Optimisation of scheduling and routing for offshore wind farm maintenance

The growing increase in the size and scope of offshore wind farms motivates the need for industry to have access to mathematical tools that reduce costs by efficiently performing daily operations and maintenance activities. Key offshore activities require the transportation of technicians to and within offshore wind farms to complete corrective and preventive maintenance tasks to keep turbines operating efficiently. We provide a new deterministic mixed integer linear programming formulation for deciding the optimal vessel routes for transporting technicians around a wind farm and the scheduling of crew transfers, by minimising downtime, travel and technician costs. The model contains sufficient flexibility to account for multiple vessels, shifts and task profiles, whilst being able to prioritise and omit tasks in environments containing limited resources. Computational experiments are performed which quantify and confirm the impact of key instance characteristics such as technician availability, task profiles and weather conditions. We implement and evaluate the impact of a novel industry safety constraint. The complexity of larger instances motivates a second continuous time formulation, in which preventive maintenance again requires no minimum duration of work before it can provide benefit. We employ a specific decomposition structure to take advantage of variable preventive maintenance and utilise an adaptive large neighbourhood search procedure to solve instances. We evaluate several distinct acceptance criteria in conjunction with random and adaptive operator selection to determine the best option for our model. We produce a statistical model of offshore weather conditions to help quantify the likelihood of limited vessel accessibility to offshore wind farms. We model the joint distribution of key meteorological and oceanographic variables over time whilst accounting for seasonal trends using multivariate kernel density estimation. Our method generates alternative metocean realisations from historical data and reproduces the important long term persistence statistics of good and adverse offshore conditions

Time-domain simulations of marine operations and their application to the offshore renewable energy sector

In the coming decades, offshore renewable energy is expected to play a crucial role in the decarbonisation of global electricity supply essential for limiting anthropogenic greenhouse gas emissions to an acceptable level. The cost of utilising expensive vessels to install and maintain these marine energy devices represents a significant proportion of their life-cycle cost and one of the major barriers to their continued development. It is vitally important to estimate accurately these costs and attempt to reduce them as much as possible. This thesis investigates the use of time-domain simulations of marine operations to estimate the likely duration and manage the inherent risks of an offshore project. The development and application of an original time-domain simulation software are described through a case study that supported construction of a Round 3 offshore wind farm. Analysis completed in advance of the project identified the most suitable installation strategy with a potential reduction in indicative cost of up to $6m. Simulations performed during the project enabled the early identification of significant deviations from initial estimates; such as the mean observed duration of a critical activity midway through the project being approximately 30% lower than initially specified, eventually leading to a 10.8% reduction in the estimated project duration. Detailed analysis of the operational data after project completion identified the importance of the learning phenomenon associated with repetitions of identical operations and the accurate representation of random delays and stoppages. Implementing the learning factor had the effect of reducing mean project duration by 10%, while accounting for technical downtime increased this estimate by 15%. The thesis shows that time-domain simulations are well-suited to the development of optimal strategies for the execution of marine operations and the subsequent minimisation of the duration and cost of offshore projects

Multiscale, Multiphysics Modelling of Coastal Ocean Processes: Paradigms and Approaches

This Special Issue includes papers on physical phenomena, such as wind-driven flows, coastal flooding, and turbidity currents, and modeling techniques, such as model comparison, model coupling, parallel computation, and domain decomposition. These papers illustrate the need for modeling coastal ocean flows with multiple physical processes at different scales. Additionally, these papers reflect the current status of such modeling of coastal ocean flows, and they present a roadmap with numerical methods, data collection, and artificial intelligence as future endeavors

Earth Observation Open Science and Innovation

geospatial analytics; social observatory; big earth data; open data; citizen science; open innovation; earth system science; crowdsourced geospatial data; citizen science; science in society; data scienc

Advanced structural health monitoring strategies for condition-based maintenance planning of offshore wind turbine support structures

Condition-based maintenance strategies need to be adopted as distance-to-shore and water depth increase in the offshore wind industry. The aim of the research presented herein is to develop advance structural health monitoring strategies that enhance the condition-based maintenance of offshore wind turbine support structures. The focus is on the selection of technologies, the implementation process, the analysis of the asset’s structural response under complex loading, the economic justification for structural health monitoring implementation and the effective structural health monitoring data analysis. Research activities consist of the provision of a comprehensive study for structural health monitoring technologies’ utilisation in the offshore wind industry. This is followed by parametric structural modelling, simulation and validation of an operational offshore wind turbine tower, support structure and soil-structure interaction, using commercial software. The evaluation of the asset’s response under complex loading subject to design changes and failure mechanisms is also undertaken. A combination of existing and newly developed methodologies is deployed for the effective data management of structural health monitoring systems and validated with industrial data for the case of strain monitoring. These include unsupervised learning algorithms (neural networks), deterministic and probabilistic methods for noise cleansing and missing data imputation. Guidelines for the structural health monitoring implementation from design stage of a wind farm are proposed and applied to a baseline scenario. This is utilised to assess the economic impact that structural health monitoring has in the lifecycle of the assets. The achieved results show that the implementation of structural health monitoring in offshore wind turbine following the Statistical Pattern Recognition paradigm and the proposed guidelines has the potential to reduce the Operational Expenditure. This reduction is much greater than the cost associated with the implementation of these systems. Monitoring from the commissioning of the assets is crucial for the system’s calibration and establishing thresholds. The developed noise cleansing and missing data imputation methodologies can successfully be employed together to produce more complete low-disturbed datasets

Engineering with Nature: an innovative solution for coastal erosion protection

Programa doutoral em Engenharia CivilCoastal zones are a much-appreciated environment by society, and support a large amount of economic and leisure activities. Growing demographic pressure on these very special territories that are associated to rapid economic growth and coastward migration has resulted in significant infrastructure and assets located in risk-prone areas, increasing exposure and vulnerability to natural disasters along the coast, including erosion, flooding and salt intrusion. In these areas, sediment transport and erosive processes are worldwide critical aspects for territory planning and management, especially in countries with long coastline like Portugal, since these phenomena often endanger human life and property protection. A research effort is still needed to find more robust and nature-based protection solutions adequate for high energetic coastal environments. The design, construction and maintenance of coastal protection structures incorporating principles of resilience to climate change impacts require a comprehensive multidisciplinary scientific approach for a deep understanding on coastal hydromorphodynamics and on the behaviour of new eco-materials in marine environments. In this research work different methodologies were applied to describe: (i) wave climate regimes under uncertainty of climate changes scenarios off Iberian Peninsula coast; (ii) coastal hydro-morphology dynamics applying numeric modelling tools; and (iii) thermo-mechanical behaviour of an innovative eco-engineering solution for recycled steel fibre reinforced concrete armour unit. The main outcomes of this research are: (i) the determination of 10-, 50-, and 100-year return period of significant wave height and wave peak period values that can be used with confidence as design parameters for structural analyses in maritime works to be built in the western coast off Iberian Peninsula; (ii) results of a comparative study on coastal protection structures to promote wave energy dissipation and sediments retention; (iii) the proposal of an optimized geometry of maritime structures under longitudinal drift reversal conditions based on hydro- and morphodynamics modelling; (iv) a deep study on thermo-mechanical behaviour of a recycled steel fibre reinforced concrete armour unit; and (v) the proposal of an innovative ecoengineering solution for breakwater armour incorporating the new scientific achievements. Globally, this research work aims at the design and assessment of innovative nature-based coastal engineering solutions based on modelling and observation of natural accretion or sedimentary stable processes, and the application of high structural multifunctional eco-materials with high durability and ductility tested through numerical modelling.A crescente pressão demográfica sobre as zonas costeiras, associada ao rápido crescimento económico e à migração de pessoas para o litoral, tem tido como consequência a implantação de infraestruturas e ativos significativos em áreas propensas a riscos, aumentando a exposição e a vulnerabilidade a desastres naturais ao longo da costa, incluindo erosão, inundações e intrusão salina. O transporte de sedimentos e os processos erosivos nestas áreas constituem aspetos críticos para o ordenamento e gestão do território, especialmente em países de costa extensa como Portugal, uma vez que estes fenómenos colocam frequentemente em risco a vida humana e a proteção de bens. O projeto, construção e manutenção de estruturas de proteção costeira baseadas na natureza em ambientes altamente energéticos, incorporando princípios de resiliência aos impactos das alterações climáticas, requerem uma abrangente abordagem científica multidisciplinar para a compreensão da hidro-morfodinâmica costeira e do comportamento de novos eco-materiais em ambientes marinhos. Neste trabalho de investigação, foram aplicadas diferentes metodologias para descrever: (i) regimes de agitação marítima em cenários de incerteza provocados por alterações climáticas na costa da Península Ibérica; (ii) modelação da dinâmica da hidro-morfologia costeira; e (iii) comportamento termo-mecânico de uma solução inovadora de eco-engenharia para blocos de mantos de quebramar em betão reforçado com fibras de aço reciclado. Os principais resultados deste trabalho de investigação são: (i) a determinação do período de retorno de 10, 50 e 100 anos para a altura de onda significativa e para valores de período de pico de onda que podem ser aplicados com confiança como parâmetros de projeto para análises estruturais em obras marítimas a construir na costa ocidental da Península Ibérica; (ii) resultados de um estudo comparativo de estruturas de proteção costeira para promover a dissipação da energia das ondas e a retenção de sedimentos; (iii) a proposta de uma geometria otimizada para estruturas marítimas sob condições de inversão longitudinal da deriva com base em modelação hidro-morfodinâmica; (iv) um estudo aprofundado sobre o comportamento termomecânico de blocos de mantos de quebramar em betão reforçado com fibras de aço reciclado; e (v) a proposta de uma solução inovadora de eco-engenharia para mantos de quebramar, incorporando os novos resultados científicos obtidos. Em resumo, este trabalho de investigação visa o projeto e avaliação de soluções inovadoras de engenharia costeira baseadas na natureza, através de modelação e observação de processos estáveis de acreção natural ou sedimentar e a aplicação de eco-materiais multifuncionais de alta durabilidade e ductilidade testados através de modelação numérica.Portuguese Foundation for Science and Technology - PhD scholarship SFRH/BD/141381/2018

Towards a scenario-based solution for extreme metocean event simulation applying urgent computing

Today, metocean investigations, combined with forecasts and analysis of extreme events, require new design and development approaches because of their complexity. Extreme metocean events forecasting and prevention is an urgent computing task from decision-making and for reaction point of view. In this case, urgent computing scenario is an essential part that should be included in the hazard simulation and prevention system However, existed urgent computing technological concepts does not perfectly fit all tasks in a frame of extreme metocean events simulation. Many of these tasks should be executed during the overall lifecycle of hazard prevention system that includes not only urgent scenario but research part, as well In this paper, we decompose all tasks in three groups by most significant computational aspects (taking into consideration different criteria of data processing and high-performance contributions) and suggest a new solution that is adaptable for both research in normal (non-urgent) and urgent computing modes, where potential tasks can be structured in the form of scenarios. Suggested solution implements CLAVIRE platform core and extends its with advanced features (regarding simulation frequency, computational performance and data-driven computing). As an example in the metocean subject area, a complex application for Baltic Sea simulations is presented. The case studies describe three scenarios with proposed infrastructure features that are the most interesting for highlighting relevant problems of metocean simulations within the Baltic Sea. These features are: computational optimization possibilities for real-time forecast system calibration; data replacement capabilities within retrospective ensemble extreme values analysis; and hard deadline features within uncertainty analysis of an urgent scenario for complex floods. © 2017 Elsevier B.V

Abundance, composition, distribution and fate of floating marine litter in the south-east Bay of Biscay

151 p.This PhD thesis presents a first overview of floating marine litter pollution in the south-east Bay of Biscay through a combination of harmonized observations, sampling methods, and numerical modelling techniques. Abundance and composition of floating marine litter (FML) were assessed combining net tows and visual observations in coastal and open waters of the Bay of Biscay. Floating riverine litter was also collected to explore the floating fraction of marine litter transported via rivers to the south-east Bay of Biscay. Simulations performed at regional (Bay of Biscay) and sub-regional scale (south-east Bay of Biscay) provided insights into the seasonal distribution patterns and fate of fishing-related and riverine litter items according to their observed buoyancy. The model was previously calibrated with data obtained from drifters released in the south-east Bay of Biscay and forced with hourly estimated and measured winds and currents. Data collection in the coastal waters of the south-east Bay of Biscay highlights the occurrence of submesoscale convergence zones for FML (¿litter windrows¿) during Spring and Summer. Fishing, shipping, and aquaculture sectors were the main source of macrolitter (size>2.5 cm) for litter windrows. Abundances derived from sampling the south-east Bay of Biscay revealed that the area is a hotspot for microplastics (size<5 mm). Most modelled particles released both in coastal andopen waters did not abandon the Bay of Biscay, reinforcing that the basin acts as accumulation region for FML. Results also demonstrated the impact of buoyancy and wind effect on FML behaviour, mainly in summer, when highly buoyant items strongly affected French Marine Protected Areas and Gipuzkoa and Pyrénées-Atlantiques regions. This thesis represents a milestone for supporting future science and policy actions in the south-east Bay of Biscay oriented to prevent and mitigate FML at local, sub-regional and regional scale