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).

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...

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

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.

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...

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...

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

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...

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.

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

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.

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

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)

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

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.

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.

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

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...

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...

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.

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

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

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...

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.

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...

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)

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.

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

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).

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

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

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.

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.

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...

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.

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.

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.

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.

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...

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 ...

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.

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.

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

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.

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.

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

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.)

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.

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.

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.

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.

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...

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.

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

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...

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....

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...

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)

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

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 ...

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...

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.

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

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

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

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)....

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.

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.

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...

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.

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

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

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...

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.

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...

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.

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.

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

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.

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.

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....

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.

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

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.

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

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.)

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...

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

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)

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.

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)

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.

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....

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

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.

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 ...

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

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...

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)

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.)

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....

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

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

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]....

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...

Numerical investigation of interactions between marine atmospheric boundary layer and offshore wind farm

Science.gov (United States)

Lyu, Pin; Chen, Wenli; Li, Hui; Shen, Lian

2017-11-01

In recent studies, Yang, Meneveau & Shen (Physics of Fluids, 2014; Renewable Energy, 2014) developed a hybrid numerical framework for simulation of offshore wind farm. The framework consists of simulation of nonlinear surface waves using a high-order spectral method, large-eddy simulation of wind turbulence on a wave-surface-fitted curvilinear grid, and an actuator disk model for wind turbines. In the present study, several more precise wind turbine models, including the actuator line model, actuator disk model with rotation, and nacelle model, are introduced into the computation. Besides offshore wind turbines on fixed piles, the new computational framework has the capability to investigate the interaction among wind, waves, and floating wind turbines. In this study, onshore, offshore fixed pile, and offshore floating wind farms are compared in terms of flow field statistics and wind turbine power extraction rate. The authors gratefully acknowledge financial support from China Scholarship Council (No. 201606120186) and the Institute on the Environment of University of Minnesota.

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.

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.

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.

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...

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...

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.

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

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...

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.

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.

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...

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.

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...

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.

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, ...

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

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....

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....

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

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...

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

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.

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.

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.

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...

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....

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.

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)

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.

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.

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.

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.

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.

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.

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.

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.

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%

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.

Design and analysis of liquefaction process for offshore associated gas resources

International Nuclear Information System (INIS)

Li, Q.Y.; Ju, Y.L.

2010-01-01

Liquefaction is the key section on floating platform. Some experts and designers selected mixed refrigerant process for floating platform, while some recommended expander cycle. However, few of them compared the two types of processes systemically before making a choice. In this paper, the liquefaction processes of propane pre-cooled mixed refrigerant cycle (C 3 /MRC), mixed refrigerant cycle (MRC) and nitrogen expander cycle (N 2 expander) for the special offshore associated gases in South China Sea have been designed and studied. These processes have been analyzed and compared systematically considering the main factors including the performance parameters, economic performance, layout, sensitivity to motion, suitability to different gas resources, safety and operability, accounting for the features of the floating production, storage and offloading unit for liquefied natural gas (LNG-FPSO) in marine environment. The results indicated that N 2 expander has higher energy consumption and poorer economic performance, while it has much more advantages than C 3 /MRC and MRC for offshore application because it is simpler and more compact and thus requiring less deck area, less sensitive to LNG-FPSO motion, has better suitability for other gas resources, has higher safety and is easier to operate. Therefore, N 2 expander is the most suitable offshore liquefaction process. In addition, the exergy analysis is conducted for N 2 expander and the results indicate that the compression equipments and after coolers, expanders and LNG heat exchangers are the main contribution to the total exergy losses. The measures to decrease the losses for these equipments are then discussed.

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.

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...

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

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...

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.

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.

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.

Consequence assessment of floating and storage and off loading (FPSO) systems

International Nuclear Information System (INIS)

Smith, Duncan; Alderman, John A.

2000-01-01

Floating Production, Storage and Off loading (FPSO) systems are increasingly being used for deep water fields where use of traditional platforms and pipelines is not cost effective. The risks associated with FPSOs are inherently different from those for onshore facilities and conventional offshore platforms.This paper focuses on some of the key issues in the application of consequence assessment to FPSOs. A review and illustration of some of the techniques used for analysis of hydrocarbon hazards associated with FPSO operations will be included. Examples covered include evaluation of heat fluxes from a jet fire from an ignited riser leak and evaluation of explosion overpressure from a gas release on the main deck of the FPSO using ARAMAS. The assessment of the impact of smoke inhalation to personnel taking shelter in the accommodation block of the FPSO during a large fire event is also explained. Experiences gained from consequence assessments and quantitative risk analyses performed for offshore platforms, FPSOs, Floating Storage and Off loading (FSO) systems, as well as onshore refinery and petrochemical facilities will be detailed. (author)

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)

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....

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....

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....

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 ...

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.

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.

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...

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....

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.

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...

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

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....

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.

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.

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....

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.

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.

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.

Offshore Wind Resource, Cost, and Economic Potential in the State of Maine

Energy Technology Data Exchange (ETDEWEB)

Musial, Walter D. [National Renewable Energy Lab. (NREL), Golden, CO (United States)

2018-02-12

This report provides information for decision-makers about floating offshore wind technologies in the state of Maine. It summarizes research efforts performed at the National Renewable Energy Laboratory between 2015 and 2017 to analyze the resource potential, cost of offshore wind, and economic potential of offshore wind from four primary reports: Musial et al. (2016); Beiter et al. (2016, 2017); and Mone et al. (unpublished). From Musial et al. (2016), Maine's technical offshore wind resource potential ranked seventh in the nation overall with more than 411 terawatt-hours/year of offshore resource generating potential. Although 90% of this wind resource is greater than 9.0-meters-per-second average velocity, most of the resource is over deep water, where floating wind technology is needed. Levelized cost of energy and levelized avoided cost of energy were computed to estimate the unsubsidized 'economic potential' for Maine in the year 2027 (Beiter et al. 2016, 2017). The studies found that Maine may have 65 gigawatts of economic potential by 2027, the highest of any U.S. state. Bottom-line costs for the Aqua Ventus project, which is part of the U.S. Department of Energy's Advanced Technology Demonstration project, were released from a proprietary report written by NREL in 2016 for the University of Maine (Mone et al. unpublished). The report findings were that economies of scale and new technology advancements lowered the cost from $300/megawatt-hour (MWh) for the two-turbine 12-megawatt (MW) Aqua Ventus 1 project, to $126/MWh for the commercial-scale, 498-MW Aqua Ventus-2 project. Further cost reductions to $77/MWh were found when new technology advancements were applied for the 1,000-MW Aqua Ventus-3 project in 2030. No new analysis was conducted for this report.

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)

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....

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...

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.)

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.

Experimental Study on New Multi-Column Tension-Leg-Type Floating Wind Turbine

Science.gov (United States)

Zhao, Yong-sheng; She, Xiao-he; He, Yan-ping; Yang, Jian-min; Peng, Tao; Kou, Yu-feng

2018-04-01

Deep-water regions often have winds favorable for offshore wind turbines, and floating turbines currently show the greatest potential to exploit such winds. This work established proper scaling laws for model tests, which were then implemented in the construction of a model wind turbine with optimally designed blades. The aerodynamic, hydrodynamic, and elastic characteristics of the proposed new multi-column tension-leg-type floating wind turbine (WindStar TLP system) were explored in the wave tank testing of a 1:50 scale model at the State Key Laboratory of Ocean Engineering at Shanghai Jiao Tong University. Tests were conducted under conditions of still water, white noise waves, irregular waves, and combined wind, wave, and current loads. The results established the natural periods of the motion, damping, motion response amplitude operators, and tendon tensions of the WindStar TLP system under different environmental conditions, and thus could serve as a reference for further research. Key words: floating wind turbine, model test, WindStar TLP, dynamic response

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...

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.

Comparative evaluation of different offshore wind turbine installation vessels for Korean west–south wind farm

Directory of Open Access Journals (Sweden)

Dang Ahn

2017-01-01

Full Text Available The purpose of this study is to evaluate various means of wind power turbines installation in the Korean west–south wind farm (Test bed 100 MW, Demonstrate site 400 MW. We presented the marine environment of the southwest offshore wind farm in order to decide the appropriate installation vessel to be used in this site. The various vessels would be WTIV (Wind turbine installation vessel, jack-up barge, or floating crane … etc. We analyzed the installation cost of offshore wind turbine and the transportation duration for each vessel. The analysis results showed the most suitable installation means for offshore wind turbine in the Korean west–south wind farm.

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...

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...

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...

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

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.

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.

Proposing offshore photovoltaic (PV) technology to the energy mix of the Maltese islands

International Nuclear Information System (INIS)

Trapani, Kim; Millar, Dean L.

2013-01-01

Highlights: ► Significant cost and carbon savings for offshore PV integration. ► Maximum savings at circa 315 MW for thin film PV integration. ► Minimum generating capacity of turbines significant in cost of electricity. ► Part-load efficiencies of current system could hugely limit the integration of renewables. - Abstract: The islands of Malta are located in the Mediterranean basin enjoying 5.3 kW h/m 2 /day of solar insolation, at a latitude of 35°50N. Electricity generation for the islands is dependent upon imported fossil fuels for combustion. The available solar resource could be exploited to offset the current generation of electricity using solar photovoltaic technology (PV). Due to the limited land availability onshore, the offshore environment surrounding the Maltese islands were considered for the installation of PV floating on the sea surface. The output from such an installation would have to be integrated with the existing conventional electricity generation infrastructure, which currently relies on gas and steam turbine technology. To assess the feasibility of floating PV being integrated with the existing fossil plant, monthly trend consumption data for Malta were analysed. The change in gasoil and heavy fuel oil (HFO) consumption resulting from the part load efficiency variation and the displacement of electricity generation from the PVs were estimated. A cost analysis was prepared for the system integration analysis specifically accounting for the reduction in combustion of fossil fuels at the power station and the capital expenditures and operating costs due to the floating PV installation. Aside from the basic cost-benefit of a floating PV installation, CO 2 savings are also considered

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...

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.

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.

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.

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.

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...

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.

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.

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...

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...

A Spatial-Economic Cost-Reduction Pathway Analysis for U.S. Offshore Wind Energy Development from 2015–2030

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); Smith, Aaron [National Renewable Energy Lab. (NREL), Golden, CO (United States); Kilcher, Levi [National Renewable Energy Lab. (NREL), Golden, CO (United States); Damiani, Rick [National Renewable Energy Lab. (NREL), Golden, CO (United States); Maness, Michael [National Renewable Energy Lab. (NREL), Golden, CO (United States); Sirnivas, Senu [National Renewable Energy Lab. (NREL), Golden, CO (United States); Stehly, Tyler [National Renewable Energy Lab. (NREL), Golden, CO (United States); Gevorgian, Vahan [National Renewable Energy Lab. (NREL), Golden, CO (United States); Mooney, Meghan [National Renewable Energy Lab. (NREL), Golden, CO (United States); Scott, George [National Renewable Energy Lab. (NREL), Golden, CO (United States)

2016-09-01

This report describes a comprehensive effort undertaken by the National Renewable Energy Laboratory (NREL) to understand the cost of offshore wind energy for markets in the United States. The study models the cost impacts of a range of offshore wind locational cost variables for more than 7,000 potential coastal sites in U.S. offshore wind resource areas. It also assesses the impact of more than 50 technology innovations on potential future costs for both fixed-bottom and floating wind systems. Comparing these costs to an initial site-specific assessment of local avoided generating costs, the analysis provides a framework for estimating the economic potential for offshore wind. The analysis is intended to inform a broad set of stakeholders and enable an assessment of offshore wind as part of energy development and energy portfolio planning. It provides information that federal and state agencies and planning commissions could use to inform initial strategic decisions about offshore wind developments in the United States.

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)

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.

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.

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...

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.

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.

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.

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...

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...

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.

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.

A Spatial-Economic Cost-Reduction Pathway Analysis for U.S. Offshore Wind Energy Development from 2015-2030

Energy Technology Data Exchange (ETDEWEB)

Beiter, Philipp; Stehly, Tyler

2016-10-05

The potential for cost reduction and economic viability for offshore wind varies considerably within the United States. This analysis models the cost impact of a range of offshore wind locational cost variables across more than 7,000 potential coastal sites in the United States' offshore wind resource area. It also assesses the impact of over 50 technology innovations on potential future costs between 2015 and 2027 (Commercial Operation Date) for both fixed-bottom and floating wind systems. Comparing these costs to an initial assessment of local avoided generating costs, this analysis provides a framework for estimating the economic potential for offshore wind. Analyzing economic potential within this framework can help establish a refined understanding across industries of the technology and site-specific risks and opportunities associated with future offshore wind development. The findings from the original report indicate that under the modeled scenario, offshore wind can be expected to achieve significant cost reductions and may approach economic viability in some parts of the United States within the next 15 years.

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...

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)

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 ...

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.

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.

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.

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

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

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....

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

A proposed national wind power R and D program. [offshore wind power system for electric energy supplies

Science.gov (United States)

Heronemus, W.

1973-01-01

An offshore wind power system is described that consists of wind driven electrical dc generators mounted on floating towers in offshore waters. The output from the generators supplies underwater electrolyzer stations in which water is converted into hydrogen and oxygen. The hydrogen is piped to shore for conversion to electricity in fuel cell stations. It is estimated that this system can produce 159 x 10 to the ninth power kilowatt-hours per year. It is concluded that solar energy - and that includes wind energy - is the only way out of the US energy dilemma in the not too distant future.

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....

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.

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...

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.

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. ...

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.

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

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.

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.

Design, numerical modelling and analysis of a spar floater supporting the DTU 10MW wind turbine

OpenAIRE

Xue, Wenfei

2016-01-01

Nowadays, wind energy is one of the most promising, sustainable and clean energy solutions for the future. The wind industry in Europe experiences a very fast development these years, moving from onshore to offshore in shallow water and then in deep water. A floating wind turbine is an offshore wind turbine mounted on a floating structure that allows the turbine to generate electricity in water depths where bottom-fixed towers are not accessible. However, the offshore wind energy still has...

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.

Feasibility study on floating nuclear power plant (1). Conceptual design study of FNPP. Contract research

International Nuclear Information System (INIS)

Yabuuchi, Noriaki; Shimazaki, Junya; Ochiai, Masaaki; Takahashi, Masao; Nakazawa, Toshio

2001-02-01

Offshore siting methods for a nuclear power plant are classified into three types as a floating type, a settled type and a land reclamation type. The floating nuclear power plant (FNPP) has a number of advantages, such as seismic isolation, standardization of design and manufacturing, and reduction of construction period. It is, however, required for FNPP to establish the safety standards, which are different from ones for land based nuclear power plant. Investigations for this subject have not been conducted sufficiently. In this report, design study on a concept for FNPP and a review on stability evaluation for the floating platform, which were performed in order to study the safety concept of the FNPP are described. The basic concept of the FNPP are described. The basic concept for FNPP is as follows: The FNPP is sited approximately 1 - 2km off the sea coast on the open sea with water depth of about 20m and it is moored of protected sea by the breakwater, it provide a floating platform for a 1,100MWe class PWR plant. The results of design study show that the floating platform for 1,100MWe class PWR plant of 300m (L) x 80m (W) x 35m (H), and displacement of approximately 300,000 ton can be constructed in a dockyard. This floating platform guarded by the breakwater is found to be stable enough to install the nuclear power plant from the analysis simulating the movement of the platform due to sea wave or wind. (author)

Feasibility study on floating nuclear power plant (1). Conceptual design study of FNPP. Construct research

Energy Technology Data Exchange (ETDEWEB)

Yabuuchi, Noriaki; Shimazaki, Junya; Ochiai, Masaaki [Department of Nuclear Energy System, Tokai Research Establishment, Japan Atomic Energy Research Institute, Tokai, Ibaraki (Japan); Takahashi, Masao [Niigata Engineering Co. Ltd., Tokyo (Japan); Nakazawa, Toshio [Japan Atomic Energy Research Inst., Oarai, Ibaraki (Japan). Oarai Research Establishment; Sato, Kazuo [Ishikawajima-Harima Heavy Industries Co. Ltd., Tokyo (Japan)

2001-02-01

Offshore siting methods for a nuclear power plant are classified into three types as a floating type, a settled type and a land reclamation type. The floating nuclear power plant (FNPP) has a number of advantages, such as seismic isolation, standardization of design and manufacturing, and reduction of construction period. It is, however, required for FNPP to establish the safety standards, which are different from ones for land based nuclear power plant. Investigations for this subject have not been conducted sufficiently. In this report, design study on a concept for FNPP and a review on stability evaluation for the floating platform, which were performed in order to study the safety concept of the FNPP are described. The basic concept of the FNPP are described. The basic concept for FNPP is as follows: The FNPP is sited approximately 1 - 2km off the sea coast on the open sea with water depth of about 20m and it is moored of protected sea by the breakwater, it provide a floating platform for a 1,100MWe class PWR plant. The results of design study show that the floating platform for 1,100MWe class PWR plant of 300m (L) x 80m (W) x 35m (H), and displacement of approximately 300,000 ton can be constructed in a dockyard. This floating platform guarded by the breakwater is found to be stable enough to install the nuclear power plant from the analysis simulating the movement of the platform due to sea wave or wind. (author)

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

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...

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.

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.

Draft environmental statement related to the proposed manufacture of floating nuclear power plants (Docket No. STN 50-437)

International Nuclear Information System (INIS)

1976-10-01

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 50-436). 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 breadwaters at specific offshore locations designated by the purchaser and after an operating license has been issued by the Nuclear Regulatory Commision. 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. 3 figs., 1 tab

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.

Developments in offshore technology. Entwicklungen in der Offshoretechnik

Energy Technology Data Exchange (ETDEWEB)

1981-01-01

This book contains the summarized lectures held on the 8th of October, 1981 within the first status Seminar 'Offshore technology' which was organized by the Federal Minstry for Research and Technology. Contents are divided into: 1. Offshore-natural gas liquefaction, conveying systems. Offshore-tanker charging with supercold liquiefied gases; development of LNG-offshore - convayance systems; 2.) Development of components and installations in offshore structures: mooving-measuring- and monitoring systems for the installation of the EPOS deck; underwater-piling with a hydraulic-pile hammer; cast steel nodes for offshore-structures (material, calculation, design); 3.) underwater tools: the underwater-working system SUPRA; test results and experience with the unmanned UW-instrument-carrier FUGE; development of a mobile diver assistance vehicle for inspection and maintenance duties; 4.) underwater-pipeline-technique: flexible offshore-pipeline/continuous production and assembly, pipeline assembly at sea according to the J-Method with flash-welding technique; construction and testing of UWAG I (underwater working device) for embedding cables and pipes in the ocean soil.

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...

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...

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...

Industrial waste - destination and valuation techniques of floating hoses: case study in Macaé, RJ

Directory of Open Access Journals (Sweden)

Marlon de Almeida Clemente Silva

2017-10-01

Full Text Available A large part of the oil extracted in Brazil today, is drained to the coast, or even transported to larger vessels through Floating Hoses. This oil unloading operation is called Offloading, it is of fundamental importance for the performance of offshore operations. These operating units use storage systems and oil relief, which can be FSO (Floating Storage Unit and Transfer or FPSO (Floating Production Unit, Stockpiling and Transfer. In this oil transshipment scenario, floating hoses have primary role therefore they are responsible for this operation. The Floating Hoses after useful life are discarded. How do the environmentally correct disposal of this waste? The destination most used for this waste are the landfills Class 2, for non-hazardous waste. In this study, we attempted to develop appropriate allocation techniques for Floating Hose, in order to obtain a greater appreciation potential of the materials that compose it, as well as presenting the risk of these being put up in a landfill, even if it is a controlled landfill. This technique is based on a so-called Reverse Manufacturing, all components are reused and recovered, with a more environmentally sound and economically viable destination. The research methodology was based on empirical studies of phenomenological framework, involving operational staff of a medium-sized company with a rising share of Treatment and Waste Disposal Market, in the city of Macaé. It was evidenced in the survey that there is a possibility of potential gains from the application of reverse manufacturing techniques of hoses, both in terms of environmental liability reductions and the financial return through the recovery of materials that compose them.

Industrial automation in floating production vessels for deep water oil and gas fields

International Nuclear Information System (INIS)

de Garcia, A.L.; Ferrante, A.J.

1990-01-01

The process supervision in offshore platforms was performed in the past through the use of local pneumatic instrumentation, based on relays, semi-graphic panels and button operated control panels. Considering the advanced technology used in the new floating production projects for deep water, it became mandatory to develop supervision systems capable of integrating different control panels, increasing the level of monitorization and reducing the number of operators and control rooms. From the point of view of field integration, a standardized architecture makes the communication between different production platforms and the regional headquarters, where all the equipment and support infrastructure for the computerized network is installed, possible. This test paper describes the characteristics of the initial systems, the main problems observed, the studies performed and the results obtained in relation to the design and implementation of computational systems with open architecture for automation of process control in floating production systems for deep water in Brazil

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.

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.

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...

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...

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.

Offshore wind power. Market opportunities for the Norwegian supply industry, and regulatory framework needed to realize these opportunities

Energy Technology Data Exchange (ETDEWEB)

Volden, G.; Bull-Berg, H.; Skjeret, F.; Finne, H.; Hofmann, M.

2010-07-01

Full text: Offshore wind power has received much attention these last few years, from governments, NGOs as well as energy companies. There are still huge technological challenges to overcome, especially concerning floating constructions on deep water, but offshore wind has a potential to become an important energy source in the future. The main objective of our study was to build more knowledge about market opportunities for the Norwegian supply industry, most of which is closely related to offshore oil and gas activities. We started by mapping and quantifying the parts of the supply industry that could be relevant to offshore wind, which is actually most of it. Then, through interviews and questionnaires, we asked potential suppliers about their attitude and strategies towards offshore wind. An over-whelming majority was optimistic about future markets internationally, whereas there was less belief in large-scale power production on the Norwegian shelf. Suppliers do not necessarily find the lack of a Norwegian 'home market' to be a barrier. However many of them expressed that the risk is high and it may be crucial to establish a national demo program, for supplier to test new technological solutions at low cost, gain references and develop industrial relations with other suppliers. We argue that being part of an industrial cluster may be a success criterion within offshore wind. By using Michael Porter's 'Diamond Model' we analyse Norway's inherent competitiveness as a potential host for an offshore wind cluster - with or without energy producers. Norway's most important advantage is the existing industrial environment, with a strong maritime sector and engineering companies with special competence in floating and fixed installations for the oil industry. Norway also has disadvantages; such as lack of traditions within wind power and wind turbine manufacturing, as well as high salaries and lack of engineers. So far it is also

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.

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

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

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.

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.

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...

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

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.

Numerical Prediction of Experimentally Observed Behavior of a Scale Model of an Offshore Wind Turbine Supported by a Tension-Leg Platform: Preprint

Energy Technology Data Exchange (ETDEWEB)

Prowell, I.; Robertson, A.; Jonkman, J.; Stewart, G. M.; Goupee, A. J.

2013-01-01

Realizing the critical importance the role physical experimental tests play in understanding the dynamics of floating offshore wind turbines, the DeepCwind consortium conducted a one-fiftieth-scale model test program where several floating wind platforms were subjected to a variety of wind and wave loading condition at the Maritime Research Institute Netherlands wave basin. This paper describes the observed behavior of a tension-leg platform, one of three platforms tested, and the systematic effort to predict the measured response with the FAST simulation tool using a model primarily based on consensus geometric and mass properties of the test specimen.

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...

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.

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...

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

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.

Oceans from Space

DEFF Research Database (Denmark)

Aage, Christian; Allan, T.D.; Lindgren, G.

The largest forces on offshore structures, either floating or fixed, are usually caused by surface waves. Therefore a good understanding of the statistics of these waves and of how they are measured are needed by anyone who is concerned with the design and construction of offshore structures, as ...

Final environmental statement related to the proposed manufacture of floating nuclear power plants: (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. 226 figs., 95 tabs

Fatigue Life of High-Strength Steel Offshore Tubular Joints

DEFF Research Database (Denmark)

Petersen, Rasmus Ingomar; Agerskov, Henning; Lopez Martinez, Luis

1996-01-01

In the present investigation, the fatigue life of tubular joints in offshore steel structures is studied. Two test series on full-scale tubular joints have been carried through. One series was on joints in conventional offshore structural steel, and the other series was on joints in high-strength......In the present investigation, the fatigue life of tubular joints in offshore steel structures is studied. Two test series on full-scale tubular joints have been carried through. One series was on joints in conventional offshore structural steel, and the other series was on joints in high......-strength steel with a yield stress of 820-830 MPa and with high weldability and toughness properties. The test specimens of both series had the same geometry. The present report concentrates on the results obtained in the investigation on the high-strength steel tubular joints.The test specimens were fabricated...... from Ø 324-610 mm tubes, and the joints were loaded in in-plane bending. Both fatigue tests under constant amplitude loading and tests with a stochastic loading that is realistic in relation to offshore structures, are included in the investigation.A comparison between constant amplitude and variable...

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....

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...

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.

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

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

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...

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.

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.

Combined Structural Optimization and Aeroelastic Analysis of a Vertical Axis Wind Turbine

DEFF Research Database (Denmark)

Roscher, Björn; Ferreira, Carlos Simao; Bernhammer, Lars O.

2015-01-01

Floating offshore wind energy poses challenges on the turbine design. A possible solution is vertical axis wind turbines, which are possibly easier to scale-up and require less components (lower maintenance) and a smaller floating structure than horizontal axis wind turbines. This paper presents...... a structural optimization and aeroelastic analysis of an optimized Troposkein vertical axis wind turbine to minimize the relation between the rotor mass and the swept area. The aeroelastic behavior of the different designs has been analyzed using a modified version of the HAWC2 code with the Actuator Cylinder...... model to compute the aerodynamics of the vertical axis wind turbine. The combined shape and topology optimization of a vertical axis wind turbine show a minimum mass to area ratio of 1.82 kg/m2 for blades with varying blade sections from a NACA 0040 at the attachment points to a NACA 0015...

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.

Validation of a vortex ring wake model suited for aeroelastic simulations of floating wind turbines

International Nuclear Information System (INIS)

Vaal, J B de; Moan, T; Hansen, M O L

2014-01-01

In order to evaluate aerodynamic loads on floating offshore wind turbines, advanced dynamic analysis tools are required. As a unified model that can represent both dynamic inflow and skewed inflow effects in it basic formulation, a wake model based on a vortex ring formulation is discussed. Such a model presents a good intermediate solution between computationally efficient but simple momentum balance methods and computationally expensive but complete computational fluid dynamics models. The model introduced is shown to be capable of modelling typical steady and unsteady test cases with reasonable accuracy

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

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...

Mooring Line Damping Estimation for a Floating Wind Turbine

Directory of Open Access Journals (Sweden)

Dongsheng Qiao

2014-01-01

Full Text Available The dynamic responses of mooring line serve important functions in the station keeping of a floating wind turbine (FWT. Mooring line damping significantly influences the global motions of a FWT. This study investigates the estimation of mooring line damping on the basis of the National Renewable Energy Laboratory 5 MW offshore wind turbine model that is mounted on the ITI Energy barge. A numerical estimation method is derived from the energy absorption of a mooring line resulting from FWT motion. The method is validated by performing a 1/80 scale model test. Different parameter changes are analyzed for mooring line damping induced by horizontal and vertical motions. These parameters include excitation amplitude, excitation period, and drag coefficient. Results suggest that mooring line damping must be carefully considered in the FWT design.

Mooring line damping estimation for a floating wind turbine.

Science.gov (United States)

Qiao, Dongsheng; Ou, Jinping

2014-01-01

The dynamic responses of mooring line serve important functions in the station keeping of a floating wind turbine (FWT). Mooring line damping significantly influences the global motions of a FWT. This study investigates the estimation of mooring line damping on the basis of the National Renewable Energy Laboratory 5 MW offshore wind turbine model that is mounted on the ITI Energy barge. A numerical estimation method is derived from the energy absorption of a mooring line resulting from FWT motion. The method is validated by performing a 1/80 scale model test. Different parameter changes are analyzed for mooring line damping induced by horizontal and vertical motions. These parameters include excitation amplitude, excitation period, and drag coefficient. Results suggest that mooring line damping must be carefully considered in the FWT design.

Lifting simulation of an offshore supply vessel considering various operating conditions

Directory of Open Access Journals (Sweden)

Dong-Hoon Jeong

2016-06-01

Full Text Available Recently, an offshore support vessel is being widely used to install an offshore structure such as a subsea equipment which is laid on its deck. The lifting operation which is one of the installation operations includes lifting off, lifting in the air, splash zone crossing, deep submerging, and finally landing of the structure with an offshore support vessel crane. There are some major considerations during this operation. Especially, when lifting off the structure, if operating conditions such as ocean environmental loads and hoisting (or lowering speed are bad, the excess of tension of wire ropes of the crane and the collision between the offshore support vessel and the structure can be occurred due to the relative motion between them. To solve this problem, this study performs the lifting simulation while the offshore support vessel installs the structure. The simulation includes the calculation of dynamic responses of the offshore support vessel and the equipment, including the wire tension and the collision detection. To check the applicability of the simulation, it is applied to some lifting steps by varying operating conditions. As a result, it is confirmed that the conditions affect the operability of those steps.

Comparative analysis of monetizing technologies for the use of offshore natural gas; Analise comparativa das tecnologias embarcadas de aproveitamento de gas natural

Energy Technology Data Exchange (ETDEWEB)

Biruel Junior, Jose

2008-09-15

The growing world need for natural gas, the issue of offshore oil and associated gas exploration in regions constantly farther from the consumer market, and the law restrictions due to greenhouses gases emissions have stimulated the development of technologies intended to monetizing stranded gas reserves. In order to compare these technologies, a Multi Criteria Decision Analysis Methodology, based on fuzzy parameters, has been developed. The Methodology enables specialists to define analysis dimensions and criteria as well as to assign weight and ratings by means of linguistic variables, resulting in a general performance index for each technology. The Methodology has been applied in a case study to compare the floating technologies FCNG (Floating Compressed Natural Gas), FLNG (Floating Liquefied Natural Gas), FGTL (Floating Gas-to-Liquid) and FGTW (Floating Gas-to- Wire). The efficacy of the Methodology depends on the comprehensiveness and quality of the information provided. Therefore, this dissertation presents a study of these technologies, placing strong emphasis on the Technological Dimension. The Methodology allows for the identification of the drawbacks of each technology so as to especially conduct R and D efforts to improve their competitiveness. (author)

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.

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.

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.

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...

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...

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...

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...

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...

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...

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...

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...

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

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...

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...

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 ...

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.

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.)

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....

Impact of offshore nuclear generating stations on recreational behavior at adjacent coastal sites

International Nuclear Information System (INIS)

Baker, E.J.; West, S.G.; Moss, D.J.; Weyant, J.K.

1977-10-01

A multi-faceted investigation was undertaken to project the impact of offshore nuclear power plants on beach visitation at adjacent beaches. Related literature was reviewed concerning human adjustment to natural hazards, risk-taking behavior, and public attitudes toward nuclear power. Approximately 2400 people were interviewed at beaches in three states with respect to: intended avoidance of beaches near a hypothetical floating nuclear plant (FNP), relative importance of proximity to a FNP, when compared to other beach attributes, onshore-offshore preference for coastal nuclear plant location, behavioral impact of NRC licensing of FNPs, relative tourism impact of coastal nuclear plant compared to coastal coal-fired plant, public concerns about nuclear safety, public attitudes toward alternative energy sources, public confidence in sources of information about nuclear power, visual impact of a FNP, and knowledge about nuclear power. Four beach areas near currently operating coastal nuclear power plants were studied to assess impacts on tourism resulting from plant construction. Data suggest that proximity of a FNP is less important than other beach attributes in determining beach attractiveness, probably no more than (and perhaps less than) 5% to 10% of current beach patrons would avoid a beach after FNP siting three miles directly offshore, and impact of a FNP would decrease exponentially as distance away increased

Modeling of 4H—SiC multi-floating-junction Schottky barrier diode

International Nuclear Information System (INIS)

Hong-Bin, Pu; Lin, Cao; Zhi-Ming, Chen; Jie, Ren; Ya-Gong, Nan

2010-01-01

This paper develops a new and easy to implement analytical model for the specific on-resistance and electric field distribution along the critical path for 4H—SiC multi-floating junction Schottky barrier diode. Considering the charge compensation effects by the multilayer of buried opposite doped regions, it improves the breakdown voltage a lot in comparison with conventional one with the same on-resistance. The forward resistance of the floating junction Schottky barrier diode consists of several components and the electric field can be understood with superposition concept, both are consistent with MEDICI simulation results. Moreover, device parameters are optimized and the analyses show that in comparison with one layer floating junction, multilayer of floating junction layer is an effective way to increase the device performance when specific resistance and the breakdown voltage are traded off. The results show that the specific resistance increases 3.2 mΩ·cm 2 and breakdown voltage increases 422 V with an additional floating junction for the given structure. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

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...

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....

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.

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.

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

Prospects of the French offshore wind power market

International Nuclear Information System (INIS)

Anon.

2011-12-01

This market study about the French offshore wind power industry presents: 1 - the bases of the offshore wind power market: wind turbine operation principle, foundations and scale change; 2 - business model of offshore wind power projects: logistical, technical and financial challenges, cost structure and profitability of projects (investment, power generation costs, incentive mechanisms), project development time; 3 - European and French regulatory framework: the energy/climate package, the French 'Grenelle de l'Environnement' commitments for the development of renewable energies; 4 - start up of the French offshore wind power market: the onshore wind power market looking for growth relaying, the lateness of the offshore market, outlines of the call for bids and of the first phase launching (schedule, selected sites and candidates), market development stakes and opportunities; 5 - offshore wind power overview in Europe - lessons for the French market prospects: status of the European market (installed power/country, projects in progress), European leaders of the market (analysis of the British, Danish and German markets successful takeoff), specificities of the French market (are all favourable conditions present?); 6 - takeoff of the French market - what opportunities on the overall value chain?: front-end of the industry (manufacturers and component suppliers: industry structure, competition, R and D, subcontractors in France), back-end of the industry (developers/operators: sector analysis, ambitions, alliances, competences), specific French know-how in offshore installation and connection of wind turbines (reconversion of harbour areas, re-positioning of shipbuilding industry). (J.S.)

Free-floating magnetic microstructures by mask photolithography

Science.gov (United States)

Huong Au, Thi; Thien Trinh, Duc; Bich Do, Danh; Phu Nguyen, Dang; Cong Tong, Quang; Diep Lai, Ngoc

2018-03-01

This work explores the fabrication of free-floating magnetic structures on a photocurable nanocomposite consisting of superparamagnetic magnetite nanoparticles (Fe3O4) and a commercial SU-8 negative tone photoresist. The nanocomposite was synthesized by mixing magnetic nanoparticles with different kinds of SU-8 resin. We demonstrated that the dispersion of Fe3O4 nanoparticles in nanocomposite solution strongly depended on the particles concentration, the viscosity of SU-8 polymer, and the mixing time. The influence of these factors was demonstrated by examining the structures fabricated by mask photolithography technique. We obtained the best quality of structures at a low concentration, below 5 wt%, of Fe3O4 nanoparticles in SU-8 2005 photoresist for a mixing time of about 20 days. The manipulation of free-floating magnetic microstructures by an external magnetic field was also demonstrated showing promising applications of this magnetic nanocomposite.

Handbook of floating-point arithmetic

CERN Document Server

Muller, Jean-Michel; de Dinechin, Florent; Jeannerod, Claude-Pierre; Joldes, Mioara; Lefèvre, Vincent; Melquiond, Guillaume; Revol, Nathalie; Torres, Serge

2018-01-01

This handbook is a definitive guide to the effective use of modern floating-point arithmetic, which has considerably evolved, from the frequently inconsistent floating-point number systems of early computing to the recent IEEE 754-2008 standard. Most of computational mathematics depends on floating-point numbers, and understanding their various implementations will allow readers to develop programs specifically tailored for the standard’s technical features. Algorithms for floating-point arithmetic are presented throughout the book and illustrated where possible by example programs which show how these techniques appear in actual coding and design. The volume itself breaks its core topic into four parts: the basic concepts and history of floating-point arithmetic; methods of analyzing floating-point algorithms and optimizing them; implementations of IEEE 754-2008 in hardware and software; and useful extensions to the standard floating-point system, such as interval arithmetic, double- and triple-word arithm...

Effect of removal of free-floating macrophytes on zooplankton habitat in shallow wetland

OpenAIRE

Choi Jong-Yun; Jeong Kwang-Seuk; La Geung-Hwan; Joo Gea-Jae

2014-01-01

Submerged macrophytes improve the structural heterogeneity of microhabitats in aquatic ecosystems, often providing an important habitat for zooplankton. However, excessive development of free-floating macrophytes on the water surface can reduce the biomass of submerged macrophytes and result in a relatively simple habitat structure. We hypothesized that controlling the development of free-floating macrophytes would result in a more complex habitat structure by promoting the development of sub...

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.

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...

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.

Development of Seismic Demand for Chang-Bin Offshore Wind Farm in Taiwan Strait

Directory of Open Access Journals (Sweden)

Yu-Kai Wang

2016-12-01

Full Text Available Taiwan is located on the Pacific seismic belt, and the soil conditions of Taiwan’s offshore wind farms are softer than those in Europe. To ensure safety and stability of the offshore wind turbine supporting structures, it is important to assess the offshore wind farms seismic forces reasonably. In this paper, the relevant seismic and geological data are obtained for Chang-Bin offshore wind farm in Taiwan Strait, the probabilistic seismic hazard analysis (PSHA is carried out, and the first uniform hazard response spectrum for Chang-Bin offshore wind farm is achieved. Compared with existing design response spectrum in the local regulation, this site-specific seismic hazard analysis has influence on the seismic force considered in the design of supporting structures and therefore affects the cost of the supporting structures. The results show that a site-specific seismic hazard analysis is required for high seismic area. The paper highlights the importance of seismic hazard analysis to assess the offshore wind farms seismic forces. The follow-up recommendations and research directions are given for Taiwan’s offshore wind turbine supporting structures under seismic force considerations.

Preparation and investigation of novel gastro-floating tablets with 3D extrusion-based printing.

Science.gov (United States)

Li, Qijun; Guan, Xiaoying; Cui, Mengsuo; Zhu, Zhihong; Chen, Kai; Wen, Haoyang; Jia, Danyang; Hou, Jian; Xu, Wenting; Yang, Xinggang; Pan, Weisan

2018-01-15

Three dimensional (3D) extrusion-based printing is a paste-based rapid prototyping process, which is capable of building complex 3D structures. The aim of this study was to explore the feasibility of 3D extrusion-based printing as a pharmaceutical manufacture technique for the fabrication of gastro-floating tablets. Novel low-density lattice internal structure gastro-floating tablets of dipyridamole were developed to prolong the gastric residence time in order to improve drug release rate and consequently, improve bioavailability and therapeutic efficacy. Excipients commonly employed in the pharmaceutical study could be efficiently applied in the room temperature 3D extrusion-based printing process. The tablets were designed with three kinds of infill percentage and prepared by hydroxypropyl methylcellulose (HPMC K4M) and hydroxypropyl methylcellulose (HPMC E15) as hydrophilic matrices and microcrystalline cellulose (MCC PH101) as extrusion molding agent. In vitro evaluation of the 3D printed gastro-floating tablets was performed by determining mechanical properties, content uniformity, and weight variation. Furthermore, re-floating ability, floating duration time, and drug release behavior were also evaluated. Dissolution profiles revealed the relationship between infill percentage and drug release behavior. The results of this study revealed the potential of 3D extrusion-based printing to fabricate gastro-floating tablets with more than 8h floating process with traditional pharmaceutical excipients and lattice internal structure design. Copyright © 2017. Published by Elsevier B.V.

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

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.

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.

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.

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.

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.

Seabird data collected by the Grand Banks offshore hydrocarbon industry 1999-2002 : results, limitations and suggestions for improvement

International Nuclear Information System (INIS)

Baillie, S.M.; Robertson, G.J.; Wiese, F.K.

2005-01-01

Offshore oil operations attract and concentrate migratory seabirds through an artificially enhanced food supply and lights. In order to understand the vulnerability of seabirds near offshore oil facilities, the degree of association of seabirds with these sites must be determined. Offshore oil and gas exploration on Newfoundland's Grand Banks began in the early 1980s, with first oil produced in 1997 at the Hibernia fixed platform. Additional production followed in 2002 from the Terra Nova Floating Production Storage and Offloading Vessel. As the Grand Banks oil industry grows, seismic surveys continue to be conducted and an estimated 30,000 litres of crude oil and synthetic based drilling fluids have been spilled from exploration drilling, development drilling and production oil operations between 1997 and 2002. Most of the spills occurred in winter when the number of seabirds on the Grand Banks are highest and most vulnerable to oil pollution. This report presents an evaluation of the current Grand Banks offshore oil and gas development seabird monitoring programs. It focuses mostly on seabird monitoring on fixed platforms. The objective was to assess the scientific quality of seabird-related industry programs by compiling and summarizing all available spatial and temporal seabird abundance data and deck stranded birds associated with Grand Banks offshore oil platforms from 1997 to 2002. Data on seabird distributions at sea and stranded bird encounters was collected from 8 offshore hydrocarbon sites on the northeastern Grand Banks. It was recommended that a standardized seabird monitoring and observer training program for the offshore operations in the Grand Banks region be implemented. 43 refs., 5 tabs., 16 figs., 3 appendices

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

Integration of Wave and Offshore Wind Energy in a European Offshore Grid

DEFF Research Database (Denmark)

Chozas, Julia Fernandez; Sørensen, H. C.; Korpås, M.

2010-01-01

of offshore renewable energy sources. According to this, the paper covers i) public and private initiatives for offshore transmission networks, ii) the synergies between the wave and the offshore wind energy sector within an offshore grid, iii) power transmission options for offshore generation and iv...

Damage to offshore infrastructure in the Gulf of Mexico by hurricanes Katrina and Rita

Science.gov (United States)

Cruz, A. M.; Krausmann, E.

2009-04-01

The damage inflicted by hurricanes Katrina and Rita to the Gulf-of-Mexico's (GoM) oil and gas production, both onshore and offshore, has shown the proneness of industry to Natech accidents (natural hazard-triggered hazardous-materials releases). In order to contribute towards a better understanding of Natech events, we assessed the damage to and hazardous-materials releases from offshore oil and natural-gas platforms and pipelines induced by hurricanes Katrina and Rita. Data was obtained through a review of published literature and interviews with government officials and industry representatives from the affected region. We also reviewed over 60,000 records of reported hazardous-materials releases from the National Response Center's (NRC) database to identify and analyze the hazardous-materials releases directly attributed to offshore oil and gas platforms and pipelines affected by the two hurricanes. Our results show that hurricanes Katrina and Rita destroyed at least 113 platforms, and severely damaged at least 53 others. Sixty percent of the facilities destroyed were built 30 years ago or more prior to the adoption of the more stringent design standards that went into effect after 1977. The storms also destroyed 5 drilling rigs and severely damaged 19 mobile offshore drilling units (MODUs). Some 19 MODUs lost their moorings and became adrift during the storms which not only posed a danger to existing facilities but the dragging anchors also damaged pipelines and other infrastructure. Structural damage to platforms included toppling of sections, and tilting or leaning of platforms. Possible causes for failure of structural and non-structural components of platforms included loading caused by wave inundation of the deck. Failure of rigs attached to platforms was also observed resulting in significant damage to the platform or adjacent infrastructure, as well as damage to equipment, living quarters and helipads. The failures are attributable to tie-down components

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.

Optimal Risk-Based Inspection Planning for Offshore Wind Turbines

DEFF Research Database (Denmark)

Rangel-Ramirez, Jose G.; Sørensen, John Dalsgaard

2008-01-01

, inspection and maintenance activities are developed. This paper considers aspects of inspection and maintenance planning of fatigue prone details in jacket and tripod types of wind turbine support structures. Based oil risk-based inspection planning methods used for oil & gas installations, a framework......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 coining years. The Support structure for offshore wind turbines is typically a steel structure consisting of a tower...... for optimal inspection and maintenance planning of offshore wind turbines is presented. Special aspects for offshore wind turbines are considered: usually the wind loading are dominating the wave loading, wake effects in wind farms are important and the reliability level is typically significantly lower than...

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.

Towards a mature offshore wind energy technology - guidelines from the opti-OWECS project

Science.gov (United States)

Kühn, M.; Bierbooms, W. A. A. M.; van Bussel, G. J. W.; Cockerill, T. T.; Harrison, R.; Ferguson, M. C.; Göransson, B.; Harland, L. A.; Vugts, J. H.; Wiecherink, R.

1999-01-01

The article reviews the main results of the recent European research project Opti-OWECS (Structural and Economic Optimisation of Bottom-Mounted Offshore Wind Energy Converters'), which has significantly improved the understanding of the requirements for a large-scale utilization of offshore wind energy. An integrated design approach was demonstrated for a 300 MW offshore wind farm at a demanding North Sea site. Several viable solutions were obtained and one was elaborated to include the design of all major components. Simultaneous structural and economic optimization took place during the different design stages. An offshore wind energy converter founded on a soft-soft monopile was tailored with respect to the distinct characteristics of dynamic wind and wave loading. The operation and maintenance behaviour of the wind farm was analysed by Monte Carlo simulations. With an optimized maintenance strategy and suitable hardware a high availability was achieved. Based upon the experience from the structural design, cost models for offshore wind farms were developed and linked to a European database of the offshore wind energy potential. This enabled the first consistent estimate of cost of offshore wind energy for entire European regions.

Seismic response analysis of floating nuclear power plant

International Nuclear Information System (INIS)

Hagiwara, Yutaka; Nakamura, Hideharu; Shiojiri, Hiroo

1988-01-01

Since Floating Nuclear Power Plants (FNPs) are considered to be isolated from horizontal seismic motion, it is anticipated to reduce seismic load for plant components and buildings on the barge. On the other hand, barge oscillation and sloshing in the closed basin might be excited by earthquakes, because natural periods of those motions correspond to relatively-long period component (between 2 and 20 seconds) of seismic motion. Therefore, it is necessary to evaluate seismic isolation effects and barge oscillation, for the rational design of FNPs. However, there do not exist any reasonable analytical tools which can evaluate seismic response of floating structures in closed basin. The purpose of the present report is to develop a seismic analysis method for FNPs. The proposed method is based on the finite element method, and the formulation includes fluid-structure interaction, water surface wave, buoyancy effect, and non-linear characteristics of mooring system. Response analysis can be executed in both time-domain and frequency-domain. Shaking table tests were conducted to validate the proposed method of analysis. The test results showed significant isolation effect of floating structure, and apparent interaction between the barge and the basin. And 2-D and 3-D frequency domain analyses and the 2-D linear and non-linear time-domain analyses were done and those analyses could simulate the test results well. (author)

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...

14 CFR 27.753 - Main float design.

Science.gov (United States)

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Main float design. 27.753 Section 27.753... STANDARDS: NORMAL CATEGORY ROTORCRAFT Design and Construction Floats and Hulls § 27.753 Main float design. (a) Bag floats. Each bag float must be designed to withstand— (1) The maximum pressure differential...

14 CFR 29.753 - Main float design.

Science.gov (United States)

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Main float design. 29.753 Section 29.753... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Design and Construction Floats and Hulls § 29.753 Main float design. (a) Bag floats. Each bag float must be designed to withstand— (1) The maximum pressure differential...

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 ...

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....

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.

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.

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.

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)

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)

Conditional analysis of floating potential fluctuations at the edge of the Texas Experimental Tokamak Upgrade (TEXT-U)

International Nuclear Information System (INIS)

Filippas, A.V.; Bengston, R.D.; Li, G.; Meier, M.; Ritz, C.P.; Powers, E.J.

1995-01-01

Fluctuations in floating potential in the scrape-off layer and plasma edge were analyzed using a conditional statistical analysis technique. The floating potential fluctuations had a nearly Gaussian probability density function with the largest deviation from a Gaussian at the shear layer. The conditional averaging technique followed the statistical evolution of selected conditions in the floating potential signal. The decay rate of a conditional feature in time or space showed a small systematic variation with the amplitude of condition chosen. Either long-lived coherent structures are not present in statistically significant numbers, or the fluctuations are dominated by a large number of coherent structures with a nearly Gaussian distribution of fluctuation amplitudes, or conditional analysis using the amplitude of the floating potential as a condition is not a sensitive technique for identifying coherent structures

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.

Offshore production flares: a PETROBRAS review

Energy Technology Data Exchange (ETDEWEB)

Pagot, Paulo R.; Burmann, Clovis P.; Araujo, Paulo Bento de; Motomura, Tsukasa [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil)

2008-07-01

The purpose of the present work is to briefly present the offshore flare system technological evolution and the main design criteria for flare and its supporting structure. In order to perform the aimed task, this work was divided into two parts: the first part presents the technological evolution of the offshore production flares and the second one discusses the flare system designing criteria. The evolution of the technology associated to the offshore production flares is organized by the authors just dividing the history in four chronological phases. Each phase is defined by the predominant use of the, by the time, most up-to-date technological alternative and it will be described with the help of sketches, drawings, photographs, data and information about the platforms where such technologies were applied. The second part of the present work discusses the dimensional criteria, interesting aspects and flaws of the offshore flare systems in two different fields, which are: definition of the flare system capacity; and flow and thermal design of the flare system. (author)

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.

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....

The Reconfiguration of Service Production Systems in Response to Offshoring

DEFF Research Database (Denmark)

Brandl, Kristin; Mol, Michael J.; Petersen, Bent

2017-01-01

Purpose: A service production system has a structure composed of task execution, agents performing tasks and a resulting service output. The purpose of this paper is to understand how such a service production system changes as a consequence of offshoring.Design/methodology/approach: Drawing...... of a service production system in response to change ignited by offshoring. The authors find recurring effects between structures that enable and constrain agents and agents who shape the structure of the production system. Research limitations/implications: The paper offers a novel contribution to the service...... operations management literature by applying practice theory. Moreover, the authors propose a detailed, activity-driven view of service production systems and service offshoring. The authors contribute to practice theory by extending its domain to operations management.Practical implications...

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...

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...

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...

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.

Review of technology for Arctic offshore oil and gas recovery

Energy Technology Data Exchange (ETDEWEB)

Sackinger, W. M.

1980-08-01

The technical background briefing report is the first step in the preparation of a plan for engineering research oriented toward Arctic offshore oil and gas recovery. A five-year leasing schedule for the ice-prone waters of the Arctic offshore is presented, which also shows the projected dates of the lease sale for each area. The estimated peak production rates for these areas are given. There is considerable uncertainty for all these production estimates, since no exploratory drilling has yet taken place. A flow chart is presented which relates the special Arctic factors, such as ice and permafrost, to the normal petroleum production sequence. Some highlights from the chart and from the technical review are: (1) in many Arctic offshore locations the movement of sea ice causes major lateral forces on offshore structures, which are much greater than wave forces; (2) spray ice buildup on structures, ships and aircraft will be considerable, and must be prevented or accommodated with special designs; (3) the time available for summer exploratory drilling, and for deployment of permanent production structures, is limited by the return of the pack ice. This time may be extended by ice-breaking vessels in some cases; (4) during production, icebreaking workboats will service the offshore platforms in most areas throughout the year; (5) transportation of petroleum by icebreaking tankers from offshore tanker loading points is a highly probable situation, except in the Alaskan Beaufort; and (6) Arctic pipelines must contend with permafrost, making instrumentation necessary to detect subtle changes of the pipe before rupture occurs.

Device for retaining oil gushing out in an uncontrolled fashion from offshore platforms. [German patent

Energy Technology Data Exchange (ETDEWEB)

Hambrock, H J

1978-11-23

The spread of oil which emerges on a water surface in case of a fault is to be prevented and its removal is to be made possible by a sort of floating fence. This type of oil barrier is formed by a blown up, floating hose on the water surface which may be filled with plastic foam. It surrounds the centrally placed possible place of emergence of the oil in a circle, this may be an offshore platform or a stationary tanker. The concentric position is ensured by radially tensioned ropes. The protective ring can normally be pulled in (above all during bad weather) and need only be expanded for a short time in case of a fault. In order to prevent oil collected inside the protective ring being washed under or over it by the wind or waves, a circular attachment in the form of a collar can be blown up in the upward direction, and a similar apron hanging downwards loaded with weights may be provided.

Load Identification of Offshore Platform for Fatigue Life Estimation

DEFF Research Database (Denmark)

Perisic, Nevena; Kirkegaard, Poul Henning; Tygesen, Ulf T.

2014-01-01

of the structure and the discrete Kalman filter which recursively estimates unknown states of the system in real time. As a test-case, the algorithm is designed to estimate the equivalent total loading forces of the structure. The loads are estimated from noised displacement measurements of a single location...... on the topside of the offshore structure. The method is validated using simulated data for two wave loading cases: regular and irregular wave loadings.......The lifetime of an offshore platform is typically governed by accumulated fatigue damage. Thus, the load time history is an essential parameter for prediction of the lifetime of the structure and its components. Consequently, monitoring of structural loads is of special importance in relation to re...

Gaining Flexibility and Innovation through Offshore Outsourcing

Directory of Open Access Journals (Sweden)

Michela Pellicelli

2018-05-01

Full Text Available Recently, offshore outsourcing has become extremely important for companies that compete worldwide. In many industries, only companies that manage to be competitive globally can aspire to attain sustainable competitive advantages. Therefore, offshore outsourcing has become essential for many companies and recently has become more and more a vital part of the long-term strategies of the leading firms. The rapidly shifting conditions in the marketplace is forcing management to constantly review and defend its core competencies. Management is now confronted with a higher level of complexity and disruptions brought about in particular by the new waves of globalization and the irresistible march of technological changes. For these reasons, offshore outsourcing is transforming the functions of the traditional firms into a network of competencies. The tendency to offshore most of the productive and economic activities and processes can lead companies to transform themselves into virtual organizations, where all the functions could be outsourced through the formation of flexible networks and agile organizational structures.

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.

Modeling and Simulation of Offshore Wind Power Platform for 5 MW Baseline NREL Turbine

Science.gov (United States)

Roni Sahroni, Taufik

2015-01-01

This paper presents the modeling and simulation of offshore wind power platform for oil and gas companies. Wind energy has become the fastest growing renewable energy in the world and major gains in terms of energy generation are achievable when turbines are moved offshore. The objective of this project is to propose new design of an offshore wind power platform. Offshore wind turbine (OWT) is composed of three main structures comprising the rotor/blades, the tower nacelle, and the supporting structure. The modeling analysis was focused on the nacelle and supporting structure. The completed final design was analyzed using finite element modeling tool ANSYS to obtain the structure's response towards loading conditions and to ensure it complies with guidelines laid out by classification authority Det Norske Veritas. As a result, a new model of the offshore wind power platform for 5 MW Baseline NREL turbine was proposed. PMID:26550605

Catamaran or semi-submersible for floating platform - selection of a better design

Science.gov (United States)

Qasim, Idrees; Gao, Liangtian; Peng, Duojin; Liu, Bo

2018-02-01

With nonstop advancement in marine engineering, more and more new structures are being designed and explored for tidal current energy. There are three different kinds of support structures for tidal current power station mostly in use, which are sea-bed mounted/gravity based system, pile mounted system and floating moored platform. Comparing all of them, the floating mooring system is most suitable for deep water systems and the application of this arrangement is widely usable. In this paper, a semi-submersible and a catamaran as floating platforms for tidal current power stations are studied are compared on the basis of its economics, efficiency of turbine and stability of the station. Based on basic ship theory and using software MAXSURF, the stability of Catamaran tidal current power station is also calculated. It is found that the catamaran design is optimal choice.

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....

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....

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.

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 ...

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

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

Validated Loads Prediction Models for Offshore Wind Turbines for Enhanced Component Reliability

DEFF Research Database (Denmark)

Koukoura, Christina

To improve the reliability of offshore wind turbines, accurate prediction of their response is required. Therefore, validation of models with site measurements is imperative. In the present thesis a 3.6MW pitch regulated-variable speed offshore wind turbine on a monopole foundation is built...... are used for the modification of the sub-structure/foundation design for possible material savings. First, the background of offshore wind engineering, including wind-wave conditions, support structure, blade loading and wind turbine dynamics are presented. Second, a detailed description of the site...

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

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.

Natural frequency and vibration analysis of jacket type foundation for offshore wind power

Science.gov (United States)

Hung, Y.-C.; Chang, Y.-Y.; Chen, S.-Y.

2017-12-01

There are various types of foundation structure for offshore wind power, engineers may assess the condition of ocean at wind farm, and arrange the transportation, installation of each structure members, furthermore, considering the ability of manufacture steel structure as well, then make an optimum design. To design jacket offshore structure, unlike onshore cases, offshore structure also need to estimate the wave excitation effect. The aim of this paper is to study the difference of natural frequency between different kinds of structural stiffness and discuss the effect of different setting of boundary condition during analysis, besides, compare this value with the natural frequency of sea wave, in order to avoid the resonance effect. In this paper, the finite element analysis software ABAQUS is used to model and analyze the natural vibration behavior of the jacket structure.

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...

14 CFR 23.753 - Main float design.

Science.gov (United States)

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Main float design. 23.753 Section 23.753... STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES Design and Construction Floats and Hulls § 23.753 Main float design. Each seaplane main float must meet the requirements of § 23.521. [Doc...

Impact of offshore nuclear generating stations on recreational behavior at adjacent coastal sites. Technical report

International Nuclear Information System (INIS)

Baker, E.J.; Moss, D.J.; West, S.G.; Weyant, J.K.

1977-12-01

A multi-faceted investigation was undertaken to project the impact of offshore nuclear power plants on beach visitation at adjacent beaches. 1. Related literature was reviewed concerning human adjustment to natural hazards, risk-taking behavior, and public attitudes toward nuclear power. 2. Approximately 2400 people were interviewed at beaches in three states with respect to: (a) intended avoidance of beaches near a hypothetical floating nuclear plant (FNP), (b) relative importance of proximity to a FNP, when compared to other beach attributes, (c) onshore-offshore preference for coastal nuclear plant location, (d) behavioral impact of NRC licensing of FNP's, (e) relative tourism impact of coastal nuclear plant compared to coastal coal-fired plant, (f) public concerns about nuclear safety, (g) public attitudes toward alternative energy sources, (h) public confidence in sources of information about nuclear power, (i) visual impact of a FNP, and (j) knowledge about nuclear power. 3. Four beach areas near currently operating coastal nuclear power plants were studied to assess impacts on tourism resulting from plant construction. Data suggest that proximity of a FNP is less important than other beach attributes in determining beach attractiveness, probably no more than (and perhaps less than) 5% to 10% of current beach patrons would avoid a beach after FNP siting three miles directly offshore, and impact of a FNP would decrease exponentially as distance away increased

Stochastic study on entrainment of floating particles with intake of cooling water of a power plant

International Nuclear Information System (INIS)

Kadoyu, Masatake; Wada, Akira

1979-01-01

The mortality of ichthyoplanktons, contained in the sea water passing through the cooling water systems of a power plant, may be associated with rising temperature and mechanical effect. In this study, the range and the rate of entrainment of the organisms like ichthyoplanktons floating in the sea caused by the intake of cooling water were stochastically investigated by simulating the average current as well as the flow caused by the intake of water and by taking into consideration random velocity fluctuation without these flows, using a mathematical model. An intake was set along the straight coastline in semi-infinite sea, and the rate of inflow of particles into the intake was simulated by a mathematical model. In the numerical simulation, the average flow as coastal current component and the flow caused by the intake of water were obtained with the hydrodynamic equations of motion and continuity, and the rate of entrainment of floating particles was examined by giving turbulence to the particles in the sea and by calculating the position of each particle every moment. The results are as follows; 1) The range of entrainment of floating particles by the intake of cooling water and its probability were obtained in consideration of the flow rate of cooling water, coast current velocity and diffusion coefficient as parameters. 2) The extent of inflow of floating particles considerably varied with tidal amplitude, diffusion coefficient and the flow rate of cooling water in the sea where the coastal flow has clear periodicity. 3) The extent of entrainment was considerably influenced by the steady current velocity, the velocity distribution in offshore direction and the intake volume in the sea where periodicity is not observed. (Nakai, Y.)

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

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...

Experimental Comparison of Dynamic Responses of a Tension Moored Floating Wind Turbine Platform with and without Spring Dampers

Science.gov (United States)

Wright, C.; O'Sullivan, K.; Murphy, J.; Pakrashi, V.

2015-07-01

The offshore wind industry is rapidly maturing and is now expanding to more extreme environments in deeper water and farther from shore. To date fixed foundation types (i.e. monopoles, jackets) have been primarily used but become uneconomical in water depths greater than 50m. Floating foundations have more complex dynamics but at the moment no design has reached commercialization, although a number of devices are being tested at prototype stage. The development of concepts is carried out through physical model testing of scaled devices such that to better understand the dynamics of the system and validate numerical models. This paper investigates the testing of a scale model of a tension moored wind turbine at two different scales and in the presence and absence of a spring damper controlling its dynamic response. The models were tested under combined wave and wind thrust loading conditions. The analysis compares the motions of the platform at different scales and structural conditions through RAO, testing a mooring spring damper for load reductions.

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)

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...

A flexible capacitive tactile sensing array with floating electrodes

International Nuclear Information System (INIS)

Cheng, M-Y; Huang, X-H; Ma, C-W; Yang, Y-J

2009-01-01

In this work, we present the development of a capacitive tactile sensing array realized by using MEMS fabrication techniques and flexible printed circuit board (FPCB) technologies. The sensing array, which consists of two micromachined polydimethlysiloxane (PDMS) structures and a FPCB, will be used as the artificial skin for robot applications. Each capacitive sensing element comprises two sensing electrodes and a common floating electrode. The sensing electrodes and the metal interconnect for signal scanning are implemented on the FPCB, while the floating electrode is patterned on one of the PDMS structures. This special design can effectively reduce the complexity of the device structure and thus makes the device highly manufacturable. The characteristics of the devices with different dimensions are measured and discussed. The corresponding scanning circuits are also designed and implemented. The tactile images induced by the PMMA stamps of different shapes are also successfully captured by a fabricated 8 × 8 array

Too much or too little of R&D offshoring : The impact of captive offshoring and contract offshoring on innovation performance

NARCIS (Netherlands)

Steinberg, Philip; Procher, Vivien D.; Urbig, Diemo

2017-01-01

Innovating firms may acquire foreign knowledge and improve their innovation performance by offshoring their R&D activities to their own foreign affiliates (captive offshoring) as well as by contracting out their R&D to external foreign parties (contract offshoring). This study examines the impact of

The method of rapid design of the folding bridge based on floating supports

Directory of Open Access Journals (Sweden)

Jan Marszałek

2016-09-01

Full Text Available The article includes a methodology for the rapid design of the folding bridge based on floating supports. This methodology includes an analysis of the possibilities of using blocks from the park pontoon PP-64 as a support for the floating folding DMS-65 bridge, built as a tem-porary crossing for civilian application. The analysis was carried out for the bridge loaded with a moving vehicle. The results of this analysis have been developed in the form of nomograms that enable rapid development of crossings in different structural systems.[b]Keywords[/b]: civil engineering, folding bridges, floating supports

Review of technology for Arctic offshore oil and gas recovery. Appendices

Energy Technology Data Exchange (ETDEWEB)

Sackinger, W. M.

1980-06-06

This volume contains appendices of the following: US Geological Survey Arctic operating orders, 1979; Det Noske Vertas', rules for the design, construction and inspection of offshore technology, 1977; Alaska Oil and Gas Association, industry research projects, March 1980; Arctic Petroleum Operator's Association, industry research projects, January 1980; selected additional Arctic offshore bibliography on sea ice, icebreakers, Arctic seafloor conditions, ice-structures, frost heave and structure icing.

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

Safety in offshore engineering an academic course covering safety in offshore wind

NARCIS (Netherlands)

Cerda Salzmann, D.J.

2011-01-01

Offshore projects are known for their challenging conditions, generally leading to high risks. Therefore no offshore project can go without a continuous and extensive assessment on safety issues. The Delft University of Technology is currently developing a course "Safety in Offshore Engineering"

What can wave energy learn from offshore oil and gas?

Science.gov (United States)

Jefferys, E R

2012-01-28

This title may appear rather presumptuous in the light of the progress made by the leading wave energy devices. However, there may still be some useful lessons to be learnt from current 'offshore' practice, and there are certainly some awful warnings from the past. Wave energy devices and the marine structures used in oil and gas exploration as well as production share a common environment and both are subject to wave, wind and current loads, which may be evaluated with well-validated, albeit imperfect, tools. Both types of structure can be designed, analysed and fabricated using similar tools and technologies. They fulfil very different missions and are subject to different economic and performance requirements; hence 'offshore' design tools must be used appropriately in wave energy project and system design, and 'offshore' cost data should be adapted for 'wave' applications. This article reviews the similarities and differences between the fields and highlights the differing economic environments; offshore structures are typically a small to moderate component of field development cost, while wave power devices will dominate overall system cost. The typical 'offshore' design process is summarized and issues such as reliability-based design and design of not normally manned structures are addressed. Lessons learned from poor design in the past are discussed to highlight areas where care is needed, and wave energy-specific design areas are reviewed. Opportunities for innovation and optimization in wave energy project and device design are discussed; wave energy projects must ultimately compete on a level playing field with other routes to low CO₂ energy and/or energy efficiency. This article is a personal viewpoint and not an expression of a ConocoPhillips position.

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.

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.

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.

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.

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....

The impact of the night float system on internal medicine residency programs.

Science.gov (United States)

Trontell, M C; Carson, J L; Taragin, M I; Duff, A

1991-01-01

To study the design, method of implementation, perceived benefits, and problems associated with a night float system. Self-administered questionnaire completed by program directors, which included both structured and open-ended questions. The answers reflect resident and student opinions as well as those of the program directors, since program directors regularly obtain feedback from these groups. The 442 accredited internal medicine residency programs listed in the 1988-89 Directory of Graduate Medical Education Programs. Of the 442 programs, 79% responded, and 30% had experience with a night float system. The most frequent methods for initiating a night float system included: decreasing elective time (42.3%), hiring more residents (26.9%), creating a non-teaching service (12.5%), and reallocating housestaff time (9.6%). Positive effects cited include decreased fatigue, improved housestaff morale, improved recruiting, and better attitude toward internal medicine training. The quality of medical care was considered the same or better by most programs using it. The most commonly cited problems were decreased continuity of care, inadequate teaching of the night float team, and miscommunication. Residency programs using a night float system usually observe a positive effect on housestaff morale, recruitment, and working hours and no detrimental effect on the quality of patient care. Miscommunication and inadequate learning experience for the night float team are important potential problems. This survey suggests that the night float represents one solution to reducing resident working hours.

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.

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.

Simplified Technique for Predicting Offshore Pipeline Expansion

Science.gov (United States)

Seo, J. H.; Kim, D. K.; Choi, H. S.; Yu, S. Y.; Park, K. S.

2018-06-01

In this study, we propose a method for estimating the amount of expansion that occurs in subsea pipelines, which could be applied in the design of robust structures that transport oil and gas from offshore wells. We begin with a literature review and general discussion of existing estimation methods and terminologies with respect to subsea pipelines. Due to the effects of high pressure and high temperature, the production of fluid from offshore wells is typically caused by physical deformation of subsea structures, e.g., expansion and contraction during the transportation process. In severe cases, vertical and lateral buckling occurs, which causes a significant negative impact on structural safety, and which is related to on-bottom stability, free-span, structural collapse, and many other factors. In addition, these factors may affect the production rate with respect to flow assurance, wax, and hydration, to name a few. In this study, we developed a simple and efficient method for generating a reliable pipe expansion design in the early stage, which can lead to savings in both cost and computation time. As such, in this paper, we propose an applicable diagram, which we call the standard dimensionless ratio (SDR) versus virtual anchor length (L A ) diagram, that utilizes an efficient procedure for estimating subsea pipeline expansion based on applied reliable scenarios. With this user guideline, offshore pipeline structural designers can reliably determine the amount of subsea pipeline expansion and the obtained results will also be useful for the installation, design, and maintenance of the subsea pipeline.

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....

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

A preliminary analysis of floating production storage and offloading facilities with gas liquefaction processes

DEFF Research Database (Denmark)

Nguyen, Tuong-Van; Carranza-Sánchez, Yamid Alberto; Junior, Silvio de Oliveira

2016-01-01

Floating, production, storage and offloading (FPSO) plants are facilities used in upstream petroleum processing. They have gained interest because they are more flexible than conventional plants and can be used for producing oil and gas in deep-water fields. In general, gas export is challenging...... because of the lack of infrastructure in remote locations. The present work investigates the possibility of integrating liquefaction processes on such facilities, considering two mixed-refrigerant and two expansion-based processes suitable for offshore applications. Two FPSO configurations are considered...... in this work, and they were suggested by Brazilian operators for fields processing natural gas with moderate to high content of carbon dioxide. The performance of the combined systems is analysed by conducting energy and exergy analyses. The integration of gas liquefaction results in greater power consumption...

Modeling and Simulation of Offshore Wind Power Platform for 5 MW Baseline NREL Turbine

Directory of Open Access Journals (Sweden)

Taufik Roni Sahroni

2015-01-01

Full Text Available This paper presents the modeling and simulation of offshore wind power platform for oil and gas companies. Wind energy has become the fastest growing renewable energy in the world and major gains in terms of energy generation are achievable when turbines are moved offshore. The objective of this project is to propose new design of an offshore wind power platform. Offshore wind turbine (OWT is composed of three main structures comprising the rotor/blades, the tower nacelle, and the supporting structure. The modeling analysis was focused on the nacelle and supporting structure. The completed final design was analyzed using finite element modeling tool ANSYS to obtain the structure’s response towards loading conditions and to ensure it complies with guidelines laid out by classification authority Det Norske Veritas. As a result, a new model of the offshore wind power platform for 5 MW Baseline NREL turbine was proposed.

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.

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

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...

Time Domain Response Analysis of Barge Floater Supporting an Offshore Wind Turbine

Directory of Open Access Journals (Sweden)

A.C. Mayilvahanan

2011-12-01

Full Text Available Wind energy is a reliable source of sustainable power generation and has been an active area of research globally to economically harness the energy for human use. Reliable source of wind energy pushed the engineers to install wind turbines near and far off the coasts. In shallow water upto 100 m, fixed structures like tripods, jackets, monopiles and gravity base are functionally and economically feasible. In deep waters, a floating substructure can be more economical for offshore wind turbine. In this study a barge type floater of different aspect ratios from 0.4 to 1.0 is investigated for its performance under wave and wind loading. All these floaters were designed with a defined transverse metacentric height (GM equal to 1.0 m and the hydrodynamic analysis is carried out using WAMIT. The barge with aspect ratio B/L = 1.0 is found to have lowest pitch RAO. The time domain surge, heave and pitch response for this barge has been obtained using Integro-differential equation of motion and the statistical response characteristics are compared for two different cases of excitation namely, wave excitation alone and combined wave and wind excitation. Statistics of surge, heave and pitch responses are obtained for three different seas states and for two different wave heading angles.

LiDAR observation of the flow structure in typhoons

Science.gov (United States)

Wu, Yu-Ting; Hsuan, Chung-Yao; Lin, Ta-Hui

2015-04-01

Taiwan is subject to 3.4 landfall typhoons each year in average, generally occurring in the third quarter of every year (July-September). Understanding of boundary-layer turbulence characteristics of a typhoon is needed to ensure the safety of both onshore and offshore wind turbines used for power generation. In this study, a floating LiDAR (Light Detection and Ranging) was deployed in a harbor to collect data of wind turbulence, atmospheric pressure, and temperature in three typhoon events (Matmo typhoon, Soulik typhoon, Trami typhoon). Data collected from the floating LiDAR and from meteorological stations located at Taipei, Taichung and Kaohsiung are adopted to analyse the wind turbulence characteristics in the three typhoon events. The measurement results show that the maximum 10-min average wind speed measured with the floating LiDAR is up to 24 m/s at a height of 200 m. Compared with other normal days, the turbulence intensity is lower in the three typhoon events where the wind speed has a rapid increase. Changes of wind direction take place clearly as the typhoons cross Taiwan from East to West. Within the crossing intervals, the vertical momentum flux is observed to have a significant pattern with both upward and downward propagating waves which are relevant to the flow structure of the typhoons.

Hiding and feeding in floating seaweed: Floating seaweed clumps as possible refuges or feeding grounds for fishes

Science.gov (United States)

Vandendriessche, Sofie; Messiaen, Marlies; O'Flynn, Sarah; Vincx, Magda; Degraer, Steven

2007-02-01

Floating seaweed is considered to be an important habitat for juvenile fishes due to the provision of food, shelter, a visual orientation point and passive transport. The importance of the presence of the highly dynamical seaweed clumps from the North Sea to juvenile neustonic fishes was investigated by analysing both neuston samples (without seaweed) and seaweed samples concerning fish community structure, and length-frequency distributions and feeding habits of five associated fish species. While the neustonic fish community was mainly seasonally structured, the seaweed-associated fish community was more complex: the response of the associated fish species to environmental variables was species specific and probably influenced by species interactions, resulting in a large multivariate distance between the samples dominated by Chelon labrosus and the samples dominated by Cyclopterus lumpus, Trachurus trachurus and Ciliata mustela. The results of the stomach analysis confirmed that C. lumpus is a weedpatch specialist that has a close spatial affinity with the seaweed and feeds intensively on the seaweed-associated invertebrate fauna. Similarly, C. mustela juveniles also fed on the seaweed fauna, but in a more opportunistic way. The shape of the size-frequency distribution suggested enhanced growth when associated with floating seaweed. Chelon labrosus and T. trachurus juveniles were generally large in seaweed samples, but large individuals were also encountered in the neuston. The proportion of associated invertebrate fauna in their diet was of minor importance, compared to the proportions in C. lumpus. Individuals of Syngnathus rostellatus mainly fed on planktonic invertebrates but had a discontinuous size-frequency distribution, suggesting that some of the syngnathids were carried with the seaweed upon detachment and stayed associated. Floating seaweeds can therefore be regarded as ephemeral habitats shared between several fish species (mainly juveniles) that use

Two-dimensional neutron scattering in a floating heavy water bridge

International Nuclear Information System (INIS)

Fuchs, Elmar C; Baroni, Patrick; Noirez, Laurence; Bitschnau, Brigitte

2010-01-01

When a high voltage is applied to pure water in two filled beakers kept close to each other, a connection forms spontaneously, giving the impression of a floating water bridge. This phenomenon is of special interest, since it comprises a number of phenomena currently tackled in modern water science. In this work, the first two-dimensional structural study of a floating heavy water bridge is presented as a function of the azimuthal angle. A small anisotropy in the angular distribution of the intensity of the first structural peak was observed, indicating a preferred orientation of a part of the D 2 O molecules along the electric field lines without breaking the local tetrahedral symmetry. The experiment is carried out by neutron scattering on a D 2 O bridge.

Two-dimensional neutron scattering in a floating heavy water bridge

Science.gov (United States)

Fuchs, Elmar C.; Baroni, Patrick; Bitschnau, Brigitte; Noirez, Laurence

2010-03-01

When a high voltage is applied to pure water in two filled beakers kept close to each other, a connection forms spontaneously, giving the impression of a floating water bridge. This phenomenon is of special interest, since it comprises a number of phenomena currently tackled in modern water science. In this work, the first two-dimensional structural study of a floating heavy water bridge is presented as a function of the azimuthal angle. A small anisotropy in the angular distribution of the intensity of the first structural peak was observed, indicating a preferred orientation of a part of the D2O molecules along the electric field lines without breaking the local tetrahedral symmetry. The experiment is carried out by neutron scattering on a D2O bridge.

Review of control algorithms for offshore wind turbines

Energy Technology Data Exchange (ETDEWEB)

Spruce, C J; Markou, H; Leithead, W E; Dominguez Ruiz, S

2005-07-01

Innovative turbine control strategies could allow the improvements to cost and performance considered essential to reduce the cost of energy from offshore wind farms around the UK. This project reviewed and investigated the possibility for further development of a power control algorithm originally developed by NEG Micon Rotors Ltd for use with offshore wind turbines in the hope that more advanced algorithms would reduce the loads on, and hence the costs of, components such as the foundation/support structure, tower, blades and bedplate. Three models (simulation model, linearisation of the simulation model and control model) were produced in order to conduct the review. Application of these models produced the conclusion that the size of the latest generation of offshore wind turbines has now reached a level where performance is starting to be constrained by fundamental factors in the dynamics caused by the machine's physical size. It was also concluded that an ideal control strategy could achieve potential cost savings for the tower and support structure of 5-10% of the total cost of the turbine plus support structure. Further work to develop controllers to reduce loads in the tower and support structure is urged. The report considers non-linear simulation, the linear model, the control model, general operation of the controller, the drive train damping filter, torque control, pitch control and advanced algorithms, and makes detailed recommendations for future work.

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.

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....

Nonconsensual clinical trials: a foreseeable risk of offshoring under global corporatism.

Science.gov (United States)

Spielman, Bethany

2015-03-01

This paper explores the connection of offshoring and outsourcing to nonconsensual global pharmaceutical trials in low-income countries. After discussing reasons why the topic of nonconsensual offshored clinical trials may be overlooked in bioethics literature, I suggest that when pharmaceutical corporations offshore clinical trials today, nonconsensual experiments are often foreseeable and not simply the result of aberrant ethical conduct by a few individuals. Offshoring of clinical trials is structured so that experiments can be presented as health care in a unique form of outsourcing from the host country to pharmaceutical corporations. Bioethicists' assessments of the risks and potential benefits of offshore corporate pharmaceutical trials should therefore systematically include not only the hoped for benefits and the risks of the experimental drug but also the risk that subjects will not have consented, as well as the broader international consequences of nonconsensual experimentation.

14 CFR 25.753 - Main float design.

Science.gov (United States)

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Main float design. 25.753 Section 25.753 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Design and Construction Floats and Hulls § 25.753 Main float design...

Internationalization in the offshore sector and the use of strategic alliances. Kongsberg Offshore AS - A case study; Internasjonalisering i offshorebransjen og bruk av strategiske allianser. Kongsberg Offshore AS - et casestudium

Energy Technology Data Exchange (ETDEWEB)

Enger, Ole Peder; Andreassen, Yngve

2000-06-01

The structure of the Norwegian offshore sector is characterized by many small technology companies and only a few big ones. At the same time, operators prefer to deal with as few contractors as possible. Thus, the small technology companies must operate as subcontractors or cooperate as joint venture companies in order to win supply contracts. This report studies Kongsberg Offshore AS, or KOS, which is a daughter company of Food Machinery Corporation (FMC). KOS is a leading supplier of ''turnkey'' systems for sub see production and measuring systems and has had great success in its internationalization.

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.

Model-Based Control of a Ballast-Stabilized Floating Wind Turbine Exposed to Wind and Waves

DEFF Research Database (Denmark)

Christiansen, Søren

2013-01-01

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 hy-drodynamics 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...

Domestic R&D and Offshoring

DEFF Research Database (Denmark)

Junge, Martin; Sørensen, Anders

2017-01-01

survey and register data. No evidence is found for a lower probability of own R&D after offshoring takes place compared to before. Moreover, offshoring does not lead to lower R&D intensity in general. However, firms that offshore R&D activity have larger R&D intensity after offshoring has taken place...

Stochastic dynamic response analysis of spar-type wind turbines with catenary or taut mooring systems

Energy Technology Data Exchange (ETDEWEB)

Karimirad, Madjid

2011-03-15

Floating wind turbines can be the most practical and economical way to extract the vast offshore wind energy resources at deep and intermediate water depths. The Norwegian Ministry of Petroleum and Energy is strongly committed to developing offshore wind technology that utilises available renewable energy sources. As the wind is steadier and stronger over the sea than over land, the wind industry recently moved to offshore areas. Analysis of the structural dynamic response of offshore wind turbines subjected to stochastic wave and wind loads is an important aspect of the assessment of their potential for power production and of their structural integrity. Of the concepts that have been proposed for floating wind turbines, spar-types such as the catenary moored spar (CMS) and tension leg spar (TLS) wind turbines seem to be well-suited to the harsh environmental conditions that exist in the North Sea. Hywind and Sway are two examples of such Norwegian concepts; they are based on the CMS and TLS, respectively. Floating wind turbines are sophisticated structures that are subjected to simultaneous wind and wave actions. The coupled nonlinear structural dynamics and motion response equations of these turbines introduce geometrical nonlinearities through the relative motions and velocities. Moreover, the hydrodynamic and aerodynamic loading of this type of structure is nonlinear. A floating wind turbine is a multi body aero-hydro-servo-elastic structural system; for such structures, the coupled nonlinear equations of motion considering nonlinear excitation and damping forces, including all wave- and wind-induced features, should be solved in the time domain. In this thesis, the motion and structural responses for operational and extreme environmental conditions were considered to investigate the performance and the structural integrity of spar-type floating wind turbines. The power production and the effects of aerodynamic and hydrodynamic damping, including wind