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Special Issue "Recent Advances in Offshore Wind Technology"

A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "Wind, Wave and Tidal Energy".

Deadline for manuscript submissions: 31 December 2019.

Special Issue Editors

Guest Editor
Prof. Dr. Muk Chen Ong

Department of Mechanical and Structural Engineering and Materials Science, University of Stavanger, 4036 Stavanger, Norway
Website | E-Mail
Interests: offshore renewable energy; marine hydrodynamics; marine structures; marine operations; marine computational fluid dynamics; scour prediction and protection; offshore foundation design
Guest Editor
Assoc. Prof. Dr. Zhiyu Jiang

Department of Engineering Sciences, Faculty of Engineering and Science, University of Agder, Postboks 422, 4604 Kristiansand, Norway
Website | E-Mail
Interests: wind turbine dynamics; offshore structures; marine operations
Guest Editor
Dr. Zhengshun Cheng

Department of Marine Technology, Norwegian University of Science and Technology, Otto Nielsens veg 10, 7491 Trondheim, Norway
Website | E-Mail
Interests: offshore renewable energy; marine structures; marine operations
Guest Editor
Dr. Kai Wang

Department of Marine Technology, Aker Solutions As, Snarøyveien 20, 1360 Fornebu PO Box 222, 1326 Lysaker, Norway
Website | E-Mail
Interests: wind turbine aerodynamics; CFD technique; marine hydrodynamics; wind turbine dynamics; offshore structures; ice loads; renewable energy; design and analysis of mooring systems

Special Issue Information

Dear Colleagues,

We are inviting submissions to a Special Issue of the journal Energies on the subject area of “Recent Advances in Offshore Wind Technology.” Offshore wind resources are abundant, yet offshore wind farms experience more issues related to design, installation, operation and maintenance, and lifetime extension compared to onshore wind farms. Almost three decades have passed since the first offshore wind farm was constructed. Today, offshore wind energy has been rapidly evolving with the aim to deploy larger wind turbines at increasing water depths and under complex external conditions. Challenges abound when it comes to the upscaling of wind turbines, and cost-effective operation and maintenance in a life-cycle perspective, and there has been continuous progress in foundation design, control strategy, installation methods, computational methods, and model testing, to name a few. This Special Issue is intended to provide a forum for academic researchers and technical professionals to exchange their recent works on technological advancements.

Prof. Dr. Muk Chen Ong
Assoc. Prof. Dr. Zhiyu Jiang
Dr. Zhengshun Cheng
Dr. Kai Wang
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Energies is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Innovative concepts and technologies
  • Hydrodynamics, structural dynamics, and aerodynamics
  • Dynamics and control
  • Field measurements and model testing
  • Drivetrain technology
  • Metocean conditions and wind farm siting
  • Scour prediction and protection
  • Foundation design
  • Fabrication and installation
  • Operations, maintenance, lifetime extension and decommissioning

Published Papers (9 papers)

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Research

Open AccessArticle
Reliability-Based Serviceability Limit State Design of a Jacket Substructure for an Offshore Wind Turbine
Energies 2019, 12(14), 2751; https://doi.org/10.3390/en12142751
Received: 13 June 2019 / Revised: 11 July 2019 / Accepted: 14 July 2019 / Published: 18 July 2019
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Abstract
The development of a structurally optimized foundation design has become one of the main research objectives for offshore wind turbines (OWTs). The design process should be carried out in a probabilistic way due to the uncertainties involved, such as using parametric uncertainties regarding [...] Read more.
The development of a structurally optimized foundation design has become one of the main research objectives for offshore wind turbines (OWTs). The design process should be carried out in a probabilistic way due to the uncertainties involved, such as using parametric uncertainties regarding material and geometric properties, and model uncertainties in resistance prediction models and regarding environmental loads. Traditional simple deterministic checking procedures do not guarantee an optimized design because the associated uncertainties are not fully considered. In this paper, a reliability analysis framework is proposed to support the optimized design of jacket foundations for OWTs. The reliability analysis mainly considers the serviceability limit state of the structure according to the requirements of the code. The framework consists of two parts: (i) an important parameter identification procedure based on statistical correlation analysis and (ii) a finite element-simulation-based reliability estimation procedure. The procedure is demonstrated through a jacket structure design of a 3 MW OWT. The analysis results show that the statistical correlation analysis can help to identify the parameters necessary for the overall structural performance. The Latin hypercube sampling and the Monte Carlo simulation using FE models effectively and efficiently evaluate the reliability of the structure while not relying on a surrogate limit state function. A comparison between the proposed framework and the deterministic design shows that the framework can help to achieve a better result closer to the target reliability level. Full article
(This article belongs to the Special Issue Recent Advances in Offshore Wind Technology)
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Open AccessArticle
A Simulation of Non-Simultaneous Ice Crushing Force for Wind Turbine Towers with Large Slopes
Energies 2019, 12(13), 2608; https://doi.org/10.3390/en12132608
Received: 24 May 2019 / Revised: 26 June 2019 / Accepted: 29 June 2019 / Published: 7 July 2019
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Abstract
When the offshore wind energy industry attempts to develop in cold regions, ice load becomes the main technological challenge for offshore wind turbine foundation design. Dynamic ice loads acting on wind turbine foundations should be calculated in a reasonable way. The scope of [...] Read more.
When the offshore wind energy industry attempts to develop in cold regions, ice load becomes the main technological challenge for offshore wind turbine foundation design. Dynamic ice loads acting on wind turbine foundations should be calculated in a reasonable way. The scope of this study is to present a numerical model that considers the non-simultaneous ice crushing failure acting on the vertical structure of a wind turbine’s foundation. The local ice crushing force at the contact surface between the ice sheet and structure is calculated. The boundary of the ice sheet is updated at each time step based on the indentation length of the ice sheet according to its structure. Ice loads are validated against two model tests with three different structure models developed by other researchers. The time series of the ice forces derived from the simulation and model tests are compared. The proposed numerical model can capture the main trends of ice–wind turbine foundation interaction. The simulation results agree well with measured data from the model tests in terms of maximum ice force, which is a key factor for wind turbine design. The proposed model will be helpful for assisting the initial design of wind turbine foundations in cold regions. Full article
(This article belongs to the Special Issue Recent Advances in Offshore Wind Technology)
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Open AccessArticle
Coupled Motion Characteristics of Offshore Wind Turbines during the Integrated Transportation Process
Energies 2019, 12(10), 2023; https://doi.org/10.3390/en12102023
Received: 4 April 2019 / Revised: 16 May 2019 / Accepted: 21 May 2019 / Published: 27 May 2019
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Abstract
The offshore wind turbine (OWT) supported by bucket foundations can be installed in the integrated transportation process by a dedicated vessel. During the integrated transportation process, the wind turbine is considered as a coupling system with the transport ship, which is easily influenced [...] Read more.
The offshore wind turbine (OWT) supported by bucket foundations can be installed in the integrated transportation process by a dedicated vessel. During the integrated transportation process, the wind turbine is considered as a coupling system with the transport ship, which is easily influenced by waves and storms. In view of the motion response and influential factors, the heave and rock stiffness of the entire floating system was proposed, and then the analytical dynamic motion model of the coupling system was established based on the movement mechanism of the traditional floating body in the wave in this paper. Subsequently, the rationality of the proposed motion model was verified based on the field observation data, with the maximum deviation of the motion responses less than 14%. Further, the influence on the heave and pitch motion of the coupling system considering different factors (vessel speed, wave height, wind speed and wave angle) and the factor sensitivity were discussed by the novel analytical model. It is explained that the heave and pitch motion responses rise with the increase of the wave height and wave angle. Simultaneously, the responses decrease as the vessel speed increases considering sailing along the waves. On the contrary, the responses show an obvious increasing trend with the increase of vessel speed in the case of the top wave sailing. In addition, it is also illustrated that the wave height has the greatest influence on the heave and pitch motion responses, followed by the vessel speed. The wave angle has the lowest sensitivity when the heave and pitch motion are far away from its harmonic resonance region. Full article
(This article belongs to the Special Issue Recent Advances in Offshore Wind Technology)
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Open AccessArticle
Vindby—A Serious Offshore Wind Farm Design Game
Energies 2019, 12(8), 1499; https://doi.org/10.3390/en12081499
Received: 25 March 2019 / Revised: 17 April 2019 / Accepted: 18 April 2019 / Published: 20 April 2019
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Abstract
To maintain the increasing interest and development in offshore wind energy, novel training tools for engineers and researchers are needed. Concurrently, educational outreach activities are in demand to inform the public about the importance of offshore wind energy. In this paper, the development [...] Read more.
To maintain the increasing interest and development in offshore wind energy, novel training tools for engineers and researchers are needed. Concurrently, educational outreach activities are in demand to inform the public about the importance of offshore wind energy. In this paper, the development of a serious game about the design and management of offshore wind farms is presented to address such demands. Such a serious game may enable a new audience to explore the field of offshore wind as well as provide researchers entering the field a better understanding of the intricacies of the industry. This requires a simulation that is realistic but also effective in teaching information and engaging outreach. Ultimately, increased public support and expanded training tools are desired to improve decision-making and to provide opportunities to test and integrate innovative solutions. The work presented here includes the game design and implementation of a prototype game. The game design involves building a game framework and developing a simplified simulation. This simulation addresses weather prediction, offshore wind farm design, operation and maintenance, energy demand, climate change, and finance. Playtesting of the prototype demonstrated immersion and informed decision-making of the players and surveys revealed that knowledge had increased while playing the game. Recommendations for future versions of the game are listed. Full article
(This article belongs to the Special Issue Recent Advances in Offshore Wind Technology)
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Open AccessArticle
Transient Response Estimation of an Offshore Wind Turbine Support System
Energies 2019, 12(5), 891; https://doi.org/10.3390/en12050891
Received: 11 February 2019 / Revised: 28 February 2019 / Accepted: 2 March 2019 / Published: 7 March 2019
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Abstract
To obtain reliable estimations of the dynamic responses of high-rising marine structures such as offshore wind turbines with obvious nonzero initial conditions, traditional frequency-domain methods cannot be employed because they provide only steady-state results. A novel frequency-domain transient response estimation method for offshore [...] Read more.
To obtain reliable estimations of the dynamic responses of high-rising marine structures such as offshore wind turbines with obvious nonzero initial conditions, traditional frequency-domain methods cannot be employed because they provide only steady-state results. A novel frequency-domain transient response estimation method for offshore wind turbines is presented in this paper. This method builds upon a recent, significant theoretical development, which found that expressions of external loads in the frequency domain can be obtained by discretizing their eigenvalues and corresponding complex coefficients rather than directly by discrete Fourier transform (DFT) analysis, which makes it possible to deal with nonzero conditions in the frequency domain. One engineering advantage of this approach is its computational efficiency, as the motion equations of the system can be solved in the frequency domain. In order to demonstrate this approach, a case of a monopile-supported wind turbine with nonzero initial conditions was investigated. The numerical results indicate that the approach matches well with the time-domain method, except for a small, earlier portion of the estimated responses. A second case study of a sophisticated, jacket support wind turbine, involving practical issues such as complex external loads and computation efficiency, is also discussed, and comparisons of the results with the time-domain method and traditional frequency-domain method using the commercial software ANSYS are included here. Full article
(This article belongs to the Special Issue Recent Advances in Offshore Wind Technology)
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Open AccessArticle
Uncertainty in the Physical Testing of Floating Wind Energy Platforms’ Accuracy versus Precision
Energies 2019, 12(3), 435; https://doi.org/10.3390/en12030435
Received: 30 November 2018 / Revised: 23 January 2019 / Accepted: 28 January 2019 / Published: 30 January 2019
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Abstract
This paper examines the impact on experimental uncertainty of introducing aerodynamic and rotor gyroscopic loading on a model multirotor floating wind energy platform during physical testing. In addition, a methodology and a metric are presented for the assessment of the uncertainty across the [...] Read more.
This paper examines the impact on experimental uncertainty of introducing aerodynamic and rotor gyroscopic loading on a model multirotor floating wind energy platform during physical testing. In addition, a methodology and a metric are presented for the assessment of the uncertainty across the full time series for the response of a floating wind energy platform during wave basin testing. It is shown that there is a significant cost incurred in terms of experimental uncertainty through the addition of rotor thrust in the laboratory environment for the considered platform. A slight reduction in experimental uncertainty is observed through the introduction of gyroscopic rotor loading for most platform responses. Full article
(This article belongs to the Special Issue Recent Advances in Offshore Wind Technology)
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Open AccessFeature PaperArticle
A Crane Overload Protection Controller for Blade Lifting Operation Based on Model Predictive Control
Energies 2019, 12(1), 50; https://doi.org/10.3390/en12010050
Received: 12 November 2018 / Revised: 10 December 2018 / Accepted: 11 December 2018 / Published: 24 December 2018
Cited by 6 | PDF Full-text (2270 KB) | HTML Full-text | XML Full-text
Abstract
Lifting is a frequently used offshore operation. In this paper, a nonlinear model predictive control (NMPC) scheme is proposed to overcome the sudden peak tension and snap loads in the lifting wires caused by lifting speed changes in a wind turbine blade lifting [...] Read more.
Lifting is a frequently used offshore operation. In this paper, a nonlinear model predictive control (NMPC) scheme is proposed to overcome the sudden peak tension and snap loads in the lifting wires caused by lifting speed changes in a wind turbine blade lifting operation. The objectives are to improve installation efficiency and ensure operational safety. A simplified three-dimensional crane-wire-blade model is adopted to design the optimal control algorithm. A crane winch servo motor is controlled by the NMPC controller. The direct multiple shooting approach is applied to solve the nonlinear programming problem. High-fidelity simulations of the lifting operations are implemented based on a turbulent wind field with the MarIn and CaSADi toolkit in MATLAB. By well-tuned weighting matrices, the NMPC controller is capable of preventing snap loads and axial peak tension, while ensuring efficient lifting operation. The performance is verified through a sensitivity study, compared with a typical PD controller. Full article
(This article belongs to the Special Issue Recent Advances in Offshore Wind Technology)
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Open AccessArticle
An Aero-acoustic Noise Distribution Prediction Methodology for Offshore Wind Farms
Energies 2019, 12(1), 18; https://doi.org/10.3390/en12010018
Received: 28 November 2018 / Revised: 17 December 2018 / Accepted: 19 December 2018 / Published: 21 December 2018
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Abstract
Recently attention has been paid to wind farm noise due to its negative health impact, not only on human beings, but also to marine and terrestrial organisms. The current work proposes a numerical methodology to generate a numerical noise map for a given [...] Read more.
Recently attention has been paid to wind farm noise due to its negative health impact, not only on human beings, but also to marine and terrestrial organisms. The current work proposes a numerical methodology to generate a numerical noise map for a given wind farm. Noise generation from single wind turbines as well as wind farms has its basis in the nature of aerodynamics, caused by the interactions between the incoming turbulent flow and the wind turbine blades. Hence, understanding the mechanisms of airfoil noise generation, demands access to sophisticated numerical tools. The processes of modeling wind farm noise include three steps: (1) The whole wind farm velocity distributions are modelled with an improved Jensen’s wake model; (2) The individual wind turbine’s noise is simulated by a semi-empirical wind turbine noise source model; (3) Propagations of noise from all wind turbines are carried out by solving the parabolic wave equation. In the paper, the wind farm wake effect from the Horns Rev wind farm is studied. Based on the resulted wind speed distributions in the wind farm, the wind turbine noise source and its propagation are simulated for the whole wind farm. Full article
(This article belongs to the Special Issue Recent Advances in Offshore Wind Technology)
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Open AccessArticle
Experimental Study on the Performance of a Crashworthy Device for the Monopile Offshore Wind Turbine against Ship Impact
Energies 2018, 11(11), 3173; https://doi.org/10.3390/en11113173
Received: 26 September 2018 / Revised: 9 November 2018 / Accepted: 13 November 2018 / Published: 15 November 2018
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Abstract
In the present work, a crashworthy device for a monopile offshore wind turbine has been proposed, which consists of the inner two-layer rubber torus and the outer thin steel shell. The performance of the crashworthy device against ship impact has been investigated experimentally. [...] Read more.
In the present work, a crashworthy device for a monopile offshore wind turbine has been proposed, which consists of the inner two-layer rubber torus and the outer thin steel shell. The performance of the crashworthy device against ship impact has been investigated experimentally. Based on the prototype of a 4 MW monopile wind turbine in the East China Sea, the scale ratio of the test model has been designed to be 1/50. The test ship model has been simplified as a “rigid car” equipped with a high-frequency force sensor in the front, which is available for changing the ship mass with different weights. The ship-impact velocity can be accurately controlled by a motion platform driven by a direct current machine. The effect of the key design parameters of the crashworthy device on its anti-impact performance has been tested and compared under typical ship impact cases. The results indicate that the crashworthy device can effectively reduce both the ship impact force and the top nacelle acceleration, and the physical mechanism that has been clarified. The outer thin steel shell can significantly use its structural deformation to absorb the ship impact energy, which is beneficial for reducing the structural damage of the offshore wind turbine (OWT)’s tower. The inner rubber torus can effectively prolong the ship impact duration, which is available for smoothing the impact force. Finally, the porous design for the outer steel shell of the crashworthy device has been proposed and tested. Full article
(This article belongs to the Special Issue Recent Advances in Offshore Wind Technology)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Type: Article
Title: A conceptual framework towards structural health monitoring and digital twins of Offshore Wind Turbines
Author: Constantine Michailides 1*
Affiliation: 1 Department of Civil Engineering and Geomatics, Cyprus University of Technology, 3036 Limassol,  Cyprus; [email protected]
* Correspondence: [email protected]; Tel.: +357-25002396
Abstract: Offshore Wind Turbines (OWTs) technology can be considered as the leading and most  mature technology in the offshore renewable energy sector. Intense growth was met in offshore  wind technology during the past two decades, while it is expected that the growth will continue the  coming years with accelerating trends. The knowledge of the structural integrity status of the  different components of the OWT as well as of the OWT as a whole during its entire life time is of  high importance for the asset’s stakeholders. At the same time, the digitalization of any possible  asset can be considered as a global century target. The purpose of the present paper is threefold.  First, it presents critical published research related to Structural Health Monitoring (SHM) of OWTs.  Second, it offers a conceptual framework to summarize the research in this field; the proposed  framework is incorporating the required critical steps for the implementation of a SHM system that  can be applied in any possible OWT. Third it presents critical advances but also needs about the  development of digital twins of OWTs with the use of SHM systems.
Keywords: Offshore Wind Turbines; Structural Health Monitoring; Digital Twins; Preventive Maintenance; Wave-Structure interaction.
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