Hyunkyoung Shin, Youngjae Yu, T. Pham, Junbae Kim, Rupesh Kumar
Since the Paris Conference of the parties in 2015, interest in renewable energy around the world is higher than ever. Korea also has plans to increase the proportion of renewable energy to 20% by 2030 through the renewable energy 3020 policy. Of these, 16.5GW is filled with wind power, the installation area is expanding from land to sea. Among them, some of big plans are using floating offshore wind turbines based on the marine environments in Korea. In this study, numerical simulations of the NREL 5MW wind turbine were performed using NREL FAST V.8. A comparison was made between two types of floaters, spar and semi-submersible, installed 58km off the Ulsan Coast with 150m water depth in the East Sea, Korea. The environmental data were obtained from the Meteorological Administration’s measured data and NASA’s reanalysis data, MERRA-2. Design Load Cases were selected by referring to IEC 61400-3. Maximum moments at both blade root and tower base, six-degrees of freedom motions and three mooring line tensions were compared.
自2015年巴黎气候变化大会以来，世界各国对可再生能源的兴趣空前高涨。韩国也计划通过“可再生能源3020”政策，到2030年将可再生能源的比重提高到20%。其中，16.5吉瓦是风力发电，安装面积正在从陆地扩展到海洋。其中，以韩国海洋环境为基础，使用浮动式海上风力发电机的大型计划也不少。在本研究中，使用NREL FAST V.8对NREL 5MW风力机进行了数值模拟。在韩国东部海域蔚山海岸58公里处、水深150米的海面上安装的浮筒和半潜式浮筒进行了比较。环境数据来自美国气象局的测量数据和美国宇航局的MERRA-2再分析数据。设计负载案例的选择参照IEC 61400-3。比较了叶片根部和塔底的最大力矩、六自由度运动和三种系缆张力。
{"title":"Numerical Simulations of OC3 Spar and OC4 Semi-Submersible Type Platforms Under Extreme Conditions in the East Sea, Korea","authors":"Hyunkyoung Shin, Youngjae Yu, T. Pham, Junbae Kim, Rupesh Kumar","doi":"10.1115/omae2019-95919","DOIUrl":"https://doi.org/10.1115/omae2019-95919","url":null,"abstract":"\u0000 Since the Paris Conference of the parties in 2015, interest in renewable energy around the world is higher than ever. Korea also has plans to increase the proportion of renewable energy to 20% by 2030 through the renewable energy 3020 policy. Of these, 16.5GW is filled with wind power, the installation area is expanding from land to sea. Among them, some of big plans are using floating offshore wind turbines based on the marine environments in Korea. In this study, numerical simulations of the NREL 5MW wind turbine were performed using NREL FAST V.8. A comparison was made between two types of floaters, spar and semi-submersible, installed 58km off the Ulsan Coast with 150m water depth in the East Sea, Korea. The environmental data were obtained from the Meteorological Administration’s measured data and NASA’s reanalysis data, MERRA-2. Design Load Cases were selected by referring to IEC 61400-3. Maximum moments at both blade root and tower base, six-degrees of freedom motions and three mooring line tensions were compared.","PeriodicalId":306681,"journal":{"name":"Volume 10: Ocean Renewable Energy","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124447089","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Fontanella, I. Bayati, F. Taruffi, A. Facchinetti, M. Belloli
This paper presents the main results of an experimental campaign about the DeepCwind semi-submersible floating offshore wind turbine (FOWT), that was carried out at Politecnico di Milano wind tunnel, adopting a hybrid hardware-in-the-loop (HIL) testing technique. Differently from previous works by the authors, this further analysis herein reported, is specifically focused on evaluating the effects of aerodynamic loads on the FOWT platform motions. In order to reproduce the FOWT response to combined wind and waves in a wind tunnel, exploiting the high-quality flow, a HIL system was used. The aerodynamic and rotor loads were reproduced by means of a wind turbine scale model operating inside the wind tunnel and were combined with numerically generated wave loads for real-time integration of the FOWT rigid-body motion equations. The resulting platform motions were imposed to the wind turbine scale model by a hydraulic actuation system. A series of HIL tests was performed to assess the rotor loads effect on the FOWT response. Free-decay tests in still water under laminar un-sheared wind were carried out to evaluate how the aerodynamic forcefield modifies the platform modes frequency and damping. Irregular wave tests for different steady winds were performed to investigate the dependency of platform motion from the wind turbine operating conditions. A FAST v8 model of the studied floating system was developed to support the analysis and numerical simulations were performed to reproduce environmental conditions equivalent to those of the experimental tests. The FAST model prediction capability is discussed against HIL wind tunnel tests results.
{"title":"Numerical and Experimental Wind Tunnel Analysis of Aerodynamic Effects on a Semi-Submersible Floating Wind Turbine Response","authors":"A. Fontanella, I. Bayati, F. Taruffi, A. Facchinetti, M. Belloli","doi":"10.1115/omae2019-95976","DOIUrl":"https://doi.org/10.1115/omae2019-95976","url":null,"abstract":"\u0000 This paper presents the main results of an experimental campaign about the DeepCwind semi-submersible floating offshore wind turbine (FOWT), that was carried out at Politecnico di Milano wind tunnel, adopting a hybrid hardware-in-the-loop (HIL) testing technique. Differently from previous works by the authors, this further analysis herein reported, is specifically focused on evaluating the effects of aerodynamic loads on the FOWT platform motions. In order to reproduce the FOWT response to combined wind and waves in a wind tunnel, exploiting the high-quality flow, a HIL system was used. The aerodynamic and rotor loads were reproduced by means of a wind turbine scale model operating inside the wind tunnel and were combined with numerically generated wave loads for real-time integration of the FOWT rigid-body motion equations. The resulting platform motions were imposed to the wind turbine scale model by a hydraulic actuation system. A series of HIL tests was performed to assess the rotor loads effect on the FOWT response. Free-decay tests in still water under laminar un-sheared wind were carried out to evaluate how the aerodynamic forcefield modifies the platform modes frequency and damping. Irregular wave tests for different steady winds were performed to investigate the dependency of platform motion from the wind turbine operating conditions. A FAST v8 model of the studied floating system was developed to support the analysis and numerical simulations were performed to reproduce environmental conditions equivalent to those of the experimental tests. The FAST model prediction capability is discussed against HIL wind tunnel tests results.","PeriodicalId":306681,"journal":{"name":"Volume 10: Ocean Renewable Energy","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130963196","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The horizontal-axis tidal current turbine is often installed in near-surface to use the high flow velocity of tidal current, and many designers have found the effect of wave on the hydrodynamic performance of tidal current turbine. The present study focuses on the hydrodynamic analysis of a tidal current turbine in a horizontal axis under the condition of regular waves, based on CFD method. The experimental data are used to verify the feasibility of the method. A non-dimensional parameter k is defined as the ratio of tip submergence to wave amplitude. It is shown that the numerical method is good to predict the hydrodynamic performance of horizontal axis turbine. By comparing the power coefficient and axial load coefficient in different tip submergence and wave amplitude, the effects of tip submergence and wave amplitude on the hydrodynamic performance of tidal current turbine are analyzed.
{"title":"CFD-Based Study of a Tidal Current Turbine in a Horizontal Axis Under Regular Waves","authors":"Jing Liu, Longfei Xiao, Feng-mei Jing","doi":"10.1115/omae2019-95231","DOIUrl":"https://doi.org/10.1115/omae2019-95231","url":null,"abstract":"\u0000 The horizontal-axis tidal current turbine is often installed in near-surface to use the high flow velocity of tidal current, and many designers have found the effect of wave on the hydrodynamic performance of tidal current turbine. The present study focuses on the hydrodynamic analysis of a tidal current turbine in a horizontal axis under the condition of regular waves, based on CFD method. The experimental data are used to verify the feasibility of the method. A non-dimensional parameter k is defined as the ratio of tip submergence to wave amplitude. It is shown that the numerical method is good to predict the hydrodynamic performance of horizontal axis turbine. By comparing the power coefficient and axial load coefficient in different tip submergence and wave amplitude, the effects of tip submergence and wave amplitude on the hydrodynamic performance of tidal current turbine are analyzed.","PeriodicalId":306681,"journal":{"name":"Volume 10: Ocean Renewable Energy","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129388956","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper presents aerodynamic simulation and analysis of a horizontal axis wind turbine using Computational Fluid Dynamics (CFD) method. The MEXICO (Model Rotor Experiments In Controlled Conditions) Experiment wind turbine is selected for simulation as the experimental data are available and can be used for validation of the CFD model used. CFD method has been used by a number of studies to predict aerodynamic behaviour of wind turbines. However, the majority of studies consider a steady wind flow at the inlet. Sometimes this is not the case when the wind flow is not steady or there are other wind turbines nearby. In this paper, the steady simulations are first conducted using different turbulence models without considering inflow wake at the inlet. Afterwards, a harmonic wake is generated at the inlet and unsteady CFD simulation is performed. Unsteady CFD simulation usually requires long runtime and therefore harmonic (frequency domain) method, which is an efficient computational method to study unsteady periodic flow at a computational cost in the order of steady-state solutions, is used for unsteady computation in this study. This paper first discusses the pressure coefficient distributions with and without harmonic wake at the inlet and compares them against the experiment. Afterwards the detailed analysis of flow around the blade subject to the unsteady harmonic wake is conducted in the meridional view and the blade-to-blade view. Next, the effect of pressure distribution on the blade structure is briefly discussed. Finally this paper concludes based on the results from the aerodynamic analysis as well as the analysis of the effect of aerodynamic loads on the blade structure.
{"title":"Aerodynamic Analysis of a Wind Turbine With Elevated Inflow Turbulence and Wake Using Harmonic Method","authors":"S. W. Naung, M. Rahmati, H. Farokhi","doi":"10.1115/omae2019-96769","DOIUrl":"https://doi.org/10.1115/omae2019-96769","url":null,"abstract":"\u0000 This paper presents aerodynamic simulation and analysis of a horizontal axis wind turbine using Computational Fluid Dynamics (CFD) method. The MEXICO (Model Rotor Experiments In Controlled Conditions) Experiment wind turbine is selected for simulation as the experimental data are available and can be used for validation of the CFD model used. CFD method has been used by a number of studies to predict aerodynamic behaviour of wind turbines. However, the majority of studies consider a steady wind flow at the inlet. Sometimes this is not the case when the wind flow is not steady or there are other wind turbines nearby. In this paper, the steady simulations are first conducted using different turbulence models without considering inflow wake at the inlet. Afterwards, a harmonic wake is generated at the inlet and unsteady CFD simulation is performed. Unsteady CFD simulation usually requires long runtime and therefore harmonic (frequency domain) method, which is an efficient computational method to study unsteady periodic flow at a computational cost in the order of steady-state solutions, is used for unsteady computation in this study. This paper first discusses the pressure coefficient distributions with and without harmonic wake at the inlet and compares them against the experiment. Afterwards the detailed analysis of flow around the blade subject to the unsteady harmonic wake is conducted in the meridional view and the blade-to-blade view. Next, the effect of pressure distribution on the blade structure is briefly discussed. Finally this paper concludes based on the results from the aerodynamic analysis as well as the analysis of the effect of aerodynamic loads on the blade structure.","PeriodicalId":306681,"journal":{"name":"Volume 10: Ocean Renewable Energy","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124657098","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The University of Maynooth is hosting a competition to develop a control strategy for a heaving point absorber wave energy converter (WEC). A linear model predictive control (MPC) design for the competition is presented. The state space model used in the MPC was derived numerically from the provided WEC-Sim model using linear system identification methods. A Kalman filter was used as the estimator, while also serving as an unknown input estimator to provide estimates of the excitation force on the WEC. The required excitation force predictions were made using an autoregressive linear prediction model. The inputs to the prediction model included estimated wave excitation forces and measured water surface elevation values from an up-field wave probe. Simulation results of the final control system design are also presented for each of the six wave cases specified by the competition organizers.
{"title":"Development of a Model Predictive Controller for the Wave Energy Converter Control Competition","authors":"Bradley A. Ling","doi":"10.1115/omae2019-95544","DOIUrl":"https://doi.org/10.1115/omae2019-95544","url":null,"abstract":"\u0000 The University of Maynooth is hosting a competition to develop a control strategy for a heaving point absorber wave energy converter (WEC). A linear model predictive control (MPC) design for the competition is presented. The state space model used in the MPC was derived numerically from the provided WEC-Sim model using linear system identification methods. A Kalman filter was used as the estimator, while also serving as an unknown input estimator to provide estimates of the excitation force on the WEC. The required excitation force predictions were made using an autoregressive linear prediction model. The inputs to the prediction model included estimated wave excitation forces and measured water surface elevation values from an up-field wave probe. Simulation results of the final control system design are also presented for each of the six wave cases specified by the competition organizers.","PeriodicalId":306681,"journal":{"name":"Volume 10: Ocean Renewable Energy","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126617848","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The WEC Control Competition is a benchmark devised to compare energy-maximising controllers for wave energy converters, first in simulation, then in real time, using a scale device in a tank test situation. For the first round of the competition, the evaluators have provided a model of a leg of a Wavestar-like device, in the WEC-Sim simulation environment. The evaluation is based on an energy-related criterion computed on six irregular waves. IFPEN’s solution is an energy-maximising model predictive control (MPC), composed of an estimation algorithm for wave excitation force moment, using measurements (or estimations) of float displacement and velocity and PTO moment; an algorithm for short-term wave force prediction from present and past wave excitation force estimates, where no information about wave elevation is used; a real-time compatible MPC algorithm using wave force prediction, which maximises the average produced electric energy, taking into account the nonlinear PTO efficiency law.
{"title":"An Energy-Maximising MPC Solution to the WEC Control Competition","authors":"P. Tona, G. Sabiron, Hoai‐Nam Nguyen","doi":"10.1115/omae2019-95197","DOIUrl":"https://doi.org/10.1115/omae2019-95197","url":null,"abstract":"\u0000 The WEC Control Competition is a benchmark devised to compare energy-maximising controllers for wave energy converters, first in simulation, then in real time, using a scale device in a tank test situation. For the first round of the competition, the evaluators have provided a model of a leg of a Wavestar-like device, in the WEC-Sim simulation environment. The evaluation is based on an energy-related criterion computed on six irregular waves.\u0000 IFPEN’s solution is an energy-maximising model predictive control (MPC), composed of an estimation algorithm for wave excitation force moment, using measurements (or estimations) of float displacement and velocity and PTO moment; an algorithm for short-term wave force prediction from present and past wave excitation force estimates, where no information about wave elevation is used; a real-time compatible MPC algorithm using wave force prediction, which maximises the average produced electric energy, taking into account the nonlinear PTO efficiency law.","PeriodicalId":306681,"journal":{"name":"Volume 10: Ocean Renewable Energy","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126150613","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An investigation into the computation of hydrodynamic loads on a suspended cylinder in regular waves is presented. The primary goal was to perform a three-way validation of the loads between experimental measurements and simulations from two computational methods. Experimental measurements of the longitudinal in-line force on a cylinder suspended at a fixed position were available from the Offshore Code Comparison Collaboration, Continued, with Correlation (OC5) project, Phase Ia. These measurements were compared to computational fluid dynamics (CFD) simulations based on the solution of Reynolds-averaged Navier-Stokes (RANS) equations, as implemented in STAR-CCM+. The study encompassed a sensitivity analysis of the loads computed in STAR-CCM+ based on wave modeling, boundary conditions, turbulence modeling, and spatial and temporal discretization. The analysis was supplemented by results generated with the offshore wind turbine engineering software OpenFAST, based on a hybrid combination of second-order potential flow and viscous drag from Morison’s equation. The focus of the investigation was on the assessment of the accuracy of the computation of first- and higher-order hydrodynamic loads. Substantial differences were observed in the numerical prediction of the second and third harmonic force contribution. Local flow field analysis with CFD was applied to study the physics of wave run-up and diffraction dynamics to identify the causes.
{"title":"Hydrodynamic Analysis of a Suspended Cylinder Under Regular Wave Loading Based on Computational Fluid Dynamics","authors":"P. Mucha, A. Robertson, J. Jonkman, F. Wendt","doi":"10.1115/omae2019-95533","DOIUrl":"https://doi.org/10.1115/omae2019-95533","url":null,"abstract":"\u0000 An investigation into the computation of hydrodynamic loads on a suspended cylinder in regular waves is presented. The primary goal was to perform a three-way validation of the loads between experimental measurements and simulations from two computational methods. Experimental measurements of the longitudinal in-line force on a cylinder suspended at a fixed position were available from the Offshore Code Comparison Collaboration, Continued, with Correlation (OC5) project, Phase Ia. These measurements were compared to computational fluid dynamics (CFD) simulations based on the solution of Reynolds-averaged Navier-Stokes (RANS) equations, as implemented in STAR-CCM+. The study encompassed a sensitivity analysis of the loads computed in STAR-CCM+ based on wave modeling, boundary conditions, turbulence modeling, and spatial and temporal discretization. The analysis was supplemented by results generated with the offshore wind turbine engineering software OpenFAST, based on a hybrid combination of second-order potential flow and viscous drag from Morison’s equation. The focus of the investigation was on the assessment of the accuracy of the computation of first- and higher-order hydrodynamic loads. Substantial differences were observed in the numerical prediction of the second and third harmonic force contribution. Local flow field analysis with CFD was applied to study the physics of wave run-up and diffraction dynamics to identify the causes.","PeriodicalId":306681,"journal":{"name":"Volume 10: Ocean Renewable Energy","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121704310","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper explores the response of a wave energy device during extreme and operational conditions and the effect of this response on the geotechnical stability of the associated taut moorings. The non-hydrostatic wave-flow model SWASH is used to simulate the response of a taut-moored wave energy converter. The predicted forces acting on the mooring system are used to compute the build-up of excess pore pressures in the soil around the mooring anchor and the resulting changes in strength and capacity. An initial loss of strength is followed by a subsequent increase in capacity, associated with long-term cyclic loading and hardening due to consolidation. The analyses show how cyclic loading may actually benefit and reduce anchoring requirements for wave energy devices. It demonstrates the viability of a close interdisciplinary approach towards an optimized and cost-effective design of mooring systems, which form a significant proportion of expected capital expenditures.
{"title":"Fluid-Structure-Soil Interaction of a Moored Wave Energy Device","authors":"J. Tom, D. Rijnsdorp, R. Ragni, D. White","doi":"10.1115/omae2019-95419","DOIUrl":"https://doi.org/10.1115/omae2019-95419","url":null,"abstract":"\u0000 This paper explores the response of a wave energy device during extreme and operational conditions and the effect of this response on the geotechnical stability of the associated taut moorings. The non-hydrostatic wave-flow model SWASH is used to simulate the response of a taut-moored wave energy converter. The predicted forces acting on the mooring system are used to compute the build-up of excess pore pressures in the soil around the mooring anchor and the resulting changes in strength and capacity. An initial loss of strength is followed by a subsequent increase in capacity, associated with long-term cyclic loading and hardening due to consolidation. The analyses show how cyclic loading may actually benefit and reduce anchoring requirements for wave energy devices. It demonstrates the viability of a close interdisciplinary approach towards an optimized and cost-effective design of mooring systems, which form a significant proportion of expected capital expenditures.","PeriodicalId":306681,"journal":{"name":"Volume 10: Ocean Renewable Energy","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126452901","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Guzman, D. Maron, P. Bueno, M. Taboada, M. Moreu
This paper describes a new floater type: the Reduced Draft Spar (RDS). The RDS is in essence a spar, and so stability in operation is achieved by having the center of gravity below the center of buoyancy. Spars thus need a relevant draft and some ballast at their bottom. The RDS instead, and compared to classic spars, increases the mass below the center of buoyancy to substantially reduce the draft. This counter-intuitive approach considerably increases the overall mass of the solution. But fortunately this additional mass can be provided by cost-effective solid ballast. In the same way gravity-based structures weigh much more than jackets or monopiles yet they can still be economically feasible, the RDS is considerably heavier than classic spars. Thereby, the RDS can have the benefits of reduced draft solutions like semis while keeping the inherent simplicity of spars. The RDS concept replaces the main cylinder of classic spars by a shorter one, which is in turn held by a large caisson at the bottom of the floater. This allows the assembly of the Wind Turbine (WT) onshore and gives to the RDS enough floating stability to perform the Transport and Installation (T&I) marine operations with a significant reduction of auxiliary means. The proposed floater is made of concrete. It supports an 8 MW turbine in a generic North Sea offshore location. Besides and like in some semis, the unit is fitted with an Active Ballast System (ABS) used to compensate the environmental mean loads (mainly the WT mean thrust). In the paper, a parametric design process is used to obtain the platform main dimensions. The intact stability, both in operation and during all marine operations phases, is checked taking into consideration reasonable design margins. The dynamic response of the RDS to extreme wind, waves and currents is also analyzed. A state-of-the-art seakeeping program coupled with a simplified aerodynamic load model accounts for the effect produced by the wind dynamics on the unit response. The performance of the platform in operation is similar to that of classic spars. Therefore, the paper focuses on the study of the survival conditions. Since the platform cross section is high, survival current loads become differentiating. The dynamic loads at the mooring lines are thus analyzed to assess their feasibility in severe storm environmental conditions, which rule over the mooring design.
{"title":"A Reduced Draft Spar Concept for Large Offshore Wind Turbines","authors":"S. Guzman, D. Maron, P. Bueno, M. Taboada, M. Moreu","doi":"10.1115/OMAE2018-77787","DOIUrl":"https://doi.org/10.1115/OMAE2018-77787","url":null,"abstract":"This paper describes a new floater type: the Reduced Draft Spar (RDS). The RDS is in essence a spar, and so stability in operation is achieved by having the center of gravity below the center of buoyancy. Spars thus need a relevant draft and some ballast at their bottom. The RDS instead, and compared to classic spars, increases the mass below the center of buoyancy to substantially reduce the draft. This counter-intuitive approach considerably increases the overall mass of the solution. But fortunately this additional mass can be provided by cost-effective solid ballast. In the same way gravity-based structures weigh much more than jackets or monopiles yet they can still be economically feasible, the RDS is considerably heavier than classic spars. Thereby, the RDS can have the benefits of reduced draft solutions like semis while keeping the inherent simplicity of spars.\u0000 The RDS concept replaces the main cylinder of classic spars by a shorter one, which is in turn held by a large caisson at the bottom of the floater. This allows the assembly of the Wind Turbine (WT) onshore and gives to the RDS enough floating stability to perform the Transport and Installation (T&I) marine operations with a significant reduction of auxiliary means. The proposed floater is made of concrete. It supports an 8 MW turbine in a generic North Sea offshore location. Besides and like in some semis, the unit is fitted with an Active Ballast System (ABS) used to compensate the environmental mean loads (mainly the WT mean thrust).\u0000 In the paper, a parametric design process is used to obtain the platform main dimensions. The intact stability, both in operation and during all marine operations phases, is checked taking into consideration reasonable design margins. The dynamic response of the RDS to extreme wind, waves and currents is also analyzed. A state-of-the-art seakeeping program coupled with a simplified aerodynamic load model accounts for the effect produced by the wind dynamics on the unit response. The performance of the platform in operation is similar to that of classic spars. Therefore, the paper focuses on the study of the survival conditions. Since the platform cross section is high, survival current loads become differentiating. The dynamic loads at the mooring lines are thus analyzed to assess their feasibility in severe storm environmental conditions, which rule over the mooring design.","PeriodicalId":306681,"journal":{"name":"Volume 10: Ocean Renewable Energy","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116887259","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In a global scenario of climate change and raising threats to the marine environment, a sustainable exploitation of offshore wind and wave energy resources is not only crucial for the consolidation of both industries, but also to provide a reliable and accessible source of renewable energy. In this context, and with the shared challenge for both industries to reduce costs, the combination of wind and wave technologies has emerged. In particular, this research deals with a novel hybrid system that integrates an oscillating water column, wave energy converter, with an offshore wind turbine substructure. In this paper, the novel hybrid wind-wave energy converter is studied in a three steps process. First, assessing a preliminary concept by means of a concept development methodology for hybrid wind-wave energy converters. Secondly, an OWC WEC sub-system is defined, on the basis of the results from the first step. Finally, the proof of concept of the WEC sub-system is carried out by means of a physical modelling test campaign at the University of Plymouth’s COAST laboratory.
{"title":"Proof of Concept of a Novel Hybrid Wind-Wave Energy Converter","authors":"C. Pérez-Collazo, D. Greaves, G. Iglesias","doi":"10.1115/OMAE2018-78150","DOIUrl":"https://doi.org/10.1115/OMAE2018-78150","url":null,"abstract":"In a global scenario of climate change and raising threats to the marine environment, a sustainable exploitation of offshore wind and wave energy resources is not only crucial for the consolidation of both industries, but also to provide a reliable and accessible source of renewable energy. In this context, and with the shared challenge for both industries to reduce costs, the combination of wind and wave technologies has emerged. In particular, this research deals with a novel hybrid system that integrates an oscillating water column, wave energy converter, with an offshore wind turbine substructure. In this paper, the novel hybrid wind-wave energy converter is studied in a three steps process. First, assessing a preliminary concept by means of a concept development methodology for hybrid wind-wave energy converters. Secondly, an OWC WEC sub-system is defined, on the basis of the results from the first step. Finally, the proof of concept of the WEC sub-system is carried out by means of a physical modelling test campaign at the University of Plymouth’s COAST laboratory.","PeriodicalId":306681,"journal":{"name":"Volume 10: Ocean Renewable Energy","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127201413","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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