. Potential temperature (θ) profiles within the IBL reveal quite a different structure to that found in the nocturnal boundary layer (NBL) over land. Over the sea, θ profiles have large positive curvature with vertical gradients increasing monotonically with height; this reflects the dominance of turbulent cooling within the layer. The behaviour is consistent with known behaviour in the NBL over land where curvature becomes negative (vertical gradients of θ decreasing with height) as radiative cooling becomes dominant. Turbulent properties are discussed in terms of non-dimensional quantities, normalised by the surface friction velocity, as functions of normalised height using the IBL depth. Vertical profiles of these and the normalised wavelength of the spectral maximum agree well with known results for the stable boundary layer over land (Caughey et al., 1979).

  13. Inverse load calculation procedure for offshore wind turbines and application to a 5-MW wind turbine support structure: Inverse load calculation procedure for offshore wind turbines

    Energy Technology Data Exchange (ETDEWEB)

    Pahn, T. [Pahn Ingenieure, Am Seegraben 17b 03051 Cottbus Germany; Rolfes, R. [Institut f?r Statik und Dynamik, Leibniz Universit?t Hannover, Appelstra?e 9A 30167 Hannover Germany; Jonkman, J. [National Renewable Energy Laboratory, 15013 Denver West Parkway Golden Colorado 80401 USA

    2017-02-20

    A significant number of wind turbines installed today have reached their designed service life of 20 years, and the number will rise continuously. Most of these turbines promise a more economical performance if they operate for more than 20 years. To assess a continued operation, we have to analyze the load-bearing capacity of the support structure with respect to site-specific conditions. Such an analysis requires the comparison of the loads used for the design of the support structure with the actual loads experienced. This publication presents the application of a so-called inverse load calculation to a 5-MW wind turbine support structure. The inverse load calculation determines external loads derived from a mechanical description of the support structure and from measured structural responses. Using numerical simulations with the software fast, we investigated the influence of wind-turbine-specific effects such as the wind turbine control or the dynamic interaction between the loads and the support structure to the presented inverse load calculation procedure. fast is used to study the inverse calculation of simultaneously acting wind and wave loads, which has not been carried out until now. Furthermore, the application of the inverse load calculation procedure to a real 5-MW wind turbine support structure is demonstrated. In terms of this practical application, setting up the mechanical system for the support structure using measurement data is discussed. The paper presents results for defined load cases and assesses the accuracy of the inversely derived dynamic loads for both the simulations and the practical application.

  14. The T-Reflection and the deep crustal structure of the Vøring Margin offshore Mid-Norway

    Science.gov (United States)

    Abdelmalak, M. M.; Faleide, J. I.; Planke, S.; Gernigon, L.; Zastrozhnov, D.; Shephard, G. E.; Myklebust, R.

    2017-12-01

    Volcanic passive margins are characterized by massive occurrence of mafic extrusive and intrusive rocks, before and during plate breakup, playing major role in determining the evolution pattern and the deep structure of magma-rich margins. Deep seismic reflection data frequently provide imaging of strong continuous reflections in the middle/lower crust. In this context, we have completed a detailed 2D seismic interpretation of the deep crustal structure of the Vøring volcanic margin, offshore mid-Norway, where high-quality seismic data allow the identification of high-amplitude reflections, locally referred to as the T-Reflection (TR). Using the dense seismic grid we have mapped the top of the TR in order to compare it with filtered Bouguer gravity anomalies and seismic refraction data. The TR is identified between 7 and 10 s. Sometimes it consists of one single smooth reflection. However, it is frequently associated with a set of rough multiple reflections displaying discontinuous segments with varying geometries, amplitude and contact relationships. The TR seems to be connected to deep sill networks and locally located at the continuation of basement high structures or terminates over fractures and faults. The spatial correlation between the filtered positive Bouguer gravity anomalies and the TR indicates that the latter represents a high impedance boundary contrast associated with a high-density/velocity body. Within an uncertainty of ± 2.5 km, the depth of the mapped TR is found to correspond to the depth of the top of the Lower Crustal Body (LCB), characterized by high P-wave velocities (>7 km/s), in 50% of the outer Vøring Margin areas, whereas different depths between the TR and the top LCB are estimated for the remaining areas. We present a tectonic scenario, where a large part of the deep structure could be composed of preserved upper continental basement and middle to lower crustal lenses of inherited and intruded high-grade metamorphic rocks. Deep

  15. The geostatistical approach for structural and stratigraphic framework analysis of offshore NW Bonaparte Basin, Australia

    International Nuclear Information System (INIS)

    Wahid, Ali; Salim, Ahmed Mohamed Ahmed; Yusoff, Wan Ismail Wan; Gaafar, Gamal Ragab

    2016-01-01

    Geostatistics or statistical approach is based on the studies of temporal and spatial trend, which depend upon spatial relationships to model known information of variable(s) at unsampled locations. The statistical technique known as kriging was used for petrophycial and facies analysis, which help to assume spatial relationship to model the geological continuity between the known data and the unknown to produce a single best guess of the unknown. Kriging is also known as optimal interpolation technique, which facilitate to generate best linear unbiased estimation of each horizon. The idea is to construct a numerical model of the lithofacies and rock properties that honor available data and further integrate with interpreting seismic sections, techtonostratigraphy chart with sea level curve (short term) and regional tectonics of the study area to find the structural and stratigraphic growth history of the NW Bonaparte Basin. By using kriging technique the models were built which help to estimate different parameters like horizons, facies, and porosities in the study area. The variograms were used to determine for identification of spatial relationship between data which help to find the depositional history of the North West (NW) Bonaparte Basin

  16. Wave kinematics and response of slender offshore structures. Vol 5: Wave forces and responses

    Energy Technology Data Exchange (ETDEWEB)

    Pedersen, L.M.; Riber, H.J.

    1999-08-01

    A load measuring system (LMS) and a wave measuring system (WMS) has been used on the North Sea platform Tyra. The LMS consists of an instrumented pipe placed vertically in the crest zone of high and steep waves. The WMS consists of an unique sonar system placed on the sea floor. Simultaneous measurements are carried out of the kinematics of waves and currents and the response of the instrumented pipe during a period of five month in the winter 1994/95. Numerical calculations with LIC22 are carried out of the response of the LMS applying the measured wave and current kinematics. The responses are compared to the measured responses of the LMS. The comparison is based on the statistical main properties of the calculated and measured response as the kinematic field is measured 150 metres away from the instrumented pipe. From the analyses the main parameters (reduced velocity V{sub R} and correlation length l{sub c}) for vortex induced vibrations (VIV) are calibrated and the main environmental conditions for VIV are determined. The hydrodynamic coefficients determining the wave and current forces on slender structures are studied (drag coefficient C{sub D} and added mass coefficient C{sub M}). Further, the effect on the drag coefficient due to air blending in the upper part of the wave is determined. (au)

  17. Wave kinematics and response of slender offshore structures. Vol 3: Description of measuring systems

    Energy Technology Data Exchange (ETDEWEB)

    Riber, H.J.

    1999-08-01

    The report presents the measuring systems used during the measurements in the North Sea at the Tyra field. The report consists of two parts: (1) Description of the wave measuring systems (WMS); (2) Description of the load mesuring system (LMS). The developed Wave Kinematics Measuring Systems (WMS) is an acoustic system based on the pulsed incoherent Doppler technique. Basically it consists of 4 sonar stations and a control and monitoring station. The sonar stations are positioned at the seabed north of the TCP-A platform in a star configuration with one station surrounded by the other three stations in a fixed distance of 37 m. From the central sonar stations an umbilical is routed to the TCP-A platform where the control and monitoring stations is positioned in the satellite communication room. The measurement periods have been concentrated to periods with storms. It was a special emphasis to measure the wave kinematics of extremely high waves. The LMS is described in terms of geometrical data, structural properties, instrumentation, and other characteristics. (LN)

  18. Seismic analysis of offshore wind turbines on bottom-fixed support structures.

    Science.gov (United States)

    Alati, Natale; Failla, Giuseppe; Arena, Felice

    2015-02-28

    This study investigates the seismic response of a horizontal axis wind turbine on two bottom-fixed support structures for transitional water depths (30-60 m), a tripod and a jacket, both resting on pile foundations. Fully coupled, nonlinear time-domain simulations on full system models are carried out under combined wind-wave-earthquake loadings, for different load cases, considering fixed and flexible foundation models. It is shown that earthquake loading may cause a significant increase of stress resultant demands, even for moderate peak ground accelerations, and that fully coupled nonlinear time-domain simulations on full system models are essential to capture relevant information on the moment demand in the rotor blades, which cannot be predicted by analyses on simplified models allowed by existing standards. A comparison with some typical design load cases substantiates the need for an accurate seismic assessment in sites at risk from earthquakes. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  19. The geostatistical approach for structural and stratigraphic framework analysis of offshore NW Bonaparte Basin, Australia

    Energy Technology Data Exchange (ETDEWEB)

    Wahid, Ali, E-mail: ali.wahid@live.com; Salim, Ahmed Mohamed Ahmed, E-mail: mohamed.salim@petronas.com.my; Yusoff, Wan Ismail Wan, E-mail: wanismail-wanyusoff@petronas.com.my [Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 32610 Tronoh, Perak (Malaysia); Gaafar, Gamal Ragab, E-mail: gaafargr@gmail.com [Petroleum Engineering Division, PETRONAS Carigali Sdn Bhd, Kuala Lumpur (Malaysia)

    2016-02-01

    Geostatistics or statistical approach is based on the studies of temporal and spatial trend, which depend upon spatial relationships to model known information of variable(s) at unsampled locations. The statistical technique known as kriging was used for petrophycial and facies analysis, which help to assume spatial relationship to model the geological continuity between the known data and the unknown to produce a single best guess of the unknown. Kriging is also known as optimal interpolation technique, which facilitate to generate best linear unbiased estimation of each horizon. The idea is to construct a numerical model of the lithofacies and rock properties that honor available data and further integrate with interpreting seismic sections, techtonostratigraphy chart with sea level curve (short term) and regional tectonics of the study area to find the structural and stratigraphic growth history of the NW Bonaparte Basin. By using kriging technique the models were built which help to estimate different parameters like horizons, facies, and porosities in the study area. The variograms were used to determine for identification of spatial relationship between data which help to find the depositional history of the North West (NW) Bonaparte Basin.

  20. Bilateral Floating Hip and Floating Knee: a Rare Complex Injury ...

    African Journals Online (AJOL)

    We report a rare complex injury of a 45-year-old man who sustained a bilateral floating hip and floating knee and hospitalised in our service six days after a traffic accident. The floating knees were open type III and II of Cauchoix score in phase of suppuration. He also presented with a floating ankle on the right side.

  1. Structural and thermal development of the Atlantic margin offshore Essaouira (Morocco) - evidence of salt extrusion and implications for hydrocarbon exploration

    Science.gov (United States)

    Neumaier, Martin; Littke, Raf; Kleine, Adrian; Schnabel, Michael; Reichert, Christian

    2013-04-01

    Along the east-west regional seismic line BGR11-202 (MIRROR campaign, 2011), several distinct salt diapirs and related structures can be identified close to the present day coast line. The subsalt structure is only very poorly imaged. Further offshore, rotated fault blocks are overlain by Mesozoic and Cenozoic sediments. Towards the west, the evidence for past volcanic activity is increasing (necks, dykes, and sills). The magnetic anomaly S1 is roughly situated west of the most western identifiable salt structure. The aim of our study is to describe and verify possible salt tectonic and related thermal models and the evolution of the petroleum systems. One salt structure in particular shows clear evidence of salt extrusion in the past. We explain the potential scenario of the salt diapir development and extrusion in a series of structurally restored sections: After deposition, probably within the syn-rift Liassic half grabens (not imaged), the salt quickly became instable due to differential loading, assisted by growing density contrast with the overburden. It forced its way up using weak zones—which could have been the active normal faults—while the overburden collapsed into the previously occupied space (salt withdrawal). Even though the salt was constantly rising, it did not reach the surface due to constant burial. Only once the sedimentation rate decreased—during the late Cretaceous and early Paleogene—the salt extruded and crept down the continental slope onto the hiatus unconformity. With the extrusion, the salt partly dissolved in contact with the ocean water, and a cap rock formed. The related paleorelief was buried by the detritical sediments provided by the Atlas orogenesis. At present day, these paleoreliefs still have a bathymetric expression, as they are providing an unstable underground and trigger normal faulting and local resedimentation. Also remobilization of the salt, even though strengthened by the cap rock, might be possible locally

  2. FLOAT Project - Task 1

    DEFF Research Database (Denmark)

    Marchalot, Tanguy; Kofoed, Jens Peter; Sørensen, Eigil V.

    .com, 2011). CRC floats could be a very cost-effective technology with enhanced loading capacity and environmental resistance, and very low maintenance requirements, affecting directly the final energy price. The project involves DEXA Wave Energy Ltd, Wave Star A/S, Aalborg University and Hi-Con A......The objective of the FLOAT project is to study the reliability of high-performance fibre-reinforced concrete, also known as Compact Reinforced Composite (CRC), for the floats of wave energy converters. In order to reach commercial breakthrough, wave energy converters need to achieve a lower price...

  3. Numerical study on aerodynamic damping of floating vertical axis wind turbines

    DEFF Research Database (Denmark)

    Cheng, Zhengshun; Aagaard Madsen, Helge; Gao, Zhen

    2016-01-01

    Harvesting offshore wind energy resources using floating vertical axis wind turbines (VAWTs) has attracted an increasing interest in recent years. Due to its potential impact on fatigue damage, the aerodynamic damping should be considered in the preliminary design of a floating VAWT based...... on the frequency domain method. However, currently the study on aerodynamic damping of floating VAWTs is very limited. Due to the essential difference in aerodynamic load characteristics, the aerodynamic damping of a floating VAWT could be different from that of a floating horizontal axis wind turbine (HAWT...... to four were considered. The aerodynamic damping under steady and turbulent wind conditions were estimated using fully coupled aero-hydro-servo-elastic time domain simulations. It is found that the aerodynamic damping ratio of the considered floating VAWTs ranges from 1.8% to 5.3%. Moreover...

  4. Floating polygon soup

    OpenAIRE

    Colleu , Thomas; Morin , Luce; Pateux , Stéphane; Labit , Claude

    2011-01-01

    International audience; This paper presents a new representation called floating polygon soup for applications like 3DTV and FTV (Free Viewpoint Television). This representation is based on 3D polygons and takes as input MVD data. It extends the previously proposed polygon soup representation which is appropriate for both compression, transmission and rendering stages. The floating polygon soup conserves these advantages while also taking into account misalignments at the view synthesis stage...

  5. Offshore Aquaculture Development in Ecuador

    Directory of Open Access Journals (Sweden)

    Julio López Alvarado

    2016-03-01

    Full Text Available Ecuador has a long tradition in aquaculture, mainly related to the cultivation of shrimp and tilapia in earthen ponds. Land-based production methods have a large environmental, economic and social impact due to the extensive use of land and its effects on the ecosystems. In order to increase the production of fish without further land use and with a lower environmental impact, a good alternative is the culture of fish in floating cages, adopting technologies used successfully in many other countries. This article analyses the current situation of offshore aquaculture (the production of fish and other aquatic organisms in the open sea in Ecuador, and the prospects for the future of this sector in the country.

  6. Vibration of an Offshore Structure Having the Form of a Hollow Column Partially Filled with Multiple Fluids and Immersed in Water

    OpenAIRE

    Lin, Hsien-Yuan; Lee, Jeng-Nan; Sung, Wen-Hao

    2012-01-01

    This paper employs the numerical assembly method (NAM) to determine the exact frequency-response amplitudes of an offshore structure such as piles or towers having the form of a hollow column filled with multiple fluids, immersed in water, carrying an eccentric tip mass supported by a translational spring and/or a rotational spring, and subjected to a harmonic force. The hollow column is modeled as a Bernoulli-Euler cantilever beam fixed at the bottom. For the case of zero harmonic force, the...

  7. The response of pile-guided floats subjected to dynamic loading : volume I final report.

    Science.gov (United States)

    2014-08-01

    Pile : - : Guided floats can be a desirable alternative to stationary berthing structures. Both floats and guide piles are subjected to dynamic : forces such as wind generated waves and impacts from vessels. This project developed a rational basis fo...

  8. 14 CFR 25.533 - Hull and main float bottom pressures.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Hull and main float bottom pressures. 25... AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Structure Water Loads § 25.533 Hull and main float bottom pressures. (a) General. The hull and main float structure, including frames and bulkheads...

  9. Project alliancing in the offshore industry

    NARCIS (Netherlands)

    Halman, Johannes I.M.; Braks, B.F.M.

    In this paper the shift towards new types of project organisation within the Offshore Industry is explained and discussed. Special focus is given to the organisational concept of Project Alliancing. The principles, structure and culture of a Project Alliance as applied within the Offshore Industry

  10. The Effect of Additional Mooring Chains on the Motion Performance of a Floating Wind Turbine with a Tension Leg Platform

    Directory of Open Access Journals (Sweden)

    Jinping Ou

    2012-04-01

    Full Text Available In this study, two types of floating offshore wind turbine (FOWT systems were proposed: a traditional tension leg platform (TLP type and a new TLP type with additional mooring chains. They were both based on the National Renewable Energy Laboratory 5 MW offshore wind turbine model. Taking the coupled effect of dynamic response of the top wind turbine, tower support structure and lower mooring system into consideration, not only were the 1/60 scale model tests for the two floating wind turbine systems done in HIT’s wind-wave tunnel according to the typical design conditions in IEC61400-3 code, but also the numerical simulations corresponding to the scaled model tests were performed by advanced numerical tools. As a result, the numerical results displayed good agreement with the test data. Moreover, the additional mooring chains could play an active role in reducing the surge displacement, surge acceleration and typical tension leg force responses of the FOWT system, which is very beneficial for ensuring the good operational performance and the safety of the FOWT system.

  11. On the hydroelastic response of box-shaped floating structure with shallow draft. Tank test with large scale model; Senkitsusui hakogata futai no harochu dansei oto ni tsuite. Ogata mokei ni yoru suiso shiken

    Energy Technology Data Exchange (ETDEWEB)

    Yago, K; Endo, H [Ship Research Inst., Tokyo (Japan)

    1997-12-31

    The hydroelastic response test was carried out in waves using an approximately 10m long large model, and the numerical analysis was done by the direct method, for a commercial-size (300m long) box-shaped floating structure with shallow draft. The scale ratio of the model is 1/30.8, and the minimum wave cycle is around 0.7s from wave-making capacity of the tank, which corresponds to 4 to 14s with the commercial-size structure. Elastic displacement and bending strain were measured. The calculated results by the direct method are in good agreement with the observed results. The fluid dynamic mutual interference effects between elements are weak in added mass but strong in damping force, indicating that the range of mutual interference is strongly related to rolling cycle in the range of mutual interference. Wave pressure on the floating structure bottom is high at the upper side of the wave, greatly damping towards the downside of the wave. However, response amplitude of elastic displacement tends to increase at the ends, both in upside and downside of the wave. For the floating structure studied, the 0 to 4th mode components are predominant in longitudinal waves, and the 6th or higher mode components are negligibly low. 21 refs., 15 figs., 2 tabs.

  12. On the hydroelastic response of box-shaped floating structure with shallow draft. Tank test with large scale model; Senkitsusui hakogata futai no harochu dansei oto ni tsuite. Ogata mokei ni yoru suiso shiken

    Energy Technology Data Exchange (ETDEWEB)

    Yago, K.; Endo, H. [Ship Research Inst., Tokyo (Japan)

    1996-12-31

    The hydroelastic response test was carried out in waves using an approximately 10m long large model, and the numerical analysis was done by the direct method, for a commercial-size (300m long) box-shaped floating structure with shallow draft. The scale ratio of the model is 1/30.8, and the minimum wave cycle is around 0.7s from wave-making capacity of the tank, which corresponds to 4 to 14s with the commercial-size structure. Elastic displacement and bending strain were measured. The calculated results by the direct method are in good agreement with the observed results. The fluid dynamic mutual interference effects between elements are weak in added mass but strong in damping force, indicating that the range of mutual interference is strongly related to rolling cycle in the range of mutual interference. Wave pressure on the floating structure bottom is high at the upper side of the wave, greatly damping towards the downside of the wave. However, response amplitude of elastic displacement tends to increase at the ends, both in upside and downside of the wave. For the floating structure studied, the 0 to 4th mode components are predominant in longitudinal waves, and the 6th or higher mode components are negligibly low. 21 refs., 15 figs., 2 tabs.

  13. IS OFFSHORING AN INTERNATIONAL PROCESS

    Directory of Open Access Journals (Sweden)

    Paulo Roberto Gião

    2012-01-01

    Full Text Available This article proposes to analyze the applicability of transaction cost economics - TCE (Coase, 1937; Williamson, 1975, 1979 through its characteristic make-or-buy expression, considering the offshoring pace and emerging economy firms. The make-or-buy decision must be flexible enough to explain offshoring characteristics and developed and emerging economy firms scenarios. As secondary objectives, and to show the trail to the main purpose, two research questions were identified and discussed during the paper: Is offshoring process an international movement only from developed countries to emerging economies? Is the main reason of offshoring the looking for low-cost work / activities? To achieve the proposed objectives, the structure of this paper begins with a reasonable or acceptable definition of offshoring. Some reasons (or “the reason” for the process are also another important starting point. The majority of articles referee the idea that low-cost is the main reason for offshoring, and if it is correct, transaction cost economics seems to be a good basis for our analysis purpose and integrative intention. Also some literature connections between offshoring and TCE are presented and, naturally TCE is presented in highlights for understanding these connections. Ending this section, some different arguments based on newer researches are presented by some authors presenting another perspective as the main reason. After this theoretical approach, a scenario analysis and some discussions are presented based on all possible interactions among firm from developed (DC and emerging economies (EE and examples of international corporations are presented to clarify and improve the understanding of our research questions and to build new contributions to international business theory.

  14. Cooperative control system of the floating cranes for the dual lifting

    OpenAIRE

    Mihee Nam; Jinbeom Kim; Jaechang Lee; Daekyung Kim; Donghyuk Lee; Jangmyung Lee

    2018-01-01

    This paper proposes a dual lifting and its cooperative control system with two different kinds of floating cranes. The Mega-erection and Giga-erection in the ship building are used to handle heavier and wider blocks and modules as ships and off-shore platforms are enlarged. However, there is no equipment to handle such Tera-blocks. In order to overcome the limit on performance of existing floating cranes, the dual lifting is proposed in this research. In the dual lifting, two floating cranes ...

  15. Structural and mechanical defects of materials of offshore and onshore main gas pipelines after long-term operation

    Science.gov (United States)

    Maruschak, Pavlo; Panin, Sergey; Danyliuk, Iryna; Poberezhnyi, Lyubomyr; Pyrig, Taras; Bishchak, Roman; Vlasov, Ilya

    2015-10-01

    The study has established the main regularities of a fatigue failure of offshore gas steel pipes installed using S-lay and J-lay methods.We have numerically analyzed the influence of preliminary deformation on the fatigue life of 09Mn2Si steel at different amplitudes of cyclic loading. The results have revealed the regularities of formation and development of a fatigue crack in 17Mn1Si steel after 40 years of underground operation. The quantitative analysis describes the regularities of occurrence and growth of fatigue cracks in the presence of a stress concentration.

  16. Protective equipment against explosions for offshore oil and gas production; Explosionsgeschuetzte Ausruestung fuer den maritimen Oel- und Gassektor

    Energy Technology Data Exchange (ETDEWEB)

    Popp, Tobias [R. STAHL AG, Waldenburg (Germany)

    2011-05-15

    Offshore oil and gas production requires a multitude of explosion-proof components, systems and solutions both offshore and onshore. They serve different functions, from extraction and separation of fossil fuels to the production and storage of transportable products, sometimes on floating offshore platforms. There are also offshore cranes and pipelines to the onshore terminals. All this requires explostion-proof control cabinets, power distribution units and other equipment. The many different requirements are illustrated by the example of the world's biggest offshore production platform FPSO in the China Sea.

  17. Structural Health and Prognostics Management for Offshore Wind Turbines: Sensitivity Analysis of Rotor Fault and Blade Damage with O&M Cost Modeling

    Energy Technology Data Exchange (ETDEWEB)

    Myrent, Noah J. [Vanderbilt Univ., Nashville, TN (United States). Lab. for Systems Integrity and Reliability; Barrett, Natalie C. [Vanderbilt Univ., Nashville, TN (United States). Lab. for Systems Integrity and Reliability; Adams, Douglas E. [Vanderbilt Univ., Nashville, TN (United States). Lab. for Systems Integrity and Reliability; Griffith, Daniel Todd [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Wind Energy Technology Dept.

    2014-07-01

    Operations and maintenance costs for offshore wind plants are significantly higher than the current costs for land-based (onshore) wind plants. One way to reduce these costs would be to implement a structural health and prognostic management (SHPM) system as part of a condition based maintenance paradigm with smart load management and utilize a state-based cost model to assess the economics associated with use of the SHPM system. To facilitate the development of such a system a multi-scale modeling and simulation approach developed in prior work is used to identify how the underlying physics of the system are affected by the presence of damage and faults, and how these changes manifest themselves in the operational response of a full turbine. This methodology was used to investigate two case studies: (1) the effects of rotor imbalance due to pitch error (aerodynamic imbalance) and mass imbalance and (2) disbond of the shear web; both on a 5-MW offshore wind turbine in the present report. Sensitivity analyses were carried out for the detection strategies of rotor imbalance and shear web disbond developed in prior work by evaluating the robustness of key measurement parameters in the presence of varying wind speeds, horizontal shear, and turbulence. Detection strategies were refined for these fault mechanisms and probabilities of detection were calculated. For all three fault mechanisms, the probability of detection was 96% or higher for the optimized wind speed ranges of the laminar, 30% horizontal shear, and 60% horizontal shear wind profiles. The revised cost model provided insight into the estimated savings in operations and maintenance costs as they relate to the characteristics of the SHPM system. The integration of the health monitoring information and O&M cost versus damage/fault severity information provides the initial steps to identify processes to reduce operations and maintenance costs for an offshore wind farm while increasing turbine availability

  18. Offshoring and International Competitiveness

    DEFF Research Database (Denmark)

    Ørberg Jensen, Peter D.; Pedersen, Torben

    2012-01-01

    During the past decade, offshoring has become an established business practice. Yet it is still more common to offshore less advanced tasks compared with offshoring more advanced tasks, i.e., tasks closer to the core activities of the firm. The latter is a new phenomenon which raises many new iss...

  19. Oil exploration and production offshore Sakhalin Island

    Energy Technology Data Exchange (ETDEWEB)

    Reed, I.C. [Sakhalin Energy Investment Company, Yuzhno-Sakhalinsk (Russian Federation)

    2006-11-15

    The offshore oil and gas exploration that is currently taking place on Sakhalin Island was discussed, with particular reference to the status of Sakhalin Energy and the challenges facing oil and exportation from the ice covered waters of Russia's Sea of Okhotsk. Sakhalin Energy, an incorporated joint venture of a consortium of companies, completed a feasibility study for oil production off the east coast of Sakhalin Island in December 1992. Sakhalin Energy has two fields, namely the Piltun Astokhskoye and Lunskoye fields. The Piltun Astokhskoye field is currently under production via the Molikpaq platform and the Lunskoye field and northern part of Piltun Astokhskoye field are currently being developed under the Phase 2 project. Since 1999, Sakhalin Energy has been producing oil from a caisson structure drilling rig which was fitted with ice protection shielding around the waterline in order to comply with Russian requirements. Production is via an undersea pipeline to a Single Anchor Leg Mooring (SALM) unit and then to a Floating Storage and Offloading unit (FSO). A brief outline of the structure was presented along with current ice management procedures and arrangements. In order to maximize the length of the production season, ice management is used to enable an early start and a late end to production. It was noted that great care is taken to ensure that the operations in ice are carried out with consideration of the environmentally sensitive area that is home to the endangered Western Gray Whale and Stellar Sea Eagle. 3 refs., 1 tab., 7 figs.

  20. Floating liquid bridge charge dynamics

    Science.gov (United States)

    Teschke, Omar; Soares, David Mendez; Gomes, Whyllerson Evaristo; Valente Filho, Juracyr Ferraz

    2016-01-01

    The interaction of liquid with electric fields is investigated in a configuration where up to 13 kV are applied between electrodes resulting in a 106 V/m electric field in the capillaries and where there is the formation of a free-standing fluid bridge in the interelectrode gap. The Mott-Gurney equation was fitted to the measured ionization current vs applied voltage curve which indicates that the ionization rate at the high-voltage anode electrode dimethylsulfoxide (DMSO) interface and space charging in the interelectrode gap determine the floating liquid bridge current for a given cathode-to-anode voltage. Space charge effects were measured in the cathode becker and also at the liquid bridge since the ionized charges at the anode migrate to the bridge outer surface and decrease the interfacial tension from 43 mJ/m2 to 29 mJ/m2. Two distinct structural regions then form the bridge, a charged plastic (bulk modulus ˜100 MPa) conducting outer layer with a surface conductivity of ˜10-9 Ω-1, which shapes and supports the floating fluid structure, and an inner liquid cylinder, where DMSO molecules flow.

  1. From Offshoring to Backshoring

    DEFF Research Database (Denmark)

    Slepniov, Dmitrij; Madsen, Erik Skov

    2015-01-01

    The purpose of this paper is to examine the evolution of offshoring over time. The paper employs qualitative methodology and on the basis of two case studies of Danish companies, it develops a framework conceptualizing the stages of offshoring and highlights the factors driving the transition...... between these stages. The framework challenges the linear nature of offshoring and proposes the existence of ‘the pendulum effect’. The pendulum effect suggests that the modes of offshoring (i.e. captive and non-captive) and geographies of offshoring (i.e. home and abroad) are not static; rather...

  2. Dutch offshore skills assessed

    Energy Technology Data Exchange (ETDEWEB)

    Schaap, P

    1988-11-01

    The position is described of the different Dutch industries involved in the oil and gas exploitation business in the North Sea. Mentioned are, in the first place, the activities of towing services Smit Tak, and Wijsmuller. A well known drilling contractor is Neddrill. Drilling rigs are often designed in cooperation with consulting engineers firms Protech International, Heerema Engineering, Global Engineering, KTI, Fluor, and Tebodin. Drilling rigs constructors Grootint, Mercon Steel Structures, Heerema Havenbedrijf, HCG, Boele, and IHC have a sound name in the offshore construction scene. Offshore contractors like Heerema, Smit Tak, Volker Stevin and Allseas Engineering should be mentioned too. Special attention is given to the operation of saving drilling rigs in the Ekofisk field. Years of exploitation of oil and gas from this field resulted in subsidence of the sea floor, which endangered the drilling rigs. Hydraudyne designed the hydraulic lifter necessary for this saving operation. Dutch firms in this field have an estimated yearly turnover of Dfl 3 x 10/sup 9/. 6 figs.

  3. Float level indicator

    International Nuclear Information System (INIS)

    Grishchuk, M.Kh.; Laptev, A.G.; Pashkov, V.A.

    1980-01-01

    Specially developed level indicator is suggested with differential to-transformer converter of the float motion, operating in line with a movable electronic block, intended for indicating the level of the dissociating nitrogen tetroxide liquid phase. On the basis of the indicator elements the device is realized to measure the time of calibrated volume fillino. in by liquid nitrogen tetroxide in steady state operation of the experimental bench-marks [ru

  4. Effect of yield to tensile (Y/T) ratio on the structural integrity of offshore pipeline: advanced engineering assessment using limit state design approach

    Energy Technology Data Exchange (ETDEWEB)

    Malatesta, G; Mannucci, G; Demofonti, G [Centro Sviluppo Materiali S.p.A., Rome (Italy); Cumino, G [TenarisDalmine (Italy); Izquierdo, A; Tivelli, M [Tenaris Group (Mexico); Quintanilla, H [TENARIS Group (Mexico). TAMSA

    2005-07-01

    Nowadays specifications require strict Yield to Tensile ratio limitation, nevertheless a fully accepted engineering assessment of its influence on pipeline integrity is still lacking. Probabilistic analysis based on structural reliability approach (Limit State Design) aimed at quantifying the Y/T ratio influence on failure probabilities of offshore pipelines was made. In particular, Tenaris seamless pipe data were used as input for the probabilistic failure analysis. The LSD approach has been applied to two actual deep water design cases that have been on purpose selected, and the most relevant failure modes have been considered. Main result of the work is that the quantitative effect of the Y/T ratio on failure probabilities of a deep water pipeline resulted not so big as expected; it has a minor effect, especially when failure modes are governed by Y only. (author)

  5. Vibration of an Offshore Structure Having the Form of a Hollow Column Partially Filled with Multiple Fluids and Immersed in Water

    Directory of Open Access Journals (Sweden)

    Hsien-Yuan Lin

    2012-01-01

    Full Text Available This paper employs the numerical assembly method (NAM to determine the exact frequency-response amplitudes of an offshore structure such as piles or towers having the form of a hollow column filled with multiple fluids, immersed in water, carrying an eccentric tip mass supported by a translational spring and/or a rotational spring, and subjected to a harmonic force. The hollow column is modeled as a Bernoulli-Euler cantilever beam fixed at the bottom. For the case of zero harmonic force, the simultaneous equations of the vibration system reduce to an eigenvalue problem so that the natural frequencies and mode shapes of the beam can also be obtained. The effect of height of filled fluids on the characteristics of free vibration is also presented.

  6. The floating knee

    DEFF Research Database (Denmark)

    Muñoz Vives, Josep; Bel, Jean-Christophe; Capel Agundez, Arantxa

    2016-01-01

    In 1975, Blake and McBryde established the concept of 'floating knee' to describe ipsilateral fractures of the femur and tibia.1This combination is much more than a bone lesion; the mechanism is usually a high-energy trauma in a patient with multiple injuries and a myriad of other lesions...... fixation when both fractures (femoral and tibial) are extra-articular.Plates are the 'standard of care' in cases with articular fractures.A combination of implants are required by 40% of floating knees.Associated ligamentous and meniscal lesions are common, but may be irrelevant in the case of an intra......-articular fracture which gives the worst prognosis for this type of lesion. Cite this article: Muñoz Vives K, Bel J-C, Capel Agundez A, Chana Rodríguez F, Palomo Traver J, Schultz-Larsen M, Tosounidis, T. The floating knee.EFORT Open Rev2016;1:375-382. DOI: 10.1302/2058-5241.1.000042....

  7. Numerical study on aerodynamic damping of floating vertical axis wind turbines

    Science.gov (United States)

    Cheng, Zhengshun; Aagaard Madsen, Helge; Gao, Zhen; Moan, Torgeir

    2016-09-01

    Harvesting offshore wind energy resources using floating vertical axis wind turbines (VAWTs) has attracted an increasing interest in recent years. Due to its potential impact on fatigue damage, the aerodynamic damping should be considered in the preliminary design of a floating VAWT based on the frequency domain method. However, currently the study on aerodynamic damping of floating VAWTs is very limited. Due to the essential difference in aerodynamic load characteristics, the aerodynamic damping of a floating VAWT could be different from that of a floating horizontal axis wind turbine (HAWT). In this study, the aerodynamic damping of floating VAWTs was studied in a fully coupled manner, and its influential factors and its effects on the motions, especially the pitch motion, were demonstrated. Three straight-bladed floating VAWTs with identical solidity and with a blade number varying from two to four were considered. The aerodynamic damping under steady and turbulent wind conditions were estimated using fully coupled aero-hydro-servo-elastic time domain simulations. It is found that the aerodynamic damping ratio of the considered floating VAWTs ranges from 1.8% to 5.3%. Moreover, the aerodynamic damping is almost independent of the rotor azimuth angle, and is to some extent sensitive to the blade number.

  8. Magnetic constraints of basement structure offshore of western Kyushu, Japan; Kyushu seiho kaiiki ni okeru jiki ijo no kaiseki

    Energy Technology Data Exchange (ETDEWEB)

    Okuma, S; Nakatsuka, T [Geological Survey of Japan, Tsukuba (Japan); Ishihara, T [Japan National Oil Corp., Tokyo (Japan)

    1996-05-01

    This paper describes the results from the qualitative analysis of magnetic anomalies offshore of western Kyushu and from an analysis by a three-dimensional two-layer model inversion. The analysis ranged from Kyushu on the east to Jeju Island on the west and from the southern part of the Korean Peninsula on the north to Tanegashima and Yakushima Islands on the south, namely, the area of 580km from east to west and 580km from south to north. The analytical data used was Magnetic Anomaly Map of Asia (GSJ and CCOP, 1994). In the qualitative analysis, a pseudogravity anomaly map and a pole gravity anomaly map were prepared from the total magnetic force anomaly map by means of a frequency filter operation. As a result, it was noted that two distinctive magnetic high belts existed in the margin of the Tunghai Shelf, extending from the sea area to the west of the Nansei Islands continuously to NNE, and being distributed transversely through the Goto sedimentary basin. Additionally, in the inversion analysis, it was demonstrated that the magnetic basement became shallow at the margin of the Tunghai Shelf north of latitude 31 degrees north, extending nearly in the NNE direction through west of the Goto Islands, west of Tsushima Island, and continuing to the southern coast of the Korean Peninsula. 6 refs., 4 figs.

  9. Panorama 2012 - Offshore hydrocarbons

    International Nuclear Information System (INIS)

    Serbutoviez, Sylvain

    2011-12-01

    Technological progress is enabling production from offshore oil and gas fields at increasingly ambitious depths (3, 000 metres). Investment in offshore production is running at around $100 billion per year, accounting for one-fifth of all investment in oil exploration and development worldwide. However, the global economic crisis that broke at the end of 2008 and the accident involving the Macondo well temporarily disrupted the race to deep offshore technology. (author)

  10. Offshore Transmission Technology

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2012-10-15

    The purpose of this document is to give an overview of offshore electricity transmission technologies. In particular this document is concerned with the use of High Voltage Direct Current (HVDC) systems and more specifically with the development of Voltage Source Converter (VSC) technology. This report outlines the current state of the main technology groups required for offshore HVDC transmission as well as giving examples of offshore projects (both current and future). Finally some indications of likely unit costs for HV assets are given.

  11. Offshore wind; proposed study areas; Havvind; forslag til utredningsomraader

    Energy Technology Data Exchange (ETDEWEB)

    Drivenes, Arvid; Eirum, Tale; Johnson, Nils Henrik; Mindeberg, Sigrun Kavli; Lunde, Synnoeve; Undem, Linn Silje; Veggeland, Kirsti; Veie-Rosvoll, Brit; Voksoe, Astrid

    2010-10-15

    The report suggests areas that may be suitable for establishing of offshore wind power, and should be further evaluated in a strategic environmental impact assessment, as it is designed to through Proposition. No. 107 (2008-2009). The proposed areas is shown in Figure 1 Eleven of the areas suitable for fixed installations and four sites suitable for floating installations. The work of the report has been carried out by a Directorate group led by the Norwegian Water Resources and Energy Directorate. (AG)

  12. Occupational health offshore

    Energy Technology Data Exchange (ETDEWEB)

    Crosbie, A.; Davies, F.

    2002-07-01

    The proceedings contain the 29 papers presented at the conference plus the opening address from the chair of the Health and Safety Commission. The papers in the first session were concerned with policy, strategy and leadership and included a perspective from the offshore industry advisory committee, details of a health planning tool for occupational health assurance and lessons from occupational health management in the offshore sector. The two sessions on the second day dealt with occupational health in the offshore design process and case studies involving physical, chemical and biological agents. Topics included the need to consider occupational health when designing offshore installations, the development of a human factors engineering strategy in petrochemical engineering projects, measuring occupational exposure to hazardous chemicals, implementation of the noise at work regulations, hand arm vibration syndrome and issues with potable water maintenance. The two sessions on the third day were concerned with human factors and psychological health, and well-being and fitness for duty. Topics covered included circadian adaption to shift change in offshore shift workers, managing stress in the offshore environment, the role of employee assistance programmes in organisational stress management, health care and first aid (the revised ACOP), well-being at work, the medical and physical fitness of offshore emergency response rescue team members, the impact of health surveillance and promotion of offshore accident rates, and the implication of safety and heath of the aging of the workforce ion the Norwegian offshore industry.

  13. Method for extracting an equivalent Winkler model of the 3D dynamic soil-structure interaction of large-diameter offshore monopile foundations

    NARCIS (Netherlands)

    Versteijlen, W.G.; De Oliveira Barbosa, J.M.; Van Dalen, K.N.; Metrikine, A.

    2015-01-01

    The motivation for this work stems from the offshore wind industry, where designers are faced with a discrepancy between the available design methods and the typical dimensions of the offshore wind foundations that call for other design approaches. Throughout the years, much valuable work has been

  14. Fatigue and extreme wave loads on bottom fixed offshore wind turbines. Effects from fully nonlinear wave forcing on the structural dynamics

    DEFF Research Database (Denmark)

    Schløer, Signe

    2013-01-01

    wind farms. As wind farms are being moved further offshore the wave loads become larger compared to the wind loads and therefore more important in the design of offshore wind turbines. Yet, the water depth is still only shallow or intermediate where the waves should be described by nonlinear irregular...

  15. Wave and offshore wind potential for the island of Tenerife

    International Nuclear Information System (INIS)

    Veigas, M.; Iglesias, G.

    2013-01-01

    Highlights: • The island aims to reduce its carbon footprint by developing renewable energy. • The substantial wave and offshore wind resources around the island are examined. • One area is appropriate for installing a hybrid wave–offshore wind farm. - Abstract: The island of Tenerife, a UNESCO Biosphere Reserve in the Atlantic Ocean, aims to be energy self-sufficient in order to reduce its carbon footprint. To accomplish this goal it should develop the renewable sources, in particular wave and offshore wind energy. The objectives of this work are twofold; (i) to characterize the wave and offshore wind power distribution around the island and (ii) to determine which offshore area is best suited for their exploitation, taking into account the resource and other conditioning factors such as the bathymetry, distance to the coastline and ports, and offshore zoning. To carry out this research, hindcast wave and wind data obtained with numerical models are used alongside observations from meteorological stations. One area, in the vicinity of Puerto de la Cruz, is identified as having great potential for installing a hybrid floating wave–wind farm. Both resources are characterized for the area selected: the wave resource in terms of wave directions, significant wave heights and energy periods; the offshore wind resource in terms of directions and speeds in addition to the seasonality for the both resources. It is found that most of the wave resource is provided by N and NNW waves with significant wave heights between 1.5 m and 3.0 m and energy periods between 10 s and 14 s. It follows that the Wave Energy Converters deployed in the area should have maximum efficiency in those ranges. As for the offshore wind resource, most of the energy corresponds to NNE and NE winds with speeds between 9 and 14 m s −1 , which should be taken into account when selecting the offshore wind turbines

  16. Ipsilateral Floating Hip and Floating Knee – A Rare Entity

    Directory of Open Access Journals (Sweden)

    Yashavantha Kumar

    2013-04-01

    Full Text Available Introduction: Ipsilateral floating hip and floating knee are very rare injuries. These injuries so uncommon that only three cases of similar kind have been reported. These injuries are due to high velocity injuries following motor vehicle accidents. Management of such complex injuries is a challenging task even in experienced hands as there are no standard treatment guidelines for such fractures. Case Report: We hereby report a 20 yr old male who sustained ipsilateral floating hip and ipsilateral floating knee injuries following motor vehicle accident. Patient was stabilized initially and later taken up for surgery. Patient was treated with interlocking nail for femur and tibia in the same sitting whereas acetabulam fracture was managed conservatively. At five months all the fractures united well with restoration of good range of motion in both hip and knee. Conclusion: Ipsilateral floating knee and floating hip are very rare injuries seen following high velocity motor vehicle accidents. There are no standard guidelines for treatment of those fractures as only a few cases of similar kind have been reported in literature. Early fixation and aggressive mobilization ensures fracture union and fewer complications. Keywords: Floating hip, Floating Knee, Ipsilateral.

  17. Dynamic response signatures of a scaled model platform for floating wind turbines in an ocean wave basin.

    Science.gov (United States)

    Jaksic, V; O'Shea, R; Cahill, P; Murphy, J; Mandic, D P; Pakrashi, V

    2015-02-28

    Understanding of dynamic behaviour of offshore wind floating substructures is extremely important in relation to design, operation, maintenance and management of floating wind farms. This paper presents assessment of nonlinear signatures of dynamic responses of a scaled tension-leg platform (TLP) in a wave tank exposed to different regular wave conditions and sea states characterized by the Bretschneider, the Pierson-Moskowitz and the JONSWAP spectra. Dynamic responses of the TLP were monitored at different locations using load cells, a camera-based motion recognition system and a laser Doppler vibrometer. The analysis of variability of the TLP responses and statistical quantification of their linearity or nonlinearity, as non-destructive means of structural monitoring from the output-only condition, remains a challenging problem. In this study, the delay vector variance (DVV) method is used to statistically study the degree of nonlinearity of measured response signals from a TLP. DVV is observed to create a marker estimating the degree to which a change in signal nonlinearity reflects real-time behaviour of the structure and also to establish the sensitivity of the instruments employed to these changes. The findings can be helpful in establishing monitoring strategies and control strategies for undesirable levels or types of dynamic response and can help to better estimate changes in system characteristics over the life cycle of the structure. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  18. ISM Approach to Model Offshore Outsourcing Risks

    OpenAIRE

    Kumar, Sunand; Sharma, Rajiv Kumar; Chauhan, Prashant

    2014-01-01

    [EN] In an effort to achieve a competitive advantage via cost reductions and improved market responsiveness, organizations are increasingly employing offshore outsourcing as a major component of their supply chain strategies. But as evident from literature number of risks such as Political risk, Risk due to cultural differences, Compliance and regulatory risk, Opportunistic risk and Organization structural risk, which adversely affect the performance of offshore outsourcing in a supply chain ...

  19. Co-sourcing in software development offshoring

    DEFF Research Database (Denmark)

    Schlichter, Bjarne Rerup; Persson, John Stouby

    2013-01-01

    Software development projects are increasingly geographical distributed with offshoring, which introduce complex risks that can lead to project failure. Co-sourcing is a highly integrative and cohesive approach, seen successful, to software development offshoring. However, research of how co-sour......-taking by high attention to of the closely interrelated structure and technology components in terms of CMMI and the actors’ cohesion and integration in terms of Scrum....

  20. Fatigue Reliability of Offshore Wind Turbine Systems

    DEFF Research Database (Denmark)

    Marquez-Dominguez, Sergio; Sørensen, John Dalsgaard

    2012-01-01

    of appropriate partial safety factors / fatigue design factors (FDF) for steel substructures of offshore wind turbines (OWTs). The fatigue life is modeled by the SN approach. Design and limit state equations are established based on the accumulated fatigue damage. The acceptable reliability level for optimal...... fatigue design of OWTs is discussed and results for reliability assessment of typical fatigue critical design of offshore steel support structures are presented....

  1. Offshore nuclear installations

    International Nuclear Information System (INIS)

    Albano, R.

    1976-01-01

    It is possible now to foresee the creation of nuclear power plants on floating or fixed islands although from the safety viewpoint, floating islands are preferable. The definition of the legal nature of artificial islands raises a first problem insofar as artificial islands are neither islands nor ships. Furthermore, their statute would differ according to whether they were sited in territorial seas or in the new 'economic zones'. This leads to consideration of the applicability of Italian maritime legislation to nuclear power plants on floating islands without setting aside that of international regulations on radioactive maritime pollution. (N.E.A.) [fr

  2. Offshoring research directions

    NARCIS (Netherlands)

    Velthuijsen, Hugo

    2012-01-01

    Outsourcing and offshoring provide companies with ways to achieve their business objectives better or more cost effectively or despite a shortage of specific resources. From a research point of view, outsourcing and offshoring have mostly been studied as something that large companies do, not small

  3. Organizational Adaptation in Offshoring

    DEFF Research Database (Denmark)

    Geisler Asmussen, Christian; Møller Larsen, Marcus; Pedersen, Torben

    2016-01-01

    Offshoring offers managers the promise of substantial economic benefits, but also comes with the risk of increased complexity and coordination challenges. We argue that offshoring firms must accumulate architectural knowledge to keep the cost of coordination of the geographically separated activi...

  4. Offshore Investment Funds

    Directory of Open Access Journals (Sweden)

    Shang-Jin Wei

    1999-12-01

    Full Text Available Offshore investment funds are alleged to have engaged in trading behavior that is different from their onshore counterparts because they may be subject to less supervision and regulation. In particular, they may trade more intensely. They could also pursue more aggressively certain trading strategies such as positive feedback trading or herding that could contribute to a greater volatility in the market. Using a unique data set, this chapter compares the trading behavior in the Korean stock market between offshore investment funds with their onshore counterparts registered in the US and UK. There are a number of interesting findings. First, there is indeed evidence suggesting that the offshore funds trade more intensely than their onshore counterparts. Second, however, there is no evidence that the offshore funds engage in positive feedback trading. In contrast, there is strong evidence that the funds from the U.S. and U.K. do. Third, while offshore funds do herd, they do so far less than onshore funds in the U.S. or UK. Fourth, offshore funds hold less glamour stocks (e.g. stocks with high P/E in their portfolio than funds in the U.S. or U.K. do. Moreover, flight to glamour stocks during the in-crisis period is less evident in the case of offshore funds. In sum, offshore funds are no especially worrisome monsters.

  5. Offshore wind development research.

    Science.gov (United States)

    2014-04-01

    Offshore wind (OSW) development is a new undertaking in the US. This project is a response to : New Jerseys 2011 Energy Master Plan that envisions procuring 22.5% of the states power : originating from renewable sources by 2021. The Offshore Wi...

  6. Sinking offshore platform. Nedsenkbar fralandsplatform

    Energy Technology Data Exchange (ETDEWEB)

    Einstabland, T.B.; Olsen, O.

    1988-12-19

    The invention deals with a sinking offshore platform of the gravitational type designed for being installed on the sea bed on great depths. The platform consists of at least three inclining pillars placed on a foundation unit. The pillars are at the upper end connected to a tower structure by means of a rigid construction. The tower supports the platform deck. The rigid construction comprises a centre-positioned cylinder connected to the foundation. 11 figs.

  7. Global offshore pipeline markets

    International Nuclear Information System (INIS)

    Knight, R.; Parsons, B.

    2001-01-01

    In this article, two experts forecast a recovery in the offshore pipeline market followed by accelerating growth. A number of clearly definable macro trends are affecting the world offshore oil and gas industry and will be of considerable significance to the offshore pipelines industry. The authors' view is of markets that show every chance of enjoying long-term growth prospects driven by the fundamentals of a continuing increase in demand for offshore oil and gas. The offshore industry however has a highly cyclical nature, due to the impact of variations in oil and gas prices and the differing state of maturity of individual regions. Therefore those companies that are able to offer the widest range of pipe types and diameters and methods of installation across the greatest range of geographic markets are likely to prosper most. Thus, this continues to be a market best suited to those able to operate on a global scale and make a corporate commitment measured in decades

  8. Innovative Offshore Wind Plant Design Study

    Energy Technology Data Exchange (ETDEWEB)

    Hurley, William L. [Glosten Associates, Inc., Seattle, WA (United States); Nordstrom, Charles J. [Glosten Associates, Inc., Seattle, WA (United States); Morrison, Brent J. [Glosten Associates, Inc., Seattle, WA (United States)

    2013-12-18

    Technological advancements in the Glosten PelaStar floating wind turbine system have led to projected cost of energy (COE) reductions from today’s best-in-class offshore wind systems. The PelaStar system is projected to deliver a COE that is 35% lower than that delivered by the current offshore wind plants. Several technology developments have been achieved that directly target significant cost of energy reductions. These include: Application of state-of-the-art steel construction materials and methods, including fatigue-resistant welding techniques and technologies, to reduce hull steel weight; Advancements in synthetic fiber tendon design for the mooring system, which are made possible by laboratory analysis of full-scale sub-rope specimens; Investigations into selected anchor technologies to improve anchor installation methods; Refinement of the installation method, specifically through development of the PelaStar Support Barge design. Together, these technology developments drive down the capital cost and operating cost of offshore wind plants and enable access to superb wind resources in deep water locations. These technology developments also reduce the uncertainty of the PelaStar system costs, which increases confidence in the projected COE reductions.

  9. Cooperative control system of the floating cranes for the dual lifting

    Directory of Open Access Journals (Sweden)

    Mihee Nam

    2018-01-01

    Full Text Available This paper proposes a dual lifting and its cooperative control system with two different kinds of floating cranes. The Mega-erection and Giga-erection in the ship building are used to handle heavier and wider blocks and modules as ships and off-shore platforms are enlarged. However, there is no equipment to handle such Tera-blocks. In order to overcome the limit on performance of existing floating cranes, the dual lifting is proposed in this research. In the dual lifting, two floating cranes are well-coordinated to add up the lift capabilities of both cranes without any loss such that virtually a single crane is lifting, maneuvering and unloading. Two main constraints for the dual lifting are as follows: First, two barges of floating cranes should be constrained as a rigid body not to cause a relative motion between two barges and main hooks of the two cranes should be controlled as main hooks of a single crane. In order words, it is necessary to develop the cooperative control of two floating cranes in order to sustain a center of gravity of the module and minimize the tilting angle during the lifting and unloading by the two floating cranes. Two floating cranes are handled as a master-slave system. The master crane is able to gather information about all working conditions and make a decision to control the individual hook speed, which communicates the slave crane by TCP/IP. The developed control system has been embedded in the real floating crane systems and the dual lifting has been demonstrated five times at SHI shipyard in 2015. The moving angles of the lifting module are analyzed and verified to be suitable for hoisting control. It is verified that the dual lifting can be applied for many heavier and wider blocks and modules to shorten the construction time of ships and off-shore platforms.

  10. Thermodynamic design of natural gas liquefaction cycles for offshore application

    Science.gov (United States)

    Chang, Ho-Myung; Lim, Hye Su; Choe, Kun Hyung

    2014-09-01

    A thermodynamic study is carried out for natural gas liquefaction cycles applicable to offshore floating plants, as partial efforts of an ongoing governmental project in Korea. For offshore liquefaction, the most suitable cycle may be different from the on-land LNG processes under operation, because compactness and simple operation are important as well as thermodynamic efficiency. As a turbine-based cycle, closed Claude cycle is proposed to use NG (natural gas) itself as refrigerant. The optimal condition for NG Claude cycle is determined with a process simulator (Aspen HYSYS), and the results are compared with fully-developed C3-MR (propane pre-cooled mixed refrigerant) JT cycles and various N2 (nitrogen) Brayton cycles in terms of efficiency and compactness. The newly proposed NG Claude cycle could be a good candidate for offshore LNG processes.

  11. Fully Coupled Three-Dimensional Dynamic Response of a Tension-Leg Platform Floating Wind Turbine in Waves and Wind

    DEFF Research Database (Denmark)

    Kumari Ramachandran, Gireesh Kumar Vasanta; Bredmose, Henrik; Sørensen, Jens Nørkær

    2014-01-01

    , which is a consequence of the wave-induced rotor dynamics. Loads and coupled responses are predicted for a set of load cases with different wave headings. Further, an advanced aero-elastic code, Flex5, is extended for the TLP wind turbine configuration and the response comparison with the simpler model......A dynamic model for a tension-leg platform (TLP) floating offshore wind turbine is proposed. The model includes three-dimensional wind and wave loads and the associated structural response. The total system is formulated using 17 degrees of freedom (DOF), 6 for the platform motions and 11...... for the wind turbine. Three-dimensional hydrodynamic loads have been formulated using a frequency-and direction-dependent spectrum. While wave loads are computed from the wave kinematics using Morison's equation, the aerodynamic loads are modeled by means of unsteady blade-element-momentum (BEM) theory...

  12. Potential for Jobs and Economic Development from Offshore Wind in California

    Energy Technology Data Exchange (ETDEWEB)

    Tegen, Suzanne

    2016-11-02

    In California's future scenarios, energy demand increases with population growth and productivity. Decision-makers will have to make choices about which energy resources to utilize, and offshore wind offers one option for carbon-free electricity with the potential for increased local jobs. This presentation discusses results from an NREL report, Floating Offshore Wind in California: Gross Potential for Jobs and Economic Impacts from Two Future Scenarios. Presenter Suzanne Tegen describes the Jobs and Economic Development Impact (JEDI) model and its results for two offshore wind scenarios in California. She discusses different assumptions and how they affect the scenarios.

  13. The crustal structures from Wuyi-Yunkai orogen to Taiwan orogen: the onshore-offshore wide-angle seismic experiment of TAIGER and ATSEE projects

    Science.gov (United States)

    Kuochen, H.; Kuo, N. Y. W.; Wang, C. Y.; Jin, X.; Cai, H. T.; Lin, J. Y.; Wu, F. T.; Yen, H. Y.; Huang, B. S.; Liang, W. T.; Okaya, D. A.; Brown, L. D.

    2015-12-01

    The crustal structure is key information for understanding the tectonic framework and geological evolution in the southeastern China and its adjacent area. In this study, we integrated the data sets from the TAIGER and ATSEE projects to resolve onshore-offshore deep crustal seismic profiles from the Wuyi-Yunkai orogen to the Taiwan orogen in southeastern China. Totally, there are three seismic profiles resolved and the longest profile is 850 km. Unlike 2D and 3D first arrival travel-time tomography from previous studies, we used both refracted and reflected phases (Pg, Pn, PcP, and PmP) to model the crustal structures and the crustal reflectors. 40 shots, 2 earthquakes, and about 1,950 stations were used and 15,319 arrivals were picked among three transects. As a result, the complex crustal evolution since Paleozoic era are shown, which involved the closed Paleozoic rifted basin in central Fujian, the Cenozoic extension due to South China sea opening beneath the coastline of southern Fujian, and the on-going collision of the Taiwan orogen.

  14. Development of floating strip micromegas detectors

    Energy Technology Data Exchange (ETDEWEB)

    Bortfeldt, Jonathan

    2014-04-28

    Micromegas are high-rate capable, high-resolution micro-pattern gaseous detectors. Square meter sized resistive strip Micromegas are foreseen as replacement of the currently used precision tracking detectors in the Small Wheel, which is part of the forward region of the ATLAS muon spectrometer. The replacement is necessary to ensure tracking and triggering performance of the muon spectrometer after the luminosity increase of the Large Hadron Collider beyond its design value of 10{sup 34} cm{sup -2}s{sup -1} around 2020. In this thesis a novel discharge tolerant floating strip Micromegas detector is presented and described. By individually powering copper anode strips, the effects of a discharge are confined to a small region of the detector. This reduces the impact of discharges on the efficiency by three orders of magnitude, compared to a standard Micromegas. The physics of the detector is studied and discussed in detail. Several detectors are developed: A 6.4 x 6.4 cm{sup 2} floating strip Micromegas with exchangeable SMD capacitors and resistors allows for an optimization of the floating strip principle. The discharge behavior is investigated on this device in depth. The microscopic structure of discharges is quantitatively explained by a detailed detector simulation. A 48 x 50 cm{sup 2} floating strip Micromegas is studied in high energy pion beams. Its homogeneity with respect to pulse height, efficiency and spatial resolution is investigated. The good performance in high-rate background environments is demonstrated in cosmic muon tracking measurements with a 6.4 x 6.4 cm{sup 2} floating strip Micromegas under lateral irradiation with 550 kHz 20 MeV proton beams. A floating strip Micromegas doublet with low material budget is developed for ion tracking without limitations from multiple scattering in imaging applications during medical ion therapy. Highly efficient tracking of 20 MeV protons at particle rates of 550 kHz is possible. The reconstruction of the

  15. Development of floating strip micromegas detectors

    International Nuclear Information System (INIS)

    Bortfeldt, Jonathan

    2014-01-01

    Micromegas are high-rate capable, high-resolution micro-pattern gaseous detectors. Square meter sized resistive strip Micromegas are foreseen as replacement of the currently used precision tracking detectors in the Small Wheel, which is part of the forward region of the ATLAS muon spectrometer. The replacement is necessary to ensure tracking and triggering performance of the muon spectrometer after the luminosity increase of the Large Hadron Collider beyond its design value of 10 34 cm -2 s -1 around 2020. In this thesis a novel discharge tolerant floating strip Micromegas detector is presented and described. By individually powering copper anode strips, the effects of a discharge are confined to a small region of the detector. This reduces the impact of discharges on the efficiency by three orders of magnitude, compared to a standard Micromegas. The physics of the detector is studied and discussed in detail. Several detectors are developed: A 6.4 x 6.4 cm 2 floating strip Micromegas with exchangeable SMD capacitors and resistors allows for an optimization of the floating strip principle. The discharge behavior is investigated on this device in depth. The microscopic structure of discharges is quantitatively explained by a detailed detector simulation. A 48 x 50 cm 2 floating strip Micromegas is studied in high energy pion beams. Its homogeneity with respect to pulse height, efficiency and spatial resolution is investigated. The good performance in high-rate background environments is demonstrated in cosmic muon tracking measurements with a 6.4 x 6.4 cm 2 floating strip Micromegas under lateral irradiation with 550 kHz 20 MeV proton beams. A floating strip Micromegas doublet with low material budget is developed for ion tracking without limitations from multiple scattering in imaging applications during medical ion therapy. Highly efficient tracking of 20 MeV protons at particle rates of 550 kHz is possible. The reconstruction of the track inclination in a single

  16. Synthesis, structural characterization and evaluation of floating B-N codoped TiO{sub 2}/expanded perlite composites with enhanced visible light photoactivity

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xin; Wang, Wei; Wang, Xuejiang, E-mail: wangxj@tongji.edu.cn; Zhang, Jing; Zhao, Jianfu; Gu, Zaoli; Zhou, Lijie

    2015-09-15

    Graphical abstract: - Highlights: • We added expanded perlite as a floating carrier to immobilize B-N codoped TiO{sub 2}. • The photo-reaction occurred on the surface of water and easily utilized the solar energy and O{sub 2} to make photodegradation efficiently. • The composites combined the adsorptivity of expanded perlite and photoactivity of B-N-TiO{sub 2}. • The floating photocatalysts give a simple way to recycle, which is important to the application of photocatalysis technology. - Abstract: Floating photocatalysts of boron-nitrogen codoped TiO{sub 2} grafted on expanded perlite (B-N-TiO{sub 2}/EP) were prepared by a facile sol–gel method. The catalysts were characterized by N{sub 2} adsorption–desorption (BET), scanning electron microscope (SEM), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and UV–vis diffuse reflectance spectroscopy (UV–vis–DRS). The results revealed that the physicochemical properties of the photocatalysts, such as BET surface area, porosity and pore size could be controlled by adjusting the calcination temperature and EP dosage. XRD patterns were mainly influenced by calcination temperature and the transformation of anatase to rutile occurred at 650 °C. Uniform TiO{sub 2} loading, higher surface area and absorption in visible light region were obtained for B-N-TiO{sub 2}/EP calcined at 550 °C with 3.0 g EP addition. Moreover, photocatalytic activity for RhB destruction under visible light irradiation was slightly influenced by TiO{sub 2} loading in the range of 1–3 g EP dosage. BNTEP550 showed the highest photocatalytic activity indicating to be a promising photocatalyst employed to remediate contaminated waters using solar irradiation.

  17. A Method for Modeling of Floating Vertical Axis Wind Turbine

    DEFF Research Database (Denmark)

    Wang, Kai; Hansen, Martin Otto Laver; Moan, Torgeir

    2013-01-01

    It is of interest to investigate the potential advantages of floating vertical axis wind turbine (FVAWT) due to its economical installation and maintenance. A novel 5MW vertical axis wind turbine concept with a Darrieus rotor mounted on a semi-submersible support structure is proposed in this paper....... In order to assess the technical and economic feasibility of this novel concept, a comprehensive simulation tool for modeling of the floating vertical axis wind turbine is needed. This work presents the development of a coupled method for modeling of the dynamics of a floating vertical axis wind turbine....... This integrated dynamic model takes into account the wind inflow, aerodynamics, hydrodynamics, structural dynamics (wind turbine, floating platform and the mooring lines) and a generator control. This approach calculates dynamic equilibrium at each time step and takes account of the interaction between the rotor...

  18. WindWaveFloat (WWF): Final Scientific Report

    Energy Technology Data Exchange (ETDEWEB)

    Weinstein, Alla; Roddier, Dominique; Banister, Kevin

    2012-03-30

    Principle Power Inc. and National Renewable Energy Lab (NREL) have completed a contract to assess the technical and economic feasibility of integrating wave energy converters into the WindFloat, resulting in a new concept called the WindWaveFloat (WWF). The concentration of several devices on one platform could offer a potential for both economic and operational advantages. Wind and wave energy converters can share the electrical cable and power transfer equipment to transport the electricity to shore. Access to multiple generation devices could be simplified, resulting in cost saving at the operational level. Overall capital costs may also be reduced, provided that the design of the foundation can be adapted to multiple devices with minimum modifications. Finally, the WindWaveFloat confers the ability to increase energy production from individual floating support structures, potentially leading to a reduction in levelized energy costs, an increase in the overall capacity factor, and greater stability of the electrical power delivered to the grid. The research conducted under this grant investigated the integration of several wave energy device types into the WindFloat platform. Several of the resulting system designs demonstrated technical feasibility, but the size and design constraints of the wave energy converters (technical and economic) make the WindWaveFloat concept economically unfeasible at this time. Not enough additional generation could be produced to make the additional expense associated with wave energy conversion integration into the WindFloat worthwhile.

  19. Scour Forecasting for Offshore Wind Parks

    DEFF Research Database (Denmark)

    Hartvig, Peres Akrawi

    In an effort to minimize the costs of offshore wind parks, the present research deals with optimizing a certain aspect of the support structure, namely the approach to scour. Scour is the phenomenon of seabed changes in the vicinity of the support structure that arises when the support structure......, scour forecasts facilitate the comparison between a scour design based on either deployment of scour-protection or enhanced structural design. The broad goal is to develop a method that produces accurate scour forecasts for offshore wind parks. The present research investigates more specifically which...

  20. Investigation on the dynamic response and strength of very long floating structures by beam modeling on an elastic foundation; Dansei shishojo no hari model ni yoru chodai futai kozo no doteki tawami kyodo tokusei ni kansuru kosatsu

    Energy Technology Data Exchange (ETDEWEB)

    Tsubogo, T.; Okada, H. [University of Osaka Prefecture, Osaka (Japan). Faculty of Engineering

    1997-08-01

    A very large floating structure was replaced with the beam on an elastic foundation to examine the response characteristics in waves. Another evidence was regularly and numerically given for the basic characteristics of a very large floating body Suzuki found. New information was also obtained. The frequency response is mainly classified into a wave number control area and proper frequency control area when buoyancy elasticity exists. When the buoyancy structure is long and flexible, the proper frequency becomes continuous and the frequency control area becomes a resonance area. In the wave number control area, the Suzuki`s characteristic wave number becomes a control parameter, and various characteristic values are indicated by characteristic wave numbers. The response in the wave number control area becomes quasi-static when the distribution mass of buoyancy is fully small. The design in which the distribution mass of buoyancy is fully large must be avoided. In the displacement amplitude, the mass on the free end is severest. The proper frequency of vertical vibration relatively moves to the high-frequency side when buoyancy is considered as an elastic foundation. Attention must be thus paid to the proper frequency of vibration on the horizontal surface. 9 refs., 12 figs., 3 tabs.

  1. Assessing offshore wind potential

    International Nuclear Information System (INIS)

    Adelaja, Adesoji; McKeown, Charles; Calnin, Benjamin; Hailu, Yohannes

    2012-01-01

    Quantifying wind potential is a pivotal initial step in developing and articulating a state’s policies and strategies for offshore wind industry development. This is particularly important in the Great Lakes States where lessons from other offshore environments are not directly applicable. This paper presents the framework developed for conducting a preliminary assessment of offshore wind potential. Information on lake bathymetry and wind resources were combined in simulating alternative scenarios of technically feasible turbine construction depths and distance concerns by stakeholders. These yielded estimates of developable offshore wind areas and potential power generation. While concerns about the visibility of turbines from shore reduce the power that can be generated, engineering solutions that increase the depths at which turbines can be sited increase such potential power output. This paper discusses the costs associated with technical limitations on depth and the social costs related to public sentiments about distance from the shoreline, as well as the possible tradeoffs. The results point to a very large untapped energy resource in the Michigan’s Great Lakes, large enough to prompt policy action from the state government. - Highlights: ▶ We build a theoretical framework for modeling offshore wind power production. ▶ Illustration of the impact of technology and social limitations on offshore wind energy development. ▶ Geospatial modeling of the offshore wind potential of the Great Lakes.

  2. Experimental Study of an Offshore Wind Turbine TLP in ULS Conditions

    DEFF Research Database (Denmark)

    Wehmeyer, Christof; Ferri, Francesco; Skourup, Jesper

    2013-01-01

    An extensive model test program has been carried out in order to assess the behavior of a tension leg moored substructure as support of a floating offshore wind turbine (FOWT). The floater was inspired by an industrial design. The tests focused on the ultimate limit state (ULS) behavior, therefor...

  3. Offshore wind energy prospects

    International Nuclear Information System (INIS)

    Gaudiosi, Gaetano

    1999-01-01

    In last two years offshore wind energy is becoming a focal point of national and non national organisations particularly after the limitations of fossil fuel consumption, adopted by many developed countries after Kyoto conference at the end of 1997 on global climate change. North Europe is particularly interested in offshore for the limited land areas still available, due to the intensive use of its territory and its today high wind capacity. Really the total wind capacity in Europe could increase from the 1997 value of 4450 MW up to 40 000 MW within 2010, according the White Paper 1997 of the European Commission; a significant percentage (25%) could be sited offshore up to 10 000 MW, because of close saturation of the land sites at that time. World wind capacity could increase from the 1997 value of 7200 MW up to 60 000 MW within 2010 with a good percentage (20%) offshore 12 000 MW. In last seven years wind capacity in shallow water of coastal areas has reached 34 MW. Five wind farms are functioning in the internal seas of Netherlands, Denmark, Sweden; however such siting is mostly to be considered as semi-offshore condition. Wind farms in real offshore sites, open seas with waves and water depth over 10 m, are now proposed in North Sea at 10-20 km off the coasts of Netherlands, Denmark using large size wind turbine (1-2 MW). In 1997 an offshore proposal was supported in Netherlands by Greenpeace after the OWEMES '97 seminar, held in Italy on offshore wind in the spring 1997. A review is presented in the paper of European offshore wind programs with trends in technology, economics and siting effects. (Author)

  4. Floating Silicon Method

    Energy Technology Data Exchange (ETDEWEB)

    Kellerman, Peter

    2013-12-21

    The Floating Silicon Method (FSM) project at Applied Materials (formerly Varian Semiconductor Equipment Associates), has been funded, in part, by the DOE under a “Photovoltaic Supply Chain and Cross Cutting Technologies” grant (number DE-EE0000595) for the past four years. The original intent of the project was to develop the FSM process from concept to a commercially viable tool. This new manufacturing equipment would support the photovoltaic industry in following ways: eliminate kerf losses and the consumable costs associated with wafer sawing, allow optimal photovoltaic efficiency by producing high-quality silicon sheets, reduce the cost of assembling photovoltaic modules by creating large-area silicon cells which are free of micro-cracks, and would be a drop-in replacement in existing high efficiency cell production process thereby allowing rapid fan-out into the industry.

  5. Import, Offshoring and Wages

    DEFF Research Database (Denmark)

    Fosse, Henrik Barslund; Maitra, Madhura

    Offshoring firms are found to pay higher average wages than purely domestic firms. We provide a unifying empirical approach by capturing the different channels through which offshoring may explain this wage difference: (i) due to change in the composition of workers (skill composition effect) (ii......) because all existing workers get higher pay (rent sharing effect). Using Danish worker-firm data we explain how much each channel contributes to higher wages. To estimate the causal effect of offshoring on wages we use China’s accession to the WTO in December 2001 - and the soon after boom in Chinese...

  6. Comparison of API & IEC Standards for Offshore Wind Turbine Applications in the U.S. Atlantic Ocean: Phase II; March 9, 2009 - September 9, 2009

    Energy Technology Data Exchange (ETDEWEB)

    Jha, A.; Dolan, D.; Gur, T.; Soyoz, S.; Alpdogan, C.

    2013-01-01

    This report compares two design guidelines for offshore wind turbines: Recommended Practice for Planning, Designing, and Constructing Fixed Offshore Platform Structures and the International Electrotechnical Commission 61400-3 Design Requirements for Offshore Wind Turbines.

  7. Present situation of floating nuclear power plants

    Energy Technology Data Exchange (ETDEWEB)

    Sakurai, A [Central Research Inst. of Electric Power industry, Tokyo (Japan)

    1975-08-01

    The present situation of investigation and the future problems of floating nuclear power plants in Japan are examined, referring to those in USA. The committee report on a new power generation system in 1970 is quoted. In this report, the site conditions are supposed to be 5 km offshore, 100m water depth, 60 m/sec wind velocity, 10 m wave height, 200 m wave length, 12 seconds wave period 0.2 g earthquake acceleration, and 2.5 knots tide current. The semisubmersible hull of double construction 15 m under water is employed. A pair of 1,000,000 kW BWR reactors are utilized. A sea water desalting unit using bleed steam from turbines is installed. The solid radioactive wastes packed in drums are disposed in the sea. The design and cost estimation were made. The names of the organizations who have made investigation in this field, namely the Civil Engineering Society, the Sience and Technology Agency and other several centers, are reported. The Chubu Electric Power Company is forwarding its project. Referring to the investigations in USA, the project of Atlantic nuclear power station unit is described. A report of plant design has been submitted by O.P.S. to United States Atomic Energy Commission in 1973. The Coastal Area Facilities Act was instituted in New Jersey in 1973. Although the Atlantic nuclear power station has been postponed, it is the most feasible project. For the realization of a floating nuclear power plant in Japan, investigation must be started on the ground construction that can endure the construction of breakwater in water depth of 14 to 30 meter.

  8. Whether and What to Offshore?

    DEFF Research Database (Denmark)

    Jensen, Peter Ørberg; Pedersen, Torben

    In this article, we explore the idea that offshoring of services and technical work should be regarded as a dynamic process that evolves over time. Firms gradually move from offshoring of simple, standardized activities towards offshoring of advanced activities when they accumulate experience...... with offshoring, and this type of offshoring comes with an entirely different set of characteristics compared to traditional, cost-seeking offshoring. Based on a unique survey among the total population of firms in the eastern region of Denmark, we analyze some of the dynamics of this process through a model...... that incorporates two different aspects of the process of offshoring. First, we approach the question of whether to offshore and establish a baseline that investigates the determinants of firms’ participation—or lack thereof—in offshoring. Secondly, we approach the question of what to offshore and the subsequent...

  9. Building and Calibration of a FAST Model of the SWAY Prototype Floating Wind Turbine: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Koh, J. H.; Robertson, A.; Jonkman, J.; Driscoll, F.; Ng, E. Y. K.

    2013-09-01

    Present efforts to verify and validate aero-hydro-servo-elastic numerical simulation tools that predict the dynamic response of a floating offshore wind turbine are primarily limited to code-to-code comparisons or code-to-data comparisons using data from wind-wave basin tests. In partnership with SWAY AS, the National Renewable Energy Laboratory (NREL) installed scientific wind, wave, and motion measurement equipment on the 1/6.5th-scale prototype SWAY floating wind system to collect data to validate a FAST model of the SWAY design in an open-water condition. Nanyang Technological University (NTU), through a collaboration with NREL, assisted in this validation.

  10. Hydrodynamic analysis of floating platform for special purposes under complex water environment

    Science.gov (United States)

    Ma, Guang-ying; Yao, Yun-long

    2018-03-01

    This article studied a new floating offshore platform for special purposes, which was assembled by standard floating modules. By using ANSYS AQWA software, the hydrodynamic model of the platform was established. The time history responses of the platform motions and the cable tension forces were calculate under complex water environments, such as wind, wave, current and mooring. The results showed that the tension of the four cables are far less than the breaking tension of the cable, so that the cable will not break. This study can be referenced by the relevant researchers and engineers.

  11. A review on design and study of floating plant mooring systems

    International Nuclear Information System (INIS)

    Nakamura, Hideharu; Kashima, Ryoichi; Hagiwara, Yutaka; Matsuura, Shinichi; Shiojiri, Hiroo

    1985-01-01

    There exists a widespread anticipation among nuclear power engineers that a floating nuclear power plant (NPP) may have a couple of advantages over other types; such as seismic isolation, standardizations of design and manufacturing etc. However, it also seems that a number of problems still remain to be clarified to adopt the floating NPP in Japan. One of them is magnitude of external forces acting on floating structure, which depend on mooring system. The purpose of the present report is to survey various kinds of mooring systems, structural analyses and design criteria, and examples of the same scale floating structures taking into consideration of the floating NPP which displaces 300,000 Ton, and furthermore, to discuss the future problems in regard to the mooring system still to be investigated before the floating plants can be constructed. (author)

  12. Dynamic Properties of Offshore Wind Turbine Foundations

    DEFF Research Database (Denmark)

    Damgaard, Mads

    ages structurally over its service life. Well-covered in the field of earthquake engineering, the dynamic response of civil engineering structures is highly dependent on the impedance of the soil–foundation system. For offshore wind turbine applications, however, the hysteretical and geometrical......, there is a general consensus that offshore wind-generated electricity is still too expensive to be competitive with conventional energy sources. As a consequence, the overall weight of the turbine and foundation is kept to a minimum resulting in a flexible and dynamically active structural system—even at low...

  13. Offshore Q & A

    Institute of Scientific and Technical Information of China (English)

    AmberStohr

    2003-01-01

    Equity International, Asia, is a leading financial service provider in China, offering planning expertise for expatriates on investing their income and savings. I recently sat down with four senior wealth managers in Shanghai to discuss Equity's approach to offshore investing.

  14. Determination of the populations and structures of multiple conformers in an ensemble from NMR data: Multiple-copy refinement of nucleic acid structures using floating weights

    International Nuclear Information System (INIS)

    Goerler, Adrian; Ulyanov, Nikolai B.; James, Thomas L.

    2000-01-01

    A new algorithm is presented for determination of structural conformers and their populations based on NMR data. Restrained Metropolis Monte Carlo simulations or restrained energy minimizations are performed for several copies of a molecule simultaneously. The calculations are restrained with dipolar relaxation rates derived from measured NOE intensities via complete relaxation matrix analysis. The novel feature of the algorithm is that the weights of individual conformers are determined in every refinement step, by the quadratic programming algorithm, in such a way that the restraint energy is minimized. Its design ensures that the calculated populations of the individual conformers are based only on experimental restraints. Presence of internally inconsistent restraints is the driving force for determination of distinct multiple conformers. The method is applied to various simulated test systems. Conformational calculations on nucleic acids are carried out using generalized helical parameters with the program DNAminiCarlo. From different mixtures of A- and B-DNA, minor fractions as low as 10% could be determined with restrained energy minimization. For B-DNA with three local conformers (C2'-endo, O4'-exo, C3'-endo), the minor O4'-exo conformer could not be reliably determined using NOE data typically measured for DNA. The other two conformers, C2'-endo and C3'-endo, could be reproduced by Metropolis Monte Carlo simulated annealing. The behavior of the algorithm in various situations is analyzed, and a number of refinement protocols are discussed. Prior to application of this algorithm to each experimental system, it is suggested that the presence of internal inconsistencies in experimental data be ascertained. In addition, because the performance of the algorithm depends on the type of conformers involved and experimental data available, it is advisable to carry out test calculations with simulated data modeling each experimental system studied

  15. Offshoring in textile industry

    OpenAIRE

    MONTÓN GARCÍA, JORGE

    2015-01-01

    [ EN] This project is about offshoring in the textile industry, focusing in the rights violated in this process, this concept can be defined as the moving of various operations of a company to another country for reasons such as lower labor costs or more favorable economic conditions in that other country. The project describes the evolution of offshoring, which started in 1960’s and has continued since then; it was characterized primarily by the transferring of factories from the develope...

  16. Offshore petroleum engineering task force report

    International Nuclear Information System (INIS)

    Ruelokke, M.

    1999-05-01

    The Offshore Petroleum Engineering Task Force was established in July 1998 in response to concerns about Newfoundland and Labrador's share of offshore petroleum engineering activity, with the aim of determining the current capability of the local sector, the demand for such companies and individuals until the year 2010, their capability to grow over that time-frame, and requirements in order to achieve that growth. The report summarizes the analysis undertaken by the Task Force as well as the conclusions it reached and associated recommendations. Section two provides an overview of the offshore engineering activity, including its origins, structure, and key success factors, and its also provides a profile of the industry, internationally, in Canada and in Newfoundland. Section three presents an analysis of the future demand for offshore engineering in Newfoundland until 2010, based on three development scenarios. Section four based on a Consulting Engineers of Newfoundland and Labrador (CENL) survey, establishes the present offshore engineering capacity and capabilities within the province. Section five examines current education and training programs and their ability to respond to future demands. Section six summarizes the conclusions of the analysis and presents recommendations designed to facilitate and promote the development of the local offshore engineering industry. 6 figs

  17. Effect of the number of blades on the dynamics of floating straight-bladed vertical axis wind turbines

    DEFF Research Database (Denmark)

    Cheng, Zhengshun; Aagaard Madsen, Helge; Gao, Zhen

    2017-01-01

    Floating vertical axis wind turbines (VAWTs) are promising solutions for exploiting the wind energy resource in deep waters due to their potential cost-of-energy reduction. The number of blades is one of the main concerns when designing a VAWT for offshore application. In this paper, the effect...

  18. A green energy for a blue growth: offshore wind energy. Proposals by France Energie Eolienne for the development of a competitive and job-creating offshore wind energy sector

    International Nuclear Information System (INIS)

    2013-06-01

    This report outlines the significant and efficient contribution of wind energy to the energy mix, highlights the high potential of offshore wind energy for France, and stresses the need of an ambitious programme as a sine qua non condition for the development of this sector. It also makes ten proposals for this development. It describes how to specify ambitious objectives for offshore wind turbines (grounded or floating) in compliance with the French potential and the European market. It analyses means to reach an ambitious objective of 15 GW of grounded offshore wind energy and 6 GW of floating offshore wind energy by 2030. It discusses how benefits can be drawn from such a development for the community and future generations

  19. Industrial opportunities - offshore

    International Nuclear Information System (INIS)

    Gerrits, D.J.

    1998-01-01

    Industrial opportunities available in the Canadian offshore petroleum industry are discussed. Oil has been produced offshore from Nova Scotia since 1992, and offshore from Newfoundland since 1997. Special needs that must be addressed in offshore operations in eastern Canada such as the cold North Atlantic environment, isolation, logistics, safety, and quality assurance, are examined. The most obvious opportunities lie with the designing, building and installing the facilities needed to extract oil and gas from beneath the sea floor and transport it to market. However, there are also opportunities in designing and fabricating clothing, customized food containers and other equipment for offshore needs. Short term opportunities also exist in the decommissioning of depleted production fields and their facilities. One of the greatest obstacles facing new entrants into the offshore oil and gas industry is the lack of a track record. To meet this challenge, the ability to seek out partners to pursue local and international opportunities through joint ventures, strategic alliances and technology sharing partnering arrangements is of great importance. It may be the difference between success and failure. 6 figs

  20. Offshore in depth

    Energy Technology Data Exchange (ETDEWEB)

    Ebdon, J F

    1968-08-01

    The world-wide scope of offshore areas is discussed. Offshore areas of the U.S. and the world are where one of the ''hottest'' hydrocarbon booms--drilling, production, and pipelining--are in action today. Most of the current activity in offshore exploration and drilling is crude oil directed. However, big non-associated natural gas finds have been made. Additionally, for every barrel of crude oil produced, either or both associated natural gas and dissolved natural gas are produced in some varying ratio as casinghead gas. Thus, with worldwide production of some 2.5-million bbl of crude oil per day from offshore areas of Free-World countries, there are vast volumes of casinghead natural gas produced, over and above that produced from non-associated natural gas wells to the seaward of land masses. If offshore gas of any classification is produced in commercial volumes close to onshore population centers, then the possibility of marketing is fairly good. If remote from population centers, it is usually flared or shut-in. The development of gas liquefaction and cryogenic tankers has started, but international ocean traffic in LNG is still in its infancy. Current offshore gas pipelines are described.

  1. Power plants structures offshore - a method for locally increasing the biologic diversity in the Baltic Sea?; Kraftverkskonstruktioner i havet - en metod foer att lokalt oeka den biologiska maangfalden i Oestersjoen?

    Energy Technology Data Exchange (ETDEWEB)

    Malm, Torleif

    2005-02-01

    Preliminary research results from Kalmar Sound (Baltic Sea) reviewed in this report indicate the the submarine constructions of an offshore wind power plant can have positive effects on stationary fish as well as benthic animals and algae. This happens even though the total surface of the wind power plants is but a minor part of the surface of the wind power park. It is reef effect, bringing in foreign substrates and structures in the marine environment that causes this effect.

  2. Effects of soil–structure interaction on real time dynamic response of offshore wind turbines on monopiles

    DEFF Research Database (Denmark)

    Damgaard, M.; Zania, Varvara; Andersen, L.V.

    2014-01-01

    , a computationally efficient modelling approach of including the dynamic soil–structure interaction into aeroelastic codes is presented with focus on monopile foundations. Semi-analytical frequency-domain solutions are applied to evaluate the dynamic impedance functions of the soil–pile system at a number...... of discrete frequencies. Based on a general and very stable fitting algorithm, a consistent lumped-parameter model of optimal order is calibrated to the impedance functions and implemented into the aeroelastic nonlinear multi-body code HAWC2 to facilitate the time domain analysis of a wind turbine under...... normal operating mode. The aeroelastic response is evaluated for three different foundation conditions, i.e. apparent fixity length, the consistent lumped-parameter model and fixed support at the seabed. The effect of soil–structure interaction is shown to be critical for the design, estimated in terms...

  3. RBI Optimization of Offshore Wind Turbines

    DEFF Research Database (Denmark)

    Ramírez, José G. Rangel; Sørensen, John Dalsgaard

    2009-01-01

    methods for oil & gas installations, a framework for optimal inspection and maintenance planning of offshore wind turbines is presented. Special aspects for offshore wind turbines considered are the fatigue loading characteristics where usually the wind loading are dominating the wave loading, wake......Wind turbines for electricity production have increased significantly the last years both in production capability and size. This development is expected to continue also in the coming years. Offshore wind turbines with an electricity production of 5-10 MW are planned. Typically, the wind turbine...... support structure is a steel structure consisting of a tower and a monopile, tripod or jacket type foundation. This paper considers aspects of inspection and maintenance planning of fatigue prone details in jacket and tripod type of wind turbine support structures. Based on risk-based inspection planning...

  4. Wide-spectral/dynamic-range skin-compatible phototransistors enabled by floated heterojunction structures with surface functionalized SWCNTs and amorphous oxide semiconductors.

    Science.gov (United States)

    Hwang, Insik; Kim, Jaehyun; Lee, Minkyung; Lee, Min-Wook; Kim, Hee-Joong; Kwon, Hyuck-In; Hwang, Do Kyung; Kim, Myunggil; Yoon, Haeyoung; Kim, Yong-Hoon; Park, Sung Kyu

    2017-11-09

    Purified semiconducting single-walled carbon nanotubes (sc-SWCNTs) have been researched for optoelectronic applications due to their high absorption coefficient from the visible to even the near-infrared (NIR) region. Nevertheless, the insufficient electrical characteristics and incompatibility with conventional CMOS processing have limited their wide utilization in this emerging field. Here, we demonstrate highly detective and wide spectral/dynamic range phototransistors incorporating floated heterojunction active layers which are composed of low-temperature sol-gel processed n-type amorphous indium gallium zinc oxide (a-IGZO) stacked with a purified p-type sc-SWCNT layer. To achieve a high and broad spectral/dynamic range photo-response of the heterogeneous transistors, photochemically functionalized sc-SWCNT layers were carefully implemented onto the a-IGZO channel area with a floating p-n heterojunction active layer, resulting in the suppression of parasitic charge leakage and good bias driven opto-electrical properties. The highest photosensitivity (R) of 9.6 × 10 2 A W -1 and a photodetectivity (D*) of 4 × 10 14 Jones along with a dynamic range of 100-180 dB were achieved for our phototransistor in the spectral range of 400-780 nm including continuous and minimal frequency independent behaviors. More importantly, to demonstrate the diverse application of the ultra-flexible hybrid photosensor platform as skin compatible electronics, the sc-SWCNT/a-IGZO phototransistors were fabricated on an ultra-thin (∼1 μm) polyimide film along with a severe static and dynamic electro-mechanical test. The skin-like phototransistors showed excellent mechanical stability such as sustainable good electrical performance and high photosensitivity in a wide dynamic range without any visible cracks or damage and little noise interference after being rolled-up on the 150 μm-thick optical fiber as well as more than 1000 times cycling.

  5. Structure of the la VELA Offshore Basin, Western Venezuela: AN Obliquely-Opening Rift Basin Within the South America-Caribbean Strike-Slip Plate Boundary

    Science.gov (United States)

    Blanco, J. M.; Mann, P.

    2015-12-01

    Bathymetric, gravity and magnetic maps show that the east-west trend of the Cretaceous Great Arc of the Caribbean in the Leeward Antilles islands is transected by an en echelon series of obliquely-sheared rift basins that show right-lateral offsets ranging from 20 to 40 km. The basins are 75-100 km in length and 20-30 km in width and are composed of sub-parallel, oblique slip normal faults that define deep, bathymetric channels that bound the larger islands of the Leeward Antilles including Aruba, Curacao and Bonaire. A single basin of similar orientation and structure, the Urumaco basin, is present to the southwest in the Gulf of Venezuela. We mapped structures and sedimentation in the La Vela rift basin using a 3D seismic data volume recorded down to 6 seconds TWT. The basin can be mapped from the Falcon coast where it is correlative with the right-lateral Adicora fault mapped onshore, and its submarine extension. To the southeast of the 3D survey area, previous workers have mapped a 70-km-wide zone of northeast-striking, oblique, right-lateral faults, some with apparent right-lateral offsets of the coastline. On seismic data, the faults vary in dip from 45 to 60 degrees and exhibit maximum vertical offsets of 600 m. The La Vela and other obliquely-opening rifts accommodate right-lateral shear with linkages to intervening, east-west-striking right-lateral faults like the Adicora. The zone of oblique rifts is restricted to the trend of the Great Arc of the Caribbean and may reflect the susceptiblity of this granitic basement to active shearing. The age of onset for the basins known from previous studies on the Leeward Antilles is early Miocene. As most of these faults occur offshore their potential to generate damaging earthquakes in the densely populated Leeward Antilles is not known.

  6. Small-scale Forearc Structure from Residual Bathymetry and Vertical Gravity Gradients at the Cocos-North America Subduction Zone offshore Mexico

    Science.gov (United States)

    Garcia, E. S. M.; Ito, Y.

    2017-12-01

    The subduction of topographic relief on the incoming plate at subduction zones causes deformation of the plate interface as well as the overriding plate. Whether the resulting geometric irregularities play any role in inhibiting or inducing seismic rupture is a topic of relevance for megathrust earthquake source studies. A method to discern the small-scale structure at subduction zone forearcs was recently developed by Bassett and Watts (2015). Their technique constructs an ensemble average of the trench-perpendicular topography, and the removal of this regional tectonic signal reveals the short-wavelength residual bathymetric anomalies. Using examples from selected areas at the Tonga, Mariana, and Japan subduction zones, they were able to link residual bathymetric anomalies to the subduction of seamount chains, given the similarities in wavelength and amplitude to the morphology of seamounts that have yet to subduct. We focus here on an analysis of forearc structures found in the Mexico segment of the Middle America subduction zone, and their potential mechanical interaction with areas on the plate interface that have been previously identified as source regions for earthquake ruptures and aseismic events. We identified several prominent residual bathymetric anomalies off the Guerrero and Oaxaca coastlines, mainly in the shallow portion of the plate interface and between 15 and 50 kilometers away from the trench axis. The residual amplitude of these bathymetric anomalies is typically in the hundreds of meters. Some of the residual bathymetric anomalies offshore Oaxaca are found landward of seamount chains on the incoming Cocos Plate, suggesting that these anomalies are associated with the prior subduction of seamounts at the margin. We also separated the residual and regional components of satellite-based vertical gravity gradient data using a directional median filter to isolate the possible gravity signals from the seamount edifices.

  7. Control development for floating wind

    International Nuclear Information System (INIS)

    Savenije, Feike; Peeringa, Johan

    2014-01-01

    Control of a floating wind turbine has proven to be challenging, but essential for lowering the cost of floating wind energy. Topic of a recent joint R and D project by GustoMSC, MARIN and ECN, is the concept design and verification with coupled simulations and model tests of the GustoMSC Tri-Floater. Only using an integral design approach, including mooring and control design, a cost effective system can be obtained. In this project, ECN developed a general floating wind turbine control strategy and applied this in a case study to the GustoMSC Tri-Floater and the OC3Hywind spar, both equipped with the NREL 5MW RWT. The designed controller ensures stable operation, while maintaining proper speed and power regulation. The motions of the floating support are reduced and substantial load reduction has been achieved

  8. ISM Approach to Model Offshore Outsourcing Risks

    Directory of Open Access Journals (Sweden)

    Sunand Kumar

    2014-07-01

    Full Text Available In an effort to achieve a competitive advantage via cost reductions and improved market responsiveness, organizations are increasingly employing offshore outsourcing as a major component of their supply chain strategies. But as evident from literature number of risks such as Political risk, Risk due to cultural differences, Compliance and regulatory risk, Opportunistic risk and Organization structural risk, which adversely affect the performance of offshore outsourcing in a supply chain network. This also leads to dissatisfaction among different stake holders. The main objective of this paper is to identify and understand the mutual interaction among various risks which affect the performance of offshore outsourcing.  To this effect, authors have identified various risks through extant review of literature.  From this information, an integrated model using interpretive structural modelling (ISM for risks affecting offshore outsourcing is developed and the structural relationships between these risks are modeled.  Further, MICMAC analysis is done to analyze the driving power and dependency of risks which shall be helpful to managers to identify and classify important criterions and to reveal the direct and indirect effects of each criterion on offshore outsourcing. Results show that political risk and risk due to cultural differences are act as strong drivers.

  9. Operational management of offshore energy assets

    Science.gov (United States)

    Kolios, A. J.; Martinez Luengo, M.

    2016-02-01

    Energy assets and especially those deployed offshore are subject to a variety of harsh operational and environmental conditions which lead to deterioration of their performance and structural capacity over time. The aim of reduction of CAPEX in new installations shifts focus to operational management to monitor and assess performance of critical assets ensuring their fitness for service throughout their service life and also to provide appropriate and effective information towards requalification or other end of life scenarios, optimizing the OPEX. Over the last decades, the offshore oil & gas industry has developed and applied various approaches in operational management of assets through Structural Health and Condition Monitoring (SHM/CM) systems which can be, at a certain level, transferable to offshore renewable installations. This paper aims to highlight the key differences between offshore oil & gas and renewable energy assets from a structural integrity and reliability perspective, provide a comprehensive overview of different approaches that are available and applicable, and distinguish the benefits of such systems in the efficient operation of offshore energy assets.

  10. Electrically floating, near vertical incidence, skywave antenna

    Science.gov (United States)

    Anderson, Allen A.; Kaser, Timothy G.; Tremblay, Paul A.; Mays, Belva L.

    2014-07-08

    An Electrically Floating, Near Vertical Incidence, Skywave (NVIS) Antenna comprising an antenna element, a floating ground element, and a grounding element. At least part of said floating ground element is positioned between said antenna element and said grounding element. The antenna is separated from the floating ground element and the grounding element by one or more electrical insulators. The floating ground element is separated from said antenna and said grounding element by one or more electrical insulators.

  11. Wave attenuation charcteristics of tethered float system

    Digital Repository Service at National Institute of Oceanography (India)

    Vethamony, P.

    incident wave height transmitted wave height G wave number float mass number of rows of floats drag power transmitted wave power incident wave power 111 112 P. Vethamony float radius wave period time velocity and acceleration of fluid... particles, respectively wave attenuation in percentage displacement, velocity and acceleration of float, respectively amplitude of float displacement added mass damping coefficient fluid particle displacement amplitude of fluid particle displacement...

  12. An Assessment of the Economic Potential of Offshore Wind in the United States from 2015 to 2030

    Energy Technology Data Exchange (ETDEWEB)

    Beiter, Philipp [National Renewable Energy Lab. (NREL), Golden, CO (United States); Musial, Walter [National Renewable Energy Lab. (NREL), Golden, CO (United States); Kilcher, Levi [National Renewable Energy Lab. (NREL), Golden, CO (United States); Maness, Michael [National Renewable Energy Lab. (NREL), Golden, CO (United States); Smith, Aaron [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2017-03-29

    This study describes an assessment of the spatial variation of levelized cost of energy (LCOE) and levelized avoided cost of energy to understand the economic viability of fixed-bottom and floating offshore wind technologies across major U.S. coastal areas between 2015 and 2030. In particular, this study offers insights into the available offshore wind resource by region at different levels of LCOE and an assessment of the economically viable resource capacity in the United States.

  13. Legal aspects of financing Canadian offshore oil and gas developments

    International Nuclear Information System (INIS)

    Green, J.M.; Hudec, A.J.

    1992-01-01

    A review is presented of the significant legal considerations involved in structuring, negotiating, and documenting commercial financing of a Canadian offshore oil and gas production facility. Emphasis is placed on the Hibernia Project in the Newfoundland offshore as an example, and more specifically the $450 million bank financing completed in November 1991. The legal framework governing offshore production financing in this case was complex, due to the project's location in international waters on the continental shelf. Complex intergovernmental arrangements have been implemented between Canada and Newfoundland to govern the offshore area and regulate the project. An agreement called the Atlantic Accord allowed the Canada Newfoundland Offshore Petroleum Board (CNOPB) to grant production licenses and to regulate offshore exploration and development, with matters relating to legislation, taxation, and royalties shared between the governments. Certain other acts were enacted or extended for application to the offshore area. The CNOPB administers a registry system for transfers and security interests in offshore licenses. Security interests including property are ensured by the Hibernia Act, which makes Newfoundland's existing security interest regime applicable to the offshore. The project owners are operating Hibernia as a joint venture, and the structure of project financing and inter-creditor arrangements is examined. The competing security interest of project lenders and non-defaulting participants is discussed, along with assignment of priorities on the security in case of default

  14. Numerical Simulation of Floating Bodies in Extreme Free Surface Waves

    Science.gov (United States)

    Hu, Zheng Zheng; Causon, Derek; Mingham, Clive; Qiang, Ling

    2010-05-01

    A task of the EPSRC funded research project 'Extreme Wave loading on Offshore Wave Energy Devices: a Hierarchical Team Approach' is to investigate the survivability of two wave energy converter (WEC) devices Pelamis and the Manchester Bobber using different CFD approaches. Both devices float on the water surface, generating the electricity from the motion of the waves. In this paper, we describe developments of the AMAZON-SC 3D numerical wave tank (NWT) to study extreme wave loading of a fixed or floating (in Heave motion) structure. The extreme wave formulation as an inlet condition is due to Dalzell (1999) and Ning et. al. (2009) in which a first or second-order Stokes focused wave can be prescribed. The AMAZON-SC 3D code (see e.g. Hu et al. (2009)) uses a cell centred finite volume method of the Godunov-type for the space discretization of the Euler and Navier Stokes equations. The computational domain includes both air and water regions with the air/water boundary captured as a discontinuity in the density field thereby admitting the break up and recombination of the free surface. Temporal discretisation uses the artificial compressibility method and a dual time stepping strategy to maintain a divergence free velocity field. Cartesian cut cells are used to provide a fully boundary-fitted gridding capability on an regular background Cartesian grid. Solid objects are cut out of the background mesh leaving a set of irregularly shaped cells fitted to the boundary. The advantages of the cut cell approach have been outlined previously by Causon et al. (2000, 2001) including its flexibility for dealing with complex geometries whether stationary or in relative motion. The field grid does not need to be recomputed globally or even locally for moving body cases; all that is necessary is to update the local cut cell data at the body contour for as long as the motion continues. The handing of numerical wave paddles and device motion in a NWT is therefore straightforward

  15. Hydroelastic analysis of a very large floating plate with large deflections in stochastic seaway

    DEFF Research Database (Denmark)

    Chen, Xu-jun; Jensen, Jørgen Juncher; Cui, Wei-cheng

    2004-01-01

    The hydroelasticity of a very large floating plate with large deflections in multidirectional irregular waves is discussed. After a brief introduction on wave loads on a flexible structure, the paper derives the generalised fluid force acting on a floating structure in multidirectional irregular ...

  16. Healthy offshore workforce? A qualitative study on offshore wind employees' occupational strain, health, and coping.

    Science.gov (United States)

    Mette, Janika; Velasco Garrido, Marcial; Harth, Volker; Preisser, Alexandra M; Mache, Stefanie

    2018-01-23

    Offshore work has been described as demanding and stressful. Despite this, evidence regarding the occupational strain, health, and coping behaviors of workers in the growing offshore wind industry in Germany is still limited. The purpose of our study was to explore offshore wind employees' perceptions of occupational strain and health, and to investigate their strategies for dealing with the demands of offshore work. We conducted 21 semi-structured telephone interviews with employees in the German offshore wind industry. The interviews were transcribed and analyzed in a deductive-inductive approach following Mayring's qualitative content analysis. Workers generally reported good mental and physical health. However, they also stated perceptions of stress at work, fatigue, difficulties detaching from work, and sleeping problems, all to varying extents. In addition, physical health impairment in relation to offshore work, e.g. musculoskeletal and gastrointestinal complaints, was documented. Employees described different strategies for coping with their job demands. The strategies comprised of both problem and emotion-focused approaches, and were classified as either work-related, health-related, or related to seeking social support. Our study is the first to investigate the occupational strain, health, and coping of workers in the expanding German offshore wind industry. The results offer new insights that can be utilized for future research in this field. In terms of practical implications, the findings suggest that measures should be carried out aimed at reducing occupational strain and health impairment among offshore wind workers. In addition, interventions should be initiated that foster offshore wind workers' health and empower them to further expand on effective coping strategies at their workplace.

  17. Structural Health and Prognostics Management for Offshore Wind Plants; Final Report of Sandia R&D Activities.

    Energy Technology Data Exchange (ETDEWEB)

    Griffith, Daniel Todd [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Wind Energy Technologies Dept.

    2015-04-01

    This final report is a compilation of resear ch efforts - funded by the US Department of Energy Wind and Water Power Technolog ies Office over a four-year period from FY11 through FY14. The goals of this re search program were to develop and evaluate technical innovati ons with promise for maxi mizing revenues and reducing levelized cost of energy (LCOE) for offs hore wind plants - more specifically the goals of the Structural H ealth and Prognostics Management (SHPM) program were to reduce O&M costs and increase energy capture through use of SHPM-based technologies. A technology roadmap was deve loped at the start of the project to guide the research efforts. This roadmap identified and outlined six major research thrust areas each having five stages of ma turity. Research was conducted in each of these thrust areas, as documented throughout this report, although a major focus was on development of damage detection strategi es for the most frequent blade damage conditions and damage mitigation and life-exte nsion strategies via changes in turbine operations (smart loads management). Th e work summarized in this compilation report is the product of the work of many researchers. A summary of the major findings, status of the SHPM Technology Ro admap and recommendations for future work are also provided.

  18. How Offshoring Elicits Reconfiguration of the Service Production System

    DEFF Research Database (Denmark)

    Brandl, Kristin; Mol, Michael J.; Petersen, Bent

    Service production systems can be seen as a structure consisting of task execution, resources executing tasks and the service output received by the client. Offshoring acts as an exogenous shock to such a service production system. Drawing on practice theory and applying a multiple case methodology...... of the impact of offshoring and to practice theory....

  19. Offshore Membrane Enclosures for Growing Algae (OMEGA: A System for Biofuel Production, Wastewater Treatment, and CO2 Sequestration

    Science.gov (United States)

    Trent, Jonathan; Embaye, Tsegereda; Buckwalter, Patrick; Richardson, Tra-My; Kagawa, Hiromi; Reinsch, Sigrid; Martis, Mary

    2010-01-01

    We are developing Offshore Membrane Enclosures for Growing Algae (OMEGA). OMEGAs are closed photo-bioreactors constructed of flexible, inexpensive, and durable plastic with small sections of semi-permeable membranes for gas exchange and forward osmosis (FO). Each OMEGA modules is filled with municipal wastewater and provided with CO2 from coastal CO2 sources. The OMEGA modules float just below the surface, and the surrounding seawater provides structural support, temperature control, and mixing for the freshwater algae cultures inside. The salinit7 gradient from inside to outside drives forward osmosis through the patches of FO membranes. This concentrates nutrients in the wastewater, which enhances algal growth, and slowly dewaters the algae, which facilitates harvesting. Thy concentrated algal biomass is harvested for producing biofuels and fertilizer. OMEGA system cleans the wastewater released into the surrounding coastal waters and functions as a carbon sequestration system.

  20. Offshore Supply Industry Dynamics

    DEFF Research Database (Denmark)

    Roslyng Olesen, Thomas

    This report is part of the research project “The competitive challenges and strategic development possibilities for The Blue Denmark”, which was launched in 2014. The project is funded by the Danish Maritime Fund and carried out by researchers at CBS Maritime which is a Business in Society Platform...... with companies in the maritime sector. This report “Offshore Supply Industry Dynamics – Business strategies in the offshore supply industry” is the second report in mapping project D. It examines the markets and business strategies of various suppliers and furthermore presents an analysis of the challenges...... at Copenhagen Business School with a focus on value creation in the maritime industries. The project embraces various maritime segments from shipping and offshore to ports and suppliers. The research questions for the individual projects have been formulated by researchers at CBS Maritime in cooperation...

  1. Emergency response in the Newfoundland offshore industry

    International Nuclear Information System (INIS)

    Dempsey, J.

    2006-01-01

    This presentation reviewed current offshore oil activities with respect to safety issues regarding year-round marine operations in a harsh environment. Considerable logistics support is required for all offshore activities, including seismic and geotechnical surveys; exploration and production drilling; well testing; subsea construction; on-site production; and, delivery to market. Response to an offshore emergency must address the urgency of the incident along with stakeholder concerns. This presentation described the different types of emergencies and addressed issues regarding contingency planning; preventative measures; response philosophy; response scope; response at site; emergency management; communications links; and, oil spill response. The following current operations were highlighted: ExxonMobil's production drilling from the gravity-based concrete platform at Hibernia; Petro-Canada's production drilling at the Terra Nova FPSO; Husky Energy's production drilling at White Rose; and Chevron Canada's exploration drilling at the Orphan Basin. It was noted that in an emergency situation, the focus is on the welfare of offshore personnel. On an average day, the total offshore population is in the order of 1000 workers, all registered in the Personnel Logistics System which is updated with the departure of every helicopter from St. John's, Newfoundland or from the offshore platform. It is possible to prepare for foreseeable emergency incidents such as fire, explosion or gas leaks; spills to the marine environment; structural damage or collisions; persons lost at sea; helicopter or support vessel accidents; vessel sinking; sabotage; serious injuries or loss of life; severe ice events; and, loss of well control. The establishment of permanent safety zones at the Hibernia, White Rose and Terra Nova production fields are among the preventative measures, along with standby vessels that provide a rescue service for offshore installations. Supply vessels are also

  2. Offshoring and financial markets

    Directory of Open Access Journals (Sweden)

    Gianfranco Battisti

    2014-06-01

    Full Text Available The paper analyses the nature and extent of the offshore world, a grey area that is playing a major role in present-day economy. The main institutions moulding this peculiar environment are discussed: preferential tax regimes, tax havens and offshore financial centers. Their role in the globalised world is outlined after a scrutiny of the specialized literature, reports by non-governmental bodies and companies’ advertisings. Finally, we present a tentative reconstruction of its geographical organization, inclusive of cartographic representations of the main international networks.

  3. Offshore Supply Industry Dynamics

    DEFF Research Database (Denmark)

    Roslyng Olesen, Thomas

    The value chains for offshore oil and gas and offshore wind are both basically driven by the demand for energy. This is heavily dependent on a number of factors including the price of various energy sources and the policy making of the states which influence legislation, indirect subsidies...... of services including includes legal advice, financing, insurance etc. The two value chains have a number of activities in common. Both include (1) a tender and concession phase where the energy company obtains the right to explore and produce energy from the authorities. (2) An exploration phase where...

  4. Gela offshore field

    Energy Technology Data Exchange (ETDEWEB)

    Pagliughi, G

    1965-06-01

    The field of Gela, off the southern shore of Sicily, is the only producing offshore field in the Mediterranean. It produces from Triassic dolimite limestones of 434-m thickness, water level at -3517 m. It is a water-drive reservoir producing 10/sup 0/F API oil and has 79 wells, some of them on shore. Most offshore wells are directional wells from shore; there are also 2 fixed platforms and a special mobile platform. The wells are on pump (stroke, 72 in.; capacity 200 tons per day). The crude goes directly to a combination refinery-petrochemical complex at Gela.

  5. Experimental and Theoretical Analysis of a Combined Floating Wave and Wind Energy Conversion Platform

    DEFF Research Database (Denmark)

    Yde, Anders; Pedersen, Mads Mølgaard; Bellew, Sarah Bellew

    This report presents results from the PSO project 2011-1-10668 entitled Poseidon 2. The project is a continuation of the previous PSO project entitled Aero-Hydro-Elastic Simulation Platform for Wave Energy Systems and floating Wind Turbines. Floating Power Plant has developed the technology...... for a novel, floating, wave- and wind-energy hybrid device. To test the technology they have scaled the design to P37, a 37 m wide test platform that has been undergoing offshore testing for four complete test phases (totaling more than 2 years). The test platform provides electricity to the grid from both...... wind and wave energy, however its purpose is purely for research and development. The PSO project has equipped the platform with comprehensive measurements equipment for measuring platform motion, wave and wind conditions and turbine loads. Data from the test periods has been used for evaluating...

  6. Energy from Offshore Wind: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Musial, W.; Butterfield, S.; Ram, B.

    2006-02-01

    This paper provides an overview of the nascent offshore wind energy industry including a status of the commercial offshore industry and the technologies that will be needed for full market development.

  7. 2016 Offshore Wind Market Report

    Energy Technology Data Exchange (ETDEWEB)

    Musial, Walter [National Renewable Energy Lab. (NREL), Golden, CO (United States); Beiter, Philipp [National Renewable Energy Lab. (NREL), Golden, CO (United States); Schwabe, Paul [National Renewable Energy Lab. (NREL), Golden, CO (United States); Tian, Tian [National Renewable Energy Lab. (NREL), Golden, CO (United States); Stehly, Tyler [National Renewable Energy Lab. (NREL), Golden, CO (United States); Spitsen, Paul [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2017-08-07

    The 2016 Offshore Wind Technologies Market Report is intended to provide stakeholders with quantitative information about the offshore wind market, technology, and cost trends in the United States and worldwide.

  8. Extended onshore control of a floating wind turbine with wave disturbance reduction

    DEFF Research Database (Denmark)

    Christiansen, S.; Knudsen, T.; Bak, Thomas

    2014-01-01

    Reaching for higher wind resources floating wind turbines are being investigated. Wave induced loads significantly increase for floating wind turbines, and applying conventional onshore control strategies to floating wind turbines has been shown to impose negative damped oscillations in fore......-aft due to the low natural frequency of the floating structure. We suggest a control loop extension of the onshore controller which stabilizes the system and reduces the wave disturbance. The result is improved performance in power fluctuations, blade pitch activity, and platform oscillations...

  9. CMOS Active-Pixel Image Sensor With Simple Floating Gates

    Science.gov (United States)

    Fossum, Eric R.; Nakamura, Junichi; Kemeny, Sabrina E.

    1996-01-01

    Experimental complementary metal-oxide/semiconductor (CMOS) active-pixel image sensor integrated circuit features simple floating-gate structure, with metal-oxide/semiconductor field-effect transistor (MOSFET) as active circuit element in each pixel. Provides flexibility of readout modes, no kTC noise, and relatively simple structure suitable for high-density arrays. Features desirable for "smart sensor" applications.

  10. Artisanal fishing net float loss and a proposal for a float design solution

    Directory of Open Access Journals (Sweden)

    Paulo de Tarso Chaves

    2016-03-01

    Full Text Available Abstract Plastic floats from fishing nets are commonly found washed up on beaches in southern Brazil. They are usually broken and show signs of having been repaired. Characteristics of floats and interviews with fishermen suggest two main causes of float loss. First, collisions between active gear, bottom trawl nets for shrimp, and passive gear, drift nets for fish, destroy nets and release fragments of them, including floats. Second, the difficulty with which floats are inserted on the float rope of the nets when they are used near the surface. Floats are inserted to replace damaged or lost floats, or they may be removed if it is desired that the nets be used in deeper waters. Floats may thus be poorly fixed to the cables and lost. Here a new float design that offers greater safety in use and for the replacement of floats is described and tested.

  11. Project alliancing in the offshore industry

    International Nuclear Information System (INIS)

    Halman, J.I.M.; Braks, B.F.M.

    1999-01-01

    In this paper the shift towards new types of project organisation within the offshore industry is explained and discussed. Special focus is given to the organisational concept of project alliancing. The principles, structure and culture of a project alliance as applied within the offshore industry are described. In the paper the organisational concept of project alliancing is discussed on its potential to reduce project costs and enhance profits, both for the operator (oil and gas company) as well as for participating contractors. A risk and reward mechanism developed to share project risks and rewards between allied parties is explained for an alliance case. Based upon an in-depth study carried out within a contractor company in the offshore industry the organisational and financial implications of project alliancing are presented. (author)

  12. Governance of Arctic Offshore Oil and Gas

    DEFF Research Database (Denmark)

    Bringing together leading experts from various disciplines, this book offers a comprehensive study of the governance of offshore oil and gas activities in the circumpolar Arctic. As a consequence of energy globalisation, and of a sharp increase in world energy demand, the Arctic Ocean is also now...... being targeted for its offshore oil and gas resources, at the same time as an increasing demand for democratic legitimisation and recognition of the rights of indigenous peoples is emerging in the civil spheres of society. The volume analyses how, in the daunting context of climate change......, the interactions between the various levels of governance structure the policy process and impact on the efficiency of environmental management and the effectiveness of public participation, including the participation of indigenous peoples. Any governance system for Arctic offshore oil and gas activities...

  13. New offshore platform in the Mexican Gulf

    Energy Technology Data Exchange (ETDEWEB)

    Beisel, T.

    1982-04-01

    After a construction period of only 10 months, the second steel Offshore platform was recently completed in the Mexican Gulf. The pattern for this structure was the Cognac platform. The erection of the new platform, called the 'Cerveza' platform, is described in the article.

  14. Offshore environmental aspects

    NARCIS (Netherlands)

    Lindeboom, H.J.; Degraer, S.

    2016-01-01

    The number of offshore wind farms (OWFs) is increasing rapidly, leading to questions about the cumulative environmental impact of such farms. The major impacts are caused by the noise produced in the building phase, the new hard substratum, the moving rotor blades, possible underwater noise in

  15. Nearshore versus Offshore

    DEFF Research Database (Denmark)

    Klinge Jacobsen, Henrik; Hevia Koch, Pablo Alejandro; Wolter, Christoph

    Currently there exist high expectations for the development of wind energy, particularly in Europe, out of whichoffshore wind turbine developments will be central as tools to achieve current energy targets. The question betweennearshore and (far)-offshore is particularly relevant, both because of...

  16. Advanced Service Offshore Outsourcing

    DEFF Research Database (Denmark)

    Brandl, Kristin; Jensen, Peter D. Ørberg; Lind, Manya Jaura

    2018-01-01

    the capabilities, where the deficient development of one capability can be mitigated by the development of another capability (firm-internal determinants). Grounded in organization and service production theory, the paper contributes to the thematic literature on service offshoring and literature on organizational...

  17. Application of partially diabatic divided wall column to floating liquefied natural gas plant

    International Nuclear Information System (INIS)

    Kim, Young Han

    2014-01-01

    The offshore operation of chemical plant requires the compactness of process equipments due to its harsh environment. A DWC (divided wall column), a compact ternary separator, is a good candidate for distillation process in the offshore operation. In this study the DWC is applied to the offshore FLNG (floating liquefied natural gas) plant, but high utility cost is required in the application because of the large difference of boiling points among feed components. A partially diabatic DWC is proposed for the reduction of the operating cost here, and its design procedure is presented along with performance and economic evaluations and the examination of thermodynamic efficiency as well. The heating duty of the proposed DWC including tray heat transfer is 35% less than that of the conventional system, and the cooling duty is 18% less. The evaluation indicates that some 16% less utility cost is used in the DWC compared with the conventional system, though 7% more investment is required. The exergy loss is reduced by 12%, and the thermodynamic efficiency is improved by 3.3 percentage point over the conventional system. - Highlights: • Diabatic divided wall column for FLNG (floating liquefied natural gas) plant. • Compact column for offshore operation. • 35% less heating duty required. • 16% lower utility necessary. • Exergy loss reduced by 12%

  18. Faults in the Collection Grid of Offshore Wind Farms

    DEFF Research Database (Denmark)

    Lunow, Morten Erlandsson; Holbøll, Joachim; Henriksen, Mogens

    2008-01-01

    This paper deals with transient conditions in the collection grid of offshore wind farms under different faults. A model of a standard wind farm was established in two versions, with a floating and a grounded collection grid respectively. Line to ground faults and three-phase to ground faults were...... applied at critical points at worst-case phase angle and the results compared. The simulations show that it is better with a grounded collection grid, since lack of a ground reference will prevent the system from recovering after a line to ground fault....

  19. Offshore 2010. Final report; Offshore 2010. Sluttrapport

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2001-07-01

    An overview of the accomplishments of the various projects that have received support from the Norwegian Research Council's program 'Offshore 2010'. The following projects are presented, some have English and some Norwegian project names: 'Critical parameters influencing inhibitor performance in multiphase flow', 'Development of the drilling optimization simulator (DDS) and a totally integrated drilling optimization system', 'Produksjonsoptimalisering og automatisk styring av broenner og roerledninger (PETRONICS)', 'Termisk isolerte undervannsroer for sikring av broenntransport over store avstander', 'Utvikling av magnetisk frekvensformer for styring av store subsea pumper paa havdyp ned mot 4000 meter', 'Flerfase stroemningsmaaler for permanent nedihulls installasjon', 'Hastighetsmaaling i flerfase stroemning ved passiv akustikk', 'Oil/water seperation offshore: optimized flow- and seperation behavior', 'Stroemningshastighet', 'A rock mechanics based reservoir simulation', 'MultiTool fase 2 - et flerbruksverktoey for nedihulls applikasjoner', 'Utvikling av undervanns olje-i-vann monitor for kontinuerlig maaling av lave oljekonsentrasjoner basert paa TR-LIFS', 'Subsea multipath ultrasonic liquid flow meter', 'Fluid characterization at elevated pressures and temperatures (Flucha II)'. The two main goals for the research program are 1. The development of new technology and competency in the field of downhole- and subsea processing and multiphase transportation, and 2. Innovation and commercialisation in small and medium sized companies (less than 100 employees). Some details on the financing and results are included (ml)

  20. 14 CFR 25.529 - Hull and main float landing conditions.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Hull and main float landing conditions. 25... AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Structure Water Loads § 25.529 Hull and main.... (b) Unsymmetrical landing for hull and single float seaplanes. Unsymmetrical step, bow, and stern...

  1. 14 CFR 25.531 - Hull and main float takeoff condition.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Hull and main float takeoff condition. 25... AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Structure Water Loads § 25.531 Hull and main float takeoff condition. For the wing and its attachment to the hull or main float— (a) The aerodynamic...

  2. Low Noise Bias Current/Voltage References Based on Floating-Gate MOS Transistors

    DEFF Research Database (Denmark)

    Igor, Mucha

    1997-01-01

    The exploitation of floating-gate MOS transistors as reference current and voltage sources is investigated. Test structures of common source and common drain floating-gate devices have been implemented in a commercially available 0.8 micron double-poly CMOS process. The measurements performed...

  3. Strength Tests on Hulls and Floats

    Science.gov (United States)

    Matthaes, K

    1942-01-01

    The present report deals with strength tests on hulls and floats intended in part for the collection of construction data for the design of these components and in part for the stress analysis of the finished hulls and floats.

  4. Coastal effects of offshore energy systems. An assessment of oil and gas systems, deepwater ports, and nuclear power plants off the coast of New Jersey and Delaware. Volume II. Parts 1 and 2. Working papers 4 thru 10

    International Nuclear Information System (INIS)

    1976-11-01

    This report consists of ten working papers prepared as background material for the assessment of the effects of three proposed offshore energy systems on the coastal areas of New Jersey and Delaware. The three proposed offshore energy systems are: exploration for and development of offshore oil and gas, deepwater ports for supertankers, and floating nuclear powerplants. The 10 working papers cover: federal and state regulation of the three systems, the biological impacts, the risk of oil spills in developing oil and gas resources and operating deepwater ports, the air and water quality impacts, regional energy supply and demand considerations, the fiscal effects of developing the three systems, environmental studies, a safety analysis of floating nuclear powerplants, an analysis of fuel and waste handling of floating nuclear powerplants, and an analysis of the economic considerations of floating nuclear powerplants

  5. A new assessment of floating exchange rates

    OpenAIRE

    Waimann, D. R.

    1981-01-01

    The switch to floating exchange rates during the 1970s has given economists the first comprehensive opportunity to assess the arguments for and against floating. Much new work has been done on various aspects of floating exchange rate behaviour. This article attempts a limited survey of the evidence concerning two important issues—whether floating exchange rates are inherently unstable and whether they harm international trade.

  6. 40 CFR 65.45 - External floating roof converted into an internal floating roof.

    Science.gov (United States)

    2010-07-01

    ... External floating roof converted into an internal floating roof. The owner or operator who elects to... 40 Protection of Environment 15 2010-07-01 2010-07-01 false External floating roof converted into an internal floating roof. 65.45 Section 65.45 Protection of Environment ENVIRONMENTAL PROTECTION...

  7. Current trends in offshore technology

    International Nuclear Information System (INIS)

    Korsgaard, J.

    1994-01-01

    Although this is a technical symposium concerning advances in the technology of producing oil and gas offshore, a keynote address would not be complete without mentioning non-technical factors which are extremely important for the business of producing oil and gas offshore. These are political factors and economic factors. Offshore operations are an easy target for political forces that are opposed to marine operations involving the production and transfer of hydrocarbons. For example, the oil pollution act of 1990 was a reaction to the Exxon Valdez grounding in Alaska and this act has added significantly to the risk and cost of operating offshore. Another example of this is that it is becoming more and more difficult to dispose of produced water offshore. Producing oil and gas offshore is a business that competes with other energy sources such as coal and oil and gas from wells on land. The offshore oil can only compete with these other resources by providing the same product at a competitive price. Since offshore operations are inherently more costly than land operations, the offshore oil field or gas field must be significantly larger than a land field in order to be produced. Also the offshore oil field or gas field is more susceptible to environmental risks from weather. On a more positive note, there are technical developments which are taking place and have continuously taken place to make offshore oil and gas both more economic and safer to produce. These developments are briefly discussed

  8. Accelerated ageing tests on repair coatings for offshore wind power structures: Presentation held at European Coatings Show Conference 2017, Nuremberg, Germany, 04th April 2017

    OpenAIRE

    Buchbach, Sascha; Momber, A.; Plagemann, P.; Winkels, I.; Marquardt, T.; Viertel, J.

    2017-01-01

    The paper reports on a statistical investigation into effects of surface preparation method, coating type and coating thickness on the performance of OWEA repair coatings under accelerated testing conditions. DoE (Design of Experiments) is used in order to design the tests and to evaluate the effects of the influencing parameters statistically. The ISO 20340 offshore testing scenario is utilized for the acceretaed ageing of the repair c oatings. The pre-existing coating on the test panel was ...

  9. Have Floating Rates Been a Success?

    Science.gov (United States)

    Higham, David

    1983-01-01

    Floating exchange rates have not lived up to all expectations, but neither have they performed as badly as some critics have suggested. Examined are the impact of floating rates on balance of payments adjustment, domestic economic policy, and inflation and the claim that floating rates have displayed excessive fluctuations. (Author/RM)

  10. Floating Microparticulate Oral Diltiazem Hydrochloride Delivery ...

    African Journals Online (AJOL)

    Purpose: To formulate and evaluate floating microparticulate oral diltiazem delivery system for possible delivery to the heart. Method: Floating microspheres were prepared using cellulose acetate and Eudragit RS100 polymers by emulsion solvent evaporation technique. The dried floating microspheres were evaluated for ...

  11. Hydroelasticity of a Floating Plate

    DEFF Research Database (Denmark)

    Chen, X.; Jensen, Jørgen Juncher; Cui, W.

    2003-01-01

    The membrane forces are included in the hydroelastic analysis of a floating plate undergoing large vertical deflections in regular monochromatic multidirectional waves. The first-order vertical displacements induced by the linear wave exciting forces are calculated by the mode expansion method in...

  12. Using decommissioned offshore oil/gas platforms for nuclear/RO desalination: the ONDP (Offshore Nuclear Desalination Platform)

    International Nuclear Information System (INIS)

    Nagar, Ankesh

    2010-01-01

    Oil platforms are manmade concrete and steel giant structures standing high on ocean floor weighing anywhere between 10,000 tonnes and 150,000 tonnes or more and designed to withstand cruel forces of nature, having an average life of 70 years. With the declining petrol reserves within next 30 years, hundreds of platforms will be scheduled for decommissioning. This issue is a hot topic as oil companies tussle with environmentalists and state lawmakers over the future. The cash strapped oil companies have a legal obligation to remove each rig entirely, returning the ocean floor to its original condition. Lean times in oil industry mean a tight cash flow. Safely removing massive structures from deep waters and shipping the pile to the shores for reuse and recycling presents a technological challenge for operators. Some conceptual applications investigated to reuse them are the conversion of offshore structures into fish farms, prisons, military outposts, hotels, for Search and Rescue operations or Centers for Waste Processing and Disposal. Decommissioning oil and gas installation is exorbitantly expensive. On an average, removing a complete platform with or without pipeline in sea waters with 'clean sea approach' costs $15 million to $ 6 billion depending on location. Global warming has adversely affected world climate. Water levels in ground and reservoirs have shown drastic decrement. In future there will be need for more and more water all over the world. Fossil fuel energy based desalination is expensive and not eco-friendly so is dismantling of oil platform with its pipeline. The oil platforms are far located from population, have sufficient tank capacity and pipeline structure to store and pump water to shore. When found economically unviable these mammoth structures with modifications can be installed with 02 or more small or medium sized nuclear reactors such as KLT 40S with required module to desalinate water and co generate electricity which can be sent to

  13. The Offshore New European Wind Atlas

    Science.gov (United States)

    Karagali, I.; Hahmann, A. N.; Badger, M.; Hasager, C.; Mann, J.

    2017-12-01

    The New European Wind Atlas (NEWA) is a joint effort of research agencies from eight European countries, co-funded under the ERANET Plus Program. The project is structured around two areas of work: development of dynamical downscaling methodologies and measurement campaigns to validate these methodologies, leading to the creation and publication of a European wind atlas in electronic form. This atlas will contain an offshore component extending 100 km from the European coasts. To achieve this, mesoscale models along with various observational datasets are utilised. Scanning lidars located at the coastline were used to compare the coastal wind gradient reproduced by the meso-scale model. Currently, an experimental campaign is occurring in the Baltic Sea, with a lidar located in a commercial ship sailing from Germany to Lithuania, thus covering the entire span of the south Baltic basin. In addition, satellite wind retrievals from scatterometers and Synthetic Aperture Radar (SAR) instruments were used to generate mean wind field maps and validate offshore modelled wind fields and identify the optimal model set-up parameters.The aim of this study is to compare the initial outputs from the offshore wind atlas produced by the Weather & Research Forecasting (WRF) model, still in pre-operational phase, and the METOP-A/B Advanced Scatterometer (ASCAT) wind fields, reprocessed to stress equivalent winds at 10m. Different experiments were set-up to evaluate the model sensitivity for the various domains covered by the NEWA offshore atlas. ASCAT winds were utilised to assess the performance of the WRF offshore atlases. In addition, ASCAT winds were used to create an offshore atlas covering the years 2007 to 2016, capturing the signature of various spatial wind features, such as channelling and lee effects from complex coastal topographical elements.

  14. Economic optimization of offshore wind farms

    International Nuclear Information System (INIS)

    Pauling, T.

    1996-09-01

    The study on the title subject continues the development of a cost model for offshore wind farms started at the Institute for Wind Energy (IW) in 1995, and applies it on different kinds of cost analyses. The model will be considered within the European research project 'Structural and Economic Optimization of Bottom-Mounted Offshore Wind Energy Converters' (Opti-OWECS, JOR3-CT95-0087) co-ordinated by the IW, where also the cost analyses and optimization will be extended. The conclusions of the investigations have already been presented at the European Union Wind Energy Conference '96 at Goeteborg, Sweden. In Chapter 1, a short overview of former offshore studies and projects is given, especially those dealing with cost analysis. Typical cost breakdowns of offshore and onshore wind farms are compared. Chapter 2 contains a brief description of the cost model in its present state. The recent improvements and extensions are documented in Chapter 3, and a validation by means of a recalculation of two former offshore studies is carried out in Chapter 4. In Chapter 5, four different offshore sites are compared with respect to the same farm size and an optimized farm design: Jade in the German part of the North Sea near Wilhelmshafen; Swansea Bay in the Bristol Channel at the British Atlantic Coast; Rostock at the German Baltic Coast, and IJmuiden in the Dutch part of the North Sea. In Chapter 6, a sensitivity study is carried out for a variety of site, design and economical parameters. The results of this project are summarized in Chapter 7, and an outlook is given in Chapter 8. The appendix contains among others a description of the SCOptiM2 code, where the model is implemented, as well as data obtained from the parameter studies and design optimizations. 30 figs., 8 tabs., 6 appendices, 40 refs

  15. Welding in hostile environment for nuclear and offshore industry

    International Nuclear Information System (INIS)

    Delauze, H.G.

    1990-01-01

    The paper reviews recent developments of duplex stainless steel and clad pipe welding and under water welding for offshore structures and for reactor fuel storage pool and remote automatic dry welding [fr

  16. Offshore Wind Power

    DEFF Research Database (Denmark)

    Negra, Nicola Barberis

    reliability models, and a new model that accounts for all relevant factors that influence the evaluations is developed. According to this representation, some simulations are performed and both the points of view of the wind farm owner and the system operator are evaluated and compared. A sequential Monte...... Carlo simulation is used for these calculations: this method, in spite of an extended computation time, has shown flexibility in performing reliability studies, especially in case of wind generation, and a broad range of results which can be evaluated. The modelling is then extended to the entire power......The aim of the project is to investigate the influence of wind farms on the reliability of power systems. This task is particularly important for large offshore wind farms, because failure of a large wind farm might have significant influence on the balance of the power system, and because offshore...

  17. Comparative study of hydroelastic responses of semisubmersible type and pontoon type very large floating structure in waves; Tachushiki semisabugata to pontoon gata choogata futai no harochu dansei oto no hikaku

    Energy Technology Data Exchange (ETDEWEB)

    Ma, N; Hirayama, T; Sato, N [Yokohama National University, Yokohama (Japan). Faculty of Engineering

    1997-12-31

    A semisubmersible very large floating structure is compared with an equivalent pontoon type in vertical displacement and longitudinal bending moment in waves. The theoretical calculation is based on the mode synthesis method, and fluid force is analyzed by the three-dimensional singularity method for the symmetric structure, in which the effects of elastic deformation are taken into account. The semisubmersible and pontoon types are not much different from each other in eigenfrequency and mode shape in the dry mode. In the wet mode, on the other hand, the pontoon type is characterized by the synthetic mode in which torsional and bending modes overlap each other, each mode having a similar eigenfrequency. These types are different in elastic response, the pontoon type having several tens times higher coefficient of attenuation than the semisubmersible type. The pontoon type is generally lower in response, but its torsional mode is excited in transverse waves, making it higher than the semisubmersible type at near eigenfrequency of this mode. 15 refs., 17 figs., 2 tabs.

  18. Comparative study of hydroelastic responses of semisubmersible type and pontoon type very large floating structure in waves; Tachushiki semisabugata to pontoon gata choogata futai no harochu dansei oto no hikaku

    Energy Technology Data Exchange (ETDEWEB)

    Ma, N.; Hirayama, T.; Sato, N. [Yokohama National University, Yokohama (Japan). Faculty of Engineering

    1996-12-31

    A semisubmersible very large floating structure is compared with an equivalent pontoon type in vertical displacement and longitudinal bending moment in waves. The theoretical calculation is based on the mode synthesis method, and fluid force is analyzed by the three-dimensional singularity method for the symmetric structure, in which the effects of elastic deformation are taken into account. The semisubmersible and pontoon types are not much different from each other in eigenfrequency and mode shape in the dry mode. In the wet mode, on the other hand, the pontoon type is characterized by the synthetic mode in which torsional and bending modes overlap each other, each mode having a similar eigenfrequency. These types are different in elastic response, the pontoon type having several tens times higher coefficient of attenuation than the semisubmersible type. The pontoon type is generally lower in response, but its torsional mode is excited in transverse waves, making it higher than the semisubmersible type at near eigenfrequency of this mode. 15 refs., 17 figs., 2 tabs.

  19. Offshore wind generators: realization?

    International Nuclear Information System (INIS)

    Roche, Catherine

    2012-01-01

    The author discusses the French legal context for the different aspects of the development of offshore wind farms in France: procedures related to electricity production installations (authorization or tender like what has been done for six sites), other administrative authorizations, and connection to the grid. Then, she addresses the various constraints: environmental, social and technical constraints (protected marine areas, constraints related to the tendering process), coast planning documents, tax policy. She finally discusses the installation dismantling

  20. Feasibility design of a floating airport and estimation of environmental forces on it; Futaishiki kuko no sekkei to kankyo gairyoku no suitei ni kansuru kento

    Energy Technology Data Exchange (ETDEWEB)

    Inoue, Y.; Tabeta, S.; Takei, Y. [Yokohama National University, Yokohama (Japan). Faculty of Engineering

    1996-12-31

    A rough design was performed on a floating airport. On this floating structure, environmental external force was estimated, mooring design was carried out, and discussions was given on the position retaining performance important for airport functions and behavior of the floating structure. The discussion was given on cases that the airport is surrounded and not surrounded by floating breakwaters. A floating structure which becomes super-large in size requires considerations on force due to sea level gradient as a result of a tide. Deriving flow condition changes and force acting on the floating structure simultaneously by using numerical calculations makes it possible to estimate current force given with considerations on influence of the flow conditions created by installing the floating airport. Estimation was carried out by using a zone dividing method on wave drifting force acting upon the floating airport. As a result, it was found that installing floating and permeating type breakwaters can reduce the wave drifting force acting on the floating airport. The wave drifting force working on the floating airport can be reduced by installing the floating and permeating type breakwaters to lower levels than when no such breakwaters are installed. The airport may be moored with less number of fenders when the fenders of the same type are used. 18 refs., 10 figs., 5 tabs.