Tesi sul tema "Wave energy"
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1
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.
Testo completoAbstract (sommario):
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.
2
Guerrero, Felipe Martinez. "Development of a wave energy basin to maximize wave energy conversion". Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/20241.
Testo completo
3
O'Boyle, Louise. "Wave fields around wave energy converter arrays". Thesis, Queen's University Belfast, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.602715.
Testo completoAbstract (sommario):
Wave energy converters, by their nature, extract large amounts of energy from incident waves. If the industry is to progress such that wave energy becomes a significant provider of power in the future, large wave farms will be required. Presently, consenting for these sites is a long and problematic process, mainly due to a lack of knowledge of the potential environmental impacts. Accurate numerical modelling of the effect of wave energy extraction on the wave field and subsequent evaluation of changes to coastal processes is therefore required. Modelling the wave field impact is also necessary to allow optimum wave farm configurations to be determined. This thesis addresses the need for more accurate representation of wave energy converters in numerical models so that the effect on the wave field, and subsequently the coastal processes, may be evaluated. Using a hybrid of physical and numerical modelling (MIKE21 BW and SW models) the effect of energy extraction and operation of a WEC array on the local wave climate has been determined. The main outcomes of the thesis are: an improved wave basin facility, in terms of wave climate homogeneity, reducing the standard deviation of wave amplitude by up to 50%; experimental measurement of the wave field around WEC arrays, showing that radiated waves account for a significant proportion of the wave disturbance; a new representation method of WECs for use with standard numerical modelling tools, validated against experimental results. The methodology and procedures developed here allow subsequent evaluation of changes to coastal processes and sediment transport due to WEC arrays.
4
Sun, Haili. "Ray-tracing internal wave/wave interactions and spectral energy transfer /". Thesis, Connect to this title online; UW restricted, 1997. http://hdl.handle.net/1773/10973.
Testo completo
5
Mackay, Edward B. L. "Wave energy resource assessment". Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/79448/.
Testo completoAbstract (sommario):
The use of satellite altimeter data for spatial mapping of the wave resource is examined. A new algorithm for estimating wave period from altimeter data is developed and validated, which enables estimates of wave energy converter (WEC) power to be derived. Maps of the long-term mean WEC power from altimeter data are of a higher spatial resolution than is available from global wave model data. They can be used for identifying promising wave energy locations along particular stretches of coastline, before a detailed study using nearshore models is undertaken. The accuracy of estimates of WEC power from wave model data is considered. Without calibration estimates of the mean WEC power from model data can be biased of the order of 10-20%. The calibration of wave model data is complicated by non-linear dependence of model parameters on multiple factors, and seasonal and interannual changes in biases. After calibration the accuracy in the estimate of the historic power production at a site is of the order of 5%, but the changing biases make it difficult to specify the accuracy more precisely. The accuracy of predictions of the future energy yield from a WEC is limited by the accuracy of the historic data and the variability in the resource. The variability in 5, 10 and 20 year mean power levels is studied for an area in the north of Scotland, and shown to be greater than if annual power anomalies were uncorrelated noise. The sensitivity of WEC power production to climate change is also examined, and it is shown that the change in wave climate over the life time of a wave farm is likely to be small in comparison to the natural level of variability. It is shown that despite the uncertainty related to variability in the wave climate, improvements in the accuracy of historic data will improve the accuracy of predictions of future WEC yield. The topic of extreme wave analysis is also considered. A comparison of estimators for the generalised Pareto distribution (GPD) is presented. It is recommended that the Likelihood-Moment estimator should be used in preference to other estimators for the GPD. The use of seasonal models for extremes is also considered. In contrast to assertions made in previous studies, it is demonstrated that non-seasonal models have a lower bias and variance than models which analyse the data in separate seasons.
6
Nikonov, M. "Energy resources: wave power". Thesis, Sumy State University, 2017. http://essuir.sumdu.edu.ua/handle/123456789/62834.
Testo completoAbstract (sommario):
The topic of renewable energy is an evergreen subject, especially, in a world dominated by fossil fuels. Renewable energy is widely discussed in the contemporary world because it is unlimited, which means it’s sustainable and does not emit greenhouse gasses that are harmful to the environment and human life. A classic example of renewable energy is wave energy.
7
Larsson, Petter, e Gustaf Rudbeck. "Wave Energy Concept Benchmarking". Thesis, KTH, Maskinkonstruktion (Inst.), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-298841.
Testo completoAbstract (sommario):
Denna rapport ämnar undersöka de vanligast förekommande typerna av teknologier för vågkraftverk (eng. Wave Energy Converter, WEC) teknologier för att jämföra de olika konceptens förmåga att absorbera vågenergi. Koncept som undersöks är punktabsorbatorer och oscillerande vattenkolumner. I denna rapport används de vanligt använda engelska översättningarna point absorber och oscillating water column (OWC). Beräkningar görs för de olika koncepten i liknande vågförhållanden för att kunna jämföra den energi som kan utvinnas. I rapporten sker beräkningar under optimala vågförhållanden. Vågorna antas vara linjära och vågkraftverken antas vara i fas med vågens svängningsrörelse. Den vågdata som använts är uppmätt utanför Belmullet i Irland. Beräkningar görs på vågor med en signifikant våghöjd på 1,25 m och en periodtid på 7,5 s. Det görs även beräkningar på den största uppmätta förekommande vågen. I huvudsak används effektberäkningar enligt en modell som Kjell Budal. Syftet är att grafiskt och numeriskt jämföra den teoretiska och faktiska maxeffekt som kan utvinnas ur respektive våg. Resultatet från undersökningen visar att den största bidragande faktorn till en hög energiutvinning beror på bojens volym. Volymen måste anpassas för de vågförhållanden som finns där bojen ska placeras.Vid beräkningar av en OWC med tvärsnittsarea på 19 m2 visar det sig att den effekt som kan utvinnas av en luftkammare med tillhörande turbin är ungefär 10 kW, 1/30 av de 300kW som kan utvinnas av en point absorber. En OWC består dock sällan utav en ensam luftkammare utan ofta i en array med ett flertal luftkammare med separata turbiner för att öka effekten.This report intends to examine the most common types of wave energy converter technologies to compare the different concepts' ability to absorb wave energy. Concepts being investigated are point absorbers and oscillating water columns (OWC). Calculations are made for the different concepts in the same wave conditions to be able to compare the energy that can be extracted. In the report, calculations are made under optimal wave conditions. The waves are assumed to be linear and the wave energy converter is assumed to be in phase with the oscillating motion of the wave. The wave data used is measured outside Belmullet in Ireland. Calculations are made on waves with a significant wave height of 1.25 m and a period time of 7.5 s. Calculations are also made on the largest measured wave present. In essence, power calculations are used according to a model developed by Kjell Budal and with the help of this be able to graphically and numerically compare the theoretical and actual maximum power that can be extracted from each scale. The results from the survey show that the largest contributing factor to high energy recovery is due to the volume of the buoy. The volume must be adapted to the wave conditions that exist where the buoy is to be placed.When calculating an OWC with a cross sectional area of 19 m2, it turns out that the power that can be extracted from an air chamber with an associated turbine is approximately 10 kW, 1/30 of the 300 kW that can be extracted by one point absorber. However, an OWC rarely consists of a single air chamber but often in a construction with several air chambers with separate turbines to increase the power.
8
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.
Testo completoAbstract (sommario):
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.
9
Lavidas, George. "Wave energy resource modelling and energy pattern identification using a spectral wave model". Thesis, University of Edinburgh, 2016. http://hdl.handle.net/1842/25506.
Testo completoAbstract (sommario):
The benefits of the Oceans and Seas have been exploited by societies for many centuries; the marine offshore and naval sectors have been the predominant users of the waters. It has been overlooked until recently, that significant amounts of energy can be harnessed by waves, providing an additional abundant resource for renewable energy generation. The increasing energy needs of current societies have led to the consideration of waves as an exploitable renewable resource. During the past decades, advancements have been made towards commercialising wave energy converters (WECs), though significant knowledge gap exists on the accurate estimation of the potential energy that can be harnessed. In order, to enhance our understanding of opportunities within wave energy highly resolved long-term resource assessment of potential sites are necessary, which will allow for not only a detailed energy estimation methodology but also information on extreme waves that are expected to affect the survivability and reliability of future wave energy converters. This research work aims to contribute the necessary knowledge to the estimation of wave energy resources from both highly energetic and milder sea environment, exhibiting the opportunities that lay within these environments. A numerical model SWAN (Simulating WAves Nearshore), based on spectral wave formulation has been utilised for wave hindcasting which was driven by high resolution temporal and spatially varying wind data. The capabilities of the model, allow a detailed representation of several coastal areas, which are not usually accurately resolved by larger ocean models. The outcome of this research provides long-term data and characterisation of the wave environment and its extremes for the Scottish region. Moreover, investigation on the applicability of wave energy in the Mediterranean Sea, an area which was often overlooked, showed that wave energy is more versatile than expected. The outcomes provide robust estimations of extreme wave values for coastal waters, alongside valuable information about the usage of numerical modelling and WECs to establish energy pattern production. Several key tuning factors and inputs such as boundary wind conditions and computational domain parameters are tested. This was done in a systematic way in order to establish a customized solution and detect parameters that may hinder the process and lead to erroneous results. The uncertainty of power production by WECs is reduced by the introduction of utilization rates based on the long-term data, which include annual and seasonal variability. This will assist to minimize assumptions for energy estimates and financial returns in business plans. Finally, the importance of continuous improvements in resource assessment is stressed in order to enhance our understanding of the wave environment.
10
Gotthardsson, Björn. "Analysis and Evaluation of the Wavebox Wave Energy Converter". Thesis, Uppsala universitet, Elektricitetslära, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-149364.
Testo completoAbstract (sommario):
Increasing attention to climate change in combination with ever-growing energy consumption worldwide has boosted the demand for new green energy sources. Wave power is developing in many different branches to become part of the new era of electricity production. This thesis deals with a wave power system in its primary stages of development. The system was investigated in order to estimate its potential to produce electric power from sea waves. It is a system consisting of a moored buoy to which the energy is transferred when the wave tilts the buoy in the pitch direction. Due to the increased pitch angle, an amount of liquid contained inside the buoy is allowed to flow via ramps to an upper container, from where it flows down through a hydroelectric turbine. A computer program was used to calculate the properties of the buoy in sea waves. Another program was written in MATLAB to simulate the movements in sea waves and from a set of given parameters calculate the power output. A brief economic study was made to determine if the power output was large enough for the concept to be of financial interest to any future investors. The results show that the wave power system produced 0.9 kW in a wave climate equal to that off the coast of Hanstholm, Denmark, and 1.6 kW in a wave climate off the coast of San Diego, USA. The economic study shows that the power output needed to be improved by a factor of at least five to have a chance of being economically viable. A number of enhancements were suggested to increase the power output of the system, and further investigation could be of use to improve the concept. The created computer simulation model, as well as the results in this thesis could be valuable in any future research on the concept.
11
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.
Testo completo
12
Sjökvist, Linnea. "Wave Loads and Peak Forces on Moored Wave Energy Devices in Tsunamis and Extreme Waves". Doctoral thesis, Uppsala universitet, Elektricitetslära, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-328499.
Testo completoAbstract (sommario):
Surface gravity waves carry enormous amounts of energy over our oceans, and if their energy could be harvested to generate electricity, it could make a significant contribution to the worlds power demand. But the survivability of wave energy devices in harsh operating conditions has proven challenging, and for wave energy to be a possibility, peak forces during storms and extreme waves must be studied and the devices behaviour understood. Although the wave power industry has benefited from research and development in traditional offshore industries, there are important differences. Traditional offshore structures are designed to minimize power absorption and to have small motion response, while wave power devices are designed to maximize power absorption and to have a high motion response. This increase the difficulty of the already challenging survivability issue. Further, nonlinear effects such as turbulence and overtopping can not be neglected in harsh operating conditions. In contrast to traditional offshore structures, it is also important to correctly account for the power take off system in a wave energy converter (WEC), as it is strongly coupled to the devices behaviour. The focus in this thesis is the wave loads and the peak forces that occur when a WEC with a limited stroke length is operated in waves higher than the maximum stroke length. The studied WEC is developed at Uppsala University, Sweden, and consists of a linear generator at the seabed that is directly driven by a surface buoy. A fully nonlinear CFD model is developed in the finite volume software OpenFOAM, and validated with physical wave tank experiments. It is then used to study the motion and the forces on the WEC in extreme waves; high regular waves and during tsunami events, and how the WECs behaviour is influenced by different generator parameters, such as generator damping, friction and the length of the connection line. Further, physical experiments are performed on full scale linear generators, measuring the total speed dependent damping force that can be expected for different loads. The OpenFOAM model is used to study how the measured generator behaviour affects the force in the connection line.
13
Feng, Zhe. "Control of wave energy converters". Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/27048.
Testo completoAbstract (sommario):
In this thesis, two types of control problems related to wave energy converters are studied. The first type of control problem is active force control. We propose a simple optimal control problem formulation for which, in theory, there is no convexity guarantee. However, we demonstrate that the discretized large-scale nonlinear programming (NLP) problem can be convex and that the convexity is related only to the system parameters and is independent from the excitation force and current state. This important feature implies that we are always able to choose a set of system parameters off-line so that, for the online closed-loop implementation, all the optimization problems are convex. In practice, for a large range of parameter sets, the resulting optimization problems are convex. The second one is known to the wave energy community as passive control. In particular, latching, declutching and latching-declutching control. We propose a unified model based on a hybrid system (a mix of discrete event and continuous-time system) for these passive control implementations. With our model, we formulate the latching-declutching control problem as a small dimensional discrete optimization problem, where the only decision variables are the bounds on the latching time and power-take-off (PTO)-active time. Based on the specific problem we have, we propose a coordinate-search algorithm, which is one of the directional direct search algorithm. The algorithm is able to efficiently solve small dimensional problems with discrete decision variables. We study derivative-free optimization algorithms and reveal a sufficient convergence condition for general directional direct search algorithms. The condition is the formalization of the intuition that: if the search directions intersect the sub-level sets, then any directional direct search algorithm should converge. We illustrate that this is not always true and regularity conditions must be added. Examples are given in order to show some interesting cases. State constraints are rarely discussed for declutching control. In the last part of the thesis we propose a formulation which is able to incorporate state constraints. The formulation results in a mixed-integer nonlinear optimal control problem, which is very hard to solve. Based on a technique known as variable time transform, we are able to reformulate the mixed-integer nonlinear optimal control problem into a large-scale nonlinear programming (NLP) problem. The transformed NLP problem can be solved efficiently by NLP solvers, such as interior point method used in IPOPT.
14
Garnaud, Xavier. "Wave Energy Extraction from buoys". Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/50603.
Testo completoAbstract (sommario):
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2009.Includes bibliographical references (p. 187-190).
Different types of Wave Energy Converters currently tested or under development are using the vertical movement of floating bodies to generate electricity. For commercial applications, arrays have to be considered in order to produce a significant power. In this thesis, we investigate the interaction between floating buoys from an hydrodynamic point of view. The objective is to derive general features of energy extraction without resorting to direct numerical simulation by applying the method of homogenization. After reviewing characteristic aspects of power extraction from a single oscillating body, we study a first configuration where many small buoys are placed close to each other. We show that a collection of point absorbers extract more energy than a single big buoy and that the bandwidth is wider. We also show that multiple scales analysis allows to treat radiation problems, and that if the incoming wave length is a multiple of the spacing between buoys, energy extraction can be reduced in a very significant way due to a very strong reflection, which prevents the wave from traveling inside the array.
by Xavier Garnaud.
S.M.
15
Du, Plessis Jacques. "A hydraulic wave energy converter". Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/19950.
Testo completoAbstract (sommario):
Thesis (MScEng)--Stellenbosch University, 2012.ENGLISH ABSTRACT: As a renewable energy source, wave energy has the potential to contribute to the increasing global demand for power. In South Africa specifically, the country’s energy needs may easily be satisfied by the abundance of wave energy at the South-West coast of the country. Commercially developing and utilizing wave energy devices is not without its challenges, however. The ability of these devices to survive extreme weather conditions and the need to achieve cost-efficacy while achieving high capacity factors are but some of the concerns. Constant changes in wave heights, lengths and directions as well as high energy levels and large forces during storm conditions often lead to difficulties in keeping the complexity of the device down, avoiding over-dimensioning and reaching high capacity factors. The point absorber device developed as part of this research is based on an innovation addressing the abovementioned issues. An approach is followed whereby standard "offthe- shelf" components of a proven hydraulics technology are used. The size of the device is furthermore adaptable to different wave climates, and the need for a control system is not necessary if the design parameters are chosen correctly. These characteristics enable low complexity of the device, excellent survivability and an exceptionally high capacity factor. This may lead to low capital as well as low operationand maintenance costs. In this paper the working principle of this concept is presented to illustrate how it utilises the available wave energy in oceans. The results obtained from theoretical tests correlate well with the experimental results, and it is proven that the device has the ability to achieve high capacity factors. As the device makes use of existing, "off-the-shelf" components, cost-efficient energy conversion is therefore made feasible through this research.
AFRIKAANSE OPSOMMING: As ’n hernubare/ herwinbare energiebron bied golfenergie die potensiaal om by te dra tot die bevrediging van die stygende globale energie-navraag. In spesifiek Suid-Afrika kan die oorvloed van beskikbare golfenergie aan die Suid-Weskus van die land gebruik word om aan die land se energiebehoeftes te voldoen. Betroubaarheid en oorlewing in erge weerstoestande, koste-effektiwiteit en die behaal van hoë kapasiteitsfaktore is beduidende struikelblokke wat oorkom moet word in die poging om ’n golfenergie-omsetter wat kommersieël vervaardig kan word, te ontwikkel. Daarby dra voortdurende veranderings in golfhoogtes, -lengtes en -rigtings sowel as hoë energievlakke en groot kragte tydens storms by to die feit dat dit moeilik is om die kompleksiteit van die stelsel laag te hou. Dit terwyl daar voorkom moet word dat die toestel oorontwerp en verhoed word dat hoë kapsiteitsfaktore bereik word. Die puntabsorbeerder-toestel wat in hierdie navorsing ontwikkel is, bestaan uit ’n ontwerp wat spesifiek ontwikkel is om die bogenoemde probleme aanspreek. ’n Unieke benadering is gevolg waardeur standaard, maklik-bekombare komponente gebruik is en die komponent-groottes ook aangepas kan word volgens golfgroottes. Indien die ontwerpsdimensies akkuraat gekies word, is die moontlikheid verder goed dat ’n beheerstelsel nie geïmplementeer hoef te word nie. Hierdie eienskappe verseker lae stelselkompleksiteit, uitstekende oorlewingsvermoë en ’n uitstaande kapasiteitsfaktor. Lae kapitaal- sowel as onderhoudskostes is dus moontlik. Die doel van hierdie dokument is om die werking van die konsep voor te stel en teoreties sowel as prakties te evalueer. Die resultate van teoretiese toetse stem goed ooreen met eksperimentele resultate, en dit is duidelik dat die toestel hoë kapasiteitsfaktore kan behaal. Aangesien die toestel verder gebruik maak van bestaande komponente wat alledaags beskikbaar is, word die koste-effektiewe omsetting van golfenergie dus moontlik gemaak deur hierdie navorsing.
16
ESPING, JONATAN. "Bearings in Wave Energy Converters". Thesis, KTH, Skolan för industriell teknik och management (ITM), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-299281.
Testo completoAbstract (sommario):
Wave energy and wave energy converters is a fast rapidly developing field of research and energy harvesting. In recent years, more and more designs have seen operational success, and more and more are in development. Wave energy converters face a challenge not properly explored until recently, high loaded, oscillating motion in a highly hostile environment. Which poses a multitude of challenges ranging from contact fatigue to corrosion wear. However, this field is still in early development, seeing little to no research published about it. This work intends to inform about the challenges these wave energy designs pose in tribology and more specifically to bearings, through a literature study and review. The review establishes a rating for different bearing designs based on how applicable a certain bearing selection would be based on available research. Reaching the conclusion that whilst currently inappropriate to employ, seawater lubricated bearings could reach commercial viability in the future for wave energy devices. Additionally, with the help of excellent sealing solutions and well conducted lubrication regimes, both sliding bearings and rolling element bearings have their advantages and disadvantages and can make use of a multitude of different materials.Vågkraft och vågkraftsgeneratorer är ett område som växer snabbt i intresse för både forskning och produktutveckling. På senare år har fler och fler vågkraftsgeneratorer och designer för dessa sett framgång i prototyptester och flera är på fortsatt utveckling. Vågkraftsgeneratorer står inför flera utmaningar, med de sammansatta faktorerna av en väldigt korrosiv miljö, höga krafter och oscillerande rörelse. Vilket stället flera krav på designers på allt ifrån korrosionsskydd till materialkunskap krig utmattning av maskinkomponenter. Dessvärre finns ytterst lite noga dokumenterad forskning kring området då det är en väldigt ung bransch. Denna rapport söker att utforska och informera kring de utmaningar som kan ställas på vågkraftsgeneratorer inom specifikt tribologi och specifikt för lager och lagerval. Arbetet fokuserar på en litteraturstudie över de möjliga utmaningarna området skapar. Grundat på relevant forskning inom liknande områden betygsattes ett urval av lagerval för vågkraftsgeneratorer. Där slutsatserna pekar på att då det möjligtvis är olämpligt i nuvarande läge att nytta saltvatten som smörjningsmedel, i framtiden kan detta bli en kommersiell verklighet. Där både glidlager och rullningslager har sina fördelar och nackdelar inom applikationen, med noga valda materialkombinationer, smörjningsmedel och tätningar.
17
Salar, Dana. "Miniature Wave Energy Converter (WEC)". Thesis, Uppsala universitet, Institutionen för teknikvetenskaper, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-366760.
Testo completoAbstract (sommario):
Abstract In this project, I present a design of a scale model of a linear generator (LG) similar to a full size Wave Energy Converter (WEC) being developed at Uppsala University since 2002 and commercialized by Seabased AB. The purpose of a WEC is to convert the energy from ocean waves into electrical energy. In order to implement the behaviour of the prototype design, a preliminary study has been done to further build it for use in education, laboratory tests and research. The challenge with this project is to scale down the WEC but maintain the shape, appearance and characteristics of the generator for educational purposes. A miniature version of a WEC, previously developed by Uppsala University in collaboration with Seabased Industry AB, has been designed with scaling rate 1:14 of the linear dimensions. In this case, the value of the output power is not important- it has simply been calculated. The electrical rated parameters of the three phase generator are power 26 W, peak line-line voltage 13 V and rated armature current 2 A. The mechanical parameters utilized in the design are the total length and the diameter of the miniature WEC, 50 cm and 25 cm, respectively. The simulated prototype model (described in Section 5.4) has been validated with an experimental setup comprising translator and stator (described in Section 5.1), where the translator is moved by a programmed industrial robot. The experimental results have shown good agreement with the simulations.
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Katsidoniotaki, Eirini. "Extreme wave conditions and the impact on wave energy converters". Licentiate thesis, Uppsala universitet, Elektricitetslära, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-441043.
Testo completoAbstract (sommario):
The amount of energy enclosed in ocean waves has been classified as one of the most promising renewable energy sources. Nowadays, different wave energy conversion (WEC) systems are being investigated, but only a few concepts have been operated in a sea environment. One of the largest challenges is to guarantee the offshore survivability of the devices in extreme wave conditions. However, there are large uncertainties related to the prediction of extreme wave loads on WECs. Highfidelity computational fluid dynamics (CFD) simulations can resolve nonlinear hydrodynamic effects associated with wave-structure interaction (WSI). This thesis explores the point-absorbing WEC developed by Uppsala University in extreme wave conditions. The dynamic response and the forces on key components (mooring line, buoy, generator's end-stop spring) of the device are studied and compared. The high nonlinear phenomena accompany the steep and high waves, i.e., breaking behavior, slamming loads can be well-captured by the highfidelity CFD simulations. A commonly used methodology for extreme waves selection, recommended by technical specifications and guidelines, is the environmental contour approach. The 100-year contour in Hamboldt Bay site in California and the 50-year contour in the Dowsing site, outside the UK, are utilized to extract the extreme waves examined in the present thesis. Popular methodologies and data from different sources (observational and hindcast data) are examined for the environmental contour generation providing useful insights. Moreover, two popular approaches for the numerical representation of the extreme sea states, either as focused wave or as equivalent regular wave, were examined and compared. A midfidelity model of the WEC is successfully verified, as the utilization of lower fidelity tools in the design stage would reduce the computational cost. Last but not least, in CFD simulations the computational grid is sensitive in large motions, something often occurs during extreme-WSI. The solution of this issue for the open source CFD software OpenFOAM is provided here.
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Ashton, Ian Gerard. "Spatial variability of wave fields over the scale of a wave energy test site". Thesis, University of Exeter, 2011. http://hdl.handle.net/10036/3471.
Testo completoAbstract (sommario):
Accurate wave measurements are required for wave energy applications, including resource assessments and performance assessments. In response, wave data are measured from deployment sites, commonly using wave buoys or other point wave sensors. Spatial variability in the wave field will introduce inaccuracies to the analysis of data captured from a single point to represent a separate location or area. This thesis describes research undertaken to quantify the effect of spatial variability on the accuracy of direct wave measurements taken at a wave energy site. An array of four timesynchronised wave buoys were deployed, separated by 500m, in a location close to the Wave Hub wave energy test site in Cornwall, UK. These data were subject to close scrutiny in terms of data processing and quality control, which raised specific issues regarding data processing and the validation of wave data for a new measurement facility. Specific recommendations are made for data captured from this facility, and bespoke quality control routines were developed. This process minimises the possible contribution of errors to the processed data, which is observed to be of the highest importance when analysing simultaneous data sets, and provides a data set that is particularly suited to the examination of the spatial characteristics of ocean waves. The differences between simultaneous data demonstrated local physical processes to be causing a deterministic difference between the waves at the measurement sites, which contributed to a significant difference between the power statistics at different locations within the site. Instantaneous differences between measurements were observed to agree well with theoretical estimations of random error, based on sampling theory. The culmination of the research is a unique analysis of the spatial properties of ocean wave fields on the scale of a wave energy test site, of direct relevance to the development and monitoring of wave energy test sites.
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Westphalen, Jan. "Extreme wave loading on offshore wave energy devices using CFD". Thesis, University of Plymouth, 2011. http://hdl.handle.net/10026.1/2878.
Testo completoAbstract (sommario):
Two commercial Navier-Stokes solvers are applied to wave-wave and wave-structure interaction problems leading to the final application of simulating a single float of the wave energy converter (WEC) Manchester Bobber in extreme waves and a fixed section of the Pelamis in regular waves. First the two software packages CFX and STAR CCM+ are validated against measured results from physical tank tests concerning the interaction of 3 non-linear focused wave groups of different steepness (Ning et al. 2007). The agreement for all of these cases is very good and could even be improved from first order to second order wave setup at the wavemaker. However, in preliminary regular wave tests, the damping of the waves is identified to be an issue, which is the reason for focusing the waves and placing the structures in the following experiments approximately one wavelength behind the wavemaker. The interaction of fixed vertical and horizontal cylinders in regular waves are simulated concerning the forces on the structures (Kriebel 1998, Dixon et al. 1979). For the horizontal cylinder non-linear force oscillations of double the wave frequency could be modelled in good agreement with physical tank data, where linearised models failed. For the vertical cylinder the problem of the secondary load cycle due to a backward-breaking wave behind the cylinder is of special interest (Stansberg 1997, Chaplin et al. 1997). Here, the horizontal forces on a slender cylinder with a diameter approximately equal to the wave height are simulated successfully. Furthermore, the highly non-linear wave run-up in front of the cylinder is resolved well in the numerical approach. The next set of simulations includes rigid body motion. Here, the forced oscillations of a cone shaped body near the still water surface is simulated. These results are compared with test data published by Drake et al. (2008). For these cases the non-linearity of the experiments is discussed by comparing the sum and differences of the force and surface elevation time histories for a set of simulations with opposite excursion of the cone. The hydrodynamic forces on the cone surface are resolved in very good agreement. The solution of the surface elevation close to the cone surface is also resolved reasonably well. After having validated the codes for fixed wave-structure interaction problems and forced motion, the CFD methods are finally applied to problems relevant to the survivability of WECs. First a single float in waves is modelled. This challenging case combines the extreme wave setup with a floating body problem in one and two degrees of freedom including the interaction of the float inertia with the inertia of a separate mass attached to it. The vertical translations of the float are compared with physical tank tests by Stallard et al. (2008). This case clearly demonstrates the capabilities and challenges in using CFD to simulate WECs. When representing the pulley and counterweight system by a simplified external body force rather than the full setup, the calculated translations of the float agreed better with the measured results from the physical tank test. Furthermore the codes are used to simulate a single fixed section of the Pelamis device in regular waves. The surface elevations close to the device are discussed and the forces acting on different strips on the structure are presented.
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Stokes, Christopher Hugo. "Coastal impacts in the lee of a wave energy site : waves, beach morphology and water-users (Wave Hub, Cornwall, UK)". Thesis, University of Plymouth, 2015. http://hdl.handle.net/10026.1/4303.
Testo completoAbstract (sommario):
The Wave Hub facility in Cornwall (South West UK) is a marine renewables test site, predominantly designed for the purpose of trialling wave energy converters prior to commercialisation. Beach water-users such as bathers and surfers are of economic importance to tourism in Cornwall, and during theWave Hub consultation there were concerns among stakeholders that wave energy extraction would reduce the height and quality of coastal waves for sur ng, as well as a ecting sediment transport and beach morphology. This thesis investigates the interaction between wave conditions, beach morphology, and beach water-users, and proposes how a wave climate altered by wave energy extraction is likely to alter these interactions. A multidisciplinary research approach is adopted, involving the collection of qualitative and quantitative social data, the collection of over 5 years of physical wave and beach morphology data, and predictive modelling of the e ects of an attenuated wave climate. Quantitative, structured interview data from 403 water-users, collected at two beaches (Perranporth and Porthtowan) in the lee of Wave Hub, indicate that the population of water-users in the area is predominantly made up of surfers (53%), but bodyboarding and swimming/bathing are also popular activities (29% and 11%, respectively). In-depth semi-structured interviews reveal that water-user perceptions of wave energy extraction and its potential coastal impacts are constructed using intuitive risk perceptions, rather than technical understanding. These risk perceptions are constructed through a weighing of their perception of wave energy devices ('technology') and their perception of the coastal environment ('nature'). To investigate how waves are perceived, nearshore wave buoy measurements collected in 14 m water depth and transformed to breaking height, are compared to concurrent visual observations of mean breaker height and period. On average water-users underestimated signi cant wave height and period by 48% and 17%, respectively. Accounting for variations in wave perception, the wave preferences of di erent water-user groups are determined. Water-users are found to share a common preference towards wave v periods of 9 - 20 s, but di erent water-user groups are found to have di erent ranges of preferred wave height, which is found to govern whether wave energy extraction will decrease or increase the occurrence of preferred waves. Previous research indicates that three-dimensional (3D) beach morphology with crescentic bar and rip features is the primary controller of surf-zone hazard, and also strongly in uences the quality of sur ng waves at the coast. A dataset of 5.5 years of quasi-weekly bar measurements, and quasi-monthly intertidal surveys from Perranporth beach is used to quantify seasonal to inter-annual changes in threedimensionality. Integrated, cumulative uctuations in wave steepness, wave power, and relative tide range that occur over seasonal time scales are shown to be well correlated to seasonal uctuations in beach three-dimensionality. 3D morphology is well related to a disequilibrium term that predicts increases or decreases in threedimensionality by examining the di erence between instantaneous wave conditions and a temporally varying equilibrium condition, based on a weighted average of antecedent waves. This indicates that periods of wave regime change between erosive winter conditions with high steepness waves and accretive summer conditions with low steepness waves are related to the growth of 3D features, and vice versa, while extended periods with similar wave conditions drive the beach towards equilibrium. Using a range of realistic and extreme coastal wave height attenuation scenarios determined from previous Wave Hub modelling studies, it is predicted that none of the scenarios will have a universally positive or negative e ect on the occurrence of wave conditions preferred by water-users. When used to predict beach threedimensionality at Perranporth beach, the attenuated wave climates are found to reduce the variability in three-dimensionality. Even an extreme and unrealistic level of wave energy extraction (100% energy capture) was shown to have an insigni cant e ect on the occurrence of preferred waves, and only under an extraction scenario where the impact was not varied with wave frequency did this level of attenuation have a signi cant e ect on the predicted beach three-dimensionality. The inshore wave attenuation from Wave Hub is therefore likely to have an insigni cant e ect on wave conditions and beach morphology of relevance to beach water-users. A number of observations and recommendations are discussed for the development of a sound and robust methodological approach, which can be used to investigate the e ects of wave energy extraction on beach water-users at future wave farm sites.
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Boström, Cecilia. "Electrical Systems for Wave Energy Conversion". Doctoral thesis, Uppsala universitet, Elektricitetslära, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-140116.
Testo completoAbstract (sommario):
Wave energy is a renewable energy source with a large potential to contribute to the world's electricity production. There exist several technologies on how to convert the energy in the ocean waves into electric energy. The wave energy converter (WEC) presented in this thesis is based on a linear synchronous generator. The generator is placed on the seabed and driven by a point absorbing buoy on the ocean surface. Instead of having one large unit, several smaller units are interconnected to increase the total installed power. To convert and interconnect the power from the generators, marine substations are used. The marine substations are placed on the seabed and convert the fluctuating AC from the generators into an AC suitable for grid connection. The work presented in the thesis focuses on the first steps in the electric energy conversion, converting the voltage out from the generators into DC, which have an impact on the WEC's ability to absorb and produce power. The purpose has been to investigate how the generator will operate when it is subjected to different load cases and to obtain guidelines on how future systems could be improved. Offshore experiments and simulations have been done on full scale generators connected to four different loads, i.e. one linear resistive load and three different non-linear loads representing different cases for grid connected WECs. The results show that the power can be controlled and optimized by choosing a suitable system for the WEC. It is not obvious which kind of system is the most preferable, since there are many different parameters that have an impact on the system performance, such as the size of the buoy, how the generator is designed, the number of WECs, the highest allowed complexity of the system, costs and so on. Therefore, the design of the electrical system should preferably be carried out in parallel with the design of the WEC in order to achieve an efficient system.Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 727
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BRACCO, GIOVANNI. "ISWEC: a Gyroscopic Wave Energy Converter". Doctoral thesis, Politecnico di Torino, 2010. http://hdl.handle.net/11583/2562362.
Testo completoAbstract (sommario):
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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Gustafsson, Egil. "Extreme loading and fatigue analysis of a wave energy device". Thesis, KTH, Marina system, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-198506.
Testo completoAbstract (sommario):
Wave energy is one of the possible solutions for meeting the future energy demand in a clean and sustainable way. Extracting large amounts of energy, a wave energy device would be subjected to extreme and fatigue loads from the waves. Designing such a device, a trade off needs to be done between making a device that is strong enough to withstand the loads and on the same time not too heavy making it inefficient and too costly. Having good estimations of extreme and fatigue loads are therefore critical when designing an efficient wave energy device. This thesis has aimed to create a tool that can be used between the already existing hydrodynamic and solid mechanic models available at CorPower Oceean. The goal has been that the tool shall extract the extreme and fatigue loads from the hydrodynamic model and format them in a way so that they can be used in the solid mechanical model. Four different tools have been created and compared for calculating fatigue using amplitude and spectral methods, where the amplitude methods also are able to estimate extreme loads. The fatigue tools have been evaluated against each other in a simple example showing that the estimated accumulated fatigue damage can be decreased by using several variables. An application of the tools has been done on a critical sub system of the wave energy device developed by CorPower Ocean. Where in this application critical points against extreme loading and fatigue have been localized. A new design has been suggested based on the strength analysis from the first one. Increasing the number of variables and using the tools developed in this thesis can significantly improve the fatigue damage estimations of the system. What fatigue method to use depends on the details for each case.
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Leijon, Jennifer. "Simulation of a linear wave energy converter with different damping control strategies for improved wave energy extraction". Thesis, Uppsala universitet, Elektricitetslära, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-287369.
Testo completoAbstract (sommario):
In this project, the wave energy converter (WEC) designed at Seabased AB and Uppsala University was modelled in the program MATLAB. In order to increase the average output power, the WEC should be controlled. Therefore, the simulation tool was used to investigate damping strategies where the damping coefficient was changed at different times of the wave period. The tests showed that a suitable damping strategy, matched to the sea state at the specific location of the site and the overall WEC design, increases the average output power, as well as may protect the WEC from damages. This can lead to a more sustainable WEC system, which may contribute to the increasing demand of renewable energy solutions.
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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.
Testo completoAbstract (sommario):
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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Nascimento, Joao Manuel Morim do. "Wave Energy Resource along the Southeast Coast of Australia". Thesis, Griffith University, 2016. http://hdl.handle.net/10072/365734.
Testo completoAbstract (sommario):
The Australian Government has set a 20% target for renewable energy by 2020 as part of a long-term commitment to decrease Australia’s greenhouse gas emissions by 60% on 2000 levels by 2050. In order to accomplish such goal, Australia will need to generate an additional 45 MWh of renewable energy yearly by 2020 where wave energy may play a significant role. Coastal waters of Australia’s southeast margin have been recognised to be suitable for exploiting wave energy resources and potentially capable of significantly contributing to Australia’s annual electricity generation. Nevertheless, until now, no thorough research has yet been conducted to adequately characterize such an unexploit-ed resource along shallow coastal waters.
This dissertation presents a detailed assessment of the wave energy resource potential for Australia’s southeast coastal waters, focusing on promising nearshore regions where full-scale wave energy converter farms could potentially be deployed. The study meth-odology employed the wave energy transformation model SWAN to predict wave con-ditions along Australia’s southeastern coast from deep to shallow water depths at hourly resolution for a period of 30 years between 1979 and 2010. The model was driven with high-resolution non-stationary winds and full directional spectra boundary conditions to account for the multimodal sea states, which often subsist along Australia’s southeast coast. SWAN was calibrated and validated against measurements from several wave rider buoy locations for a wide range of sea states.Thesis (Masters)
Master of Philosophy (MPhil)
Griffith School of Engineering
Science, Environment, Engineering and Technology
Full Text
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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.
Testo completo
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Li, Linghan. "Numerical investigation of wave structure interaction with application to wave energy devices". Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/413590/.
Testo completoAbstract (sommario):
Wave energy has become one of the most promising energy resources and hence has attracted more attention from the governments and energy companies. In order to meet the growing demands on global energy, the next generation of energy extracting device needs to be more efficient with less operation cost, and as an offshore structure, the survivability also needs to be taken into consideration. Therefore, it is vital that the hydrodynamic behaviour of the energy device can be predicted accurately at the initial design stage. In this research, the wave structure interaction with application to wave energy device is studied numerically through an open source CFD library: OpenFOAM. The computational fluid dynamic (CFD) analysis based on the Reynolds Average Navier Stokes (RANS) equations is used to investigate the interaction between wave and structure, and array effects among devices. The numerical method with a reasonable computational cost can be an alternative to physical experimental test in offshore engineering. The background to this research is firstly introduced, including methodologies adopted in this study, followed by a series of case study to demonstrate the applicability of the numerical model. These include wave generation validation, hydrodynamic behaviour determination, and the predication of the performance of wave point absorber and wave point absorbers array. It has been shown that the numerical model is capable of modelling wave propagation and interaction with structure including nonlinear effect with a reasonable degree of accuracy. The wave point absorber energy device has been chosen as the object to study. The RANS approach in time domain improves the accuracy when compared with the potential theory based method. The influence of wave point absorber devices array on their performance is then investigated under the irregular wave conditions in order to improve the overall performance. The influence factors include array configuration, separation distance and wave direction. The study yields an improved understanding of wave-structure problem and has extended the range of RANS model used in wave energy research.
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Magagna, Davide. "Oscillating water column wave pump : a wave energy converter for water delivery". Thesis, University of Southampton, 2011. https://eprints.soton.ac.uk/349009/.
Testo completoAbstract (sommario):
The research presented in this dissertation investigates the development and the performances of a new type of Wave Energy Converter (WEC) aimed to provide water delivery and energy storage in the form of potential energy. The Oscillating Water Column Wave Pump (OWCP) concept was proposed and tested through a series of experimental investigations supported by scientific theory. The OWCP was developed after an extensive study of the existing wave energy technology available, from which it emerged that the Oscillating Water Column (OWC) device could be further implemented for water delivery purposes. The existing theory of the OWC was employed to develop a mathematical theory able to describe the system wave response and water removal of the OWCP. In order to understand and validate the mathematical models of the OWCP, experimental investigations were carried out under the influence of incident linear waves in a two-dimensional (2D) and three-dimensional (3D) wave flume. The experimental equipment and methodology are outlined, including the description of wave flumes, models and data acquisition equipment. Experimental tests were used to verify the concept of the OWCP and assess its performances, investigating both the response of the device to the waves with and without water removal. In order to increase the efficiencies of delivery, array configurations of multiple OWCPs were adopted. The research demonstrated that up to 14% of the energy carried by the incoming waves can be converted into useful potential energy for a single device. Moreover a further increase of the efficiencies can be obtained with the array configuration improving the overall capability of the OWCP, for optimal separation distance between the array components. Further model tests are required to extended this research to validate the developed mathematical models as an effective prediction tool of the performances of the OWCP and further increase the efficiency of water removal that can be achieved.
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De, Marichalar Alegre Alexandra. "Overtopping Converter Prototype for Electrical Generation from Wave Energy : Laboratory Test". Thesis, KTH, Energiteknik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-38883.
Testo completoAbstract (sommario):
It is not a coincidence that over half the world‟s population live in coastal areas using the sea as a mean to develop its industry, thus the sea is present in most aspects of daily life. Because of the vital relationship with the marine environment, for many years mankind is aware of the high energy potential contained in waves. During the last hundred years, thousands patents of devices for the extraction of the energy from waves have been published. However, the researching still faces the challenge of develop the optimal wave energy converter that matches robustness, to withstand extreme marine conditions, and sensitivity, to respond the different sea states. In this thesis a scale model of a wave overtopping converter has been designed, built and tested. In this type of wave electricity converter the waves ascend a ramp, filling a reservoir located at a certain height above sea level. The stored water in the reservoir is discharged back into the sea, powering a turbine, thus generating electricity. The system is composed of a wave energy converter, at a scale of 1:100 without turbine, a test channel and a plunger type wave maker. Different sea conditions have been simulated, to assess how the different configurations of the device influence the obtained hydraulic power and flow. It has been concluded that there is an appropriate configuration of the wave electricity converter for each wave period and height. The simulated sea conditions were composed of wave periods of around a second and wave heights of about two centimeters. Finally by applying scale transformations, an estimation of the hydraulic power that the wave electricity converter would extract with this configuration in the deep waters of Tenerife South has been calculated. Summarizing, in this thesis the methodology of testing and the comparison with real conditions has been developed.
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Hoen, Marthe Kristine Tautra. "Modeling and Control of Wave Energy Converters". Thesis, Norwegian University of Science and Technology, Department of Engineering Cybernetics, 2009. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-8960.
Testo completoAbstract (sommario):
Wave Power is a technology that was founded in the 70's, but which still not has reached full industrial recognition as a energy source. In this thesis there is a literature study on different concepts of Wave Energy Converters(WEC) which has been build in full scale, and there is a great variety in the concepts. There is a theory chapter where ocean waves theory, mass-spring-damper dynamics, hydrodynamics and maximum power capture are presented. The modeling work was done on a axisymmetric point absorber WEC, which can be said to have the greatest potential for energy absorption because it is small relative to the wavelength of the incident waves. To be able to simulate on the model, a control strategy must be included, and I have included PID control and Model Predictive Control as strategies to be able to capture maximum power with Phase Latching. I believe that Model Predictive Control will be the best choice for control system, although it is not as robust as PID control, but because of its predictive behavior. At last there is a chapter where further work and some concluding remarks are given.
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Hals, Jørgen. "Modelling and phase controlof wave-energy converters". Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for marin teknikk, 2010. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-11952.
Testo completoAbstract (sommario):
Current prognoses are that, unless counteracted by very strong political measures, the world will meet both energy shortage and climate crisis within a horizon of a few decades, both of which are strongly related to our dependence on fossil fuels. Renewable energy sources may be harvested sustainably, and developing technology for their exploitation therefore forms an obvious part of strategies to reduce emissions and secure energy supply. Wave energy is a resource with relatively high power density, readily available along the coasts, and thus coinciding with the areas where industry and people tend to be accumulated. In some regions this resource is large enough to form a significant part of the energy mix. The technology for harnessing the power of ocean waves is today still on the research and development stage. The challenge is to make a design where the costs of investment, operation and maintenance (in terms of money, resources and energy) can be justified by the availability and potential earnings. This thesis focuses on two aspects of systems for wave energy conversion: How to model such systems, which is important for understanding and design, and how to control their motion, which is crucial for the primary power conversion – the inevitable step that forms the basis for revenues and energy output from such a device. The dissertation is based on articles published in scientific conferences and journals, as well as an account for background of the undertaken research and the methods used. The bond graph modelling language has been chosen as a promising aid for the modelling of the power converter dynamics. It enables a systematic and transparent approach to the path from drawing board to mathematical equations. Examples show how energy conversion systems may be modelled and simulated within this framework. These include heave-motion models for a semi-submerged sphere, a platform/buoy two-body system and a smallscale oscillating water column (OWC), as well as wave-to-wire models of two made-up systems. The OWC model was also studied by laboratory experiments. A range of control strategies has been studied and compared by numerical simulation, and in one case also by laboratory experiments. These strategies include phase control by latching and by clutching, approximations to complex-conjugate control, and model predictive control (MPC). Constraint handling and real-time parameter tuning are discussed, too. The constrained optimal power absorption is investigated, and for the example of a semi-submerged heaving sphere in irregular waves it is found that MPC in combination with a Kalman filter predictor is able to provide an absorbed power in excess of 90% as compared to the non-causal (and hence not completely realisable) constrained optimum. Other causal controller implementations gives an absorbed power ranging from 10 to 90% of that achieved with MPC. The best performing control strategies, however, involve a large flow of reactive power through the machinery, which in normal irregular-wave operation may give peak-to-average power ratio as high as 25 and above. This represents a challenge to the design of machinery and controller. An interesting observation from the numerical simulations is the possibility of increased absorbed power in irregular waves as compared to regular waves having about the same wavelength characteristics and the same wave power level. An explanation is suggested for this phenomenon.
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Fang, Fang, e Dinkoo Mehrdad. "Wave Energy of an Antenna in Matlab". Thesis, Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-16587.
Testo completoAbstract (sommario):
In the modern world, because of increasing oil prices and the need to control greenhouse gas emission, a new interest in the production of electric cars is coming about. One of the products is a charging point for electric cars, at which electric cars can be recharged by a plug in cable. Usually people are required to pay for the electricity after recharging the electric cars. Today, the payment is handled by using SMS or through the parking system. There is now an opportunity, in cooperation with AES (the company with which we are working), to equip the pole with GPRS, and this requires development and maintenance of the antenna. The project will include data analysis of the problem, measurements and calculations. In this work, we are computing energy flow of the wave due to the location of the antenna inside the box. We need to do four steps. First, we take a set of points (determined by the computational mesh) that have the same distance from the antenna in the domain. Second, we calculate the angles between the ground and the points in the set. Third, we do an angle-energy plot, to analyse which angle can give the maximum energy. And last, we need to compare the maximum energy value of different position of the antenna. We are going to solve the problem in Matlab, based on the Maxwell equation and the Helmholtz equation, which is not time-dependent.
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Ericsson, Emil, e Eric Gregorson. "Quantitative Risk Assessment of Wave Energy Technology". Thesis, Uppsala universitet, Elektricitetslära, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-342033.
Testo completoAbstract (sommario):
European Commission (2011) aims to reduce the greenhouse gas emission sby 85-95% by 2050 in comparison to 1990’s levels. Wave energy could be an important step to archiving this goal. This report aims to develop a quantitative risk assessment for the Uppsala University's wave energy converter. Failure rates have been collected from various databases and reports and have been processed accordingly in order to implement them in the risk analysis. CAPEX, OPEX and possible downtime windows have been estimated. A fault tree analysis (FTA) has estimated the total unavailability, unreliability and downtime. Furthermore an economical assessment model using Monte Carlo and the unreliability data from the FTA has been developed, estimating the expected LCOE and OPEX/WEC for parks consisting of 20, 100, and 200 WECs (wave energy converters). The result show that the O-ring seal has the largest impact on both the unavailability, and the economy of the OPEX/WEC. Second biggest contributor is the translator bearing failure. The study also shows that the CAPEX cost has to be reduced to make the LCOE competitive in comparison to other renewable sources. A comparison between the system unavailability and unreliability has also been done in terms of different component parameters.
36
Giassi, Marianna. "Optimization of Point Absorber Wave Energy Parks". Licentiate thesis, Uppsala universitet, Elektricitetslära, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-337772.
Testo completoAbstract (sommario):
Renewable energies are believed to play the key role in assuring a future of sustainable energy supply and low carbon emissions. Particularly, this thesis focus on wave energy, which is created by extracting the power stored in the waves of the oceans. In order for wave energy to become a commercialized form of energy, modular deployment of many wave energy converters (WECs) together will be required in the upcoming future. This design will thus allow to benefit, among others, from the modular construction, the shared electrical cables connections and moorings, the reduction in the power fluctuations and reduction of deployment and maintenance costs. When it comes to arrays, the complexity of the design process increase enormously compared with the single WEC, given the mutual influence of most of the design parameters (i.e. hydrodynamic and electrical interactions, dimensions, geometrical layout, wave climate etc.). Uppsala University has developed and tested WECs since 2001, with the first offshore deployment held in 2006. The device is classified as a point absorber and consists in a linear electric generator located on the seabed, driven in the vertical direction by the motion of a floating buoy at the surface. Nowadays, one of the difficulties of the sector is that the cost of electricity is still too high and not competitive, due to high capital and operational costs and low survivability. Therefore, one step to try to reduce these costs is the development of reliable and fast optimization tools for parks of many units. In this thesis, a first attempt of systematic optimization for arrays of the Uppsala University WEC has been proposed. A genetic algorithm (GA) has been used to optimize the geometry of the floater and the damping coefficient of the generator of a single device. Afterwards, the optimal layout of parks up to 14 devices has been studied using two different codes, a continuous and a discrete variables real coded GA. Moreover, the method has been extended to study arrays with devices of different dimensions. A deterministic evaluation of small array layouts in real wave climate has also been carried out. Finally, a physical scale test has been initiated which will allow the validation of the results. A multi--parameter optimization of wave power arrays of the Uppsala University WEC has been shown to be possible and represents a tool that could help to reduce the total cost of electricity, enhance the performance of wave power plants and improve the reliability.
37
Warner, John M. "Wave energy conversion in a random sea". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ31537.pdf.
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Thies, Philipp Rudolf. "Advancing reliability information for Wave Energy Converters". Thesis, University of Exeter, 2012. http://hdl.handle.net/10036/4053.
Testo completoAbstract (sommario):
Marine renewable energy promises to provide a significant contribution to the future electricity supply. It is estimated that 17% of today's UK electricity demand could be generated from wave and tidal sources. The ambition to harvest this resource is in the public interest, as it eases the pressures on energy security, holds the potential to reduce carbon emissions and has the prospect to create a new UK industry sector worth £15 billion. From an engineering perspective, marine energy is one of the least developed renewable energy technologies and has to be regarded as unproven. The reliability of components and devices in the harsh marine environment is one of the main engineering challenges. Reliability assessments and the assurance of acceptable reliability levels are dependant on the adequacy of failure information, which is scantily available for marine energy. This thesis shows that large failure rate uncertainties impede the reliability assessment for wave energy converters and how a suite of experimental, numerical and statistical methods can be applied to improve scarcely available reliability information. The analysis of component load conditions identifies fatigue as failure mode of concern and the fatigue life of mooring lines and marine power cables is quantified in a floating wave energy application. A Bayesian statistical approach and dedicated service-simulation component testing is proposed, and implemented to improve the quality of reliability estimates and to provide relevant data and assurance. The methods presented, along with the results, will assist reliability assessment and design during early development stages, and will inform the prediction of maintenance requirements during operation. Reliable marine energy systems will be the technical enabler for the successful transition of prototype devices to a commercially viable marine energy industry.
39
Price, Alexandra A. E. "New perspectives on wave energy converter control". Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/3109.
Testo completoAbstract (sommario):
This work examines some of the fundamental problems behind the control of wave energy converters (WECs). Several new perspectives are presented to aid the understanding of the problem and the interpretation of the literature. The first of these is a group of methods for classifying control of WECs. One way to classify control is to consider the stage of power transfer from the wave to the final energy carrier. Consideration of power transfer can also be used to classify WECs into families. This approach makes it possible to classify all WECs, including those that had previously eluded classification. It also relates the equations of motion of different classes of WECs to a generalised equation of motion. This in turn clarifies why some types of control are suited to some WECs, but not others. These classification systems are used to demarcate the boundary for the theoretical work that follows. The theory applies to WECs with governing equations of motion that are linear, and to control systems that are linear, aim to maximise power, and which regulate the PTO stage of power flow. Another important perspective is the new wet and dry oscillator paradigm, which is used to differentiate between frequency domain modelling and a commonly used technique, monochromatic modelling. This distinction is necessary background for many of the new ideas discussed. It is used to resolve an ongoing debate in wave energy research: whether frequency domain modelling can be applied to cases that are not monochromatic. It is the key to an extension to the theory of capture width, a widely used performance indicator. This distinction is also the rationale behind an improved method of presenting frequency domain results: the frequency responses due to both monochromatic and polychromatic forcing are represented on the same graph. These responses are different because the optimal control problem is acausal, a topic that is also discussed in depth. This visual tool is used to investigate and confirm various ideas about the control of WECs, and to demonstrate how the newly redefined capture width encapsulates the essential control problem of WECs. The optimal control problem is said to be acausal because information about the future is required to achieve optimal control. Another vantage point offered is that of the duration of the prediction interval required for optimal control. This is given by a new parameter emerging from this work, which has been termed the premonition time. The premonition time depends on the amount of knowledge required, which is determined by the geometry of the WEC, and the amount of information available, which is largely determined by the bandwidth of the sea state. The new perspectives introduced are the various systems of classification, the wet and dry oscillator paradigm, the presentation of monochromatic and polychromatic results on the same axes, premonition time, and the revised theory on capture width. These are all used to discuss the interrelationship between WEC geometry, the control strategy and the sea-state. The opportunities for, and limitations of, the use of intelligent control techniques such as artificial neural networks are discussed. The potential contribution of various control strategies and associated design principles is explored. This discussion culminates in a series of recommendations for control strategies that are suited to each class of WEC, and for the areas of research that have the potential to bring about the greatest reductions in the cost of harnessing energy from sea waves.
40
Turner, Rosalind Hilary Clare. "Wave energy dissipation at cliffed saltmarsh margins". Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612840.
Testo completo
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Medina-López, Encarnación. "Thermodynamic processes involved in wave energy extraction". Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/31422.
Testo completoAbstract (sommario):
Wave energy is one of the most promising renewable energy sources for future exploitation. This thesis focuses on thermodynamic effects within Oscillating Water Column (OWC) devices equipped withWells turbines, particularly humidity effects. Previous theoretical studies of the operation of OWCs have resulted in expressions for the oscillation of the water surface in the chamber of an OWC based on linear wave theory, and the air expansion{compression cycle inside the air chamber based on ideal gas theory. Although in practice high humidity levels occur in OWC devices open to the sea, the influence of atmospheric conditions such as temperature and moisture on the performance of Wells turbines has not yet been studied in the field of ocean energy. Researchers have reported substantial differences between predicted and measured power output, and performance rates of OWCs presently coming into operation. The effect of moisture in the air chamber of the OWC causes variations on the atmospheric conditions near the turbine, modifying its performance and efficiency. Discrepancies in available power to the turbine are believed to be due to the humid air conditions, which had not been modelled previously. This thesis presents a study of the influence of humid air on the performance of an idealised Wells turbine in the chamber of an OWC using a real gas model. A new formulation is presented, including a modified adiabatic index, and subsequent modified thermodynamic state variables such as enthalpy, entropy and specific heat. The formulation is validated against experimental data, and found to exhibit better agreement than the ideal approach. The analysis indicates that the real gas behaviour can be explained by a non{dimensional number which depends on the local pressure and temperature in the OWC chamber. A first approach to the OWC formulation through the calculation of real air flow in the OWC is given, which predicts a 6% decrease in efficiency with respect to the ideal case when it is tested with a hypothetical pulse of pressure. This is important because accurate prediction of efficiency is essential for the optimal design and management of OWC converters. A numerical model has also been developed using computational fluid dynamics (CFD) to simulate the OWC characteristics in open sea. The performance of an OWC turbine is studied through the implementation of an actuator disk model in Fluent®. A set of different regular wave tests is developed in a 2D numerical wave flume. The model is tested using information obtained from experimental tests on a Wells{type turbine located in a wind tunnel. Linear response is achieved in terms of pressure drop and air flow in all cases, proving effectively the applicability of the actuator disk model to OWC devices. The numerical model is applied first to an OWC chamber containing dry air, and then to an OWC chamber containing humid air. Results from both cases are compared, and it is found that the results are sensitive to the degree of humidity of the air. Power decreases when humidity increases. Finally, results from the analytical real gas and numerical ideal gas models are compared. Very satisfactory agreement is obtained between the analytical and the numerical models when humidity is inserted in the gaseous phase. Both analytical and numerical models with humid air show considerable differences with the numerical model when dry air is considered. However, at the resonance frequency, results are independent of the gas model used. At every other frequency analysed, the real gas model predicts reduced values of power that can fall to 50% of the ideal power value when coupled to the radiation-diffraction model for regular waves. It is recommended that real gas should be considered in future analyses of Wells turbines in order to calculate accurately the efficiency and expected power of OWC devices.
42
Bliss, Nice Sam. "Qualitative risk analysis on wave energy technologies". Thesis, Uppsala universitet, Institutionen för elektroteknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-423092.
Testo completoAbstract (sommario):
Wave energy as an industry is yet to emerge as a reliable energy technology. As of now, no wave energy device is said to be a commercial success. Survival in the harsh ocean environment, the low frequency of waves and the variability of wave resources are the basic challenges that a wave power concept or a developer has to overcome. In addition to these challenges, there are number of other barriers such as economic and regulatory risks which hinder the development. A number of concepts or devices have failed one after another, to be commercially successful. Many of the failures were due to economic reasons and others were due to technical or environmental factors. Mistakes or failures can be repeated if they are not shared within the industry. This thesis attempts to identify the barriers to wave energy concepts and to analyse them qualitatively. Efforts have been taken to include the previous instances of failures and their causes so as to avoid them in future. The data was collected through literature review of published papers, reports, news articles and through a survey which was distributed among experts in the industry and academia. It can be seen that one barrier can trigger others and that they are interconnected. In the same way, solving one barrier can clear the others too. The risks faced by wave energy technologies are identified, analysed and some mitigation methods are discussed.
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Narra, Pedro Miguel Fragoso. "Attenuation of wave energy in mangrove forests". Master's thesis, Universidade de Aveiro, 2012. http://hdl.handle.net/10773/10522.
Testo completoAbstract (sommario):
Mestrado em Engenharia CivilMangrove forests are a very important ecosystem in protected coastal zones. These forests provide food and habitat for numerous species and have an important role in the coastal stabilization, trapping sediments and reducing erosion. They also contribute to wave attenuation, which might add to the safety of a coastal environment. Although the importance of mangrove forests in wave attenuation is widely recognized, the amount of comprehensive studies to understand the quantitative effect of the mangroves in the attenuation of wave energy is still insufficient. This thesis aims to increase knowledge on wave attenuation in mangroves by studying this process in the field. Results are presented of a fieldwork campaign executed in the Trang province, Thailand, between November 2010 and May 2011. It is the first known study that includes quantitative information on the vegetation in the field, presenting rates of vegetation density along the studied transects. Two different transects were chosen in Trang province – Kantang and Palian – showing differences in slopes and vegetation. Measurements included surface elevation, vegetation density and pressure fluctuations. After the measurements, the pressure data was carefully selected and analyzed using spectral analysis and wave linear theory concepts. The entire procedure is described in this thesis in order to provide a good basis for future studies in the field. The results show the presence of waves with periods mostly exceeding 5 seconds. At Kantang most of the waves have periods between 10 and 20 seconds. Wave attenuation is found to be about 2.5 J/m2 in 100 meters of mangrove forest at Palian and 0.8 J/m2 per 100 meters of mangroves at Kantang. This difference can be explained by a more accentuated slope, a denser forest and the presence of higher frequency waves that are easily attenuated at Palian. In general, the wave attenuation reaches values around 60% attenuation along the transects. Comparison with other studies shows that the results in this thesis resemble the findings of previous researches. The wave attenuation in mangroves was also compared to wave attenuation in salt marshes and it was concluded that the salt marshes have better wave attenuating capacity if the water depth is not too high, but with increasing water depths they rapidly loose this capacity, in contrary to mangroves.
As florestas de mangue são um ecossistema muito importante em zonas de costa protegida. Estas florestas fornecem alimento e habitat a inúmeras espécies e têm um papel importante na estabilização costeira, retendo sedimentos e reduzindo a erosão. Estas florestas também influenciam a atenuação das ondas, contribuindo para a segurança costeira. Embora seja amplamente reconhecida a importância das florestas de mangue na atenuação da energia das ondas, constata-se que a bibliografia sobre este tema é ainda insuficiente. Esta tese tem como objetivo aumentar o conhecimento sobre este fenómeno. Para tal, são analisados os dados relativos a um trabalho de campo executado na província de Trang, Tailândia, entre Novembro de 2010 e Maio de 2011. Este é o primeiro estudo a incluir informação quantitativa sobre a vegetação na zona em análise, apresentando valores para a densidade da vegetação ao longo dos trajetos estudados. Foram selecionados dois trajetos distintos na província de Trang – Kantang e Palian. Estes locais apresentam diferenças na inclinação do terreno e na densidade da vegetação. As medições realizadas incluem levantamento o topográfico do terreno, a densidade da vegetação e as variações de pressão ao longo do trajeto. Após as medições, os dados relativos à sobre a variação de pressão foram cuidadosamente selecionados e analisados usando análise espectral e conceitos da teoria de onda linear. Todo o procedimento é descrito nesta tese de modo a proporcionar uma boa base para futuros estudos na área. Os resultados mostram, na sua maioria, a presença de ondas com períodos superiores a 5 segundos. Em Kantang, a maior parte das ondas têm períodos entre os 10 e 20 segundos. A atenuação da energia hidrodinâmica num percurso de 100 metros de floresta é estimada em cerca de 2,5 J/m2 em Palian e 0,8 J/m2 em Kantang. Esta diferença pode ser explicada pela mais acentuada inclinação do terreno, uma maior densidade de vegetação e pela presença de ondas com períodos menores (que são mais facilmente atenuadas) em Palian. Em geral, a atenuação das ondas atinge valores de cerca de 60% ao longo dos trajetos. A comparação com outros estudos mostra que as conclusões retiradas nesta tese são semelhantes às conclusões de pesquisas anteriores. A atenuação da energia hidrodinâmica em florestas de mangue também foi comparada com a atenuação em pântanos salgados. Conclui-se que estes ecossistemas têm maior capacidade de atenuação se o nível do mar for baixo, mas que com maiores profundidades esta capacidade reduz-se rapidamente, ao contrário das florestas de mangue.
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Thomas, Simon. "Control of Wave Energy Converters in arrays". Licentiate thesis, Uppsala universitet, Elektricitetslära, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-364096.
Testo completoAbstract (sommario):
One way to lower the levelized cost of energy for wave power plants and paving so the way for commercial success, is to increase the power absorption by use of advanced control algorithms. This thesis investigates the influence of the generator inertia, the generator damping and the layout on power absorption and presents a new model free strategy of controlling wave energy converters. The evaluation of all control strategies was done in a numerical simulation and in experimental 1:10 model scale wave tank tests conducted in the COAST laboratory at the University of Plymouth. The WECs used are inspired by the wave energy concept developed at Uppsala University. The influence of the generator inertia on the power absorption was tested with an uncontrolled WEC. Compared to a conventional WEC the power output could be significantly increased for small waves and high wave periods. As a simple and easy to implement control strategy, a WEC with sea state optimized generator damping was used to create a power matrix. The optimal damping factor depends on both, wave period and wave height. The power absorption increases with the wave height and when the wave period converges towards the oscillation period of the WEC. A genetic algorithm was used to obtain the optimized layouts for wave energy farms, which suggest that the converter should be placed in rows parallel to the wave front, and the position in the array has nearly no influence on the optimal control parameter. Then a collaborative learning approach using machine learning is presented, with several identical wave energy converters in a row to parallelise the search of the optimal control parameter. It was implemented to control the generator damping factor and the latching time. With the latter the power could be increased significantly.Vågkraft kan bli en viktig del från framtidens elektriska energikälla. Men därför kostnaden per producerat energienheten måste minskas. En väg att minska kostnaden är att förbättra effektiviteten med ett avancerat styrsystem. Den här avhandlingen tester olika kontrollstrategier för att hitta en bra strategi för vågkraftverk i parker. Alla strategier testas med an numerisk simulering och ett fysiskt test med en 1:10 skalad modell i en våg bassäng. Först är en elektrisk vågkraft konverter (WEC) med optimerad naturlig frekvens men utan styrsystem är testad. WECen absorberar hög effekt i ett litet område med de vanligaste vågklimatet. Storlek på området kan varieras med generatorns dämpning och bästa vågperiod kan ändras med WECens tröghet. En generator med optimal dämpningsfaktor testas, för att en justerbar generator dämpning är relativt lätt att implementerar. Numerisk simulering visade att optimal dämpningsfaktor beror på vågperiod och minskar när våghöjden ökar. Beroende av effekten från våghöjd kan ses i numerisk simulation och fysiksals test, men beroende av effekten från vågperiod kan ses bara i numerisk simulation. Därefter, en modell oberoende strategi (som kallas CL) för vågkraftkonverter i arrayer är presenterat och testad för att styra (1) generator dämpningsfaktor och (2) latching tid. Resultat är att den CL kontrollerade generatorn dämpning endast visar små fördelar med absorberat energi. Men med en CL optimerat latching tid, absorberat effekten ökas mer som 100\% i vissa vågklimat.
SUPERFARMS
45
Nové-Josserand, Clotilde. "Converting wave energy from fluid-elasticity interactions". Thesis, Sorbonne Paris Cité, 2018. http://www.theses.fr/2018USPCC124/document.
Testo completoAbstract (sommario):
Le développement des systèmes houlomoteurs ainsi que la gestion du littoral reposent sur une bonne compréhension des mécanismes liés aux interactions houle-structure. Dans cette thèse, nous nous intéressons à l'étude d'un champ de structures flexibles soumises à des ondes de surface, en vue de développer un système qui puisse à la fois atténuer les vagues et absorber l'énergie qui leur est associée de manière efficace. Les résultats présentés se basent autour d'expériences réalisées dans des installations de petite échelle, dans lesquelles la disposition spatiale des objets flexibles est le principal paramètre étudié. Dans un premier temps, nous caractérisons notre champ modèle afin d'évaluer l'influence de divers paramètres (configuration, flexibilité, fréquences des vagues) sur la distribution de l'énergie dans le système. Sur la base de ces résultats, nous développons ensuite un modèle d'interférences permettant de décrire les observations globales du système à partir de paramètres locaux connus, associés à une portion unitaire du champ. Ce modèle nous sert ensuite d'outil pour l'exploration d'une multitude de configurations spatiales, afin de déterminer le choix optimal vis-à-vis de l'atténuation et de l'absorption des vagues incidentes. Enfin, une campagne de mesures supplémentaire est utilisée afin d'expliquer les résultats obtenus avec le modèle et d'identifier les principes sous-jacents à cette optimisationUnderstanding the mechanisms involved in wave-structure interactions is of high interest for the development of efficient wave energy harvesters as well as for coastal management. In this thesis, we study the interactions of surface waves with a model array of slender flexible structures, in view of developing an efficient system for both attenuating and harvesting wave energy. The presented results are based around experimental investigations, by means of small scale facilities, in which the spatial arrangement of the flexible objects is the key parameter of study. The model array is first characterised by evaluating the role played by various parameters (configuration, flexibility, wave frequency) on the energy distribution in our system. Following these first observations, an interference model is then developed in order to describe the observed global effects of the array on both the wave field and the blade dynamics, based on known local parameters of a unit item of the array. This model then serves as a tool for exploring many possible array configurations, in order to determine the optimal choice regarding both the attenuation and the absorption of the imposed waves. A final experimental study is presented, in which the key results from the interference model are evaluated and the underlying principles of array optimisation are identified
46
Jansson, Elisabet. "Multi-buoy Wave Energy Converter : Electrical Power Smoothening from Array Configuration". Thesis, Uppsala universitet, Elektricitetslära, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-293689.
Testo completoAbstract (sommario):
This master thesis is done within the Energy Systems Engineering program at Uppsala University and performed for CorPower Ocean. Wave energy converters (WECs) are devices that utilize ocean waves for generation of electricity. The WEC developed by CorPower Ocean is small and intended to be deployed in an array. Placed in an array the different WECs will interact hydrodynamically and the combined power output is altered. The aim of this thesis is to model and investigate how the array configuration affects the electric power output. The goal is to target an optimal array layout for CorPower Ocean WECs, considering both average power and power smoothness in the optimization. In this thesis multiple buoys have been implemented in the time-domain model at CorPower Ocean. The hydrodynamic interactions are computed using an analytical interactions theory together with a recently developed calibration method able of handling WEC bodies of complicated shapes. The array behavior in regular waves is analyzed and it is identified how the beneficial separation distances vary with wave length. It is observed that the best separation distances for high average power does not exactly correspond to the best for minimizing the peak-to-average power. Simulation results show that it is possible to obtain both high average array power as well as increased power smoothening in a regular wave. A genetic algorithm for optimizing the array configuration is designed and tested for two different array patterns. Initial simulations are conducted in realistic multi-directional irregular waves. The power smoothening capacity of the array remains even in these conditions but the exact extent of it is still uncertain. This thesis delivers a WEC array simulation model as well as an initial view on the array characteristics of the phase controlled CorPower Ocean WEC. Additionally, it demonstrates an optimization algorithm taking both average power and power smoothness into account.
47
Ditlefsen, Arne Marius. "Wave Energy Conversion : Simulation Verification and Linearization of Direct Drive Wave Energy Converter with Variable DC-link Voltage Control". Thesis, Norwegian University of Science and Technology, Department of Electrical Power Engineering, 2009. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-9912.
Testo completoAbstract (sommario):
Lowering the cost of wave energy conversion is an essential task for it to succeed as a future energy resource. In this work a converter, assumed cheaper than the regular back to back converter setting, have been investigated for a electric direct drive point absorber. Both experimental work and simulations are used in the analysis. In the experimental work, a permanent magnet generator with a 6-pulse diode rectifier, a DC-link and a DC/DC converter equivalent, was used. Steady state, dynamic and transient measurements were preformed and a simulation model was compared to the measurements. Good results were obtained and deviations were in general small, mostly +-3% for voltage and current measurements and +-8% for torque measurements. Based on transient measurements and simulations a general linearization of the system was made in order to obtain useful information about the system. A step up converter was used in the simulation and it demonstrated stable passive loading control. By using the information obtained by the linearization, the performance of the simulation model was improved by decreasing the DC-link capacitance. The modified simulation model had significant less torque ripple than the initial. The linearization model also can been used to identify time delay represented by the power take off unit in a wave energy converter. This will be done for a commercial size wave energy converter summer 2009.
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Evans, E. M. "Tidal stream energy". Thesis, University of Plymouth, 1987. http://hdl.handle.net/10026.1/515.
Testo completo
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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.
Testo completo
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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.
Testo completoAbstract (sommario):
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.