Global concerns around climate change and the volatility of conventional fuel prices have prompted researchers and technologists to make significant efforts to identify and exploit alternative energy sources that are cleaner and more sustainable. Wind energy has seen considerable development among these alternative energy sources, mainly due to its abundance and global availability for extraction and the existing knowledge within the aviation and aerospace fields. Many nations, including European countries, already operate offshore wind farms (OWFs) and are progressively carrying out new projects and expanding on other projects. The Australian offshore environment provides unique opportunities for wind energy extraction, particularly along the southern coast of mainland Australia and the regions around Tasmania, where substantially strong winds blow most of the year. A significant challenge to establishing wind farms is the selection of site locations with optimal outputs. This can become a complex decision-making problem if there are numerous options and no information from previous projects. This paper aims to develop a decision-making framework to select the optimal location for installing OWFs while addressing financial, performance-related, and availability-related objectives. This paper adopts a game-theoretical approach to develop a decision-support tool to account for the interdependencies of influencing factors and possible conflicts amongst the parties. The game model is applied to an OWF development case study in the Bass Strait, known for its dominant and strong winds.

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High strength steels such as X80 steels have recently been used more frequently in production of offshore structures. However, they may still be subject to degradation processes such as corrosion considering the conditions in marine environment. Pitting corrosion is a destructive form of corrosion which reduces the material resistance and may result in failure accidents with severe financial, human life and environmental consequences. The process of pitting corrosion is inconsistent and largely stochastic being influenced by a number of parameters with a high level of uncertainty. This makes it very difficult to predict corrosion in terms of its initiation time and spatial behavior. Therefore, it is vital to investigate pitting corrosion phenomena in offshore structures using a probabilistic approach for the assessment of structural reliability and operational safety. In this study, an in-situ experiment has been conducted on X80 steel in an NaCl solution in a laboratory environment to observe the generation and growth of corrosion pits. A probabilistic model based on Hierarchical Bayesian Approach (HBA) is developed for predicting the pitting corrosion growth rate using experimental results. In order to model the process more realistically, the proposed methodology considers the degradation process to be consisting of the time needed for pit initiation and propagation. The results indicate that the proposed methodology is capable of predicting the time required to reach a specific pit size. The methodology developed in this study can be applied to estimate the remaining useful life of subsea structures.

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The significant cost required for implementation of WEC sites and the uncertainty associated with their performance, due to the randomness of the marine environment, can bring critical challenges to the industry. This paper presents a probabilistic methodology for predicting the long-term power generation of WECs. The developed method can be used by the operators and designers to optimize the performance of WECs by improving the design or in selecting optimum site locations. A Markov Chain model is constructed to estimate the stationary distribution of output power based on the results of hydrodynamic analyses on a point absorber WEC. To illustrate the application of the method, the performance of a point absorber is assessed in three locations in the south of Tasmania by considering their actual long-term sea state data. It is observed that location 3 provides the highest potential for energy extraction with a mean value for absorbed power of approximately 0.54MW, while the value for locations 1 and 2 is 0.33MW and 0.43MW respectively. The model estimated that location 3 has the capacity to satisfy industry requirement with probability 0.72, assuming that the production goal is to generate at least 0.5MW power.

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Wave energy converters (WEC) are reaching a pinnacle in their prototype phase. World leaders in the energy sector are looking for renewable energy sources to replace the expiry of fossil-fuel energy capacity. For WECs to become a viable solution to the fossil-fuel challenges, there is a need to have a deeper understanding of the associated costs and the operational impacts of this technology. This study investigates the relationship between these two characteristics and finds an improved implementation strategy by developing a dynamic risk-based methodology. The methodology developed from this study will aid WEC technology to move towards a commercialised state by implementing an array or farm of WEC devices. Bayesian network (BN) is adopted to analyse the probability of a collision accident within the farm as well as the likelihood of meeting the desired level of power production. The BN is later extended to an influence diagram (ID) for selecting the optimum configuration of the WEC farm. The ID assists in decision-making based on the investigated probabilities, required capital investment, and economic impact of the accident scenario. To demonstrate the application of the developed method, a case study is adopted including three decision alternatives, each representing a farm with different layouts of point absorber WECs. The performance of the facility is assessed under real-life offshore environmental conditions. The developed methodology assists in finding the WEC layout which minimises the economic risk of an array implementation and also increases the reliability of these structures.@en

Degradation of subsea pipelines in the presence of corrosive agents and cyclic loads may lead to the failure of these structures. In order to improve their reliability, the deterioration process through pitting and corrosion-fatigue phenomena should be considered simultaneously for prognosis. This process starts with pitting nucleation, transits to fatigue damage and leads to fracture and is influenced by many factors such as material and process conditions, each incorporating a high level of uncertainty. This study proposes a novel probabilistic methodology for integrated modelling of pitting and corrosion-fatigue degradation processes of subsea pipelines. The entire process is modelled using a Dynamic Bayesian Network (DBN) methodology, representing its temporal nature and varying growth rates. The model also takes into account the factors influencing each stage of the process. To demonstrate its application, the methodology is applied to estimate the remaining useful life of high strength steel pipelines. This information along with Bayesian updating based on monitoring results can be adopted for the development of effective maintenance strategies.

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The increasing demand for energy and the high probability of finding vast reserves have shifted offshore exploration and production activity into colder and harsher environments. Offshore activity increases risk of oil spills in these colder and harsher marine environments. The development of a spill contingency plan requires the prediction of fate and transport of oil. Oil spill trajectory and fate modeling in cold marine environments is an exceedingly complex problem, in which variability of physical environment and oil-ice interactions must be addressed. This paper explores the usefulness of the fugacity approach for spill fate and transport modeling in ice-infested waters through a simulation model that combines surface oil weathering algorithms with Level IV fugacity models. Four bulk compartments are used for modeling: air, ice cover, water and sediment. Weathering of surface oil on and under the ice cover is represented by a system of differential equations. Unsteady state mass balance equations are also developed for each of the four bulk phases. The outputs of the multimedia fate model are time-dependent profiles of oil slick area, fraction evaporated, water content in oil, viscosity, and concentration of oil in air, ice cover, water, and sediment. The application of the proposed model is illustrated through the simulation of a hypothetical oil spill in the Labrador Sea. The proposed model is simple but has the promise that it can be further developed to become directly useful to the simulation of spill behavior in ice-infested waters.

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