408 research outputs found

    Education for Offshore Engineering and Application to a Platform Design

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    This thesis considers some of the patterns and requirements of education available in the United Kingdom for offshore engineering at the level of first degree and postgraduate courses. These requirements are illustrated by a design study for an offshore oil platform and associated steel jacket for waters east of West Malaysia in the South China Sea. Proposals are then made for courses in offshore engineering suitable for Malaysia. The first part of the thesis traces the rise of the offshore industry which is mainly the offshore oil industry and the growth of tertiary education for this industry. It draws attention to the breadth of interests required and the absence of undergraduate courses which treat offshore engineering as a totally distinct branch of engineering under the accreditation procedure of a professional engineering institution. Demand is met by courses which represent sub-specialisation for students who begin in other branch of engineering. A similar pattern exist in the postgraduate education which if anything draws from a wider background. Design of an offshore oil production platform illustrates the breadth of education required although the thesis limits numerical consideration to the design of steel lattice jacket under operational and environmental loadings. The relatively shallow water off the Malaysian coast is less severe compared to the North Sea. The oil industry requires manpower at all levels of expertise and the last part of the thesis considers a pattern for this education for technicians, professional and postgraduate engineers in Malaysia together with appropriate syllabuses

    Life Cycle Cost Analysis of a Floating Wind Farm Located in the Norwegian Sea

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    This thesis aims to investigate the levelized cost of energy of an offshore floating wind farm, as well as evaluate its financial feasibility. Thus, the research question is as follows: How to estimate the life cycle costs of a floating wind farm off the coast of Norway? The investigated wind farm is located off the coast of Norway, more specifically in the Troll field area west of Bergen. This area has a water depth of 325 m and a distance to shore of 65 km. The wind farm is set to consist of 50 wind turbines and has a lifespan of 25 years. The OC4 Deepwind semisubmersible floater developed by the National Renewable Energy Laboratory, complemented with a 15 MW turbine, is used as the research model. To find the capital expenditures of the planned wind farm, the Offshore Renewables Balance-of-system and Installation Tool is used, while the operational expenditures are calculated based on the theoretical energy output. The total levelized cost of energy of the wind farm is calculated to be 100.69 /MWh.Capitalexpenditureisthemostprominentcostandconstitutes63.1expendituresconstitutetheremaining36.9lifespan,capacityfactor,andprojectdiscountratearethefactorswiththemostpotentialtoinfluencethelevelizedcostofenergy.Thefinancialcalculationsshowthatthewindfarmisnoteconomicallyfeasibleasithasacomputednetpresentvalueofnegative/MWh. Capital expenditure is the most prominent cost and constitutes 63.1 % of the total cost, thus, operational expenditures constitute the remaining 36.9 %. Further, sensitivity analyses show that the lifespan, capacity factor, and project discount rate are the factors with the most potential to influence the levelized cost of energy. The financial calculations show that the wind farm is not economically feasible as it has a computed net present value of negative 561 900 000. Finally, novel offshore wind energy solutions involving the utilization of shared substructures and mooring lines have been studied, and the findings suggest the possibility of a diminished levelized cost of energy

    Life Cycle Cost Analysis of a Floating Wind Farm Located in the Norwegian Sea

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    This thesis aims to investigate the levelized cost of energy of an offshore floating wind farm, as well as evaluate its financial feasibility. Thus, the research question is as follows: How to estimate the life cycle costs of a floating wind farm off the coast of Norway? The investigated wind farm is located off the coast of Norway, more specifically in the Troll field area west of Bergen. This area has a water depth of 325 m and a distance to shore of 65 km. The wind farm is set to consist of 50 wind turbines and has a lifespan of 25 years. The OC4 Deepwind semisubmersible floater developed by the National Renewable Energy Laboratory, complemented with a 15 MW turbine, is used as the research model. To find the capital expenditures of the planned wind farm, the Offshore Renewables Balance-of-system and Installation Tool is used, while the operational expenditures are calculated based on the theoretical energy output. The total levelized cost of energy of the wind farm is calculated to be 100.69 /MWh.Capitalexpenditureisthemostprominentcostandconstitutes63.1expendituresconstitutetheremaining36.9lifespan,capacityfactor,andprojectdiscountratearethefactorswiththemostpotentialtoinfluencethelevelizedcostofenergy.Thefinancialcalculationsshowthatthewindfarmisnoteconomicallyfeasibleasithasacomputednetpresentvalueofnegative/MWh. Capital expenditure is the most prominent cost and constitutes 63.1 % of the total cost, thus, operational expenditures constitute the remaining 36.9 %. Further, sensitivity analyses show that the lifespan, capacity factor, and project discount rate are the factors with the most potential to influence the levelized cost of energy. The financial calculations show that the wind farm is not economically feasible as it has a computed net present value of negative 561 900 000. Finally, novel offshore wind energy solutions involving the utilization of shared substructures and mooring lines have been studied, and the findings suggest the possibility of a diminished levelized cost of energy

    Life Cycle Cost Analysis of a Floating Wind Farm Located in the Norwegian Sea

    Get PDF
    This thesis aims to investigate the levelized cost of energy of an offshore floating wind farm, as well as evaluate its financial feasibility. Thus, the research question is as follows: How to estimate the life cycle costs of a floating wind farm off the coast of Norway? The investigated wind farm is located off the coast of Norway, more specifically in the Troll field area west of Bergen. This area has a water depth of 325 m and a distance to shore of 65 km. The wind farm is set to consist of 50 wind turbines and has a lifespan of 25 years. The OC4 Deepwind semisubmersible floater developed by the National Renewable Energy Laboratory, complemented with a 15 MW turbine, is used as the research model. To find the capital expenditures of the planned wind farm, the Offshore Renewables Balance-of-system and Installation Tool is used, while the operational expenditures are calculated based on the theoretical energy output. The total levelized cost of energy of the wind farm is calculated to be 100.69 /MWh.Capitalexpenditureisthemostprominentcostandconstitutes63.1/MWh. Capital expenditure is the most prominent cost and constitutes 63.1 % of the total cost, thus, operational expenditures constitute the remaining 36.9 %. Further, sensitivity analyses show that the lifespan, capacity factor, and project discount rate are the factors with the most potential to influence the levelized cost of energy. The financial calculations show that the wind farm is not economically feasible as it has a computed net present value of negative 561 900 000. Finally, novel offshore wind energy solutions involving the utilization of shared substructures and mooring lines have been studied, and the findings suggest the possibility of a diminished levelized cost of energy

    Reliability assessment approach through geospatial mapping for offshore wind energy

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    To meet the increased energy demands, uphold commitments made in the Paris agreement and provide energy security to its consumers, the United Kingdom is rapidly expanding its wind energy industry at offshore locations. While harnessing the improved wind resource further offshore, the industry has faced reliability challenges in the dynamic marine environment which contribute to an increase in the cost of energy. This thesis promotes the argument for location - intelligent decisions in the industry by developing a methodology to allocate a combined risk - return performance metric for offshore locations. In the absence of comprehensive spatially distributed field reliability data for offshore wind turbines, the limit state design methodology is employed to model structural damage. Exposed to stochastic loading from wind and wave regimes, offshore wind turbines are fatigue-critical structures. The aero- and hydro-dynamic loads at representative sites across eight sub-regions in the UK continental shelf are quantified by processing modelled metocean data through established aero-hydro-servo-elastic design tools. These simulated loads and the inherent material fatigue properties provide site-specific lifetime accumulated damage. Normalising this damage based on the potential energy production at each site provides an improved understanding of the feasibility of the sub-region for offshore wind deployment. Results indicate that although sheltered sub-regions display lower resource potential, they have the benefit of the reduced associated structural damage compared to more dynamic locations. A similar observation is made when the methodology is employed on a larger scale incorporating the UK continental shelf and its adjoining areas. Furthermore, not only the energy potential displays an increase with an increase in distance-to-shore, but also the damage per unit energy produced. The research outcomes of this project are useful for identifying the potential of structural reserves for lifetime extension considerations as more turbines reach their design lifetimes. Additionally, it may be used to inform design parameters, optimise siting of future installations and determine suitable maintenance strategies to improve the economic viability of offshore wind

    Advances in foundation design and assessment for strategic renewable energy

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    In order to meet EU legislation on emissions, significant effort is being invested into the development of cost-effective renewable power generation technologies. The two leading technologies are solar and wind power because of their potential for the lowest levelised cost of energy and for showing a growth in installed capacity and technological development. Various research findings have suggested that significant cost savings in the capital expenditure of renewable energy projects can be made through the optimisation of their support foundations, the understanding of which has formed the main goal of the research. [Continues.

    Investigation of decommissioning of offshore wind mono-pile foundations

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    Decommissioning process intricacy level varies depending on the offshore wind turbine components. Decommissioning superstructure components -blades, nacelle, tower, etc.- is a straightforward process, which is the reverse of the installation. The full removal decommissioning strategy that applies to the superstructure extends to include a few offshore wind foundations. For instance, the decommissioning of suction bucket foundation is through release and extract by applying pressure. Nonetheless, for the pile foundation, which is the most common type, with a total installation of more than 7,000 [4,914 single and 2,934 group piles], the decommissioning is complicated; one reason is that excavation is required in the two strategies - full and partial removal [cutting the pile externally]. However, the current industry-proposed methods may not always be adopted, and developing novel foundation decommissioning methods such as extraction [full removal] becomes mandatory/ beneficial. The reason is that offshore wind currently initiated to alter the method for decommissioning some of its turbine components, e.g., blades, from landfilling the material to recycling. For extraction method feasibility validation, an investigation was carried out through an experimental campaign and a techno-economic assessment. For the experimental campaign, a series of 1g model pile extraction tests using displacement and force control and 400mm long open-ended steel piles with diameters of 88.9 and 101.6 mm were conducted in unsaturated and saturated soil. Experimental campaign results showed the tensile capacity of both piles had reduced by up to 90% compared to the compression capacity in both conditions. In the unsaturated case, with maintaining the soil density constant, results had evident the impact of extraction rate -by reducing- the tensile capacity of the pile regardless of diameter. Nonetheless, in the saturated soil, the tensile capacity decreased due to the pore water pressure; for the 101.6 mm pile, the decline was by 50 and 18% for displacement and force extraction applications, respectively. Compared with displacement extraction application, the tensile capacities of the 88.9 and 101.6 mm piles under force decreased [lowest] by 25 and 23% in unsaturated soil and saturated soil by 6 and 11%, respectively. Despite higher capacity under displacement extraction, the application exhibited local shear failure -partial drainage occurrence due to the application mechanism- where piles had extracted soil-free, which was not the case for the force application. The experimental results validated the theoretical method developed in aiding extraction of OWPile foundations and demonstrated the feasibility and efficiency of extraction application, displacement, and required total energy [velocity and time]. For the techno-economic assessment, a model developed to determine the most economical decommissioning strategy and method for offshore wind foundations in terms of timing and costs by comparing the industry-preferred strategy [partial removal] with the novel-proposed one. The model inputs’ parameters included foundation removal operations duration, wait-on-weather, and vessels’ strategies and types, which are key drivers that significantly influence the total decommissioning costs. Additionally, sensitivity analysis was carried out for the input parameters because are subject to a high degree of uncertainty. For the sensitivity analysis, the parameters’ baseline estimated values had increased by conservative percentages; offshore wind foundations decommissioning methods activities’ estimated duration by 100%, ranging the weather adjustment factor by 50 – 100%, and vessels’ day rate by ± 20%. The model results showed that the economical vessels’ strategy, regardless of decommissioning strategy/ method, is the transiting -utilising two vessels of the same type-compared to the sender one. Analysing results further, heavy lift vessels (HLV) carry out decommissioning activities in less time than wind turbine installation vessels (WTIV), nevertheless increasing the costs due to their low availability. The sensitivity analysis results showed that despite increasing weather factor adjustment factor and vessels’ day rate, the total cost for the novel decommissioning proposed method is more economical than the industry-proposed one. Including the learning curve in the analysis, the total cost of offshore wind foundations decommissioning, regardless of methods, could reduce by up to 35%.Decommissioning process intricacy level varies depending on the offshore wind turbine components. Decommissioning superstructure components -blades, nacelle, tower, etc.- is a straightforward process, which is the reverse of the installation. The full removal decommissioning strategy that applies to the superstructure extends to include a few offshore wind foundations. For instance, the decommissioning of suction bucket foundation is through release and extract by applying pressure. Nonetheless, for the pile foundation, which is the most common type, with a total installation of more than 7,000 [4,914 single and 2,934 group piles], the decommissioning is complicated; one reason is that excavation is required in the two strategies - full and partial removal [cutting the pile externally]. However, the current industry-proposed methods may not always be adopted, and developing novel foundation decommissioning methods such as extraction [full removal] becomes mandatory/ beneficial. The reason is that offshore wind currently initiated to alter the method for decommissioning some of its turbine components, e.g., blades, from landfilling the material to recycling. For extraction method feasibility validation, an investigation was carried out through an experimental campaign and a techno-economic assessment. For the experimental campaign, a series of 1g model pile extraction tests using displacement and force control and 400mm long open-ended steel piles with diameters of 88.9 and 101.6 mm were conducted in unsaturated and saturated soil. Experimental campaign results showed the tensile capacity of both piles had reduced by up to 90% compared to the compression capacity in both conditions. In the unsaturated case, with maintaining the soil density constant, results had evident the impact of extraction rate -by reducing- the tensile capacity of the pile regardless of diameter. Nonetheless, in the saturated soil, the tensile capacity decreased due to the pore water pressure; for the 101.6 mm pile, the decline was by 50 and 18% for displacement and force extraction applications, respectively. Compared with displacement extraction application, the tensile capacities of the 88.9 and 101.6 mm piles under force decreased [lowest] by 25 and 23% in unsaturated soil and saturated soil by 6 and 11%, respectively. Despite higher capacity under displacement extraction, the application exhibited local shear failure -partial drainage occurrence due to the application mechanism- where piles had extracted soil-free, which was not the case for the force application. The experimental results validated the theoretical method developed in aiding extraction of OWPile foundations and demonstrated the feasibility and efficiency of extraction application, displacement, and required total energy [velocity and time]. For the techno-economic assessment, a model developed to determine the most economical decommissioning strategy and method for offshore wind foundations in terms of timing and costs by comparing the industry-preferred strategy [partial removal] with the novel-proposed one. The model inputs’ parameters included foundation removal operations duration, wait-on-weather, and vessels’ strategies and types, which are key drivers that significantly influence the total decommissioning costs. Additionally, sensitivity analysis was carried out for the input parameters because are subject to a high degree of uncertainty. For the sensitivity analysis, the parameters’ baseline estimated values had increased by conservative percentages; offshore wind foundations decommissioning methods activities’ estimated duration by 100%, ranging the weather adjustment factor by 50 – 100%, and vessels’ day rate by ± 20%. The model results showed that the economical vessels’ strategy, regardless of decommissioning strategy/ method, is the transiting -utilising two vessels of the same type-compared to the sender one. Analysing results further, heavy lift vessels (HLV) carry out decommissioning activities in less time than wind turbine installation vessels (WTIV), nevertheless increasing the costs due to their low availability. The sensitivity analysis results showed that despite increasing weather factor adjustment factor and vessels’ day rate, the total cost for the novel decommissioning proposed method is more economical than the industry-proposed one. Including the learning curve in the analysis, the total cost of offshore wind foundations decommissioning, regardless of methods, could reduce by up to 35%

    Adaptive Neural Network Fixed-Time Control Design for Bilateral Teleoperation With Time Delay.

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    In this article, subject to time-varying delay and uncertainties in dynamics, we propose a novel adaptive fixed-time control strategy for a class of nonlinear bilateral teleoperation systems. First, an adaptive control scheme is applied to estimate the upper bound of delay, which can resolve the predicament that delay has significant impacts on the stability of bilateral teleoperation systems. Then, radial basis function neural networks (RBFNNs) are utilized for estimating uncertainties in bilateral teleoperation systems, including dynamics, operator, and environmental models. Novel adaptation laws are introduced to address systems' uncertainties in the fixed-time convergence settings. Next, a novel adaptive fixed-time neural network control scheme is proposed. Based on the Lyapunov stability theory, the bilateral teleoperation systems are proved to be stable in fixed time. Finally, simulations and experiments are presented to verify the validity of the control algorithm

    Trends and challenges for wind energy harvesting : workshop, March 30-31, 2015, Coimbra, Portugal

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