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Special Issue "Probabilistic Methods for Design and Planning of Operation and Maintenance of Wind Turbines"

A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "B2: Wind, Wave and Tidal Energy".

Deadline for manuscript submissions: closed (30 May 2019) | Viewed by 13560

Special Issue Editors

Prof. Dr. John Dalsgaard Sørensen
E-Mail Website
Guest Editor
Department of the Built Environment, Aalborg University, 9220 Aalborg, Denmark
Interests: structural reliability; operation and maintenance; probabilistic design; offshore structures; risk analysis; wind turbines
Dr. Mahmood Shafiee
E-Mail Website
Guest Editor
Cranfield University, Department of Energy & Power, Centre of Offshore Energy Engineering, Cranfield, Bedforshire, UK
Interests: Offshore Wind; Operation and Maintenance (O&M); Risk and Reliability; Asset Integrity; Probabilistic modelling
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Special Issue Information

Dear Colleagues,

Wind turbines are renewable energy devices that have the potential to contribute significantly to the production of electricity worldwide. Probabilistic design of wind turbines can be based on the general decision making levels for engineering design as stated in ISO2394:2015, these are: 1) risk-informed decision making; 2) reliability-based decision making (probabilistic design); 3) semi-probabilistic approach (using partial safety factors). For the probabilistic design of wind turbines, reliability analyses are essential to be carried out for critical components in a wind turbine, which can be divided into three categories of structural, mechanical and electrical components. Design load cases to be considered in probabilistic design includes: fatigue, extreme loads during operation, in parked position and in fault conditions. Another important aspect in the stochastic modelling is to include all available information from experience, and tests on the coupon level, subcomponent level and full-scale level as well as measurements on climatic conditions. Further, choice of the target/minimum reliability level is important.

For offshore wind turbines costs to Operation and Maintenance (OM) can be significant contributors to the Levelized Cost of Energy (LCOE). Further, OM costs are highly dependent on the reliability of components and systems. OM is typically performed using a corrective strategy supplemented with preventive maintenance, which to some extend is based on information from condition monitoring. Generally, for wind turbines, more and more OM is being performed based on a preventive maintenance strategy. Further, risk-based approaches are being developed where a life-cycle approach is used considering the total expected costs.

Papers for this Special Issue should focus on probabilistic design, reliability assessment and reliability- and risk-based planning of OM for wind turbines.

Prof. Dr. John Dalsgaard Sørensen
Dr. Mahmood Shafiee
Guest Editors

Manuscript Submission Information

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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 2200 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

  • probabilistic design
  • wind turbines
  • operation and maintenance
  • risk-based methods
  • reliability

Published Papers (7 papers)

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Research

Article
Resilience Informed Integrity Management of Wind Turbine Parks
Energies 2019, 12(14), 2729; https://doi.org/10.3390/en12142729 - 17 Jul 2019
Cited by 5 | Viewed by 1580
Abstract
A novel framework for resilience modeling of wind turbine parks is proposed in support of optimization of decisions on asset integrity management. The concept of resilience originating from natural and social sciences is adapted here to facilitate the joint optimization of decision alternatives [...] Read more.
A novel framework for resilience modeling of wind turbine parks is proposed in support of optimization of decisions on asset integrity management. The concept of resilience originating from natural and social sciences is adapted here to facilitate the joint optimization of decision alternatives related to design, with decision alternatives addressing organizational performance. The generic probabilistic systems representation framework by the Joint Committee on Structural Safety (JCSS) (2008) is utilized to establish a scenario-based modeling of how different types of disturbances may lead to damages and failures of systems and sub-systems of wind turbine parks, together with associated direct and indirect consequences. Special emphasis is directed on the consistent probabilistic representation of the uncertainties and the stochastic and causal dependencies within the wind turbine park system. The framework facilitates the identification of optimal asset integrity management decision alternatives that fulfill given requirements to resilience. The potentials associated with the use of the framework are highlighted by an example considering a wind turbine park with ten identical wind turbines, with each modelled as a system of mechanical, electrical, and structural sub-systems. The resilience performance characteristics of the wind turbine park, such as the expected value of generated service life benefits, the expected value of production down time, and the probability of resilience failure are modelled and quantified such as to support the ranking of decision alternatives relating to the design of the wind turbine sub-systems, the level of organizational preparedness, the percentage of the generated service life benefits to be kept to ensure sufficient economic capacity to deal with future disturbances, and the stock-keeping of essential spare parts. Full article
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Article
Risk Assessment and Value of Action Analysis for Icing Conditions of Wind Turbines Close to Highways
Energies 2019, 12(14), 2653; https://doi.org/10.3390/en12142653 - 10 Jul 2019
Cited by 11 | Viewed by 2096
Abstract
The paper presents research results from the Marie Skłodowska-Curie Innovative Training Network INFRASTAR in the field of reliability approaches for decision-making for wind turbines and bridges. This paper addresses the application of Bayesian decision analysis for installation of heating systems in wind turbine [...] Read more.
The paper presents research results from the Marie Skłodowska-Curie Innovative Training Network INFRASTAR in the field of reliability approaches for decision-making for wind turbines and bridges. This paper addresses the application of Bayesian decision analysis for installation of heating systems in wind turbine blades in cases where an ice detection system is already installed in order to allow wind turbines to be placed close to highways. Generally, application of ice detection and heating systems for wind turbines is very relevant in cases where the wind turbines are planned to be placed close to urban areas and highways, where risks need to be considered due to icing events, which may lead to consequences including human fatality, functional disruptions, and/or economic losses. The risk of people being killed in a car passing on highways near a wind turbine due to blades parts or ice pieces being thrown away in cases of over-icing is considered in this paper. The probability of being killed per kilometer and per year is considered for three cases: blade parts thrown away as a result of a partial or total failure of a blade, ice thrown away in two cases, i.e., of stopped wind turbines and of wind turbines in operation. Risks due to blade parts being thrown away cannot be avoided, since low strengths of material, maintenance or manufacturing errors, mechanical or electrical failures may result in failure of a blade or blade part. The blade (parts) thrown away from wind turbines in operation imply possible consequences/fatalities for people near the wind turbines, including in areas close to highways. Similar consequences are relevant for ice being thrown away from wind turbine blades during icing situations. In this paper, we examine the question as to whether it is valuable to put a heating system on the blades in addition to ice detection systems. This is especially interesting in countries with limited space for placing wind turbines; in addition, it is considered if higher power production can be obtained due to less downtime if a heating system is installed. Full article
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Article
Maintenance Optimization of Offshore Wind Turbines Based on an Opportunistic Maintenance Strategy
Energies 2019, 12(14), 2650; https://doi.org/10.3390/en12142650 - 10 Jul 2019
Cited by 12 | Viewed by 1400
Abstract
Owing to the late development of offshore wind power in China, operational data and maintenance experience are relatively scarce. Due to the harsh environmental conditions, a reliability analysis based on limited sample fault data has been regarded as an effective way to investigate [...] Read more.
Owing to the late development of offshore wind power in China, operational data and maintenance experience are relatively scarce. Due to the harsh environmental conditions, a reliability analysis based on limited sample fault data has been regarded as an effective way to investigate maintenance optimization for offshore wind farms. The chief aim of the present work is to develop an effective strategy to reduce the maintenance costs of offshore wind turbines in consideration of their accessibility. The three-parameter Weibull distribution method was applied to failure rate estimation based on limited data. Moreover, considering the impacts of weather conditions on the marine maintenance activities, the Markov method and dynamic time window were used to depict the weather conditions. The opportunistic maintenance strategy was introduced to cut down on the maintenance costs through optimization of the preventive maintenance age and opportunistic maintenance age. The simulation analysis we have performed showed that the maintenance costs of the opportunistic maintenance strategy were 10% lower than those of the preventive maintenance strategy, verifying the effectiveness of the proposed maintenance strategy. Full article
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Article
Response-Based Assessment of Operational Limits for Mating Blades on Monopile-Type Offshore Wind Turbines
Energies 2019, 12(10), 1867; https://doi.org/10.3390/en12101867 - 16 May 2019
Cited by 18 | Viewed by 1944
Abstract
Installation of wind-turbine blades on monopile-type offshore wind turbines is a demanding task. Typically, a jack-up crane vessel is used, and blades are individually lifted from the vessel deck and docked with the preinstalled hub. During the process of mating, large relative motions [...] Read more.
Installation of wind-turbine blades on monopile-type offshore wind turbines is a demanding task. Typically, a jack-up crane vessel is used, and blades are individually lifted from the vessel deck and docked with the preinstalled hub. During the process of mating, large relative motions are developed between the hub and root due to combined effects of wind-generated blade-root responses and wave-generated monopile vibrations. This can cause impact loads at the blade root and induce severe damages at the blade-root connection. Such events are highly likely to cause the failure of the mating task, while affecting the subsequent activities, and thus require competent planning. The purpose of this paper is to present a probabilistic response-based methodology for estimating the allowable sea states for planning a wind-turbine blade-mating task, considering impact risks with the hub as the hazardous event. A case study is presented where the installation system consisting of blade-lift and monopile system are modelled using multibody formulations. Time-domain analyses are carried out for various sea states, and impact velocities between root and hub are analyzed. Finally, an extreme value analysis using the Gumbel fitting of response parameters is performed and limiting sea state curves are obtained by comparing characteristic extreme responses with allowable values. It is found that the limiting sea states for blade-root mating tasks are low for aligned wind–wave conditions, and further increase with increased wind–wave misalignment. The results of the study also show that the parameter T p is essential for estimating limiting sea states given that this parameter significantly influences monopile vibrations during the blade-root mating task. Overall, the findings of the study can be used for a safer and more cost-effective mating of wind-turbine blades. Full article
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Article
Guidelines and Cost-Benefit Analysis of the Structural Health Monitoring Implementation in Offshore Wind Turbine Support Structures
Energies 2019, 12(6), 1176; https://doi.org/10.3390/en12061176 - 26 Mar 2019
Cited by 20 | Viewed by 2668
Abstract
This paper investigates how the implementation of Structural Health Monitoring Systems (SHMS) in the support structure (SS) of offshore wind turbines (OWT) affects capital expenditure (CAPEX) and operational expenditure (OPEX) of offshore wind farms (WF). In order to determine the added value of [...] Read more.
This paper investigates how the implementation of Structural Health Monitoring Systems (SHMS) in the support structure (SS) of offshore wind turbines (OWT) affects capital expenditure (CAPEX) and operational expenditure (OPEX) of offshore wind farms (WF). In order to determine the added value of Structural Health Monitoring (SHM), the balance between the reduction in OPEX and the increase in CAPEX is evaluated. In this paper, guidelines for SHM implementation in offshore WF are developed and applied to a baseline scenario. The application of these guidelines consist of a review of present regulations in the United Kingdom and Germany, the development of SHM strategy, where the first stage of the Statistical Pattern Recognition (SPR) paradigm is explored, failure modes that can be monitored are identified, and SHM technologies and sensor distributions within the turbines are described for a baseline scenario. Furthermore, an inspection strategy where the different structural inspections to be carried out above and below water is also developed, together with an inspection plan for the lifetime of the structures, for the aforementioned baseline scenario. Once the guidelines have been followed and the SHM and inspection strategies developed, a cost-benefit analysis is performed on the baseline case (10% instrumented assets) and three other scenarios with 20%, 30% and 50% of instrumented assets. Finally, a sensitivity analysis is conducted to evaluate the effects of SHM hardware cost and the time spent in completing the inspections on OPEX and CAPEX of the WF. The results show that SHM hardware cost increases CAPEX significantly, however this increase is much lower than the reduction in OPEX caused by SHM. The results also show that an increase in the percentage of instrumented assets will reduce OPEX and this reduction is considerably higher than the cost of SHM implementation. Full article
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Article
Cost-Optimal Maintenance Planning for Defects on Wind Turbine Blades
Energies 2019, 12(6), 998; https://doi.org/10.3390/en12060998 - 14 Mar 2019
Cited by 10 | Viewed by 1330
Abstract
Due to the considerable increase in clean energy demand, there is a significant trend of increased wind turbine sizes, resulting in much higher loads on the blades. The high loads can cause significant out-of-plane deformations of the blades, especially in the area nearby [...] Read more.
Due to the considerable increase in clean energy demand, there is a significant trend of increased wind turbine sizes, resulting in much higher loads on the blades. The high loads can cause significant out-of-plane deformations of the blades, especially in the area nearby the maximum chord. This paper briefly presents a discrete Markov chain model as a simplified probabilistic model for damages in wind turbine blades, based on a six-level damage categorization scheme applied by the wind industry, with the aim of providing decision makers with cost-optimal inspection intervals and maintenance strategies for the aforementioned challenges facing wind turbine blades. The in-history inspection information extracted from a database with inspection information was used to calibrate transition probabilities in the discrete Markov chain model. With the calibrated transition probabilities, the damage evolution can be statistically simulated. The classical Bayesian pre-posterior decision theory, as well as condition-based maintenance strategy, was used as a basis for the decision-making. An illustrative example with transverse cracks is presented using a reference wind turbine. Full article
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Article
Wind Turbulence Intensity at La Ventosa, Mexico: A Comparative Study with the IEC61400 Standards
Energies 2018, 11(11), 3007; https://doi.org/10.3390/en11113007 - 01 Nov 2018
Cited by 12 | Viewed by 2142
Abstract
Wind speed turbulence intensity is a crucial parameter in designing the structure of wind turbines. The IEC61400 considers the Normal Turbulence Model (NTM) as a reference for fatigue load calculations for small and large wind turbines. La Ventosa is a relevant region for [...] Read more.
Wind speed turbulence intensity is a crucial parameter in designing the structure of wind turbines. The IEC61400 considers the Normal Turbulence Model (NTM) as a reference for fatigue load calculations for small and large wind turbines. La Ventosa is a relevant region for the development of the wind power sector in Mexico. However, in the literature, there are no studies on this important parameter in this zone. Therefore, we present an analysis of the turbulence intensity to improve the understanding of local winds and contribute to the development of reliable technical solutions. In this work, we experimentally estimate the turbulence intensity of the region and the wind shear exponent in terms of atmospheric stability to analyze the relation of these design parameters with the recommended standard for large and small wind turbines. The results showed that the atmosphere is strongly convective and stable in most of the eleven months studied. The turbulence intensity analysis showed that for a range of wind speeds between 2 and 24 m/s, some values of the variable measured were greater than those recommended by the standard, which corresponds to 388 hours of turbulence intensity being underestimated. This may lead to fatigue loads and cause structural damage to the technologies installed in the zone if they were not designed to operate in these wind speed conditions. Full article
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