Journal of Marine Science and Engineering

Research

24 pages, 10507 KiB

Open AccessArticle

Dynamic Analysis of Crane Vessel and Floating Wind Turbine during Temporary Berthing for Offshore On-Site Maintenance Operations

by Jinkun Shi, Mingfeng Hu, Yifan Zhang, Xiaodong Chen, Sheng Yang, Thiago S. Hallak and Mingsheng Chen

J. Mar. Sci. Eng. 2024, 12(8), 1393; https://doi.org/10.3390/jmse12081393 - 14 Aug 2024

Cited by 1 | Viewed by 1173

Abstract

With the increased scale and deployment of floating wind turbines in deep sea environments, jack-up installation vessels are unable to conduct maintenance operations due to limitations in water depth. This has led to the recognition of the advantages of floating cranes in offshore [...] Read more.

With the increased scale and deployment of floating wind turbines in deep sea environments, jack-up installation vessels are unable to conduct maintenance operations due to limitations in water depth. This has led to the recognition of the advantages of floating cranes in offshore maintenance activities. However, the dynamic coupling between the crane and the floating wind turbine under wave and wind action can result in complex responses, which also relate to complex mooring configurations. The ability to maintain stability during maintenance operations has become a primary concern. In order to address this issue, a method of connecting a floating crane with a floating wind turbine is proposed, simulating the berthing of a floating offshore wind turbine (FOWT) to a crane. Thus, a systematic comparison was conducted with frequency- and time-domain simulation using ANSYS-AQWA software. The simulation results demonstrated the feasibility and dynamic efficiency of this novel berthing approach. Connecting the crane vessel to a floating wind turbine significantly reduced the crane tip movement. Simulations showed that the crane tip movement in the X-, Y-, and Z-directions was reduced by over 30%, which implies that it may be feasible to conduct offshore on-site maintenance operations for the FOWT by using floating crane vessels if the two bodies were properly constrained. Full article

(This article belongs to the Special Issue Innovative Development of Offshore Wind Technology)

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21 pages, 12995 KiB

Open AccessArticle

Numerical Study of an Innovative Concept for a Multibody Anti-Pitching Semi-Submersible Floating Wind Turbine

by Tianhui Fan, Jianhu Fang, Xinkuan Yan and Yuan Ma

J. Mar. Sci. Eng. 2024, 12(4), 553; https://doi.org/10.3390/jmse12040553 - 26 Mar 2024

Viewed by 1233

Abstract

The floating offshore wind turbine provides a feasible solution for the development of renewable ocean energy. However, the sizeable rotor diameter of the wind turbine results in large wind heeling moments and pitch amplitude. It will increase the structural loads and cause safety [...] Read more.

The floating offshore wind turbine provides a feasible solution for the development of renewable ocean energy. However, the sizeable rotor diameter of the wind turbine results in large wind heeling moments and pitch amplitude. It will increase the structural loads and cause safety problems. Additionally, the contradictory nature between the stability and the sea-keeping of the floating structure requires that the more flexible method should be adopted to reduce the motion response of the floating offshore wind turbine. Therefore, an innovative concept of a multibody anti-pitching semi-submersible floating offshore wind turbine, named the MBAPSF, is proposed in this paper. The MBAPSF consists of a 5 MW braceless semi-submersible wind turbine and three wave energy converters. The multibody coupled numerical model is established by using an F2A tool, and the dynamic performance of the MBAPSF is compared with that of the traditional semi-submersible wind turbine named the TSSF. The results show that the innovative concept proposed in this paper can reduce pitch motion up to approximately 27% under different load cases, and the maximum bending moment and shearing force at the tower base are also reduced by more than 10%. Meanwhile, WECs are beneficial for increases in the total power generation capacity. Full article

(This article belongs to the Special Issue Innovative Development of Offshore Wind Technology)

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25 pages, 14574 KiB

Open AccessArticle

Coupled Dynamic Characteristics of a Spar-Type Offshore Floating Two-Bladed Wind Turbine with a Flexible Hub Connection

by Zonghao Wu, Kai Wang, Tianyu Jie and Xiaodi Wu

J. Mar. Sci. Eng. 2024, 12(4), 547; https://doi.org/10.3390/jmse12040547 - 25 Mar 2024

Viewed by 1286

Abstract

To reduce manufacturing, transportation, lifting and maintenance costs of increasingly larger and larger floating wind turbines, a Spar-type floating two-bladed wind turbine based on the 5 MW OC3-Hywind floating wind turbine model from the National Renewable Energy Laboratory (NREL) is studied in this [...] Read more.

To reduce manufacturing, transportation, lifting and maintenance costs of increasingly larger and larger floating wind turbines, a Spar-type floating two-bladed wind turbine based on the 5 MW OC3-Hywind floating wind turbine model from the National Renewable Energy Laboratory (NREL) is studied in this paper. The two-bladed wind turbine can cause serious problems with large dynamic loads, so a flexible hub connection was introduced between the hub mount and nacelle carrier to alleviate the dynamic effect. The paper focuses on studying the dynamic responses of the proposed Spar-type floating two-bladed wind turbine with a flexible hub connection at rated and extreme environmental conditions. Fully coupled time-domain simulations are carried out by integrating aerodynamic loads on blades, hydrodynamic loads on the spar, structural dynamics of the tower, blades and mooring lines, control system and flexible hub connection. The analysis results show that the application of a flexible hub connection between the hub mount and nacelle carrier can make a contribution to enable the Spar-type floating two-bladed wind turbine to effectively dampen the motion of the floating platform, while significantly reducing the tower load and blade deflection. Full article

(This article belongs to the Special Issue Innovative Development of Offshore Wind Technology)

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18 pages, 14693 KiB

Open AccessArticle

Design Methodology of Wind Turbine Rotor Models Based on Aerodynamic Thrust and Torque Equivalence

by Yuan Ma, Chaohe Chen, Guang Yin, Muk Chen Ong, Hongchao Lu and Tianhui Fan

J. Mar. Sci. Eng. 2024, 12(1), 1; https://doi.org/10.3390/jmse12010001 - 19 Dec 2023

Cited by 1 | Viewed by 1153

Abstract

Limited by scaling effects, the physical model tests of FOWTs (floating offshore wind turbines) cannot simulate the aerodynamic loads on rotors correctly. To solve this problem, the real-time hybrid model tests in wind tunnels were developed and provided a feasible solution for the [...] Read more.

Limited by scaling effects, the physical model tests of FOWTs (floating offshore wind turbines) cannot simulate the aerodynamic loads on rotors correctly. To solve this problem, the real-time hybrid model tests in wind tunnels were developed and provided a feasible solution for the aerodynamic simulation. To perform the wind tunnel tests, the design of aerodynamic equivalent rotor models is most critical. In this study, an innovative methodology of aerodynamic equivalent design for the wind turbine rotors is developed based on GA (genetic algorithm). The NREL (National Renewable Energy Laboratory) 5 MW and DTU (Technical University of Denmark) 10 MW rotors are employed for the case studies to validate the proposed methodology. According to the results, the model-scale aerodynamic thrust performance can be accurately matched with the prototype in the entire region between cut-in and cut-out wind speeds, which allows the rotor model to provide correct thrust at different wind speeds. The variance of the aerodynamic torque with the wind speeds for the developed model is also in good agreement with the prototype, which could be beneficial for the design of the model-scale active pitch control strategy. Moreover, the applicability of the fitness functions of GA is discussed. Full article

(This article belongs to the Special Issue Innovative Development of Offshore Wind Technology)

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16 pages, 6099 KiB

Open AccessArticle

The Lateral Behavior of Large-Diameter Monopiles for Offshore Wind Turbines Based on the p-y Curve and Solid FEM Methods

by Tao Li, Xinran Yu, Ben He and Song Dai

J. Mar. Sci. Eng. 2023, 11(12), 2354; https://doi.org/10.3390/jmse11122354 - 13 Dec 2023

Cited by 1 | Viewed by 1479

Abstract

With the rapid increase in offshore wind turbines in China, monopiles with diameters exceeding 2 m are widely used. As these piles are subjected to lateral loads caused by wind, waves, and currents, the designs of the pile foundations supporting the offshore wind [...] Read more.

With the rapid increase in offshore wind turbines in China, monopiles with diameters exceeding 2 m are widely used. As these piles are subjected to lateral loads caused by wind, waves, and currents, the designs of the pile foundations supporting the offshore wind turbines are significantly influenced by their lateral behaviors. For this reason, field tests of the largest monopile on the sea and additional analysis based on the solid finite element method (FEM) and p-y curves are carried out to reveal the response of monopiles subjected to lateral loads and to figure out key technical issues related to the design process. The results revealed that the p-y curves proposed by the API code for clay showed a much “softer” response, which resulted in the conservative design of the piles. The solid FEM relied heavily on the choosing of the parameters used. At relatively small deflections, the solid FEM presented reasonable results as compared with the tests which were, however, supposed to overestimate the ultimate capacity of the piles. The results also indicated the importance of the influence of the pile–soil gap and the application of parameter analysis to achieve relatively conservative results, if the solid FEM is adopted in the design. Full article

(This article belongs to the Special Issue Innovative Development of Offshore Wind Technology)

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16 pages, 2848 KiB

Open AccessArticle

Optimization of the Number, Hub Height and Layout of Offshore Wind Turbines

by Haiying Sun, Hongxing Yang and Siyu Tao

J. Mar. Sci. Eng. 2023, 11(8), 1566; https://doi.org/10.3390/jmse11081566 - 9 Aug 2023

Cited by 4 | Viewed by 2139

Abstract

In order to make full use of the potential of wind resources in a specific offshore area, this paper proposes a new method to simultaneously optimize the number, hub height and layout of a wind farm. The wind farm is subdivided by grids, [...] Read more.

In order to make full use of the potential of wind resources in a specific offshore area, this paper proposes a new method to simultaneously optimize the number, hub height and layout of a wind farm. The wind farm is subdivided by grids, and the intersection points are set as the potential wind turbine positions. The method adopts a genetic algorithm and encodes wind farm parameters into chromosomes in binary form. The length of chromosomes is decided by the number of potential positions and the hub heights to be selected. The optimization process includes selection, crossover, and mutation, while the efficiency of wind farm is set as the optimization objective. The proposed method is validated by three benchmark cases. It has proven to be effective in deciding the number of turbines and improving the efficiency of the wind farm. Another advantage of the proposed method is that it can be widely applied to wind farms of any shape. A case study applying the new method to an irregularly shaped wind farm in Hong Kong is demonstrated. By comparing the results with the original regularly shaped wind farm, the new method can improve power generation by 6.28%. Therefore, the proposed model is a supportive tool for designing the best number, hub heights and positions of wind turbines. Full article

(This article belongs to the Special Issue Innovative Development of Offshore Wind Technology)

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22 pages, 2298 KiB

Open AccessArticle

Inverse Evaluation of Monopile Pile–Soil Interaction Parameters Using Random Search

by Hou Qiao, Wei Li, Zhenqiang Jiang, Xi Sheng and Chuanrui Guo

J. Mar. Sci. Eng. 2023, 11(7), 1329; https://doi.org/10.3390/jmse11071329 - 29 Jun 2023

Viewed by 1041

Abstract

To deal with the uncertainties in modeling offshore wind turbines, we propose a parameter inversion method for the pile–soil interaction model based on structural health monitoring results and the numerical model. The proposed parameter inversion method has a numerical model, an objective function [...] Read more.

To deal with the uncertainties in modeling offshore wind turbines, we propose a parameter inversion method for the pile–soil interaction model based on structural health monitoring results and the numerical model. The proposed parameter inversion method has a numerical model, an objective function selected using both the numerical and identified results, and an inverse optimization using a random search algorithm in the assumed parameter space. The parameter results in the minimum optimization objective function are identified as the in situ parameter. The proposed method is confirmed to converge after some number of iterations, depending on what the initial parameter values are. However, different initial parameter cases may converge to slightly different optimal parameters, implying that the pile results are sensitive to geological parameters. Moreover, a comparison with the original design results shows design redundancy or risks. Though the proposed method has several flaws, it can shed light on the influence of parameter uncertainties on offshore wind turbines. Full article

(This article belongs to the Special Issue Innovative Development of Offshore Wind Technology)

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19 pages, 7231 KiB

Open AccessEditor’s ChoiceArticle

Fatigue Analysis of Inter-Array Power Cables between Two Floating Offshore Wind Turbines Including a Simplified Method to Estimate Stress Factors

by Dennis Beier, Anja Schnepf, Sean Van Steel, Naiquan Ye and Muk Chen Ong

J. Mar. Sci. Eng. 2023, 11(6), 1254; https://doi.org/10.3390/jmse11061254 - 20 Jun 2023

Cited by 7 | Viewed by 4198

Abstract

The use of floating offshore wind farms for electrical energy supply is expected to rise significantly over the coming years. Suspended inter-array power cables are a new design to connect floating offshore wind turbines (FOWTs) with shorter cable lengths than conventional setups. The [...] Read more.

The use of floating offshore wind farms for electrical energy supply is expected to rise significantly over the coming years. Suspended inter-array power cables are a new design to connect floating offshore wind turbines (FOWTs) with shorter cable lengths than conventional setups. The present study investigates the fatigue life of a suspended power cable with attached buoys connecting two spar-type FOWTs. Typical environmental conditions for the North Sea are applied. The nonlinear bending behavior of the power cable is considered in the analysis. Fatigue assessment is performed using the numerical software OrcaFlex based on stress factors obtained from cross-section analysis. An effective method for obtaining the stress factors is proposed for early engineering design stages and compared with the finite element software UFLEX simulation results. The simplified method delivers similar results for axial tension loads and conservative results for bending loads compared with results obtained from the finite element software. Stress components resulting from curvature variation are identified as the main contributors to fatigue damage. The most critical locations along the power cable for fatigue life are close to the hang-off points. Full article

(This article belongs to the Special Issue Innovative Development of Offshore Wind Technology)

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25 pages, 13191 KiB

Open AccessArticle

Adaptive Graph-Learning Convolutional Network for Multi-Node Offshore Wind Speed Forecasting

by Jingjing Liu, Xinli Yang, Denghui Zhang, Ping Xu, Zhuolin Li and Fengjun Hu

J. Mar. Sci. Eng. 2023, 11(4), 879; https://doi.org/10.3390/jmse11040879 - 21 Apr 2023

Cited by 6 | Viewed by 2219

Abstract

Multi-node wind speed forecasting is greatly important for offshore wind power. It is a challenging task due to unknown complex spatial dependencies. Recently, graph neural networks (GNN) have been applied to wind forecasting because of their capability in modeling dependencies. However, existing methods [...] Read more.

Multi-node wind speed forecasting is greatly important for offshore wind power. It is a challenging task due to unknown complex spatial dependencies. Recently, graph neural networks (GNN) have been applied to wind forecasting because of their capability in modeling dependencies. However, existing methods usually require a pre-defined graph structure, which is not optimal for the downstream task and limits the application scope of GNN. In this paper, we propose adaptive graph-learning convolutional networks (AGLCN) that can automatically infer hidden associations among multi-nodes through a graph-learning module. It simultaneously integrates the temporal and graph convolutional modules to capture temporal and spatial features in the data. Experiments are conducted on real-world multi-node wind speed data from the China Sea. The results show that our model achieves state-of-the-art results in all multi-scale wind speed predictions. Moreover, the learned graph can reveal spatial correlations from a data-driven perspective. Full article

(This article belongs to the Special Issue Innovative Development of Offshore Wind Technology)

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