Wind, Wave and Tidal Energy Technologies in China

Journal Name	Impact Factor	CiteScore	Launched Year	First Decision (median)	APC
Atmosphere atmosphere	2.5	4.6	2010	16.1 Days	CHF 2400	Submit
Energies energies	3.0	6.2	2008	16.8 Days	CHF 2600	Submit
Journal of Marine Science and Engineering jmse	2.7	4.4	2013	16.4 Days	CHF 2600	Submit
Sustainability sustainability	3.3	6.8	2009	19.7 Days	CHF 2400	Submit
Wind wind	-	-	2021	35.7 Days	CHF 1000	Submit

17 pages, 6958 KiB

Open AccessArticle

Effect of Combined Wave and Current Loading on the Hydrodynamic Characteristics of Double-Pile Structures in Offshore Wind Turbine Foundations

by Yongqing Lai, Li Cai, Xinyun Wu, Bin Wang, Yiyang Hu, Yuwei Liang, Haisheng Zhao and Wei Shi

Energies 2025, 18(10), 2573; https://doi.org/10.3390/en18102573 - 15 May 2025

Viewed by 149

Abstract

The multi-pile structure is a common and reliable foundation form used in offshore wind turbines (such as jacket-type structures, etc.), which can withstand hydrodynamic loads dominated by waves and water flow, providing a stable operating environment. However, the hydrodynamic responses between adjacent monopiles [...] Read more.

The multi-pile structure is a common and reliable foundation form used in offshore wind turbines (such as jacket-type structures, etc.), which can withstand hydrodynamic loads dominated by waves and water flow, providing a stable operating environment. However, the hydrodynamic responses between adjacent monopiles affected by combined wave and current loadings are seldom revealed. In this study, a generation module for wave–current combined loading is developed in waves2Foam by considering the wave theory coupled current effect. Subsequently, a numerical flume model of the double-pile structure is established in OpenFOAM based on computational fluid dynamics (CFD) and SST k-ω turbulence theory, and the hydrodynamic characteristics of the double-pile structure are investigated. It can be found that, under the combined wave–current loading, the maximum wave run-up at the leeward side of the upstream monopile is significantly reduced by about 24% on average compared with that of the individual monopile when the spacing is 1.25 and 1.75 times the wave length. At the free water surface height, the maximum discrepancy between the maximum surface pressure on the downstream monopile and the corresponding result of the individual monopile is significantly reduced from 37% to 19%. Compared to the case applying the wave loading condition, the wave–current loading reduces the influence of spacing on the wave run-up along the downstream monopile surface, the maximum surface pressure at specific positions on both upstream and downstream monopile, and the overall maximum horizontal force acting on the double-pile structure. Full article

(This article belongs to the Topic Wind, Wave and Tidal Energy Technologies in China)

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30 pages, 9748 KiB

Open AccessArticle

Horizontal Cyclic Bearing Characteristics of Bucket Foundation in Sand for Offshore Wind Turbines

by Hanbo Zhai, Puyang Zhang and Junqi Ren

Energies 2025, 18(3), 572; https://doi.org/10.3390/en18030572 - 25 Jan 2025

Viewed by 622

Abstract

During the service period, the offshore wind turbine foundation mainly bears the wind load from the upper structure and the periodic loads such as wave load and sea currents from the lower structure. Long-term cyclic loads have an important impact on the cumulative [...] Read more.

During the service period, the offshore wind turbine foundation mainly bears the wind load from the upper structure and the periodic loads such as wave load and sea currents from the lower structure. Long-term cyclic loads have an important impact on the cumulative deformation, foundation stiffness changes, and horizontal ultimate bearing capacity of the offshore wind turbine bucket foundation. This paper conducts cyclic loading tests on mono-bucket foundations under unidirectional and multidirectional cyclic loading conditions based on the multidirectional intelligent cyclic loading system of offshore wind turbine foundations and analyzes the cumulative effects of the loading direction, vertical load, and drainage status on the mono-bucket foundation during the cyclic loading process, effects of rotation angle, cyclic stiffness, and monotonic bearing capacity of foundation after cycles. The research results show that multidirectional cyclic loading significantly reduces the cyclic cumulative rotation angle of the mono-bucket foundation, and the maximum reduction rate can reach more than 50%. After unidirectional and multidirectional cyclic loading, the bearing capacity of the bucket foundation can be increased by up to 30% and 20%, respectively. At the same time, this paper proposes calculation formulas for vertical load, number of cyclic loading, and normalized cumulative rotation and establishes a calculation method for vertical load and bearing capacity of the foundation after cycles. Full article

(This article belongs to the Topic Wind, Wave and Tidal Energy Technologies in China)

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27 pages, 16018 KiB

Open AccessArticle

Investigation of Structural Nonlinearity Effects on the Aeroelastic and Wake Characteristics of a 15 MW Wind Turbine

by Zhenju Chuang, Lulin Xia, Yan Qu, Wenhua Li and Jiawen Li

J. Mar. Sci. Eng. 2025, 13(1), 116; https://doi.org/10.3390/jmse13010116 - 10 Jan 2025

Cited by 1 | Viewed by 952

Abstract

As wind turbines increase in size, blades become longer, thinner, and more flexible, making them more susceptible to large geometric nonlinear deformations, which pose challenges for aeroelastic simulations. This study presents a nonlinear aeroelastic model that accounts for large deformations of slender, flexible [...] Read more.

As wind turbines increase in size, blades become longer, thinner, and more flexible, making them more susceptible to large geometric nonlinear deformations, which pose challenges for aeroelastic simulations. This study presents a nonlinear aeroelastic model that accounts for large deformations of slender, flexible blades, coupled through the Actuator Line Method (ALM) and Geometrically Exact Beam Theory (GEBT). The accuracy of the model is validated by comparing it with established numerical methods, demonstrating its ability to capture the bending–torsional coupled nonlinear characteristics of highly flexible blades. A bidirectional fluid–structure coupling simulation of the IEA 15MW wind turbine under uniform flow conditions is conducted. The effect of blade nonlinear deformation on aeroelastic performance is compared with a linear model based on Euler–Bernoulli beam theory. The study finds that nonlinear deformations reduce predicted angle of attack, decrease aerodynamic load distribution, and lead to a noticeable decline in both wind turbine performance and blade deflection. The effects on thrust and edgewise deformation are particularly significant. Additionally, nonlinear deformations weaken the tip vortex strength, slow the momentum exchange in the wake region, reduce turbulence intensity, and delay wake recovery. This study highlights the importance of considering blade nonlinear deformations in large-scale wind turbines. Full article

(This article belongs to the Topic Wind, Wave and Tidal Energy Technologies in China)

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24 pages, 23935 KiB

Open AccessArticle

Local Structure Optimization Design of Floating Offshore Wind Turbine Platform Based on Response Surface Analysis

by Yajun Ren, Mingxuan Huang, Jungang Hao, Jiazhi Wang, Shuai Li, Ling Zhu, Haisheng Zhao and Wei Shi

Energies 2024, 17(24), 6316; https://doi.org/10.3390/en17246316 - 14 Dec 2024

Viewed by 1173

Abstract

The floating platform is a critical component of the floating offshore wind turbine (FOWT), and its internal structure design plays a key role in ensuring the safe operation of the FOWT. In this study, the local model of the floating platform was firstly [...] Read more.

The floating platform is a critical component of the floating offshore wind turbine (FOWT), and its internal structure design plays a key role in ensuring the safe operation of the FOWT. In this study, the local model of the floating platform was firstly parameterized, and a response surface model was obtained by conducting an orthogonal test. The response surface model was then optimized using a gradient descent algorithm. Finally, the internal structure arrangement was validated through a safety calibration. The optimization results indicate that the maximum stress of the optimized model is reduced by 22.12% compared to the original model, while maintaining the same mass, centroid, and other mass-related parameters. The optimization significantly improves the safety of the structure and provides valuable references for the design and construction of a FOWT platform. Full article

(This article belongs to the Topic Wind, Wave and Tidal Energy Technologies in China)

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29 pages, 14237 KiB

Open AccessArticle

The Dynamic Characteristics of the Water Entry of a Lifeboat

by Wenxin Yi, Hui Liu, Jiahe Zou, Conghong Lu, Wenqing Luo and Bo Zhou

J. Mar. Sci. Eng. 2024, 12(12), 2175; https://doi.org/10.3390/jmse12122175 - 28 Nov 2024

Cited by 1 | Viewed by 864

Abstract

The International Convention for the Safety of Life at Sea (SOLAS) stipulates that all ships must be equipped with lifesaving devices. The freefall lifeboat has the advantages of simple operation, fast release speed, and good safety performance, so it is widely used. The [...] Read more.

The International Convention for the Safety of Life at Sea (SOLAS) stipulates that all ships must be equipped with lifesaving devices. The freefall lifeboat has the advantages of simple operation, fast release speed, and good safety performance, so it is widely used. The interaction between the hull and the water body of the freefall lifeboat during the water entry process is a complex fluid–structure interaction process that has great influence on the motion characteristics and structural force of the lifeboat. In order to improve the safety of lifeboats used in the lifesaving process, this paper establishes a 3D, full-scale model of a lifeboat and the fluid area, uses the ALE method to deal with the fluid–structure interaction problem, and numerically simulates the water entry of a lifeboat. Key information such as the hull motion trajectory, motion speed, and impact load are obtained, and three typical modes of lifeboat movement are summarized. At the same time, the influence of different skid angles, skid heights, and skid lengths on the lifeboat launch process is explored. The results show that increasing the angle, height, and length of the skid to a certain extent is conducive to the rapid escape of the lifeboat from a danger zone. The research results of this paper can provide a reference for the design of lifesaving systems for offshore floating facilities such as ships, which is of great significance for ensuring the safety of marine personnel. Full article

(This article belongs to the Topic Wind, Wave and Tidal Energy Technologies in China)

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24 pages, 28615 KiB

Open AccessArticle

Modal Parameter Identification of Jacket-Type Offshore Wind Turbines Under Operating Conditions

by Chen Zhang, Xu Han, Chunhao Li, Bernt Johan Leira, Svein Sævik, Dongzhe Lu, Wei Shi and Xin Li

J. Mar. Sci. Eng. 2024, 12(11), 2083; https://doi.org/10.3390/jmse12112083 - 18 Nov 2024

Cited by 1 | Viewed by 1347

Abstract

Operational modal analysis (OMA) is essential for long-term health monitoring of offshore wind turbines (OWTs), helping identifying changes in structural dynamic characteristics. OMA has been applied under parked or idle states for OWTs, assuming a linear and time-invariant dynamic system subjected to white [...] Read more.

Operational modal analysis (OMA) is essential for long-term health monitoring of offshore wind turbines (OWTs), helping identifying changes in structural dynamic characteristics. OMA has been applied under parked or idle states for OWTs, assuming a linear and time-invariant dynamic system subjected to white noise excitations. The impact of complex operating environmental conditions on structural modal identification therefore requires systematic investigation. This paper studies the applicability of OMA based on covariance-driven stochastic subspace identification (SSI-COV) under various non-white noise excitations, using a DTU 10 MW jacket OWT model as a basis for a case study. Then, a scaled (1:75) 10 MW jacket OWT model test is used for the verification. For pure wave conditions, it is found that accurate identification for the first and second FA/SS modes can be achieved with significant wave energy. Under pure wind excitations, the unsteady servo control behavior leads to significant identification errors. The combined wind and wave actions further complicate the picture, leading to more scattered identification errors. The SSI-COV based modal identification method is suggested to be reliably applied for wind speeds larger than the rated speed and with sufficient wave energy. In addition, this method is found to perform better with larger misalignment of wind and wave directions. This study provides valuable insights in relation to the engineering applications of in situ modal identification techniques under operating conditions in real OWT projects. Full article

(This article belongs to the Topic Wind, Wave and Tidal Energy Technologies in China)

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17 pages, 10845 KiB

Open AccessArticle

Numerical Study of Hydrodynamic Characteristics of a Three-Dimensional Oscillating Water Column Wave-Power Device

by Jun-Lin Zhu, Peng Tang, Hong-Sheng Zhang and Peng-Bo Zheng

J. Mar. Sci. Eng. 2024, 12(7), 1161; https://doi.org/10.3390/jmse12071161 - 10 Jul 2024

Cited by 1 | Viewed by 1230

Abstract

The impact of wave-induced forces on the integrity of stationary oscillating water column (OWC) devices is essential for ensuring their structural safety. In our study, we built a three-dimensional numerical model of an OWC device using the computational fluid dynamics (CFDs) software OpenFOAM-v1912. [...] Read more.

The impact of wave-induced forces on the integrity of stationary oscillating water column (OWC) devices is essential for ensuring their structural safety. In our study, we built a three-dimensional numerical model of an OWC device using the computational fluid dynamics (CFDs) software OpenFOAM-v1912. Subsequently, the hydrodynamic performance of the numerical model is comprehensively validated. Finally, the hydrodynamic performance data are analyzed in detail to obtain meaningful conclusions. Results indicate that the horizontal wave force applied to the OWC device is approximately 6.6 to 7.9 times greater than the vertical wave force, whereas the lateral wave force is relatively small. Both the horizontal and vertical wave forces decrease as the relative water depth increases under a constant wave period and height. In addition, the highest dynamic water pressure is observed at the interface between the water surface and device, both within and outside the front wall of the gas chamber. The dynamic water pressure at different locations on the front chamber increases and subsequently decreases as the wave frequency increases. Full article

(This article belongs to the Topic Wind, Wave and Tidal Energy Technologies in China)

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30 pages, 10193 KiB

Open AccessArticle

A Comprehensive Investigation of Linear and Nonlinear Beam Models on Flexible Wind Turbine Blade Load Calculations

by Xinwen Ma, Xianghua Peng, Jingwei Sun, Yan Chen and Zhihong Huang

J. Mar. Sci. Eng. 2024, 12(4), 548; https://doi.org/10.3390/jmse12040548 - 25 Mar 2024

Cited by 2 | Viewed by 1949

Abstract

This study was performed to investigate the effects of structural nonlinearity and large deformations on the aeroelastic loads of flexible wind turbine blades. First, a blade structural analysis model was established using the geometrically exact beam (GEB) theory. Subsequently, the blade element momentum [...] Read more.

This study was performed to investigate the effects of structural nonlinearity and large deformations on the aeroelastic loads of flexible wind turbine blades. First, a blade structural analysis model was established using the geometrically exact beam (GEB) theory. Subsequently, the blade element momentum (BEM) theory was corrected using the geometrically exact method leading to the development of a geometrically exact blade element momentum (GE-BEM) model. The results from the GE-BEM model indicated that flapwise deformations always reduce blade fatigue loads, while torsional deformations decrease fatigue loads under low wind speeds but increase them under high wind speeds. Finally, the linear Euler–Bernoulli beam and the GEB were compared to explore the influence of geometric nonlinearity on the blade aeroelastic loads, which revealed that the Euler beam model underestimates the blade loads. The simulations that used the GEB model produced torsional root twist fatigue loads that were 57.49% greater than those generated when the Euler beam model was used. Furthermore, the flapwise bending moment fatigue loads at the root were 8.24% greater than those obtained by the Euler beam model. The smallest discrepancy between the results of the two models was 7.26%, and it corresponded to the edgewise fatigue load. Full article

(This article belongs to the Topic Wind, Wave and Tidal Energy Technologies in China)

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14 pages, 5015 KiB

Open AccessArticle

Downscaling and Wind Resource Assessment of Climatic Wind Speed Data Based on Deep Learning: A Case Study of the Tengger Desert Wind Farm

by Hao Zhou, Qi Luo and Ling Yuan

Atmosphere 2024, 15(3), 271; https://doi.org/10.3390/atmos15030271 - 24 Feb 2024

Cited by 3 | Viewed by 2489

Abstract

Analyzing historical and reanalysis datasets for wind energy climatic characteristics offers crucial insights for wind farms and short-term electricity generation forecasting. However, large-scale wind farms in Chinese deserts, the Gobi, and barren areas often lack sufficient wind measurement data, leading to challenges in [...] Read more.

Analyzing historical and reanalysis datasets for wind energy climatic characteristics offers crucial insights for wind farms and short-term electricity generation forecasting. However, large-scale wind farms in Chinese deserts, the Gobi, and barren areas often lack sufficient wind measurement data, leading to challenges in assessing long-term power generation revenue and introducing uncertainty. This study focuses on the Tengger Desert as the study area, processes the Coupled Model Intercomparison Project Phase 6 (CMIP6) data, and analyzes and compares wind energy’s future characteristics utilizing a developed deep learning (DL) downscaling algorithm. The findings indicate that (1) the Convolutional Neural Network (CNN) downscaling model, with the Weather Research and Forecasting Model (WRF) numerical simulation results as the targets, exhibits spatial distribution consistency with WRF simulation results in the experimental area. (2) Through testing and validation with three practical wind measurements, the annual average wind speed error is below 4%. (3) In the mid-term future (~2050), the average wind speed in the experimental area remains stable with a multi-year average of approximately 7.00 m·s⁻¹. The overall wind speed distribution range is significant, meeting the requirements for wind farm development. Full article

(This article belongs to the Topic Wind, Wave and Tidal Energy Technologies in China)

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17 pages, 4234 KiB

Open AccessArticle

Study and Quantitative Analysis of Mode Localization in Wind Turbine Blades

by Tao Jiang, Xin Guo, Yongpeng Zhang and Dongsheng Li

J. Mar. Sci. Eng. 2024, 12(1), 67; https://doi.org/10.3390/jmse12010067 - 27 Dec 2023

Viewed by 1510

Abstract

The study of damage mechanisms for wind turbine blades is important. Generally, modal localization tends to accelerate structural damage. This is a new approach to studying these damage mechanisms for wind turbine blades through modal localization theory. Therefore, this paper investigates whether modal [...] Read more.

The study of damage mechanisms for wind turbine blades is important. Generally, modal localization tends to accelerate structural damage. This is a new approach to studying these damage mechanisms for wind turbine blades through modal localization theory. Therefore, this paper investigates whether modal localization phenomena exist in wind turbine blades, as well as the impact of different forms of detuning on modal localization. Based on perturbation theory, a mechanism for mode localization is described quantitatively using the degree of detuning, the degree of mode density, and the mode assurance criterion. A finite element model for wind turbine blades was established using ANSYS software (R15.0), and three detuning cases were simulated by changing the density, elastic modulus, and installation angles of the blades. Moreover, an improved mode localization factor is proposed to quantitatively evaluate the degree of mode localization in wind turbine blades. The numerical results indicate that the degree of modal localization increases with an increasing degree of detuning, but the increase in modal localization gradually slows. Finally, the detuning modal shape composition, which includes harmonic components, is analyzed. The results show that the closer the composition of the detuning modes is, the stronger the degree of mode localization. Full article

(This article belongs to the Topic Wind, Wave and Tidal Energy Technologies in China)

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23 pages, 5917 KiB

Open AccessArticle

A New Ocean Rock Mass Rating and Its Application to Determine the Ultimate Bearing Capacity of an Offshore Wind Monopile Foundation

by Qi Zhang, Yixin Shen, Xiaokang Guo, Chenhao Zhang, Yifeng Lin and Xiaojun Wang

J. Mar. Sci. Eng. 2023, 11(12), 2310; https://doi.org/10.3390/jmse11122310 - 6 Dec 2023

Viewed by 1602

Abstract

Offshore wind power is a new trend in renewable energy development. However, during the operation of offshore wind turbines, the rock-socketed monopile foundation is subjected to long-term cyclic loads, which will cause the seawater to erode the rock around the monopile foundation and [...] Read more.

Offshore wind power is a new trend in renewable energy development. However, during the operation of offshore wind turbines, the rock-socketed monopile foundation is subjected to long-term cyclic loads, which will cause the seawater to erode the rock around the monopile foundation and reduce the ultimate end-bearing capacity. There is no suitable rock mass classification for evaluating the quality of marine bedrock and no theoretical method for accurately calculating the ultimate end-bearing capacity of the monopile foundation. Therefore, based on the existing rock mass classification, an ocean rock mass classification (OMR) that is applicable to marine bedrock is proposed. The ratings of four geological indices (R₁, R₂, R₃, and R₄) in the OMR classification are reset by the analysis hierarchy process and modified according to the geological conditions of marine bedrock. Then, an accelerated test of seawater erosion is used over 60 days to simulate seawater erosion for up to 12 years to determine the adjustment factor for the effect of time, F_t, in the OMR classification. Based on the OMR classification, a theoretical calculation method of the ultimate end-bearing capacity of the offshore wind monopile foundation under the overall sliding failure mode of rock mass is proposed. The theoretical calculation method was employed for offshore wind engineering, and the reliability of the theoretical calculation and three-dimensional numerical simulation was validated. The results show that the theoretical and numerical results for the ultimate end-bearing capacity without seawater erosion are similar to the measured results, with a relative error of less than 9%. The theoretical results are always larger than the numerical results, with a relative error of less than 7%. Finally, the theoretical and numerical results were used to guide the design and construction of an offshore wind turbine. The offshore wind turbine has been operating for 8 years, and its displacement is 15.3 mm, which is less than the numerical result of 16.94 mm. Full article

(This article belongs to the Topic Wind, Wave and Tidal Energy Technologies in China)

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25 pages, 7849 KiB

Open AccessArticle

Design and Control of Hydraulic Power Take-Off System for an Array of Point Absorber Wave Energy Converters

by Dengshuai Wang, Zhenquan Zhang, Yunpeng Hai, Yanjun Liu and Gang Xue

Sustainability 2023, 15(22), 16092; https://doi.org/10.3390/su152216092 - 19 Nov 2023

Cited by 2 | Viewed by 1968

Abstract

The development of wave energy converter (WEC) arrays is an effective way to reduce the cost of levelized energy and facilitate the commercialization of WECs. This study proposes a hydraulic power take-off (PTO) system for an array of point absorber wave energy converters [...] Read more.

The development of wave energy converter (WEC) arrays is an effective way to reduce the cost of levelized energy and facilitate the commercialization of WECs. This study proposes a hydraulic power take-off (PTO) system for an array of point absorber wave energy converters (PA-WECs) and designs a control system using a novel algorithm called the improved simplified universal intelligent PID (ISUIPID) controller and the adaptive matching controller including an improved artificial gorilla troops optimizer (IGTO) to improve and stabilize the output power of PA-WEC arrays. Simulations under varying irregular wave states have been carried out to verify the validity of the mathematical model and the control system. The results show that the designed IGTO has faster convergence speed and better convergence accuracy in solving the optimal linear damping coefficient of the generator, and the proposed ISUIPID controller provides superior performance in tracking the speed of the hydraulic motor under the changing sea states. In addition, the capture power and output power of the array of PA-WECs are improved and the electrical energy can be output stably under the designed control system. The array of PA-WECs with the proposed control system will become an independent, stable, efficient, and sustainable power supply system. Full article

(This article belongs to the Topic Wind, Wave and Tidal Energy Technologies in China)

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26 pages, 10179 KiB

Open AccessArticle

GAN-Based Abrupt Weather Data Augmentation for Wind Turbine Power Day-Ahead Predictions

by Renfeng Liu, Yinbo Song, Chen Yuan, Desheng Wang, Peihua Xu and Yaqin Li

Energies 2023, 16(21), 7250; https://doi.org/10.3390/en16217250 - 25 Oct 2023

Cited by 8 | Viewed by 2079

Abstract

This study introduces a data augmentation technique based on generative adversarial networks (GANs) to improve the accuracy of day-ahead wind power predictions. To address the peculiarities of abrupt weather data, we propose a novel method for detecting mutation rates (MR) and local mutation [...] Read more.

This study introduces a data augmentation technique based on generative adversarial networks (GANs) to improve the accuracy of day-ahead wind power predictions. To address the peculiarities of abrupt weather data, we propose a novel method for detecting mutation rates (MR) and local mutation rates (LMR). By analyzing historical data, we curated datasets that met specific mutation rate criteria. These transformed wind speed datasets were used as training instances, and using GAN-based methodologies, we generated a series of augmented training sets. The enriched dataset was then used to train the wind power prediction model, and the resulting prediction results were meticulously evaluated. Our empirical findings clearly demonstrate a significant improvement in the accuracy of day-ahead wind power prediction due to the proposed data augmentation approach. A comparative analysis with traditional methods showed an approximate 5% increase in monthly average prediction accuracy. This highlights the potential of leveraging mutated wind speed data and GAN-based techniques for data augmentation, leading to improved accuracy and reliability in wind power predictions. In conclusion, this paper presents a robust data augmentation method for wind power prediction, contributing to the potential enhancement of day-ahead prediction accuracy. Future research could explore additional mutation rate detection methods and strategies to further enhance GAN models, thereby amplifying the effectiveness of wind power prediction. Full article

(This article belongs to the Topic Wind, Wave and Tidal Energy Technologies in China)

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19 pages, 7886 KiB

Open AccessArticle

Analysis of Sharp Eagle Oscillating Surge Wave Energy Converter Based on a Two-Dimensional Numerical Wave Flume Model

by Liang Sun, Zewang Yang, Mingsheng Chen and Fen Li

J. Mar. Sci. Eng. 2023, 11(8), 1607; https://doi.org/10.3390/jmse11081607 - 17 Aug 2023

Cited by 2 | Viewed by 1830

Abstract

To investigate the overtopping and slamming phenomena that occur in the interactions between waves and oscillating surge wave energy converters (OSWECs), a two-dimensional numerical wave flume was established using computational fluid dynamics (CFD) software Fluent by adding the momentum source terms into the [...] Read more.

To investigate the overtopping and slamming phenomena that occur in the interactions between waves and oscillating surge wave energy converters (OSWECs), a two-dimensional numerical wave flume was established using computational fluid dynamics (CFD) software Fluent by adding the momentum source terms into the original Navier–Stokes equation. Numerical convergence studies of the mesh sizes and time steps were firstly performed to ensure the sufficient accuracy of the numerical model. The variations in the wave heights along the wave propagation direction in the wave-generating area, working area, and wave-absorbing area were analyzed. The dynamics of the flap-type OSWEC were simulated using the overset mesh function embedded in Fluent. In addition, the numerical results were compared with the experimental data, and good agreements were achieved. External torque was applied to the hinge joint of the OSWEC to simulate the forces due to the power take-off (PTO) system, and the identified optimal PTO damping was compared with the numerical results based on the potential flow theory, which verified the correctness of the numerical PTO system. On this basis, nonlinear wave slamming by the sharp-eagle OSWEC was analyzed. The results show that under certain incident wave conditions, the sharp-eagle OSWEC can effectively reduce the maximum rotation angle and angular velocity compared with those of the flap-type OSWEC, and there is no overtopping that occurring for the sharp-eagle OSWEC. Furthermore, the sharp-eagle OSWEC performs better than the flap-type OSWEC. Full article

(This article belongs to the Topic Wind, Wave and Tidal Energy Technologies in China)

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17 pages, 4852 KiB

Open AccessArticle

Analysis of Regular Wave Floating Characteristics of Mono-Column Composite Bucket Foundation during Towing

by Jiandong Xiao, Junfeng Liu, Yifeng Lin, Puyang Zhang and Yang Gao

Energies 2023, 16(13), 5076; https://doi.org/10.3390/en16135076 - 30 Jun 2023

Cited by 5 | Viewed by 1309

Abstract

The mono-column composite bucket foundation has gained practical application in offshore wind power due to its advantages of simple fabrication, fast construction, and low cost. To ensure the safe and stable transportation of this structure to its designated sinking position, this study focuses [...] Read more.

The mono-column composite bucket foundation has gained practical application in offshore wind power due to its advantages of simple fabrication, fast construction, and low cost. To ensure the safe and stable transportation of this structure to its designated sinking position, this study focuses on producing a scaled model of the mono-column composite bucket foundation. Through model testing, the floating characteristics of the structure during towing in regular waves are examined. The conclusion of the study is as follows: a significant towing force is required to provide the initial velocity of the structure. As the wave period and height increase, the structure necessitates a larger towing force, experiences greater pitch and heave responses, and exhibits more noticeable fluctuations in internal air pressure. The paper aims at providing practical engineering insights. Full article

(This article belongs to the Topic Wind, Wave and Tidal Energy Technologies in China)

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20 pages, 11982 KiB

Open AccessArticle

Optimization of the Energy Capture Performance of the Lift-Drag Hybrid Vertical-Axis Wind Turbine Based on the Taguchi Experimental Method and CFD Simulation

by Jintao Zhang, Chao Wang, Wenhao Liu, Jianyang Zhu, Yangyang Yan and Hui Zhao

Sustainability 2023, 15(11), 8848; https://doi.org/10.3390/su15118848 - 31 May 2023

Cited by 4 | Viewed by 2365

Abstract

In order to improve the energy capture performance of vertical axis lift wind turbines in a low wind speed environment, the drag wind turbine is employed to couple with the design of existing vertical axis lift wind turbines. In contrast to the existing [...] Read more.

In order to improve the energy capture performance of vertical axis lift wind turbines in a low wind speed environment, the drag wind turbine is employed to couple with the design of existing vertical axis lift wind turbines. In contrast to the existing literature, in this work, a computational model is proposed that can simulate the interaction between the turbine and the fluid. The effects of pitch angle (β), installation angle (θ), overlap ratio (ε) and diameter ratio (DL) on the energy capture performance of hybrid vertical axis wind turbines are systematically analyzed based on Taguchi and CFD methods. The results show that under the optimized parameter combination, the peak energy capture coefficient of the lift-drag hybrid wind turbine can be increased to 0.2328, compared with 0.0309 and 0.0287 of the pure lift and drag turbine, respectively. In addition, the result of the prototype test show that the optimized hybrid wind turbine not only has a better-starting performance but also has 2.0 times the output power of that of the lift wind turbine. Full article

(This article belongs to the Topic Wind, Wave and Tidal Energy Technologies in China)

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32 pages, 4564 KiB

Open AccessReview

A Review of Offshore Wind and Wave Installations in Some Areas with an Eye towards Generating Economic Benefits and Offering Commercial Inspiration

by Yi Zhang, Dapeng Zhang and Haoyu Jiang

Sustainability 2023, 15(10), 8429; https://doi.org/10.3390/su15108429 - 22 May 2023

Cited by 6 | Viewed by 2785

Abstract

Wind and wave energy have gained significant attention in recent years as high-quality renewable energy sources. Commercial applications of these technologies are still in their infancy and do not offer significant benefits to the general public due to their low economic efficiency. The [...] Read more.

Wind and wave energy have gained significant attention in recent years as high-quality renewable energy sources. Commercial applications of these technologies are still in their infancy and do not offer significant benefits to the general public due to their low economic efficiency. The main objective of this paper is to contribute to the commercialization of wind and wave energy. The first step toward achieving this goal is to review equation models related to the economic benefits of wind and wave energy. A case study approach is then used to examine several successful offshore wind and wave energy conversion devices. As a result of this examination, we identify limitations and difficulties in commercializing and developing wind and wave energy. Finally, we propose various measures to address these challenges, including technological innovation, policy support, and market regulation. Research and decision-makers interested in the promotion of renewable energy sources will gain valuable insights from this study, which will ultimately lead to the adoption of sustainable energy practices for the benefit of society and the environment. Full article

(This article belongs to the Topic Wind, Wave and Tidal Energy Technologies in China)

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25 pages, 12306 KiB

Open AccessReview

The Evolution and Future Prospects of China’s Wave Energy Policy from the Perspective of Renewable Energy: Facing Problems, Governance Optimization and Effectiveness Logic

by Meng Qi, Xin Dai, Bei Zhang, Junjie Li and Bangfan Liu

Sustainability 2023, 15(4), 3274; https://doi.org/10.3390/su15043274 - 10 Feb 2023

Cited by 6 | Viewed by 2950

Abstract

Wave energy is a kind of new marine renewable energy with broad development prospects. Many countries have launched aggressive public policies to promote the use of wave-energy technology. In this paper, 729 wave-energy policy documents were visually analyzed by Citespace software, and 31 [...] Read more.

Wave energy is a kind of new marine renewable energy with broad development prospects. Many countries have launched aggressive public policies to promote the use of wave-energy technology. In this paper, 729 wave-energy policy documents were visually analyzed by Citespace software, and 31 Chinese wave-energy policy documents were visually analyzed by Nvivo software. It was found that, on the one hand, wave-energy policy research presents an upward trend. Compared with foreign wave-energy policy research, the research foundation of China’s wave-energy policy is weak, the research is not in-depth enough, and the research enthusiasm is not high. On the other hand, China’s wave-energy policy is gradually improving, showing a development trend from extensive to detailed, with diversified policy tools and specific policy objectives, although there is still room for improvement. Full article

(This article belongs to the Topic Wind, Wave and Tidal Energy Technologies in China)

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12 pages, 3818 KiB

Open AccessArticle

Design and Mass Optimization of Numerical Models for Composite Wind Turbine Blades

by Zhiqiang Zhang, Chunyan Zhang, Yinhu Qiao, Yudie Zhou and Shuaishuai Wang

J. Mar. Sci. Eng. 2023, 11(1), 75; https://doi.org/10.3390/jmse11010075 - 3 Jan 2023

Cited by 7 | Viewed by 3770

Abstract

In this paper, a constrained optimization by linear approximation (COBYLA) algorithm is used to optimize the design of a 5 MW wind turbine blade. In the process of blade material modeling, the actual manufacturing conditions are considered, and the load of blades under [...] Read more.

In this paper, a constrained optimization by linear approximation (COBYLA) algorithm is used to optimize the design of a 5 MW wind turbine blade. In the process of blade material modeling, the actual manufacturing conditions are considered, and the load of blades under 50 m/s wind conditions is analyzed based on the blade element momentum (BEM) method. Mass optimization was achieved by removing material from the shear webs. In addition, constraints such as tip displacement, stress, and frequency during blade design were considered. The results show that the mass is reduced by about 1.7% after removing material from blade webs, while the structural response of the blade remains unchanged. This case provides a practical reference for commercial wind turbine blades. Full article

(This article belongs to the Topic Wind, Wave and Tidal Energy Technologies in China)

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26 pages, 7256 KiB

Open AccessArticle

Dynamic Analysis and Extreme Response Evaluation of Lifting Operation of the Offshore Wind Turbine Jacket Foundation Using a Floating Crane Vessel

by Mingsheng Chen, Guibo Yuan, Chun Bao Li, Xianxiong Zhang and Lin Li

J. Mar. Sci. Eng. 2022, 10(12), 2023; https://doi.org/10.3390/jmse10122023 - 18 Dec 2022

Cited by 18 | Viewed by 4141

Abstract

The jacket is the most widely-used fixed foundation for offshore wind turbines due to its superior strength and low installation cost in relatively deep waters. Floating crane vessels are commonly used to install jacket foundations. However, the dynamic coupling between the jacket and [...] Read more.

The jacket is the most widely-used fixed foundation for offshore wind turbines due to its superior strength and low installation cost in relatively deep waters. Floating crane vessels are commonly used to install jacket foundations. However, the dynamic coupling between the jacket and the floating vessel might generate complex dynamic responses under wave action. The complexity of the multi-body system requires comprehensive time-domain simulations and statistical analysis to obtain reliable results, especially for the evaluation of the operational safety of offshore lift installations of a jacket foundation. In this context, this study performs numerical simulations and statistical analyses to predict the extreme responses and the preliminary allowable sea states for guiding the lowering operation of a jacket using a floating crane vessel. First, ANSYS-AQWA is used to obtain the hydrodynamic coefficients of the vessel in the frequency domain. A nonstationary time-domain simulation of jacket lowering with winches is performed to identify several preliminary critical vertical positions of the jacket from the time series in an irregular wave. The extreme responses of a target probability are evaluated by the extreme distribution model after a large number of steady-state time-domain simulations of the critical vertical positions in irregular waves. The most critical vertical position is determined from three preliminary critical vertical positions by comparing the extreme responses. Eigenvalue analysis and spectrum analysis of the most critical vertical position of the jacket are carried out to find the natural periods of the system and the dynamic coupling characteristics between different components. The influence of wave direction, significant wave height, and spectrum peak period on the dynamic responses are also analyzed in the most critical vertical position. Furthermore, the optimal wave direction is determined as the head sea. Preliminary allowable sea states are derived by comparing the calculated dynamic amplification coefficient with the defined operational criteria. Full article

(This article belongs to the Topic Wind, Wave and Tidal Energy Technologies in China)

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20 pages, 3807 KiB

Open AccessArticle

Dynamic Load Effects and Power Performance of an Integrated Wind–Wave Energy System Utilizing an Optimum Torus Wave Energy Converter

by Wei Shi, Jinghui Li, Constantine Michailides, Mingsheng Chen, Shuaishuai Wang and Xin Li

J. Mar. Sci. Eng. 2022, 10(12), 1985; https://doi.org/10.3390/jmse10121985 - 13 Dec 2022

Cited by 14 | Viewed by 2534

Abstract

To increase the utilization of wave and other renewable energy resources, an integrated system consisting of an offshore wind turbine and a wave energy converter (WEC) could be used to harvest the potential energy. In this study, a dimensionless optimization method is developed [...] Read more.

To increase the utilization of wave and other renewable energy resources, an integrated system consisting of an offshore wind turbine and a wave energy converter (WEC) could be used to harvest the potential energy. In this study, a dimensionless optimization method is developed for shape optimization of a hollow cylindrical WEC, and an optimal shape is obtained using a differential evolution (DE) algorithm. The frequency domain response characteristics of the WEC with different geometric shapes and viscous damping loads are studied. The numerical model of the wind-wave integrated system, which consists of a semisubmersible platform and the WEC, is developed and used. The dynamic responses of the integrated system with and without using the WEC optimum section are compared. The results show that the dimensionless optimization method utilized in this paper is very applicable for hollow cylindrical WECs. A smaller inner radius and larger draft increase the heave RAO amplitude of the WEC significantly. In addition, optimization of the WEC shape and power take-off (PTO) damping coefficient can significantly improve the energy capture of the integrated system, which increases by 32.03%. The research results of this paper provide guidance for achieving the optimum design of offshore wind-wave energy integrated systems and quantify the benefits of using optimum designs in the produced wave energy power. In addition, the proposed dimensionless optimization method is generic and can be widely applied to different types of WECs. Full article

(This article belongs to the Topic Wind, Wave and Tidal Energy Technologies in China)

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24 pages, 21186 KiB

Open AccessArticle

Wake Interactions of Two Tandem Semisubmersible Floating Offshore Wind Turbines Based on FAST.Farm

by Lei Xue, Jundong Wang, Liye Zhao, Zhiwen Wei, Mingqi Yu and Yu Xue

J. Mar. Sci. Eng. 2022, 10(12), 1962; https://doi.org/10.3390/jmse10121962 - 9 Dec 2022

Cited by 11 | Viewed by 2857

Abstract

Wake effects commonly exist in offshore wind farms, which will cause a 10–20% reduction of whole power production as well as a 5–15% increase of fatigue loading on the wind turbine main structures. Obviously wake interaction between floating offshore wind turbine (FOWT) is [...] Read more.

Wake effects commonly exist in offshore wind farms, which will cause a 10–20% reduction of whole power production as well as a 5–15% increase of fatigue loading on the wind turbine main structures. Obviously wake interaction between floating offshore wind turbine (FOWT) is more complicated, and needs careful assessment which is a prerequisite for active wake control (AWC). The primary objective of the present research is to investigate in detail how the wake inflow condition, streamwise spacing, turbulence intensity, and wind shear influence the power performance, platform motion dynamic and structural loading of FOWT. FAST.Farm, developed by the National Renewable Energy Laboratory (NREL), was used for simulating two tandem FOWTs in different conditions. Comparisons were made between FOWTs in different conditions on power performance and platform motion dynamic, which were presented through both time and frequency domain analysis. Damage equivalent loads change in FOWTs interference under typical working conditions were discussed and summarized. Half wake inflow would pose many challenges to the downstream FOWT. These research studies can be incorporated into further offshore wind farm wake models, providing applicable AWC strategies to reduce wake interference effects for higher energy production and for the longer life of FOWT. Full article

(This article belongs to the Topic Wind, Wave and Tidal Energy Technologies in China)

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22 pages, 12435 KiB

Open AccessArticle

Feasibility Study of a Novel Open Ocean Aquaculture Ship Integrating with a Wind Turbine and an Internal Turret Mooring System

by Hanyu Liu, Mingsheng Chen, Zhaolong Han, Hao Zhou and Lin Li

J. Mar. Sci. Eng. 2022, 10(11), 1729; https://doi.org/10.3390/jmse10111729 - 11 Nov 2022

Cited by 30 | Viewed by 3399

Abstract

Marine aquaculture has been expanded into more remote areas due to the increasing demand for high value-added fish products, bringing more challenges in fuel supply and mooring safety to open ocean aquaculture farms. Therefore, the idea of integrating aquaculture farms with offshore renewable [...] Read more.

Marine aquaculture has been expanded into more remote areas due to the increasing demand for high value-added fish products, bringing more challenges in fuel supply and mooring safety to open ocean aquaculture farms. Therefore, the idea of integrating aquaculture farms with offshore renewable energy has attracted tremendous interest. This study proposes a novel open ocean aquaculture ship integrated with a NREL 5 MW wind turbine. In addition, an internal turret mooring system is installed at the bow of the aquaculture ship, making the wind turbine always face the wind blowing direction due to the weathervaning effect. In this study, a preliminary study of the dynamics and wind power generation of the proposed open ocean aquaculture ship was conducted. The aerodynamic and elastic effects of the wind turbine and the effect of nets under the wave and current behavior on the dynamics of the single-point moored aquaculture ship were investigated. Furthermore, the effects of the dynamics of the aquaculture ship on the power generation of the wind turbine were also studied to investigate the feasibility of the idea to integrate an aquaculture ship with a wind turbine. Full article

(This article belongs to the Topic Wind, Wave and Tidal Energy Technologies in China)

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20 pages, 5832 KiB

Open AccessArticle

Research on an All-Flow Velocity Control Strategy for a 120 kW Variable-Pitch Horizontal Axis Tidal Current Turbine

by Bingzhen Wang, Wei Ke, Yuanfei Zhang and Yunqi Duan

J. Mar. Sci. Eng. 2022, 10(11), 1578; https://doi.org/10.3390/jmse10111578 - 25 Oct 2022

Cited by 3 | Viewed by 2174

Abstract

Horizontal-axis tidal current turbines have considerable potential to harvest renewable energy from ocean tides. The pitch control system is a critical part of variable-pitch tidal turbines. Existing control strategies for tidal turbines mainly rely on flow measurement devices to obtain tidal velocities, which [...] Read more.

Horizontal-axis tidal current turbines have considerable potential to harvest renewable energy from ocean tides. The pitch control system is a critical part of variable-pitch tidal turbines. Existing control strategies for tidal turbines mainly rely on flow measurement devices to obtain tidal velocities, which are costly and subject to many limitations in practical applications, making them unsuitable for small off-grid tidal turbines. In this paper, we propose a pitch control strategy for a 120 kW horizontal-axis tidal current turbine based on the output power of the generator. The torque of the turbine was calculated based on the blade element momentum theory, and a dynamic model of the tidal turbine was established. The dynamic characteristics of the turbine and generator were studied under various flow rates and pitch angles. On the basis of the characteristic analysis, the generating efficiency of the unit was improved under a low flow rate, and the output power was limited to a rated value under high-current velocity by regulating the pitch angle. Furthermore, a novel protection and start up strategy is proposed to protect the unit and make full use of the tidal energy when the tidal current velocity exceeds the limit value. We performed simulations, the obtained results of which demonstrate the effectiveness and advantages of the designed control strategies. Full article

(This article belongs to the Topic Wind, Wave and Tidal Energy Technologies in China)

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18 pages, 14851 KiB

Open AccessArticle

A Simplified Panel Method (sPM) for Hydrodynamics of Air Cushion Assisted Platforms

by Fengmei Jing, Song Wang, Zhiqun Guo and Yurui Ni

J. Mar. Sci. Eng. 2022, 10(10), 1554; https://doi.org/10.3390/jmse10101554 - 20 Oct 2022

Cited by 1 | Viewed by 2161

Abstract

Air-cushion-assisted platforms (ACAPs) are floating platforms supported by both buoyancy pontoon and air cushion, which have merits of wave bending moment reduction, better stability, and hydrodynamic performance. However, there is barely a concise method that can quickly predict the motion response of ACAPs. [...] Read more.

Air-cushion-assisted platforms (ACAPs) are floating platforms supported by both buoyancy pontoon and air cushion, which have merits of wave bending moment reduction, better stability, and hydrodynamic performance. However, there is barely a concise method that can quickly predict the motion response of ACAPs. In this paper, a simplified panel method (sPM) was presented for evaluating the hydrodynamics of ACAPs. The sPM extends the conventional boundary integral equation (BIE) to include the radiation solutions of pulsating air pressure but ignores some unimportant air-water cross terms in motion equations whose coefficients cannot be directly derived from conventional Green’s function methods. The effectiveness of the sPM was validated by experimental data from an ACAP model with one air chamber and analytical results from an oscillating water column (OWC). The numerical results demonstrate that the sPM can give desirable predictions for motion responses of the ACAP and inner pressure of the OWC as compared with results from the literature, which suggests the sPM could be approximately applied to evaluation of hydrodynamic performance of ACAPs and OWCs. Full article

(This article belongs to the Topic Wind, Wave and Tidal Energy Technologies in China)

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24 pages, 12330 KiB

Open AccessArticle

Study on the Wind and Wave Environmental Conditions of the Xisha Islands in the South China Sea

by Ze Sun, Mengchun Bian, Jun Ding, Jiarui Liu, Haicheng Zhang and Daolin Xu

J. Mar. Sci. Eng. 2022, 10(10), 1459; https://doi.org/10.3390/jmse10101459 - 9 Oct 2022

Cited by 5 | Viewed by 2697

Abstract

Wind and waves are the main factors of environmental loading on ships and offshore structures. Thus, detailed understanding of wind and wave conditions can improve the design and maintenance of these structures. This paper developed a validated long-term wind and wave hindcast database [...] Read more.

Wind and waves are the main factors of environmental loading on ships and offshore structures. Thus, detailed understanding of wind and wave conditions can improve the design and maintenance of these structures. This paper developed a validated long-term wind and wave hindcast database covering the recent 32 years from 1988 to 2019. The spatial distribution of wind and wave characteristics for the whole Xisha Islands’ domain were analyzed. Frequency and directional distributions of wind speeds and significant wave heights were investigated at several locations around typical islands. Extreme value models were used to estimate the wind speed for 100-year return levels, whereas environmental contour approaches were utilized to establish the extreme sea-state parameters for 50- and 100-year return periods. It was found that the Weibull distribution was better fitted to the significant wave heights of the Xuande Atoll’s sites in the open sea, while the exponential Weibull distribution provided a better fit at the Yongle Atoll’s sites where waves are sheltered. Full article

(This article belongs to the Topic Wind, Wave and Tidal Energy Technologies in China)

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15 pages, 3740 KiB

Open AccessArticle

Numerical Modeling of the Impact of Sea Level Rise on Tidal Asymmetry in Hangzhou Bay

by Ying Li, Enshang Yang, Yun Pan and Yun Gao

J. Mar. Sci. Eng. 2022, 10(10), 1445; https://doi.org/10.3390/jmse10101445 - 7 Oct 2022

Cited by 3 | Viewed by 2460

Abstract

The tidal asymmetry under the action of sea level rise in Hangzhou Bay. Coastlines dominated by the tide are not only directly affected by the rise of the mean sea level but also by the tidal dynamics. The computational domain of the hydrodynamic [...] Read more.

The tidal asymmetry under the action of sea level rise in Hangzhou Bay. Coastlines dominated by the tide are not only directly affected by the rise of the mean sea level but also by the tidal dynamics. The computational domain of the hydrodynamic model covers the entire Hangzhou Bay and takes into account the feedback between the tidal motion and the erodible bottom. Its main application fields include: the simulation of different sea level rise (SLR) rates, the interaction between tidal duration and skewness and the interaction between tidal range and astronomical tide. The results on tidal asymmetry in Hangzhou Bay is a systematic process consisting of four aspects: Firstly, the tide increase, which is affected by the sea level rise, is between 25% and 50%. Secondly, the value of the sea level rise is about two times the added value of the tidal range, and the tidal range increased to the left side of the tidal wave propagation direction, which accelerated the propagation velocity. Thirdly, the sea level rise amplified the M₂ tidal amplitude and delayed the M₂ tidal phase in the inner bay, which reduced about 50%. Finally, the change of the tidal range caused by tide level had the same magnitude as the change caused by the mean sea level rise. The purpose of this study was to emphasize the importance of the predictions of the response area affected by tidal asymmetry based on the action of the sea level rise in Hangzhou Bay. Full article

(This article belongs to the Topic Wind, Wave and Tidal Energy Technologies in China)

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25 pages, 8759 KiB

Open AccessArticle

Investigation on Dynamic Responses’ Characteristics and Fatigue Damage Assessment for Floating Offshore Wind Turbine Structures

by Min Zhang, Zhiji Zhou, Kun Xu, Yuanyuan Shi, Yanjian Wu and Junfeng Du

Sustainability 2022, 14(19), 12444; https://doi.org/10.3390/su141912444 - 29 Sep 2022

Cited by 2 | Viewed by 2361

Abstract

Dynamic response analysis and fatigue damage assessment of floating offshore wind turbine (FOWT) structures are carried out in this paper with a focus on the statistical characteristics of the dynamic responses under wind–wave excitation. A proper spectral fatigue damage model is proposed to [...] Read more.

Dynamic response analysis and fatigue damage assessment of floating offshore wind turbine (FOWT) structures are carried out in this paper with a focus on the statistical characteristics of the dynamic responses under wind–wave excitation. A proper spectral fatigue damage model is proposed to obtain better fatigue damage estimation. The OC3 floating spar (Hywind) with a 5 MW baseline wind turbine developed by the American National Renewable Energy Laboratory (NREL) is applied as the target model, and the fully coupled dynamic responses of the model are calculated in the time domain. The non-Gaussian nature is revealed based on the study of the statistical properties of the dynamic response of key components (the tower base and fairlead of the mooring line). Dirlik distribution is proved to be the best probability distribution function (PDF) that can fit the statistical distribution feature of the dynamic responses among several PDFs. The corresponding spectral fatigue damage models are applied to estimate fatigue damage of the tower base and mooring line following the proposed fatigue assessment procedure in the frequency domain, of which the results are compared with results from the time-domain analysis method. The results indicate that for non-Gaussian feature dynamic responses as FOWTs, the spectral fatigue damage model based on the Dirlik distribution can provide more accurate assessments of fatigue damage. Full article

(This article belongs to the Topic Wind, Wave and Tidal Energy Technologies in China)

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13 pages, 6762 KiB

Open AccessArticle

Effect of Different Types of Erosion on the Aerodynamic Performance of Wind Turbine Airfoils

by Xiaohang Wang, Zhenbo Tang, Na Yan and Guojun Zhu

Sustainability 2022, 14(19), 12344; https://doi.org/10.3390/su141912344 - 28 Sep 2022

Cited by 6 | Viewed by 2012

Abstract

Taking the S823 airfoil as the research object, this study investigates the influence of different types of leading-edge erosion on the aerodynamic performance of airfoil by using the computational fluid dynamics method. The effect of leading-edge erosion on the inception of stall vortex [...] Read more.

Taking the S823 airfoil as the research object, this study investigates the influence of different types of leading-edge erosion on the aerodynamic performance of airfoil by using the computational fluid dynamics method. The effect of leading-edge erosion on the inception of stall vortex is also analysed. The results show that when the angle of attack (AoA) is greater than 5°, the leading-edge erosion results in a significant decrease in the lift coefficient and an increase in the drag coefficient. The deterioration in the drag coefficient of the airfoil caused by leading-edge erosion is much greater than that of the lift coefficient. Moreover, the maximum promotion rate of the drag coefficient can reach 357% at Re = 300,000. The exacerbation of the erosion level leads to a dramatic expansion of the stall vortex on the airfoil suction side at a large AoA and results in a reduction in the pressure difference between the pressure and suction sides of the airfoil. This is also the reason erosion causes the degradation of the aerodynamic performance of the wind turbine airfoil. This work is beneficial to establish the reasonable maintenance cycle of the wind turbine blades working in a sand blown environment. Full article

(This article belongs to the Topic Wind, Wave and Tidal Energy Technologies in China)

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16 pages, 15337 KiB

Open AccessArticle

Prediction Method for Ocean Wave Height Based on Stacking Ensemble Learning Model

by Yu Zhan, Huajun Zhang, Jianhao Li and Gen Li

J. Mar. Sci. Eng. 2022, 10(8), 1150; https://doi.org/10.3390/jmse10081150 - 19 Aug 2022

Cited by 6 | Viewed by 3049

Abstract

Wave heights are important factors affecting the safety of maritime navigation. This study proposed a stacking ensemble learning method to improve the prediction accuracy of wave heights. We analyzed the correlation between wave heights and other oceanic hydrological features, according to eleven features, [...] Read more.

Wave heights are important factors affecting the safety of maritime navigation. This study proposed a stacking ensemble learning method to improve the prediction accuracy of wave heights. We analyzed the correlation between wave heights and other oceanic hydrological features, according to eleven features, such as measurement time, horizontal velocity, temperature, and pressure, as the model inputs. A fusion model consisting of two layers was established according to the principle of stacking ensemble learning. The first layer used the extreme gradient boosting algorithm, a light gradient boosting machine, random forest, and adaptive boosting to determine the deep relations between the wave heights and the input features. The second layer used a linear regression model to fit the relation between the first layer outputs and the actual wave heights, using the data from the four models of the first layer. The fusion model was trained based on the 5-fold cross-verification algorithm. This paper used real data to test the performances of the proposed fusion model, and the results showed that the mean absolute error and the mean squared error of the fusion model were at least 35.79% and 50.52% better than those of the four models. Full article

(This article belongs to the Topic Wind, Wave and Tidal Energy Technologies in China)

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18 pages, 4856 KiB

Open AccessArticle

Analysis of Spatial and Temporal Variations of the Near-Surface Wind Regime and Their Influencing Factors in the Badain Jaran Desert, China

by Ziying Hu, Guangpeng Wang, Yong Liu, Peijun Shi, Guoming Zhang, Jifu Liu, Yu Gu, Xichen Huang, Qingyan Zhang, Xu Han, Xueling Wang, Jiewen Du, Ruoxin Li and Lianyou Liu

Atmosphere 2022, 13(8), 1316; https://doi.org/10.3390/atmos13081316 - 18 Aug 2022

Cited by 3 | Viewed by 2440

Abstract

Wind regime is one of the main natural factors controlling the evolution and distribution of aeolian sand landforms, and sand drift potential (DP) is usually used to study the capacity of aeolian sand transport. The Badain Jaran Desert (BJD) is located where polar [...] Read more.

Wind regime is one of the main natural factors controlling the evolution and distribution of aeolian sand landforms, and sand drift potential (DP) is usually used to study the capacity of aeolian sand transport. The Badain Jaran Desert (BJD) is located where polar cold air frequently enters China. Based on wind data of eight nearby meteorological stations, this research is intended to explore the temporal variation and spatial distribution features of wind speed and DP using linear regression and cumulative anomaly method, and reveal the relationship between atmospheric circulation and wind speed with correlation analysis. We found that the wind speed and frequency of sand-blowing wind in the BJD decreased significantly during 1971–2016, and the wind speed obviously mutated in 1987. The regional wind speed change was affected by the Asian polar vortex, the northern hemisphere polar vortex and the Tibet Plateau circulation. The wind rose of the annual sand-blowing wind in this region was the “acute bimodal” type. Most of the annual wind directions clustered into the W-NW, and the prevailing wind direction was WNW. During 1971–2016, the annual DP, the resultant drift potential (RDP) and the directional variability (PDP/DP) in the desert showed an obvious downtrend, with a “cliff-like” decline in the 1980s and relative stable fluctuation thereafter. The BJD was under a low-energy wind environment with the acute bimodal wind regime. Wind speed, sand-blowing wind frequency and DP were high in the northeast and low in the southwest. Full article

(This article belongs to the Topic Wind, Wave and Tidal Energy Technologies in China)

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27 pages, 6537 KiB

Open AccessArticle

Technical and Economic Feasibility Analysis of a Conceptual Subsea Freight Glider for CO₂ Transportation

by Pawel Klis, Shuaishuai Wang and Yihan Xing

J. Mar. Sci. Eng. 2022, 10(8), 1108; https://doi.org/10.3390/jmse10081108 - 12 Aug 2022

Cited by 2 | Viewed by 2943

Abstract

This study analyses the technical and economic aspects of a novel subsea freight glider (SFG). The SFG is an excellent replacement for tanker ships and submarine pipelines transporting liquefied CO₂. The main aim of the SFG is to ship CO₂ [...] Read more.

This study analyses the technical and economic aspects of a novel subsea freight glider (SFG). The SFG is an excellent replacement for tanker ships and submarine pipelines transporting liquefied CO₂. The main aim of the SFG is to ship CO₂ from an offshore facility to an underwater well where the gas can be injected; as an advantage, the SFG vehicle may be used to transport all kinds of cargo. The SFG travels below the sea surface, making the vessel weather-independent. The research is divided into two steps. Firstly, the technical feasibility analysis is performed by designing a baseline design with a length of 56.5 m, a beam of 5.5 m, and a cargo volume of 1194 m³. The SFG is developed using DNVGL-RU-NAVAL-Pt4Ch1, which was initially created for military submarine designs. Two additional half-scaled 469 m³ and double-scaled 2430 m³ models are created when the baseline design fulfils the technical requirements. Secondly, the economic analysis is carried out using the freely accessible MUNIN D9.3 and ZEP reports. The economic feasibility analysis is illustrated through a case study with a CO₂ transport capacity range of 0.5 to 2.5 mtpa (million tons per annum) and a transport length range of 180 km to 1500 km. The prices of CO₂ per ton for the SFG, crew and autonomous tankers, and offshore pipelines are comprehensively compared. According to the results, SFGs with capacities of 469 m³, 1194 m³, and 2430 m³ are technically possible to manufacture. Moreover, the SFGs are competitive with a smaller CO₂ capacity of 0.5 mtpa at distances of 180 and 500 km and a capacity of 1 mtpa at a distance of 180 km. Full article

(This article belongs to the Topic Wind, Wave and Tidal Energy Technologies in China)

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15 pages, 4073 KiB

Open AccessArticle

A Theoretical Approach for Resonance Analysis of Wind Turbines under 1P/3P Loads

by Jijian Lian, Huan Zhou and Xiaofeng Dong

Energies 2022, 15(16), 5787; https://doi.org/10.3390/en15165787 - 9 Aug 2022

Cited by 7 | Viewed by 4170

Abstract

Wind turbines (WTs) are exposed to a dynamic/cyclic load environment, and are subjected to 1P/3P loads under operational conditions. Recent studies introduced the Sommerfeld Effect to explain the dynamic response amplification induced by 1P/3P loads. This study establishes a theoretical model to analyze [...] Read more.

Wind turbines (WTs) are exposed to a dynamic/cyclic load environment, and are subjected to 1P/3P loads under operational conditions. Recent studies introduced the Sommerfeld Effect to explain the dynamic response amplification induced by 1P/3P loads. This study establishes a theoretical model to analyze the resonance of WTs under 1P/3P loads. Sensitiveness analysis was conducted for parameters b, c, S, F, and T to explore their influence on the dynamic response. The resonance phenomenon induced by 1P/3P frequency passing the natural frequency is discussed. The results show that there is no Sommerfeld Effect in soft–stiff WTs. Only if the imbalance reaches a much higher value (19200 kg·m in this study) should the Sommerfeld Effect be considered for soft WTs; otherwise, it can be ignored. The 3P resonance appeared when the 3P frequency approached the natural frequency, but it was not the Sommerfeld Effect. Full article

(This article belongs to the Topic Wind, Wave and Tidal Energy Technologies in China)

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15 pages, 8826 KiB

Open AccessArticle

Experimental Study on Static Pressure Sedimentation for a Thick-Walled Bucket Foundation in Sand

by Hao Zhao, Hongjie Zheng and Jijian Lian

Energies 2022, 15(16), 5786; https://doi.org/10.3390/en15165786 - 9 Aug 2022

Cited by 1 | Viewed by 1869

Abstract

As an emerging foundation structure for offshore wind turbines, bucket foundations with superior bearing capacities and efficient construction procedures have attracted significant attention in China. Thick-walled bucket foundations with concrete skirts can effectively reduce the cost and prevent the buckling problem of steel [...] Read more.

As an emerging foundation structure for offshore wind turbines, bucket foundations with superior bearing capacities and efficient construction procedures have attracted significant attention in China. Thick-walled bucket foundations with concrete skirts can effectively reduce the cost and prevent the buckling problem of steel skirts during construction, transportation, and installation. However, great challenges are encountered during the sinking process, and the accurate calculation of sinking resistance is a critical process. Static-pressure tests of thin-walled and thick-walled models in sand were performed to measure the penetration resistance and soil pressure at the sidewalls and ends. The horizontal-soil-pressure coefficients of different models were calculated, and the end and skin-friction coefficients in the cone-penetration test method are recommended. The drag-reduction effects of the anti-drag ring and pressure-pull-out loading method were examined, and the drag-reduction effect was evident for the bucket foundation. The drag-reduction effect of the pressure-pull-out loading method is mainly reflected in the end zone. Full article

(This article belongs to the Topic Wind, Wave and Tidal Energy Technologies in China)

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18 pages, 4110 KiB

Open AccessArticle

Hydrodynamic Analysis of a Novel Modular Floating Structure System Integrated with Floating Artificial Reefs and Wave Energy Converters

by Yanwei Li, Nianxin Ren, Xiang Li and Jinping Ou

J. Mar. Sci. Eng. 2022, 10(8), 1091; https://doi.org/10.3390/jmse10081091 - 9 Aug 2022

Cited by 10 | Viewed by 3445

Abstract

A novel modular floating structure (MFS) system moored by tension legs was proposed, which is composed of hexagonal floating modules, floating artificial reefs and wave energy converters (WECs). The integration of floating artificial reefs and WECs into the MFS can improve the marine [...] Read more.

A novel modular floating structure (MFS) system moored by tension legs was proposed, which is composed of hexagonal floating modules, floating artificial reefs and wave energy converters (WECs). The integration of floating artificial reefs and WECs into the MFS can improve the marine environment and produce considerable electricity. The effects of both wave characteristics and the module quantity on the hydrodynamic responses of the MFS system were studied in depth, based on a time-domain numerical model. Both the modules’ hydrodynamic interaction effect and the connectors’ mechanical coupling effect were considered. The results indicate that floating artificial reefs combined with WECs can effectively reduce wave loads and convert wave energy into electricity for the MFS system. More modules involved in the MFS system could significantly reduce motion response and produced more wave energy output, which indicates that the MFS system is suitable for large-scale expansion. The effect of different power take-off (PTO) damping coefficients on the WECs’ performance was further investigated, and the optimal damping coefficient was recommended for the MFS system. Finally, the main extreme responses of the MFS system were further investigated, and its safety was checked thoroughly. One survival strategy was proposed, which could efficiently reduce extreme connector loads by more than 50%. Full article

(This article belongs to the Topic Wind, Wave and Tidal Energy Technologies in China)

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18 pages, 4044 KiB

Open AccessArticle

Dynamic Response of SPAR-Type Floating Offshore Wind Turbine under Wave Group Scenarios

by Baolong Liu and Jianxing Yu

Energies 2022, 15(13), 4870; https://doi.org/10.3390/en15134870 - 2 Jul 2022

Cited by 10 | Viewed by 3674

Abstract

Numerical simulations are performed within the time domain to investigate the dynamic behaviors of an SPAR-type FOWT under wave group conditions. Towards this goal, the OC3 Hywind SPAR-type FOWT is adopted, and a JONSWAP (Joint North Sea Wave Project)-based wave group is generated [...] Read more.

Numerical simulations are performed within the time domain to investigate the dynamic behaviors of an SPAR-type FOWT under wave group conditions. Towards this goal, the OC3 Hywind SPAR-type FOWT is adopted, and a JONSWAP (Joint North Sea Wave Project)-based wave group is generated by the envelope amplitude approach. The FOWT motion under wave group conditions, as well as the aerodynamic, hydrodynamic, and mooring performances, is simulated by our established in-house code. The rotating blades are modelled by the blade element momentum theory. The wave-body interaction effect is calculated by the three-dimensional potential theory. The mooring dynamics are also taken into consideration. According to the numerical results, the SPAR buoy motions are slightly increased by the wave group, while the heave motion is significantly amplified. Both the aerodynamic performance and the mooring tension are also influenced by the wave group. Furthermore, the low-frequency resonant response could be more easily excited by the wave group. Full article

(This article belongs to the Topic Wind, Wave and Tidal Energy Technologies in China)

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