•A model is proposed to assess the failure rate of components of floating offshore wind turbines based on onshore turbine data.•A failure rate correction model is presented for the relations of ...failure between onshore and floating offshore wind turbines.•The results indicate that the failure rates of components of floating wind turbines are higher than those of onshore devices.•A Bayesian network is constructed to analyze the failure rate and reliability of the entire floating offshore wind turbine.•The performance of the proposed model is validated by a comprehensive comparison with the existing studies and models.
A model is proposed to assess the failure rates of components of floating offshore wind turbines based on the knowledge of failure data of corresponding structures of onshore wind turbines with sufficient failure data. A failure rate correction model is first presented to map the relations of failure features between onshore and floating offshore wind turbines. Subsequently, a failure rate analogy model is established to infer the failure rates of elements of support structures that have no correspondence in onshore devices. The results indicate that the failure rates of components of floating offshore wind turbines are higher than those of onshore devices. Accordingly, a Bayesian network is constructed to analyze the failure rate and reliability of the entire floating offshore wind turbine. The uncertainty of the model is investigated to illustrate the factors that significantly affect the predicted failure rates and reliability. Moreover, the performance of the proposed model is validated by a comprehensive comparison with the existing studies and models. The model presented contributes to the risk, failure, and reliability analysis and assessment under insufficient data conditions.
This paper extends the conventional failure mode and effect analysis methodology by introducing weights of its indices that are severity, occurrence, and detection as a basis to analyze the failures ...of the support structure of a generic floating offshore wind turbine. Critical failure causes, failure modes, as well as systems of the support structure of the floating offshore wind turbine are ascertained. Moreover, based on the analysis, recommendations on corrections and preventive actions are suggested aiming at ensuring the safe and economic operations of the support structure. The validation of the proposed technique is finalized by a comparison study between the results of conventional failure mode and effect analysis methodology and that of the proposed method. The comparison indicates that the proposed technique is more in line with practice and flexible for use and has the merit in removing the limitations of conventional failure mode and effect analysis methodology that different failure causes generate the same risk priority number.
•The conventional FMEA is extended to analyze the failures of the support structure of a generic floating wind turbine.•Critical failure causes, failure modes, and systems of the support structure of the floating wind turbine are ascertained.•Recommendations on corrections are suggested aiming at ensuring the safe and economic operation of the support structure.•A comparison is made between the results of conventional FMEA methodology and that of the proposed method.•The proposed technique is more flexible for use and has the merit in partly removing the limitations of conventional FMEA.
A review of some representative floating wave energy converter (WEC) projects in the world, including the wave energy capturing technology, development history, main dimensions and tested sea sites ...is presented. The design essentials of WEC mooring system are discussed and a mooring system design procedure for WEC is proposed, which includes the introduction of related design codes and mooring analysis methods. In the last part, a comprehensive review of mooring system design in the current WECs projects is conducted. Different mooring systems and mooring materials are introduced and discussed. Based on the discussions, recommendations are made for the suitable mooring design according to the WEC's dimensions and working principles. It is shown that the elastic synthetic rope has great potential in the application of WEC mooring system, and the hybrid mooring system could be a good solution for WEC station keeping problem.
•A review of some representative floating wave energy converter (WEC) projects in the world, is presented.•The design essentials of WEC mooring system are discussed and a mooring system design procedure for WEC is proposed.•A comprehensive review of mooring system design in the current WECs projects is conducted.•Different mooring systems and mooring materials are introduced and discussed.•Recommendations are made for the suitable mooring design according to the WEC's dimensions and working principles.
With the development of offshore wind power, the reliability analysis of offshore wind turbines is increasingly significant due to the system complexity and negative impacts in harsh operating ...conditions. In this study, the Fault Tree Analysis method is adopted for both qualitative and quantitative evaluation of semi-submersible floating offshore wind turbine failure characteristics. The floating offshore wind turbine is divided into several assemblies, including support structures, pitch and hydraulic system, gearbox, generator and the other systems. Failure rates of relevant offshore structures are collected from previous studies, reports and reliability databases. On this basis, the quantitative assessment of Minimum Cut Sets and Importance Measures are achieved. The calculated results are generally in conformity with statistical data, indicating that most of the failures are caused by several basic factors. Marine conditions, especially the salt-spray and high wind speed, show the most significant impact on floating offshore wind turbine performance.
•Fault Tree Analysis method is proposed for evaluation of floating offshore wind turbine failure.•The floating offshore wind turbine is divided into several assemblies.•Failure rates of relevant offshore structures are collected from previous studies.•Quantitative assessment of Minimum Cut Sets and Importance Measures are achieved.•Salt-spray and high wind speed, show the most significant impact on wind turbine performance.
This study presents a novel method for the selection of sites for floating wind farms based on marine spatial optimization. After providing a review of the present state of the art, a tool based on ...geographic information systems is presented, consisting of three main stages and built in Python language. The first stage collects and analyses the information of the different regulatory bodies, marine spatial planning, maritime concessions and other sources. The second stage excludes not feasible sites for floating wind farms, based mostly on marine space use and on environmental constraints. The third stage characterises the available locations based on five major categories that are spatially dependent: metocean data, viability data, logistics, facilities, marine environment and techno-economic data. The proposed methodology is implemented at the Europe Atlantic coast, with specific reference to Portugal, Spain and France. These three countries together combine 3.362.408 km2 of the Atlantic Exclusive Economic Zone, where in only 0.22% of that area could host floating offshore wind turbines. While further detailed studies about locations and legislative considerations are required, the effort made has contributed to eliminate unsuitable areas and identify those where sustainability can be maximized.
•An efficient tool to select suitable alternatives for floating wind generation.•This methodology simplifies the selection process and reduces the possible impacts.•The GIS proposed achieves the goals of marine spatial optimization.•The offshore floating wind farms locations in the European Atlantic Coast are identified.
•A study is made to assess the human error contribution in ship accidents in different weather conditions.•A Bayesian Belief Network model is developed, which includes variables related to the ...different wave conditions.•The accident database of the Portuguese Maritime Authority is used, which includes records of 1997–2006.•Several significant wave height databases are used.•The results show high risk acceptance in fishing vessels and a low risk perception in recreational vessels.
The paper describes a study aiming to assess the human error contribution in ship accidents in different weather conditions and the contribution that high significant wave heights have in the occurrence of certain accident typologies. To this aim, a Bayesian Belief Network model is developed, which includes variables related to the maritime accident but also to the different wave conditions. For the quantification of the conditional probability tables the maritime accident database of the Portuguese Maritime Authority is used, which includes 857 validated accidents registered in the period 1997–2006. Similarly, several significant wave height databases are used to populate the node correspondent to this variable. The importance of accurate estimation of the significant wave height is also discussed. To substantiate this discussion a comparison between hard evidence (ε) and a soft one (μ,σ) is performed for the significant wave height node of the BBN model. The application of different combinations of evidence in the model allows the identification of patterns of influence of the human error cause in comparison with others, namely with the sea and weather one. The results show one apparent high-risk acceptance within the crews of the fishing vessels and low risk perception in the recreational vessels. Based on the results, are provided recommendations to decrease the risk associated to specific probable causes.
This paper proposes an improved methodology for handling ships without command by incorporating evidential reasoning and Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) in ...the decision making of emergency responses. The kernel of this method is to use evidential reasoning to integrate the influencing factors expressed by incomplete information of each of the involved organizations, and to employ the TOPSIS method to make the final decision with the asymmetric information distribution among the involved organizations. A ship with main engine failure is considered as the study case to apply the proposed methodology. The result demonstrates that the new method is beneficial for handling ships that are not under command.
•An improved methodology for handling ships without command is proposed, incorporating evidential reasoning and TOPSIS.•The kernel is to use evidential reasoning to integrate the influencing factors expressed by incomplete information.•It employs the TOPSIS to make the final decision with the asymmetric information among the involved organizations.•A ship with main engine failure is considered as the study case to apply the proposed methodology.•The result demonstrates that the new method is beneficial for handling ships that are not under command.
This paper estimates the failure rate of an offshore wind turbine gearbox based on the data available for similar, known onshore wind turbine systems. The gearbox is one critical element of the wind ...turbine system and its failure may cause long downtime and consequently high operational and maintenance costs. First, a detailed Failure Mode and Effects Analysis is conducted and then the main Reliability Influencing Factors on the failure causes are identified. A reliability prediction method is then illustrated stepwise to estimate the total failure rate of an offshore wind turbine gearbox. Furthermore, a case study is used to demonstrate the importance of this technique for comparing the failure rate of subsequent components of onshore and offshore wind turbine gearbox. It is expected that the analysis conducted will help in understanding the field performance of offshore wind turbine gearbox in an offshore environment. Also, the approach adopted in this paper can be helpful to predict reliability for other wind turbine components.
•This paper estimates the failure rate of an offshore wind turbine gearbox based on the data available for similar systems.•A detailed FMEA is conducted and then the main Reliability Influencing Factors on the failure causes are identified.•A reliability prediction method is then illustrated to estimate total failure rate of an offshore wind turbine gearbox.•A case study is used to demonstrate the importance of this technique.
A practical and robust system identification modelling method for ship manoeuvring motion is presented, to alleviate the impact of noise-induced problems, such as parameter drift or over-fitting, on ...the model reliability. The method is based on ν(“nu”)-Support Vector Machine (ν-SVM) algorithm, which can automatically control the number of support vectors to ensure the sparsity of the solution. Multiple standard manoeuvring datasets are simultaneously used as training data to cope with the parameter drift issues. The proposed method is validated by using polluted simulated data of three different levels. The results demonstrate that the identified model has good generalisation, verifying the robustness and efficiency of the algorithm.
•A practical and robust system identification modelling method for ship manoeuvring motion is presented.•The method is based on “nu”-SVM algorithm, which can automatically control the number of support vectors.•Multiple standard manoeuvring datasets are simultaneously used as training data.•The proposed method is validated by using polluted simulated data of three different levels.•The results demonstrate that the identified model verifies the robustness and efficiency of the algorithm.
A ten year wind hindcast is presented for the Iberian Peninsula coast. Simulations are conducted with the WRF model at 9 and 3 km of spatial resolution and 6 hourly output. The amount of energy that ...can be generated by an energy conversion device as well as the annual operating hours and capacity factors are estimated and presented as wind resource maps. The spatial variation of the error and the annual and seasonal variations of the wind energy resource are also depicted. Comparisons with observational data show the WRF model is a proficient wind generating tool, whether in coastal waters as in the open ocean, even when the model is run at a lower spatial resolution. The results show that wind farm planning offshore the Iberian coast is an eligible choice, with average annual energy density reaching up to 971 W/m2, 549 W/m2 and 398 W/m2 in the north, centre and southern regions respectively. The potential production by offshore energy conversion devices in selected sub-regions further indicates that wind farm implementation offshore the Iberian coast will produce high amounts of electricity.
•The wind potential of the Iberian coast is estimated for a 10 year period.•Spatial distribution of wind speed and direction error is examined.•WRF performance is evaluated for distinct wind speed intervals.•Spatio-temporal variability of the offshore wind resources is determined.•A wind resource map is presented for the recent decade.
