Offshore Wind Turbine Installation Research Articles

Development and application of a simulator for offshore wind turbine blades installation

In an offshore environment, offshore wind energy resources are more available and stable, but the investment cost is much higher than that of onshore wind. The installation cost is a crucial factor of the investment. With the increasing number of planned and approved offshore wind farms, offshore wind turbine installation and relevant operations have received tremendous attention. Therefore, expediting the turbine-structure mating operations through a higher level of automation in offshore wind turbine installations may provide important economic benefits. To achieve a higher automation level and reduce the weather waiting time during the installation of offshore wind turbines, a flexible simulation-verification framework with high fidelity is needed. However, state-of-the-art wind turbine numerical analysis code is neither convenient nor open enough for applications concerning the design and verification of control algorithms. MATLAB/Simulink is among the most widely utilized numerical platforms by control engineers and researchers. This paper describes the development of a modularized blade installation simulation toolbox for the purpose of control design in MATLAB/Simulink. The toolbox can be used to simulate several blade installation configurations, both onshore and offshore. The paper presents the key features and equations of the different modules, exemplified by a single blade installation operation. Code-to-code verification results are presented and discussed with both quasi-steady wind and three-dimensional turbulent wind field.

Multi-Criteria Decision Analysis for Benchmarking Human-Free Lifting Solutions in the Offshore Wind Energy Environment

With single components weighing up to hundreds of tonnes and lifted to heights of approximately 100 m, offshore wind turbines can pose risks to personnel, assets, and the environment during installation and maintenance interventions. Guidelines and standards for health and safety in lifting operations exist; however, having people directly beneath the load is still common practice in offshore wind turbine installations. Concepts for human-free offshore lifting operations in the categories of guidance and control, connections, and assembly are studied in this work. This paper documents the process of applying Multi-Criteria Decision Analysis (MCDA), using experts’ opinions for the importance of defined criteria obtained by conducting an industry survey, to benchmark the suitability of the concepts at two stages. Stage one streamlined possible options and stage two ranked the remaining suite of options after further development. The survey results showed that criteria such as ‘reduction of risk’, ‘handling improvement’ and ‘reliability of operation’ were most important. The most viable options, weighted by industry opinion, to remove personnel from areas of high risk are: Boom Lock and tag lines, a camera system with mechanical guidance, and automated bolt installation/fastening for seafastening. The decision analysis framework developed can be applied to similar problems to inform choices subject to multiple criteria.

Damage detection in grouted connections using electromechanical impedance spectroscopy

Grouted connections are structural joints formed by a cementitious grout cast between two concentric circular tubes. They are widely used in the offshore construction of oil and gas platforms, and for offshore wind turbines (monopiles and jackets). However, their application in offshore wind turbine installations can be critical due to the high bending moments coming from wind loading. Recently, it was found that grouted connections show limited performance in offshore wind turbine installations leading to settlements between the steel tubes and steel/grout debonding. Hence, structural health monitoring techniques for grouted connections are needed that ensure a safe and reliable operation of offshore wind turbines. This short communication describes the successful application of electromechanical impedance spectroscopy for damage detection in grouted connections.

Assessing offshore wind turbine reliability and availability

The renewables sector and particularly offshore wind energy is a fast developing industry over the last few years. Especially, activities related to the installation, and operation and maintenance of offshore wind turbines become a challenging task with inherent risks. This article assesses the risks related to the above stages of a wind farm lifecycle using the failure mode, effects and criticality analysis and hazard identification methods. All works, from installation to operation and maintenance, are considered together with the wind turbine main components. An integrated risk analysis methodology is presented addressing personnel Safety (S), Environmental impact (E), Asset integrity (A), and Operation (O). The above is supplemented by a cost analysis with the aid of Bayesian belief networks method to assist the decision-making process related to installation, and operation and maintenance tasks. All major risks and critical wind turbine components are identified as well as measures are suggested to prevent or mitigate them. Moreover, inspection and maintenance plans are elaborated in general for the mentioned activities.

Improved Methodology of Weather Window Prediction for Offshore Operations Based on Probabilities of Operation Failure

The offshore wind industry is building and planning new wind farms further offshore due to increasing demand on sustainable energy production and already occupied prime resource locations closer to shore. Costs of operation and maintenance, transport and installation of offshore wind turbines already contribute significantly to the cost of produced electricity and will continue to increase, due to moving further offshore, if the current techniques of predicting offshore wind farm accessibility are to stay the same. The majority of offshore operations are carried out by specialized ships that must be hired for the duration of the operation. Therefore, offshore wind farm accessibility and costs of offshore activities are primarily driven by the expected number of operational hours offshore and waiting times for weather windows, suitable for offshore operations. Having more reliable weather window estimates would result in better wind farm accessibility predictions and, as a consequence, potentially reduce the cost of offshore wind energy. This paper presents an updated methodology of weather window prediction that uses physical offshore vessel and equipment responses to establish the expected probabilities of operation failure, which, in turn, can be compared to maximum allowable probability of failure to obtain weather windows suitable for operation. Two case studies were performed to evaluate the feasibility of the improved methodology, and the results indicated that it produced consistent and improved results. In fact, the updated methodology predicts 57% and 47% more operational hours during the test period when compared to standard alpha-factor and the original methodologies.

Designing for safe operations: promoting a human-centred approach to complex vessel design

ABSTRACTThe benefits of a human-centred approach to design have been widely recognised throughout industry, in the research community and by regulatory bodies. In the maritime domain, it is also beginning to make an impact. This article explores how a human-centred approach may successfully be achieved within the context of ship design using a case study from a project to create conceptual designs for two offshore wind turbine installation vessels. Using vessel designs as a mediating tool between designers, users and human factors specialists, basic task analysis and link analysis methods were used to incorporate operational knowledge into the design process. After applying this to the integration of a dynamic positioning system on one of the vessels, the designers concluded that a human-centred approach had improved not only ship safety, but also safety, efficiency and cost-effectiveness in operations.

Towards a Risk-based Decision Support for Offshore Wind Turbine Installation and Operation & Maintenance

Costs of operation & maintenance, assembly, transport and installation of offshore wind turbines contribute significantly to the total cost of offshore wind farm. These operations are mostly carried out by specific ships that have to be hired for the operational phase and for duration of installation process, respectively. Duration, and therefore ship hiring costs is, among others, driven by waiting time for weather windows for weather-sensitive operations. Today, state of the art decision making criteria for weather-sensitive operations are restrictions to the significant wave height and the average wind velocity at reference height. However, actual limitations are physical, related to response of equipment used e.g. crane wire tension, rotor assembly motions while lifting, etc. Transition from weather condition limits to limits on physical equipment response in decision making would improve weather window predictions, potentially reducing cost of offshore wind energy. This paper presents a novel approach to weather window estimation using ensemble weather forecasts and statistical analysis of simulated installation equipment response.

Assessment of the Dynamic Responses and Allowable Sea States for a Novel Offshore Wind Turbine Installation Concept Based on the Inverted Pendulum Principle

This paper presents a numerical study for preliminary assessment of the dynamic responses and allowable sea states for the installation of an offshore wind turbine (OWT) tower and rotor nacelle assembly (RNA) based on a novel method. This method is based on the inverted pendulum principle and consists of various sequential activities for which the allowable limits of sea states need to be established. For critical installation activities, numerical analyses methodologies have been applied to model the actual operations. For the parameters limiting the execution of the operations, response statistics are provided. It is found that at least 45 seeds are required to achieve convergence of snap force statistics during the OWT lift-off. The response statistics are used to calculate a characteristic value corresponding to a target probability of non-exceedance. For the lift-off and mating operations, these characteristic values are compared with the allowable limits of the response parameters to establish the allowable limits of sea states. In addition, sensitivity study on key modeling parameters are conducted. Spring coefficients of contact elements and hinged connections, winch speed, and hoist wire stiffness are shown to be important modeling parameters. The results provided in this paper are important for future finite element modeling (FEM) and cost-effective design of the structural components.

Methodology for assessment of the operational limits and operability of marine operations

This paper deals with a general methodology for assessment of the operational limits and the operability of marine operations during the planning phase with emphasis on offshore wind turbine (OWT) installation activities. A systematic approach based on operational procedures and numerical analyses is used to identify critical events and corresponding response parameters. Identifying them is important for taking mitigation actions by modifying the equipment and procedures. In the proposed methodology, the operational limits are established in terms of allowable limits of sea states. In addition, the operational limits of a complete marine operation are determined by taking into account several activities, their durations, continuity, and sequential execution. This methodology is demonstrated in a case study dealing with installation of an offshore wind turbine monopile (MP) and a transition piece (TP). The developed methodology is generic and applicable to any marine operation for which operational limits need to be established and used on-board as a basis for decision-making towards safe execution of operations.

A benders decomposition approach for solving the offshore wind farm installation planning at the North Sea

Wind farm installation and particularly offshore wind farm installation is highly complex due to high dependency on weather and remarkably large components. Amongst others projects at North Sea face considerable interruptions due to severe weather conditions. The problem we refer to consists of determining the renting period of the offshore installation vessels and the scheduling of the operations for building the wind farm. Planners need to make these decisions under the uncertain wind states. A deterministic offshore wind turbine installation model is not suitable to capture the uncertainties which may leave the vessel resource unused or vessel being sent offshore in unfavorable conditions. Accordingly, this study proposes a model that considers disruptions arising from uncertain weather conditions which stand as the main challenge for such projects. As the compact formulation fails to provide solutions due to the large number of scenarios, an approach based on Benders decomposition is developed. The tool is applied to two major wind farm projects, “Bard 1” and “Borkum West” at the North Sea using real weather data over two years. The two-stage model leans to conservatively use the suitable conditions in advance to avoid huge waiting costs incurred under severe weather. Motivated by experts at Wagenborg and MPI Offshore, we extend our experiments to analyze cases where plants are build further away from the shore. The tool presented in this study is suitable for being used in the planning of wind farm projects providing competent solutions.

Comparative evaluation of different offshore wind turbine installation vessels for Korean west–south wind farm

The purpose of this study is to evaluate various means of wind power turbines installation in the Korean west–south wind farm (Test bed 100 MW, Demonstrate site 400 MW). We presented the marine environment of the southwest offshore wind farm in order to decide the appropriate installation vessel to be used in this site. The various vessels would be WTIV (Wind turbine installation vessel), jack-up barge, or floating crane … etc. We analyzed the installation cost of offshore wind turbine and the transportation duration for each vessel. The analysis results showed the most suitable installation means for offshore wind turbine in the Korean west–south wind farm.

Assessment of Allowable Sea States During Installation of Offshore Wind Turbine Monopiles With Shallow Penetration in the Seabed

Installation of offshore wind turbines (OWTs) requires careful planning to reduce costs and minimize associated risks. The purpose of this paper is to present a method for assessing the allowable sea states for the initial hammering process (shallow penetrations in the seabed) of a monopile (MP) using a heavy lift floating vessel (HLV) for use in the planning of the operation. This method combines the commonly used installation procedure and the time-domain simulations of the sequential installation activities. The purpose of the time-domain simulation is to quantitatively study the system dynamic responses to identify critical events that may jeopardize the installation and the corresponding limiting response parameters. Based on the allowable limits and the characteristic values of the limiting response parameters, a methodology to find the allowable sea states is proposed. Case studies are presented to show the application of the methodology. The numerical model of the dynamic HLV–MP system includes the coupling between HLV and MP via a gripper device, and soil–MP interaction at different MP penetration depths. It is found that the limiting parameters are the gripper force and the inclination of the MP. The systematic approach proposed herein is general and applies to other marine operations.

Dynamic response analysis of offshore wind turbine installation suspended by a floating crane

In this paper, a dynamic model for the offshore wind turbine installation is proposed. And this model is coupled by the wind turbine and the floating crane considering 6-DOF floating crane, 5-DOF wind turbine and elastic stretch of the hoisting cable. And when the wind turbine lands on the supporting structure, the displacement constraint is applied at the wind turbine. During the process, the relaxation of the hoisting cable is considered. In addition, the nonlinear hydrostatic force, environmental force, hoisting cable force and mooring force are considered as the external force. The motions of wind turbine and the floating crane are studied. From the numerical analysis, it is found that the release velocity, the release height and wave condition have a great effect on the motion of wind turbine.

海上风电安装船结构强度分析

本文对一艘86.7 m海上风电安装船在作业过程中可能遇到环境载荷、设计载荷与功能载荷进行计算，并确定了包括自升固定，正常作业起吊与预压在内的8种计算工况。应用大型商用有限元计算软件ABAQUS进行全船有限元建模，并对8种典型工况下的船舶关键部位进行了结构强度分析，为海上风电安装船结构强度分析提供了可供参考的数值方法。 The environment load, design load and functional load acting on 86.7 m offshore wind turbine installation vessel were calculated in this paper, and 8 cases including jack-up fixing, lifting and pre-pressure of normal operation were determined. Commercial FEM software—ABAQUS was applied to model the whole hull and structural strength of key components of ship was analyzed. The numerical simulation process could be referred on design of offshore wind turbine installation vessel.

Design and model confirmation of the intermediate scale VolturnUS floating wind turbine subjected to its extreme design conditions offshore Maine

AbstractFloating offshore wind turbines are gaining considerable interest in the renewable energy sector. Design standards for floating offshore wind turbines such as the American Bureau of Shipping (ABS) Guide for Building and Classing Floating Offshore Wind Turbine Installations are relatively new and few if any floating wind turbines have yet experienced the prescribed design extreme environmental conditions. Only a few pilot floating turbines have been deployed in Europe and Japan. These turbines have been designed for long return period storm events and are not likely to see their extreme design conditions during early deployment periods because of the low probability of occurrence. This paper presents data collected for an intermediate scale floating semi‐submersible turbine intentionally placed offshore Maine in a carefully selected site that subjects the prototype to scale extreme conditions on a frequent basis. This prototype, called VolturnUS 1:8, was the first grid‐connected offshore wind turbine in the Americas, and is a 1:8 scale model of a 6 MW prototype. The test site produces with a high probability 1:8 scale wave environments, and a commercial turbine has been selected so that the wind environment/rotor combination produces 1:8‐scale aerodynamic loads appropriate for the site wave environment. In the winter of 2013–2014, this prototype has seen the equivalent of 50 year to 500 year return period storms exercising it to the limits prescribed by design standards, offering a unique look at the behavior of a floating turbine subjected to extreme design conditions. Performance data are provided and compared to full‐scale predicted values from numerical models. There are two objectives in presenting this data and associated analysis: (i) validate numerical aeroelastic hydrodynamic coupled models and (ii) investigate the performance of a near full‐scale floating wind turbine in a real offshore environment that closely matches the prescribed design conditions from the ABS Guide. Copyright © 2015 John Wiley & Sons, Ltd.

모노파일 해상풍력발전의 이송과 설치를 위한 일정계획 및 비용분석 시뮬레이션

For reasons such as global warming, depletion of fossil fuels and the danger of nuclear energy the research and development of renewable energy is actively underway. Wind energy has advantages over another renewable energy in terms of location requirements, energy efficiency and reliability. Nowadays the research and development area is expanded to offshore because it can supply more wind reliability and free from noise pollution. In this study, the monopile offshore wind turbine transportation and installation (T&I) process are investigated. In addition, the schedule and cost for the process are estimated by discrete event simulation. For the simulation, simulation models for various means of T&I are developed. The optimum T&I execution plan with shortest duration and lowest cost can be found by using different mission start day and T&I means.

A Study on Static Water Resistance Prediction of Offshore Wind Turbine Installation Vessel

A mathematical model is proposed for predicting static water resistance of offshore wind turbine installation vessel and to calculate the resistance of a certain type of offshore wind turbine installation vessel. In order to verify the efficiency of this mathematical model, the comparison between results calculated by it and actual model test has been made. The conclusion indicates that the estimation method is reliable, and it can provide reference for resistance calculation of similar type vessels. Currently in China, there are no references for the effective prediction and calculation of the resistance for offshore wind turbine installation vessel. Therefore the proposed method has important value of engineering application in the areas of effective resistance estimation method of offshore wind turbine installation vessel, as well as the numerical calculation of ship hydrodynamics.

Capacitive sensors for offshore scour monitoring

One of the main challenges in the design and operation of offshore wind turbines arises from the uncertainty about maximum scour depth around their foundations. Scour action can lead to excessive excavation of the surrounding seabed and is being considered as a major risk for offshore wind farm developments. An ability to gather information concerning the evolution of scouring will enable the validation of models derived from laboratory-based studies, the assessment of different engineering designs and the development of improved scour countermeasure techniques. However, real-time scour data are not being collected due to a lack of available instrumentation techniques. This paper proposes a new scour monitoring technology for offshore wind turbine installations. The monitoring system consists of arrays of small capacitive scour probes installed around the foundation structure and linked to a wireless network to enable remote data acquisition. Based on this research, it is concluded that the sensor is capable of exhibiting high sensitivity to scour and sediment deposition processes for common sea floor mediums under different temperature conditions in saline water. The proposed monitoring system has considerable potential for field applications that will contribute to improving the resilience and sustainability of offshore structures.

Structural health and prognostics management for the enhancement of offshore wind turbine operations and maintenance strategies

ABSTRACTOffshore wind turbines are an attractive source for clean and renewable energy for reasons including their proximity to population centers and higher capacity factors. One obstacle to the more widespread installation of offshore wind turbines in the USA, however, is that recent projections of offshore operations and maintenance costs vary from two to five times the land‐based costs. One way in which these costs could be reduced is through use of a structural health and prognostics management (SHPM) system as part of a condition‐based maintenance paradigm with smart loads management. This paper contributes to the development of such strategies by developing an initial roadmap for SHPM, with application to the blades. One of the key elements of the approach is a multiscale simulation approach developed to identify how the underlying physics of the system are affected by the presence of damage and how these changes manifest themselves in the operational response of a full turbine. A case study of a trailing edge disbond is analysed to demonstrate the multiscale sensitivity of damage approach and to show the potential life extension and increased energy capture that can be achieved using simple changes in the overall turbine control and loads management strategy. The integration of health monitoring information, economic considerations such as repair costs versus state of health, and a smart loads management methodology provides an initial roadmap for reducing operations and maintenance costs for offshore wind farms while increasing turbine availability and overall profit. Copyright © 2013 John Wiley & Sons, Ltd.

Predicting underwater radiated noise levels due to the first offshore wind turbine installation in the United States

Noise generated by offshore impact pile driving radiates into the air, water, and sediment. Predicting noise levels around the support structures at sea is required to estimate the effects of the noise on marine life. Based on high demands developing renewable energy source, the United States will begin the first pile driving within one to two years. It is necessary to investigate acoustic impact using our previously verified coupled Finite Element (Commercial FE code Abaqus) and Monterey Miami Parabolic Equation (2D MMPE) models [J. Acoust. Soc. Am. 131(4), 3392 (2012)]. In the present study, we developed a new coupled FE-MMPE model for the identification of zone of injury due to offshore impact pile driving. FE analysis produced acoustic pressure outputs on the surface of the pile, which are used as a starting field for a long range 2D MMPE propagation model. It calculates transmission loss for N different azimuthal directions as function of distance from the location of piling with the inputs of corresponding bathymetry and sediment properties. We will present predicted zone of injury by connecting N different distances of equivalent level fishes may get permanent injury due to the first offshore wind farm installation in the United States.