Special Issue "Offshore Wind Energy"

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Energy".

Deadline for manuscript submissions: closed (31 January 2019)

Special Issue Editor

Guest Editor
Dr. Mohsen N. Soltani

Associate Professor, Department of Energy Technology, Aalborg University, Esbjerg 6700, Denmark
Website | E-Mail
Interests: wind power; floating wind turbines; modeling; fault diagnosis; control systems

Special Issue Information

Dear Colleagues,

Offshore Wind Energy is growing continuously around the world, led by Europe, aiming to reach its goal of 35 GW offshore wind by 2020. Constant wind at sea will enable wind turbines to increase their full load hours during the year, and thereby, offshore wind becomes a reliable source of power with significant contributions to stabilizing the renewable-based grid. Further development and growth of offshore wind energy requires a continuation of technology improvements that lower the costs of offshore wind energy.

This Special Issue focuses on recent research and technology improvements, including, but not limited to:

  • Transportation of offshore wind turbines
  • Installation technologies
  • Foundation technologies including floating offshore wind turbines
  • Optimization of offshore wind farm layouts
  • Optimization of used components and controls
  • Improvements in aerodynamics and aero-elasticity
  • Increased reliability and condition monitoring
  • Optimal operation and (predictive) maintenance
  • Improvement of power systems for offshore conditions
  • Generator and power electronics for offshore wind
  • Offshore data collection including communication, processing, and learning from data

Dr. Mohsen N. Soltani
Guest Editor

Manuscript Submission Information

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Keywords

  • Offshore wind foundation
  • Offshore wind installation
  • Floating wind turbine
  • Condition monitoring
  • Wind turbine Control
  • Wind farm control
  • Wind turbine reliability
  • Wind turbine maintenance
  • Data processing
  • Aerodynamics/ Aero-servo-elasticity
  • Wind Farm layout
  • Offshore power system

Published Papers (5 papers)

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Research

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Open AccessArticle Investigation of Hydrodynamic Forces for Floating Offshore Wind Turbines on Spar Buoys and Tension Leg Platforms with the Mooring Systems in Waves
Appl. Sci. 2019, 9(3), 608; https://doi.org/10.3390/app9030608
Received: 28 December 2018 / Revised: 1 February 2019 / Accepted: 4 February 2019 / Published: 12 February 2019
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Abstract
This study aims to develop a modularized simulation system to estimate dynamic responses of floating Offshore Wind Turbines (OWTs) based on the concepts of spar buoy and Tension Leg Platform (TLP) corresponding with two typical mooring lines. The modular system consists of the [...] Read more.
This study aims to develop a modularized simulation system to estimate dynamic responses of floating Offshore Wind Turbines (OWTs) based on the concepts of spar buoy and Tension Leg Platform (TLP) corresponding with two typical mooring lines. The modular system consists of the hydrodynamic simulator based the Cummins time domain equation, the Boundary Element Method (BEM) solver based on the 3D source distribution method, and an open-source visualization software ParaView to analyze the interaction between floating OWTs and waves. In order to realize the effects of mooring loads on the floating OWTs, the stiffness and damping matrices are applied to the quasi-static mooring system. The Response Amplitude Operators (RAOs) are compared between our predicted results and other published data to verify the modularized simulation system and understand the influence of mooring load on the motion responses in regular or irregular waves. It is also demonstrated that the quasi-static mooring system is applicable to different types of mooring lines as well as determining real-time motion responses. Eventually, wave load components at the resonance frequencies of different motion modes for selected floating OWTs would be present in the time domain. Full article
(This article belongs to the Special Issue Offshore Wind Energy)
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Open AccessArticle Wind Farm Power Production Assessment: Introduction of a New Actuator Disc Method and Comparison with Existing Models in the Context of a Case Study
Appl. Sci. 2019, 9(3), 431; https://doi.org/10.3390/app9030431
Received: 17 December 2018 / Revised: 19 January 2019 / Accepted: 21 January 2019 / Published: 28 January 2019
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Abstract
The aim of the present study is to perform a comparative analysis of two actuator disc methods (ACD) and two analytical wake models for wind farm power production assessment. To do so, wind turbine power production data from the Lillgrund offshore wind farm [...] Read more.
The aim of the present study is to perform a comparative analysis of two actuator disc methods (ACD) and two analytical wake models for wind farm power production assessment. To do so, wind turbine power production data from the Lillgrund offshore wind farm in Sweden is used. The measured power production for individual wind turbines is compared with results from simulations, done in the WindSim software, using two ACD methods (ACD (2008) and ACD (2016)) and two analytical wake models widely used within the wind industry (Jensen and Larsen wake models). It was found that the ACD (2016) method and the Larsen model outperform the other method and model in most cases. Furthermore, results from the ACD (2016) method show a clear improvement in the estimated power production in comparison to the ACD (2008) method. The Jensen method seems to overestimate the power deficit for all cases. The ACD (2016) method, despite its simplicity, can capture the power production within the given error margin although it tends to underestimate the power deficit. Full article
(This article belongs to the Special Issue Offshore Wind Energy)
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Open AccessFeature PaperArticle Simultaneous Optimisation of Cable Connection Schemes and Capacity for Offshore Wind Farms via a Modified Bat Algorithm
Appl. Sci. 2019, 9(2), 265; https://doi.org/10.3390/app9020265
Received: 12 December 2018 / Revised: 1 January 2019 / Accepted: 9 January 2019 / Published: 13 January 2019
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Abstract
Offshore wind energy has attracted worldwide attention and investments in the last decade due to the stability and abundance of wind resources. As one of the main components of this, internal array cables have a great impact on the levelised cost of energy [...] Read more.
Offshore wind energy has attracted worldwide attention and investments in the last decade due to the stability and abundance of wind resources. As one of the main components of this, internal array cables have a great impact on the levelised cost of energy of offshore wind farms, and thus their connection layout is a matter of concern. In this paper, a classical mathematical problem—the traveling salesman problem, which belongs to the field of graph theory—is applied to solve the offshore wind farm cable connection layout optimization problem. Both the capital investment on cables, cable laying, and the cost of power losses associated with array cables are considered in the proposed model. A modified bat algorithm is presented to resolve the problem. Furthermore, a cable crossing detection method is also adopted to avoid obtaining crossed cable connection layouts. The effectiveness was verified through a case study. Full article
(This article belongs to the Special Issue Offshore Wind Energy)
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Open AccessArticle Response Characteristics of the DeepCwind Floating Wind Turbine Moored by a Single-Point Mooring System
Appl. Sci. 2018, 8(11), 2306; https://doi.org/10.3390/app8112306
Received: 19 October 2018 / Revised: 14 November 2018 / Accepted: 16 November 2018 / Published: 20 November 2018
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Abstract
In recent years, the SPM (Single-Point Mooring) concept has been widely employed in several branches of the naval architecture and marine engineering field, such as FPSOs (Floating Production, Storage and Offloading units), offshore oil rigs, etc., but not yet popular in the offshore [...] Read more.
In recent years, the SPM (Single-Point Mooring) concept has been widely employed in several branches of the naval architecture and marine engineering field, such as FPSOs (Floating Production, Storage and Offloading units), offshore oil rigs, etc., but not yet popular in the offshore wind energy. To investigate the response characteristics of an SPM-moored FWT (Floating Wind Turbine), in the present work, we perform a numerical study on the DeepCwind semisubmersible wind turbine, using the state-of-the-art open-source tool FAST. The free-decay test results show that the SPM layout affects the natural periods of the wind turbine in rotational modes, as well as the mooring stiffness of the diagonal rotational and crossing rotational-translational terms, especially in relation to the yaw mode. Comparisons of the RAOs (Response Amplitude Operators) elucidate that the presence of wind influences significantly the sway, roll and yaw motions of the SPM layout. Finally, the weathervane test shows that an asymmetry exists in the free-yaw motion response when the semisubmersible wind turbine is moored by an SPM system. Full article
(This article belongs to the Special Issue Offshore Wind Energy)
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Review

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Open AccessReview Decision Support Models for Operations and Maintenance for Offshore Wind Farms: A Review
Appl. Sci. 2019, 9(2), 278; https://doi.org/10.3390/app9020278
Received: 11 December 2018 / Revised: 31 December 2018 / Accepted: 4 January 2019 / Published: 14 January 2019
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Abstract
This paper reviews the state of the art in offshore wind farm operations and maintenance with a focus on decision support models for the scheduling of maintenance. Factors influential to maintenance planning are collected from the literature and their inclusion in state-of-the-art models [...] Read more.
This paper reviews the state of the art in offshore wind farm operations and maintenance with a focus on decision support models for the scheduling of maintenance. Factors influential to maintenance planning are collected from the literature and their inclusion in state-of-the-art models is discussed. Methods for modeling and optimization are presented. The methods currently used and possible alternatives are discussed. The existing models are already able to aid the decision-making process. They can be improved by applying more advanced mathematical methods, including uncertainties in the input, regarding more of the influential factors, and by collecting, analyzing, and subsequently using more accurate data. Full article
(This article belongs to the Special Issue Offshore Wind Energy)
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