Dissertations / Theses: 'Marine Renewable Energy'

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Chen, Lifen. "Modelling of marine renewable energy." Thesis, University of Bath, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.675715.

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The development of marine renewable energy is attracting increasing attention due to its great potential in meeting human energy demands with limited negative environment impact. Various wave energy converter concepts have been proposed in attempt to convert wave energy into usable energy. Both experimental and numerical methods have been widely used to investigate the hydrodynamic performance of these devices in operational conditions and their survival characteristics in extreme sea states. This study focuses on developing a numerical procedure that can predict wave loads and run-up on fixed and moving offshore and coastal structures more accurately. The wave induced motions of flap-type wave energy converter (WEC) and its efficiencies are also investigated. The ultimate objectives of the study are to develop a rigorous approach for the safe and cost efficient design of general offshore structures and leading to the better design of wave energy converters with increased efficiency, and provide best practice guideline to the wave energy converter developers and researchers and engineers in the field. Non-linear hydrodynamic modelling in viscous flow has been used in the simulations. Even for moderate waves, nonlinear effects are important due to wave-structure interaction and also the expected large motions under operational conditions. It seems likely that estimates of performance will be unreliable unless the nonlinear effects associated with such large amplitude motions are properly accounted for. Extreme conditions are also be analysed to ensure device integrity. OpenFOAM, a free, open-source CFD package, has been applied in this work due to its strong capability in coastal and offshore engineering. The built-in viscous solvers interFoam and interDyMFoam have been selected and extended to model wave interactions with fixed and moving offshore and coastal structures, respectively. The solvers have been firstly extended to generate various wave conditions, including regular waves, focused wave groups and tsunami waves etc. New module has also been developed to advance the wave absorption capability in attempt to reduce computational cost of the numerical model by using smaller computational domain. In order to simulate the motion of WECs in waves, the code has been further developed to have functions on determining the wave-induced motions of WECs and on updating the computational domain automatically according to the motion of the WEC. By comparing with published experimental data, theoretical and numerical results on various physical problems, including wave interactions with varied seabed, a fixed vertical circular cylinder, a rotating half-submerged rectangular barge and a flap-type wave energy converter etc. it is confident to say that OpenFOAM is very capable of modelling nonlinear wave interactions with coastal and offshore structures accurately.

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Campbell, Maria Shauna. "Fisheries, marine conservation, marine renewable energy and displacement : a fresh approach." Thesis, University of Plymouth, 2017. http://hdl.handle.net/10026.1/8336.

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Fishers are among the biggest commercial resource users in the marine environment. In order to meet international, national and local policies, the UK has to designate a suite of marine protected areas (MPAs) and reach marine renewable energy (MRE) targets. Inevitably, there will be conflict between these two industries and marine conservation. This study uses a multi-disciplinary approach to examine evaluate the suitability of various sources of data, which could be used to detect, assess, and ultimately predict, fishing effort displacement within the different sectors of the > 15 m fleet in the South West of the UK. Gear-specific Vessel Monitoring System (VMS) data from 2005-2008 was used to assess potential effort displacement due to Haig Fras, a proposed MPA and Wave Hub, a marine renewable energy installation (MREI). The spatial distribution of fishing activity was highly heterogeneous and distinct areas of intense fishing could be identified for all gear-types. A closure of Haig Fras would have the greatest impact on gillnetters. Scallop dredgers also occasionally use the area. The current closure at Wave Hub has the greatest impact on potters and whelkers whose geographic specialisation is most pronounced and who use the area extensively. Longliners also use the area disproportionately would be affected. A simple index of variability was developed in order to determine baselines and two other sources of data were used. High resolution seabed data and low resolution catch data. A semi structured interview was conducted with forty fishers to elicit further information on the challenges, barriers to progress and priority issues in relation to MRE those fishers face. The theme of discontent with the consultation process scored highly throughout. Fishers’ Knowledge (FK) another source of data also scored highly, although further work must be carried out to identify what aspects of this data are useful in assessment of fishing effort displacement.

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Lundin, Staffan. "Marine Current Energy Conversion." Doctoral thesis, Uppsala universitet, Elektricitetslära, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-280763.

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Marine currents, i.e. water currents in oceans and rivers, constitute a large renewable energy resource. This thesis presents research done on the subject of marine current energy conversion in a broad sense. A review of the tidal energy resource in Norway is presented, with the conclusion that tidal currents ought to be an interesting option for Norway in terms of renewable energy. The design of marine current energy conversion devices is studied. It is argued that turbine and generator cannot be seen as separate entities but must be designed and optimised as a unit for a given conversion site. The influence of support structure for the turbine blades on the efficiency of the turbine is studied, leading to the conclusion that it may be better to optimise a turbine for a lower flow speed than the maximum speed at the site. The construction and development of a marine current energy experimental station in the River Dalälven at Söderfors is reported. Measurements of the turbine's power coefficient indicate that it is possible to build efficient turbines for low flow speeds. Experiments at the site are used for investigations into different load control methods and for validation of a numerical model of the energy conversion system and the model's ability to predict system behaviour in response to step changes in operational tip speed ratio. A method for wake measurements is evaluated and found to be useful within certain limits. Simple models for turbine runaway behaviour are derived, of which one is shown by comparison with experimental results to predict the behaviour well.

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Baker, Nicholas Jon. "Linear generators for direct drive marine renewable energy converters." Thesis, Durham University, 2003. http://etheses.dur.ac.uk/696/.

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This thesis is concerned with the development of linear generators for use as the power take off mechanism in marine renewable energy converters. Delivering significant power at the low velocities demanded by wave and tidal stream energy converters requires a large force, which must be reacted by an electrical machine in a direct drive system. Attention is focused on the development of two novel topology linear permanent magnet machines suitable for use in this application. For each topology, models are presented that are capable of predicting the force characteristics and dynamic generator performance. The models, which are verified experimentally, reveal significant behavioural differences between the two topologies. The designer is thus provided with an interesting choice when considering a direct drive power take off strategy. In short, a variable reluctance machine is shown to develop a high shear force in its airgap, offering the potential of a compact generator, yet its performance is hindered by a poor power factor and the presence of significant airgap closure forces. The second machine, an air cored stator encompassing a permanent magnet translator, is shown to lend itself favourably as a generator, but only at the expense of requiring a large quantity of magnetic material and developing a significantly lower shear stress. Mechanical issues involved in the direct integration of linear electrical machines into the marine environment are examined. Details of two existing marine renewable energy devices are used to hypothesise about the characteristics of realistic sized generators of both the topologies investigated. Direct drive power take off is shown to represent a feasible alternative to the complex systems frequently proposed in these applications.

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Francisco, Francisco. "Sonar for environmental monitoring of marine renewable energy technologies." Licentiate thesis, Uppsala universitet, Elektricitetslära, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-314065.

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Human exploration of the hydrosphere is ever increasing as conventional industries grow and new industries emerge. A new emerging and fast-growing industry is the marine renewable energy. The last decades have been characterized by an accentuated development rate of technologies that can convert the energy contained in stream flows, waves, wind and tides. This growth benefits from the fact that human society has become notably aware of the well-being of the environment that we all live in. This brings a human desire to implement technologies which cope better with the natural environment. Yet, this environmental awareness poses difficulties in approving new renewable energy projects such as offshore wind, wave and tidal energy farms. Lessons have been learned that lack of consistent environmental data can become an impasse when consenting permits for testing and deployments marine renewable energy technologies. An example is the European Union in which a majority of the member states requires rigorous environmental monitoring programs to be in place when marine renewable energy technologies are commissioned and decommissioned. To satisfy such high demands and to simultaneously boost the marine renewable sector, long-term environmental monitoring framework that gathers multi-variable data are needed to keep providing data to technology developers, operators as well as to the general public. Technologies based on active acoustics might be the most advanced tools to monitor the subsea environment around marine manmade structures especially in murky and deep waters where divining and conventional technologies are cost. The main objective of this PhD project has develop and test an active acoustic monitoring system for offshore renewable energy farms, by integrating a multitude of appropriate monitoring sonar, hydrophones and cameras systems to be developed with standards suitable for subsea environmental monitoring. In this project, a first task was to identify, secondly acquire and test sonar systems, then a platform was designed and built, a data acquisition device control systems were developed, finally additional instruments such as video cameras and sonars were added. This systems integration followed by calibration of devices was conducted. The sonar systems were used for quantitative measurements of the occurrence of e.g. large marine animals and schools of fish near marine renewable energy converters. The sonar systems were also used for seabed inspections, depth measurements and capitating flow observations. So far, the combination of multibeam and dual-beam sonar systems produced good results of target detection, bottom inspection, depth measurements and biomass estimation. The multibeam sonar system was capable of resolving isolated targets located near high acoustic retroreflective objects. Panoramic acoustic images of wave and instream energy converters were acquired using a multibeam sonar operating at frequencies near 1 GHz. The Dual-beam and split-beam sonar systems produced data referent to acoustic background intensity of targets that helps to classify targets according to its size, composition and 3-Dimensional location within the water column. The next phase of this project will deploy the platform for longer periods in order to gather consistent acoustic and optical backscattering data of marine animal behaviour within marine renewable energy farms.

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Hamlyn, Victoria Jane. "The legal regimes governing marine renewable energy in England and Wales." Thesis, University of Plymouth, 2015. http://hdl.handle.net/10026.1/3545.

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This thesis involves an examination of the main international, regional and national legal regimes regulating marine renewable energy in England and Wales. Deriving from a complex patchwork of law and policy, developments have ensued in the absence of a distinct governing ‘legal regime’ and within a number of competing paradigms. This original synthesis attempts to identify lacunae, conflicts and connections within and between the span of legal genres that MRE evokes. Against a backdrop of climate change mitigation, the key findings show that despite the presence of political will for offshore renewable energies, MRE development faces a number of legal obstacles, all of which seek to protect other important public and private interests. Although predominantly satisfactory at the international level (international law of the sea), national private property rights, environmental protection laws and regulatory development controls each encompass particular legal incongruities that have the potential to act as barricades to development. This thesis discusses these issues and reaches conclusions as to potential areas for reform.

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Heita, Natalia Ndatilohamba. "The development of Namibia's renewable energy regime." Master's thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/15167.

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As is the case with many countries, Namibia has an economy dependent on fossil fuels. The country is, however, blessed with abundant and diverse - but as yet unexploited - renewable energy (RE) resources that could be used for improving the livelihood of the vast majority of its 2.2 million people. Today the conflict between energy production from fossil fuels and protection of the environment is intensifying and this compels all countries to search for means of resolving this conflict. Developing RE through the enactment of enabling legislation and implementation of relevant policy is one important step towards attaining the ideal of an energy-secure future. This state of affairs is not unique to Namibia, as most countries with abundant RE sources are striving to promote and deploy RE in their respective regimes through appropriate policies and legal frameworks. This study examines Germany and Ghana from, respectively, the developed and developing world, as leading countries that have established a proactive RE regime. However, such a regime can only be successfully achieved if countries, including Namibia, adopt laws and policies that promote and encourage the use of RE in order to move away from fossil fuel dependence to a greener economy. Thus the study seeks to investigate RE resources in Namibia and their potential development. It outlines the current legislation pertaining to the regulation of RE in Namibia. As such, the study further examines the Organisation for Economic Cooperation and Development (OECD) guidelines and draws examples from other regimes, particularly Germany and Ghana, in order to provide a guideline for the enactment of a general Energy Act with a particular chapter on RE. It concludes with recommendations as to how Namibia can secure a sustainable energy future.

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Chisom, Christopher M., and Jack C. II Templenton. "Analysis of Marine Corps renewable energy planning to meet installation energy security requirements." Thesis, Monterey, California: Naval Postgraduate School, 2013. http://hdl.handle.net/10945/38899.

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Approved for public release; distribution is unlimited. The purpose of this thesis is to analyze Marine Corps installation energy consumption and the pursuit of increased renewable energy generation goals across Marine Corps installations. The main objective of this report is to determine the cost of interruption and the net present value (NPV) of renewable energy generation needed to meet the Marine Corps energy security objectives. First, we determine installation-specific energy consumption, resource requirements, and current renewable energy generation projects. Second, we analyze current Marine Corps installation energy portfolios to determine shortfalls from minimum energy targets and the cost to generate those shortfalls through renewable energy technologies. Finally, we identify installation energy security requirements, determine cost of interruption, and conduct a sensitivity analysis of the cost-benefit of renewable energy generation alternatives to meet energy security requirements. This study determines how investment in renewable energy to meet baseline energy consumption requirements increases energy security across Marine Corps installations. Furthermore, considering the cost of interruption, the investment in renewable energy technologies yields a positive NPV at the majority of Marine Corps installations. Based on this research, we recommend that the Marine Corps develops a quantitative method for assessing energy security and invest to meet energy security goals at each installation.

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Wade, Helen Mary. "Investigating the potential effects of marine renewable energy developments on seabirds." Thesis, University of the Highlands and Islands, 2015. https://pure.uhi.ac.uk/portal/en/studentthesis/investigating-the-potential-effects-of-marine-renewable-energy-developments-on-seabirds(a13794b8-f416-4e96-8199-5fbd3af39d32).html.

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Marine renewable energy developments (MREDs) are becoming an increasing feature of the marine environment. Scotland has considerable potential for generating energy from the marine environment in the form of extensive wind, wave and tidal-stream resources. Scotland also hosts numerous internationally important breeding populations of seabirds and Scottish territorial waters represent a key overwintering area for many species. EU legislation requires that MREDs do not damage the integrity of protected seabird populations but potential effects of MREDs on seabirds are not yet fully understood. This thesis aims to address gaps in knowledge regarding how MREDs may affect seabird populations. I generate vulnerability and confidence indices to predict the effects of offshore wind, wave and tidal-stream renewable energy developments on Scottish seabird populations; track the movements of a seabird species identified as lacking in data to better understand overlap with MREDs; and investigate seabird use of a high current flow environment leased as a tidal-stream energy development site. Overall, this thesis indicates that seabird responses to MREDs are likely to be species-specific and will vary dependent on the development location and design of the energy generating technology. My findings indicate that effects of MREDs will differ dependent on individual foraging strategies, age and life stage of individuals, which implies that MREDs are likely to differently affect subsections of seabird populations.

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Philpott, Evelyn. "Examining potential effects of marine renewable energy developments on top predators." Thesis, University of Aberdeen, 2013. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=210583.

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This thesis uses data collected over three summers in 2010, 2011 and 2012 at the Isle of May National Nature Reserve, Scotland to examine top predator presence and behaviour in a moderately fast tidal stream site. Fieldwork consisted of an intensive land based observation survey of seabirds at sea, acoustic monitoring of small cetaceans and the deployment of a suite of oceanographical tools to simultaneously collect data on a fine temporal scale over a study area of ~1.5km2. The aim of the study was to examine the potential effects of marine renewable energy developments on top predator behaviour in a tidal stream site by addressing some of the key data gaps such as habitat use in tidal stream areas, dive behaviour and collision and disturbance risk assessment. Acoustic detections of harbour porpoises were investigated as a function of physical environmental variables. Strong links between porpoise presence and increased thermal stratification and chlorophyll levels were detected along with a very strong diurnal pattern with increased detections at night. There was no relationship with tidal state. The habitat use of five species of breeding birds at sea adjacent to breeding cliffs was examined to gauge what environmental factors drive habitat use at these sites. Counts of foraging kittiwakes were examined in relation to environmental variables and while strong temporal trends emerged there was no link with oceanographic features. The study site was predominately used for loafing (non foraging behaviour) and so species specific temporal variation in loafing behaviour was analysed. Strong seasonal and diurnal trends in loafing emerged for all species which could be linked to differences in their breeding phenology. These results can be used in assessing and mitigating disturbance to these birds from marine renewables developments. Age specific variation in dive behaviour in the European shag was examined to determine whether newly fledged juveniles were at a greater risk of collision with tidal turbines than adults. Juveniles initially demonstrated a shorter dive duration than adults but after 4-6 weeks their dive duration had significantly increased. However age specific difference in dive behaviour in relation to water depth iii remained unchanged over time with juveniles showing no relationship between dive duration and water depth while adults increased dive duration in deeper water. The implications of this result for assessing age specific collision risk for this species is discussed. Results from this study were used to populate a framework for assessing collision and disturbance risk to seabirds in the near shore area adjacent to the breeding colony from a small scale tidal turbine development scenario. A method was developed to quantify risk by combining relative abundance data, behavioural data and published data on activity budgets for four species; guillemots, razorbills, puffins and shags. The output from this thesis has practical applications for informing the temporal and spatial scale of data collection and survey design in environmental impact assessments regarding marine renewable energy developments with emphasis on understanding the mechanistic links driving predator behaviour. Results can also be used to design appropriate mitigation procedures to prevent disturbance to loafing or foraging birds.

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Wilhelmsson, Dan. "Aspects of offshore renewable energy and the alterations of marine habitats /." Stockholm : Department of Zoology, Stockholm University, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-31157.

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de, Groot Jiska Reinarda. "Attitudes towards marine energy : understanding the values." Thesis, University of Plymouth, 2015. http://hdl.handle.net/10026.1/3470.

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Marine Renewable Energy (MRE) in the form of wave, tidal and offshore wind has emerged as a potentially major component of strategies to reduce carbon dioxide emissions and combat climate change. One factor influencing the implementation of MRE technologies is acceptance by people living near developments. This study investigated (i) attitudes towards MRE in small island communities as likely host communities for MRE developments; (ii) the underlying factors and values shaping these attitudes; (iii) how communities viewed MRE with regard to their place attachments; (iv) the inclusion of communities attitudes into MRE decision-making; and (v) contributions to policy and practice of MRE development. Data were collected using a mixed-methods approach, employing questionnaire surveys and interviews in three case study communities: 1) the Orkney Islands in Scotland which have considerable experience with MRE; 2) the Shetland Islands, also a Scottish community but with somewhat less experience; and 3) the Isles of Scilly, an English community with limited MRE experience. These study sites provided an opportunity to examine attitudes towards MRE in areas with different levels of MRE experience and differing government administrations and consenting procedures, thus offering novel insights into how local contexts shape attitudes towards MRE. The theoretical position adopted was place attachment, and the study made steps towards understanding how place attachment processes operate when people evaluate MRE development locally. Processes of place attachment were found to be based on a continuous flow of interactions between people and places based on an evaluation of what happens in specific local contexts and how these are valued against sets of local priorities and preferences. The study found generally positive attitudes towards MRE, and identified local context, place-based values and the perceived effects of MRE as dominant in shaping support. The study thus found two important contributors that shaped attitudes: (i) local references and influences through which people observed issues, including socio-historical references, relational factors, and pragmatic factors, and (ii) local values, through which MRE was evaluated, which were established by residents based on evaluations of local characteristics, and how they related to strategies to maintain the long-term community continuity, and whether they were considered to be a threat, and therefore, a priority for continuity or for change. Based on these factors, a heuristic model was developed to visualise how attitudes towards MRE developed based on local contexts. Although complex interplays of local factors were observed, support for MRE development was largely based on its perceived local socio-economic benefits and perceptions of minimal environmental disruption. To incorporate local attitudes into decision-making, a place-based approach instead of a technology-based approach was advocated in which community priorities becomes the first focal point of siting processes. This approach is based both on the identified importance of local context for engaging the community and on ensuring appropriate siting based on engagement processes in which communities are appropriately represented and processes are tailored to local circumstances. An added important benefit from such an approach is that it allows for the inclusion of local knowledge and expertise in MRE siting.

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Sjolte, Jonas. "Marine renewable energy conversion : Grid and off-grid modeling, design and operation." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elkraftteknikk, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-26004.

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The global energy production from renewable sources is increasing, with high penetration of both wind and solar in key regions. Ocean Wave Energy is projected to contribute with an increasing share of the future power supply, and the focus of this work is to investigate the requirements for connecting wave energy to the power grid, in context of the Fred. Olsen (FO) Wave Energy Project. Most Wave Energy Converters (WECs) produce highly distorted power due to the reciprocal motion induced by the ocean waves. Some WEC systems have integrated energy storage that overcomes this limitation, but adds significant expenses. As an alternative approach, this work investigates direct power export that relies on aggregate smoothing among several WECs. By optimizing the position of the WEC devices with respect to the incoming waves, fluctuations may be mutually canceled out between the devices. FO has closely monitored the global development within wave energy for about two decades, and has worked actively on developing WECs since 2002. The latest WEC system, named Lifesaver, has been in operation since April 2012 and is the basis of this thesis work. The Lifesaver system is described in detail, and comprehensive data on operational performance is presented. The major cost driver for grid integration is the peak to average power ratio, which can be as high as 20 in the early power conversion stages. Thus, it is crucial to improve the power quality early in the conversion chain so that the downstream power system is efficiently utilized. The simulations undertaken in this work indicate that a high quality power output can be achieved at the farm level, but that significant oversize factors will be required in the intermediate power systems within the farm. Cost-benefit analysis of the system show that a grid connected system at the current technology level will return marginal profitability. Therefore, several alternative approaches are investigated that could serve as a bridge towards future large scale systems. This includes autonomous systems that could supply power to remote ocean based units such as measurement and surveillance buoys, aquaculture facilities and support systems for the off-shore oil and gas industry. In general, the findings show that the WEC system is well suited for grid integration, although it becomes clear that significant development remains before wave energy can become an important supplement in the energy mix. Moreover, there seems to be a market for autonomous systems that is economically viable at the current technology level that could allow for immediate deployment of commercial systems.

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Bray, Laura. "Preparing for offshore renewable energy development in the Mediterranean." Thesis, University of Plymouth, 2017. http://hdl.handle.net/10026.1/10099.

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The development of offshore wind farms and marine renewable energy devices in the Mediterranean is central to both national, and international, energy strategies for countries bordering the Mediterranean Sea. The ecological impacts of marine renewable energy development in the Mediterranean region, although essential for policy makers, are as yet unknown. The Northern Adriatic is identified as a plausible site for offshore wind farm development. Using the wider region (Adriatic and Northern Ionian) as a case study, this thesis examines the likely impact to the marine environment if an offshore wind farm is established. Site suitability, based on wind speed, bathymetry, and larvae connectivity levels are investigated along with the plausibility of the turbines operating as artificial reefs in the area. As offshore wind farms may alter the larval connectivity and supply dynamics of benthic populations, a connectivity map was constructed to identify areas of high and low connectivity in the Adriatic Sea. The Puglia coast of Italy is a likely larval sink, and displays some of the highest connectivity within the region, suggesting potential inputs of genetic materials from surrounding populations. Considering offshore wind farms could operate as artificial reefs, an in-situ pilot project was established to simulate the presence of wind turbines. Macroinvertebrates colonized the new substrata within the first few months but were lower in abundance when compared to a natural hard substrata environment. Time, turbine location, and the material used for turbine construction all affected the macro-invertebrate communities. In addition, fish abundances, and diversity were lower around the simulated OWF foundations in comparison to a natural hard substrata environment, and no increases in fish abundance occurred around the simulated turbines when compared to reference sites of soft substrata. This observation was validated with the use of an ecosystem modelling software (Ecopath with Ecosim), which simulated the overall ecosystem level impacts that would occur if 50 offshore monopile wind turbines were introduced to the Northern Ionian and colonized by macroinvertebrate communities. When compared to the baseline scenario (no simulated introduction of an OWF), the introduction of new habitat had no discernible impacts to the structure or functioning of the marine ecosystem. Noticeable changes to the ecosystem were only apparent if fishing restrictions were enforced in parallel with the simulated offshore wind farm; the ecosystem appears to become more structured by top down predation. In addition seabirds are also impacted by the reduction of fishing discards as a food source. These results are the first attempt to quantify the suspected benefits of offshore wind farms operating as de-facto marine protected areas.

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Apelfröjd, Senad. "Grid Connection of Permanent Magnet Generator Based Renewable Energy Systems." Doctoral thesis, Uppsala universitet, Elektricitetslära, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-304659.

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Renewable energy is harnessed from continuously replenishing natural processes. Some commonly known are sunlight, water, wind, tides, geothermal heat and various forms of biomass. The focus on renewable energy has over the past few decades intensified greatly. This thesis contributes to the research on developing renewable energy technologies, within the wind power, wave power and marine current power projects at the division of Electricity, Uppsala University. In this thesis grid connection of permanent magnet generator based renewable energy sources is evaluated. A tap transformer based grid connection system has been constructed and experimentally evaluated for a vertical axis wind turbine. Full range variable speed operation of the turbine is enabled by using the different step-up ratios of a tap transformer. This removes the need for a DC/DC step or an active rectifier on the generator side of the full frequency converter and thereby reduces system complexity. Experiments and simulations of the system for variable speed operation are done and efficiency and harmonic content are evaluated. The work presented in the thesis has also contributed to the design, construction and evaluation of a full-scale offshore marine substation for wave power intended to grid connect a farm of wave energy converters. The function of the marine substation has been experimentally tested and the substation is ready for deployment. Results from the system verification are presented. Special focus is on the transformer losses and transformer in-rush currents. A control and grid connection system for a vertical axis marine current energy converter has been designed and constructed. The grid connection is done with a back-to-back 2L-3L system with a three level cascaded H-bridge converter grid side. The system has been tested in the laboratory and is ready to be installed at the experimental site. Results from the laboratory testing of the system are presented. Wind Power Wave Power Marine Currnet Power

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Mulcan, Amanda. "Environmental siting suitability analysis for commercial scale ocean renewable energy| A southeast Florida case study." Thesis, Florida Atlantic University, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=1527082.

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Rouse, Sally. "Quantifying benthic secondary productivity on artificial structures : maximising the benefit of marine renewable energy devices." Thesis, University of Aberdeen, 2016. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=231790.

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Marine renewable energy developments (MRED) will result in large quantities of infrastructure being deployed in coastal habitats, and the localised exclusion of fishing. The ecological consequences of this scale of deployment are largely unknown, particularly for benthic species. Infrastructure has the capacity to act as artificial reefs (ARs), providing novel habitat, and this may viewed as a benefit of MRED, or a means to mitigate the exclusion of fishing. At present, the functioning of AR ecosystems remains poorly understood. As a measure of ecosystem function, secondary productivity can be used to assess the implications of MRED. The lack of suitable methodology, deployable at relevant scales within time and/or cost constraints, has limited benthic secondary productivity (BSP) quantifications on ARs. Techniques to measure potential BSP and particle flux were developed and applied to the Loch Linnhe Artificial Reef (functionally similar to scour protection material). Variations in BSP and mobile epifaunal densities on, and between, structures in different environments were quantified. Reefs exposed to intermediate current had the highest potential productivity. The BSP on internal areas of structures contributed to the total productive output, but the relative contribution varied according to reef location and design. BSP was primarily determined by particle supply, but the response was not consistent among locations. Mobile epifaunal densities related to reef location, but not reef design, and were highest on reefs in the deepest water and exposed to the fastest currents. The evidence presented in this thesis highlights the need to account for the receiving environment when predicting the ecological consequences of MRED, or when modelling the productive capacity of structures. Such information can be used to suggest modifications to proposed or existing structures in order to maximise their benefit to coastal ecosystems.

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Abdul, Rahman Anas. "Numerical modelling of full scale tidal turbines using the actuator disc approach." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/31246.

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In recent years, the actuator disc approach which employs the Reynolds-Averaged Navier-Stokes (RANS) solvers has been extensively applied in wind and tidal energy field to estimate the wake of a horizontal axis turbine. This method is simpler to administer and requires moderate computational resources in modelling a tidal turbines rotor. Nonetheless, the use of actuator disc approximation in predicting the performance of tidal devices has been limited to studies involving an extremely small disc (e.g. rotor diameter of 0.1 meter). The drawback of a small scale actuator disc model is the overestimation of essential parameters such as the mesh density and the resolution of the vertical layers, making them impractical to be replicated in a regional scale model. Hence, this study aims to explore the methodology on implementation of the Three- Dimensional (3D) actuator disc-RANS model in an ocean scale simulation. Additionally, this study also aspires to examine the sensitivity of the applied momentum source term and its validity in representing full-size tidal devices. Nonetheless, before the effectiveness of an actuator disc in a regional model can be tested, tidal flow models for the area of interest needed to be set up first. This was essential for two reasons: (a) to ensure accurate hydrodynamic flow conditions at the deployment site were replicated, (b) to give confidence in the outputs produced by the regional scale actuator disc simulations, since in-situ turbine measurement data from a real deployment site were difficult to source. This research was undertaken in two stages; in the first stage, a numerical model which can simulate the tidal flow conditions of the deployment sites was constructed, and, in the second stage, the actuator disc method which is capable of modelling an array of real scale-sized tidal turbines rotors has been implemented. In the first stage, tidal flow simulations of the Pentland Firth and Orkney Waters (PFOW) were conducted using two distinct open-source software - Telemac3D, which is a finite element based numerical model, and Delft3D, which is a finite difference based model. Detailed methodologies in developing a 3D tidal flow model for the PFOW using both numerical models were presented, where their functionality, as well as limitations were explored. In the calibration and validation processes, both models demonstrated excellent comparison against the measured data. However, Telemac3D was selected for further modelling of the actuator disc considering the model's capability to perform parallel computing, together with its flexibility to combine both structured and unstructured mesh. In the second stage, to examine the actuator disc's accuracy in modelling a full size tidal device, the momentum source term was initially applied in an idealised channel study, where the presence of a 20-meter diameter turbine was simulated for both single and array configurations. The following parameters were investigated: (i) size of the unstructured mesh utilised in the computational domain, (ii) variation in disc's thickness, (iii) resolution of the imposed structured grid to represent turbine's enclosure, (iv) variation in the vertical layers, and (v) influence of hydrostatic and non-hydrostatic formulations on the models' outputs. It is to be noted that the turbine's support structures have not been included in the modelling. The predicted velocities and computed turbulence intensities from the models were compared against laboratory measurement data sourced from literature, where excellent agreement between the model outputs and the data from literature was observed. In essence, these studies highlighted the efficiency and robustness of the applied momentum source term in replicating the wake profiles and turbulence characteristics downstream of the disc, hence providing credence in implementing the actuator disc method for a regional scale application. Subsequently, the validated actuator disc method was applied to the Inner Sound region of the Pentland Firth to simulate arrays of up to 32 tidal turbine rotors. The wake development, flow interactions with the rotor arrays, and flow recovery at the Inner Sound region have been successfully mapped. Also, this study highlighted the importance of employing optimal numerical margins, specifically for the structured grid and horizontal planes, as both parameters were relevant in defining the disc's swept area. As published materials on the implementation of actuator disc approach within a regional scale model is still scarce, it was aspired that this work could provide some evidence, guidance and examples of suggested best practice in effort to fill the research gap in modelling tidal turbine arrays using the actuator disc approach.

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Burchell, Joseph William. "Advancement of direct drive generator systems for offshore renewable energy production." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/33263.

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As machine topologies and technologies mature, the fundamental function of the device is honed. Direct drive machines have the potential to launch the renewable energy sector into a new era of large scale, reliable, offshore power generation. With advancements in new technologies, such as superconductivity, the reduction of generator mass due to incorporation of machine and device structures, the continued advancements in component and system reliability; direct drive generators have the ability to outsize geared wind systems and simplify submerged linear and rotary power generation. The research held within this thesis will focus on improving direct drive power take off systems for offshore renewable energy power generation by splitting the area into four parts. The first part will discuss the various methods of energy extraction within the offshore and marine environment. The future of the sector will be discussed, and a forecast of technological advancement and existing reliability issues will be provided based on current data. The second part will focus on drive trains and direct drive generators, assessing the current topologies and suggesting alternatives that may thrive in a variety of large and small offshore renewable machines. The third part investigates the application of novel linear bearings in direct drive systems for offshore and submerged operation. A brief study of the loads found in wave applications will be presented and the testing of several polymer bearing materials will be outlined. The final part will discuss the potential benefits of flooding the airgap of a direct drive generator with sea water for marine applications. Results will be presented from two linear test rigs and the marinisation of devices will conclude the report.

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Bray, Samuel. "Multiscale hydro-environmental modelling of marine renewable energy devices, with particular application to the Severn Barrage." Thesis, Cardiff University, 2017. http://orca.cf.ac.uk/111199/.

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This research study presents enhancements to the hydro-environmental model Environmental Fluid Dynamics Code (EFDC), improving the predictive capabilities of the impacts of tidal range renewable proposals and dissolved phosphate concentrations in estuaries. Refinements to the representation of turbines and sluice gates, including updates to the discharge relationships used and momentum conservation were applied to the Severn Tidal Power Group’s Cardiff-Weston Barrage, providing an accurate assessment of the barrage’s potential impacts and highlighting the importance of correct hydraulic structure representation. The Severn Barrage was found to have minor impacts on peak water levels as far-field as the west coast of Scotland. The refinements reduced predicted peak water levels by up to 1 m upstream of the barrage. The applicability of the updated model in assisting with the design and optimisation of tidal lagoons was then tested by running a suite of different configurations of the Bridgwater Bay Lagoon, varying the turbine numbers from 60 to 360. It was demonstrated that additional turbines can negatively impact energy output, by reducing average generating time and generating over a lower head difference. Previous laboratory and field studies demonstrated a link between salinity and phosphate sorption to sediments due to the competition for sorption sites between seawater anions and phosphate. Since sediment-associated nutrients are not readily available for biological uptake, the dissolved proportion of phosphate is of particular importance when trying to predict the grown of phytoplankton and the potential for eutrophication. The salinity-linked sorption relationship was incorporated into the EFDC model to improve the prediction for dissolved phosphate across the estuary by taking into account the salinity variation. The refinement to the numerical calculation for the phosphate partition coefficient in the model caused a measurable change to the predicted dissolved phosphate levels, bringing them closer to measured data from the estuary.

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Gordelier, Tessa Jane. "Enhancing wave energy deployments through mooring system reliability assessment." Thesis, University of Exeter, 2016. http://hdl.handle.net/10871/24917.

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Wave energy generation is a promising renewable energy source but it faces certain challenges before it can become commercially viable. In comparison to conventional energy generation it is expensive, furthermore it has been plagued by reliability challenges due to the harsh operating demands of the marine environment. This Thesis investigates the reliability of wave energy devices, and specifically focuses on mooring system reliability. Two major themes are developed: Firstly, an assessment is conducted on a conventional mooring component, reviewing safety factors suggested in mooring system design guidelines and investigating whether there is a potential to reduce these safety factors (and in so doing, reduce system costs). Numerical modelling, laboratory testing and field testing demonstrate that excessively large safety factors are published in design guidance for static loading scenarios. However, when considering fatigue loading regimes (a critical aspect of wave energy generation), the proposed safety factors are found to be appropriate. In fatigue design, the importance of selecting an appropriate stress concentration factor for use with generic S-N curves is highlighted. These findings indicate the publication of additional stress concentration factors and a standard approach for mean stress adjustment would be a valuable addition to mooring system design guidance for fatigue. The second theme introduces a novel mooring component, The Exeter Tether, designed to reduce mooring loads and thus reduce system costs. The introduction of any novel technology brings new reliability considerations, and a reliability assessment of the tether and sub-components is presented in this Thesis. Following a failure modes and effects analysis, a bespoke range of physical tests is developed to investigate reliability concerns unique to this novel component. Laboratory testing of the tether assembly shows promising fatigue performance, however field trials highlight concerns regarding bio-fouling and marine debris ingress. Sub-component testing of the EPDM (Ethylene propylene diene monomer) polymer core suggests an increase in material stiffness with both marine ageing and repeated compression cycles. This finding supports results from assembly trials in the laboratory and at sea, where tether assembly dynamic axial stiffness is observed to increase over time. The overarching design philosophy behind the Exeter Tether is to reduce mooring system loads, so establishing the `worked' operating profile of the tether is crucial for the design intentions to be realised without compromising the reliability of the overall mooring system. Trials on the anti-friction membrane establish optimum performance when using two layers of UHMWPE (Ultra high molecular weight polyethylene) tape. Further areas requiring research are highlighted, and suggestions are made to improve the reliability of future design iterations of The Exeter Tether. The two reliability approaches presented demonstrate the potential for cost reduction in mooring system design and highlight the importance of physical component testing, both in the field and in laboratory conditions, to optimise component design whilst ensuring overall system reliability.

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Braune, Yann. "Investments in Academic Renewable Electricity Generation Technology Spin-Offs : A Qualitative Study on High Capital Limitations for Underexplored Renewable Energy Sources." Thesis, Uppsala universitet, Industriell teknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-413527.

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Due to an intensified climate change discourse, renewable energy technologies find higher attention within the energy system and increasingly compete with traditional energy conversion systems. Electricity is progressively being generated through renewable electricity generation technologies (REGT) which harness naturally existing energy fluxes (wind, tide, heat, sun) and convert it to electricity. High investments are currently being made into well-developed REGT using explored energy sources such as wind, hydro or solar. In order to increase cost- and energy efficiency of REGTs, university research projects are developing new REGTs that harvest underexplored energy sources such as the marine energy source. These capital-intensive marine energy research projects are entering the market through university spin-off firms but are often confronted with funding gaps, for the current or future operations. Capital rich investors could provide these funds but are often investing in well explored energy sources rather than into underexplored but more cost- and energy-efficient energy sources. Utilizing a qualitative, grounded theory-influenced approach and combining empirical material of semi-structured interviews, data from a participant observation of an innovation system workshop attendance and data from continuous meetings with an academic REGT spin-off from Uppsala University, this study investigates 1) the drivers and barriers within the funding ecosystem for academic REGT spin-offs in Sweden, 2) the limited access of high capital to underexplored energy sources on the specific case of the marine energy source and 3) a potential common ground for investors with high capital and academic REGT spin-offs in order to allow an accelerated diffusion of the marine energy source. The results indicate that the physical properties of the underexplored marine source should not be accounted for as driver but rather as the foundation of an academic REGT spin-off. This frame allows to bridge practitioners of both the investment field and the academic field of REGT spin-offs through the degree of utilization. An inversion of relations, where not only entrepreneurs increasingly link their field of study to economy and business, but also investors adapt cross-disciplinary knowledge towards academia and natural sciences via the degree of utilization, could be beneficial for an accelerated diffusion of academic REGTs. Bridging practitioners of both fields through the degree of utilization and other means might together with a full commercial application and proof of marine REGTs reduce the funding gap of academic spin-offs in the marine sector and allow access to investors with high capital.

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Garrett, Joanne Katherine. "Interdisciplinary study into the effect of a marine renewable energy testing facility on the underwater sound in Falmouth Bay." Thesis, University of Exeter, 2015. http://hdl.handle.net/10871/21032.

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Wave energy has the potential to contribute considerably to the UK's energy mix. The marine environment is already subjected to many anthropogenic pressures. There is a need to develop the industry as sustainably as possible. A key concern is the potential for underwater noise to affect marine life. A wave energy converter (WEC; BOLT Lifesaver, Fred Olsen Ltd.) was deployed at the Falmouth Bay marine renewable energy test site (FaBTest). The underwater sound levels were recorded at this site for a two week baseline period, a five-day installation period and intermittent operational and non-operational activity from March 2012 - November 2013. The recordings were also analysed for the Marine Strategy Framework Directive (MSFD) indicator third octave bands of 63-Hz and 125-Hz for shipping noise. The median and modal sound levels in Falmouth Bay were found to be loudest in the frequency range 100 Hz - 1 kHz and affected by local shipping activity. During installation activity, the sound levels were louder at all frequencies recorded as compared to similar periods with no installation activity, with a mean difference of 6.9 dB Hz-1 in the range 10 Hz to 48 kHz. Long term marine renewable energy construction projects may affect the MSFD indicator bands. There was little overall difference in the average sound levels for the operational and non-operational periods as the median PSD levels were louder by an average of 0.04 dB Hz-1 during the operational activity as compared to the non-operational activity. The results of this study indicate that the effect of a single WEC device on the overall sound levels in Falmouth Bay is relatively low considering the substantial presence of shipping in the area. However, in the immediate vicinity of the device (<200 m), the sound produced was found to be of significance to marine animals. It therefore requires considering in future deployments, particularly at a site with little anthropogenic activity.

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Nguyen, Thi Hong Minh, and Van Hanh Vu. "Bioethanol production from marine algae biomass: prospect and troubles." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-99282.

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The increase of petroleum cost as well as global warming and climate change result in investigation to discover new renewable energy resources. Bioenergy is one of the most important sources that is concerning the scientists and industrial sector. Although bioethanol had to be known as one of the most important renewable energy sources in order to reduce greenhouse gases and global warming, there is a limited number of publications reporting on them. In this review, a brief overview is offered about bioethanol production from algae. It can be given a deeper insight in dificulties and promising potential of bioethanol from algae Sự gia tăng giá nhiên liệu hóa thạch cùng với cảnh báo toàn cầu về biến đổi khí hậu hướng đến việc nghiên cứu tìm ra những nguồn năng lượng có thể tái tạo. Năng lượng sinh học là một trong những nguồn quan trọng được các nhà khoa học và doanh nghiệp quan tâm. Mặc dù ethanol sinh học đã được biết đến như là một trong những dạng năng lượng tái tạo quan trọng nhất để giảm thiểu các khí nhà kính và cảnh báo toàn cầu, nhưng chỉ có một số ít bài báo về nó. Trong bài tổng quan này, chúng tôi giới thiệu vắn tắt việc sản xuất ethanol sinh học từ tảo. Nó đưa ra cái nhìn sâu hơn về những khó khăn và tiềm năng hứa hẹn của sản xuất ethanol sinh học từ tảo

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Martinez, Fabien. "Drag study of the nacelles of a tidal stream device using CFD." Thesis, Cranfield University, 2010. http://dspace.lib.cranfield.ac.uk/handle/1826/7440.

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Nowadays, renewable energy is in full growth. In particular, offshore wind farms will be at the centre of UK energetic strategy in the coming years. However, other types of marine renewable are still at an early development stage. That is the case for tidal energy. Many projects have been undertaken but there is no candidate for competitive commercial applications yet. Deltastream is one of these numerous pioneering projects. It consists of a set of three marine current turbines mounted on a triangular base put down onto the seabed. The device is not moored and no harm is done to the environment. However, that makes the structure more sensitive to water flows. And it is important to ensure that it will remain at its location and not being carried along with the tidal streams. Using CFD, the present study aims to evaluate the drag on the nacelles of the structure and come up with solutions to reduce it as much as possible.

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Alexander, Karen. "Offshore power production and marine stakeholders : from understanding conflict to impact mitigation." Thesis, University of the Highlands and Islands, 2012. https://pure.uhi.ac.uk/portal/en/studentthesis/offshore-power-production-and-marine-stakeholders(92df071b-42b0-4d65-a4b4-798d4300169b).html.

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Little is known about the impact of marine renewable energy installations upon the marine environment and those who use it. Harnessing marine energy will involve the offshore siting of energy extraction devices and their associated infrastructure. This will alter the local environment and substantially modify use and access for a variety of marine stakeholders, potentially leading to conflict. Using the Ecosystem Approach (EA) as a conceptual framework, this thesis aimed to answer the question: What is the potential for conflict between the marine renewable energy industry and marine stakeholders, and how can this be mitigated? The research consisted of three components which used a variety of methods: i) stakeholder identification through a review of the literature and use of a novel interactive mapping method; ii) an investigation of the potential consequences for the priority stakeholder which used a mail survey and in-depth interviews; and iii) an exploration of potential mitigation which used ecosystem modelling. The stakeholder most likely to be affected by marine renewable energy device (MRED) deployment was the fishing industry. Potential consequences included: navigation and safety hazards, loss of access and alternative employment. Further exploration revealed that a loss of livelihood was the all-encompassing concern for fishers, and that skills shortages (transferable skills) may mean that should a loss of livelihood occur there may not be acceptable alternative employment. The modelling exercise indicated that it is not currently possible to definitively predict whether any opportunities which may be created by MRED installation will mitigate any negative effects, and that exclusion zones may actually decrease catches for most fleets. The findings of this study have implications for ‘conflict-free’ development of the marine renewable energy industry. To address this, several policy recommendations were offered as regards to operationalising the EA in terms of marine renewable energy.

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Langhamer, Olivia. "Wave energy conversion and the marine environment : Colonization patterns and habitat dynamics." Doctoral thesis, Uppsala universitet, Elektricitetslära, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-107193.

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A wave energy park has been established on the Swedish west coast outside Lysekil and pioneer work about its interactions with the marine environment has been conducted. So far, little is known about the effects of offshore energy installations on the marine environment, and this thesis assists in minimizing environmental risks as well as in enhancing potential positive effects on the marine environment. The Lysekil research site is situated about two kilometres offshore and has been under development since 2005. During this time 26 “environmental devices”, without generators, consisting of a steel buoy attached via a wire to a foundation on 25 m depth have been placed out for ecological studies on macrofauna in surrounding sediments and on colonization of the foundations and the buoys. Sediment samples to examine macrofauna in the seabed have been taken during five seasons. Biomass, abundance and diversity of infauna in the test site were generally low, but higher than in a nearby control site. The species composition was typical for the area and depth. In addition to sediment analysis, the effect of wave power concrete foundations on the marine environment has been investigated by scuba diving. The surface orientation and its effect on colonization by sessile organisms was examined on the first five foundations, placed out in 2005, and observations of habitat use by fish and crustaceans were made. The results show a succession of colonization over time (three years of investigation) with a higher cover by sessile organisms on vertical surfaces. Mobile fauna abundance on and around the foundations was generally low. Three months after the deployment of the 21 new foundations in 2007, assemblages of mobile organisms were examined visually. Also here, mobile species exhibit a low density, but still higher than on surrounding soft bottoms. The edible crab used artificial holes in the foundations frequently. The foundations were placed in two different clusters, north and south, and the degree to which early recruits covered the foundations and the succession of epibenthic communities were documented during two years. Sessile organisms colonized the northern foundations more rapidly, producing a higher diversity which suggests that the placement of wave energy devices affects colonization patterns. Biofouling on buoys was examined and blue mussels, Mytilus edulis, dominated with a cover about 90%. Wave exposed buoys were particularly favoured by M. edulis which there had a higher biomass and larger shells compared to those on sheltered buoys. Biofouling on wave power buoys, independent whether these had a cylindrical or toroidal shape, was insufficient to markedly affect their energy production. Finally, the thesis incorporates a review describing wave power projects in general pointing out the need of future research on for instance no-take zones, marine bioacoustics and electromagnetic fields. The main conclusions are that large-scale renewable wave energy conversion will cause ecological impact primarily by adding new hard substrate to an area but not by harming organisms or decreasing biodiversity within wave power parks.

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Haikonen, Kalle. "Underwater radiated noise from Point Absorbing Wave Energy Converters : Noise Characteristics and Possible Environmental Effects." Doctoral thesis, Uppsala universitet, Elektricitetslära, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-235016.

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The conversion of wave energy into electrical energy has the potential to become a clean and sustainable form of renewable energy conversion. However, like all forms of energy conversion it will inevitably have an impact on the marine environment, although not in the form of emissions of hazardous substances (gases, oils or chemicals associated with anticorrosion). Possible environmental issues associated with wave energy conversion include electromagnetic fields, alteration of sedimentation and hydrologic regimes and underwater radiated noise. Underwater noise has the potential to propagate over long distances and thus have the potential to disturb marine organisms far away from the noise source. There is great variation in the ability to perceive sound between marine organisms, one sound that is clearly audible to one species can be completely inaudible to another. Thus, to be able to determine potential environmental impact from WECs associated with underwater noise, the noise radiated from the WECs must be known. This thesis presents results from studies on the underwater radiated noise from four different full-scale WECs in the Lysekil Wave Power Project. Hydrophones were used to measure the underwater radiated noise from operating point absorbing linear WECs. The main purpose was to study the radiated noise from the operating WECs with emphasis on characteristics such as spectrum levels, Sound Pressure Level (SPL), noise duration and repetition rate. This to be able to determine the origin of the noise and if possible, implement design changes to minimize radiated noise. The results identified two main operational noises (transients with the bulk of the energy in frequencies <1 kHz). The SPL of the radiated noise fluctuated significantly, depending on wave height. Broadband SPLrms of the measurements ranged between ~110 dB and ~140 dB re 1 µPa and SPLpeak of specific noises ranges between ~140 and ~180 dB re µPa. Audibility was estimated range from 1km to 15 km depending critically on species and on assumptions of propagation loss. The noise is not expected to have any negative effects on behaviour or mask any signals, unless in the vicinity (<150m) of the WECs in significant wave heights. No physical damage, even in close vicinity are expected on either fish or marine mammals. Having the aim to have as little impact on the environment a possible, these studies are important. This way precautions can be implemented early in the technical development of this kind of renewable energy converters. The benefits from the WECs the Lysekil wave power project are believed to outweigh possible environmental impacts due to underwater radiated noise. Vid avhandlingens tryckläggning upptäcktes inte att tidpunkt för disputation var fel.

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Taormina, Bastien. "Potential impacts of submarine power cables from marine renewable energy projects on benthic communities A review of potential impacts of submarine power cables on the marine environment: Knowledge gaps, recommendations and future directions, in Renewable and Sustainable Energy Reviews 96, November 2018 Optimizing image-based protocol to monitor macroepibenthic communities colonizing artificial structures, in ICES Journal of marine science 77(2), March 2020." Thesis, Brest, 2019. http://theses-scd.univ-brest.fr/2019/These-2019-SML-Ecologie_marine-TAORMINA_Bastien.pdf.

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Dans un contexte de développement rapide des projets d’énergies marines renouvelables, le but de cette thèse était d’améliorer les connaissances sur les impacts potentiels des câbles électriques sous-marins sur les écosystèmes benthiques côtiers. En se focalisant sur la phase de fonctionnement, ce travail était essentiellement dédié à la caractérisation de l’effet récif généré par ces câbles et leurs structures associées (protection, stabilisation) sur les communautés épibenthiques fixées et la mégafaune mobile. L’étude était principalement basée sur l’utilisation d’images sous-marines (photo et vidéo) prises in situ par des plongeurs. Ce travail a mené à des réflexions méthodologiques sur la manière la plus efficace d’analyser ce genre de données afin d’appréhender pleinement la dynamique de colonisation des structures artificielles et leur rôle d’habitat pour des espèces commerciales. Outre cet effet récif, certains organismes se retrouvent exposés à des champs magnétiques émis par les câbles électriques. Ceci m’a conduit à mesurer expérimentalement l’impact de champs magnétiques artificiels sur le comportement du homard Européen (Homarus gammarus) au stade juvénile. Finalement, nous avons étudié in situ les potentiels bénéfices pour la macrofaune benthique de l’exclusion d’activités anthropiques autour de la route de câbles électriques. Le couplage d’approches in situ et ex situ m’a permis de mieux appréhender les impacts environnementaux associés aux câbles électriques sous-marins. Ces résultats permettront d’améliorer l’évaluation de l’empreinte écologique des futurs raccordements électriques In a global context of rapid development of marine renewable energy projects, the aim of this PhD thesis was to better characterise the potential impacts of submarine power cables on coastal benthic ecosystems. The work specifically focused on the impacts associated with the operational phase. The major part of this work was dedicated to the reef effect created by these cables and their protective and stabilising structures on sessile epibenthic communities and mobile megafauna. This work was mainly based on underwater imagery, either video or photo collected in situ by divers. The challenge of working with underwater imagery has led me to optimise image analyses so as to effectively monitor benthic colonisation and to quantify artificial reef habitat provision to commercial species.In addition to this reef effect, colonising organisms are exposed to magnetic fields generated by the power cables. Thus, I designed an experimental study to assess the impact of realistic magnetic fields on the behaviour of juvenile European lobsters (Homarus gammarus). Finally, we explored the ecological impacts of excluding anthropogenic activity from the cables routes and potential benefits for benthic macrofauna. By coupling both in situ and ex situ approaches, my PhD research better characterises the environmental impacts associated with submarine power cables. These results will help to assess the ecological footprint of future power grid connections

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Macleod, Adrian K. A. "The role of marine renewable energy structures and biofouling communities in promoting self-sustaining populations of non-native species." Thesis, University of the Highlands and Islands, 2013. https://pure.uhi.ac.uk/portal/en/studentthesis/the-role-of-marine-renewable-energy-structures-and-biofouling-communities-in-promoting-selfsustaining-populations-of-nonnative-species(0c7f0d89-74e8-4468-83c9-4216e4f2b1a8).html.

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Novel environments and biological communities created by the large-scale deployment of Marine Renewable Energy Devices (MREDs) have the potential to promote the spread of non-native species (NNS). Knowledge of how community composition resident on MREDs is shaped by geography, local hydrodynamics and the duration of deployment, will clarify how these technologies will interact with natural habitats, including the provision of suitable habitat for NNS. A network of navigation buoys was used to study biofouling communities in areas proposed for MRED deployment. Significant differences in community structure were observed in different geographic areas. A significant reduction in number of taxa present and community wet-weight was observed where buoys were deployed in greater tidal flow rates. However, overall community composition was not significantly different between ‘high’ (>1 ms-1) and ‘low’ (<1 ms-1) flow areas and for buoys deployed for different time durations (1-7 years). These finding have important implications for the longevity of devices and their interaction with natural habitats, including proposed ‘artificial reef’ effects. In total five non-native species were identified on the buoys sampled, supporting the need to monitor MREDs as the industry grows. Hydrodynamic and biotic features of the epibenthic communities were used to predict the presence of the most prevalent NNS, the amphipod Caprella mutica, in addition to other native amphipod species. Caprella mutica presence was found to be significantly affected by increasing flow speed compared with the native amphipod Jassa herdmani. Behavioural flume studies investigating flow-related processes governing the presence of non-native amphipods supported these findings. This study details how the hydrodynamic and biological environments created by MREDs determine their suitability for the establishment of self-sustaining populations, and therefore their dispersal potential for NNS. These findings inform design criteria and management options to minimise the biosecurity risk that these structures will pose as the industry expands.

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Brammer, James. "Physical and numerical modelling of Marine Renewable Energy technologies, with particular focus on tidal stream and tidal range devices." Thesis, Cardiff University, 2014. http://orca.cf.ac.uk/58699/.

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The past decade has seen a significant rise in the interest of deploying Marine Renewable Energy technologies. Tidal stream technology is developing rapidly, and developers are favouring horizontal axis turbines (HAT’s). However, vertical axis turbines (VAT’s) are better suited for shallow waters, and higher efficiencies can potentially be gained by utilising shallow water blockage effects. The Severn Estuary is an ideal deployment area in this context. Additionally, due to a large tidal range the estuary has long been the subject of tidal barrage proposals. The original ebb-only STPG barrage has recently been superseded by a two-way generation scheme, therefore the need exists for renewed research into the hydrodynamic impacts of this proposal. Furthermore, little is known about the interaction between tidal range and tidal stream technologies, and if they could coexist in the Severn Estuary. This thesis uses physical and numerical modelling techniques to assess a range of MRE technologies, with particular focus on their deployment in the Severn Estuary. Physical model tests of a number of VAT’s were conducted in a recirculating flume. Device performance and the wake characteristics were assessed, and it was demonstrated that VATS’s could potentially provide competitive performance values if deployed in shallow waters. The CFD code ANSYS CFX was used to predict the unsteady turbine behaviour at the physical model scale; good agreement was achieved with the laboratory data, particularly in predicting the wake behaviour. The CFD model TRIVAST was then applied to the Severn Estuary. Comparisons were made of the Severn Barrage schemes, as well as two hypothetical HAT and VAT arrays. The model results confirmed that vertical axis turbines are better suited to the Severn Estuary, provided that the technology is feasible. Finally, whilst the Severn Barrage proposals would eradicate the HAT resource, a lesser impact on the VAT resource was observed.

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Stokes, Christopher Hugo. "Coastal impacts in the lee of a wave energy site : waves, beach morphology and water-users (Wave Hub, Cornwall, UK)." Thesis, University of Plymouth, 2015. http://hdl.handle.net/10026.1/4303.

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The Wave Hub facility in Cornwall (South West UK) is a marine renewables test site, predominantly designed for the purpose of trialling wave energy converters prior to commercialisation. Beach water-users such as bathers and surfers are of economic importance to tourism in Cornwall, and during theWave Hub consultation there were concerns among stakeholders that wave energy extraction would reduce the height and quality of coastal waves for sur ng, as well as a ecting sediment transport and beach morphology. This thesis investigates the interaction between wave conditions, beach morphology, and beach water-users, and proposes how a wave climate altered by wave energy extraction is likely to alter these interactions. A multidisciplinary research approach is adopted, involving the collection of qualitative and quantitative social data, the collection of over 5 years of physical wave and beach morphology data, and predictive modelling of the e ects of an attenuated wave climate. Quantitative, structured interview data from 403 water-users, collected at two beaches (Perranporth and Porthtowan) in the lee of Wave Hub, indicate that the population of water-users in the area is predominantly made up of surfers (53%), but bodyboarding and swimming/bathing are also popular activities (29% and 11%, respectively). In-depth semi-structured interviews reveal that water-user perceptions of wave energy extraction and its potential coastal impacts are constructed using intuitive risk perceptions, rather than technical understanding. These risk perceptions are constructed through a weighing of their perception of wave energy devices ('technology') and their perception of the coastal environment ('nature'). To investigate how waves are perceived, nearshore wave buoy measurements collected in 14 m water depth and transformed to breaking height, are compared to concurrent visual observations of mean breaker height and period. On average water-users underestimated signi cant wave height and period by 48% and 17%, respectively. Accounting for variations in wave perception, the wave preferences of di erent water-user groups are determined. Water-users are found to share a common preference towards wave v periods of 9 - 20 s, but di erent water-user groups are found to have di erent ranges of preferred wave height, which is found to govern whether wave energy extraction will decrease or increase the occurrence of preferred waves. Previous research indicates that three-dimensional (3D) beach morphology with crescentic bar and rip features is the primary controller of surf-zone hazard, and also strongly in uences the quality of sur ng waves at the coast. A dataset of 5.5 years of quasi-weekly bar measurements, and quasi-monthly intertidal surveys from Perranporth beach is used to quantify seasonal to inter-annual changes in threedimensionality. Integrated, cumulative uctuations in wave steepness, wave power, and relative tide range that occur over seasonal time scales are shown to be well correlated to seasonal uctuations in beach three-dimensionality. 3D morphology is well related to a disequilibrium term that predicts increases or decreases in threedimensionality by examining the di erence between instantaneous wave conditions and a temporally varying equilibrium condition, based on a weighted average of antecedent waves. This indicates that periods of wave regime change between erosive winter conditions with high steepness waves and accretive summer conditions with low steepness waves are related to the growth of 3D features, and vice versa, while extended periods with similar wave conditions drive the beach towards equilibrium. Using a range of realistic and extreme coastal wave height attenuation scenarios determined from previous Wave Hub modelling studies, it is predicted that none of the scenarios will have a universally positive or negative e ect on the occurrence of wave conditions preferred by water-users. When used to predict beach threedimensionality at Perranporth beach, the attenuated wave climates are found to reduce the variability in three-dimensionality. Even an extreme and unrealistic level of wave energy extraction (100% energy capture) was shown to have an insigni cant e ect on the occurrence of preferred waves, and only under an extraction scenario where the impact was not varied with wave frequency did this level of attenuation have a signi cant e ect on the predicted beach three-dimensionality. The inshore wave attenuation from Wave Hub is therefore likely to have an insigni cant e ect on wave conditions and beach morphology of relevance to beach water-users. A number of observations and recommendations are discussed for the development of a sound and robust methodological approach, which can be used to investigate the e ects of wave energy extraction on beach water-users at future wave farm sites.

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33

Hodgins, Neil. "High speed electrical power takeoff for oscillating water columns." Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/4642.

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This thesis describes research into electrical power takeoff mechanisms for Oscillating Water Column (OWC) wave energy devices. The OWC application is studied and possible alternatives to the existing Induction Generator (IG) are identified. The Permanent Magnet Generator (PMG) is found to be the most promising. Results showed that the IG could almost match the output of the PMG if it could be operated significantly above its rated capacity. This improvement would require only limited changes to the overall OWC system. The ability to operate overloaded is determined by the losses and cooling of the IG. The losses in a suitable IG were measured in tests at Nottingham University. Steady state measurements were made of the cooling ability of the OWC airflow at the LIMPET wave power plant operated by Wavegen (the sponsor company) on Islay. Thermal modelling combining the loss and cooling measurements allowed the maximum capacity of the induction generator in an OWC to be found. A simplified model that accurately represents this system is proposed for use in system design and generator control.

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34

Varing, Audrey. "Wave characterization for coastal and nearshore marine renewable energy applications : focus on wave breaking and spatial varaibility of the wave field." Thesis, Brest, 2019. http://www.theses.fr/2019BRES0105.

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Les énergies marines renouvelables (EMR) sont soumises aux vagues générées par le vent. Une caractérisation précise de ces vagues est nécessaire dans les zones côtières et littorales où les vagues interagissent fortement avec le fond, générant de la réfraction et du déferlement parmi d’autres processus.Une étude approfondie sur l’initiation du déferlement est développée. La validité du critère de déferlement conventionnel uc/c (rapport entre la vitesse orbitale horizontale à la crête et la vitesse de phase) est examinée numériquement. Cette étude nous mène à définir un nouveau critère cinématique basé sur le rapport entre la vitesse orbitale maximale ||um|| et c. Ce nouveau critère améliore la détection de l’initiation du déferlement, car la position d’où s’initie l’instabilité conduisant au déferlement est mieux capturée à partir de ||um||. La variabilité spatiale du champ de vagues en zone côtière est majoritairement étudiée à partir de modèles spectraux. La capacité d’un modèle à phase-résolue (type Boussinesq BT) à fournir des informations complémentaires pour les EMR est étudiée. Les modèles spectraux et BT produisent des résultats très différents en termes de hauteur de vagues et de puissance en présence d’une forte réfraction causée par la variabilité de la bathymétrie. On définit une méthode innovante pour extraire des informations liées aux vagues à partir d’images satellites, issues d’un radar à synthèse d’ouverture (SAR), et les comparer aux sorties des modèles. Nos résultats montrent des similitudes encourageantes entre le modèle BT et les données SAR Since Marine Renewable Energy (MRE) systems are submitted to wind generated waves. Accurate wave characterization is required in the coastal and nearshore environment where the waves are strongly modified by their interaction with the sea bottom, inducing refraction and wave breaking among other processes.A comprehensive study regarding the wave breaking initiation process is developed. The conventional kinematic criterion uc/c (ratio between the horizontal orbital velocity at the crest and the phase velocity) validity is numerically investigated. Our study leads us to a new kinematic wave breaking criterion based on the ratio between the maximum fluid velocity ||um|| near the wave crest and c. This new criterion improves the detection of the breaking initiation, since ||um|| accurately captures the location of the fluid instability leading to breaking.The wave field spatial variability in coastal areas is mostly studied with spectral wave models. We explore the ability of a phase-resolving model (Boussinesq-type, BT) to provide additional wave information for MRE applications.Spectral and BT models lead to significantly different spatial wave height and power patterns in the presence of strong bottom-induced refraction. We define an innovative methodology to extract wave information from satellite Synthetic Aperture Radar (SAR) images for comparison with models’ outputs. Our results highlight encouraging similarities between the BT model and SAR data

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Thies, Philipp Rudolf. "Advancing reliability information for Wave Energy Converters." Thesis, University of Exeter, 2012. http://hdl.handle.net/10036/4053.

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Marine renewable energy promises to provide a significant contribution to the future electricity supply. It is estimated that 17% of today's UK electricity demand could be generated from wave and tidal sources. The ambition to harvest this resource is in the public interest, as it eases the pressures on energy security, holds the potential to reduce carbon emissions and has the prospect to create a new UK industry sector worth £15 billion. From an engineering perspective, marine energy is one of the least developed renewable energy technologies and has to be regarded as unproven. The reliability of components and devices in the harsh marine environment is one of the main engineering challenges. Reliability assessments and the assurance of acceptable reliability levels are dependant on the adequacy of failure information, which is scantily available for marine energy. This thesis shows that large failure rate uncertainties impede the reliability assessment for wave energy converters and how a suite of experimental, numerical and statistical methods can be applied to improve scarcely available reliability information. The analysis of component load conditions identifies fatigue as failure mode of concern and the fatigue life of mooring lines and marine power cables is quantified in a floating wave energy application. A Bayesian statistical approach and dedicated service-simulation component testing is proposed, and implemented to improve the quality of reliability estimates and to provide relevant data and assurance. The methods presented, along with the results, will assist reliability assessment and design during early development stages, and will inform the prediction of maintenance requirements during operation. Reliable marine energy systems will be the technical enabler for the successful transition of prototype devices to a commercially viable marine energy industry.

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BRACCO, GIOVANNI. "ISWEC: a Gyroscopic Wave Energy Converter." Doctoral thesis, Politecnico di Torino, 2010. http://hdl.handle.net/11583/2562362.

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ISWEC (Inertial Sea Wave Energy Converter) is a Wave Energy Converter transforming the wave-induced rocking motion of a buoy into electrical power by means of the gyroscopic effects produced from a spinning flywheel carried inside the buoy. A unique feature of ISWEC with respect to most of the existing converters is that externally it is composed only of a floating body without moving parts working into sea water or spray, thus achieving a high reliability and reduced maintenance costs. In this Thesis the analysis of the ISWEC both on the numerical and the experimental levels is performed. The converter dynamics is analyzed in order to obtain a mathematical model and experimental tests are carried out in the wave tank of the University of Edinburgh on a 1:45 model to validate such mathematical model. The validated models are used to design a larger scale prototype (1:8) and to make considerations on the design of a full scale ISWEC system.

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Lalander, Emilia, Mårten Grabbe, and Mats Leijon. "On the velocity distribution for hydro-kinetic energy conversion from tidal currents and rivers." Uppsala universitet, Elektricitetslära, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-195499.

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Tidal currents and rivers are promising sources of renewable energy given that suitable turbines for kinetic energy conversion are developed. To be economically and technically feasible, a velocity distribution that can give a high degree of utilization (or capacity factor), while the ratio of maximum to rated velocity is low would be preferable. The rated velocity is defined as the velocity at which rated power is achieved. Despite many attempts to estimate the resource, however, reports on the possible degree of utilisation from tidal currents and rivers are scarce. In this paper the velocity distribution from a number of regulated rivers, unregulated rivers and tidal currents have been analysed regarding the degree of utilisation, the fraction of converted energy and the ratio of maximum to rated velocity. Two methods have been used for choosing the rated velocity; one aiming at a high fraction of converted energy and one aiming at a high degree of utilisation. Using the first method, with a rated velocity close to the maximum velocity, it is unlikely that the turbine will reach the cut-out velocity. This results in, on average, a degree of utilisation of 23% for regulated rivers, 19% for unregulated rivers and 17% for tidal currents while converting roughly 30-40% of the kinetic energy. Choosing a rated velocity closer to the mean velocity resulted in, on average, a degree of utilisation of 57% for regulated rivers, 52% for unregulated rivers and 45% for tidal currents. The ratio of maximum to rated velocity would still be no higher than 2.0 for regulated rivers, 1.2 for unregulated rivers and 1.6 for tidal currents. This implies that the velocity distribution of both rivers and tidal currents is promising for kinetic energy conversion. These results, however, do not include weather related effects or extreme velocities such as the 50-year velocity. A velocity factor is introduced to describe what degree of utilisation can be expected at a site. The velocity factor is defined as the ratio U-max/U-rate at the desired degree of utilisation, and serves as an early indicator of the suitability of a site.

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Bellew, Sarah Louise. "Investigation of the response of groups of wave energy devices." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/investigation-of-the-response-of-groups-of-wave-energy-devices(3db5db0d-a6af-4715-9f0b-19d53cf6dcf4).html.

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Placing wave energy devices within close proximity to each other can be beneficial as the costs of deployment, maintenance and infrastructure are reduced significantly compared to if the devices are deployed in isolation. A mathematical model is presented in this thesis which combines linear wave theory with a series of linear driven harmonic oscillators to model an array (group) of floating wave energy devices which move predominantly in heave (vertically) in a train of incident regular waves. Whilst similar mathematical models have been used previously to investigate interactions between fluids and groups of structures, much of the published work does not address array configurations or device constraints that are relevant to designers of structure-supported array devices. The suitability of linear theory for application to closely spaced arrays is assessed in this thesis through comparison to small-scale experimental data and by evaluation of the magnitude of second-order hydrodynamic forces. Values of mechanical damping and mass are determined for each element of an array in order to achieve the maximum power from an array of floats without requiring the knowledge of the motion of every float within the array in order to apply the forces to any one float. Further to this, the analysis of floats of varying geometry is performed in order to assess the possibility of array optimisation through the variation of float geometries within a closely spaced array.It is shown in this thesis that linear theory provides a reasonable prediction of the response of floats that are sufficiently close together to interact for most wave frequencies to which the arrays are likely to be subjected. Under the assumption of easily implementable mechanical damping, it is determined that the power output from an array of floats of equal geometry can be increased by specifying different magnitudes of mechanical damping on each float independently of the radiation damping. Variations in submerged float geometries for the purpose of manipulating array characteristics according to the incident wave frequency are best applied through the variation in draft of a single geometry. Variations in submerged float geometry which occur close to the free surface are found to be of the greatest significance. Where the float is uniform in cross-section, the most appropriate method to select float drafts within an array is found to be based on the evaluation of the total damping on each float.

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Fleming, Conor F. "Tidal turbine performance in the offshore environment." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:f51fd313-1589-4e9c-98cc-ae6e64c1184b.

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A three dimensional computational model of a full scale axial flow tidal turbine has been used to investigate the effects of a range of realistic environmental conditions on turbine performance. The model, which is based on the Reynolds averaged Navier-Stokes equations, has been developed using the commercial flow solver ANSYS Fluent. A 1:30 scale tidal turbine is simulated in an open channel for comparison to existing experimental data. The rotor blades are directly resolved using a body-fitted, unstructured computational grid. Rotor motion is enabled through a sliding mesh interface between the rotor and the channel boundaries. Reasonably good agreement in thrust and power is observed. The computed performance curves are offset from the measured performance curves by a small increment in rotor speed. Subsequently, a full scale axial flow turbine is modelled in a variety of conditions representative of tidal channel flows. A parametric study is carried out to investigate the effects of flow shear, confinement and alignment on turbine performance, structural loading, and wake recovery. Mean power and thrust are found to be higher in sheared flow, relative to uniform flow of equivalent volumetric flow rate. Large fluctuations in blade thrust and torque occur in sheared flow as the blade passes through the high velocity freestream flow in the upper portion of the profile and the lower velocity flow near the channel bed. A stronger shear layer is formed around the upper portion of the wake in sheared flow, leading to enhanced wake mixing. Mean power and thrust are reduced when the turbine is simulated at a lower position in a sheared velocity profile. However, fluctuations in blade loading are increased due to the higher velocity gradient. The opposite effects are observed when the turbine operates at greater heights in sheared flow. Flow misalignment has a negative impact on mean rotor thrust and power, as well as on unsteady blade loading. Although the range of unsteady loading is not increased significantly, additional perturbations are introduced due to interactions between the blade and the nacelle. A deforming surface is introduced using the volume-of-fluid method. Linear wave theory is combined with the existing free surface model to develop an unsteady inflow boundary condition prescribing combined sheared flow and free surface waves. The relative effects of the sheared profile and wave-induced velocities on turbine loading are identified through frequency analysis. Rotor and blade load fluctuations are found to increase with wave height and wave length. In a separate study, the performance of bi-directional ducted tidal turbines is investigated through a parametric study of a range of duct profiles. A two dimensional axi-symmetric computational model is developed to compare the ducted geometries with an unducted device under consistent blockage conditions. The best-performing ducted device achieves a peak power coefficient of approximately 45% of that of the unducted device. Comparisons of streamtube area, velocity and pressure for the flow through the ducted device shows that the duct limits the pressure drop across the rotor and the mass flow through the rotor, resulting in lower device power.

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Xin, Bai. "Numerical simulation of a marine current turbine in turbulent flow." Thesis, Queen Mary, University of London, 2014. http://qmro.qmul.ac.uk/xmlui/handle/123456789/7900.

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The marine current turbine (MCT) is an exciting proposition for the extraction of renewable tidal and marine current power. However, the numerical prediction of the performance of the MCT is difficult due to its complex geometry, the surrounding turbulent flow and the free surface. The main purpose of this research is to develop a computational tool for the simulation of a MCT in turbulent flow and in this thesis, the author has modified a 3D Large Eddy Simulation (LES) numerical code to simulate a three blade MCT under a variety of operating conditions based on the Immersed Boundary Method (IBM) and the Conservative Level Set Method (CLS). The interaction between the solid structure and surrounding fluid is modelled by the immersed boundary method, which the author modified to handle the complex geometrical conditions. The conservative free surface (CLS) scheme was implemented in the original Cgles code to capture the free surface effect. A series of simulations of turbulent flow in an open channel with different slope conditions were conducted using the modified free surface code. Supercritical flow with Froude number up to 1.94 was simulated and a decrease of the integral constant in the law of the wall has been noticed which matches well with the experimental data. Further simulations of the marine current turbine in turbulent flow have been carried out for different operating conditions and good match with experimental data was observed for all flow conditions. The effect of waves on the performance of the turbine was also investigated and it has been noticed that this existence will increase the power performance of the turbine due to the increase of free stream velocity.

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Elver-Evans, Joanna Claire. "Off-shore weather-windows for the purposes of managing costs in the marine renewable industry : a study of the Shetland Isles, Pentland Firth & Orkneys and Western Isles." Thesis, University of Aberdeen, 2016. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=231079.

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In order to increase energy security and meet carbon emission reduction targets set by the EU and UK government, the UK energy sector has increased its reliance on renewable energy. The marine renewable sector is set to become a major contributor to the UK's energy portfolio but incumbent on the offshore renewable sector are the high development, operation and maintenance costs. Prevailing metocean conditions at an offshore energy site contribute significantly to the life-cycle costs of an offshore energy project. Where access to a site is limited by a lack of suitable weather-windows, leading to high instances of downtime, weather-induced costs increase. Determination of suitable metocean weather-windows, defined by maximum operating thresholds and the length of time required to perform a task can assist with the risk management of a project and the reduction of downtimes, thus reducing costs. Metocean weather-windows are determined using 31 years (the “climatological norm”) of ECMWF ERA-40 reanalysis data. The annual, seasonal and monthly distribution parameters for wind and wave regimes at three sites are derived, using three different distribution parameter estimation models. Probabilities of defined weather-windows are determined using the derived distribution parameters and compared with empirical probabilities, based on the frequentist approach. Wind regimes fit a Weibull distribution and wave regimes fit a 3P gamma distribution and unique annual, seasonal and monthly distribution parameters are required for accurate weather-window determination. When fitted to appropriate PDFs, the shape and scale values determined by the different estimation techniques result in significantly different probabilities. Empirical probabilities converge with those determined using the MLE model but both significantly differ from those derived using the LSM and MoM derived parameters. In the absence of a dataset spanning the climatological norm, this suggests that the MLE method of parameter estimation is more accurate for the successful determination of weather-windows.

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Ashley, Matthew. "The implications of co-locating marine protected areas around offshore wind farms." Thesis, University of Plymouth, 2014. http://hdl.handle.net/10026.1/3202.

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Offshore wind farm (OWF) construction in the UK is progressing rapidly alongside increasing spatial pressures on marine ecosystems and social and economic activities. A need for increased protection of habitats, species and ecological processes that support environmental and economic benefits is being met by designation of marine protected areas (MPAs). Mitigation and spatial planning solutions are required to enable protection of vital ecological habitats, features and processes and support sustainable economic development. A potential solution is to co-locate OWFs and MPAs. This study uses a multi-disciplinary approach to examine if evidence on the environmental effects of existing OWFs and associated effects on fishing activity (as an existing resource use) benefits MPA goals. Through a systematic review and meta-analyses of existing data, knowledge of OWF effects on species abundance and economic effects on fishing were identified as key evidence gaps. The ecological evidence need was approached through a case study of ecological effects of North Hoyle OWF, North Wales, UK, using existing pre and post-construction monitoring data, as well as primary baited remote underwater video data, collected 5 years later (8 years post-construction). Results suggested habitat and species recovered to a stable state that showed some community differences to pre-construction conditions. The presence of OWF monopiles is likely to have increased existing heterogeneity of substratum and increased opportunities for scavenging species. Species benefitting and disadvantaged by habitat provided within the OWF reflected meta-analyses trends. Extended baseline monitoring to provide confident identification of natural levels of variation in sediment and fauna was lacking. Analysis of fishing activity and landings before and after OWF construction in three UK case study regions approached effects on resource users. Fishing activity in the three case study areas showed broad scale similarity to national trends. Small-scale activity patterns indicated greater reductions in mobile (towed) fishing gear effort near to operating OWFs than in static gear activity (using pots or static nets). Semi-structured interviews conducted with fishermen in each region revealed loss of ground and disruption as negative effects from OWFs, in addition to existing pressures. Benefits including habitat creation and species augmentation, as well as reduction of cumulative lost ground, were identified by fishermen from co-location of MPAs and OWFs. Ecological effects of OWFs suggested benefits from habitat creation, species augmentation and potential for protection of sandbank habitats between monopiles. Mitigation requirements were identified to maximise these potential benefits to an MPA network.

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Grecian, William James. "Factors influencing the marine spatial ecology of seabirds : implications for theory, conservation and management." Thesis, University of Plymouth, 2011. http://hdl.handle.net/10026.1/873.

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Seabirds are wide-ranging apex-predators and useful bio-indicators of marine systems. Nevertheless, changes are occurring in the marine environment, and seabirds require protection from the deleterious effects of climate change, fisheries, pollution, offshore development, introduced predators and invasive species. The UK supports internationally important populations of seabirds but also has vast wind and wave resources, therefore understanding how seabirds use the marine environment is vital in order to quantify the potential consequences of further exploiting these resources. In this thesis I first describe the range of wave energy converting devices operational or in development in the UK, and review the potential threats and benefits these developments may have for marine birds. I then synthesise data from colony-based surveys with detailed information on population dynamics, foraging ecology and near-colony behaviour, to develop a projection model that identifies important at-sea areas for breeding seabirds. These models show a positive spatial correlation with one of the most intensive at-sea seabird survey datasets, and provide qualitatively similar findings to existing tracking data. This approach has the potential to identify overlap with offshore energy developments, and could be developed to suit a range of species or whole communities and provide a theoretical framework for the study of factors such as colony size regulation. The non-breeding period is a key element of the annual cycle of seabirds and conditions experienced during one season may carry-over to influence the next. Understanding behaviour throughout the annual cycle has implications for both ecological theory and conservation. Bio-logging can provide detailed information on movements away from breeding colonies, and the analysis of stable isotope ratios in body tissues can provide information on foraging during the non-breeding period. I combine these two approaches to describe the migration strategies of northern gannets Morus bassanus breeding at two colonies in the north-west Atlantic, revealing a high degree of both winter site fidelity and dietary consistency between years. These migratory strategies also have carry-over effects with consequences for both body condition and timing of arrival on the breeding grounds. Finally, I investigate the threats posed to seabirds and other marine predators during the non-breeding period by collating information on the distributions of five different species of apex predator wintering in the Northwest African upwelling region. I describe the threat of over-fishing and fisheries bycatch to marine vertebrates in this region, and highlight the need for pelagic marine protected areas to adequately protect migratory animals throughout the annual cycle. In summary, the combination of colony-based studies, bio-logging, stable isotope analysis and modelling techniques can provide a comprehensive understanding of the interactions between individuals and the marine environment over multiple spatial and temporal scales.

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Lindroth, [formerly Tyrberg] Simon. "Buoy and Generator Interaction with Ocean Waves : Studies of a Wave Energy Conversion System." Doctoral thesis, Uppsala universitet, Elektricitetslära, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-160085.

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On March 13th, 2006, the Division of Electricity at Uppsala University deployed its first wave energy converter, L1, in the ocean southwest of Lysekil. L1 consisted of a buoy at the surface, connected through a line to a linear generator on the seabed. Since the deployment, continuous investigations of how L1 works in the waves have been conducted, and several additional wave energy converters have been deployed. This thesis is based on ten publications, which focus on different aspects of the interaction between wave, buoy, and generator. In order to evaluate different measurement systems, the motion of the buoy was measured optically and using accelerometers, and compared to measurements of the motion of the movable part of the generator - the translator. These measurements were found to correlate well. Simulations of buoy and translator motion were found to match the measured values. The variation of performance of L1 with changing water levels, wave heights, and spectral shapes was also investigated. Performance is here defined as the ratio of absorbed power to incoming power. It was found that the performance decreases for large wave heights. This is in accordance with the theoretical predictions, since the area for which the stator and the translator overlap decreases for large translator motions. Shifting water levels were predicted to have the same effect, but this could not be seen as clearly. The width of the wave energy spectrum has been proposed by some as a factor that also affects the performance of a wave energy converter, for a set wave height and period. Therefore the relation between performance and several different parameters for spectral width was investigated. It was found that some of the parameters were in fact correlated to performance, but that the correlation was not very strong. As a background on ocean measurements in wave energy, a thorough literature review was conducted. It turns out that the Lysekil project is one of quite few projects that have published descriptions of on-site wave energy measurements.

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Roche, Sylvain. "Réenchanter le maritime par la promesse énergétique : technologies, trajectoires, discours." Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0064.

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Cette thèse analyse les dynamiques de changement du système énergétique en se focalisant sur les énergies marines renouvelables (EMR). A travers l’examen de dix études de cas (études à la fois sectorielles et territoriales), elle s’interroge sur les raisons du retour de ces technologies au tournant des années 2000. Mises à la marge du paradigme dominant de la production d’électricité des années 1980, nous montrons que les énergies marines renouvelables sont revenues sur le devant de la scène dans un contexte de crise systémique des 3E (environnementale, économique et énergétique). A l’interface des politiques énergétiques (celles de la transition énergétique) et des politiques maritimes (celles de la croissance bleue), les énergies marines renouvelables ont été légitimées au moment où la mer est devenue un terrain pour (re)construire des discours visionnaires, avant-gardistes et technopolitiques. Par ce biais, nous mettons en lumière l’importance des croyances et des représentations collectives sur l’activité technologique. Au regard de la diversité des trajectoires technologiques examinées (énergie des marées et des courants, énergie des vagues, énergie thermique des mers et éolien marin), nous montrons que « la filière » des énergies marines renouvelables se présente en France comme une construction politique sans cohérence technologique affirmée entre des univers techniques différents. Cette thèse permet également de relativiser la notion d’innovation de rupture et de destruction créatrice en mettant en évidence des phénomènes de résurgence technologique pouvant durer plusieurs décennies, voire plusieurs siècles, dans l’exploitation de sources d’énergies renouvelables. Enfin, en s’inscrivant dans une démarche rétro-prospective, cette thèse défend l’idée que les processus fondamentaux dans la dynamique de changement du système énergétique ne sont pas la création et la nouveauté mais plutôt l’actualisation et la réinterprétation. Elle entend ainsi apporter une contribution originale aux interrogations à la fois des économistes, des sociologues et des historiens des techniques, qui chacun dans leur domaine tentent de comprendre les trajectoires de l'innovation et les conditions de réussite des technologies de l’énergie This thesis sheds light on the dynamics of change in the energy system by taking the example of marine renewable energies (MRE). By exploring ten case studies (both sectoral and territorial), it reflects on the reasons for the return of these technologies in the 2000’s. Previously excluded from the dominant paradigm of French electricity production, in the 1980s, marine renewable energies are currently making a comeback in the context of the systemic crisis of the 3Es (environmental, economic and energy). At the interface of energy policies (energy transition policies) and maritime policies (blue growth policies), marine renewable energies were legitimized when the sea became a new horizon for (re)building visionary, avant-garde and technopolitical discourses. Through this, we highlight the importance of beliefs and collective representations of technological activity. Through the diversity of technological trajectories discussed in this thesis (tidal stream and tidal range energy, wave energy, ocean thermal energy conversion and offshore wind energy), we show that, in France, the industry of marine renewable energies presents itself as a political construction without asserted technological consistency, at the interface between different technical worlds. This thesis put into perspective the notion of disruptive innovation and creative destruction by highlighting phenomena of technological rebirth, which can take several decades and even centuries. Through a retroprospective analysis, this thesis defends the idea that the dynamics of change of the energy system are not mainly driven by creation and novelty, but could, rather, be construed as a process of update and reinterpretation of existing technological principles. This thesis aims to provide insights to economists, sociologists and historians of technology who try to understand the trajectories of innovation and the conditions for success of energy technologies

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Kuriakose, Jaise. "The resilience of low carbon electricity provision to climate change impacts : the role of smart grids." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/the-resilience-of-low-carbon-electricity-provision-to-climate-change-impacts-the-role-of-smart-grids(c139ce36-d73c-4d8b-913e-f66826496405).html.

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The UK’s decarbonisation strategy to increasingly electrify heating and transport will change the demand requirement on the electricity system. Additionally, under a climate change future, it is projected that the decarbonised grid will need to be able to operate under higher average temperatures in the UK, increasing the need for comfort cooling during summer and leading to additional electricity demand. These new demands will result in greater variation between minimum and peak demand as well as a significant increase in overall demand. Concurrently, supply-side decarbonisation programmes may lead to more intermittent renewables such as wind, PV, tidal and wave, elevating variability in electricity generation. Coupled with the anticipated higher variation in demand this brings on several challenges in operating the electricity grid. In order to characterise these challenges this research develops a bespoke electricity dispatch model which builds on hourly models of demand and generation. The hourly demand profiles are based on a high electrification of heating, transport and cooling coupled with future temperatures premised on the UKCP09 high emission scenario climate projections. The demand profiles show a significant increase in peak demand by 2050 reaching 194 GW, mainly due to summer cooling loads which contribute 70% of the demand. The cumulative CO2 emissions budgets of the GB power sector that are consistent with avoiding global climate change to 2°C are used to develop two low carbon generation scenarios distinguished by the amount of intermittent renewable generation technologies. The dispatch model tests the capability of generation scenarios with the use of hourly generation models in meeting future demand profiles out to 2050.The outputs from dispatch model indicate that there are shortages and excesses of generation relative to demand from 2030 onwards. The variability analysis outlines low and high generation periods from intermittent technologies along with the pace at which intermittent generation increases or decreases within an hour. The characterisation of variability analysis reveals the type of reserve capacity or smart solutions that are required to maintain the security of electricity supply. The solutions that could address the challenges quantified from the model outputs in operating a decarbonised GB electricity grid are explored using expert interviews. The analysis of the stakeholder interviews suggests smart grid solutions that include technologies as well as changes in operational procedures in order to enhance the operational resilience of the grid. Active Network Management through monitoring and control, demand management, storage systems and interconnectors are proposed to address challenges arising from varying demand and generation variability.

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Lande-Sudall, David. "Co-located offshore wind and tidal stream turbines." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/colocated-offshore-wind-and-tidal-stream-turbines(72acb21d-1b88-45ad-b944-3f9664330420).html.

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Co-location of offshore wind turbines at sites being developed for tidal stream arrays has been proposed as a method to increase capacity and potentially reduce the cost of electricity compared to operating either technology independently. This research evaluates the cost of energy based on capital expenditure and energy yield. It is found that, within the space required around a single 3 MW wind turbine, co-location provides a 10-16% cost saving compared to operating the same size tidal-only array without a wind turbine. Furthermore, for the same cost of electricity, a co-located farm could generate 20% more yield than a tidal-only array. These results are based on analysis of a case-study site in the Pentland Firth. Wind energy is assessed using an eddy viscosity wake model in OpenWind, with a 3 MW rated power curve and thrust coefficient from a Vestas V90 turbine. Three years of wind resource data is from the UK Met Office UK Variable (UKV) 1.5 km numerical model and corrected against a 400 m Weather Research and Forecasting (WRF) model run over the site. Tidal stream energy is modelled using a semi-empirical superposition of self-similar plane wakes, with a generic 1 MW rated power curve and thrust based on a full-scale, fixed-pitch turbine. Coincident tidal resource data is from the Forecasting Ocean Assimilation Model (FOAM) at 7.5 km resolution and correlated with a 150 m ADvanced CIRCulation model (ADCIRC). Wave parameters are corrected from ERA-Interim data with six months of wave buoy data. Multiple tidal turbine array layouts are considered, with maximum tidal energy generated for a staggered array with spacing of 20 tidal turbine diameters, Dt , streamwise and 1.5Dt cross-stream. However, cheapest cost of electricity from the tidal-only array, was found for a single row of turbines, due to minimal wake effects. Laboratory experiments were undertaken to validate the superposition wake model for use with large, shared support structures. Two rotors mounted either side of a central tower generate a peak wake velocity deficit 70% greater than predicted by superposition. This was due to high local blockage and a complex near-wake structure, with a corresponding increase in tower drag of 9%. Further experiments evaluated the impact of oblique inflow on turbines yawed at +/-15 degrees. These results validated a theoretical cosine correction for thrust coefficient and characterised the centreline wake drift with downstream distance. Extreme environmental loads for a shared support structure, compared to structures for wind-only and tidal-only, have also been modelled. A non-linear wave model was used to represent a single wave form with 1% occurrence for each hour of time-series data. Overturning moment about the base of a shared support, with one wind and two tidal turbines, was found to be 4.5% larger than for a wind-only turbine in strong current and with turbines in different operational states. Peak loads across the tidal array were found to vary by 2.5% and so little load reduction benefit could be gained by locating a shared support in a more sheltered area of the array.

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Rocha, Thiago Peternella. "Estudo numérico de unidade flutuante monocoluna para conversão de energia de ondas do mar." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/3/3135/tde-05012018-083552/.

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O uso contínuo de combustíveis fósseis já se mostrou deletério há anos, além de ser um meio energético finito. Por este motivo, a demanda atual e futura por sistemas de energia limpa é grande. Muito embora já existam diversas estruturas dedicadas a extrair energia do mar, o conceito em que se pretende trabalhar é inovador e de tecnologia nacional. Este tema foi desenvolvido inicialmente em uma abordagem teórica pelo então aluno de engenharia naval Daniel Prata Vieira e sua colega Ana Luísa Orsolini, como Trabalho Final do curso de Engenharia Naval e Oceânica da Escola Politécnica da USP, orientados pelo Prof. Dr. André Luis Condino Fujarra. Vieira & Orsolini (2011) [1] abordaram de uma forma diferente o tema de geração de energia por ondas do mar, trazendo à tona o uso da já consagrada plataforma monocoluna - protótipo que rendeu diversos prêmios de inventor do ano da Petrobrás, além de patente, ao Tanque de Provas Numérico, laboratório do departamento de engenharia naval da POLI-USP. O trabalho dos alunos Daniel e Ana também foi reconhecido nacionalmente recebendo o Prêmio Petrobras de Tecnologia 2011 no tema de Tecnologia de Energia. A continuação do trabalho consiste em levar a fundo alguns pontos importantes relacionados ao dimensionamento da plataforma para otimizar a geração de energia através do movimento relativo entre ela e um corpo flutuante interno ao seu moonpool. O objetivo do trabalho é definir melhores geometrias através da parametrização das dimensões principais e da utilização de métodos numéricos num estudo mais detalhado e aprofundado. O método de desenvolvimento leva em conta todos os fatores que influenciam na dinâmica do sistema como a hidrodinâmica de dois corpos (plataforma e corpo interno flutuante) e a dinâmica do gerador de energia (tipo de gerador e seu impacto no amortecimento do sistema global). The continued use of fossil fuels has proved harmful for years, besides being a means finite energy. For this reason, the current and future demand for clean energy systems are great. Although there are already several structures dedicated to extracting energy from the sea, the concept on which it intends to work is innovative and with local technology. This theme has been already developed in a theoretical approach by the student of naval engineering Daniel Prata Vieira and his classmate Ana Luisa Orsolini, such as Final Paper Course of Naval Architecture and Ocean Engineering from the Escola Politécnica of USP, directed by Prof. Dr. André Luis Condino Fujarra. Vieira \\& Orsolini (2010) [1] studied in a different way the theme of energy generation from ocean waves, bringing up the use of already established monocolumn platform - prototype that earned several inventor of the year from Petrobras awards, besides patent, to the Numerical Offshore Tank, laboratory of the Naval Engineering Department of Poli - USP. The work of students Daniel and Ana was also recognized nationally getting the Petrobras Technology Award 2011 in the Energy Technology theme. The continuation of this work is to bring the background some important points related to platform design to optimize power generation through the relative motion between it and an internal floating body into moonpool. The objective is to define best geometries through the parameterization of the key dimensions and the use of numerical methods in a more detailed and in-depth study. The development method takes into account all the factors that influence the dynamics of the system such as the hydrodynamics of two bodies (platform and floating internal body) and the dynamics of the generator (type of generator and its impact on the damping of the global system).

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McIntyre, Andrew III. "Behavioral responses of sub-adult Atlantic Sturgeon (Acipenser oxyrinchus oxyrinchus) to electromagnetic and magnetic fields under laboratory conditions." VCU Scholars Compass, 2017. http://scholarscompass.vcu.edu/etd/4866.

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Electromagnetic fields (EMF) produced by high voltage (HV), submarine transmission cables leading from offshore wind energy generation facilities could affect foraging or migratory behaviors of electro-receptive fishes, including endangered Atlantic Sturgeon. However, no published studies have quantitatively evaluated the possible behavioral effects of EMF exposure on sturgeon during residence in coastal waters. This study evaluated behavioral responses by sub-adult Atlantic Sturgeon to electromagnetic and magnetic fields under controlled laboratory conditions. Fabricated EMF generators were used to emulate a range of field EMF conditions that migratory fishes could encounter in proximity to submarine HV sources. Sensor arrays and digital video recorders synoptically quantified EMF conditions and fish behaviors during experimental trials. This thesis will describe the unique, experimental EMF generator/sensor array, present results of the behavior study, and suggest implications of the findings for Atlantic Sturgeon management and conservation. 45 trials were conducted over the course of the study. Study fish were subjected to 3 different field strengths (5µT, 100 µT, 1000 µT), generated using both AC and DC current. Time spent in generated field area, number of passes through the field area, and swimming speed were used to quantify behavioral changes in test subjects. From the data collected and analyzed there was no evidence indicating a change in fish behavior due to the influence of field strengths, field orientations, or field types used during the study.

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Allsop, Steven Christopher. "Hydrodynamic modelling for structural analysis of tidal stream turbine blades." Thesis, University of Exeter, 2018. http://hdl.handle.net/10871/33219.

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The predictable nature of the tides offers a regular, reliable source of renewable energy that can be harnessed using tidal stream turbines (TSTs). The UK's practically extractable tidal stream energy resource has the potential to supply around 7 % of the country's annual electricity demand. As of 2016, the world's first commercial scale arrays have been deployed around the UK and France. The harsh nature of the marine operating environment poses a number of engineering challenges, where the optimal turbine design solution remains under investigation. In this thesis, a numerical model is developed to assess the power production and hydrodynamic behaviour of horizontal axis tidal turbines. The developed model builds upon well established and computationally efficient Blade Element Momentum Theory (BEMT) method for modern three-bladed wind turbines. The main novel contribution of this thesis is extending the application to an alternative design of a ducted, high solidity and open centre TST. A validation study using measurements from multiple different scale model experimental tank tests has proven the applicability of the model and suitability of the imposed correction factors. The analytical modifications to account for ducted flow were subsequently indirectly verified, where predictions of turbine power and axial thrust forces under optimal operating speeds were within 2 % of those using more advanced computational fluid dynamics (CFD) methods. This thesis presents a commercial application case of two turbines designed by OpenHydro, examining the BEMT performance with a sophisticated blade resolved CFD study. A comparison of results finds that the model is capable of predicting the average peak power to within 12 %, however it under predicts thrust levels by an average of 35 %. This study concludes that the model is applicable to ducted turbine configurations, but is limited in capturing the complex flow interactions towards the open centre, which requires further investigation. The computational efficiency of the newly developed model allowed a structural analysis of the composite blades, thus demonstrating it is suitable to effectively evaluate engineering applications. Stresses are seen to be dominated by flap-wise bending moments, which peak at the mid-length of the blade. This tool will further enable EDF to perform third party assessments of the different turbine designs, to aid decision making for future projects.

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Dissertations / Theses on the topic 'Marine Renewable Energy'

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