Tesis: "Ocean wave power"

1

Noad, Imogen Frances. "Absorbing power from ocean waves : a mathematical approach to modelling wave energy converters". Thesis, University of Bristol, 2018. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.752773.

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Joubert, J. R. "An investigation of the wave energy resource on the South African Coast, focusing on the spatial distribution of the South West coast". Thesis, Link to the Internet, 2008. http://hdl.handle.net/10019.1/351.

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3

Xu, Xu. "Nonlinear dynamics of parametric pendulum for wave energy extraction". Thesis, University of Aberdeen, 2005. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=189414.

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A new concept, extracting energy from sea waves by parametric pendulor, has been explored in this project. It is based on the conversion of vertical oscillations to rotational motion by means of a parametrically-excited pendulor, i.e. a pendulum operating in rotational mode. The main advantage of this concept lies in a direct conversion from vertical oscillations to rotations of the pendulum pivot. This thesis, firstly, reviewed a number of well established linear and nonlinear theories of sea waves and Airy’s sea wave model has been used in the modelling of the sea waves and a parametric pendulum excited by sea waves. The third or fifth order Stokes’s models can be potentially implemented in the future studies. The equation of motion obtained for a parametric pendulum excited by sea waves has the same form as for a simple parametrically-excited pendulum. Then, to deepen the fundamental understanding, an extensive theoretical analysis has been conducted on a parametrically-excited pendulum by using both numerical and analytical methods. The numerical investigations focused on the bifurcation scenarios and resonance structures, particularly, for the rotational motions. Analytical analysis of the system has been performed by applying the perturbation techniques. The approximate solutions, resonance boundary and existing boundary of rotations have been obtained with a good correspondence to numerical results. The experimental study has been carried out by exploring oscillations, rotations and chaotic motions of the pendulum.

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4

Bracewell, Rob. "FROG and PS FROG : a study of two reactionless ocean wave energy converters". Thesis, Lancaster University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301820.

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5

Ridge, Alexander Nicholas. "Modelling and control of tubular linear generators for wave-power applications". Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709031.

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6

Li, Wei. "Numerical Modelling and Statistical Analysis of Ocean Wave Energy Converters and Wave Climates". Doctoral thesis, Uppsala universitet, Elektricitetslära, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-305870.

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Ocean wave energy is considered to be one of the important potential renewable energy resources for sustainable development. Various wave energy converter technologies have been proposed to harvest the energy from ocean waves. This thesis is based on the linear generator wave energy converter developed at Uppsala University. The research in this thesis focuses on the foundation optimization and the power absorption optimization of the wave energy converters and on the wave climate modelling at the Lysekil wave converter test site. The foundation optimization study of the gravity-based foundation of the linear wave energy converter is based on statistical analysis of wave climate data measured at the Lysekil test site. The 25 years return extreme significant wave height and its associated mean zero-crossing period are chosen as the maximum wave for the maximum heave and surge forces evaluation. The power absorption optimization study on the linear generator wave energy converter is based on the wave climate at the Lysekil test site. A frequency-domain simplified numerical model is used with the power take-off damping coefficient chosen as the control parameter for optimizing the power absorption. The results show a large improvement with an optimized power take-off damping coefficient adjusted to the characteristics of the wave climate at the test site. The wave climate modelling studies are based on the wave climate data measured at the Lysekil test site. A new mixed distribution method is proposed for modelling the significant wave height. This method gives impressive goodness of fit with the measured wave data. A copula method is applied to the bivariate joint distribution of the significant wave height and the wave period. The results show an excellent goodness of fit for the Gumbel model. The general applicability of the proposed mixed-distribution method and the copula method are illustrated with wave climate data from four other sites. The results confirm the good performance of the mixed-distribution and the Gumbel copula model for the modelling of significant wave height and bivariate wave climate.

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7

Garcia, Teran Jessica. "Positional Analysis of Wave Power : Applied at the Pacific Ocean in Mexico". Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-195854.

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The energy transition has started. The key is to find an alternative to uneconomical and unsustainable energy production. In this sense it is a challenge to develop renewable energy technologies suitable for the present and proper for the future. Uppsala University is driving the Lysekil project at its Division of Electricity. The aim is to design an environmentally friendly energy system with wave energy converters (WECs) that are simple and strong in design. However, little has been done to know more about its economically feasibility and the social impact of its benefits. Therefore, this research focuses on a positional analysis of a 3 MW Wave Power Park to understand the relevant aspects of implementing this kind of technology. The target area will be at Rosarito, Baja California at the Pacific Ocean in the Northeast of Mexico, a region experiencing increasing energy demand. This thesis combines technical, economical and social aspects. The technical part describes how the device works. The analysis is complemented by describing the current energy situation in Mexico and the social benefits of sustainable energy. Finally, the economical analysis is presented, it is focused on the perspective of the Merchant Power Plant. The review shows that wave power could be economically viable due to its high degree of utilisation. Energy diversification and security, economic and sustainable development, and clean energy are some of the advantages of wave power. Therefore, wave power is an interesting alternative for generating electricity in Mexico. However, the energy sector is highly subsidised, making it difficult for new technologies to enter the market without government participation. Another finding is that in the long run if the equipment cost decreases or subsidies are applied, the technology might be successfully implemented. Environmental consequences are described briefly, concluding that little is known and more research is needed. The environmental constraints, economic implications and uncertainties of a high energy future are disturbing. In that sense, renewable energy appears to be unequivocally better than rely to a greater extent on fossil fuels, in the sense that they offer a sustainable development and less environmental damage.

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8

Easton, Matthew Colin. "An assessment of tidal energy and the environmental response to extraction at a site in the Pentland Firth". Thesis, University of the Highlands and Islands, 2013. https://pure.uhi.ac.uk/portal/en/studentthesis/an-assessment-of-tidal-energy-and-the-environmental-response-to-extraction-at-a-site-in-the-pentland-firth(0ada05c2-3f33-463d-8f92-c9faad77a614).html.

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Shelf tidal streams are accelerated by coastal features, such as headlands and islands. In the search for sustainable forms of electricity generation, such locations may become attractive for tidal stream power. For many prospective sites, however, little is known about the intricacies of the local tidal dynamics: knowledge which is crucial to understanding the resource and the potential environmental consequences of its extraction. This thesis explores tidal stream energy in the Pentland Firth (Scotland, UK). This channel contains some of the most promising tidal stream energy sites in the world and is set to become host to the first large-scale arrays of tidal stream turbines, but its detailed characteristics were previously unknown. A hydrodynamic model was used to investigate the complex tidal dynamics of the Pentland Firth. This demonstrated, for the first time, the hydrodynamic mechanisms driving the exceptionally fast tidal currents through this channel. The model was then refined at a key site within the Pentland Firth, the Inner Sound. The results provided insight into complex flow characteristics, such as displacement and misalignment of peak flood and ebb tides, which must be considered when contemplating the exploitation of this energy resource. Tidal stream turbines were simulated in the hydrodynamic model. Artificial energy extraction was parameterised at the sub-grid-scale via added seabed drag. Turbine drag of varying magnitude was represented by a novel analytical model based on published characteristics of horizontal axis turbines. This new formulation reflects the non-linear dynamics of tidal turbine operation. Using the new turbine model, arrays of turbines were simulated within the Inner Sound. Complex interactions between the dynamics of energy extraction and flow required individual turbines to be parameterised in-concert with all other turbines in the array. This required extra effort, but offered enhanced insight into the behaviour of turbine arrays. Accounting for nonlinear turbine dynamics at high current speeds limited the magnitude of peak energy dissipation. Tidal stream velocities decreased both upstream and downstream of the extraction zone and were accelerated around it. At peak energy extraction, changes in tidal velocity were detectable several kilometres from the array, but were confined to the shallow waters of the Inner Sound and its environs. Implications for array modelling are discussed in the context of environmental impact assessments.

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9

Nie, Zanxiang Jack. "Emulation and power conditioning of outputs from a direct drive linear wave energy converter". Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609008.

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10

Rahm, Magnus. "Ocean Wave Energy : Underwater Substation System for Wave Energy Converters". Doctoral thesis, Uppsala universitet, Elektricitetslära, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-112915.

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This thesis deals with a system for operation of directly driven offshore wave energy converters. The work that has been carried out includes laboratory testing of a permanent magnet linear generator, wave energy converter mechanical design and offshore testing, and finally design, implementation, and offshore testing of an underwater collector substation. Long-term testing of a single point absorber, which was installed in March 2006, has been performed in real ocean waves in linear and in non-linear damping mode. The two different damping modes were realized by, first, a resistive load, and second, a rectifier with voltage smoothing capacitors and a resistive load in the DC-link. The loads are placed on land about 2 km east of the Lysekil wave energy research site, where the offshore experiments have been conducted. In the spring of 2009, another two wave energy converter prototypes were installed. Records of array operation were taken with two and three devices in the array. With two units, non-linear damping was used, and with three units, linear damping was employed. The point absorbers in the array are connected to the underwater substation, which is based on a 3 m3 pressure vessel standing on the seabed. In the substation, rectification of the frequency and amplitude modulated voltages from the linear generators is made. The DC voltage is smoothened by capacitors and inverted to 50 Hz electrical frequency, transformed and finally transmitted to the on-shore measuring station. Results show that the absorption is heavily dependent on the damping. It has also been shown that by increasing the damping, the standard deviation of electrical power can be reduced. The standard deviation of electrical power is reduced by array operation compared to single unit operation. Ongoing and future work include the construction and installation of a second underwater substation, which will connect the first substation and seven new WECs.

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11

Horton, Bryan. "Rotational motion of pendula systems for wave energy extraction". Thesis, Available from the University of Aberdeen Library and Historic Collections Digital Resources, 2009. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?application=DIGITOOL-3&owner=resourcediscovery&custom_att_2=simple_viewer&pid=25873.

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12

Sinha, Sanjay. "Directional wave effects on large offshore structures of arbitrary shape". Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/25139.

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A numerical method is described to study directional wave effects on large offshore structures of arbitrary shape, based on an extension of linear diffraction wave theory for regular waves. A computer program has been developed to compute loading transfer functions and response amplitude operators and hence the loading and response spectra for both long- and short-crested random waves. Cosine powered directional spreading functions which are independent of frequency have been used to account for the shortcrestedness of waves. Comparisions of the results for long- and short-crested seas show that there is a significant reduction in the loading, and hence in the response, due to shortcrestedness of waves. The probabilistic properties of the components of the loading and response are described. Since the sea surface is assumed to follow a Gaussian distribution, these are also random Gaussian variables. In short-crested waves, the loading and response components occur both in-line and transverse to the principal wave direction. Thus the maximum horizontal loading and response may occur in an arbitrary horizontal direction. An analytical method is developed to describe also the probabilistic properties of the maxima of the components and the maxima of their horizontal resultants. In the present study, results are described for a freely floating box. Comparisons are made with published results and are found to be quite favourable.
Applied Science, Faculty of
Civil Engineering, Department of
Graduate

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13

Mantellini, Mattia <1993&gt. "Optimization of the power electronics system associated with ocean wave electric generators". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2022. http://amsdottorato.unibo.it/10151/1/Optimization%20of%20the%20power%20electronics%20system%20associated%20with%20ocean%20wave%20electric%20generators%20-%20Mantellini%20IBES%2034th%20cycle.pdf.

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The present thesis is focused on wave energy, which is a particular kind of ocean energy, and is based on the activity carried out during the EU project SEA TITAN. The main scope of this work is the design of a power electronic section for an innovative wave energy extraction system based on a switched-reluctance machine. In the first chapter, the general features of marine wave energy harvesting are treated. The concept of Wave Energy Converter (WEC) is introduced as well as the mathematical description of the waves, their characterization and measurement, the WEC classification, the operating principles and the standardization framework. Also, detailed considerations on the environmental impact are presented. The SEA TITAN project is briefly described. The second chapter is dedicated to the technical issues of the SEA TITAN project, such as the operating principle, the performance optimization carried out in the project, the main innovations as well as interesting demonstrations on the behavior of the generator and its control. In the third chapter, the power electronics converters of SEA TITAN are described, and the design choices, procedures and calculations are shown, with a further insight into the application given by analyzing the MATLAB Simulink model of the system and its control scheme. Experimental tests are reported in the fourth chapter, with graphs and illustrations of the power electronic apparatus interfaced with the real machine. Finally, the conclusion in the fifth chapter offers a global overview of the project and opens further development pathways.

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14

Du, Qingjie y 杜青杰. "Numerical study of the hydrodynamic performance of a point-absorbing wave energy converter". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B47152849.

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As fossil energy is depleting and global warming effect is worsening rapidly, developing renewable energies becomes the top priority in most countries. In recent years, wave energy has attracted more and more attention due to its high energy density and enormous global capacity. The goal of this study is to carry out a numerical study of the hydrodynamic performance of a point-absorbing wave energy converter. In this study, an accurate and efficient numerical wave fume was established first. Commercial software code FLUENT?, which is a state-of-the-art computer program package for modeling fluid flow and heat transfer, was used for the numerical simulation. Based on the Navier-Stokes equations for viscous, incompressible fluid and Volume of fluid (VOF) method, a numerical wave tank was developed. Dynamic meshing method was used to simulate the wavemaker, and Geo-Reconstruct scheme was used to capture and reconstruct the free surface. A wave-absorbing method employing porous medium model was proposed to act as the wave absorbing beach, which can absorb the wave energy efficiently. A series of regular waves were simulated using the proposed numerical method. Validation has been made by physical experiments. After developing the wave flume model, a cylinder, which represents the point-absorbing wave energy converter (WEC), was added into the wave flume. The hydrodynamic behavior of the WEC was studied. The numerical results were also compared with physical experiments. Based on the numerical simulation results, suggestions on optimizing the point-absorber are provided. In this study, eight wave cases, with different wave period and wave length were simulated. The results show that the numerical simulation can match well with the physical wave tank result. Both the wave height and wave period in different cases can match well between the numerical simulation and physical wave tank results. In the wave-cylinder simulation, the results also show a good match in the numerical study and physical study. This numerical model is very significant in ocean structure design. The cylinder tested in this study can be easily changed to a ship or an offshore-platform. Compared with the physical experiment, numerical simulation is more flexible. The simulation can be carried on a large time span and spatial scale. The geometry can be changed easily. Also the cost of numerical simulation is relatively cheap compared with the physical experiment.
published_or_final_version
Mechanical Engineering
Master
Master of Philosophy

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15

Waters, Rafael. "Energy from Ocean Waves : Full Scale Experimental Verification of a Wave Energy Converter". Doctoral thesis, Uppsala universitet, Elektricitetslära, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-9404.

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A wave energy converter has been constructed and its function and operational characteristics have been thoroughly investigated and published. The wave energy converter was installed in March of 2006 approximately two kilometers off the Swedish west coast in the proximity of the town Lysekil. Since then the converter has been submerged at the research site for over two and a half years and in operation during three time periods for a total of 12 months, the latest being during five months of 2008. Throughout this time the generated electricity has been transmitted to shore and operational data has been recorded. The wave energy converter and its connected electrical system has been continually upgraded and each of the three operational periods have investigated more advanced stages in the progression toward grid connection. The wave energy system has faced the challenges of the ocean and initial results and insights have been reached, most important being that the overall wave energy concept has been verified. Experiments have shown that slowly varying power generation from ocean waves is possible. Apart from the wave energy converter, three shorter studies have been performed. A sensor was designed for measuring the air gap width of the linear generator used in the wave energy converter. The sensor consists of an etched coil, a search coil, that functions passively through induction. Theory and experiment showed good agreement. The Swedish west coast wave climate has been studied in detail. The study used eight years of wave data from 13 sites in the Skagerrak and Kattegatt, and data from a wave measurement buoy located at the wave energy research site. The study resulted in scatter diagrams, hundred year extreme wave estimations, and a mapping of the energy flux in the area. The average energy flux was found to be approximately 5.2 kW/m in the offshore Skagerrak, 2.8 kW/m in the near shore Skagerrak, and 2.4 kW/m in the Kattegat. A method for evaluating renewable energy technologies in terms of economy and engineering solutions has been investigated. The match between the technologies and the fundamental physics of renewable energy sources can be given in terms of the technology’s utilization. It is argued that engineers should strive for a high utilization if competitive technologies are to be developed.

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16

Helfrich, L. Cody. "Estimating oceanic internal wave energy from seismic reflector slope spectra". Laramie, Wyo. : University of Wyoming, 2008. http://proquest.umi.com/pqdweb?did=1594476671&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.

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17

Defne, Zafer. "Multi-criteria assessment of wave and tidal power along the Atlantic coast of the southeastern USA". Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/33864.

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The increasing demand for energy and the increased depletion rate of nonrenewable energy resources call for research on renewable alternatives. Mapping the availability of these resources is an important step for development of energy conversion projects. For this purpose, the wave power potential along the Atlantic coast of the southeastern USA, and the tidal stream power along the coast of Georgia are investigated in this study. Wave power potential is studied in an area bounded by latitudes 27 N and 38 N and longitudes 82 W and 72 W (i.e. North Carolina, South Carolina, Georgia, and northern Florida). The available data from National Data Buoy Center wave stations in the given area are examined. Power calculated from hourly significant wave heights and average wave periods is compared to power calculated using spectral wave energy density. The mean power within 50 km of the shore is determined to be low, whereas higher power is available further offshore beyond the 3500 m contour line. The tidal stream power potential along the coast of the state of Georgia is evaluated based on the NOAA tidal predictions for maximum tidal currents and three dimensional numerical modeling of the currents with Regional Ocean Modeling System (ROMS). The modeling results are validated against the available measurements. This region has low to moderate average tidal currents along most of the coast, but with the possibility of very strong local currents within its complex network of tidal rivers and inlets between barrier islands. Tidal stream power extraction is simulated with a momentum sink in the numerical models at the estuary scale to investigate effect of power extraction on the estuarine hydrodynamics. It is found that different power extraction schemes might have counterintuitive effects on the estuarial hydrodynamics and the extraction efficiency. A multi-criteria method that accounts for the physical, environmental and socioeconomic constraints for tidal power conversion schemes is proposed to select favorable locations and to rank them according to their suitability. For this purpose, the model results are incorporated into a Geographical Information System (GIS) database together with other geospatial datasets relevant to the site selection methodology. The methodology is applied to the Georgia coast and the candidate areas with potential are marked.

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18

Banerjee, S. "Ocean energy assessment : an integrated methodology". Thesis, Coventry University, 2011. http://curve.coventry.ac.uk/open/items/16196d0d-e671-489a-ba71-f20cdb6c8df3/1.

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The huge natural energy resources available in the world’s oceans are attracting increasing commercial and political interest. In order to evaluate the status and the degree of acceptability of future Ocean Energy (OE) schemes, it was considered important to develop an Integrated Assessment Methodology (IAM) for ascertaining the relative merits of the competing OE devices being proposed. Initial studies included the gathering of information on the present status of development of the ocean energy systems on wave, OTEC and tidal schemes with the challenges faced for their commercial application. In order to develop the IAM, studies were undertaken for the development and standardization of the assessment tools focussing on: • Life Cycle Assessment (LCA) on emission characteristics. • Energy Accounting (EA) studies. • Environmental Impact Assessment (EIA) over different environmental issues. • Resource captures aspects. • Defining economy evaluation indices. The IAM developed from such studies comprised of four interrelated well defined tasks and six assessment tools. The tasks included the identification of the modus operandi on data collection to be followed (from industry) for assessing respective OE devices, and also advancing relevant guidelines as to the safety standards to be followed, for their deployment at suitable sites. The IAM as developed and validated from case studies in ascertaining relative merits of competing OE devices included: suitable site selection aspects with scope for resource utilisation capability, safety factors for survivability, scope for addressing global warming & energy accounting, the environmental impact assessment both qualitatively and quantitatively on different environmental issues, and the economic benefits achievable. Some of the new ideas and concepts which were also discovered during the development of the IAM, and considered useful to both industry and researchers are given below: • Relative Product Cost (RPC) ratio concept- introduced in making an economic evaluation. This is considered helpful in sensitivity analysis and making design improvements (hybridising etc) for the cost reduction of OE devices. This index thus helps in making feasibility studies on R&D efforts, where the capital cost requirement data and life span of the device is not well defined in the primary stages of development. • Determination of the threshold limit value of the barrage constant - considered useful in determining the efficacy of the planning process. The concept ascertained the relative efficiency achieved for various barrage proposals globally. It could also be applied to suggest the revisions required for certain barrage proposals and also found useful in predicting the basin area of undefined barrage proposal for achieving economic viability. • Estimations made on the future possibility of revenue earnings from the by-products of various OTEC types, including the scope of chemical hubs from grazing type OTEC plants. • Determination of breakeven point- on cost versus life span of wave and OTEC devices studied, which is useful in designing optimum life of the concerned devices. The above stated multi-criterion assessment methodology, IAM, was extended leading to the development of a single criterion model for ascertaining sustainability percent achievable from an OE device and termed IAMs. The IAMs was developed identifying 7 Sustainability Development Indices (SDI) using some the tools of the IAM. A sustainability scale of 0-100 was also developed, attributing a Sustainability Development Load Score (SDLS) percentage distribution pattern over each SDIs, depending on their relative importance in achieving sustainability. The total sum of sustainability development (SD) gained from each SDI gave the IAMs (for the concerned device), indicating the total sustainable percentage achieved. The above IAMs developed, could be applied in ranking OE devices alongside the unsustainable coal power station. A mathematical model of estimating the IAMs was formulated, in order to ascertain the viability to the sustainable development of any energy device. The instruments of IAM and IAMs which have been developed would be helpful to the OE industry in ascertaining the degree of acceptability of their product. In addition it would also provide guidelines for their safe deployment by assessing the relative merits of competing devices. Furthermore, IAM and IAMs would be helpful to researchers undertaking feasibility studies on R&D efforts for material development research, ‘hybridization studies’ (as also new innovations), cost reduction, the performance improvement of respective devices, and any economic gains. With future advancements in OE systems and the availability of field data from large scale commercial applications, the specific values/data of the IAM & IAMs may be refined, but the logic of the models developed in this research would remain the same.

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19

Carter, Caroline Jane. "Tidal energy, underwater noise & marine mammals". Thesis, University of the Highlands and Islands, 2008. https://pure.uhi.ac.uk/portal/en/studentthesis/tidal-energy-underwater-noise-and-marine-mammals(9963d662-76e1-4e70-a3ac-e18a96b23101).html.

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Sourcing energy from renewable sources is currently a key theme in modern society. Consequently, the pace of development of these emerging technologies is likely to increase in the near future, particularly in marine renewables. However, the environmental and ecological impact of many of these new developments in the marine environment is largely unknown. My thesis has focused on one unknown area of interaction; the potential effect of tidal-stream devices on marine mammals. Collision risk is often cited as a key concern. Therefore, my premise was - for marine mammals to avoid a collision with a marine renewable device (assuming they are on a collision course) they must first detect the device. It is well understood that marine mammals use sound and hearing as their primary sense for communication, foraging, navigation and predator avoidance, so it is highly likely that the primary cue for device detection will be acoustic. However, it is not known how operational marine renewable devices might modify the acoustic landscape in these areas, or whether they will be audible to marine mammals in time to alert them to the presence of devices. It has been suggested that the high level of natural and anthropogenic background noise in tidal-stream areas may mask (drown out) the signal of the tidal devices. The acoustic characteristics of underwater noise in shallow coastal waters are currently not well known. My thesis adds data to this knowledge gap by measuring and mapping underwater noise levels in tidal-stream areas.

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20

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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21

Billing, Suzannah-Lynn. "The role of agents for change in the sustainable development of wave energy in the Highlands and Islands region of Scotland". Thesis, University of the Highlands and Islands, 2016. https://pure.uhi.ac.uk/portal/en/studentthesis/the-role-of-agents-for-change-in-the-sustainable-development-of-wave-energy-in-the-highlands-and-islands-region-of-scotland(adb7d446-a88e-4451-b39c-a7c0f9acffab).html.

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With the Scottish Government's commitment to sourcing 100% of the national electricity demand from renewable sources by 2020, within the global framework of climate change mitigation, the potential of the marine environment around the Highlands and Islands Region of Scotland to add to Scotland's renewables portfolio has led to the expansion of the wave and tidal industries in recent years. Nevertheless, to date, there has been limited research conducted on the social systems around marine renewable energy development, excluding offshore wind. In answer to this deficit, this study explores a well-established concept within the academic arenas of business, health, and rural development, among others, of agents for change (AFCs), within the context of the rapidly emerging wave energy sector. Two case studies, Lewis in the Outer Hebrides, and Orkney, were chosen based on their localities and the interest that they have garnered from wave energy developers due to their high energy marine environments. A grounded approach was taken to data collection and a social power analysis was conducted in order to find AFCs working within or closely with the wave energy industry that were not part of structured or hierarchical organisations. One emergent theme was that there was a noteworthy barrier to wave energy development in the case studies and to the work that the agents for change were doing in the form of a complex dynamic between financial investments in the sector, national grid, national energy policy, and the technology itself. The agents for change were found to act as catalysts for the wave energy industry through their perseverance and visionary approach to development. The motivations of the AFCs is discussed and the shifting roles that they took as a project progresses is described and compared to other change process models, namely Lewin (1958) and Kotter (1995).

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22

Langton, Rebecca. "Simulating breeding seabirds in order to aid marine spatial planning". Thesis, University of Aberdeen, 2013. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=196166.

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23

Schneider, Bettina. "Economic feasibility study for the wave energy technology of Gaia Power Group Pty Ltd". Thesis, Stellenbosch : Stellenbosch University, 2011. http://hdl.handle.net/10019.1/79331.

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Thesis (MBA)--Stellenbosch University, 2011.
Gaia Power is a South African start-up in the renewable energy industry. Among other products, they developed a wave energy converter, which is a device used to extract energy from ocean waves. This research deals with the economic feasibility study of the wave energy converter. Wave energy is a young field of research, especially in the South African context. Therefore sources for multiple angles of the project had to be found, analysed and brought into the Gaia Power context. Understanding the cost drivers of a wave energy plant was the foundation of the research itself. The Gaia Power specific levelised cost of electricity generation was calculated based on actual supplier quotes, reference costs found in the literature as well as assumptions. Still, such a calculation is actually more an estimation due to a high uncertainty level in all cost components. Especially the construction cost as well as the discount rate used have therefore been tested for sensitivity. Gaia Power‟s target production cost was R0.54 kWh, which equalled the Eskom tariff at the time of this research. Taking into account a R0.10/kWh fee payable to Eskom, the target cost sank to R0.44, which is about 25 percent lower than the minimum value for electricity generation cost found in the literature. This target was therefore expected to be and proved to be difficult to reach. The calculated levelised electricity cost was R0.99/kWh, with a possible range of R0.54/kWh to R1.60/kWh observed in the sensitivity analysis. These results show that the Gaia Power wave energy converter in the given specifications was not economically feasible. It was therefore recommended to rethink the specifications in order to reduce construction cost, which proved to be the largest cost driver. Besides the quantitative findings, this research also has a strong qualitative side. During the whole research it became obvious that there was an overall high risk level in the project due to the lack of experience with wave energy in general and in South Africa specifically, as well as the high impact of weather on the construction. Those risks were identified, analysed and recommended mitigation actions were derived.

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24

Thorburn, Karin. "Electric Energy Conversion Systems : Wave Energy and Hydropower". Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7081.

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25

Martin, Dillon Minkoff. "Hydrodynamic Design Optimization and Wave Tank Testing of Self-Reacting Two-Body Wave Energy Converter". Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/80298.

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As worldwide energy consumption continues to increase, so does the demand for renewable energy sources. The total available wave energy resource for the United States alone is 2,640 TWh/yr; nearly two thirds of the 4,000 TWh of electricity used in the United States each year. It is estimated that nearly half of that available energy is recoverable through wave energy conversion techniques. In this thesis, a two-body 'point absorber' type wave energy converter with a mechanical power-takeoff is investigated. The two-body wave energy converter extracts energy through the relative motion of a floating buoy and a neutrally buoyant submerged body. Using a linear frequency-domain model, analytical solutions of the optimal power and the corresponding power-takeoff components are derived for the two-body wave energy converter. Using these solutions, a case study is conducted to investigate the influence of the submerged body size on the absorbed power of the device in regular and irregular waves. Here it is found that an optimal mass ratio between the submerged body and floating buoy exists where the device will achieve resonance. Furthermore, a case study to investigate the influence of the submerged body shape on the absorbed power is conducted using a time-domain numerical model. Here it is found that the submerged body should be designed to reduce the effects of drag, but to maintain relatively large hydrodynamic added mass and excitation force. To validate the analytical and numerical models, a 1/30th scale model of a two-body wave energy converter is tested in a wave tank. The results of the wave tank tests show that the two-body wave energy converter can absorb nearly twice the energy of a single-body 'point absorber' type wave energy converter.
Master of Science

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26

Li, Xiaofan. "Design, Analysis and Testing of a Self-reactive Wave Energy Point Absorber with Mechanical Power Take-off". Diss., Virginia Tech, 2020. http://hdl.handle.net/10919/100800.

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Ocean wave as a renewable energy source possesses great potential for solving the world energy crisis and benefit human beings. The total theoretical potential wave power on the ocean-facing coastlines of the world is around 30,000 TWh, although cannot all be adopted for generating electricity, the amount of the power can be absorbed still can occupy a large portion of the world's total energy consumption. However, multiple reasons have stopped the ocean wave energy from being widely adopted, and among those reasons, the most important one is immature of the Power Take-off (PTO) technology. In this dissertation, a self-reactive two-body wave energy point absorber that is embedded with a novel PTO using the unique mechanism of Mechanical Motion Rectifier (MMR) is investigated through design, analysis and testing to improve the energy harvesting efficiency and the reliability of the PTO. The MMR mechanism can transfer the reciprocated bi-directional movement of the ocean wave into unidirectional rotation of the generator. As a result, this mechanism brings in two advantages towards the PTO. The first advantage it possess is that the alternating stress of the PTO is changed into normal stress, hence the reliability of the components are expected to be improved significantly. The other advantage it brings in is a unique phenomenon of engagement and disengagement during the operation, which lead to a piecewise nonlinear dynamic property of the PTO. This nonlinearity of the PTO can contribute to an expanded frequency domain bandwidth and better efficiency, which are verified through both numerical simulation and in-lab experiment. During the in-lab test, the prototyped PTO achieved energy transfer efficiency as high as 81.2%, and over 40% of efficiency improvement compared with the traditional non-MMR PTO under low-speed condition, proving the previously proposed advantage. Through a more comprehensive study, the MMR PTO is further characterized and a refined dynamic model. The refined model can accurately predict the dynamic response of the PTO. The major factors that can influence the performance of the MMR PTO, which are the inertia of the PTO, the damping coefficient, and the excitation frequency, are explored through analysis and experiment comprehensively. The results show that the increase on the inertia of the PTO and excitation frequency, and decrease on the damping coefficient can lead to a longer disengagement of the PTO and can be expressed analytically. Besides the research on the PTO, the body structure of the point absorber is analyzed. Due to the low-frequency of the ocean wave excitation, usually a very large body dimension for the floating buoy of the point absorber is desired to match with that frequency. To solve this issue, a self-reactive two-body structure is designed where an additional frequency between the two interactive bodies are added to match the ocean wave frequency by adopting an additional reactive submerged body. The self-reactive two-body structure is tested in a wave to compare with the single body design. The results show that the two-body structure can successfully achieve the frequency matching function, and it can improve more than 50% of total power absorption compared with the single body design.
Doctor of Philosophy
Ocean wave as a renewable energy source possesses great potential for solving the world energy crisis and benefit human beings. The total theoretical potential wave power on the ocean-facing coastlines of the world is around 30,000 TWh, although impossible to be all transferred into electricity, the amount of the power can be absorbed still can cover a large portion of the world's total energy consumption. However, multiple reasons have stopped the ocean wave energy from being widely adopted, and among those reasons, the most important one is immature of the Power Take-off (PTO) technology. In this dissertation, a novel two body wave energy converter with a PTO using the unique mechanism of Mechanical Motion Rectifier (MMR) is investigated through design, analysis, and testing. To improve the energy harvesting efficiency and the reliability of the PTO, the dissertation induced a mechanical PTO that uses MMR mechanism which can transfer the reciprocated bi-directional movement of the ocean wave into unidirectional rotation of the generator. This mechanism brings in a unique phenomenon of engagement and disengagement and a piecewise nonlinear dynamic property into the PTO. Through a comprehensive study, the MMR PTO is further characterized and a refined dynamic model that can accurately predict the dynamic response of the PTO is established. The major factors that can influence the performance of the MMR PTO are explored and discussed both analytically and experimentally. Moreover, as it has been theoretically hypothesis that using a two-body structure for designing the point absorbers can help it to achieve a frequency tuning effect for it to better match with the excitation frequency of the ocean wave, it lacks experimental verification. In this dissertation, a scaled two-body point absorber prototype is developed and put into a wave tank to compare with the single body structure. The test results show that through the use of two-body structure and by designing the mass ratio between the two bodies properly, the point absorber can successfully match the excitation frequency of the wave. The highest power capture width ratio (CWR) achieved during the test is 58.7%, which exceeds the results of similar prototypes, proving the advantage of the proposed design.

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27

Duman, Cagatay. "Evaluation And Comparison Of The Wave Energy Potential In Selected Coastal Regions In Turkey". Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612626/index.pdf.

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In order to meet energy needs in world, studies on wave energy, alternative energy, are becoming more and more important with each passing day. The purpose of this study is to identify the wave energy potential along the coastline of Turkey. For this purpose, the data of wind speed and direction, swell and wind wave height, period and direction for certain duration with the six hours time intervals are obtained from ECMWF for the wind and wave climate computations. In order to compute the wind and wave climate at any selected coastal location, software is developed by Serhan Aldogan in his MSc thesis. By the help of the specifically developed software, for every location, by utilizing existing wind data, depending on geographical location of station, in the direction of energy thought to produce, by using calculated average wind speed of storm which is above the selected wind speed u0, characteristics (Hs
Tm) of the waves of this storm and power (P, W/m) per unit length will be calculated. The duration curves for power, Hs and T, can be obtained. The duration curve represents the occurrence of the parameter (wave height, wave period, wave energy or wave power). It can also be called occurrence curve or availability curve. From these curves, for various percentages of the total storm duration, P, Hs and T&rsquo
s values can be determined. Also, in the analysis, the shapes of these curves can provide important information about the available wave energy for the selected coasts.

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28

Reinecke, Josh. "Effect of a diffuser on the power production of an ocean current turbine". Thesis, Stellenbosch : University of Stellenbosch, 2011. http://hdl.handle.net/10019.1/6529.

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29

Joubert, James Rattray. "Design and development of a novel wave energy converter". Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/85817.

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Thesis (PhD)--Stellenbosch University, 2013.
ENGLISH ABSTRACT: The design, development and evaluation of a novel wave energy converter (WEC) device, called the ShoreSWEC, in a South African port development is presented. Based on the device requirements, site selection criteria were specified and applied to identify a suitable deployment location. A wave modeling procedure was developed to determine the operational wave conditions and available wave power resource at the selected location. The site was found to have a low mean annual average resource of approximately 2.3 kilowatt per meter wave crest (kW/m) due to its relatively sheltered location. The wave model was further used to determine design storm conditions and a structural stability analysis of the device was conducted. Experimental tests were performed to evaluate the hydrodynamic conversion efficiency of a single chamber of the device at its most conservative orientation, under a variety of wave energy conditions. The effect of a floor incline and an additional chamber on the performance of the system was investigated. The incline improved efficiency for low wave heights, making it ideal for the low wave power resource conditions of the site, whilst the multi-chamber system experienced increased performance at high wave periods. A comparison between the ShoreSWEC and a conventional oscillating water column (OWC) WEC showed that the OWC extracted 72% more energy, highlighting the sensitivity of performance on device orientation. A three-dimensional (3D) numerical model of the experimental setup was developed. The numerical model provided comparable water surface elevations inside the flume and chamber, yet predicted significantly higher internal chamber pressures and overall efficiency. The electricity generation potential of a 10 chamber ShoreSWEC at the specified location, approximated from the experimental results and 11 years of hindcast wave data, was found to be 6 kW on average for a 15 kW capacity system. Results of this study highlighted the need for greater understanding of the hydrodynamic characteristics of a full length device. Experimental tests in a 3D wave basin on a scaled full length ShoreSWEC model are therefore recommended. Once conducted, South Africa will be one step closer to the deployment of the full scale SWEC device.
AFRIKAANSE OPSOMMING: Die ontwerp, ontwikkeling en evaluasie van ‘n unieke golfenergieomsetter (GEO), genaamd die ShoreSWEC, in ‘n Suid-Afrikaanse haweontwikkeling word aangebied. Terrein evaluasie kriteria, gebaseer op die omsettervereistes, is ontwikkel en toegepas om die mees belowende terrein te identifiseer. ‘n Golfmodeleringsprosedure is ontwikkel om die operasionele golfkondisies en beskikbare golfdrywinghulpbron te bepaal. Daar is gevind dat die terrein ‘n lae gemiddelde golfdrywing van bykans 2.3 kilowat per meter golfkruin het as gevolg van die beskutte ligging. Die golfmodel is verder gebruik om ontwerpstormkondisies te bepaal en ‘n stabiliteitsanalise was op die toestel struktuur uitgevoer. Eksperimentele toetse van verskeie golfenergie kondisies is gedoen om die hidrodinamiese omsettingseffektiwiteit van ‘n enkel kamer van die toestel te bepaal teen sy konserwatiefste orientasie. Die effek van ‘n vloerhelling en ‘n addisionele kamer op die uitsette van die sisteem is ondersoek. Die helling het effektiwiteit verbeter vir lae golfhoogtes wat dit ideaal maak vir die lae hulpbron by die terrein, terwyl die veelvoudige-kamer-sisteem beter gevaar het by hoë golfperiodes. ‘n Vergelyking tussen die ShoreSWEC en ‘n konvensionele ossilerende waterkolom (OWK) GEO het gewys dat die OWK 72% meer energie onttrek. Dit beklemtoon die sisteem se sensitiwiteit vir die inkomende golfrigting. ‘n Drie-dimensionele (3D) numeriese model van die eksperimentele opstelling is ontwikkel. Die numeriese model het aansienlik hoër drukke binne die kamer, en gevolglik algehele effektiwiteit, voorspel as die eksperimentele toetse. Die elektriese opwekkingskapasiteit van ‘n 10 kamer ShoreSWEC by die terrein, gebaseer op die eksperimentele resultate en 11 jaar se golfdata, is bereken as 6 kW gemiddeld vir ‘n 15 kW kapasiteit stelsel. Die bevindinge van hierdie studie het die behoefte aan ‘n beter begrip van die hidrodinamiese eienskappe van ‘n vollengte sisteem beklemtoon. Eksperimentele toetse in ‘n 3D golfbak op ‘n geskaleerde vollengte ShoreSWEC model word dus aanbeveel. Sodra dit voltooi is, sal Suid-Afrika een stap nader wees aan die ontplooiing van ‘n volskaalse SWEC toestel.

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30

Schoonees, Jacobus Stefanus. "Longshore sediment transport : applied wave power approach, field data analysis and evaluation of formulae". Thesis, Stellenbosch : Stellenbosch University, 2001. http://hdl.handle.net/10019.1/52327.

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Thesis (PhD)--University of Stellenbosch, 2001.
ENGLISH ABSTRACT: The process of sand being moved parallel to the coast by wave and current action is called longshore (sediment) transport. Knowledge oflongshore transport is essential for the design of breakwaters at harbour entrances, for navigation channels and for calculating the amount of dredging they require, for beach improvement schemes and for the determination of the stability of inlets and estuaries. Different aspects oflongshore transport have been investigated, namely, (1) analysis offield data, (2) evaluation oflongshore transport formulae and (3) the development of the wave power approach as an alternative method to calculate longshore transport. In the development of a better understanding oflongshore sediment transport, the following has been done for the first time: (1) a comprehensive data set has been compiled covering almost a full range of conditions occurring on natural beaches; and (2) virtually all longshore transport formulae have been evaluated against this extensive data set. A new improved method, the applied wave power approach, has been developed and extensively calibrated against the same data set. Based on this evaluation, guidelines are now available for design engineers as to which are the best bulk and detailed predictors oflongshore sediment transport. These are respectively, the recalibrated Kamphuis formula and the applied wave power approach. Another useful first, is the derivation of confidence intervals for a longshore transport formula, showing what accuracy can be obtained and that accurate predictions are now possible. In addition, it has now been determined what the minimum required measurement period should be and what the most cost-effective way is for obtaining the true long-term mean net longshore transport rate at a particular site.
AFRIKAANSE OPSOMMING: Die proses waarvolgens sand ewewydig aan die kus deur golf- en stroomwerking vervoer word, word langsstrandse (sediment-) vervoer oflangsvervoer genoem. Kennis van langsvervoer is noodsaaklik vir die ontwerp van golfbrekers by hawe-ingange, navigasiekanale en vir die berekening van die hoeveelheid baggerwerk daarvoor benodig, strandverbeteringskemas en vir die bepaling van die stabiliteit van inlate en getyriviere. Verskillende aspekte van langsvervoer is ondersoek, naarnlik, (1) die ontleding van velddata, (2) die beoordeling van langsvervoerformules en (3) die ontwikkeling van die golfdrywingsbenadering as 'n altematiewe metode om langsvervoer mee te bereken .. Tydens die ontwikkeling van 'n beter begrip van langsstrandse sedimentvervoer is die volgende vir die eerste keer gedoen: (1) 'n omvattende datastel is versamel wat bykans aIle toestande wat aan natuurlike strande voorkom, dek; en (2) feitlik aile langsvervoerformules is teen hierdie uitgebreide datastel beoordeel. 'n Nuwe verbeterde metode, die aangewende golfdrywingsbenadering, is ontwikkel en omvattend teen dieselfde datastel geyk. Gebaseer op hierdie beoordeling, is riglyne nou vir ontwerp-ingenieurs beskikbaar rakende watter totaal- en detail-iangsvervoervoorspellers die beste is. Dit is onderskeidelik die hergeykte Kamphuisformule en die aangewende golfdrywingsbenadering. Nog 'n nuttige eerste is die afleiding van betroubaarheidsgrense vir 'n langsvervoerformule, wat wys watter akkuraatheid nou haalbaar is en dat noukeurige voorspellings nou moontlik is. Verder is dit nou vasgestel wat die vereiste meettydperk behoort te wees en wat die mees koste-effektiewe manier is waarop die ware langtermyn-gemiddelde netto langsvervoertempo by 'n spesifieke terrein verkry kan word.

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31

Afonja, Adetoso J. "Dynamics of Pitching Wave Energy Converter with Resonant U-Tank Power Extraction Device". Thesis, Virginia Tech, 2020. http://hdl.handle.net/10919/98782.

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This research revolves around the concept design and theoretical validation of a new type of wave energy converter (WEC), comprising a pitching floater integrated with a resonant U-tank (RUT) and a Wells turbine as power take-off (PTO). Theoretical formulation of a fully coupled multi-body dynamic system, incorporating the thermodynamic processes of the RUT air chamber, its interaction with the PTO dynamics and their coupling with the floater is presented. Inaccuracies of the dynamic modeling of RUT based on Lloyd's low order model, which assumes constant hydrodynamic parameters irrespective of the frequency, are demonstrated by a series of high fidelity CFD simulations. These simulations are a systematic series of fully viscous turbulent simulations, using unsteady RANSE solvers, of the water sloshing at different frequencies of oscillation. Calibration of Lloyd’s model with CFD results evidenced that the RUT hydrodynamic parameters are not invariant to frequency. A numerical model was developed based on Simulink WEC-Sim libraries to solve the non-linear thermo-hydrodynamic equations of the device in time domain. For power assessment, parametric investigations are conducted by varying the main dimensions of the RUT and power RAOs were computed for each iteration. Performance in irregular sea state are assessed using a statistical approach with the assumption of linear wave theory. By superimposing spectrum energy density from two resource sites with RAO, mean annual energy production (MEAP) are computed. The predicted MEAP favorably compares with other existing devices, confirming the superior efficiency of the new proposed device over a larger range of incident wave frequency.
M.S.
This study present results of an investigation into a new type of wave energy converter which can be deployed in ocean and by its pitch response motion, it can harvest wave energy and convert it to electrical energy. This device consist of a floater, a U-tank (resonant U-tank) with sloshing water free to oscillate in response to the floater motion and a pneumatic turbine which produces power as air is forced to travel across it. The pneumatic turbine is used as the power take-off (PTO) device. A medium fidelity approach was taken to carry out this study by applying Lloyd’s model which describes the motion of the sloshing water in a resonant U-tank. Computational fluid dynamics (CFD) studies were carried out to calibrate the hydrodynamic parameters of the resonant U-tank as described by Lloyd and it was discovered that these parameters are frequency dependent, therefore Lloyd’s model was modelled to be frequency dependent. The mathematical formulation coupling the thermodynamic evolution of air in the resonant U-tank chamber, modified Lloyd’s sloshing water equation, floater dynamics and PTO were presented for the integrated system. These set of thermo-hydrodynamic equations were solved with a numerical model developed using MATLAB/Simulink WEC-Sim Libraries in time domain in other to capture the non-linearity arising from the coupled dynamics. To assess the annual energy productivity of the device, wave statistical data from two resource sites, Western Hawaii and Eel River were selected and used to carrying out computations on different iterations of the device by varying the tank’s main dimensions. This results were promising with the most performing device iteration yielding mean annual energy production of 579 MWh for Western Hawaii.

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32

Jarocki, Dmitri. "Wave Energy Converter Performance Modeling and Cost of Electricity Assessment". DigitalCommons@CalPoly, 2010. https://digitalcommons.calpoly.edu/theses/278.

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California is experiencing a rapid increase in interest for the potential of converting ocean waves into clean electricity. Numerous applications have been submitted for the permitting of such renewable energy projects; however the profitability, practicability, and survivability have yet to be proven. Wave energy conversion technology has steadily matured since its naissance in the 1970’s, several wave energy power installations currently exist, and numerous plans for commercial power plant are in the works on the shores of multiple continents. This study aims to assess the economic viability of two proposed commercial wave energy power plant projects on the Central California Coast. A theoretical 25 MW capacity wave energy plant located at a site five nautical miles off of Point Arguello, in Santa Barbara County is compared to a site five nautical miles off of Morro Bay, in the County of San Luis Obispo. The Pacific Gas and Electric Company and Green Wave Energy Solutions, LLC have proposed full-scale commercial wave power plants at these sites, and are currently undergoing the federal permitting processes. Historical wave resource statistics from 1980 to 2001 are analyzed with performance specifications for the AquaBuOY, Pelamis P1, and WaveDragon wave energy converters (WECs) to calculate the annual electrical output of each device at each site. Sophisticated computer modeling of the bathymetric influence on the wave resource at each site is presented using the program Simulating Waves Nearshore (SWAN) developed by the Delft University of Technology. The wave energy flux, significant wave height, and peak period are computed at each site for typical summer and winter swell cases, using seafloor depth measurements at a 90 meter rectangular grid resolution. The economic viability of commercial electricity generation is evaluated for each WEC at each site by the calculation of the net present value of an estimated 25-year project life-cycle, the internal rate of return, and the required cost of electricity for a 10-year project simple payback period. The lowest required price of electricity is $0.13/kWh and occurs at the Point Arguello site using the AquaBuOY WEC. The highest annual capacity factor is 18% using the Pelamis WEC. The net present value and internal rate of return calculations suggest that the AquaBuOY WEC is profitable at both sites for electricity prices above $0.14/kWh. Shallow water wave propagation SWAN modeling demonstrated favorable wave energy flux states for WEC operation and power generation at both sites, with typical winter energy fluxes of 30-37 kW/m.

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33

Yang, Xiufeng. "Ocean current energy resource assessment for the United States". Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50352.

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Ocean currents are an attractive source of clean energy due to their inherent reliability, persistence and sustainability. The Gulf Stream system is of particular interest as a potential energy resource to the United States with significant currents and proximity to the large population on the U.S. east coast. To assess the energy potential from ocean currents for the United States, the characterization of ocean currents along the U.S. coastline is performed in this dissertation. A GIS database that maps the ocean current energy resource distribution for the entire U.S. coastline and also provides joint velocity magnitude and direction probability histograms is developed. Having a geographical constraint by Florida and the Bahamas, the Florida Current has the largest ocean current resource which is fairly stable with prevalent seasonal variability in the upper layer of the water column (~200m). The core of the Florida Current features higher stability than the edges as a result of the meandering and seasonal broadening of the current flow. The variability of the Gulf Stream significantly increases as it flows past the Cape Hatteras. The theoretical energy balance in the Gulf Stream system is examined using the two-dimensional ocean circulation equations based on the assumptions of the Stommel model for quasi-geostrophic subtropical gyres. Additional turbine drag is formulated and incorporated in the model to represent power extraction by turbines. Parameters in the model are calibrated against ocean observational data such that the model can reproduce the volume and kinetic energy fluxes in the Gulf Stream. The results show that considering extraction over a region comprised of the entire Florida Current portion of the Gulf Stream system, the theoretical upper bound of averaged power dissipation is around 5.1 GW, or 45 TWh/yr. If the extraction area comprises the entire portion of the Gulf Stream within 200 miles of the U.S. coastline, the theoretical upper bound of averaged power dissipation becomes approximately 18.6 GW or 163 TWh/yr. The impact of the power extraction is primarily constrained in the vicinity of the turbine region, and includes a significant reduction of flow strength and water level drop in the power extraction site. The turbines also significantly reduce residual energy fluxes in the flow, and cause redirection of the Gulf Stream. A full numerical simulation of the ocean circulation in the Atlantic Ocean is performed using Hybrid Coordinate Ocean Model (HYCOM) and power extraction from the Florida Current is modeled as additional momentum sink. Effects of power extraction are shown to include flow rerouting from the Florida Strait channel to the east side of the Bahamas. Flow redirection is stronger during peak summer flow resulting in less seasonal variability in both power extraction and residual fluxes in the Florida Current. A significant water level drop is shown at the power extraction site, and so is a slight water level rise along the coasts of Florida and the Gulf. The sum of extracted power and the residual energy flux in the Florida Current is lower than the original energy flux in the baseline case, indicating a net loss of energy reserve in the Florida Current channel due to flow redirection. The impact from power extraction on the mean flow field is concentrated in the near field of the power extraction site, while shifts in the far flow field in time and space have little impact on the overall flow statistics.

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34

Jiang, Boxi. "Performance Analysis and Tank Test Validation of a Hybrid Wave-Current Energy Converter with a Single Power Takeoff". Thesis, Virginia Tech, 2020. http://hdl.handle.net/10919/99211.

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Marine and hydrokinetic (MHK) energy, including ocean waves, tidal current, ocean current and river current, has been recognized as a promising power source due to its full-day availability and high energy potential. At this stage, ocean current energy, tidal energy and ocean wave energy are currently the most competitive sourves among all the categories of MHK. The state of art MHK energy harvesting technology mainly focus on harvesting either ocean wave energy or current energy, but not both. However, a significant amount of ocean waves and tidal/ ocean current coexist in many sites and traditional devices that harvest from a single form of MHK energy, cannot make full use of the coexisting ocean energy. Furthermore, MHK energy harvesting devices need to advance to be cost-effective and competitive with other energy sources. This is difficult to achieve. Ocean wave excitation is irregular, which means that ocean wave height and wave periods are unpredictable and excitation forces on energy harvesting devices can have large variance in amplitude and frequency. Such problems/ restrictions can be possibly addressed by the concept of a hybrid energy converter. In this sense, a hybrid wave-current ocean energy conveter (HWCEC) that simutaneously harvests energy from current and wave with one single power takeoff (PTO) is designed.The wave energy is extracted through relative heaving motion between a floating buoy and a submerged second body, while the current energy is extracted using a marine current turbine (MCT). Energy from both sources are integrated by a hybrid PTO whose concept is based on a mechanical motion rectifier (MMR). In this study, different working modes are investigated together with switching criteria.Simulations were conducted with hydrodynamic coefficients obtained from computational fluid dynamics analysis and boundary element method. Tank tests were conducted for a HWCEC under co-existing wave and current inputs. For comparison, separate baseline tests of a turbine and a two-body point absorber, each acting in isolation, are conducted. Experimental results validate the dynamic modeling and show that a HWCEC can increase the output power with a range between 29-87 percent over either current turbine and wave energy converter acting individually, and it can reduce by up to 70 percent the peak-to-average power ratio compared with the wave energy converter on the tested conditions.Such results demonstrate the potential of the HWCEC as an efficient and cost-effective design.
Master of Science
Ocean energy has been recognized as a promising power source due to its full-day availability and high energy potential. At this stage, ocean current energy, tidal energy and ocean wave energy are currently the most competitive sourves among all the categories of ocean energy. The state of art ocean energy harvesting technology mainly focus on harvesting either ocean wave energy or current energy, but not both. However, a significant amount of ocean waves and tidal/ ocean current coexist in many sites and traditional devices that harvest from a single form of ocean energy, cannot make full use of the coexisting energy resource. Furthermore, MHK energy harvesting devices need to advance to be cost-effective and competitive with other energy sources. This is difficult to achieve. Ocean wave height and wave periods are unpredictable and excitation forces on energy harvesting devices can have large variance in amplitude and frequency. Such restrictions can be possibly addressed by the concept of a hybrid energy converter. In this sense, a hybrid wave-current ocean energy conveter (HWCEC) that simutaneously harvests energy from current and wave with one single power takeoff (PTO), which consists of ball screw, gearbox, and generator, is designed.The wave energy is extracted through relative heaving motion between a floating buoy and a submerged second body, while the current energy is extracted using a marine current turbine (MCT). Energy from both sources are integrated by a hybrid PTO whose concept is based on a mechanical motion rectifier (MMR). In this study, different working modes are investigated together with switching criteria.Simulations were conducted with hydrodynamic coefficients obtained from computational fluid dynamics analysis and boundary element method. Tank tests were conducted for a HWCEC under co-existing wave and current inputs. For comparison, separate baseline tests of a turbine and a two-body, wave-energy-harvesting sructure, each acting in isolation, are conducted. Experimental results validate the dynamic modeling and show that a HWCEC can increase the output power with a range between 29-87 percent over either current turbine and wave energy converter acting individually, and it can reduce by up to 70 percent the peak-to-average power ratio compared with the wave energy converter on the tested conditions.Such results demonstrate the potential of the HWCEC as an efficient and cost-effective design.

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35

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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36

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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37

Gravråkmo, Halvar. "Buoy Geometry, Size and Hydrodynamics for Power Take Off Device for Point Absorber Linear Wave Energy Converter". Doctoral thesis, Uppsala universitet, Elektricitetslära, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-220344.

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Wave energy converters of point absorber type have been developed and constructed. Full scale experiments have been carried out at sea and electricity has been successfully delivered. Linear permanent magnet generators together with a subsea substation and buoys of various geometric shapes have been investigated theoretically and experimentally. The design has in large extent an electronic approach, keeping the mechanical part of it as simple as possible, due to the long life span and reliability of electric components. Because of the nature of a linear generator, the internal translator with permanent magnets has a limited stroke length which will be reached when the buoy is exposed to large wave heights. Internal springs at the top and bottom of the generator prevent the translator from hitting the generator hull. Inertial forces due to the mass and velocity of the translator and the buoy and its heave added mass compresses the spring. The added mass is a rather large part of the total moving mass. Simulations of a converter with a vertical cylindrical buoy and with a toroidal buoy were conducted, as well as real sea experiments with converters with cylindrical buoys of two different sizes and a toroidal buoy. The overloads are likely to affect the design and service life of the generator, the buoy and the wire which interconnects them. Buoy shapes with as much excitation force as possible and as little heave added mass as possible were sought. A toroidal buoy caused less overloads on the generator at sea states with short wave periods and relatively large wave height, but for sea states with very long wave periods or extremely high waves, the magnitude of the overloads was mainly determined by the maximum displacement of the buoy. Snap loads on the interconnecting wire, as the slack wire tensed up after a very deep wave trough, were found to be greater but of the same order of magnitude as forces during the rest of the wave cycle. During a 4 day period at various wave conditions, two converters with cylindrical buoys proved efficiency between 11.1 % and 24.4 %. The larger buoy had 78 % larger water plane area than the other buoy which resulted in 11 % more power production. Short wave period was beneficial for the power production. Infinite frequency heave added mass was measured for a cylindrical buoy at real sea and found to be greater than the linearly calculated theoretical added mass.

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38

Apotsos, Alex. "Setup in the surfzone". Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/42219.

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Thesis (Ph. D.)--Joint Program in Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering; and the Woods Hole Oceanographic Institution), 2007.
Includes bibliographical references.
Surfzone wave height transformation and wave-breaking-driven increases in the mean sea level (setup) are examined on alongshore-uniform beaches with alongshore homogeneous and inhomogeneous wave forcing. While previously derived models predict wave heights adequately (root-mean-square errors typically less than 20%), the models can be improved by tuning a free parameter or by using a new parameterization based on the deep-water wave height. Based on a sensitivity analysis of the cross-shore momentum balance used to predict setup, a one-dimensional (1-D) model is developed that includes wave rollers and bottom stress owing to the mean offshore-directed flow. The model predicts setup accurately at three alongshore homogeneous field sites, as well as at a site where the incident wave field is alongshore non-uniform, suggesting that setup is driven primarily by the cross-shore (1-D) forcing. Furthermore, alongshore gradients of setup can be important to driving alongshore flows in the surfzone, and the 1-D setup model predicts these gradients accurately enough to simulate the observed flows.
by Alex Apotsos.
Ph.D.

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39

Castellucci, Valeria. "Sea Level Compensation System for Wave Energy Converters". Doctoral thesis, Uppsala universitet, Elektricitetslära, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-295603.

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The wave energy converter developed at Uppsala University consists of a linear generator at the seabed driven by the motion of a buoy on the water surface. The energy absorbed by the generator is negatively affected by variations of the mean sea level caused by tides, changes in barometric pressure, strong winds, and storm surges. The work presented in this doctoral thesis aims to investigate the losses in energy absorption for the present generation wave energy converter due to the effect of sea level variations, mainly caused by tides. This goal is achieved through the modeling of the interaction between the waves and the point absorber. An estimation of the economic cost that these losses imply is also made. Moreover, solutions on how to reduce the negative effect of sea level variations are discussed. To this end, two compensation systems which adjust the length of the connection line between the floater and the generator are designed, and the first prototype is built and tested near the Lysekil research site. The theoretical study assesses the energy loss at about 400 coastal points all over the world and for one generator design. The results highlight critical locations where the need for a compensation system appears compelling. The same hydro-mechanic model is applied to a specific site, the Wave Hub on the west coast of Cornwall, United Kingdom, where the energy loss is calculated to be about 53 %. The experimental work led to the construction of a buoy equipped with a screw jack together with its control, measurement and communication systems. The prototype, suitable for sea level variations of small range, is tested and its performance evaluated. A second prototype, suitable for high range variations, is also designed and is currently under construction. One main conclusion is that including the compensation systems in the design of the wave energy converter will increase the competitiveness of the technology from an economic point of view by decreasing its cost per kWh. The need for a cost-effective wave energy converter with increased survivability emphasizes the importance of the presented research and its future development.

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40

Horko, Michael. "CFD optimisation of an oscillating water column wave energy converter". University of Western Australia. School of Mechanical Engineering, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0089.

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Although oscillating water column type wave energy devices are nearing the stage of commercial exploitation, there is still much to be learnt about many facets of their hydrodynamic performance. This research uses the commercially available FLUENT computational fluid dynamics flow solver to model a complete OWC system in a two dimensional numerical wave tank. A key feature of the numerical modelling is the focus on the influence of the front wall geometry and in particular the effect of the front wall aperture shape on the hydrodynamic conversion efficiency. In order to validate the numerical modelling, a 1:12.5 scale experimental model has been tested in a wave tank under regular wave conditions. The effects of the front lip shape on the hydrodynamic efficiency are investigated both numerically and experimentally and the results compared. The results obtained show that with careful consideration of key modelling parameters as well as ensuring sufficient data resolution, there is good agreement between the two methods. The results of the testing have also illustrated that simple changes to the front wall aperture shape can provide marked improvements in the efficiency of energy capture for OWC type devices.

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41

Wang, Liguo. "Modelling and Advanced Control of Fully Coupled Wave Energy Converters Subject to Constraints: the Wave-to-wire Approach". Doctoral thesis, Uppsala universitet, Elektricitetslära, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-320906.

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Ocean wave energy is a promising renewable source to contribute to supplying the world’s energy demand. The Division of Electricity at Uppsala University is developing a technology to capture energy from ocean waves with a wave energy converter (WEC) consisting of a linear permanent magnet generator and a point absorber. The linear generator is placed on sea bed and is driven directly by the floating absorber. Since March 2006, multiple wave energy converters have been deployed on the Swedish west coast outside the town of Lysekil. The technology is verified by long-term operation during at sea and satisfactory reliability of the electricity generation. This thesis focuses on developing advanced control strategies for fully coupled wave energy converters subject to constraints. A nonlinear control strategy is studied in detail for a single WEC subject to constraints under regular and irregular waves. Besides, two coordinated control strategies are developed to investigate the performance of a wave energy farm subject to constraints. The performance of the WECs using these control strategies are investigated in case studies, and optimal PTO damping coefficients are found to maximize the output power. The results show that these control strategies can significantly improve the performance of the WECs, in terms of mean power, compared to a conventional control. Besides these control strategies, a wave-to-wire simulation platform is built to study the power generation control of the WEC subject to constraints. The wave-to-wire simulation platform allows both nonlinear and linear control force. The results show that there is a good agreement between the desired value and the actual value after advanced control.

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42

Amine, Ramdani Ahmed y Sebastian Rudnik. "Design and Construction of High Current Winding for a Transverse Flux Linear Generator Intended for Wave Power Generation". Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-240366.

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There is currently a high demand for electric power from renewablesources. One source that remains relatively untapped is the motionof ocean waves. Anders Hagnestål has been developing a uniquelyefficient and simplified design for a point-absorb buoy generator byconverting its linear motion directly into alternating electric power usinga linear PM engine. To test this method, a smaller prototype isbuilt. Its characteristics present some unusual challenges in the designand construction of its winding.Devices of this type typically use relatively low voltage (690V typicallyfor a wind turbine, compared to the 10kV range of traditionalpower plants). To achieve high power, they need high current, whichin turn requires splitting the conductors in the winding into isolatedparallel strands to avoid losses due to eddy currents and current crowding.However, new losses from circulating currents can then arise. Inorder to reduce said losses, the parallel conductors should be transposedin such a way that the aggregate electromotive force the circuitsthat each pair of them forms is minimized.This research and prototyping was performed in absence of advancedindustrial means of construction, with limited space, budget,materials, manpower, know-how, and technology. Manual ingenuityand empirical experimentation were required to find a practical implementationfor: laying the cables, fixing them in place, transferringthem to the machine, stripping their coating at the ends and establishinga reliable connection to the current source.Using theoretical derivations and FEM simulation, a sufficientlygood transposition scheme is proposed for the specific machine thatthe winding is built for. A bobbin replicating the shape of the enginecore is built to lay down the strands.The parallel strands are then organized each into their respectivebobbin, with a bobbin rack and conductor funneling device being designedand constructed to gather them together into a strictly-organizedbundle. An adhesive is found to set the cables in place.Problems with maintaining the orientation and configuration of thecables in the face of repeated torsion are met and solved. A chemicalsolution is used to strip the ends of the conductors, and a reliableconnection is established by crimping the conductors into a bi-metalCu-Al lug.ivIn conclusion, the ideal transposition schemes required to cancelout circulating currents due to magnetic flux leakage are impossibleto put in practice without appropriate technological means. The feasibletransposition scheme turns out to be a simple mirroring of conductors’positions, implemented by building each half of the windingseparately around replicas of the core and then connecting them usingcrimping lugs.
Efterfrågan på el från förnybara källor är hög och inget tyder på att det kommer ändras den närmsta tiden. En källa till förnybar el som än idag står relativt orörd är den där man använder energin från havsvå- gor. Det är denna förnybara källa Anders Hagnestål haft i åtanke när han nu bygger en unikt effektiv generator med syftet att i ett senare skede utvinna el med hjälp av flytande punktabsorberande vågkraft- system. Generatorn är av den linjära typen och omvandlar det punk- tabsorberande systemet rörelse till el. För att testa denna generator- modell så påbörjades bygget av två fullskaliga prototyper 2017. Denna uppsats behandlar specifikt arbetet med generatorlindningen till pro- totyperna och innefattar processen från design till själva byggnatio- nen. Lindingen består av flertalet mindre och isolerade lindningsleda- re med uppgift att bland annat minska skinneffekt och virvelströms- förluster. När man använder denna metod så uppkommer dock ett nytt problem vilket härstammar från att lindningsledarna är samman- kopplade i vardera ända och bildar på så sätt n slutna strömkretsar. Konsekvensen kan vara stora förluster från cirkulerande strömmar på grund av det magnetiska ströflöde som finns runt järnkärnan som lindningen omsluter. Utgångspunkten för att minimera dessa cirkule- rande strömmar är att transponera alla lindningsledare på ett sätt så att den resulterande elektromotoriska spänningen för varje strömkrets blir så liten som möjligt. Med hjälp av förenklade modeller samt FEM simuleringar så bestämdes ett lämpligt sätt att transponera lindningstrådarna utifrån oli- ka kriterier. Lösningen blev att lindningstrådarna endast transponera- des en gång med en så kallad 180 grader transponering. Detta ger en tillräckligt god minimering av de cirkulerande ström- marna, men den stora fördelen med denna lösning är att det är möjligt att linda maskinen med de små resurser projektet hade tillgång till, dock var detta till en stor nackdel då väldigt mycket tid gick till att hitta egna tillvägagångsätt för att utföra byggandet av lindningen på ibland okonventionella sätt.

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43

Roc, Thomas. "Numerical modelling for hydrodynamic impact and power assessments of tidal current turbine arrays". Thesis, University of Plymouth, 2013. http://hdl.handle.net/10026.1/1557.

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Channel constrictions in which strong currents are mainly driven by tidal processes represent sites with high potential for harvesting renewable and predictable tidal stream energy. Tidal Current Turbines (TCTs) deployed in arrays appear to be the most promising solution to efficiently capturing this carbon neutral energy resource. However to ensure the sustainable character of such projects, the balance between power extraction maximization and environmental impact minimization must be found so that device layout optimization takes into account environmental considerations. This is particularly appropriate since both resource and impact assessments go intrinsically hand in hand. The present method proposes the use and adaptation of ocean circulation models as an assessment tool framework for tidal current turbine (TCT) array-layout optimization. By adapting both momentum and turbulence transport equations of an existing model, the present TCT representation method is proposed to extend the actuator disc concept to 3-D large scale ocean circulation models. Through the reproduction of physical experiments to reasonable accuracy, grid and time dependency tests and an up-scaling exercise, this method has shown its numerical validity as well as its ability to simulate accurately both momentum and turbulent turbine-induced perturbations in the wake. These capabilities are demonstrated for standalone devices and device arrays, and are achieved with a relatively short period of computation time. Consequently the present TCT representation method is a very promising basis for the development of a TCT array layout optimization tool. By applying this TCT representation method to realistic cases, its capability is demonstrated for power capture assessment and prediction of hydrodynamic interactions as would be required during the layout deployment optimization process. Tidal energy has seen considerable development over the last decade and the first commercial deployments are likely to take place within the next 5 years. It is hoped that this new tool and the numerical approaches described herein will contribute to the development of TCT array power plants around the world.

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44

McNatt, J. Cameron. "Wave field patterns generated by wave energy converters". Thesis, 2012. http://hdl.handle.net/1957/33939.

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The eventual deployment of wave energy converters (WECs) on a commercial scale will necessitate the grouping of devices into arrays or "wave farms," in order to minimize overhead costs of mooring, maintenance, installation, and electrical cabling for shoreward power delivery. Closely spaced WECs will interact hydrodynamically through diffracted and radiated waves. Recent research has focused on the WEC wave field and used its structures to design constructive WEC arrays as well as to describe the means of WEC energy absorption. In this study, the WEC wave field is investigated for a single WEC and a five WEC array with linear wave theory and experimental results. Both regular waves and spectral seas are considered. Computational results are produced with the linear boundary-element-method (BEM) hydrodynamic software WAMIT for a simple WEC geometry. Experimental data comes from WEC array tests that took place at Oregon State University over the winter of 2010-11 [1]. The experimental measurements help validate the computational modeling, and the computational models serve as an aid to interpreting the experimental data. Results reveal two universal WEC wave field features - partially standing waves and a wave shadow, both of which are the result of the coherent interaction of the planar incident wave with the circular generated wave, composed of the diffracted and radiated waves. The partial standing waves in the offshore are seen qualitatively in experimental data but could not be exactly reproduced computationally, because the computational model is only a simple representation of the physical model. In the lee of the WEC, the measured longshore structure of the wave shadow is in good agreement with theoretical expectations as well as computational results. It is believed that the agreement is because the formation of the wave shadow is dominated by energy extraction, which was approximately the same for both the computational and physical models. A study of the linear WEC wave field in regular waves and spectral seas reveals patterns such as the wave shadow that have also been found in experimental data. The positions and magnitudes of the offshore partially standing waves are very sensitive to wavelength, and WEC geometry, motions and location, and in spectral seas, they are smoothed when considering significant wave height. All of which suggest that it may be difficult to use them advantageously in the design of WEC arrays. The wave shadow is a dominant feature of the WEC wave field for both regular waves and spectral seas. It appears to be fairly generic and to be based on power absorption. In the design of WEC arrays, rather than attempting constructive interference by using standing wave crests, perhaps the best one can do is to avoid destructive interference of the wave shadow.
Graduation date: 2013

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45

Senapati, Debashis y Rahul Singh. "Harnessing of Wave Power from Horizontal Flow Dynamics of Shallow Waves". Thesis, 2009. http://ethesis.nitrkl.ac.in/298/1/dev_rahul.pdf.

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Harnessing Ocean Wave power is a potential source of renewable form of energy. Our project was aimed at finding the constraints and proposing a suitable solution to utilize this form of energy. Ocean Wave Power is the most predictable, periodic and concentrated source among all renewable sources, but the constraints imposed on its harnessing are a result of its Ocean environment. Ocean wave dissipates energy in several strata of circular oscillation. But with depth induced water pressure these circular oscillation are squished into ellipse that approximates to back & forth motion. Statistically the horizontal oscillation shares the 68% of energy spectrum of wave energy. But due to irregular flow and variable pressure conventional hydropower harnessing techniques become improbable. In our project we have proposed a simple solution that takes the direct advantage of utilizing this energetic horizontal momentum of ocean waves, without in between conversion. In our project we have delved into finding the relevant parameters that govern the functioning of our device. Through the Spectral Analysis of Ocean Waves we have estimated the rate of input power and optimized the dimensions of our device to maximize its output. Finally we have tried to chart its efficiency along conventional lines. Our project has worked to realize a novel idea and model it on relevant information.

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46

Porter, Aaron K. "Laboratory observations and numerical modeling of the effects of an array of wave energy converters". Thesis, 2012. http://hdl.handle.net/1957/33928.

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This thesis investigates the effects of wave energy converters (WECs) on water waves through the analysis of extensive laboratory experiments, as well as subsequent numerical simulations. Data for the analysis was collected during the WEC-Array Experiments performed at the O.H. Hinsdale Wave Research Laboratory at Oregon State University, under co-operation with Columbia Power Technologies, using five 1:33 scale point-absorbing WECs. The observed wave measurement and WEC performance data sets allowed for a direct computation of power removed from the wave field for a large suite of incident wave conditions and WEC array sizes. To numerically represent WEC effects the influence of the WECs upon the wave field was parameterized using the power absorption data from the WECs. Because a large driver of the WECs influence on the wave field is absorbed wave power by the WEC, it is reasonable to attempt a parameterization based on this process. It was of interest as to whether this parameterization, which does not account for wave scattering among other physics, could provide a good estimate of far-field effects. Accurately predicting WEC-array effects in the far-field requires empirical validation. Previous WEC analysis and modeling studies had limited data available for model verification, and additionally had used idealized WEC performance. In the present work we develop a WEC-array parameterization for use in phase-averaged wave models (e.g. SWAN). This parametrization only considers the wave absorption effects of the WECs and the model predictions of far-field effects are compared to observations. Further testing of the SWAN model was performed against a phase-resolving model, WAMIT, to determine the significance of physics the WEC absorption parameterization does not capture, such as scattered waves. Considering the complexity of the problem, the parameterization of WECs by only power absorption is a reasonable predictor of the effect of WECs on the far field.
Graduation date: 2013

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47

Thomas, Giles(Giles Anthony). "Wave slam response of large high-speed catamarans". Thesis, 2003. https://eprints.utas.edu.au/22112/1/whole_ThomasGilesAnthony2003_thesis.pdf.

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The rapid evolution of high-speed sea transportation has led to the development of large, fast, lightweight vessels. The structural design optimisation of such vessels requires knowledge of the effect of sea loads on their structure. Of particular importance for high-speed catamarans are severe wet-deck slam events, which can impart a large global load onto a vessel's structure and as a consequence cause significant structural damage. The dynamic whipping response of the structure may also be important by making a significant contribution to fatigue damage. Extensive full-scale hull stress, motion and wave measurements were conducted on two Incat high-speed catamaran ferries. A definition of a slam event, for these vessels, was proposed and used to identify slam events from the data records. The character and effects of these slamming events are investigated with respect to a number of factors. Slam events were found to produce bending moments up to 700% of the largest underlying global wave loads. The data from the full-scale slam events, including an extreme slam event that caused extensive structural damage, was used in conjunction with finite element modelling to develop a realistic quasi-static slam loading scenario for structural design purposes. This slam load case gives a maximum bending moment approximately 16% greater than that stipulated by classification society Det Norske Veritas, with a greater bias towards the bow of the vessel. A method for scaling the design load case for use with new designs is also proposed. A technique for predicting the mode shape and frequency of the whipping behaviour utilising finite element analysis including the fluid-structure interaction is presented. The hydrodynamic added mass of the surrounding fluid was calculated using a two-dimensional panel method for a range of speeds. The calculated whipping modes are then compared favourably with those found through the full-scale measurements and exciter experiments. The exciter experiments were conducted on two vessels with the anchors being dropped and instantaneously arrested to excite the vessels' first longitudinal mode of vibration. The level of damping of the whipping behaviour is investigated through the full-scale results and exciter experiments. Methods for evaluating the various hydrodynamic components which constitute the damping are also presented including wavemaking damping, viscous damping and acoustic damping. It is concluded that structural damping is the dominant damping component. Fatigue life estimates, utilising full-scale slam data and derived whipping behaviour information, were conducted which found that slamming and whipping behaviour have a large influence on fatigue life. Finally, knowledge of the dynamic slamming response was utilised to develop a dynamic extreme slam design load case. This dynamic load case more realistically simulates the dynamic structural response of the vessel to a slam. It is the core component of a new practical methodology for the structural design of large high-speed catamarans for slamming.

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48

Lorang, Mark. "Wave competence and morphodynamics of boulder and gravel beaches". Thesis, 1997. http://hdl.handle.net/1957/27300.

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49

Chan, Tak yin Taky. "Protection of wave power generating system". Thesis, 2004. https://vuir.vu.edu.au/17913/.

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Ocean Power Technology Project is an innovative technology for generating green energy at low cost, with minimum pollution and producing electrical power from enormous quantities of dependable renewable energy which is available throughout the world in abundance in the form of ocean waves. An experimental 20kW power system project using Ocean Wave Technology has been build by Powercor Australia at Portland Victoria. This experimental power system consists of a permanent magnet generator, step up and down transformers, submarine cables and a set of inverters and together it supplies 2 0 k W for the loads that is mainly connected to the remote area power system. This research project has been generated to analyse and develop the protection of variable frequency A C systems. Design and simulations are carried out on a computer using M A T L A B algorithmic language software package and Power System Blockset. The mathematical model comprises of permanent magnet generator SIMULINK model, transmission lines, transformers, rectifiers, load buses, etc. The simulation made is to investigate the behaviour of the system during steady state, low and high load simulation is made to investigate the maximum possible output of the generators under overload conditions and fault studies. Consequently, the simulation is obtained by using a set of characteristic of parameters of protection system in order to implement it on a microprocessor based circuit breaker.

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50

Hiles, Clayton E. "On the use of computational models for wave climate assessment in support of the wave energy industry". Thesis, 2010. http://hdl.handle.net/1828/3648.

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Effective, economic extraction of ocean wave energy requires an intimate under- standing of the ocean wave environment. Unfortunately, wave data is typically un- available in the near-shore (<150m depth) areas where most wave energy conversion devices will be deployed. This thesis identities, and where necessary develops, ap- propriate methods and procedures for using near-shore wave modelling software to provide critical wave climate data to the wave energy industry. The geographic focus is on the West Coast of Vancouver Island, an area internationally renowned for its wave energy development potential. The near-shore computational wave modelling packages SWAN and REF/DIF were employed to estimate wave conditions near-shore. These models calculate wave conditions based on the off-shore wave boundary conditions, local bathymetry and optionally, other physical input parameters. Wave boundary condition were sourced from theWaveWatchIII off-shore computational wave model operated by the National Oceanographic and Atmospheric Administration. SWAN has difficulty simulating diffraction (which can be important close to shore), but is formulated such that it is applicable over a wide range of spatial scales. REF/DIF contains a more exact handling of diffraction but is limited by computational expense to areas less than a few hundred square kilometres. For this reason SWAN and REF/DIF may be used in a complementary fashion, where SWAN is used at an intermediary between the global-scale off-shore models and the detailed, small scale computations of REF/DIF. When operating SWAN at this medium scale a number of other environmental factors become important. Using SWAN to model most of Vancouver Island's West Coast (out to the edge of the continental shelf), the sensitivity of wave estimates to various modelling param- eters was explored. Computations were made on an unstructured grid which allowed the grid resolution to vary throughout the domain. A study of grid resolution showed that a resolution close to that of the source bathymetry was the most appropriate. Further studies found that wave estimates were very sensitive to the local wind condi- tions and wave boundary conditions, but not very sensitive to currents or water level variations. Non-stationary computations were shown to be as accurate and more computationally efficient than stationary computations. Based on these findings it is recommended this SWAN model use an unstructured grid, operate in non-stationary mode and include wind forcing. The results from this model may be used directly to select promising wave energy development sites, or as boundary conditions to a more detailed model. A case study of the wave climate of Hesquiaht Sound, British Columbia, Canada (a small sub-region of the medium scale SWAN model) was performed using a high resolution REF/DIF model. REF/DIF was used for this study because presence of a Hesquiaht Peninsula which has several headlands around which diffraction was thought to be important. This study estimates the most probable conditions at a number of near-shore sites on a monthly basis. It was found that throughout the year the off-shore wave power ranges from 7 to 46kW/m. The near-shore typically has 69% of the off-shore power and ranges from 5 to 39kW/m. At the near-shore site located closest to Hot Springs Cove there is on average 13.1kW/m of wave power, a significant amount likely sufficient for wave power development. The methods implemented in this thesis may be used by groups or individuals to assess the wave climate in near-shore regions of the West Coast of Vancouver Island or other regions of the world where wave energy extraction may be promising. It is only with detailed knowledge of the wave climate that we can expect commercial extraction of wave energy to commence.
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